The Preliminary Study On The Changes Of Vegetation In Chaiwopu Lake Wetland

With the population increase of Urumqi City in recent years and water demand increase such as excess reclamation of farmland around Chaiwopu Lake. Chaiwopu Lake surrounding grassland degradation and ecological environment deterioration. Therefore, it is very important to make research on grassland and vegetation change around Chaiwopu Lake and make clear the causes of grassland degeneration. This research uses grassland around Chaiwopu Lake as research object, take the ground sampling combined with remote sensing image visual interpretation methods, Analysis in 1982 and 2013, around Chaiwopu Lake grassland plant community change, the area of the grassland and non grassland change, provided the scientific basis for rational utilization and protection of Chaiwopu Lake. The main research results are as follows:(1) As the change of time, the important values of plant original dominant species such as Achnatherum splendens, Carex sp. etc are gradually reduce in around Chaiwopu Lake, while the original companion species Phragmites australis, Suaeda glauca important value increases. Due to the interference intensity increasing, community of grass is gradually replaced by Suaeda glauca, this change and drought caused by grassland vegetation degradation succession characteristics. Due to reduction of lake surface, Chaiwopu Lake around lake salinization is aggravating, inhibits the growth of the main dominant species, reduce their competitive advantage, make some more salt-tolerant plants number, height, biomass, and dominance index increased, show the salt-tolerant plants coverage increased.(2) Around Chaiwopu Lake shannon-wiener index(D1) and Species richness index(R1) in the drought degree aggravating sample area from 1982 to 2013 reduced(P<0.05), while in the salinization degree aggravating sample area increased(P<0.05). From 1982 to 2013, Pielou index(J1) and Simpson index(H) showed increasing trend(P<0.05).(3) Compared with the 1980 s, Chaiwopu Lake surrounding grassland class does not change. But the grassland type are greatly reduced and vegetation coverage decreased. By 1980 s 2 classes of 4 sub classes of 20 grassland types were reduced to 2 classes of 3 sub classes of 6 grassland types. 30% of farmland in the 1980 s due to groundwater levels fall.(4) Drought and salinization makes species in plant community tend to be single and restricts growth of original dominant species, the number of some salt tolerance species and forb are increasing, so the grassland degradation. The causes for grassland degeneration around Chaiwopu Lake are groundwater drawdown, and overgrazing.