Pastoralists' responses to variation of rangeland resources in time and space.

We explore the response of pastoralists to rangeland resource variation in time and space, focusing on regions where high variation makes it unlikely that an economically viable herd can be maintained on a single management unit. In such regions, the need to move stock to find forage in at least some years has led to the evolution of nomadism and transhumance, and reciprocal grazing agreements among the holders of common-property rangeland. The role of such informal institutions in buffering resource variation is well documented in some Asian and African rangelands, but in societies with formally established private-property regimes, where we focus, such institutions have received little attention. We examine agistment networks, which play an important role in buffering resource variation in modern-day Australia. Agistment is a commercial arrangement between pastoralists who have less forage than they believe they require and pastoralists who believe they have more. Agistment facilitates the movement of livestock via a network based largely on trust. We are concerned exclusively with the link between the characteristics of biophysical variation and human aspects of agistment networks, and we developed a model to test the hypothesis that such a link could exist. Our model builds on game theory literature, which explains cooperation between strangers based on the ability of players to learn whom they can trust. Our game is played on a highly stylized landscape that allows us to control and isolate the degree of spatial variation and spatial covariation. We found that agistment networks are more effective where spatial variation in resource availability is high, and generally more effective when spatial covariation is low. Policy design that seeks to work with existing social networks in rangelands has potential, but this potential varies depending on localized characteristics of the biophysical variability.     

Changes in body size, abundance, and energy allocation in rockfish assemblages of the northeast Pacific.

Fish body size, a key driver of many aspects of fish population biology and ecology, is affected by fisheries that deplete the largest individuals. Rockfish (genus Sebastes) are a diverse group that has been heavily fished on the U.S. West Coast in recent decades. We examined trawl survey data from 1980 to 2001 to determine spatial and temporal trends in body size and density of 16 shelf rockfish species, including six that are considered overfished. Mean individual mass and maximum observed mass declined in the majority of species in one or more zoogeographic regions between central California and Washington. Density changes were far more variable in time and space, but in all regions, density declines were most often associated with large-bodied rockfish. We next estimated the impact of size and density changes on energy consumption and fecundity in a five-species rockfish assemblage that includes bocaccio (S. paucispinis), a large-bodied, overfished species. Indexes of both consumption and fecundity by the assemblage increased in the southern portion of the study area between 1980 and 2001 but decreased in the northern portion. Allocation of energy and reproductive potential within the assemblage shifted dramatically: relative to bocaccio, total energy consumption and fecundity indexes for the other four species increased by orders of magnitude from 1980 to 2001. These changes in community structure may affect the ability of bocaccio and other large rockfish species to recover from overfishing, especially in light of long-term declines in zooplankton production that may also be affecting rockfish size and production. Addressing these issues may require a regional, multispecies management approach.     

Terrestrische ökotoxikologische Testmethoden für die Tropen

Goal, Scope, and Background

Soil organisms play a crucial role in terrestrial ecosystems. Plant Protection Products (PPPs) are known to affect these organisms and might have negative impacts on soil functions influenced by these organisms. Little research has been done to day on the impact of PPPs on tropical ecosystems. Therefore, in this study it was investigated whether the effects of pesticides differ between tropical and temperate regions and whether data generated under temperate conditions can be used for the Environmental Risk Assessment (ERA) in tropical regions.

Methods

The effects of one fungicide (Carbendazim) and one insecticide (lambda-Cyhalothrin) on soil invertebrates (earthworms and arthropods) and functional parameters (organic matter (OM) breakdown, feeding rate) were evaluated in semi-field tests using Terrestrial Model Ecosystems (TMEs) and in field tests using litter-bags. The soil for the TMEs was extracted from the same site near Manaus (Amazonas, Brazil) where the field test was conducted (see Part 1, Römbke et al. 2005 〈DOI: http://dx.doi.org/10.1065/uswf2004.12.088.1〉). The soil was acid clay, typical for tropical regions. In the TMEs the standard test species as well as native tropical species were introduced. Several application scenarios, selected according to their relevance for practical conditions, were realized in TME-tests and field (duration: 150 and 365 days, respectively). Finally, an Environmental Risk Assessment (ERA) for the two chemicals was performed.

