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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    Leaf and stem traits are linked to liana growth rate in a subtropical cloud forest
    Bai, Xiao Long ; Zhang, Yun Bing ; Liu, Qi ; Wang, Yang Si Ding ; Yang, Da ; Zhang, Jiao Lin - \ 2020
    Forests 11 (2020)10. - ISSN 1999-4907 - 15 p.
    Functional traits - Nutrient concentrations - Stem hydraulic conductivity - Subtropical forest - Vein density - Woody climbers
    There is accumulating evidence that the abundance and biomass of lianas are increasing with global climate change in the Neotropics. However, our knowledge of growth-trait relationships among lianas is surprisingly rare. Here, we monitored the relative growth rate of 2860 individuals from seven deciduous and four evergreen liana species in a 20 ha subtropical cloud forest dynamics plot at high elevation (2472-2628 m a.s.l.) in southwest China. We linked the relative growth rate of lianas with nine leaf traits associated with leaf morphology, nutrient concentrations, and water hydraulic capacity as indicated by leaf vein density, and five stem wood traits related to stem water transport capacity and wood density. Our results showed that deciduous lianas have higher relative growth rates than their evergreen counterparts. Across all lianas studied, the relative growth rate was positively correlated with the leaf area and specific leaf area, but negatively correlated with leaf dry matter content. The relative growth rate of lianas was strongly correlated with nitrogen concentration after excluding the legume liana species. The relative growth rate was decoupled from leaf phosphorus and potassium concentrations, leaf vein density, and stem vessel traits across all lianas investigated. For four evergreen lianas, there were positive associations of the relative growth rate with the leaf thickness and diameter of the largest vessels. This study is the first to illustrate the relationships of liana growth with leaf and stem traits in the high-elevation subtropical cloud forest. More studies from diverse forest ecosystems are needed to comprehensively understand the mechanism underlying liana growth patterns.
    Ecomorphology of largemouth bass relative to a native trophic analogue explains its high invasive impact
    Luger, A.M. ; South, J. ; Alexander, M.E. ; Ellender, B.R. ; Weyl, O.L.F. ; Nagelkerke, L.A.J. - \ 2020
    Biological Invasions 22 (2020). - ISSN 1387-3547 - p. 2223 - 2233.
    Competition - Conservation - Freshwater - Functional traits - Handling time

    Predicting and understanding the impact of biological invaders is a global ecological imperative. Progress has been made through the application of phenomenological analysis via comparative functional response analysis. However, little is known about the mechanisms which drive high-magnitude functional responses of invasive species, especially when compared to trophically analogous natives. Largemouth bass Micropterus salmoides is a freshwater invasive species evaluated as a more efficient predator, with a higher-magnitude functional response, compared to a native analogue, the Cape kurper Sandelia capensis. In order to determine what traits drive this difference we quantified handling time behaviours (detection time, catch time, processing time) of both predator species and prey/predator size ratio, and employ an ecomorphological approach to determine whether largemouth bass is a more specialised predator than Cape kurper. There was no difference in detection time between the species, but largemouth bass were significantly and on average five times faster at catching prey than Cape kurper. Both species’ processing time was positively related to prey size, but Cape kurper was on average 4.5 times faster than largemouth bass. Ecomorphological data indicate that largemouth bass was the more specialised pursuit hunter for fish, whereas Cape kurper was better at ambush hunting. This suggests that the ecological impact of largemouth bass may be exacerbated in areas where there is habitat simplification which can lead to the extirpation of local small-bodied fish. In addition, there may be non-consumptive detrimental effects on trophically analogous natives through competitive exclusion.

