Guodong Wang

Duration of farming is an indicator of natural restoration potential of sedge meadows

Soil seed banks can be important components of ecological restoration, particularly if the species remain viable in the soil for long periods of time. A germination experiment was conducted in the greenhouse to determine seed bank viability based on length of time farmed. Soils from sedge meadows farmed between 0 and 50 years were collected in Sanjiang Plain, China. Most dominant sedges (e.g., Carex schmidtii, C. lasiocarpa) and grasses (e.g. Calamagrostis angustifolia) survived as seeds if farmed for less than 5 years, therefore fields farmed for short periods of time are the best candidates for wetland restoration. Certain important structural components (tussock-forming Carex spp.) are not retained in seed banks when farmed for 6–15 years, but the seed banks still contained viable seeds of other important sedge meadow species, which could contribute to the restoration of wetland communities. However, most sedge meadow species were missing in fields farmed for more than 16 years, which make these fields difficult to restore via natural recolonization. We conclude that the duration of farming can be used as a general indicator of the potential of natural restoration for sedge meadows. This information could be used to determine which wetlands might be targeted for restoration.

Structure and Richness of Carex meyeriana Tussocks in Peatlands of Northeastern China

Tussocks in sedge meadows may be able to support biodiversity because of their structural complexity. We studied Carex meyeriana tussocks to look at their role in creating micro-heterogeneity and supporting biodiversity in northeastern China. We investigated vegetation in paired plots on and between tussocks of C. meyeriana, and measured water depth, soil water content, soil temperature, soil organic carbon, litter depth, soil total N and P on and between tussocks. We found a total of 75 taxa in the sedge meadows. Species richness was higher on rather than between tussocks. Soil temperature, organic carbon, soil total P, and litter depth were higher on tussocks rather than between tussocks. Water depth, soil water content and soil total N were lower on tussocks compared to between tussocks. Species richness on tussocks increased with increasing tussock basal area, height and surface area. Plant composition was mostly related to the environmental variables based on canonical correspondence analysis. The main gradient is determined, from on tussocks to between tussocks, by an increase in water depth, soil water content and total N and a decrease in soil temperature and soil total P. We conclude that tussocks create different microhabitats in sedge meadows that support different species.

Patterns and controls of temperature sensitivity of soil respiration in a meadow steppe of the Songnen Plain, Northeast China

Quantifying the temporal and spatial patterns of temperature sensitivity (Q10) of soil respiration (Rs) as well as its controlling factors is critical to reveal the response the soil ecological processes to global warming and improve carbon budget estimations at a regional scale. The seasonal and annual variations in the temperature response of Rs were assessed during the two growing seasons in 2011 and 2012 in four different vegetation sites in a meadow steppe of the Songnen Plain, China. The Q10 values across all sites exhibited significant seasonal variations with a minimum value (1.81–2.34) occurring during summer and a peak value (3.82–4.54) occurring in either spring or autumn. The mean seasonal Q10 values showed no significant differences among the four different vegetation types. On the annual scale, however, the Chloris virgata site had significantly higher annual Q10 values (3.67–4.22) than the other three community sites in 2011 and 2012 and over the two years (2.01–3.67), indicating that the response of the Rs to climate warming may vary with vegetation type. The soil temperature and moisture had interactive effects on the variations of Q10 values. Soil temperature was the dominant factor influencing Q10 values, while soil moisture was an additional contributor to the variations of Q10. Due to the significant temporal and spatial variations in soil respiration response to temperature, acclimation of Rs to temperature variation should be taken into account in forecasting future terrestrial carbon cycle and its feedback to global warming.

Effects of vegetation type on surface elevation change in Liaohe River Delta wetlands facing accelerated sea level rise

Rising sea levels threaten the sustainability of coastal wetlands around the globe. The ability of coastal marshes to maintain their position in the intertidal zone depends on the accumulation of both organic and inorganic materials, and vegetation is important in these processes. To study the effects of vegetation type on surface elevation change, we measured surface accretion and elevation change from 2011 to 2016 using rod surface elevation table and feldspar marker horizon method (RSET-MH) in two Phragmites and two Suaeda marshes in the Liaohe River Delta. The Phragmites marshes exhibited higher rates of surface accretion and elevation change than the Suaeda marshes. The two Phragmites marsh sites had average surface elevation change rates at 8.78 mm/yr and 9.26 mm/yr and surface accretion rates at 17.56 mm/yr and 17.88 mm/yr, respectively. At the same time, the two Suaeda marsh sites had average surface elevation change rates at 5.77 mm/yr and 5.91 mm/yr and surface accretion rates at 13.42 mm/yr and 14.38 mm/yr, respectively. The elevation change rates in both the Phragmites marshes and the Suaeda marshes in the Liaohe River Delta could keep pace and even continue to gain elevation relative to averaged sea level rise in the Bohai Sea reported by the 2016 State Oceanic Administration, People’s Republic of China projection (2.4–5.5 mm/yr) in current situations. Our data suggest that vegetation is important in the accretionary processes and vegetation type could regulate the wetland surface elevation. However, the vulnerability of coastal wetlands in the Liaohe River Delta need further assessment considering the accelerated sea level rise, the high rate of subsidence, and the declining sediment delivery, especially for the Suaeda marshes.

Diurnal variation of soil CO 2 efflux and its optimal measuring time-window of temperate meadow steppes in western Songnen Plain, China

In order to study the diurnal variation of soil CO2 efflux from temperate meadow steppes in Northeast China, and determine the best time for observation, a field experiment was conducted with a LI-6400 soil CO2 flux system under five typical plant communities (Suaeda glauca (Sg), Chloris virgata (Cv), Puccinellia distans (Pd), Leymus chinensis (Lc) and Phragmites australis (Pa)) and an alkali-spot land (As) at the meadow steppe of western Songnen Plain. The results showed that the diurnal variation of soil CO2 efflux exhibited a single peak curve in the growing season. Diurnal maximum soil respiration (Rs) often appeared between 11:00 and 13:00, while the minimum occurred at 21:00–23:00 or before dawn. Air temperature near the soil surface (Ta) and soil temperature at 10 cm depth (T10) exerted dominant control on the diurnal variations of soil respiration. The time-windows 7:00–9:00 could be used as the optimal measuring time to represent the daily mean soil CO2 efflux at the Cv, Pd, Lc and Pa sites. The daily mean soil CO2 efflux was close to the soil CO2 efflux from 15:00 to 17:00 and the mean of 2 individual soil CO2 efflux from 15:00 to 19:00 at the As and Sg sites, respectively. During nocturnal hours, negative soil CO2 fluxes (CO2 downwards into the soil) were frequently observed at the As and Sg sites, the magnitude of the negative CO2 fluxes were 0.10–1.55 μmol/(m2·s) and 0.10–0.69 μmol/(m2·s) at the two sites. The results implied that alkaline soils could absorb CO2 under natural condition, which might have significant implications to the global carbon budget accounting.