Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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A global synthesis reveals biodiversity-mediated benefits for crop production
Dainese, Matteo ; Martin, Emily A. ; Aizen, Marcelo A. ; Albrecht, Matthias ; Bartomeus, Ignasi ; Bommarco, Riccardo ; Carvalheiro, Luisa G. ; Chaplin-Kramer, Rebecca ; Gagic, Vesna ; Garibaldi, Lucas A. ; Ghazoul, Jaboury ; Grab, Heather ; Jonsson, Mattias ; Karp, Daniel S. ; Kennedy, Christina M. ; Kleijn, David ; Kremen, Claire ; Landis, Douglas A. ; Letourneau, Deborah K. ; Marini, Lorenzo ; Poveda, Katja ; Rader, Romina ; Smith, Henrik G. ; Tscharntke, Teja ; Andersson, Georg K.S. ; Badenhausser, Isabelle ; Baensch, Svenja ; Bezerra, Antonio D.M. ; Bianchi, Felix J.J.A. ; Boreux, Virginie ; Bretagnolle, Vincent ; Caballero-Lopez, Berta ; Cavigliasso, Pablo ; Ćetković, Aleksandar ; Chacoff, Natacha P. ; Classen, Alice ; Cusser, Sarah ; Silva E Silva, Felipe D. Da; Groot, A. de; Dudenhöffer, Jan H. ; Ekroos, Johan ; Fijen, Thijs ; Franck, Pierre ; Freitas, Breno M. ; Garratt, Michael P.D. ; Gratton, Claudio ; Hipólito, Juliana ; Holzschuh, Andrea ; Hunt, Lauren ; Iverson, Aaron L. ; Jha, Shalene ; Keasar, Tamar ; Kim, Tania N. ; Kishinevsky, Miriam ; Klatt, Björn K. ; Klein, Alexandra Maria ; Krewenka, Kristin M. ; Krishnan, Smitha ; Larsen, Ashley E. ; Lavigne, Claire ; Liere, Heidi ; Maas, Bea ; Mallinger, Rachel E. ; Pachon, Eliana Martinez ; Martínez-Salinas, Alejandra ; Meehan, Timothy D. ; Mitchell, Matthew G.E. ; Molina, Gonzalo A.R. ; Nesper, Maike ; Nilsson, Lovisa ; O'Rourke, Megan E. ; Peters, Marcell K. ; Plećaš, Milan ; Potts, Simon G. ; L. Ramos, Davi de; Rosenheim, Jay A. ; Rundlöf, Maj ; Rusch, Adrien ; Sáez, Agustín ; Scheper, Jeroen ; Schleuning, Matthias ; Schmack, Julia M. ; Sciligo, Amber R. ; Seymour, Colleen ; Stanley, Dara A. ; Stewart, Rebecca ; Stout, Jane C. ; Sutter, Louis ; Takada, Mayura B. ; Taki, Hisatomo ; Tamburini, Giovanni ; Tschumi, Matthias ; Viana, Blandina F. ; Westphal, Catrin ; Willcox, Bryony K. ; Wratten, Stephen D. ; Yoshioka, Akira ; Zaragoza-Trello, Carlos ; Zhang, Wei ; Zou, Yi ; Steffan-Dewenter, Ingolf - \ 2019
Science Advances 5 (2019)10. - ISSN 2375-2548

Human land use threatens global biodiversity and compromises multiple ecosystem functions critical to food production. Whether crop yield-related ecosystem services can be maintained by a few dominant species or rely on high richness remains unclear. Using a global database from 89 studies (with 1475 locations), we partition the relative importance of species richness, abundance, and dominance for pollination; biological pest control; and final yields in the context of ongoing land-use change. Pollinator and enemy richness directly supported ecosystem services in addition to and independent of abundance and dominance. Up to 50% of the negative effects of landscape simplification on ecosystem services was due to richness losses of service-providing organisms, with negative consequences for crop yields. Maintaining the biodiversity of ecosystem service providers is therefore vital to sustain the flow of key agroecosystem benefits to society.

Heritability of growth and leaf loss compensation in a long-lived tropical understorey palm
Jansen, Merel ; Zuidema, Pieter A. ; Ast, Aad van; Bongers, Frans ; Malosetti, Marcos ; Martínez-Ramos, Miguel ; Núñez-Farfán, Juan ; Anten, Niels P.R. - \ 2019
PLoS ONE 14 (2019)5. - ISSN 1932-6203

Introduction Defoliation and light competition are ubiquitous stressors that can strongly limit plant performance. Tolerance to defoliation is often associated with compensatory growth, which could be positively or negatively related to plant growth. Genetic variation in growth, tolerance and compensation, in turn, plays an important role in the evolutionary adaptation of plants to changing disturbance regimes but this issue has been poorly investigated for long-lived woody species. We quantified genetic variation in plant growth and growth parameters, tolerance to defoliation and compensation for a population of the understorey palm Chamaedorea elegans. In addition, we evaluated genetic correlations between growth and tolerance/compensation. Methods We performed a greenhouse experiment with 711 seedlings from 43 families with twelve or more individuals of C. elegans. Seeds were collected in southeast Mexico within a 0.7 ha natural forest area. A two-third defoliation treatment (repeated every two months) was applied to half of the individuals to simulate leaf loss. Compensatory responses in specific leaf area, biomass allocation to leaves and growth per unit leaf area were quantified using iterative growth models. Results We found that growth rate was highly heritable and that plants compensated strongly for leaf loss. However, genetic variation in tolerance, compensation, and the individual compensatory responses was low. We found strong correlations between family mean growth rates in control and defoliation treatments. We did not find indications for growth-tolerance/ compensation trade-offs: genetic correlation between tolerance/compensation and growth rate were not significant. Implications The high genetic variation in growth rate, but low genetic variation in tolerance and compensation observed here suggest high ability to adapt to changes in environment that require different growth rates, but a low potential for evolutionary adaptation to changes in damage or herbivory. The strong correlations between family mean growth rates in control and defoliation treatments suggest that performance differences among families are also maintained under stress of disturbance.

