科學(xué)家說,，太平洋沿岸夏季霧的減少可能脅迫具有象征意義的沿岸紅杉樹和其他地方生態(tài)系統(tǒng),。利用一種云幕高度以及陸地溫度的綜合指數(shù),，James Johnstone 和Todd Dawson發(fā)現(xiàn)了在1901年到2008年間加利福尼亞沿岸霧的頻率減少了33%。
海岸紅杉是太平洋沿岸包括加利福尼亞紅杉在內(nèi)的巨大樹木的成員之一,，它是全世界最高和壽命最長的樹木之一,。這組作者說，這種樹在干旱的夏季月份里依靠夏季霧從而幫助保存水,，它可能因為對更干燥的空氣做出反應(yīng)而遇到干旱敏感度提高的情況,。這項研究挑戰(zhàn)了此前一些觀測和建模研究提出的北加利福尼亞沿岸霧由于變暖的陸地溫度而會變得比此前更加頻繁的理論。這組作者發(fā)現(xiàn)海洋大氣循環(huán)以及溫度變化很可能壓倒由于溫室變暖造成的霧增加的假想情況,，導(dǎo)致自從20世紀(jì)早期開始的霧的凈減少,。這組作者說，這些發(fā)現(xiàn)把大尺度的陸地和東太平洋溫度變化與更干燥的空氣對加利福尼亞的沿岸環(huán)境與生態(tài)系統(tǒng)的潛在負面影響聯(lián)系了起來,。（生物谷Bioon.com）
生物谷推薦原始出處：
PNAS February 16, 2010, doi: 10.1073/pnas.0915062107
Climatic context and ecological implications of summer fog decline in the coast redwood region
James A. Johnstonea,1 and Todd E. Dawsona,b
aDepartment of Environmental Science, Policy, and Management, and
bDepartment of Integrative Biology, University of California, Berkeley, CA 94720
Biogeographical, physiological, and paleoecological evidence suggests that the coast redwood [Sequoia sempervirens (D. Don) Endl.] is closely associated with the presence of summer marine fog along the Pacific coast of California. Here we present a novel record of summer fog frequency in the coast redwood region upon the basis of direct hourly measurements of cloud ceiling heights from 1951 to 2008. Our analysis shows that coastal summer fog frequency is a remarkably integrative measure of United States Pacific coastal climate, with strong statistical connections to the wind-driven upwelling system of the California Current and the broad ocean temperature pattern known as the Pacific Decadal Oscillation. By using a long-term index of daily maximum land temperatures, we infer a 33% reduction in fog frequency since the early 20th century. We present tree physiological data suggesting that coast redwood and other ecosystems along the United States west coast may be increasingly drought stressed under a summer climate of reduced fog frequency and greater evaporative demand.
