Long‐term change within a Neotropical forest: assessing differential functional and floristic responses to disturbance and drought

Disentangling the relative roles of biotic and abiotic forces influencing forest structure, function, and local community composition continues to be an important goal in ecology. Here, utilizing two forest surveys 20‐year apart from a Central American dry tropical forest, we assess the relative role of past disturbance and local climatic change in the form of increased drought in driving forest dynamics. We observe: (i) a net decrease in the number of trees; (ii) a decrease in total forest biomass by 7.7 Mg ha^?1 but when calculated on subquadrat basis the biomass per unit area did not change indicating scale sensitivity of forest biomass measures; (iii) that the decrease in the number of stems occurred mainly in the smallest sizes, and in more moist and evergreen habitats; (iv) that there has been an increase in the proportion of trees that are deciduous, compound leaved and are canopy species, and a concomitant reduction in trees that are evergreen, simple‐leaved, and understory species. These changes are opposite to predictions based on recovery from disturbance, and have resulted in (v) a uniform multivariate shift from a more mesic to a more xeric forest. Together, our results show that over relatively short time scales, community composition and the functional dominance may be more responsive to climate change than recovery to past disturbances. Our findings point to the importance of assessing proportional changes in forest composition and not just changes in absolute numbers. Our findings are also consistent with the hypothesis that tropical tree species exhibit differential sensitivity to changes in precipitation. Predicted future decreases in rainfall may result in quick differential shifts in forest function, physiognomy, and species composition. Quantifying proportional functional composition offers a basis for a predictive framework for how the structure, and diversity of tropical forests will respond to global change.     

Frequent,low‐amplitude disturbances drive high tree turnover rates on a remote,cyclone‐prone Polynesian island

Aim How important are frequent, low‐intensity disturbances to tree community dynamics of a cyclone‐prone forest? We tested the following hypotheses concerning the ‘inter‐cataclysm’ period on a remote Polynesian island: (1) tree turnover would be high and recruitment rates would be significantly higher than mortality; (2) low‐intensity disturbance would result in a marginal increase in tree mortality in the short term; (3) turnover would vary among species and would be associated with plant traits linked to differences in life history; and (4) mortality and recruitment events would be spatially non‐random. Location Tutuila, a volcanic island in the Samoan Archipelago, Polynesia. Methods We censused the tree (stem diameter ≥ 10 cm) community in 3.9 ha of tropical forest three times over a 10‐year period, 1998–2008. We calculated annual mortality, recruitment and turnover rates for 36 tree species. We tested for non‐random spatial patterns and predictors of mortality, and non‐random spatial patterns of tree recruitment. A 2004 cyclone passing within 400 km allowed us to measure the effects of a non‐cataclysmic disturbance on vital rates. Results Annual turnover was 2.8% and annual recruitment was 3.6%; these are some of the highest rates in the tropics, and likely to be a response to a cyclone that passed < 50 km from Tutuila in 1991. Species turnover rates over 10 years were negatively correlated with wood specific gravity, and positively correlated with annual stem diameter increment. Mortality was spatially aggregated, and a function of site, species and an individual’s growth rate. Recruitment was highest on ground with low slope. The low‐magnitude cyclone disturbance in 2004 defoliated 29% of all trees, but killed only 1.8% of trees immediately and increased annual mortality over 5 years by 0.7%. Main conclusions The inter‐cataclysm period on Tutuila is characterized by frequent, low‐amplitude disturbances that promote high rates of tree recruitment and create a dynamic, non‐equilibrium or disturbed island disequilibrium tree community. Species with low wood density and fast growth rates have enhanced opportunities for recruitment between cataclysms, but also higher probabilities of dying. Our results suggest that increases in the frequency of cyclone activity could shift relative abundances towards disturbance‐specialist species and new forest turnover rates.     

