Mitch Sternberg

Reforestation in the Lower Rio Grande Valley (LRGV) of Texas began in the 1960s and to date over 6,475 ha of land has been reforested. However, there has been minimal assessment to understand differential species success, compositional trends, and the aboveground carbon sequestration potential of these developing forests. We coupled quantitative planting information of >50 native woody tree and shrub species with surveys of 5,223 stems of 4,606 individuals in a chronosequence of restored forests ranging in age from 1 to 33 years to estimate species‐specific mortality rates, biomass accumulation and recruitment, as well as compositional trends in the herbaceous understory. We show that 7–15 years are required for mortality rates of the transplanted cohort to stabilize to background levels observed in other dry forests. A small number of species, mostly N‐fixing trees with a deep rooting habit, persisted on the landscape beyond 15 years. Even so, aboveground biomass (corrected for differences in initial planting density) accumulated at an average rate of 1.41 Mg ha−1 yr−1 compared to 0.35 Mg ha−1 yr−1 for a fallow old‐field. Species biomass growth rates increased with decreasing mortality, as did the abundance of recruits, suggesting a degree of reproduction by initial planted cohorts. However, a suite of highly competitive exotic grasses increases in density over a 25‐year period, which we link to suppressed seedling recruitment. This poses a serious challenge to the long‐term sustainability of planted forests in the LRGV. We highlight potential avenues of research and modification to restoration methodologies.

Dispersal of animals among populations helps to increase genetic variability and population viability. The endangered ocelot (Leopardus pardalis) in south Texas persists in two small populations separated by 30 km and cutoff from populations in northeastern Mexico. Despite the relatively short distance separating the two south Texas populations, movement between them has been limited, leading researchers to believe landscape connectivity is poor in the region. We developed habitat suitability maps using remote sensing and GPS‐collared ocelots and ran connectivity analyses to assess current habitat linkages, important areas for conservation, and areas where connectivity could be improved through habitat restoration. First, we developed a resource selection function using random forest models and GPS data from ten ocelots collared at Laguna Atascosa National Wildlife Refuge combined with spatial layers derived from LiDAR and remotely sensed imagery. We then used these results as the b...

Agriculture and urban development have destroyed 95% of native brushland habitat in the Lower Rio Grande Valley (LRGV) of south Texas. Therefore, habitat restoration is an important issue in the LRGV. Since 1982, the U.S.Fish and Wildlife Service has been replanting areas in the LRGV to native brushland species to establish a wildlife corridor along the lower reach of the Rio Grande. Vegetation composition of a mature brushland, a replanted habitat and an unaided secondary succession site (fallow field) were examined at one locale in the LRGV in 1999. The mature brushland edge plot had the highest species richness (43) followed by the replanted edge plot (37), mature brushland interior (35), replanted interior plot (33) and fallow field interior (12) and edge (11) plots. Edge and interior plots in the same habitat were similar in species composition (mature brushland, 74%; replanted, 63 %; fallow field, 70%). Community similarity was greater for mature brushland and replanted habitats (47%) than the mature brushland and fallow field (32%), or the replanted and fallow field habitats (28%). These data suggest that current replanting techniques used by the U.S. Fish and Wildlife Service in the LRGV achieve a more diverse plant community in a shorter length of time than unaided secondary succession of fallow fields.

Reforestation in the Lower Rio Grande Valley (LRGV) of Texas began in the 1960s and to date over 6,475 ha of land has been reforested. However, there has been minimal assessment to understand differential species success, compositional trends, and the aboveground carbon sequestration potential of these developing forests. We coupled quantitative planting information of >50 native woody tree and shrub species with surveys of 5,223 stems of 4,606 individuals in a chronosequence of restored forests ranging in age from 1 to 33 years to estimate species‐specific mortality rates, biomass accumulation and recruitment, as well as compositional trends in the herbaceous understory. We show that 7–15 years are required for mortality rates of the transplanted cohort to stabilize to background levels observed in other dry forests. A small number of species, mostly N‐fixing trees with a deep rooting habit, persisted on the landscape beyond 15 years. Even so, aboveground biomass (corrected for ...