Effects Of Stock Density And Site On Root Of Platycladus Orientalis Plantation In Beijing Mountain Area

The effects of stock density and site on root component and root distribution of Platycladus orientalis plantation in Beijing mountain area was systematically studied in the paper. Results were as follows:Root length density and root surface area density was significant increased with the stock density, but the increase trend was decrease when soil layer was deeper. The relationship between specific root length, specific root surface area and stock density was the same with that between root length density, root surface area density and stock density. This phenomenon shows that in a rang of stock density, trees develop more fine root to harvest nutrient and water with increasing stock density. Root biomass density changed in parabola form with increasing stock density at the soil layer of 0-10cm, and it reached the peak at the stock density of 4000 individual/hm~2, but decreased at the lower (<2000 individual/hm~2 )or higher(>5000 individual/hm~2) stock density. We concluded that, trees were not stimulate to develop more root in the stands with low stock density because of relative feebleness in intraspecific competition and relative abundance in soil resources. And the intraspecific competition was stronger trees when stock density was higher, so that trees allocated more carbohydrates to root for foraging more soil resources. But trees competed intensively for soil resources when the stock density was farther increasing so that the root development was constrained.Root length density, root surface area density and root volume in soil layer of 10 cm was significantly influenced by site condition, and the influence was feebler when soil layer was deeper.