Guangchun Lei

Delayed Flood Recession in Central Yangtze Floodplains Can Cause Significant Food Shortages for Wintering Geese: Results of Inundation Experiment

Carex meadows are critical habitat for wintering geese in the floodplains of the middle and lower reaches of Yangtze River, China. These meadows follow a growth cycle closely tied to the seasonal hydrological fluctuation: as water levels recede in the fall, exposed mudflats provide habitat for Carex spp. growth. The seasonal growth of Carex overlaps the arrival of wintering geese and provides an important food source for the migrants. Recent alterations to the Yangtze’s hydrology, however, have disrupted the synchronous relationship between water levels, Carex growth and wintering geese at Dongting Lake. In October 2012, we carried out an outdoor mesocosm experiment to investigate potential impacts of delayed water recession on the germination and growth of Carex heterolepis, the dominant Carex species at Dongting Lake, to understand how changes in hydrology might impact wintering goose habitat. Results showed that the delayed flood recession exerted significant impact on the first growth cycle of Carex growth. Prolonged inundation significantly lowered the intrinsic growth rate (Pxa0=xa00.03) and maximum growth rates (Pxa0=xa00.02). It also took significantly longer time to reach the peak growth rate (Pxa0=xa00.04 and 0.05 for number of shoot and biomass, respectively). As a result, biomass accumulation was reduced by 45, 62 and 90xa0% for 10-day, 20-day and 30-day inundation treatments, respectively. These results indicate a severe risk of food shortage for wintering geese when water recession delayed. This potential risk should be taken into consideration when operating any hydrological control structures that alter the flood regimes in Dongting Lake.

Soil Organic Carbon and its Fractions in Relation to Degradation and Restoration of Wetlands on the Zoigê Plateau, China

Through restoration, degraded wetlands are thought to recover their carbon storage function over time. However, little is known about the dynamics of soil organic carbon (SOC) and its fractions after restoration of degraded wetlands. In this study, we selected four wetlands, two degraded (one grazed and one graze-released site), one restored for 6xa0years and one natural site from the Zoigê wetlands on the Qinghai–Tibetan Plateau, China to investigate the dynamics of SOC following restoration. The concentrations of SOC, dissolved organic carbon (DOC), light fraction organic carbon (LFOC), and heavy fraction organic carbon (HFOC) in the degraded sites were significantly lower than those in the natural wetland. In contrast, soil δ13C (i.e. 13C/12C ratio) in the degraded sites was significantly higher than that in the natural site. After 8xa0years of restoration, the restored and the natural wetland sites did not differ significantly in SOC, DOC, LFOC, HFOC or δ13C. Therefore, restored wetlands regained some of their role in carbon storage over time. SOC turnover was slower in the natural wetland than in the degraded and restored sites.

Seasonal variability in baseline δ15N and usage as a nutrient indicator in Lake Poyang, China

Seasonal variation in nitrogen isotope ratios (δ15N) of four baseline candidates belonging to the planktonic and benthic food webs of Lake Poyang, China, was investigated. These baseline candidates were particulate organic matter (POM), sediment organic matter (SOM), a filterer mussel (Corbicula flumine), and a grazer snail (Bellamya aeruginosa). δ15N values of POM and SOM varied significantly among the sampling seasons, while no significant seasonal variation was observed among the δ15N values of the mussels and snails sampled in different seasons. POM δ15N was correlated with lake water PO4-P, while SOM δ15N was correlated with NO3-N. Mussel δ15N and lake water TN, NO3-N, and PO4-P were significantly correlated as were snail δ15N and TN, TP, and NO3-N. SOM and snails were better bioindicators of the water column nutrient concentration of Lake Poyang. The significant correlations between mussel δ15N and POM, as well as between snail δ15N and SOM, indicated the potential use of these baselines in trophic evaluations in planktonic and benthic food webs in this water-level fluctuating lake.

