Escaping the flames: large termitaria as refugia from fire in miombo woodland

At finer scales, spatial heterogeneity can influence fire intensity and severity. To test whether Macrotermes termite mounds act as fire refugia for woody plants, we assessed effects of fire on individual plants, woody plant structure and composition in a miombo woodland in Zimbabwe, where elephants have decreased tree cover, leading to increased grass cover, fuelling greater intensity fires. We compared exposure to fire on 47 paired mound-matrix plots at three sites. Mound-based woody plants were less exposed to fire than those in matrix positions. Woody species composition differed between mound and matrix, and there were more tall trees on mounds. We assessed grass cover, elephant damage, fire damage and resprouting response for all woody plants found on 10 paired mound-matrix plots that had been equally exposed to severe late dry season fires. Grass cover was three times greater for matrix sites, where 85 % of woody species experienced heavy fire damage, compared to 29 % for mounds. Matrix species were nearly 31 times more likely than mound species to exhibit a vigorous resprouting response after fire damage, all else being equal. The distinct composition of termitaria vegetation has been attributed to edaphic factors. To this should be added the fire-retardant properties of mounds, allowing woody species that might otherwise have been excluded, to persist in a fire-prone system. Thus, spatial pattern created by termitaria is reinforced through exclusion of fire, allowing different species composition and structure. Since termitaria are important for productivity and biodiversity, the refuge effect is significant for the system.     

Chromosome counts in wild and cultivated species of Abelmoschus Medikus. from the Indian sub-continent

Summary

Abelmoschus is regarded as a polyploid-polyspecies complex and a genus with variable genome organisation and resultant ambiguity in its speciation. A cytogenetic basis for taxonomy can be significant, due to the fact that many of the taxonomic units of Abelmoschus are heterogeneous in nature with deviant numbers of chromosomes. In the present investigation, 39 wild and cultivated accessions of Abelmoschus from India, belonging to three representative taxa, were used to record clear and authentic chromosome counts. From these data, the numbers of somatic chromosomes in A. angulosus var. grandiflorus, A. moschatus ssp. moschatus, and A. moschatus ssp. tuberosus are reported to be 2n = 66, 2n = 72, and 2n = 72, respectively. The present study also confirmed 2n = 130 to be the authentic number of somatic chromosomes in A. esculentus. Earlier conflicting reports are ruled out. Reports of the occurrence of cytotypes in A. esculentus are not acceptable, due to its wide area of cultivation.     

Genomic selection allowing for marker‐by‐environment interaction

Genomic selection has been routinely implemented in plant breeding in two stages. The first stage usually omits the marker information and estimates adjusted means of genotypes across environments. The second stage uses the adjusted means to predict genomic breeding values. However, if the effects of markers vary substantially between different environments, it may be important to account for this variation for varieties adapted to different environments. Using two maize data sets, we investigated whether modelling the marker‐by‐environment interaction can improve the predictive ability of genomic selection relative to modelling genotype‐by‐environment interaction alone. Modelling the marker‐by‐environment interaction did not substantially increase the predictive ability relative to modelling only the genotype‐by‐environment interaction for the two tested data sets. Thus, genomic selection, carried out in a stagewise fashion, such that the marker information is omitted until the last stage of the process, may suffice for most practical purposes. Moreover, predictive ability did not reduce substantially even when the number of markers with consistent effects across environments used for genomic prediction was reduced to about 50.     

J-integral evaluation in cracked wood specimen using the mark tracking method

In this paper, an experimental analysis of the fracture parameters via the invariant J-integral for a cracked specimen made of wood is presented. The experimental test is realized using a sample made of Douglas fir loaded in opening mode. The sample geometry is a mix between the single edge notch and wedge splitting specimens, and the crack advances in the radial-longitudinal system, parallel to the wood rings. By using the optical mark tracking method, the displacement field evolution close to the crack tip is recorded during the test. The stress and strain fields are calculated using a finite element model generated from the experimental displacement fields. Further, the energy release rate is evaluated for different circular paths or crowns defined around the crack tip and for different loading values.     

Variability and estimating in fruiting of shea tree (Vitellaria paradoxa C.F. Gaertn) associated to climatic conditions in West Africa: implications for sustainable management and development

ABSTRACT

Shea tree (Vitellaria paradoxa) is one of the main native oil plants with high economic value in Africa. Its fruits are used for food, medicinal, cultural and exportation purposes. However, the lack of efficient tools to assess annual fruit production of the species limits the sustainable management of its resources. Therefore, production statistics are useful to organize the activities of the shea sector. This study aimed to (i) assess the interannual variation in fruit production along a climatic gradient in Burkina Faso, (ii) examine fruit production patterns according to climatic zones and tree size, (iii) assess the contribution of high-yielding trees in the annual potential production and (iv) develop allometric equations for estimating fruit yields of the species. The yield of 212 trees distributed across three climatic zones was monitored over four successive years. Within each climatic zone, fruit production was significantly different among years. Fruit production was positively and significantly correlated with tree size. The interannual variation in fruit production at tree individual level was higher in drier climatic conditions. The mean interindividual synchrony was less than 50% in each zone, suggesting a large range in fruit production patterns of the species. Annually, more than 55% of the total fruit production was supported by high-yielding trees. The best regression models for estimating fruit yields had R ² values of 69–73% with prediction errors ranging from ?7% to 4%. Our findings are useful tools for the planning of rational exploitation of shea tree’s resources and its sustainable management.     