Results and Conclusions

The results from the TME-tests show that both test chemicals (depending on their concentration) had toxic effects on the tested organisms and organic matter breakdown, but not on the feeding rates. In the field organic matter breakdown was affected for some time too, but effects on single species were, with one exception (the native earthworm Andiorrhinus amazonicus) not observed; a result probably influenced by the small size of the test plots. Observed differences in OM breakdown between control and treated TMEs were often significant, while due to the higher variability even with differences >10% between means this was not the case in the field.

Recommendation and Perspective

According to the preliminary results of the Environmental Risk, Assessment presented here, the use of the three model chemicals in the tropics (e.g. in Brazil) can cause a damage to the environmental compartment soil. Therefore, a more detailed investigation of these PPPs is recommended, in particular a better evaluation of the exposure (residue analysis). In general, the work performed in Amazonia can be summarised as follows: (1) Depending on the properties of the PPP, the effects of pesticides in tropical resp, temperate regions can differ. (2) If a PPP is going to be used in the tropics, data from tests modified for these conditions should be performed and their results should be incorporated in an Environmental Risk Assessment (ERA) for tropical regions.     

Age-related foetal sex ratio bias in Iberian red deer (<Emphasis Type="Italic">Cervus elaphus hispanicus</Emphasis>): are male calves too expensive for growing mothers?

Several theories predict offspring biases towards males or females with increasing reproductive resources of the mother to maximize reproductive returns by offspring, or as a result of prohibitive cost of the most expensive sex for young mothers or those in poor condition. This study examines foetus sex of 221 harvested hinds in a food-supplemented game estate for 10 years, according to hind age class (yearlings, subadults or adults), precise age, body mass and condition, and jaw length. A logistic model showed that hinds had a greater probability of bearing a male foetus with increasing age class, but not with any other variable. The greatest bias was found in yearling hinds. After controlling for age class and mass, jaw length was smaller in pregnant compared to non-pregnant yearlings and subadults, which suggests a trade-off between reproduction and growth. The bias towards females in yearlings increased as gestation proceeded, which suggests that the bias might be a result of selective abortion of male foetuses. Although results do not exclude an investment in males to increase number of grand-offspring, they suggest that young hinds may produce daughters as a trade-off between low energetic-cost offspring and their need to grow.Communicated by S. Krackow     

Parasite-dependent protocooperation

We thank A. Ferreira, UNESP, for his continued assistance in our studies, and E., A. and H. Fowler for their constant assistance and moral support.     

Impact of generated solar radiation on simulated crop growth and yield

The availability of observed daily solar radiation (OSR) is restricted to recent years. Its estimation through different methods is necessary to develop long-term data sets for agricultural and environmental applications. The objective of this study was to analyze the impact of using generated daily solar radiation (GSR) on simulated growth and yield of cotton, maize, and peanut. Nine locations representing Georgia's major crop belt were selected. Daily weather data from the Georgia Automated Environmental Monitoring Network (AEMN), including solar radiation, maximum and minimum temperature, and precipitation, were duplicated. The OSR was removed from one set and then generated using a stochastic procedure. The Cropping System Models (CSM)-CROPGRO-Cotton, CERES-Maize, and CROPGRO-Peanut of the Decision Support System for Agrotechnology Transfer (DSSAT) v4 were used to simulate crop growth and yield at each location with both OSR and GSR and for rainfed and irrigated conditions. The statistical analysis included summary statistics, Pearson's coefficient of correlation, mean squared deviation (MSD) and its components, namely: squared bias (SB), squared difference between standard deviations (SDSD), lack of correlation weighted by the standard deviations (LCS), and regressions. Within locations, for the three crops under rainfed and irrigated conditions, GSR did not significantly affect simulated total evapotranspiration and aboveground biomass and yields. For the three crops, deviations of simulated water use and yields from GSR with respect to simulated water use and yields from OSR were lower for the rainfed than for the irrigated conditions. Yields from the CSM-CROPGRO-Cotton and -Peanut models had lower deviations than yields from the CSM-CERES-Maize model. LCS was the major component of the MSD suggesting that the extent of the difference between standard deviations of GSR and OSRG could affect the outputs of the crop models. Nevertheless, for most locations none of the MSD components of the GSR showed significant correlation with simulated yields and the overall performance of the models was not affected. It can be concluded based on the results of this study that GSR can be used as an input for crop model simulation models when OSR is not available.     

