广西澄江喀斯特湿地沉水植物碳、氮、磷化学计量特征

沉水植物是水生生态系统中重要的初级生产者。当前有关沉水植物生态化学计量特征的研究主要集中在非喀斯特区，而在喀斯特区的相关研究较为缺乏。因此，以广西澄江喀斯特典型湿地中的7种沉水植物为研究对象，分析沉水植物地上部分及底泥的碳（C）、氮（N）、磷（P）化学计量特征。结果显示，（1）7种沉水植物地上部分总碳、总氮和总磷平均含量最大值均出现在小茨藻（Najas minor）分别为（325.4±5.01） g/kg、（33.07±1.59） g/kg和（3.79±0.16） g/kg；C ： N、C ： P、N ： P平均值分别为10.14±0.18、96.23±3.56和9.47±0.32，C ： N最大值（11.89±0.54）出现在苦草（Vallisneria natans），C ： P和N ： P最大值（113.27±18.14和11.13±1.63）均出现在穗花狐尾藻（Myriophyllum spicatum）。（2）底泥有机碳、总氮、总磷、碱解氮和速效磷含量平均值分别为（15.05±0.56） g/kg、（2.06±0.08） g/kg、（0.58±0.01） g/kg、（162.53±9.16） mg/kg和（21.73±0.86） mg/kg，有机碳、总氮、总磷、碱解氮和速效磷的平均含量最大值均出现在小茨藻（N.minor）分别为（18.54±1.04） g/kg、（2.55±0.25） g/kg、（0.66±0.03） g/kg、（214.82±32.05） mg/kg和（26.37±3.31） mg/kg；底泥的C ： N、C ： P和N ： P平均值分别是7.33±0.14、25.7±0.72和3.53±0.09，C ： N、C ： P和N ： P最大值分别出现在金鱼藻（Ceratophyllum demersum）（7.45±0.32）、小茨藻（N. minor）（28.29±1.29）和黑藻（Hydrilla verticillata）（3.89±0.25）。（3）沉水植物的地上部分总碳与底泥的有机碳和总氮均呈显著负相关性；沉水植物的地上部分总氮与底泥有机碳、碱解氮、C ： P均呈显著正相关性；沉水植物地上部分C ： N、C ： P均与底泥有机碳、总氮、总磷、碱解氮、C ： P、N ： P呈显著负相关，表明不同喀斯特湿地沉水植物和底泥之间的养分耦联性不同。本研究为喀斯特湿地生态系统生态化学计量学研究提供理论依据。

Stoichiometric characteristics of submerged macrophytes in the Chengjiang karst wetland, Guangxi, China

Submerged macrophytes are important primary producers in aquatic ecosystems and play an important role in maintaining clean water, nutrient cycling, and ecosystem structure. Ecological stoichiometry is used to study the relationships between the balance of several chemical elements and energy in ecological interactions. At present, the research on the stoichiometric characteristics of submerged macrophytes focus on non-karst areas, but it is a lack of research on karst wetland. To research community level stoichiometric characteristics of submerged macrophytes and their factors, the study analyzed the submerged macrophytes and sediment in Chengjiang karst wetland in Guangxi, southwestern China. Results showed that (1) the mean contents of total carbon (TC), total nitrogen (TN) and total phosphorous (TP) of seven submerged macrophytes were (297.59±4.38) g/kg, (29.78±0.52) g/kg and (3.4±0.13) g/kg, respectively. The highest contents of TC, TN and TP were in Najas minor with (325.4±5.01) g/kg, (33.07±1.59) g/kg and (3.79±0.16) g/kg, respectively. The mean ratios of C:N, C:P and N:P of submerged macrophytes were 10.14±0.18, 96.23±3.56 and 9.47±0.32, respectively. The highest C:N ratio was in Vallisneria natans (11.89±0.54), while the highest ratios of C:P and N:P were in Myriophyllum spicatum (113.27±18.14 and 11.13±1.63). (2) The mean contents of soil organic carbon (SOC), TN, TP, alkaline hydrolysis nitrogen (AN) and available phosphorus (AP) of sediment were (15.05±0.56) g/kg, (2.06±0.08) g/kg, (0.58±0.01) g/kg, (162.53±9.16) mg/kg, and (21.73±0.86) mg/kg, respectively. The highest contents of SOC, TN, TP, AN and AP were in N. minor with (18.54±1.04) g/kg, (2.55±0.25) g/kg, (0.66±0.03) g/kg, (214.82±32.05) mg/kg and (26.37±3.31) mg/kg, respectively. The mean ratios of C:N, C:P and N:P of submerged macrophytes were 7.33±0.14, 25.7±0.72 and 3.53±0.09, respectively. The highest ratios of C:N, C:P and N:P were in Ceratophyllum demersum (7.45±0.32), N. minor (28.29±1.29), and Hydrilla verticillata (3.89±0.25). (3) There were significantly negative correlations between TC of submerged macrophytes and SOC, TN of sediment, while significantly positive correlations were found between TN of submerged macrophytes and SOC, AN and C:P of sediment. In addition, ratios of C:N and C:P of submerged macrophytes showed significantly negative correlation with the SOC, TN, TP, AN, C:P and N:P of sediment, indicating that nutrient correlations are different between submerged macrophytes and sediment. Based on the ecological stoichiometric, it was preliminarily inferred that V. natans and M. spicatum may be more suitable as pioneer species for the restoration of submerged macrophytes in eutrophic karst wetland. The results support the research of ecological stoichiometry wetland ecosystems in karst areas.