Abstract: Western Jilin Province lies in the semi-arid agro-pastoral interweaving belt (APIB),within which,agriculture and animal husbandry interplay or alternate each other frequently.To understand the alternation between arable land and grass land and its induced variation in eco-value could provide scientific basis for the protection of regional environment and the sustainability of eco-function.This paper analyzed the changes of land area,type and gravity center during 1954-2000,and calculated the ecosystem service value in the process of alteration through extending the existent evaluation method.The results showed that from 1954 to 2000,the arable land in this area increased by 3.96×10⁵ hm²,while pastoral land decreased by 9.07×10⁵ hm².The frequency of alteration between arable and pastoral lands increased,and their gravity center inclined to the west.Due to the lower ecosystem service value of unit area arable land,this alternation led to an overall declination of regional ecosystem service value.The decreased value caused by the change of agricultural and pastoral lands was $ 1.22×10⁸,accounting for 23 % of the total decreased value,among which,the degradation of lower coverage grass land occupied 71.78%.It was concluded that the extensive reclaimation of sparse grass land would still bring out an un-negligible impact on regional environment,despite the lower eco-value of this land.

Key words: Salt stress, Transgenic wheat, Respiration pathway