Plant community and landscape patterns of a floodplain wetland in Maputaland, Northern KwaZulu-Natal, South Africa

The lower Mkuze River floodplain is located east of the Lebombo Mountains on the Maputaland Coastal Plain in northern KwaZulu‐Natal, South Africa. The vegetation ecology of the floodplain was examined using the hierarchical framework described by landscape ecology theory. The smallest spatial scale to which the vegetation of the floodplain was described was the relatively homogeneous units of plant communities. From a landscape ecology perspective this level of analysis is referred to as the grain. Six plant communities were identified using two‐way indicator species analysis (TWINSPAN) classification. The distribution of these plant communities were correlated to an underlying inundation‐sedimentation gradient using the ordination technique, detrended correspondence analysis (DCA). This correlation provided a useful foundation for the examination of ecological processes and phenomena at the next higher, spatially coarser level within the landscape hierarchy, namely the reference level. This reference level was described by three functional types delimited by differing flooding and sedimentation regimes. The use of landscape ecology theory guided the interpretation of results by explicitly recognizing the importance of spatial heterogeneity, hierarchical organization and dynamics, and proved invaluable in developing process‐based understanding of the vegetation ecology of the lower Mkuze River floodplain.     

HIV-1 down-modulates gamma signaling chain of Fc gamma R in human macrophages: a possible mechanism for inhibition of phagocytosis

HIV-1 infection impairs a number of macrophage effector functions, thereby contributing to development of opportunistic infections and the pathogenesis of AIDS. FcgammaR-mediated phagocytosis by human monocyte-derived macrophages (MDM) is inhibited by HIV-1 infection in vitro, and the underlying mechanism was investigated in this study. Inhibition of phagocytosis directly correlated with the multiplicity of HIV-1 infection. Expression of surface FcgammaRs was unaffected by HIV-1 infection, suggesting that inhibition of phagocytosis occurred during or after receptor binding. HIV-1 infection of MDM markedly inhibited tyrosine phosphorylation of the cellular proteins, which occurs following engagement of FcgammaRs, suggesting a defect downstream of initial receptor activation. FcgammaR-mediated phagocytosis in HIV-infected MDM was associated with inhibition of phosphorylation of tyrosine kinases from two different families, Hck and Syk, defective formation of Syk complexes with other tyrosine-phosphorylated proteins, and inhibition of paxillin activation. Down-modulation of protein expression but not mRNA of the gamma signaling subunit of FcgammaR (a docking site for Syk) was observed in HIV-infected MDM. Infection of MDM with a construct of HIV-1 in which nef was replaced with the gene for the gamma signaling subunit augmented FcgammaR-mediated phagocytosis, suggesting that down-modulation of gamma-chain protein expression in HIV-infected MDM caused the defective FcgammaR-mediated signaling and impairment of phagocytosis. This study is the first to demonstrate a specific alteration in phagocytosis signal transduction pathway, which provides a mechanism for the observed impaired FcgammaR-mediated phagocytosis in HIV-infected macrophages and contributes to the understanding of how HIV-1 impairs cell-mediated immunity leading to HIV-1 disease progression.     

Seed dormancy,soil type and protective shelters influence seedling emergence at Shark Bay,Western Australia: Insight into global dryland revegetation

Seedling emergence is a major constraint on dryland revegetation success. In this study, we investigated seedling emergence of six framework shrub species as influenced by seed treatment, soil type and protective shelters using a large field trial in arid Western Australia. We observed the main effects of seed treatment and soil type to account for the majority of the variation in emergence. For species that exhibit pronounced dormancy, we found emergence of dormancy‐alleviated or treated (T) seed to be significantly greater than dormant or untreated (UT) seed, with responses varying across species (e.g. 41 times greater for Acacia ligulata Benth., and 10 times greater for Stylobasium spathulatum Desf.). For shallowly or nondormant species like Senna glutinosa (DC) Randall, UT seed emergence was slightly greater than for T seed. Compared to subsoil, topsoil was more receptive to infiltration (3.44 vs. 0.38 mm/min), and less prone to compaction (1.24 vs. 1.67 g/cm³) and crusting (0.6 vs. 1.3 kg/cm²); however, subsoil had greater moisture retention. Shelters failed to benefit soil moisture retention in either soil type, but enhanced emergence for most species. This study provides insight into how various cost‐effective treatments can be utilized to manipulate seed dormancy to optimize seedling emergence, the intrinsic value of topsoil as a superior growth medium and the benefit of novel, low‐cost shelters for enhancing seedling emergence. In arid environments, sowing T seed in combination with UT seed increases the likelihood of capitalizing on inherently variable precipitation events.     

Synthesis and biological evaluation of 2',4'- and 3',4'-bridged nucleoside analogues

Most nucleosides in solution typically exist in equilibrium between two major sugar pucker forms, N-type and S-type, but bridged nucleosides can be locked into one of these conformations depending on their specific structure. While many groups have researched these bridged nucleosides for the purpose of determining their binding affinity for antisense applications, we opted to look into the potential for biological activity within these conformationally-locked structures. A small library of 2',4'- and 3',4'-bridged nucleoside analogues was synthesized, including a novel 3',4'-carbocyclic bridged system. The synthesized compounds were tested for antibacterial, antitumor, and antiviral activities, leading to the identification of nucleosides possessing such biological activities. To the best of our knowledge, these biologically active compounds represent the first example of 2',4'-bridged nucleosides to demonstrate such properties. The most potent compound, nucleoside 33, exhibited significant antiviral activity against pseudoviruses SF162 (IC(50)=7.0 μM) and HxB2 (IC(50)=2.4 μM). These findings render bridged nucleosides as credible leads for drug discovery in the anti-HIV area of research.     

