土地利用/覆盖对感潮河流碳分布格局的影响
Land Use Drives the Spatial Patterns of Carbon in a Tidal River Basin
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摘要: 河流是陆海碳输送的主要通道,在全球碳循环中发挥着重要作用。随着城市化进程的加快,河流碳分布格局将会改变。本研究于2019年11月(枯水期)和2020年7月(丰水期)对珠江三角洲地区潭江流域干支流开展有机碳、无机碳等水质指标监测,基于土地利用数据划定流域分区和沿河岸不同距离(500、1000、1500、2000和2500m)缓冲区,采用差异性分析、Pearson相关性分析、冗余分析(RDA)等手段,分析土地利用方式对感潮河流碳浓度分布格局的影响。结果表明:①水体TOC、TIC平均值分别为3.5±0.92 mg/L、2.61±2.10 mg/L,区域TOC、TIC浓度存在时空分布差异,丰水期TOC、TIC浓度均显著高于枯水期,感潮区TOC浓度显著高于非感潮区,建设用地占比高、林地占比低的核心城市生态区河流的TOC浓度较高。②1500 m缓冲区是流域内景观格局对碳浓度变化作用最强的河岸带宽度,对碳的总解释率为20.03%;城市区域的排放对有机物浓度影响严重,耕地、林地的拦截吸附作用使得河流中的有机碳浓度相对较低,大面积分布的坑塘、养殖池等对河流中营养盐浓度的影响较大。③水体中TOC、TIC浓度与其他水质指标也存在相关关系,温度越高,水域碳浓度越高;碳、氮、磷等营养盐浓度间普遍正相关。因此,加强缓冲区坑塘、养殖池等的污染控制以及建成区与河流间绿化建设,是控制潭江水体碳浓度以及入海碳通量的关键管理手段。Abstract: Carbon transfer along the land-river-ocean continuum is a key component of the global carbon cycle. Combined pressures from coastal development and land use change are dramatically altering carbon dynamics in tidal rivers. To explore the carbon patterns in subtropical tidal rivers, we collected 27 water samples from the mainstream and tributaries of the Tanjiang River in November 2019 (dry season) and July 2020 (wet season), and detected the concentrations of total organic carbon (TOC), total inorganic carbon (TIC) and general water quality indices. In addition, the characteristics of land use and landscape patterns in various regions and multiscale buffer zones (500, 1000, 1500, 2000 and 2500 m) were analyzed. Pearson correlation analysis, redundancy analysis (RDA) and other methods were used to quantify the impacts of land use change on the concentrations of carbon. The results showed that: (1) The overall mean concentrations of TOC and TIC were 3.5±0.92 mg/L and 2.61±2.10 mg/L, respectively, with significant spatial and temporal variability. Both TOC and TIC were significantly higher during the wet season than during the dry season. The high TOC was easily observed within the tidal reach of the core urban ecological area, which had a high proportion of urban land use and low proportion of forest land use. (2) The landscape pattern index of the buffer zone at different spatial scales had a good explanatory degree for water quality, and the landscape structure of the buffer zone at 1500 meters had the strongest explanatory ability for carbon concentration (20.03%). The sewage-dominated urban river network had more organic matter, while the rural branch had less organic matter due to plant interception and absorption. Surrounding ponds accounted for the high nutrient concentrations in rivers. (3) Meanwhile, water temperature, salinity and nutrients were related to carbon concentration. This research reveals that decreasing the carbon concentration in rivers and flux to estuaries can be achieved by strengthening management policies for land use patterns in buffer zones, especially those regarding pollution control for the surrounding ponds, and creating green belts between urban construction and rivers.
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Key words:
- land-use change /
- Tanjiang River basin /
- total organic carbon /
- total inorganic carbon
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