Light- and nitrogen-use and biomass allocation along productivity gradients in multilayer plant communities
Failid
Kuupäev
2013-05-11
Autorid
Ajakirja pealkiri
Ajakirja ISSN
Köite pealkiri
Kirjastaja
Abstrakt
Taimed vajavad ellujäämiseks, kasvuks ja paljunemiseks piisavalt keskkonnaressursse. Kõige sagedamini piiravad taimede kasvu valgus ja mulla lämmastik. Lämmastiku omastamine mullast on väga energiakulukas. Seetõttu on oluline, et taim kasutaks neid ressursse efektiivselt. Millised strateegiad võimaldavad erinevates kasvutingimustes paremini toime tulla? Kas efektiivsed lämmastikukasutajad võivad samaaegselt olla ka efektiivsed valguse kasutamises? Sellele vastamiseks uuriti muutusi nimetatud ressursside kasutamises liigi ja koosluse tasandil piki kasvukoha viljakuse gradiente niidu- ja metsakooslustes Lääne-Eestis Laelatul ja Lõuna-Eestis Arul. Koostati kahe-ressursiline mudel, kus kättesaadav lämmastik ja valgus on parameetrid, mis kirjeldavad lehestiku massi vertikaalset jaotumist koosluses erinevate rinnete vahel. Ülemise rindeni jõuab suurema intensiivsusega valgusvoog, võrreldes alumiste rinnetega. Alumisi rindeid iseloomustab efektiivsem lämmastiku kasutamine ja/või parem võime omastada mullast lämmastikku. Rohurinde kasvu piki produktsiooni gradienti limiteerivad nii kättesaadav valgus kui ka lämmastik. Samblarinde kasvu piirab põhiliselt rindeni jõudev valgus. Kahe niidukoosluse andmete põhjal saab püstitada hüpoteesi, et valguse omastamise efektiivsuse muutumist produktsiooni gradiendil iseloomustab optimumiga kõver. Edaspidi on vajalik uurida, kas analoogiline seos kehtib ka teiste taimekoosluste puhul. Antud uurimuse ja kirjanduse põhjal võib järeldada, et taimedel esineb lõivsuhe valgus- ja lämmastikuressursi paremaks kasutamiseks tehtavate kulutuste vahel. See tähendab, et taimed ei saa olla efektiivsed mõlema ressursi kasutamises ühekorraga. Niiduliikide võrdlemisel selgus, et dominandid ja alusliigid reageerivad kasvutingimuste muutumisele erinevalt. Täpsemalt, maapealse biomassi ja lämmastikusisalduse jaotumise varieeruvus tekitab erinevad valguse ja lämmastiku kasutusmustrid ning sellest tulenevalt kujunevad liikidel erinevad ellujäämisstrateegiad.
Plants need various resources in sufficient quantities for their growth, reproduction and survival. Light and nitrogen availability are two factors most frequently limiting plant growth. Nitrogen acquisition from soil is an expensive process. Consequently, it is vital that those resources are utilized efficiently. Which strategies enable plants to cope better in various conditions and competition? Can effective nitrogen users be concurrently effective in light use? To answer the questions, changes in resource-use at species and community levels were studied along productivity gradients in grassland and deciduous forest communities (Laelatu in West-Estonia and Aru in South-Estonia). A two-resource model was developed with available nitrogen and light as parameters, which describe vertical distribution of foliage mass by vegetation layers in a community. The overstory receives more light resource compared to lower layers, while the lower layers have greater nitrogen-use efficiency and/or a better capability to acquire soil nitrogen. The growth of the herbaceous layer is co-limited by light and nitrogen availability. The growth of the moss layer is limited primarily by light availability. On the basis of two grasslands, the hypothesis was established that an optimum of light acquisition efficiency exists along a productivity gradient. Further studies are needed to clarify if an analogous relationship exists in other community types? On the basis of the thesis and literature, it is possible to conclude that plants have to compromise between effective light- and nitrogen-use. Plants cannot be effective in utilizing both resources simultaneously. Comparison of grassland species revealed clear differences in acclimation patterns among species that become dominant and that remain as subordinates. More precisely, plasticity in aboveground growth patterns and nitrogen allocation varies among species, thus leading to substantially different strategies for survival.
Plants need various resources in sufficient quantities for their growth, reproduction and survival. Light and nitrogen availability are two factors most frequently limiting plant growth. Nitrogen acquisition from soil is an expensive process. Consequently, it is vital that those resources are utilized efficiently. Which strategies enable plants to cope better in various conditions and competition? Can effective nitrogen users be concurrently effective in light use? To answer the questions, changes in resource-use at species and community levels were studied along productivity gradients in grassland and deciduous forest communities (Laelatu in West-Estonia and Aru in South-Estonia). A two-resource model was developed with available nitrogen and light as parameters, which describe vertical distribution of foliage mass by vegetation layers in a community. The overstory receives more light resource compared to lower layers, while the lower layers have greater nitrogen-use efficiency and/or a better capability to acquire soil nitrogen. The growth of the herbaceous layer is co-limited by light and nitrogen availability. The growth of the moss layer is limited primarily by light availability. On the basis of two grasslands, the hypothesis was established that an optimum of light acquisition efficiency exists along a productivity gradient. Further studies are needed to clarify if an analogous relationship exists in other community types? On the basis of the thesis and literature, it is possible to conclude that plants have to compromise between effective light- and nitrogen-use. Plants cannot be effective in utilizing both resources simultaneously. Comparison of grassland species revealed clear differences in acclimation patterns among species that become dominant and that remain as subordinates. More precisely, plasticity in aboveground growth patterns and nitrogen allocation varies among species, thus leading to substantially different strategies for survival.
Kirjeldus
Väitekirja elektrooniline versioon ei sisalda publikatsioone.