    The role of fine‐root mass, specific root length and lifespan in tree performance: a whole‐tree exploration
    Weemstra, Monique ; Kiorapostolou, Natasa ; Ruijven, Jasper van; Mommer, Liesje ; Vries, Jorad de; Sterck, Frank - \ 2020
    Wageningen University & Research
    carbon balance - fine roots - Functional traits - root economics spectrum - tree performance - whole-plant model - temperate trees - interspecific root traits
    1. The root economics spectrum (RES) hypothesis predicts that fast-growing tree species have short-lived roots with high specific root length (SRL) to allow rapid resource uptake, and opposite trait expressions for slow-growing species. Yet, the mixed support for this hypothesis suggests that trees can adopt alternative strategies to increase resource uptake, besides an increase in SRL. 2. We combined a novel mechanistic whole-tree model and empirical fine-root data of ten tree species to test the effects of one of these alternative strategies, notably increasing fine-root mass, on the tree’s net C gain (used here as a proxy for tree performance), and to assess how fine-root lifespan influences the relative importance of SRL and fine-root mass for the C balance of trees. 3. Our results indicate that accounting for the short lifespan of high-SRL roots has important implications for explaining tree performance and the role of roots herein. Without considering their faster turnover, high-SRL roots and low fine-root mass resulted in the highest performance as predicted from the RES. Yet, when their higher turnover rates were accounted for, a high fine-root mass and low SRL lead to the highest performance. Both our model outcomes and field data further show a negative relationship between SRL and fine-root mass through which species aim to realise a similar root length density. This trade-off further indicates how high a SRL and low fine-root mass as well as opposite trait values can both lead to a positive C balance in a similar environment. 4. Our study may explain why high-SRL roots do not necessarily lead to the fastest tree growth as often hypothesised and demonstrates the importance of fine-root mass in combination with fine-root lifespan for explaining interspecific differences in tree performance. More generally, our work demonstrates the value of identifying and investigating different belowground strategies across species from a whole-plant modelling perspective, and identifies the relationship between SRL, fine-root biomass and lifespan as an important functional dimension to variation in species’ performance.
    How do lianas and trees change their vascular strategy in seasonal versus rain forest?
    Dias, Arildo S. ; Oliveira, Rafael S. ; Martins, Fernando R. ; Bongers, F. ; Anten, Niels P.R. ; Sterck, F. - \ 2019
    Perspectives in plant ecology, evolution and systematics 40 (2019). - ISSN 1433-8319
    Cambial variant - Functional traits - Plant hydraulics - Tropical forests - Wood density - Xylem structure and function

    Plants can alter wood anatomy to adjust water supply and mechanical stability demands. However, the different ways in which species can adjust rates of water supply through variation in size and number of vessels in the sapwood, and how this variation is related to the trade-off between hydraulic and mechanical functions remain unclear. We tested the hypothesis that plants with higher investment in mechanical support have relatively less margin to change their potential hydraulic conductivity in terms of vascular strategy: the total area of conducting tissue (vessel lumen fraction) and the combination of vessel sizes and numbers (vessel composition). We measured hydraulic and mechanical traits of xylem tissue and compared the relationship between those traits between trees and lianas co-occurring in a semi-deciduous seasonally dry forest (SDF) and an evergreen rainforest (RF). Along the axis of hydraulic-mechanical trait variation, SDF lianas showed a trait combination towards investment in hydraulic conductivity (higher vessel lumen area, percentage of xylem represented by vessels and potential hydraulic conductivity), whereas trees from both forests were characterized by investment in mechanical support (higher wood density, percentage of xylem represented by fibres and number of vessel per area) and RF lianas were intermediate between these spectrum. The main difference between trees and lianas was in vessel lumen fraction and vessel composition, indicating that not only the vessel size but the distribution between the size and number of vessels is important to explain the higher hydraulic conductivity of lianas. Between forests, trees did not differ in wood density (construction costs). Similarly, lianas did not differ in wood density among forests either; therefore, confirming that differences in potential hydraulic conductivity resulted from changes in the distribution between the size and number of vessels (vascular strategy). Our results suggest that vessel lumen fraction and the vessel composition are important dimensions driving variation in construction costs across woody plants. Thus, what makes lianas hydraulically distinctive from trees is the way vessel lumen fraction and vessel composition vary across environments rather than simply having wider vessels.

