| Spartina alterniflora Lois.is a strong invasive species of coastal wetland in China.It has the characteristics of strong reproductive proliferation ability,strong interspecific competition ability and wide distribution area.It inhibits the survival of local dominant species such as mangrove,Suaeda salsa(Linn.)Pall.and Phragmites australis(Cav.)Trin.ex Steud.to a certain extent,but at the same time it has high biomass energy and provides a suitable environment for survival and reproduction of carapace and other benthic animals.Spartina alterniflora Lois.has a great influence on the biodiversity of the coastal wetland and the stability of the ecosystem.In 1983,Spartina alterniflora was first introduced in Tongli Wumen Beach,Yuhuan County,Zhejiang Province,and then expanded rapidly.As far,it is distributed along the entire eastern beach of Zhejiang.Therefore,the estimation of the biomass of Spartina alterniflora Lois.in the coastal wetland of Zhejiang Province and the factors influencing its spatial distribution have important guiding significance for the study of wetland biodiversity conservation and wetland ecological restoration.The study area of this paper is the Spartina alterniflora Lois.wetland in the east of Zhejiang Province.This paper used the remote sensing information extracted from the Landsat8 OLI image in July 2016 and the above-ground and under-ground biomass(dry weight)of Spartina alterniflora Lois.during the same period as the data source,compared univariate linear,nonlinear regression models,and multivariate linear stepwise regression models which were based on different remote sensing information to obtain the best above-ground and under-ground biomass estimation model for Spartina alterniflora Lois.of coastal wetlands in Zhejiang Province.In addition,this study conducted an inversion of Spartina alterniflora Lois.biomass,analyzed the spatial distribution pattern and explored the effects of soil factors on the growth and distribution of Spartina alterniflora Lois.by examining the correlation between Spartina alterniflora Lois.growth traits and soil factors.The main findings are as follows:(1)The remote sensing information including Band4,Band7,NDVI,SAVI,EVI,RVI was significantly correlated with the above-ground biomass of Spartina alterniflora Lois.(P<0.05).The optimal above-ground biomass estimation model of Spartina alterniflora was a cubic polynomial model with the normalized vegetation index NDVI and the estimation accuracy was 87.99%;There was a significant correlation between underground biomass and above-ground biomass(P<0.05).The best estimate model of underground biomass is a one-dimensional linear regression model based on above-ground biomass with an estimated accuracy of 92.6%.(2)The decision tree classification method was used to extract Spartina alterniflora Lois.from the coastal wetland in Zhejiang Province.The overall accuracy was 96.2%,and the overall Kappa coefficient was 92.04.In 2016,the total area of Spartina alterniflora Lois.in Zhejiang Province was 1.56×107 m~2.The main distribution areas were ranked from largest to smallest as follows:Hangzhou Bay>Sanmen Bay>Puba Port>Feiyun River Estuary>Xiangshan Port>Dongchen Township of Xiangshan County>Yueqing Bay,with a distribution area of 1.05×107m~2?1.33×106m~2?1.3×106m~2?8.29×105m~2?7.81×105m~2?5.4×105m~2?3.32×105m~2,respectively.(3)Using the optimal model to estimate the biomass of Spartina alterniflora Lois.,it was found that the total biomass of Spartina alterniflora Lois.in Zhejiang Province was 8.505×1010g,and the total above-ground biomass was 5.837×1010g,accounting for 68.6% of the total biomass.And the total underground biomass was 2.668×1010g,accounting for 31.4% of the total biomass.The total biomass of Spartina alterniflora Lois.in each region was ranked as follows: Hangzhou Bay>Sanmen Bay>Puba Port>Xiangshan Port>Feiyun River>Dongchen Township of Xiangshan County>Yueqing Bay,with the total biomass of 5.85 × 1010 g ?7.06×109g?6.5×109g?4.53×109g?4.09×109g?2.9×109g?1.7×109g,respectively.The average biomass of Spartina alterniflora Lois.in each region was ranked as follows: Hangzhou Bay>Xiangshan Port>Dongchen Township of Xiangshan County>Sanmen Bay>Yueqing Bay>Puba Port>Feiyun Rive,with the average biomass of 5571g/m~2?5504g/m~2?5376g/m~2?5326g/m~2?5116g/m~2?5011g/m~2?4937g/m~2,respectively.(4)This study analyzed the soil factors and growth factors of Spartina alterniflora Lois.and found that the most important soil factors affecting the growth and biomass of Spartina alterniflora Lois.in the coastal wetland of Zhejiang were water-soluble salts,total nitrogen,available phosphorus and p H.The soil environment has a great influence on the growth of Spartina alterniflora Lois.Soil salinity and nutrient content promote the growth of Spartina alterniflora Lois.in a certain range,while high salinity and high nutrients inhibit its growth and development. |
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