植物寄生对生态系统结构和功能的影响

寄生植物是生态系统中的特殊类群之一。植物寄生可以驱动生态系统中生物与非生物因子的变化,在生态系统结构与功能中起关键作用。寄生植物可以通过对寄主营养的集聚、改变凋落物的质量与数量、改变根的周转与分泌物格局、改变土壤水势,从而影响土壤理化特性。寄生植物会改变寄主的行为,改变寄主与非寄主植物之间的相互作用,从而影响植物群落的结构、多样性和动态,进而影响植被演替和植被生产力等。寄生植物与寄主均可被消费者取食,可直接或间接地影响生态系统的食草动物,包括草食昆虫等。寄生植物与寄主的其它寄生物存在竞争关系,可以直接或间接地影响寄主的其它寄生植物或病原真菌。寄生植物可以明显地改变土壤地球化学循环,将固有的不可动的成分转变为可利用的营养成分,改变土壤生物群落的结构与功能,从而显著影响地下生物群落。这些表明,植物寄生对生态系统的结构和功能有重要影响。针对特殊的被入侵的植物群落,该地寄生植物可以通过影响入侵植物寄主的生长、繁殖、生物量分配格局,改变土壤的理化特性,促进非寄主的非优势本地植物的生长,从而改变被入侵植物群落结构与多样性,达到生物防治及生态恢复的目的。

Impacts of plant parasitism on structure and function of ecosystems

Parasitic plants, represented by 4200 species, are ubiquitous in both natural and managed ecosystems. They acquire some or all of their water, carbon and nutrients by attaching to host roots or shoots using specialist structures known as haustoria. Most of them belong to the families of Orobanchaceae, Loranthaceae, Santalaceae, Viscaceae and Cuscutaceae. Some of the parasitic plants are pathogenic angiosperms, and their parasitic behaviour can drive changes in the biotic and abiotic factors and thereby exert strong impacts on the structure and function of ecosystems. Parasitic plants can uptake nutrients from their hosts, change the quality and quantity of litter, consequently influencing soil physical and chemical properties. Parasitism can drive the growth and turnover of host roots, change the pattern of root exudation, change the carbon and nitrogen input into the soil, consequently changing soil physical and chemical properties. The high transpiration rate of parasitic plants can change the soil water potential. Plant parasitism can also change the atmospheric CO₂ and temperature. Parasitic plants can alter their hosts' behavior, which can lead to changing interaction and competition between the host and the non-host species, thereby affecting the community structure, biodiversity and succession. Plant parasitism can reduce or increase ecosystem productivity dependent on the community traits and environmental conditions. Parasitic plants and their hosts can be consumed by herbivores including plant-feeding insects, consequently affecting the consumer behavior and consumer community structure. Plant parasites and non-plant parasites may share the same hosts and therefore they may compete with each other for host resources. Such interaction can directly or indirectly also affect other parasitic plants or pathogenic fungi. Parasitic plants can alter soil biogeochemical cycles. They can unlock tightly and long-held nutrients, making them more available to more host and non-host plants and altering the structure and function of the soil biotic community. Plant parasitism may also play an important role in the structure and function of ecosystems invaded by alien species. For instance, in an invaded plant community, native parasitic plants can use the invasive plants as hosts and thereby affect the growth, reproduction, biomass allocation of the invasive hosts, which may lead to changes in competitive balances between invasive host plants and non-host native plants, with repercussions for community structure and diversity. As a result, the physical, chemical and microbial properties of the soil under the invaded plant community may be altered, which may facilitate and promote the growth of non-dominant native plants, thereby changing the structure and diversity of the invaded plant community. Thus, native parasitic plants might be useful as biological control agents and they may contribute greatly to ecological restoration of invaded communities.