Wet and dry tropical forests show opposite successional pathways in wood density but converge over time
Poorter, L. ; Rozendaal, Danaë ; Bongers, F. ; Almeida-Cortez, Jarcilene S. ; Almeyda Zambrano, Angélica María ; Álvarez, Francisco S. ; Andrade, José Luís ; Villa, Luis Felipe Arreola ; Balvanera, Patricia ; Becknell, Justin M. ; Bentos, Tony V. ; Bhaskar, Radika ; Boukili, Vanessa ; Brancalion, Pedro H.S. ; Broadbent, Eben N. ; César, Ricardo Gomes ; Chave, Jerome ; Chazdon, Robin L. ; Colletta, Gabriel Dalla ; Craven, Dylan ; Jong, Ben H.J. de; Denslow, Julie S. ; Dent, Daisy H. ; DeWalt, Saara J. ; García, Elisa Díaz ; Dupuy, Juan M. ; Durán, Sandra M. ; Espírito Santo, Mário Marcos ; Fandiño, María C. ; Fernandes, Geraldo Wilson ; Finegan, Bryan ; Moser, Vanessa Granda ; Hall, Jefferson S. ; Hernández-Stefanoni, José Luis ; Jakovac, A.C. ; Junqueira, André B. ; Kennard, Deborah ; Lebrija-Trejos, Edwin ; Letcher, Susan G. ; Lohbeck, M.W.M. ; Lopez, Omar R. ; Marín-Spiotta, Erika ; Martínez-Ramos, Miguel ; Martins, Sebastião Venâncio ; Massoca, Paulo E.S. ; Meave, Jorge A. ; Mesquita, Rita ; Mora, Francisco ; Souza Moreno, Vanessa De; Müller, Sandra C. ; Muñoz, Rodrigo ; Muscarella, Robert ; Oliveira Neto, Silvio Nolasco De; Nunes, Yule Roberta Ferreira ; Ochoa-Gaona, Susana ; Paz, Horacio ; Pena Claros, M. ; Piotto, Daniel ; Ruíz, Jorge ; Sanaphre-Villanueva, Lucía ; Sanchez-Azofeifa, Arturo ; Schwartz, Naomi B. ; Steininger, Marc K. ; Thomas, William Wayt ; Toledo, Marisol ; Uriarte, Maria ; Breugel, Michiel van; Wal, Hans van der - \ 2019
secondary succession - community assembly - community-weighted mean - wood density - Neotropics - tropical forest - Latin America
We analyse how community wood density (WD) recovers during secondary tropical forest succession. In wet forests succession proceeds from low to high WD, in dry forests from high to low WD, resulting in convergence of community WD of dry and wet forests over time, as vegetation cover builds up.
Wet and dry tropical forests show opposite successional pathways in wood density but converge over time
Poorter, Lourens ; Rozendaal, Danaë M.A. ; Bongers, Frans ; Almeida-Cortez, Jarcilene S. de; Almeyda Zambrano, Angélica María ; Álvarez, Francisco S. ; Andrade, José Luís ; Villa, Luis Felipe Arreola ; Balvanera, Patricia ; Becknell, Justin M. ; Bentos, Tony V. ; Bhaskar, Radika ; Boukili, Vanessa ; Brancalion, Pedro H.S. ; Broadbent, Eben N. ; César, Ricardo G. ; Chave, Jerome ; Chazdon, Robin L. ; Colletta, Gabriel Dalla ; Craven, Dylan ; Jong, Ben H.J. de; Denslow, Julie S. ; Dent, Daisy H. ; DeWalt, Saara J. ; García, Elisa Díaz ; Dupuy, Juan Manuel ; Durán, Sandra M. ; Espírito Santo, Mário M. ; Fandiño, María C. ; Fernandes, Geraldo Wilson ; Finegan, Bryan ; Moser, Vanessa Granda ; Hall, Jefferson S. ; Hernández-Stefanoni, José Luis ; Jakovac, Catarina C. ; Junqueira, André B. ; Kennard, Deborah ; Lebrija-Trejos, Edwin ; Letcher, Susan G. ; Lohbeck, Madelon ; Lopez, Omar R. ; Marín-Spiotta, Erika ; Martínez-Ramos, Miguel ; Martins, Sebastião V. ; Massoca, Paulo E.S. ; Meave, Jorge A. ; Mesquita, Rita ; Mora, Francisco ; Souza Moreno, Vanessa de; Müller, Sandra C. ; Muñoz, Rodrigo ; Muscarella, Robert ; Oliveira Neto, Silvio Nolasco de; Nunes, Yule R.F. ; Ochoa-Gaona, Susana ; Paz, Horacio ; Peña-Claros, Marielos ; Piotto, Daniel ; Ruíz, Jorge ; Sanaphre-Villanueva, Lucía ; Sanchez-Azofeifa, Arturo ; Schwartz, Naomi B. ; Steininger, Marc K. ; Thomas, William Wayt ; Toledo, Marisol ; Uriarte, Maria ; Utrera, Luis P. ; Breugel, Michiel van; Sande, Masha T. van der; Wal, Hans van der; Veloso, Maria D.M. ; Vester, Hans F.M. ; Vieira, Ima C.G. ; Villa, Pedro Manuel ; Williamson, G.B. ; Wright, S.J. ; Zanini, Kátia J. ; Zimmerman, Jess K. ; Westoby, Mark - \ 2019
Nature Ecology & Evolution 3 (2019). - ISSN 2397-334X - p. 928 - 934.

Tropical forests are converted at an alarming rate for agricultural use and pastureland, but also regrow naturally through secondary succession. For successful forest restoration, it is essential to understand the mechanisms of secondary succession. These mechanisms may vary across forest types, but analyses across broad spatial scales are lacking. Here, we analyse forest recovery using 1,403 plots that differ in age since agricultural abandonment from 50 sites across the Neotropics. We analyse changes in community composition using species-specific stem wood density (WD), which is a key trait for plant growth, survival and forest carbon storage. In wet forest, succession proceeds from low towards high community WD (acquisitive towards conservative trait values), in line with standard successional theory. However, in dry forest, succession proceeds from high towards low community WD (conservative towards acquisitive trait values), probably because high WD reflects drought tolerance in harsh early successional environments. Dry season intensity drives WD recovery by influencing the start and trajectory of succession, resulting in convergence of the community WD over time as vegetation cover builds up. These ecological insights can be used to improve species selection for reforestation. Reforestation species selected to establish a first protective canopy layer should, among other criteria, ideally have a similar WD to the early successional communities that dominate under the prevailing macroclimatic conditions.

