Long‐term belowground effects of grassland management: the key role of liming

Abstract

The functioning of human-managed grassland ecosystems strongly depends on how common management practices will affect grassland "belowground compartment" including soil biogeochemistry and plant roots. Key questions remain about how animal grazing, liming (e.g., the addition of CaCO to soils), and nutrient fertilization might affect, in the long-term, soil nutrient cycling and multiple root traits. Here we focus on a mesotrophic grassland located in Berkshire, UK, where contrasting levels of rabbit grazing, liming, and different inorganic fertilizers have been applied since 1991. We ask how (1) soil nitrogen (N) availability and cycling, (2) total root mass, (3) root mass decomposition, and (4) arbuscular mycorrhizal fungal (AMF) root colonization might respond to 22 years of very different management. We found that liming strongly affected total root mass, root decomposition, root AMF colonization as well as soil N availability and cycling and that these effects were mainly driven by liming-induced increases in soil pH. Increases in soil pH were associated with significant (1) decreases in root mass, (2) increases in root mass decomposability and in the mineralization of N in decomposing root detritus, and (3) increases in AMF infection. Soil pH was also significantly related to greater N availability (i.e., soil NO levels) and to lower δ N natural abundance, which suggests more efficient N uptake by plants in limed soils as we found in our study. The application of multiple nutrients (N, P, K, Mg) also reduced total root mass, while N-only fertilization was associated with greater AMF infection. Surprisingly the long-term impact of grazing was generally weak and not significant on most plant and soil parameters. Despite soil pH affecting most belowground variables, changes in soil pH were not associated with any change in soil C and N stocks. Because liming can improve nutrient cycling (and benefits soil pH and grass yields) without negatively affecting soil C sequestration, we suggest that regular liming applications may provide management solutions for increasing the long-term sustainability of permanent grassland.

Changes and Interactions between Grassland Ecosystem Soil and Plant Properties under Long-Term Mineral Fertilization

“…Continual fertilization, in addition to an increased content of nutrients in above-ground biomass, also affects the plant C:N:P stoichiometric responses and nutrients cycling in grassland as well. In this study, N, P, and K fertilizer application significantly decreased plant C:N, C:P, N:P, and N:K ratios comparing to unfertilized control, which is consistent with research findings by Heyburn et al [35] and Zheng et al [64]. Similarly to our study, some authors [65,66] observed that plant C:N ratio was negatively correlated with plant N content and was not associated with C dynamics.…”

“…The pH of the soil depends on the extent to which the input of the base cations coming from artificial and organic fertilizers, from the atmosphere, from the geochemical atmospheric agents, from the vegetable waste, from the water that flows into the ground, can offset the exit in the ground, in the drainage water, in the absorption of plants, and in the removal of animals and crops [33]. Soil acidification is an environmental problem that is driven by various factors and was documented on grasslands [34,35] and in the other crop systems as well [36,37]. Our results showed that soil has been significantly acidified under all treatments.…”

Unraveling spatiotemporal variability of arbuscular mycorrhizal fungi in a temperate grassland plot

“…Similarly, the newly emerging plant species may have had more acidic root exudates, which would have reduced the OTU richness of Glomus, as Glomus OTU richness decreased with decreasing soil pH. A similar effect of pH on AMF OTU richness in grassland ecosystems was also observed by Heyburn et al (2017). Even when they were evaluated over all six sampling dates throughout the season, the effects of soil texture, pH and sampling date remained significant.…”

“…A similar effect of pH on AMF OTU richness in grassland ecosystems was also observed by Heyburn et al . (). Even when they were evaluated over all six sampling dates throughout the season, the effects of soil texture, pH and sampling date remained significant.…”

Livestock grazing and topographic site effects on grassland plant communities after long-term grazing cessation

“…Gornish and Ambrozio dos Santos 2016). In fact, many researchers consider grazing effects on above-ground plant communities as essentially an indirect effect of grazing pressure on below-ground (microhabitat) factors (Heyburn et al 2017). Clearly, researchers must account for inherent site heterogeneity across these complex landscapes to improve understanding of real plant-animal interactions.…”