Xinsheng Zhao

Effect of mangrove restoration on crab burrow density in Luoyangjiang Estuary, China

BackgroundMangrove restoration seeks to restore or rebuild degraded mangrove systems. The methods of mangrove restoration include ecological projects and restoration-oriented technologies, the latter of which are designed to restore the structure, processes as well as related physical, chemical and biological characteristics of wetlands and to ensure the provision of ecosystem services. As important components of mangrove ecosystem, benthic organisms and crabs play a key role in nutrient cycling. In addition, mangrove restoration, such as vegetation restoration measures, can lead to changes in the benthic faunal communities. This study investigates whether the presence of different mangrove species, age and canopy cover of mangrove communities affect the density of crab burrows.MethodsThe Luoyangjiang Estuary, in the southeast of Fujian Province, was selected as our research area. A survey, covering 14 sites, was conducted to investigate the impacts of mangrove restoration on the density of crab burrows in four rehabilitated forests with different stand ages and canopy.ResultsIt was found that differences in vegetation types had a large impact on crab density and that the density of crab burrows was lower on exposed beaches (non-mangrove) than under mature Kandelia candel, Aegiceras corniculatum and Avicennia marina communities. In general, the amount of leaf litter and debris on mangrove mudflats was greater than on the beaches as food sources for crabs. Two-factor analysis of variance (ANOVA) shows that changes in mangrove species and age since restoration had different effects on crab burrow density. The effect of canopy cover was highly significant on crab burrow density.ConclusionsThe results suggest that in the process of mangrove restoration the combined effects of mangrove stand age, canopy cover and other factors should be taken into account. This study further supports the findings of the future scientific research and practice on mangrove restoration and management measures.

Identification and modelling the HRT distribution in subsurface constructed wetland

This study focused on the identification of the hydrodynamics of a horizontal subsurface constructed wetland (HSSF-CW) located in Beijing wildlife rescue and rehabilitation center, Beijing. The effects of plant growth of iris tectorum on the hydrodynamic behaviours were studied and the distribution of the hydraulic residence time was simulated by several mathematical models in order to understand the fluctuations and mixing processes of pollutants in the HSSF-CW. Treatment performance of the HSSF-CW was evaluated by comparing the area-based removal rates of different pollutants. According to the results, water depth has a negative effect on the plant growth and a larger hydraulic loading rate is not conducive to the growth of wetland plants. Modelling the probability density of the residence time distribution indicated that the shorter hydraulic residence time of 10.16 hours compared with a theoretical hydraulic residence time of 12.81 hours was responsible for the lower removal efficiency of pollutants (T-P: 0.17 ± 0.04 g m(-2) day(-1), T-N: 1.10 ± 0.05 g m(-2) day(-1), PO(4)-P: 0.08 ± 0.04 g m(-2) day(-1), NH(4)-N: 0.19 ± 0.02 g m(-2) day(-1), NO(3)-N: 0.52 ± 0.03 g m(-2) day(-1), Chl_a: 18.26 ± 0.09 g m(-2) day(-1)). The results of a superposition simulation of residence time distribution indicated that the asymmetric double sigmoidal (asym2sig) model is competent at providing a reasonable match between the measured and the predicted values to some extent. Based on the good fit of the experimental datasets by the asym2sig probability density function, the mathematical expectation approximated to the actual hydraulic residence time (10.16 hours) of the HSSF-CW.

Distribution patterns of plant communities and their associations with environmental soil factors on the eastern shore of Lake Taihu, China

