Limited response to nursery-stage mycorrhiza inoculation of <Emphasis Type="Italic">Shorea</Emphasis> seedlings planted in rubber agroforest in Jambi,Indonesia

We transplanted Shorea selanica and Shorea lamellata seedlings that either had or had not received ectomycorrhiza (EcM) Scleroderma columnare inoculum, commercially available and prescribed as standard practice in nursery, into rubber gardens of different age and plot history. The objective was to assess whether or not absence of fungal inoculants restricted seedling survival, growth, nutrient uptake and EcM formation in the first 2 years after out-planting in Jambi. Inoculation with EcM fungi in nursery had only limited positive effects on growth in height and diameter or N and P uptake, but it enhanced survival in the period 6–24 months after outplanting in all plots. With or without nursery stage inoculation, S. selanica and S. lamellata can be used for enrichment planting or reforestation in Sumatra as the species respond well to high light intensities. Presence of up to five morphotypes of EcM confirmed the availability of inoculum also in second generation rubber agroforests. Internal transcribe spacer sequencing revealed no S. columnare could be identified from the ectomycorrhizal roots of S. lamellata and S. selanica.     

The importance of integrating landscape ecology in habitat models: isolation-driven occurrence of north island robins in a fragmented landscape

Although the role of habitat fragmentation in species declines is well recognised, the effect of habitat quality on species distributions is often studied using presence–absence models that ignore metapopulation dynamics. We compared three approaches to model the presence–absence of North Island robins in 400 sites among 74 fragments of native forest in a 15,000-ha agricultural landscape in New Zealand. The first approach only considered local habitat characteristics, the second approach only considered metapopulation factors (patch size and isolation), and the third approach combined these two types of factors. The distribution of North Island robins was best predicted by patch isolation, as their probability of occurrence was negatively correlated with isolation from neighbouring patches and from the closest major forests, which probably acted as a source of immigrants. The inclusion of habitat factors gave only a slight increase in predictive power and indicated that robins were more likely to occur in areas with tall canopy, tall understory and low density of young trees. We modelled the effect of isolation using an index of functional patch connectivity based on dispersal behaviour of radio-tracked juveniles, and this functional index greatly improved the models in comparison to classical indices relying on Euclidean distances. This study highlights the need to incorporate functional indices of isolation in presence–absence models in fragmented landscapes, as species occurrence can otherwise be a misleading predictor of habitat quality and lead to wrong interpretations and management recommendations.     

A reevaluation of alternate bearing in pistachio

Studies documenting pistachio fruiting patterns (Pistacia vera L.) conclude this species shows evidence of alternate bearing; fruit production fluctuates between an ‘on’ year of high yields and an ‘off’ year of low yields. However, alternate bearing in pistachio has never been statistically tested. We collected yields of 4288 trees over six years to test for alternate bearing in a mature orchard planted with ‘Kerman’ scions grafted onto P. integerrima rootstock – the combination planted on the bulk of the acreage in California. A majority (58%) of the trees exhibited statistically significant alternate bearing patterns. Yet 42% showed yield patterns that were indistinguishable from random fluctuations, the standard measure of alternate bearing (I) was only modest (mean I = 0.48), and I varied considerably among trees (range = 0.04–0.83). These findings support that pistachio shows alternate bearing behavior but suggest alternate bearing is less ubiquitous and fruiting patterns are more complex than previously suspected. The presence of such a diversity of yield dynamics creates considerable challenges for crop management and research.     

