Interception loss from eucalypt forest: Lysimeter determination of hourly rates for long term evaluation

Analyses of the response by a weighing lysimeter in Kioloa State Forest during and after rainfall provided values of interception loss rate. The derived rates for time scales between 0.1 and 1.0mm h−1 were generally similar throughout storm events to losses determined from throughfall and stemflow observations. During post-rainfall periods of canopy drying, enhanced rates of lysimeter evaporation were consistent with micrometeorological determinations of the partitioning of available radiant energy, based on atmospheric gradients of humidity and temperature. Interception losses from the eucalypt forest, deduced from the lysimeter response, varied between 10 and 15 per cent of gross rainfall in three consecutive 12 month periods whereas the corresponding rainfall ranged between 590 and 1530 mm yr−1. Daytime losses accounted for about two-thirds of total interception loss with a similar fraction occurring during rain periods. Storage capacity of the evergreen forest canopy was inferred to be 0.35 mm. Hourly loss rates during rainfall ranged up to 0.8 mm h−1 but with decreasing mean values and variability with increasing time scale resulting in a monthly mean value computed for the total number of hours of rain of approximately 0.1 mm h−1. A preliminary analysis of loss rate in terms of storm windspeed and rainfall intensity explained about half of its variation in statistically derived relationships. Improved time resolution of the order of seconds was considered a prerequisite to the physical understanding of turbulent transport from saturated canopies. The small value of interception storage capacity was considered in relation to that for pine forest as a basis for explaining observed differences in interception behaviour between eucalypt forest and coniferous plantations in the same area. Large differences in interception losses between the Kioloa site and evergreen forest in the South Island of New Zealand and also eucalypt forest in Western Australia were attributed to dissimilar meteorological conditions at the various sites.

[1]  I. R. Cowan,et al.  Transfer processes in plant canopies in relation to stomatal characteristics. , 1987 .

[2]  J. Gash.  An analytical model of rainfall interception by forests , 1979 .

[3]  J. Gash,et al.  The average surface resistance of a pine forest derived from Bowen ratio measurements , 1975 .

[4]  E. Pook.  Canopy dynamics of Eucalyptus maculata Hook. IV. Contrasting responses to two severe droughts. , 1986 .

[5]  A. Pearce,et al.  Rainfall Interception In A Multi-Storied, Evergreen Mixed Forest: Estimates Using Gash's Analytical Model , 1981 .

[6]  A. Rutter,et al.  A predictive model of rainfall interception in forests, 1. Derivation of the model from observations in a plantation of Corsican pine , 1971 .

[7]  C. R. Lloyd,et al.  Comparative estimates of interception loss from three coniferous forests in Great Britain , 1980 .

[8]  E. F. Bradley,et al.  Flux-Gradient Relationships in a Forest Canopy , 1985 .

[9]  M. Feller.  Water balances in Eucalyptus regnans, E. obliqua, and Pinus radiata forests in Victoria , 1981 .

[10]  J. Garratt.  The inland boundary layer at low latitudes , 1985 .

[11]  J. Gash,et al.  An application of the Rutter model to the estimation of the interception loss from Thetford Forest , 1978 .

[12]  A. Aston.  Heat storage in a young eucalypt forest , 1985 .

[13]  F. Dunin,et al.  A weighing lysimeter in a regenerating eucalypt forest: Design, construction, and performance , 1988 .

[14]  M. Sharma.  Evapotranspiration from a Eucalyptus Community , 1984 .

[15]  E. O'Loughlin,et al.  A Lysimeter Characterization of Evaporation by Eucalypt Forest and its Representativeness for the Local Environment , 1985 .

[16]  L. Rowe,et al.  Rainfall interception by an evergreen beech forest, Nelson, New Zealand , 1983 .

[17]  G. Szeicz,et al.  The effect of intercepted rainfall on the water balance of a hardwood forest , 1979 .

[18]  D. Whitehead,et al.  A comparison of two methods of estimating transpiration rates from a Sitka spruce plantation , 1985 .

[19]  J. Stewart,et al.  Evaporation from the wet canopy of a pine forest , 1977 .

[20]  A. Aston.  The effect of vertical separation of psychrometers on the determination of Bowen ratios over a young eucalypt forest , 1985 .

[21]  A. Pearce,et al.  Nighttime, wet canopy evaporation rates and the water balance of an evergreen mixed forest , 1980 .

[22]  A. R. Aston,et al.  Rainfall interception by eight small trees , 1979 .