鄱阳湖湿地灰化苔草生长季氮磷含量与储量的变化

湿地植物在营养元素生物地球化学循环过程中起着重要作用,研究植物氮磷元素的吸收、分配和积累特征对于正确理解氮磷循环关键过程及其生态作用具有重要意义。基于野外实地观测和室内实验分析,研究了鄱阳湖淡水湿地灰化苔草春草生长季内不同部位生物量、氮磷含量及氮磷储量的动态变化。结果表明:在生长季内,灰化苔草各部位生物量随时间推移而增加,地上部分生物量在各生长期均高于地下部分,地下部分生物量积累速率相对稳定,而地上部分和总体平均积累速率表现为生长前期高于生长后期;各部位氮磷含量经历了先减少再增加的变化过程,其中地上部分氮元素在灰化苔草生长的中后期显著高于地下部分,而磷元素在中前期两者差异更为显著;生物量与氮磷储量均呈显著正相关,是灰化苔草氮磷储量动态变化的主导因子,氮磷元素主要储存在灰化苔草的地上部分;研究期间灰化苔草平均氮磷比介于3.32—3.83之间,按营养限制理论进行判断,氮元素可能是灰化苔草生长的限制性营养因子。

Nitrogen and phosphorus concentration, and storage dynamics of Carex cinerascens during the spring growing season in Poyang Lake wetland

Wetland plants play an important role in the biogeochemical cycling of nutrients. Studying the absorption, distribution, and accumulation of nitrogen (N) and phosphorus (P) in plants is of great significance in understanding the key processes of nutrient cycling and their ecological functions. Therefore, field observations and laboratory measurements were used to study the dynamic changes in biomass as well as the N and P contents and their storages in Carex cinerascens in the spring growing season in Poyang Lake wetland. The results showed that there was a time-dependent increase in the biomasses of different components of C. cinerascens during the spring growing season whereas the aboveground biomass was higher than that of the belowground in each growing period. Furthermore, the accumulation rate of the belowground biomass was relatively constant whereas that of the aboveground and total biomasses was higher in the early growing stage than it was in the late growing stage. The N and P contents in the different parts of C. cinerascens decreased from March to April and then increased from April to May. The N content of the aboveground part was higher than that of the belowground part in each growing period, and the difference was significant in April and May (P < 0.01). The P content had similar distribution characteristics to those of the N content, but the difference was more significant in March and April (P < 0.01) than it was in other months. The N and P storages in C. cinerascens showed a significantly positive correlation with the biomass (P < 0.01), and their dynamics were determined based on the biomass variation of C. cinerascens. Further, the aboveground part of C. cinerascens contained the main N and P pools. The N/P ratio is an important ecological indicator that can be used to detect the nutrient limitation. Based on the theory of nutrient limitation, N may be a key nutrient factor that limits the primary productivity of C. cinerascens.