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

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

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。

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.