Competition influences tree growth, but not mortality, across environmental gradients in Amazonia and tropical Africa
Rozendaal, Danaë M.A. ; Phillips, Oliver L. ; Lewis, Simon L. ; Affum-Baffoe, Kofi ; Alvarez-Davila, Esteban ; Andrade, Ana ; Aragão, Luiz E.O.C. ; Araujo-Murakami, Alejandro ; Baker, Timothy R. ; Bánki, Olaf ; Brienen, Roel J.W. ; Camargo, José Luis C. ; Comiskey, James A. ; Djuikouo Kamdem, Marie Noël ; Fauset, Sophie ; Feldpausch, Ted R. ; Killeen, Timothy J. ; Laurance, William F. ; Laurance, Susan G.W. ; Lovejoy, Thomas ; Malhi, Yadvinder ; Marimon, Beatriz S. ; Marimon Junior, Ben Hur ; Marshall, Andrew R. ; Neill, David A. ; Núñez Vargas, Percy ; Pitman, Nigel C.A. ; Poorter, Lourens ; Reitsma, Jan ; Silveira, Marcos ; Sonké, Bonaventure ; Sunderland, Terry ; Taedoumg, Hermann ; Steege, Hans ter; Terborgh, John W. ; Umetsu, Ricardo K. ; Heijden, Geertje M.F. van der; Vilanova, Emilio ; Vos, Vincent ; White, Lee J.T. ; Willcock, Simon ; Zemagho, Lise ; Vanderwel, Mark C. - \ 2020
Ecology 101 (2020)7. - ISSN 0012-9658
climatic water deficit - competition - forest dynamics - mortality - neighborhood effects - soil fertility - trait-based models - tree growth - tropical forest - wood density
Competition among trees is an important driver of community structure and dynamics in tropical forests. Neighboring trees may impact an individual tree’s growth rate and probability of mortality, but large-scale geographic and environmental variation in these competitive effects has yet to be evaluated across the tropical forest biome. We quantified effects of competition on tree-level basal area growth and mortality for trees ≥10-cm diameter across 151 ~1-ha plots in mature tropical forests in Amazonia and tropical Africa by developing nonlinear models that accounted for wood density, tree size, and neighborhood crowding. Using these models, we assessed how water availability (i.e., climatic water deficit) and soil fertility influenced the predicted plot-level strength of competition (i.e., the extent to which growth is reduced, or mortality is increased, by competition across all individual trees). On both continents, tree basal area growth decreased with wood density and increased with tree size. Growth decreased with neighborhood crowding, which suggests that competition is important. Tree mortality decreased with wood density and generally increased with tree size, but was apparently unaffected by neighborhood crowding. Across plots, variation in the plot-level strength of competition was most strongly related to plot basal area (i.e., the sum of the basal area of all trees in a plot), with greater reductions in growth occurring in forests with high basal area, but in Amazonia, the strength of competition also varied with plot-level wood density. In Amazonia, the strength of competition increased with water availability because of the greater basal area of wetter forests, but was only weakly related to soil fertility. In Africa, competition was weakly related to soil fertility and invariant across the shorter water availability gradient. Overall, our results suggest that competition influences the structure and dynamics of tropical forests primarily through effects on individual tree growth rather than mortality and that the strength of competition largely depends on environment-mediated variation in basal area.
Tropical forest warming: looking backwards for more insights - Letter
Zuidema, P.A. ; Brienen, R.J. ; Schöngart, J. - \ 2012
Trends in Ecology and Evolution 27 (2012)4. - ISSN 0169-5347 - p. 193 - 194.
rain-forests - tree growth
What are the main climate drivers for shrub growth in Northeastern Siberian tundra?
Blok, D. ; Sass-Klaassen, U. ; Schaepman-Strub, G. ; Heijmans, M.M.P.D. ; Sauren, P. ; Berendse, F. - \ 2011
Biogeosciences 8 (2011)5. - ISSN 1726-4170 - p. 1169 - 1179.
plant functional types - alaskan arctic tundra - summer temperature - nitrogen mineralization - tree growth - manipulation experiment - environmental-change - cassiope-tetragona - vegetation types - northern alaska
Deciduous shrubs are expected to rapidly expand in the Arctic during the coming decades due to climate warming. A transition towards more shrub-dominated tundra may have large implications for the regional surface energy balance, permafrost stability and carbon storage capacity, with consequences for the global climate system. However, little information is available on the natural long-term shrub growth response to climatic variability. Our aim was to determine the climate factor and time period that are most important to annual shrub growth in our research site in NE-Siberia. Therefore, we determined annual radial growth rates in Salix pulchra and Betula nana shrubs by measuring ring widths. We constructed shrub ring width chronologies and compared growth rates to regional climate and remotely sensed greenness data. Early summer temperature was the most important factor influencing ring width of S. pulchra (Pearson's r=0.73, p
Models for supporting forest management in a changing environment
Fontes, L. ; Bontemps, J.D. ; Bugmann, H. ; Oijen, M. van; Gracia, C. ; Kramer, K. ; Lindner, M. ; Rötzer, T. ; Skovsgaard, J.P. - \ 2010
Forest Systems 19 (2010). - ISSN 2171-5068 - p. 8 - 29.
