Quantitative Division of Vegetation Ecotones in Northeast China

Abstract

Abstract. The present study aims to quantitatively divide the forest vegetation transition zones, the transition zone between humid forest and semi-humid meadow steppe and that between semi-humid meadow steppe and semi-arid grassland in Northeast China, using the rate of eco-climatic guarantee of the warmth and humidity index. The results indicated that there are two categories of vegetation ecotones in the Northeast China. 1) The first one has the major determinant of temperature factor. There are two sub classifications under this category. One lies in the place between cold temperate coniferous forest and temperate broad-leaved coniferous mixed forest, distributing mainly in the Northern Da Hinggan Mountains. The warmth index of it is the range of 37.8-52.2°C month. The other one locates at the place between warm temperate deciduous broad-leaved forest and temperate broad-leaved coniferous mixed forest, the warmth index value of which is 77.8-92.2°C month. It mostly distributes in the zone between Changbai Mountains and the mountains of Eastern Liaoning Province and, 2) the second category of vegetation ecotones is mainly decided by water factor. One is located between humid forest and semihumid meadow steppe, the humidity index of which is the range of 6.63-8.37 mm/(°C month), mainly distributing in the Heilongjiang-Songhua-Wusuli Rivers Plain (the Sanjiang Plain) and in the transition region between the Northeast China mountains area and the Liaohe-Songhua-Nenjiang Rivers Plain (the Songliao Plain). The other one is the transition zone between semi-humid meadow steppe and semi-arid grassland, whose humidity index value is 4.47-6.53 mm/(°C month), mostly locating in the Hulun Buir plateau and the narrow and long region in the Songliao Plain.