Welington Braz Carvalho Delitti

Improved allometric models to estimate the aboveground biomass of tropical trees

Terrestrial carbon stock mapping is important for the successful implementation of climate change mitigation policies. Its accuracy depends on the availability of reliable allometric models to infer oven-dry aboveground biomass of trees from census data. The degree of uncertainty associated with previously published pantropical aboveground biomass allometries is large. We analyzed a global database of directly harvested trees at 58 sites, spanning a wide range of climatic conditions and vegetation types (4004 trees ≥ 5 cm trunk diameter). When trunk diameter, total tree height, and wood specific gravity were included in the aboveground biomass model as covariates, a single model was found to hold across tropical vegetation types, with no detectable effect of region or environmental factors. The mean percent bias and variance of this model was only slightly higher than that of locally fitted models. Wood specific gravity was an important predictor of aboveground biomass, especially when including a much broader range of vegetation types than previous studies. The generic tree diameter-height relationship depended linearly on a bioclimatic stress variable E, which compounds indices of temperature variability, precipitation variability, and drought intensity. For cases in which total tree height is unavailable for aboveground biomass estimation, a pantropical model incorporating wood density, trunk diameter, and the variable E outperformed previously published models without height. However, to minimize bias, the development of locally derived diameter-height relationships is advised whenever possible. Both new allometric models should contribute to improve the accuracy of biomass assessment protocols in tropical vegetation types, and to advancing our understanding of architectural and evolutionary constraints on woody plant development.

Litterfall and litter nutrient content in two Brazilian Tropical Forests

Litterfall and transfer of nutrients was estimated in two tropical coastal forests of Brazil - the Atlantic and the Restinga Forests at Cardoso Island, Sao Paulo. Samples were collected monthly, from June 1990 to May 1991, using thirty 0.25 m2 traps. There were significant differences in litter production between the Atlantic Forest (6.3 t.ha-1.year-1) and the Restinga Forest (3.9 t.ha-1.year-1). Litterfall was continuous throughout the year with maximum in the beginning of the rainy season in both sites. The annual return of mineral elements through litter in the Atlantic Forest was (kg.ha-1): 101.8 N, 3.8 P, 20.3 K, 60.0 Ca, 18.0 Mg, and 14.6 S and in the Restinga Forest was: 27.5 N, 1.0 P, 6.5 K, 30.0 Ca, 10.9 Mg, and 6.6 S. The return, although small, is relevant due to the low fertility of the soils in those ecosystems, especially in Restinga. The Restinga Forest seems to be an ecosystem well adapted to oligotrophic conditions, lying among those presenting higher nutrient use efficiency.

Gas exchange, growth, and chemical parameters in a native Atlantic forest tree species in polluted areas of Cubatão, Brazil.

The Atlantic forest species near the industrial complex of Cubatão, Brazil have been subjected to heavy air pollution for decades. In this study, we used some physiological parameters (gas exchange, growth and chemical contents) to biomonitor the effects of air pollution on Tibouchina pulchra, one of the most common tree species in this forest. Under standardized conditions, saplings were exposed to the environment from April to July and from July to September of 1998, at three different sites in the vicinity of the industrial complex: the Valley of Pilões River (VP), the control area; the Valley of Mogi River (VM), near fertilizer, metallurgical, and cement industries sustaining high concentrations of fluorides, N and S oxides, and particulate materials; and Caminho do Mar (CM), near petrochemical industries under N and S oxides, photooxidants, and organic compounds. Plants exposed to CM and VM conditions presented visible injuries, reductions in net photosynthesis, growth parameters, and ascorbate concentrations, and increased F, N, and S foliar concentrations. These results indicate that the environmental conditions around these industries are still harmful to plants.

Allometric models for estimating the phytomass of a secondary Atlantic Forest area of southeastern Brazil

The purpose of this study was to develop and validate equations to estimate the aboveground phytomass of a 30 years old plot of Atlantic Forest. In two plots of 100 m2, a total of 82 trees were cut down at ground level. For each tree, height and diameter were measured. Leaves and woody material were separated in order to determine their fresh weights in field conditions. Samples of each fraction were oven dried at 80 °C to constant weight to determine their dry weight. Tree data were divided into two random samples. One sample was used for the development of the regression equations, and the other for validation. The models were developed using single linear regression analysis, where the dependent variable was the dry mass, and the independent variables were height (h), diameter (d) and d2h. The validation was carried out using Pearson correlation coefficient, paired t-Student test and standard error of estimation. The best equations to estimate aboveground phytomass were: lnDW = -3.068+2.522lnd (r2 = 0.91; sy/x = 0.67) and lnDW = -3.676+0.951ln d2h (r2 = 0.94; sy/x = 0.56).

