Relations of vegetation and water indices to volumetric soil water content in the Pantanal of Mato Grosso, Brazil

Abstract

ABSTRACTThe measurement of the spatial distribution of volumetric soil water content in the Pantanal is highly difficult, but it can be performed indirectly from vegetation and water indices estimated by remote sensors. Thus, we assessed the relationship between volumetric soil water content (VSWC) and indices of the vegetation and water by TM Landsat 5 images in pasture and forest in the Pantanal of State of Mato Grosso. The VSWC was measured daily by a TDR on a non-flooded pasture in the Fazenda Miranda (FMI) and on a floodplain monodominant area of Vochysia divergens Pohl in the RPPN SESC Pantanal, locally known as Cambarazal (Cam). The VSWC in FMI was significantly correlated with the local rainfall, but it was 5 months delayed with rainfall in Cam. The temporal dynamics of vegetation and water indices were significantly correlated with VSWC. However, some spectral indices were negatively correlated with VSWC in Cam. It suggested different responses to VSWC in each study site. As the vegetation in FMI is water limited, the biomass increased directly with the VSWC during the wet season. The combined effect of the presence of dense woody vegetation and the occurrence of flooding in Cam influenced on the non-positive correlation between VSWC and vegetation and water indices. This article demonstrates the need for further research on the relationship of VSWC and spectra indices in the Pantanal.