草甸草原植物碳氮磷化学计量特征的季节性变化对氮添加的响应OA

The ecological stoichiometric characteristics of plant carbon(C),nitrogen(N),and phosphorus(P)reflect interactions between plants and their environment and provide an important basis for assessing plant responses to environmental changes.Most existing studies have focused on periods of maximum plant biomass,whereas relatively few have examined continuous seasonal dynamics,and even fewer have investigated the effects of nitrogen addition across seasons.This study focused on Leymus chinensis and Thermopis lanceolata,which differ in their nitrogen utilization strategies,and examined the effects of nitrogen addition on the C∶N∶P stoichiometric characteristics of roots,stems,and leaves across different seasons.The results showed that 1)nitrogen addition had no significant effect on the above-and belowground biomass of L.chinensis throughout the growing season but significantly affected the aboveground biomass of T.lanceolata by extending the period of maximum aboveground biomass.For both species,seasonal effects on aboveground biomass were greater than those on belowground biomass.2)T.lanceolata was initially limited by nitrogen at the beginning of the growing season and subsequently became limited by phosphorus,whereas L.chinensis was nitrogen-limited throughout the growing season.Nitrogen addition at a rate of 10 g·(m2·a)-1 was insufficient to alleviate nitrogen limitation in either species during the growing season.3)Vegetative organs of the two species exhibited distinct responses to seasonal changes in nitrogen content,with the strongest effects observed in leaves,followed by stems and then roots.4)Following nitrogen addition,the rates of decline in nitrogen and phosphorus contents in the leaves of both species during the growing season were faster than those under the control(CK)treatment,while the rates of increase in C∶P and N∶P ratios were also higher than those in the CK treatment.Similarly,nitrogen content in the stems of both species declined more rapidly under nitrogen addition than under the CK treatment,accompanied by faster increases in C∶N and C∶P ratios.Nitrogen addition significantly increased the nitrogen content(P<0.05)and the N∶P ratio,while decreasing the C∶N ratio,in the leaves and roots of L.chinensis,but had no significant effect on the leaves of T.lanceolata.Overall,seasonal variations in the stoichiometric characteristics of carbon,nitrogen,and phosphorus in meadow steppe plants exhibited differential responses to nitrogen addition.This research contributes to improved understanding of nutrient utilization and allocation,supports the optimization of nutrient management,and enhances the accuracy and scientific rigor of sampling strategies.