    Spatial heterogeneity in root litter and soil legacies differentially affect legume root traits
    Saar, Sirgi ; Semchenko, Marina ; Barel, Janna M. ; Deyn, Gerlinde B. de - \ 2018
    Plant and Soil 428 (2018)1-2. - ISSN 0032-079X - p. 253 - 264.
    Functional traits - Local and systemic response - Plant-soil feedback - Root litter - Soil heterogeneity - Spatial root distribution
    Background and Aims: Plants affect the soil environment via litter inputs and changes in biotic communities, which feed back to subsequent plant growth. Here we investigated the individual contributions of litter and biotic communities to soil feedback effects, and plant ability to respond to spatial heterogeneity in soil legacy. Methods: We tested for localised and systemic responses of Trifolium repens to soil biotic and root litter legacy of seven grassland species by exposing half of a root system to control soil and the other half to specific inoculum or root litter. Results: Soil inoculation triggered a localised reduction in root length while litter locally increased root biomass independent of inoculum or litter species identity. Nodule formation was locally suppressed in response to soil conditioned by another legume (Vicia cracca) and showed a trend towards systemic reduction in response to conspecific soil. V. cracca litter also caused a systemic response with thinner roots produced in the part of the root system not directly exposed to the litter. Conclusions: Spatial heterogeneity in root litter distribution and soil communities generate distinct local and systemic responses in root morphology and nodulation. These responses can influence plant-mutualist interactions and nutrient cycling, and should be included in plant co-existence models.
    Habitat heterogeneity promotes intraspecific trait variability of shrub species in Australian granite inselbergs
    Smedt, P. de; Ottaviani, G. ; Wardell-Johnson, G. ; Sýkora, K.V. ; Mucina, L. - \ 2018
    Folia Geobotanica 53 (2018)2. - ISSN 1211-9520 - p. 133 - 145.
    Fire-refugia - Functional traits - Global biodiversity hotspot - Mediterranean-type climate - Plant resource strategies - Proteaceae
    The role of intraspecific trait variability is increasingly recognized as a key factor shaping plant fitness and community assembly worldwide. Studying the direct effects of habitat heterogeneity on trait expression of individual plants of the same species is a useful tool to quantify intraspecific trait variability locally. We investigated how habitat heterogeneity on granite inselbergs affected intraspecific trait variability of 19 functional traits in three shrub species of the family Proteaceae in south western Australia, a global biodiversity hotspot. We used pairwise comparison (single trait) and multivariate analysis (multiple traits, functional space) to detect shifts in trait patterns. Consistent with our predictions, we found that individuals developing in putatively more stressful habitats (highly sun-irradiated, shallow-soil patches on the outcrops) were characterized by trait expressions indicative of more conservative resource-related strategies when compared with plants occurring in the surrounding woodlands that were experiencing more benign ecological conditions. These results were significant for two out of three species. Granite inselbergs promoted plant longevity, a signal that these granite inselbergs might offer refugial conditions defined as protection against fire.
    Relationships between leaf mass per area and nutrient concentrations in 98 Mediterranean woody species are determined by phylogeny, habitat and leaf habit
    Riva, Enrique G. de la; Villar, Rafael ; Pérez-Ramos, Ignacio M. ; Quero, José Luis ; Matías, Luis ; Poorter, Lourens ; Marañón, Teodoro - \ 2018
    Trees-Structure and Function 32 (2018)2. - ISSN 0931-1890 - p. 497 - 510.
    Functional traits - Leaf economics spectrum - Nitrogen - Phosphorus - Phylogenetic independent contrast (PIC) - Stoichiometry
    Key message: This study reinforces the existence of the leaf economics spectrum in Mediterranean woody species, and demonstrates the strong influence of phylogeny, leaf habit and environmental context as main drivers of variability in structural and nutrient traits of leaves. Abstract: Leaf structural and nutrient traits are key attributes of plant ecological strategies, as these traits are related to resource-use strategies and plant growth. However, leaf structure and nutrient composition can vary among different habitats, leaf habits or phylogenetic groups. In this study, we measured 13 leaf traits (one structural—leaf mass per area, LMA—and 12 nutrient traits) in 98 Mediterranean woody species growing over a wide range of environmental conditions, with the final aim of discerning the main causes of leaf trait variability. The variance decomposition results show that phylogeny, leaf habit and habitat type affected in several ways the structural and nutrient traits studied. Leaf nutrient concentrations are strongly positively correlated amongst themselves, and negatively correlated with LMA, in accordance with the “leaf economics spectrum”. We found that leaf habit and phylogeny were important causes of variation in LMA and in a broad number of leaf nutrients (i.e., C, N, Mg, S, K), while other micronutrients seemed to be more dependent on the environment (i.e., Cu and Mn). In summary, our study reinforces the existence of the leaf economics spectrum in a broad pool of Mediterranean woody species, and demonstrates the strong influence of phylogeny, leaf habit and environmental context as the main drivers of variability in some leaf structural and nutrient traits.
    Soil-mediated filtering organizes tree assemblages in regenerating tropical forests
    Pinho, Bruno Ximenes ; Melo, Felipe Pimentel Lopes de; Arroyo-Rodríguez, Víctor ; Pierce, Simon ; Lohbeck, Madelon ; Tabarelli, Marcelo - \ 2018
    Journal of Ecology 106 (2018)1. - ISSN 0022-0477 - p. 137 - 147.
    Atlantic forest - Brazil - Community assembly - Determinants of plant community diversity and structure - Environmental filtering - Forest regeneration - Functional traits - Secondary succession - Soil fertility - Soil nutrients

    Secondary forests are increasingly dominant in human-modified tropical landscapes, but the drivers of forest recovery remain poorly understood. Soil conditions influence plant community composition, and are expected to change over a gradient of succession. However, the role of soil conditions as an environmental filter driving community assembly during forest succession has rarely been explicitly assessed. We evaluated the role of stand basal area and soil conditions on community assembly and its consequences for community functional properties along a chronosequence of Atlantic forest regeneration following sugar cane cultivation. Specifically, we tested whether community functional properties are related to stand basal area, soil fertility and soil moisture. Our expectations were that edaphic environmental filters play an increasingly important role along secondary succession by increasing functional trait convergence towards more conservative attributes. We sampled soil and woody vegetation features across 15 second-growth (3-30 years) and 11 old-growth forest plots (300 m2 each). We recorded tree functional traits related to resource-use strategies (specific leaf area, SLA; leaf dry matter content, LDMC; leaf area, LA; leaf thickness, LT; and leaf succulence, LS) and calculated community functional properties using the community-weighted mean (CWM) of each trait and the functional dispersion (FDis) of each trait separately and all traits together. With exception of LA, all leaf traits were strongly associated with stand basal area; LDMC and SLA increased, while LT and LS decreased with forest development. Such changes in LDMC, LT and LS were also related to the decrease in soil nutrient availability and pH along succession, while soil moisture was weakly related to community functional properties. Considering all traits, as well as leaf thickness and succulence separately, FDis strongly decreased with increasing basal area and decreasing soil fertility along forest succession, presenting the lowest values in old-growth forests. Synthesis. Our findings suggest that tropical forest regeneration may be a deterministic process shaped by soil conditions. Soil fertility operates as a key filter causing functional convergence towards more conservative resource-use strategies, such as leaves with higher leaf dry matter content.

