Diverse Effects of Climate, Land Use, and Insects on Dung and Carrion Decomposition

Abstract

Land-use intensification and climate change threaten ecosystem functions. A fundamental, yet often overlooked, function is decomposition of necromass. The direct and indirect anthropogenic effects on decomposition, however, are poorly understood. We measured decomposition of two contrasting types of necromass, rat carrion and bison dung, on 179 study sites in Central Europe across an elevational climate gradient of 168–1122 m a.s.l. and within both local and regional land uses. Local land-use types included forest, grassland, arable fields, and settlements and were embedded in three regional land-use types (near-natural, agricultural, and urban). The effects of insects on decomposition were quantified by experimental exclusion, while controlling for removal by vertebrates. We used generalized additive mixed models to evaluate dung weight loss and carrion decay rate along elevation and across regional and local land-use types. We observed a unimodal relationship of dung decomposition with elevation, where greatest weight loss occurred between 600 and 700 m, but no effects of local temperature, land use, or insects. In contrast to dung, carrion decomposition was continuously faster with both increasing elevation and local temperature. Carrion reached the final decomposition stage six days earlier when insect access was allowed, and this did not depend on land-use effect. Our experiment identified different major drivers of decomposition on each necromass form. The results show that dung and carrion decomposition are rather robust to local and regional land use, but future climate change and decline of insects could alter decomposition processes and the self-regulation of ecosystems.

Dung‐visiting beetle diversity is mainly affected by land use, while community specialization is driven by climate

“…Moreover, in Harris et al (2019) and Williams et al (2014), increasing temperatures and low precipitation, respectively, were found to potentially decrease the abundance and diversity of some ground‐dwelling beetles. In a previous study, Englmeier et al (2022) found a hump‐shaped pattern of dung removal rates along an elevational gradient, indicating that environmental conditions at intermediate altitudes are more beneficial for dung beetles than in lowlands. Therefore, we assume that climate warming might exacerbate the access to and decomposition of dung by insects, which could explain the potential future emigration of coprophilic beetles to cooler regions as observed by Menéndez et al (2014).…”

Season, decay stage, habitat, temperature and carrion beetles allow estimating the post‐mortem interval of wild boar carcasses

“…In most cases, warmer and more humid conditions are associated with faster decomposition (Moore et al., 2004), as shown, for example, for deadwood (Seibold et al., 2021) and carrion (Benbow et al., 2013, 2019; Probst et al., 2020). However, within a temperate zone, elevation had a positive effect on rats carcass decay rates during summer, which was explained by more humid conditions and less mummification (Englmeier et al., 2023). For a carrion species with a larger body size, as in our study, the effect of elevation gradient is less well‐studied.…”

“…Here, beetle community composition was predictive of the decay process, supporting previous work showing that beetle community composition, affected by the mean annual temperature, significantly affected mice carrion decomposition (Farwig et al., 2014). An insect exclusion experiment found clear effects of reduced rat carcass decay when insects were excluded (Englmeier et al., 2023). Therefore, the occurrence of specific taxa, for example, Diptera or Coleoptera, significantly affects carcass decomposition and PMI estimates (Kadlec et al., 2019; Pechal, Benbow, et al., 2014; Popescu et al., 2023).…”

“…The organisms involved in this process range from microbes to insects and vertebrates, forming complex and highly dynamic processes and communities (Benbow et al., 2019). Therefore, estimating the decay rate or the post‐mortem interval (PMI) remains challenging (Bradford et al., 2014; Brooks, 2016; Dawson et al., 2023; Englmeier et al., 2023; Pechal, Crippen, et al., 2014; Probst et al., 2020; Woodcock et al., 2002).…”

Drastic changes in ground-dwelling beetle communities following high-intensity deer culling: insights from an island ecosystem

“…Decomposer and scavenger communities depend on the carcass remains of large herbivores as a food resource and breeding substrate, while other decomposer species depend on dung for survival ( Nichols et al 2008 , Butterworth et al 2022 ). These decomposers play a key role in maintaining biodiversity and ecosystem functions and services such as nutrient and energy cycling ( Barton et al 2013 , Englmeier et al 2022 ). The sudden removal of a large number of herbivore species from an ecosystem may have unintended negative consequences on dependent species, which in turn could have bottom-up effects on the food web and broader ecosystem function ( Iida et al 2016 ).…”