Displaying publications 1 - 20 of 33 in total

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  1. Stephenson NL, Das AJ, Condit R, Russo SE, Baker PJ, Beckman NG, et al.
    Nature, 2014 Mar 6;507(7490):90-3.
    PMID: 24429523 DOI: 10.1038/nature12914
    Forests are major components of the global carbon cycle, providing substantial feedback to atmospheric greenhouse gas concentrations. Our ability to understand and predict changes in the forest carbon cycle--particularly net primary productivity and carbon storage--increasingly relies on models that represent biological processes across several scales of biological organization, from tree leaves to forest stands. Yet, despite advances in our understanding of productivity at the scales of leaves and stands, no consensus exists about the nature of productivity at the scale of the individual tree, in part because we lack a broad empirical assessment of whether rates of absolute tree mass growth (and thus carbon accumulation) decrease, remain constant, or increase as trees increase in size and age. Here we present a global analysis of 403 tropical and temperate tree species, showing that for most species mass growth rate increases continuously with tree size. Thus, large, old trees do not act simply as senescent carbon reservoirs but actively fix large amounts of carbon compared to smaller trees; at the extreme, a single big tree can add the same amount of carbon to the forest within a year as is contained in an entire mid-sized tree. The apparent paradoxes of individual tree growth increasing with tree size despite declining leaf-level and stand-level productivity can be explained, respectively, by increases in a tree's total leaf area that outpace declines in productivity per unit of leaf area and, among other factors, age-related reductions in population density. Our results resolve conflicting assumptions about the nature of tree growth, inform efforts to undertand and model forest carbon dynamics, and have additional implications for theories of resource allocation and plant senescence.
    Matched MeSH terms: Trees/growth & development
  2. Loader NJ, Walsh RP, Robertson I, Bidin K, Ong RC, Reynolds G, et al.
    Philos Trans R Soc Lond B Biol Sci, 2011 Nov 27;366(1582):3330-9.
    PMID: 22006972 DOI: 10.1098/rstb.2011.0037
    Stable carbon isotope (δ(13)C) series were developed from analysis of sequential radial wood increments from AD 1850 to AD 2009 for four mature primary rainforest trees from the Danum and Imbak areas of Sabah, Malaysia. The aseasonal equatorial climate meant that conventional dendrochronology was not possible as the tree species investigated do not exhibit clear annual rings or dateable growth bands. Chronology was established using radiocarbon dating to model age-growth relationships and date the carbon isotopic series from which the intrinsic water-use efficiency (IWUE) was calculated. The two Eusideroxylon zwageri trees from Imbak yielded ages of their pith/central wood (±1 sigma) of 670 ± 40 and 759 ± 40 years old; the less dense Shorea johorensis and Shorea superba trees at Danum yielded ages of 240 ± 40 and 330 ± 40 years, respectively. All trees studied exhibit an increase in the IWUE since AD 1960. This reflects, in part, a response of the forest to increasing atmospheric carbon dioxide concentration. Unlike studies of some northern European trees, no clear plateau in this response was observed. A change in the IWUE implies an associated modification of the local carbon and/or hydrological cycles. To resolve these uncertainties, a shift in emphasis away from high-resolution studies towards long, well-replicated time series is proposed to develop the environmental data essential for model evaluation. Identification of old (greater than 700 years) ringless trees demonstrates their potential in assessing the impacts of climatic and atmospheric change. It also shows the scientific and applied value of a conservation policy that ensures the survival of primary forest containing particularly old trees (as in Imbak Canyon and Danum).
    Matched MeSH terms: Trees/growth & development
  3. Usinowicz J, Chang-Yang CH, Chen YY, Clark JS, Fletcher C, Garwood NC, et al.
    Nature, 2017 10 05;550(7674):105-108.
