Abstract:The responses of Suaeda salsa to the environmental gradients of water table depth and soil salinity in the Yellow River Delta, China were analyzed from the aspect of ecological thresholds which were developed from the Gaussian model. Based on the correlation analysis of population biomass, density, height, coverage and abundance of Suaeda salsa, population biomass was selected as the population index for further analysis. The results indicated that the optimum water table depth for the growth of Suaeda salsa was about -0.42 m, the ecological thresholds were from -0.92 m to 0.08 m, and the optimum ecological thresholds were from -0.67 m to -0.17 m. To the soil salinity gradient, the optimum was about 12.71 g/kg, the ecological thresholds were from 5.17 g/kg to 20.25 g/kg, and the optimum ecological thresholds were from 8.94 g/kg to 16.48 g/kg. However, the effect of water-salinity interaction seemed to be important to the growth of Suaeda salsa, which was discussed through analyzing the water table depth-soil salinity relationship and their interactions. By using Ward cluster analysis and Gamma distances, 69 sampling sites were classified into 7 kinds of Suaeda salsa communities. It was found that there was a remarkable response of the community structure of Suaeda salsa to the water table depth and soil salinity gradients, which can be a switchover from xeromorphic and saline-alkali plants to limnophytes, and vice versa.

Abstract:84 quadrats from 5 vertical transects of Luhuitou fringing reef are investigated in detail by using video-quadrat and indoor-interpretation methods. The results show that (1) the reef consists of 69 species of hermatypic corals belonging to 24 genera and 13 families which are unevenly distributed in abundance. (2) Among all the corals, Porites lutea is the most dominant species with importance value percentage up to 36.62%; Porites and Acropora are dominant genera with importance value percentages 43.85% and 22.88%, respectively. (3) There exist distinct spatial differences in coral communities. Both the coral covers and coral diversity indices on the northeastern transects are higher than those on the central and southern transects. (4) Coral communities also show remarkable zonal characteristics with less coral species occurring on reef flat than on reef slope. The importance value percentage of the sole dominant coral genus, Porites, is over 50%, while on the reef slope, the importance value percentages are 28.33% for the first dominant genus Acropora and 26.71% for the second dominant genus Porites. Our further analysis suggests that the spatial and zonal differences of coral diversity pattern are correlated with both natural environmental changes and human activities. The shallow water reef flat is frequently exposed at low tide and it receives more anthropogenic influences (including dredging and trampling) than the deep water reef slope. Thus, the coral community on the reef flat is not as well developed as that on reef slope. The relatively poor coral covers and coral diversity indices on the central and southern transects are closely related to heavy human activities around these sites such as aquaculture, fishing and coastal sewage drainage. Therefore, the impact of human activities must be taken into account in developing strategies for the protection of this coral reef.

Abstract:Deep soil desiccations are increasingly threatening artificial forests on the Loess Plateau of China. Soil moisture in 0–1000 cm soil layers of 23 kinds of tree and shrub forestlands was measured. Average soil moisture in 0–1000 cm soil profile of the forestlands was 10.84%, obviously lower than soil moisture in local natural grasslands and soil stable moisture. Average soil desic-cation intensity reached a medium level. Maximum soil water use depth was close to or over 1000 cm, and the thickness of desic-cated soil layers in forestlands reached or passed 800 cm.

Abstract:We investigated the morphological characteristics of Tamarix ramosissima Nebkhas in the desert-oasis ecotones that were located in Jinta County and Ejin, China. Also, we quantitatively analyzed the relationships among the morphological parameters, spatial pattern and spatial heterogeneity. The results indicate that (1) Most of Tamarix ramosissima Nebkhas is of independent type. The average values of Nebkhas height, volume and plant canopy diameter in the Gobi are smaller than those in the desert, whereas the average values of plant height and coverage are on the contrary. All parameter values in Ejin are larger than those in Jinta. (2) There are linear relationships between the long and the short axes, and the volume and the plant canopy diameter of the Tamarix ramosissima Nebkhas. The regression curve of Nebkhas height and area is parabolic, and that of the plant height and canopy diameter is parabolic in the Gobi while linear in the desert. (3) The spatial pattern shows a mosaic pattern in the Gobi, while it forms Nebkhas chain distribution along the wind orientation in the desert. (4) The spatial heterogeneity is mostly caused by the non-stochastic reason, and it is higher in Ejin than in Jinta. In addition, the conclusions indicate that the stimulative action of deep sand bury, caused by high strength aeolian accumulation, to the growth of Tamarix ramosissima and the feedback effect between Tamarix ramosissima and Nebkha are the adaptability mechanisms of Tamarix ramosissima Nebkhas.

Abstract:The meadow moth, Loxostege sticticalis L., is an important outbreak pest in Northeast China. The spring population in Northeast China was considered as immigrants from North China; however, the population dynamics during 1996–2007 was not consistent with this traditional theory. In this study, the source area of the spring population of the meadow moth in Northeast China was identified by trajectory analysis using the wind field simulated by mesoscale numerical forecast model MM5. The results indicated that the population of the meadow moth in North China was able to migrate into Northeast China, but had not made a crucial contribution to the outbreaks there since the weather systems were generally adverse for such a long range migration in most of the years. On the other hand, high density cocoons of L. sticticalis have frequently been found in autumn in Northeast China since 1996. The trajectory analyses indicated that most of L. sticticalis in Northeast China in spring emerged from the cocoons that had overwintered either locally or in neighboring countries, i.e. Mongolia and Russia. The development of overwintering areas at higher latitudes coincides with the increased frequency of second-generation larvae; both phenomena might be attributed to the regional climate change associated with global warming.