Kuivendussüsteemi rekonstrueermise mõju hariliku männi kasvule
Laen...
Kuupäev
2022
Kättesaadavus
07.09.2022
Autorid
Ajakirja pealkiri
Ajakirja ISSN
Köite pealkiri
Kirjastaja
Eesti Maaülikool
Abstrakt
Liigniiske metsamaa puistu tootlikkuse parandamiseks on rajatud Eestis hulgaliselt
kuivendussüsteeme, kuid need amortiseeruvad aja jooksul. Kuivenduskraavid, mis ei tööta (st
puhastamata või rekonstrueerimata) ei täida enam oma ülesannet. Senised uuringud ei kajasta
kuivendussüsteemi rekonstrueerimise mõju puude juurdekasvule, antud lünga täitmine on
käesoleva töö eesmärgiks. Töös analüüsitakse rekonstrueerimisega seotud efekti tagavara
kasvukäigule sõltuvalt puistu takseer- ja muudest tunnustest (näiteks tagavara kraavide
puhastamise ajal, kõrgusindeks, turbahorisondi paksus).
Tööks vajalikud andmed on kogutud KIKi projekti raames 2021. aasta suvel. Välitööde käigus
rajati proovialad, igal proovialal neli proovitükki (kraavi kaugustel 20, 40, 60 ja 80 m) ning koguti
takseerandmed ja puursüdamikke (kasutati tagavara juurdekasvu arvutamiseks üksikpuu ja
proovitüki tasemel). Töö aluseks on võetud soomlaste (Sarkkola et al 2012) metoodika.
Töös uuriti keskmise hektaritagavara juurdekasvu muutust 5 ja 10 aasta jooksul peale
kuivendussüsteemi rekonstrueerimist. Tulemustest saab järeldada, et antud maaparandustööde
efekt puude juurdekasvule sõltub puistu tagavarast ning on märgatavam madala hektaritagavaraga
puistutes. Mida saab selgitada ka sellega, et puistu tagavara kasvades, kasvab ka puistu
veetarbimine ning see jääb puistule optimaalsele tasemele. Seega väike tagavara ja kõrge
veetaseme puhul on rekonstrueerimise efekt suurem. Töö tulemustest võib järeldada, et mida
kõrgem on põhjavee tase rekonstrueerimise hetkel, seda suurem on efekt puistu juurdekasvule.
Antud töös saadud tulemused on kooskõlas ka sarnaste uuringute tulemustega, mida tehti Soomes
ja Rootsis.
Antud töös püstitatud hüpotees, et rekonstrueerimise efekt puude juurdekasvule sõltub puistu
tagavarast kraavide puhastamise ajal, leidis kinnitust. Kuivenduskraavid vajavad teatud aja tagant
puhastamist ning hiljem ka rekonstrueerimist, et kuivenduskraavid oleksid töökorras.
Varasematest töödest on teada, et kraavide seisukord võib halveneda juba 15 aastat pärast nende
rajamist, ning neid tuleks selle aja jooksul puhastada.
Metsamajandamise seisukohalt on metsakuivendus positiivne, sest kõrge põhjavee taseme
alandamine parandab puude kasvu ning kvaliteetse puidu materjali osakaal suureneb, samuti
paranevad ka metsamaterjali varumise ja väljaveo tingimused.
