Abstract
Although seasonally dry tropical forests are considered invaluable to a greater understanding of global carbon fluxes, they remain as one of the ecosystems with the fewest observations. In this context, ecological and ecosystem models can be used as alternative methods to answer questions related to the interactions between the biosphere and the atmosphere in dry forests. The objective of this study was to calibrate the simple tropical ecosystem model (SITE) and evaluate its performance in characterizing the annual and seasonal behavior of the energy and carbon fluxes in a preserved fragment of the Caatinga biome. The SITE model exhibited reasonable applicability to simulate variations in CO2 and energy fluxes (r > 0.7). Results showed that the calibrated set of vegetation parameters adequately simulated gross primary productivity (GPP) and net ecosystem CO2 exchange (NEE). The SITE model was also able to accurately retrieve the time at which daily GPP and NEE peaked. The model was able to simulate the partition of the available energy into sensible and latent heat fluxes and soil heat flux when the calibrated parameters were used. Therefore, changes in the dynamics of dry forests should be taken into consideration in the modeling of ecosystem carbon balances.
Highlights
With the intensification of global climate change, phenomena such as El Niño and LaNiña are becoming more frequent and progressively affecting larger areas [1]
The study was conducted in a preserved fragment of a seasonally dry tropical forest, the Caatinga biome, in the semiarid lands of the Northeast Brazil (6◦ 340 4200 S, 37◦ 150 0500 W, 205 m above sea level)
The net ecosystem CO2 exchange (NEE) simulated by the model is most sensitive to the Vmax parameter (Figure 2; Table 2)
Summary
With the intensification of global climate change, phenomena such as El Niño and LaNiña are becoming more frequent and progressively affecting larger areas [1]. Simulations show that global climate change can adversely affect arid and semiarid regions by extending the dry period and jeopardizing the biodiversity of the ecosystem [2,3]. The Caatinga is a biodiversity-rich area [6], but its landscape is changing due to intense human activities, deforestation and fires (slash-and-burn practices), with large native vegetation areas being replaced by pastures [5]. Such a process has important implications in land-use changes, and in mass and heat fluxes changes in the soil–vegetation–atmosphere interface [7]. It is relevant to understand and quantify processes related to the Caatinga energy balance and carbon flux, which can be essential for the formulation of environmental and public policies
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