    What plant functional traits can reduce nitrous oxide emissions from intensively managed grasslands?
    Abalos Rodriguez, Diego ; Groenigen, Jan Willem van; Deyn, Gerlinde B. De - \ 2018
    Global Change Biology 24 (2018)1. - ISSN 1354-1013 - p. e248 - e258.
    Functional traits - Grassland - Nitrogen - Nitrous oxide - Plant traits - Plant-microbe interactions

    Plant species exert a dominant control over the nitrogen (N) cycle of natural and managed grasslands. Although in intensively managed systems that receive large external N inputs the emission of the potent greenhouse gas nitrous oxide (N2O) is a crucial component of this cycle, a mechanistic relationship between plant species and N2O emissions has not yet been established. Here we use a plant functional trait approach to study the relation between plant species strategies and N2O emissions from soils. Compared to species with conservative strategies, species with acquisitive strategies have higher N uptake when there is ample N in the soil, but also trigger N mineralization when soil N is limiting. Therefore, we hypothesized that (1) compared to conservative species, species with acquisitive traits reduce N2O emissions after a high N addition; and (2) species with conservative traits have lower N2O emissions than acquisitive plants if there is no high N addition. This was tested in a greenhouse experiment using monocultures of six grass species with differing above- and below-ground traits, growing across a gradient of soil N availability. We found that acquisitive species reduced N2O emissions at all levels of N availability, produced higher biomass and showed larger N uptake. As such, acquisitive species had 87% lower N2O emissions per unit of N uptake than conservative species (p < .05). Structural equation modelling revealed that specific leaf area and root length density were key traits regulating the effects of plants on N2O emission and biomass productivity. These results provide the first framework to understand the mechanisms through which plants modulate N2O emissions, pointing the way to develop productive grasslands that contribute optimally to climate change mitigation.

    Hydrodynamic conditioning of diversity and functional traits in subtidal estuarine macrozoobenthic communities
    Wal, Daphne van der; Lambert, Gwladys I. ; Ysebaert, Tom ; Plancke, Yves M.G. ; Herman, Peter M.J. - \ 2017
    Estuarine Coastal and Shelf Science 197 (2017). - ISSN 0272-7714 - p. 80 - 92.
    Estuarine gradients - Flow - Functional traits - Hydrodynamics - Macrozoobenthos - Westerschelde
    Variations in abundance and diversity of estuarine benthic macrofauna are typically described along the salinity gradient. The influence of gradients in water depth, hydrodynamic energy and sediment properties are less well known. We studied how these variables influence the distribution of subtidal macrofauna in the polyhaline zone of a temperate estuary (Westerschelde, SW Netherlands). Macrofauna density, biomass and species richness, combined in a so-called ecological richness, decreased with current velocities and median grain-size and increased with organic carbon of the sediment, in total explaining 39% of the variation. The macrofauna community composition was less well explained by the three environmental variables (approx. 12–15% in total, with current velocity explaining approx. 8%). Salinity, water depth and distance to the intertidal zone had a very limited effect on both ecological richness and the macrofauna community. The proportion of (surface) deposit feeders (including opportunistic species), decreased relative to that of omnivores and carnivores with increasing current velocity and sediment grain-size. In parallel, the proportion of burrowing sessile benthic species decreased relative to that of mobile benthic species that are able to swim. Correspondingly, spatial variations in hydrodynamics yielded distinct hotspots and coldspots in ecological richness. The findings highlight the importance of local hydrodynamic conditions for estuarine restoration and conservation. The study provides a tool based on a hydrodynamic model to assess and predict ecological richness in estuaries.
    Substrate homogenization affects survival and fitness in the lowland stream caddisflies Micropterna sequax and Potamophylax rotundipennis : A mesocosm experiment
    Westveer, Judith J. ; Verdonschot, Piet F.M. ; Verdonschot, Ralf C.M. - \ 2017
    Freshwater Science 36 (2017)3. - ISSN 2161-9549 - p. 585 - 594.
    Functional traits - Habitat heterogeneity - Habitat preference - Macroinvertebrates - Substrate patchiness - Trichoptera

