Response of C, N, and P stoichiometry characteristics of Broussonetia papyrifera to altitude gradients and soil nutrients in the karst rocky ecosystem, SW China

Background and aims The ecological stoichiometry of forest ecosystem has rapidly increased in recent years, but studies on C, N, P stoichiometric characteristics of plant fine root-leaf-litter-soil continuum are very weak and the coupling relationships between underground and aboveground ecosystems are urgently to be studied, especially in the kart rocky desertification ecosystem of Southwest China. The aims of the present study is to clarify the response of C, N, and P stoichiometric characteristics of Broussonetia papyrifera to altitude gradients and soil nutrients in the karst rocky ecosystem and conclude the adaptative strategies of B. papyrifera to the karst rocky desertification environments. Methods Six sampling zones of B. papyrifera were set between the altitude gradient of 500-1100 m in the study area for random sampling. The organic carbon (C), total nitrogen (N), and total phosphorus (P) contents of B. papyrifera fine root, leaf, litter, and rhizosphere soil were determined, respectively. Data were analyzed statistically by linear regression, Pearson correlation analysis, LSD multiple comparison and principal component analysis. Results There are significant positive correlations between N and P contents in fine root, litter, and rhizosphere soil. The nutrient contents and ratios of fine root and litter were the key indexes to evaluate the stoichiometric characteristics of B. papyrifera continuum. Altitude can significantly influence on nutrient contents and stoichiometric ratios of B. papyrifera fine root, leaf, litter and soil. N resorption efficiency of B. papyrifera decreased significantly when altitude increased, and the P resorption efficiency of high altitude plants was lower than that of low altitude plants. Moreover, there were significant correlations between nutrient contents and ratios in B. papyrifera fine root, leaf, litter and rhizosphere soil. Conclusions The B. papyrifera growth in the karst rocky desertification ecosystem of Southwest China was mainly restricted by P element. Rhizosphere soil P content was the most significant factor in the leading to the change of stoichiometric characteristics of B. papyrifera fine root and leaf. There were obvious responses of C, N and P stoichiometric characteristics in B. papyrifera leaf - fine root - litter - rhizosphere soil continuum to altitudinal gradients. B. papyrifera had good adaption strategies to the poor soil nutrient and high altitudinal environments in the karst rocky desertification ecosystem.

Automated summary

The study found that in the karst rocky desertification ecosystem of Southwest China, plant species have different nutrient requirements, with higher altitude Broussonetia papyrifera plants being more restricted by phosphorus. B. papyrifera showed significant responses of C, N, and P stoichiometric characteristics to altitudinal gradients.