Hooldusraietega kaasnevad negatiivsed tegurid ja nende leevendamis võimalused
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Kuupäev
2016
Kättesaadav alates
Autorid
Ajakirja pealkiri
Ajakirja ISSN
Köite pealkiri
Kirjastaja
Abstrakt
Hooldusraied aitavad suurendada metsast saadavat kasumit. Need raied mõjutavad kogu
metsa ökosüsteemi ning sealhulgas elustikku, patogeenidele levikut ning süsinikuringet.
Hooldusraiete poolt tekitatud muutused metsades võivad soodustada paljude liikide
elutingimusi ja olla metsa tervislikule seisundile positiivsed, kuid nendega võivad kaasneda
ka ebasoodsad mõjud. Bakalaureusetöö eesmärgiks oli teada saada, millised negatiivsed
mõjud kaasnevad hooldusraietega ning kuidas neid tegureid oleks võimalik leevendada.
Sellele küsimusele vastuse saamiseks uuriti järgnevas lõputöös kogu maailma boreaalse- ja
parasvöötme kohta avaldatud teaduskirjanduse tulemusi, eeskätt keskendudes hooldusraiete
negatiivsetele mõjudele. Kirjanduses avaldatu näitas, et suurele osale elustikust on harvendus
positiivse mõjuga, kuid on ka tundlikke liike, kelle elutingimused halvenevad hooldusraiest
tulenevatest häiringutest. See oli sageli põhjustatud puurinde liigse ühtlustumise, surnud ja
surevate puude kadumise või vähenenud varjulisuse tõttu. Üldpõhimõttena võis uuringute
põhjal järeldada, et suurel pinnal ühesuguste majandamisvõtete kasutamine vähendab mitmete
liikide elupaikade arvu ning soovitav on kasutada mitmekesisemaid majandamisviise.
Metsakahjustuste uuringud näitasid, et harvendamine muudab puid vastuvõtlikumaks
seenpatogeenidele ja putukakahjustustele ning suurendab neist tuleneva suremuse kasvu, eriti
esimestel aastatel peale raiet, kui puud polnud jõudnud veel raie tekitatud mehaanilistest
vigadest taastuda. Nende tegurite leevendamiseks soovitasid uuringud teha raieid talvisel ajal
või kasutada selleks spetsiaalseid vahendeid nii väikese- kui ka suurediameetriliste kändude
hooldamisel. Puistu liigilist mitmekesisust tuleks ka hoida, kuna üheliigilised puistud on
vastuvõtlikumad negatiivsetele mõjudele. Hõredamat puistut eelistas ka põder, kes on oma
tegevusega võimeline puistut kahjustama. Harvendamine vähendas lisaks selle ka metsasisest
süsinikuvaru ning puidu kvaliteeti. Kirjanduse põhjal võib kokkuvõtlikult öelda, et
harvendusega kaasnevad negatiivsed tegurid, mida peab metsade majandamisel kindlasti
arvesse võtma.
Thinning is essential part of forest management. However, these manmade changes in forest ecosystem have effect on biodiversity, infection and carbon stocks. These changes may be beneficial economically and support the lives of many species, but they can also have negative effect on forests. Research objective was to find out what these negative aspects are and how to mitigate them. Following study uses global research to summarize negative effects of thinning and looks for ways to mitigate them. Results showed that thinning is indeed beneficial for a lot of species, but there are also sensitive species that respond negatively to thinning. This was mostly caused by reduction of structural variety, cover and dead trees. It is important to keep different structure elements in forests when it comes to biodiversity. Absence of variety is negative for species diversity and before thinning it was advised to use territorial strategy that takes its species needs into consideration. Research showed also that thinning has ability to make stands more vulnerable to fungus infection and insect damage. Therefore rate of mortality was increased especially in first few years because trees did not have time to recover from mechanical damage done by machines. These aspects can be reduced when thinning takes place in winter or when stumps are worked with special tools. Variety of tree species is also beneficial when it comes to keeping stand safe from infections. Thinned forests were also preferred by moose. Thinning had negative effect on wood quality and carbon stock as well. These results show that thinning has some negative effects and they should be considered when used in management plans.
Thinning is essential part of forest management. However, these manmade changes in forest ecosystem have effect on biodiversity, infection and carbon stocks. These changes may be beneficial economically and support the lives of many species, but they can also have negative effect on forests. Research objective was to find out what these negative aspects are and how to mitigate them. Following study uses global research to summarize negative effects of thinning and looks for ways to mitigate them. Results showed that thinning is indeed beneficial for a lot of species, but there are also sensitive species that respond negatively to thinning. This was mostly caused by reduction of structural variety, cover and dead trees. It is important to keep different structure elements in forests when it comes to biodiversity. Absence of variety is negative for species diversity and before thinning it was advised to use territorial strategy that takes its species needs into consideration. Research showed also that thinning has ability to make stands more vulnerable to fungus infection and insect damage. Therefore rate of mortality was increased especially in first few years because trees did not have time to recover from mechanical damage done by machines. These aspects can be reduced when thinning takes place in winter or when stumps are worked with special tools. Variety of tree species is also beneficial when it comes to keeping stand safe from infections. Thinned forests were also preferred by moose. Thinning had negative effect on wood quality and carbon stock as well. These results show that thinning has some negative effects and they should be considered when used in management plans.
Kirjeldus
Märksõnad
bakalaureusetööd, raie, harvendusraie, hooldusraie