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Räpina poldri linnustik enne ja pärast projekti „Natura 2000 Biotoopide Kaitse Räpina Poldril“

Uuspalu, Rasmus (2015) Räpina poldri linnustik enne ja pärast projekti „Natura 2000 Biotoopide Kaitse Räpina Poldril“. [thesis] [en] The Avifauna of Räpina Polder, Before and After the „Conservation of Natura 2000 Biotopes in Räpina Polder“ Project.

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Abstract

Räpina polder rajati nõukogude perioodil põllumajanduse eesmärgil. Poldril asuvaid põlde kasutati sööda kasvatamiseks kahele poldri äärsele suurfarmile. Sellel põhjusel loodi poldril ca 45 km pikkune teedevõrk. Hoiualal asuvaid metsamaid ei ole metsamajandusliku eesmärgi huvides peaaegu et üldse kasutatud. Suurimaks metsaomanikuks on RMK. Räpina polder on kõige rohkem tuntud oma mitmekesise elustiku poolest. Räpina poldri hoiualal on kohatud 31 liiki imetajaid, 6 liiki kahepaikseid ning 190 linnuliiki. Räpina poldrit kasutavad tuhanded läbirändavad linnud toitumiseks ja peatumiseks. Samuti on Räpina polder soodne pesitsuspaik paljudele veelindudele, kelle hulka kuuluvad ka naerukajakad, väikekajakad, mustviiresed ja valgetiib-viiresed. Selle tõttu valiti Räpina poldri hoiuala 2001. aastal tähtsaks linnualaks ning Natura 2000 linnukaitsealaks. „Natura 2000 biotoopide kaitse Räpina poldril“ projekti peamiseks eesmärgiks oli tähtsate ja kaitsealuste linnuliikide sobivate elupaikade kaitsestaatuse saavutamine. Üheks suureks ohuks Räpina poldri hoiualal arvati olevat poldri pindala vähenemine. Probleem seisnes poldri alade väheses kasutuses, mille tõttu olid paljud alad kasvanud suurel määral võssa ning vajasid niitmist. Maa uuesti kasutusele võtmisega loodeti taastada rohumaade, karjamaade ja põllumaade väärtus erinevate linnuliikide toitumis-peatumis- või sigimispaigana. Projekti valmimise hetkel puudus Räpina poldri hoiualal kehtiv kaitsekord. Selle tõttu kardeti poldri alade väärkasutamist ja valesti majandamist, mis oleks toonud pöördumatut kahju. Et kindlustada hoiuala soodne kaitsestaatus, töötati välja „Räpina poldri kaitsekorralduskava aastateks 2006-2014“. Suurimad probleemid Räpina poldri hoiualal olid ebaregulaarsed üleujutused, mille tõttu veelinnustiku populatsioon Räpina poldril kõikus suurelt. Samuti seadsid üleujutused ohtu kaitsealuste ja ohustatud liikide elupaigad. Ohuga võitlemiseks loodi stabiilne märgala, suurusega 200 ha, Räpina poldri põhjaossa, kus olid kõige rohkem levinud ka üleujutused. Projekti käigus loodud märgalal ei täheldatud teistele ümbritsevatele biotoopidele suurt mõju. Autor leidis, et haneliste arvukuses Räpina poldril on toimunud positiivne muutus. Autor arvab, et arvukuse tõusu põhjustas poldri alade majandamine (niitmine ja karjatamine), mis võimaldas hanelistele suurema toidulaua. Naerukajakate arvukus suurel määral ei tõusnud, küll aga tõusis pesitsusedukus peaaegu kahekordselt. Autori arvates on kasvanud pesitsusedukuse põhjuseks loodud stabiilne märgala ning seda ümbritsev niiske pinnas, mis on naerukajakatele soodsaks pesitsemispaigaks. Väikekajakate arvukuseks loendati rekordiline arv, 945 isendit. Pesitsema jäi väikekajakaid aga 23 paari, mis näitab, et enamus lindudest oli vaid läbirändel. Pesitsusedukus võrreldes varasemaga oli palju kõrgem. Seega usub autor, et poldrile loodud märgala pakkus väikekajakatele piisavalt häid tingimusi nii toitumiseks kui ka selle lähedal pesitsemiseks. Mustviireste arv tõusis umbes veerandi võrra. Poegi 2005. aastal ei täheldatud, küll aga leiti 2010. aastal neid 43 pesas. Kuna mustviiresed eelistavad elupaigaks madalaid veekogusid, leiab autor, et nende arvukuse ja ka pesitsemisedukuse tõusu taga on poldrile loodud märgala . Valgetiib-viireste arvukus kasvas võrreldavate aastate jooksul üle nelja korra, 2010. aastal loendati neid kokku 400 isendit. Ka pesitsusedukus tõusis märgatavalt, poegi esines 49 pesas. Valgetiib-viireste elupaiga eelistused on sarnased mustviirestele. Seetõttu julgeb autor arvata, et valgetiib-viireste suure tõusu põhjuseks on samuti poldri põhjaossa loodud stabiilne märgala. Öölaulikute poolest olid ainsad liigid, mis säilitasid võrreldavate aastate jooksul stabiilse arvukuse, hüüp ja väikehuik. Mõlema liigi arvukuseks hinnati olevat 3 paari. Rooruikade, täpikhuikade ja rukkirääkude arvukused aga langesid märgatavalt. Hüübid, rooruigad ja väikehuigad eelistavad elupaikadena roostikke ning märjemaid alasid. Selle põhjal usub autor, et oleks pidanud antud liikide arvukus just tõusma, sest loodud märgala ümbrus peaks neile liikidele hästi sobima ning Lämmijärve ääres asuvat roostikku „Natura 2000 biotoopide kaitse Räpina poldril“ projekti käigus ei mõjutatud. Autori arvates on öölaulikute arvukuse seas toimunud langus ebatavaline, kuna „Natura 2000 biotoopide kaitse Räpina poldril“ käigus läbi viidud tegevused oleksid pidanud ka öölaulikute arvukust suurendama. Öölaulikute madala arvukuse põhjuseks võib viidata ka ebasoodsale aastale ning adekvaatsema hinnangu saamiseks tuleks sarnaseid uuringuid kindlasti korrata. Autori arvates oli „Natura 2000 biotoopide kaitse Räpina poldril“ projektist pigem kasu, kuna maid hooldatakse ning peatunud on poldriala vähenemine, suuremas osas on linnuliikide arvukused ning pesitsemisedukused tõusnud. Autori arvates tuleks aga välja uurida, miks öölaulikute arvukus langes ning üritada välja töötada lahendused, et nende arvukused Räpina poldril tulevikus siiski tõuseksid.

