Subnivean Development of Plants

the growth and formation of plant organs under the snow in winter. Subnivean development characterizes many herbaceous perennials of broadleaf forests, forest steppes, tundras, and alpine and sub-alpine meadows. Among annuals capable of subnivean development are winter crops, including cereal grains, which are prepared in the autumn for wintering. Subnivean development of perennial plants is largely made possible by the stored nutrients deposited in such underground organs as rhizomes, tubers, and bulbs.

In the first half of winter, most perennial herbs are in a state of dormancy. Toward the end of winter the vegetative and generative organs undergo accelerated differentiation, and there is a noticeable increase in the size of buds and growing shoots. Shoots may even appear above the soil surface. For example, the shoots of Siberian squill (Scilla sibirica) and Gagea rise 2–7 cm above the soil surface (however, they are still covered with a heavy layer of snow). In tundras and alpine meadows blossoming is sometimes observed under the snow in the spring, when the thickness of the snow cover is reduced to 5–8 cm. At this time, the snow crystallizes, and the sun’s rays easily penetrate and warm the soil cover and the young sprouts. Photosynthesis can then occur. As a result of this and the respiration of mosses and other plants, the snow thaws slightly, and cavities form, within which temperatures may exceed external temperature by 1.5° to 17.0°C. Under such conditions, the plants begin to vegetate and blossom. The subnivean development of species inhabiting forests and forest steppes proceeds under a thick, opaque layer of snow at temperatures close to 0°C.

The subnivean development of plants is an adaptation to life in tundras and at high altitudes under conditions of a short vegetative period. In broad-leaf forests, plants that have undergone such development make maximal use of the short period when there is light in the forest. This period extends from the beginning of the thaw until the opening of leaves on the trees.