Ecosystem effects of integrating human-made runoff-harvesting systems into natural dryland watersheds

Abstract

Runoff-harvesting systems (RHSs) design to collect runoff water and nutrients from small rocky watersheds into ponds bounded by soil dikes (termed limans) that are used as an afforestation grove. Our study aimed at quantifying the influence of RHSs using two indicators: soil quality (SQ) and aboveground net primary productivity (ANPP) in a small watershed scale. The SQ index was estimated by 13 physical, chemical, and biological soil properties. ANPP was evaluated by a spaceborne-derived vegetation index of total biomass (woody and annual) and field measurements of annuals. The study was conducted in four small RHS watersheds, as well as in a reference watershed without a liman, located in the Negev Desert, Israel. Our findings are: (1) there is a significantly higher soil organic matter, total water content, and phosphorus values in all the limans than in the other locations (upstream and downstream area); and (2) significantly higher SQ and total ANPP values in the limans than in the downstream areas, amplifying the overall watershed fertility and enhance ecosystem services. We conclude that integrating RHS as a fertility island, be adjusted their size and location, can be essential techniques to sustain ecosystem services and maintain the natural ecosystem in the watershed.