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Plant community responses to simultaneous changes in temperature, nitrogen availability, and invasion.

Gornish ES, Miller TE - PLoS ONE (2015)

Bottom Line: We quantified the resident community using ordination scores, then used structural equation modeling to examine hypotheses related to how plants respond to a network of experimental treatments and environmental variables.We did not find effects of warming on the native plant community in the absence of invasion.This work highlights the variation in the biotic and abiotic factors responsible for explaining independent and collective climate change effects over a short time scale.

View Article: PubMed Central - PubMed

Affiliation: Department of Plant Sciences, University of California Davis, Davis, California, United States of America.

ABSTRACT

Background: Increasing rates of change in climate have been observed across the planet and have contributed to the ongoing range shifts observed for many species. Although ecologists are now using a variety of approaches to study how much and through what mechanisms increasing temperature and nutrient pollution may influence the invasions inherent in range shifts, accurate predictions are still lacking.

Methods and results: In this study, we conducted a factorial experiment, simultaneously manipulating warming, nitrogen addition and introduction of Pityopsis aspera, to determine how range-shifting species affect a plant community. We quantified the resident community using ordination scores, then used structural equation modeling to examine hypotheses related to how plants respond to a network of experimental treatments and environmental variables. Variation in soil pH explained plant community response to nitrogen addition in the absence of invasion. However, in the presence of invasion, the direct effect of nitrogen on the community was negligible and soil moisture was important for explaining nitrogen effects. We did not find effects of warming on the native plant community in the absence of invasion. In the presence of invasion, however, warming had negative effects on functional richness directly and invasion and herbivory explained the overall positive effect of warming on the plant community.

Conclusions and significance: This work highlights the variation in the biotic and abiotic factors responsible for explaining independent and collective climate change effects over a short time scale. Future work should consider the complex and non-additive relationships among factors of climate change and invasion in order to capture more ecologically relevant features of our changing environment.

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Related in: MedlinePlus

Results of the nitrogen SEM.Nitrogen effects on plant community NMDS scores in the (A) absence (χ² = 1.79, d.f. = 9, p = 0.994) and (B) presence of invasion (χ² = 6.08, d.f. = 9, p = 0.732). Black arrows with values indicate significant paths, gray arrows indicate insignificant paths, solid arrows indicate positive relationships, and dashed arrows indicate negative relationships. Path values indicate unstandardized (top) and standardized (bottom) coefficients. Within box values indicate R2 values, which represent the proportion of variance explained for each response variable.
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pone.0123715.g001: Results of the nitrogen SEM.Nitrogen effects on plant community NMDS scores in the (A) absence (χ² = 1.79, d.f. = 9, p = 0.994) and (B) presence of invasion (χ² = 6.08, d.f. = 9, p = 0.732). Black arrows with values indicate significant paths, gray arrows indicate insignificant paths, solid arrows indicate positive relationships, and dashed arrows indicate negative relationships. Path values indicate unstandardized (top) and standardized (bottom) coefficients. Within box values indicate R2 values, which represent the proportion of variance explained for each response variable.

Mentions: In the absence of invasion, the most parsimonious model predicting nitrogen effects demonstrated that species richness in 2011 and 2012 had opposing relationships with the native plant community (Fig 1A). There was a positive relationship between species richness in 2011 and NMDS2 scores (increased functional richness and cover by a dominant graminoid), but these community values had a negative relationship with species richness in 2012. Elevated soil pH increased functional species richness (Table 1), possibly explained by changes in species-specific plant growth capabilities (e.g., [46, 47, 48]). The subsequent change in NMDS1 scores was likely due to disproportionate benefit of dominant and invasive species to the modification of soil pH [49]. Nitrogen addition likely affected unmeasured plant traits related to competition, such as the growth rate or stomatal conductance of rare species, subsequently modifying the dominance structure of the community. Finally, the direct path from nitrogen to NMDS2 indicates that a portion of the nitrogen treatment effect on changes in the native plant community was not accounted for by any of the environmental variables present in the model (Fig 1A).