    Loss of substrate heterogeneity or patchiness is common in lowland streams with disturbed hydrological regimes. At the reach scale, peak discharges tend to homogenize the stream bed and decrease the availability of specific microhabitat types. This spatial shift in habitats toward a more homogeneous landscape could have large negative effects on species that perform essential ecosystem processes. We conducted an aquatic mesocosm experiment to test the effect of habitat homogenization on survival and fitness of 2 species of Trichoptera (Micropterna sequax and Potamophylax rotundipennis). We used caddisflies as model organisms because of their abundance in lowland streams, their representativeness of the total shredder community, and their important role in leaf-litter decomposition. We reared larvae in artificial recirculating channels containing leaf and sand patches in 3 spatial configurations, differing in homogeneity of substrates, varying from few large patches to many small patches. We used emergence rate as a measure of survival and biomass and wing span of the adults as fitness correlates. For M. sequax, survival was lower in the homogeneous than in the heterogeneous configurations, but patch configuration did not affect fitness. For P. rotundipennis, spatial configuration of the patches did not affect survival, but the longest forewings for both males and females were found in the homogeneous configuration. Our results suggest that both species experience intraspecific resource competition arising from the spatial distribution of patches, expressed as an investment in wing development (e.g., dispersal capacity) in P. rotundipennis and resulting in lower survival rates in M. sequax. Our results indicate the importance of knowledge of trait-based responses and highlight the effects of the configuration of stream bottom substrate for its inhabitants on microscale.

    Does introduction of clover in an agricultural grassland affect the food base and functional diversity of Collembola?
    Annibale, Alessandra D'; Sechi, Valentina ; Larsen, Thomas ; Christensen, Søren ; Krogh, Paul Henning ; Eriksen, Jørgen - \ 2017
    Soil Biology and Biochemistry 112 (2017). - ISSN 0038-0717 - p. 165 - 176.
    Functional diversity - Functional traits - Legumes - Mesofauna - Stable isotopes

    Introduction of legumes (i.e. white clover) in agricultural grasslands is a common practice to improve yields, but how this affects soil fauna populations, particularly mesofauna, is still poorly understood. We investigated taxonomical and functional differences of Collembola communities between plots with either perennial ryegrass (Lolium perenne L.), white clover (Trifolium repens L.) or a mixture of both in a Danish agricultural grassland 6 and 14 months after establishing the leys (September and May, respectively). Diet preferences were investigated via stable isotope analyses (SIA) of carbon (13C) and nitrogen (15N). Collembolan abundance data were used to analyse morphological and ecological traits of the collected taxa and calculate functional diversity indices. Our stable isotope results show that root-derived resources made larger contributions to epedaphic and hemiedaphic species in the white clover than ryegrass plots. Changes in taxa specific density and traits distribution as a response to the C:N ratio of plant material, suggest that plant material quality was the main factor affecting the collembolan community, especially when comparing the two sampling occasions. Functional richness decreased under conditions of low quality material. In contrast to our hypothesis, population densities did not increase under mixture treatment and functional richness decreased. Our results suggest that habitat changes, via different plant composition, can affect some functional groups, having in turn effects on the functional diversity of the community.

