Leaf Functional Traits and Biomass of Wetland Plants in Forest and Steppe Zones

Resumo

Leaf traits, the rate of gas exchange, and biomass were examined in five plurizonal species (Alisma plantago-aquatica L., Carex acuta L., Eleocharis palustris (L.) Roem. et Schult., Phalaris arundinacea L., and Typha angustifolia L.) of emergent plants growing in wetlands of forest (Middle Urals) and steppe (South Urals) zones. It was found that changes in the leaf thickness, leaf mass per area (LMA), the transpiration rate, and characteristics of the pigment complex associated with a rise in aridity were species-specific. Structural reorganization of the leaves of wetland plants growing in conditions of steppe wetland showed a general pattern of an increase in leaf density (1.2–2 times) and a reduction in leaf area (by 42–54%). This trend was accompanied by a reduction in the photosynthesis rate per 1 m² (1.2–3.4 times) or per 1 mg of chlorophyll (by 29–63%). In two species, P. arundinacea and T. angustifolia, we detected a decrease in stomatal conductance by 2 and 4.8 times, respectively, in more arid conditions. Analysis of interspecific relations between plant productivity and leaf parameters has shown that plant biomass positively correlated with leaf area (r = 0.84, P < 0.01) and with the photosynthesis rate per leaf area unit (r = 0.97, P < 0.001) both in the regions of the Middle and South Urals. On the whole, structural changes in the leaves associated with adaptation of plant water relations to semiarid climate lead to a decrease in photosynthetic activity of leaves and, therefore, a decline of plant height and productivity of emergent plants growing in steppe wetland.