climate, soil and biotic relationships along an annual grass invasion gradient
TRANSCRIPT
Results• Invasive annual grass cover was negatively correlated
with native perennial grass cover (r = -0.64). This was the strongest relationship to any of the measured abiotic or biotic variables for grasses.
• Annual grass cover was positively correlated with soil temperatures (r = 0.59), while perennial grass cover and native species diversity were negatively correlated with soil (r = -0.54) and air temperatures (r = -0.81).
• The abundances of annual forbs, shrubs and soil microbes did not have strong relationships to any climate variables.
• Structural equation modeling confirmed that the negative effect of warmer temperatures on native plants would indirectly favor the spread of annual grasses.
ConclusionOur findings indicate that biotic relationships are relatively strong in invaded sagebrush-steppe habitat, and therefore species distribution models based solely on climate variables may underestimate changes in invasive and native species’ ranges that are expected to occur with climate change in sagebrush-steppe.
• We assessed 100 climate, soil, biotic and disturbance variables associated with annual grass invasion in sagebrush-steppe across 90 field sites in eastern Oregon.
• We compared the relative correlative strength (r values) of the abundances (cover, biomass, density) of invasive and native species and diversity to each abiotic and biotic variable.
• Structural equation modeling (SEM) was used to demonstrate how multiple ecological factors can interact to influence native and invasive species abundances.
Materials and Methods
Introduction• Changes in species distributions are predicted to
follow changes in climate.
• Biotic interactions (e.g., competition) are increasingly recognized as important drivers of species distributions at micro and macroecological scales.
HYPOTHESIS: Differences between native and invasive species responses to climate may intensify competitive interactions and accelerate changes in species distributions faster than predicted from models based on climate alone.
Sheel Bansal, PhD Research Ecologist
Olympia Forestry Sciences LaboratoryOlympia, Washington 98512
[email protected]; [email protected]
This research was funded through the USDA-Agricultural Research Service Areawide Project for Ecologically-based Invasive Plant Management of Annual Grasses in the Great Basin Ecosystem
Distribution of Invasive and Native Species in Sagebrush-Steppe: The Relative Importance of Climate, Soil Properties, Biotic Interactions and Disturbance
Sheel Bansal1,2 and Roger Sheley1
1USDA Agricultural Research Service, Eastern Oregon Agricultural Research Center2USDA Forest Service, Pacific Northwest Research Station
I
litterheight
NativeSpecies
Richness
PF cover
AG density
AG seed/m2
bareground
coarsewood
rocks
invasiverichness
pH
mineral N
soil C
Plant community Plant functionalgroups
Disturbance
Ground layer
Soil physicalproperties
Soil chemicalproperties
elevation
max air T
spring precip.
shrub density
Climate/Geography
Soil biotic properties
SIR/soil C
SLA shrub
SLA tree
shrub heightPlant traits
PF height
snowfree
GWCWHC
soil N
InvasiveSpecies
Richness
nativerichness
shrub cover
AG density
AG seed/m2
BSC
litterheight
baregroundcoarsewood
sand
C: N
AUMs
Plant community Plant functionalgroups
Disturbance
Ground layer
Soil physicalproperties
Soil chemicalproperties
latitude
min air T
AF cover
Climate/Geography
Soil biotic properties
SLA AG Plant traits
litter cover
RQ
basalrespiration
PG cover
aspect AF height
rock covermineral P
silt
PerennialGrassCover
PF cover
AG cover
AG seed/m2
BSC
litterheight
roots
residentrichness
pH
mineral N
soil C
bulk density
Plant community Plant functionalgroups
Disturbance
Ground layer
Soil physicalproperties
Soil chemicalproperties
elevation
mean soil T
spring precip.
shrub density
Climate/Geography
Soil biotic properties
SIR/soil C
SLA shrub
SLA PG
shrubfootprint
Plant traits
PG height
snowfree
GWCWHC
soil N
AnnualGrassCover
invasiverichness
nativerichness
shrub density
PG density
AG seed/m2
BSC
litterheight
baregroundcoarsewood
GWC
mineral N
grazingutilization
Plant community Plant functionalgroups
Disturbance
Ground layer
Soil physicalproperties
Soil chemicalproperties
elevation
min soil T
spring precip.
PF cover
Climate/Geography
Soil biotic properties
SLA shrub
shrub heightPlant traitsAG height
total plant cover
litter cover
Abbreviations: annual grass (AG); annual forb (AF); perennial grass (PG); perennial forb (PF); specific leaf area (SLA); biological soil crust (BSC); carbon (C) to nitrogen (N) ratio (C:N); temperature (T); animal unit months (AUMs); water holding capacity (WHC); gravimetric water content (GWC); respiratory quotient (RQ); substrate-induced respiration (SIR);
Positive (blue solid lines) and negative (red dashed lines) correlative relationships between richness and abundance of invasive and native species to abiotic and biotic factors. Thicker lines correspond to higher r values
Invasives
Natives
Temperature
PG SLA
Perennial forb cover
Mineral N
Microbial biomassSoil C
Root biomass m-3
Annual grass coverPerennial grass
cover
R2 = 0.51
R2 = 0.31
R2 = 0.36
R2 = 0.29
R2 = 0.63
-0.56-0.27
-0.44
-0.60-0.45
0.33
0.50
0.21
0.59
0.48
0.20
CLIMATE
VEGETATION
SOIL
Precipitation
Resident speciesrichness
0.29
χ2 = 26.65, P = 0.23; df = 22
Solid lines with adjacent standardized coefficients indicate positive (blue) and negative (red) significant relationships; paths with precipitation were examined, but were not significant. Values of R2 are squared multiple correlations for each functional group.
SEM of integrated climate, vegetation and soil factors
5th Annual Pacific Northwest Climate Science Conference 2014