Effect Of Stocking Rate On Carbon Isotope In The Main Species Of Stipa Breviflora Steppe

The Stipa breviflora grassland is one of the representative type of desert grasslands,and is mainly used to graze.Plant growth microenvironments could be impacted by grazing through animal's selective feeding,trampling,and fecal excretion.Subsequently,plant resource utilization and nutritional element content would be altered.In order to better understand effects of grazing on the physiology and ecological mechanism of plant,to analysis the change of plant viability after grazing disturbance.A randomized complete block design was used with four stocking rates in the present study.The?¹³C values of major plant species were determined by the stable isotope method,Leaf nitrogen(N_leaf)and hydrothermal factors were also measured to assess effects of stocking rate on plant resource utilization of different species and functional groups.The main results are as follows:?1?In the two consecutive years of growth,there was a negative correlation between S.breviflora,Artemisia frigida,Convolvulus ammannii,Cleistogenes songorica,Kochia prostrata and stocking rate;?¹³C values of C3 plants decreased with the increase of stocking rate?p<0.05?.Conversely,?¹³C values of annuals and perennials increased with an increase of stocking rate.While?¹³C values of small semi-shrubs and C4 were not affected by grazing.?2?The?¹³C values of S.breviflora was negatively correlated to N_leaf and positively correlated to C/N.Conversely,?¹³C values of A.frigida and Neopallasia pectinate were positively related to N_leaf and negtively correlated to C/N.There were no significant correlations between?¹³C values and N_leaf and C/N for C.ammannii,K.prostrata and Salsola collina.The?¹³C values of perennials and C3 plants were negatively correlated to N_leaf and positively correlated to C/N,while?¹³C values of annuals and small semi-shrubs were positively correlated to Nleaf and negatively correlated to C/N.?3?Year significantly affected?¹³C values of S.breviflora,which were no impacted by stocking rate.The?¹³C value of S.breviflora were significantly negatively correlated with annual precipitation.