Integrating UAV data for assessing the ecological response of Spartina alterniflora towards inundation and salinity gradients in coastal wetland.

The overwhelming spread of Spartina alterniflora (smooth cordgrass) has put many native plant communities and coastal environments at risk. A better understanding of how S. alterniflora responds to inundation and salinity gradients will help manage the invasion of this species. However, current spatial quantitative analyses are insufficient. Thus, unmanned aerial vehicles (UAVs) and field sampling data were integrated to assess the ecological response of S. alterniflora to inundation and salinity gradients. This study aimed to determine the optimum ecological range of flooding and saline for S. alterniflora in Dafeng Milu National Nature Reserve in Jiangsu, China. Our results showed that the optimum ecological amplitude of S. alterniflora to flooding depth was [-0.07 m, 0.82 m] and the optimum mean growing point was 0.38 m. Furthermore, the optimum flooding time was [0 h,11.87 h], and the optimum mean growing point was 4.13 h. Our analyses also showed that soil salinity had significant effects on the growth of S. alterniflora. The optimum ecological amplitude of S. alterniflora to soil salinity was [13.77 g/kg, 22.57 g/kg], and the optimum mean growing point was 18.19 g/kg. This is the first spatially quantitative analysis to study the eco-hydrological mechanism driving both the aboveground biomass and height of S. alterniflora over the intertidal zone to the best of our knowledge. Determining the optimal ecological range for flooding and salt will provide a scientific basis for measures to establish the ecological control of S. alterniflora and to predict the expansion of S. alterniflora in response to rising sea levels.

Impacts of intensified agriculture developments on marsh wetlands.

A spatiotemporal analysis on the changes in the marsh landscape in the Honghe National Nature Reserve, a Ramsar reserve, and the surrounding farms in the core area of the Sanjiang Plain during the past 30 years was conducted by integrating field survey work with remote sensing techniques. The results indicated that intensified agricultural development had transformed a unique natural marsh landscape into an agricultural landscape during the past 30 years. Ninety percent of the natural marsh wetlands have been lost, and the areas of the other natural landscapes have decreased very rapidly. Most dry farmland had been replaced by paddy fields during the progressive change of the natural landscape to a farm landscape. Attempts of current Chinese institutions in preserving natural wetlands have achieved limited success. Few marsh wetlands have remained healthy, even after the establishment of the nature reserve. Their ecological qualities have been declining in response to the increasing threats to the remaining wetland habitats. Irrigation projects play a key role in such threats. Therefore, the sustainability of the natural wetland ecosystems is being threatened by increased regional agricultural development which reduced the number of wetland ecotypes and damaged the ecological quality.

The ecological response of Carex lasiocarpa community in the Riparian Wetlands to the environmental gradient of water depth in Sanjiang Plain, Northeast China.

The response of Carex lasiocarpa in riparian wetlands in Sanjiang Plain to the environmental gradient of water depth was analyzed by using the Gaussian Model based on the biomass and average height data, and the ecological water-depth amplitude of Carex lasiocarpa was derived. The results indicated that the optimum ecological water-depth amplitude of Carex lasiocarpa based on biomass was [13.45 cm, 29.78 cm], while the optimum ecological water-depth amplitude of Carex lasiocarpa based on average height was [2.31 cm, 40.11 cm]. The intersection of the ecological water-depth amplitudes based on biomass and height confirmed that the optimum ecological water-depth amplitude of Carex lasiocarpa was [13.45 cm, 29.78 cm] and the optimist growing water-depth of Carex lasiocarpa was 21.4 cm. The TWINSPAN, a polythetic and divisive classification tool, was used to classify the wetland ecological series into 6 associations. Result of TWINSPAN matrix classification reflected an obvious environmental gradient in these associations: water-depth gradient. The relation of biodiversity of Carex lasiocarpa community and water depth was determined by calculating the diversity index of each association.

[Spatial distribution characteristics and ecological effects of carbon and nitrogen of soil in Huolin River catchment wetland].

This paper studied the spatial distribution characteristics and ecological effects of organic carbon and nitrogen in soils of Huolin River catchment wetland in horizontal and vertical levels. The results showed that the differences of horizontal and vertical distribution of organic carbon and nitrogen were very obvious, and of all the factors such as the period of wetting and drying cycles, leaching, plant and flood etc., the period of wetting and drying cycles was contents the critical one, which caused the differences. Soil organic carbon was significantly correlated with soil nitrogen (r = 0.977). The ratio of carbon and nitrogen (C/N) changed along with the humidity gradient, and soil pH values obviously influenced the concentration of organic carbon and nitrogen. The correlation of C/N values and organic carbon and nitrogen contents in wetland soil and in grassland soil were remarkably different, and the ecological effects mainly included production effect and clarification effect.