AIMS Mountain West approach3 EEAS

This study was conducted in Gibson Jack Creek (42.7843°, -112.448°) a headwater stream located in the Caribou-Targhee National Forest, Pocatello, Idaho. Gibson Jack Creek is a tributary of the Portneuf River, that flows into the Snake River, which ultimately flows into the Columbia River. It drains a large area within the Bannock Range (~ 16.1 km2 from Portneuf confluence) with elevations ranging from ~1500 to 2200 m. The climate is semi-arid steppe, with annual mean temperature ranging from below 0 to 35 °C and precipitation from 38 to 76 cm, 65 % of which is snowfall. The vegetation on the south-facing slope is mostly sagebrush, grass, and juniper, with mostly coniferous trees on the north-facing slop. The bedrock consists of quartzite and shale in the northern portion and limestone in the south and the soil is composed primarily of silt loam, fine sandy clay loam and gravel. This synoptic survey was designed in support of the sampling goals of the Aquatic Intermittency effects on Microbiomes in Streams (AIMS) Project. During June 2023, a field team co-collected datasets characterizing the hydrology, biogeochemistry, and ecology across 50 locations within a sub-drainage of Gibson Jack Creek. The sites were selected to balance multiple competing priorities: (i) strategically targeting existing monitoring infrastructure with long-term data; (ii) including sites near several known springs and tributary junctions; and (iii) including a range of drainage area and topographic wetness index (TWI) values, both of which have been correlated with flow permanence. Briefly, the sites selected based on drainage area and TWI were chosen by binning drainage area into 10 bins and then binning TWI into quintiles within each drainage area bin. We then randomly selected a point in each bin after accounting for points selected based on existing infrastructure, springs, and tributaries; and enforcing a minimum spacing of 100 m between locations. We then made minor adjustments to points to account for field conditions, for instance adjusting locations with respect to a road crossing. Water (if present), biofilm, leaf litter and sediment samples were collected at each locations and the activity of microbial enzymes related to the decomposition of organic matter (β-glucosidase, phenol oxidase and peroxidase) and the mineralization of organic nitrogen (N-acetylglucosaminidase) and organic phosphorus (phosphatase) were determined fluorometrically using 4-methylumbelliferyl (MUB)-linked substrates or colorimetrically using 4-nitrophenyl (pNP)-linked substrates and 3,4-dihydroxyphenylalanine (L-DOPA)-linked substrates.

本研究开展于吉布森杰克溪（Gibson Jack Creek，坐标42.7843°，-112.448°），该溪流为位于爱达荷州波卡特洛市卡里布-塔吉国家森林内的源头溪流。吉布森杰克溪是波特尼夫河（Portneuf River）的支流，最终汇入斯内克河（Snake River），再经斯内克河注入哥伦比亚河（Columbia River）。该溪流的流域覆盖班诺克岭（Bannock Range）内大片区域，自与波特尼夫河汇流处起算的流域面积约16.1平方千米，海拔范围介于1500至2200米之间。区域气候为半干旱干草原气候，年平均气温介于0℃以下至35℃，年降水量38至76厘米，其中65%为降雪。南坡植被以蒿属、草本植物和杜松为主，北坡则以针叶树占优。流域北部基岩以石英岩和页岩为主，南部则为石灰岩；土壤主要由粉砂壤土、细砂质粘壤土及砾石组成。本次概览性调查旨在为《溪流水文间歇对微生物组的影响》（Aquatic Intermittency effects on Microbiomes in Streams, 简称AIMS）项目的采样目标提供支撑。2023年6月，野外作业团队在吉布森杰克溪的一处子流域内的50个采样点位同步采集了涵盖水文、生物地球化学与生态学特征的多套数据集。采样点位的选取兼顾了多项相互冲突的优先目标：（i）优先覆盖具备长期监测数据的现有监测设施；（ii）纳入多个已知泉水及支流汇口附近的点位；（iii）涵盖一系列流域面积与地形湿度指数（Topographic Wetness Index, TWI）的取值——二者均与水流持久性存在相关性。具体而言，基于流域面积与TWI选取的点位需遵循以下步骤：先将流域面积分箱为10个区间，再在每个流域面积区间内将TWI分箱为五分位；随后在扣除已基于现有监测设施、泉水及支流选定的点位后，在每个区间内随机选取一个点位，并确保点位间最小间距不小于100米。之后根据野外实际条件对点位进行小幅调整，例如针对道路穿越区域调整点位位置。在每个点位采集水样（若存在）、生物膜、落叶凋落物及沉积物样本，并通过以下方式测定与有机质分解相关的微生物酶活性（β-葡萄糖苷酶、酚氧化酶与过氧化物酶），以及有机氮矿化相关的N-乙酰氨基葡萄糖苷酶和有机磷矿化相关的磷酸酶：使用4-甲基伞形酮（4-methylumbelliferyl, MUB）偶联底物采用荧光光度法检测，或使用4-硝基苯基（4-nitrophenyl, pNP）偶联底物与3,4-二羟基苯丙氨酸（L-DOPA）偶联底物采用比色法检测。