Biodiversity recovery of Neotropical secondary forests
Rozendaal, Danaë M.A. ; Bongers, Frans ; Aide, T.M. ; Alvarez-Dávila, Esteban ; Ascarrunz, Nataly ; Balvanera, Patricia ; Becknell, Justin M. ; Bentos, Tony V. ; Brancalion, Pedro H.S. ; Cabral, George A.L. ; Calvo-Rodriguez, Sofia ; Chave, Jerome ; César, Ricardo G. ; Chazdon, Robin L. ; Condit, Richard ; Dallinga, Jorn S. ; Almeida-Cortez, Jarcilene S. De; Jong, Ben de; Oliveira, Alexandre De; Denslow, Julie S. ; Dent, Daisy H. ; Dewalt, Saara J. ; Dupuy, Juan Manuel ; Durán, Sandra M. ; Dutrieux, Loïc P. ; Espírito-Santo, Mario M. ; Fandino, María C. ; Fernandes, G.W. ; Finegan, Bryan ; García, Hernando ; Gonzalez, Noel ; Moser, Vanessa Granda ; Hall, Jefferson S. ; Hernández-Stefanoni, José Luis ; Hubbell, Stephen ; Jakovac, Catarina C. ; Hernández, Alma Johanna ; Junqueira, André B. ; Kennard, Deborah ; Larpin, Denis ; Letcher, Susan G. ; Licona, Juan-Carlos ; Lebrija-trejos, Edwin ; Marín-Spiotta, Erika ; Martínez-Ramos, Miguel ; Massoca, Paulo E.S. ; Meave, Jorge A. ; Mesquita, Rita C.G. ; Mora, Francisco ; Müller, Sandra C. ; Muñoz, Rodrigo ; Oliveira Neto, Silvio Nolasco De; Norden, Natalia ; Nunes, Yule R.F. ; Ochoa-Gaona, Susana ; Ortiz-Malavassi, Edgar ; Ostertag, Rebecca ; Peña-Caros, Marielos ; Pérez-García, Eduardo A. ; Piotto, Daniel ; Powers, Jennifer S. ; Aguilar-Cano, José ; Rodriguez-Buritica, Susana ; Rodríguez-Velázquez, Jorge ; Romero-Romero, Marco Antonio ; Ruíz, Jorge ; Sanchez-Azofeifa, Arturo ; Almeida, Arlete Silva De; Silver, Whendee L. ; Schwartz, Naomi B. ; Thomas, William Wayt ; Toledo, Marisol ; Uriarte, Maria ; Sá Sampaio, Everardo Valadares De; Breugel, Michiel van; Wal, Hans van der; Martins, Sebastião Venâncio ; Veloso, Maria D.M. ; Vester, Hans F.M. ; Vicentini, Alberto ; Vieira, Ima C.G. ; Villa, Pedro ; Williamson, G.B. ; Zanini, Kátia J. ; Zimmerman, Jess ; Poorter, Lourens - \ 2019
Science Advances 5 (2019)3. - ISSN 2375-2548 - 10 p.
Old-growth tropical forests harbor an immense diversity of tree species but are rapidly being cleared, while secondary forests that regrow on abandoned agricultural lands increase in extent. We assess how tree species richness and composition recover during secondary succession across gradients in environmental conditions and anthropogenic disturbance in an unprecedented multisite analysis for the Neotropics. Secondary forests recover remarkably fast in species richness but slowly in species composition. Secondary forests take a median time of five decades to recover the species richness of old-growth forest (80% recovery after 20 years) based on rarefaction analysis. Full recovery of species composition takes centuries (only 34% recovery after 20 years). A dual strategy that maintains both old-growth forests and species-rich secondary forests is therefore crucial for biodiversity conservation in human-modified tropical landscapes.
Implementation of PROMETHEUS 4‐step approach for evidence use in EFSA scientific assessments: benefits, issues, needs and solutions
Aiassa, Elisa ; Martino, Laura ; Barizzone, Fulvio ; Ciccolallo, Laura ; Garcia, Ana ; Georgiadis, Marios ; Guajardo, Irene Muñoz ; Tomcikova, Daniela ; Alexander, Jan ; Calistri, Paolo ; Gundert‐remy, Ursula ; Hart, Andrew David ; Hoogenboom, Ron Laurentius ; Messean, Antoine ; Naska, Androniki ; Navarro, Maria Navajas ; Noerrung, Birgit ; Ockleford, Colin ; Wallace, Robert John ; Younes, Maged ; Abuntori, Blaize ; Alvarez, Fernando ; Aryeetey, Monica ; Baldinelli, Francesca ; Barrucci, Federica ; Bau, Andrea ; Binaglia, Marco ; Broglia, Alessandro ; Castoldi, Anna Federica ; Christoph, Eugen ; Sesmaisons‐Lecarré, Agnes De; Georgiadis, Nikolaos ; Gervelmeyer, Andrea ; Istace, Frederique ; López‐Gálvez, Gloria ; Manini, Paola ; Maurici, Daniela ; Merten, Caroline ; Messens, Winy ; Mosbach‐Schulz, Olaf ; Putzu, Claudio ; Bordajandi, Luisa Ramos ; Smeraldi, Camilla ; Tiramani, Manuela ; Martínez, Silvia Valtueña ; Sybren, Vos ; Hardy, Anthony Richard ; Hugas, Marta ; Kleiner, Juliane ; Seze, Guilhem De - \ 2018
EFSA Supporting Publications 15 (2018)4. - ISSN 2397-8325
In 2014, the European Food Safety Authority (EFSA) started the PROMETHEUS (PROmoting METHods for Evidence Use in Scientific assessments) project to improve further and increase the consistency of the methods it uses in its scientific assessments. The project defined a set of principles for the scientific assessment process and a 4‐step approach (plan/carry out/verify/report) for their fulfilment, which was tested in ten case studies, one from each EFSA panel. The present report describes the benefits, issues, needs and solutions related to the implementation of the 4‐step approach in EFSA, identified in a dedicated workshop in October 2017. The key benefits of the approach, which was deemed applicable to all types of EFSA scientific assessment including assessments of regulated products, are: 1) increased ‘scientific value’ of EFSA outputs, i.e. the extent of impartiality, methodological rigour, transparency and engagement; 2) guarantee of fitness‐for‐purpose, as it implies tailoring the methods to the specificities of each assessment; 3) efficiency gain, since preparing a protocol for the assessment upfront helps more streamlined processes throughout the implementation phase; 4) innovation, as the approach promotes the pioneering practice of ‘planning before doing’ (well established in primary research) for broad scientific assessments in regulatory science; and 5) increased harmonisation and consistency of EFSA assessments. The 4‐step approach was also considered an effective system for detecting additional methodological and/or expertise needs and a useful basis for further defining a quality management system for EFSA's scientific processes. The identified issues and solutions related to the implementation of the approach are: a) lack of engagement and need for effective communication on benefits and added value; b) need for further advances especially in the field of problem formulation/protocol development, evidence appraisal and evidence integration; c) need for specialised expertise in the previous aspects; and specific needs for d) assessments of regulated products and e) outsourced projects.
Data from: Towards smarter harvesting from natural palm populations by sparing the individuals that contribute most to population growth or productivity
Jansen, M. ; Anten, N.P.R. ; Bongers, F. ; Martínez-Ramos, Miguel ; Zuidema, P.A. - \ 2018
Chamaedorea - forest management - harvest simulations - individual heterogenity - Integral Project Model - leaf harvesting - NFTP - sustainability - Chamaedorea elegans
1. Natural populations deliver a wide range of products that provide income for millions of people and need to be exploited sustainably. Large heterogeneity in individual performance within these exploited populations has the potential to improve population recovery after exploitation and thus help sustaining yields over time. 2. We explored the potential of using individual heterogeneity to design smarter harvest schemes, by sparing individuals that contribute most to future productivity and population growth, using the understorey palm Chamaedorea elegans as a model system. Leaves of this palm are an important non-timber forest product and long-term inter-individual growth variability can be evaluated from internode lengths. 3. We studied a population of 830 individuals, half of which was subjected to a 67 % defoliation treatment for three years. We measured effects of defoliation on vital rates and leaf size – a trait that determines marketability. We constructed integral projection models in which vital rates depended on stem length, past growth rate, and defoliation, and evaluated transient population dynamics to quantify population development and leaf yield. We then simulated scenarios in which we spared individuals that were either most important for population growth or had leaves smaller than marketable size. 4. Individuals varying in size or past growth rate responded similarly to leaf harvesting in terms of growth and reproduction. By contrast, defoliation-induced reduction in survival chance was smaller in large individuals than in small ones. Simulations showed that harvest-induced population decline was much reduced when individuals from size and past growth classes that contributed most to population growth were spared. Under this scenario cumulative leaf harvest over 20 years was somewhat reduced, but long-term leaf production was sustained. A three-fold increase in leaf yield was generated when individuals with small leaves are spared. 5. Synthesis and applications This study demonstrates the potential to create smarter systems of palm leaf harvest by accounting for individual heterogeneity within exploited populations. Sparing individuals that contribute most to population growth ensured sustained leaf production over time. The concepts and methods presented here are generally applicable to exploited plant and animal species which exhibit considerable individual heterogeneity.
Legume abundance along successional and rainfall gradients in Neotropical forests
Gei, Maga ; Rozendaal, Danaë M.A. ; Poorter, Lourens ; Bongers, Frans ; Sprent, Janet I. ; Garner, Mira D. ; Aide, T.M. ; Andrade, José Luis ; Balvanera, Patricia ; Becknell, Justin M. ; Brancalion, Pedro H.S. ; Cabral, George A.L. ; César, Ricardo Gomes ; Chazdon, Robin L. ; Cole, Rebecca J. ; Colletta, Gabriel Dalla ; Jong, Ben De; Denslow, Julie S. ; Dent, Daisy H. ; Dewalt, Saara J. ; Dupuy, Juan Manuel ; Durán, Sandra M. ; Espírito Santo, Mário Marcos Do; Fernandes, G.W. ; Nunes, Yule Roberta Ferreira ; Finegan, Bryan ; Moser, Vanessa Granda ; Hall, Jefferson S. ; Hernández-Stefanoni, José Luis ; Junqueira, André B. ; Kennard, Deborah ; Lebrija-Trejos, Edwin ; Letcher, Susan G. ; Lohbeck, Madelon ; Marín-Spiotta, Erika ; Martínez-Ramos, Miguel ; Meave, Jorge A. ; Menge, Duncan N.L. ; Mora, Francisco ; Muñoz, Rodrigo ; Muscarella, Robert ; Ochoa-Gaona, Susana ; Orihuela-Belmonte, Edith ; Ostertag, Rebecca ; Peña-Claros, Marielos ; Pérez-García, Eduardo A. ; Piotto, Daniel ; Reich, Peter B. ; Reyes-García, Casandra ; Rodríguez-Velázquez, Jorge ; Romero-Pérez, I.E. ; Sanaphre-Villanueva, Lucía ; Sanchez-Azofeifa, Arturo ; Schwartz, Naomi B. ; Almeida, Arlete Silva De; Almeida-Cortez, Jarcilene S. ; Silver, Whendee ; Souza Moreno, Vanessa De; Sullivan, Benjamin W. ; Swenson, Nathan G. ; Uriarte, Maria ; Breugel, Michiel Van; Wal, Hans Van Der; Veloso, Maria Das Dores Magalhães ; Vester, Hans F.M. ; Vieira, Ima Célia Guimarães ; Zimmerman, Jess K. ; Powers, Jennifer S. - \ 2018
