Growth and reproduction of vascular plants in polluted environments: a synthesis of existing knowledge

Identification of factors explaining diversity in plant responses to industrial pollution is crucial for predicting fates of polluted ecosystems. Meta-analysis based on 203 publications demonstrated that plants growing near point polluters showed similar decreases in characters reflecting growth (-13.1%) and reproduction processes (-8.5%). In herbaceous plants, root growth was reduced, while aboveground biomass did not change, because the decrease in leaf size was compensated by an increase in leaf number. In contrast, woody plants demonstrated no changes in allometry and their growth was reduced to a greater extent than growth of herbaceous plants. Raunkiaer's classification of life forms appeared the best predictor of species' responses to pollution. Within woody plants, trees and shrubs, but not dwarf shrubs, showed strong decreases in growth and reproduction. Within herbaceous plants, significant growth reduction was observed only in annuals. Longevity of foliage or plant phylogeny did not explain variation in species' responses. Adverse effects of pollution were stronger in regions with higher temperature and precipitation, hinting that existing pollution loads may become more harmful for plants as climate changes. Relatively minor explanatory value of the characteristics of individual polluters removes one of the principal obstacles to accounting for the effects of pollution in vegetation models and allows extrapolation of the effects observed near point polluters to both regional and global scales. We conclude that losses in productivity of plant communities due to aerial pollution can be approximately estimated on the basis of the life form spectra and climate. Key words: biomass, climate, life forms, point polluters, plant species, resource allocation, temperature. L'identification des facteurs expliquant la diversite des reactions des plantes envers la pollution industrielle represente un enjeu critique pour predire le devenir des eecosystemes polluees. Une meta-analyse portant sur 203 publications demontre que les plantes poussant pres de pollutions ponctuelles montrent des diminutions similaires pour des domrees refletant la croissance (-13.1 %) et les processus de reproduction (-8.5 %). Chez les plantes herbaceees, on observe une diminution de la croissance racinaire, alors que la biomasse eepigeee ne change pas, parce que l'augmentation du nombre de feuilles compense la dimension de leur surface. Au contraire, les plantes ligneuses ne demontrent aucun changement dans l'alleilomeetrie et leur croissance montre une plus forte diminution que les plantes herbaceees. La classification des formes de vie des plantes semble constituer le meilleur moyen pour predire les reactions des plantes a la pollution. Chez les plantes ligneuses, seuls les arbres et les arbustes, mais pas les arbustes nains, montrent de fortes diminutions de croissance et de reproduction. Chez les plantes herbaceees, l'on observe de fortes diminutions de croissance seulement chez les plantes annuelles. La longevite du feuillage et la phylogeenie veegetale n'expliquent pas la variation dans les reactions des especes. Les effets de la pollution s'aggravent dans les regions chaudes a fortes precipitations, ce qui suggere que les charges polluantes en place pourraient devenir plus nuisibles pour les plantes avec les changements climatiques. La valeur explicative relativement faible des caracteristiques des polluants individuels elimine un des principaux obstacles pour rendre compte des effets de la pollution dans les modeles de vegetation, permettant d'extrapoler les effets observes pres des pollutions ponctuelles, aux echelles regionales et globales. Les auteurs concluent que l'on peut estimer approximativement les pertes de productivite des communautesveegetales dues a la pollution aerienne sur la base des spectres des formes de vie et du climat. Mots-cles: biomasse, climat, formes de vie, polluants ponctuels, especes vegetales, allocation des ressources, temperature. [Traduit par la Redaction]
Introduction Vegetation shapes terrestrial ecosystems and serves several crucial functions in the biosphere. Due to both the economic and psychological importance of vegetation for mankind, deterioration of plant communities caused [...]