The effects of riparian forest management on the freshwater environment: a literature review of best management practice

摘要

National Forests and Water Guidelines require the establishment of riparian buffers to help protect the freshwater environment from disturbance by silvicultural operations on the adjacent land. The main functions of the riparian buffer are considered to be sediment removal and erosion control, protection of water quality. moderation of shade and water temperature, maintenance of habitat structural diversity and ecological integrity, and improvement of landscape quality. This review paper assesses how these functions are affected by the design and management of the riparian forest zone, with a focus on the width of the buffer, the structure of the vegetation and species choice. It is not possible to specify a definitive riparian buffer width that will protect the freshwater environment front every potential threat. Forestry agencies usually recommend widths between 10 and 30 in. Buffer widths towards the lower end of this scale tend to protect the physical and chemical characteristics of a stream, while the maintenance of ecological integrity requires widths at the upper end. In terms of structure and species, the benefits are greatest where the riparian buffer replicates native riparian woodland with an open canopy of mixed species of varied age class. The optimum level of shade is difficult to quantify but limited work suggests that a good balance is achieved where around 50% of the stream surface is open to sunlight and the remainder covered by dappled shade. Within the management of riparian woodland there is a need to consider a stream's sensitivity and intrinsic value. Some sites will benefit from active intervention such as thinning, coppicing or pollarding, while others will be favoured by a hands-off approach. Long-term continuity of management is important to ensure that the potential benefits to the freshwater environment are realised.