Small‐plot studies comparing pheromone and juice baits for mass‐trapping invasive Synanthedon myopaeformis in Canada

Recent introduction of Synanthedon myopaeformis (Borkhausen) (Lepidoptera: Sesiidae) into organic apple‐growing areas of Canada has stimulated research on semiochemical‐based management of this European pest. Replicated, small‐plot (0.16 ha) experiments were conducted to compare sex pheromone, 3Z,13Z‐octadecadienyl acetate (10 mg), Concord grape juice (300 ml), or their combination, as mass‐trapping lures at trap densities equivalent to 12.5, 25, 50, and 100 traps ha^?1. Total numbers of male and female moths removed from test plots increased significantly with trap density in all juice‐based mass‐trapping experiments. In pheromone mass‐trapping experiments, however, total catches of males did not increase significantly as trap densities were increased and catches appeared to plateau with 25–50 traps ha^?1. With pheromone‐based mass‐trapping, significantly fewer males were caught in pheromone‐baited assessment traps at the centre of each mass‐trapping plot than in identical traps in untreated plots. This reduction is indicative of significant trap interference or trap ‘shut‐down’. Increasing the density of juice‐based mass‐trapping had no effect on catches of male or female moths in juice‐baited assessment traps, indicating a short range of attraction and lack of interference between juice traps. Pheromone‐ and juice‐based mass trapping removed similar numbers of males at each trap density tested, respectively, but summed catches of males and females were greatest with juice baits. Combining pheromone and juice into a single mass‐trapping treatment (50 traps ha^?1) did not significantly increase catches of males or females relative to either treatment alone. If a practical bisexual mass‐trapping system is going to be developed for S. myopaeformis, then identification of volatile kairomones in Concord grape juice may be useful.     

Optimal pheromone trap density for mass trapping cacao mirids

Sahlbergella singularis Haglund and Distantiella theobroma (Distant) (Heteroptera: Miridae) are the key insect pests of cacao in Ghana and elsewhere in West Africa. Since 1954, spraying with synthetic insecticides has been the principal means of controlling these pests. In West Africa, environmental concerns, economic stimuli, and unreliable access to insecticides have stimulated interest in ecologically more benign mirid control strategies as an alternative to a total reliance on insecticides. Males of both mirid species, and those of the less damaging Bryocoropsis laticollis Schumacher, respond to the same synthetic sex pheromone blend, so pheromone‐based strategies may provide control as well as monitoring opportunities. Pheromone traps were deployed for 3 months at nine densities between two and 30 traps per 0.1 ha plot (20–300 traps ha^?1) plus an untreated control treatment in a replicated large‐scale field experiment on mature mixed Upper Amazon hybrid cacao in Ghana, in order to determine the optimal dispenser density for mass trapping, lure‐and‐kill, and/or lure‐and‐infect. At the end of the trapping period, mirid populations in the various treatments were assessed by insecticide knockdown on 400 trees and by searches to hand height on 1 200 trees, together with an assessment of mirid damage. In total 781 S. singularis and 235 D. theobroma were captured in the pheromone traps. The optimal dispenser density for S. singularis was 150 traps ha^?1. Over 300 traps ha^?1 was probably optimal for D. theobroma as a smaller proportion of the population was captured, and numbers caught per trap displayed no decline with increasing trap density. From insecticide knockdowns, mirid population density was estimated at 220–230 ha^?1, 63% of which were D. theobroma. Too few pods and orthotropic shoots were damaged by mirids to establish the efficacy of pheromone trapping for mirid control.     

