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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    Data from: Patterns of nitrogen-fixing tree abundance in forests across Asia and America
    Menge, Duncan N.L. ; Chisholm, Ryan A. ; Davies, Stuart J. ; Abu Salim, Kamariah ; Allen, David ; Alvarez, Mauricio ; Bourg, Norm ; Brockelman, Warren Y. ; Bunyavejchewin, Sarayudh ; Butt, Nathalie ; Ouden, Jan den; Jansen, Patrick - \ 2019
    Dryad
    Determinants of plant community diversity and structure - Forest - Smithsonian ForestGEO - legume - symbiosis - nutrient limitation - nitrogen fixation
    Symbiotic nitrogen (N)‐fixing trees can provide large quantities of new N to ecosystems, but only if they are sufficiently abundant. The overall abundance and latitudinal abundance distributions of N‐fixing trees are well characterised in the Americas, but less well outside the Americas. Here, we characterised the abundance of N‐fixing trees in a network of forest plots spanning five continents, ~5,000 tree species and ~4 million trees. The majority of the plots (86%) were in America or Asia. In addition, we examined whether the observed pattern of abundance of N‐fixing trees was correlated with mean annual temperature and precipitation. Outside the tropics, N‐fixing trees were consistently rare in the forest plots we examined. Within the tropics, N‐fixing trees were abundant in American but not Asian forest plots (~7% versus ~1% of basal area and stems). This disparity was not explained by mean annual temperature or precipitation. Our finding of low N‐fixing tree abundance in the Asian tropics casts some doubt on recent high estimates of N fixation rates in this region, which do not account for disparities in N‐fixing tree abundance between the Asian and American tropics. Synthesis. Inputs of nitrogen to forests depend on symbiotic nitrogen fixation, which is constrained by the abundance of N‐fixing trees. By analysing a large dataset of ~4 million trees, we found that N‐fixing trees were consistently rare in the Asian tropics as well as across higher latitudes in Asia, America and Europe. The rarity of N‐fixing trees in the Asian tropics compared with the American tropics might stem from lower intrinsic N limitation in Asian tropical forests, although direct support for any mechanism is lacking. The paucity of N‐fixing trees throughout Asian forests suggests that N inputs to the Asian tropics might be lower than previously thought.
    Patterns of nitrogen-fixing tree abundance in forests across Asia and America
    Menge, Duncan N.L. ; Chisholm, Ryan A. ; Davies, Stuart J. ; Abu Salim, Kamariah ; Allen, David ; Alvarez, Mauricio ; Bourg, Norm ; Brockelman, Warren Y. ; Bunyavejchewin, Sarayudh ; Butt, Nathalie ; Cao, Min ; Chanthorn, Wirong ; Chao, Wei Chun ; Clay, Keith ; Condit, Richard ; Cordell, Susan ; Silva, João Batista da; Dattaraja, H.S. ; Andrade, Ana Cristina Segalin de; Oliveira, Alexandre A. de; Ouden, Jan den; Drescher, Michael ; Fletcher, Christine ; Giardina, Christian P. ; Savitri Gunatilleke, C.V. ; Gunatilleke, I.A.U.N. ; Hau, Billy C.H. ; He, Fangliang ; Howe, Robert ; Hsieh, Chang Fu ; Hubbell, Stephen P. ; Inman-Narahari, Faith M. ; Jansen, Patrick A. ; Johnson, Daniel J. ; Kong, Lee Sing ; Král, Kamil ; Ku, Chen Chia ; Lai, Jiangshan ; Larson, Andrew J. ; Li, Xiankun ; Li, Yide ; Lin, Luxiang ; Lin, Yi Ching ; Liu, Shirong ; Lum, Shawn K.Y. ; Lutz, James A. ; Ma, Keping ; Malhi, Yadvinder ; McMahon, Sean ; McShea, William ; Mi, Xiangcheng ; Morecroft, Michael ; Myers, Jonathan A. ; Nathalang, Anuttara ; Novotny, Vojtech ; Ong, Perry ; Orwig, David A. ; Ostertag, Rebecca ; Parker, Geoffrey ; Phillips, Richard P. ; Abd. Rahman, Kassim ; Sack, Lawren ; Sang, Weiguo ; Shen, Guochun ; Shringi, Ankur ; Shue, Jessica ; Su, Sheng Hsin ; Sukumar, Raman ; Fang Sun, I. ; Suresh, H.S. ; Tan, Sylvester ; Thomas, Sean C. ; Toko, Pagi S. ; Valencia, Renato ; Vallejo, Martha I. ; Vicentini, Alberto ; Vrška, Tomáš ; Wang, Bin ; Wang, Xihua ; Weiblen, George D. ; Wolf, Amy ; Xu, Han ; Yap, Sandra ; Zhu, Li ; Fung, Tak - \ 2019
    Journal of Ecology 107 (2019)6. - ISSN 0022-0477 - p. 2598 - 2610.
