Understanding the relationships between plant traits and ecosystem properties at large spatial sc... more Understanding the relationships between plant traits and ecosystem properties at large spatial scales is important for predicting how compositional change will affect carbon cycling in tropical forests. Here, we examine the relationships between species wood density, maximum height and wood production for 60 Amazonian forest plots. Firstly, we examine how community-level species traits vary across Amazonia. Average species maximum height and wood density are low in western, compared to eastern, Amazonia and are negatively correlated with aboveground wood productivity and soil fertility. Secondly, we compare biomass growth rates across functional groups defined on the basis of these two traits. In similar size classes, biomass growth rates vary little between trees that differ in wood density and maximum height. However, biomass growth rates are generally higher in western Amazonia across all functional groups. Thirdly, we ask whether the data on the abundance and average biomass growth rates of different functional groups is sufficient to predict the observed, regional-scale pattern of wood productivity. We find that the lower rate of wood production in eastern compared to western Amazonia cannot be estimated on the basis of this information. Overall, these results suggest that the correlations between community-level trait values and wood productivity in Amazonian forests are not causative: direct environmental control of biomass growth rates appears to be the most important driver of wood production at regional scales. This result contrasts with findings for forest biomass where variation in wood density, associated with variation in species composition, is an important driver of regional-scale patterns. Tropical forest wood productivity may therefore be less sensitive than biomass to compositional change that alters community-level averages of these plant traits.
Evaporation in the boreal zone during summer: physics and vegetation. %B Global Biogeochemical Cycles in the Climate System. %E Schulze et al. %I Academic Press
Background: Patterns in tropical forest nitrogen cycling are poorly understood. In particular, th... more Background: Patterns in tropical forest nitrogen cycling are poorly understood. In particular, the extent to which leguminous trees in these forests fix nitrogen is unclear. Aims: We aimed to determine factors that explain variation in foliar δ 15 N (δ 15 N F ) for Amazon forest trees, and to evaluate the extent to which putatively N 2 -fixing Fabaceae acquire nitrogen from the atmosphere. Methods: Upper-canopy δ 15 N F values were determined for 1255 trees sampled across 65 Amazon forest plots. Along with plot inventory data, differences in δ 15 N F between nodule-forming Fabaceae and other trees were used to estimate the extent of N 2 fixation. Results: δ 15 N F ranged from −12.1‰ to +9.3‰. Most of this variation was attributable to site-specific conditions, with extractable soil phosphorus and dry-season precipitation having strong influences, suggesting a restricted availability of nitrogen on both young and old soils and/or at low precipitation. Fabaceae constituted fewer than 10% of the sampled trees, and only 36% were expressed fixers. We estimated an average Amazon forest symbiotic fixation rate of 3 kg N ha −1 year −1 . Conclusion: Plant δ 15 N indicate that low levels of nitrogen availability are only likely to influence Amazon forest function on immature or old weathered soils and/or where dry-season precipitation is low. Most Fabaceae species that are capable of nodulating do not fix nitrogen in Amazonia.
Vertical profiles in leaf mass per unit leaf area (M A ), foliar 13 C composition (δ 13 C) and le... more Vertical profiles in leaf mass per unit leaf area (M A ), foliar 13 C composition (δ 13 C) and leaf nitrogen (N), phosphorus (P), carbon (C), potassium (K), magnesium (Mg) and calcium (Ca) concentrations were estimated for 204 rain forest trees growing in 57 sites across the Amazon Basin. Data was analysed using a multilevel modelling approach, 5 allowing a separation of gradients within individual tree canopies (intra-tree gradients) as opposed to stand level gradients occurring because of systematic differences occurring between different trees of different heights (inter-tree gradients). Significant positive intra-tree gradients (i.e. increasing values with increasing sampling height) were observed for M A and [C] DW (the subscript denoting on a dry weight basis) with 10 negative intra-tree gradients observed for δ 13 C, [Mg] DW and [K] DW . No significant intra-tree gradients were observed for [N] DW , [P] DW or [Ca] DW . Although the magnitudes of inter-tree gradients were not significantly different for M A , δ 13 C, [C] DW , [K] DW , [N] DW , [P] DW and [Ca] DW , for [Mg] DW there no systematic difference observed between trees of different heights, this being in contrast to the strongly negative intra-tree 15
Soil samples were collected in six South American countries in a total of 71 different 1 ha fores... more Soil samples were collected in six South American countries in a total of 71 different 1 ha forest plots across the Amazon Basin as part of the RAINFOR project. They were analysed for total and exchangeable cations, C, N, pH with various P fractions also determined. Physical properties were also examined and an index of soil physical 5 quality proposed. A diverse range of soils was found. For the western areas near the Andean cordillera and the southern and northern fringes, soils tend to be distributed among the lower pedogenetic levels, while the central and eastern areas of Amazonia have more intensely weathered soils. This gives rise to a large variation of soil chemical and physical properties across the Basin, with soil properties varying predictably along 10
Introduction Conclusions References Tables Figures Back Close Full Screen / Esc Printer-friendly ... more Introduction Conclusions References Tables Figures Back Close Full Screen / Esc Printer-friendly Version Interactive Discussion
Journal of Geophysical Research: Biogeosciences, 2014
Studies of carbon allocation in forests provide essential information for understanding spatial a... more Studies of carbon allocation in forests provide essential information for understanding spatial and temporal differences in carbon cycling that can inform models and predict possible responses to changes in climate. Amazon forests play a particularly significant role in the global carbon balance, but there are still large uncertainties regarding abiotic controls on the rates of net primary production (NPP) and the allocation of photosynthetic products to different ecosystem components. We evaluated three different aspects of stand-level carbon allocation (biomass, NPP, and its partitioning) in two amazon forests on different soils (nutrient-rich clay soils versus nutrient-poor sandy soils) but otherwise growing under similar conditions. We found differences in carbon allocation patterns between these two forests, showing that the forest on clay soil had a higher aboveground and total biomass as well as a higher aboveground NPP than the sandy forest. However, differences between the two forest types in terms of total NPP were smaller, as a consequence of different patterns in the carbon allocation of aboveground and belowground components. The proportional allocation of NPP to new foliage was relatively similar between them. Our results of aboveground biomass increments and fine-root production suggest a possible trade-off between carbon allocation to fine roots versus aboveground compartments, as opposed to the most commonly assumed trade-off between total aboveground and belowground production. Despite these differences among forests in terms of carbon allocation, the leaf area index showed only small differences, suggesting that this index is more indicative of total NPP than its aboveground or belowground components.
