Comparative Analysis of Tuber Development in Six Sweet Potato (Ipomoea batatas (L.) Lam) Cultivars: 1. Tuber initiation, tuber growth and partition of assimilate

Differences in tuber initiation, tuber growth and partitionof assimilate during development were investigated in six localsweet potato cultivars. Study of the quantitative morphogenesisof root types in the sweet potato root system indicated thattuber initiation was completed by 8 weeks after planting inmost cultivars and frustrated thereafter. Subsequent differencesin patterns of tuber development were not obviously relatedto final tuber yield. Thus, high yield resulted either froma short period of rapid tuber growth or a longer period of slowertuber growth. Maximum shoot growth was achieved by week 12 inall except one cultivar, and the cessation of shoot growth resultedin either increases or decreases in tuber growth rate or hadno affect on the rate of tuber growth (cv. A28/7). The partitionof assimilate to tubers at final harvest was the parameter mostclosely related to the yield of the six cultivars studied, butthere was some evidence that such partition was related to totaldry weight. It is suggested that limiting factors in sweet potatotuber yield, e.g. assimilate production and transport or capacityfor tuber growth varied with the cultivar studied.     

Detection of resistance to aphids in cereals

Resistance to Sitobion avenae and Metopolophium dirhodum was assessed by caging aphids on the upper part of mature tillers. Despite variation in the results, considered to be due mainly to differences amongst plants of different ages, certain cultivars consistently supported fewer aphids. Winter wheats Anna Migliori and Marsters Al and Indian spring barleys EB 921 and DL 107 were identified as resistant cultivars useful for reference in further work.     

The Continuous Culture of Luminous Bacteria: a Luminostat

A method has been designed for the continuous culture of luminous bacteria. The control system for the culture uses a combination of luminescence and optical density as a light signal received by a photomultiplier. This combined signal operates pumps which exchange the growth medium. Using this method, a culture of brightly luminescing bacteria was maintained for periods up to 3 weeks.     

Multi‐species distribution modelling highlights the Adelaide Geosyncline,South Australia,as an important continental‐scale arid‐zone refugium

The mainland portion of the Adelaide Geosyncline (Mount Lofty and Flinders Ranges) has been postulated as an important arid‐zone climate refugium for Australia. To test the sensitivity of this putative Australian arid biome refugium to contemporary climate change, we compared Generalized Additive Modelling and MaxEnt distribution models for 20 vascular plant species. We aimed to identify shared patterns to inform priority areas for management. Models based on current climate were projected onto a hypothetical 2050 climate with a 1.5°C increase in temperature and 8% decrease in rainfall. Individual comparisons and combined outputs of logistic models for all 20 species showed range contraction to shared refugia in the Flinders Ranges and southern Mount Lofty Ranges. Modelling suggests the Flinders Ranges will experience species turnover while suitable climatic habitat will be retained in the Mount Lofty Ranges for the current suite of species. Fragmentation of the southern Mount Lofty Ranges poses management challenges for conserving species diversity with warming and drying. Although projected models must be interpreted carefully, they suggest the region will remain an important but threatened refugium for mesic species at a continental scale.     

Phenology determines seasonal variation in ectoparasite loads in a natural insect population

1. The extent to which individuals are parasitised is a function of exposure to parasites and the immune response, which in ectotherms may be associated with temperature. 2. We test the hypothesis that seasonal variation in ectoparasite burden is driven by temperature using an extensive mark‐release‐recapture study of adult Coenagrion puella (L.) (Zygoptera) as a model system. Mite counts were taken both at capture and on a subset of subsequent recaptures over two entire, consecutive breeding seasons. 3. Emergence date was the most significant factor in determining individual differences in mite burden, and mean counts for individuals emerging on the same days showed strong unimodal relationships with time of season. Subsequent recounting of mites on a subset of individuals showed that patterns of loss of mites were similar between seasons. 4. While temperature did not significantly affect mite burdens within seasons and ectoparasite prevalence was very similar across the two seasons, intensity of infection and rate of mite gain in unparasitised individuals were significantly higher in the cooler season. 5. We demonstrate that, while temperature may modulate the invertebrate immune response, this modulation does not manifest in variations in mite burdens in natural populations.     

