A Premilinary Study On The Resistance Of Pinus Tabulaeformis-Robinia Pseudoacacia Mixed Forest To Dendrolimus Punctatus Spectablis (Butler)

In this paper, two types of forests, Chinese pine-Silver chain Mixed Forest and Chinese Pine Pure Forest, were investigated for their pest resistance on the Pine lappet, in Qinglong county of Hebei province(China). The main results were as follows:1. During continuous 4 years from 2001 to 2004, we made a research on the overwintering larvae of Pine lappet in the Chinese pine-Silver chain Mixed Forest and Chinese Pine Pure Forest. Comparing with the Chinese Pine pure forest, the population density of Mixed Forest reduced 74.7 percent. The percentage of affected trees reduced 47.6 percent.2. The Litter Dry Weight in Chinese pine-Silver chain Mixed Forest increased 35.67 percent, the soil water content increased 4.36 percent, the content of total nitrogen,availability of potassium and phosphorus,organic matter in soil of Mixed Forest were all higher than these in Pure Forest.3. The DBH of Chinese pine in Chinese pine-Silver chain Mixed Forest are higher than the DBH of Chinese pine in Chinese Pine Pure Forest by a 16.98% rate, Diameter-Height increased by a 9.98% rate,single tree volume increased by a 36.92% rate,needle quantity increased by a 82.67% rate,furthermore capability of bearing the weight of Pine lappet enhanced by a 82.67% rate。4. As for as the 20-Year-Old Chinese pine, the capability of bearing Pine lappet of reserving 10 wheel branches differed with over six times number than reserving 4 wheel branches, using 25 percent of losing needles as control threshold . The contained number of insects were 53 heads and 8 heads, discrepancy around 7 times. In the past, branch pruning disbenefited...