Application.Even if frost heaving of forest tree seedlings is difficult to control, it could be reduced by determining the susceptibility of soils to frost action and then taking appropriate ameliorative measures such as fertilizing, sowing or planting at the proper time, planting big seedlings and modifying the soil environment by draining, shading and the use of mulches. Site preparation should be restricted to the minimum necessary for control of competing vegetation and preparation of favorable seedbeds. Retaining some portion of the natural plant cover on areas to be seeded or planted could greatly reduce frost heaving.Abstract. Soil frost heaving is the result of the formation of ice lenses in the soil caused by a segregation of the soil water. Ice lenses are growing from below and pushed upward. Seedlings heave when they are pushed out of the ground by the ice sheet formed at the surface of the soil. Frost heaving may greatly reduce growth and survival of forest tree seedlings particularly in regions where freezing and thawing are accompanied by high soil moisture. Resistance to frost heaving increases with size of seedling as the ability of a seedling to anchor itself increases. A few methods, such as fertilizing, choice of planting spots, sowing or planting at the proper time, shading, and use of mulches, appear to be effective in controlling frost heaving. Shade from natural plant cover can greatly reduce frost heaving.

Wave mortality in subalpine Abies forests of the northeastern United States is characterized by the progressive dieback of overstory dominants in a compact zone that advances systematically through mature stands and is followed by vigorous regeneration of the overstory species. The principal driving force for this dieback appears to be exposure at the edge of canopy gaps to very high winds. In this study, individual trees at the leading edge of a dieback front and trees in a thinned plot within the mature stand downwind of the advancing wave both experienced a substantial decline in foliage mass and, consequently, in prebudbreak foliar starch pool over a 2-year period. In the case of the thinned stand, this reduction was attributed to a large increase in wintertime green litter fall. Increased exposure at the wave front and in the thinned stand also resulted in a dramatic increase in root damage relative to control trees. Coincidental to breakage of roots, root xylem discoloration (attributed to wounding and invasion by root pathogens) was greater on trees at the wave front than on trees in the mature zone. Loss of active foliage and roots was accompanied by a two- to five-fold reduction in annual wood increment among dieback zone trees. These data suggest that exposed trees, which suffer a substantial reduction in crown size and foliage carbohydrate pool in an environment where growth is marginal to begin with, may not be able to keep up with the increased energy demand for root and foliage turnover and eventually suffer death by attrition of both tissues.

Vertical uplift of seedlings and rods on the soil surface and at a depth of 5 cm, and of reference trees, was monitored using a theodolite from autumn to spring in two adjacent field experiments on a silt soil in northern Sweden. Treatments involving scarification (control and square patches of 0.1, 0.2, 0.4, and 0.8 m at natural snow cover) and snow cover (simulated maximum cover, snow free, and natural cover for control and 0.4-m patches) were compared. For snow free and natural snow cover, diurnal variation of soil surface temperature, duration and magnitude of freezing temperatures, and uplift increased with patch size. At the end of the winter under natural snow cover, uplift of the soil surface and shallow soil was between 4.4 and 5.3 cm for the control treatment without scarification and the 0.1-m patch while the uplift for the 0.4- and 0.8-m patches reached 7.6–11.5 cm. The highest uplift value, 14.6 cm, was observed for the snow-free treatment with 0.4-m patches. Maximum uplift of trees averaged 4.4 cm, which was similar to values observed for seedlings and rods with an intact humus layer and a natural snow cover, indicating that the highest observed uplift was mainly due to needle and soil surface ice. In conclusion, size of the scarified area and duration and thickness of snow cover largely influence frost heaving of tree seedlings in a susceptible soil.

No abstract