6 Major Physiographic Zones of the Lower Rio Grande Valley, Texas (from Hathcock et al. 2014, in press)

South Texas Refuge Complex

STRC MISSION To restore, enhance, and protect the natural diversity of the Lower Rio Grande Valley of Texas

Two-Pronged Approach

Acquisition -- land/easements • Create corridors* • Conserve unique biota • Very high, immediate priority

Restoration -- mature riparian woodlands • Create corridors* • Augment and enhance habitat blocks • Long-term ecosystem sustainability STRC Restoration Program

• Facilitate succession • 5,000 ha planted since mid-1980’s • Early sites direct-seeded/low-density (<600 plants/ha) transplants • Currently 200 ha/year @ 1,000-2,000 plants/ha (50-60 species) • Additional 3,000 ha slated for future Seedlings in “Mini” (6” x 1.5”) Plant Bands

Texas ebony Ebanopsis ebano

all-thorn goat-bush Castela erecta Evaluation of Effectiveness

Traditional • Focus on maximum area/numbers of plants • 1st-Year Survivorship (re-plant?) • No long-term data Current • Increased focus on similarity to natural climax communities • Poor results observed anecdotally at many past sites • Possible to evaluate 15 to 25-year-old sites

Study Methods

• Non-Systematic, Qualitative Surveys – 2 distinct association-level mature woodland communities – noted dominant species within 4 vertical strata • Belt-Transect Surveys – 9 Sites (3 direct-seed, 5 transplant, 1 control) – counted all individual woody plants within 2 to 3-m belt

Ebenopsis ebano – Ehretia anacua / Condalia hookeri Forest Texas Ebony – Anacua / Brasíl Forest (from International Vegetation Classification, NatureServe 2012)

Santa Ana National Wildlife Refuge, Alamo Edge of Ebony-Anacua/Brasĺl Forest, Ranchito Tract Tamaulipan Coastal Shrubland, saline Tamaulipan Coastal Shrubland, non-saline Condalia hookeri (brasíl) Ziziphus obtusifolia (lotebush) Zanthoxylum fagara (colima)

Forestiera angustifolia (elbow-bush) Guaiacum angustifolium (guayacán) Ebony-Anacua/Brasíl Forest Structure • Canopy 7-8 m tall; 80-100% closed • Dense mid-story • Open understory (80% litter/bare ground, 20% forbs/weak shrubs)

Dominant Woody Species • Canopy (3): Ebenopsis ebano, Ehretia anacua, Prosopis glandulosa • Sub-Canopy (6): Condalia hookeri, Havardia pallens, Amyris madrensis, Guaiacum angustifolium, Diospyros texana, Acacia farnesiana • Mid-Story (3): Phaulothamnus spinescens, Ziziphus obtusifolia, Celtis pallida • Understory (1): Malpighia glabra

Total Woody Species: 30 Tamaulipan Coastal Shrubland

Structure • Canopy: overall sparse (10-50% closed), 4-5 m high • Mid-story: 1-2.5 m; patchy to dense • Understory: 0-1 m, dense Dominant Woody Species • Canopy (3): Prosopis glandulosa, Yucca treculeana, Ebenopsis ebano • Mid-Story (5): Forestiera angustifolia, Phaulothamnus spinescens,, Ziziphus obtusifolia, Celtis pallida, Zanthoxylum fagara (non-saline sites)

Total Woody Species: 25 25-Year-Old Direct-Seed Site, Ranchito Tract 18-Year-Old Direct-Seed Site, Ranchito Tract

Acacia farnesiana (huisache) Leucaena pulverulenta (tepeguaje) Prosopis glandulosa (honey mesquite) Parkinsonia aculeata (retama) 12-Year-Old Transplant Site, Ranchito Tract Preliminary Results of Belt-Transect Surveys at Ranchito and La Coma Tracts

Area Plant Simpson Planting Year(s) Sampled Density No. Diversity Site Method Planted (ha) (No./ha) Species Index

1994- Ranchito Transplant 2.4 720 33 0.93 2005

Direct 1989, Ranchito 2.4 883 18 0.71 Seed 1996

None Ranchito 1989 1.0 777 14 0.50 (Control)

La Coma Transplant 1995 0.2 4,219 27 0.81 Preliminary Results – Species Composition

No. Late- Planting % Early % Late Succ. Dominant Site Method n Succ. Succ. Sp. Late-Succ. Sp.

E. ebano (21%) Ranchito Transplant 1,698 51.4 40 25 7 other sp. (60%)

Direct Ranchito 2,140 49.8 50.2 12 E. ebano (95%) Seed

None Ranchito 752 93.9 6.1 8 --- (Control)

H. pallens (40%) La Transplant 926 45.8 54.2 21 Z. fagara (20%) Coma E. anacua (11%) Discussion

• Transplant sites had higher overall diversity and proportion of late-successional species • Recruitment highest, with more desirable species, at transplant sites (esp. La Coma) • Transplant sites and mature sites were fairly similar in species richness and dominants with exceptions… Discussion (cont.)

Under-Represented Species

– Forestiera angustifolium (elbow-bush) – Phaulothamnus spinescens (snake-eyes) – Diospyros texana (chapote) – Guaiacum angustifolia (guayacán) – Condalia hookeri (brasíl; La Coma only) – Zanthoxylum fagara (colima; Ranchito only) – Amyris madrensis (Sierra Madre torchwood; Ranchito only)

Aspects Applicable to Other Restoration Projects

• Qualitative Descriptions of Association- Level Dominants/Sub-Dominants (e.g., IVC Descriptions, non-systematic samples) • Measures of Recruitment/Survivorship • Control Plots (=Evidence of Project Merit) Acknowledgements

American Forests (Global Re-Leaf Grant) Florentino Caldera (USFWS) Chris Pérez (USFWS) Rene Ruíz (USFWS) Mitch Sternberg (USFWS)