Epidemiology and effects of verticillium wilt on yield of olive trees (cvs. Barnea and Souri) irrigated with saline water in Israel

Epidemiology ofVerticillium dahliae on olive trees (cvs. ‘Barnea’ and ‘Souri’) irrigated with saline water was studied over a period of 3 years. Disease incidence in cv. Barnea increased from 18.9% to 40.5% in the first year, while disease severity decreased from 4.2 to 2.4 (on a scale of 2–10). In the first month after pruning of diseased branches (June 1999), disease incidence was 26.9% and it increased to 60.6% by May 2000. No changes in disease severity were observed from this time until the end of the study. In cv. Souri, disease incidence doubled during the 3 years of the study (from 22.1% to 44.8%), and disease severity increased from 2.4 to 2.9. The disease caused significant reduction of yield in cv. Barnea in 1999 and 2000 (48.3% and 12.0%, respectively). In cv. Souri yield was measured only in 2001, where a reduction of 66.8% was observed.V. dahliae was isolated from both diseased and symptomless trees. A significant decrease in the isolation rate ofV. dahliae from diseased cv. Barnea trees occurred between the first year (47.9%) and the third year (5.3%); positive isolations were obtained in all seasons, without differences between seasons. In cv. Souri, the fungus was isolated in significantly higher rates during the winter and spring (55% and 50%, respectively). Our findings strongly support the assumption that natural recovery occurs in cv. Barnea 4–5 years after planting, but not in cv. Souri. http://www.phytoparasitica.org posting July 10, 2003.     

Production of UV-light-detectable faeces from house mice (Mus musculus domesticus) after consumption of encapsulated fluorescent pigment in monitoring bait

BACKGROUND: The authors investigated whether fluorescent pigment in thermoset melamine microcapsules incorporated into monitoring baits would be excreted in the faeces of wild house mice in a quantity and intensity that would be detectable by a human observer. RESULTS: Experimental mice produced 24–116 UV‐visible faecal pellets per 24 h; the mean dry weight was 582 mg. The number and weight of the faeces was independent of mouse sex and weight. The defecation of UV‐visible faeces began at 2–3 h, peaked at 5–8 h and was complete at 17 h after bait ingestion. The detectability of the highly fluorescent faecal pellets using a small UV flashlight approached 100%, and no false positives were recorded. CONCLUSION: The tested formulation is of significant value for rodent pest monitoring because faeces that are highly visible by UV light are produced for 15 h by mice after ingestion, and their detection is easy and unambiguous. Copyright © 2011 Society of Chemical Industry     

A matter of time: self-regulated tree regeneration in a natural Norway spruce (<Emphasis Type="Italic">Picea abies</Emphasis>) forest at Mt. Brocken,Germany

European natural mountain Norway spruce (Picea abies) forests are currently subject to extensive disturbances. An improved understanding of the self-regulated regenerative capacity of this forest type is therefore needed. We used the last remnant of natural mountain Norway spruce forests in central northwestern Europe (BNF Brocken natural forest), to analyze (1) the diversity of structure and age distribution of the tree population and (2) the effect of disturbances on self-regulated tree regeneration over the last 264 years. To this end, we combined an assessment of stand structure with dendrochronological investigations and a review of disturbance history. We hypothesized that BNF exhibits a high diversity of tree ages and dimensions and that recruitment and survival of tree regeneration were largely independent from disturbances. BNF showed a high structural and age diversity. Disturbances exhibited no regular temporal pattern. Their effect on tree regeneration was rather complex and changed with observation period. Impeding and facilitating effects of past disturbances on recruitment were significant from 1736 to 1910. From 1911 until 2000, recruitment decoupled from preceding disturbances. Subsequent disturbances facilitated survival of established trees from 1736 to 1820, while afterward no significant influence could be proved. Our study showed that in the course of self-regulated development the tree population of BNF has gradually acquired, or maintained, a diverse structure. Disturbances served as an important driver of diversification. We concluded that increasing deadwood availability and limiting browsing are the key to securing immediate regeneration.     

