| Since the 1960s,Triarrhena lutarioriparia was widely planted in Dongting Lake wetland for papermaking,its distribution area has gradually expanded,and it has become the dominant plant community in Dongting Lake wetland.As an internationally important wetland,national nature reserve and biodiversity conservation priority area,the large area and concentrated harvest of T.lutarioriparia in Dongting Lake has aroused widespread attention to the ecological environment,and whether to abandon the harvest has become a difficult problem for the management of the wetland ecosystem in Dongting Lake.This paper focuses on five typical ecological service functions of T.lutarioriparia:production and supply,carbon fixation and oxygen release,atmospheric temperature and humidity regulation,pollution degradation and soil and water conservation.Using the combination of field investigation and indoor analysis,using the market value method and replacement cost method to carry out quantitative evaluation value,trying to figure out the ecological value of T.lutarioriparia in the Dongting Lake wetland,so as to provide a decision-making basis for whether to abandon or not and the wetland ecosystem management.（1）The average biomass of T.lutarioriparia community in Dongting Lake wetland was2716.79 g m-2.Stem biomass was the highest(1139.98 g m-2),accounting for 41.96%of the total biomass,head biomass was the lowest(14.14 g m-2),accounting for 0.52%of the total biomass.The order of biomass of organs from high to low was stem>rhizome>root>leaf>bud>head.In addition,there was a certain relationship between organ biomass and soil environment,and there was a significant positive regression relationship between root biomass,total biomass and soil total phosphorus concentration（P<0.05）,and a significant positive regression relationship between rhizomes biomass and soil p H,total potassium concentration and organic matter concentration（P<0.05）.There was a significant negative regression relationship between soil moisture concentration and soil electrical conductivity（P<0.05）.（2）Based on the productivity of the T.lutarioriparia community,the value of material supply,carbon sequestration and oxygen release of the community were calculated as 1.11yuan m-2,0.83 yuan m-2 and 1.30 yuan m-2,respectively,using the market value method.The biomass supply value,carbon sequestration value and oxygen release value of the community in Dongting Lake wetland were 647 million yuan,485 million yuan and 758 billion yuan respectively.（3）The monitoring of atmospheric temperature and humidity of the T.lutarioriparia in Dongting Lake wetland showed that the monthly average temperature of the community increased by 1.46℃compared with that of the control,showing a strong thermal insulation effect.The monthly average relative humidity of the community decreased by 1.32%compared with that of the control group,showing a drying effect.The value of regulating temperature and humidity was 17.91 yuan m-2 and 4.52 yuan m-2,respectively.In the whole Dongting Lake wetland,the value of regulating temperature and humidity was 10.466 billion yuan and 2.644 billion yuan respectively.（4）The nitrogen and phosphorus absorption of the typical community of T.lutarioriparia in Dongting Lake wetland showed that the nitrogen and phosphorus absorption of each organ of T.lutarioriparia ranged from 1.90 to 26.90 g kg-1 and 0.20 to 2.43 g kg-1.There were significant differences in nitrogen and phosphorus absorption among different organs.The order of nitrogen absorption was head>leaf>bud>rhizomes>root>stem,and the order of phosphorus absorption was head>leaf>root>bud>rhizomes>stem.Nitrogen absorption was 6.42 g m-2 and phosphorus was 0.68 g m-2.In the whole dongting Lake wetland,the absorption of N and P was 3754.80 t and 399.30 t,respectively.（5）The in situ decomposition experiment of leaf and stem litter of T.lutarioriparia showed that the mass residual rate of stem and leaf decreased with the extension of decomposition time,and the decomposition rate of leaf was higher.There were differences in decomposition of litter at different soil depths.The decomposition coefficient of stem was higher at 5 cm soil depth than that of leaf at 0 cm soil depth.With the extension of decomposition time,phosphorus release rate of litter increased.Nitrogen release rate showed two different trends,leaf nitrogen release rate showed an increasing trend,while stem nitrogen release rate showed a decreasing trend first and then increasing trend,and generally less than0,indicating that stem litter appeared nitrogen enrichment.Based on the annual nitrogen and phosphorus absorption and release data,the nitrogen and phosphorus regulation per unit area were 0.76 g m-2 and 0.19 g m-2,respectively.In the whole community,nitrogen regulation was441.40 t and phosphorus regulation was 108.60 t.Using the substitution cost method,the nitrogen regulation value and phosphorus regulation value per unit area of the community were 1.13×10-3 yuan m-2 and 0.46×10-3 yuan m-2 respectively.The regulation value of nitrogen and phosphorus was 662,100 yuan and 271,500 yuan respectively.（6）With the increase of soil depth,the maximum soil water holding capacity of T.lutarioriparia community and bare land（control）decreased,and soil water concentration decreased first and then increased.The maximum water holding capacity and water concentration in the upper and middle layers of soil were higher than those in bare soil,and the community had higher water holding capacity and water retention capacity.In terms of soil fertility,N and P concentrations decreased with soil depth.The N and P concentrations in0-20 cm soil were significantly higher than those in bare soil,indicating that the soil in this layer had a stronger effect on fertilizer conservation.The water retention per unit area was25.52 kg m-2with a value of 0.20 yuan m-2,the nitrogen retention was 0.18 kg m-2 with a value of 0.35 yuan m-2,and the phosphorus retention was 0.008 kg m-2with a value of 0.008 yuan m-2.The total value of water conservation,fertilizer conservation and soil and water conservation is 114 million yuan,211 million yuan,325 million yuan.In conclusion,the value of the community material production,carbon sequestration and oxygen release of the Dongting Lake wetland is 647 million yuan,1.243 billion yuan,the value of climate regulation is 13.11 billion yuan,the value of degradation pollution is 933,600 yuan,the value of soil and water conservation is 325 million yuan,and the total value is about 15.326billion yuan.It has high ecological service value and should be paid attention to. |
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