    Data from: Environmental gradients and the evolution of successional habitat specialization: a test case with 14 Neotropical forest sites
    Letcher, Susan G. ; Lasky, Jesse R. ; Chazdon, Robin L. ; Norden, Natalia ; Wright, S.J. ; Meave, Jorge A. ; Pérez-García, Eduardo A. ; Muñoz, Rodrigo ; Romero-Pérez, Eunice ; Andrade, Ana ; Balvanera, Patricia ; Bongers, Frans ; Lohbeck, Madelon - \ 2016
    State University of New York (SUNY)
    Determinants of plant community diversity and structure - Life History Evolution - Precipitation gradient - Tropical wet forest - Tropical dry forest - Functional traits - phylogeny - Pioneer species
    1. Successional gradients are ubiquitous in nature, yet few studies have systematically examined the evolutionary origins of taxa that specialize at different successional stages. Here we quantify successional habitat specialization in Neotropical forest trees and evaluate its evolutionary lability along a precipitation gradient. Theoretically, successional habitat specialization should be more evolutionarily conserved in wet forests than in dry forests due to more extreme microenvironmental differentiation between early and late successional stages in wet forest. 2. We applied a robust multinomial classification model to samples of primary and secondary forest trees from 14 Neotropical lowland forest sites spanning a precipitation gradient from 788 to 4000 mm annual rainfall, identifying species that are old growth specialists and secondary forest specialists in each site. We constructed phylogenies for the classified taxa at each site and for the entire set of classified taxa, and tested whether successional habitat specialization is phylogenetically conserved. We further investigated differences in the functional traits of species specializing in secondary vs. old-growth forest along the precipitation gradient, expecting different trait associations with secondary forest specialists in wet vs. dry forests since water availability is more limiting in dry forests and light availability more limiting in wet forests. 3. Successional habitat specialization is non-randomly distributed in the angiosperm phylogeny, with a tendency towards phylogenetic conservatism overall and a trend toward stronger conservatism in wet forests than in dry forests. However, the specialists come from all the major branches of the angiosperm phylogeny, and very few functional traits showed any consistent relationships with successional habitat specialization in either wet or dry forests. 4. Synthesis: The niche conservatism evident in the habitat specialization of Neotropical trees suggests a role for radiation into different successional habitats in the evolution of species-rich genera, though the diversity of functional traits that lead to success in different successional habitats complicates analyses at the community scale. Examining the distribution of particular lineages with respect to successional gradients may provide more insight into the role of successional habitat specialization in the evolution of species-rich taxa.
    Winners and losers : Tropical forest tree seedling survival across a West African forest-savanna transition
    Cardoso, Anabelle W. ; Medina-Vega, José A. ; Malhi, Yadvinder ; Adu-Bredu, Stephen ; Ametsitsi, George K.D. ; Djagbletey, Gloria ; Langevelde, Frank van; Veenendaal, Elmar ; Oliveras, Immaculada - \ 2016
    Ecology and Evolution (2016). - ISSN 2045-7758 - p. 3417 - 3429.
    Drought - Fire - Forest encroachment - Functional traits

    Forest encroachment into savanna is occurring at an unprecedented rate across tropical Africa, leading to a loss of valuable savanna habitat. One of the first stages of forest encroachment is the establishment of tree seedlings at the forest-savanna transition. This study examines the demographic bottleneck in the seedlings of five species of tropical forest pioneer trees in a forest-savanna transition zone in West Africa. Five species of tropical pioneer forest tree seedlings were planted in savanna, mixed/transition, and forest vegetation types and grown for 12 months, during which time fire occurred in the area. We examined seedling survival rates, height, and stem diameter before and after fire; and seedling biomass and starch allocation patterns after fire. Seedling survival rates were significantly affected by fire, drought, and vegetation type. Seedlings that preferentially allocated more resources to increasing root and leaf starch (starch storage helps recovery from fire) survived better in savanna environments (frequently burnt), while seedlings that allocated more resources to growth and resource-capture traits (height, the number of leaves, stem diameter, specific leaf area, specific root length, root-to-shoot ratio) survived better in mixed/transition and forest environments. Larger (taller with a greater stem diameter) seedlings survived burning better than smaller seedlings. However, larger seedlings survived better than smaller ones even in the absence of fire. Bombax buonopozense was the forest species that survived best in the savanna environment, likely as a result of increased access to light allowing greater investment in belowground starch storage capacity and therefore a greater ability to cope with fire. Synthesis: Forest pioneer tree species survived best through fire and drought in the savanna compared to the other two vegetation types. This was likely a result of the open-canopied savanna providing greater access to light, thereby releasing seedlings from light limitation and enabling them to make and store more starch. Fire can be used as a management tool for controlling forest encroachment into savanna as it significantly affects seedling survival. However, if rainfall increases as a result of global change factors, encroachment may be more difficult to control as seedling survival ostensibly increases when the pressure of drought is lifted. We propose B. buonopozense as an indicator species for forest encroachment into savanna in West African forest-savanna transitions.

    Land-use intensification effects on functional properties in tropical plant communities
    Carreno Rocabado, Geovana ; Peñoa-Claros, Marielos ; Bongers, Frans ; Díaz, Sandra ; Quétier, Fabien ; Chuviñoa, José ; Poorter, Lourens - \ 2016
    Ecological Applications 26 (2016)1. - ISSN 1051-0761 - p. 174 - 189.
    Agriculture - Bolivia - Functional diversity - Functional traits - Land-use intensity - Pastureland - Plant community - Secondary forest - Tropical forest