How varying pest and trap densities affect Tribolium castaneum capture in pheromone traps

The red flour beetle, Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae), is an important insect pest in food processing facilities. Pheromone trapping is frequently used to monitor red flour beetle populations in structures; however, the optimal trap density and the relationship between trap captures and beetle density is not known. Two experiments were performed concurrently in environmentally controlled 30‐m² walk‐in chambers to determine the relationship between aggregation pheromone trap captures of red flour beetles and beetle and trap number. In one experiment, beetle density was kept constant at 200 individuals per chamber while trap number was varied from 1 to 8, and in the other experiment trap number remained constant at one per chamber while beetle density varied from 20 to 800 individuals. Results indicated that approximately one out of 23 red flour beetles were captured in a trap. Number of beetles captured in traps increased significantly as beetle density increased; however, the proportion of beetles captured remained consistent across beetle densities with a mean of 4.7 ± 0.6% of individuals captured. Trap captures varied significantly with trap placement within experimental chambers, indicating that subtle differences in the trapping environment can influence trap captures. Data suggested that trap densities of 0.07–0.10 m^?2 (2–3 traps per chamber) would maximize trap capture, whereas a trap density of 0.13 m^?2 (four traps per chamber) would maximize the predictive ability of a trapping equation estimating beetle density from trap captures. Results provide information needed to more thoroughly explore how environmental factors might influence red flour beetle trap capture in the absence of changes in beetle density. Further understanding of these relationships will allow for more accurate assessments of absolute beetle density from pheromone trap capture data.     

Persistent effects of aerial applications of disparlure on gypsy moth: trap catch and mating success

In forest plots treated aerially with a plastic laminated flake formulation (Disrupt^® II) of the gypsy moth sex pheromone disparlure to disrupt gypsy moth, Lymantria dispar (L.) (Lepidoptera: Lymantriidae), mating was monitored the year of treatment and 1–2 years after treatment to determine the effects of the treatment on suppression of trap catch and mating success. In the year of treatment, there was a greater than 95% reduction in trap catch and a greater than 98% reduction in mating success compared to controls. One year after treatment at a dosage of 37.5 g active ingredient (a.i.) ha^?1, trap catch was reduced by 46–56% and mating success was reduced by 60–79%. Both trap catch and mating success were significantly reduced compared to controls in plots treated 1 year previously at 15 g a.i. ha^?1. Trap catch, but not mating success, was significantly reduced 2 years after treatment at 37.5 g a.i. ha^?1. The efficacy of mating disruption (MD) treatments in the Slow‐the‐Spread of the Gypsy Moth program was significantly reduced 2 years compared to 1 year after treatment. No such reduction was observed in plots treated with aerial applications of Bacillus thuringiensis kurstaki. The higher apparent efficacy of MD treatments 1 year after application may result to some extent from the suppression of moth capture in pheromone traps from the persistent effects of the previous year's treatment.     

Carbon pool densities and a first estimate of the total carbon pool in the Mongolian forest‐steppe

The boreal forest biome represents one of the most important terrestrial carbon stores, which gave reason to intensive research on carbon stock densities. However, such an analysis does not yet exist for the southernmost Eurosiberian boreal forests in Inner Asia. Most of these forests are located in the Mongolian forest‐steppe, which is largely dominated by Larix sibirica. We quantified the carbon stock density and total carbon pool of Mongolia's boreal forests and adjacent grasslands and draw conclusions on possible future change. Mean aboveground carbon stock density in the interior of L. sibirica forests was 66 Mg C ha^?1, which is in the upper range of values reported from boreal forests and probably due to the comparably long growing season. The density of soil organic carbon (SOC, 108 Mg C ha^?1) and total belowground carbon density (149 Mg C ha^?1) are at the lower end of the range known from boreal forests, which might be the result of higher soil temperatures and a thinner permafrost layer than in the central and northern boreal forest belt. Land use effects are especially relevant at forest edges, where mean carbon stock density was 188 Mg C ha^?1, compared with 215 Mg C ha^?1 in the forest interior. Carbon stock density in grasslands was 144 Mg C ha^?1. Analysis of satellite imagery of the highly fragmented forest area in the forest‐steppe zone showed that Mongolia's total boreal forest area is currently 73 818 km², and 22% of this area refers to forest edges (defined as the first 30 m from the edge). The total forest carbon pool of Mongolia was estimated at ~ 1.5?1.7 Pg C, a value which is likely to decrease in future with increasing deforestation and fire frequency, and global warming.     

