The Geographical Distribution And Ecological Effect Evaluation Of Miscanthus Lutarioriparius,an Endemic Plant Of China

Miscanthus lutarioriparius is a unique plant of Miscanthus spp.in China,which has great ecological value and can deliver biomass raw material.It has many advantages such as high biomass yield with C₄ photosynthetic pathway,high cellulose content and as well as stress tolerance.In recent years,with more and more attention paid to environmental protection,Miscanthus lutarioriparius which is ecological friendly plant has been favored by researchers.However,up to now,the detailed geographical distribution of Miscanthus lutarioriparius in China and the potential ecological benefits and risks caused by its large-scale cultivation are unclear.In this paper,the focus was to answer the two scientific questions:-What is the distribution area of Miscanthus lutarioriparius?-What are the ecological effects of Miscanthus lutarioriparius for large-scale cultivation?For this purpose,different aspects had been studied including geographical distribution characteristics,habitat restriction factors,potential distribution area,ecological benefits and risks for its large-scale cultivation and so on.The main research results are as follows:1.Geographical distribution of Miscanthus lutarioripariusThrough field investigation,we found that the natural distribution area of Miscanthus lutarioriparius in China include 252 counties which comprised of eight provinces and municipalities that consist of Hunan,Hubei,Zhejiang,Anhui,Jiangsu,Jiangxi,Henan and Shanghai.The horizontal distribution of M.lutarioriparius was 111.17°～121.74°E and26.47°～33.97°N,the vertical distribution range is-1～299 m.The floristics distribution of M.lutarioriparius is Huanghuai Plain Subregion,Jianghan Plain Subregion,South Zhejiang Mountain Subregion,South Jiangxi-East Hunan Hills Subregion,Qinling-Bashan Subregion and Sichuan-Hubei-Hunan Broder Subregion.According to the geographical distribution characteristics of Miscanthus lutarioriparius,Dongting lake,Poyang lake and Taihu lake were the distribution center of Miscanthus lutarioriparius.2.Habitat characteristics of M.lutarioripariusThe habitat types of M.lutarioriparius are abundant and its main habitat characteristic is"hygrophyte".Among the distribution area,81.83%of M.lutarioriparius are found in the habitats near the water and the other 18.17%are far from the water.The main associated plants of M.lutarioriparius are Phragmites communis,Paederia scandens,Broussonetia papyrifera and Setaria viridis.The natural M.lutarioriparius populations mostly grow on the infertile soil with a nearly neutral p H.In the distribution area of M.lutarioriparius,the average annual temperature ranged from 14.13 to 18.15°C and the yearly average precipitation ranged from 763.00 to1817.00 mm.In the floristics distribution of M.lutarioriparius,the difference of water factors was large,followed by the heat factors whereas the impact of light factors was small.According to the difference of water factors,the floristics distribution of M.lutarioriparius could be divided into three types（high wettability,medium wettability and low wettability）.The phenotypic traits were significantly different among the natural M.lutarioriparius populations with the variation coefficient ranging from 17.05%to 78.98%and the Shannon‘s index（expressing the genetic diversity） from 1.61 to 1.78.Heat was the main limiting factor for the distribution of M.lutarioriparius,followed by water factors and altitude.The main heat factors that limited the distribution of M.lutarioriparius were mean temperature of coldest quarter（Bio11）,temperature seasonality（Bio4）and mean temperature of driest quarter（Bio9）.The main water factors that limited the distribution of M.lutarioriparius were precipitation of warmest quarter（Bio18）and precipitation of wettest quarter.The main soil factors that affect the plant height and yield of M.lutarioriparius were the content of available potassium and organic matter.3.The potential distribution area of M.lutarioripariusThe best sample size by using Maxent model to predict the potential distribution of M.lutarioriparius was"120",and the predicted results were also accurate.The potential distribution area of M.lutarioriparius was narrow,and the high suitability area of M.lutarioriparius mainly concentrated in Jianghan Plain Subregion,Huanghuai Plain Subregion and Sichuan-Hubei-Hunan Broder Subregion.In addition,the total suitable area of M.lutarioriparius is 6.658×10⁵ km²,which accounts for 6.96%land area of China.4.Ecological benefits of M.lutarioriparius for large-scale cultivationM.lutarioriparius has a strong carbon sequestration ability,the net primary productivity of which ranged from 1.34 to 15.55 kg·m^-2·a^-1and the carbon sequestration capacity ranged from 0.59 to 6.79 kg·m^-2·a^-1.The carbon sequestration potential of M.lutarioriparius in Dongting lake his the highest carbon sequestration with the carbon sequestration capacity ranged from 0.89 to 6.79 kg·m^-2·a^-1and the annual solid carbon ranged from 7.12×10⁶ to5.43×10⁷ t,whereas the carbon sequestration potential of M.lutarioriparius in Taihu lake was low and has a large room to improvement.The nutrient content of the soil was significantly increased by large-scale cultivation of M.lutarioriparius.For example,total nitrogen content of soil was increased by12.74%,followed by the total phosphorus（11.91%）and the organic matter content（6.63%）.The effect of M.lutarioriparius for large-scale cultivation on soil total potassium content was small.The results showed that the improvement of soil nutrient content in acidic soil was better than that in alkaline soil by large-scale cultivation of M.lutarioriparius.Furthermore,the impact of large scale cultivation was more pronounced on soil layer from 0 to 20 cm compared with 20 to 40 cm.5.Ecological risks of M.lutarioriparius for large-scale cultivationThe ecological risk assessment system formulated as a part of this study,was composed of 33 questions related to ecological risk traits based onliterature and expert consultations.The trait‘s scoring process was calculated using the yaahp10.1 software by analytic hierarchy process（AHP）.Additionally,10 tall herbaceous species,whose ecological risks were already defined,were used to test the accuracy of the ERA system.The results showed that the ERA system could accurately confirm the ecological risk of the evaluated plants.Based on the accuracy testing results,the classification of the different ecological risk levels for our ERA system was conducted.The results were as following:Species with the ERA score higher than 74.5 were defined as the species with high invasion risk（named?Rejection‘）;species with the scores of 54.5–74.5 were defined as uncertain ecological risk,which requires further evaluation（named?Evaluate‘）;species with the scores lower than 54.5 were defined as the ecologicaly safe plants（named?Accept‘）.The ecological risks for large-scale cultivation of four promising miscanthus species（Miscanthus sinensis,M.floridulus,M.sacchariflorus,M.lutarioriparius）and the European commercially used variety of Miscanthus×giganteus were quantified based on the ERA system.The results showed that ecological risks of the large-scale miscanthus cultivation generally were ranked in this order M.sinensis>M.sacchariflorus>M.floridulus>M.lutarioriparius>M.×giganteus with their ecological risk scores of 71,66,60,53 and 52,respectively.According to the risk definition criteria of the ERA system,the M.lutarioriparius and M.×giganteus were defined as the ecological safe plants（i.e.accept for large-scale cultivation）;whereas the M.sinensis,M.sacchariflorus,M.floridulus were defined as plants with uncertain ecological risk,therefore these species require further investigations about their ecological safety prior to large-scale cultivation.