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The effectiveness of reflective tarpaulins in protecting tree seedling against heat stress

University of British Columbia

Reflective tarpaulins are used extensively in western Canada to protect tree seedlings against solar radiation during on-site storage and transportation. This project determined heat transfer characteristics of new and used reflective tarpaulins, and a FIST (Fiberglass Insulated Seedling Transporter) canopy. Containerized white spruce (Picea glauca (Moench) Voss) seedlings in shipping boxes were stored under tarpaulins and in the FIST canopy for up to six days in June, 1992. An unprotected seedling box was used as the control. Average seedling box temperatures per each 15-minute period were recorded for 144 h. Solar irradiance and wind speed at the test site were recorded simultaneously with box temperatures. The electrical conductivity of needles was measured after storage. Seedlings were withdrawn daily for six days and outplanted in a nursery plot in a split-plot randomized complete block design with repeated measurements within each experimental unit. Root collar diameter, total height and survival were recorded for three growing seasons. Samples of the tarpaulins were also tested under controlled conditions for ability to resist heat transfer. Seedling box temperatures ranged up to 35°C. Significant differences in 144-hour heat sums were found between: new and used tarpaulins; various used tarpaulins; tarpaulins and control; three new tarpaulins and the FIST canopy. Relative conductivities indicated no storage-induced damage to cell membranes. Survival after three years was 99.8%. Significant differences in growth were found but were more likely related to differences in soil nutrient differences within the plot. Storage temperature and length had no effect on growth and survival. A laboratory experiment tested for storage-induced pre-conditioning effects. Controls and seedlings pre-conditioned 4 and 8 days for 3 h at 30°C, were heat stressed for 8 h or 48 h at 30, 35, and 40°C. Electrical conductivities of needles were measured. Seedlings were outplanted in two plots with a completely randomized design. Root collar diameter, total height and survival were recorded for two growing seasons. No cell membrane damage was observed. Survival after two years was 99.5%. Evidence for a pre-conditioning effect is inconclusive. The 8-day pre-conditioning may have resulted in higher growth in seedlings heat stressed for 48 h.

Thesis/Dissertation

application/pdf

2009-01-15

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http://hdl.handle.net/2429/3664

Forestry

University of British Columbia

UBCV

DSpace