Density-dependent growth performance of Indian major carps in rainwater reservoirs

The study was carried out to evaluate growth performance of Indian major carps at different stocking densities in rainwater reservoirs. In this experiment, the absolute growth performance of Catla catla, Labeo rohita and Cirrhinus mrigala at stocking densities of 5000, 8000 and 11 000 fingerlings per hectare was 377.7, 215.4 and 241.9; 370.2, 186.7 and 219.1; and 306.7, 163.4 and 180.6 g, respectively. The recorded biomass yield at 5000, 8000 and 11 000 fingerlings per hectare was 1035, 1572 and 1573 kg ha^?1 per 180 days of culture. The effect of stocking density on production performance (performance index, PI) was highly significant (P < 0.05) at the higher stocking density of 11 000 ha^?1, while there was no significant variation between PI at stocking densities of 5000 and 8000 ha^?1. This indicates optimum production performance at 8000 ha^?1, where yield is significantly higher (P < 0.05) than yield at 5000 ha^?1 and almost equal to the yield at 11 000 ha^?1. An increase in stocking density from 8000 to 11 000 ha^?1, however, showed a sharp decline in average mean body weight of each species, even with supplemental feeding. With an increase in stocking density, the biomass yield increased to an optimum (1572 kg ha^?1), with no substantial increase thereafter. Reductions in growth, which occurred at high density, did not appear to be due to poor water quality as the water quality did not differ significantly among various treatments. Thus, the reduced survival and growth at high density appears to be a behavioural interaction or physiological response to density itself.     

Evaluating a sustainability index for nutrients in a short rotation energy cropping system

In dryland environments 3–5 year rotations of tree crops and agriculture represent a major potential bioenergy feedstock and a means to restore landscape hydrologic balances and phytoremediate sites, while maintaining food production. In soils with low natural fertility, the long‐term viability of these systems will be critically affected by site nutrient status and subsequent cycling of nutrients. A nutrient assimilation index (NAI) was developed to allow comparison of species and tree component nutrient assimilation and to optimize nutrient management, by quantifying different strategies to manage site nutrients. Biomass, nutrient export and nutrient use efficiency were assessed for three short rotation tree crop species. Nutrient exports following harvest at 3 years of high density (4000 trees ha^?1) were consistently higher in Pinus radiata, with values of 85 kg ha^?1 of N, 11kg ha^?1 of P, and 62 kg ha^?1 of K, than Eucalyptus globulus and Eucalyptus occidentalis. Component NAI was generally in the order of leaf?1 for N in leaves of P. radiata to 4.7 Mg kg^?1 for P in stem‐wood of E. occidentalis, indicating higher sustainability of wood biomass compared with leaf biomass. The leaves for each species contained between 40 and 60% of the total nutrient contents while comprising around 25–30% of the total biomass. These nutrient exports via biomass removal are similar to those that follow 3 years of wheat production in the same region, indicating there is no additional drawdown of nutrient reserves during the tree cropping phase of the rotation.     

Carbon storage,structure and composition of miombo woodlands in Tanzania’s Eastern Arc Mountains

We determine the aboveground biomass and carbon storage (ABGC) of trees and the herbaceous layer in miombo woodland in the Eastern Arc Mountains (EAM) of Tanzania. In four 1‐ha sample plots in Nyanganje and Kitonga Forests, we measured all trees ≥10 cm diameter alongside height and wood mass density. The plots contained an average of 20 tree species ha^?1 (range 11–29) and 344 stems ha^?1 (range 281–382) with Shannon diversity values of 1.05 and 1.25, respectively. We weighted nine previously published woody savannah allometric models based on whether: (i) the model was derived from the same geographical region; (ii) the model included tree height/wood mass density in addition to stem diameter; and (iii) sample size was used to fit the model. The weighted mean ABGC storage from the nine models range from 13.5 ± 2 to 29.8 ± 5 Mg ha^?1. Measured ABGC storage in the herbaceous layer, using the wet combustion method, adds 0.55 ± 0.02 Mg C ha^?1. Estimates suggest that EAM miombo woodlands store a range of 13–30 Mg ha^?1 of carbon. Although the estimates suggest that miombo woodlands store significant quantities of carbon, caution is required as this is the first estimate based on in situ data.     

