Nitrate losses from forest during snowmelt: An underestimated source in mid-high latitude watershed

文献类型： 外文期刊

第一作者： Cui, Xintong

作者： Cui, Xintong;Ouyang, Wei;Guo, Zewei;Cui, Xintong;Ouyang, Wei;Liu, Lianhua;Zhu, Weihong

作者机构：

关键词： Forest nitrate loss; Snowmelt season; Watershed diffuse pollution; SWAT; Nutrient export

期刊名称：WATER RESEARCH （ 影响因子：12.8； 五年影响因子：13.3 ）

ISSN： 0043-1354

年卷期： 2024 年 249 卷

页码：

收录情况： SCI

摘要： The forest nitrate cycle is a crucial part of the watershed nitrate load but has received limited attention compared to that of agricultural and residential land. Here, we analyzed the status and sources of riverine nitrate fluxes and identified the characteristics and contribution of forest nitrate loss to the riverine system in a mid-high latitude forested watershed using monthly field sampling and a modified Soil and Water Assessment Tool (SWAT) with enhanced forest nutrient cycle representation. The results indicate that nitrate losses in the headwater stream and downstream exhibit different seasonal characteristics. The nitrate losses in the headwater stream show a bimodal pattern due to lower temperatures and snowmelt runoff. Redundancy analysis (RDA) revealed that, unlike nitrogen (N) fertilizer-induced nitrate loss in the rainy season, forest loss has a positive effect on headwater stream nitrate concentration during the snowmelt season. The modified SWAT was then utilized to simulate nitrate losses in forest lands. The forest nitrate export per unit area of the headwater stream (1.58 +/- 1.78 kg/ha/yr) was observed to be higher than that of the downstream (0.67 +/- 0.74 kg/ha/yr) due to high snowmelt and mineralization of active organic N. At watershed scale, forest lands contributed 8.18 +/- 3.94 % of the total nitrate losses to the water system in the headwater watersheds during the snowmelt season, representing the highest level within the entire basin. A comparison with forest streams in similar low-temperature conditions worldwide revealed that increasing nitrate loss occurred after extreme cold weather or soil freezing events, with an average increment of 6.32 kg/ha/yr. Therefore, forest nitrate losses should be better characterized and included in future watershed N budgets in low-temperature regions, which might help to reduce the N budget uncertainty and improve watershed management.

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