Interactions in a warmer world: effects of experimental warming, conspecific density, and herbivory on seedling dynamics

Burt, Melissa A.; Dunn, Robert R.; Nichols, Lauren M.; Sanders, Nathan J.

doi:10.1890/es13-00198.1

Cited by 11 publications

(16 citation statements)

References 67 publications

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“…As a result, L. tulipifera can produce large numbers of seedlings in any given year and likely experiences stronger density-dependent mortality than other tree species. In our study, L. tulipifera averaged 11.35 individuals m −2 , substantially lower than the densities of seedlings observed in either Burt et al (2014) or Bell, Freckleton & Lewis (2006) (10–80 or 100–1,000 individuals m −2 , respectively) but similar to densities of P. serotina recorded by Packer & Clay (2000) (1–15 individuals m −2 ). Our results therefore suggest that L. tulipifera is subject to density-dependent mortality even at relatively low seedling densities.…”

Section: Discussioncontrasting

confidence: 63%

“…Many other temperate tree species, like Quercus spp. or Prunus serotina , are also resistant to herbivory or pathogens unless simultaneously subject to high densities of conspecific neighbors and, as a result, intense intraspecific competition (Packer & Clay, 2000; Bell, Freckleton & Lewis, 2006; Burt et al, 2014). Seedling density is therefore likely an important predictor of herbivore-driven mortality (Paine et al, 2012).…”

Section: Discussionmentioning

confidence: 99%

“…Although several studies have characterized the effects of insect herbivores on seedling growth and mortality in treefall gaps (Norghauer & Newbery, 2014), few track the effects of insects over multiple years. Interannual studies are especially important given yearly fluctuations in insect abundances, temperature, and rainfall (Burt et al, 2014; Norghauer & Newbery, 2014). We show that gap age is an important determinant of the effects of insects on tree seedlings; insects had weaker impacts in older gaps and on older seedlings.…”

Section: Discussionmentioning

confidence: 99%

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Insect herbivores increase mortality and reduce tree seedling growth of some species in temperate forest canopy gaps

Lemoine

Burkepile

Parker

2017

PeerJ

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Insect herbivores help maintain forest diversity through selective predation on seedlings of vulnerable tree species. Although the role of natural enemies has been well-studied in tropical systems, relatively few studies have experimentally manipulated insect abundance in temperate forests and tracked impacts over multiple years. We conducted a three-year experiment (2012–2014) deterring insect herbivores from seedlings in new treefall gaps in deciduous hardwood forests in Maryland. During this study, we tracked recruitment of all tree seedlings, as well as survivorship and growth of 889 individual seedlings from five tree species: Acer rubrum, Fagus grandifolia, Fraxinus spp., Liriodendron tulipifera, and Liquidambar styraciflua. Insect herbivores had little effect on recruitment of any tree species, although there was a weak indication that recruitment of A. rubrum was higher in the presence of herbivores. Insect herbivores reduced survivorship of L. tulipifera, but had no significant effects on A. rubrum, Fraxinus spp., F. grandifolia, or L. styraciflua. Additionally, insects reduced growth rates of early pioneer species A. rubrum, L. tulipifera, and L. styraciflua, but had little effect on more shade-tolerant species F. grandifolia and Fraxinus spp. Overall, by negatively impacting growth and survivorship of early pioneer species, forest insects may play an important but relatively cryptic role in forest gap dynamics, with potentially interesting impacts on the overall maintenance of diversity.

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Section: Discussioncontrasting

confidence: 63%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Insect herbivores increase mortality and reduce tree seedling growth of some species in temperate forest canopy gaps

Lemoine

Burkepile

Parker

2017

PeerJ

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“…In years with late spring frosts, early budburst can damage leaf tissues and erase any carbon gains due to longer growing seasons (Augspurger, 2009(Augspurger, , 2013. Many other factors can potentially interact with phenology to limit increases in carbon sequestration of forests in the future, such as drought, herbivory, heat stress, or disease (Taylor & Whitelaw, 2001;Burt et al, 2014).…”

Section: Warming Effects On Leaf Senescence and Growing Season Lengthmentioning

confidence: 99%

Temperature alone does not explain phenological variation of diverse temperate plants under experimental warming