Simulating switchgrass biomass production across ecoregions using the DAYCENT model

The production potential of switchgrass (Panicum virgatum L.) has not been estimated in a Mediterranean climate on a regional basis and its economic and environmental contribution as a biofuel crop remains unknown. The objectives of the study were to calibrate and validate a biogeochemical model, DAYCENT, and to predict the biomass yield potential of switchgrass across the Central Valley of California. Six common cultivars were calibrated using published data across the US and validated with data generated from four field trials in California (2007–2009). After calibration, the modeled range of yields across the cultivars and various management practices in the US (excluding California) was 2.4–41.2 Mg ha^?1 yr^?1, generally compatible with the observed yield range of 1.3–33.7 Mg ha^?1 yr^?1. Overall, the model was successfully validated in California; the model explained 66–90% of observed yield variation in 2007–2009. The range of modeled yields was 2.0–41.4 Mg ha^?1 yr^?1, which corresponded to the observed range of 1.3–41.1 Mg ha^?1 yr^?1. The response to N fertilizer and harvest frequency on yields were also reasonably validated. The model estimated that Alamo (21–23 Mg ha^?1 yr^?1) and Kanlow (22–24 Mg ha^?1 yr^?1) had greatest yield potential during the years after establishment. The effects of soil texture on modeled yields tended to be consistent for all cultivars, but there were distinct climatic (e.g., annual mean maximum temperature) controls among the cultivars. Our modeled results suggest that early stand maintenance of irrigated switchgrass is strongly dependent on available soil N; estimated yields increased by 1.6–5.5 Mg ha^?1 yr^?1 when residual soil mineral N was sufficient for optimal re‐growth. Therefore, management options of switchgrass for regional biomass production should be ecotype‐specific and ensure available soil N maintenance.     

Productivity and water use efficiency of Agave americana in the first field trial as bioenergy feedstock on arid lands

Agave species are high‐yielding crassulacean acid metabolism (CAM) plants, some of which are grown commercially and recognized as potential bioenergy species for dry regions of the world. This study is the first field trial of Agave species for bioenergy in the United States, and was established to compare the production of Agave americana with the production of Agave tequilana and Agave fourcroydes, which are produced commercially in Mexico for tequila and fiber. The field trial included four experimental irrigation levels to test the response of biomass production to water inputs. After 3 years, annual production of healthy A. americana plants reached 9.3 Mg dry mass ha^?1 yr^?1 (including pup mass) with 530 mm of annual water inputs, including both rainfall and irrigation. Yields in the most arid conditions tested (300 mm yr^?1 water input) were 2.0–4.0 Mg dry mass ha^?1 yr^?1. Agave tequilana and Agave fourcroydes were severely damaged by cold in the first winter, and produced maximum yields of only 0.04 Mg ha^?1 yr^?1 and 0.26 Mg ha^?1 yr^?1, respectively. The agave snout weevil (Scyphophorus acupunctatus) emerged as an important challenge for A. americana cropping, killing a greater number of plants in the higher irrigation treatments. Physiological differences in A. americana plants across irrigation treatments were most evident in the warmest season, with gas exchange beginning up to 3 h earlier and water use efficiency declining in treatments with the greatest water input (780 mm yr^?1 water input). Yields were lower than previous projections for Agave species, but results from this study suggest that A. americana has potential as a bioenergy crop and would have substantially reduced irrigation requirements relative to conventional crops in the southwestern USA. Challenges for pest management and harvesting must still be addressed before an efficient production system that uses Agave can be realized.     

