Abstract:
The Dry Valleys of Victoria Land, Antarctica, contain naturally simple ecosystems operating under extreme climatic conditions. Nutrients are limited and are thought to come from external sources from more productive parts of the landscape or from other ecosystems entirely, such as the lakes occurring in the valleys. A ‘legacy’ model suggests the origin of present day soil organic matter to be
... material laid down in ancient lake beds rather than aeolian dispersal from modern aquatic environments, as previously thought. This does not appear to hold true for smaller dry valleys and instead a ‘subsidy’ model was investigated by testing several hypotheses with a combination of: a survey of the physical and biological characteristics of the eight key landscape elements identified in the valley, experimentally measuring the benefit of wind-blown subsidies to terrestrial microbial populations and the nature of the beneficial component of the subsidies. In each of the landscapes, the soil respiration, terrestrial photosynthesis (moss colonies and cyanobacterial mats on the soil), terrestrial nitrogen fixation, approximate area covered by communities undertaking carbon and nitrogen fixation and the transfer of organic material between aquatic and terrestrial environments was quantified. The results of these measurements will be a carbon and nitrogen budget for terrestrial communities in the valley system. The parameters and landscape scale resource budgets were tested by comparing the conditions in the Garwood Valley with those in the western Wright Valley, which is characterised by an entirely internal drainage system (the Onyx River flowing into Lake Vanda), a much less productive lake that occupies a much smaller areal proportion of the total valley floor, and a climate more influenced by the extremes of arid katabatic winds. Studies were in the 04/05 and 05/06 seasons in the Garwood Valley (Lake Colleen and Buddha Lake) and the Wright Valley (Lake Vanda). 
