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This research utilized tower-based eddy covariance to quantify the trends in net ecosystem mass (CO 2 and H 2 O vapor) and energy exchange of important land-cover types of NW Mato Grosso during the March-December 2002 seasonal transition. Measurements were made in a mature transitional (ecotonal) tropical forest near Sinop, Mato Grosso, and a cattle pasture near Cotriguaçú , Mato Grosso, located 500 km WNW of Sinop. Pasture net ecosystem CO 2 exchange (NEE) was considerably more variable than the forest NEE over the seasonal transition, and the pasture had significantly higher rates of maximum gross primary production in every season except the dry-wet season transition (September-October). The pasture also had significantly higher rates of whole-ecosystem dark respiration than the forest during the wetter times of the year. Average ( AE 95% CI) rates of total daily NEE during the March-December 2002 measurement period were 26 AE 15 mmol m À2 day À1 for the forest (positive values indicate net CO 2 loss by the ecosystem) and À38 AE 26 mmol m À2 day À1 for the pasture. While both ecosystems partitioned more net radiation (R n ) into latent heat flux (L e ), the forest had significantly higher rates of L e and lower rates of sensible heat flux (H) than the pasture; a trend that became more extreme during the onset of the dry season. Large differences in pasture and forest mass and energy exchange occurred even though seasonal variations in micrometeorology (air temperature, humidity, and radiation) were relatively similar for both ecosystems. While the short measurement period and lack of spatial replication limit the ability to generalize these results to pasture and forest regions of the Amazon Basin, these results suggest important differences in the magnitude and seasonal variation of NEE and energy partitioning for pasture and transitional tropical forest.

The photosynthetic light response of Amazonian semi-deciduous forest trees of the rain forest–savanna transition near Sinop Mato Grosso, Brazil was measured between July 2000 and September 2003 to test the hypothesis that the photosynthetic capacity of trees acclimated to different growth light environments will decline during the dry season. Maximum photosynthesis (Amax) and stomatal conductance (gmax) were significantly higher during the wet season; however, the physiological response to drought was not a clear function of growth light environment. For some species, such as Psychotria sp. growing in the mid-canopy, internal leaf CO2 concentration (Ci) was >30% lower during the dry season suggesting that declines in Amax were caused in part by stomatal limitations to CO2 diffusion. For other species, such as Brosimum lactescens growing at the top of the canopy, Tovomita schomburgkii growing in the mid-canopy, and Dinizia excelsa growing in the understorey, dry season Ci declined by <20% suggesting that factors independent of CO2 diffusion were more important in limiting Amax. Dry-season declines in gmax appeared to be important for maintaining a more consistent leaf water potential for some species (T. schomburgkii and D. excelsa) but not others (Psychotria sp.). These results indicate that while seasonal drought exerts an important limitation on the physiological capacity of semi-deciduous Amazonian forest trees, the mechanism of this limitation may differ between species.

One of the major concerns in geoenvironmental projects is the soil and water contamination caused by the waste disposal. The geophysical methods applied are a good way to get some information required in a site characterization program. This work shows some results obtained through resistivity, EM inductive and GPR surveys in the search of informations about the impact caused by a waste disposal area in Cuiabá, State of Mato Grosso, Brazil.

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