Search

Abstract: In arid rangelands, soil seed bank characteristics vary with rainfall patterns, livestock pressure and habitat heterogeneity. We investigated this issue by assessing spatio-temporal patterns in soil seed bank density and richness in a degraded (heavy grazing) and non-degraded (light grazing) Nama Karoo ecosystem. To account for variation in seed distribution, different microsites were compared, and the effect of diaspore size on the patterning analyzed. Long-term heavy grazing increased seed densities and species richness of the soil seed bank by favoring small-seeded and tiny-seeded annual species. The spatial patterning of the soil seed bank was, however, similar to that found under sustainable grazing. The overall seed distribution was dictated by the small-scale environmental heterogeneity, which interacted with diaspore size. Our results suggest that the degraded environment is still efficient in controlling secondary dispersal and retaining seeds. This is through low stature barriers like surface rocks, which replace the function of grazing-sensitive perennial grasses in trapping and storing small diaspores. Soil seed banks were persistent and accumulated readily-germinable seeds over time. Observed temporal pattern across the study sites indicates that both condition and sequence of preceding rainfall seasons are likely to have a profound effect on soil seed banks of subsequent years. [ABSTRACT FROM AUTHOR]

Abstract Moving towards more integrative approaches within the invasion sciences has been recognized as a means of improving linkages between science, policy, and practice. Yet despite the recognition that biological invasions pose complex social-ecological challenges, the invasion literature poorly covers social-ecological or distinctly integrative research. Various initiatives and investments have been made towards building research capacity and conducting more integrative research aimed at improving the management of biological invasions. Using a combination of social network and thematic analysis approaches, and the South African Working for Water (WfW) program as a case study for the management of invasive species, we identify and explore the roles of core authors in shaping collaboration networks and research outputs, based on bibliographic records. We found that research produced under the auspices of WfW is authored by a handful of core authors, conducting primarily ecologically-focused research, with social research significantly underrepresented. Core authors identified in this study play an essential role in mediating relationships between researchers, in addition to potentially controlling access to those seeking to form collaborations, maintaining network cohesion and connectivity across institutional and disciplinary boundaries. Research projects should be designed to span disciplines and institutions if they are to adequately address complex challenges. Highlights • Social research is underrepresented and peripheral to other IAP management related research. • Core researchers play essential roles in shaping collaboration networks and knowledge production. • Removing core researchers will result in network inefficiency and fragmentation. • Core researchers act as gatekeepers to others seeking to join the network. • Core researchers can both inhibit and enhance innovation and adaptive capacity. [ABSTRACT FROM AUTHOR]

Abstract: Relationships between species richness per plant life form and the soil properties: infiltrability, clay plus silt content, salinity, and pH were investigated at eighteen study sites located in western South Africa and Namibia. Plant species data were categorized into five life forms: phanerophytes, chamaephytes, hemicryptophytes, therophytes, and geophytes. A boundary line approach was used to determine ranges of soil properties across which plant richness was constrained or potentially maximal. Ranges of soil properties at which richness was potentially maximal differed between life forms as follows: total plant richness (∼50–200mmh−1 infiltrability, ∼5–20% clay & silt, <100mSm−1 EC and 6.5–8.5 pH); phanerophytes (∼200–500mmh−1, <5%, <100mSm−1, 5.5–7.0); hemicryptophytes (∼100–250mmh−1, 5–18%, <200mSm−1, 6.0–8.0), therophytes (∼50–250mmh−1, 5–10%, >50mSm−1, 6.5–8.5), chamaephytes (<250mmh−1, 5–25%, >50mSm−1, 7.0–8.0), and geophytes (<200mmh−1, 5–20%, ∼50–100mSm−1, 6.5–8.0). Soil infiltrability, clay plus silt content, EC and pH seem to be useful properties to consider within plant richness investigations. Depending on physiological adaptations of plants these properties may constrain species distribution. Causality cannot be demonstrated from the relationships; however they can lead to plausible hypotheses as to the ecological processes governing plant distribution patterns. [Copyright &y& Elsevier]

Abstract: Can markets assist by providing support for ecological restoration, and if so, under what conditions? The first step in addressing this question is to develop a consistent methodology for economic evaluation of ecological restoration projects. A risk analysis process was followed in which a system dynamics model was constructed for eight diverse case study sites where ecological restoration is currently being pursued. Restoration costs vary across each of these sites, as do the benefits associated with restored ecosystem functioning. The system dynamics model simulates the ecological, hydrological and economic benefits of ecological restoration and informs a portfolio mapping exercise where payoffs are matched against the likelihood of success of a project, as well as a number of other factors (such as project costs and risk measures). This is the first known application that couples ecological restoration with system dynamics and portfolio mapping. The results suggest an approach that is able to move beyond traditional indicators of project success, since the effect of discounting is virtually eliminated. We conclude that systems dynamic modelling with portfolio mapping can guide decisions on when markets for restoration activities may be feasible. [Copyright &y& Elsevier]