Desiccation tolerance in Pleurostima purpurea (Velloziaceae)

Previous works suggested that Pleurostima purpurea (Velloziaceae—Barbacenioideae) shows a remarkable capacity to endure desiccation of its vegetative tissues. P. purpurea occurs in monocotyledons mats on soil islands in the Pão de Açucar (Sugar Loaf) one of the most recognizable rock outcrops of the world, in Rio de Janeiro, southeastern Brazil. Mats of P. purpurea occur in cliffs by the sea some meters above the tidal zone. Although living in rock outcrops almost devoid of any soil cover, P. purpurea seems to occur preferably on less exposed rock faces and slightly shady sites. Usually, less extreme adaptations to drought would be expected in plants with the habitat preference of P. purpurea. Relying on this observation, we argue if a combination of different strategies of dealing with low water availability can be found in P. purpurea as on other desiccation tolerant angiosperms. This study aims to examine the occurrence of desiccation tolerant behavior in P. purpurea together with the expression of drought avoidance mechanisms during dehydration progression. For this, it was analyzed the gas exchanges, leaf pigments and relative leaf water content during desiccation and rehydration of cultivated mature individuals. P. purpurea behaved like typical drought avoiders under moderated drought condition with stomatal closure occurring around a relative leaf water content up to 90%. During this process, it was observed a delay in the leaf relative water content (RWCleaf) decrease comparing to the plant-soil relative water content (RWCplant-soil). As soil dehydration worsened, gas exchanges restrictions progressed until a lack of activity which characterizes anabiosis. The loss of chlorophyll occurs before the end of total dehydration, characterizing the presence of poikilochlorophylly. The chlorophyll degradation follows the RWCleaf decrease, which achieved the minimum average value of 17% without incurring in leaf abscission. The chlorophyll re-synthesis seems to start well after the full rehydration of the leaf. During all of this process, carotenoid content remained stable. These results are coherent with a combination of drought avoidance and desiccation tolerance in P. purpurea which seems to be coherent with the amplitude of water availability in the rock outcrop habitat where it occurs, suggesting that the periods of water availability are sufficiently long for the success of the costly desiccation tolerant behavior but too short to make a typical drought avoider species win the competition for exploring the rock outcrop substrate where P. purpurea occurs.

Leaf antioxidant fluctuations and growth responses in saplings of Caesalpinia echinata Lam. (brazilwood) under an urban stressing environment.

We intended to establish how efficient the leaf antioxidant responses of C. echinata are against oxidative environmental conditions observed in an urban environment and their relations to growth and biomass parameters. Plants were grown for 15 months in four sites: Congonhas and Pinheiros, affected by pollutants from vehicular emissions; Ibirapuera, affected by high O(3) concentrations; and a greenhouse with filtered air. Fifteen plants were quarterly removed from each site for analysis of antioxidants, growth and biomass. Plants growing in polluted sites showed alterations in their antioxidants. They were shorter, had thicker stems and produced less leaf biomass than plants maintained under filtered air. The fluctuations in the levels of antioxidants were significantly influenced by combined effects of climatic and pollution variables. The higher were the antioxidant responses and the concentrations of pollutant markers of air contamination in each site the slower were the growth and biomass production.

Variação sazonal em antioxidantes em folhas de plantas jovens de Caesalpinia echinata Lam. (pau-brasil)

The urban environmental factors generate conditions of oxidative stress in plants. Cellular antioxidants, such as ascorbic acid (AA),thiols (Ti), peroxidases (POD) and superoxide dismutase (SOD) are induced to different levels depending on their capacity to tolerate stressing conditions. In the first part of this study we determined the profile of these defenses in leaves of different ages of young plants of C. echinata. The levels of antioxidants were similar in all leaves analyzed, independently of the age. Secondly, we evaluated the same antioxidants and glutathione (GSH) in 130 young plants kept in a greenhouse with constant monitoring of temperature, relative humidity and irradiance during 18 months, in order to establish the seasonal variations occurring in response to climatic factors. During this period, leaf antioxidants were analyzed every three months. In general, AA concentrations and POD activity in C. echinata were higher than the levels reported for other tropical tree species. Seasonal variations were observed. GSH concentration and POD activity were significantly influenced by temperature and SOD by temperature and humidity.

