Nutrient limitation is a common feature limiting productivity of ecosystems around the globe. The magnitude and availability of nutrients (nitrogen (N), and phosphorus (P)) affects ecosystem functioning and productivity. In deserts, nutrient limitation co-occurs with water limitation and both strongly affecting soil microbial activity. Microbial activity, in turn has direct effect on ecosystem functioning.
To understand how microbial activity are affected by N, P, and water availability, we conducted a field experiment where nutrients were added alone or in combinations to bare desert soil and manipulated successive drying and wetting cycles.
Using nitric, nitrous, and C oxides emissions as an index of microbial activity, we present evidence suggesting that frequent drying and wetting cycle enhances the emission of NO, N¬2O, and CO2 in the Negev desert. Addition of both N and P coupled with frequent drying and wetting cycles increased significantly gaseous emissions from soil compared to the nutrients added individually. In contrast to soil gaseous emissions, frequent drying and wetting cycles inhibited the potential soil nitrification and mineralization. Similarly, the post-wetting flush of microbial biomass in the soil was negatively affected the multiple drying and wetting cycles with the addition of water producing higher flush of microbial biomass than the nutrient treatments, concluding that frequent drying and wetting inhibiting potential microbial activity of soils but not the emission of N gases and CO2 in our soils.
