Water Availability Is the Main Climate Driver of Neotropical Tree Growth (original) (raw)
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Intra-annual tree growth responds to micrometeorological variability in the central Amazon
iForest - Biogeosciences and Forestry, 2021
Intra-annual distribution of precipitation in central Amazonia leads to a short mild dry season, which is associated with an increase in irradiance and temperature and a decline in relative humidity; however, the independent effect of each individual climatic variable on tree growth is still under investigation. The objective of this study was to determine how tree growth (inferred from radial stem increment) responds to monthly variations of micrometeorological variables in the central Amazon. During five years (2013-2017) we measured tree growth in 51 trees from nine species and, above the forest canopy, collected environmental data, such as photosynthetically active radiation (PAR), air temperature (T), precipitation, air relative humidity (RH), air vapor pressure deficit (VPD), reference evapotranspiration (ETo), and soil water content (SWC). We used principal component regression to evaluate the effect of micrometeorological variability on tree growth. Mean tree growth across species was responsive to variations in almost all the micrometeorological variables examined, with the exception of mean and minimum temperature, maximum RH, and minimum VPD. Mean tree growth across species increased with increasing precipitation, RHmean, RHmin and SWC, while it decreased with increasing PAR, Tmax, and ETo. It was also shown that an increase in VPDmean and VPDmax has a negative effect on tree growth. These results contribute to improve our understanding of effect of climate variability on tree growth, and shed light on the potential effect of severe droughts in the central Amazon.
Understanding tree growth in response to rainfall distribution is critical to predicting forest and species population responses to climate change. We investigated inter-annual and seasonal variation in stem diameter by three emergent tree species in a seasonally dry tropical forest in southeast Pará, Brazil. Annual diameter growth rates by Swietenia macrophylla demonstrated strong positive correlation with annual rainfall totals during 1997-2009; Hymenaea courbaril growth rates demonstrated weak positive correlation, whereas Parkia pendula exhibited weak negative correlation. For both Swietenia and Hymenaea, annual diameter growth rates correlated positively and significantly with rainfall totals during the first 6 mo of the growing year (July to December). Vernier dendrometer bands monitored at 4-wk intervals during 3-5 yr confirmed strong seasonal effects on stem diameter expansion. Individuals of all three species expanded in unison during wet season months and were static or even contracted during dry season months. Stems of the deciduous Swietenia contracted as crowns were shed during the early dry season, expanded slightly as new crowns were flushed, and then contracted further during 3-5 wk flowering periods in the late dry season by newly mature crowns. The three species' physiographic distribution patterns at the study site may partially underlie observed differences in annual and seasonal growth. With most global circulation models predicting conditions becoming gradually drier in southeast Amazonia over the coming decades, species such as Swietenia that perform best on the 'wet end' of current conditions may experience reduced growth rates. However, population viability will not necessarily be threatened if life history and ecophysiological responses to changing conditions are compensatory.
Agricultural and Forest Meteorology, 2014
We analyzed the effects of climate and drought on radial growth using dendrochronology in seven deciduous tree species coexisting in a Bolivian tropical dry forest subjected to seasonal drought. Precipitation, temperature and a multiscalar drought index were related to tree-ring width data at different time-scales (from one month to 42 years). Precipitation affected positively tree growth in all species, mainly during the wet season, while temperature affected it negatively in five species. Tree growth responses to precipitation and temperature were species-specific and peaked at short-time scales, specifically from one to nine months. At inter-annual scales tree growth always responded positively to less dry conditions at short-time scales, particularly from two to seven months, and also at long-time scales from six to 30 years. Tree growth was mainly sensitive to multi-annual droughts and such sensitivity differed among species. Our findings suggest that tree species of the studied tropical dry forest are predominantly sensitive in terms of growth reduction to long-lasting droughts. This time-dependency of growth responses to drought should be explicitly considered as an additional constraint of the community dynamics in evaluations of the future responses of tropical dry forests to climate warming.
