Effects of rainwater harvesting on herbage diversity and productivity in degraded Aravalli hills in western India

Abstract

Over-exploitation and rural growth have severely damaged native vegetations of Aravalli hills in Rajasthan, India. This study was conducted to evaluate the effects of different restoration practices (i.e., rainwater harvesting (RWH) and planting of tree seedlings) on improvement in soil water and nutrients and growth and biomass of herbaceous vegetation. Contour trench (CT), Gradonie (G), Box trench (BT), V-ditch (VD) and a control were imposed on 75 plots (each of 700 m 2 ) in natural slope gradient defined as <10%, 10%−20% and >20% slopes in 2005. Each plot had three micro-sites of 1-m 2 at up (USP), middle (MSP) and lower (LSP) part of the plot for observation in 2008. The existed gradient (due to soil texture and topographic features) of soil pH, EC, SOC, NH 4 -N, NO 3 -N and PO 4 -P in June 2005 between >20% to <10% slopes were decreased in 2008 after applying RWH techniques. Such improvement in soil status promoted vegetation growth and biomass in higher slope gradients. Soil water, species diversity and herbage biomass increased from USP to LSP, and RWH techniques had positive role in improving SOC, nutrients, vegetation population, evenness and growth at MSP. Despite of lowest SWC, regular rain and greater soil water usage enhanced green and dry herbage biomasses in 10%−20% and >20% slopes, comparedwith <10% slope. The highest diversity in CT treatment was related to herbage biomass, which was enhanced further by highest concentrations of SOC and PO 4 -P. Further, CT treatment was found to be the best treatment in minimizing biomass variance in different slopes. Conclusively, soil texture and topographic features controlled soil water and nutrients availability. Rainwater harvesting techniques increased soil water storage and nutrient retention and also enhanced vegetation status and biomass by minimizing the effects of hillslopes. Thus depending upon the site conditions, suitable RWH technique could be adopted to increase herbage biomass while rehabilitating the degraded hills.

Effect of rangeland rehabilitation on the herbaceous species composition and diversity in Suswa catchment, Narok County, Kenya

“…Moreover, lower biomass production and percentage cover of perennial grasses in the degraded area could be a result of year round grazing which could not allow quick vegetation recovery in the study area (Verdoodt et al 2010). These findings corroborates with those of Singh et al (2011) who reported higher biomass production and percent cover in areas rehabilitated through rainwater harvesting. Similarly, Monsour et al (2013) found a higher percentage cover and biomass production in areas rehabilitated with stone terraces compared to unterraced ones.…”

“…This is in agreement with previous studies which have indicated that vegetation growth is directly related with phosphorus, soil organic carbon, potassium, and total nitrogen (Marcuzzo et al 2013). Singh et al (2011) in his study on Aravalli hills in western India found higher herbaceous biomass production and percent cover on lower slopes than in upper slopes.…”

“…The findings of this study are consistent with those of Mureithi et al (2016) who while working in Laikipia, reported a higher species richness and diversity in areas under community conservation than in open communal areas. Similarly, Singh et al (2011) working in the degraded Aravalli hills in Western India found a higher species diversity in areas with soil and water conservation structures.…”

“…The significantly higher species richness, relative abundance, and diversity of perennial grasses compared to forbs and annual grasses in the rehabilitated area could be attributed to improved soil fertility as a result of reduced runoff and erosion due to the establishment of soil and water conservation structures in the study area (Singh et al 2011). Rehabilitation of severely degraded areas have been found to enhance vegetation recovery which in turn reduces soil erosion and enhances soil fertility and plant biodiversity (Tongway and Ludwig 2011).…”

“…Aboveground biomass and ground cover are positively correlated with the amount of water and nutrients in the soil which are the main limiting components in severely degraded areas (Singh et al 2011). Further, improved ground cover and above ground biomass of perennial grasses compared to forbs and annuals in the rehabilitated area could be due to reduced grazing pressure in the rehabilitated sites.…”