We analysed 1040 individual trees, located in 62 plots across the Amazon Basin for leaf mass per unit area (M-A), foliar carbon isotopic composition (delta C-13) and leaf level concentrations of C, N, P, Ca, Mg, K and Al. All trees were identified to the species level with the dataset containing 58 families, 236 genera and 508 species, distributed across a wide range of soil types and precipitation regimes. Some foliar characteristics such as M-A, [C], [N] and [Mg] emerge as highly constrained by the taxonomic affiliation of tree species, but with others such as [P], [K], [Ca] and delta C-13 also strongly influenced by site growing conditions. By removing the environmental contribution to trait variation, we find that intrinsic values of most trait pairs coordinate, although different species ( characterised by different trait suites) are found at discrete locations along a common axis of coordination. Species that tend to occupy higher fertility soils are characterised by a lower M-A and have a higher intrinsic [N], [P], [K], [Mg] and delta C-13 than their lower fertility counterparts. Despite this consistency, different scaling patterns were observed between low and high fertility sites. Inter-relationships are thus substantially modified by growth environment. Analysing the environmental component of trait variation, we found soil fertility to be the most important predictor, influencing all leaf nutrient concentrations and delta C-13 and reducing M-A. Mean annual temperature was negatively associated with leaf level [N], [P] and [K] concentrations. Total annual precipitation positively influences M-A, [C] and delta C-13, but with a negative impact on [Mg]. These results provide a first basis for understanding the relationship between the physiological functioning and distribution of tree species across Amazonia

Abstract. We analysed 1040 individual trees, positioned in sixty three plots across the Amazon Basin for leaf mass per area (MA), leaf carbon isotope composition (δ13C) and leaf level concentrations of C, N, P, Ca, Mg, K and Al. All trees were identified to the species with the dataset containing 58 families, 236 genera and 508 species, distributed across a wide range of soil types and precipitation regimes. Some foliar characters such as MA, [C], [N] and [Mg] emerge as highly constrained by the taxonomic affiliation of tree species, but with others such as [P], [K], [Ca] and δ13C also strongly influenced by site growing conditions. By removing the environmental contribution to trait variation, we find that intrinsic values of most trait pairs coordinate, although different species (characterised by different trait suites) are found at discrete locations along a common axis of coordination. Species that tend to occupy higher fertility soils are characterised by a lower MA and have a higher intrinsic [N], [P], [K], [Mg] and δ13C than their lower fertility counterparts. Despite this consistency, different scaling patterns were observed between low and high fertility sites. Inter-relationships are thus substantially modified by growth environment. Analysing the environmental component of trait variation, we found soil fertility to be the most important predictor, influencing all leaf nutrient concentrations and δ13C composition and reducing MA. Mean annual temperature was negatively associated with leaf level [N], [P] and [K] concentrations. Total annual precipitation positively influences MA, [C] and δ13C, but with a negative impact on [Mg]. These results provide a first basis for understanding the relationship between the physiological functioning and distribution of tree species across Amazonia.

A temperatura do solo (TS) é um dos elementos importantes na caracterização do microclima havendo poucos estudos sobre sua variabilidade em ambientes florestais. Um estudo experimental foi realizado dentro de um fragmento de Mata Atlântica remanescente, no município de Coruripe, Alagoas, no período entre junho/2009 a maio/2011, com o objetivo de caracterizar a variabilidade da temperatura anual e sazonal e a influência da cobertura de liteira no solo. Os dados foram obtidos através de uma torre micrometeorológica de 26 m de altura instalada dentro da floresta. Para os perfis de temperatura do solo foram utilizados termopares tipo cobre/constantan, nas profundidades 1, 5, 10, 15, 20, 25, 50 e 100 cm, no primeiro ano de estudo e de 1, 5, 10, 20 e 50 cm nas áreas com e sem cobertura por liteira, no segundo ano de estudo em que os resultados obtidos apresentaram maior variabilidade da TS entre as camadas mais superficiais. O comportamento da TS foi bastante distinto entre os períodos com o seco apresentando uma amplitude térmica maior enquanto, por sua vez, o chuvoso registrou as maiores variações da TS com a profundidade cujos resultados ainda indicaram que a cobertura por liteira produziu maior variação da TS com a profundidade do solo. Variability of soil temperature as function of litter in fragment of Atlantic Forest remanant A B S T R A C TThe soil temperature (TS) is an important element in characterization of the microclimate and there are few studies on the variability in forest environments. A study was performed inside a fragment of Atlantic Forest remnant in the municipality of Coruripe, Alagoas, during the period between June/2009 to May/2011, with the objective to characterize the variability of annual and seasonal temperature and the influence of litter coverage on soil. The data were obtained from a micrometeorological tower of 26 m installed inside the forest. The temperature profiles were obtained using thermocouples type copper/constantan at depths of 1, 5, 10, 15, 20, 25, 50 and 100 cm during the first experimental year and at 1, 5, 10, 20 and 50 cm in areas with a complete coverage of litter and no coverage of litter during the second experimental year. The results obtained presented higher variability of the TS between the more superficial layers. The behavior of TS was quite different between the two periods, the dry showing a greater thermal amplitude, while the wet registered the largest variations of TS with depth. The results also indicate that higher coverage of litter produced variation of TS with soil depth.

Abstract:Despite being inundated for up to 9 mo of the year, black-water floodplain forests in the Brazilian Amazon are susceptible to fire. Post-fire tree mortality is higher and fire spreads further in the floodplain, compared with adjacent upland forest. To understand these differences between the two forest types, we compared how leaf decomposition and fine-fuel loads change with inundation and soil texture. Litterbags containing leaves of Clitoria fairchildiana were placed on upland forest floor and submerged at two depths in a backwater of the Rio Negro. We used 80 bags per treatment and retrieved subsets every ~16 d from which the contents were cleaned, dried, weighed and discarded. Over the 81-d experiment, upland leaves decomposed two to three times faster than submerged leaves. Fine-fuel biomass (litter + root mat) was measured at 28 upland forest sites and 29 floodplain forest sites of the middle Rio Negro. Floodplain forests held about twice the fine fuel (25.9 ± 10.6 Mg ha−1) of uplands (10.9 ± 2.3 Mg ha−1). Upland soils had more sand but a carpet of fine apogeotropic tree roots was more common and thicker in floodplains. We infer that slow decomposition of submerged leaves leads to high tree mortality from fire in black-water floodplains by (1) increasing fire intensity due to high fine-litter fuel load and (2) making tree roots more vulnerable to burning because they form a peat-like mat to absorb nutrients from the thick litter.