2017-01-012024-05-18https://scholars.lib.ntu.edu.tw/handle/123456789/697915Abstract: Biodiversity loss is a pressing concern for ecosystem sustainability, because various theoretical studies and experiments have demonstrated a positive relationship between biodiversity and ecosystem functioning (known as BEF). However, observational studies in natural systems revealed complicated patterns (positive, negative, uni-modal and no clear BEF); these findings are inconsistent with manipulative experimental results. The inconsistency may arise because several unrealistic assumptions have been made in overly simplified experimental design that cannot be justified in natural systems: 1) most of existing experiments consider only single trophic level, 2) environmental conditions are hold constant in experiment, and 3) relative small gradient of diversity was considered. To fill the knowledge gap, we propose to study multi-trophic level diversity effects on ecosystem functioning in the context of natural environmental changes in Feitsui Reservoir in northern Taiwan. Here, for ecosystem functioning, we focus on production (using biomass as a proxy) and trophic transfer efficiency (using predator/prey biomass ratio as a proxy), because these functionings are closely related to ecosystem services that human beings necessarily rely upon! Specifically, we focus on the predator-prey pair, and we investigate their diversity relationship as well as the effects of multi-trophic level diversities on ecosystem functioning. We have the following hypotheses to guide our research. H1: Predator diversity increases with prey diversity, according to the niche diversification theory. H2: Trophic transfer efficiency increases with predator diversity but decreases with prey diversity. This is because predator consumption increases with predator diversity but decreases with prey diversity, and/or, prey defense increases with prey diversity but decreases with predator diversity. As a comparison, we also test the classic hypothesis, H3: Production increases with diversity within a trophic level; the caveat of this hypothesis is that predator-prey interaction is not considered. To begin to tackle this complex issue, we focus on the predator (zooplankton) versus prey (phytoplankton ). Biodiversity quantification includes taxonomic diversity and trait diversity where data are available, through traditional microscopic counting and image analysis. Due to the difficulty in gathering traits data in field, here we focus only on size, as bodysize has been considered as the master trait of organisms. For ecosystem functioning, we focus on production and trophic transfer efficiency across adjacent trophic levels; those processes are critical for foodweb integrity. In addition, the environmental effects (e.g. temperature, light, nutrients, and etc.) will have to be accounted for statistically. Note that we choose to carry out sampling and measurements in the natural environment across a large gradient of environmental conditions as well as diversity to study the BEF, instead of artificially manipulating the gradient by introducing species, to avoid unrealistic setting. Our samplings on zooplankton and phytoplankton as well as various environmental factors in Feitsui Reservoir have been carried out biweekly since 2008. This is the unique long-term ecological monitoring program in Taiwan. To the best of our knowledge, no such kind of high-frequency, comprehensive sampling program exists in other places in Taiwan. More importantly, Feitsui Reservoir provides critical drinking water for Taipei city. Its ecological integrity should be monitored and managed. To understand effects of environmental changes on ecosystem functionings and service of Feitsui Reservoir, the monitoring program should continue.Biodiversitymultiple trophic levelstrait-based approachtrophic interactionsclimate changeecosystem functioningecosystem integrity