Seasonal dynamics of above‐ and below‐ground biomass and nitrogen partitioning in Miscanthus × giganteus and Panicum virgatum across three growing seasons

The first replicated productivity trials of the C4 perennial grass Miscanthus × giganteus in the United States showed this emerging ligno‐cellulosic bioenergy feedstock to provide remarkably high annual yields. This covered the 5 years after planting, leaving it uncertain if this high productivity could be maintained in the absence of N fertilization. An expected, but until now unsubstantiated, benefit of both species was investment in roots and perennating rhizomes. This study examines for years 5–7 yields, biomass, C and N in shoots, roots, and rhizomes. The mean peak shoot biomass for M. × giganteus in years 5–7 was 46.5 t ha^?1 in October, declining to 38.1 t ha^?1 on completion of senescence and at harvest in December, and 20.7 t ha^?1 declining to 11.3 t ha^?1 for Panicum virgatum. There was no evidence of decline in annual yield with age. Mean rhizome biomass was significantly higher in M. × giganteus at 21.5 t ha^?1 compared to 7.2 t ha^?1 for P. virgatum, whereas root biomass was similar at 5.6–5.9 t ha^?1. M. × giganteus shoots contained 339 kg ha^?1 N in August, declining to 193 kg ha^?1 in December, compared to 168 and 58 kg ha^?1 for P. virgatum. The results suggest substantial remobilization of N to roots and rhizomes, yet still a substantial loss with December harvests. The shoot and rhizome biomass increase of 33.6 t ha^?1 during the 2‐month period between June and August for M. × giganteus corresponds to a solar energy conversion of 4.4% of solar energy into biomass, one of the highest recorded and confirming the remarkable productivity potential of this plant.     

Survival and growth of early life stages of leaf fish (Monocirrhus polyacanthus,Heckel 1840) cultured under different stocking densities and live food densities

The objective of this study was to evaluate the effects of different live foods, (Artemia sp. and Moina minuta), and different stocking densities on the larval rearing success of the leaf fish, Monocirrhus polyacanthus. A completely randomized factorial design (3 × 3; three replicates) was used. Two subsequent experiments were performed for each live food, using three food densities (100, 200 and 300 prey per larva) and three stocking densities (10, 15 and 20 larvae L^?1). Fish were fed twice a day. Water quality parameters pH (4.08–4.02), dissolved oxygen (3.7–3.6 mg L^?1), temperature (27.9–27.8°C), conductivity (147.2–127.4 μs cm^?1) and total ammonia (0.78–0.38 μg L^?1) were determined. Weight gain, specific growth rate (SGR), body mass, relative condition factor and survival were evaluated. The water quality was influenced by the live food and stocking densities. Fish fed M. minuta showed better weight gain, specific growth ratio (SGR), biomass gain, relative condition factor and survival than in the other treatment. Artemia sp. showed no improved influence on the larvae performance subjected to different treatments. The beneficial role in growth and survival of leaf fish larva when fed with M. minuta is discussed.     

First record of Beauveria bassiana (Ascomycota: Clavicipitaceae) infecting Cerambyx welensii (Coleoptera: Cerambycidae) and pathogenicity tests using a new bioassay method

The pathogenicity of Beauveria bassiana on Cerambyx welensii is first reported. Three native fungal isolates from Badajoz (Spain) were bioassayed on neonates using cork oak disks and LC₅₀s were 1.16–1.76 × 10⁵ and 0.30–0.61 × 10⁵ spores/ml on the 7th and 14th day post-inoculation. The fungus is potentially a biocontrol agent of C. welensii.     

Density‐dependent reproduction and pollen limitation in an invasive milkweed,Calotropis procera (Ait.) R. Br. (Apocynaceae)