Plant community responses to simultaneous changes in temperature, nitrogen availability, and invasion.

Gornish ES, Miller TE - PLoS ONE (2015)

Results of the nitrogen SEM.Nitrogen effects on plant community NMDS scores in the (A) absence (χ² = 1.79, d.f. = 9, p = 0.994) and (B) presence of invasion (χ² = 6.08, d.f. = 9, p = 0.732). Black arrows with values indicate significant paths, gray arrows indicate insignificant paths, solid arrows indicate positive relationships, and dashed arrows indicate negative relationships. Path values indicate unstandardized (top) and standardized (bottom) coefficients. Within box values indicate R2 values, which represent the proportion of variance explained for each response variable.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4400009&req=5

pone.0123715.g001: Results of the nitrogen SEM.Nitrogen effects on plant community NMDS scores in the (A) absence (χ² = 1.79, d.f. = 9, p = 0.994) and (B) presence of invasion (χ² = 6.08, d.f. = 9, p = 0.732). Black arrows with values indicate significant paths, gray arrows indicate insignificant paths, solid arrows indicate positive relationships, and dashed arrows indicate negative relationships. Path values indicate unstandardized (top) and standardized (bottom) coefficients. Within box values indicate R2 values, which represent the proportion of variance explained for each response variable.
Mentions: In the absence of invasion, the most parsimonious model predicting nitrogen effects demonstrated that species richness in 2011 and 2012 had opposing relationships with the native plant community (Fig 1A). There was a positive relationship between species richness in 2011 and NMDS2 scores (increased functional richness and cover by a dominant graminoid), but these community values had a negative relationship with species richness in 2012. Elevated soil pH increased functional species richness (Table 1), possibly explained by changes in species-specific plant growth capabilities (e.g., [46, 47, 48]). The subsequent change in NMDS1 scores was likely due to disproportionate benefit of dominant and invasive species to the modification of soil pH [49]. Nitrogen addition likely affected unmeasured plant traits related to competition, such as the growth rate or stomatal conductance of rare species, subsequently modifying the dominance structure of the community. Finally, the direct path from nitrogen to NMDS2 indicates that a portion of the nitrogen treatment effect on changes in the native plant community was not accounted for by any of the environmental variables present in the model (Fig 1A).

Bottom Line: We quantified the resident community using ordination scores, then used structural equation modeling to examine hypotheses related to how plants respond to a network of experimental treatments and environmental variables.We did not find effects of warming on the native plant community in the absence of invasion.This work highlights the variation in the biotic and abiotic factors responsible for explaining independent and collective climate change effects over a short time scale.

View Article: PubMed Central - PubMed

Affiliation: Department of Plant Sciences, University of California Davis, Davis, California, United States of America.

ABSTRACT

Background: Increasing rates of change in climate have been observed across the planet and have contributed to the ongoing range shifts observed for many species. Although ecologists are now using a variety of approaches to study how much and through what mechanisms increasing temperature and nutrient pollution may influence the invasions inherent in range shifts, accurate predictions are still lacking.

Methods and results: In this study, we conducted a factorial experiment, simultaneously manipulating warming, nitrogen addition and introduction of Pityopsis aspera, to determine how range-shifting species affect a plant community. We quantified the resident community using ordination scores, then used structural equation modeling to examine hypotheses related to how plants respond to a network of experimental treatments and environmental variables. Variation in soil pH explained plant community response to nitrogen addition in the absence of invasion. However, in the presence of invasion, the direct effect of nitrogen on the community was negligible and soil moisture was important for explaining nitrogen effects. We did not find effects of warming on the native plant community in the absence of invasion. In the presence of invasion, however, warming had negative effects on functional richness directly and invasion and herbivory explained the overall positive effect of warming on the plant community.

Conclusions and significance: This work highlights the variation in the biotic and abiotic factors responsible for explaining independent and collective climate change effects over a short time scale. Future work should consider the complex and non-additive relationships among factors of climate change and invasion in order to capture more ecologically relevant features of our changing environment.

Show MeSH
Related in: MedlinePlus