Studying the influence of streamside wet areas - stream indicator results

Riparian zones contain areas of strong hydrological connectivity between land and stream, referred to as variable source areas (VSAs), and are considered biogeochemical control points. However, little is known about whether VSAs influence stream communities and whether this connectivity is affected by forest management. To address this, we used multiple biotic and abiotic indicators to: 1) examine the influence of VSAs on riparian vegetation and stream ecosystems by comparing VSA and non-VSA reaches; and 2) explore how forest management may affect the influence of VSAs on stream ecosystems. Attached are the results for the abiotic and biotic stream-indicators we measured in 7 streams in northern New Brunswick (Canada). In each stream we sampled a VSA and a non-VSA site (14 sites in total). Abiotic indicators include water chemistry and dissolved organic matter quality, which were sampled three different times. Biotic indicators include: a) leaf decomposition, which was calculated by incubating leaf packs in the streams and measuring mass loss, b) composition and function of microbial communities growing on leaf pack biofilms, c) composition and function of benthic macroinvertebrate communities collected by electroshocking, and d) biomass of algae and biofilm, which was calculated by deploying tiles in streams and measuring growth. We detected some significant differences between VSA and non-VSA reaches in the riparian vegetation (greater understory and lower tree density) and stream ecosystem indicators (greater dissolved organic matter aromaticity, microbial biomass, peroxidase activity and collector-gatherer density, and lower dissolved organic carbon concentrations, algal biomass and predatory macroinvertebrate density), which suggests that VSAs may create a more heterotrophic ecosystem locally. However, we show some evidence that forest management activities (specifically, road density) can alter the influence of VSAs and eliminate the differences observed at lower forest management intensities, and that the most hydrologically-connected areas seem more sensitive to disturbance. The research resulting from this data is reported in: Erdozain, M., Emilson, C., Kreutzweiser, D., Kidd, K., Mykytczuk, N., Sibley, P. (in press). Forest management influences the effects of streamside wet areas on stream ecosystems. Ecological Applications.河岸带（riparian zone）涵盖陆地与溪流间具备强水文连通性的区域，这类区域被称为可变源区（variable source areas, VSAs），且被视作生物地球化学控制点。然而目前学界对于可变源区是否会影响溪流群落，以及该水文连通性是否受森林经营活动干扰，仍缺乏足够认知。为解答这一科学问题，本研究采用多种生物与非生物指标开展两项工作：1）通过对比可变源区与非可变源河段，探究可变源区对河岸植被及溪流生态系统的影响；2）解析森林经营活动如何调控可变源区对溪流生态系统的作用。 本数据集附带了我们在加拿大新不伦瑞克省北部7条溪流中测得的非生物与生物溪流指标结果。每条溪流均布设了可变源区与非可变源区采样点位各1处，共计14个采样点位。非生物指标涵盖水体化学性质与溶解性有机物（dissolved organic matter）品质，采样共开展3次。生物指标包括：a）叶片分解（leaf decomposition）速率：通过将叶片包置于溪流中培养并测定质量损失率计算得到；b）叶片包生物膜（biofilm）上附着的微生物群落组成与功能；c）通过电激法（electroshocking）采集的底栖大型无脊椎动物（benthic macroinvertebrate）群落组成与功能；d）藻类与生物膜生物量：通过在溪流中放置载玻片并测定其生长量计算得到。 本研究发现，河岸带的可变源区与非可变源河段间存在多项显著差异：河岸植被方面，可变源区的林下植被更为繁茂，树木密度更低；溪流生态系统指标方面，可变源区的溶解性有机物芳香性、微生物生物量、过氧化物酶活性以及收集-聚集者（collector-gatherer）密度均更高，而溶解性有机碳浓度、藻类生物量以及捕食性大型无脊椎动物密度则更低，这表明可变源区可在局域尺度构建更为异养的生态系统。此外，本研究提供证据表明，森林经营活动（具体为道路密度）可改变可变源区的生态效应，抵消低森林经营强度下观测到的两类河段间差异，且水文连通性最强的区域似乎对干扰更为敏感。 基于本数据集产出的研究成果已发表于： Erdozain, M., Emilson, C., Kreutzweiser, D., Kidd, K., Mykytczuk, N., Sibley, P. (in press). 森林经营调控溪流滨水湿地区对溪流生态系统的影响. Ecological Applications.