Abstract Detail



Ecology

Aiello, Erin [1], Parker, Ingrid [2], Haubensak, Karen [3], Grove, Sara [4].

Combined stressors of drought and invasion reduce Douglas fir performance.

Anthropogenic change is increasing the prevalence of plant stressors such as species invasions and drought. Invading plants may hinder a native plant’s adaptive responses to drought, while drought stress may reduce a plant’s ability to compete with invasive species. The converse of these predictions is also possible – some invasive species may ameliorate drought stress by shading or hydraulic lift, for example. Likewise, if the invasive plant requires more water than the native, drought could hinder the invader’s success in competition. Further complicating these interactions, soil microbes can alter plant responses to both abiotic stress and competition. In particular, mycorrhizal symbionts often ameliorate stress by increasing access to resources such as nutrients and water.
Here, we measured the combined effects of drought, species invasions, and soil biota manipulations on physiological stress and survival of potted Douglas fir (Pseudotsuga menziesii) seedlings. Douglas fir forest in the Pacific Northwest is failing to regenerate in areas where we see increased drought and invasion by Scotch broom (Cytisus scoparius). We used a greenhouse experiment to grow Douglas fir seedlings in live or sterilized field soil with and without C. scoparius competitors, and we exposed half of the pots to a dry-down treatment to simulate drought. We found that both drought and C. scoparius invasion had strong effects on stress and survival. Invasion significantly reduced mycorrhizal colonization on Douglas fir seedlings. Contrary to expectation, soil biota did not ameliorate the stress imposed by the effects of drought and invasion but worsened them. Douglas fir forests are among many ecosystems threatened by drought and invasion due to anthropogenic change. Our results suggest that increased drought will reduce resilience to invasion, and that mycorrhizal symbioses may not always ameliorate water stress in an invasion scenario. Interactions between factors associated with global change may need to be considered, rather than effects of single factors alone. 


1 - 414 Koshland Way, Santa Cruz, CA, 95064, United States
2 - University Of California Santa Cruz, Department Of Ecology And Evolutionary Biology, 130 McAllister Way, Coastal Biology Building, Santa Cruz, CA, 95060, United States
3 - Northern Arizona University, 1899 S San Francisco St, Flagstaff, AZ, 86011, USA
4 - UC Santa Cruz, Ecology and Evolutionary Biology, 1156 High St,, Santa Cruz, CA, 95064, USA

Keywords:
Cytisus
invasion ecology
Drought
interactions
Mycorrhizae
plant stress
global change
compounding stressors
soil microbes.

Presentation Type: Oral Paper
Number: ECO5002
Abstract ID:827
Candidate for Awards:Ecological Section Best Graduate Student Paper


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