    forest - legume - nitrogen fixation - nutrient limitation - Smithsonian ForestGEO - symbiosis

    Symbiotic nitrogen (N)-fixing trees can provide large quantities of new N to ecosystems, but only if they are sufficiently abundant. The overall abundance and latitudinal abundance distributions of N-fixing trees are well characterised in the Americas, but less well outside the Americas. Here, we characterised the abundance of N-fixing trees in a network of forest plots spanning five continents, ~5,000 tree species and ~4 million trees. The majority of the plots (86%) were in America or Asia. In addition, we examined whether the observed pattern of abundance of N-fixing trees was correlated with mean annual temperature and precipitation. Outside the tropics, N-fixing trees were consistently rare in the forest plots we examined. Within the tropics, N-fixing trees were abundant in American but not Asian forest plots (~7% versus ~1% of basal area and stems). This disparity was not explained by mean annual temperature or precipitation. Our finding of low N-fixing tree abundance in the Asian tropics casts some doubt on recent high estimates of N fixation rates in this region, which do not account for disparities in N-fixing tree abundance between the Asian and American tropics. Synthesis. Inputs of nitrogen to forests depend on symbiotic nitrogen fixation, which is constrained by the abundance of N-fixing trees. By analysing a large dataset of ~4 million trees, we found that N-fixing trees were consistently rare in the Asian tropics as well as across higher latitudes in Asia, America and Europe. The rarity of N-fixing trees in the Asian tropics compared with the American tropics might stem from lower intrinsic N limitation in Asian tropical forests, although direct support for any mechanism is lacking. The paucity of N-fixing trees throughout Asian forests suggests that N inputs to the Asian tropics might be lower than previously thought.

    Loss of animal seed dispersal increases extinction risk in a tropical tree species due to pervasive negative density dependence across life stages
    Caughlin, T.T. ; Ferguson, J.M. ; Lichstein, J.W. ; Zuidema, P.A. ; Bunyavejchewin, S. ; Levey, D.J. - \ 2015
    Proceedings of the Royal Society. B: Biological Sciences 282 (2015)1798. - ISSN 0962-8452 - 9 p.
    spatial-patterns - rain-forest - recruitment - consequences - neighborhood - defaunation - habitat - uncertainty - diversity - abundance
    Overhunting in tropical forests reduces populations of vertebrate seed dispersers. If reduced seed dispersal has a negative impact on tree population viability, overhunting could lead to altered forest structure and dynamics, including decreased biodiversity. However, empirical data showing decreased animal-dispersed tree abundance in overhunted forests contradict demographic models which predict minimal sensitivity of tree population growth rate to early life stages. One resolution to this discrepancy is that seed dispersal determines spatial aggregation, which could have demographic consequences for all life stages. We tested the impact of dispersal loss on population viability of a tropical tree species, Miliusa horsfieldii, currently dispersed by an intact community of large mammals in a Thai forest. We evaluated the effect of spatial aggregation for all tree life stages, from seeds to adult trees, and constructed simulation models to compare population viability with and without animal-mediated seed dispersal. In simulated populations, disperser loss increased spatial aggregation by fourfold, leading to increased negative density dependence across the life cycle and a 10-fold increase in the probability of extinction. Given that the majority of tree species in tropical forests are animal-dispersed, overhunting will potentially result in forests that are fundamentally different from those existing now.
