The cold range limit of trees

Low-temperature range limits of tree species result from the interaction of phenology, freezing tolerance at flushing, and season length requirements for maturation. At the low-temperature treeline, trees become victims of their height. It is the aerodynamics of the life-form tree that impose critically low, growth-limiting air temperatures on trees, from which small-stature plants escape. Humans cannot shift the low-temperature limit of trees (the treeline), but they may have removed trees from the treeline by logging or burning. The treeline tracks seasonal low-temperature means, the tree species range limit tracks low-temperature extremes. The treeline is a most important global bioclimatic reference line against which other bioclimatic zones and the associated biomes can be defined. At high elevation or latitude, trees reach low-temperature range limits. In attempting an explanation, the range limits of individual tree species (set by freezing tolerance) and the general limit of the life-form tree (set by thermal growth constraints) need to be distinguished. The general cold edge of the fundamental niche of trees is termed the treeline, by definition, the lower edge of the alpine belt, a most important bioclimatological reference line. Trees can be absent from the treeline due to disturbances or biotic interactions. The actual local edge of tree distribution, the delineation of the realized niche, is driven by stochastic effects. Therefore, treeline theory and hypothesis testing is inevitably tied to the fundamental niche concept. At high elevation or latitude, trees reach low-temperature range limits. In attempting an explanation, the range limits of individual tree species (set by freezing tolerance) and the general limit of the life-form tree (set by thermal growth constraints) need to be distinguished. The general cold edge of the fundamental niche of trees is termed the treeline, by definition, the lower edge of the alpine belt, a most important bioclimatological reference line. Trees can be absent from the treeline due to disturbances or biotic interactions. The actual local edge of tree distribution, the delineation of the realized niche, is driven by stochastic effects. Therefore, treeline theory and hypothesis testing is inevitably tied to the fundamental niche concept. the action of moving air (wind) that causes enhanced transfer of heat and gases (convection and forced diffusion). the naturally treeless land above the high-elevation treeline across the globe. the naturally treeless land beyond the low-temperature driven, high-latitude treeline. the mechanical or fire-driven removal of plants or their parts (logging, burning, wind throw, browsing, erosion, avalanches, etc.). the transition zone between two types of land cover (here from montane forest to alpine vegetation). a genotype with traits evidently advantageous in a given environment. the environmental space occupied by a taxon, as defined by its physiological potential. geographical information system. the period during which plants develop and grow. Since not all developmental and growth processes are visible, the beginning and end are often defined by threshold temperatures. a line of constant temperature in the landscape, most commonly for means of air temperature. the tissue that creates new cells, where cells divide and differentiate. This is where plants grow and invest photoassimilates in structures. There are apical meristems at the tip of shots and roots and lateral ones, such as the cambium, that forms tree rings. the visible part of plant development such as bud break, leaf flushing, flowering, leaf senescence, leaf shedding. These visible phenomena are underpinned by nonvisible settings by active genes, hormones, and meristematic activities. the actual space occupied by a taxon as set by history of spreading, all sorts of biotic interactions, disturbances, etc. a severe physiological constraint that causes loss of tissue or substantial fitness reductions (e.g., freezing stress). Not every limitation of growth and development is a stress. Mild stress may improve fitness. the low-temperature range limit of the life-form tree at high elevation or high latitude.