Małgorzata Wistuba

Dendrochronological methods for reconstructing mass movements — An example of landslide activity analysis using tree-ring eccentricity

Dendrochronological methods can be applied to the reconstruction of different types of environmental events such as climate changes, fires, glacier movements, floods, earthquakes, volcano activity. In the field of geomorphology dendrochronology is increasingly frequently used for the absolute dating of different types of mass-movements (rock falls, landslides and debris flows, etc.). Trees growing on slopes transformed by mass-movements are tilted and wounded while their stems and root systems are exposed or buried under sediment. These events are recorded in wood anatomy as eccentric growth, reaction wood, scar overgrowth by callous tissue, changes in cell size or adventitious root production. Dating changes in wood anatomy allows to date and precisely reconstruct the spatial and temporal occurrence of mass-movements with at least one year resolution. The paper provides a review of existing dendrochronological tools used in geomorphology and also an example of the application of eccentric tree-growth to reconstruct landsliding. Using tree-ring eccentricity allows to (1) obtain a dynamic depiction of slopes, (2) study landslide activity, not only contemporary, but also in the last tens of hundreds of years (depending on the stand age).

Activity of Slow-Moving Landslides Recorded in Eccentric Tree Rings of Norway Spruce Trees (Picea Abies Karst.) — An Example from the Kamienne MTS. (Sudetes MTS., Central Europe)

Abstract We found ubiquitous evidence of ongoing slope instability by analysing the variability of tree-ring eccentricity index in trees growing on three apparently relict landslide slopes in the Sudetes (Poland, Central Europe). Slow movement of these landslide bodies occurs in the present-day conditions and is recorded almost every year, although with variable intensity. Correlation of dendrochronological record with the rainfall record from a nearby station in Mieroszów for the 1977–2007 period is very poor for two deep-seated rotational slides at Mt Suchawa and Mt Turzyna but considerably better for a shallow flowslide at Mt Garbatka. While this may reflect higher permeability of heavily jointed rocks involved in deep-seated sliding this could be linked with imperfections in the rainfall record. Dendrochronology proved capable of detecting minor displacements within landslides which otherwise show no geomorphic evidence of recent activity. Therefore, claims for the entirely relict nature of the landslides are not substantiated.

Charcoal kilns as a source of data on the past iron industry (an example from the River Czarna valley, Central Poland)

Abstract Charcoal was the primary fuel used for iron smelting and processing until the end of the 19th century. It was produced through burning piles of wood called charcoal kilns. The aim of the study was to identify and record traces of charcoal kilns related to past ironworks in the valley of the River Czarna (Małopolska Upland, Central Poland). Detailed analysis was conducted in areas adjacent to historical centres of iron processing in Maleniec, Kołoniec and Machory. A quantitative analysis of the traces of charcoal kilns in the topography was done based on DEM from airborne LiDAR. Soil profiles were analysed at the sites where traces of charcoal kilns were identified from DEM. Radiocarbon dating and palaeobotanical analyses were performed for selected charcoal from kiln remnants. In the study area we identified over 11,500 charcoal kilns. The radiocarbon age of these charcoals indicate that the charcoal kilns under study were used in the 15th, 18th and 19th century. Thus the results suggest that the iron industry in the studied area is c 100 years older than the historical written sources indicate. Palaeobotanical analyses show that coniferous trees were used for charcoal production. The large number of traces of charcoal kilns and their wide spatial distribution indicate that past charcoal production has had a significant impact on the environment and landscape change in the River Czarna valley and adjacent areas.

Precipitation as a factor triggering landslide activity in the Kamień massif (Beskid Niski Mts, Western Carpathians)

Abstract On the landslide slope in the Beskid Niski Mts (Western Carpathians) 48 silver firs were cored for dendrochronological samples. Tree-ring widths were measured for the upslope and downslope sides of each stem. Events of landslide activity were dated using the method of the eccentricity index. The tree-ring record of landsliding was compared with the occurrence of precipitation in the study area. The nature of the relation between precipitation and landsliding is complex. We have found a statistically significant correlation between landsliding and the number of days with 24-hour precipitation totals above 20 mm and high 3-, 5-, and 10-day precipitation totals during winter half-years. Thus landsliding in the Kamień massif is triggered mainly by high precipitation totals in the preceding winter period. No such relation was found for annual precipitation totals and different types of precipitation totals in the summer period. Single landsliding events related to high summer precipitation totals were found, but the correlation is not statistically significant. In addition some landsliding events are 1–2 years lagged after the occurrence of high long-term precipitation totals. It seems that the strongest landsliding events resulted from sequences of wet summer, wet winter and once again wet summer seasons directly following one another.

Dendrochronological dating as the basis for developing a landslide hazard map – An example from the Western Carpathians, Poland

Abstract Most landslide hazard maps are developed on the basis of an area’s susceptibility to a landslide occurrence, but dendrochronological techniques allows one to develop maps based on past landslide activity. The aim of the study was to use dendrochronological techniques to develop a landslide hazard map for a large area, covering 3.75 km2. We collected cores from 131 trees growing on 46 sampling sites, measured tree-ring width, and dated growth eccentricity events (which occur when tree rings of different widths are formed on opposite sides of a trunk), recording the landslide events which had occurred over the previous several dozen years. Then, the number of landslide events per decade was calculated at every sampling site. We interpolated the values obtained, added layers with houses and roads, and developed a landslide hazard map. The map highlights areas which are potentially safe for existing buildings, roads and future development. The main advantage of a landslide hazard map developed on the basis of dendrochronological data is the possibility of acquiring long series of data on landslide activity over large areas at a relatively low cost. The main disadvantage is that the results obtained relate to the measurement of anatomical changes and the macroscopic characteristics of the ring structure occurring in the wood of tilted trees, and these factors merely provide indirect information about the time of the landslide event occurrence.

