The Serendipitous Value of Soil Fauna in Ecosystem Functioning: The Unexplained Explained

Abstract

Soil fauna is crucial to soil formation, litter decomposition, nutrient cycling, biotic regulation, and for promoting plant growth. Yet soil organisms remain underrepresented in soil processes and in existing modeling exercises. This is a consequence of assuming that much of the below-ground diversity is just ecologically "redundant" and that soil food webs exhibit a higher degree of omnivory. However, evidence is accumulating on the strong influence of abiotic filters (temperature, moisture, soil pH) and soil habitat characteristics in controlling their spatial and temporal patterns. From this, new emerging concepts such as "hot moments," "biological accessibility," and "trophic cascades" have been coined to enable plausible explanations of the observed faunal responses to environmental changes. Here, I argue that many of these findings are indeed "happy accidents" (i.e., "eureka discoveries") that remain disjointed between disciplines, impeding us from making significant breakthroughs. Therefore, here I provide some new perspectives on soil fauna research and highlight some experimental approaches to better explore the great variety of organisms living in soils and their complex interactions. A more comprehensive and dynamic holistic approach is needed to couple soil pedological and biological processes and to combine current experimental and theoretical knowledge if we aim to improve our predictive capacities in determining the persistence of soil organic matter and soil ecosystem functioning.

Soil Quality and Regenerative, Sustainable Farming Systems

“…For these reasons it is not a good agronomic practice to expose raw organic matter to germinating crop seeds, or seedlings, without making sure that the humification cycle has been completed (Lampkin 1999). A polymerization of the molecules yielded prior to the mineralization stage of the humification process stabilizes the complex carbon molecules that have now been converted in humus, which accumulates in the horizon or topsoil of most soil profiles (Brady and Weil 2002). Conditions necessary for a correct ecology of the humification cycle are aerobic conditions, diversity of the biomass undergoing the process, and diversity of the microbial community (Zucconi 1996).…”

“…• Conserving and stabilizing soil organic matter (SOM) content to acceptable levels, through regular applications of livestock manure, and a cultivation of cover crops, green manures, to enhance the soil water retention capability (Reij et al 1996;Zucconi 1996) • Employing the use of crop residues and other biomass available at the farm as mulch to decrease water loss (evaporation) from the soil (Brady and Weil 2002) • Using more diversification strategies in the design of the farm and soil management, such as intercalated crops, agroforestry, and an employment of rotational grazing for livestock species • Adapting water management according to soil use and topography, to avoid floods, erosion, and lixiviation of soil nutrients, due to heavy rain precipitation Soil conservation practices that foster soil quality may also be promoted through indirect management approaches through:…”

Soil Microarthropods and Soil Health: Intersection of Decomposition and Pest Suppression in Agroecosystems

“…These activities are critical to ecological processes that decompose soil organic matter (SOM) to release or immobilize nutrients, stabilize soil by forming aggregates, and promote plant growth [2][3][4][5]. Plants benefit from interactions with soil microfauna by way of protection from pathogens and pests, attraction of beneficial insects, and increased tolerance to abiotic and biotic stress [6,7].…”

“…Size class is a practical method to classify fauna. There are three groups defined by body width: microfauna (<0.1 mm), mesofauna (0.1-2 mm) and macrofauna (>2 mm) [7]. Among the soil fauna, microarthropods comprise a large proportion of the meso-and macrofauna and play a long-recognized role in litter transformation and nutrient cycling [12,13].…”

Soil microarthropods and soil health: Intersection of decomposition and pest suppression

“…These activities are critical to ecological processes that decompose soil organic matter (SOM) to release or immobilize nutrients, stabilize soil by forming aggregates, and promote plant growth [2][3][4][5]. Plants benefit from interactions with soil microfauna by protection from pathogens and pests, attraction of beneficial insects, and increased tolerance to abiotic and biotic stress [6,7].…”