    No evidence for consistent long-term growth stimulation of 13 tropical tree species: results from tree-ring analysis
    Groenendijk, P. ; Sleen, J.P. van der; Vlam, M. ; Bunyavejchewin, S. ; Bongers, F. ; Zuidema, P. - \ 2015
    Global Change Biology 21 (2015)10. - ISSN 1354-1013 - p. 3762 - 3776.
    The important role of tropical forests in the global carbon cycle makes it imperative to assess changes in their carbon dynamics for accurate projections of future climate–vegetation feedbacks. Forest monitoring studies conducted over the past decades have found evidence for both increasing and decreasing growth rates of tropical forest trees. The limited duration of these studies restrained analyses to decadal scales, and it is still unclear whether growth changes occurred over longer time scales, as would be expected if CO2-fertilization stimulated tree growth. Furthermore, studies have so far dealt with changes in biomass gain at forest-stand level, but insights into species-specific growth changes – that ultimately determine community-level responses – are lacking. Here, we analyse species-specific growth changes on a centennial scale, using growth data from tree-ring analysis for 13 tree species (~1300 trees), from three sites distributed across the tropics. We used an established (regional curve standardization) and a new (size-class isolation) growth-trend detection method and explicitly assessed the influence of biases on the trend detection. In addition, we assessed whether aggregated trends were present within and across study sites. We found evidence for decreasing growth rates over time for 8–10 species, whereas increases were noted for two species and one showed no trend. Additionally, we found evidence for weak aggregated growth decreases at the site in Thailand and when analysing all sites simultaneously. The observed growth reductions suggest deteriorating growth conditions, perhaps due to warming. However, other causes cannot be excluded, such as recovery from large-scale disturbances or changing forest dynamics. Our findings contrast growth patterns that would be expected if elevated CO2 would stimulate tree growth. These results suggest that commonly assumed growth increases of tropical forests may not occur, which could lead to erroneous predictions of carbon dynamics of tropical forest under climate change.
    15N in tree rings as a bio-indicator of changing nitrogen cycling in tropical forests: an evaluation at three sites using two sampling methods
    Sleen, J.P. van der; Vlam, M. ; Groenendijk, P. ; Anten, N.P.R. ; Bongers, F. ; Bunyavejchewin, S. ; Hietz, P. ; Pons, T.L. ; Zuidema, P. - \ 2015
    Frontiers in Plant Science 6 (2015). - ISSN 1664-462X
    rain-forest - natural-abundance - soil-nitrogen - isotope fractionation - wood deterioration - growth-rates - n deposition - dynamics - ecosystem - lowland
    Anthropogenic nitrogen deposition is currently causing a more than twofold increase of reactive nitrogen input over large areas in the tropics. Elevated N-15 abundance (delta N-15) in the growth rings of some tropical trees has been hypothesized to reflect an increased leaching of N-15-depleted nitrate from the soil, following anthropogenic nitrogen deposition over the last decades. To find further evidence for altered nitrogen cycling in tropical forests, we measured long-term delta N-15 values in trees from Bolivia, Cameroon, and Thailand. We used two different sampling methods. In the first, wood samples were taken in a conventional way: from the pith to the bark across the stem of 28 large trees (the "radial" method). In the second, delta N-15 values were compared across a fixed diameter (the "fixed-diameter" method). We sampled 400 trees that differed widely in size, but measured delta N-15 in the stem around the same diameter (20 cm dbh) in all trees. As a result, the growth rings formed around this diameter differed in age and allowed a comparison of delta N-15 values over time with an explicit control for potential size-effects on delta N-15 values. We found a significant increase of tree-ring delta N-15 across the stem radius of large trees from Bolivia and Cameroon, but no change in tree-ring delta N-15 values over time was found in any of the study sites when controlling for tree size. This suggests that radial trends of delta N-15 values within trees reflect tree ontogeny (size development). However, for the trees from Cameroon and Thailand, a low statistical power in the fixed-diameter method prevents to conclude this with high certainty. For the trees from Bolivia, statistical power in the fixed-diameter method was high, showing that the temporal trend in tree-ring delta N-15 values in the radial method is primarily caused by tree ontogeny and unlikely by a change in nitrogen cycling. We therefore stress to account for tree size before tree-ring delta N-15 values can be properly interpreted.
