Abstract
The resorption of substantial amounts of nutrients from plant vegetative organs has large implications for plant nutrient economy and ecosystem biogeochemical cycles. Most studies focus on leaf nutrient resorption only. Here we show that nitrogen (N) in culms of four dominant grasses of northern Chinese steppes contributed from 17 to 36% to the total pool of N resorbed from aboveground senescing parts and accounted for 25 to 52% of aboveground litter N. While previous studies demonstrated the impact of large soil fertility changes on leaf nutrient resorption, we show here that even micro-scale variations in resource availability (soil inorganic N; soil moisture) can strongly impact on both leaf and culm N resorption proficiencies (RP) and absolute leaf N resorption of grasses. Moreover, plasticity was responsible for 86 and 43% of within-site variance in leaf and culm RP, respectively, the rest being due to interspecific differences between the four grasses. Thus, plant litter quality varies even at micro-scale with heterogeneity in soil resource availability, thereby potentially feeding back on soil properties and sustaining micro-scale soil fertility patchiness. In parallel, plants of more fertile patches resorbed a greater absolute amount of N with likely beneficial effects on their competitive and/or reproductive abilities.
Lü, Xiao-Tao