Journal of Forest Science - In Press
The use of LiDAR for the documentation and modelling of cultural heritage sites hidden by the forest canopyOriginal Paper
Nikola Žižlavská, Stanislav Herber
The large number of charcoal kiln sites (CHKS) preserved as cultural heritage monuments demonstrates how extensive forest management for charcoal production has influenced the present forest dynamics and contributed to industrial expansion. Therefore, it is necessary not only to have a reliable methodology for detecting and documenting individual kiln sites for management and protection purposes but also to present the results in a meaningful way to the public. The aim is to optimise the data processing workflow from Airborne Laser Scanning (ALS) point cloud to printable model (from LAS format to STL), determine the influence of vegetation cover at the time of data collection on the quality of the resulting model, verify the quality of printed models using photogrammetry, and finally, produce printed models of CHKS as cultural heritage objects in a form that can be effectively presented to the public. After comparison of different ground filtering methods, we conclude that the most accurate method for creating precise ground representation for our area of interest was the Cloth Simulation Filtering (CSF) algorithm. From the filtered point cloud, a high-resolution raster surface was generated, which served as the basis for CHKS detection. Using our proposed methodology – combining the Topographic Position Index (TPI) with a 0–5% slope threshold – we achieved a significant improvement in detection performance compared to using a zero-slope threshold alone, with the F1 score increasing from 0.667 to 1.000. Subsequently, the most representative kiln site was selected, which was then processed and optimised using various software tools, resulting in an exchangeable STL file suitable for dissemination and 3D printing. The accuracy of the printable model was then evaluated. We conclude that point cloud from the winter flight campaign achieved higher accuracy. The average height differences were similar; however, the spatial distribution varied between the two clouds. The model from the winter flight campaign had more evenly distributed deviations and overall was better for modelling the CHKS.
Himalayan fir growth from central Bhutan reflects variability of temperature and precipitationOriginal Paper
Jiří Lehejček, Gabriel Vávrů, Sangay Wangchuk, Miroslav Svoboda, Katrien Boonen
Mountain ecosystems, especially those at the highest altitudes, are sensitive to current climate change. Proxy archives may provide an insightful tool to better understand ongoing changes and evaluate future scenarios. Trees have traditionally been used as such archives, as they often respond sensitively to environmental change. Thus, we studied tree-ring records of forest-line species Abies densa Griff. growing in the Eastern Himalayas, central Bhutan, to evaluate the effect of climate on the growth of this species. The annual chronologies were generated using standard dendrochronological methods and then compared with climatic data from the CRU TS database. The results demonstrate a negative effect of summer temperatures on the width of the annual rings, suggesting possible stress caused by higher temperatures during the monsoon season. On the other hand, a positive effect of temperatures on tree growth was observed during late winter months. The response to rainfall was mixed, with a positive effect on growth in November and a negative effect in May and January, suggesting a later onset of the vegetation season. To our knowledge, we present the first dendroclimatological study on this long-lived species in central Bhutan, portraying its potential for future climate and environmental research and applications.
Foliar nutrients and tree growth of planted Cupressus arizonica in pure and mixed stands
Mahdieh Safizadeh
This study aimed to compare pure and mixed plantation stands on vegetative and nutritional characteristics of Cupressus arizonica. Systematic-random sampling method was employed using a grid of 75 × 75 m with 20 x 20 m square plots established for data collection. Sampling and chemical analysis of nitrogen, phosphorus and potassium levels in leaves was conducted at the third end of the tree crown. The diameter at breast height (DBH) of all trees and the two crossed crown diameters of all trees were used to calculate the mean crown diameter and mean crown area. Characteristics that were measured included average DBH, average basal area per ha, number per ha, number in diameter classes per ha, mean crown diameter, mean crown area, mean crown area in diameter classes and the regression relationship between the DBH and crown area. The study analyzed data using SPSS20 software, employing one-way ANOVA and Tukey test analysis for mean comparison at 95% level. Results indicated the mixed with broad-leaved stand had a favourable effect on the vegetative characteristics of Cupressus arizonica and among two different studied types of mixed stands (mixed broad-leaved, mixed coniferous), only mixed with broad-leaved stand resulted in the improvement of nutritional status of Cupressus arizonica.