Báo cáo lâm nghiệp: Changes of partitioning and increased root lengths of spruce and beech exposed to ambient pollution concentrations in southern England

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Báo cáo lâm nghiệp: "Changes of partitioning and increased root lengths of spruce and beech exposed to ambient pollution concentrations in southern England"Changes of partitioning and increased rootlengths of spruce and beech exposed to ambientpollution concentrations in southern England P.H. Freer-Smith 2 1 Taylor 2 M.C. DobsonG.Division of Biology, University of Lancaster, Lancaster LA1I 4 YQ, and2 Forestry Commission, Alice Holt Lodge Farnham, Surrey GUiO 4 LH, U.K and shoots may be altered such that theIntroduction allocation of biomass to roots is restricted (U.K. TERG, 1988). Extrapolation of such results to the field, in particular, to largeMuch circumstantial evidence exists to trees is unwise, since the concentrationssuggest that drought may act as an incit- used in such experiments are generally ining factor, accelerating the decline of excess of those experienced presently inforest trees exposed to chronic doses of rural Britain, and the fumigations are oftenair pollution. For instance, many reports conducted over extremely short time pe-suggest that major increases in the de- riods on a limited number of small trees. Incline of spruce occurred after hot and dry addition, little research in Britain has in and Germany. Similarly, Lingsummers focussed on drought and 0 which are , 3Ashmore (1987) suggested that for beech, known to occur together during summerloss of green leaves, production of small months, particularly in southern England.leaves and altered patterns of shoot The Forestry Commission has recentlygrowth were amongst the symptoms developed 3 rural sites, each with 16 openassociated with the decline of this species. top chambers, to study the effects of ambient concentrations of pollution on tree Experimental work on trees in controlled growth and physiology for a period of upenvironments has shown that exposure to to 5 yr. The work reported here describesgaseous pollution may increase suscepti- data collected from the southern Englandbility to drought in at least 2 ways. Firstly, site at Headley, Hampshire, where duringstomatal behaviour may be altered, caus- the 1988 growing season concentrationsing both decreases and increases in water of 0 reached 85 ppb on at least 5 occa-loss (Mansfield and Freer-Smith, 1984) 3 sions.and, secondly, partitioning between roots** address: St. Marv’ rollege. q Hill, W:aldearave Road. Twickenham TW1 4SX. U.K.PresentPm. During July 1988, trees of both species wereMaterials and Methods harvested and, in addition to measurements of dry weight, root lengths were also assessed, using an automated device. For beech, roots 1Experiment were sampled in 10 cm sections to a depth ofTransplants (2 + 1 ) of beech (Fagus sylvatica 50 cm.L.) were rooted into 1 m plastic tubes containingcompost. Tubes were sunk into the ground inopen top chambers sited at Headley, Hamp-shire (Willson et al., 1987). Eight chambers used, 4 which received ambient air filteredwere Results and Discussionthrough charcoal and 4 which received unfil-tered air. Regular measurements of gas ex-change were made from May until September Fig. 1 illustrates the effects of filtering on1988, using field portable instruments. the rates of stomatal conductance for beech and spruce. For both species, sto-Experiment 2 matal conductance was restricted for trees grown in unfiltered (polluted) air, com-Clonal material of Sitka spruce (Picea sitchen-sis (Bong) Carr), was also placed into the same pared with the values in filtered (clean) air.chambers during April 1988. Plants were rooted Differences between mean values wereinto compost. Measurements of gas exchange tested using t tests and showed that this(photosynthesis, transpiration and stomatal effect was significant on 3 occasions forconductance) were made using ...