Use of a weighing lysimeter system to assess the effects of trampling on evapotranspiration of montane plant communities

The aim was to investigate the impacts of trampling on water loss and partitioning in vegetation with contrasting structure and species composition. A new design of weighing lysimeter was used in glasshouse experiments to compare evapotranspiration from intact and trampled blocks of vegetation. The lysimeter system was able to detect differences between treatments after only a few hours. Evapotranspiration was recorded for six communities, representative of cryptogam - vascular plant communities found in the Cairngorm Mountains of Scotland. Vegetation blocks of Racomitrium and Vaccinium/Hylocomium heath communities had the greatest cumulative evapotranspiration and lichen heath the least over 48 h. Blocks from three of the communities (Agrostis/Festuca grassland, Calluna wet heath, and lichen heath) were used in a trampling experiment with five levels of damage. Trampling progressively destroyed the structure of the vegetation of all communities and increased the rates of water loss from the blocks. The grassland community vegetation was the most resilient. These results help to link the massive changes in vegetation structure resulting from trampling to effects on water loss and microclimate.