Mapping Atlantic rainforest degradation and regeneration history with indicator species using convolutional network

The Atlantic rainforest of Brazil is one of the global terrestrial hotspots of biodiversity. Despite having undergone large scale deforestation, forest cover has shown signs of increases in the last decades. Here, to understand the degradation and regeneration history of Atlantic rainforest remnants near São Paulo, we combine a unique dataset of very high resolution images from Worldview-2 and Worldview-3 (0.5 and 0.3m spatial resolution, respectively), georeferenced aerial photographs from 1962 and use a deep learning method called U-net to map (i) the forest cover and changes and (ii) two pioneer tree species, Cecropia hololeuca and Tibouchina pulchra. For Tibouchina pulchra, all the individuals were mapped in February, when the trees undergo mass-flowering with purple and pink blossoms. Additionally, elevation data at 30m spatial resolution from NASA Shuttle Radar Topography Mission (SRTM) and annual mean climate variables (Terraclimate datasets at ∼ 4km of spatial resolution) were used to analyse the forest and species distributions. We found that natural forests are currently more frequently found on south-facing slopes, likely because of geomorphology and past land use, and that Tibouchina is restricted to the wetter part of the region (southern part), which annually receives at least 1600 mm of precipitation. Tibouchina pulchra was found to clearly indicate forest regeneration as almost all individuals were found within or adjacent to forests regrown after 1962. By contrast, Cecropia hololeuca was found to indicate older disturbed forests, with all individuals almost exclusively found in forest fragments already present in 1962. At the regional scale, using the dominance maps of both species, we show that at least 4.3% of the current region’s natural forests have regrown after 1962 (Tibouchina dominated, ∼ 4757 ha) and that ∼ 9% of the old natural forests have experienced significant disturbance (Cecropia dominated)

Nitrogen uptake strategies of edaphically specialized Bornean tree species

The association of tree species with particular soil types contributes to high b diversity in forests, but the mechanisms producing such distributions are still debated. Soil nitrogen (N) often limits growth and occurs in differentially available chemical forms. In a Bornean forest where tree species composition changes dramatically along a soil gradient varying in supplies of different N-forms, we investigated whether tree species’ N-uptake and soil specialization strategies covaried. We analyzed foliar 15N natural abundance for a total of 216 tree species on clay or sandy loam (the soils at the gradient’s extremes) and conducted a 15N-tracer experiment with nine specialist and generalist species to test whether species displayed flexible or differential uptake of ammonium and nitrate. Despite variation in ammonium and nitrate supplies and nearly 4 % difference in foliar δ15N between most soil specialists and populations of generalists on these soils, our 15N tracer experiment showed little support for the hypothesis that soil specialists vary in N-form use or the ratios in which they use these forms. Instead, our results indicate that these species possess flexible capacities to take up different inorganic N forms. Variation between soil specialists in uptake of different N forms is thus unlikely to cause the soil associations of tree species and high b diversity characteristic of this Bornean rain forest. Flexible uptake strategies would facilitate N-acquisition when supply rates of N-forms exhibit spatiotemporal variation and suggest that these species may be functionally redundant in their responses to N gradients and influences on ecosystem N-cycles

Is leaf water repellency related to vapor pressure deficit and crown exposure in tropical forests?

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Environmental conditions can have major influences in shaping biophysical properties of leaf surfaces. In moist environments, high leaf water repellency (LWR) is expected because the presence of a water film on leaf surfaces can block stomatal pores, reduce the diffusion of CO(2), promote pathogen incidence, colonization of epiphylls and leaching of leaf nutrients. However, LWR can also increase in dry environments as a consequence of higher epicuticular wax deposition induced by high temperatures, high radiation loads and vapor pressure deficits (VPD), which could also lead to a high leaf mass per area (LMA). The aim of this study was to determine how LWR varies among tropical trees with contrasting crown exposures and subjected to distinct vapor pressure deficits at different altitudes in the Atlantic Rain Forest. We hypothesized that (i) LWR will be higher in overstory species because they are more frequently exposed to higher radiation and higher vapor pressure deficit; (ii) In the Montane Forest, LWR will be higher for overstory species in comparison to those in Lowland Forest because radiation and VPD increase with altitude; (iii) Overstory species will also show higher LMA in response to exposure to drier conditions. We measured LWR by observing angles of droplets on adaxial and abaxial leaf surfaces in five species co-occurring at lowland and a montane forest. LWR was positively related to crown exposure and VPD at both sites but not to LMA. LWR was significantly higher in the Montane forest (mean angle 66.25 degrees) than in the Lowland forest (mean angle 61.33 degrees). We suggest that atmospheric conditions associated with contrasting crown exposures may exert important controls over leaf surface properties involved in the repellence or direct absorption of water. (C) 2010 Elsevier Masson SAS. All rights reserved.366645649Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)COTEC/IF [41.065/2005]IBAMA/CGEN [093/2005]Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)FAPESP [03/12595-7]COTEC/IF [41.065/2005]IBAMA/CGEN [093/2005

Elevated CO2 atmosphere enhances production of defense-related flavonoids in soybean elicited by NO and a fungal elicitor

