Anthropogenic controls on large wood input, removal and mobility: Examples from rivers in the Czech Republic

摘要

Anthropogenic controls on large wood in streams and rivers, and its wider geomorphological and ecological consequences, have come under increasing scrutiny in recent years. However, while the anthropogenic controls on riparian vegetation have been extensively studied, the direct effect of removal of wood from rivers and its mobility have not been widely assessed. This paper specifically considers anthropogenic input, removal and mobility of large wood in rivers. The analysis is based on data from ten semi-natural rivers in the Czech Republic. An increase in number of large wood pieces because of anthropogenic activity was documented in all of the river reaches studied. Anthropogenic activity was responsible for on average 9 per cent of large wood pieces within rivers, rising to over 20 per cent in extreme cases. Large wood unintentionally recruited to rivers by human activity was of smaller dimensions than natural large wood and therefore does not significantly contribute to total large wood volume. Deliberate removal of large wood was also a significant process and in some river reaches natural large wood loads have been reduced by almost 50 per cent. Large wood removal tends to target the largest wood pieces. All pieces of wood bearing signs of anthropogenic impact were susceptible to transport. This may have a negative effect on the public perception of in-channel large wood. Despite the fact that the river reaches examined were classified as natural or semi-natural (based on channel morphology and riparian vegetation), the human impact on large wood loads and dynamics (mobility) was surprisingly high. The results suggest that determination of natural large wood loads and dynamics in rivers flowing through the Central European cultural landscape remain difficult to quantify.