| Coastal wetland is the most active transitional zone in the interacting processes among land, sea and atmospheric. The change of structure and function of salt marsh vegetation can affect the global biogeochemical cycles and energy exchange. Smooth Cordgrass (Spartina alterniflora), a perennial grass, belongs to Spartina in Gramineae, which usually grow on the tidal marsh from the lower level of high tide to the upper level of middle tide. Had being introduced to China in 1979, S. alterniflora expand increasingly in population. Beside the advantage in expanding land, protecting beach, changing soil salinity, breeding livestock, etc., it had also brought serious ecological, economic and social threats. Physical, chemical and biological methods of the control and management of S. alterniflora are very difficult and expensive. Therefore, utilization and development of its potential biomass and bioenergy, is expected to be one of the most promising way to manage and make use of this invasive species.3S technology has been widely applied in spatial investigating and dynamic monitoring of vegetations in coastal zone, especially for invasive plant. CBERS-02/02B multi-spectral remote sensing images, dated from 2006 to 2008, combined with relevant statistical data, was classified to investigate spatial distribution of the S. alterniflora in China, using the Maximum Likelihood Classifier in ENVI 4.5. An extensive field survey in situ was then carried out to directly verify and revise the results of the classification and other published distributions of S. alterniflora were also referenced. The revised classification was integrated with a GIS platform, in which the spatial distribution and quantity of the S. alterniflora were analyzed. Meanwhile, average biomass and average calorific value of S. alterniflora in coastal provinces was calculated by integrating the research of our field sample and others previous studies. Combined with the total area, total biomass and bioenergy of S. alterniflora in our entire coastal beach were estimated.The results showed that the total area of the S. alterniflora in China was 34178 hm2, and the population was distributed extensively on the tidal flats from the Beitangkou in Tianjin to Shankou reserve in Guangxi. The total annual biomass was 2.05×106t, and the annual bioenergy was 3.30×107 GJ, equivalent to 1.13×106t standard coal (calorific value of standard coal is 29306 J/g). The above-ground annual biomass was 1.01×106t, providing 1.63×107 GJ bioenergy per year, equivalent to 5.56×105t standard coal. The area and bioenergy of the S. alterniflora in Jiangsu Province accounted for more than half of the total number of the whole country and its whole biomass, above-ground biomass and above-ground also accounted for nearly half of all. Liaoning Province in northern China had no S. alterniflora yet, while Jiangsu, Shanghai, Zhejiang and Fujian provinces had the largest share of 94.22% of the total area, and other three northern provinces and Guangdong and Guangxi shared 4.02% and 1.76%.We found that the main causes of this distribution were coastal types as well as precipitation, temperature, nitrogen pollution etc. The degree of reclamation in the intertidal zone was also important to the introduction, invasion and spread of S. alterniflora. Since efficient photosynthesis system, S. alterniflora ecosystem had high productivity (the average biomass is 6007 g/m2) and high bioenergy (the average calorific value is 16050 J/g). Due to its reproduction characteristic, mainly by vegetation propagation as well as seed propagation, S. alterniflora spreaded rapidly and now widely distributed from in Beitangkou in Tianjin to Shankou reserve in Guangxi. In addition, because the growing season of S. alterniflora is long and it does not take arable land, therefore the bioenergy utilization of S. alterniflora is possible.Those results provided us paradigm for investigating and monitoring invasive plants at large scale by CBERS, a strong foundation for development of biomass and bioenergy of S. alterniflora and also a scientific basis for utilization and protection of tidal flats resources in China.
|
PDF Full Text Request