Soil nematode communities are ecologically more mature beneath late- than early-successional stage biological soil crusts

Abstract

Biological soil crusts are key mediators of carbon and nitrogen inputs for arid land soils and often represent a dominant portion of the soil surface cover in arid lands. Free-living soil nematode communities reflect their environment and have been used as biological indicators of soil condition. In this study, we test the hypothesis that nematode communities are successionally more mature beneath well-developed, late-successional stage crusts than immature, early-successional stage crusts. We identified and enumerated nematodes by genus from beneath early-and late-stage crusts from both the Colorado Plateau, Utah (cool, winter rain desert) and Chihuahuan Desert, New Mexico (hot, summer rain desert) at 0-10 and 10-30 cm depths. As hypothesized, nematode abundance, richness, diversity, and successional maturity were greater beneath well-developed crusts than immature crusts. The mechanism of this aboveground-belowground link between biological soil crusts and nematode community composition is likely the increased food, habitat, nutrient inputs, moisture retention, and/or environmental stability provided by late-successional crusts. Canonical correspondence analysis of nematode genera demonstrated that nematode community composition differed greatly between geographic locations that contrast in temperature, precipitation, and soil texture. We found unique assemblages of genera among combinations of location and crust type that reveal a gap in scientific knowledge regarding empirically derived characterization of dominant nematode genera in deserts soils and their functional role in a crust-associated food web.

Natural Recovery of Biological Soil Crusts After Disturbance

“…Later, surface-bound cyanobacterial colonizers are favored by the stable surface created by the filamentous cyanobacteria. These taxa are rich in sunscreen pigments and, combined with an increase in biomass, give biocrusts their common dark color, as well as the often-cited gradient from light to dark biocrusts, which indicates succession Darby et al 2007;Dojani et al 2011;Yeager et al 2004). As biocrusts darken and host more species, the ecological maturity of the microfauna also increases (Darby et al 2007).…”

“…These taxa are rich in sunscreen pigments and, combined with an increase in biomass, give biocrusts their common dark color, as well as the often-cited gradient from light to dark biocrusts, which indicates succession Darby et al 2007;Dojani et al 2011;Yeager et al 2004). As biocrusts darken and host more species, the ecological maturity of the microfauna also increases (Darby et al 2007). In regions where succession proceeds beyond "dark" cyanobacterial crusts, typically mosses and/or lichens are reported as becoming more abundant or even dominant Kidron et al 2008;Jia et al 2008;Lan et al 2012;Lázaro et al 2008;Büdel et al 2009).…”

Biogeomorphology of a Mojave Desert landscape — Configurations and feedbacks of abiotic and biotic land surfaces during landform evolution

“…Presence of small mammals can, in turn, create further surface heterogeneity by creating new habitats and facilitating overall biodiversity of these mosaics (Davidson and Lightfoot, 2008). Bars and swales with abundant moss, lichen, and dark algal crusts may be potential habitats for invertebrates specialized in feeding on these resources (Belnap, 2006;Darby et al, 2007), whereas shrub zone units, which were preferentially associated with light algal crusts, may provide suitable stability for burrows used by small reptiles (Zaady and Bouskila, 2002).…”

A natural odor attraction between lactic acid bacteria and the nematode Caenorhabditis elegans

“…This shows that nematodes can find and consume various bacteria in fruit. Previous studies report that increased numbers of nematodes are found in areas of the soil that are populated with increased diversity of bacteria (Bongers, 1990;Darby et al, 2007). Our hypothesis is that diacetyl acts as a cue to allow nematodes to locate large and diverse bacterial bonanzas growing in an area where nutrients for microbial growth are abundant.…”

“…The exact reason for this is not fully known; however, rotten fruit and vegetation are a rich source of bacteria for worms to feed on. Rhabditid nematodes like C. elegans are considered enrichment-type nematodes (Bongers, 1990;Darby et al, 2007). They normally exist in a semi-hibernating dauer larval stage in nature (Barriere and Felix, 2005), but when they come upon a rich source of bacteria, the dauers will quickly grow to sexually mature adults, rapidly reproduce in very large numbers, and consume much of the bacteria present (Bongers, 1990).…”