    PMID: 28953870 DOI: 10.1038/nature24038
    The tropical forests of Borneo and Amazonia may each contain more tree species diversity in half a square kilometre than do all the temperate forests of Europe, North America, and Asia combined. Biologists have long been fascinated by this disparity, using it to investigate potential drivers of biodiversity. Latitudinal variation in many of these drivers is expected to create geographic differences in ecological and evolutionary processes, and evidence increasingly shows that tropical ecosystems have higher rates of diversification, clade origination, and clade dispersal. However, there is currently no evidence to link gradients in ecological processes within communities at a local scale directly to the geographic gradient in biodiversity. Here, we show geographic variation in the storage effect, an ecological mechanism that reduces the potential for competitive exclusion more strongly in the tropics than it does in temperate and boreal zones, decreasing the ratio of interspecific-to-intraspecific competition by 0.25% for each degree of latitude that an ecosystem is located closer to the Equator. Additionally, we find evidence that latitudinal variation in climate underpins these differences; longer growing seasons in the tropics reduce constraints on the seasonal timing of reproduction, permitting lower recruitment synchrony between species and thereby enhancing niche partitioning through the storage effect. Our results demonstrate that the strength of the storage effect, and therefore its impact on diversity within communities, varies latitudinally in association with climate. This finding highlights the importance of biotic interactions in shaping geographic diversity patterns, and emphasizes the need to understand the mechanisms underpinning ecological processes in greater detail than has previously been appreciated.
    Matched MeSH terms: Trees/growth & development
  4. Hector A, Fowler D, Nussbaum R, Weilenmann M, Walsh RP
    Philos Trans R Soc Lond B Biol Sci, 2011 Nov 27;366(1582):3165-7.
    PMID: 22006959 DOI: 10.1098/rstb.2011.0174
    With a focus on the Danum Valley area of Sabah, Malaysian Borneo, this special issue has as its theme the future of tropical rainforests in a changing landscape and climate. The global environmental context to the issue is briefly given before the contents and rationale of the issue are summarized. Most of the papers are based on research carried out as part of the Royal Society South East Asia Rainforest Research Programme. The issue is divided into five sections: (i) the historical land-use and land management context; (ii) implications of land-use change for atmospheric chemistry and climate change; (iii) impacts of logging, forest fragmentation (particularly within an oil palm plantation landscape) and forest restoration on ecosystems and their functioning; (iv) the response and resilience of rainforest systems to climatic and land-use change; and (v) the scientific messages and policy implications arising from the research findings presented in the issue.
    Matched MeSH terms: Trees/growth & development*
  5. Malhi Y, Riutta T, Wearn OR, Deere NJ, Mitchell SL, Bernard H, et al.
    Nature, 2022 Dec;612(7941):707-713.
    PMID: 36517596 DOI: 10.1038/s41586-022-05523-1
    Old-growth tropical forests are widely recognized as being immensely important for their biodiversity and high biomass1. Conversely, logged tropical forests are usually characterized as degraded ecosystems2. However, whether logging results in a degradation in ecosystem functions is less clear: shifts in the strength and resilience of key ecosystem processes in large suites of species have rarely been assessed in an ecologically integrated and quantitative framework. Here we adopt an ecosystem energetics lens to gain new insight into the impacts of tropical forest disturbance on a key integrative aspect of ecological function: food pathways and community structure of birds and mammals. We focus on a gradient spanning old-growth and logged forests and oil palm plantations in Borneo. In logged forest there is a 2.5-fold increase in total resource consumption by both birds and mammals compared to that in old-growth forests, probably driven by greater resource accessibility and vegetation palatability. Most principal energetic pathways maintain high species diversity and redundancy, implying maintained resilience. Conversion of logged forest into oil palm plantation results in the collapse of most energetic pathways. Far from being degraded ecosystems, even heavily logged forests can be vibrant and diverse ecosystems with enhanced levels of ecological function.
    Matched MeSH terms: Trees/growth & development
  6. Dhandapani S, Ritz K, Evers S, Yule CM, Sjögersten S
    Sci Total Environ, 2019 Mar 10;655:220-231.