2014
We analyzed the effects of climate and drought on radial growth using dendrochronology in seven deciduous tree species coexisting in a Bolivian tropical dry forest subjected to seasonal drought. Precipitation, temperature and a multiscalar drought index were related to tree-ring width data at different timescales (from one month to 42 years). Precipitation affected positively tree growth in all species, mainly during the wet season, while temperature affected it negatively in five species. Tree growth responses to precipitation and temperature were species-specific and peaked at short-time scales, specifically from one to nine months. At inter-annual scales tree growth always responded positively to less dry conditions at shorttime scales, particularly from two to seven months, and also at long-time scales from six to 30 years. Tree growth was mainly sensitive to multi-annual droughts and such sensitivity differed among species. Our findings suggest that tree species of the studied tropical dry forest are predominantly sensitive in terms of growth reduction to long-lasting droughts. This time-dependency of growth responses to drought should be explicitly considered as an additional constraint of the community dynamics in evaluations of the future responses of tropical dry forests to climate warming.
Identifying climatic drivers of tropical forest dynamics
Biogeosciences Discussions, 2015
In the context of climate changes, identifying and then predicting the impacts of climatic drivers on tropical forest dynamics is becoming a matter of urgency. We used a coupled model of tropical tree growth and mortality, calibrated with forest dynamic data from the 20 year study site of Paracou, French Guiana, in order to introduce and test a set 5 of climatic variables. Three major climatic drivers were identified through the variable selection procedure: drought, water saturation and temperature. Drought decreased annual growth and mortality rates, high precipitation increased mortality rates and high temperature decreased growth. Interactions between key functional traits, stature and climatic variables were investigated, showing best resistance to drought for trees with 10 high wood density and for trees with small current diameters. Our results highlighted strong long-term impacts of climate variables on tropical forest dynamics, suggesting potential deep impacts of climate changes during the next century. 20 demonstrable success in the past Grogan and Schulze, 2012; Brando et al., 2010). Tree growth is mainly related to water availability, resulting in growth during the wet months and static or even contracted states during the dry season months (Grogan and Schulze, 2012). The use of a convenient water availability estimator like the relative extractable water (REW) shows that 25 low levels of REW rather than lack of rainfall per se are the key drivers of the decrease 2
Biotropica, 2011
Understanding tree growth in response to rainfall distribution is critical to predicting forest and species population responses to climate change. We investigated inter-annual and seasonal variation in stem diameter by three emergent tree species in a seasonally dry tropical forest in southeast Pará, Brazil. Annual diameter growth rates by Swietenia macrophylla demonstrated strong positive correlation with annual rainfall totals during 1997-2009; Hymenaea courbaril growth rates demonstrated weak positive correlation, whereas Parkia pendula exhibited weak negative correlation. For both Swietenia and Hymenaea, annual diameter growth rates correlated positively and significantly with rainfall totals during the first 6 mo of the growing year (July to December). Vernier dendrometer bands monitored at 4-wk intervals during 3-5 yr confirmed strong seasonal effects on stem diameter expansion. Individuals of all three species expanded in unison during wet season months and were static or even contracted during dry season months. Stems of the deciduous Swietenia contracted as crowns were shed during the early dry season, expanded slightly as new crowns were flushed, and then contracted further during 3-5 wk flowering periods in the late dry season by newly mature crowns. The three species' physiographic distribution patterns at the study site may partially underlie observed differences in annual and seasonal growth. With most global circulation models predicting conditions becoming gradually drier in southeast Amazonia over the coming decades, species such as Swietenia that perform best on the 'wet end' of current conditions may experience reduced growth rates. However, population viability will not necessarily be threatened if life history and ecophysiological responses to changing conditions are compensatory.
Oecologia, 2014
controls on tree growth rates. The strength of the growth seasonality response among trees is significantly correlated to functional traits: consistent with a hypothesised tradeoff between maximum potential growth rate and hydraulic safety, tall and fast-growing trees with broad stems had the most strongly seasonal biomass accumulation, suggesting that they are more productive in the wet season, but more vulnerable to water limitation in the dry season.
