Factors determining plant and lichen species diversity and composition in Estonian Calamagrostis and Hepatica site type forests
Date
2010-12-20
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Abstract
Töö tulemusena selgus, et puidul kasvavate sammalde liigirikkusele avaldab metsade majandamine vahetut mõju – nii metskastiku kui ka sinilille kasvukohatüübi vähemajandatud metsades kasvab erinevat liiki samblaid oluliselt rohkem kui intensiivselt majandatud metsades. Kuigi sinilille kasvukohatüübi majandatud metsades kasvab kändudel majandamata metsadega võrreldes rohkem liike, tuleb siinjuures silmas pidada, et raiekändudele iseloomulikud liigid on tavalised metsaliigid, mida kasvab enamasti ohtrasti ka teistel substraatidel, seega kogu koosluse liigirikkus raiekändudel esinevate liikide arvel ei suurene.
Ehkki puistu vanuse olulist mõju sammalde ja samblike liigirikkusele ei tuvastatud, osutus see kastikuloo metsades tähtsaks sammalde ja samblike liigilist koosseisu määravaks faktoriks. Vanus kirjeldas olulise osa ka sinilille kasvukohatüübi metsade sammalde liigilisest koosseisust kõdupuidul. Siiski, sammalde ja samblike mitmekesisus loometsades sõltub enam erinevate substraatide olemasolust kui puistu vanusest. Sammalde ja samblike liigilise mitmekesisuse seisukohalt on loometsades eriti olulisteks substraatideks kõdupuit ja kadakas. Kõdupuit on väga mitmekesine mikrokasvukohtade poolest; kadaka tähtsus tuleneb eelkõige tema koore suuremast aluselisusest teiste puudega (mänd, kuusk ja kask) võrreldes, võimaldades seeläbi okasmetsade kooslustes kasvada ka lehtpuudele omastel epifüütsetel sammaldel ja samblikel. Küllalt palju samblaliike kasvas ka tuuleheitel. Kuna mullakiht on loometsades õhuke ja puude juured ei saa väga sügavale tungida, on tuuleheited seal küllalt sagedased.
Maapinna taimkatte analüüsimisel 1 m2 suuruste prooviruutude põhjal selgus, et rohu- ja samblarinne käituvad uuritud keskkonnaparameetrite suhtes erinevalt. Samblarinde liigirikkus suureneb koos metsaaluse ulatuslikuma varjutatusega ülemiste rinnete poolt, samal ajal rohurinde liigirikkus seostub just paremate valgustingimustega. Valguse oluline mõju rohurinde liigirikkusele ilmneb ka koosluste tasemel. Lisaks valgusele suurendab soontaimede liigirikkust oluliselt mulla lämmastikusisalduse tõus, seevastu mulla suurema eripinna väärtusega kaasneb liigirikkuse vähenemine.
Peamiseks faktoriks, millest sõltub sinilille kasvukohatüübi metsakoosluste erinevate rinnete liigiline koosseis, osutus analüüsitavate metsade geograafiline asukoht – Loode-Eesti metsad erinevad oluliselt Lõuna-Eesti metsadest. Teised liigilist kooseisu määravad faktorid varieeruvad eri rinnetes, millest ilmneb iga rinde teatav eripära liikide ja keskkonnaparameetrite vahelistes suhetes.
The influence of various factors on the species richness and composition in different scales, layers and site types has diverse character. The direct management effect on the species diversity was essential for bryophyte species growing on wood; in both forest types the richness of bryophyte species is higher in subnatural than in intensively managed stands. Still, the number of bryophyte species growing on stumps in Hepatica site type forests is higher in managed forests than in the unmanaged ones. At the same time, the species having high indicator value for man-cut stumps are very common species in boreal forests and grow on other substrata as well. Though the effect of tree stand age appeared to be insignificant for cryptogam species richness, it is essential for determining the bryophyte and lichen species composition in Calamagrostis site type forests. The stand age described also a considerable part of bryophyte species variance on logs and stumps in Hepatica site type forests. Nevertheless, availability of different substrata appeared even more essential for cryptogam diversity and species composition than forests age or management intensity. Decaying wood and Juniperus communis appeared to be important substrata for cryptogam species diversity in alvar forests. The bark of J. communis is less acid (pH > 5) than that of Picea abies, Pinus sylvestris or Betula pendula, being similar to that of deciduous trees. This seems to be the reason why a larger number of species can grow on J. communis as compared with other coniferous trees. Forest openness promotes herb-layer diversity. In addition to lightness, the increase in soil humus horizon nitrogen content enhances vascular plant species richness, but increase of soil special surface area has an opposite effect. The main factor on what the species composition of different layers in Hepatica site type forests depends is the geographic location of these stands: forests of north-western Estonia are significantly different from those in southern Estonia. Other factors which determine species composition varied in case of different layers as for every layer its own system of relationships between the species as well between the species and environmental factors is characteristic. Still, some significant factors overlap for different layers, e.g. habitat lightness and humus horizon depth for moss, herb and bush layer. Bryophyte species composition is influenced by the other layers, especially by herb layer cover. Herb layer species composition is determined more by soil characteristics than by other layers.
The influence of various factors on the species richness and composition in different scales, layers and site types has diverse character. The direct management effect on the species diversity was essential for bryophyte species growing on wood; in both forest types the richness of bryophyte species is higher in subnatural than in intensively managed stands. Still, the number of bryophyte species growing on stumps in Hepatica site type forests is higher in managed forests than in the unmanaged ones. At the same time, the species having high indicator value for man-cut stumps are very common species in boreal forests and grow on other substrata as well. Though the effect of tree stand age appeared to be insignificant for cryptogam species richness, it is essential for determining the bryophyte and lichen species composition in Calamagrostis site type forests. The stand age described also a considerable part of bryophyte species variance on logs and stumps in Hepatica site type forests. Nevertheless, availability of different substrata appeared even more essential for cryptogam diversity and species composition than forests age or management intensity. Decaying wood and Juniperus communis appeared to be important substrata for cryptogam species diversity in alvar forests. The bark of J. communis is less acid (pH > 5) than that of Picea abies, Pinus sylvestris or Betula pendula, being similar to that of deciduous trees. This seems to be the reason why a larger number of species can grow on J. communis as compared with other coniferous trees. Forest openness promotes herb-layer diversity. In addition to lightness, the increase in soil humus horizon nitrogen content enhances vascular plant species richness, but increase of soil special surface area has an opposite effect. The main factor on what the species composition of different layers in Hepatica site type forests depends is the geographic location of these stands: forests of north-western Estonia are significantly different from those in southern Estonia. Other factors which determine species composition varied in case of different layers as for every layer its own system of relationships between the species as well between the species and environmental factors is characteristic. Still, some significant factors overlap for different layers, e.g. habitat lightness and humus horizon depth for moss, herb and bush layer. Bryophyte species composition is influenced by the other layers, especially by herb layer cover. Herb layer species composition is determined more by soil characteristics than by other layers.
Description
Väitekirja elektrooniline versioon ei sisalda publikatsioone.
Keywords
dissertatsioonid, bioloogia, taimed, samblikud, liigirikkus, kasvukohatüüp