    There is consensus that plant diversity and ecosystem processes are negatively affected by land-use intensifi cation (LUI), but, at the same time, there is empirical evidence that a large heterogeneity can be found in the responses. This heterogeneity is especially poorly understood in tropical ecosystems. We evaluated changes in community functional properties across fi ve common land-use types in the wet tropics with different land-use intensity: mature forest, logged forest, secondary forest, agricultural land, and pastureland, located in the lowlands of Bolivia. For the dominant plant species, we measured 12 functional response traits related to their life history, acquisition and conservation of resources, plant domestication, and breeding. We used three single-trait metrics to describe community functional properties: community abundance-weighted mean (CWM) traits values, coeffi cient of variation, and kurtosis of distribution. The CWM of all 12 traits clearly responded to LUI. Overall, we found that an increase in LUI resulted in communities dominated by plants with acquisitive leaf trait values. However, contrary to our expectations, secondary forests had more conservative trait values (i.e., lower specifi c leaf area) than mature and logged forest, probably because they were dominated by palm species. Functional variation peaked at intermediate land-use intensity (high coeffi cient of variation and low kurtosis), which included secondary forest but, unexpectedly, also agricultural land, which is an intensely managed system. The high functional variation of these systems is due to a combination of how response traits (and species) are fi ltered out by biophysical fi lters and how management practices introduced a range of exotic species and their trait values into the local species pool. Our results showed that, at local scales and depending on prevailing environmental and management practices, LUI does not necessarily result in communities with more acquisitive trait values or with less functional variation. Instead of the widely expected negative impacts of LUI on plant diversity, we found varying responses of functional variation, with possible repercussions on many ecosystem services. These fi ndings provide a background for actively mitigating negative effects of LUI while meeting the needs of local communities that rely mainly on provisioning ecosystem services for their livelihoods.

    Environmental gradients and the evolution of successional habitat specialization : A test case with 14 Neotropical forest sites
    Letcher, Susan G. ; Lasky, Jesse R. ; Chazdon, Robin L. ; Norden, Natalia ; Wright, S.J. ; Meave, Jorge A. ; Pérez-García, Eduardo A. ; Muñoz, Rodrigo ; Romero-Pérez, Eunice ; Andrade, Ana ; Balvanera, Patricia ; Bongers, Frans ; Lohbeck, Madelon - \ 2015
    Journal of Ecology 103 (2015)5. - ISSN 0022-0477 - p. 1276 - 1290.
    Determinants of plant community diversity and structure - Functional traits - Life-history evolution - Phylogeny - Pioneer species - Precipitation gradient - Tropical dry forest - Tropical wet forest

    Successional gradients are ubiquitous in nature, yet few studies have systematically examined the evolutionary origins of taxa that specialize at different successional stages. Here we quantify successional habitat specialization in Neotropical forest trees and evaluate its evolutionary lability along a precipitation gradient. Theoretically, successional habitat specialization should be more evolutionarily conserved in wet forests than in dry forests due to more extreme microenvironmental differentiation between early and late-successional stages in wet forest. We applied a robust multinomial classification model to samples of primary and secondary forest trees from 14 Neotropical lowland forest sites spanning a precipitation gradient from 788 to 4000 mm annual rainfall, identifying species that are old-growth specialists and secondary forest specialists in each site. We constructed phylogenies for the classified taxa at each site and for the entire set of classified taxa and tested whether successional habitat specialization is phylogenetically conserved. We further investigated differences in the functional traits of species specializing in secondary vs. old-growth forest along the precipitation gradient, expecting different trait associations with secondary forest specialists in wet vs. dry forests since water availability is more limiting in dry forests and light availability more limiting in wet forests. Successional habitat specialization is non-randomly distributed in the angiosperm phylogeny, with a tendency towards phylogenetic conservatism overall and a trend towards stronger conservatism in wet forests than in dry forests. However, the specialists come from all the major branches of the angiosperm phylogeny, and very few functional traits showed any consistent relationships with successional habitat specialization in either wet or dry forests. Synthesis. The niche conservatism evident in the habitat specialization of Neotropical trees suggests a role for radiation into different successional habitats in the evolution of species-rich genera, though the diversity of functional traits that lead to success in different successional habitats complicates analyses at the community scale. Examining the distribution of particular lineages with respect to successional gradients may provide more insight into the role of successional habitat specialization in the evolution of species-rich taxa.

    How do light and water acquisition strategies affect species selection during secondary succession in moist tropical forests?
    Schönbeck, Leonie ; Lohbeck, Madelon ; Bongers, Frans ; Ramos, Miguel Martínez ; Sterck, Frank - \ 2015
    Forests 6 (2015)6. - ISSN 1999-4907 - p. 2047 - 2065.
    Chiapas - Environmental filtering - Evaporative flux method - Functional traits - Leaf drought tolerance - Leaf shade tolerance - Mexico - Secondary succession - Tropical moist forest - Vulnerability

    Pioneer tree species have acquisitive leaf characteristics associated with high demand of light and water, and are expected to be shade and drought intolerant. Using leaf functional traits (specific leaf area, photosynthetic rate, relative water content and stomatal conductance) and tree performance (mortality rate) in the field, we assessed how shade and drought tolerance of leaves are related to the species' positions along a successional gradient in moist tropical forest in Chiapas, Mexico. We quantified morphological and physiological leaf shade and drought tolerance indicators for 25 dominant species that characterize different successional stages. We found that light demand decreases with succession, confirming the importance of light availability for species filtering during early stages of succession. In addition, water transport levels in the leaves decreased with succession, but high water transport did not increase the leaf's vulnerability to drought. In fact, late successional species showed higher mortality in dry years than early successional ones, against suggestions from leaf drought tolerance traits. It is likely that pioneer species have other drought-avoiding strategies, like deep rooting systems and water storage in roots and stems. More research on belowground plant physiology is needed to understand how plants adapt to changing environments, which is crucial to anticipate the effects of climate change on secondary forests.