Nature Ecology & Evolution 2 (2018)7. - ISSN 2397-334X - p. 1104 - 1111.
The nutrient demands of regrowing tropical forests are partly satisfied by nitrogen-fixing legume trees, but our understanding of the abundance of those species is biased towards wet tropical regions. Here we show how the abundance of Leguminosae is affected by both recovery from disturbance and large-scale rainfall gradients through a synthesis of forest inventory plots from a network of 42 Neotropical forest chronosequences. During the first three decades of natural forest regeneration, legume basal area is twice as high in dry compared with wet secondary forests. The tremendous ecological success of legumes in recently disturbed, water-limited forests is likely to be related to both their reduced leaflet size and ability to fix N2, which together enhance legume drought tolerance and water-use efficiency. Earth system models should incorporate these large-scale successional and climatic patterns of legume dominance to provide more accurate estimates of the maximum potential for natural nitrogen fixation across tropical forests.
Towards smarter harvesting from natural palm populations by sparing the individuals that contribute most to population growth or productivity
Jansen, Merel ; Anten, Niels P.R. ; Bongers, Frans ; Martínez-Ramos, Miguel ; Zuidema, Pieter A. - \ 2018
Journal of Applied Ecology 55 (2018)4. - ISSN 0021-8901 - p. 1682 - 1691.
Chamaedorea - Forest management - Harvest simulations - Individual heterogeneity - Integral Projection Model - Leaf harvesting - Non-timber forest product - Palm leaves - Population dynamics - Sustainability
Natural populations deliver a wide range of products that provide income for millions of people and need to be exploited sustainably. Large heterogeneity in individual performance within these exploited populations has the potential to improve population recovery after exploitation and thus help sustain yields over time. We explored the potential of using individual heterogeneity to design smarter harvest schemes, by sparing individuals that contribute most to future productivity and population growth, using the understorey palm Chamaedorea elegans as a model system. Leaves of this palm are an important non-timber forest product and long-term inter-individual growth variability can be evaluated from internode lengths. We studied a population of 830 individuals, half of which was subjected to a 67% defoliation treatment for 3 years. We measured effects of defoliation on vital rates and leaf size-a trait that determines marketability. We constructed integral projection models in which vital rates depended on stem length, past growth rate and defoliation and evaluated transient population dynamics to quantify population development and leaf yield. We then simulated scenarios in which we spared individuals that were either most important for population growth or had leaves smaller than marketable size. Individuals varying in size or past growth rate responded similar to leaf harvesting in terms of growth and reproduction. By contrast, a reduction in survival chance was smaller in large individuals than in small ones. Simulations showed that harvest-induced population decline was greatly reduced when sparing individuals from size and past growth classes that contributed most to population growth. Under this scenario, cumulative leaf harvest over 20 years was somewhat reduced, but long-term leaf production was sustained. A threefold increase in leaf yield was generated when individuals with small leaves were spared. Synthesis and applications. This study demonstrates the potential to create smarter systems of palm leaf harvest by accounting for individual heterogeneity within exploited populations. Sparing individuals that contribute most to population growth ensured sustained leaf production over time. The concepts and methods presented here are generally applicable to exploited plant and animal species which exhibit considerable individual heterogeneity.
Biodiversity and climate determine the functioning of Neotropical forests
Poorter, L. ; Sande, M.T. van der; Arets, E.J.M.M. ; Ascarrunz, N. ; Enquist, B.J. ; Finegan, B. ; Licona, J.C. ; Martinez-Ramos, M. ; Mazzei, L. ; Meave, J. ; Munoz, R. ; Nytch, C.J. ; Oliveira, A.A. de; Perez-Garcia, E.A. ; Prado-Junior, J.A. ; Rodriguez-Velazquez, J. ; Ruschel, A.R. ; Salgado Negret, B. ; Schiavini, I. ; Swenson, N.G. ; Tenorio, E.A. ; Thompson, J. ; Toledo, M. ; Uriarte, M. ; Hout, P. van der; Zimmerman, J.K. ; Pena Claros, M. - \ 2017
biodiversity - biomass - carbon - ecosystem functioning - forest dynamics - productivity - soil fertility - tropical forest - water
Tropical forests account for a quarter of the global carbon storage and a third of the terrestrial productivity. Few studies have teased apart the relative importance of environmental factors and forest attributes for ecosystem functioning, especially for the tropics. This study aims to relate aboveground biomass (AGB), biomass dynamics (i.e., net biomass productivity and its underlying demographic drivers: biomass recruitment, growth and mortality) to forest attributes (tree diversity, community-mean traits, and stand basal area) and environmental conditions (water availability, soil fertility and disturbance). We used data from 26 sites, 201 one-ha plots and >92,000 trees distributed across the Neotropics. We quantified for each site water availability and soil total exchangeable bases and for each plot three key community-weighted mean functional traits that are important for biomass stocks and productivity. We used structural equation models to test the hypothesis that all drivers have independent, positive effects on biomass stocks and dynamics. Of the relationships analysed, vegetation attributes were more frequently significantly associated with biomass stocks and dynamics than environmental conditions (in 67% versus 33% of the relationships). High climatic water availability increased biomass growth and stocks, light disturbance increased biomass growth, and soil bases had no effect. Rarefied tree species richness had consistent positive relationships with biomass stocks and dynamics, probably because of niche complementarity, but was not related to net biomass productivity. Community-mean traits were good predictors of biomass stocks and dynamics. Water availability has a strong positive effect on biomass stocks and growth, and a future predicted increase in (atmospheric) drought might, therefore, potentially reduce carbon storage. Forest attributes – including species diversity and community-weighted mean traits – have independent and important relationships with AGB stocks, dynamics, and ecosystem functioning, not only in relatively simple temperate systems, but also in structurally complex hyper-diverse tropical forests.
Biodiversity and climate determine the functioning of Neotropical forests
Poorter, Lourens ; Sande, Masha T. van der; Arets, Eric J.M.M. ; Ascarrunz, Nataly ; Enquist, Brian ; Finegan, Bryan ; Licona, Juan Carlos ; Martínez-Ramos, Miguel ; Mazzei, Lucas ; Meave, Jorge A. ; Muñoz, Rodrigo ; Nytch, Christopher J. ; Oliveira, Alexandre A. de; Pérez-García, Eduardo A. ; Prado-junior, Jamir ; Rodríguez-Velázques, Jorge ; Ruschel, Ademir Roberto ; Salgado-Negret, Beatriz ; Schiavini, Ivan ; Swenson, Nathan G. ; Tenorio, Elkin A. ; Thompson, Jill ; Toledo, Marisol ; Uriarte, Maria ; Hout, Peter van der; Zimmerman, Jess K. ; Peña-Claros, Marielos - \ 2017
Global Ecology and Biogeography 26 (2017)12. - ISSN 1466-822X - p. 1423 - 1434.
Aim: Tropical forests account for a quarter of the global carbon storage and a third of the terrestrial productivity. Few studies have teased apart the relative importance of environmental factors and forest attributes for ecosystem functioning, especially for the tropics. This study aims to relate aboveground biomass (AGB) and biomass dynamics (i.e., net biomass productivity and its underlying demographic drivers: biomass recruitment, growth and mortality) to forest attributes (tree diversity, community-mean traits and stand basal area) and environmental conditions (water availability, soil fertility and disturbance). Location: Neotropics. Methods: We used data from 26 sites, 201 1-ha plots and >92,000 trees distributed across the Neotropics. We quantified for each site water availability and soil total exchangeable bases and for each plot three key community-weighted mean functional traits that are important for biomass stocks and productivity. We used structural equation models to test the hypothesis that all drivers have independent, positive effects on biomass stocks and dynamics. Results: Of the relationships analysed, vegetation attributes were more frequently associated significantly with biomass stocks and dynamics than environmental conditions (in 67 vs. 33% of the relationships). High climatic water availability increased biomass growth and stocks, light disturbance increased biomass growth, and soil bases had no effect. Rarefied tree species richness had consistent positive relationships with biomass stocks and dynamics, probably because of niche complementarity, but was not related to net biomass productivity. Community-mean traits were good predictors of biomass stocks and dynamics. Main conclusions: Water availability has a strong positive effect on biomass stocks and growth, and a future predicted increase in (atmospheric) drought might, therefore, potentially reduce carbon storage. Forest attributes, including species diversity and community-weighted mean traits, have independent and important relationships with AGB stocks, dynamics and ecosystem functioning, not only in relatively simple temperate systems, but also in structurally complex hyper-diverse tropical forests.
Demographic drivers of functional composition dynamics
Muscarella, Robert ; Lohbeck, Madelon ; Martínez-Ramos, Miguel ; Poorter, Lourens ; Rodríguez-Velázquez, Jorge Enrique ; Breugel, Michiel van; Bongers, Frans - \ 2017
Ecology 98 (2017)11. - ISSN 0012-9658 - p. 2743 - 2750.
community-weighted mean traits - leaf phosphorus - seed size - specific leaf area - succession - tropical forests - wood density

