Fog deposition by snow tussock grassland on the Otagouplands:response to a recent review of the evidence

摘要

We challenge a recent, rather selective 'reviewof the evidence' by Davie et al. (2006)explaining the recorded high water yieldsfrom snow tussock grasslands on the Otagouplands. We refute their dismissal of theimportance to water yield of fog depositionon the fine wispy foliage of the dominant talltussock plant cover. We stand by the resultsof our previous study on the stable isotope(δ~(18)Oand δ~2H) values of fog-, rain- andgroundwater from three upland snow tussockgrassland sites. We also provide evidencefrom several direct measures using natural orsimulated tussocks at three fog-prone uplandlocations which the reviewers ignored. Overalland importantly, the value of upland snowtussock grassland in maximising water yieldis not in dispute, and we continue to endorsethe relevance of low evapo-transpirationfrom the dominant tussock cover. The waterproduction capability of the upland snowtussock grasslands is a sufficiently importantecosystem service to justify formal recognitionin land-use planning responsibilities of localauthorities. Further, this important ecosystemservice of upland tall snow tussock grasslandsshould also feature in central government'scurrent Sustainable Water Programme ofAction and in the development of NationalPolicy Statement and National Environmental Standard for water under the ResourceManagement Act.