Global signal of top-down control of terrestrial plant communities by herbivores

Jia, Shihong; Wang, Xugao; Yuan, Zuoqiang; Lin, Fei; Ye, Ji; Hao, Zhanqing; Luskin, Matthew Scott

doi:10.1073/pnas.1707984115

Cited by 101 publications

(139 citation statements)

References 63 publications

(136 reference statements)

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“…The lack of explanatory power of these experimental and biological moderators may be due to lack of true effect; recent meta‐analyses also found limited support for productivity in moderating effects of herbivores on plants (Jia et al, ; Koerner et al, ). However, we suspect that small sample size within components ( n = 8 for soil carbon, n = 7 for carbon flux) and unreported variation in other biotic conditions (e.g.…”

Section: Insights From Well‐studied Ecosystem Functionsmentioning

confidence: 99%

“…The lack of explanatory power of these experimental and biological moderators may be due to lack of true effect; recent metaanalyses also found limited support for productivity in moderating effects of herbivores on plants (Jia et al, 2018;Koerner et al, 2018).…”

Section: Carbon Cycling: a Case Studymentioning

confidence: 99%

“…The lack of synthesis is surprising given that (a) large taxa are often suggested to have disproportionately influential roles on ecosystem function (Owen -Smith, 1988;Pringle, Palmer, Goheen, McCauley, & Keesing, 2010) (Figure 1), and (b) multiple efforts have attempted to synthesize effects of excluding large, wild herbivores on producers (e.g. Gruner et al, 2008, Jia et al, 2018) and smaller consumers (Daskin & Pringle, 2016;Foster, Barton, & Lindenmayer, 2014).…”

Section: Introductionmentioning

confidence: 99%

“…For instance, their large body size allows for very high plant consumption (Clauss, Steuer, Müller, Codron, & Hummel, 2013), large geographic ranges of movement, long-distance transport of nutrients via their waste (Wolf, Doughty, & Malhi, 2013), and unique capability to physically modify habitats via soil compaction and cracking, erosion, and by breaking woody vegetation (Beck, Thebpanya, & Filiaggi, 2010;Long, Wambua, Goheen, Palmer, & Pringle, 2017;Pringle, 2008;van Klink, van der Plas, van Noordwijk, WallisDeVries, & Olff, 2015). The effects of large herbivores on both producers and consumers are often, but not always (see Jia et al, 2018 andKoerner et al, 2018) mediated by environmental variables, for example ecosystem productivity (Burkepile et al, 2017;Daskin & Pringle, 2016), which may mediate herbivore effects on several ecosystem functions ( Figure 1). analyses of large herbivores' effects on individual functions, and (b) improved, increased systematic exclosure research focusing on effects of large herbivores' exclusion on functions.…”

Section: Introductionmentioning

confidence: 99%

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Synthesizing the effects of large, wild herbivore exclusion on ecosystem function

et al. 2019

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Wild large herbivores are declining worldwide. Despite extensive use of exclosure experiments to investigate herbivore impacts, there is little consensus on the effects of wild large herbivores on ecosystem function. Of the ecosystem functions likely impacted, we reviewed the five most‐studied in exclosure experiments: ecosystem resilience/resistance to disturbance, nutrient cycling, carbon cycling, plant regeneration, and primary productivity. Experimental data on large wild herbivores' effects on ecosystem functions were predominately derived from temperate grasslands (50% grasslands, 75% temperate zones). Additionally, data were from experiments that may not be of adequate size (median size 400 m2 despite excluding all experiments below 25 m2) or duration (median duration 6 years) to capture ecosystem‐scale responses to these low‐density and wide‐ranging taxa. Wild herbivore removal frequently impacted ecosystem functions; for example, net carbon uptake increased by three times in some instances. However, the magnitude and direction of effects, even within a single function, were highly variable. A focus on carbon cycling highlighted challenges in interpreting effects on a single function. While the effect of large herbivore exclusion on carbon cycling was slightly positive when its components (e.g. pools vs. fluxes of carbon) were aggregated, effects on individual components were variable and sometimes opposed. Given modern declines in large wild herbivores, it is critical to understand their effects on ecosystem function. However, this synthesis highlights strong variability in direction, magnitude, and modifiers of these effects. Some variation is likely due to disparity in what components are used to describe a given function. For example, for the carbon cycle we identified eight distinctly meaningful components, which are not easily combined yet are potentially misrepresentative of the larger cycle when considered alone. However, much of the observed difference in responses likely reflects real ecological variability across complex systems. To move towards a general predictive framework we must identify where variation in effect is due to methodological differences and where due to ecosystem context. Two critical steps forward are (a) additional quantitative synthetic analyses of large herbivores' effects on individual functions, and (b) improved, increased systematic exclosure research focusing on effects of large herbivores' exclusion on functions. A free Plain Language Summary can be found within the Supporting Information of this article.

