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Abstract Invasive plants are a major problem for land managers and have widespread and lasting environmental impacts. The invasive shrub Amur honeysuckle (
Lonicera maackii ) is a pervasive and noxious plant in the Midwest region of the United States.Despite this, many land managers may be uncomfortable with herbicide control of this and other invasive plants due to unknown impacts on ecosystem components including soils.
To examine if herbicide control of Amur honeysuckle impacts soil enzyme activity and soil communities, we treated Amur honeysuckle with Garlon®4 (triclopyr) suspended in Basal Bark Oil, Basal Bark Oil alone and untreated controls, then assessed soil community, soil enzyme activity and arbuscular mycorrhizal density changes among treatments and across the subsequent growing season.
We found that basal bark herbicide treatments of Amur honeysuckle do not negatively impact soil enzyme activity, nor do they impact fungal, prokaryotic or oomycotan diversity or community structure. There was a slight but likely ecologically unimportant effect on community structure associated with basal bark oil applications, but not with herbicide applications. Arbuscular mycorrhizal colonization was negatively affected by herbicide use but this is likely due to reduction in host health and/or mortality.
Taken together, this suggests that herbicide control of Amur honeysuckle does not impact soils and land managers can treat these invasive plants without concern for negative soil outcomes.
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Drought suppresses soil predators and promotes root herbivores in mesic, but not in xeric grasslandsPrecipitation changes among years and locations along gradients of mean annual precipitation (MAP). The way those changes interact and affect populations of soil organisms from arid to moist environments remains unknown. Temporal and spatial changes in precipitation could lead to shifts in functional composition of soil communities that are involved in key aspects of ecosystem functioning such as ecosystem primary production and carbon cycling. We experimentally reduced and increased growing-season precipitation for 2 y in field plots at arid, semiarid, and mesic grasslands to investigate temporal and spatial precipitation controls on the abundance and community functional composition of soil nematodes, a hyper-abundant and functionally diverse metazoan in terrestrial ecosystems. We found that total nematode abundance decreased with greater growing-season precipitation following increases in the abundance of predaceous nematodes that consumed and limited the abundance of nematodes lower in the trophic structure, including root feeders. The magnitude of these nematode responses to temporal changes in precipitation increased along the spatial gradient of long-term MAP, and significant effects only occurred at the mesic site. Contrary to the temporal pattern, nematode abundance increased with greater long-term MAP along the spatial gradient from arid to mesic grasslands. The projected increase in the frequency of extreme dry years in mesic grasslands will therefore weaken predation pressure belowground and increase populations of root-feeding nematodes, potentially leading to higher levels of plant infestation and plant damage that would exacerbate the negative effect of drought on ecosystem primary production and C cycling.more » « less
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Abstract The fraction of primary productivity allocated below‐ground accounts for a larger flow of carbon than above‐ground productivity in most grassland ecosystems. Here, we addressed the question of how root herbivory affects below‐ground allocation of a dominant shortgrass prairie grass in response to water availability. We predicted that high levels of root herbivory by nematodes, as seen under extreme drought in sub‐humid grasslands, would prevent the high allocation to root biomass normally expected in response to low water availability.
We exposed blue grama
Bouteloua gracilis , which accounts for most of the net primary productivity in the shortgrass steppe of the central and southern Great Plains, to three levels of water availability from extreme low to intermediate and extreme high crossed with a gradient of rootherbivore per cent abundance relative to the total nematode community in soil microcosms.As hypothesized, the effect of water availability on below‐ground biomass allocation was contingent on the proportion of root herbivores in the nematode community. The relationship between below‐ground biomass allocation and water availability was negative in the absence of root herbivory, but tended to reverse with increasing abundance of root feeders. Increasing abundance of root‐feeding nematodes prevented grasses from adjusting their allocation patterns towards root mass that would, in turn, increase water uptake under dry conditions. Therefore, below‐ground trophic interactions weakened plant responses and increased the negative effects of drought on plants.
Our work suggests that plant responses to changes in precipitation result from complex interactions between the direct effect of precipitation and indirect effects through changes in the below‐ground trophic web. Such complex responses challenge current predictions of increasing plant biomass allocation below‐ground in water‐stressed grasslands, and deserve further investigation across ecosystems and in field conditions.
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null (Ed.)Abstract Earthworms are an important soil taxon as ecosystem engineers, providing a variety of crucial ecosystem functions and services. Little is known about their diversity and distribution at large spatial scales, despite the availability of considerable amounts of local-scale data. Earthworm diversity data, obtained from the primary literature or provided directly by authors, were collated with information on site locations, including coordinates, habitat cover, and soil properties. Datasets were required, at a minimum, to include abundance or biomass of earthworms at a site. Where possible, site-level species lists were included, as well as the abundance and biomass of individual species and ecological groups. This global dataset contains 10,840 sites, with 184 species, from 60 countries and all continents except Antarctica. The data were obtained from 182 published articles, published between 1973 and 2017, and 17 unpublished datasets. Amalgamating data into a single global database will assist researchers in investigating and answering a wide variety of pressing questions, for example, jointly assessing aboveground and belowground biodiversity distributions and drivers of biodiversity change.more » « less
