New perspectives on forest decline

Blank, Lutz W.; Roberts, T. M.; Skeffington, R. A.

doi:10.1038/336027a0

Cited by 84 publications

(25 citation statements)

References 12 publications

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“…For the past decade, older trees have been affected increasingly by injury, the cause of which is still not fully know'n. It is now generally felt that atmospheric pollution, both wet and dry deposited, is partly responsible and that pathogens can be ruled out as a primary cause (Blank, Roberts & Skeffington, 1988). Air pollutants suspected to be involved include oxides of sulphur and nitrogen, ozone and wet deposition of nitrogen.…”

Section: Discussionmentioning

confidence: 99%

Needle chlorosis in Sitka spruce following a three‐year exposure to low concentrations of ozone: changes in mineral content, pigmentation and ascorbic acid

1993

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S LI M M .A R YTwo-year-old seedlings of Sitka spruce were e.xposed to 70 nl 1 ' ozone or to filtered air over three successive summers in outdoor large-scale fumigation chambers (Solardomes). Seven months after the last period of exposure to the pollutant and just prior to hudhurst, upper-surface chlorisis affecting only the older needles of ozone-exposed trees was observed. In many respects, the symptoms appeared to be similar to those characteristic of type 1 spruce damage occurring in parts of mainland Europe. Chlorophyll pigments were reduced in the ozoneexposed older foliage, but no change in the ratio of chlorophylls to carotene was observed. The content of ascorbic acid was clearly related to the amount of foliar damage observed on the trees exposed to ozone and the largest increases were seen in those trees which were most visibly damaged. Although none of the foliage examined was deficient in any of the nutrient cations which were measured, the concentration of Mg in the older needles was significantly reduced by exposure to ozone, irrespective of damage symptoms. Exposure to ozone also resulted in increases in the ratios of K:Mg and Ca:Mg. In the older needles, leaching of Mg-" and K* by 05 mM H.^SO4, pH 3-0, was enhanced by prior exposure to ozone, but the amounts removed were small ( < 6 ""). It is suggested that long-term exposure to ozone has a cumulative effect on plant tissue and that the observed chlorosis was the result of accelerated senescence.

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Section: Discussionmentioning

confidence: 99%

Needle chlorosis in Sitka spruce following a three‐year exposure to low concentrations of ozone: changes in mineral content, pigmentation and ascorbic acid

1993

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“…This might have induced some kind of permanent physiological shock to foliage and terminal leaders, manifested by the tremendous foliage loss in recent years. Needle loss in excess of c. 30 % might significantly lower the potential for radial growth and for capturing resources to maintain energy-consuming cold tolerance (Schweingruber, Kontic & Winkler-Seifert, 1983;Klein & Perkins, 1988;Blank, Roberts & Skeffington, 1988;De Hayes, 1992, McLaughlin & Kohut, 1992Innes, 1993). This contention is supported by progressive cumulative defoliation after 1987.…”

Section: Crown Conditionsmentioning

confidence: 99%

Rise and demise of cold‐climate Picea abies forest in Sweden

Kullman

1996

New Phytologist

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SUMMARYThe study focuses on structural and compositional dynamics of high-elevation (boreal) mixed Picea-Betula forest in the Swedish Scandes. Data from seven years' monitoring of crown condition (defoHation), seed viability, soil and air temperatures, a tree-ring chronology and the age structure of Picea are presented. Real long-term dynamism of the tree cover was inferred from radiocarbon dates of buried subfossil wood. At all time-scales, the forest has responded sensitively to thermal variability. Picea seed viability, demography and radial growth correlated positively with summer temperature. The current Picea population largely results from warming during the first half of the 20th century. However, cooler climate in the past c. five decades has led to reduced population and radial growth as well as accelerating crown defohation. This decline is related primarily to winter soil temperatures. The mechanism of needle loss is deduced to be winter desiccation and resulting cavitation of the xylem. It is hypothesized that previous similar episodes have been balanced by periods of spruce expansion. The successional history leading up to the present stage includes fire disturbance and subsequent coohng during the Little Ice Age, which prolonged and consolidated the early post-fire Betula phase. Pinus was incapable of penetrating these unusually dense birch stands, whereas the shade-intolerant spruce could establish progressively as chmate warmed. This course of structural and compositional dynamism relates to complex interactions of disturbance, chmate change and reproductive responses.

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“…An overload of sulfuric deposition can disturb terrestrial ecosystems not only by causing changes in the vegetation (Blank et al 1988;Schulze 1989;Innes and Boswell 1990) but also by altering the nutrient dynamics in soil (Oren et al 1988;Tamm and Hallbacken 1988;Johnson et al 1994;Hallett and Hornbeck 1997). The efflux of sulfur (S) in forest ecosystems plays an important role in the acidification of mountainous stream water and surface water.…”

mentioning

confidence: 99%