Long-term impacts of harvest residue management on nutrition, growth and productivity of an exotic pine plantation of sub-tropical Australia

Residue retention is an important issue in evaluating the sustainability of production forestry. However, its long-term impacts have not been studied extensively, especially in sub-tropical environments. This study investigated the long-term impact of harvest residue retention on tree nutrition, growth and productivity of a F1 hybrid (Pinus elliottii var. elliottii × Pinus caribaea var. hondurensis) exotic pine plantation in sub-tropical Australia, under three harvest residue management regimes: (1) residue removal, RR0; (2) single residue retention, RR1; and (3) double residue retention, RR2. The experiment, established in 1996, is a randomised complete block design with 4 replicates. Tree growth measurements in this study were carried out at ages 2, 4, 6, 8 and 10 years, while foliar nutrient analyses were carried out at ages 2, 4, 6 and 10 years. Litter production and litter nitrogen (N) and phosphorus (P) measurements were carried out quarterly over a 15-month period between ages 9 and 10 years. Results showed that total tree growth was still greater in residue-retained treatments compared to the RR0 treatment. However, mean annual increments of diameter at breast height (MAID) and basal area (MAIB) declined significantly after age 4 years to about 68-78% at age 10 years. Declining foliar N and P concentrations accounted for 62% (p < 0.05) of the variation of growth rates after age 4 years, and foliar N and P concentrations were either marginal or below critical concentrations. In addition, litter production, and litter N and P contents were not significantly different among the treatments. This study suggests that the impact of residue retention on tree nutrition and growth rates might be limited over a longer period, and that the integration of alternative forest management practices is necessary to sustain the benefits of harvest residues until the end of the rotation.

Long-term response of corn to limited irrigation and crop rotations

Dwindling water supplies for irrigation are prompting alternative management choices by irrigators. Limited irrigation, where less water is applied than full crop demand, may be a viable approach. Application of limited irrigation to corn was examined in this research. Corn was grown in crop rotations with dryland, limited irrigation, or full irrigation management from 1985 to 1999. Crop rotations included corn following corn (continuous corn), corn following wheat, followed by soybean (wheat-corn-soybean), and corn following soybean (corn-soybean). Full irrigation was managed to meet crop evapotranspiration requirements (ETc). Limited irrigation was managed with a seasonal target of no more than 150 mm applied. Precipitation patterns influenced the outcomes of measured parameters. Dryland yields had the most variation, while fully irrigated yields varied the least. Limited irrigation yields were 80% to 90%> of fully irrigated yields, but the limited irrigation plots received about half the applied water. Grain yields were significantly different among irrigation treatments. Yields were not significantly different among rotation treatments for all years and water treatments. For soil water parameters, more statistical differences were detected among the water management treatments than among the crop rotation treatments. Economic projections of these management practices showed that full irrigation produced the most income if water was available. Limited irrigation increased income significantly from dryland management.

Long-term assessment of efficacy of permeable pond covers for odour reduction

Three anaerobic ponds used to store and treat piggery wastes were fully covered with permeable materials manufactured from polypropylene geofabric, polyethylene shade cloth and supported straw. The covers were assessed in terms of efficacy in reducing odour emission rates over a 40-month period. Odour samples were collected from the surface of the covers, the surface of the exposed liquor and from the surface of an uncovered (control) pond at one of the piggeries. Relative to the emission rate of the exposed liquor at each pond, the polypropylene, shade cloth and straw covers reduced average emission rates by 76%, 69% and 66%, respectively. At the piggery with an uncovered control pond, the polypropylene covers reduced average odour emission rates by 50% and 41%, respectively. A plausible hypothesis, consistent with likely mechanisms for the odour reduction and the olfactometric method used to quantifying the efficacy of the covers, is offered.

Long-term variation of tropical rock lobster panulirus ornatus (decapoda, palinuridae) growth inTorres Strait, Australia

This analysis of all carapace length measurements collected between 1989 and 2009, during scientific surveys, describes the variation of tropical rock lobster, Panulirus ornatus, somatic growth in Torres Strait. Multiple models of carapace length frequency distributions were compared by maximum likelihood to determine which hypotheses were most supported by the data. The best model assumed sex and cohort-specific Von Bertalanffy's parameters. These estimates are consistent with results derived from tagging data collected in the 1980s and provide new information on parameters' uncertainty. In the past two decades, growth rates have fluctuated inter-annually without displaying any distinctive trend. Associated uncertainties are large, suggesting that sampling will need to be intensified in order to detect an effect of climate change.

Validation of the effects of a single one second hypochlorite floral dip on Botrytis cinerea incidence following long-term shipment of cut roses

The effect of a pre-shipment hypochlorite treatment on botrytis incidence was evaluated in a large number of rose cultivars and under different long-term storage conditions. Application parameters, stability and sources of hypochlorite were investigated. Irrespective of the type of packaging and shipment conditions, roses that received a pre-shipment treatment with 100 to 150 mg/L hypochlorite showed a significantly decreased botrytis incidence compared to non-hypochlorite treated roses. The hypochlorite treatment generally was more effective than a comparable treatment with commercial fungicides. Dipping the flower heads for approximately one second in a hypochlorite solution was more effective than spraying the heads. In few cases minor hypochlorite-induced damage on the petal tips was observed at higher concentrations (>200 mg/L). Apart from the effect on botrytis incidence, the treatment resulted in reduced water loss that may have an additional beneficial effect on the eventual flower quality. It is concluded that, apart from other obvious measures to reduce botrytis incidence (prevention of high humidity at the flower heads) a pre-shipment floral dip in 100 to 150 mg/L hypochlorite from commercial household bleach is an easy and cost effective way to reduce botrytis incidence following long term storage/transportation of roses. © 2015, International Society for Horticultural Science. All rights reserved.

