Edge and herbivory effects on leaf litter decomposability in a subtropical dry forest

Abstract

It is increasingly recognized that understanding the functional consequences of landscape change requires knowledge of aboveground and belowground processes and their interactions. For this reason, we provide novel information addressing insect herbivory and edge effects on litter quality and decomposition in fragmented subtropical dry forests in central Argentina. Using litter from Croton lachnostachyus (a common shrub species in the region) in a decomposition bed experiment, we evaluated whether litter quality (carbon and nitrogen content; carbon: nitrogen ratio) and decomposability (percentage of remaining dry weight) differ between litter from forest interiors or edges (origin) and with or without herbivory (damaged/undamaged leaves). We found that edge/interior origin had a strong effect on leaf litter quality (mainly on carbon content), while herbivory was associated with a smaller increase in nitrogen content. Herbivore damage increased leaf litter decomposability, but this effect was related to origin during the initial period of litter incubation. Overall, undamaged leaf litter from the forest edge showed the lowest decomposability, whereas damaged leaf litter decomposed at rates similar to those observed in litter from the forest interior. The interacting edge and herbivory effects on leaf litter quality and decomposability shown in our study are important because of the increasing dominance of forest edges in human‐modified landscapes and the profound effect of leaf litter decomposition on nutrient cycling.

Tree diversity and functional leaf traits drive herbivore‐associated microbiomes in subtropical China

“…However, both the results herein and some previous reports suggest a positive relationship between LDMC and leaf herbivory (Lepidoptera richness in this study; Schuldt et al, 2012), probably because there are herbivores specifically adapted to tough leaves (Pérez et al, 2003) and herbivores have to consume more of less nutritious foliage to gain the same nitrogen accumulation rates (Scriber & Slansky, 1981).…”

“…As mentioned above, the phyllosphere appears to be a key source for herbivore microbiomes and is moderated by tree characteristics such as leaf structure (also, LDMC is directly affected by leaf thickness, structure, and specific leaf area and reflects the ability of plants to obtain resources). LDMC and LT are usually expected to negatively associate with herbivory because structurally robust leaves are relatively difficult to consume (Pérez et al, 2003).…”

Intraspecific leaf trait variation mediates edge effects on litter decomposition rate in fragmented forests

“…Studies have shown that intraspecific trait shifts in response to environmental change, including abiotic and biotic drivers (Coq et al, 2018; Henneron et al, 2017), can affect leaf decomposability. In terms of habitat fragmentation, for example, Moreno et al (2017) observed that within the same species, plants growing at the forest edge had a higher leaf carbon‐to‐nitrogen ratio and, thus, reduced litter quality, and in a common garden decomposition experiment they showed that such ITV caused a reduction in litter decomposition rates of leaves from “edge” plants. In addition, habitat fragmentation also influences litter decomposition rates by altering site conditions (Bradford et al, 2015; Wardle et al, 2004), which can themselves drive intraspecific shifts in plant traits (e.g., Moreno et al, 2017), leading to challenges in discriminating confounding “donor effects” (plant traits) from “recipient effects” (site conditions) on litter decomposition in the field.…”

“…In terms of habitat fragmentation, for example, Moreno et al (2017) observed that within the same species, plants growing at the forest edge had a higher leaf carbon‐to‐nitrogen ratio and, thus, reduced litter quality, and in a common garden decomposition experiment they showed that such ITV caused a reduction in litter decomposition rates of leaves from “edge” plants. In addition, habitat fragmentation also influences litter decomposition rates by altering site conditions (Bradford et al, 2015; Wardle et al, 2004), which can themselves drive intraspecific shifts in plant traits (e.g., Moreno et al, 2017), leading to challenges in discriminating confounding “donor effects” (plant traits) from “recipient effects” (site conditions) on litter decomposition in the field. So far, previous studies investigating drivers of litter decomposition in fragmented forests focused on either leaf trait effects alone using common garden decomposition experimental manipulation (e.g., Moreno et al, 2017) or environmental drivers using common litter substrate experiments (e.g., Didham, 1998; Riutta et al, 2012), leaving the relative effects of these collinear drivers of litter decomposition elusive in fragmented forests.…”

The impacts of shrub abundance on microclimate and decomposition in the Canadian Low Arctic

“…The quality of the litter influences mineralization rates by microbial communities, which play a major role in controlling soil N cycling (Aerts et al, 2006;Wallenstein et al, 2007). The C:N is a ratio of the mass of C to N in a substance and can indicate the decomposability of the material (Di Palo & Fornara, 2015;Moreno et al, 2017). For example, graminoid and moss vegetation have a higher C:N ratio relative to other litters (e.g.…”