Seasonal shifts from plant diversity to consumer control of grassland productivity

Zaret, Max; Kuhs, Molly; Anderson, Jonathan; Seabloom, Eric W.; Borer, Elizabeth T.; Kinkel, Linda L.

doi:10.1111/ele.13993

Cited by 10 publications

(12 citation statements)

References 58 publications

(83 reference statements)

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“…Such prominent changes in biomass and primary productivity could have further implications for other consumers in our system. The strong response of plant biomass to differences in disease in our field experiment provides another important example of the effects of diseases on ecosystems (Mitchell 2003, Seabloom et al 2017, Zaret et al 2022).…”

Section: Discussionmentioning

confidence: 94%

Disease decreases variation in host community structure in an old-field grassland

Grunberg

Halliday

Heckman

et al. 2022

Preprint

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Disease may modulate variation in host community structure by modifying the interplay of deterministic and stochastic processes. For instance, deterministic processes like ecological selection can benefit species less impacted by disease. When disease consistently selects for certain host species, this can reduce variation in host community composition. On the other hand, when host communities are less impacted by disease and selection is weaker, stochastic processes (e.g., drift, dispersal) may play a bigger role in host community structure, which can increase variation in structure among communities. While effects of disease on host community structure have been quantified in field experiments, few have addressed the role of disease in modulating variation in structure among host communities. To address this, we conducted a field experiment spanning three years, using a tractable system: foliar fungal pathogens in an old-field grassland community dominated by the grass Lolium arundinaceum, tall fescue. We reduced foliar fungal disease burden in replicate host communities (experimental plots in intact vegetation) in three fungicide regimens that varied in the duration of fungicide exposure and included a fungicide-free control. We measured host diversity, biomass, and variation in community structure among replicate communities. Disease reduction generally decreased plant richness and increased aboveground biomass relative to communities experiencing ambient levels of disease. Despite changes in structure of the plant communities over three years, the effects of disease reduction on plant richness and biomass were consistent across years. However, disease reduction did not reduce variation in host community structure, providing little evidence for ecological selection by competition or other deterministic processes. Instead, disease reduction tended to amplify variation in host community structure among replicate communities (i.e., within fungicide treatment groups), suggesting that disease diminished the degree to which host communities were structured by stochastic processes. These results of experimental disease reduction both highlight the potential importance of stochastic processes in plant communities and reveal the potential for disease to regulate variation in host community structure.

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Section: Discussionmentioning

confidence: 94%

Disease decreases variation in host community structure in an old-field grassland

Grunberg

Halliday

Heckman

et al. 2022

Preprint

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“…Nutrient impacts should increase later in the growing season, as finite resources become depleted in unfertilized plots (Klaus et al, 2016). Previous work in our study system suggests that consumer impacts on plant biomass can also be greatest in the later parts of the growing season as more plant C becomes available for offtake by herbivores and pathogens (Zaret et al, 2022). Taken together, these results suggest that nutrient and consumer impacts on ecosystem C flux also will be greatest later in the growing season.…”

Section: Introductionmentioning

confidence: 84%

“…Normalized difference vegetation index (NDVI) was used as a nondestructive index of above‐ground plant biomass, following methods from other studies at this site (Zaret et al, 2022). Every 2 weeks, from May to August in 2020, we used a MSR5 multispectral radiometer (Cropscan, Inc.) to measure reflected radiation (reflectance) in all experimental plots of the consumer manipulation experiment.…”

Section: Methodsmentioning

confidence: 99%

“…Using these combined treatments, we determine the independent and joint effects of nutrients and each consumer group on grassland carbon cycling. Given the within‐season variation of ecosystem C fluxes and plant biomass production (Xiao et al, 2008; Zaret et al, 2022), we also look at a different time scales and test for within‐season variation of consumer and nutrient controls on grassland C cycling using monthly Normalized Difference Vegetation Index (NDVI, a proxy for plant biomass production) and C flux measurements from the same experiment. Using these data, we tested the following hypotheses:H1 Consumer reductions and nutrient addition independently lead to increases in GPP, ER and plant biomass .…”

