Emerging Restoration Approaches for Disturbed Mojave Desert Shrublands and the Search for Suitable Native Plant Materials

Transcription

1 Emerging Restoration Approaches for Disturbed Mojave Desert Shrublands and the Search for Suitable Native Plant Materials Lesley A. DeFalco USGS, Western Ecological Research Center Henderson, Nevada Conference on Ecological and Ecosystem Restoration New Orleans, Louisiana July 30 th, 2014

2 Mojave Desert Shrublands Low and middle elevation shrublands comprise 87% of area GrB CoP Creosote bush-bursage Blackbrush-Joshua tree >1 million acres burned or re-burned in 2005/2006 (~4%) ~5% of federally-designated critical habitat for desert tortoise in NV and AZ impacted SoD Brooks & Matchett (2006)

3 Wildfire Impacts Habitat for Desert Tortoises UNBURNED BURNED

4 Not a Fire Adapted System: One-time vs Repeated Fires Dry Middle Fire Jacob 06 Fire Disruption of nurse plant / fertile island Invasive annuals Altered disturbance regime ( fire-grass cycle ) Propagule limitation hinders regeneration

5 Monitoring the Effectiveness of Treatments on a Network of Restoration Sites

6 Evaluating Tools for Arid Land Restoration Does broadcast seeding promote shrub and perennial herb establishment? Do seeding effects persist in the seed bank? Do herbicides suppress exotic annuals and promote native species? Hand seeding Seed bank assay College of Southern Nevada Herbicide experimental plots

7 Seeding Promotes Establishment of Native Perennials: One-time Fires Density of seeded species (plants/100 m 2 ) S S Seeded burn Unseeded burn * * * * S a S b b b bc c c Seeded burn Unseeded burn Live canopy cover (%) Short-lived perennial forbs Desert globemallow Desert marigold Shrubs Perennial grasses

8 Seeding Effects Persist in the Seed Bank (One-Time Fire): 5 Yrs Post-Seeding Functional group Control (#/m 2 ) Seeded (#/m 2 ) Seeded perennial forb 11 a 66 b Other perennial forb Seeded shrub 22 a 3 b Perennial grass 4 3 Exotic annual grass 10,093 11,511 Exotic annual forb 3,637 3,309 Native annual grass 2,376 2,618 Native annual forb 1,588 1,452 lsmeans presented; shading emphasizes difference from control (P < 0.05)

9 Plateau Suppresses Exotic Annuals and Promotes Native Species Red brome Six-weeks fescue

10 Herbicide Application Enhances Seeding: One-time Fires Density of seeded species (plants/100 m 2 ) Unseeded Seeded 300 Control Plateau Journey RoundUp Oust b b ab a a ]a Seeding Herbicide

11 Can We Restore Repeatedly Burned Shrublands? Despite suppression of exotic annual species, supplemental seeding did not promote establishment Inadequate weather conditions for seedling emergence? Seed predation by harvester ants and small mammals? Seed source poorly adapted to restoration site? Pakoon Basin, Grand Canyon-Parashant Nat l Monument, Arizona Jacob 06 Fire

12 Novel Restoration Approaches that Account for Granivores Seed Dispersal Shrub islands Kangaroo rat Seed Predator Seed encapsulation Can we establish shrub islands to promote seed dispersal by small mammals? Can we protect native seeds from granivores and enhance seedling emergence?

13 Can We Create Habitat Islands? Nevada joint-fir Blackbrush Shrub island Joint-fir had higher survival after 3.5 years (61%) than blackbrush (4%) Factors other than soil moisture amendments corresponded with higher survival (site, herbicide, herbivore protection) Water reservoir planted with seedling

14 Does Seed Encapsulation Promote Emergence? Wafer (W) Ball (B) Control (C)

15 Emerging Restoration Tools for Arid Land Restoration Herbicide application: 50-80% reduction in exotic annual production Native seeding: Enhanced native seedling establishment 4-7 yrs after seeding Shrub islands: >60% survival of Nevada joint-fir seedlings after 3.5 yrs Seed encapsulation: Improving survival over unprotected seed

16 How Important is Seed Source? How far away can seeds of a species be collected and used for restoration? Geographic distance Environmental distance Are some native species more suitable for restoration, and for commercial production, than others? How do we choose best-performing species as our climate changes?

17 Seasonal Zones Rain Temps West-East Win/spg Summer Summer Win/spg

18 Common Gardens Evaluate genetic variability among populations where seeds are collected for restoration Correlate climate variables associated with plant performance to match seed source with restoration site environments Ft. Irwin National Training Center, California Garden Utah Division of Wildlife Resources Garden

19 2014 Gardens Desert globemallow (Sphaeralcea ambigua) Herbaceous forb/sub-shrub 521 seedlings, 9 collections Creosote bush (Larrea tridentata) Evergreen shrub 248 seedlings, 10 populations Bursage (Ambrosia dumosa) Drought-deciduous shrub 1,340 seedlings, 19 populations Chicago Botanic Garden CLM Interns

20 Plants Grown for Common Gardens Seed Zone Represented Species Plants Populations Desert globemallow X X X Creosote bush X X X X X X Bursage 1, X X X X X X Zone 3 Ft. Irwin Nat l Training Center Garden Zone 2 Utah Division of Wildlife Resources Garden Zone 6 Joshua Tree NP/Mojave Science & Cultural Center Garden

21 Partners and Collaborators US Geological Survey Bureau of Land Management Nevada, California, Arizona National Park Service Lake Mead NRA, Joshua Tree NM Bureau of Reclamation, Lower Colorado Regional Office Department of Defense, Ft. Irwin National Training Center Department of Energy, Nevada National Security Site Utah Division of Wildlife Resources Clark County Desert Conservation Program Nevada Division of Forestry Mojave Science & Cultural Center Friends of Gold Butte College of Southern Nevada Nevada Conservation Corps Student Conservation Association Rancho Santa Ana Botanic Garden Chicago Botanic Garden