Zoning for management in wetland nature reserves: a case study using Wuliangsuhai Nature Reserve, China

BackgroundZoning is a fundamental tool for the effective management of nature reserves. A three-zone model (core zone, buffer zone, and experimental zone) has been applied to nature reserves in China since 1980s; however, this model appears not fit for all types of nature reserves, especially wetlands.Case descriptionWuliangsuhai is such a typical wetland reserve, which can represent most of the other wetland reserves in China, for both its human utilization, and for its function as the bird habitat. The “Component-Process-Service” (CPS) framework of the Convention on Wetlands allows a determination of the “ecological character” of the wetland and also allows identification of potential threats, providing thus a perspective for management opportunities and challenges.Discussion and evaluationApplying the CPS framework to Wuliangsuhai wetland nature reserve, we have had a better understanding of the ecosystem services and its relationship with the ecological process and components of the wetland. A comparison of effectiveness in maintaining ecosystem services by the two zoning models (the existing three-zone model, and the new zoning model) was made.ConclusionsThe study suggested introducing an additional risk-control zone to be more effective in managing and alleviating threats to the ecological character than the standard 3-zone system. Furthermore, a “dynamic” zoning that takes into account the annual variation in habitat and avifauna distribution, as an elaboration of the Four-zone structure, may achieve the desired conservation objectives in an even more effective manner. The proposed zonation structure has the added benefit of promoting harmonization between nature conservation and local sustainable development.

Resource availability determines food chain length in Chinese subtropical rivers

AbstractnThree prevailing hypotheses, namely resource availability, ecosystem size, and disturbance, are often used to explain variations in food chain length (FCL). Rivers vary widely in size, resources, and disturbance dimensions, even within the same catchment, providing an ideal platform to test ecological drivers of FCL in aquatic systems. In this study, we tested how resource availability (indicated by macroinvertebrate biomass), ecosystem size (indicated by basin area), and disturbance (indicated by daily water-level coefficients of variation) affected stable isotope-based estimates of FCL in subtropical rivers in the Province Jiangxi, China. The FCL varied widely among the studied rivers with a mean of 3.09 (range 2.00–3.99). Model-selection results indicated that resource availability could explain 60xa0% of the observed variation in FCL. The FCL of the studied rivers was positively correlated with fish richness and the total area of fish community δ13C–δ15N bi-plot space, thereby indicating that an increase in fish diversity could influence the trophic structure within the food web and lead to a longer FCL. Taken together, our results suggest that resource availability could predict FCL in subtropical rivers and plays a significant role in maintaining longer FCLs by providing more energy to support upper trophic-level fishes.

Activity Patterns of four Cranes in Poyang Lake, China: Indication of Habitat Naturalness

Poyang Lake is one of the most important wintering habitats for cranes in China, and thousands of cranes including Siberian Crane (leucogeranus leucogeranus), White-naped Crane (Grus vipio), Hooded Crane (G. monacha) and Common Crane (G. grus) winter here annually. Despite their different conservation status, the four cranes have substantial ecological niche overlap and often form mixed flocks in their wintering grounds. To understand the persistence and coexistence of the species, we used time-budgeting to investigate how these sympatric cranes allocate time to their activities. Our results indicate that the cranes had more foraging time and less vigilance time at Poyang Lake than at other wintering sites. Also, the four cranes displayed significantly different activity patterns in the shared habitat. Compared with the smaller sized Common Cranes and Hooded Cranes, the larger sized Siberian Cranes and White-naped Cranes tended to be more relaxed, suggesting foraging ability decides the crane community structure as evidenced in many ecosystems. Our results suggested that Poyang Lake is crucial for the cranes conservation, which needs a transregional even global management strategy.

Water regulation: a Sword of Damocles for migratory waterbirds in China?

Dams and reservoirs, regulating water levels for irrigation, hydropower and flood control, are sometimes considered as artificial managed wetlands. Recent research has shown that increased water surface of reservoirs have become habitats for some species of migratory waterbird. However, hydraulic engineering can be a Sword of Damocles for birds. Regulating water levels may dramatically alter a wetland ecosystem and ecological processes, change suitable habitats and influence food resource production and availability. These are crucial issues for migratory waterbirds, and a flexible management strategy, which balances the habitat requirements of waterbirds and the regulatory role of the hydraulic structure, is critical for long-term biodiversity conservation.