Mechanisms of community assembly and ecosystem function are often analyzed using community-weighted mean trait values (CWMs). We present a novel conceptual framework to quantify the contribution of demographic processes (i.e., growth, recruitment, and mortality) to temporal changes in CWMs. We used this framework to analyze mechanisms of secondary succession in wet tropical forests in Mexico. Seed size increased over time, reflecting a trade-off between colonization by small seeds early in succession, to establishment by large seeds later in succession. Specific leaf area (SLA) and leaf phosphorus content decreased over time, reflecting a trade-off between fast growth early in succession vs. high survival late in succession. On average, CWM shifts were driven mainly (70%) by growth of surviving trees that comprise the bulk of standing biomass, then mortality (25%), and weakly by recruitment (5%). Trait shifts of growing and recruiting trees mirrored the CWM trait shifts, and traits of dying trees did not change during succession, indicating that these traits are important for recruitment and growth, but not for mortality, during the first 30 yr of succession. Identifying the demographic drivers of functional composition change links population dynamics to community change, and enhances insights into mechanisms of succession.

Explaining long-term inter-individual growth variation in plant populations : persistence of abiotic factors matters
Jansen, Merel ; Anten, Niels P.R. ; Bongers, Frans ; Martínez-Ramos, Miguel ; Gavito, Mayra E. ; Zuidema, Pieter A. - \ 2017
Oecologia 185 (2017)4. - ISSN 0029-8549 - p. 663 - 674.
Chamaedorea elegans - Forest understorey - Individual heterogeneity - Life history - Population dynamics

An unanswered question in ecology is whether the environmental factors driving short-term performance also determine the often observed long-term performance differences among individuals. Here, we analyze the extent to which temporal persistence of spatial heterogeneity in environmental factors can contribute to long-term inter-individual variation in stem length growth. For a natural population of a long-lived understorey palm, we first quantified the effect of several environmental factors on stem length growth and survival. We then performed individual-based simulations of growth trajectories, in which we varied, for two environmental factors: (1) the strength of the effect on stem length growth and (2) the temporal persistence. Short-term variation in stem length growth was strongly driven by light availability. Auto-correlation in light availability and soil pH increased simulated variation in stem length growth among 20-year-old palms to levels similar to the observed variation. Analyses in which we varied both the strength of the effect on stem length growth and the temporal persistence of the environmental factors revealed that a large fraction of observed long-term growth differences can be explained, as long as one of these effects is strong. This implies that environmental factors that are relatively unimportant for short-term performance can still drive long-term performance differences when the environmental variation is sufficiently persistent over time.