Hierarchical spatial organization and prioritization of wetlands: a conceptual model for wetland rehabilitation in South Africa

Wetland rehabilitation planning needs to take into account many different aspects of the wetland and its context. In South Africa, much emphasis is placed on the delivery of ecosystem services, poverty relief and skills development for those involved in labour-intensive rehabilitation measures. A framework is presented that facilitates decision-making with regards to wetland rehabilitation planning. This starts with prioritizing which wetlands need attention within a catchment. This is followed by decisions regarding which rehabilitation measures would be effective in improving certain ecosystem services based upon the aims of rehabilitation and the social context of the surrounding catchment. The functional unit that is most suitable to work with for rehabilitation is the Hydrogeomorphic (HGM) Unit, defined as a section of a wetland with more or less uniform hydrological and geomorphological characteristics. An individual wetland may comprise several HGM units, and a HGM Unit itself can be sub-divided into several smaller habitat or vegetation units. Different rehabilitation measures have been identified which are appropriate for the different scales in this spatial framework. Two case studies are presented as examples of how this spatial framework impacts upon the decisions made by the rehabilitation practitioner.     

Comparing ecological restoration in South Africa and Western Australia: the benefits of a ‘travelling workshop’

Researchers and practitioners of ecological restoration from South Africa and Western Australia recently undertook a travelling workshop across several South African biomes to discuss and evaluate the various approaches currently being utilised in the field. Key findings from the workshop highlighted the contrasting nature of ecological restoration undertaken in these two ecologically similar, but socially and politically different regions.     

Improving Upper Elementary Students’ Humane Attitudes and Prosocial Behaviors through an In-class Humane Education Program

Humane education is a long-standing field of education that endeavors to nurture kindness, compassion, and concern for nonhuman animals, people, and the environment. Despite its long history, however, few randomized control studies have evaluated its effectiveness to promote the development of relevant outcomes. The current study sought to address this dearth by investigating the effects of a humane education program on not only participating students’ attitudes, but also their behaviors. Classes of under-served, fourth-grade students in two major US cities were randomly assigned to participate in either a school-based humane education program or a chess club (the control group); all students participated in their respective activity during the same period once a week for 11 weeks. Data were collected on the attitudes (n = 236) and behaviors (n = 167) of participating students exactly one week before and exactly one week after these programs were conducted. Students self-reported their attitudes about the treatment of animals and the environment via the Intermediate Attitude Scale. Teachers rated each students’ prosocial and disruptive behaviors through sub-scales of the Teacher Observation of Classroom Adaptation– Checklist. Nested multilevel models of change found that the development of prosocial behaviors and self-reported attitudes significantly interacted with group assignment: Students who participated in the humane education program showed stronger growth in both of these outcomes compared with students in the control group. Changes in disruptive behaviors, how-ever, were not found to differ between groups. The results support the effectiveness of a humane education program to teach a relatively large and diverse group of upper elementary students to learn about animal welfare issues and to improve their prosocial behaviors. Effects appeared strongest on attitudes; behavioral effects were found to be largely limited to behaviors directly addressed by the humane education program.     

Growth and allocation by a keystone wetland plant, <Emphasis Type="Italic">Panicum hemitomon</Emphasis>, and implications for managing and rehabilitating coastal freshwater marshes,Louisiana, USA

This paper attempts to establish linkages between growth by a keystone wetland plant, Panicum hemitomon Schultes, and the independent and interactive effect of nutrient and hydrologic regime to inform management and rehabilitation of thick-mat floating marsh (TMFM). To do so a manipulative glasshouse experiment employing created TMFM similar to that under consideration for field trials and two levels each of N, P and hydrology was conducted. P. hemitomon grew vigorously under saturated (flooding level with the surface of the mat) when compared to inundated (+15 cm flooding) hydrologic conditions, and under enriched (50 g m⁻² year⁻¹) when compared to non-enriched (25 g m⁻² year⁻¹) N. Further, and as inferred from net CO₂ assimilation, shoot biomass and rhizome biomass and length, N-enriched conditions seemed to lessen inundation stress. For all variables the interaction between N and hydrology was non-significant and there was no observable effect of P. We were unable to infer root or mat buoyancy from root specific gravity measurements but it was evident at harvest that saturation or minimal flooding is required for vigorous root and rhizome growth. This study provides insight to the notion that decreased mat buoyancy (and increased flooding level) resulting from sediment deposition associated with Mississippi River diversions could adversely affect TMFM sustainability, but more clearly demonstrates the need to maintain saturated hydrologic conditions for achieving the type of root and rhizome growth we feel is required for TMFM rehabilitation.     

Water depth and biotic insulation: Major determinants of back-swamp plant community composition

Based on phytosociological data, a polythetic divisive classification technique resulted in the delineation of eight broad vegetation types in the back-swamp areas of the Maunachira River System of the Okavango Delta, Botswana. A detrended correspondence analysis indicated that water depth was the major environmental factor influencing the distribution of submerged, floating-leaved and tall, emergent species dominated communities. The remaining communities, with relatively distinct boundaries between each of them, were of short emergent species assemblages rooted in peat deposits with a water depth of less than 0.7 m. Their species composition was not related to water depth, conductivity, pH, redox potential, water temperature or total nitrogen or phosphorus concentrations in the water. The relationship between the present day wetland plant community composition and its environment may be masked by long term, biotic, insulating processes such as the accumulation of resources during peat formation and clonal plant growth. This insulation process does not lead necessarily to long term community stability as has been previously suggested (Mitsch and Gosselink 1986).