近25年来新疆森林的动态变化

Dynamic Change of Forests in Xinjiang in Recent 25 Years

新疆森林主要有落叶针叶林、常绿针叶林、落叶阔叶林以及特殊灌木林4种类型,面积约为全疆植被面积的2%,但新疆森林在经济、社会和生态效益等方面却发挥着重要的作用。不同森林类型具有不同的NDVI变化特征,利用GIMMSNDVI数据集首先对新疆植被进行专家分类,然后分析近25年来新疆森林面积、蓄积量和密度的动态变化及其可能原因。结果发现:近25年来,森林面积和蓄积量分别增加5.83×105hm2和4.02×107m3,森林密度以0.019%的相对年变化率增长,说明新疆森林整体向良性方向发展。虽然,近25年来阔叶林密度呈下降趋势(相对密度变化率为-0.62%),但是,造林面积增加导致的蓄积量增加大于阔叶林密度减少造成的蓄积量减少,因此阔叶林蓄积量整体增加。可见,在新疆干旱气候区实施林业工程,对保护当地的生态具有举足轻重的作用。

Four types of forests （i.e.,deciduous coniferous forest,evergreen coniferous forest,deciduous broadleaved forest and shrub） are distributed in Xinjiang. Forest coverage is only 2% of vegetation area,but the forests play an important role in social effects,economic returns and ecological benefits. The forests in Xinjiang were firstly classified with an expert classification method based on the seasonal change of NDVI curves of the forest types and the GIMMS NDVI datasets during the periods of 1982-1984,1984-1988,1989-1993,1994-1998,1999-2003 and 2004-2006,and then the changes of area,growing stock volume and density of the forests as well as their affecting factors were analyzed. The results show that the forest area and the growing stock volume were increased by 5.83×105 hm2 and 4.02×107 m3 in recent 25 years respectively,and the forest density was increased with an annual increase rate of 0.019%,indicating that the forests in Xinjiang were developed in a virtuous circle. Moreover,the forest density of deciduous broadleaved forests was decreased with an annual change rate of-0.62%,while the growing stock volume of deciduous broadleaved forests was increased because of the enlargement of plantation area. Therefore,both afforestation and reforestation can significantly contribute to the conservation of ecological environment in arid Xinjiang.