闽江河口芦苇与短叶茳芏空间扩展对湿地系统磷赋存特征的影响

Effects of spatial expansion of Phragmites australis and Cyperus malaccensis on distributions and stocks of phosphorus in marshes in the Minjiang River estuary,China

本研究选择闽江河口鳝鱼滩芦苇和短叶茳芏空间扩展前的芦苇湿地、短叶茳芏湿地,以及二者空间扩展形成的交错带湿地为对象,探讨了两种植物空间扩展过程中植物-土壤系统的全磷(TP)赋存特征及其主要影响因素。结果表明:在空间扩展影响下,湿地植物和土壤的TP含量均发生了明显变化。其中,交错带湿地土壤的TP含量比芦苇湿地和短叶茳芏湿地土壤分别增加了20.0%和7.1%。这与芦苇和短叶茳芏空间扩展过程中土壤的颗粒组成以及植物的生物量、根冠比变化有关。除叶外,交错带芦苇不同器官的TP含量整体均低于短叶茳芏的相应器官。这与二者在交错带生境中对P养分吸收利用与转运方式的差异有关。另外,空间扩展导致的竞争作用使二者的P分配比也发生较大变化,与纯群落相比,交错带芦苇提高了根、叶的P分配比,而交错带短叶茳芏提高了根的P分配比。芦苇和短叶茳芏为了应对空间扩展过程中的竞争可能采取了不同的P养分利用策略,前者通过加强根部P养分吸收和提高叶片光合作用的方式来占据竞争优势,而后者通过提高根系生物量以增强对P养分吸收利用的方式来抗衡来自芦苇的竞争。

To investigate the distributions and stocks of total phosphorus(TP)in plant-soil systems of marshes in Shanyutan of the Minjiang River estuary and explore its influencing factors,Phragmites australis(PA)marsh and Cyperus malaccensis(CM)marsh before spatial expansion and ecotonal marsh(EM,P.australis and C.malaccensis in EM were denoted by PA′and CM′,respectively)during spatial expansion were studied.Results showed that,as affected by spatial expansion,the contents of TP in both plant and soil in different marshes showed great variations.Compared with PA and CM marshes,soil TP in EM increased by 20.0%and 7.1%,respectively.The variation of soil TP in EM might be attributed to the alteration of soil particle composition,plant bio-mass and root/shoot ratio during spatial expansion.Except for leaves,TP in organs of P.australis in P.australis-C.malaccensis community(PA′)was lower than that in C.malaccensis in P.australis-C.malaccensis community(CM′),due to the differences in absorption,utilization and translocation way of P among organs between the two species.The competition effect caused by spatial expansion greatly changed plant P allocation ratio of the two species.Compared with PA and CM,the allocations of P in roots and leaves of PA′increased,while only that in roots of CM′rose.During spatial expansion,the two species might adopt different adaptation strategies for P absorption and utilization to maintain their competitiveness.The PA might compete primarily by strengthening the P accumulation capacities of its roots and promoting leaf photosynthesis,whereas the CM might resist the spatial expansion of PA by increasing its underground biomass to enhance P absorption.