Global Change Biology, 2015
Tropical forest responses to climatic variability have important consequences for global carbon cycling, but are poorly understood. As empirical, correlative studies cannot disentangle the interactive effects of climatic variables on tree growth, we used a tree growth model (IBTREE) to unravel the climate effects on different physiological pathways and in turn on stem growth variation. We parameterized the model for canopy trees of Toona ciliata (Meliaceae) from a Thai monsoon forest and compared predicted and measured variation from a tree-ring study over a 30-year period. We used historical climatic variation of minimum and maximum day temperature, precipitation and carbon dioxide (CO2 ) in different combinations to estimate the contribution of each climate factor in explaining the inter-annual variation in stem growth. Running the model with only variation in maximum temperature and rainfall yielded stem growth patterns that explained almost 70% of the observed inter-annual variation in stem growth. Our results show that maximum temperature had a strong negative effect on the stem growth by increasing respiration, reducing stomatal conductance and thus mitigating a higher transpiration demand, and - to a lesser extent - by directly reducing photosynthesis. Although stem growth was rather weakly sensitive to rain, stem growth variation responded strongly and positively to rainfall variation owing to the strong inter-annual fluctuations in rainfall. Minimum temperature and atmospheric CO2 concentration did not significantly contribute to explaining the inter-annual variation in stem growth. Our innovative approach - combining a simulation model with historical data on tree-ring growth and climate - allowed disentangling the effects of strongly correlated climate variables on growth through different physiological pathways. Similar studies on different species and in different forest types are needed to further improve our understanding of the sensitivity of tropical tree growth to climatic variability and change.
Pan-Tropical Analysis of Climate Effects on Seasonal Tree Growth
PLoS ONE, 2014
Climate models predict a range of changes in tropical forest regions, including increased average temperatures, decreased total precipitation, reduced soil moisture and alterations in seasonal climate variations. These changes are directly related to the increase in anthropogenic greenhouse gas concentrations, primarily CO 2 . Assessing seasonal forest growth responses to climate is of utmost importance because woody tissues, produced by photosynthesis from atmospheric CO 2 , water and light, constitute the main component of carbon sequestration in the forest ecosystem. In this paper, we combine intraannual tree growth measurements from published tree growth data and the corresponding monthly climate data for 25 pan-tropical forest sites. This meta-analysis is designed to find the shared climate drivers of tree growth and their relative importance across pan-tropical forests in order to improve carbon uptake models in a global change context. Tree growth reveals significant intra-annual seasonality at seasonally dry sites or in wet tropical forests. Of the overall variation in tree growth, 28.7% was explained by the site effect, i.e. the tree growth average per site. The best predictive model included four climate variables: precipitation, solar radiation (estimated with extrasolar radiation reaching the atmosphere), temperature amplitude and relative soil water content. This model explained more than 50% of the tree growth variations across tropical forests. Precipitation and solar radiation are the main seasonal drivers of tree growth, causing 19.8% and 16.3% of the tree growth variations. Both have a significant positive association with tree growth. These findings suggest that forest productivity due to tropical tree growth will be reduced in the future if climate extremes, such as droughts, become more frequent.
Global Change Biology, 2010
Tropical forests will experience relatively large changes in temperature and rainfall towards the end of this century. Little is known about how tropical trees will respond to these changes. We used tree rings to establish climate-growth relations of a pioneer tree, Mimosa acantholoba, occurring in tropical dry secondary forests in southern Mexico. The role of large-scale climatic drivers in determining interannual growth variation was studied by correlating growth to sea surface temperature anomalies (SSTA) of the Atlantic and Pacific Oceans, including the El Niño-Southern Oscillation (ENSO). Annual growth varied eightfold over 1970–2007, and was correlated with wet season rainfall (r=0.75). Temperature, cloud cover and solar variation did not affect growth, although these climate variables correlated with growth due to their relations with rainfall. Strong positive correlations between growth and SSTA occurred in the North tropical Atlantic during the first half of the year, and in the Pacific during the second half of the year. The Pacific influence corresponded closely to ENSO-like influences with negative effects of high SSTA in the eastern Pacific Niño3.4 region on growth due to decreases in rainfall. During El Niño years growth was reduced by 37%. We estimated how growth would be affected by the predicted trend of decreasing rainfall in Central America towards the end of this century. Using rainfall predictions of two sets of climate models, we estimated that growth at the end of this century will be reduced by 12% under a medium (A1B) and 21% under a high (A2) emission scenario. These results suggest that climate change may have repercussions for the carbon sequestration capacity of tropical dry forests in the region.