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Section: Insights From Well‐studied Ecosystem Functionsmentioning

confidence: 99%

Section: Carbon Cycling: a Case Studymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Synthesizing the effects of large, wild herbivore exclusion on ecosystem function

et al. 2019

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“…Their selective foraging and role of mobilizing nutrients through their digestion and defecation of plant products directly affect plant communities (Hobbs, 1996). The abundance and diversity of herbivore species and their respective foraging patterns have the ability to alter the structure and composition of plant communities and alter successional pathways (Augustine & McNaughton, 1998;Dannell et al, 2006;Jia et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

Metabarcoding reveals diet diversity in an ungulate community in Thailand

McShea

Sukmasuang

Erickson³

et al. 2019

Biotropica

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The diverse large mammal communities found in Asian dry forests and savannas should segregate based on their diet selection. We examined the diet composition of sympatric ungulate species using metabarcoding to determine whether their diet was segregated and whether obvious attributes (i.e., body size, phylogeny, ecology) explained the structure. We collected fecal samples from eight ungulate species in Huai Kha Khaeng Wildlife Sanctuary in the western forest complex of Thailand. The fecal collections occurred around a plot where all woody species were codified within a genetic barcode library, and this library was supplemented with samples from plant species known to be consumed by these species. Of 273 plant species tested, at least 93 were found within the fecal samples. Over half of the identified species were not previously known by experts as forage species. All ungulate species showed a strong consumption of grasses and forbs. For the three species with sufficient sample size (sambar, banteng, and guar), there were seasonal differences in their diet, with each showing increased occurrence of woody plants during the dry season. The pattern of forage consumption did not follow obvious paradigms of body size or taxonomy, with significant diet differences found in two similar‐sized bovids (gaur, banteng), while the diet of sambar was more similar to bovids than to the other deer species. Asian ungulates differ in their forage consumption and metabarcoding should allow for testing of diet shifts in response to seasonal rains and fires which dominate the phenology of Asian dry forests and savannas.

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The effects of herbivore aggregations at water sources on savanna plants differ across soil and climate gradients

Titcomb

Amooni

Mantas

et al. 2021

Ecological Applications

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Water sources in arid and semiarid ecosystems support humans, wildlife, and domestic animals, forming nodes of activity that sculpt surrounding plant communities and impact critical grazing and soil systems. However, global aridification and changing surface water supply threaten to disrupt these water resources, with strong implications for conservation and management of these ecosystems. To understand how effects of herbivore aggregation at water impact plant communities across contexts, we measured herbivore activity, plant height, cover (trees, grasses, forbs, and bare ground), diversity, and composition at 17 paired water sources and matrix sites across a range of abiotic factors in a semiarid savanna in Kenya. The effects of proximity to surface water and herbivore aggregation on plant communities varied substantially depending on soil and rainfall. In arid areas with nutrient‐poor sandy soils, forb and tree cover were 50% lower at water sources compared to neighboring matrix sites, bare ground was 20% higher, species richness was 15% lower, and a single globally important grazing grass (Cynodon dactylon) dominated 60% of transects. However, in mesic areas with nutrient‐rich finely textured soils, species richness was 25% higher, despite a 40% increase in bare ground, concurrent with the decline of a dominant tall grass (Themeda triandra) and increase in C. dactylon and other grass species near water sources. Recent rainfall was important for grasses; cover was higher relative to matrix sites only during wet periods, a potential indication of compensatory grazing. These findings suggest that effects of herbivore aggregation on vegetation diversity and composition will vary in magnitude, and in some cases direction, depending on other factors at the site. Where moisture and nutrient resources are high and promote the dominance of few plant species, herbivore aggregations may maintain diversity by promoting grazing lawns and increasing nondominant species cover. However, in arid conditions and sites with low nutrient availability, diversity can be substantially reduced by these aggregations. Our results highlight the importance of considering abiotic conditions when managing for effects of herbivore aggregations near water. This will be particularly important for future managers in light of growing global aridification and surface water changes.

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Global signal of top-down control of terrestrial plant communities by herbivores

Cited by 101 publications

References 63 publications

Synthesizing the effects of large, wild herbivore exclusion on ecosystem function

Synthesizing the effects of large, wild herbivore exclusion on ecosystem function

Metabarcoding reveals diet diversity in an ungulate community in Thailand

The effects of herbivore aggregations at water sources on savanna plants differ across soil and climate gradients

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