ABSTRACT Introduction: Plant communities and soil factors might interact with each other in different temporal and spatial scales, which can influence the patterns and processes of the wetland ecosystem. To get a better understanding of the distribution of plants in wetlands and analyze their associations with environmental soil factors, the structure and types of plant communities in the eastern shore area of Lake Taihu were analyzed by two-way indicator species analysis and canonical correspondence analysis (CCA) ordination. The spatial distribution patterns of vegetation and the main factors affecting the distributions were investigated.Outcomes: Sixty-six sampling sites were selected to obtain vegetation species and soil environmental factor data. Results showed that 22 species from the 66 sites could be divided into seven communities: I: Arundo donax; II: A. donax + Phragmites australis; III: Zizania latifolia + Typha orientalis; IV: P. australis + Alternanthera philoxeroides + Polygonum hydropiper; V: P. australis; VI: P. australis + Humulus scandens; and VII: Erigeron acer + Ipomoea batatas + Rumex acetosa. Plant species and soil factors in the CCA analysis showed that I. batatas, E. acer, Chenopodium album, Polygonum lapathifolium, and Acalypha australis were mainly affected by pH, whereas Echinochloa crus-galli, Setaria viridis, and H. scandens were mainly affected by soil total phosphorus. Mentha canadensis and A. donax were mainly affected by soil conductivity, A. philoxeroides was mainly affected by soil organic matter and, Z. latifolia, Metaplexis japonica and P. hydropiper were mainly affected by available phosphorus.Conclusion:These results indicated that different plants adapted to different soil environmental factors and provided basic information on the diversity of Lake Taihu wetland vegetation.

Inhibition Effects of Full Degradation Barley Straws on Algal

How to control water eutrophication bloom having been the difficulties in the field of environmental engineering. Various measures have been taken to control the occurrence of algal blooms and slow down the outbreak of the frequency, such as source control (non-point source pollution control and abatement nutrient loading, sediment dredging, etc.), inhibition algaecide measures (artificial salvage or kill algae, etc.) have failed to achieve the desired effect, which had the effect only in the short term, even some improper physical or chemical methods had exacerbated the fragile wetland ecosystem. Therefore, to explore effective, economical, and no secondary pollution, low ecological risk control algal blooms method is an important task for environmental science. In this paper, barley straws with pretreated (nitrogen and phosphorus) were added to the eutrophication water bodies, to analyze the inhibition effect of full degradation barley straws on algal. We prepared a number of 50×20×25 cm glass tanks and aerators, and selected mature dry barley straw as the test material. Barley straws were cut into <;1 cm small pieces or crushed directly. Barley straw in the water (the natural state placed more than two weeks to remove chlorine ion) in the aeration state before continuing degradation of 15 to 30 days, then remove the water the same way again (in this case water use culture medium) to continue the degradation of 15 to 30 days. The temperature was maintained at 20 to 25 °C; barley straw in the degradation process of the full removal of nitrogen and phosphorus. Algae was collected from wild algae bloom, Microcysis aeruginosa, Aphanizomenon flosaquae, Spirogyra communis, Oscillatoria and Scenedesmus with microscope monitoring. Barley straw used 0.1g/m<;sup>;3<;/sup>; as the gradient, and 0.3g/m<;sup>;3<;/sup>; 0.5g/m<;sup>;3<;/sup>; and 2g/m<;sup>;3<;/sup>; concentration began to do under three parallel; while using not add to the degradation of barley straw “medium” + “algae” to deal with control. pH, EC, chla, algae type and quantity were observed every three days in 30 days. The results show that the physical and chemical changes in the nature of the water for the inhibition effects of degradation of barley straw. The change of pH and EC made barley straw in the chemical degradation process, the development of biological response to a favorable direction, which conducive to the generation and accumulation of algal material. Without suppression of the handle direct degradation of barley straw algae is not obvious, the full effects of algal addition to nitrogen and phosphorus in barley straw degradation significantly higher than that of the control, test period algae proliferate phenomenon, but over time was gradually reduced trend. Inhibition effect is a slight difference between the two, but not significant. Performance of the inhibition effect of different gradient content of the degradation of barley straw: 2.0g/m<;sup>;3<;/sup>;>;0.5g/m<;sup>;3<;/sup>;>;0.3g/m<;sup>;3<;/sup>;>;0.1g/m<;sup>;3<;/sup>;, when the concentration of degradation of barley straw when 0.1g/m<;sup>;3<;/sup>; basic loss of algal function; show that the degradation of barley straw algal role of broad-spectrum resistance. Microcystis aeruginosa water bloom beam filament algae, the Britain algae (P<;0.01) and water cotton algae and gate columns algae inhibit the degradation of barley straw (P<;0.01). Our results provide a reference for the control of water algal blooms.