Water Quality, Biodiversity and Codes of Practice in Relation to Harvesting Forest Plantations in Streamside Management Zones

[摘要] Streamside management zones (SMZs) are special landscape units that include riparian areas and adjacent lands that mitigate the movement of sediment, nutrients and other chemicals from upland forest and agricultural management areas into streams. The size, shape, and management of SMZs are governed by various combinations of economic, ecological, and regulatory factors. Although SMZs used around the world have a wide range of widths, in many cases they are similar at 5-20 m. Streamside management zones are important barriers or treatment areas that protect water resources from non-point source pollution. Vegetation and the geomorphic characteristics of SMZs result in infiltration, filtering, and deposition from sediment- and nutrient-laden water flowing off intensively managed forestry, agriculture, and urban lands. The effectiveness of SMZs for trapping sediment depends upon the velocity of water flow, size distribution of sediments, slope and length of slope above the SMZ, slope and length of the SMZ itself, depth of water flow into the SMZ, and vegetation characteristics such as type, density, and height. Nutrient removal is a function of SMZ width, runoff water residence time in the SMZ, the vigor of SMZ vegetation, and the amount of runoff water infiltrated into the soil during its transit of the SMZ.This report examines important SMZ processes and illustrates them with examples from forest management operations and agriculture. A number of international case studies are used to illustrate the effectiveness of SMZs in protecting water quality and biodiversity. The report provides a review of codes of forest practice internationally as they relate to SMZs, with a focus on Australia, New Zealand, and the USA. Some codes from Canada, Europe and Asia are also cited. This report includes an emphasis on an aspect of SMZs that has previously not been reviewed to this extent, i.e. the effects of harvesting forests within SMZs. A literature search on harvesting in SMZs highlighted the limited amount of scientific research on harvesting in SMZs in the farm forestry (agro-forestry) context. Scientific research on harvesting activities in SMZs is largely confined to large plantation forest estates. Our review indicates that: 1. Harvesting of tree stands within SMZs, if conducted carefully using best management practices (BMPs), can occur without substantial detrimental effects on water quality. 2. Not only can there be a lack of a within-SMZ harvesting effects on water quality, but the establishment of SMZ plantations in an agricultural landscape can provide considerable water quality, biodiversity and other farm benefits. 3. Managers of agricultural landscapes can be reassured that forested and grassed SMZs can be successfully integrated into farming operations for multiple benefits. 4. Use of SMZ plantations are a realistic option for agriculture and forestry, because they can be established and harvested with little risk to water quality.

[发布日期] 2012-01-13 [发布机构] CSIRO

[学科分类] 地球科学(综合)