fagus-sylvatica l. - of-the-art - general quantitative theory - central-european forests - state-space approach - growth-model - tree growth - ecosystem management - climate-change - site index
Forests are experiencing an environment that changes much faster than during the past several hundred years. In addition, the abiotic factors determining forest dynamics vary depending on its location. Forest modeling thus faces the new challenge of supporting forest management in the context of environmental change. This review focuses on three types of models that are used in forest management: empirical (EM), process-based (PBM) and hybrid models. Recent approaches may lead to the applicability of empirical models under changing environmental conditions, such as (i) the dynamic state-space approach, or (ii) the development of productivity-environment relationships. Twenty-five process-based models in use in Europe were analyzed in terms of their structure, inputs and outputs having in mind a forest management perspective. Two paths for hybrid modeling were distinguished: (i) coupling of EMs and PBMs by developing signal-transfer environment-productivity functions; (ii) hybrid models with causal structure including both empirical and mechanistic components. Several gaps of knowledge were identified for the three types of models reviewed. The strengths and weaknesses of the three model types differ and all are likely to remain in use. There is a trade-off between how little data the models need for calibration and simulation purposes, and the variety of input-output relationships that they can quantify. PBMs are the most versatile, with a wide range of environmental conditions and output variables they can account for. However, PBMs require more data making them less applicable whenever data for calibration are scarce. EMs, on the other hand, are easier to run as they require much less prior information, but the aggregated representation of environmental effects makes them less reliable in the context of environmental changes. The different disadvantages of PBMs and EMs suggest that hybrid models may be a good compromise, but a more extensive testing of these models in practice is required.
Analyses of the impact of changes in atmospheric deposition and climate on forest growth in European monitoring plots: A stand growth approach
Solberg, S. ; Dobbertin, M. ; Reinds, G.J. ; Andreassen, K. ; Lange, H. ; Garcia Fernandez, P. ; Hildingsson, A. ; Vries, W. de - \ 2009
Forest Ecology and Management 258 (2009)8. - ISSN 0378-1127 - p. 1735 - 1750.
nitrogen deposition - acid deposition - picea-abies - tree growth - carbon sequestration - soil acidification - density index - norway - spruce - responses
During the last 15 years a number of studies have shown increasing forest growth in central Europe, rather than a decline as was expected due to negative effects of air pollution. We have here used data from intensive monitoring plots spread over Europe for a five year period in order to examine the influence of environmental factors on forest growth. Evaluations focussed on the influence of nitrogen, sulphur and acid deposition, temperatures, precipitation and on a drought index calculated as deviation from the long-term mean. The study included the main tree species Norway spruce, Scots pine, common beech as well as European and sessile oak and was based on data from 363 plots. As many other factors besides nitrogen and temperature influence tree growth, expected stem volume increments were modelled using site productivity, stand age and a stand density index. Relative volume increment was then calculated as actual increment in % of expected increment. The site productivity, assumed to be given by site conditions and past environmental conditions, was either taken from expert estimates or computed from site index curves from northern, central and southern Europe. The model explained between 18% and 39% of the variance with site productivity being positively related and age negatively related to actual increment. The various models and statistical approaches were fairly consistent, and indicated a fertilizing effect of nitrogen deposition, with slightly above one percent increase in volume increment per kg of nitrogen deposition per ha and year. This was most clear for spruce and pine, and most pronounced for plots having soil C/N ratios above 25. Also, we found a positive relationship between relative increment and summer temperature, i.e. May–August mean temperature deviation from the 1961–1990 means. The cause–effect relationship here is, however, less certain. Other influences were uncertain. Possibly, sulphur and acid deposition have effects on growth, but these effects are obscured by, and outweighed by the positive effect of nitrogen deposition, because of collinearity between these variables. Drought effects were uncertain also, and one reason for this might be large uncertainties in the precipitation data: precipitation measured on some 50% of the plots correlated poorly with the precipitation data obtained from Europe-wide databases. The major finding of this study was a positive relationship between higher than normal volume increment on one hand and nitrogen deposition on the other hand.