Nonparasitic Nematoda provide evidence for a linear response of functionally important soil biota to increasing livestock density

Abstract

Soil acidity, nutrient availability and livestock density have a major influence on the belowground ecological community. As fast decomposition rates are due mostly to bacterial-based pathways and slower decomposition rates mostly to fungal-based pathways, it is helpful to condense empirical information in the so-called Nematode Channel Ratio (NCR). The NCR is shown to be a good indicator of efficiency in soil decomposition processes. We argue that in intensive agroecosystems, other fungivore members of the decomposer food web may outcompete the hyphal-feeding nematodes. We demonstrate how the NCR can be used to set ecological standards for sustainable use of the soil in agroecosystems. To summarize the interactions between the microbial resources and the decomposer nematofauna according to increasing land management, we propose the use of the fifth percentile as proxy for a sustainable environmental quality of grasslands on sandy soils, and the NCR mean as the upper threshold for low-stocked farms.

Driving forces from soil invertebrates to ecosystem functioning: the allometric perspective

“…Nematodes have promising characteristics as field bioindicators (Breure et al 2005) and a facultative self-fertilising reproduction that enables a laboratory finetuning (Walker et al 2000). The physiognomic characters of the nematodes' buccal cavities (Yeates et al 1993;Warwick and Clarke 1998) can be chosen to assess effects on the basal fauna (Mulder et al 2003a(Mulder et al , 2005d and to express the efficiency of soil decomposition processes (Table 1). In contrast to non-parasitic nematodes, collembolans (springtails) are often selective or even preferential species.…”

“…Those root-derived compounds lost by exudation include low molecular mass exudates, secretions, polysaccharide mucilages and lysate (Bardgett et al 1998;Bonkowski 2004;Moore et al 2004;De Boer et al 2005). As the (infested) roots are an important source of carbon for microbes (Coleman et al 1983;Yeates et al 1998), it is likely that any changes of FOM in perennial grasslands may significantly affect the functional diversity and the metabolic activity of rhizosphere communities Bardgett et al 1999Bardgett et al , 2003Bardgett et al , 2005Beerling and Woodward 2001;Chapin and Eviner 2003;Cole et al 2004;Gange 1993;Klironomos et al 2000;Legendre and Rivkin 2002;Mulder et al 2003aMulder et al , 2005dScheu and Setälä 2002;Setälä 2002;Wardle 1995Wardle , 2002Wardle et al 1999 Enchytraeids and earthworms, nematode channel ratio, bacteria to fungi ratio, fresh organic matter, priming effect, soil organic matter, soil acidity (power of hydrogen) Breure 2004;Breure et al 2005;Didden 2003;Fontaine et al 2003Fontaine et al , 2004Ingham et al 1985;Laakso and Setälä 1999;Liiri et al 2002;Moore et al 2004;Mulder et al 2003aMulder et al , 2003bMulder et al , 2005aNeedham et al 2004;Scheu and Setälä 2002;Setälä 2002;…”

“…Numerical abundance and biodiversity of archaea and bacteria, extent of washout of nitrogen and phosphate, clean soilBegon et al 2006;Breure 2004;Breure et al 2005;Fitter et al 2005;Legendre and Rivkin 2002;Mulder et al 2003aMulder et al , 2005d Pest control in agriculture Agrobiodiversity, genetic resources, biological control of pathogens microbial abundance, bacteria to fungi ratio, (arbuscular) mycorrhizal fungiBegon et al 2006;Cairney 2000;Fountain and Hopkin 2005;Gange et al 2005;Hammer et al 2003;Watkinson and Freckleton 1997 Dunne 2005;Jonsson et al 2005; Mulder et al 2005c,d; Cohen 2004, 2005;Wardle et al 2004;West and Brown 2005;Woodward et al 2005 …”

Impact of heavy metal pollution on plants and leaf-miners

“…The Gaussian logistic regression is widely used in the assessment of aboveground-belowground relationships (Mulder et al 2005b). This stepwise model allows us to relate for each vascular host-plant its probability of occurrence p to a given chemical stressor.…”

Aboveground Herbivory Shapes the Biomass Distribution and Flux of Soil Invertebrates

“…Increased land use results in rapid decline of soil organic matter due to reduced input rates and decreased physical protection to decomposition by cropping and tillage. Animals linked to either labile or recalcitrant substrates support the complementarity action of “energy transfer agents” (nematodes and enchytraeids) or “habitat engineers” (earthworms), and controversy exists over whether soil invertebrates control (‘bottom–up’) aboveground primary productivity, or whether belowground changes in soil invertebrates follow (‘top–down’) changes in agroecosystems [1]–[6]. Such opposite, controversial trends also contributed to several other relevant questions [7].…”