Voles mediate functional trait diversity along a resource gradient
Authors/Creators
- 1. University of California, Riverside
- 2. University of Montana
Description
Disentangling the effect of multiple ecological processes on plant trait composition is complicated by the fact that both top-down and bottom-up processes may affect similar traits. We examined the interacting role of resource variation and vole herbivory on functional trait patterns in an annual California grassland. We manipulated vole herbivory via exclosures at eight grassland sites along a steep resource gradient and measured plant composition and functional traits over three years. Plants with resource acquisitive functional traits were favored at sites with increasing resources. Vole herbivory influenced community-weighted mean (CWM) leaf nitrogen (N) and seed mass, suggesting these traits may mediate plant susceptibility to vole herbivory. After three years, CWM leaf N increased in the absence of the voles, as did CWM seed mass, although this increase in CWM seed mass only occurred at higher resource sites. Vole exclusion at high resources sites also increased the functional diversity of leaf N and seed mass by the end of the experiment. Overall, environmental filtering primarily structured the dominant plant trait strategies, but vole herbivory also influenced the functional diversity of traits that influence herbivore susceptibility, particularly at resource rich sites. Thus, habitat filtering and herbivory can operate on different dimensions of plant functional composition to influence the species and functional composition of communities.
Notes
There are four files for this data set: 1) Site environmental data, 2) Plot community species cover data 3) Plant species trait data and 4) Vole runway activity data.
Site Environmental Data: Three soils samples up to 10cm in depth were collected from each large 9mx9m plot (n=16) and processed for soil resources. These data are reported here. Additionally, the mean live aboveground biomass and mean litter from six 10cmx50cm subplots are reported. These data were included in a principal components analysis that generated two PCA axis. The first, PCA1 was used as the resource gradient described in the manuscript.
Plot Community Species Cover Data: With each block, 12 0.5m 0.5m plots were sample in each of three years (2015, 2016, 2017). For this sampling the visual cover of each observed species was recorded, with cover adding over 100 to allow for multiple canopy layers. These data are the cover estimates for each plant species in each plot over time. The Site.Prod column indicates the how these data were stratified to match up with species trait that were collected at the low or high end of the resource gradient.
Plant species trait data: These data are species-level trait data for species observed at the field site. Specific Leaf Area (SLA), leaf water content (LWC), leaf area (Area.cm2), leaf dry matter content (LDMC), maximum vegetative height (Height.max.cm) were sampled on 5-10 different individuals in the field. These plant leaves were used for leaf nitrogen (Leaf.N), leaf carbon (Leaf.C), and carbon to nitrogen ratios (C.N.Ratio). Seed mass was extracted from the Kew database, Baker seed collection at the Jepson Herbarium, site collected samples, or purchased seed.
Vole Runway data: These data are the average runways observed in 8 transects sampled in the presence of voles (i.e. open plots).
Funding provided by: National Science Foundation
Crossref Funder Registry ID: http://dx.doi.org/10.13039/100000001
Award Number: 1309014
Funding provided by: National Science Foundation
Crossref Funder Registry ID: http://dx.doi.org/10.13039/100000001
Award Number: DEB-1553518