Fall lifting and long-term freezer storage of ponderosa pine seedlings: effects on starch, root growth, and field performance

Abstract

To determine the response of seedlings lifted in fall and stored at temperatures below 0 °C until outplanting, ponderosa pine (Pinusponderosa Dougl. ex Laws.) seedlings from two Oregon seed sources were harvested in September, October, and November (stored below 0 °C until late winter–spring planting) and compared with seedlings lifted in March (stored above 0 °C until planting). Growth potential at the time of planting was measured by monitoring changes in root initiation, fresh weight, and root starch concentration and content under greenhouse conditions. Field performance was determined by measuring survival and growth at two field sites. Dry weight and root starch decreased 5–13% and 82–99%, respectively, in storage, and the majority of change occurred during the first 3 months of storage. Less than 15% of the seedlings from the September lifting and storage treatment initiated new roots, and fresh weight decreased more than 30% during the greenhouse test. Seedlings from this treatment had less than 25% field survival during the 1st and 2nd years after outplanting. Greater than 62% of seedlings lifted in late fall and spring had new roots; these seedlings exhibited less than 14% loss in fresh weight, and greater than 75% field survival. In the greenhouse test, initial root starch concentration was not related to subsequent root growth (new root weight or days to root initiation). Similarly, neither initial root starch concentration nor content at the time of planting was strongly associated with field survival or growth in the field after planting.

The role of stored carbohydrates and nitrogen in the growth and stress tolerance of planted forest trees

“…Poor field performance of cold stored plants has been attributed in part to strong reduction in NSC levels (Ritchie 1982, Table 5). However, few studies have found a close relationship between field performance and seedling NSC following storage (Puttonen 1986;Cannell et al 1990;Omi et al 1994). Similarly, seedlings exposed to prolonged drought stress either after spring shoot growth or when planted under deep shade, such as in the understory of forest stands, might also show severe reductions in tissue NSC levels (O'Brien et al 2014).…”