Calotropis procera (Ait.) R.Br. (Apocynaceae), an invasive woody milkweed, has expanded its range in northern Australia affecting rangeland and pastoral productivity. While self‐compatibility should enhance the species range expansion, spread of C. procera is limited by the availability of larger wasp and bee species that are able to vector its solid pollinia. Pollination efficiency is thus likely dependent on both pollinator abundance and plant density. Calotropis procera flowers year round in Australia but fruiting is limited to the warm months of the year when pollinators are most abundant, indicating that seasonal regulation of reproduction may be due to pollinator limitation. We examine the propositions that C. procera reproduction is regulated by the interaction between plant population density and pollinator pressure and that low pollinator pressure causes low per capita plant fecundity. All pollinators belonged to Order Hymenoptera and pollinator composition was similar at six of the seven sites. Fruit production per plant (fecundity) was lower above and below intermediate densities (350–550 plants ha^?1) of flowering plants with evidence of a weak Allee effect at lower plant density. Pollinator visitation rates per plant were low at high and low plant densities, and greatest at intermediate densities, while pollen supplementation experiments showed that C. procera is pollen limited (Pollen Limitation Index_fruit = 0.9) even at intermediate densities. Pollen limitation caused by low pollinator pressure at low plant densities and pollinator satiation at high plant densities may account for these fruit production trends. Management should be conducted in the colder months when pollinator pressure is low and plants are not reproducing. In addition, where stand eradication cannot be achieved in one attempt, management should reduce flowering plants to below intermediate densities where the fecundity per plant is low.     

Growth response of cultured larvae of silver therapon Leiopotherapon plumbeus (Kner, 1864) in outdoor tanks in relation to fertilizer type and fish density

This study evaluated the effects of fertilizer type and fish density on early growth and survival of silver therapon Leiopotherapon plumbeus (Kner, 1864) larvae reared in outdoor tanks. In the first experiment, larvae (1.92 ± 0.09 mm total length) were stocked into nine, 4 m³ tanks at an initial density of 0.5 larvae L^?1 and reared for 42 days at an ambient temperature of 28.8–30.7°C. Three treatments with three replicates each were compared: organic (chicken manure, OF) or inorganic fertilizers (ammonium phosphate, IF) applied once every 2 weeks, and the unfertilized (NF) tanks serving as the control group. Water quality, zooplankton densities, survival or growth of L. plumbeus larvae did not vary significantly in either fertilized or unfertilized tanks. Fertilization resulted in elevated nutrient concentrations, which did affect survival (2.10%–6.07%) of the fish larvae. In the second experiment, larvae were stocked at densities of 0.4 or 0.6 larvae L^?1 in tanks fertilized at 4–5 days interval with OF and IF for 30 days. Growth performance of L. plumbeus larvae was affected by fish density, with significantly larger (20.04 ± 2.65 mm in total length) and higher specific growth rate (SGR; 6.97 ± 0.48% day^?1) at 0.4 larvae L^?1 than at 0.6 L^?1. Fry production did not vary significantly between fish density treatment groups given the same fertilizer types, but survival rates were improved at 0.4 L^?1. Together, production of L. plumbeus larvae in outdoor tanks can be optimized at a lower stocking density, regardless of the type of fertilizer used.     

Soil nutrient budgets following projected corn stover harvest for biofuel production in the conterminous United States

Increasing demand for food and biofuel feedstocks may substantially affect soil nutrient budgets, especially in the United States where there is great potential for corn (Zea mays L) stover as a biofuel feedstock. This study was designed to evaluate impacts of projected stover harvest scenarios on budgets of soil nitrogen (N), phosphorus (P), and potassium (K) currently and in the future across the conterminous United States. The required and removed N, P, and K amounts under each scenario were estimated on the basis of both their average contents in grain and stover and from an empirical model. Our analyses indicate a small depletion of soil N (?4 ± 35 kg ha^?1) and K (?6 ± 36 kg ha^?1) and a moderate surplus of P (37 ± 21 kg ha^?1) currently on the national average, but with a noticeable variation from state to state. After harvesting both grain and projected stover, the deficits of soil N, P, and K were estimated at 114–127, 26–27, and 36–53 kg ha^?1 yr^?1, respectively, in 2006–2010; 131–173, 29–32, and 41–96 kg ha^?1 yr^?1, respectively, in 2020; and 161–207, 35–39, and 51–111 kg ha^?1 yr^?1, respectively, in 2050. This study indicates that the harvestable stover amount derived from the minimum stover requirement for maintaining soil organic carbon level scenarios under current fertilization rates can be sustainable for soil nutrient supply and corn production at present, but the deficit of P and K at the national scale would become larger in the future.     