    PMID: 30471590 DOI: 10.1016/j.scitotenv.2018.11.046
    Tropical peatlands are globally important ecosystems with high C storage and are endangered by anthropogenic disturbances. Microbes in peatlands play an important role in sustaining the functions of peatlands as a C sink, yet their characteristics in these habitats are poorly understood. This research aimed to elucidate the responses of these complex ecosystems to disturbance by exploring greenhouse gas (GHG) emissions, nutrient contents, soil microbial communities and the functional interactions between these components in a primary and secondary peat swamp forest in Peninsular Malaysia. GHG measurements using closed chambers, and peat sampling were carried out in both wet and dry seasons. Microbial community phenotypes and nutrient content were determined using phospholipid fatty acid (PLFA) and inductively-coupled plasma mass spectrometry (ICP-MS) analyses respectively. CO2 emissions in the secondary peat swamp forest were > 50% higher than in the primary forest. CH4 emission rates were ca. 2 mg m-2 h-1 in the primary forest but the secondary forest was a CH4 sink, showing no seasonal variations in GHG emissions. Almost all the nutrient concentrations were significantly lower in the secondary forest, postulated to be due to nutrient leaching via drainage and higher rates of decomposition. Cu and Mo concentrations were negatively correlated with CO2 and CH4 emissions respectively. Microbial community structure was overwhelmingly dominated by bacteria in both forest types, however it was highly sensitive to land-use change and season. Gram-positive and Gram-negative relative abundance were positively correlated with CO2 and CH4 emissions respectively. Drainage related disturbances increased CO2 emissions, by reducing the nutrient content including some with known antimicrobial properties (Cu & Na) and by favouring Gram-positive bacteria over Gram-negative bacteria. These results suggest that the biogeochemistry of secondary peat swamp forest is fundamentally different from that of primary peat swamp forest, and these differences have significant functional impacts on their respective environments.
    Matched MeSH terms: Trees/growth & development
  7. Osuri AM, Ratnam J, Varma V, Alvarez-Loayza P, Hurtado Astaiza J, Bradford M, et al.
    Nat Commun, 2016 04 25;7:11351.
    PMID: 27108957 DOI: 10.1038/ncomms11351
    Defaunation is causing declines of large-seeded animal-dispersed trees in tropical forests worldwide, but whether and how these declines will affect carbon storage across this biome is unclear. Here we show, using a pan-tropical data set, that simulated declines of large-seeded animal-dispersed trees have contrasting effects on aboveground carbon stocks across Earth's tropical forests. In our simulations, African, American and South Asian forests, which have high proportions of animal-dispersed species, consistently show carbon losses (2-12%), but Southeast Asian and Australian forests, where there are more abiotically dispersed species, show little to no carbon losses or marginal gains (±1%). These patterns result primarily from changes in wood volume, and are underlain by consistent relationships in our empirical data (∼2,100 species), wherein, large-seeded animal-dispersed species are larger as adults than small-seeded animal-dispersed species, but are smaller than abiotically dispersed species. Thus, floristic differences and distinct dispersal mode-seed size-adult size combinations can drive contrasting regional responses to defaunation.
    Matched MeSH terms: Trees/growth & development
  8. Wurster CM, Bird MI, Bull ID, Creed F, Bryant C, Dungait JA, et al.
    Proc Natl Acad Sci U S A, 2010 Aug 31;107(35):15508-11.
    PMID: 20660748 DOI: 10.1073/pnas.1005507107
    Today, insular Southeast Asia is important for both its remarkably rich biodiversity and globally significant roles in atmospheric and oceanic circulation. Despite the fundamental importance of environmental history for diversity and conservation, there is little primary evidence concerning the nature of vegetation in north equatorial Southeast Asia during the Last Glacial Period (LGP). As a result, even the general distribution of vegetation during the Last Glacial Maximum is debated. Here we show, using the stable carbon isotope composition of ancient cave guano profiles, that there was a substantial forest contraction during the LGP on both peninsular Malaysia and Palawan, while rainforest was maintained in northern Borneo. These results directly support rainforest "refugia" hypotheses and provide evidence that environmental barriers likely reduced genetic mixing between Borneo and Sumatra flora and fauna. Moreover, it sheds light on possible early human dispersal events.
    Matched MeSH terms: Trees/growth & development*
  9. Katayama A, Kume T, Komatsu H, Ohashi M, Matsumoto K, Ichihashi R, et al.
    Tree Physiol, 2014 May;34(5):503-12.