Abstract [en]

Räpina polder was built during the Soviet era for farming purposes. The fields situated on the polder were used to grow feed for two farms situated near the polder area. The road system, 45 km in length, was built for that purpose as well. The forest lands on the conversation area have seen very little use for forestry purposes. Biggest owner of the forest lands is RMK. Räpina polder is very well known for its very diverse biota. There has been sightings of 31 species of mammals, 6 species of amphibians and 190 species of birds. Thousands of birds use the polder area for feeding and resting during the migration. Räpina polder is also a favorable nesting site for numerous species of waterfowl such as peewits, little gulls, black terns and white wing terns. The diverse population of different species of birds is the main reason why Räpina polder was chosen to be a Natura 2000 Special Protection Area. The main goal of „Conservation of Natura 2000 biotopes in Räpina polder“ project was to achieve appropriate habitat for important and endangered bird species. During the project a big problem with the polder was foreseen – decrease in its total area. The polder wasn’t being used as much as in the soviet era, thus a lot of the fields were starting to turn into shrubland and were in dire need of mowing. With restarting the use of the polder areas was in mind, the project was hoping to restore the value of grasslands, rangelands and farmlands as a suitable place for feeding and resting for different species of birds. While the project was planned there was no active management plan for the polder. It was feared, that without it, the polder area will be misused, which could have potentially brought irreversible damage to the area. To ensure the suitable protection status a management plan „Räpina poldri kaitsekorralduskava aastateks 2006-2014“ was formed. The biggest problem on the Räpina polder was irregular floodings, which caused huge fluctuations in the population of waterfowls and also compromising the habitats of endangered bird species. To fight the irregular floodings, creation of a stable wetland (200 ha) in the northern part of the Räpina polder areas, was decided. It was also the area, where irregular floodings were with the biggest impact on the polder. The created wetland didn’t have any impact on its surrounding areas. After the project the population of different species of geese on Räpina polder has seen a positive change. The author believes that the change was caused by the maintenance (mowing and herding) of the polder areas, which provided the geese with a bigger area for feeding. The population of peewits did not rise, although their breeding success nearly doubled in numbers. This was most likely caused by the stable wetlands and the wet ground surrounding it, both of which are favorable habitats for peewits. The population of little gulls went up to 945 individuals, but only 23 pairs were found nesting. This shows that most of the little gulls were just migrating. Comparing to the earlier times, breeding success of little gulls improved marginally. This leads the author to believe, that the above-mentioned stable wetlands provided good feeding and nesting conditions for little gulls. Black terns also saw a small increase in their population. No black terns were seen nesting in 2005, but in 2010 nestlings were found in 43 nests. Black terns prefer shallow bodies of water as their habitat, from which the author concluded that the stable wetlands are the reason for the rise in the population of black terns. The population of white wing terns on Räpina polder quadrupled between the comparable years. Their breeding success also increased greatly, nestlings were found in 49 nests. White wing terns prefer a similar habitat to the black terns. The author concludes, that the created stable wetlands were yet again the reason for the increase in white wing terns population and breeding success. There were some birds whose population did not have an increase: bittern, corncrake, little crake, water rail and spotted crake. Of the aforementioned birds only two, bittern and little crake, maintained a stable population of 3 pairs. Water rail, spotted crake and corncrake had a significant decrease in their population. Bitterns, water rails, and little crakes prefer wetlands as their habitat. The author believes that based on their preferred habitat, Räpina polder should be one of the best places for these species. Instead of seeing a decrease in their populations, we should have seen an increase. Another reason for the decline in the population of the previously mentioned birds could be that it may have been an unfavorable year for them. To get a more adequate evaluation of what really was the reason for the decline in population similar research should be conducted. The author believes that „Conservation of Natura 2000 biotopes in Räpina polder“ project was executed well and did more good than bad. The areas on Räpina polder are being used and maintained again, which stopped the decrease in the polders area. The populations and breeding success of different birds have been going up. The author suggests that further investigation and research must be conducted to find out why the population of water rails, spotted crakes and corncrakes has decreased and conduct necessary actions for their populations numbers to rise again.

Item Type: thesis
Advisor: Oliver Kalda
Subjects: Technoecology > Environmental Protection > Introduction to Ecology
Technoecology > Environmental Protection > Estonian Biota and Biocenosis
Divisions: Institute of Circular Economy and Technology > Environmental Technology and Management
Depositing User: Rasmus Uuspalu
Date Deposited: 17 Jun 2015 06:11
Last Modified: 17 Jun 2015 06:11
URI: http://eprints.tktk.ee/id/eprint/986

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