Maastikuelementide mõju tolmeldajate arvukusele põllumajandusmaastikus
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Kuupäev
2014
Kättesaadav alates
Autorid
Ajakirja pealkiri
Ajakirja ISSN
Köite pealkiri
Kirjastaja
Abstrakt
Euroopas kasvatatavatest põllukultuuridest on tolmeldamisest sõltuv umbes 84%, kuid kuna
putukatele ei piisa toitumiseks vaid monokultuursest põllukultuurist (sest ei õitse kogu
tolmeldamise hooaja vältel) siis erinevat tüüpi põlluservad pakuvad tolmeldajatele
alternatiivseid toiduallikaid.
Käesoleva töö eesmärgiks oli selgitada, kas ja millisel määral erinevat tüüpi maastikuelemendid
ja mitteharitavate maade osakaal mõjutavad põllumajandusmaastikus esinevate tolmeldajate
arvukust. Vaatluse all oli kolm eri tüüpi vaatlussektorit (raadius 1 km), milles oli erinev
looduslike, pool-looduslike ja mitteharitavate maade (v.a maanteed, raudteed, veekogud,
õuealad, elamud) osakaal (kõrge 38%, keskmine 22%, madal 7%), sektori sees asetses
talirapsipõld. Sektoreid oli kokku 18 (igas tüübis 6).
Vaatlusaluseid maastikuelemente (kultuurpõlluga piirnev looduslikum ala) oli kokku viis: mets,
puiskoridor, põlluserv, rohumaa, haljaskesa. Laiadel aladel (mets, rohumaa, haljaskesa) oli
vaadeldava transekti pikkuseks 50 m elemendi servas ja 50 m elemendi sees (vahe 12,5 m).
Kitsaste elementide korral oli tegemist 100 m pikkuse transektiga. Maastikuelementidel
loendati meemesilasi, kimalasi, liblikalisi, sirelasi ja erakmesilasi. Hinnati ka õitearvukust.
Selgus, et kimalasi ja meemesilasi oli kõige rohkem õiterikkal haljaskesal, erakmesilasi
sobivaid elutsemistingimusi pakkuvas puiskoridoris. Liblikaliste ja sirelaste puhul erinevust ei
märgatud. Vaadeldes eraldi metsa sise- ja servaala, siis selgus, liblikaliste ja sirelaste arvukus
oli metsaservas kõrgem, mis oli ka oodatav tulemus. Mesilaste arvukus oli mõlemal pool väike.
Puudus ka erinevus rohumaa ja haljaskesa sise- ja servaalal esinenud tolmeldajate arvukusel.
Vastupidiselt erinevatele uuringutele, esines meil tolmeldajaid rohkem madala
maastikugradiendiga aladel, kuhu nad arvatavasti olid koondunud, sest fragementeerunud
maastikus kasutatakse olemasolevat toiduressurssi maksimaalselt ära. Samas kõrgema
looduväärtusega aladel olid tolmeldajad tõenäoliselt hajutanud erinevate looduslike- ja
poollooduslike alade vahe
Pollinators play an important role in the reproduction of cultural and wild plants. They are able to increase crop production and content of micronutrients in plants. Approximately 84% of crop species are dependent on pollination in Europe. Since pollination cannot only be left to honeybees, it is necessary to protect and conseve naturally occurring wild pollinators. Different natural and semi-natural areas with lush herbaceous flora that surrounds crop fields offer nesting and foraging habitats for the pollinators. Because there is not enough food for pollinators in the monocultural fields (the main culture does not offer flowers throughout the whole vegetation period) it is needed to maintain different kind of field margins that offer alternative food ressources. The aim of this master’s thesis was to find out whether and to what extent different landscape elements and the proportion of non-arable land in the agricultural landscape have an effect on pollinator abundances. We studied 18 landscape sectors (high value 38%, intermediate value 22%, low 7%) with three different proportions of natural, semi-natural and non-cropped land (excluded roads, railways, water bodies, courtyards, residential buildings). In addition, in the center of landscape sector was oilseed rape field. Every sector contained landscape elements situated next to the field. There were five different elements: woody areal (forest edge and inside), woody linear, herbaceous linear (field margin), herbaceous areal (grassland) and fallow. The length of transect in areal elements was 50 m in the edge and 50 m inside the element (distance 12,5 m). In linear elements, the length of transect was 100 m. Five differentpollinator groups were observed: honeybees, bumblebees, Lepidoptera, hoverflies and solitary bees. Also, the flower abundance was assessed. The results showed that the abundance of honey- and bumblebees was the highest in fallows and lowest in woody areals. Solitary bee abundance was also lowest in woody areals contrary to woody linear (offers them suitable conditions for nesting and foraging), which had the highest abundance. There were non-significant differences between the abundance of Lepidoptera and hoverflies in different landscape elements. However, if we compare woody areal edge and interior transect separately, the greater abundance was found in the edge offorest than inside of it, which was the expected result. The abundance of bees was small in both transects. There was no difference in pollinator abundance between edge and interiortransects in fallow or herbaceous areal. Observed pollinator groups were differently affected by the species compositions of