Treelines—Approaches at Different Scales

Friedrich-Karl Holtmeier,Gabriele Broll

doi:10.3390/su9050808

Abstract

Scales in treeline research depend on the objectives and must match the underlying natural processes. Factors and processes at one scale may not be as important at another scale. In the global view, the number of factors influencing climatic treeline position can be reduced to the effects of heat deficiency. Emphasis, however, should be laid on differentiation of the treeline by their regionally and locally varying physiognomy, diversity, spatial and temporal features, and heterogeneity. An assessment of the relative importance of the factors shaping regional/local treeline physiognomy, spatial patterns, and dynamics should have priority. This can be achieved only by syndisciplinary research. Such studies are indispensable for assessing treeline response to climate change at the regional and landscape scales.

Highlights

Altitudinal and polar treelines are very heterogeneous and show a great physiognomic, genetic, and ecological variety due to their geographical position, tree species and history of vegetation, climate, and landscape
Factors and processes at one scale may not be as important at another scale
This has probably been, and still is, the main problem for treeline researchers from different disciplines in understanding better the complex nature of their common research object and in comprehending each other’s arguments. It is not a question of whether or not treeline research has to be carried out at large or fine scales, but the scale depends on the objectives and must match the underlying processes [1,2]

Summary

Introduction

Altitudinal and polar treelines are very heterogeneous and show a great physiognomic, genetic, and ecological variety due to their geographical position (climatic zone or region, climate character), tree species and history of vegetation, climate, and landscape (e.g., steep or gentle mountain slopes, gently rolling landscape). The focus may be, for example, on the physiological responses of trees to heat deficiency or insufficient moisture and nutrient supply at the treeline in general or on regional and local treeline spatial patterns and dynamics under the influence of numerous mostly interacting factors. Heterogeneity of treeline and spatial pattern and ecological variety increases from the global/zonal to finer scales (Figure 1). At the local scale and microscales, soil conditions may play an important role, at the seedling stage and, for treeline dynamics and high-altitude afforestation as well.

TTreeline Dynamics at Different Spatial and TeemmppoorraallSSccaalleess

Conclusions