Section: Introductionmentioning

confidence: 99%

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Soil nutrients cause threefold increase in pathogen and herbivore impacts on grassland plant biomass

et al. 2023

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Grasslands play a critical role in the global carbon (C) cycle, covering a quarter of the Earth's land surface and contributing up to 20% to the total terrestrial C sink (Xia et al., 2014). As with most ecosystems, C accumulation in grasslands reflects the balance and seasonal variation of C inputs via photosynthesis (gross primary production, GPP) and C emissions from respiration by microbes, plants and animals (ecosystem respiration, ER). Observational studies and field experiments manipulating food webs have shown that plant consumers

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“…Our findings suggest that, by removing tissue, insect herbivores may have a similar impact on seedlings as vertebrate herbivores, as even small levels of tissue removal will have a disproportionately large impact on plants that may only have a few leaves. The impact of fungal pathogens, which degrade but do not actively remove tissue, may not reduce plant survival but instead limit biomass and competitive ability later in life (Mitchell, 2003; Zaret et al ., 2022). Literature suggests that the effect of enemy release may be observed for certain life stages but not others: for example, pesticides applied to a whole forest community reduced invader recruitment success (due to disproportionately benefiting existing native vegetation), but later improved the height and diameter of invading trees (Heckman et al ., 2022).…”

Section: Discussionmentioning

confidence: 99%

Aboveground enemy release increases seedling survival in grasslands

Brian,

Shepherd,

Pérez-Navarro

et al. 2023

Preprint

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The enemy release hypothesis is a popular hypothesis to explain the success of invasive plants. Enemy release studies typically focus on single species or types of communities, feature indirect experimental manipulations that apply pesticides to whole communities not individual species, and only examine responses of established plants or plant populations, limiting their generality. Using a novel species-specific approach, we examine whether enemy release can enhance seedling survival and recruitment of 16 grassland species by experimentally linking enemy release with enhanced plant performance.We planted seedlings of 16 native grassland species from two functional groups (C4 grasses and non-legume forbs) into two grassland sites (early and mid succession). We hand-painted 1,548 individual seedlings with pesticides (insecticide and fungicide) over the course of a growing season to enforce aboveground species-specific enemy release, and tested whether it enhanced survival relative to untreated controls. Using native species enabled us to directly test effects of enemy release, while avoiding confounding factors like unknown invasion histories. Of the 16 native study species, 13 are naturalised/invasive outside of their native ranges.Release from insects increased seedling survival by 80% on average, with no additional benefit of release from fungal pathogens. This effect was consistent across functional groups and community successional stages, and was strongest in resource-acquisitive species. The size of species’ performance benefits from enemy release were positively correlated with the number of regions globally where each species has been introduced and naturalised.Synthesis. Previous studies of enemy release have centred on adults and findings have varied among species. We found a positive effect of release from insect herbivores early in colonisation – a trend that held across functional groups and types of resident community. We posit that the consistent vulnerability of seedlings vis-à-vis later life stages leads to this more ubiquitous benefit of enemy release. Enemy release may therefore aid initial recruitment of most, if not all, plants during the invasion process, even if enemies rapidly accumulate. The positive correlations between the benefits of enemy release for seedlings, species’ life history strategies and global naturalisation patterns provide compelling hypotheses for future research.

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Seasonal shifts from plant diversity to consumer control of grassland productivity

Abstract: Plant biomass production provides the energy for most of Earth's terrestrial biological processes, supports a variety of ecosystem services and plays a vital role in regulating climate as human activities alter the global carbon cycle (

Cited by 10 publications

References 58 publications

Disease decreases variation in host community structure in an old-field grassland

Disease decreases variation in host community structure in an old-field grassland

Soil nutrients cause threefold increase in pathogen and herbivore impacts on grassland plant biomass

Aboveground enemy release increases seedling survival in grasslands

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