Photosynthetic Responses of Tropical Trees to Short-Term Exposure to Ozone

Saplings of the tropical trees Tibouchina pulchra (Cham.) Cogn., Caesalpinia echinata Lam., and Psidium guajava L. cv. Paluma were exposed in open-top chambers with charcoal filtered air and measurements of gas exchange and chlorophyll fluorescence were made before (t1) and after exposure to non-filtered air plus O3 (t2), simulating 6-h peaks of O3 similar to those observed in São Paulo city (SE Brazil, reaching an AOT40 of 641 nmol mol−1). After the fumigation, the net photosynthetic rate, stomatal conductance, transpiration rate, and Fv/Fm were reduced (p<0.05) for the three species. C. echinata was the most sensitive species and P. guajava cv. Paluma the most resistant.

Acúmulo foliar de enxofre e suas relações com alterações no crescimento de plantas jovens de Tibouchina pulchra Cogn. (Melastomataceae) expostas nas proximidades do polo industrial de Cubatão, SP

The aim of this study was to verify, under field conditions, if SO2 imissions from the industrial complex of Cubatao, since absorbed and accumulated in leaves, may cause changes in the growth of saplings of T. pulchra. The study was performed along 1997 by exposing potted plants during three consecutive periods of 16 weeks in three sites: Piloes river valley (RP; under low levels of SO2); Caminho do Mar and Mogi river valley (CM and VM respectively; under high SO2). After each exposure, foliar accumulation of sulfur and changes in growth and biomass parameters, besides the statistical relations among them, were determined. Significant foliar accumulation of sulfur was observed in plants exposed at CM (exposures 1 to 3) and at VM (exposures 2 and 3). The growth of plants from both polluted sites was strongly modified, especially height and number of leaves and branches. Changes in biomass of leaves, stem+branches and roots were rarely detected, but significant reductions in the root/shoot ratio were observed in plants exposed at CM and VM (exposures 1 and 3). The decrease in height and in stem+branch and root biomass (exposure 2) and the increase in height and in leaf and branch production, as well as the decrease in number of leaves (main stem), in root biomass and in root/shoot ratio (exposure 3) were significantly explained by the accumulation of sulfur in leaves (p < 0.01).

Regression models to estimate aboveground phytomass of the Floresta Baixa de Restinga

Este estudo teve como objetivo desenvolver modelos preditores de fitomassa epigea da vegetacao arborea da Floresta Baixa de Restinga. Foram selecionadas 102 arvores de 29 especies ocorrentes na area de estudo e 102 individuos de jeriva (Syagrus romanzoffiana (Cham.) Glassman), distribuidos proporcionalmente entre as classes de diâmetro da vegetacao arborea. As arvores foram cortadas, ao nivel do solo e foram medidos a altura total e o diâmetro a altura do peito (DAP) de cada arvore. As folhas foram separadas do lenho e a massa fresca da porcao lenhosa e foliar medidas separadamente. Amostras de cada fracao foram secas a 70 °C, ate peso constante, para determinacao da massa seca das arvores. Os modelos foram desenvolvidos atraves de analise de regressao linear, sendo a variavel dependente a massa seca (MS) das arvores e as variaveis independentes a altura (h), o diâmetro a altura do peito (d) e as relacoes d2 h e d2 h multiplicada pela densidade da madeira (ρ d2 h). Os modelos desenvolvidos indicam que o diâmetro explica grande parte da variabilidade da fitomassa das arvores da restinga e a altura e a variavel explanatoria da equacao especifica para o jeriva. Os modelos selecionados foram: ln MS (kg) = -1,352 + 2,009 ln d (R2 = 0,96; syx = 0,34) para a comunidade vegetal sem jeriva, ln MS (kg) = -2,052 + 0,801 ln d2 h (R2 = 0,94; syx = 0,38) para a comunidade incluindo o jeriva, e ln MS (kg) = -0,884 + 2,40 ln h (R2 = 0,92; syx = 0,49) para o jeriva.