A global synthesis of the effects of diversified farming systems on arthropod diversity within fields and across agricultural landscapes
Lichtenberg, Elinor M. ; Kennedy, Christina M. ; Kremen, Claire ; Batáry, Péter ; Berendse, Frank ; Bommarco, Riccardo ; Bosque-Pérez, Nilsa A. ; Carvalheiro, Luísa G. ; Snyder, William E. ; Williams, Neal M. ; Winfree, Rachael ; Klatt, Björn K. ; Åström, Sandra ; Benjamin, Faye ; Brittain, Claire ; Chaplin-Kramer, Rebecca ; Clough, Yann ; Danforth, Bryan ; Diekötter, Tim ; Eigenbrode, Sanford D. ; Ekroos, Johan ; Elle, Elizabeth ; Freitas, Breno M. ; Fukuda, Yuki ; Gaines-Day, Hannah R. ; Grab, Heather ; Gratton, Claudio ; Holzschuh, Andrea ; Isaacs, Rufus ; Isaia, Marco ; Jha, Shalene ; Jonason, Dennis ; Jones, Vincent P. ; Klein, Alexandra Maria ; Krauss, Jochen ; Letourneau, Deborah K. ; Macfadyen, Sarina ; Mallinger, Rachel E. ; Martin, Emily A. ; Martinez, Eliana ; Memmott, Jane ; Morandin, Lora ; Neame, Lisa ; Otieno, Mark ; Park, Mia G. ; Pfiffner, Lukas ; Pocock, Michael J.O. ; Ponce, Carlos ; Potts, Simon G. ; Poveda, Katja ; Ramos, Mariangie ; Rosenheim, Jay A. ; Rundlöf, Maj ; Sardiñas, Hillary ; Saunders, Manu E. ; Schon, Nicole L. ; Sciligo, Amber R. ; Sidhu, C.S. ; Steffan-Dewenter, Ingolf ; Tscharntke, Teja ; Veselý, Milan ; Weisser, Wolfgang W. ; Wilson, Julianna K. ; Crowder, David W. - \ 2017
Global Change Biology 23 (2017)11. - ISSN 1354-1013 - p. 4946 - 4957.
Agricultural management schemes - Arthropod diversity - Biodiversity - Evenness - Functional groups - Landscape complexity - Meta-analysis - Organic farming - Plant diversity
Agricultural intensification is a leading cause of global biodiversity loss, which can reduce the provisioning of ecosystem services in managed ecosystems. Organic farming and plant diversification are farm management schemes that may mitigate potential ecological harm by increasing species richness and boosting related ecosystem services to agroecosystems. What remains unclear is the extent to which farm management schemes affect biodiversity components other than species richness, and whether impacts differ across spatial scales and landscape contexts. Using a global metadataset, we quantified the effects of organic farming and plant diversification on abundance, local diversity (communities within fields), and regional diversity (communities across fields) of arthropod pollinators, predators, herbivores, and detritivores. Both organic farming and higher in-field plant diversity enhanced arthropod abundance, particularly for rare taxa. This resulted in increased richness but decreased evenness. While these responses were stronger at local relative to regional scales, richness and abundance increased at both scales, and richness on farms embedded in complex relative to simple landscapes. Overall, both organic farming and in-field plant diversification exerted the strongest effects on pollinators and predators, suggesting these management schemes can facilitate ecosystem service providers without augmenting herbivore (pest) populations. Our results suggest that organic farming and plant diversification promote diverse arthropod metacommunities that may provide temporal and spatial stability of ecosystem service provisioning. Conserving diverse plant and arthropod communities in farming systems therefore requires sustainable practices that operate both within fields and across landscapes.
Demographic Drivers of Aboveground Biomass Dynamics During Secondary Succession in Neotropical Dry and Wet Forests
Rozendaal, Danaë M.A. ; Chazdon, Robin L. ; Arreola-Villa, Felipe ; Balvanera, Patricia ; Bentos, Tony V. ; Dupuy, Juan M. ; Hernández-Stefanoni, J.L. ; Jakovac, Catarina C. ; Lebrija-Trejos, Edwin E. ; Lohbeck, Madelon ; Martínez-Ramos, Miguel ; Massoca, Paulo E.S. ; Meave, Jorge A. ; Mesquita, Rita C.G. ; Mora, Francisco ; Pérez-García, Eduardo A. ; Romero-Pérez, I.E. ; Saenz-Pedroza, Irving ; Breugel, Michiel van; Williamson, G.B. ; Bongers, Frans - \ 2017
Ecosystems 20 (2017)2. - ISSN 1432-9840 - p. 340 - 353.
Biomass accumulation - carbon sink - forest dynamics - Neotropics - second-growth tropical forest - species’ dominance - tree demography

The magnitude of the carbon sink in second-growth forests is expected to vary with successional biomass dynamics resulting from tree growth, recruitment, and mortality, and with the effects of climate on these dynamics. We compare aboveground biomass dynamics of dry and wet Neotropical forests, based on monitoring data gathered over 3–16 years in forests covering the first 25 years of succession. We estimated standing biomass, annual biomass change, and contributions of tree growth, recruitment, and mortality. We also evaluated tree species’ contributions to biomass dynamics. Absolute rates of biomass change were lower in dry forests, 2.3 and 1.9 Mg ha−1 y−1, after 5–15 and 15–25 years after abandonment, respectively, than in wet forests, with 4.7 and 6.1 Mg ha−1 y−1, in the same age classes. Biomass change was largely driven by tree growth, accounting for at least 48% of biomass change across forest types and age classes. Mortality also contributed strongly to biomass change in wet forests of 5–15 years, whereas its contribution became important later in succession in dry forests. Biomass dynamics tended to be dominated by fewer species in early-successional dry than wet forests, but dominance was strong in both forest types. Overall, our results indicate that biomass dynamics during succession are faster in Neotropical wet than dry forests, with high tree mortality earlier in succession in the wet forests. Long-term monitoring of second-growth tropical forest plots is crucial for improving estimates of annual biomass change, and for enhancing understanding of the underlying mechanisms and demographic drivers.

Multiple successional pathways in human-modified tropical landscapes : New insights from forest succession, forest fragmentation and landscape ecology research
Arroyo-Rodríguez, Víctor ; Melo, Felipe P.L. ; Martínez-Ramos, Miguel ; Bongers, Frans ; Chazdon, Robin L. ; Meave, Jorge A. ; Norden, Natalia ; Santos, Bráulio A. ; Leal, Inara R. ; Tabarelli, Marcelo - \ 2017
Biological Reviews 92 (2017)1. - ISSN 1464-7931 - p. 326 - 340.
Biodiversity conservation - Ecosystem services - Forest recovery - Land-use transformation - Landscape restoration - Landscape structure

Old-growth tropical forests are being extensively deforested and fragmented worldwide. Yet forest recovery through succession has led to an expansion of secondary forests in human-modified tropical landscapes (HMTLs). Secondary forests thus emerge as a potential repository for tropical biodiversity, and also as a source of essential ecosystem functions and services in HMTLs. Such critical roles are controversial, however, as they depend on successional, landscape and socio-economic dynamics, which can vary widely within and across landscapes and regions. Understanding the main drivers of successional pathways of disturbed tropical forests is critically needed for improving management, conservation, and restoration strategies. Here, we combine emerging knowledge from tropical forest succession, forest fragmentation and landscape ecology research to identify the main driving forces shaping successional pathways at different spatial scales. We also explore causal connections between land-use dynamics and the level of predictability of successional pathways, and examine potential implications of such connections to determine the importance of secondary forests for biodiversity conservation in HMTLs. We show that secondary succession (SS) in tropical landscapes is a multifactorial phenomenon affected by a myriad of forces operating at multiple spatio-temporal scales. SS is relatively fast and more predictable in recently modified landscapes and where well-preserved biodiversity-rich native forests are still present in the landscape. Yet the increasing variation in landscape spatial configuration and matrix heterogeneity in landscapes with intermediate levels of disturbance increases the uncertainty of successional pathways. In landscapes that have suffered extensive and intensive human disturbances, however, succession can be slow or arrested, with impoverished assemblages and reduced potential to deliver ecosystem functions and services. We conclude that: (i) succession must be examined using more comprehensive explanatory models, providing information about the forces affecting not only the presence but also the persistence of species and ecological groups, particularly of those taxa expected to be extirpated from HMTLs; (ii) SS research should integrate new aspects from forest fragmentation and landscape ecology research to address accurately the potential of secondary forests to serve as biodiversity repositories; and (iii) secondary forest stands, as a dynamic component of HMTLs, must be incorporated as key elements of conservation planning; i.e. secondary forest stands must be actively managed (e.g. using assisted forest restoration) according to conservation goals at broad spatial scales.

Super-performance in a palm species
Jansen, Merel - \ 2016
Wageningen University. Promotor(en): Niels Anten; Pieter Zuidema, co-promotor(en): Frans Bongers; M. Martínez-Ramos. - Wageningen : Wageningen University - ISBN 9789462579996 - 193
chamaedorea elegans - understorey - tropical forests - spatial variation - leaves - growth - population ecology - defoliation - genetic variation - chamaedorea elegans - onderlaag - tropische bossen - ruimtelijke variatie - bladeren - groei - populatie-ecologie - ontbladering - genetische variatie

The world is changing rapidly due to anthropogenic disturbance. Effects include: global warming, massive pollution, a changed global nitrogen cycle, high rates of land-use change, and exotic species spread. This has a tremendous impact on both natural and agricultural systems. To understand these impacts, good understanding of ecological systems and underlying drivers is necessary. Ecological systems can be studied at different levels of aggregation. Different levels of aggregation influence each other and are also influenced by external drivers like the environment. The population level is of particular interest, because many important ecological processes occur at the population level, like evolution, extinction, and invasion. Ecologists are increasingly recognizing that population processes are strongly influenced by one level of aggregation lower, the individual level. Individual heterogeneity (i.e. differences between individuals in performance), determines many population processes including population growth rate. However, the exact relations between individual heterogeneity, the external drivers of it, and the population level are not always well understood. Furthermore, methods to analyze these relations are not always available.

