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Transcript
Chaparral Habitats: Vulnerability Briefing Sensitivity1 Climate and climate-‐driven stressors • Drought • Precipitation and soil moisture • Temperature (minimum winter air temperature) Disturbance regimes • Wildfire High community diversity will likely contribute to diverse responses to climate change, and may lead to community shifts. Drought may favor sprouting species, while periods of high p recipitation may favor seeding species. Warming temperatures may affect community composition as minimum winter air temperatures h ave historically limited some species. Chaparral communities are largely adapted to and regenerate quickly after wildfire, but they are vulnerable to increasing fire frequencies, which are exacerbated by drought, increased anthropogenic ignitions, and the presence of non-‐native grasses and forbs. Increasing fire frequencies may limit the regeneration of obligate seeders and/or lead to vegetation type conversion to sage scrub or annual grassland. Non-‐climate stressors • Development • Invasive species • Transportation corridors • Air pollution Human development has significantly destroyed and fragmented chaparral h abitat in southern California. In addition, expanding low-‐density rural populations, as well as transportation corridors, contribute to altered ecological processes (e.g., increased fire frequency, enhanced invasive species establishment), compounding climate-‐ driven changes and degrading habitat quality. It is unknown h ow nitrogen deposition will affect this habitat in the future. Exposure Future projected changes Increasing air temperatures (+2.5°C to +9°C by 2100) and variable precipitation Increased wildfire frequency and severity Anticipated chaparral habitat response Potential refugia Microsites • Increased probability and duration of drought conditions and moisture stress, which may alter chaparral community composition within heterogeneous (e.g., obligate-‐ and facultative-‐sprouters may become more and complex dominant) landscapes; north-‐facing • More frequent fires may negatively affect the reproductive ability aspects; of seeding species by limiting contributions to the seedbank remote and • More frequent fires may facilitate type conversions to sage scrub isolated areas and/or annual grassland Chaparral habitats are projected to decline under most future climate scenarios, being replaced by grasslands (warmer/drier scenarios) or via forest encroachment (warmer/wetter scenarios). Adaptive Capacity Ecosystem condition Chaparral occupies a diversity of elevations and microclimates. Coastal and interior chaparral feature large habitat swaths, but are threatened by future development and fragmentation. Montane chaparral has experienced higher historical conversion. Resistance & Chaparral may be more resilient to climate stressors, but less resistant and able to recover from fire, invasive species, land use conversion, and other non-‐climatic stressors. recovery Diversity Chaparral habitats harbor fairly high diversity, and host a variety of endemic vegetation and native fauna. Management Valued for aesthetics, biodiversity, recreation, carbon sequestration, nitrogen retention, flood/erosion protection, air quality, water supply/quality/sediment transport, and fire regime potential controls. Fire suppression, maintaining connectivity, land use regulations, restricting fuel manipulation, and managing invasive species may be key management opportunities. 1 See detailed sensitivity information on next page. Chaparral Habitats: Sensitivity Chart Stressor Climate & climate-‐driven sensitivities Drought Precipitation and soil moisture Non-‐climate stressors Disturbance regimes Temperature 1 Wildfire Development Invasive species Transportation corridors Air pollution Potential impact on chaparral habitats • Altered community composition o Sprouters (obligate and facultative): enhanced dominance o Seeders (obligate and facultative): reduced reproductive success1 • Shorter fire-‐return intervals • High precipitation may favor obligate-‐ and facultative-‐seeders • Increased minimum winter air temperatures may alter community composition • Warmer air temperatures will likely increase the duration of moisture stress during summer • Stimulates stand regeneration (i.e., many chaparral species are fire-‐adapted), and can facilitate expansion into adjacent burned areas • Increased fire frequencies may reduce abundance of obligate seeding species by limiting seedbank regeneration • Increased fire frequencies (<5-‐10 year fire return intervals) may facilitate vegetation type conversion to sage scrub and/or annual grassland • Habitat destruction and/or fragmentation • Altered fire frequencies via increased human ignition • Increased invasive species introductions • More frequent fires, facilitating shifts to sage scrub and/or annual grassland • Increased invasive species introductions • Increased ignition potential • It is unknown how nitrogen deposition may affect or exacerbate changes in this habitat; it could enhance the productivity of annual grasses and contribute to increased fire frequencies Participants: please see the chaparral specific habitat questions (separate sheet) and help verify that the information provided regarding drought response is correct.