Using education as a public relations tool for biotechnology

The advances in the biotechnology industry, and in biosciences research are impressive by any measure, but it is not sufficient just to continue to make spectacular scientific breakthroughs. It is important that the general public is assisted to keep up with the pace of technological change. Some efforts have been made, but they have not been enough. A public relations strategy is required. The biotechnology industry needs to influence public opinion as well as lead discovery. The aims of a public relations campaign should not be just to inform and convince legislators and regulators, but should target the average consumer of the 21st century. There are two areas where the science community must direct its attention if the international public is to be brought along on this biotechnological odyssey: the compulsory school sector – including teachers, students and policy makers; and key sector groups that can be specifically targeted such as farmers, indigenous peoples, horticulturists, food sector people, health professionals, and in particular, the recently retired. If the potential of biotechnological advances is to be realised, scientists must be proactive in educating the general public. This will also involve educating the educators. No amount of public education will completely remove the opposition to genetic engineering, but with an educated public there is an increased opportunity for a fair debate and scare tactics, half-truths and innuendo will gain less traction.     

Contractual National Parks and the Makuleke Community

Contractual national parks in South Africa are established on land owned either by the state or by a group of private individuals, but managed by South African National Parks (SANP) according to the terms of a joint management agreement drawn up by a joint management committee consisting of representatives from SANP and the landowners. Since majority rule in 1994, contractual national parks have been seen as a model through which the country's conservation as well as development objectives can be met, particularly where landowners are previously disadvantaged communities. This study looks at the Makuleke region of Kruger National Park in order to ascertain how successful the contractual national park model is in meeting conservation, social, and economic objectives for the area.     

Spatial and trophic partitioning in cryptic fish communities of shallow subtidal reefs in False Bay, South Africa

Thirty-nine species of cryptic fishes belonging to 16 families were captured on shallow reefs (0-20 m) in False Bay, South Africa using the ichthyocide rotenone. Five samples were collected in each of four depth zones (0-5, 6-10, 11-15 and 16-20 m). The area from which fish were collected in each sample was measured to give an estimate of density. The overall density of cryptic fishes in the area was 3.41 fish m^-2, with the families Congrogadidae and Clinidae being numerically dominant, representing 27.9% and 22.3% of the total sample respectively. The Clinidae were by far the most diverse group, being represented by 17 species, while no other family was represented by more than three species. Multivariate analysis of numerical density revealed that partitioning of spatial resources did occur, with the shallowest samples (0-5 m) forming a group discrete from the deeper samples (6-20 m). Further analysis indicated that the amount of algal cover present was the most important factor influencing community structure, although the abundance of algae is in turn related to depth. The shallowest samples were dominated by members of the families Clinidae, Gobiesocidae and Bythitidae, while the Cheilodactylidae, Tripterygiidae and Ariidae were more important components of deeper water communities (6–20 m). Analysis of percentage volume of prey items in the diets of 21 species revealed that only two species shared diets that were more than 50% similar, and that partitioning of trophic resources was considerable. This revised version was published online in July 2006 with corrections to the Cover Date.     

Changes in Prokaryote and Eukaryote Assemblages Along a Gradient of Hydrocarbon Contamination in Groundwater

Groundwater biota are particularly sensitive to environmental perturbations such as groundwater contamination. The diversity of prokaryotic and eukaryotic biota has been examined along a gradient of chlorinated hydrocarbon (CHC) contamination in the Botany Sands, an urban coastal sand-bed aquifer (Sydney, Australia). Molecular techniques were used to analyze the richness and composition of prokaryote and eukaryote assemblages using 16S and 18S rDNA, respectively. Taxon richness did not change significantly along the gradient for either prokaryotes or eukaryotes; however, significant shifts in assemblage composition were evident for both groups. Assemblage changes were most strongly correlated with concentrations of the major CHC, cis-1,2-dichloroethene, but the concentrations of a number of the contaminants were also correlated, making it difficult to infer if effects were due to any particular contaminant. The presence of cis-1,2-dichloroethene and other secondary ethenes suggests in situ breakdown of the primary CHCs via natural attenuation. The current focus of management of the Botany aquifer is to stop the contaminant plume reaching the adjoining estuary. This approach is clearly justified given the changes evident in the microbial assemblages in the groundwater, which are a likely consequence of the contamination.