Comparative water budgets of a lower and an upper montane cloud forest in the Wet Tropics of northern Australia

This chapter presents a comparison of the water budgets of a lower and an upper montane cloud forest in Australia's Wet Tropics region based on field measurements of rainfall, throughfall ( TF ), stemflow ( SF ), transpiration, and cloud water interception ( CWI ). The proportions of total precipitation measured as TF and SF varied between the two sites. At the lower montane cloud forest site (Upper Barron), SF was 7% while TF was just 64%. The upper montane cloud forest site (Bellenden Ker) showed higher SF at 10% while TF was also high at 83%. CWI at the two sites was quantified using a wet-canopy water balance methodology and was found to contribute up to 65% of the monthly water input during dry season months. At Upper Barron, CWI was 19% of average annual precipitation while at Bellenden Ker it was as much as 29%. These measurements resulted in an overall canopy interception evaporation loss of 29% at Upper Barron and just 7% at Bellenden Ker. About 20% of total precipitation was lost through transpiration at Upper Barron and just 5% at Bellenden Ker. Transpiration losses were less than water losses through wet-canopy evaporation at both sites. Both sites have a large annual net surplus of water to sustain streamflow and groundwater recharge. Total evaporation losses at Upper Barron accounted for about 50% of total precipitation input, leaving 50% for runoff and groundwater recharge. […]