Insights on common dolphin (<Emphasis Type="Italic">Delphinus delphis</Emphasis>) social organization from genetic analysis of a mass-stranded pod

Compared to terrestrial mammals, little is known of cetacean social systems as they are generally less accessible to behavioral investigations due to their aquatic environment. The present study investigates group structure of the pelagic common dolphin, Delphinus delphis, using genetic markers. Tissue samples from 52 individuals representing a recent live mass-stranding event were compared to 42 single strandings taken from presumably different groups. The mass-stranding event occurred in 2002 on the French coast of the English Channel, whereas the single strandings were collected between 1993 and 2003 along the western coast of France (Bay of Biscay and English Channel). Analysis of mitochondrial DNA control region sequences indicated that genetic variability within the mass-stranded pod was similar to variability observed in single strandings. The mass-stranded group was composed of 41 different mitochondrial haplotypes or matrilines while the single strandings revealed 29 different haplotypes. Analysis of 11 microsatellite loci revealed that average relatedness of the mass-stranded pod was not different from average relatedness among all single strandings suggesting that individuals within the group had no closer kin relationships than animals taken from presumably different groups. These results do not support a matriarchal system and suggest that common dolphins constituting a pod are not necessarily genetically related.     

Analysis of temporal and spatial dichotomous PM air samples in the El Paso-Cd. Juarez air quality basin.

This paper presents and discusses the results obtained from the gravimetric and chemical analyses of the 24-hr average dichotomous samples collected from five sites in the El Paso-Cd. Juarez air quality basin between August 1999 and March 2000. Gravimetric analysis was performed to determine the temporal and spatial variations of PM2.5 (particulate matter less than 2.5 microm in diameter) and PM25-10 (particulate matter less than 10 pm but greater than 2.5 microm in diameter) mass concentrations. The results indicate that approximately 25% of the PM10 (i.e., PM25 + PM25-10) concentration is composed of PM2.5. Concurrent measurements of hourly PM concentrations and wind speed showed strong diurnal patterns of the regional PM pollution. Results of X-ray fluorescence (XRF) elemental analyses were compared to similar but limited studies performed by the Texas Natural Resource Conservation Commission (TNRCC) in 1990 and 1997. Major elements from geologic sources-Al, Si, Ca, Na, K, Fe, and Ti-accounted for 35% of the total mass concentrations in the PM2.5-10 fraction, indicating that geologic sources in the area are the dominant PM sources. Levels of toxic trace elements, mainly considered as products of anthropogenic activities, have decreased significantly from those observed in 1990 and 1997.     

Remote Antarctic feeding ground important for east Australian humpback whales

Understanding the dynamics of population recovery is particularly complex when an organism has multiple, remote breeding and feeding grounds separated by one of the longest known migration routes. This study reports on the most comprehensive assessment of humpback whale (Megaptera novaeangliae) movements between remote Antarctic waters south of New Zealand and east Australia (EA), and the migratory corridors and breeding grounds of Australia and Oceania. A total of 112 individual whales were identified; 57 from microsatellites and 61 by fluke with 23 % (n = 26) matched to sites outside Antarctica. Despite large datasets from other southern regions being included in the comparison, the whales were predominantly linked to EA (n = 24). Only two matches to the Oceania catalogues directly north was surprising; therefore the primary feeding grounds of these endangered whales still remain unknown. The confirmation of the Balleny Islands as an important feeding ground for EA whales could provide an insight into reasons behind the rapid recovery of this population. Determining the feeding grounds of Oceania’s whales may explain whether prey energetics or migration length are limiting factors to their recovery and will allow an understanding of future ecosystem changes in these whales.