    Data from: Loss of animal seed dispersal increases extinction risk in a tropical tree species due to pervasive negative density dependence across life stages
    Caughlin, T.T. ; Ferguson, J.M. ; Lichstein, J.W. ; Zuidema, Pieter ; Bunyavejchewin, S. ; Levey, D.J. - \ 2014
    University of Florida
    tropical forests - Anthropocene - fruit production - neighborhood model - seed addition experment - Saccopetalum - extinction - germination - tree demography - seedling demography - tree population - seedlings - neighborhood - tropical forest dynamics - negative density dependence - Miliusa - Annonaceae - seed dispersal - spatial model - Frugivory - Miliusa horsfieldii - overhunting
    Overhunting in tropical forests reduces populations of vertebrate seed dispersers. If reduced seed dispersal has a negative impact on tree population viability, overhunting could lead to altered forest structure and dynamics, including decreased biodiversity. However, empirical data showing decreased animal-dispersed tree abundance in overhunted forests contradict demographic models which predict minimal sensitivity of tree population growth rate to early life stages. One resolution to this discrepancy is that seed dispersal determines spatial aggregation, which could have demographic consequences for all life stages. We tested the impact of dispersal loss on population viability of a tropical tree species, Miliusa horsfieldii, currently dispersed by an intact community of large mammals in a Thai forest. We evaluated the effect of spatial aggregation for all tree life stages, from seeds to adult trees, and constructed simulation models to compare population viability with and without animal-mediated seed dispersal. In simulated populations, disperser loss increased spatial aggregation by fourfold, leading to increased negative density dependence across the life cycle and a 10-fold increase in the probability of extinction. Given that the majority of tree species in tropical forests are animal-dispersed, overhunting will potentially result in forests that are fundamentally different from those existing now.
    Temperature and rainfall strongly drive temporal growth variation in Asian tropical forest trees
    Vlam, M. ; Baker, P.J. ; Bunyavejchewin, S. ; Zuidema, P.A. - \ 2014
    Oecologia 174 (2014)4. - ISSN 0029-8549 - p. 1449 - 1461.
    Climate change effects on growth rates of tropical trees may lead to alterations in carbon cycling of carbon-rich tropical forests. However, climate sensitivity of broad-leaved lowland tropical trees is poorly understood. Dendrochronology (tree-ring analysis) provides a powerful tool to study the relationship between tropical tree growth and annual climate variability. We aimed to establish climate–growth relationships for five annual-ring forming tree species, using ring-width data from 459 canopy and understory trees from a seasonal tropical forest in western Thailand. Based on 183/459 trees, chronologies with total lengths between 29 and 62 years were produced for four out of five species. Bootstrapped correlation analysis revealed that climate–growth responses were similar among these four species. Growth was significantly negatively correlated with current-year maximum and minimum temperatures, and positively correlated with dry-season precipitation levels. Negative correlations between growth and temperature may be attributed to a positive relationship between temperature and autotrophic respiration rates. The positive relationship between growth and dry-season precipitation levels likely reflects the strong water demand during leaf flush. Mixed-effect models yielded results that were consistent across species: a negative effect of current wet-season maximum temperatures on growth, but also additive positive effects of, for example, prior dry-season maximum temperatures. Our analyses showed that annual growth variability in tropical trees is determined by a combination of both temperature and precipitation variability. With rising temperature, the predominantly negative relationship between temperature and growth may imply decreasing growth rates of tropical trees as a result of global warming.
