Litter chemistry and abiotic effects on plant recruitment success in denuded areas of Patagonian Monte rangelands

Abstract

Grazing disturbance reduces the cover of preferred species and increase soil gaps in arid ecosystems. Litter amendment is a management tool often used for soil and plant restoration in denuded areas, but its efficacy has rarely been tested in theseecosystems. We evaluated the effect of litter chemistry (C/N ratio) combinedwith different levels of UV radiation exposure and soil water on soilinorganic-N (SNin) and recruitment of two dominant perennial grasses preferredby herbivores (Poa ligularis and Nassella tenuis), one preferred shrub(Atriplex lampa), and one non-preferred evergreen shrub (Larrea divaricata),that has chemical defenses against herbivores in denuded areas of thePatagonian Monte, Argentina. Microcosms with soil of denuded areas and seeds ofall species were sown in separated cells, subjected to the combined effects oflitter cover (without litter (NL), litter with C/N ratio =15 and C/N ratio=48), UV radiation (near ambient (Am-UV) and reduced (Re-UV)), and volumetricsoil water (high (15-25% HSW) and low (5-15% LSW)). We assessed SN inconcentration periodically and species recruitment (probability of transitionfrom seed to established plant) after six months. Low C/N ratio in litter and Am-UV increased SNin. Soil water enhanced SNin only at one date. Perennialgrass species and A. lampa recruitment was increased with augmented SNin. Nonefactor affected the recruitment of L. divaricata. We concluded that litter amendment combined with exposure to UV radiation throughout the effect on soil inorganic N may modulate plant recruitment success of species preferred by herbivores indenuded areas.