Responses to a fluctuating environment: effects of water depth on growth and biomass allocation in Eleocharis cellulosa Torr. (Cyperaceae)

Abstract

Fluctuating water levels, which characterize freshwater marshes of the Florida Everglades, U.S.A., constrain growth in emergent macrophytes. We studied acclimation of Eleocharis cellulosa Torr. (Cyperaceae) in mesocosms to water depths of 7 and 54 cm and to switching between these water depths. After 80 weeks at fixed depths, deepwater plants produced (i) taller, thicker, and fewer shoots; (ii) fewer ramets; (iii) less biomass; and (iv) greater shoot biomass relative to root and rhizome biomass. Despite large differences in shoot lengths between water depths, shoot heights above the water surface were similar. Emergent shoot tissues had thick secondary walls in the epidermal cells and several palisade layers beneath; submerged shoots lacked this anatomy. When shallow-water plants were transferred to deep water, shoots elongated rapidly, with younger shoots elongating more than older ones. When deepwater plants were transferred to shallow water, emergent shoots quickly died and were replaced by new shoots. Overall, plants exposed to rapid changes in water level adjusted biomass allocation patterns after 9 weeks towards those of control plants in their new environment, but deepwater plants responded more slowly than shallow-water plants. These shifts may allow E. cellulosa to produce shoots that optimize biomechanical support and aeration.Key words: biomass allocation, Eleocharis cellulosa, Everglades, gas exchange, shoot demography, wetland plants.

Recent and Historic Drivers of Landscape Change in the Everglades Ridge, Slough, and Tree Island Mosaic

“…High flow depths also displace floating mats of periphyton and Utricularia away from the bed, diminishing their contribution to the depth-averaged frontal area (Larsen et al, 2009b). In addition, many wetland emergent species, including Eleocharis spp., respond to high water levels by increasing their stem diameter (Baksh and Richards, 2006;Edwards et al, 2003) while decreasing overall biomass and number of shoots (Edwards et al, 2003). For these reasons, researchers have observed a positive relationship between flow velocity and flow depth in Shark River Slough (He et al, 2010;Lee et al, 2004;Leonard et al, 2006), Taylor Slough (Lee et al, 2004), and WCA-2A (Lee et al, 2004).…”

Changes in vegetation and soil seed bank of meadow after waterlogging caused by Castor fiber

“…Changes in light intensity or soil properties may result in a population decline caused by death of water stress-exposed individuals and/or in modification of selected characteristics of their life history by reduction of biomass or changing the pattern of biomass allocation as well as decreasing vegetative and/or generative propagation [12][13][14][15][16][17][18]. Seed bank reserves in the soil have a fundamental role in maintenance of plant communities under long-term stress caused by waterlogging.…”

Quantitative Comparison of Plant Community Hydrology Using Large-Extent, Long-Term Data

“…A major driver of wetland vegetation distribution and community dynamics is the hydrologic regime (Ross et al 2003;Ogden et al 2005;Mitsch and Gosselink 2007;Larsen et al 2011;McVoy et al 2011). Hydrologic tolerances and optima for wetland plant species are typically defined by laboratory, mesocosm or field experiments in which individual plants are grown under controlled water depths and hydroperiods (Grace 1989;David 1996;Newman et al 1996;Edwards et al 2003;Busch et al 2004;Jones et al 2006;Macek et al 2006;Deegan et al 2007;Spalding and Hester 2007). These studies, however, can provide information for only a limited number of species and can rarely be extrapolated to more complex natural settings, where species interactions and other environmental factors influence community composition.…”