降雨季节岷江上游高山森林溪流非木质残体氮和磷贮量特征

高山森林生态系统氮和磷可随溪流非木质残体的输出和降解而流失,进而影响下游水体环境,但目前缺乏必要关注.因此,本文以岷江上游高山森林为研究对象,于2013年8月(雨量最大季节)调查了18条溪流中的非木质残体(树皮、树叶和1 cm树枝)氮和磷贮量特征.结果表明,该区域溪流中非木质残体氮在单位面积集水区的贮量为2684 mg·hm-2,在单位面积溪流的氮贮量为774 mg·m-2,其中,树皮、树叶和1 cm树枝在单位面积溪流的贮量分别为112、154和508 mg·m-2,分别占总氮贮量的14%、20%和66%;溪流中非木质残体磷在单位面积集水区的贮量为468 mg·hm-2,在单位面积溪流的磷贮量为135 mg·m-2,其中,树皮、树叶和1 cm树枝在单位面积溪流的贮量分别为15、31和89mg·m-2,分别占总磷贮量的11%、23%和66%.回归分析结果表明,非木质残体氮和磷贮量均随溪流长度和面积的增加而显著增加,但随溪流流量的增加表现为先增加再降低的趋势.这些结果为深入认识岷江上游高山森林氮和磷流失途径及其对下游生态系统的潜在影响提供了新的思路.

Storage of nitrogen and phosphorus in non-woody debris in alpine forest streams in the upper reaches of the Minjiang River in rainy season

Nitrogen and phosphorus could be lost through the output and degradation of non-woody debris from headwater streams in alpine forest ecosystems. In this study, the non-woody debris containing bark, leaf and <1 cm branch were collected in 18 headwater streams in an alpine forest in the upper reaches of the Minjiang River in August 2013 (the rainy season with the greatest rainfall). The storages of nitrogen and phosphorus in the non-woody debris were analyzed. The results showed that the nitrogen storage in non-woody debris was 2684 mg · hm^-2 per unit area of watershed, and was 774 mg · m^-2 per unit area of stream. Bark, leaf and <1 cm branch stored 112, 154 and 508 mg · m^-2 per unit area of stream, which accounted for 14%, 20% and 66% of total nitrogen storage, respectively, in these alpine forest streams. Moreover, the phosphorus storage in non-woody debris was 468 mg · hm^-2 per unit area of watershed, and was 135 mg · m^-2 per unit area of stream. Bark, leaf and <1 cm branch showed 11% (15 mg · m^-2), 23% (31 mg · m^-2) and 66% (89 mg · m^-2) of the total phosphorus storage, respectively. Moreover, the storages of both nitrogen and phosphorus in non-woody debris significantly increased with the increase of stream length and area, but exhibited an increase and then decrease tendency with the increasing flow of stream. These results are useful in exploring the flux pathways of nitrogen and phosphorus in the alpine forests and the associated potential effects of nutrient losses on water environment in downstream of the Minjiang River.