Phytophthora species associated with dieback of sweet chestnut in Western Turkey

Sweet chestnut (Castanea sativa) is an important tree species in the Marmara and Aegean regions of Turkey as these two regions produce the great majority of edible nuts, especially those used for marron glacé production. Chestnut forests and orchards in these regions showing severe dieback symptoms not associated with chestnut blight were investigated to determine the role of Phytophthora spp. in the decline syndrome. Soil samples were collected from around 108 symptomatic chestnut trees at 29 sites and Phytophthora spp. isolated using soil baiting technique and selective medium. Species isolated were identified by cultural characteristics and ITS sequencing. Phytophthora x cambivora was the dominant species detected in 13 sites, followed by P. cinnamomi (5 sites), P. plurivora (3 sites) and P. cryptogea (1 site). Phytophthora x cambivora was present in both regions, while P. cinnamomi was found only in the Marmara region in coastal areas around Istanbul. When inoculated at the stem bases of 3‐year‐old chestnut saplings, P. cinnamomi produced significantly longer necrotic lesions (7.8–12.0 cm) than P. x cambivora (2.6–6.3 cm) by 12 days after inoculation. Phytophthora plurivora was the least aggressive species causing only small lesions. Phytophthora cryptogea, which represents the first record on chestnut in Turkey, produced intermediate sized lesions in between P. x cambivora and P. plurivora. These results indicate that P. x cambivora and in some areas P. cinnamomi play major roles in the observed dieback of sweet chestnut in western Turkey.     

Manganese Biogeochemistry in a Central Czech Republic Catchment

Mn biogeochemistry was studied from 1994 to 2003 in a small forested catchment in the central Czech Republic using the watershed mass balance approach together with measurements of internal stores and fluxes. Mn inputs in bulk deposition were relatively constant during a period of sharply decreasing acidic deposition, suggesting that the Mn source was terrestrial, and not from fossil fuel combustion. Mn inputs in bulk deposition and Mn supplied by weathering each averaged 13 mg m^?2 year^?1 (26 mg m^?2 year^?1 total input), whereas Mn export in streamwater and groundwater averaged 43 mg m^?2 year^?1. Thus an additional Mn source is needed to account for 17 mg m^?2 year^?1. Internal fluxes and pools of Mn were significantly greater than annual inputs and outputs. Throughfall Mn flux was 70 mg m^?2 year^?1, litterfall Mn flux was 103 mg m^?2 year^?1, and Mn net uptake by vegetation was 62 mg m^?2 year^?1. Large pools of labile or potentially labile Mn were present in biomass and surficial soil horizons. Small leakages from these large pools likely supply the additional Mn needed to close the watershed mass balance. This leakage may reflect an adjustment of the ecosystem to recent changes in atmospheric acidity.     

Seasonal patterns of cellulase concentration in desert soil

The concentration of cellulose in plant material greatly affects the decomposition rate of plant-derived litter and hence carbon availability. The disappearance of pure cellulose in soil was studied as a measure of plant decomposition and carbon turnover. Our objective was to understand the effect of various cellulose concentrations and plant material added to soil and collected during different seasons, on cellulase concentrations under laboratory conditions (e.g. constant soil moisture and incubation temperature). The percentage of recovery of the enzyme in the control soil and in samples amended with known amounts of cellulose powder was estimated. Several methods for estimating soil cellulase concentrations/activity are available, most based on the determination of released reducing sugars. The method used in this study is based on the cleavage of a cellulose-azure substrate by cellulase to spectrophotometrically detectable fragments. Our results showed a significant correlation (p<0.05) between cellulose concentration and cellulase levels in soil, which varied along the study period. When pure cellulose was added to the soil, cellulase was detected after 7 days of incubation, whereas when plant material was added to the soil, cellulase was detected after 14 days. The recovery of cellulase from soil was also found to be seasonally dependent. The method of cellulase determination used in this study was simple, safe and rapid. From the results presented in this study, it can be assumed that there are seasonally dependent factors that affect the existence and concentration of cellulase in soils of the arid Negev Desert, in addition to organic matter, water and temperature.     

Indoor Aerosol Particle Deposition in an Empty Office

The size- and time-resolved indoor/outdoor aerosol concentration relationships were studied experimentally in an empty office without internal particle sources. Two Scanning Mobility Particle Sizers (SMPS) and an Aerodynamic Particle Sizer (APS) sampled alternately from indoor and outdoor, together covering the size range 3–10,000 nm. The results showed that the indoor aerosol concentration depends mainly on the air exchange and deposition rates, and the outdoor concentration. At higher air exchange rates the indoor aerosol concentration approaches the outdoor one. This was observed for the accumulation mode particles. The size-dependent deposition rates were estimated using a simple aerosol dynamics experiment. It was based on equilibration of the indoor/outdoor concentrations by opening windows and analyzing the concentration decay curves after the windows were closed. For this purpose a simple mass balance model was used. The overall loss rate and the asymptotic value of indoor concentration were found by applying a non-linear least squares method on the time dependence of the indoor concentrations. The air exchange rate was estimated from the overall loss rate and the steady state values of the indoor/outdoor concentration of the accumulation mode particles.