Structural Changes of Desertified and Managed Shrubland Landscapes in Response to Drought: Spectral, Spatial and Temporal Analyses

Abstract

Drought events cause changes in ecosystem function and structure by reducing the shrub abundance and expanding the biological soil crusts (biocrusts). This change increases the leakage of nutrient resources and water into the river streams in semi-arid areas. A common management solution for decreasing this loss of resources is to create a runoff-harvesting system (RHS). The objective of the current research is to apply geo-information techniques, including remote sensing and geographic information systems (GIS), on the watershed scale, to monitor and analyze the spatial and temporal changes in response to drought of two source-sink systems, the natural shrubland and the human-made RHSs in the semi-arid area of the northern Negev Desert, Israel. This was done by evaluating the changes in soil, vegetation and landscape cover. The spatial changes were evaluated by three spectral indices: Normalized Difference Vegetation Index (NDVI), Crust Index (CI) and landscape classification change between 2003 and 2010. In addition, we examined the effects of environmental factors on NDVI, CI and their clustering after successive drought years. The results show that vegetation cover indicates a negative ∆NDVI change due to a reduction in the abundance of woody vegetation. On the other hand, the soil cover change data indicate a positive ∆CI change due to the expansion of the biocrusts. These two trends are evidence for degradation processes in terms of resource conservation and bio-production. A considerable part of the changed area (39%) represents OPEN ACCESSRemote Sens. 2014, 6 8135 transitions between redistribution processes of resources, such as water, sediments, nutrients and seeds, on the watershed scale. In the pre-drought period, resource redistribution mainly occurred on the slope scale, while in the post-drought period, resource redistribution occurred on the whole watershed scale. However, the RHS management is effective in reducing leakage, since these systems are located on the slopes where the magnitude of runoff pulses is low.

Remote Sensing of Shrubland Drying in the South-East Mediterranean, 1995–2010: Water-Use-Efficiency-Based Mapping of Biomass Change

“…Implementation of remote sensing for the identification of structural changes in shrublands in response to droughts was presented by Paz-Kagan [5]. A study of damages to Mediterranean forests in Israel has been reported by, among others, Volcani et al [48] and Dorman et al [49], the latter using a normalized-difference water index to represent water content in trees.…”

“…However, there is no information where such reduced rainfall had taken place, and what impact it had on natural ecosystems. According to existing studies, decreasing water availability is expected to reduce productivity in desert-fringe ecosystems in general and in semi-arid shrublands in particular [5][6][7][8]. This article aims at assessing trends of biomass change in the shrublands of the climatic gradient between sub-humid and arid zones in Central Israel as indicators of rainfall variations.…”

Drought impacts on vegetation activity in the Mediterranean region: An assessment using remote sensing data and multi-scale drought indicators

“…The availability of longer satellite time series, covering the entire globe, such as the GIMMS dataset, has allowed the analysis of the relationships between climate variability on vegetation dynamics and crop yields both at global or continental scales (Lobell and Field, 2007, Gouveia et al, 2008, Zeng et al, 2013. Different studies for the Mediterranean analyzed the impact of droughts on the natural vegetation and crops using remote sensing data, Lloret et al (2007) and Vicente-Serrano (2007) in Northeast Spain, Lobo and Maisongrande (2006) in France, Gouveia (2009 and in Portugal, Dorman et al (2013), Trigo et al (2010) in the eastern Mediteranean area, Paz-Kagan et al, (2014) GlobCover classification over Mediterranean region was resampled for the GIMMS-NDVI spatial resolution (8 km) based on the mode rule for degradation of thematic maps (Figure 1). …”

Spatio-Temporal Dynamics of Land-Use and Land-Cover in the Mu Us Sandy Land, China, Using the Change Vector Analysis Technique

“…In this study, one standard deviation (STD) was determined as a threshold based on previous experience with change detection analysis [53,56,57]. The direction of the change is computed by the angle (θ) of the change vector from the pixel value at these two dates:…”