Parasitic plants indirectly regulate below-ground properties in grassland ecosystems

Abstract

Parasitic plants are one of the most ubiquitous groups of generalist parasites in both natural and managed ecosystems, with over 3,000 known species worldwide. Although much is known about how parasitic plants influence host performance, their role as drivers of community- and ecosystem-level properties remains largely unexplored. Parasitic plants have the potential to influence directly the productivity and structure of plant communities because they cause harm to particular host plants, indirectly increasing the competitive status of non-host species. Such parasite-driven above-ground effects might also have important indirect consequences through altering the quantity and quality of resources that enter soil, thereby affecting the activity of decomposer organisms. Here we show in model grassland communities that the parasitic plant Rhinanthus minor, which occurs widely throughout Europe and North America, has strong direct effects on above-ground community properties, increasing plant diversity and reducing productivity. We also show that these direct effects of R. minor on the plant community have marked indirect effects on below-ground properties, ultimately increasing rates of nitrogen cycling. Our study provides evidence that parasitic plants act as a major driver of both above-ground and below-ground properties of grassland ecosystems.

Genetic variation changes the interactions between the parasitic plant-ecosystem engineer Rhinanthus and its hosts

“…Presence of Rhinanthus can influence plant [60,61], soil [32] and arthropod [36] community structure as well as the cycling of nutrients within the system [33]. From other research we know that genetic variation within a focal plant can change the outcome of interactions with arthropods, soil microbes [6,11] and the effects of an associated ecosystem engineer [10].…”

“…In addition to the effects of Rhinanthus on associated plant communities, presence of the parasitic plant is associated with changes in soil microbial communities [32], long-term nutrient availability [33] and the outcome of host-mycorrhizal interactions [34,35]. Rhinanthus also influences host interactions with aphid herbivores [36] and above-ground arthropod community structure (S. Hartley 2010, personal communication).…”

Microbial contributions to climate change through carbon cycle feedbacks

“…For example, N enrichment has direct and differential impacts on extracellular enzymes involved in decomposition processes (Carreiro et al, 2000;Frey et al, 2004), and on the abundance and diversity of different components of the soil microbial community, including bacteria, saprophytic fungi (Donnison et al, 2000;Bardgett et al, 2006) and mycorrhizal fungi (Egerton-Warburton and Allen, 2000;Frey et al, 2004), which are also affected directly and indirectly by climate change. Also, N deposition can indirectly influence soil microbes and decomposition processes through altering vegetation composition and productivity (for example, Stevens et al, 2004;van der Heijden et al, 2008) and by alleviating progressive N limitation of plant growth, which typically occurs under elevated atmospheric CO 2 (Finzi et al, 2002).…”

Modelling interactions in fungi

“…Within ecological systems, fungi have extremely important functional roles as nutrient recyclers and decomposers (Johnson et al 2005) and are a life support network for most plants (Bardgett et al , 2006 providing soilborne nutrients that are difficult for plants to access in exchange for carbon (White 2003) and protecting plants against below-ground pathogens (Smith & Read 1997). Fungal colonies grow as an interconnected network of hyphae, the mycelium, through the pore channels in soil and impact on its physical structure improving porosity (Ritz & Young 2004).…”