    PMID: 24876294 DOI: 10.1093/treephys/tpu041
    Difficult access to 40-m-tall emergent trees in tropical rainforests has resulted in a lack of data related to vertical variations in wood CO2 efflux, even though significant variations in wood CO2 efflux are an important source of errors when estimating whole-tree total wood CO2 efflux. This study aimed to clarify vertical variations in wood CO2 efflux for emergent trees and to document the impact of the variations on the whole-tree estimates of stem and branch CO2 efflux. First, we measured wood CO2 efflux and factors related to tree morphology and environment for seven live emergent trees of two dipterocarp species at four to seven heights of up to ∼ 40 m for each tree using ladders and a crane. No systematic tendencies in vertical variations were observed for all the trees. Wood CO2 efflux was not affected by stem and air temperature, stem diameter, stem height or stem growth. The ratios of wood CO2 efflux at the treetop to that at breast height were larger in emergent trees with relatively smaller diameters at breast height. Second, we compared whole-tree stem CO2 efflux estimates using vertical measurements with those based on solely breast height measurements. We found similar whole-tree stem CO2 efflux estimates regardless of the patterns of vertical variations in CO2 efflux because the surface area in the canopy, where wood CO2 efflux often differed from that at breast height, was very small compared with that at low stem heights, resulting in little effect of the vertical variations on the estimate. Additionally, whole-tree branch CO2 efflux estimates using measured wood CO2 efflux in the canopy were considerably different from those measured using only breast height measurements. Uncertainties in wood CO2 efflux in the canopy did not cause any bias in stem CO2 efflux scaling, but affected branch CO2 efflux.
    Matched MeSH terms: Trees/growth & development
  10. Granados A, Brodie JF, Bernard H, O'Brien MJ
    Ecol Appl, 2017 10;27(7):2092-2101.
    PMID: 28660670 DOI: 10.1002/eap.1592
    Vertebrate granivores destroy plant seeds, but whether animal-induced seed mortality alters plant recruitment varies with habitat context, seed traits, and among granivore species. An incomplete understanding of seed predation makes it difficult to predict how widespread extirpations of vertebrate granivores in tropical forests might affect tree communities, especially in the face of habitat disturbance. Many tropical forests are simultaneously affected by animal loss as well as habitat disturbance, but the consequences of each for forest regeneration are often studied separately or additively, and usually on a single plant demographic stage. The combined impacts of these threats could affect plant recruitment in ways that are not apparent when studied in isolation. We used wire cages to exclude large (elephants), medium, (sambar deer, bearded pigs, muntjac deer), and small (porcupines, chevrotains) ground-dwelling mammalian granivores and herbivores in logged and unlogged forests in Malaysian Borneo. We assessed the interaction between habitat disturbance (selective logging) and experimental defaunation on seed survival, germination, and seedling establishment in five dominant dipterocarp tree species spanning a 21-fold gradient in seed size. Granivore-induced seed mortality was consistently higher in logged forest. Germination of unpredated seeds was reduced in logged forest and in the absence of small to large-bodied mammals. Experimental defaunation increased germination and reduced seed removal but had little effect on seed survival. Seedling recruitment however, was more likely where logging and animal loss occurred together. The interacting effects of logging and hunting could therefore, actually increase seedling establishment, suggesting that the loss of mammals in disturbed forest could have important consequences for forest regeneration and composition.
    Matched MeSH terms: Trees/growth & development
  11. Katayama A, Kume T, Ichihashi R, Nakagawa M
    Tree Physiol, 2019 06 01;39(6):1000-1008.
    PMID: 30976804 DOI: 10.1093/treephys/tpz022
    Limited knowledge about vertical variation in wood CO2 efflux (Rwood) is still a cause of uncertainty in Rwood estimates at individual and ecosystem scales. Although previous studies found higher Rwood in the canopy, they examined several tree species of similar size. In contrast, in the present study, we measured vertical variation in Rwood for 18 trees including 13 species, using a canopy crane for a more precise determination of the vertical variation in Rwood, for various species and sizes of trees in order to examine the factors affecting vertical variation in Rwood and thus, to better understand the effect of taking into account the vertical and inter-individual variation on estimates of Rwood at the individual scale. We did not find any clear pattern of vertical variation; Rwood increased significantly with measurement height for only one tree, while it decreased for two more trees, and was not significantly related with measurement height in 15 other trees. Canopy to breast height Rwood ratio was not related to diameter at breast height or crown ratio, which supposedly are factors affecting vertical variation in Rwood. On average, Rwood estimates at individual scale, considering inter-individual variation but ignoring vertical variation, were only 6% higher than estimates considering both forms of variation. However, estimates considering vertical variation, while ignoring inter-individual variation, were 13% higher than estimates considering both forms of variation. These results suggest that individual measurements at breast height are more important for estimating Rwood at the individual scale, and that any error in Rwood estimation at this scale, due to the absence of any more measurements along tree height, is really quite negligible. This study measured various species and sizes of trees, which may be attributed to no clear vertical variation because factors causing vertical variation can differ among species and sizes.
