Zifa Deng

China's Natural Wetlands: Past Problems, Current Status, and Future Challenges

Abstract Natural wetlands, occupying 3.8% of Chinas land and providing 54.9% of ecosystem services, are unevenly distributed among eight wetland regions. Natural wetlands in China suffered great loss and degradation (e.g., 23.0% freshwater swamps, 51.2% costal wetlands) because of the wetland reclamation during Chinas long history of civilization, and the population pressure and the misguided policies over the last 50 years. Recently, with an improved understanding that healthy wetland ecosystems play a vital role in her sustainable economic development, China started major efforts in wetland conservation, as signified by the policy to return reclaimed croplands to wetlands, the funding of billions of dollars to restore degraded wetlands, and the national plan to place 90% of natural wetlands under protection by 2030. This paper describes the current status of the natural wetlands in China, reviews past problems, and discusses current efforts and future challenges in protecting Chinas natural wetlands.

Genetic structure and habitat selection of the tall form Spartina alterniflora Loisel. in China

Spartina alterniflora Loisel., a highly invasive species on the Chinese coast, is a focus of increasing management concerns due to its high expansion rate in tideland and the significant damages on native ecosystems, since its introduction into China in 1979. There are both tall and dwarf forms of the species in China. The tall form with strongly invasive ability has widely expanded. Genetic variation was examined within and among three tall form S. alterniflora populations in Jiangsu Province using amplified fragment length polymorphisms (AFLP) markers. Three populations were sampled along the coastal line, and each population was divided into three subpopulations relating with the three microenvironments: Foreland, mid-marsh and upland. Genetic diversity was low at both the population level (PPB = 22%, HE = 0. 0657 and Hpop = 0.099) and at the species level (PPB = 24.65%, HT = 0.0814 and Hsp = 0.1225). A low level of genetic differentiation among populations was detected based on analyses of coefficients of genetic differentiation (9.51%), Shannon’s diversity index (9.48%) and AMOVA (10.69%). The mean value of Gst among nine subpopulations was 22.02%. Habitat selections may occur and affect the genetic structure of S. alterniflora in the process of its spread because there are 7.2, 3.4 and 5.9% specific bands out of 158 polymorphic bands in foreland, mid-marsh, and upland, respectively. This genetic differentiation may result from seedling survival and colonization success based on the selection of specialized microhabitats. The results indicated that high capability of genetic differentiation within populations and strong adaptability of tall form S. alterniflora may be the reasons for the widespread expansion of the tall form S. alterniflora.

Nitrogen level changes the interactions between a native (Scirpus triqueter) and an exotic species (Spartina anglica) in Coastal China.

The exotic species Spartina anglica, introduced from Europe in 1963, has been experiencing a decline in the past decade in coastal China, but the reasons for the decline are still not clear. It is hypothesized that competition with the native species Scirpus triqueter may have played an important role in the decline due to niche overlap in the field. We measured biomass, leaf number and area, asexual reproduction and relative neighborhood effect (RNE) of the two species in both monoculture and mixture under three nitrogen levels (control, low and high). S. anglica showed significantly lower biomass accumulation, leaf number and asexual reproduction in mixture than in monoculture. The inter- and intra-specific RNE of S. anglica were all positive, and the inter-specific RNE was significantly higher than the intra-specific RNE in the control. For S. triqueter, inter- and intra-specific RNE were negative at the high nitrogen level but positive in the control and at the low nitrogen level. This indicates that S. triqueter exerted an asymmetric competitive advantage over S. anglica in the control and low nitrogen conditions; however, S. anglica facilitated growth of S. triqueter in high nitrogen conditions. Nitrogen level changed the interactions between the two species because S. triqueter better tolerated low nitrogen. Since S. anglica is increasingly confined to upper, more nitrogen-limited marsh areas in coastal China, increased competition from S. triqueter may help explain its decline.

The headwater loss of the western plateau exacerbates China's long thirst

Abstract China is a country poor in water resources, with an annual 2800 km3 of freshwater storage and 2300 m3 of water availability per capita. Both the water shortage and low use efficiency make modern China thirsty. Furthermore, the loss of glaciers and wetlands in the western plateau that feed the major rivers of China as their headwaters will exacerbate this thirst in the future. Although groundwater might be tapped as a resource, most regions already use their aquifers excessively. China needs to focus on its urgent water-shortage problems to safeguard its booming economy and to contribute more to world development.

Eco-physiological responses of the declining population Spartina anglica to N and P fertilizer addition

Abstract Nitrogen and phosphorus are both important life elements. N, P and combined N-P fertilizers were added to the declining population Spartina anglica Hubbard in coastal China. Some growth parameters and eco-physiological responses of S. anglica to different fertilizer treatments (N, P and combined N-P fertilizer addition with high, medium and low levels, respectively) were measured. The fertilizer addition had a highly significant effect on the dynamics of its height-growth, number of leaves, number of roots and total biomass. Only N addition had a significant effect on leaf area and leaf thickness in all fertilizer treatments. On the dynamics of its height-growth, the effect of N addition was the most apparent, and the effect of N-P addition was not greater than those of N and P addition separately. The photosynthesis rate was enhanced and the yield was the highest with the highest N, the highest N-P and the medium P addition. The rates were higher than those of CK by 19.08 μmol·m−2·s−1, 15.47 μmol·m−2·s−1 and 11.23 μmol·m−2·s−1, respectively. The activity of SOD and POD increased with the treatments after freshwater stress for 14 days. Effects of medium N and P addition were significant for SOD activity. However, POD activity was significantly higher with the treatment of higher N and higher N-P addition. In a word, fertilizer addition improved the growth of the declining population S. anglica. The results indicated that the decline of S. anglica was correlated with the nutriment deficiency in soil, especially with the lack of N.