Local and landscape effects on butterfly assemblages in managed forests
Date
2019-07-08
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Abstract
Elurikkuse vähenemine on üleilmne probleem, mida peamiselt põhjustab looduslike ja poollooduslike elupaikade kadumine. Elupaikade liigilist mitmekesisust mõjutab ka ümbritsev maastik: mida rohkem on elupaigad üksteisest eraldatud, seda enam need liigiliselt vaesuvad. Ehkki kaitsealad on elurikkuse hoidmisel väga tähtsad, ainuüksi neist ei piisa. Järjest enam püütakse leida võimalusi liigirikkuse säilitamiseks ja suurendamiseks ka tugevate inimmõjutustega maastikes. Suurenev nõudlus puidu ja puidutoodete järele on järjest intensiivsemaks muutnud ka metsade majandamise. Metsamajanduse intensiivistumine on paljudele metsaliikidele ohuks, samas leidub ka neid, kellele majandatav metsamaastik elupaigaks sobib. Doktoritöö tulemused viitavad, et üheks selliseks liigirühmaks on metsapäevaliblikad. Paljude liikide röövikud toituvad puudel, põõsastel ja alustaimestiku taimedel, valmikud aga leiavad nektaritaimi raiesmikelt. Niisiis on metsapäevaliblikatele oluline mosaiikne metsamaastik tervikuna – doktoritöös leidsingi, et mida rohkem on ümbritsevas maastikus metsamaad, seda kõrgem on metsaliblikate liigirikkus raiesmikul. Oma töös lähen aga sammu võrra kaugemale ja näitan, et lisaks metsaliikidele pakub majandatav metsamaastik oma mitmesuguste avakooslustega elupaika ka paljudele avamaastikuliikidele. Selgus, et raiesmikud on elupaigaks enamikule regionaalsest päevaliblikafaunast, kellest suurt osa on tavapäraselt seostatud poollooduslike niitudega. Seejuures asustavad niiduliigid ka täielikult metsaga ümbritsetud raiesmikke, millest järeldub, et puistu raiesmikele jõudmisel neile oluliseks takistuseks ei ole. Nii niiduliikide kui metsaliikide koosluseid mõjutavad aga metsa lokaalsed kasvukohatingimused – teatud liigid esinevad sagedamini ja arvukamalt näiteks palumetsades, teised jällegi laane- või salumetsades. Seega on päevaliblikate liigirikkuse seisukohalt oluline elupaikade mitmekesisus, erinevad metsatüübid täiendavad teineteist.
Decrease of biodiversity is a global problem mainly caused by loss of natural and semi-natural habitats. Local diversity is also affected by surrounding landscape: isolation of habitats leads to decline of species richness. Despite being important, protected areas alone may be insufficient to maintain biodiversity. The focus is shifting towards sustaining and enhancing species diversity in landscapes of significant human impact. Intensification of forest management due to increasing demand for timber, poses a threat for many forest species. However, some species may find favourable habitat in managed forests. The results of this thesis indicate that forest butterflies are among those. At caterpillar stage, forest butterflies feed on trees, bushes and understorey plants, whereas adults find nectar plants from clear-cuts. Therefore, the whole mosaic of managed forest landscape is important for forest butterflies. Indeed, I found higher species richness of forest butterflies in clear-cuts containing higher proportion of woodland in the surrounding landscape. Furthermore, my thesis shows that managed forest landscape containing various open habitats is also suitable for many open-habitat species. I found that clear-cuts serve as habitats for the majority of regional species pool of butterflies traditionally associated with semi-natural grasslands. Moreover, grassland species reach even to clear-cuts completely surrounded with forest, which implies that forest is not a significant barrier for colonisation. Assemblages of grassland species and forest species are both affected by local environmental conditions of forest: different forest types provide habitat for distinct butterfly assemblages. The diversity of forest types is therefore important for maintaining species richness of butterflies, as different forest habitat types complement each other.
Decrease of biodiversity is a global problem mainly caused by loss of natural and semi-natural habitats. Local diversity is also affected by surrounding landscape: isolation of habitats leads to decline of species richness. Despite being important, protected areas alone may be insufficient to maintain biodiversity. The focus is shifting towards sustaining and enhancing species diversity in landscapes of significant human impact. Intensification of forest management due to increasing demand for timber, poses a threat for many forest species. However, some species may find favourable habitat in managed forests. The results of this thesis indicate that forest butterflies are among those. At caterpillar stage, forest butterflies feed on trees, bushes and understorey plants, whereas adults find nectar plants from clear-cuts. Therefore, the whole mosaic of managed forest landscape is important for forest butterflies. Indeed, I found higher species richness of forest butterflies in clear-cuts containing higher proportion of woodland in the surrounding landscape. Furthermore, my thesis shows that managed forest landscape containing various open habitats is also suitable for many open-habitat species. I found that clear-cuts serve as habitats for the majority of regional species pool of butterflies traditionally associated with semi-natural grasslands. Moreover, grassland species reach even to clear-cuts completely surrounded with forest, which implies that forest is not a significant barrier for colonisation. Assemblages of grassland species and forest species are both affected by local environmental conditions of forest: different forest types provide habitat for distinct butterfly assemblages. The diversity of forest types is therefore important for maintaining species richness of butterflies, as different forest habitat types complement each other.
Description
Väitekirja elektrooniline versioon ei sisalda publikatsioone
Keywords
päevaliblikad, kooslused, metsad, elupaigad, metsamajandus, raielangid, metsaökoloogia, Eesti