Tropical Dry Forest Landscape Restoration in Central Veracruz, Mexico

Until recently, it was thought that native tropical dry forest (TDF) in central Veracruz was completely gone. Fortunately, recent research using Landsat images and ground-truth verification showed the presence of TDF remnants. There is still 7% of the original forest in the region, although one-third is secondary vegetation (F. López-Barrera, Instituto de Ecología A.C., pers. comm.).

Tropical dry forest landscape restoration has been carried out in only a few places. The most integral restoration experience started in Parque Nacional Santa Rosa, Costa Rica, which was expanded to become Area de Conservación Guanacaste, a region ten times larger (Janzen 2008). Other restoration efforts are being carried out on the Pacific coast of Panama (Griscom et al. 2009), Paraná River Valley in Central Brazil (Sampaio et al. 2007), Hojancha and Cañas in Costa Rica (Fonseca-González and Morera 2008), the Ayuquila River watershed in Jalisco (Ortiz-Arrona et al. 2004), and the Tembembe river in Morelos, Mexico (Bonfil et al. 2004). Most TDF restoration experiences indicate that besides establishing native species plantations, restorationists should rely on the resprouting ability of the trees characteristic of these forests (Griscom et al. 2009) and different management techniques to facilitate this natural regeneration capacity (Sampaio et al. 2007). We recognize that natural tree regeneration is not only the least expensive method possible; it is also a tool for designing restoration efforts (Janzen 2008, Viera and Scariot 2006).

This study is part of Project ReForLan, which focuses on the restoration of dryland forest landscapes for biodiversity conservation and rural development in Latin America (Newton 2008). Our goal was to test restoration techniques and identify the main constraints to forest restoration. The two objectives were to define a reference system through the determination of forest structure and tree species composition, and to define a set of tree species to be used in restoration efforts.

Figure 1.

Survival percentages (October 2007–June 2009) for six tree species planted in restoration experiments in central Veracruz, Mexico. Survival of cedro (Cedrela odorata) was significantly lower than other species (one-way ANOVA, F = 3.7, df = 5,18, p = 0.02).

The study area is located in central Veracruz, Mexico (19°17′N, 96°26′W, 100–250 m asl). The climate is hot and dry. Mean minimum and maximum temperatures are 19.8°C and 30.7°C, respectively. Total annual precipitation is 966 mm (range: 502–1,466 mm). The dry season extends from October to May. Soils are mainly Cambisol and Vertisol. In this region, land is mainly used for cattle ranching, generally on a small scale by private landowners; but for common land tenants (ejidatarios), the main activity is growing corn and other crops, such as papaya, bean, green chili, watermelon, sugar cane, and mango. This area is rich in history related to pre-Hispanic settlements (600 to 1500 A.D.) and the Mexican Independence (19th century). In addition, the region includes an important observation point, the River of Raptors, for one of the largest annual migrations of raptors in the world.

The TDF reference system was determined through the selection of ten forest remnants and five early successional sites, 1 to 72 months after the last abandonment, with different land use histories (Williams-Linera and Lorea 2009, Williams-Linera et al. 2010). Vegetation structure was characterized in terms of density, basal area, and height for canopy trees (≥ 5 cm dbh) and understory woody plants (< 5 cm dbh). Mean density was 1,014 ± 104 and 2,532 ± 2,272 individuals/ha, with basal area 30.2 ± 2.11 m²/ha and 1.96 ± 0.12 m²/ha, for canopy and understory vegetation, respectively. The forest mean height was 10 m and reached a maximum of 15 m. The early successional sites had a basal area and density ranging from 0.40 to 3.88 m²/ha and from 900 to 5,450 individuals/ha, respectively.

We recorded 122 woody plant species in the forest fragments (Williams-Linera and Lorea 2009...