Identification of disease resistances in wheat-<Emphasis Type="Italic">Leymus multicaulis</Emphasis> derivatives and characterization of <Emphasis Type="Italic">L. multicaulis</Emphasis> chromatin using microsatellite DNA markers

To identify resistance to Fusarium head blight (FHB), cereal yellow dwarf virus (CYDV), stem rust (Sr), and powdery mildew (Pm) in 24 common wheat (Triticum aestivum)-Leymus multicaulis addition/translocation lines that were developed cytogenetically and to verify the authenticity of these lines using microsatellite (SSR) DNA markers. Resistance to FHB was identified in the wheat-L. multicaulis addition lines, Line 9 and Line 26, which both contained L. multicaulis-specific fragments as shown by SSR markers. The translocation line, Trans 1, and the addition lines, Line 5 and Line 29, have resistance to stem rust (IT 0). Resistance to CYDV was evaluated based on virus titers measured by enzyme linked immunosorbent assay (ELISA). The addition line, Line 23, showed low virus titer (0.15), indicating resistance to CYDV. The segregation distribution of CYDV resistance in 98 F₂ plants of Line 23/CS showed a significant deviation from 3:1. Inoculation with a set of 14 differential Blumeria graminis f. sp. tritici (Bgt) isolates did not detect powdery mildew resistance in translocation line Trans 1, addition line Line 9 and the amphiploid of wheat-L. multicaulis. However, Line 26 exhibited the resistance response pattern of Kavkaz, which carries Pm8, indicating that Line 26 most likely has the powdery mildew resistance gene Pm8 inherited from its parent lines Feng Kang 7 or Feng Kang 10. Twelve SSR markers, distributed on different homeologous chromosome groups of wheat, which distinguished L. multicaulis addition/translocation chromosomes, were used to verify the presence of L. multicaulis chromatin in the putative wheat-L. multicaulis addition/translocation lines. Of the 24 addition/translocation lines investigated using the 12 polymorphic SSR markers, 18 wheat-L. multicaulis derivatives showed the expected L. multicaulis-specific fragments, indicating that all of these 18 addition/translocation lines would most likely have the introgressed L. multicaulis chromosome(s). Chromosomal rearrangements also were detected in some of the wheat-L. multicaulis introgression lines.     

An Assessment of Nonequilibrium Dynamics in Rangelands of the Aru Basin,Northwest Tibet,China

An assessment of nonequilibrium rangeland dynamics was conducted in the Aru basin, a semiarid site located in the very dry northwest part of the Chang Tang Nature Reserve, Tibet, China. A grazing gradient approach was used to examine the effects of different livestock grazing intensities on vegetation, providing data to determine if plant–herbivore interaction has been a major structuring force of the plant community and thus to indicate what type of dynamic might apply in the study area. No significant differences were found between a highly grazed site and a lightly grazed site in vegetation cover, standing biomass, and Shannon–Wiener species diversity index of total, graminoid, forb, and tomtza (Oxytropis glacialis Benth. ex Bunge) functional groups, with the exception that tomtza coverage was significantly higher at the highly grazed (1.04%) than at the lightly grazed site (0.02%). Grazing intensity alone did not explain a significant amount of variation in the plant species data. These results indicate that a dominance of nonequilibrium dynamics appears to be the case in the basin, probably one of the least-arid sites in the northwest Chang Tang region of the Tibetan Plateau. Thus, opportunistic livestock management strategies adapted to variable vegetation production from year to year, rather than the setting of a rigid stocking rate that assumes a stable carrying capacity, is probably the most plausible approach for managing livestock and its relationship to biodiversity values in this region.     

Control of brown rot of stone fruits by brief heated water immersion treatments

The effectiveness of brief (30 or 60 s) immersion in water at 24, 50, 55, 60, 65, or 70 °C was evaluated for the control of brown rot, caused by Monilinia fructicola, on California-grown peaches, nectarines, and plums. Inoculated fruits were treated and either stored at 20 °C for 5 days or at 0 °C and 95% RH for 30 days followed by 5 days at 20 °C to simulate commercial marketing conditions. Immersion in water at 55 °C for 60 s or at 60 °C for 30 or 60 s significantly reduced both decay incidence and severity among the remaining wounds that developed the disease. Water temperatures of 65 °C or higher were phytotoxic and caused moderate to severe surface injuries. Immersion in water at 60 °C for 60 s was effective for plums and it reduced the incidence of brown rot from more than 80% among control fruit to less than 2%. In nectarines, this treatment reduced decay incidence from 100 to less than 5% on fruit stored at 20 °C and from 73 to 28% on cold-stored fruit. Therefore, brief immersion in heated water can be an effective approach to manage postharvest brown rot of stone fruits, especially for the organic fruit industry.     

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