Carrion decomposition and nutrient cycling in a semiarid shrub–steppe ecosystem

Abstract

Vertebrate carrion decomposition and nutrient cycling have both direct and indirect effects on the soil properties, fauna, and flora associated with an animal's carcass. While few comprehensive quantitative studies have been undertaken, those that have show considerable variability in decomposition processes and rates, their regulating variables, and the resultant ecosystem effects. In this two-part study, decomposition rates of vertebrate species were measured in a semiarid, shrub-steppe environment (Wyoming, USA). First, decomposition loss rates of mass, energy, and nutrients were measured for rat carcasses (Rattus norvegicus) in four seasons and two microsites (surface and underground burrows). Decomposition rates varied significantly between microsites (burrow . surface in spring and summer) and among seasons (spring . summer . autumn ' winter), with mass loss amounts linearly correlated with ambient air temperatures. Energy and nutrient losses were related to phased carcass organ/tissue losses, with energy, K, Na, N, and S being lost more quickly than skeletal components (P, Mg, Ca). Overall, the nutrient loss sequence was K ¼ Na .Carcass quality (N concentration) declined through time as a function of decay stage. Second, decomposition rates of 10 vertebrate species (mule deer [Odocoileus hemionus], dog [Canis familiaris], white-tailed jackrabbit [Lepus townsendii], Uinta ground squirrel [Spermophilus armatus], least chipmunk [Tamias minimus], deer mouse [Peromyscus maniculatus], Magpie [Pica hudsonia], Sage Sparrow [Amphispiza belli], terrestrial garter snake [Thamnophis elegans], and northern leopard frog [Lithobates pipiens])were measured with vertebrate scavengers present or absent. Mass loss rates varied among species and were generally faster in the presence of scavengers. Carcass body mass, N content, or labile/recalcitrant fractions did not correlate with decomposition rate, though surface area to volume ratios of mammal carcasses were positively correlated with wet-mass decomposition rate. Nutrient measures of sub-carcass soils showed soil N, P, and Na increased during decomposition. Increased soil nutrient amounts represented up to 15.6% of the available carcass N, 28.8% of carcass P, and 28.7% of carcass Na. At a landscape scale in the shrubsteppe ecosystem, carrion decomposition constituted ,1% of the nutrient-cycling budget but contributed significantly to localized soil nutrient dynamics.

Ecosystem carbon exchange in response to locust outbreaks in a temperate steppe

“…Similar observations have been reported that insect outbreaks reduce NEP during outbreaks but increase NEP in the year after the outbreaks (Mattson and Addy 1975;Cook et al 2008;Albani et al 2010;Amiro et al 2010). The enhanced plant productivity after outbreaks in both grassland and forest ecosystems (Risley and Crossley 1993;Towne 2000;Parmenter and MacMahon 2009) could be primarily attributable to the enhanced decomposition of plant and insect litter and subsequent increase in soil N availability. Moreover, the stimulations in 2011 compensated for the reductions in 2010 under the experimental locust outbreaks, resulting in neutral change in NEE within the 2-year experimental period.…”

Delayed insect access alters carrion decomposition and necrophagous insect community assembly

“…We demonstrated that delayed insect access altered subsequent insect community assembly and was associated with a slower decomposition process. Changes in decomposition is known to modify the rate of nutrient transformation and availability in the local habitat, and overall effect the ecosystem function of removing decomposing organic matter from a terrestrial habitat (Parmenter and MacMahon 2009, Hawlena et al 2012, Woodward et al 2012). Reducing the quantity or rate of nutrient reintroduction into the environment could ultimately impact other members of the community that respond to nutrient pulses (Post and Kwon 2000).…”

“…Resource pulses such as carrion are defined as infrequent, short-lived resources that can have large impacts on ecosystem processes (Yang et al 2008). For instance, carrion nutrient transfer between ecosystems can result from blow fly (Diptera: Calliphoridae) consumption and dispersal (Hocking and Reimchen 2006, Hocking et al 2009, Parmenter and MacMahon 2009 or vertebrate scavenging (Wilson andWolkovich 2011, Beasley et al 2012). Necrophagous arthropod attraction, colonization, development, and migration can affect nutrient transformation and release and thus local biodiversity (Hocking and Reimchen 2006, Lisi and Schindler 2011, Tomberlin et al 2011, Hawlena et al 2012, which can ultimately impact landscape biodiversity depending on the density and frequency of carrion (Yang et al 2008, Barton et al 2013.…”

“…(Salmoniformes: Salmonidae) (Hocking and Reimchen 2006), can be the primary resource subsidy for their associated ecosystems (Lisi and Schindler 2011). Carrion decomposition reintroduces essential nutrients such as nitrogen, potassium, calcium and magnesium into an ecosystem (Towne 2000, Carter et al 2007, Parmenter and MacMahon 2009. In a recent study, the differences in carcass quality (i.e., grasshoppers nonstressed vs. stressed by predators) was reported to affect soil microbial communities and subsequent decomposition processes; the addition of stressed carcasses significantly reduced plant litter decomposition rates (Hawlena et al 2012).…”

Keratin subsidies promote feather decomposition via an increase in keratin-consuming arthropods and microorganisms in bird breeding colonies

“…Consequently, large amounts of keratin likely accumulate in bird colonies (Sugiura and Ikeda 2014). Although the decomposition process of vertebrate carcasses has been frequently investigated (Carter et al 2007;Parmenter and MacMahon 2009;Mondor et al 2012;Pechal et al 2014), very few studies have focused on the decomposition of keratin materials such as feathers under field conditions (Sugiura and Ikeda 2014). Keratin is one of the most abundant and highly stable animal proteins on earth (Sharma and Rajak 2003).…”