Abstract
Aneurolepidium chinense grassland which distributes from Northeastern China to Inner Mongolia and is classified as meadow steppe produced a large amount of high quality forages and has been valuable natural resources. However, it is said that the grassland has been alkalined and severely degraded, owing to the irrational use in the recent 20-30 years. In order to clarify the ecology of degraded grassland from conservational point of view, a survey was carried out in the northwestern part of Harbin. The following results were obtained. 1. The coverage percentage of the bare ground in lightly degraded pastures was 27-33%, whereas that of heavily degraded was 47-78%. 2. Annual plants such as Chloris virgata and alkali-tolerant plants such as Iris loctea invaded into degraded grazing pastures indicating disturbance by heavy grazing. However, neither annual plants nor the bare ground was found in cutting pastures. 3. Soil pH was 8.47-8.90 in grazing pastures, whereas it was 6.17-6.46 in cutting pastures. Similarly, the soil electric conductivity and the soil hardness were higher in grazing pastures than those in cutting pastures. This fact indicates that physical and chemical properties of soil are severely devastated in grazing pastures. 4. The bare ground and three vegetation types were distributed in corresponding with the microtopography. These occurred in sequence from lower to higher land level as follows ; the bare ground, the Chloris virgata type, the Puccinellia tenuifolia type and the Aneurolepidium chinense type. The soil pH of the bare ground was 10.30 and that of the vegetation types described above were 9.08, 8.90 and 8.53, respectively. This fact indicates that different vegetation types develop in accordance with the soil alkalinity, and that no plant is able to survive in the highest alkali spot. It is considered that the soil alkalinity induce the bare ground and accelerates ecological degradation of grassland.