Individual heterogeneity occurs at different temporal scales, ranging from short- to long-term performance differences between individuals, where short- and long-term refer to the expected lifespan of the species in question. Short-term differences between individuals are relatively easily identifiable and are common in almost all species. But long-term differences are much harder to determine especially for long-lived organisms. Long-term differences between individuals in reproduction have been identified for several animal species, and in growth for several tree species, but less is known about the existence of such differences in other life forms (e.g. palms, lianas or clonal plants). Quantifying the extent to which individuals differ is essential for understanding the influence of individual heterogeneity on population processes. Super-performing individuals (i.e. individuals that persistently grow faster and reproduce more than others), probably contribute more to the growth of the population and therefore to future generations. Future populations will, therefore, have the genetic characteristics of the super-performers. Which characteristics this will be, depends on the genetic and environmental drivers of super-performance. Full understanding of the influence of individual heterogeneity on population processes, therefore, requires knowledge of the underlying causes of individual heterogeneity.

For many species, it is known that spatial variation in environmental conditions can cause short-term performance differences between individuals, but it is often not clear if the same environmental factors that cause short-term performance differences are also the environmental factors that cause long-term performance differences. Furthermore, genetic variation is known to cause performance differences, but to what extent is not well studied in natural long-lived plant populations. Within-population genetic variation can be maintained in habitats that are characterized by strong temporal or spatial heterogeneity in environmental conditions if the performance of a genotype relative to others depends on the environment it experiences.

Super-performing individuals possibly play an important role in the resistance and resilience of populations to disturbance (i.e. maintaining and recovering population growth rate under stress), because super-performers potentially contribute more to the recovery of the population. However, this depends on the relative tolerance to disturbance of super-performers compared to under-performers. A positive relation between performance and tolerance would make super-performers more important, while a negative relation would make them less important. Many types of disturbances entail leaf loss and tolerance to leaf loss is associated with performance being larger than what one would assume based on the amount of leaf area loss. Tolerance can be achieved by compensating for leaf loss in terms of growth rate, which entails either allocating more new assimilates to leaves, allocating new assimilates more efficiently to leaf area (i.e. by increasing specific leaf area), or growing faster with existing leaf area (i.e. by increasing net assimilation rate). Genetic variation in tolerance and compensatory responses would allow populations to adapt to changes in disturbance events that entail leaf loss.

Individual heterogeneity could also have implications for management. Plant and animal populations are managed at many different levels ranging from harvest from natural populations to modern agricultural practices. When harvesting from natural populations, it might be beneficial to spare the individuals that are most important for future production. Individuals could be spared, either because they contribute most to population growth, because they are tolerant to harvesting (which is relevant when only part of a plant is harvested), or when they start producing less or lower quality product. The productivity of natural populations could also be increased by actively promoting those environmental conditions and genotypes that allow for high productivity, which is the basis of agriculture and common practice in forest management. To determine how this can best be done, knowledge of the causes of individual heterogeneity is necessary.

The general aim of this thesis is to identify and quantify the mechanisms that determine individual heterogeneity and to determine how this heterogeneity, in turn, affects population level processes. This aim was divided into four main questions that I addressed: (1) To what extent do individuals differ in performance? (2) What causes individual heterogeneity in performance? (3) What are the demographic consequences of individual heterogeneity? (4) Can individual differences be used to improve the management of populations? To answer these questions, we used the tropical forest understorey palm Chamaedorea elegans as a study system, of which the leaves are an important non-timber forest product that is being used in the floral industry worldwide. We collected demographic data, measured spatial variation in environmental conditions, and applied a defoliation treatment to simulate leaf harvesting, in a natural population in Chiapas, Mexico. Furthermore, we grew seedlings from different mothers from our study population in the greenhouses of Wageningen University, where we also applied a defoliation treatment.

In Chapter 2 we quantified the extent to which individuals differ in long-term growth rate, and analyzed the importance of fast growers for population growth. We reconstructed growth histories from internodes and showed that growth differences between individuals are very large and persistent in our study population. This led to large variation in life growth trajectories, with individuals of the same age varying strongly in size. This shows that not only in canopy trees but also in species in the light limited understorey growth differences can be very large. Past growth rate was found to be a very good predictor of current performance (i.e. growth and reproduction). Using an Integral Projection Model (i.e. a type of demographic model) that was based on size and past growth rate, we showed that fast-growing individuals are much more important for population growth than others: the 50% fastest growing individuals contributed almost two times as much to population growth as the 50% slowest growing individuals.

In Chapter 3 we analyzed the extent to which observed long-term growth differences can be caused by environmental heterogeneity. Short-term variation in performance was mainly driven by light availability, while soil variables and leaf damage had smaller effects, and spatial heterogeneity in light availability and soil pH were autocorrelated over time. Using individual-based simulation models, we analyzed the extent to which spatial environmental heterogeneity could explain observed long-term variation in growth, and showed that this could largely be explained if the temporal persistence of light availability and soil pH was taken into account. We also estimated long-term inter-individual variation in reproduction to be very large. We further analyzed the importance of temporal persistence in environmental variation for long-term performance differences, by analyzing the whole range of values of environmental persistence, and the strength of the effect of the environmental heterogeneity on short-term performance. We showed that long-term performance differences become large when either the strength of the effect of the environmental factor on short-term performance is large, or when the spatial variation in the environmental factor is persistent over time. This shows that an environmental factor that in a short-term study might have been dismissed as unimportant for long-term performance variation, might, in reality, contribute strongly.

In Chapter 4 we tested for genetic variation in growth potential, tolerance to leaf loss, compensatory growth responses, and if growth potential and tolerance were genetically correlated in our study population. We quantified compensatory responses with an iterative growth model that takes into account the timing of leaf loss. Genetic variation in growth potential was large, and plants compensated strongly for leaf loss, but genetic variation in tolerance and compensatory growth responses was very limited. Growth performances in defoliated and undefoliated conditions were positively genetically correlated (i.e. the same genotypes perform relatively well compared to others, both with and without the stress of leaf loss). The high genetic variation in growth potential and the positive correlation between treatments suggests that the existence of super-performing individuals in our study population likely has (at least in part) a genetic basis. These super-performing individuals, that grow fast even under the stress of leaf loss, possibly contribute disproportionately to population resistance and resilience to disturbance. The low genetic variation in tolerance and compensatory responses, however, suggests that populations might have limited ability to adapt to changes in disturbance regimes that entail increases in leaf loss. Furthermore, the high genetic variation in growth potential could potentially be used in management practices like enrichment planting.

