ABSTRACT

Despite near-extinction in the nineteenth century, after efficient restoration measures the population of Eurasian beaver (Castor fiber L.) in Latvia currently is viable and growing. While the ecological effect of the species on water quality and biodiversity is generally positive, the high number of animals in production forests often creates challenges for management. Drainage ditches are among the most favoured habitats of beavers resulting in flooded stands, reduced tree growth and economical losses. The aim of the study was to evaluate the chemical properties of water in forest drainage ditches, affected by beaver activity, and their changes after the dam removal. Chemical composition of surface water in ditches was analysed in sampling points above dam, below dam and in the ditch itself after removal of the dam; results compared to pristine beaver site nearby on a small stream. Results did not show significant differences between concentrations above and below dams. After removal of the dams, significant increase in DOC, N-NO₃ ^-, N-NH₄ ⁺ and TSS concentrations and significant decrease in TP concentrations were observed in some of the sites. Observed concentrations of all measured parameters were significantly lower in pristine beaver site than in beaver sites on drainage ditches.

摘要

尽管在19世纪濒临灭绝，但经过有效的恢复措施后，欧亚海狸的种群（蓖麻纤维L.）在拉脱维亚目前是可行的并且正在增长。虽然该物种对水质和生物多样性的生态影响总体上是积极的，但生产林中的大量动物通常给管理带来挑战。排水沟是海狸最喜欢的栖息地之一，会导致林分泛滥，树木生长减少和经济损失。该研究的目的是评估受海狸活动影响的森林排水沟中水的化学性质及其在拆除大坝后的变化。在拆除大坝后，在大坝上方，大坝下方和沟渠本身的采样点分析了沟渠中地表水的化学成分；结果与附近一条小溪上的原始海狸遗址相比。结果未显示大坝上方和下方浓度之间的显着差异。₃ ^-，N-NH ₄ ⁺和TSS浓度和TP浓度显著减少在一些网站的观察。原始海狸部位的所有测量参数的观测浓度均明显低于排水沟中的海狸部位。