Changfang Zhou

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.

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.