Plant competitive behaviour: relationships with functional traits and soil processes
Date
2019-11-19
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Abstract
Kuna kõik taimed vajavad kasvamiseks samu ressursse, oleks taimedel kasulik olla head „võitlejad“ ning haarata võimalikult kiiresti palju ressursse just endale. Teisalt on taimedel vaja olla ka head „kannatajad“, et naabertaimede tekitatud survele vastu pidada.
Uurisime, millised tunnused on taimede jaoks olulised maa-aluses olelusvõitluses ning leidsime, et enim survestavad konkurente taimeliigid, mis kasvatavad suurema ning horisontaalselt laiuvama juurestiku. Parimateks kannatajateks osutusid aga hoopis vähem harunenud ning sügavale ulatuva juurestikuga taimed. Taimed võimekus kasvatada konkurentsivõimet erinevatel viisidel võimaldabki paljudel liikidel koosluses kooseksisteerida.
Taimejuurte ruumilise paigutuse uurimiseks kasutasime loomaökoloogiast pärinevaid meetodeid ning käsitlesime ühe taime juuri ühselulise “kolooniana”, mille liikmete (juurte) eesmärgiks on kogu pesa (taime) optimaalne toimetulek. Leidsime erinevaid käitumismustreid nii juurte paigutuse kui ka kodupiirkonna suuruse osas. Selgus, et eri liigist taimed hõivasid mullaruumi erineva efektiivsusega, mis mõjutas taimede võimet konkurentsis püsida.
Lisaks liikidevahelisele konkurentsile võtsime vaatluse alla ka taimede konkurentsi liigikaaslastega ja võimet lähisugulasi ära tunda ning nendega konkurentsi vältida. Leidsime, et geneetiliselt lähedaste sugulaste äratundmine taimekooslustes ei pruugi olla väga tavaline. Katses kasvatatud kaheksast liigist vaid üks, valge ristik, käitus sugulastega koos kasvades kooperatiivselt, püüdes vähendada otsest konkurentsi ning investeerides kaugemale levimisse. Kasvades koos mittesugulastega panustasid taimed pigem ressursside haaramisse naabertaimede arvelt.
Sugulaste äratundmine naabrite hulgast tõi kaasa muutusi taimede kasvus ja keemilises koostises, mis omakorda mõjutas läbi surnud juurte ja mikroobide elutegevuse ka toitainete ringlust mullas. Taolised muutused võivad osutuda oluliseks just liigivaestes kooslustes, kus laialt levinud liigi geneetiline mitmekesisus võib kujundada mulla viljakust.
All plants need roughly the same resources to survive and reproduce. To be successful members in a community, plants have to be good “fighters”, capturing resources at the expense of their neighbours, and be resilient “sufferers” in order to withstand suppression from neighbouring plants. One aim of my doctoral thesis was to determine which belowground traits enhance species’ ability to suppress and tolerate neighbours. It turns out that a larger and wider root system hampers neighbouring plants’ growth the most. On the other hand, plants with less branched and deeper root systems are better at tolerating competitive pressure from neighbouring plants. Plants can use different approaches to increase their competitive ability, this in turn enables the opportunty for different species to stably co-exist in the same community. In the second experiment, we used novel methods to examine how plant root systems occupy soil space and defend it from competitors. We examined eight common grassland species and found that these species lacked territorial behaviour as their foraging areas overlapped extensively in species mixtures. However, several species defended their core foraging areas to some extent by aggregating their roots and preventing invasion by other species. We also wanted to find out how widespread kin recognition is in plants and how plants modify their morphology in response to kin. It appears that kin recognition may not be very common in grasslands. According to our results, only one speies of eight, Trifolium repens, exhibited clear responses to neighbours of different genetic relatedness and showing cooperative behaviour towards kin by reducing competition and investing more into seed production. Kin recognition in plants may have wider implications at the ecosystem level, including changes in interactions with soil microorganisms. We found that kin recognition may be important in species-poor plant communities where genetic diversity in the dominant plant species influences the chemical composition of dead plant material which in turn modifies microbial activity in the soil
All plants need roughly the same resources to survive and reproduce. To be successful members in a community, plants have to be good “fighters”, capturing resources at the expense of their neighbours, and be resilient “sufferers” in order to withstand suppression from neighbouring plants. One aim of my doctoral thesis was to determine which belowground traits enhance species’ ability to suppress and tolerate neighbours. It turns out that a larger and wider root system hampers neighbouring plants’ growth the most. On the other hand, plants with less branched and deeper root systems are better at tolerating competitive pressure from neighbouring plants. Plants can use different approaches to increase their competitive ability, this in turn enables the opportunty for different species to stably co-exist in the same community. In the second experiment, we used novel methods to examine how plant root systems occupy soil space and defend it from competitors. We examined eight common grassland species and found that these species lacked territorial behaviour as their foraging areas overlapped extensively in species mixtures. However, several species defended their core foraging areas to some extent by aggregating their roots and preventing invasion by other species. We also wanted to find out how widespread kin recognition is in plants and how plants modify their morphology in response to kin. It appears that kin recognition may not be very common in grasslands. According to our results, only one speies of eight, Trifolium repens, exhibited clear responses to neighbours of different genetic relatedness and showing cooperative behaviour towards kin by reducing competition and investing more into seed production. Kin recognition in plants may have wider implications at the ecosystem level, including changes in interactions with soil microorganisms. We found that kin recognition may be important in species-poor plant communities where genetic diversity in the dominant plant species influences the chemical composition of dead plant material which in turn modifies microbial activity in the soil
Description
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Keywords
plants (botany), competition (biol.), root system, morphological variation, plant ecology