Nara Luisa Reis de Andrade

Seasonal variations in litter production and its relation with MODIS vegetation indices in a semi-deciduous forest of Mato Grosso

Litter production is related to canopy processes including the timing and amount of leaf development, reproduction and net primary production. However, quantifying spatial and temporal patterns in litter production is complicated in Amazonian semi-deciduous forests because of high spatial heterogeneity and seasonal variation in rainfall. Here, we use monthly measurements of litter production and Moderate Resolution Imaging Spectroradiometer (MODIS) Normalized Difference Vegetation Index (NDVI) and Enhanced Vegetation Index (EVI) composites over a 6-year period to assess whether MODIS can be used to quantify litter production of tropical semi-deciduous forests. Original MODIS NDVI and EVI values were poorly related to the seasonal periodicity in litter production, but after using singular spectrum analysis (SSA) signal extraction techniques, clear relationships between litter production and the NDVI and EVI emerged. These results indicate that MODIS NDVI and EVI data are useful for detecting temporal patterns in litter production for Amazonian semi-deciduous forests if signal extraction analyses such as SSA are conducted.

Partição do saldo de radiação em áreas de floresta amazônica e floresta de transição Amazônia - cerrado

In this work the seasonal behavior and the daily cycle of micrometeorological parameters and energy fluxes, in Amazonian forest (Rebio Jaru) and Transitional Amazonia-Cerrado forest (Maracai Farm) is analyzed. The measurements were done by equipments installed in the micrometeorological towers of LBA project (Large Scale Biosphere-Atmosphere Experiment in Amazonia), one located near from Ji-Parana city, RO (area of Amazonian forest) and other located near from Sinop city, MT (area of Transitional forest). The results analysis indicate the existence of a well defined seasonality with dry and wet seasons in both localities, which is reflected in the behavior of the precipitation, air humidity and temperature and, consequently, in the latent heat (λE) and sensible heat (H) fluxes. In the energy balance, the daily means show a different behavior of λE, in both areas, indicating more adaptation capacity of Amazonia forest to the dry period. The Rn/λE partition values showed similar seasonal behavior for both areas, with larger values for the wet season, decreasing for the dry season.

Macro-nutrientes no lençol freático em Floresta Intacta, Floresta de Manejo e Pastagem no norte de Mato Grosso

Forest removal for other land uses has been a constant in the north of Mato Grosso and can alter the hydrological and biochemical cycles. In this context, the present work aims to identify the variation of phosphorus and nitrogen in the water sheet in areas of Mature Forest, Management Forest and Pasture in the north of Mato Grosso. The water level was measured monthly and water samples for analysis were collected monthly from January/2005 to November/2006. We verified the precipitation and the air temperature seasonality, and in the dry season the quality of the water sheet presented greater values of total phosphorus and total Kjeldhal nitrogen in the studied areas. The phosphorus and nitrogen presented greater values in forest ecosystems (Forest and Management Forest) as indicative of the function of the vegetal covering in the nutrient cycle.

Mudanças no uso da terra e o particionamento de energia no sudoeste da Amazônia

The significant rate of deforestation in the Amazon region has become a global concern. This process consists substantially in the conversion from forest to agricultural systems, which is the activity that drives the local economy. This new ecosystem formed requires studies that elucidate its operation, seeking to understand how this region interacts with the atmosphere. To investigate the behavior of energy balance components in a grassland ecosystem, a study was conducted at Fazenda Nossa Senhora (FNS), in Ouro Preto do Oeste, Rondonia. This study examined net radiation and sensible, latent and soil heat fluxes patterns, in the periods: wet, wet-dry, dry and dry-wet from 2000 to 2005. Measurements of sensible and latent heat fluxes were performed using the eddy covariance method. The results of these analyses showed that the partitioning of energy in the grassland were 77.8, 69.6, 50.6 and 75.2%, respectively in the wet, wet-dry, dry and dry-wet periods, for the latent heat flux and 22.5, 31.2, 46.7 and 24.7% for the sensible heat flux, indicating a higher vulnerability of grassland to seasonal changes.