Changes in evapotranspiration, transpiration and evaporation across natural and managed landscapes in the Amazon, Cerrado and Pantanal biomes

Land-use and land-cover change (LULCC) can dramatically affect the magnitude, seasonality and main drivers of evaporation (E) and transpiration (T), together as evapotranspiration (ET), with effects on overall ecosystem function, as well as both the hydrological cycle and climate system at multiple scales. Our understanding of tropical ecosystem responses to LULCC and global change processes is still limited, mainly due to a lack of ground-based observations that cover a variety of ecosystems, land-uses and land-covers. In this study, we used a network of nine eddy covariance flux towers installed in natural (forest, savanna, wetland) and managed systems (rainfed and irrigated cropland, pastureland) to explore how LULCC affects ET and its components in the Amazon, Cerrado and Pantanal biomes. At each site, tower-based ET measurements were partitioned into T and E to investigate how these fluxes varied between different land-uses and seasons. We found that ET, T and E decreased significantly during the dry season, except in Amazon forest ecosystems where T rates were maintained throughout the year. In contrast to Amazon forests, Cerrado and Pantanal ecosystems showed stronger stomatal control during the dry season. Cropland and pasture sites had lower ET and T compared to native vegetation in all biomes, but E was greater in Pantanal pasture when compared to Pantanal forest. The T fraction of ET was correlated with LAI and EVI, but relationships were weaker in Amazon forests. Our results highlight the importance of understanding the effects of LULCC on water fluxes in tropical ecosystems, and the implications for climate change mitigation policies and land management

Seasonal And Interanual Variability Of The Fractal Dimention Of Temperature And Relative Humidity Series In The Amazonia And Pantanal [variabilidade Sazonal E Interanual Da Dimensão Fractal De Séries De Temperatura E Umidade Relativa Da Amazônia E Pantanal]

The rise in global average temperature, change in rainfall regime, the occurrence of more stringent droughts and floods, as well as the accelerated deforestation, all stress the need of describing and understanding the ecosystems. The time series analysis approach of the dynamic systems theory allows to characterize the nonlinear behavior of forest systems. The aim of this study was to analyze data from micrometeorological towers measured above the forest canopy in experimental sites in the Amazon and the Brazilian Pantanal, searching for climatic attractors with low fractal dimensions of the temperature (T) and relative humidity (RH) variables in the period 2005-2010. The annual and inter-annual sensitive variation of the estimates of fractal dimension, the exponent correlation dimension D2 (D2(T)Amaz= 1,73 ± 0,29; D 2(RH)Amaz= 1,89 ± 0,30; D 2(T)Pant= 2,08 ±0,26; D2(RH)Pant= 2,23 ±0,18) and the embedding dimension m (m(T)Amaz= 8 ± 2; m (RH)Amaz= 9 ± 2; m (T)Pant= 9 ±1; m(RH)Pant= 10 ±1) strongly suggest the existence of periodic attractors and low dimension chaotic attractors governing the dynamics of these biomes. The exponent D2 of the attractors varied in phase seasonally and was sensitive to forest fires.3811769776Hdi, A., Brow, R., Sidorowich, J.J., Tsimring, L.S., The analysis of observed chaotic data in physical systems (1993) Rev. Mod. 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Desempenho agronômico de linhagens de trigo em diferentes ambientes no Sudoeste paulista

O objetivo desse estudo foi avaliar a adaptabilidade e estabilidade de 18 linhagens e duas cultivares de trigo quanto à produção de grãos, altura de plantas, tolerância ao alumínio (Al3+) e outros caracteres em experimentos instalados em solos ácidos e corrigidos, no período de 2006 a 2008. Nas linhagens 13 e 17, tolerantes a 8 e 10 mg L-1 de Al3+, observaram-se adaptabilidade e estabilidade ampla para produção de grãos, maior massa de cem grãos e resistência ao acamamento. A cultivar IAC-370 e a linhagem 6, tolerantes a 4 e 8 mg L-1 de Al3+, foram responsivas à melhoria do ambiente. A linhagem 20, tolerante a 10 mg L-1 de Al3+, revelou adaptação a ambientes desfavoráveis e maior número de espiguetas por espiga. As linhagens exibiram porte semianão com exceção da linhagem 3 (porte anão). Foram identificados genótipos superiores para resistência à ferrugem-da-folha (linhagem 12), número de espiguetas e de grãos por espiga (linhagem 15), comprimento de espigas (linhagens 5 e 8) e número de grãos por espigueta (linhagem 18). Houve tendência de os genótipos mais produtivos ficarem com porte semianão mais alto e grãos mais pesados em solo ácido e corrigido. Os genótipos mais tolerantes na presença de 2 a 6 mg L-1 de Al3+, em solução nutritiva, foram os mais produtivos em solo ácido