AIMS_SE_Approach2_PaintRock_EEAS

This study was conducted in the Paint Rock watershed (outlet: 34.9686, -86.1650) which lies on private land in Jackson County, AL, near Estillfork. It drains a non-perennial tributary to Burks Creek and spans 2.97 km² of deciduous forest in the Cumberland Plateau. Elevation ranges from 211 to 550 m, and the watershed feeds into the Paint Rock River (Tennessee basin). The climate is humid subtropical, with mean January and July temperatures of 4.4°C and 25.4°C, and annual precipitation of 1,390 mm. This watershed was included in a seasonal sampling survey (AIMS Approach 2) conducted from January 2022 to January 2024 as part of the Aquatic Intermittency effects on Microbiomes in Streams (AIMS) Project. The field team collected data on hydrology, biogeochemistry, and microbial ecology at 7 sites within each watershed. Site selection balanced three priorities: (1) targeting locations with existing long-term monitoring infrastructure; (2) including sites near springs and tributary confluences; and (3) capturing variability in drainage area and topographic wetness index (TWI), which are linked to flow permanence. At each site, samples of water (when present), biofilm, leaf litter, and sediment were collected. Microbial enzyme activities were measured to assess organic matter decomposition (β-glucosidase, phenol oxidase, peroxidase) and nutrient mineralization (N-acetylglucosaminidase for nitrogen, phosphatase for phosphorus). Enzyme activities were quantified using fluorometric methods with 4-methylumbelliferyl (MUB) substrates or colorimetric methods using 4-nitrophenyl (pNP) and L-DOPA substrates.本研究于美国阿拉巴马州杰克逊县埃斯蒂尔福克斯附近的私人土地上的佩恩特罗克流域（出水口坐标：34.9686, -86.1650）开展。该流域为汇入伯克斯溪（Burks Creek）的间歇性支流，流域面积达2.97 km²，覆盖坎伯兰高原的落叶阔叶林区域，海拔范围为211至550米，最终汇入田纳西流域的佩恩特罗克河。其气候类型为亚热带湿润气候，1月与7月平均气温分别为4.4℃与25.4℃，年降水量为1390毫米。该流域被纳入2022年1月至2024年1月开展的季节性采样调查（AIMS方法2），该调查作为“溪流微生物组的水生间歇效应（Aquatic Intermittency effects on Microbiomes in Streams, AIMS）”项目的组成部分。野外采样团队在该流域内的7个采样点采集了水文、生物地球化学及微生物生态学相关数据。采样点位的选取平衡了三项优先原则：（1）优先选取已具备长期监测基础设施的点位；（2）涵盖泉水及支流汇口附近的点位；（3）覆盖汇水面积与地形湿度指数（Topographic Wetness Index, TWI）的变异性——二者均与水流持久性相关。在每个采样点，当存在水体时，研究人员采集了水样、生物膜、落叶凋落物及沉积物样本。为评估有机质分解（β-葡萄糖苷酶、酚氧化酶、过氧化物酶）与养分矿化过程（氮相关的N-乙酰氨基葡萄糖苷酶、磷相关的磷酸酶），团队测定了微生物酶活性。酶活性检测采用以4-甲基伞形酮（4-methylumbelliferyl, MUB）为底物的荧光法，或以4-硝基苯基（4-nitrophenyl, pNP）与L-多巴（L-DOPA）为底物的比色法。