The effect of row configuration on yield reliability in grain sorghum: II. Modelling the effects of row configuration

In recent years many sorghum producers in the more marginal (<600 mm annual rainfall) cropping areas of Qld and northern NSW have utilised skip row configurations in an attempt to improve yield reliability and reduce sorghum production risk. But will this work in the long run? What are the trade-offs between productivity and risk of crop failure? This paper describes a modelling and simulation approach to study the long-term effects of skip row configurations. Detailed measurements of light interception and water extraction from sorghum crops grown in solid, single and double skip row configurations were collected from three on-farm participatory research trials established in southern Qld and northern NSW. These measurements resulted in changes to the model that accounted for the elliptical water uptake pattern below the crop row and reduced total light interception associated with the leaf area reduction of the skip configuration. Following validation of the model, long-term simulation runs using historical weather data were used to determine the value of skip row sorghum production as a means of maintaining yield reliability in the dryland cropping regions of southern Qld and northern NSW.

Standard yet unusual mechanisms of long-distance dispersal: Seed dispersal of Corymbia torelliana by bees

Mellitochory, seed dispersal by bees, has been implicated in long-distance dispersal of the tropical rain forest tree, Corymbia torelliana (Myrtaceae). We examined natural and introduced populations of C. torelliana for 4 years to determine the species of bees that disperse seeds, and the extent and distance of seed dispersal. The mechanism of seed dispersal by bees was also investigated, including fruit traits that promote dispersal, foraging behaviour of bees at fruits, and the fate of seeds. The fruit structure of C. torelliana, with seed presented in a resin reward, is a unique trait that promotes seed dispersal by bees and often results in long-distance dispersal. We discovered that a guild of four species of stingless bees, Trigona carbonaria, T. clypearis, T. sapiens, and T. hockingsi, dispersed seeds of C. torelliana in its natural range. More than half of the nests found within 250 m of fruiting trees had evidence of seed transport. Seeds were transported minimum distances of 20-220 m by bees. Approximately 88% of seeds were dispersed by gravity but almost all fruits retained one or two seeds embedded in resin for bee dispersal. Bee foraging for resin peaked immediately after fruit opening and corresponded to a peak of seed dispersal at the hive. There were strong correlations between numbers of seeds brought in and taken out of each hive by bees (r = 0.753-0.992, P < 0.05), and germination rates were 95 ± 5%. These results showed that bee-transported seeds were effectively dispersed outside of the hive soon after release from fruits. Seed dispersal by bees is a non-standard dispersal mechanism for C. torelliana, as most seeds are dispersed by gravity before bees can enter fruits. However, many C. torelliana seeds are dispersed by bees, since seeds are retained in almost all fruits, and all of these are dispersed by bees.

Impacts of a fuel oil spill on seagrass meadows in a subtropical port, Gladstone, Australia - The value of long-term marine habitat monitoring in high risk areas.

We used an established seagrass monitoring programme to examine the short and longer-term impacts of an oil spill event on intertidal seagrass meadows. Results for potentially impacted seagrass areas were compared with existing monitoring data and with control seagrass meadows located outside of the oil spill area. Seagrass meadows were not significantly affected by the oil spill. Declines in seagrass biomass and area 1 month post-spill were consistent between control and impact meadows. Eight months post-spill, seagrass density and area increased to be within historical ranges. The declines in seagrass meadows were likely attributable to natural seasonal variation and a combination of climatic and anthropogenic impacts. The lack of impact from the oil spill was due to several mitigating factors rather than a lack of toxic effects to seagrasses. The study demonstrates the value of long-term monitoring of critical habitats in high risk areas to effectively assess impacts.

Long-term frequent prescribed fire decreases surface soil carbon and nitrogen pools in a wet sclerophyll forest of Southeast Queensland, Australia

Prescribed fire is one of the most widely-used management tools for reducing fuel loads in managed forests. However the long-term effects of repeated prescribed fires on soil carbon (C) and nitrogen (N) pools are poorly understood. This study aimed to investigate how different fire frequency regimes influence C and N pools in the surface soils (0–10 cm). A prescribed fire field experiment in a wet sclerophyll forest established in 1972 in southeast Queensland was used in this study. The fire frequency regimes included long unburnt (NB), burnt every 2 years (2yrB) and burnt every 4 years (4yrB), with four replications. Compared with the NB treatment, the 2yrB treatment lowered soil total C by 44%, total N by 54%, HCl hydrolysable C and N by 48% and 59%, KMnO4 oxidizable C by 81%, microbial biomass C and N by 42% and 33%, cumulative CO2–C by 28%, NaOCl-non-oxidizable C and N by 41% and 51%, and charcoal-C by 17%, respectively. The 4yrB and NB treatments showed no significant differences for these soil C and N pools. All soil labile, biologically active and recalcitrant and total C and N pools were correlated positively with each other and with soil moisture content, but negatively correlated with soil pH. The C:N ratios of different C and N pools were greater in the burned treatments than in the NB treatments. This study has highlighted that the prescribed burning at four year interval is a more sustainable management practice for this subtropical forest ecosystem.