As florestas na Amazônia são um componente chave, mas ainda pouco entendido, no ciclo global do c... more As florestas na Amazônia são um componente chave, mas ainda pouco entendido, no ciclo global do carbono. Se, como já foi previsto, essas florestas ficarem mais secas neste século, elas podem acelerar as mudanças climáticas por meio da perda de carbono e alterações no balanço de energia em sua superficie. Neste artigo, utilizamos registros de mútiplas parcelas localizadas na Amazônia para determinar a resposta da floresta à intensa seca de 2005 como uma possível analogia a eventos futuros. A seca de 2005 causou perda de biomassa florestal, invertendo o processo de sequestro de carbono que ocorre em grande escala temporal e espacial. Em locais onde a seca foi excepcionalmente intensa, impactos ainda maiores foram observados. Em comparação com condições pré-2005, as florestas sujeitas à um acréscimo de 100mm no déficit hídrico perderam 5.3 Mg da biomassa de carbono acima do solo (intervalo de confiança da análise bootstrap entre 3.0, 8.1). A seca de 2005 teve um impacto total na biomassa de carbono de 1.2-1.6 Pg (0.6, 2.6). Florestas na Amazônia, portanto, parecem ser vulneráveis à intensificação do estresse hidríco e podem ainda gerar um mecanismo de retroalimentação positivo para as mudanças climáticas, uma vez que em condições de seca estas florestas sofrem um decréscimo em sua biomassa de carbono.
We stud ied the in flu ence of two ir radi an ces on cold ac cli ma tion and re cov ery of pho to... more We stud ied the in flu ence of two ir radi an ces on cold ac cli ma tion and re cov ery of pho to syn the sis in Scots pine (Pinus sylvestris L.) seed lings to as sess mech a nisms for quench ing the ex cess en ergy cap tured by the photosynthetic ap pa ratus. A shift in tem per a ture from 20 to 5 °C caused a greater decrease in photosynthetic ac tiv ity, mea sured by chlo ro phyll flu o res cence and ox y gen evo lu tion, in plants ex posed to moder ate light (350 µmol m -2 s -1 ) than in shaded plants (50 µmol m -2 s -1 ). In re sponse to the tem per a ture shift, max i mal pho tochem i cal ef fi ciency of photosystem II (PSII), mea sured as the ra tio of vari able to max i mal chlo ro phyll flu o res cence (F v /F m ) of dark-adapted sam ples, de creased to 70% in ex posed seedlings, whereas shaded seed lings main tained F v /F m close to initial val ues. Af ter a fur ther tem per a ture de crease to -5 °C, only 8% of ini tial F v /F m re mained in ex posed plants, whereas shaded plants re tained 40% of ini tial F v /F m . Seven days af ter transfer from -5 to 20 °C, re cov ery of pho to chem i cal ef fi ciency was more com plete in the shaded plants than in the ex posed plants (87 and 65% of the ini tial F v /F m value, re spec tively).
Carbon Dioxide Uptake by an Undisturbed Tropical Rain Forest in Southwest Amazonia, 1992 to 1993
Science, 1995
Gi i + l(w) and Gi +1 - i + 2((o) due to power broadening becomes significant, then the peak of F... more Gi i + l(w) and Gi +1 - i + 2((o) due to power broadening becomes significant, then the peak of F(w) should experiencea red shift. This is the case of MPEvia the vibrational modes at about 2110 cm-' (Fig. 5). In thelatter case,an alternative explanation is that the homogeneous ...
Low conductances for CO2 diffusion from stomata to the sites of carboxylation in leaves of woody species
Plant, Cell and Environment, 1992
Concurrent measurements of leaf gas exchange and on-line 13 C discrimination were used to evaluat... more Concurrent measurements of leaf gas exchange and on-line 13 C discrimination were used to evaluate the CO 2 conductance to diffusion from the stomatal cavity to the sites of carboxylation within the chloroplast (internal conductance; g i ). When photon irradiance was varied it ...
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