中国温带疏林的地理分布、生态地位及成因

 中国分布的疏林类型众多,除了在热带分布的疏林(或稀树干草原)外,还有温带阔叶疏林和温带山地针叶疏林两种生态系统,具体包括榆树(Ulmus pumila)疏林、天山云杉(Picea schrekiana)疏林、侧柏(Platycladus orientalis)疏林、杜松(Juniperus rigida)疏林、樟子松(Pinus sylvestnis var. mongolica)疏林、西藏落叶松(Larix tibetica)疏林、亚东冷杉(Abies densa)疏林、巨柏(Cupressus gigantea)疏林、大果圆柏(Sabina tibetica)疏林、滇藏方枝柏(Sabina wallichiana)疏林、方枝柏(Sabina saltuaria)疏林、大果红杉(Larix potaninii var. macrocarpa)疏林、西藏柏木(Cupressus torulosa)疏林、密枝圆柏(Sabina convallium)疏林、长叶松(Pinus roxburghii)疏林、云南松(Pinus yunnanensis)疏林、川西云杉(Picea likiangensis var. balfouriana)疏林、黄榆(Ulmus macrocarpa)疏林、臭椿(Ailanthus altissima)疏林等生态系统类型,疏林生态系统(或疏林植被)应该是介于森林和草原(或灌丛)之间的一种过渡的植被类型,是一种地带性植被类型.疏林的分布是系列生态因子综合作用的结果,但其决定因子是水分.在中国大陆,沿纬度梯度从低到高的地带性植被应为雨林、季雨林、常绿阔叶林、落叶阔叶林、疏林、灌丛或草原,从东到西沿经度梯度依次为(阔叶和针叶)森林、(阔叶和针叶)疏林、草原、荒漠.在高原地区,沿海拔梯度的分布从低到高主要是森林、疏林、灌丛、草原或草甸.与森林、灌丛和草原相比,疏林的分布面积相对较小.中国疏林的分布区域大体位于农牧交错带地区,即从森林到草原过渡的地区.对疏林成因的理解,有利于区域生态恢复措施的选择.

Geographical Distribution,Ecological Position,and Formation Causes of Temperate Zone Sparse Forest in China

China possesses various types of sparse forests. Except sparse forests in tropic regions of China, other two types of sparse forests are classified, namely, temperate zone spare forests and temperate zone mountain spare forests. In temperate zone of China, there are many types of sparse forests, such as Ulmus pumila sparse forest, Picea schrekiana sparse forest, Platycladus orientalis sparse forest, Juniperus rigida sparse forest, Pinus sylvestnis var. mongolica sparse forest, Larix tibetica sparse forest, Abies densa sparse forest, Cupressus gigantean sparse forest, Sabina tibetica sparse forest, Sabina wallichiana sparse forest, Sabina saltuaria sparse forest, Larix potaninii var. macrocarpa sparse forest, Cupressus torulosa sparse forest, Sabina convallium sparse forest, Pinus roxburghii sparse forest, Pinus yunnanensis sparse forest, Picea likiangensis var. balfouriana sparse forest, Ulmus macrocarpa sparse forest, and Ailanthus altissima sparse forest, etc. Sparse forest ecosystem is a transition between forest and grassland or shrub ecosystem. It belongs to a zonal vegetation type. Comprehensive ecological factors have determined its geographical distribution; however, the key factor is water (local rainfall amount). In the mainland of China from south to north, there are rain forests, season rain forests, evergreen broad leaf forests, summer green broad leaf forests, sparse forests, and grassland or shrubs along altitudinal gradient. From east to west, there are forests, sparse forest, shrubs, and grassland or meadow along longitudinal gradient. Compared with the distribution area of forests and grassland,the distribution of sparse forest occupies the smaller areas. Temperate zone sparse forests of China mainly distribute in the transition area between agriculture region and pasture region. Understanding the causes of sparse forest formation could give the help to select the best methods for ecological restoration.