    Matched MeSH terms: Trees/growth & development
  12. Dong SX, Davies SJ, Ashton PS, Bunyavejchewin S, Supardi MN, Kassim AR, et al.
    Proc Biol Sci, 2012 Oct 7;279(1744):3923-31.
    PMID: 22833269
    The response of tropical forests to global climate variability and change remains poorly understood. Results from long-term studies of permanent forest plots have reported different, and in some cases opposing trends in tropical forest dynamics. In this study, we examined changes in tree growth rates at four long-term permanent tropical forest research plots in relation to variation in solar radiation, temperature and precipitation. Temporal variation in the stand-level growth rates measured at five-year intervals was found to be positively correlated with variation in incoming solar radiation and negatively related to temporal variation in night-time temperatures. Taken alone, neither solar radiation variability nor the effects of night-time temperatures can account for the observed temporal variation in tree growth rates across sites, but when considered together, these two climate variables account for most of the observed temporal variability in tree growth rates. Further analysis indicates that the stand-level response is primarily driven by the responses of smaller-sized trees (less than 20 cm in diameter). The combined temperature and radiation responses identified in this study provide a potential explanation for the conflicting patterns in tree growth rates found in previous studies.
    Matched MeSH terms: Trees/growth & development*
  13. Volkov I, Banavar JR, He F, Hubbell SP, Maritan A
    Nature, 2005 Dec 1;438(7068):658-61.
    PMID: 16319890
    The recurrent patterns in the commonness and rarity of species in ecological communities--the relative species abundance--have puzzled ecologists for more than half a century. Here we show that the framework of the current neutral theory in ecology can easily be generalized to incorporate symmetric density dependence. We can calculate precisely the strength of the rare-species advantage that is needed to explain a given RSA distribution. Previously, we demonstrated that a mechanism of dispersal limitation also fits RSA data well. Here we compare fits of the dispersal and density-dependence mechanisms for empirical RSA data on tree species in six New and Old World tropical forests and show that both mechanisms offer sufficient and independent explanations. We suggest that RSA data cannot by themselves be used to discriminate among these explanations of RSA patterns--empirical studies will be required to determine whether RSA patterns are due to one or the other mechanism, or to some combination of both.
    Matched MeSH terms: Trees/growth & development
  14. Lai J, Yang B, Lin D, Kerkhoff AJ, Ma K
    PLoS One, 2013;8(10):e77007.
    PMID: 24116197 DOI: 10.1371/journal.pone.0077007
    Precise estimation of root biomass is important for understanding carbon stocks and dynamics in forests. Traditionally, biomass estimates are based on allometric scaling relationships between stem diameter and coarse root biomass calculated using linear regression (LR) on log-transformed data. Recently, it has been suggested that nonlinear regression (NLR) is a preferable fitting method for scaling relationships. But while this claim has been contested on both theoretical and empirical grounds, and statistical methods have been developed to aid in choosing between the two methods in particular cases, few studies have examined the ramifications of erroneously applying NLR. Here, we use direct measurements of 159 trees belonging to three locally dominant species in east China to compare the LR and NLR models of diameter-root biomass allometry. We then contrast model predictions by estimating stand coarse root biomass based on census data from the nearby 24-ha Gutianshan forest plot and by testing the ability of the models to predict known root biomass values measured on multiple tropical species at the Pasoh Forest Reserve in Malaysia. Based on likelihood estimates for model error distributions, as well as the accuracy of extrapolative predictions, we find that LR on log-transformed data is superior to NLR for fitting diameter-root biomass scaling models. More importantly, inappropriately using NLR leads to grossly inaccurate stand biomass estimates, especially for stands dominated by smaller trees.
    Matched MeSH terms: Trees/growth & development*
  15. Chave J, Condit R, Muller-Landau HC, Thomas SC, Ashton PS, Bunyavejchewin S, et al.
    PLoS Biol, 2008 Mar 04;6(3):e45.
