Effects of plant species diversity on nematode community composition and diversity in a long-term biodiversity experiment

Abstract

Diversity loss has been shown to change the soil community; however, little is known about long-term consequences and underlying mechanisms. Here, we investigated how nematode communities are affected by plant species richness and whether this is driven by resource quantity or quality in 15-year-old plant communities of a long-term grassland biodiversity experiment. We extracted nematodes from 93 experimental plots differing in plant species richness, and measured above- and belowground plant biomass production and soil organic carbon concentrations (Corg) as proxies for resource quantity, as well as C/Nleaf ratio and specific root length (SRL) as proxies for resource quality. We found that nematode community composition and diversity significantly differed among plant species richness levels. This was mostly due to positive plant diversity effects on the abundance and genus richness of bacterial-feeding, omnivorous, and predatory nematodes, which benefited from higher shoot mass and soil Corg in species-rich plant communities, suggesting control via resource quantity. In contrast, plant-feeding nematodes were negatively influenced by shoot mass, probably due to higher top–down control by predators, and were positively related to SRL and C/Nleaf, indicating control via resource quality. The decrease of the grazing pressure ratio (plant feeders per root mass) with plant species richness indicated a higher accumulation of plant-feeding nematodes in species-poor plant communities. Our results, therefore, support the hypothesis that soil-borne pathogens accumulate in low-diversity communities over time, while soil mutualists (bacterial-feeding, omnivorous, predatory nematodes) increase in abundance and richness in high-diversity plant communities, which may contribute to the widely-observed positive plant diversity–productivity relationship.

A global meta‐analysis of the impacts of tree plantations on biodiversity

“…Likewise, belowground biodiversity was positively correlated with soil organic carbon in reforestation (Figure S7a). Mixed plantations provide greater quantity and more diverse substrates, allowing for more diverse soil microbes and soil fauna that feed on microorganisms (Dietrich et al, 2021;Ren et al, 2017). Furthermore, our results showed that intensive management might not favour wildlife persistence in tree plantations by simplifying the habitat structure (Castaño-Villa et al, 2019), such as uniform tree age structure, lower canopy coverage, sparse undergrowth, less stable microclimate and greater human disturbance (Chung et al, 2000;Danielsen & Heegaard, 1995;Peh et al, 2006), and thereby resulted in a lower biodiversity in managed plantations than that in restoration-oriented tree plantations.…”

Eco-evolutionary dynamics modulate plant responses to global change depending on plant diversity and species identity

“…Our findings that A. elatius and D. glomerata plants in soil of high-diversity communities produce more biomass than in soil of low-diversity communities are in line with several greenhouse studies showing that soil conditioned by multiple plant species has a more positive impact on plant growth than soil conditioned by only one or two plant species ( Guerrero‐Ramírez et al, 2019 ; Yang et al, 2015 ). Plants probably suffered more from pathogens when grown in soil of low-diversity communities and/or benefitted more from interactions with soil mutualists in soil of high-diversity communities ( Dietrich et al, 2021 ; Guerrero‐Ramírez et al, 2019 ; Schnitzer et al, 2011 ). Interestingly, this soil legacy effect was only found in A. elatius and D. glomerata , which were both highly productive species in the long-term field experiment.…”

“…When treated with drought, there was no significant difference, but nitrogen input had a more positive impact on plants originated from high-diversity than from low-diversity communities. Possibly plants at high diversity were selected for greater niche complementarity ( Zuppinger-Dingley et al, 2014 ), while plants at low diversity were selected for increased defense against species-specific pathogens ( Eisenhauer et al, 2019 ), that accumulate in low-diversity environments ( Dietrich et al, 2021 ; van Ruijven et al, 2020 ). Consequently, the offspring of individuals originated from high-diversity communities may be more efficient in allocating additional resources in increased growth, explaining our results.…”

“…We chose six-species plots as ‘high-diversity communities’, because they were available with different community compositions and could better represent the effects of species richness as a measure of diversity than the replicates of the 9-species plots with the same species composition. Moreover, previous studies have shown that plant productivity and soil biota communities already differ between 2- and 6-species communities ( Dietrich et al, 2021 ; Roscher et al, 2007 ). The selected plots were evenly distributed in the four blocks of the experiment ( Roscher et al, 2004 ).…”

Long-Term Giant Hogweed Invasion Contributes to the Structural Changes of Soil Nematofauna

“…Increasing the number of studies in recent years has demonstrated that individual plant species differently affect the communities of the soil food web they support [37][38][39], whereas several biodiversity experiments have revealed the adverse effect of plant species loss on soil Nematoda [40][41][42]. This suggest that shifts in plant community composition in the habitats where alien plant invasion have taken place could have substantial impacts on the communities' structure of native soil nematodes.…”