Raiel säilitatud puude koguse mõju elustikule
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Kuupäev
2014
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Ajakirja pealkiri
Ajakirja ISSN
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Abstrakt
Lageraiet planeerides ei ole oluline mõelda mitte ainult puude järelkasvule, vaid ka kogu
ülejäänud elurikkuse säilimisele ning järjepidevusele. Elustiku mitmekesisust raiejärgsel
langil aitavad tagada säilikpuud. Antud uurimustöös on analüüsitud raiel säilitatud puude
koguse mõju elustikule, uurides, kuidas see mõjutab raielangil koosluste liigirikkust ning
arvukust.
Töö eesmärgiks on Rosenvald ja Lõhmus (2008) ülevaateartiklis avaldatud metaanalüüsi
andmestiku laiendamine, et parandada meta-analüüsi üldistusvõimet. Käesolev
analüüs on tehtud 176 teadusartikli seast kogutud 24 andmestiku põhjal, eesmärgiga anda
ülevaade üle maailma säilikpuude kohta koostatud uuringute üldistatud tulemustest.
Meta-analüüsi sobivates artiklis võrreldi lageraiet, kus pole säilikpuid jäetud (või ainult
kuni 2 puud hektarile) ning säilikpuudega katseala, kus on säilitatud mitte rohkem kui
50% puudest.
Uurimustöö raames läbi viidud analüüsid ei näidanud ühegi liigirühma puhul
säilikpuudest tingitud olulist negatiivset mõju (ülemine 95% usalduspiir jäi üle 0-telje
piiri ka juhul, kui keskmine jäi alla 0-telge). Oluliselt positiivne säilikpuude mõju leiti
lindude ning mükoriissete seente arvukusele ning liigirikkusele. Erinevalt viimati
mainitust oli säilikpuude nõrka (statistiliselt mitteolulist) ebasoodsat mõju täheldada putukate ja soontaimede rühmades. Ilmselt seetõttu, et nimetatud rühmad koosnevad väga
erineva vajadusega liikidest.
Näib, et suurem säilikpuude arv võiks mõjutada nii arvukust kui liigirikkust positiivselt.
Kõige parem keskmine positiivne mõju kõigi liigirühmade kokkuvõttes nii liigirikkusele
kui arvukusele oli raielankidel, kus puid oli säilitatud üle 15%. Tulemused olid sarnased
Rosenvald-Lõhmuse (2008) meta-analüüsi tulemustega. Sellest järeldub, et suurem
andmehulk ei muuda meta-analüüsi tulemust.
Lähtudes käesoleva uurimustöö meta-analüüsi tulemustest ning võrreldes 2011. aasta
keskmisi säilikpuude mahtusid hektari kohta Eestis võib öelda, et praegu Metsaseadusega
sätestatud kohustuslikud lageraiel säilitatavate puude mahud Eestis ei ole piisavad, et
säilikpuude mõju oleks elustiku kaitsel võimalikult efektiivne. Mahtusid tuleks
suurendada selliselt, et lageraiejärgselt säiliks vähemalt 15% puudest, millest osa võiks
kasuteguri suurendamiseks paikneda gruppidena üle langi.
Before planning the clear-cut, also the conservation, continuity and sustainability of biodiversity, must be taken under the consideration. Faunal diversity on the post-harvest site can be ensured with the help of residual trees. This research has analyzed the impact of different retention levels to the biota, how it affects communities’ species richness and abundance on the post-harvest site. Main target of the work was to expand the statistical data from review article „For what, when, and where is green-tree retention better than clear-cutting? A review of the biodiversity aspects. “(Forest Ecology and Management 255 (2008) 1–15) by Raul Rosenvald and Asko Lõhmus, in order to improve generalization ability of meta-analysis. Current analysis is made based on 24 datasets, collected from among 176 research articles, in order to give an overview of the global research generalized results about retention trees. In suitable articles were compared to each other clear-cut test area (with 0% trees left or only a few trees, up to two trees per hectare), and Green-tree retention cutting test area, which has been stored for not more than 50% of the trees. Analyses that were performed with this research did not show due to retention trees significant negative response in any case of species group (upper 95% probability remained above 0-axis even in case average staid below 0-axis). Rather, it was observed a significant positive impact on species richness and abundance of birds and mycorrhizal fungi. These latter positive impacts differ from the weak negative tendencies in vascular plants and insects. Greater amount of retention trees seems to have positive effects to species richness and abundance. Best average positive effects to all species groups’ richness and abundance appeared for the highest levels of retention where the trees were retained more than 15% of the growing stock. The results were similar to the results of Rosenvald-Lõhmuse (2008) meta- analysis. It may be concluded that a higher amount of the data does not change the result of meta-analysis. In result of meta-analysis of this research and comparing the average volumes of retention trees per hectare performed in 2011, can be said that mandatory amounts of retention trees per hectare establish with the requirements by the Rules of Forest Management are not sufficient enough that the impact of retention trees would be most effective in protecting the biota of the forest stand. Volumes should be increased so, that after clear-cutting at least 15% of trees will be maintained. In order to achieve higher efficiency the trees should be retained in groups over cutting area.
Before planning the clear-cut, also the conservation, continuity and sustainability of biodiversity, must be taken under the consideration. Faunal diversity on the post-harvest site can be ensured with the help of residual trees. This research has analyzed the impact of different retention levels to the biota, how it affects communities’ species richness and abundance on the post-harvest site. Main target of the work was to expand the statistical data from review article „For what, when, and where is green-tree retention better than clear-cutting? A review of the biodiversity aspects. “(Forest Ecology and Management 255 (2008) 1–15) by Raul Rosenvald and Asko Lõhmus, in order to improve generalization ability of meta-analysis. Current analysis is made based on 24 datasets, collected from among 176 research articles, in order to give an overview of the global research generalized results about retention trees. In suitable articles were compared to each other clear-cut test area (with 0% trees left or only a few trees, up to two trees per hectare), and Green-tree retention cutting test area, which has been stored for not more than 50% of the trees. Analyses that were performed with this research did not show due to retention trees significant negative response in any case of species group (upper 95% probability remained above 0-axis even in case average staid below 0-axis). Rather, it was observed a significant positive impact on species richness and abundance of birds and mycorrhizal fungi. These latter positive impacts differ from the weak negative tendencies in vascular plants and insects. Greater amount of retention trees seems to have positive effects to species richness and abundance. Best average positive effects to all species groups’ richness and abundance appeared for the highest levels of retention where the trees were retained more than 15% of the growing stock. The results were similar to the results of Rosenvald-Lõhmuse (2008) meta- analysis. It may be concluded that a higher amount of the data does not change the result of meta-analysis. In result of meta-analysis of this research and comparing the average volumes of retention trees per hectare performed in 2011, can be said that mandatory amounts of retention trees per hectare establish with the requirements by the Rules of Forest Management are not sufficient enough that the impact of retention trees would be most effective in protecting the biota of the forest stand. Volumes should be increased so, that after clear-cutting at least 15% of trees will be maintained. In order to achieve higher efficiency the trees should be retained in groups over cutting area.
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