Polytolerance to abiotic stresses: how universal is the shade-drought tolerance trade-off in woody species?

AIMS: According to traditional ecophysiological theories stress tolerance of plants is predominately determined by universal physiochemical constraints. Plant acclimation to environmental stress therefore compromises plant performance under a different stress, hindering successful toleration of several abiotic stress factors simultaneously. Yet, recent studies have shown that these trade-offs are less exclusive than postulated so far, leaving more wiggle room for gaining polytolerance through adaptations We tested whether the polytolerance to shade and drought depends on cold and waterlogging tolerances - hypothesizing that polytolerance patterns in different species groups (angiosperms vs. gymnosperms; deciduous vs. evergreen; species originating from North America, Europe and East Asia) depend on the length of the vegetation period and species's dormancy through limiting the duration of favourable growing season. LOCATION: Northern hemisphere.
METHODS: Our study analyzed four main abiotic stress factors - shade, drought, cold and waterlogging stress - for 806 Northern hemisphere woody species using cross-calibrated tolerance rankings. The importance of trade-offs among species ecological potentials was evaluated using the species-specific estimates of polytolerance to chosen factors.
RESULTS: We found that both cold and waterlogging tolerance are negatively related to species' capabilities of simultaneously tolerating low light and water conditions. While this pattern was different in angiosperms and gymnosperms, species region of origin and leaf type had no effect on this relationship. MAIN
CONCLUSIONS: Our results demonstrate that adaptation to different abiotic stress factors in woody plants is highly complex. Vegetation period length and dormancy are the key factors explaining why woody plants are less capable of tolerating both shade and drought in habitats where vegetation period is relatively short and water table high. While dormancy enables angiosperms to more successfully face additional stress factors besides shade and drought, gymnosperms have lower polytolerance, but are better tolerators of shade and drought when other environmental factors are favorable.