Responses of nutrient resorption to warming and nitrogen fertilization in contrasting wet and dry years in a desert grassland

Abstract

As global climate warms and atmospheric nitrogen deposition increases, plants are likely to respond by altering community composition, thus affecting the nutrient cycle. Although it is well-known that feedback between plants and soils is linked by nutrient resorption occurring during senescence, our understanding of how long-term warming and nitrogen deposition (> 10 years) influence nutrient resorption remains limited. In a desert grassland in northern China, we explored the effects of warming and nitrogen fertilization on leaf nutrient resorption for three dominant species during two hydrologically contrasting years (wet with 52% above the long-term mean precipitation of 222 mm, and dry with precipitation 16% below the mean), based on a manipulative experiment initiated in 2006. In the wet year, both warming and nitrogen fertilization significantly increased nitrogen and phosphorus concentrations in soils and plants and thus decreased resorption efficiency of both nitrogen and phosphorus with significant interactions, but these effects did not occur in the dry year. Changes in resorption efficiency were associated with plant available nitrogen and phosphorus in soils and water availability. Our study suggests that the responses of nutrient resorption to warming and nitrogen fertilization could be modified by natural precipitation variations in a desert grassland that is sensitive to abrupt changes in weather patterns.