plants. The greatest abundance of bumblebees and honeybees was in the areas, where fabaceous plants (clovers) were dominating – fallows (highest flower abundance), grasslands and field margins. Solitary bees preferred areas where Fabaceae, Apiaceae, Asteraceae and Lamiaceae were prevaileing (woody linear, field margins). Hoverflies also presented in areas where more Apiaceae, Asteraceae and Fabaceae were grown. Contrary to other studies, where it has been shown that pollinator abundance decreases with the decrease of semi-natural areas, we could not find that kind of pattern. Rather, the abundance was higher in low landscape sector areas. Probably, they were concentrated to those scarce areas were food resource was accessible. In the landscape sectors, where there were more natural areas, they could be more diluted in the landscape. Some other factor can also affect the abundance of bumblebees and honeybees. Home gardens play an important role to bumblebees (in this work, this effect has not been taken into consideration). Honeybees are affected by the abundance and presence of beehives in the surrounding landscape.
Pollinators play an important role in the reproduction of cultural and wild plants. They are able to increase crop production and content of micronutrients in plants. Approximately 84% of crop species are dependent on pollination in Europe. Since pollination cannot only be left to honeybees, it is necessary to protect and conseve naturally occurring wild pollinators. Different natural and semi-natural areas with lush herbaceous flora that surrounds crop fields offer nesting and foraging habitats for the pollinators. Because there is not enough food for pollinators in the monocultural fields (the main culture does not offer flowers throughout the whole vegetation period) it is needed to maintain different kind of field margins that offer alternative food ressources. The aim of this master’s thesis was to find out whether and to what extent different landscape elements and the proportion of non-arable land in the agricultural landscape have an effect on pollinator abundances. We studied 18 landscape sectors (high value 38%, intermediate value 22%, low 7%) with three different proportions of natural, semi-natural and non-cropped land (excluded roads, railways, water bodies, courtyards, residential buildings). In addition, in the center of landscape sector was oilseed rape field. Every sector contained landscape elements situated next to the field. There were five different elements: woody areal (forest edge and inside), woody linear, herbaceous linear (field margin), herbaceous areal (grassland) and fallow. The length of transect in areal elements was 50 m in the edge and 50 m inside the element (distance 12,5 m). In linear elements, the length of transect was 100 m. Five differentpollinator groups were observed: honeybees, bumblebees, Lepidoptera, hoverflies and solitary bees. Also, the flower abundance was assessed. The results showed that the abundance of honey- and bumblebees was the highest in fallows and lowest in woody areals. Solitary bee abundance was also lowest in woody areals contrary to woody linear (offers them suitable conditions for nesting and foraging), which had the highest abundance. There were non-significant differences between the abundance of Lepidoptera and hoverflies in different landscape elements. However, if we compare woody areal edge and interior transect separately, the greater abundance was found in the edge offorest than inside of it, which was the expected result. The abundance of bees was small in both transects. There was no difference in pollinator abundance between edge and interiortransects in fallow or herbaceous areal. Observed pollinator groups were differently affected by the species compositions of plants. The greatest abundance of bumblebees and honeybees was in the areas, where fabaceous plants (clovers) were dominating – fallows (highest flower abundance), grasslands and field margins. Solitary bees preferred areas where Fabaceae, Apiaceae, Asteraceae and Lamiaceae were prevaileing (woody linear, field margins). Hoverflies also presented in areas where more Apiaceae, Asteraceae and Fabaceae were grown. Contrary to other studies, where it has been shown that pollinator abundance decreases with the decrease of semi-natural areas, we could not find that kind of pattern. Rather, the abundance was higher in low landscape sector areas. Probably, they were concentrated to those scarce areas were food resource was accessible. In the landscape sectors, where there were more natural areas, they could be more diluted in the landscape. Some other factor can also affect the abundance of bumblebees and honeybees. Home gardens play an important role to bumblebees (in this work, this effect has not been taken into consideration). Honeybees are affected by the abundance and presence of beehives in the surrounding landscape.
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