Predicting Effects of Modifying Tussock Grassland

by D. L. Murray, Univ of Otago, Dunedin, New Zealand,
R. M. Jackson, Univ of Otago, Dunedin, New Zealand,
D. I. Campbell, Univ of Otago, Dunedin, New Zealand,
B. D. Fahey, Univ of Otago, Dunedin, New Zealand,

Document Type: Proceeding Paper

Part of: Grouting in Geotechnical Engineering


Measurements of rainfall, drainage, and weight change of a 6 m2 surface area cylindrical lysimeter containing nine snow tussocks (Chionochloa rigida) were used to estimate evaporation on an hourly basis for 16 months in Otago, New Zealand. For most of the period it was possible to distinguish evaporation from dry (transpiration) and wet foliage (interception loss). Components of the Penman-Monteith evaporation equation for a tussock canopy were derived and included in a comparison with short pasture and young coniferous forest. The analysis showed tussock is similar to forest in its transpiration rates and controls, with generally lower rates than pasture. Interception losses from the wet tussock canopy are at lower rates than for forest. Therefore changing vegetation from tussock to either forest or pasture should reduce water yield. These interpretations are extended to data from a paired catchment study.

Subject Headings: Rangeland | Evaporation | Comparative studies | Forests | Measuring instruments | Rainfall | Drainage | Transpiration | New Zealand | Oceania

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