DISSERTATION RESEARCH: Impacts of human activities on aquatic insect emergence and effects on terrestrial food webs

落入溪流的树叶为许多水生生物提供了食物。同样，溪流也为陆地环境贡献了物质。水生昆虫以幼虫的形式在水中度过大部分时间，但成年后会飞入森林，为蜘蛛、蜥蜴、鸟类和蝙蝠等陆地捕食者提供重要的食物。因此，溪流和它们邻近的森林紧密相连。人类活动可能会影响这些生态系统之间能量和物质的相互运动。我们早就认识到人类活动对物质从风景到溪流的移动的影响。例如，众所周知，密集的农业活动通过减少敏感的水生昆虫、有利于昆虫对污染的耐受性、营养物质的增加以及集约化农业产生的低氧条件，改变了溪流中水生昆虫的群落组成。这些与土地利用有关的水生昆虫群落的变化可以反映在出现的昆虫的种类和数量以及它们向陆地的移动上，从而对陆地捕食者及其猎物造成后果。然而，关于土地利用变化如何影响材料从溪流到陆地的运输，人们知之甚少。什么？S·莫尔，我们关于水生昆虫向陆地移动的大部分知识来自于对温带森林地区的研究，这让我们在理解河流到陆地的物质移动如何影响人类改变的系统中的陆地食物网方面留下了空白，尤其是在热带地区。这项拟议的研究包括广泛的本科生培训和指导，通过NSF GK-12计划进行的教师培训，社区推广，以及对拉丁美洲研究生的支持。哥斯达黎加的初步研究表明，水生昆虫密度和生物量以及河边陆生蜘蛛密度随着农业土地利用强度的增加而增加，水生昆虫的群落组成随着土地利用梯度的变化而变化。通过实地实验，该项目旨在了解这些变化背后的机制，以及对陆地昆虫密度和群落组成的影响。这项计划中的实验将操纵水生昆虫在四条森林覆盖的溪流和四条农用土地密集的溪流登陆，并量化蜘蛛和它们的陆地猎物的反应。该方法将测试土地利用对水生昆虫的影响是否是观察到的河边蜘蛛数量随着农业土地使用的增加而增加的机制，并将测试土地利用对水生昆虫的影响是否通过陆地食物网传播，从而影响蜘蛛的陆地昆虫猎物。

Leaves falling into streams provide food for many aquatic organisms. Likewise, streams contribute materials to the terrestrial environment. Aquatic insects spend most of their life in the water as larvae, but emerge as adults and fly into forests, providing important food for terrestrial predators such as spiders, lizards, birds, and bats. Streams and their adjacent forests are thus intimately connected. Human activities may affect this reciprocal movement of energy and materials between these ecosystems. We have long recognized the effect of human activities on the movement of materials from the landscape to streams. For instance, intense agricultural activities are known to change the community composition of aquatic insects in streams by decreasing sensitive aquatic insects and favoring insects tolerant to pollution, increased nutrients, and the low oxygen conditions resulting from intense agriculture. These land-use-associated changes to aquatic insect communities could be reflected in the kinds and amount of insects emerging and their movement to land, with consequences for terrestrial predators and their prey. Little is known, however, about how land use change could affect the transport of materials from streams to land. What?s more, most of our knowledge on the movement of aquatic insects to land comes from research in temperate, forested areas, leaving a gap in our understanding of how the movement of materials from streams to land affects terrestrial food webs in human-altered systems, particularly in the tropics. The proposed research integrates extensive undergraduate training and mentoring, teacher training through the NSF GK-12 program, community outreach, and support for a Latin American graduate student.Initial research in Costa Rica suggests that aquatic insect density and biomass, and streamside terrestrial spider density increase with the intensity of agricultural land-use, and the community composition of aquatic insects changes across a land use gradient. Using a field experiment, this project aims to understand the mechanisms behind these changes, and the consequences for terrestrial insect density and community composition. The planned experiment will manipulate the movement of aquatic insects to land at four forested streams and four streams with intensive agricultural land use, and quantify the response of spiders and their terrestrial prey. The approach will test whether land use effects on aquatic insects is the mechanism for the observed increase in riparian spiders with increasing agricultural land use, and will test whether land-use effects on aquatic insects propagate through the terrestrial food web to affect terrestrial insect prey of spiders.