氮添加对科尔沁典型草原植物种间关联及生态位的影响OA

To explore the effects of nitrogen(N)deposition on interspecific associations and niches of grassland plants,this study was conducted in the Horqin typical steppe.Nine treatments were set up,including the addi-tion of inorganic N(I)and organic N(O)at three rates(0,4,and 8 g·m-2·a-1)and their combinations(I0O0,I4O0,I8O0,I0O4,I0O8,I4O4,I8O4,I4O8,and I8O8).The results showed that the plant community exhibited a random distribution under the treatments without inorganic N addition,a positive association under the I4O0 treatment and a negative association under the I8O0 treatment.Niche responses were species-specific:the niche breadth of Bassia prostrata in the I8O4 treatment was 58.3%higher than that in the I4O8 treatment(P<0.05);Agropyron cristatum maintained a relatively high and stable niche breadth(0.32～0.36)across all treatments,and the proportion of high niche overlap of this species reached 87%under the I8O8 treatment.The ecological response rate(R=2.65-2.97)and niche overlap index(ΔOik=0.120～0.138)of A.cristatum were relatively stable;the R value of Artemisia scoparia surged to 140.50 under the I8O0 treatment;the R value of Lespedeza davurica remained negative(-1.62 to-0.66)with ΔOik<0.In conclusion,N addition enhances the nega-tive interspecific associations of the community and niche differentiation,leading to variations in resource use efficiency among species.