Reductions in tree-ring widths of silver fir (Abies alba Mill.) as an indicator of air pollution in southern Poland

Abstract The aim of the study was to investigate how the emission of pollutants to the atmosphere from the late 19th century until modern times has been recorded in rings of silver fir trees growing in southern Poland. Samples were collected from 24 firs growing in the Beskid Niski Mountains (Western Carpathians). Using a Pressler borer, a single core was collected from each tree. Within the samples, tree-ring widths were measured. On this basis, reductions of tree-ring widths were calculated and subsequently divided into three classes according to their severity. Study results indicate that growth reductions at the site studied were influenced by the pollution emitted from the now-defunct Central Industrial Region, which developed most rapidly from 1920 to 1940, and began to decline after World War II. These emissions were probably responsible for reductions in the trees sampled in the years 1928–1947. On the other hand, reductions of tree-ring widths dating from 1951 to 1989 were caused by the post-war development of heavy industry throughout Poland, and in particular in the Upper Silesian Industrial Region, which developed at its most rapid rate from 1960 to 1990. The results obtained demonstrate that reductions of tree-ring widths in the silver firs studied are related to industrial air pollution in the 20th century. As industrial production declined and environmentally friendly technologies were introduced in the early 1990s, air pollution levels decreased and an increase in tree-ring widths followed in the silver firs studied. Further reductions of tree-ring widths have been observed in recent years (since 2009), which may be caused by air pollution due to low-stack emissions from domestic boilers. The analysis conducted demonstrates that a reduction in tree-ring widths in silver fir is a sensitive bioindicator of air pollution.

Relief evolution of landslide slopes in the Kamienne Mts (Central Sudetes, Poland) – analysis of a high-resolution DEM from airborne LiDAR

Abstract The aim of the study is to reconstruct the development of landslide relief in the Kamienne Mountains (Central Sudetes, SW Poland) based on a DEM from LiDAR data. Analyses of relief and geological maps in ArcGIS 10.5 and of slope cross-sections in Surfer 14 allowed to distinguish different types of landslide relief, developed in latites and trachybasalts lying above claystones and mudstones. The types vary from small, poorly visible landslides to vast landslides with complex relief. They were interpreted as consecutive stages of geomorphic evolution of hillslope-valley topography of the study area. Two main schemes have been established which explain the development of landslide slopes in the Kamienne Mts: (1) upslope, from the base of the slope towards the mountain ridge and (2) downslope, beginning on the top of the mountain ridge. The direction of landslide development depends on the thickness of volcanic rocks in relation to underlying sedimentary rocks. When the latter appear only in the lowest part of the slope, landslides develop upslope. If sedimentary rocks dominate on the slope and volcanic rocks form only its uppermost part, landslides develop downslope. The results show that landsliding leads to significant modifications of relief of the study area, including complete degradation of mountain ridges.

A tree-ring and GIS assessment of mass-movement hazard in the Moxi basin (Sichuan, China)

The goal of our study is to estimate the frequencies and magnitudes of mass movements of differing origin and scale endangering the population of the Moxi basin. The ages of 30 trees were determined indicating the date of the last large debris flow. In addition we determined the dates of smaller debris flows wounding the stems of 43 trees and the dates of rockfalls injuring the stems of 15 trees. The results allowed the recurrence intervals of the mass movements observed in each study site to be calculated. Based on the results from three study sites representing typical mass-movement hazards, the densely inhabited main valley of the Moxi basin is affected by 40 large debris flows, hundreds of smaller debris flows and thousands of single rockfalls per century. The GIS-based survey indicates that the hazard affects as much as 27.07% of developed area of the Moxi basin. However, thanks to sustainable land use, the majority is affected by manageable, high frequency, but middle- to low-magnitude phenomena.

Reconstructing the evolution of hillslope-valley topography based on DTM from airborne LiDAR (Central Sudetes, Poland)

The aim of this study is to check whether it is possible to reconstruct the evolution of hillslope-valley topography of the Kamienne Mts. by using airborne LiDAR data. Detailed analysis of relief and geological maps in ArcMap 10.5 and analysis of slope and valley cross sections in Surfer 13 allowed to outline specific types of hillslope-valley topography. These types vary from small landslides with poorly developed relief to vast landslides with main scarps exceeding the mountain ridge. The types represent subsequent stages of geomorphic evolution which leads to disintegration of the mountain ridge studied. All consecutive stages of relief development were found in present relief as different landslide slopes are probably of different age or develop slower or faster. The study carried out in the Kamienne Mts. shows that DTM from airborne LiDAR data can be a useful tool not only in quantitative analyses of relief but also for qualitative analyses such as reconstructing relief evolution.

Landslide activity as a threat to infrastructure in river valleys – An example from outer Western Carpathians (Poland)

Intensive development of the area of Polish Carpathians increases the scale of landslide risk. Thus detecting landslide hazards and risks became important issue for spatial planning in the area. We applied dendrochronological methods and GIS analysis for better understanding of landslide activity and related hazards in the test area (3,75 km2): Salomonka valley and nearby slopes in the Beskid Żywiecki Mts., Outer Western Carpathians, southern Poland. We applied eccentricity index of radial growth of trees to date past landslide events. Dendrochronological results allowed us to determine the mean frequency of landsliding at each sampling point which were next interpolated into a map of landslide hazard. In total we took samples at 46 points. In each point we sampled 3 coniferous trees. Landslide hazard map shows a medium (23 sampling points) and low (20 sampling points) level of landslide activity for most of the area. The highest level of activity was recorded for the largest landslide. Results of the den...