A comparison of various mating disruption technologies for control of two internally feeding Lepidoptera in apples

Sex pheromone mating disruption (MD) is an approach used to control several moth pest species of pome fruit by disrupting the ability of the males to find females and consequently prevent mating. The following experiments were performed to determine the effectiveness of several new and experimental sex pheromone MD technologies, and dispenser densities for simultaneous control of the codling moth (CM), Cydia pomonella (L.), and the oriental fruit moth (OFM), Grapholita molesta (Busck) (both Lepidoptera: Tortricidae), in Pennsylvania apple orchards. In one study, three MD approaches to control CM and oriental fruit moth – CM and OFM Disrupt Micro‐Flakes, Isomate CM/OFM TT, and both a CideTrak OFM and a CideTrak CM dispenser containing both codlemone and pear ester – and an insecticides‐only treatment were compared over the course of 2 years. In the other studies, the efficacy of several CheckMate Duel dispenser densities (i.e., 250, 375, 425, and 500 dispensers ha^?1) were compared against Isomate CM/OFM TT, and an insecticides‐only treatment. The CideTrak CM/pear ester combination and Isomate CM/OFM TT treatments both substantially reduced CM captures in traps in 2007 and 2008. Meanwhile, OFM trap shutdown was highest in the CheckMate Duel densities of 375 (99.9 ± 0.08%) and 500 dispensers ha^?1 (98.9 ± 0.07%) and the Isomate CM/OFM TT treatment (98.0 ± 1.13%), and lowest in the 250 dispensers ha^?1 density treatment (94.3 ± 3.23%). In orchards where OFM is the dominant pest species, a CheckMate Duel dispenser density of 375 ha^?1 is necessary for effective control, whereas higher densities are needed to control CM.     

Changes in soil carbon stocks under perennial and annual bioenergy crops

Bioenergy crops are expected to provide biomass to replace fossil resources and reduce greenhouse gas emissions. In this context, changes in soil organic carbon (SOC) stocks are of primary importance. The aim of this study was to measure changes in SOC stocks in bioenergy cropping systems comparing perennial (Miscanthus × giganteus and switchgrass), semi‐perennial (fescue and alfalfa), and annual (sorghum and triticale) crops, all established after arable crops. The soil was sampled at the start of the experiment and 5 or 6 years later. SOC stocks were calculated at equivalent soil mass, and δ¹³C measurements were used to calculate changes in new and old SOC stocks. Crop residues found in soil at the time of SOC measurements represented 3.5–7.2 t C ha^?1 under perennial crops vs. 0.1–0.6 t C ha^?1 for the other crops. During the 5‐year period, SOC concentrations under perennial crops increased in the surface layer (0–5 cm) and slightly declined in the lower layers. Changes in δ¹³C showed that C inputs were mainly located in the 0–18 cm layer. In contrast, SOC concentrations increased over time under semi‐perennial crops throughout the old ploughed layer (ca. 0–33 cm). SOC stocks in the old ploughed layer increased significantly over time under semi‐perennials with a mean increase of 0.93 ± 0.28 t C ha^?1 yr^?1, whereas no change occurred under perennial or annual crops. New SOC accumulation was higher for semi‐perennial than for perennial crops (1.50 vs. 0.58 t C ha^?1 yr^?1, respectively), indicating that the SOC change was due to a variation in C input rather than a change in mineralization rate. Nitrogen fertilization rate had no significant effect on SOC stocks. This study highlights the interest of comparing SOC changes over time for various cropping systems.     

