不同生境条件下滨海芦苇湿地C、N、P化学计量特征

为阐明不同生境对黄河三角洲滨海芦苇湿地土壤和植物碳(C)氮(N)磷(P)含量及生态化学计量特征的影响,选取新生湿地和退耕湿地两种湿地类型为研究对象,对土壤和植物体C、N、P含量及其化学计量特征进行研究。研究表明:1)退耕芦苇湿地土壤TC、TN的含量明显增加,TP的含量变化不大。2)新生湿地和退耕湿地土壤R_(C、N、P)分别为42.6:1.6:1、71.2:2.0:1,R_(NP)低于全球平均水平(13.1)和我国平均水平(5.2),土壤表现为N限制。新生湿地土壤剖面中,R_(CN)和R_(CP)变化剧烈;R_(NP)值随深度的增加而减小;退耕湿地土壤R_(C、N、P)值规律性较好,R_(CN)随深度的增加而变大,R_(CP)和R_(NP)值随深度的增加而减小。3)新生湿地和退耕湿地中芦苇整株R_(CN)、R_(CP)和R_(NP)平均值分别为78.2、1753、22.4;67.0、1539、23.0。开垦活动可以降低芦苇植物体R_(CN)和R_(CP)值,但由于芦苇植物体本身对R_(NP)的约束性较高,对R_(NP)值的影响不大,芦苇植株R_(NP)约为23。以上结论可以为黄河三角洲国家级自然保护区正在进行的湿地保护与恢复工作提供借鉴和参考。

The stoichiometry characterization of carbon, nitrogen and phosphorus in different reed-dominated coastal wetland habitats

Carbon (C), nitrogen (N), and phosphorus (P) are the three major chemical elements which exist in non-arbitrary ratios in different ecosystems. It has been showed that marine plankton is composed of C, N, and P in a characteristic molar ratio of 106:16:1, which is similar to the ratio of C, N, and P in marine water. The empirically developed stoichiometric ratio method, which has become widespread in marine and freshwater phytoplankton studies, has opened an avenue for coastal wetland ecosystems exploration. C, N, and P stoichiometry at different scales from molecules to organisms, and from ecosystems to the biosphere in previous studies have already been proven to be valuable in understanding various connections between trophic interactions and nutrient cycling. In order to reveal the impact of different reed-dominated coastal wetland habitats on the contents and the stoichiometry characterization of C, N and P of soil and plant in the Yellow River Delta, two typical wetlands of New-born wetland (NW) and farmland converted into wetland (FW) were selected as investigation subjects in the study. The results showed that the average content of soil total carbon (TC) and total nitrogen (TN) in NW was higher than that in FW. The significant difference of total phosphorus (TP) is not observed between NW and FW. The atomic C:N:P ratios (R_CNP) in the soils (42.6:1.6:1, 71.2:2.0:1, respectively) and the plants (1753:22.4:1, 1539:23.0:1, respectively) of NW and FW were not well constrained. The average value for R_NP was 1.6-2.0 in the soil, which was significantly lower than average global level (13.1) and China (5.2), suggested that N was limited in the soils of the Yellow River Delta. The R_CN and R_CP changed considerably with no obvious distribution patterns from the surface to bottom in the soil profiles of NW. The R_NP was higher in the top soil and decreased slowly with depth. In the soil profiles of FW, the R_CN changed dramatically and increased with depth and the R_CP and R_NP also decreased with depth. The R_CN, R_CP, and R_NP of the reed plants averaged 78.2, 1753, and 22.4, respectively, for intact reed plants in new wetland, and 67.0, 1539, and 23.0, respectively, in farmland converted into wetland. Our results indicated that the decreases of R_CN and R_CP values for the reed tissues were subjected to anthropogenic cultivation. Although R_CN and R_CP varied widely among different wetland soils and plants, average R_NP in the intact reed plant (about 23) was well constrained in the reed-dominated wetlands at regional scale of the Yellow River Delta. The results could potentially provide a useful reference for ongoing wetland conservation and restoration in the Yellow River Delta Natural Reserves.