Generality and specificity in light harvesting, carbon gain capacity and shade tolerance among plant functional groups

Date

2009-08-24T09:53:04Z

Journal Title

Journal ISSN

Volume Title

Publisher

Abstract

The general aim of this study was to identify the suites of traits responsible for species shade tolerance and light harvesting in different plant functional groups. In particular, to understand how plant responses to light availability depend on species-specific functional traits in different plant functional groups at common light availability (genotypic plasticity) and within light gradients (phenotypic patterns). The results showed complex interactions between phenotypic plasticity and inherent species-specific differences, influencing the ability of plants to cope with limited light conditions, created by the surrounding vegetation. Alternative strategies, which can be partly explained by dynamics of light availability during leaf life-span, were observed among deciduous and evergreen woody species, graminoids and forbs. (1) In temperate woody flora of the Northern Hemisphere, species shade tolerance was positively related to leaf life-span and negatively related to leaf dry mass per area (LMA), nitrogen content per leaf area (Na) and photosynthetic capacity (Aa). However, there were also remarkable differences between the functional groups as shade tolerance decreased with photosynthetic capacity per leaf dry mass (Am) within deciduous broad-leaved group and increased within evergreen conifers’ group. (2) Within the deciduous tree canopy LMA and Na increased significantly along vertical gradient of light availability. In the herbaceous canopy, on the contrary, LMA and Na were generally not related to current light conditions, reflecting limited re-acclimation potential of mature leaves. (3) Community-level patterns in light capture, biomass and nitrogen partitioning were largely attributable to changes in species composition along a productivity gradient in herbaceous stands. Species, which became dominant at high soil resources had lower tissue nitrogen concentrations (high aNUE) and lower leaf area ratio (LAR), leading to community-level increase in aNUE and decrease in LAR along the productivity gradient. However, some subordinate species increased LAR with increasing soil fertility, indicating that dominant and subordinate species have distinct strategies to cope with increased competition for limited light resource.Minu doktoritöö eesmärgiks oli uurida, kuidas taimelehtede funktsionaalsed tunnused ning maapealse biomassi jaotus sõltuvad valgustingimustest nii liigisiseselt kui liikide vahel. Antud töö tulemuste põhjal võib öelda, et (1) põhjapoolkera parasvöötme puittaimedel on varjutaluvus üldiselt liigispetsiifilise keskmise lehe eluea ja -eripinnaga positiivses seoses ning lämmastikusisalduse ja fotosünteesivõimega (väljendatuna pindalaühiku kohta) negatiivses seoses, kuid funktsionaalsete gruppide siseselt esineb seoses üksikute lehe tunnustega märkimisväärseid erinevusi; (2) puittaimedel on seosed lehe tunnuste (eripind ning klorofülli- ja lämmastikusisaldus) ja valgustingimuste vahel piki lehestikusisest vertikaalset valgusgradienti tugevamad kui rohttaimedel ning (3) rohttaimede lämmastikukasutuse efektiivsuse ja maapealse biomassi jaotuse liigiomased erinevused mõjutavad oluliselt koosluse tasemel avalduvaid seoseid taimkattes neeldunud valgusega.

Description

Keywords

Citation