A Rainout-shelter design for intercepting different amounts of rainfall

LAURA YAHDJIAN; OSVALDO E. SALA

Tucson, Arizona, USA

Congreso; 87th Annual Meeting of the ESA; 2002

Ecological Society of America

Field manipulative experiments represent a straightforward way of exploring temporal relationships between annual precipitation and productivity. We developed fixed-location rainout shelters with roofs consisting of bands of transparent acrylic that blocked different amounts of rainfall while minimally affecting other environmental variables. We used three kinds of shelters for passively intercepting 30%, 55%, and 80% of the precipitation in a field experiment in a shrub steppe in Río Mayo, Chubut (Argentina). We tested the effectiveness of the design with a random-block design n=10 and evaluated changes in soil water content and microclimate. Water collected by each rainout-shelter type was significantly different (p<0.001) and was the same as expected for the 30% and 55 % interception treatments. The 80% shelters intercepted only 71% of incoming rainfall which was lower than the expected value (p<0.05). Soil water content was significantly higher (p<0.05) in control than in rainout-shelter plots at all dates, except in January (summer). Photosynthetically active radiation was not affected by the 30% interception treatment, but the roof with the largest number of acrylics bands (80% interception treatment) reduced incident radiation throughout the day by 10%. Air and soil temperature were lower under than outside the shelters with a maximum difference of 6°C at midday. The two characteristics of the shelter, fixed design and low cost, allow for proper replication in space, which is required in ecological field experiments.