Fluctuating water table affects gross ecosystem production and gross radiation use efficiency in a sedge-grass marsh

Abstract

The eddy covariance method was used for continuous measurement of the seasonal courses of the following parameters of the carbon cycle in a sedgegrass marsh type of wetland ecosystem (49°01 0 29 00 N, 14°46 0 13 00 E, South Bohemia, Czech Republic, Central Europe): gross ecosystem production (GEP), net ecosystem production (NEP) and ecosystem respiration. During a 3-year series of measurements, we recorded marked fluctuations of the water table, which affected the overall water regime of the wetland studied. Between-year differences in the water regime strongly influenced the total annual carbon sequestration. The lowest annual GEP and NEP of 996 and 152 g m -2 of carbon, respectively, were recorded in 2006, a year with two large floods, one in the spring, the other in the summer. By contrast, in the dry year of 2007, with no flood, the highest annual GEP and NEP were recorded: 1,328 and 274 g m -2 , respectively. Significant differences were found in the efficiency of solar energy use for GEP [gross radiation use efficiency, GRUE = GEP/PhAR (photosynthetically active radiation), i.e., amount of carbon gained per energy unit]. The highest GRUE was recorded immediately after the 2006 summer flood. In 2007, the GRUE decreased linearly with rising water table. A variable water regime thus markedly affects the processes of carbon accumulation and the efficiency of solar energy use for organic matter production in freshwater wetlands of the sedge-grass marsh type.

Water level, vegetation composition, and plant productivity explain greenhouse gas fluxes in temperate cutover fens after inundation

“…They were comparable to temperate Typha latifolia (82 g CH 4 −C m −2 yr −1 ; Whiting and Chanton, 2001) and T. angustifolia marshes (51 g CH 4 −C m −2 yr −1 , Chu et al, 2015; 127 g CH 4 −C m −2 yr −1 , Strachan et al, 2015). The constantly high water levels made us expect a net CO 2 uptake at GK Typha-Hydrocharis and GK CarexLysimachia, as was found for Typha latifolia and T. angustifolia marshes (Whiting and Chanton, 2001;Strachan et al, 2015), for a water saturated temperate sedge fen in the Czech Republic (Dušek et al, 2012), and in the wet year for Carex acutiformis and Typha latifolia (Günther et al, 2014). However, in contrast to our first hypothesis the sites GK Typha-Hydrocharis and GK Carex-Lysimachia were net CO 2 sources.…”

“…As climatic conditions during the first year of the present study were similar to the long term average, other factors, like reduced GPP because of shading from old standing leaves may have been important, as there was much dry biomass present. Also the high water levels and their strong fluctuations may have imposed stress on the vegetation (Dušek et al, 2012), as indicated by changes in the cover of the dominant species between years (Table A1) and the early aging of the sedges. High R eco fluxes from the floating tall sedge -Typha latifolia reeds could be the result of increased maintenance respiration because of environmental stress (Chapin et al, 2002) combined with high heterotrophic respiration from decomposing dead plant material which formed the main part of the sedge tussocks (estimated from photographic documentation).…”

Modeling of Soil Co2 Efflux During Water Table Fluctuation Based on in Situ Measured Data From a Sedge-Grass Marsh

“…The water table and its possible fluctuation determine whether conditions are anoxic or anaerobic and thus they also determine the prevailing biogeochemical processes in wetland soils and in the whole wetland ecosystem (Reddy and DeLaune, 2008). Therefore, the water table level significantly affects CO 2 exchange between the ecosystem and the atmosphere (Dusek et al, 2009;Jimenez et al, 2012), and thus also affects the gross ecosystem production, including the gross radiation use efficiency (Dusek et al, 2012a).…”

Seasonal dynamics of biomass partitioning in a tall sedge, Carex acuta L.

“…A tall sedge, Carex acuta L., has been chosen for this study as a common dominant of temperate wet grasslands. It dominates a sedge-grass marsh in which the carbon exchange has been studied since 2006 (Dušek et al, 2009(Dušek et al, , 2012. This species has also been investigated in relation to its life history (Soukupová, 1988(Soukupová, , 2002, production , adaptation to wetland conditions (Končalová, 1990) and tolerance of eutrophication (Čížková- Končalová and Bauer, 1993;Končalová et al, 1993).…”