Why Pinus sylvestris *** plantation forests in southeastern Keerqin sandy land of China decline?
会议名称：《第三世界生态高峰会》
会议日期：2007年
学科分类：0907[农学-林学] 08[工学] 0829[工学-林业工程] 09[农学]
关 键 词：Decline Pinus sylvestris var mongolica plantation forest sandy land regeneration
摘 要：Pinus sylvestris ***(PSM)is a geographical variation of Scots pine(***).PSM forests on sandy land naturally distributes in Honghuaerji,Hulunbeier sandy plain of China(N47°35′ -48°36′E118°58′-120°32′).The first introduction of PSM to the southeastern Keerqin sandy land,northern China(N42°43.508′ E122°32.89′)was carried out in the beginning of *** about 40 years since the introduction,decline phenomena occulted in the PSM plantation forests(1989).Comparing with the natural PSM forests on sandy land,we found that the PSM plantation forests in Keerqin sandy land had the following features:1)the shorter lifetime than natural forests;2)the declined appearance characterized by low growth rate,top,twig and needle withered,and tree death;and 3)no natural *** reasons why the differences existed between the natural and plantation forests on sandy land were analyzed from ecological views based on long-term observations and the results of a series of experiments including the analysis on ecological conditions, effects of water stresses,photosynthesis observation and collection of eetomycorrhizal fungi etc..The results indicated that PSM trees in plantation forests grew faster tban those in natural forests in the early period of introduction because of higher heat and rainfall with almost the same soil nutrient in the plantation *** the declined appearance did not occur at the plantation sites,the lifetime of plantation forests was only about half of the natural ***, the conditions such as water,temperature and silvicultural measures in the plantation sites did not fit the furtber growth and development of the plantation trees after a certain years since the introduction, especially for the large-area pure PSM plantation forests;then the tree growth slowed down,and the vigor decreased,top,twig and needle withered,diseases and insects occurred *** results led to the appearance of evident decline characteristics