Effects of hydrological regime on development of Carex wet meadows in East Dongting Lake, a Ramsar Wetland for wintering waterbirds

Abstract

Wet meadows are one of the most important ecological components in floodplain, and are among the most dynamic ecosystems. Understanding the development of wet meadows and contributing environmental factors can provide better support for wetland management. Carex meadows in East Dongting Lake National Nature Reserve (EDLNNR) provide vital wintering ground for thousands of migratory waterbirds, and their ecological functions are under threated due to hydrological alternation. We measured wet meadow expansion in EDLNNR from 1989 to 2014, and explored its responses to hydrological and climatic factors within the generalised additive models (GAM) framework. We found an overall expansion of wet meadows over the study period. However, in contrast to many previous studies, our results showed that water level fluctuations at the hydrologic indicator site had only limited impacts on their development. Instead, sampling year, timing of water level recession, and local rainfall exerted significant effects. The effects of sampling year reflected the changes in sedimentation within Dongting Lake; and effects of timing of water withdrawal might be explained by the life history of the dominant sedge species. Our study suggested that the impacts of large scale hydrological alternation on vegetation may operate indirectly through its effects on sediment balance.

Estimating the biomass of Carex cinerascens (Cyperaceae) in floodplain wetlands in Poyang Lake, China

“…This result was consistent with those of other studies (Feng et al 2016). The high elevation generally has a deep water table level, which means that the first exposure area usually have the higher air temperature that can affect the growth of C. cinerascens (Miguez et al 2008;Jing et al 2017). C. cinerascens preferred a relatively shallow groundwater table (Xu et al 2015).…”

“…Through the growth model established in our study at different growth times combined with the functional traits that the geese feed, managers could provide suitable habitats for the waterbirds by controlling the growth and distribution of C. cinerascens meadows, to evaluate the carrying capacity of the lake on the geese. Given that the growth process of C. cinerascens was primarily affected by the timing of water recession (Jing et al 2017), we can manage the biomass of C. cinerascens by controlling the water level and the timing of water recession.…”

“…The overlap between the growth of C. cinerascens and the arrival of wintering waterbirds makes C. cinerascens an important food source for many herbivorous wintering waterbird species, particularly geese (Cao et al 2008). Moreover, the implementation of the Poyang Lake water conservancy hub project, which is planned to establish and/or change the timing of water level recessions, is an important factor that can influence the biomass of C. cinerascens in wetlands (Guan et al 2014;Jing et al 2017). Therefore, estimating the biomass of C. cinerascens in Poyang Lake wetland during the flood recession period is important to elucidate the functions of wetland in providing habitats for waterbirds (Liao et al 2013), and to evaluate the effects from the Poyang Lake water conservancy hub project.…”

Behavioural plasticity and trophic niche shift: How wintering geese respond to habitat alteration

“…early September to late October) as it coincides with the arrival of wintering waterfowl (Guan et al, 2016). In the 6 years since the start of the project, we have never observed the geese foraging on old mature grass (Guan et al, 2016;Jing et al, 2017). The species often forms a monocultural wet meadow (cover excesses 95%, Guan et al, 2016;Zou et al, 2017) and is the primary food resource of wintering herbivorous geese.…”

“…The geese feed primarily on the short, newly grown grass shoots, which are highest in protein and lowest in structural carbohydrates (Guan et al, 2016). In the 6 years since the start of the project, we have never observed the geese foraging on old mature grass (Guan et al, 2016;Jing et al, 2017).…”