The roles of local disturbance history and microhabitat parameters for stream biota

摘要: The identification of factors that cause the patchy distribution organisms in space and time within natural ecosystems is a central concern ecology. In running waters, disturbance by bed-moving flows has been recognized to contribute this patchiness, but mechanisms behind process are still poorly understood. Recent research revealed most spates floods small-scale mosaic stream bed patches different substratum stabilities (sediment scour, sediment deposition, stable patches). aim present was investigate separate combined roles “local history” microhabitat parameters determining distributions benthic (bacteria, algae invertebrates). The first three chapters my thesis bacteria, invertebrates after two gravel-bed streams, Schmiedlaine Bavaria, Germany, Kye Burn South Island New Zealand. final chapter describes manipulative experiment which disturbed manually obtain better understanding how history affects organisms. Local movement patterns during several disturbances were determined using metal-link scour chains. same chains also used as reference points when selecting for manipulation experimental disturbance. Quantitative samples collected times from random sites before each fill addition sampling invertebrates, we measured primary production under controlled conditions both streams bacterial Burn. For site, abiotic biotic known influence biota, e.g. water depth, composition, near-bed current velocity standing stock particulate organic matter (POM). The results correlative studies suggest local plays an important role invertebrates. Disturbance related all organism groups directly indirectly (via effects on habitat parameters) significant parameter previously undetected cases, indicating strong interaction between explored parameters. Bacterial microdistribution at least often any other nine studied (except surface area sampled stones Schmiedlaine). relationships with algal not quite strong. flood-prone Schmiedlaine, characteristics history. relatively more Burn, there no direct influences algae. Substratum characteristics, POM highest numbers relationships. However, influenced indirect particularly Primary always similar across stability types streams. Averaged invertebrate only than depth distributions. Further size epilithic biomass. The observed densities investigated largely accordance previous These show bacteria appear be invertebrates. The findings generally supported those research, lending weight generality results. Local often, followed velocity, total density stone. types. contrast study solely stone area. had via distribution. distribution, second-highest number velocity. Indirect similarly common confirming better- parameters. The provide substantial evidence important, unrecognised factor contributing time.