Application of trait-based mechanisms to resilience of ecosystem service provision in an arid riparian corridor Moira Hough, David Chan, Christopher Scott, Brian Enquist, Mitchell Pavao-Zuckerman University of Arizona

Land-cover approach 1990 2006 Burkhard 2012

Trait-based Approach Response: traits associated with the response of plants to environmental factors such as resources and disturbances Effect: traits that determine effects of plants on ecosystem functions such as biogeochemical cycling or propensity to disturbance Suding New Phytologist 2008

Key Questions Should we consider environmental impacts at intraspecific, interspecific, or land-cover type level? Most research leading to development of these concepts has taken place in alpine grasslands: Is it applicable to arid riparian woodlands?

Study Site: San Pedro River Scott et al 2000 Dry Wet Prior work by Dr Stromberg, Wet/Dry/Int Classification of reaches TNC Wet/Dry Mapping Intermediate USGS

Hypothesized Framework Should we consider environmental impacts at intraspecific, interspecific, or land cover type level? Hypothesized Framework Driver Response Trait Effect Trait Distance to Perennial Flow Litter C 13C Litter N Leaf C Water Availability Leaf Traits Response: traits associated with the response of plants to environmental factors such as resources and disturbances Effect: traits that determine effects of plants on ecosystem functions such as biogeochemical cycling or propensity to disturbance Soil Processes Leaf N Depth to Groundwater SLA Landscape Position Soil N Soil C SOM

Intraspecific & Interspecific Variation Cottonwood p=0.001 Willow p=0.0698 Mesquite P<0.001 Species mean differences at p=0.05: Salix/Populus vs Tamarix/Prosopis Non-parametric: Kruskal-walis Salt Cedar P<0.001 p<0.05

Land-cover Level Variation Riparian p=0.068 Tamarix P<0.001 Mesquite Bosque SLA, CN follow similar pattern: change for mesquite but not riparian or tam P<0.001 *Different at p<0.05 *

What is the relevant level of analysis? Driver Response Trait Effect Trait Intraspecific Interspecific Land-cover Interspecific Water Availability Leaf Traits Soil Processes Add diagram showing intra, inter, land cover

Observed Relationships Driver Response Trait Effect Trait Litter C Distance to Perennial Flow 13C Leaf C Litter N r²=0.77 Water Availability Leaf economics Leaf N Depth to Groundwater Soil C r²=0.85 Soil N r²=0.5431 Landscape Position SLA SOM r²=0.402

Hypothesized Framework Driver Response Effect Distance to Perennial Flow Litter C 13C Leaf C Litter N Water Availability Leaf Traits Soil Processes Leaf N Depth to Groundwater SLA Landscape Position Soil N Soil C Response: traits associated with the response of plants to environmental factors such as resources and disturbances Effect: traits that determine effects of plants on ecosystem functions such as biogeochemical cycling or propensity to disturbance SOM Operationally: Response traits alter when environmental conditions change Effect traits change ecosystem processes/properties when they are altered

Conclusions At what scale should we consider impacts of environmental change? Regional species means may be ideal for predicting trait effects on ecosystems Most research leading to development of these concepts has taken place in alpine grasslands: Is it applicable to arid riparian woodlands? Yes: Traits do seem to be related to soil properties, BUT… No because we need to look at the responses of specific species because they have such dominance that they become very important!

Which traits?

Implications for Resistance/Resilience Driver Response Effect Distance to Perennial Flow Litter C 13C Leaf C Litter N Water Availability Leaf economics Soil Processes Leaf N Depth to Groundwater SLA Soil N Landscape Position Soil C Response: traits associated with the response of plants to environmental factors such as resources and disturbances Effect: traits that determine effects of plants on ecosystem functions such as biogeochemical cycling or propensity to disturbance Resistance SOM Resilience? Carbon Storage Nutrient Cycling Ecosystem Services Values & Human Use

Questions