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

Adolfsson, Percy (2017) BIOK01 20171
Degree Projects in Biology
Abstract
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... (More)
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. (Less)
Popular Abstract (Swedish)
Lämnas det träd vid vattendrag efter en avverkning?

Vid skogsbruksåtgärder ska det lämnas kantzoner (trädbevuxna ytor) som miljöhänsyn vid vattendrag, helst ska dessa ytor bestå till stor del av lövträd. Även på våta marker ska det lämnas träd. Det är också meningen att man inte ska köra med maskiner i kantzonerna eller på våta marker. Förekomsten av kantzoner kontrolleras med jämna mellanrum av Skogs-styrelsen, men det görs på landsdelsnivå. Skogsstyrelsen i Halland var nyfikna på hur det ser ut på mer lokal nivå, därför har jag inventerat 25 olika lokaler där en avverkning har skett vid Fylleåns vattendrag och biflöden.

Områdena togs fram med hjälp av en databas för avverkningar och ett kartprogram. Sedan inventerades områdena... (More)
Lämnas det träd vid vattendrag efter en avverkning?

Vid skogsbruksåtgärder ska det lämnas kantzoner (trädbevuxna ytor) som miljöhänsyn vid vattendrag, helst ska dessa ytor bestå till stor del av lövträd. Även på våta marker ska det lämnas träd. Det är också meningen att man inte ska köra med maskiner i kantzonerna eller på våta marker. Förekomsten av kantzoner kontrolleras med jämna mellanrum av Skogs-styrelsen, men det görs på landsdelsnivå. Skogsstyrelsen i Halland var nyfikna på hur det ser ut på mer lokal nivå, därför har jag inventerat 25 olika lokaler där en avverkning har skett vid Fylleåns vattendrag och biflöden.

Områdena togs fram med hjälp av en databas för avverkningar och ett kartprogram. Sedan inventerades områdena efter vissa målbilder som Skogsstyrelsen och skogsbolagen har tagit fram gemensamt, som ska fungera som riktlinjer för god miljöhänsyn. Det kontrollerades bland annat om där fanns kantzoner vid vattendraget, hur stora de var, vilka trädslag de bestod av, om något hade avverkats nere vid vattnet, och om där fanns några körskador. Det noterades också hur vanligt det var med vindfällda träd i kantzonerna.

Om man lade ihop sträckan längs vattendragen för alla områden så saknades det kantzon ända ned till vattnet på en fjärdedel av sträckan. Sammanlagt hade nästan 40 % av den totala ytan nära vattendrag avverkats. Dock bestod alla ytorna som avverkats nästan helt och hållet av granskog; bara enstaka lövträd hade huggits ned. Visserligen hade delar av de avverkade ytorna sedan återplanterats med gran när de borde ha fått bli lövskog i framtiden. Därför verkar det som att man vill ha ny granskog på de återplanterade ytorna som man kan avverka igen.

Av kantzonerna som hittades så var alla någon sorts blandskog där gran oftast var det vanligaste trädslaget, följt av björk, tall, och sedan klibbal. Tyvärr så var det vanligt med körskador, mer än hälften av områdena hade någon typ av körskada. Vanligast var det med körspår på våt mark nära vattnet, men det förekom också många skador i våta områden längre från vattnet. Vindfällda träd hittades på de flesta lokaler, variationen mellan områdena var dock stor. På de flesta lokalerna hade bara en bråkdel av kantzonsträden blåst ned. Det vanligaste trädslaget som blåste ned var gran, och de glesare kantzonerna verkade mest sårbara för blåst. En viss mängd fallna träd i zonerna är bra, det kan gynna arter av till exempel svampar och insekter.

Resultaten visar att körskador vid vattendrag och på våta marker är ett stort problem vid skogsbruksåtgärder, och att det ofta återplanteras gran för nära vattnet. Det finns också en brist på fungerande kantzoner och de som finns består till för stor del av gran. Några aktiva åtgärder för att återskapa kantzoner verkar inte förekomma alls. Avverkning av lövträd är dock sällsynt, vilket var positivt. Målbilderna för god miljöhänsyn är fortfarande ganska nya, så förhoppningsvis kan de bidra till att minska de här problemen i framtiden.

Handledare: Eva Waldemarson, Johan Persson
Examensarbete 15 hp i Biologi 2017
Biologiska institutionen, Lunds universitet
Skogsstyrelsen Halland (Less)
Please use this url to cite or link to this publication:
author
Adolfsson, Percy
supervisor
organization
course
BIOK01 20171
year
type
M2 - Bachelor Degree
subject
language
Swedish
id
8925682
date added to LUP
2017-09-15 09:52:33
date last changed
2017-09-15 09:52:33
@misc{8925682,
  abstract     = {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.},
  author       = {Adolfsson, Percy},
  language     = {swe},
  note         = {Student Paper},
  title        = {Påverkan på kantzoner i Fylleåns avrinningsområde efter föryngrings-avverkning och återbeskogning},
  year         = {2017},
}