Paulo Henrique Zanella de Arruda

Variations in aboveground vegetation structure along a nutrient availability gradient in the Brazilian pantanal

Background and aimsForest expansion into seasonally flooded (hyperseasonal) savanna of the Brazilian Pantanal has been occurring for decades. Our goal was to evaluate how ecosystem physiognomy varied across a nutrient availability gradient and if hyperseasonal savanna had adequate nutrient stocks to support forest expansion.MethodsWe quantified soil properties, aboveground ecosystem structure, and nutrient stocks of three savanna and three forest stands in the Pantanal of Mato Grosso, Brazil, and used correlation analysis to assess how aboveground vegetation structure varied across a soil nutrient availability gradient.ResultsWood and foliage carbon storage and leaf area index were positively correlated with soil extractable phosphorus (P), calcium (Ca2+), and magnesium (Mg2+) concentrations but not soil organic matter or texture. Soil profiles indicated that vegetation enriched surface P and K+ availability but not Ca2+ and Mg2+. Savanna ecosystems had adequate K+, Ca2+, and Mg2+ to support gallery and riparian forests but not palm forest, while the savanna P stock was inadequate to support forest expansion.ConclusionsHyperseasonal savanna has adequate nutrients (except P) to support forest expansion. Forest trees likely invade P-deficient savanna by surviving in P-rich microsites. Over time, biotic enrichment of soil may accelerate forest expansion into P-poor savanna.

Large net CO2 loss from a grass‐dominated tropical savanna in south‐central Brazil in response to seasonal and interannual drought

The savanna vegetation of Brazil (Cerrado) accounts for 20–25% of the land cover of Brazil and is the second largest ecosystem following Amazonian forest; however, Cerrado mass and energy exchange is still highly uncertain. We used eddy covariance to measure the net ecosystem CO2 exchange (NEE) of grass-dominated Cerrado (campo sujo) over 3 years. We hypothesized that soil water availability would be a key control over the seasonal and interannual variations in NEE. Multiple regression indicated that gross primary production (GPP) was positively correlated (Pearsons r = 0.69; p < 0.001) with soil water content, radiation, and the Moderate Resolution Imaging Spectroradiometer (MODIS)-derived enhanced vegetation index (EVI) but negatively correlated with the vapor pressure deficit (VPD), indicating that drier conditions increased water limitations on GPP. Similarly, ecosystem respiration (Reco) was positively correlated (Pearsons r = 0.78; p < 0.001) with the EVI, radiation, soil water content, and temperature but slightly negatively correlated with rainfall and the VPD. While the NEE responded rapidly to temporal variations in soil water availability, the grass-dominated Cerrado stand was a net source of CO2 to the atmosphere during the study period, which was drier compared to the long-term average rainfall. Cumulative NEE was approximately 842 gC m−2, varying from 357 gC m−2 in 2011 to 242 gC m−2 in 2012. Our results indicate that grass-dominated Cerrado may be an important regional CO2 source in response to the warming and drying that is expected to occur in the southern Amazon Basin under climate change.

Sazonalidade do Balanço de Energia e Evapotranspiração em Área Arbustiva Alagável no Pantanal Mato-Grossense

The Pantanal has flood periods that model the landscape and act as a filter to the establishment and development of plants Anthropogenic or natural disturbances can alter the available energy distribution in the ecosystem. Due to the need of understanding the temporal variability of the energy balance in flood natural landscapes, the objective of this study was to analyze the seasonality of the energy balance in flooded shrub area consisting of Combretum lanceolatum Pohl in Mato Grosso Pantanal. The estimates of latent (LE) and sensible (H) heat flux, and evapotranspiration (ET) were obtained by the method of Bowen ratio between May 2012 and April 2013. The available energy was intended primarily to LE (64.1%), followed by H (35.8%) and almost zero to heat flow in soil (0.1%). The components of the energy balance showed strong seasonality, with highest LE in the wet season and highest H in the dry season. The evapotranspiration was lower during the dry season due to the lower soil water content and transpiration of dominant vegetation in the study area. Results suggest that the study area was limited by the availability of energy and water.

Desenvolvimento e Calibração de um Termohigrômetro para uso em Pesquisas de Micrometeorologia, Agrometeorologia e Clima (Development and calibration of a Thermohygrometer for use in Research Micrometeorology, Agrometeorology and Climatological)

A utilizacao de sensores para medidas de temperatura e umidade relativa do ar (UR) sao fundamentais para o desenvolvimento da micrometeorologia, na agrometeorologia para o manejo de irrigacao, clima urbano, pesquisas ambientais de microclima e climatologia. Apesar de simples, o alto custo desses sensores dificulta sua aquisicao para que haja a disponibilidade de series temporais, dessas variaveis, nas cidades, campo e florestas brasileiras. Nesse contexto, desenvolvemos um termohigrometro, utilizando o chip sensor SHT75, para medir a Temperatura e Umidade Relativa do Ar em ambientes externos, de acordo com a (WMO) e com eficiencia compativel com os mais conceituados disponiveis no mercado. Apos o desenvolvimento, foram feitas as calibracoes dos sensores, utilizando equipamentos similares comerciais certificados. Realizamos comparacoes atraves do ajuste de modelos lineares dos dados. Os resultados mostraram que houve alta correlacao entre os valores obtidos pelos sensores, construidos e os de referencia, com R2 acima de 99% e reducao de custos de ate 90%.

Determinação do fluxo de CO2 no norte do Pantanal mato-grossense

ABSTRACT: DETERMINATION OF CO 2 FLOW IN THE NORTHERN “MATO-GROSSENSE” PANTANALIn the Brazilian Pantanal region, there are some monodominant species which are suited as environmental changes indicators. The study of the dynamics of CO 2 exchange between those plants communities and the atmosphere contributes to evaluate those ecosystems behavior. Therefore, the purpose of this study was to determine the CO 2 flux (Acf) of Vochysia divergens Pohl mono species forest in northern Pantanal. The CO 2 flux was estimated by the modified Bowen ratio method. For this, net solar radiation, surface heat flux and soil temperature and air humidity data and CO 2 concentration profiles, collected at a 32m high tower installed in this area were used. The CO 2 concentrations along the canopy profiles ware greater during clear sky conditions in nighttime periods. The Acf over Vochysia divergens Pohl canopy was positive in nighttime period and negative during daytime. The highest Acf values ware collected during clear sky conditions, 75% higher than partly cloudy sky conditions.