Landscape Patterns of Sapling Density,Leaf Area,and Aboveground Net Primary Production in Postfire Lodgepole Pine Forests,Yellowstone National Park (USA)

Causes and implications of spatial variability in postfire tree density and understory plant cover for patterns of aboveground net primary production (ANPP) and leaf area index (LAI) were examined in ninety 11-year-old lodgepole pine (Pinus contorta var. latifolia Engelm.) stands across the landscape of Yellowstone National Park (YNP), Wyoming, USA. Field studies and aerial photography were used to address three questions: (1) What is the range and spatial pattern of lodgepole pine sapling density across the burned Yellowstone landscape and what factors best explain this variability? (2) How do ANPP and LAI vary across the landscape and is their variation explained by abiotic factors, sapling density, or both? (3) What is the predicted spatial pattern of ANPP and LAI across the burned Yellowstone landscape? Stand density spanned six orders of magnitude, ranging from zero to 535,000 saplings ha^?1, and it decreased with increasing elevation and with increasing distance from unburned forest (r ²?=?0.37). Postfire densities mapped from 1:30,000 aerial photography revealed that 66% of the burned area had densities less than 5000 saplings ha^?1 and approximately 25% had densities greater than 10,000 saplings ha^?1; stand density varied spatially in a fine-grained mosaic. New allometric equations were developed to predict aboveground biomass, ANPP, and LAI of lodgepole pine saplings and the 25 most common herbaceous and shrub species in the burned forests. These allometrics were then used with field data on sapling size, sapling density, and percent cover of graminoid, forb, and shrub species to compute stand-level ANPP and LAI. Total ANPP averaged 2.8 Mg ha^?1y^?1 but ranged from 0.04 to 15.12 Mg ha^?1y^?1. Total LAI averaged 0.80 m² m^?2 and ranged from 0.01 to 6.87 m² m^?2. Variation in ANPP and LAI was explained by both sapling density and abiotic factors (elevation and soil class) (ANOVA, r ²?=?0.80); abiotic variables explained 51%–54% of this variation. The proportion of total ANPP contributed by herbaceous plants and shrubs declined sharply with increasing sapling density (r ²?=?0.72) and increased with elevation (r ²?=?0.36). However, total herbaceous productivity was always less than 2.7 Mg ha^?1 y^?1, and herbaceous productivity did not compensate for tree production when trees were sparse. When extrapolated to the landscape, 68% of the burned landscape was characterized by ANPP values less than 2.0 Mg ha^?1y^?1, 22% by values ranging from 2 to 4 Mg ha^?1y^?1, and the remaining 10% by values greater than 4 Mg ha^?1y^?1. The spatial patterns of ANPP and LAI were less heterogeneous than patterns of sapling density but still showed fine-grained variation in rates. For some ecosystem processes, postfire spatial heterogeneity within a successional stage may be similar in magnitude to the temporal variation observed through succession.     

Miscanthus × giganteus leaf senescence,decomposition and C and N inputs to soil

Energy crops are currently promoted as potential sources of alternative energy that can help mitigate the climate change caused by greenhouse gases (GHGs). The perennial crop Miscanthus × giganteus is considered promising due to its high potential for biomass production under conditions of low input. However, to assess its potential for GHG mitigation, a better quantification of the crop's contribution to soil organic matter recycling under various management systems is needed. The aim of this work was to study the effect of abscised leaves on carbon (C) and nitrogen (N) recycling in a Miscanthus plantation. The dynamics of senescent leaf fall, the rate of leaf decomposition (using a litter bag approach) and the leaf accumulation at the soil surface were tracked over two 1‐year periods under field conditions in Northern France. The fallen leaves represented an average yearly input of 1.40 Mg C ha^?1 and 16 kg N ha^?1. The abscised leaves lost approximately 54% of their initial mass in 1 year due to decomposition; the remaining mass, accumulated as a mulch layer at the soil surface, was equivalent to 7 Mg dry matter (DM) ha^?1 5 years after planting. Based on the estimated annual leaf‐C recycling rate and a stabilization rate of 35% of the added C, the annual contribution of the senescent leaves to the soil C was estimated to be approximately 0.50 Mg C ha^?1yr^?1 or 10 Mg C ha^?1 total over the 20‐year lifespan of a Miscanthus crop. This finding suggested that for Miscanthus, the abscised leaves contribute more to the soil C accumulation than do the rhizomes or roots. In contrast, the recycling of the leaf N to the soil was less than for the other N fluxes, particularly for those involving the transfer of N from the tops of the plant to the rhizome.