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Isotopic assessment of the hydrologic importance of fog deposition on tall snow tussock grass on southern New Zealand uplands
Author(s) -
Ingraham Neil L.,
Mark Alan F.
Publication year - 2000
Publication title -
austral ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.688
H-Index - 87
eISSN - 1442-9993
pISSN - 1442-9985
DOI - 10.1046/j.1442-9993.2000.01052.x
Subject(s) - tussock , snow , interception , environmental science , deposition (geology) , hydrology (agriculture) , altitude (triangle) , snowmelt , precipitation , groundwater , atmospheric sciences , swamp , physical geography , ecology , geology , geography , meteorology , sediment , biology , geomorphology , geometry , geotechnical engineering , mathematics
The stable isotopic composition of rain, fog and groundwater was determined for three sites on the Otago upland snow tussocklands, southeastern South Island, New Zealand, for the snow‐free period of November to June in 1996–1998. The rain and fog were collected concurrently, but the rain was consistently isotopically more depleted than the fog. The compositions of the rain form a line of the equation δD = 8.31δ 18 O + 13.6, which is similar to the line of δD = 8.11δ 18 O + 13.6 formed by the fog. The groundwater has compositions usually between those of the fog and rain, shows no isotopic evidence of evaporation, and is assumed to be a mixture of the two in sub‐equal proportions. This pattern has been observed previously only in forested regions where the tree crowns act as collection mechanisms for fog water. On the Otago uplands, the only fog collection mechanism is interception gains through fog deposition on the relatively short (0.8–1.2 m) fine wispy foliage of the native tall snow tussock grasses ( Chionochloa spp.). These results support earlier but debated claims that interception of fog by the foliage of the dominant tall snow tussock grasses makes a substantial contribution to the water yield from these uplands.