ABSTRACT
Determining the age of landslide events is crucial for determining landslide risk, triggers, and also for predicting future landslide occurrence. Currently, the most accurate method for dating historical landslide events is dendrogeomorphic analysis. Unfortunately, the standard use of macroscopic growth responses of damaged trees for dating landslide activity suffers from many shortcomings. Thus, the aim of this study is to analyze in detail the growth response of trees to landslide movements at the anatomical level, a completely groundbreaking methodological approach. Ten specimens of European beech (Fagus sylvatica L.) were analyzed at two sampling heights, growing in two morphologically contrasting zones of the landslide area. Detailed anatomical analysis was focused on changes in morphometric parameters of the vessels and in the number of radial rays. The period (2008-2012) with the occurrence of the largest landslide movement (2010) recorded by long-term monitoring was analyzed. The results obtained revealed different anatomical responses in trees growing in different morphological zones of landslide. The tree responses on the ridge corresponded to the manifestations of tension wood formation, which corresponded to the stem tilting due to the landslide block movement. In the case of the trees in the trenches, root damage due to the subsidence of the landslide block blocked the flux of phytohormones, and their accumulation caused a significant reduction in the parameters of vessels and an increase in the number of rays. The study also includes recommendations in the future application of anatomical analyses in landslide research resulting from the obtained results. Thus, the obtained findings will improve the acquisition of chronological data for the purpose of landslide risk assessment.
Subject(s)
Fagus , Landslides , Fagus/physiology , Trees , WoodABSTRACT
The Kinzl Glacier is a unique dendritic-type glacier of the Peruvian Cordillera Blanca and is surrounded by well-developed Little Ice Age (LIA) moraines. Based on field observations and analysis of historical photographs (since 1932) and remotely sensed images (since 1948), we interpret distinct mechanisms of landslides in these moraines and link them to glacier retreat and thinning. Three types of landslides are distinguished according to the cross-profile morphology: (i) type "N", (ii) type "M" and (iii) type "A". Our data show that sliding of type "N" is an ice-contact slope failure that occurs as a gradual process simultaneously to glacier downwasting. In contrast, type "A" can occur at any time once the glacier has downwasted below the sliding plane and cannot buttress the nearly vertical inner slopes of the moraine anymore. We further argue that the type "M" can gradually evolve from type "N" or can occur as an episodic event. Probably due to overconsolidation of moraine material, landslides of types "N" and "M" keep their shape during sliding and move in form of several hundred meters long unbroken blocks. In contrast type "A" is internally disintegrated during landsilding. All investigated landslide types are characterized by increased width-length ratio and movement perpendicular to the direction of the flow of the glacier. We opine that the occurrence of these landslide types is directly or indirectly associated with glacial ice loss occurring since the end of the LIA. The observed landslides in the LIA moraines of the Kinzl Glacier are unique in the regional context considering their estimated size on the order of 106 m3 and contribute significantly to the paraglacial adjustment of moraine slopes and landform evolution in the post-LIA context. Apart from their role in moraine evolution, these landslides can trigger hazardous cascading process-chains in high-alpine environments.
