闽江河口芦苇与短叶茳芏空间扩展植物-土壤系统硫含量变化特征

2015年7月,选取闽江河口鳝鱼滩的芦苇湿地、短叶茳芏湿地以及二者交错带湿地为对象,研究了两种植被空间扩展过程中植物-土壤系统全硫(TS)含量的空间变化特征。结果表明,不同湿地表层土壤的TS含量表现为交错带湿地短叶茳芏湿地芦苇湿地,其差异主要与两种植被的空间扩展改变了交错带湿地土壤的质地及有机质等参数,进而对硫的迁移及转化过程产生重要影响有关;交错带不同植被的根系分布及其对土壤硫养分的竞争导致土壤TS含量的水平和垂直变异性均较芦苇或短叶茳芏纯群落发生较大改变,其土壤的TS含量受芦苇根系分布的影响更为明显,含量和储量均在深层土壤中较高。芦苇与短叶茳芏的空间扩展改变了两种植被的株高、密度及生物量分配格局,尽管二者在交错带中的地下生物量分配比均高于纯群落,但芦苇地下空间占据能力要高于短叶茳芏。研究发现,芦苇与短叶茳芏的空间扩展是双向过程,二者在空间扩展中通过不同的硫养分吸收、累积与分配策略适应竞争环境,即交错带湿地中的芦苇通过增加根部对硫养分的累积能力来保持其竞争力,而短叶茳芏则通过拓展地上空间及提高地上器官的硫养分累积能力来抗衡芦苇的空间扩展。

Variations in total sulfur content in plant-soil systems of Phragmites australis and Cyperus malaccensis in the process of their spatial expansion in the Min River estuary

To investigate the variation in total sulfur (TS) content in plant-soil systems of Phragmites australis and Cyperus malaccensis in the process of their spatial expansion in Shanyutan of the Min River estuary, the P. australis marsh (PM), C. malaccensis marsh (CM), and their ecotone (P. australis-C. malaccensis marsh, PCM) were studied in July 2015. Results showed that the TS content in soils of different marshes were generally in the order of CM > PCM > PM and the differences among them were primarily related to the alteration of soil texture and organic matter caused by the spatial expansion of P. australis and C. malaccensis, which substantially influenced the S transfer and transformation processes. The horizontal and vertical variation in TS content in the PCM soils was significantly different from those in the PM or CM community, and this difference was caused by the root distribution of different plants in the ecotone and their competition for the S nutrient. The TS content in soils of the PCM was more affected by the root distribution of P. australis, and TS content and stocks were generally higher in deep soil. The spatial expansion greatly altered the height, density, and biomass allocation of the two plants, and although their allocation patterns of belowground biomass in the ecotone were generally higher than those in the pure communities, P. australis exhibited a higher occupancy capacity in belowground space than did C. malaccensis. This study determined that the space expansion of P. australis and C. malaccensis was bi-directional, and could adapt to the competitive environment by using different strategies for S uptake, accumulation, and allocation. P. australis in the ecotone competed primarily by increasing the S accumulation capacity of its roots, whereas C. malaccensis in the ecotone was able to resist the space expansion of P. australis by expanding in the aboveground space and increasing the S accumulation capacity of aboveground organs.