    Understanding recruitment failure in tropical tree species: Insights from a tree ring study
    Vlam, M. ; Baker, P.J. ; Bunyavejchewin, S. ; Mohren, G.M.J. ; Zuidema, P.A. - \ 2014
    Forest Ecology and Management 312 (2014). - ISSN 0378-1127 - p. 108 - 116.
    mahogany swietenia-macrophylla - big-leaf mahogany - historical stand dynamics - western thailand - rain-forests - disturbance history - size distributions - amazon forest - canopy tree - large-scale
    Many tropical tree species have population structures that exhibit strong recruitment failure. While the presence of adult trees indicates that appropriate regeneration conditions occurred in the past, it is often unclear why small individuals are absent. Knowing how, when and where these tree species regenerate provides insights into their life history characteristics. Based on tree age distributions inferences can be made on past forest dynamics and information is obtained that is important for forest management. We used tree-ring analyses to obtain tree ages and reconstruct >200 years of estimated establishment rates in a sparsely regenerating population of Afzelia xylocarpa (Fabaceae), a light-demanding and long-lived canopy tree species. We sampled all 85 Afzelia trees >5 cm diameter at breast height (dbh) in a 297-ha plot in a seasonal tropical forest in the Huai Kha Khaeng (HKK) Wildlife Sanctuary, western Thailand. The age distribution of the sampled Afzelia trees revealed two distinct recruitment peaks centred around 1850 and 1950. The presence of distinct age cohorts provides a strong indication of disturbance-mediated recruitment. Additionally we found three lines of evidence supporting this interpretation. (1) Similarly aged trees were spatially aggregated up to ~500 m, a scale larger than single tree-fall gaps. (2) High juvenile growth rates (5–10 mm dbh year-1) of extant small and large trees indicate that recruitment took place under open conditions. (3) A significant positive correlation between tree age and local canopy height indicates that trees recruited in low-canopy forest patches. Likely causes of these severe canopy disturbances include windstorms and ground fires, which are common in the region. In addition, successful establishment seems to be favoured by wetter climate conditions, as the estimated establishment rate was correlated to the Palmer Drought Severity Index (PDSI). Thus, the co-occurrence of canopy disturbance and favourable climatic conditions may provide a window of opportunity for Afzelia establishment. Our results indicate that forest patches with occurrence of large Afzelia trees have undergone high-severity canopy disturbance prior to establishment, suggesting that these disturbances have shaped forests at HKK. Tree-ring analyses provide a powerful tool to understanding tropical tree establishment patterns. Rare, high-severity canopy disturbances may play a key role in the regeneration of long-lived tropical canopy tree species with recruitment failure, potentially in interaction with climate variability to determine variation in establishment success over decades or centuries.
    Disturbance History of a Seasonal Tropical Forest in Western Thailand: A Spatial Dendroecological Analysis
    Middendorp, R.S. ; Vlam, M. ; Rebei, K.T. ; Baker, P.J. ; Bunyavejchewin, S. ; Zuidema, P.A. - \ 2013
    Biotropica 45 (2013)5. - ISSN 0006-3606 - p. 578 - 586.
    central amazon forest - tree-ring analysis - stand dynamics - age structure - rain-forests - new-zealand - large-scale - growth - patterns - ecology
    Disturbances play an important role in forest dynamics across the globe. Researchers have mainly focused on the temporal context of disturbances, but have largely ignored the spatial patterns of tree recruitment they create. Geostatistical tools enable the analysis of spatial patterns and variability in tropical forest disturbance histories. Here, we examine the potential of combining dendroecological analysis and spatial statistics to reconstruct the disturbance history of a seasonal dry evergreen tropical forest plot at the Huai Kha Khaeng Wildlife Sanctuary (HKK), western Thailand. We used tree-ring-derived age estimates for 70 individuals of the shade-intolerant pioneer species Melia azederach (Meliaceae) and tree locations across a 316-ha study plot to identify the timing and spatial extent of past disturbances. Although the age distribution for Melia suggested that regeneration had been continuous over the past 60 yr, spatial analyses (mark correlation function and kriging) demonstrated the presence of three spatially discrete age cohorts. Two of these cohorts suggested a severe disturbance ~20 yr before present. A third cohort appears to have established ~50 years ago. Using historical records, we conclude that fire disturbance is the most likely disturbance factor affecting HKK. Nevertheless, we do not rule out other disturbance factors. The combined application of tree-ring analysis and spatial statistics as applied in this study could be readily applied to reconstruct disturbance histories in other tropical regions where tree species with annual growth rings are present.
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