Põhjavee taseme aastasisene dünaamika kuivendatud männienamusega puistutes
Laen...
Kuupäev
2023
Kättesaadavus
07.09.2023
Autorid
Ajakirja pealkiri
Ajakirja ISSN
Köite pealkiri
Kirjastaja
Eesti Maaülikool
Abstrakt
Eestis on rajatud palju kuivendussüsteeme, et parandada liigniiskete metsamaade puistute
tootlikkust. Kahjuks amortiseeruvad need süsteemid aja jooksul ning kuivenduskraavid, mis ei ole
hooldatud ega rekonstrueeritud, ei suuda enam oma ülesannet täita. Töö eesmärgiks on kirjeldada
põhjavee taseme dünaamikat vegetatsiooni perioodi jooksul, seal hulgas uurida veetaseme
varieeruvust sõltuvalt erinevatest teguritest ning kuivendussüsteemi rekonstrueerimise lühiajalisi
mõjusid põhjavee tasemele.
Töö jaoks vajalikud andmed on kogutud 2021. ja 2022. aasta kasvuperioodidel välitööde käigus.
Proovialad valiti kuivendatud ja kuivendamata puistute seas. Kuivendatud alale oli planeeritud
kuivendussüsteemi rekonstrueerimine. 2021. aastal koguti enne rekonstrueerimist andmeid, et
võrrelda neid rekonstrueerimisjärgse perioodiga ehk aastaga 2022. Proovialadel toimus 14
kordusmõõtmist, iga kordusmõõtmise vahe oli 10 päeva. Aladel tehti ringproovitükke ja mõõdeti
turbahorisondi paksus.
Töös uuriti põhjavee taseme muutust enne ja pärast kuivendussüsteemide rekonstrueerimist.
Tulemustest saab järeldada, et rekonstrueerimine kuivendatud aladel avaldas mõju. Keskmiselt
langes põhjavee tase 10 cm. Tuginedes Soomes ja Rootsis tehtud uuringutele, on leitud
samasugune seos. Tulemustest on võimalik järeldada, et põhjavee tase on seotud õhutemperatuuri
ja sademete hulgaga. Kuivendatud aladel oli statistiliselt oluline vaid sademed, aga kuivendamata
aladel olid olulised sademed ja temperatuur. Antud tööd võiks edasi arendada, et uurida ka puude
radiaalse juurdekasvu antud proovialal ning kuidas põhjavee tase ja ilmastikuolud seda mõjutavad.
Varasemates töödes on mainitud parimaks kuivenduskraavide rekonstrueerimise ajaks 25-30
aastat pärast kuivenduskraavi rajamist, sest vanad kraavid amortiseeruvad ning puidu juurdekasv
väheneb.
Metsamajandamise seisukohalt on kuivendusel positiivne mõju. Põhjavee tase langeb, paraneb
puude kasv. Negatiivseteks mõjudeks oleks kasvuhoonegaaside emiteerumine ning veereostus.
In Estonia, many drainage systems have been set up to improve the productivity of stands in forested areas that are too wet. Unfortunately, these systems amortize over time and drainage ditches that are not maintained and reconstructed can no longer fulfil their function. The aim of this work is to describe the dynamics of groundwater levels during the vegetation period, including the variability of water levels depending on different factors and the short-term effects of drainage system reconstruction on groundwater levels. The data required for this work have been collected during fieldwork in the growing seasons of 2021 and 2022. Sample plots were selected among drained and undrained stands. A reconstruction of the drainage system was planned for the drained area. In 2021, data were collected prior to the reconstruction in order to be compared with the post-reconstruction period, i.e. 2022. 14 remeasurements were taken in the sample areas, each remeasurement 10 days apart. The areas were circularly sampled and the thickness of the peat horizon was measured. The study investigated groundwater level changes before and after the reconstruction of drainage systems. From the results it can be concluded that the reconstruction of the drained areas had an impact. On average, groundwater levels decreased by 10 cm. Based on studies in Finland and Sweden, a similar relationship has been found. From the results it can be concluded that groundwater levels are related to air temperature and precipitation. Only precipitation was statistically significant in drained areas, while in undrained areas precipitation and temperature were significant. This work could be further developed to investigate also the radial increment of trees in a given sample area and how this is influenced by groundwater level and climatic conditions. Previous work has indicated that the best time to reconstruct drainage ditches is 25-30 years after the drainage ditch is constructed, as old ditches become obsolete and tree growth declines. Drainage has a positive impact on forest management. Groundwater levels will be lowered and tree growth will improve. Negative effects would be greenhouse gas emissions and water pollution.
In Estonia, many drainage systems have been set up to improve the productivity of stands in forested areas that are too wet. Unfortunately, these systems amortize over time and drainage ditches that are not maintained and reconstructed can no longer fulfil their function. The aim of this work is to describe the dynamics of groundwater levels during the vegetation period, including the variability of water levels depending on different factors and the short-term effects of drainage system reconstruction on groundwater levels. The data required for this work have been collected during fieldwork in the growing seasons of 2021 and 2022. Sample plots were selected among drained and undrained stands. A reconstruction of the drainage system was planned for the drained area. In 2021, data were collected prior to the reconstruction in order to be compared with the post-reconstruction period, i.e. 2022. 14 remeasurements were taken in the sample areas, each remeasurement 10 days apart. The areas were circularly sampled and the thickness of the peat horizon was measured. The study investigated groundwater level changes before and after the reconstruction of drainage systems. From the results it can be concluded that the reconstruction of the drained areas had an impact. On average, groundwater levels decreased by 10 cm. Based on studies in Finland and Sweden, a similar relationship has been found. From the results it can be concluded that groundwater levels are related to air temperature and precipitation. Only precipitation was statistically significant in drained areas, while in undrained areas precipitation and temperature were significant. This work could be further developed to investigate also the radial increment of trees in a given sample area and how this is influenced by groundwater level and climatic conditions. Previous work has indicated that the best time to reconstruct drainage ditches is 25-30 years after the drainage ditch is constructed, as old ditches become obsolete and tree growth declines. Drainage has a positive impact on forest management. Groundwater levels will be lowered and tree growth will improve. Negative effects would be greenhouse gas emissions and water pollution.
Kirjeldus
Bakalaureuse töö
Metsanduse õppekaval
Märksõnad
bakalaureusetööd, kuivendussüsteemi rekonstrueerimine, põhjavee tase, ilmastikuolud, harilik mänd