Påverkan på kantzoner i Fylleåns avrinningsområde efter föryngrings-avverkning och återbeskogning

Sammanfattning: Riparian buffer zones have become an established concept in the forestry industry, meant to preserve species richness, stabilize the shoreline, and prevent leakage of nutrients and sediments to forest streams and lakes. It is a common perception in the Swedish Forest Agency in Halland that the handling of buffer zones in the forestry industry is insufficient to protect the freshwater streams and lakes in the forest. This review attempts to assess the impact on riparian buffer zones in proximity of recently clear-cut forest areas in Fylleåns catchment basin. 25 different locations near clear-cuts by streams was randomly selected. These locations were examined when it comes to buffer zone width, composition of the zone, deforested parts of the zone, skidding in the zone or in the groundwater discharge area, and wind felled trees in the zone. The parameters were chosen based on targets for retention that were developed by SFA together with the forestry industry and other organisations. Of the total length along streams 76% had at least some width of buffer zone, while 24% was entirely lacking buffer zone. In the total buffer zone area within 10 metres from the stream, 39% was deforested. However, all of the deforested areas had consisted of planted spruce trees. Of the deforested area, 41% had been replanted with new spruce, indicating that it was not intended to become a buffer zone but would instead be deforested again in the future. Of the total stream length replanted with spruce, 64% was planted all the way down to the water. The existing buffer zones were mixed stands consisting mostly of spruce, both within 10 metres of the stream (44%) and further upland. Birch was the second most common tree, followed by pine. Skidding was common, occurring in 52% of the locations. The majority of track damages (58%) were in discharge areas within 10 metres from the water, 6% were within 10 metres that was not discharge areas, and 36% of track damages were in discharge areas further from the water. Wind felled trees was found in 88% of the localities, with a total of 164 wind felled trees. 8 of the sites had 63% of the total number of wind felled trees. The site with most trees felled had 17 of them, while most sites had only a fraction of the trees wind felled in the buffer zones. It is concerning that such a large proportion of the trees by the streams consisted of planted spruce, but encouraging that no significant amount of deciduous trees had been felled. Most of the deforested zone area (59%) had not been replanted with spruce, but it remains to be seen if it is allowed to form a buffer zone in the long run. Wind felled trees could pose a problem, but mostly in the thinner stands that seems more susceptible to wind. A smaller amount of wind felled trees can also benefit biodiversity in the zones. The frequent occurrence of skidding in wet areas is a clear sign that improvements are much needed. The targets for retention that were agreed upon by both SFA and the forestry industry are still fairly new. Hopefully they can decrease the magnitude of these problems in the future, and lead to better, more established buffer zones.