Key problems in ecological research on vegetations in Northeast China

There exist many controversial problems in ecological research on vegetations in Northeast China, in despite of systemic studies for half century. In this paper, some comments were put forward on the recent researches of our concerned problems: 1) The zonal distribution pattern of vegetations in Northeast China could be quantificationally explained according to Kira's warmth index (WI), coldness index (CI), and Xu Wenduo's humidity index (HI). 2) There exists tundra vegetation in the north of Daxinganling Mountains with 1400 m altitude and above, which is the third tundra in China found by us firstly in 1963, and its WI<15 °C ·month.3) The vegetation boundary between Daxinganling and Xiaoxinganling Mountains is one of the first class lines in vegetation sub-area. It locates in Aihui-Guosonggou-the Nen River, and the WI here is 45 °C ·month.4) In Daxinganling Mountains, the vegetation has significant zonal differentiation. In the south, the vegetation is typical steppe; in the middle, the vegetation is forest-steppe; and in the north, the vegetation is boreal coniferous forest. The HI here are 3.5-5.5, 5.5-7.5, and >7.5mm/°C ·month, respectively. The broadleaved forest in the east of Daxinganling Mountains is the forest vegetation type in forest-steppe zone. 5) In the eastern mountains of Northeast China, Betula ermanii forest is an important composition of vegetation vertical zone in mountains, and it is the timberline. The forest (WI is 20-15 °C ·month) is the zonal vegetation type, whereas the forest (WI >20 °C ·month) is the non-zonal vegetation type. 6) In Hunshandake Sandy Land in Inner Mongolia Autonomous Region, spruce forest is the peculiar forest ecosystem type in continent, but which composition the spruce species belongs to is a controversial problem in plant class in China for a long time. It is proved further that it is a new species, namely, Picea mongolica (H. Q. Wu) W. D. Xu, cmb. nov.-Picea meyeri Rehd. et Wils var. mongolica (H. Q. Wu), according to the karyotype analysis and isozyme experiment.