    PMID: 18318600 DOI: 10.1371/journal.pbio.0060045
    In Amazonian tropical forests, recent studies have reported increases in aboveground biomass and in primary productivity, as well as shifts in plant species composition favouring fast-growing species over slow-growing ones. This pervasive alteration of mature tropical forests was attributed to global environmental change, such as an increase in atmospheric CO2 concentration, nutrient deposition, temperature, drought frequency, and/or irradiance. We used standardized, repeated measurements of over 2 million trees in ten large (16-52 ha each) forest plots on three continents to evaluate the generality of these findings across tropical forests. Aboveground biomass increased at seven of our ten plots, significantly so at four plots, and showed a large decrease at a single plot. Carbon accumulation pooled across sites was significant (+0.24 MgC ha(-1) y(-1), 95% confidence intervals [0.07, 0.39] MgC ha(-1) y(-1)), but lower than reported previously for Amazonia. At three sites for which we had data for multiple census intervals, we found no concerted increase in biomass gain, in conflict with the increased productivity hypothesis. Over all ten plots, the fastest-growing quartile of species gained biomass (+0.33 [0.09, 0.55] % y(-1)) compared with the tree community as a whole (+0.15 % y(-1)); however, this significant trend was due to a single plot. Biomass of slow-growing species increased significantly when calculated over all plots (+0.21 [0.02, 0.37] % y(-1)), and in half of our plots when calculated individually. Our results do not support the hypothesis that fast-growing species are consistently increasing in dominance in tropical tree communities. Instead, they suggest that our plots may be simultaneously recovering from past disturbances and affected by changes in resource availability. More long-term studies are necessary to clarify the contribution of global change to the functioning of tropical forests.
    Matched MeSH terms: Trees/growth & development
  16. Kuznetsov AN, Kuznetsova SP
    Izv. Akad. Nauk. Ser. Biol., 2013 Mar-Apr;?(2):206-16.
    PMID: 23789426
    This study was carried out during the period 1989-2011. The following areas were included: Vietnam, Laos, Cambodia, Indonesia, and Malaysia. Climax tropical forest and anthropogenically transformed ecosystems, including those damaged by the chemical warfare program of the United States in Vietnam, were investigated. Some regularities in the structure dynamics and functioning of forests ecosystems under a tropical monsoon climate have been revealed. The principles of classification of tropical forests have been elaborated. The major results of investigation of the tropical monsoon forests in Vietnam are given.
    Matched MeSH terms: Trees/growth & development
  17. Nazeri M, Jusoff K, Madani N, Mahmud AR, Bahman AR, Kumar L
    PLoS One, 2012;7(10):e48104.
    PMID: 23110182 DOI: 10.1371/journal.pone.0048104
    One of the available tools for mapping the geographical distribution and potential suitable habitats is species distribution models. These techniques are very helpful for finding poorly known distributions of species in poorly sampled areas, such as the tropics. Maximum Entropy (MaxEnt) is a recently developed modeling method that can be successfully calibrated using a relatively small number of records. In this research, the MaxEnt model was applied to describe the distribution and identify the key factors shaping the potential distribution of the vulnerable Malayan Sun Bear (Helarctos malayanus) in one of the main remaining habitats in Peninsular Malaysia. MaxEnt results showed that even though Malaysian sun bear habitat is tied with tropical evergreen forests, it lives in a marginal threshold of bio-climatic variables. On the other hand, current protected area networks within Peninsular Malaysia do not cover most of the sun bears potential suitable habitats. Assuming that the predicted suitability map covers sun bears actual distribution, future climate change, forest degradation and illegal hunting could potentially severely affect the sun bear's population.
    Matched MeSH terms: Trees/growth & development
  18. Katayama A, Kume T, Komatsu H, Saitoh TM, Ohashi M, Nakagawa M, et al.
    J Plant Res, 2013 Jul;126(4):505-15.
