Seasonal Variation of Nitrogen Distribution Gradient for Leaves of Phyllostachys Pubescens and Its Response to Precipitation Exclusion

Abstract:

Nitrogen is an important limiting factor for the productivity of forest ecosystems. In this paper, the leaf nitrogen content in different canopy position for different ages of individuals for Phyllostachys pubescens was studied systematically with the season change. At the same time, the canopy and seasonal differences of leaf nitrogen content and its response to drought stress were studied in combination with the experiment of precipitation exclusion in the bamboo field. The results showed that (1) under different treatments (natural growth and precipitation exclusion treatment), the leaf nitrogen content of bamboo varied with seasons and in the decreasing order of spring, autumn, summer and winter, and the seasonal differences were not significant. In the same season, the treatments difference was not significant. (2) The change of leaf nitrogen content with bamboo age was also affected by the growing season. Precipitation exclusion treatment changed the seasonal and age difference of leaf nitrogen content in bamboo. In spring, the age differences in leaf nitrogen content of bamboo were significant (p<0.05), and there was no significant difference between treatments. In the other growing seasons, the differences in ages and treatments of bamboo were not significant. (3) The leaf nitrogen content of bamboo varied with the height of the canopy, and the vertical distribution gradient was affected by the growing season. It increased with the increase of canopy height in summer and autumn, which also proved the applicability of the “light-nitrogen” hypothesis to the bamboo. (4) Under natural growth and precipitation exclusion treatments, the leaf nitrogen content was linearly positively correlated with bamboo age, but it was not significant. It changed with the change of soil water content in different growing seasons under treatments. And under precipitation exclusion, it was more sensitive to soil water content. This study confirmed the existence of the vertical distribution gradient of nitrogen in the leaves of Phyllostachys pubescens and its variation with the growing season. It provides a theoretical basis for the sustainable and efficient management of bamboo plantation in the global climate background.