Aegjärksel raiel loodusliku uuenduse teket mõjutavad tegurid
Laen...
Kuupäev
2014
Kättesaadav alates
Autorid
Ajakirja pealkiri
Ajakirja ISSN
Köite pealkiri
Kirjastaja
Abstrakt
Aegjärkne raie on kõige laialdasemalt kasutatav turberaieviis, mille peamine eesmärk on metsa uuendamine looduslikul teel. Metsa ülarinde ja järelkasvule turvet pakkuvate puude säilitamisega luuakse soodsad uuenemistingimused. Loodusliku uuenduse kordaminek ei ole aga alati tagatud ning see sõltub erinevatest teguritest.
Käesolevas töös on uuritud uuenduse edukust mõjutavaid tegureid sarnaste, kuni 11 aasta vanuste aegjärksete raiealade paaride siseselt nii Harjumaal, kui Lõuna-Eestis, kus üks paarilisest on hästi ja teine halvasti uuenenud. Kokku mõõdeti kahekümne paarilise ehk 40 puistu kohta selle struktuuri, raiet, avatust ning kasvukohaheadust iseloomustavaid tunnuseid. Potentsiaalselt mõjutavate tegurite analüüsimiseks kasutati üldist lineaarset mudelit (GLMM) kolme erineva uuenduse headust iseloomustava tunnuse puhul (okaspuu uuenduse arvukus ha-1, uuenemisindeks, loodusliku uuenduse aastane kogupikkuskasv).
Kõigi uuendusnäitajate puhul oli üksikanalüüsi tulemuste põhjal olulised tunnused (p<0,05) mineraliseerimine, ülarinde puude arv ha-1, puistu avatus, väljaraie maht (tm/ha) ja raiutud puude %. Sealjuures oli mineraliseerimisel kõige olulisem mõju ning võib väita, et ka peamine uuenduse edukust määrav tegur. Koosanalüüsides tulid okaspuu arvukuse puhul oluliseks tunnuseks mineraliseerimine ja ülarinde puude arv. Ülejäänud uuenemisnäitajate puhul lisandus antud tunnustele ka väljaraie maht. Nii täius, kui ka mineraalainete sisaldus ning vahekord erilist mõju uuenduse kordaminekul ei oma. Võib järeldada, et lisaks mineraliseerimisele on uuenduse kordaminekul oluline säilitada ülarinde puid võimalikult optimaalselt ning raiudes rohkem tagavarast.
Uniform shelterwood cuttings system is the most widely used shelterwood method. The main goal of this system is to regenerate forest naturally. Retaining some of the overstory trees will assist regeneration by providing shelter and suitable growing conditions. The success of natural regeneration process is not always quaranteed and will depend on various factors. In current research there have been investigated natural regeneration affecting factors in Harju county and South-Estonia forest sites managed 3 to 11 years ago under uniform shelterwood cuttings system. A total of twenty pairs of sites in which one pair was successfully regenerated and the other one unsuccessfully. Within forty sites there were examined different site characteristics such as cutting and site properties, stand openess and structure. Potentially affecting factors were analyzed using general linear mixed model (GLMM) in three types of different regeneration indicators (conifer regeneration abundance ha-1, regeneration index, annual total growth index). For all regeneration indicators, soil scarification, retained trees ha-1, openness, removed volume (m3 ha-1) and the percentage of removed trees were statistically significant (p<0,05) affecting factors in individual analysis. Scarification had the greatest impact on successful regeneration. In conifer regeneration abundance mixed model, significant factors were also scarification and retained trees ha-1, while for other indicators removed volume (m3 ha-1) was added in the final model. Stocking density, mineral substances content and their ratio were not significally affecting regeneration success. It can be concluded that in addition to soil scarification, retaining overstory trees in optimum degree and increasing removal volume will benefit natural regeneration.
Uniform shelterwood cuttings system is the most widely used shelterwood method. The main goal of this system is to regenerate forest naturally. Retaining some of the overstory trees will assist regeneration by providing shelter and suitable growing conditions. The success of natural regeneration process is not always quaranteed and will depend on various factors. In current research there have been investigated natural regeneration affecting factors in Harju county and South-Estonia forest sites managed 3 to 11 years ago under uniform shelterwood cuttings system. A total of twenty pairs of sites in which one pair was successfully regenerated and the other one unsuccessfully. Within forty sites there were examined different site characteristics such as cutting and site properties, stand openess and structure. Potentially affecting factors were analyzed using general linear mixed model (GLMM) in three types of different regeneration indicators (conifer regeneration abundance ha-1, regeneration index, annual total growth index). For all regeneration indicators, soil scarification, retained trees ha-1, openness, removed volume (m3 ha-1) and the percentage of removed trees were statistically significant (p<0,05) affecting factors in individual analysis. Scarification had the greatest impact on successful regeneration. In conifer regeneration abundance mixed model, significant factors were also scarification and retained trees ha-1, while for other indicators removed volume (m3 ha-1) was added in the final model. Stocking density, mineral substances content and their ratio were not significally affecting regeneration success. It can be concluded that in addition to soil scarification, retaining overstory trees in optimum degree and increasing removal volume will benefit natural regeneration.
Kirjeldus
Märksõnad
raie, aegjärkne raie, turberaied, looduslik metsauuendus, puistud, kasvukohad, Eesti, magistritööd