Characteristics Of Natural Quercus Liaotungensis Communities And The Gap Effects On The Understory Regeneration In The Loess Plateau, China

Vegetation restoration is the key task of ecological construction in the loess plateau of China. Quercus liaotungensis contributed the ecological system to peak community in the loess plateau in China. Currently, there are a lots of studies about Quercus liaotungensis, but little on the relation of gap characteristics and Quercus liaotungensis regeneration in the Quercus liaotungensis forest. Forest gap is the most common disturbance and a important way of forest regeneration. Study on gap regeneration and characteristics of natural Quercus liaotungensis communities is benefit for us to evaluate the regeneration capability of natural Quercus liaotungensis forest, and the situation of gap disturbance and forest succession patterns, to disscuss mechanism of gap regeneration. Therefore, we conducted Quercus liaotungensis forest in the Ziwuling Mountain of the Loess Plateau of Northern Shaanxi Province in this paper, combining with field investigations and laboratory test, using an approach of canonical correspondence analysis. We studied characteristics of natural Quercus liaotungensis communities and the gap effects on the understory regeneration in the Loess Plateau. The main conclusions were as follows:1. Quercus liaotungensis, Crataegus kansuensis, Pyrus betulaefolia was the dominant species in tree layer of natural Quercus liaotungensis communities. Spiraea fritschiana, Quercus liaotungensis, Ostryopsis davidiana, Lonicera ferdinandii was the dominant species in shrub layer. Quercus liaotungensis was dominate species both in the tree layer and the shrub layer. The DBH mainly distributed in 10～20cm and the height mainly distributed in 7～10m.2. Most gap disturbance are small scale disturbance by natural in Quercus liaotungensis communities. The size of forest expanded gaps are mainly 100～150m2. Average expanded gap area is 131.61m2. The main formation of gaps was breakage at trunk base. The DBH of gaps border tree mainly distributed in 10～20cm.There is less the large diameter and small diameter. The average DBH is 20.88cm and the height mainly distributed in 6～9m. There was a significant difference between species diversity in gaps and under canopy, diversity indices and richness indices are slightly higher in gaps(P<0.05). 3. The results through canonical correspondence analysis indicated that: The environmental factors in different layers of communities were different. Available phosphorus and total nitrogen plays the most important role in the forming of community distribution pattern in tree layer;Soil organic matter and gradient plays the most important role in the forming of community distribution pattern in shrub layer;Aspect plays the most important role in the forming of community distribution pattern in herb layer. On P<0.05 significant level, the significant environmental impact factors are soil organic matter, available phosphorus , total nitrogen, position of slope and gradient by manual select method analysis.This study is helpful to know the effects of gap on forest regeneration and to find the methods of aritificial accelerate vegetation restoration.