亚热带典型农林混合流域河岸带景观格局对河流磷输出的影响

为进一步明确流域河岸带景观尺度范围差异性及对河流磷(P)输出的影响,量化解析河岸带尺度下景观与河流P之间的关系。以亚热带典型农林混合流域为研究对象,基于长期水文、水质监测数据,利用冗余分析明确不同河岸带尺度景观格局特征与不同水文季节河流P浓度的关系,并采用变点分析量化导致丰水期、平枯水期河流P浓度突变的核心景观指数的阈值范围。结果表明:(1)河岸带景观格局对河流P浓度的影响具有显著的空间尺度性特征,300,400 m分别是影响丰水期和平枯水期河流磷浓度变化的关键临界尺度。(2)河岸带居民地斑块最大斑块面积指数(LPI_居)和农田斑块分散指数(SPLIT_农)分别是影响平枯水期和丰水期河流磷浓度的核心景观格局特征指数,当SPLIT_农＞15.76~23.83,LPI_居＜28.8%~36.5%时,能够降低河流P浓度的突变概率。研究结果可为以缓解P面源污染为目标的土地利用和景观规划提供重要理论依据。

Influences of Riparian Landscape Pattern on River Phosphorus Output in Typical Subtropical Agroforestry Mixed Watershed

In order to further clarify the difference of riparian landscape scale and its impact on river phosphorus (P), the relationship between landscape and river P at riparian scale was analyzed quantitatively. Based on long-term hydrological and water quality monitoring data, this study used redundancy analysis to clarify the relationship between landscape pattern characteristics at different riparian scales and river P concentrations in different hydrological seasons. Change point analysis was used to quantify the threshold range of the core landscape metrics leading to the abrupt change of river P concentrations in wet and dry seasons. The results showed that:(1) The effects of landscape pattern buffer zones on river P concentration have significant spatial scale characteristics, 300 and 400 meters are the critical scales affecting river P concentration in wet season and dry season, respectively. (2) SPLIT of farmland patches (SPLIT_farm) and LPI of residential land patches (LPI_res) were the core landscape pattern characteristic indexes that affect river P concentration in dry season and wet season respectively. When the SPLIT_farm exceeded 15.76~23.83 and LPI_re was less than 28.8%~36.5%, the abrupt probability of P concentrations in wet and dry rivers can be reduced respectively. The results can provide important theoretical basis for land use and landscape planning aiming at mitigating P non-point source pollution.