We used a repeated-measures factorial field experiment to ask whether the arrangement and stability of leafy debris affect the density of chironomids in leaf packs in dynamic, streambed landscapes. We replaced natural debris in 24 streambed landscapes with leaf packs suspended from wires that snagged organic debris as it moved downstream. We arranged 64 wires (each with 3 leaf packs) in each landscape so that they were distributed among 8 large (aggregated) or 64 small (fragmented) patches. We manipulated landscape stability by removing accumulated debris from 0% (stable), 50% (semi-stable), or 100% (unstable) of the patches in each landscape 3 d after a flood. We determined chironomid density in leaf packs 2 d before the flood, 3 d after the flood, and 5 d after manipulating stability (8 d after the flood). We mapped the debris in each landscape and used multiple regression to evaluate the effect of landscape characteristics on density. Mean patch area was significantly smaller, and the number of patches, landscape perimeter, and landscape perimeter to area (P:A) ratio were significantly greater in fragmented than in aggregated landscapes. Chironomid density was significantly higher in fragmented than in aggregated landscapes and significantly lower in all landscapes after the flood. Density was ∼30% higher in unstable landscapes than in stable or semi-stable landscapes after debris removal. Density was negatively correlated with patch area, and debris accumulation may have caused patches to lose their value as refugia by making patches too large for chironomids to enter. Thus, disturbances that maintain fragmented patch arrangements with small patches and high landscape P:A ratios may be critically important for retention of individuals and to population persistence in dynamic landscapes.
You have requested a machine translation of selected content from our databases. This functionality is provided solely for your convenience and is in no way intended to replace human translation. Neither BioOne nor the owners and publishers of the content make, and they explicitly disclaim, any express or implied representations or warranties of any kind, including, without limitation, representations and warranties as to the functionality of the translation feature or the accuracy or completeness of the translations.
Translations are not retained in our system. Your use of this feature and the translations is subject to all use restrictions contained in the Terms and Conditions of Use of the BioOne website.
Vol. 23 • No. 1