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Experiments on the causes of altitudinal differences in the leaf nutrient contents, size and δ 13 C of Alchemilla alpina
Author(s) -
MORECROFT MICHAEL D.,
WOODWARD F. IAN
Publication year - 1996
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/j.1469-8137.1996.tb04364.x
Subject(s) - altitude (triangle) , nitrogen , nutrient , effects of high altitude on humans , population , botany , horticulture , phosphorus , biology , chemistry , zoology , ecology , geometry , mathematics , demography , organic chemistry , anatomy , sociology
SUMMARY This paper describes experiments carried out to investigate the causes of high leaf nitrogen concentrations and high δ 13 C values in Alchemilla alpina L. growing at high altitudes. We investigated whether genetic adaptation, high levels of nitrogen input or low temperatures could account for these trends. In a field experiment, plants from two altitudes in the Scottish Highlands were transplanted to Great Dun Fell, a site in the Pennines of northern England. The experimental design was fully factorial: two altitudinal origins × two altitudes of growth × two nitrogen levels. A second experiment used a controlled environment to test the effects of temperature alone. The effects of altitude in the field transplant experiment were very similar to those in naturally growing plants. Leaf nitrogen concentration and δ 13 were both higher at the high altitude, whilst growth declined and nitrogen per leaf was unaffected. An increase in potassium concentration with altitude was also found. Nitrogen addition caused increased leaf nitrogen concentrations but also increased nitrogen per leaf; δ 13 C was not affected and potassium and phosphorus concentrations decreased. The addition of nitrogen also increased mortality. Altitude of origin had relatively few effects but the population from the higher altitude did have a higher specific leaf area. Low temperature in the controlled environment caused increased δ 13 C, decreased leaf size and increased nitrogen and carbon contents, although the effect was less clear than the effects of altitude in the field. Gas exchange measurements suggested that the δ 13 C effect was caused by a reduction in stomatal conductance. We conclude that the effects of altitude on this species are principally the result of direct environmental modifications to growth rather than genetic adaptation. Of the various factors that change with altitude, temperature and a short growing season are particularly important; enhanced nitrogen supply through atmospheric deposition promotes increasing leaf nitrogen concentrations but must be considered in conjunction with other variables.