The Ecological Adaptation Of Burning Of Stipa Steppe In Different Seasons

This paper studies the influence of winter and spring burning in thecommunity characteristics and soil properties at Stipa bungeana steppe, aswell as the changes of physiological indexes of S. bungeana undercorresponding buring treatments。The results were as follows:(1) Different burning treatments had different effects on communitycharacteristics. Fire can decrease community aboveground biomass, it waslowered in burned plot than in unburned plot during the whole growingseason, and the burning in spring was more obvious. And spring burningreduced community coverage, especially in the initial stage of growth. Forthe constructive species stipa bungeana, its height and abovegroundbiomass were decreased in varying degrees after burning, the coverage ofspring burning significantly decreased, and demonstrated inhibitiveinfluences of burning on S. bungeana growth, especially in spring burning.For companion species Cleistogenes squarrosa, its coverage, abovegroundbiomass and density were increased after the burning, reflecting thebeneficial effect of burning on it. Whether it is early or late growth stage,the spring burning increased the diversity and evenness of the community,but the winter burning did not produce significantly changes.(2) There have been some changes in soil properties after the burning.Soil bulk density decreased in the early stage after the burning, later nosignificant differences. The soil moisture content was not significantlydifferent in the early, but later showed downward trend, this was related tothe use of plants. Either spring or winter burning, soil pH is significantlyhigher than unburned, but there was no significant difference between thetwo. For soil total nutrients, the organic matter、total N content of winterburning significantly lower, but the total P content was significantly higher.For Available nutrient, the N, P, K was all increased in the early stage afterthe burning, and the differences may be more obvious at surface, but onlyavailable P of spring burning increased significantly. Because of there have very little litterand sparse in the experiment area，the effect of burning inincrease soil available nutrient was not very significant.(3) Burning promoted the update of S. Bungeana leaves, thechlorophyll content of the burned is higher than unburned in May, the springburning may be more obvious, but later, the changes affected by integratedinfluences of varied environmental factors, it is difficult to reflect the role ofburning. The changes of other physiological indicators did not havesignificant effects on burning yet, but more showing the changes with theseasonal changes of precipitation and sunshine duration.