Wetlands: conservation's poor cousins

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Balanced exploitation and coexistence of interacting,size‐structured,fish species

This paper examines some effects of exploitation on a simple ecosystem containing two interacting fish species, with life histories similar to mackerel (Scomber scombrus) and cod (Gadus morhua), using a dynamic, size‐spectrum model. Such models internalize body growth and mortality from predation, allowing bookkeeping of biomass at a detailed level of individual predation and growth and enabling scaling up to the mass balance of the ecosystem. Exploitation set independently for each species with knife‐edge, size‐at‐entry fishing can lead to collapse of cod. Exploitation to achieve a fixed ratio of yield to productivity across species can also lead to collapse of cod. However, harvesting balanced to the overall productivity of species in the exploited ecosystem exerts a strong force countering such collapse. If balancing across species is applied to a fishery with knife‐edge selection, size distributions are truncated, changing the structure of the system and reducing its resilience to perturbations. If balancing is applied on the basis of productivity at each body size as well as across species, there is less disruption to size‐structure, resilience is increased, and substantially greater biomass yields are possible. We note an identity between the body size at which productivity is maximized and the age at which cohort biomass is maximized. In our numerical results based on detailed bookkeeping of biomass, cohort biomass reaches its maximum at body masses <1 g, unlike standard yield‐per‐recruit models, where body growth and mortality are independent externalities, and cohort biomass is maximized at larger body sizes.     

Is spawning stock biomass a robust proxy for reproductive potential?

Reference points based on fishing mortality (F) and spawning stock biomass (SSB) are a requirement of many fisheries management frameworks. SSB is assumed to be a proxy for stock reproductive potential (SRP). Limit reference points based on SSB are used to indicate the level of biomass below which productivity is affected. SSB fails to account for changes in fecundity, egg viability and sex ratio, and it has been argued that total egg production (TEP) provides a better reflection of SRP. We explore how accounting for TEP impacts limit reference points and evidence for a relationship between stock and recruit. Time series of SSB and TEP are compared for three North Sea stocks: cod (Gadus morhua), herring (Clupea harengus) and plaice (Pleuronectes platessa). Dynamics based on TEP are different from those based on SSB for cod and plaice, but the stock–recruit relationships were not ‘improved’ using TEP. Shifts in productivity (spawner per recruit) occur in all three time series and SSB underestimated uncertainty. Yet again, it was shown that assumptions of stationarity about fish population productivity are incorrect. We argue that the use of TEP does improve the realism in our understanding of stock dynamics, and demographically, more complex management strategy evaluation is required to develop management procedures that are robust to uncertainty and integrate F and the demographic health of a stock. Empirical feedback control systems based on fisheries independent indices including surveys of eggs, larvae, recruits, juveniles or spawning adults should be evaluated and compared to traditional approaches.     

Identification of <Emphasis Type="Italic">Ascochyta rabiei</Emphasis> disease resistance in chickpea genotypes

Ascochyta blight (AB) disease, caused by the fungus Ascochyta rabiei, is a major yield limiting factor of chickpea in Australia and around the world. The aggressiveness of six A. rabiei isolates was identified using 3 chickpea varieties (Jimbour, Flipper and Yorker). These AB isolates were isolated from chickpea fields in northern NSW, one of the major chickpea production regions in Australia. Each of the six isolates produced a different aggressiveness pattern and isolate 4859 was found to be the most aggressive. The AB resistance in 16 international and Australian chickpea genotypes was then investigated by inoculating the plants with the most aggressive isolate and a mixture of the other 5 isolates. Resistance to both the most aggressive isolate and the mixed isolates has been identified in 5 genotypes (ICCV 98813, Flipper, ICCV 05111, ICCV 98801, Jimbour #1) while 10 entries (Howzat, ICCV 06108 and ICCV 98818, Jimbour, ICCV 96852, ICCV 06107, ICCV 98816, Yorker, FLIP97-114C, ICCV 96853) were moderately resistant. Only one genotype (Bumper) appeared to be susceptible to both inoculums. There was large variation observed in the pathogenicity of the isolates suggesting that the six AB isolates represent several different pathogen strains. Significant differences in leaf infection rate, plant infection rate, plant death rate and disease development were identified among the chickpea genotypes tested. These findings suggest that these chickpea genotypes carry different resistant genes, which can be exploited in breeding programmes to develop high levels of disease resistance.