    Phylogenetic patterns are not proxies of community assembly mechanisms (they are far better)
    Gerhold, Pille ; Cahill, J.F. ; Winter, Marten ; Bartish, I.V. ; Prinzing, Andreas - \ 2015
    Functional Ecology 29 (2015)5. - ISSN 0269-8463 - p. 600 - 614.
    Coexistence - Competition - Evolution - Functional traits - Habitat filtering - Inter-actions - Lineage-pool - Macroevolutionary diversification - Phylogeny

    The subdiscipline of 'community phylogenetics' is rapidly growing and influencing thinking regarding community assembly. In particular, phylogenetic dispersion of co-occurring species within a community is commonly used as a proxy to identify which community assembly processes may have structured a particular community: phylogenetic clustering as a proxy for abiotic assembly, that is habitat filtering, and phylogenetic overdispersion as a proxy for biotic assembly, notably competition. We challenge this approach by highlighting (typically) implicit assumptions that are, in reality, only weakly supported, including (i) phylogenetic dispersion reflects trait dispersion; (ii) a given ecological function can be performed only by a single trait state or combination of trait states; (iii) trait similarity causes enhanced competition; (iv) competition causes species exclusion; (v) communities are at equilibrium with processes of assembly having been completed; (vi) assembly through habitat filtering decreases in importance if assembly through competition increases, such that the relative balance of the two can be thus quantified by a single parameter; and (vii) observed phylogenetic dispersion is driven predominantly by local and present-day processes. Moreover, technical sophistication of the phylogenetic-patterns-as-proxy approach trades off against sophistication in alternative, potentially more pertinent approaches to directly observe or manipulate assembly processes. Despite concerns about using phylogenetic dispersion as a proxy for community assembly processes, we suggest there are underappreciated benefits of quantifying the phylogenetic structure of communities, including (i) understanding how coexistence leads to the macroevolutionary diversification of habitat lineage-pools (i.e. phylogenetic-patterns-as-result approach); and (ii) understanding the macroevolutionary contingency of habitat lineage-pools and how it affects present-day species coexistence in local communities (i.e. phylogenetic-patterns-as-cause approach). We conclude that phylogenetic patterns may be little useful as proxy of community assembly. However, such patterns can prove useful to identify and test novel hypotheses on (i) how local coexistence may control macroevolution of the habitat lineage-pool, for example through competition among close relatives triggering displacement and diversification of characters, and (ii) how macroevolution within the habitat lineage-pool may control local coexistence of related species, for example through origin of close relatives that can potentially enter in competition. 2015 British Ecological Society.

    Going beyond limitations of plant functional types when predicting global ecosystem-atmosphere fluxes : Exploring the merits of traits-based approaches
    Bodegom, P.M. van; Douma, J.C. ; Witte, J.P.M. ; Ordoñez, J.C. ; Bartholomeus, R.P. ; Aerts, R. - \ 2012
    Global Ecology and Biogeography 21 (2012)6. - ISSN 1466-822X - p. 625 - 636.
    Assembly theory - Bioclimatic limits - DGVM - Earth system models - Functional traits - Habitat filtering - Land surface model - PFT - Plant strategies - Trait convergence

    Aim Despite their importance for predicting fluxes to and from terrestrial ecosystems, dynamic global vegetation models have insufficient realism because of their use of plant functional types (PFTs) with constant attributes. Based on recent advances in community ecology, we explore the merits of a traits-based vegetation model to deal with current shortcomings. Location Global. Methods A research review of current concepts and information, providing a new perspective, supported by quantitative analysis of a global traits database. Results Continuous and process-based trait-environment relations are central to a traits-based approach and allow us to directly calculate fluxes based on functional characteristics. By quantifying community assembly concepts, it is possible to predict trait values from environmental drivers, although these relations are still imperfect. Through the quantification of these relations, effects of adaptation and species replacement upon environmental changes are implicitly accounted for. Such functional links also allow direct calculation of fluxes, including those related to feedbacks through the nitrogen and water cycle. Finally, a traits-based model allows the prediction of new trait combinations and no-analogue ecosystem functions projected to arise in the near future, which is not feasible in current vegetation models. A separate calculation of ecosystem fluxes and PFT occurrences in traits-based models allows for flexible vegetation classifications. Main conclusions Given the advantages described above, we argue that traits-based modelling deserves consideration (although it will not be easy) if one is to aim for better climate projections.

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