Environmental and economic costs of soil erosion and conservation benefits

Soil erosion is a major environmental threat to the sustainability and productive capacity of agriculture. During the last 40 years, nearly one-third of the world's arable land has been lost by erosion and continues to be lost at a rate of more than 10 million hectares per year. With the addition of a quarter of a million people each day, the world population's food demand is increasing at a time when per capita food productivity is beginning to decline.     

Rainfall variability,carbon cycling,and plant species diversity in a mesic grassland

Ecosystem responses to increased variability in rainfall, a prediction of general circulation models, were assessed in native grassland by reducing storm frequency and increasing rainfall quantity per storm during a 4-year experiment. More extreme rainfall patterns, without concurrent changes in total rainfall quantity, increased temporal variability in soil moisture and plant species diversity. However, carbon cycling processes such as soil CO2 flux, CO2 uptake by the dominant grasses, and aboveground net primary productivity (ANPP) were reduced, and ANPP was more responsive to soil moisture variability than to mean soil water content. Our results show that projected increases in rainfall variability can rapidly alter key carbon cycling processes and plant community composition, independent of changes in total precipitation.     

Electrical synapses control hippocampal contributions to fear learning and memory

The role of electrical synapses in synchronizing neuronal assemblies in the adult mammalian brain is well documented. However, their role in learning and memory processes remains unclear. By combining Pavlovian fear conditioning, activity-dependent immediate early gene expression, and in vivo electrophysiology, we discovered that blocking neuronal gap junctions within the dorsal hippocampus impaired context-dependent fear learning, memory, and extinction. Theta rhythms in freely moving rats were also disrupted. Our results show that gap junction-mediated neuronal transmission is a prominent feature underlying emotional memories.     

Who Complains About Alligators? Cognitive and Situational Factors Influence Behavior Toward Wildlife

Understanding perceptual and situational factors underlying nuisance complaints can help managers maintain carnivore populations while mitigating conflicts with people. Our study uses data from a mail survey (n = 467 complainants about nuisance alligators, and n = 669 random Florida residents) and a three-step binary logistic regression analysis to examine how general attitudes, specific beliefs, and situational factors influence the behavior of reporting nuisance alligators. Residence adjacent to fresh water, the presence of outdoor pets, higher risk belief scores, higher nuisance belief scores, higher education, and older age were all related to complaining about an alligator, whereas general attitude toward alligators was not. Results are consistent with the “specificity principle” for attitude–behavior correspondence and emphasize the importance of situational factors as behavioral determinants. Targeted harvest areas can help to manage complaints in marginal habitats where risk from alligators is persistent. Information about protective behaviors and benefits of alligators can motivate residents to avoid dangerous encounters.     

Reducing aggression between freshwater crayfish (Cherax destructor Clark: Decapoda, Parastacidae) by increasing habitat complexity

The culture of decapod crustaceans occurs worldwide. Aggressive behaviour is common in many of the species, including crayfish. This is problematic when it physically damages stock and reduces quality. Numerous biological factors influence crayfish fighting behaviour but the influence of environmental factors is not well known. This study investigated the effect of habitat complexity on the agonistic interactions of Australian freshwater crayfish, more commonly referred to locally as ‘yabbies’ (Cherax destructor Clark). Solid objects that provided structure but not shelter were used to manipulate the complexity of the environment. The number, duration and dynamic of aggressive interactions within groups of animals were observed and recorded in simple and complex environments. Habitat complexity reduced both the number of agonistic interactions and the total time spent interacting. It is suggested that the structure in the environment distracts crayfish from the presence of others or physically blocks contact between them. These results extend our knowledge of crayfish social behaviour and may provide opportunities for reducing detrimental aggressive interactions in the aquaculture industry.     

Survival and growth of western rock lobster Panulirus cygnus (George) fed formulated diets with and without fresh mussel supplement

Two trials were conducted to compare the growth and survival of western rock lobster Panulirus cygnus post-pueruli and year 1 juveniles fed different diets. Trial 1 compared lobsters fed a formulated pelletised feed developed for Panulirus ornatus supplemented with fresh mussels (Mytilus edulis) two days per week, with lobsters fed a daily diet of pellets. Trial 2 compared lobsters fed the pellet-mussel supplement diet with those fed a daily diet of fresh mussels.In the first trial, diet treatment did not significantly affect survival, although it was higher in tanks supplemented with mussels. Growth of post-pueruli and year 1 juveniles fed the pellet diet (0.03 g/day; 0.14 g/day, respectively) was significantly lower than growth of post-pueruli and year 1 juveniles fed pellet-mussel supplement diets (0.07 g/day; 0.2 g/day, respectively). Year 1 lobsters fed the pellet-mussel supplement diet consumed considerably less pellet (0.27 vs 0.40 g pellet dry matter/day (DM/day)) than those fed pellets indicating that they will preferentially favour mussel over pellet diets. Feed conversion ratio (FCR) was significantly better for lobsters fed the pellet-mussel supplement diet as a result of the poor growth of pellet-fed lobsters.In the second trial, survival was significantly higher for lobsters fed mussels only. Growth of post-pueruli fed a mussel diet (0.14 g/day) was significantly higher than those fed pellet-mussel diets (0.11 g/day), but there was no significant difference in growth for year 1 juveniles (0.33 g/day). Feed intake of mussel on a dry matter basis was higher than pellet intake for both size classes, with mussel intake being more than double pellet intake for post-pueruli (0.20 vs 0.49 g DM/day).Poor growth of P. cygnus on a pellet only diet indicates that the current formulation for P. ornatus may be inadequate for P. cygnus. However, as pellet intake declined dramatically for year 1 lobsters offered a mussel supplement, and pellet consumption was significantly lower than mussel consumption, it is more likely that poor growth may be attributed to inadequate palatability and intake. The similarly good survival of lobsters fed pellet and pellet-mussel diets indicates that the pellet diet is an acceptable maintenance diet for P. cygnus, but is not suitable for maximising growth for this species. Further research is needed to improve palatability, intake and potentially nutritional composition of this pellet diet before its suitability for P. cygnus is assured.     

Planning for appropriate forestry enterprises: lessons from rural development experience in Third World Countries

Over the last decade, forestry has become increasingly more involved with and integrated into the more general rural development (RD) process in the Third World. In doing so, forestry joins an activity that has itself been developing and maturing for some three decades and more, in the course of which a good deal of useful experience has been accumulated. This paper attempts to distill from that experience lessons that will be helpful in forestry development planning. This focus is first on the constraints that have affected RD, sometimes quite severely, in terms of resources, organization, policy, and the socio-political sphere. Second, the paper evaluates the experience with rural institutions as vehicles for promoting and nurturing RD, with particular emphasis on local organizations and popular participation in them. The third focus is on applying some of these lessons to the forestry sector, using as examples the issues of employment creation, regional growth, women's participation and distributional equity of development benefits.