Author(s): Tianming Gao; Ruiqiang Zhang; Tiejun Liu
Linked Author(s):
Keywords: Xilamuren Grassland; Irrigation; Vegetation; Soil seed bank; Recovery effect
Abstract: Due to the drought climate and over grazing, the grassland degrades severely recently, which not only influences local environment, but also threatens ecology safety of north China. Urgently control of degraded grassland and prevent advanced deterioration are needed. Recently, irrigation plays vital role on the recovery of degraded grassland in northern pastoral areas. Different amount irrigation experiment (adequate and moderate irrigation amount) was carried out from 2007 to 2009 on Xilamuren Grassland, Inner Mongolia, north China. The experiment plots’ vegetation quantitative characteristics (including community height, coverage, species number and upper ground biomass) and soil seed bank were investigated during 2007-2012. Compared with never irrigated plot, we have concluded that: ①D i fferent i rri gati on amount have the same obvious effect on improving the grassland production during 2007-2009. And the two irrigated plots’ Shannon-Wiener biodiversity index were 1. 4～1. 6, and their Bray-Curtis similarity coefficient were nearly 0. 8 in 2007-2009. Indicated that different irrigation amount had no obvious influence on community composition as well as biodiversity. ②Irrigation stopped in 2010, the two ever irrigated plot’s production equally decreased severely, and even worse than the never irrigated plot. These indicated that the advantage of irrigation on improving production disappeared immediately with stopping irrigation. The two irrigated plots’ Shannon-Wiener biodiversity index were lower than the never irrigated plot in 2010 and 2011, however were at the same low level in 2012, illustrated for one thing, great change of water supporting affected the interspecies competition and thus decreased biodiversity of the community which were accustomed to irrigation, on the other hand, long-term enclosure went against biodiversity. What’s more, from 2010 to 2012, the adequate irrigation plot’s Bray-Curtis similarity coefficient had been still about 0. 6, and the moderate irrigation plot’s had been increased to 0. 84 from 0. 55, indicated the species composition in moderate irrigation plot was approaching the never irrigated plot. Namely, different irrigation amount had the different effect on plant survival strategy after irrigation stopped. ③Soil seed bank reflect the vegetation growth condition of last year. Local variable interannual climatic condition was the main affection on plant sexual reproduction so as to on soil seed bank. The two irrigated plots presented temporary increase first and then prolonged decrease trend of seed amount compare to never irrigated plot, however seed species decreased gradually to about 3 specie/m2 from 5～8 specie/m2 and finally tend to be stable in three plots. The seed amount of two ever irrigated plots can not reflect the vegetation status due to irrigation. By comparison, soil seed bank of moderate irrigation plot was a little better than the adequate irrigation plot during and after irrigation, indicated the different irrigation amount could arouse slight affection on plant reproductive strategy. In short, moderate irrigation amount is superior to adequate irrigation amount.
Year: 2013