In Chapter 5 we explore the potential of using individual heterogeneity to design smarter harvest schemes, by sparing individuals that contribute most to future productivity. We tested if fast and slow growers, and small and large individuals, responded differently to leaf loss in terms of vital rates, but found only very limited evidence for this. Using Integral Projection Models that were based on stem length and past growth rate, we simulated leaf harvest over a period of 20 years, in several scenarios of sparing individuals, which we compared to “Business as usual” (i.e. no individuals being spared, BAU). Sparing individuals that are most important for population growth, was beneficial for population size (and could, therefore, reduce extinction risk), increased annual leaf harvest at the end of the simulation period, but cumulated leaf harvest over 20 years was much lower compared to BAU. Sparing individuals that produced leaves of non-commercial size (i.e. <25cm), therefore allowing them to recover, also resulted in a lower total leaf harvest over 20 years. However, a much higher harvest (a three-fold increase) was found when only leaves of commercial size were considered. These results show that it is possible to increase yield quality and sustainability (in terms of population size) of harvesting practices, by making use of individual heterogeneity. The analytical and modeling methods that we present are applicable to any natural system from which either whole individuals, or parts of individuals, are harvested, and provide an extra tool that could be considered by managers and harvest practitioners to optimize harvest practices.

In conclusion, in this thesis, I showed that in a long-lived understorey palm growth differences are very large and persistent (Chapter 2) and that it is likely that long-term differences in reproduction are also very large (Chapter 3). I also showed that spatial heterogeneity in environmental conditions can to a large extent explain these differences and that when evaluating the environmental drivers of individual heterogeneity, it is important to take the persistence of spatial variation into account (Chapter 3). Individual heterogeneity also is partly genetically determined. I showed that genetic variation in growth potential to be large (Chapter 4), and that fast growers keep on growing fast under the stress of leaf loss (Chapters 4,5). Therefore it is likely that genetic variation contributes to long-term differences between individuals. Genetic variation for tolerance and compensatory responses was estimated to be low (Chapter 4), suggesting that the adaptive potential of our study population to changes in disturbance events that entail leaf loss might be low. I also showed that super-performing individuals are much more important for the growth of the population (Chapter 2) and that individuals that are important for future production could be used to improve the management of natural populations (Chapter 5).

This study provides improved insight into the extent of individual heterogeneity in a long-lived plant species and its environmental and genetic drivers, and clearly shows the importance of individual heterogeneity and its drivers for population processes and management practices. It also presents methods on how persistent performance differences between individuals can be incorporated into demographic tools, how these can be used to analyze individual contributions to population dynamics, to extrapolate short-term to long–term environmental effects, and to analyze smart harvesting scenarios that take differences between individuals into account. These results indicate that individual heterogeneity, underlying environmental and genetic drivers, and population processes are all related. Therefore, when evaluating the effect of environmental change on population processes, and in the design of management schemes, it is important to keep these relations in mind. The methodological tools that we presented provide a means of doing this.

Natural forest regeneration and ecological restoration in human-modified tropical landscapes
Martínez-Ramos, Miguel ; Pingarroni, Aline ; Rodríguez-Velázquez, Jorge ; Toledo-Chelala, Lilibeth ; Zermeño-Hernández, Isela ; Bongers, Frans - \ 2016
Biotropica 48 (2016)6. - ISSN 0006-3606 - p. 745 - 757.
agricultural land uses - dispersal limitation - establishment limitation - Mexico - second growth forests - secondary succession - tree demography - tropical rain forest

In human-modified tropical landscapes (HMLs) the conservation of biodiversity, functions and services of forest ecosystems depends on persistence of old growth forest remnants, forest regeneration in abandoned agricultural fields, and restoration of degraded lands. Understanding the impacts of agricultural land uses (ALUs) on forest regeneration is critical for biodiversity conservation in HMLs. Here, we develop a conceptual framework that considers the availability of propagules and the environment prevailing after field abandonment as two major determinants of forest regeneration in HMLs. The framework proposes that regeneration potential decreases with size, duration and severity of agricultural disturbance, reducing propagule availability and creating ill-suited environmental conditions for regeneration. We used studies from Southern Mexico to assess this framework. First, we identify regeneration bottlenecks that trees face during transit from seed to follow-up life stages, using demographic analysis of dominant pioneer species in recently abandoned fields. Then, we explore effects of ALUs on forest regeneration at the field and landscape scales, addressing major legacies. Finally, we integrate agricultural disturbance with landscape composition to predict attributes of successful second growth forests in HMLs, and provide indicators useful to select tree native species for active restoration. An indicator of disturbance inflicted by ALUs, based on farmers’ information, predicted better regeneration potential than measurements of soil and microclimate conditions at time of abandonment. Cover of cattle pastures in the landscape was a stronger indicator of forest regenerating attributes than cover of old growth forest remnants. To conclude, we offer recommendations to promote forest regeneration and biodiversity conservation in HMLs.

The importance of biodiversity and dominance for multiple ecosystem functions in a human-modified tropical landscape
Lohbeck, M.W.M. ; Bongers, F. ; Martinez-Ramos, M. ; Poorter, L. - \ 2016
Ecology 97 (2016)10. - ISSN 0012-9658 - p. 2772 - 2779.
Many studies suggest that biodiversity may be particularly important for ecosystem multifunctionality, because different species with different traits can contribute to different functions. Support, however, comes mostly from experimental studies conducted at small spatial scales in low-diversity systems. Here, we test whether different species contribute to different ecosystem functions that are important for carbon cycling in a high-diversity human-modified tropical forest landscape in Southern Mexico. We quantified aboveground standing biomass, primary productivity, litter production, and wood decomposition at the landscape level, and evaluated the extent to which tree species contribute to these ecosystem functions.

We used simulations to tease apart the effects of species richness, species dominance and species functional traits on ecosystem functions. We found that dominance was more important than species traits in determining a species’ contribution to ecosystem functions. As a consequence of the high dominance in human-modified landscapes, the same small subset of species mattered across different functions.

In human-modified landscapes in the tropics, biodiversity may play a limited role for ecosystem multifunctionality due to the potentially large effect of species dominance on biogeochemical functions. However, given the spatial and temporal turnover in species dominance, biodiversity may be critically important for the maintenance and resilience of ecosystem functions.
Successional dynamics in Neotropical forests are as uncertain as they are predictable
Norden, Natalia ; Angarita, H.A. ; Bongers, Frans ; Martínez-Ramos, Miguel ; Cerda, I.G. De la; Breugel, Michiel Van; Lebrija-Trejos, Edwin ; Meave, J.A. ; Vandermeer, John ; Williamson, G.B. ; Finegan, Bryan ; Mesquita, Rita ; Chazdon, R.L. - \ 2015
Proceedings of the National Academy of Sciences of the United States of America 112 (2015)26. - ISSN 0027-8424 - p. 8013 - 8018.
Dynamical models - Predictability - Succession - Tropical secondary forests - Uncertainty

Although forest succession has traditionally been approached as a deterministic process, successional trajectories of vegetation change vary widely, even among nearby stands with similar environmental conditions and disturbance histories. Here, we provide the first attempt, to our knowledge, to quantify predictability and uncertainty during succession based on the most extensive long-term datasets ever assembled for Neotropical forests. We develop a novel approach that integrates deterministic and stochastic components into different candidate models describing the dynamical interactions among three widely used and interrelated forest attributes - stem density, basal area, and species density. Within each of the seven study sites, successional trajectories were highly idiosyncratic, even when controlling for prior land use, environment, and initial conditions in these attributes. Plot factors were far more important than stand age in explaining successional trajectories. For each site, the best-fit model was able to capture the complete set of time series in certain attributes only when both the deterministic and stochastic components were set to similar magnitudes. Surprisingly, predictability of stem density, basal area, and species density did not show consistent trends across attributes, study sites, or land use history, and was independent of plot size and time series length. The model developed here represents the best approach, to date, for characterizing autogenic successional dynamics and demonstrates the low predictability of successional trajectories. These high levels of uncertainty suggest that the impacts of allogenic factors on rates of change during tropical forest succession are far more pervasive than previously thought, challenging the way ecologists view and investigate forest regeneration.

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