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Increased atmospheric pollutants including carbon dioxide (CO2) and nitric oxide (NO) have a large impact on vegetation, with detrimental or beneficial influences on plant growth and metabolism. Here, we evaluated the effect of an elevated CO2 atmosphere on the production of soybean defensive secondary chemicals induced by NO and a fungal elicitor. We hypothesized that an excess of carbon may alter the production of specific flavonoids that were previously shown to be induced by NO in soybean cotyledons. Pots containing soybean seeds (Glycine max [L] Merr.) were submitted to 380 and 760 mu mol mol(-1) of atmospheric CO2 in open-top chambers. After nine days, plantlets grown under these conditions were assessed for biochemical and physiological parameters. Defense-related flavonoids were evaluated in detached cotyledon diffusates elicited with two different NO donors and with the beta-glucan elicitor from Phytophthora sojae. A CO2-enriched atmosphere stimulated initial growth, photosynthetic assimilation, and an altered C/N ratio in soybean plantlets resulting in allocation of precursors into different branches of the phenylpropanoid pathway in the cotyledons. Under elevated CO2, the biotic elicitor caused accumulation of phytoalexins (glyceollins) as the natural end products of the phenylpropanoid pathway. In contrast, elevated CO2 combined with NO resulted in an increase of intermediates and diverted end products (daidzein-127%, coumestrol-93%, genistein-93%, luteolin-89% and apigenin-238%) with a concomitant increase of 1.5-3.0 times in the activity of enzymes related to their biosynthetic routes. These observations point to changes in the pool of defense-related flavonoids that are related to increased carbon availability in soybeans. This may alter the responsiveness of soybean plants to pathogens when they are grown in CO2 atmospheric concentrations close to those predicted for the upcoming several decades. (C) 2008 Elsevier B.V. All rights reserved.6541700319329Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)[2005154246-4]Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)FAPESP [2005/04139-7]CNPq [475192/04-4][2005154246-4

Diversity in nighttime transpiration behavior of woody species of the Atlantic Rain Forest, Brazil

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Nighttime transpiration (NT) has been documented in many plant species but we do not yet have a thorough understanding of the abiotic and biotic controls of this phenomenon. In this study we examined interspecific variation in NT behaviors in plants with distinct crown exposures (CE) and occurring at lowland (100 m) and montane forests (1000 m) in the Brazilian Atlantic rainforest to answer the following questions: are there different NT behaviors in plants subjected to distinct conditions associated with degree of CE and/or altitude? Are there higher rates of NT relative to daily maximum values at the montane forest due to higher vapor pressure deficit (VPD)? Taking into account that low VPD should generally produce low relative NT fluxes, should we expect that understory species in both altitudes will have quite uniform low relative rates of NT in comparison to overstory species owing to the buffered nature of within-canopy microclimate? NT did show differences between altitude and species. Of most significance was a prominent non-linear relationship between the NT and VPD, observed at the montane site. This non-linearity is in contrast to most previously published NT kinetics and suggests stomatal and/or leaf energy balance controls on NT. Our findings raise a new perspective concerning thermodynamic contributions to non-linear NT kinetics and some possible reasons for this interesting behavior are discussed. (C) 2012 Elsevier BM. All rights reserved.1581320Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)COTEC/IF [41.065/2005]IBAMA/CGEN [093/2005]Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)FAPESP [03/12595-7]COTEC/IF [41.065/2005]IBAMA/CGEN [093/2005

Spatial patterns of photosynthesis in thin- and thick-leaved epiphytic orchids: unravelling C-3-CAM plasticity in an organ-compartmented way

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Background and Aims A positive correlation between tissue thickness and crassulacean acid metabolism (CAM) expression has been frequently suggested. Therefore, this study addressed the question of whether water availability modulates photosynthetic plasticity in different organs of two epiphytic orchids with distinct leaf thickness. Methods Tissue morphology and photosynthetic mode (C-3 and/or CAM) were examined in leaves, pseudobulbs and roots of a thick-leaved (Cattleya walkeriana) and a thin-leaved (Oncidium 'Aloha') epiphytic orchid. Morphological features were studied comparing the drought-induced physiological responses observed in each organ after 30 d of either drought or well-watered treatments. Key Results Cattleya walkeriana, which is considered a constitutive CAM orchid, displayed a clear drought-induced up-regulation of CAM in its thick leaves but not in its non-leaf organs (pseudobulbs and roots). The set of morphological traits of Cattleya leaves suggested the drought-inducible CAM up-regulation as a possible mechanism of increasing water-use efficiency and carbon economy. Conversely, although belonging to an orchid genus classically considered as performing C-3 photosynthesis, Oncidium 'Aloha' under drought seemed to express facultative CAM in its roots and pseudobulbs but not in its leaves, indicating that such photosynthetic responses might compensate for the lack of capacity to perform CAM in its thin leaves. Morphological features of Oncidium leaves also indicated lower efficiency in preventing water and CO2 losses, while aerenchyma ducts connecting pseudobulbs and leaves suggested a compartmentalized mechanism of nighttime carboxylation via phosphoenolpyruvate carboxylase (PEPC) (pseudobulbs) and daytime carboxylation via Rubisco (leaves) in drought-exposed Oncidium plants. Conclusions Water availability modulated CAM expression in an organ-compartmented manner in both orchids studied. As distinct regions of the same orchid could perform different photosynthetic pathways and variable degrees of CAM expression depending on the water availability, more attention should be addressed to this in future studies concerning the abundance of CAM plants.11211729Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES