Phenology of Mixed Woody-herbaceous Ecosystems Following Extreme Events: Net and Differential Responses

• Published in: Ecology (Durham) Vol. 89; no. 2; pp. 342 - 352
• Main Authors: Rich, P.M, Breshears, D.D, White, A.B
• Format: Journal Article
• Language: English
• Published: United States Ecological Society of America 01-02-2008
• Subjects: air temperature; bioavailability; Bouteloua gracilis; case studies; Climate change; Climate models; die-off; Disasters; disturbance; Drought; Ecology; Ecosystem; Ecosystems; environmental factors; extreme events; fire; Forests; Global warming; Greenhouse Effect; herbaceous plants; Herbs; Juniperus monosperma; Mesita del Buey; Mortality; normalized difference vegetation index; nutrients; Phenology; Pinus; Pinus - growth & development; Pinus edulis; pinyon-juniper; piñon; plant communities; plant ecology; plant response; Plants; Population Density; Population Dynamics; Population Growth; Precipitation; primary productivity; seasonal variation; Seasons; semiarid woodlands; semiarid zones; Soil water; soil water content; Special Feature: Phenology: response, Driver, and Integrator; Species Specificity; temporal variation; tree mortality; Trees; Water Supply; wet environmental conditions; wildfires; woodlands; woody and herbaceous plants; woody plants; New Mexico
• ISSN: 0012-9658; 1939-9170
• DOI: 10.1890/06-2137.1

Ecosystem responses to key climate drivers are reflected in phenological dynamics such as the timing and degree of "green-up" that integrate responses over spatial scales from individual plants to ecosystems. This integration is clearest in ecosystems dominated by a single species or life form, such as seasonally dynamic grasslands or more temporally constant evergreen forests. Yet many ecosystems have substantial contribution of cover from both herbaceous and woody evergreen plants. Responses of mixed woody—herbaceous ecosystems to climate are of increasing concern due to their extensive nature, the potential for such systems to yield more complex responses than those dominated by a single life form, and projections that extreme climate and weather events will increase in frequency and intensity with global warming. We present responses of a mixed woody—herbaceous ecosystem type to an extreme event: regional-scale piñon pine mortality following an extended drought and the subsequent herbaceous green-up following the first wet period after the drought. This example highlights how reductions in greenness of the slower, more stable evergreen woody component can rapidly be offset by increases associated with resources made available to the relatively more responsive herbaceous component. We hypothesize that such two-phase phenological responses to extreme events are characteristic of many mixed woody—herbaceous ecosystems.