再生水补水河道芦苇碳氮化学计量特征及其对环境的响应

在再生水补水河道内，芦苇（Phragmites australis）受高氮再生水的长期影响，具有独特的碳（C）、氮（N）化学计量特征。为查明芦苇C、N化学计量特征及其对高氮环境的响应，在芦苇生长季节（5、7、9月份），分析了再生水补水的潮白河顺义段内河水、土壤及芦苇各器官（根、茎和叶）中C、N含量及碳氮比（C/N）。结果表明：河水中C、N含量和C/N比分别在22.20-37.25 mg/L、2.24-11.20 mg/L和3.33-9.92之间。土壤中C、N含量和C/N比的范围为5.69-35.17、0.28-2.63、8.77-25.39。在整个生长季节的所有采样点内，芦苇根、茎和叶中C含量的平均值分别为（170.84±63.56）、（369.02±39.12）、（431.80±96.70） mg/g；N含量的平均值分别为（8.20±3.96）、（14.11±6.22）和（30.73±8.66） mg/g；C/N比的平均值分别为23.89±12.84、32.65±18.48、15.21±5.60。方差分析表明，芦苇各器官中C、N计量特征具有显著的季节性差异（P<0.05），这主要与芦苇在生长过程中的生理作用有关。环境中C、N计量特征具有显著的空间差异（P<0.05），受环境变量的影响，芦苇叶中N含量和C/N比从上游到下游显著降低（P<0.05）。逐步回归分析的结果显示，土壤和河水中的C、N含量能够解释芦苇叶中71.0%的变量（P<0.05）；土壤中C、N含量和河水中N含量能够解释芦苇叶C/N比82.6%的变量（P<0.05）。相关分析指出，河水中N含量与土壤中N含量显著正相关（P<0.05），说明土壤受到高氮再生水的影响而具有较强的供N能力。高氮环境下，芦苇叶中N含量较高；相较于芦苇茎和叶，根中C含量较小。研究证明在再生水补水河道中，芦苇对环境中的N有良好的吸收能力，其C、N计量特征对高氮环境表现出明显的响应。

Carbon and nitrogen stoichiometry of Phragmites australis and its response to environment in river reaches restored by reclaimed water

In river reaches restored by reclaimed water, Phragmites australis showed distinct carbon (C) and nitrogen (N) stoichiometry due to the long-term influence of reclaimed water with high nitrogen. To identify the C and N stoichiometric characteristics of P. australis and its response to high N environment, contents of C and N and carbon: nitrogen ratio (C/N) in river water, soil and organs of P. australis (root, stem, and leaf) were analyzed in the growing seasons (May, July, and September) of P. australis. The results showed that the C, N contents and C/N ratio in river water ranged between 22.20-37.25 mg/L, 2.24-11.20 mg/L, and 3.33-9.92, respectively. The contents in soil were 5.69-35.17 mg/g for C, 0.28-2.63 mg/g for N, and 8.77-25.39 for C/N ratio, respectively. At all sampling sites during the growing seasons, mean values of C contents in roots, stems, and leaves of P. australis were (170.84±63.56), (369.02±39.12), and (431.80±96.70) mg/g, respectively; for N contents, they were (8.20±3.96), (14.11±6.22), and (30.73±8.66) mg/g, respectively; for C/N ratios, they were respective 23.89±12.84, 32.65±18.48, and 15.21±5.60. The C and N stoichiometry in different organs of P. australis had significantly seasonal differences (P<0.05) in variance analysis, which was mainly caused by the physiological processes of P. australis in the growing seasons. The C and N stoichiometry in the environment had significantly spatial differences (P<0.05), leading to significant decrease of N content and C/N ratio in leaf of P. australis from upstream to downstream (P<0.05). Regression analysis indicated that the C and N contents in soil and river water could explain 71.0% of the variances of N content in P. australis leaf (P<0.05), while C and N contents in soil and the N content in river water could explain 82.6% of the variances of C/N ratio in P. australis leaf (P<0.05). Significantly positive correlation between N in river water and N in soil (P<0.05) were implied by correlation analysis, indicating close N exchange between river water and soil. Under the influence of the reclaimed water with high nitrogen, it showed strong N supplying capacity by soil, which caused high N content in P. australis leaf, and lower C content in root compared with stem and leaf of P. australis. Consequently, P. australis had strong storage capacity of N in the river reaches restored by the reclaimed water since its C and N stoichiometry showed strong responsiveness to high N environment.