Distinguishing Sensitivity of Free-Living Soil Nematode Genera to Physical and Chemical Disturbances

Abstract

During the past 50 yr, ecological and agricultural scientists have pursued an integrated definition and metric of soil quality. In the past 20 yr, considerable attention has been paid to nematodes, demonstrating that these ubiquitous members of the soil community reflect change in ecological structure and function of soils in ways more predictable and efficient than for other soil flora or fauna. With the help of multivariate analysis, we studied the application of free‐living nematode communities as model indicators of physical and chemical disturbance of agricultural soil. We used canonical correspondence analysis (CCA) and partial CCA to segregate effects of tillage and chemical/nutrient treatments. With the results of CCA, we assigned relative direct and indirect tillage sensitivity and chemical/nutrient sensitivity ratings to soil genera found in two test data sets, each containing three matrices: (1) sites by species or genera, (2) sites by soil properties, and (3) sites by management practices. Of 46 total genera, the ones most sensitive to direct effects of tillage include Aphelenchoides, Eucephalobus, Eudorylaimus, Heterocephalobus, and Wilsonema compared to the tolerant genera Achromadora, Anatonchus, Cephalobus, Chiloplacus, Clarkus, Epidorylaimus, Mylonchulus, Plectus, and Tylencholaimellus. Some genera are more sensitive to indirect than direct effects of tillage: these include Achromadora, Cephalobus, Microdorylaimus, Monhystera, Panagrolaimus, and Prionchulus. With the exception of Discolaimus and Prismatolaimus, genera sensitive to chemical/nutrient treatments differ from those sensitive to tillage treatments including Alaimus, Cylindrolaimus, Mesorhabditis, Odontolaimus, and Protorhabditis. Likewise, genera uniquely sensitive to indirect but not direct effects of chemical/nutrient treatments are Aphelenchus, Aporcelaimellus, and Diplogaster. Eudorylaimus and Eumonhsytera are sensitive to indirect effects of both tillage and chemical/nutrient treatments. Our results suggest that physical and chemical/nutrient disturbances can alter populations of nematode genera differently, and that indirect effects of management are greater than direct effects. This methodology aids in distinguishing nematode genera that have distinctive responses to agricultural management practices from those that are ambiguous. This knowledge is useful for both interpretation and enhancement of free‐living nematode community indices.

Nematode community profiling as a soil biology monitoring tool in support of sustainable tomato production: A case study from South Africa

“…The resilience of Cephalobus spp. to tillage was confirmed in our study (Fiscus and Neher, 2002) and Helicotylenchus spp. was identified as a candidate soil health indicator in the specific agroecosystem studied (to be discussed in more detail in section 4.4).…”

Species and genera of soil nematodes in forest ecosystems of the Vihorlat Protected Landscape Area, Slovakia

“…Cp values of species and genera were derived from cp values for families as given by Bongers & Bongers (1998) using Bongers' (1988 allocations to families. Trophic diversity T (Freckman & Ettema, 1993) and Sum Maturity Index ∑MI (Yeates, 1994) were calcu- lated either from the number of nematoda taxa in trophic groups or in cp groups, respectively; i.e. supposing that all species (genera) were present in a community and had the same abundance.…”

Populations ofLongidorus elongatus(Nematoda: Longidoridae) in two New Zealand soils under grazed pasture

“…The "extra" plant growth in the elevated Co 2 rings, resulting from postulated "Co 2 fertilisation", appears to allow for more L. elongatus than in ambient rings. Fiscus & Neher (2002) reported the susceptibility of dorylaimid nematodes such as L. elongatus to stresses due to fertiliser addition. In the present study, soil in the open field had a lower Olsen P content (15 mg P kg -1 ) than that from either ring (ambient 34 mg P kg -1 , elevated 21.0 mg P kg -1 ).…”