Patterns of larch establishment following deglaciation of Ventina glacier, central Italian Alps

Rapid glacier retreat often results in extensive areas of deglaciated terrain where primary successional processes occur. We studied biotic and abiotic factors underlying the invasion of larch (Larix decidua Mill.) on a glacier foreland and tested the hypothesis that the pattern of its establishment was controlled primarily by terrain age. The time span between deglaciation and establishment of larch and the importance of the position and shape of the glacier on the forest structure were studied over similar to 150 years of glacial retreat. We related three data sets (forest structure, topography and spatial position) using ordination methods. Simple and partial Mantel tests and kriging interpolation were used to map and identify the key factors underlying the spatial patterns of larch establishment. The elapsed time between deglaciation and the germination of the larch trees was estimated between 14 and 34 years, with lower values found closer to the glacier terminus. Sparse and young stands developed near the glacier terminus and Mantel tests indicated significant correlations between spatial distance and ecological distance. The kriging interpolation showed strong agreement between tree age and the spatial pattern of the retreating glacier. The most influential factors in determining stand density and age were proximity to the glacier terminus and seed sources, as well as litter cover and elevation. The age of trees was strongly influenced by terrain age or time since deglaciation, but as succession progressed forest structure became more complex.