Marchin

Salk

Hoffmann

et al. 2015

Global Change Biology

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Anthropogenic climate change has altered temperate forest phenology, but how these trends will play out in the future is controversial. We measured the effect of experimental warming of 0.6-5.0 °C on the phenology of a diverse suite of 11 plant species in the deciduous forest understory (Duke Forest, North Carolina, USA) in a relatively warm year (2011) and a colder year (2013). Our primary goal was to dissect how temperature affects timing of spring budburst, flowering, and autumn leaf coloring for functional groups with different growth habits, phenological niches, and xylem anatomy. Warming advanced budburst of six deciduous woody species by 5-15 days and delayed leaf coloring by 18-21 days, resulting in an extension of the growing season by as much as 20-29 days. Spring temperature accumulation was strongly correlated with budburst date, but temperature alone cannot explain the diverse budburst responses observed among plant functional types. Ring-porous trees showed a consistent temperature response pattern across years, suggesting these species are sensitive to photoperiod. Conversely, diffuse-porous species responded differently between years, suggesting winter chilling may be more important in regulating budburst. Budburst of the ring-porous Quercus alba responded nonlinearly to warming, suggesting evolutionary constraints may limit changes in phenology, and therefore productivity, in the future. Warming caused a divergence in flowering times among species in the forest community, resulting in a longer flowering season by 10-16 days. Temperature was a good predictor of flowering for only four of the seven species studied here. Observations of interannual temperature variability overpredicted flowering responses in spring-blooming species, relative to our warming experiment, and did not consistently predict even the direction of flowering shifts. Experiments that push temperatures beyond historic variation are indispensable for improving predictions of future changes in phenology.

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“…Species with different functional types or growth strategies may respond differently to warmed conditions (Burt, Dunn, Nichols, & Sanders, ; Post, ; Post & Pedersen, ). We found that warming increased the growth rate of Salix but decreased the growth rate of Carex .…”

Section: Discussionmentioning

confidence: 99%

Direct effects of warming increase woody plant abundance in a subarctic wetland

Carlson

Beard

Adler

2018

Ecology and Evolution

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Both the direct effects of warming on a species’ vital rates and indirect effects of warming caused by interactions with neighboring species can influence plant populations. Furthermore, herbivory mediates the effects of warming on plant community composition in many systems. Thus, determining the importance of direct and indirect effects of warming, while considering the role of herbivory, can help predict long‐term plant community dynamics. We conducted a field experiment in the coastal wetlands of western Alaska to investigate how warming and herbivory influence the interactions and abundances of two common plant species, a sedge, Carex ramenskii, and a dwarf shrub, Salix ovalifolia. We used results from the experiment to model the equilibrium abundances of the species under different warming and grazing scenarios and to determine the contribution of direct and indirect effects to predict population changes. Consistent with the current composition of the landscape, model predictions suggest that Carex is more abundant than Salix under ambient temperatures with grazing (53% and 27% cover, respectively). However, with warming and grazing, Salix becomes more abundant than Carex (57% and 41% cover, respectively), reflecting both a negative response of Carex and a positive response of Salix to warming. While grazing reduced the cover of both species, herbivory did not prevent a shift in dominance from sedges to the dwarf shrub. Direct effects of climate change explained about 97% of the total predicted change in species cover, whereas indirect effects explained only 3% of the predicted change. Thus, indirect effects, mediated by interactions between Carex and Salix, were negligible, likely due to use of different niches and weak interspecific interactions. Results suggest that a 2°C increase could cause a shift in dominance from sedges to woody plants on the coast of western Alaska over decadal timescales, and this shift was largely a result of the direct effects of warming. Models predict this shift with or without goose herbivory. Our results are consistent with other studies showing an increase in woody plant abundance in the Arctic and suggest that shifts in plant–plant interactions are not driving this change.

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Interactions in a warmer world: effects of experimental warming, conspecific density, and herbivory on seedling dynamics

Cited by 11 publications

References 67 publications

Insect herbivores increase mortality and reduce tree seedling growth of some species in temperate forest canopy gaps

Insect herbivores increase mortality and reduce tree seedling growth of some species in temperate forest canopy gaps

Temperature alone does not explain phenological variation of diverse temperate plants under experimental warming

Direct effects of warming increase woody plant abundance in a subarctic wetland

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