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Adjacent Trees (adjacent + tree)
Selected AbstractsEpidemiology of sharka disease in SpainEPPO BULLETIN, Issue 2 2006M. Cambra PPV was first detected in Spain in 1984 in Japanese plum (Prunus salicina Lindl) cv. Red Beaut and spread very quickly to other Japanese and European plums and apricot cultivars but left peach cultivars unaffected. In the years following the detection of PPV, the predominant aphid species visiting Prunus orchards in Mediterranean areas were Aphis gossypii followed by Aphis spiraecola, the latter being the main aphid species found at present. Both species are considered to be the main vectors of PPV in Spanish early Prunus growing areas. Spatial analysis of the spread of PPV-D in Japanese plum and apricot trees confirmed the lack of significant association between immediately adjacent trees. The observed spatial pattern of sharka suggests a lack of movement of PPV-viruliferous aphid vectors to immediately adjacent trees and indicates their preferential movement to trees several tree spaces away. PPV-D is the only type currently present in Spain, with the exception of a PPV-M outbreak that was detected in and successfully eradicated from Aragón in 2002. The short-distance spread of PPV-M infection occurred as far as 12 m along the rows of peach trees. However, PPV-D has not been observed to spread through peach cultivars, despite being grown in the vicinity of heavily infected plots of apricot or Japanese plum trees. [source] Monitoring Subsurface Contamination Using Tree BranchesGROUND WATER MONITORING & REMEDIATION, Issue 1 2007Gayathri Gopalakrishnan This paper proposes a method of assessing the distribution of chlorinated solvents in soil and ground water using tree branches. Sampling branches is a potentially more cost-effective and easier method than sampling tree cores, with less risk of damage to the tree. This approach was tested at Argonne National Laboratory, where phytoremediation is being used to remove tetrachloroethene (PCE), trichloroethene (TCE), and carbon tetrachloride (CCl4) from soil and ground water. The phytoremediation system consists of shallow-rooted willows planted in an area with contaminated soil and deep-rooted poplars planted in an area with clean soil and contaminated ground water. Branch samples were collected from 126 willows and 120 poplars. Contaminant concentrations from 31 soil borings and six monitoring wells were compared to those from branches of adjacent trees. Regression equations with correlation coefficients of at least 0.89 were obtained, which were found to be chemical specific. Kriged profiles of TCE concentration based on soil and willow branch data were developed and showed good agreement. Profiles based on ground water data could not be developed due to lack of sufficient monitoring wells for a meaningful statistical analysis. An analytical model was used to simulate TCE concentrations in tree branches from soil concentrations; the diffusion coefficient for TCE in the tree was used as the fitting parameter and the best-fit value was two orders of magnitude greater than literature values. This work indicates that tree branch sampling is a useful approach to assess contaminant distribution and potentially to determine where to locate monitoring wells or perform detailed soil analysis. Further research is necessary prior to using this method as a quantitative monitoring tool for soil and ground water. [source] Preventing crown collisions increases the crown cover and leaf area of maturing lodgepole pineJOURNAL OF ECOLOGY, Issue 3 2006SHAWN X. MENG Summary 1Crown collisions induced by tree sway are hypothesized to reduce crown closure and leaf area in maturing cold temperate forests. These declines are thought to lead to the decline in productivity when a stand ages. 2We tethered groups of lodgepole pine (Pinus contorta Dougl. Ex Loud. Var. latifolia Engelm.) trees in a web pattern at 10 m height, in four 15-m tall stands in western Alberta, Canada, to determine whether preventing crown collisions would increase crown cover and leaf area. 3The stands all had less than 65% crown closure at the beginning of study. Photographs of the canopy were taken in each control and webbed plot in 1998 and at the same point in 2004. Six years after webbing, crown cover had increased by 14.4%, compared to a 2.1% increase for the control plots. 4Webbing also resulted in significant increases in mean branch length, leaf area per branch and foliage density of individual branches from top and middle sections of the crown. Polishing of branches, caused by chronic contact with adjacent trees, was three times as common on control trees compared to webbed trees. The mean leaf area per tree was larger for the webbed trees. 