    PMID: 23283581 DOI: 10.1007/s10265-012-0544-0
    To clarify characteristics of carbon (C) allocation in a Bornean tropical rainforest without dry seasons, gross primary production (GPP) and C allocation, i.e., above-ground net primary production (ANPP), aboveground plant respiration (APR), and total below-ground carbon flux (TBCF) for the forest were examined and compared with those from Amazonian tropical rainforests with dry seasons. GPP (30.61 MgC ha(-1) year(-1), eddy covariance measurements; 34.40 MgC ha(-1) year(-1), biometric measurements) was comparable to those for Amazonian rainforests. ANPP (6.76 MgC ha(-1) year(-1)) was comparable to, and APR (8.01 MgC ha(-1) year(-1)) was slightly lower than, their respective values for Amazonian rainforests, even though aboveground biomass was greater at our site. TBCF (19.63 MgC ha(-1) year(-1)) was higher than those for Amazonian forests. The comparable ANPP and higher TBCF were unexpected, since higher water availability would suggest less fine root competition for water, giving higher ANPP and lower TBCF to GPP. Low nutrient availability may explain the comparable ANPP and higher TBCF. These data show that there are variations in C allocation patterns among mature tropical rainforests, and the variations cannot be explained solely by differences in soil water availability.
    Matched MeSH terms: Trees/growth & development
  19. Iida Y, Poorter L, Sterck F, Kassim AR, Potts MD, Kubo T, et al.
    Ecology, 2014 Feb;95(2):353-63.
    PMID: 24669729
    Tree architecture, growth, and mortality change with increasing tree size and associated light conditions. To date, few studies have quantified how size-dependent changes in growth and mortality rates co-vary with architectural traits, and how such size-dependent changes differ across species and possible light capture strategies. We applied a hierarchical Bayesian model to quantify size-dependent changes in demographic rates and correlated demographic rates and architectural traits for 145 co-occurring Malaysian rain-forest tree species covering a wide range of tree sizes. Demographic rates were estimated using relative growth rate in stem diameter (RGR) and mortality rate as a function of stem diameter. Architectural traits examined were adult stature measured as the 95-percentile of the maximum stem diameter (upper diameter), wood density, and three tree architectural variables: tree height, foliage height, and crown width. Correlations between demographic rates and architectural traits were examined for stem diameters ranging from 1 to 47 cm. As a result, RGR and mortality varied significantly with increasing stem diameter across species. At smaller stem diameters, RGR was higher for tall trees with wide crowns, large upper diameter, and low wood density. Increased mortality was associated with low wood density at small diameters, and associated with small upper diameter and wide crowns over a wide range of stem diameters. Positive correlations between RGR and mortality were found over the whole range of stem diameters, but they were significant only at small stem diameters. Associations between architectural traits and demographic rates were strongest at small stem diameters. In the dark understory of tropical rain forests, the limiting amount of light is likely to make the interspecific difference in the effects of functional traits on demography more clear. Demographic performance is therefore tightly linked with architectural traits such as adult stature, wood density, and capacity for horizontal crown expansion. The enhancement of a demographic trade-off due to interspecific variation in functional traits in the understory helps to explain species coexistence in diverse rain forests.
    Matched MeSH terms: Trees/growth & development*
  20. O'Brien MJ, Burslem DF, Caduff A, Tay J, Hector A
    New Phytol, 2015 Feb;205(3):1083-94.
    PMID: 25358235 DOI: 10.1111/nph.13134
    Drought regimes can be characterized by the variability in the quantity of rainfall and the duration of rainless periods. However, most research on plant response to drought has ignored the impacts of rainfall variation, especially with regard to the influence of nonstructural carbohydrates (NSCs) in promoting drought resistance. To test the hypothesis that these components of drought differentially affect NSC dynamics and seedling resistance, we tracked NSC in plant tissues of tropical tree seedlings in response to manipulations of the volume and frequency of water applied. NSC concentrations decreased in woody tissues under infrequent-high watering but increased under no watering. A faster decline of growth relative to stomatal conductance in the no watering treatment was consistent with NSC accumulation as a result of an uncoupling of growth and photosynthesis, while usage of stored NSCs in woody tissues to maintain function may account for the NSC decline under infrequent-high watering. NSCs, and specifically stem NSCs, contributed to drought resistance under severe water deficits, while NSCs had a less clear role in drought resistance to variability in water availability. The contrasting response of NSCs to water variability and deficit indicates that unique processes support seedling resistance to these components of drought.
    Matched MeSH terms: Trees/growth & development
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