I. Extent of thornscrub in North America; Biome types
Whittaker:
1) Thornwoods of arid tropical climates
2) Warm semi-desert
Kuchler:1) Dsi (Broadleaf, deciduous, shrubform, frequently not touching)
2) Gdsp (Grass and broadleaf deciduous shrubform)
Walter:1) Tropical with summer rains
2) Subtropical arid
Correl & Johnston:
1) Rio Grande plains or Tamaulipan brushlands
II. Climate
A. Dry warm-temperate and subtropical
B. Tropical climates more arid than those of seasonal forests
C. Grows adjacent to desert biomes (upslope; closer to oceanic influences)
III. Characteristics
of thornscrub vegetation:
A. Spiny species of Acacia and other genera of legume are widespread
B. Small drought-deciduous leaflets
C. Succulents in more arid environments
D. Rich and diverse shrub communities
IV. Losses: grazing,
brush removal, commercial plant collection, irrigated farming
CASE
HISTORY
Lower Rio Grande
Valley National Wildlife Refuge (slide show)
V. Size
In
1995, 62,443 acres
Proposed, 132,000 acres
VI. Two general brush
habitats
A. Riparian and scrub forests (larger vegetation)
B. Upland thornscrub and thorn woodland
VII. Associated
wildlife: ocelot, jaguarundi, coati, javelina, chachalaca, parrots,
green jay
VIII Human impacts
A. Agricultural conversion
B. Pesticides
C. Water development
floodway system
Falcon and Amistad reservoirs
pumping stations and irrigation
D. Brush removal
mechanical
chemical
E. Urbanization
F. Recreation
IX. Current management
A. Land purchase
B. Easements
C. Land lease and land management agreements
D. Restoration on abandoned or purchased cropland
X. Refuge strategy
A. Priority communities
B. Corridor approach
C. Anchor refugia
D. Management units
E. Control of unique terrestrial islands