Structure, composition and carbon stocks of woody plant community in assisted and unassisted ecological succession in a Tamaulipan thornscrub, Mexico

Background

Ecological restoration is a process that helps the recovery of an ecosystem that has been degraded, damaged or destroyed. The success of restoration actions depend on the understanding of the processes, mechanisms and factors that guide vegetation dynamics. The restoration of plant communities can be made by unassisted (passive restoration, where the community recover by itself) and assisted (active restoration) ecological succession. It is imperative to know the scope of both types of activities to guide future restoration actions by evaluating the properties and functioning of the intervened communities.

Methods

Variance analysis of the carbon (C) stocks, basal area, canopy area, Shannon–Weaver index values, specific richness and abundance of three Tamaulipan thornscrub communities (assisted natural succession area, unassisted natural succession area and control area) was performed. Furthermore, a similarity analysis between the sampling areas using the floristic composition (abundance) was performed.

Results

In total, 11 families, 17 genera and 20 species of vascular plants were registered. The richness of species and abundance ranked as follows per area: assisted ecological natural succession > control > unassisted ecological natural succession. The species composition between sampling areas showed a low number of common species between plant communities.

Conclusions

The values of species richness, diversity, abundance, basal area, and canopy area of the assisted natural succession vegetal community was statistical similar to the control plan community. The values of C stocks showed that assisted ecological succession could recover not only structure and composition attributes but also this key ecosystem property.

Plant water use characteristics of five dominant shrub species of the Lower Rio Grande Valley, Texas, USA: implications for shrubland restoration and conservation

The biogeographic distribution of plant species is inherently associated with the plasticity of physiological adaptations to environmental variation. For semi-arid shrublands with a legacy of saline soils, characterization of soil water-tolerant shrub species is necessary for habitat restoration given future projection of increased drought magnitude and persistence in these ecosystems. Five dominant native shrub species commonly found in the Lower Rio Grande Valley, TX, USA, were studied, namely Acacia farnesiana, Celtis ehrenbergiana, Forestiera angustifolia, Parkinsonia aculeata and Prosopis glandulosa. To simulate drought conditions, we suspended watering of healthy, greenhouse-grown plants for 4 weeks. Effects of soil salinity were also studied by dosing plants with 10% NaCl solution with suspended watering. For soil water deficit treatment, the soil water potential of P. glandulosa was the highest (-1.20 MPa), followed by A. farnesiana (-4.69 MPa), P. aculeata (-5.39 MPa), F. angustifolia (-6.20 MPa) and C. ehrenbergiana (-10.02 MPa). For the soil salinity treatment, P. glandulosa also had the highest soil water potential value (-1.60 MPa), followed by C. ehrenbergiana (-1.70 MPa), A. farnesiana (-1.84 MPa), P. aculeata (-2.04 MPa) and F. angustifolia (-6.99 MPa). Within the species, only C. ehrenbergiana and F. angustifolia for soil water deficit treatment and A. farnesiana for the salinity treatment had significantly lower soil water potential after 4 weeks of treatment (P < 0.05). We found that soil water potential, stomatal conductance and net photosynthesis of the species significantly reduced over time for both treatments (P < 0.05). We conclude that while all species exhibited capacities to withstand current water availability, some species demonstrated limited tolerance for extreme water stress that may be important for management of future shrub diversity in Lower Rio Grande Valley.