泰湖国家湿地公园天然植物群落碳储量空间分异规律及主控因素研究

Spatial differentiation law and main control factors of carbon storage in natural plant communities of Taihu National Wetland Park of northeastern China

【目的】揭示温带半干旱区嫩江流域泰湖国家湿地公园天然植物群落的生态系统碳储量沿湖岸至高地环境梯度的空间分布格局及成因,为我国温带半干旱区天然植被长期碳汇实践提供科学依据。【方法】采用相对生长方程、碳/氮分析仪测定法,同步测定沿湖岸至高地环境梯度依次分布的狭叶香蒲沼泽(XYP)、小香蒲沼泽(XP)、芦苇沼泽(L)、草丛沼泽(C)、拂子茅草甸(F)、湿生羊草草地(S)、旱生羊草草地(H)和沙丘榆树疏林(Y)8种植物群落的生态系统(植被和土壤)碳储量、植被净初级生产力与年净固碳量及其相关环境因子(水位、土壤有机质、全氮和全磷等),揭示其空间分异规律及其形成机制。【结果】(1)植被碳储量(0.98~27.86 t/hm^(2))沿湖岸至高地环境梯度呈先降后升的变化趋势(Y>L,XYP,XP>C,F,S,H),草本层碳储量(0.30~8.11 t/hm^(2))呈阶梯式递减趋势(L,XYP,XP>C,F,S>H,Y)。(2)土壤碳储量(38.49~321.72 t/hm^(2))沿湖岸至高地环境梯度呈阶梯式递减规律,且存在明显的水平空间(XYP,XP各土壤层均最高;L,C大部分土壤层较高;F,S,H仅表层较高;Y各土壤层均最低)和垂直空间(XYP,XP,L随土壤深度递减;F,S,H中上部土壤层递减;C和Y各层相近)分异规律。(3)生态系统碳储量(66.35~329.94 t/hm^(2))沿湖岸至高地环境梯度也呈阶梯式递减规律,且其分配格局多以土壤碳储量占绝对优势(95.43%~99.04%),仅Y土壤碳储量占比低(58.2%)。(4)植被净初级生产力(2.11~16.28 t/(hm^(2)·a))和年净固碳量(0.68~7.00 t/(hm^(2)·a))沿湖岸至高地环境梯度呈下降趋势,XYP、XP与L显著高于其他5种群落0.3~9.3倍,且L与XYP的年净固碳量高于我国和全球植被固碳平均值10.6%~70.7%。(5)处于环境梯度下段永久积水生境的植物群落生态系统各组分碳储量与年净固碳量均受水位所控制;处于环境梯度中段季节性积水生境的植物群落生态系统各组分碳储量与年净固碳量受土壤有机质、全氮、全磷和速效钾所控制;处于环境梯度上段干旱生境的植物群落生态系统各组分碳储量与年净固碳量受土壤有机质和速效磷所控制。【结论】嫩江流域泰湖国家湿地公园沿湖岸至高地的微地形对水分和养分再分配引起的空间异质性控制着植物群落分布及其碳汇作用的发挥,故对这类环境梯度的完整性应加以重点保护。

[Objective]This paper aims to reveal the spatial distribution pattern and the cause of formation of the natural plant ecosystem carbon storage in the semi-arid area of temperate Nenjiang River of Taihu National Wetland Park of Northeastern China along the lakeshore to the highland environmental gradient,and to provide a scientific basis for the long term carbon sink management of natural vegetation in the temperate semi-arid area of China.[Method]The ecosystem carbon storage(vegetation carbon storage and soil carbon storage),net primary productivity(NPP),annual net carbon sequestration(ANCS)and related environmental factors(water level,total nitrogen and total phosphorus,etc.)of eight plant communities,i.e.Typha angustifolia wetland(XYP),Typha minima wetland(XP),Phragmites australis wetland(L),tussock wetland(C),Calamagrostis epigeios meadow(F),wet Leymus chinensis grassland(S),dry Leymus chinensis grassland(H),sand dune Ulmus pumila sparse forest(Y)distributed along the lakeshore to the highland environmental gradient were simultaneously determined by relative growth equation and carbon/nitrogen analyzer method,so as to reveal its spatial differentiation law and its formation mechanism.[Result](1)The vegetation carbon storage(0.98−27.86 t/ha)showed a downward and then ascending tendency along the lakeshore to the highland environmental gradient(Y>L,XYP,XP>C,F,S,H),and herbaceous carbon storage(0.30−8.11 t/ha)showed a stepwise decreasing trend(L,XYP,XP>C,F,S>H,Y).(2)The soil carbon storage(38.49−321.72 t/ha)showed a stepwise decreasing trend along the lakeshore to the highland environmental gradient,and there were obvious horizontal spaces(XYP,XP were the highest at all soil layers;L,C were higher at most soil layers;F,S,H only was higher at the surface layer;Y was the lowest at all soil layers)and vertical space(XYP,XP,L decreased with soil depth;F,S,H at middle and upper soil layers decreased;C and Y were similar at all layers)differentiation regularity.(3)Ecosystem carbon storage(66.35−329.94 t/ha)also showed a stepwise decreasing trend along the lakeshore to the highland environmental gradient,and its distribution pattern was mostly dominated by soil carbon storage(95.43%−99.04%),only Y soil carbon storage accounted for low proportion(58.2%);(4)The NPP(2.11−16.28 t/(ha·year))and ANCS(0.68−7.00 t/(ha·year))of vegetation showed a decreasing trend along the lakeshore to the highland environmental gradient(XYP,XP and L were significantly higher than the other five communities by 0.3−9.3 times),and the ANCS of L and XYP was higher than the average carbon sequestration of vegetation in China and the world by 10.6%−70.7%;(5)Ecosystem carbon stocks and annual net carbon sequestration of vegetation of plant communities in permanently flooded habitat in the lower part of the environmental gradient were controlled by water level;plant communities in seasonally flooded habitat in the middle environment gradient were controlled by SOM,TN,TP and AK;plant communities in arid habitats in the upper environmental gradient were controlled by SOM and AP.[Conclusion]Therefore,the spatial heterogeneity of water and nutrient redistribution caused by the microtopography controls the distribution of plant communities and their carbon sinks along the lakeshore to the highland environmental gradient in the Nenjiang River of Taihu National Wetland Park of China,so the integrity of such environmental gradients should be protected.