Industrial Symbiosis in China: A Case Study of the Guitang Group

The Guitang Group (GG), which operates one of China's largest sugar refineries, has been developing and implementing an internal and external industrial symbiosis strategy for more than four decades. The GG first invested in developing its own collection of downstream companies to utilize nearly all byproducts of sugar production. This strategy has generated new revenues and reduced environmental emissions and disposal costs, while simultaneously improving the quality of sugar. Internally, the GG's complex consists of interlinked production of sugar, alcohol, cement, compound fertilizer, and paper and includes recycling and reuse. Externally, the GG has established a strong customer base as a result of its product quality, has worked to maintain and expand its supply base through technological and economic incentives to farmers (and even to competitors), and has had to react to a strong government presence that fundamentally affects its operations. Operations to date support some of the fundamental concepts of industrial symbiosis. Significant challenges exist, though, if the company is to continue to prosper in the volatile globalized sugar market.     

Forest succession and prey availability influence the strength and scale of terrestrial‐aquatic linkages in a headwater salamander system

1. Trophic linkages between terrestrial and aquatic ecosystems are common and sensitive to disruption. However, there is little information on what causes variation in the strength and spatial scale of these linkages. 2. In the highly aquatic adults of the headwater salamander Gyrinophilus porphyriticus (family Plethodontidae), use of terrestrial prey decreases along a gradient from early‐ to late‐successional riparian forests. To understand the cause of this relationship, we tested the predictions that (i) terrestrial prey abundance is lower in late‐successional forests, and (ii) G. porphyriticus adults cannot move as far from the stream to forage in late‐successional forests, thus limiting access to terrestrial prey. 3. We established 100‐m long study reaches on six headwater streams in the Hubbard Brook Experimental Forest, New Hampshire. Three reaches were in early‐successional forests and three were in late‐successional forests. We conducted pitfall trapping for invertebrate prey in June and July of 2005, with three traps at 0, 2, 5 and 10 m from the stream at each reach. In June, July and August of 2004 and 2005, nighttime salamander surveys were conducted at each reach along ten, 10‐m long by 2.5‐m wide transects perpendicular to the stream. 4. Abundance of terrestrial prey was consistently lower in late‐successional forests, suggesting that consumption of terrestrial prey by G. porphyriticus is affected by prey abundance. Contrary to our prediction, G. porphyriticus adults moved farther from the stream in late‐successional forests, suggesting that habitat conditions in late‐successional forests do not limit movement away from the stream, and that lower abundances of terrestrial prey in these forests may cause salamanders to move farther from streams. 5. Our results provide novel insight on the extent of terrestrial habitat use by G. porphyriticus. More broadly, these results indicate that major habitat gradients, such as forest succession, can affect the strength and scale of terrestrial‐aquatic linkages. Application of this insight to the design of vegetation buffers along headwater streams would have widespread benefits to freshwater ecosystems.     

Influences of logging history and riparian forest characteristics on macroinvertebrates and brook trout (Salvelinus fontinalis) in headwater streams (New Hampshire, U.S.A.)

1. Logging can strongly affect stream macroinvertebrate communities, but the direction and magnitude of these effects and their implications for trout abundance are frequently region‐specific and difficult to predict. 2. In first‐order streams in northern New England (U.S.A.) representing a chronosequence of logging history (<2 to >80 years since logging), we measured riparian forest conditions, stream macroinvertebrate community characteristics and brook trout (Salvelinus fontinalis) abundance. Principal component analysis was used to collapse forest data into two independent variables representing variation in logging history, riparian forest structure and canopy cover. We used these data to test whether logging history and associated forest conditions were significant predictors of macroinvertebrate abundance and functional feeding group composition, and whether brook trout abundance was related to logging‐associated variation in invertebrate communities. 3. Catchments with high PC1 scores (recently logged, high‐density stands with low mean tree diameter) and low PC2 scores (low canopy cover) had significantly higher total macroinvertebrate abundance, particularly with respect to chironomid larvae (low PC2 scores) and invertebrates in the grazer functional feeding group (high PC1 scores). In contrast, proportional representation of macroinvertebrates in the shredder functional feeding group increased with time since logging and canopy cover (high PC2 scores). Brook trout density and biomass was significantly greater in young, recently logged stands (high PC1 scores) and was positively related to overall macroinvertebrate abundance. In addition, three variables – trout density, invertebrate abundance and shredder abundance – successfully discriminated between streams that were less‐impacted versus more‐impacted by forestry. 4. These results indicate that timber harvest in northern New England headwater streams may shift shredder‐dominated macroinvertebrate communities supporting low trout abundance to a grazer/chironomid‐dominated macroinvertebrate community supporting higher trout abundance. However, while local effects on brook trout abundance may be positive, these benefits may be outweighed by negative effects of brook trout on co‐occurring species, as well as impairment of habitat quality downstream. Research testing the generality of these patterns will improve understanding of how aquatic ecosystems respond to anthropogenic and natural trajectories of forest change.