In Estonia, a number of drainage systems were established to improve the productivity of forest stands in sites where high soil moisture is limiting tree growth. However, over time drainage ditches deteriorate and therefore the whole ditch network stops functioning if not maintained. Previous studies made in Estonia do not address the issues related to tree growth dynamics after the ditch cleaning operations. The aim of the current study was to analyze the impact of ditch network maintenance (DNM) on the Scots pine volume growth rate depending on various stand characteristics such as stand stocking (at the moment of DNM), site index and peat layer thickness. In the summer 2021, the data for current study have been collected within the framework of the Estonian Environmental Investment Centre project. Four sample plots (distance from ditch 20, 40, 60, 80 m) were established in each of 30 treatment and 9 control study sites. Forest mensuration data and increment cores were collected from each sample plots to estimate the diameter growth on a single tree and stand level. Volume growth series were derived based on the radial increment data (tree-ring series), height-diameter and stem volume models for single trees. Annual volume growth increase (VGI) was calculated for each sample plot for 5 and 10 post-treatment years. The methodology for calculating the VGI values is based on the work of Finnish forest researchers (Sarkkola et al 2012). We can conclude that the volume growth response to DNM is better detected in the case of lower stocked stands. This can be explained so, that as the stand stocking increases then the stand water consumption also increases and the groundwater remains at the optimal level. So, in the lower stocked stands the pre-treatment groundwater level is higher, but DNM is followed by a more abrupt change in the groundwater level (compared to higher stocked stands) which results in greater volume growth response. From the study, we can conclude that trees respond better to DNM in stands with higher groundwater level. Current study confirms the results of previous research made in Finland and Sweden, concluding that there is a significant relationship between tree growth response to DNM and groundwater level affected by stand growing stock. The results of the study show that after 5 years there was a slight effect, but after 10 years the effect was more noticeable. DNM should be performed in order to enable the water management in forest stands. Previous studies suggest, that the drainage ditches can deteriorate already after 15 years from establishment, and therefore should be cleaned periodically. From the forest management point of view, forest drainage has numerous positive sides, lowering of groundwater level improves site conditions, which results in increasing stand growth rate and wood quality, also more efficient management of forest stands is enabled due to improved soil bearing capacity.
In Estonia, a number of drainage systems were established to improve the productivity of forest stands in sites where high soil moisture is limiting tree growth. However, over time drainage ditches deteriorate and therefore the whole ditch network stops functioning if not maintained. Previous studies made in Estonia do not address the issues related to tree growth dynamics after the ditch cleaning operations. The aim of the current study was to analyze the impact of ditch network maintenance (DNM) on the Scots pine volume growth rate depending on various stand characteristics such as stand stocking (at the moment of DNM), site index and peat layer thickness. In the summer 2021, the data for current study have been collected within the framework of the Estonian Environmental Investment Centre project. Four sample plots (distance from ditch 20, 40, 60, 80 m) were established in each of 30 treatment and 9 control study sites. Forest mensuration data and increment cores were collected from each sample plots to estimate the diameter growth on a single tree and stand level. Volume growth series were derived based on the radial increment data (tree-ring series), height-diameter and stem volume models for single trees. Annual volume growth increase (VGI) was calculated for each sample plot for 5 and 10 post-treatment years. The methodology for calculating the VGI values is based on the work of Finnish forest researchers (Sarkkola et al 2012). We can conclude that the volume growth response to DNM is better detected in the case of lower stocked stands. This can be explained so, that as the stand stocking increases then the stand water consumption also increases and the groundwater remains at the optimal level. So, in the lower stocked stands the pre-treatment groundwater level is higher, but DNM is followed by a more abrupt change in the groundwater level (compared to higher stocked stands) which results in greater volume growth response. From the study, we can conclude that trees respond better to DNM in stands with higher groundwater level. Current study confirms the results of previous research made in Finland and Sweden, concluding that there is a significant relationship between tree growth response to DNM and groundwater level affected by stand growing stock. The results of the study show that after 5 years there was a slight effect, but after 10 years the effect was more noticeable. DNM should be performed in order to enable the water management in forest stands. Previous studies suggest, that the drainage ditches can deteriorate already after 15 years from establishment, and therefore should be cleaned periodically. From the forest management point of view, forest drainage has numerous positive sides, lowering of groundwater level improves site conditions, which results in increasing stand growth rate and wood quality, also more efficient management of forest stands is enabled due to improved soil bearing capacity.
Kirjeldus
Bakalaureusetöö
Metsanduse õppekaval
Märksõnad
bakalaureusetööd, harilik mänd, metsaparandus, kuivendussüsteemi rekonstrueerimine, tagavara juurdekasv