5Crowns of webbed trees were more symmetrical than those of control trees. Trees from webbed plots, however, had a decline in leaf area density. The branches of control trees were typically curved upward with twigs pointed inward, making the crowns more compact compared to the outwardly expanding crowns of trees from the webbed plots. 6The fact that crowns expanded laterally after webbing, despite little change in light regime, provides strong evidence against the hypothesis that loss of crown closure in maturing stands is caused by a lack of light. 7The study indicates that the decline in crown closure and leaf area in maturing and tall stands is at least partly related to wind-induced sway of trees abrading the edges of crowns. [source] Progress, spread and natural transmission of Bahia bark scaling of citrus in BrazilANNALS OF APPLIED BIOLOGY, Issue 3 2006F.F. Laranjeira Abstract Progress, spread and natural transmission of Bahia bark scaling of citrus were evaluated in a trial where 240 screenhouse-nursed nucellar grapefruit plants ,,Clason', ,Little River Seedless', ,Red Blush', ,Reed' and ,Howell Seedless' cvs , were planted alongside and 5 m apart from a 10-year-old symptomatic ,Marsh Seedless' grapefruit orchard. Plants were distributed in 16 rows of 15 trees, with three plants of each cultivar per row. Eight trial plants were kept in screen cages. Incidence of symptomatic plants was assessed at 3-months intervals, for 5 years, and for further 2 years at irregular intervals. Cumulative maps of disease incidence were produced for each assessment date and used in all analyses. Temporal progress was analysed by nonlinear fitting of three disease progress models. Spread was characterised in three levels of spatial hierarchy by the following analyses: ordinary runs, binomial dispersion index, binary power law fitting, isopath mapping and nonlinear fitting of disease gradient models. The first symptomatic plant was detected 2 years after planting. In the last disease assessment, 5 years after the first, 98% of the unprotected plants were symptomatic. None of the screen-caged trees showed any symptoms. Bahia bark scaling progress was polyetic and best described by the logistic model. Ordinary runs analysis showed little if any evidence of transmission between adjacent trees. Diseased plants showed a very aggregated pattern inside quadrats (D > 5 and b > 1.53). Isopath mapping showed that main spread was only because of the primary inoculum source. Secondary foci were also observed, but they were never dissociated from main initial disease focus. Disease gradient followed wind direction, starting near the original inoculum source and was best described by exponential model. These results support a hypothesis of Bahia bark scaling transmission by air-borne vectors with limited dispersion ability. [source] Spatial distribution of communal nests in a colonial breeding bird: benefits without costs?AUSTRAL ECOLOGY, Issue 5 2008URS CHRISTIAN GIEßELMANN Abstract The spatial organization of individuals, or groups of individuals, within a population can provide valuable information about social organization and population dynamics. We analysed the spatial distribution of nests of the sociable weaver (Philetairus socius) on two farms in the Kalahari. Sociable weavers build large communal nests on big savannah trees, forming a pattern of trees with and without nests. We used two spatial statistics, Ripley's K and the pair correlation function, to describe characteristics of the point patterns over a range of distances. (i) At distances of 200 and 300 m, communal nests were clustered. (ii) At distances greater than 1000 m, communal nests were regularly distributed. These findings are independent of the spatial distribution of trees. Furthermore, we used Moran's I to analyse spatial autocorrelation of nest sizes. We expected negative autocorrelation because of competition between nests. But on both farms there was no significant autocorrelation of nest sizes for any distance class. The regular distribution observed at larger distances may indicate competition and/or territoriality among different nests, but the lack of spatial autocorrelation between nest sizes suggests that these interactions may happen between nest clusters rather than between single nests. This was confirmed by significant clustering of nests on small scales. We thus suggest, that colonies of P. socius consist of several nests on adjacent trees forming a cluster of subcolonies. The question why sociable weavers establish subcolonies instead of adding more chambers to the natal nest, could not simply be answered by limitation of nesting space. We suggest a strategy to avoid costs due to increasing colony size. [source] | ||||||||||