Study on the Influence of Canopy Density on Cycling of Soil Available N in Different Landform of Loess Plateau in China

Abstract

In this paper, a total of 330 soil samples with 0-100cm soil depth of 66 planted square forest (10*10m) with different canopy density in the Loess Plateau were selected for the determination and analysis of soil N content in different soil layers, and the effects of different canopy density on soil N cycle under different topographic factors of planted forest were studied. The results showed as follows: (1) the migration mechanism of different N forms to the root surface was different, the migration of nitrate nitrogen to the root surface mainly depended on mass flow, there was enrichment phenomenon near the root, ammonium nitrogen mainly through diffusion, resulting in deficiency and loss in the near rhizosphere, and the leaching loss of nitrate nitrogen was affected by soil water and root growth. (2) The thickness, composition and decomposition rate of litter were different due to different canopy density, which affected the content of ammonium nitrogen and nitrate nitrogen in forest soil. (3) Although the change of different regions in this region was spatially different, keeping the stand cover in the middle and high range of 0.75-0.8 can be conducive to maintaining the balance between the consumption of soil nutrients by the stand and the supplement of nutrient consumption, which can also be conducive to the sustainable recovery and growth of the stand in this region.