Laboratory spectroscopy in visible and infrared regions is an important tool for studies dealing with plant ecophysiology and early recognition of plant stress due to changing environmental conditions. Leaf optical properties are typically acquired with a spectroradiometer coupled with an integration sphere (IS) in a laboratory or with a contact probe (CP), which has the advantage of operating flexibility and the provision of repetitive in-situ reflectance measurements. Experiments comparing reflectance spectra measured with different devices and device settings are rarely reported in literature. Thus, in our study we focused on a comparison of spectra collected with two ISs on identical samples ranging from a Spectralon and coloured papers as reference standards to vegetation samples with broadleaved (Nicotiana Rustica L.) and coniferous (Picea abies L. Karst.) leaf types. First, statistical measures such as mean absolute difference, median of differences, standard deviation and paired-sample t-test were applied in order to evaluate differences between collected reflectance values. The possibility of linear transformation between spectra was also tested. Moreover, correlation between normalised differential indexes (NDI) derived for each device and all combinations of wavelengths between 450 nm and 1800 nm were assessed. Finally, relationships between laboratory measured leaf compounds (total chlorophyll, carotenoids and water content), NDI and selected spectral indices often used in remote sensing were studied. The results showed differences between spectra acquired with different devices. While differences were negligible in the case of the Spectralon and they were possible to be modelled with a linear transformation in the case of coloured papers, the spectra collected with the CP and the ISs differed significantly in the case of vegetation samples. Regarding the spectral indices calculated from the reflectance data collected with the three devices, their mean values were in the range of the corresponding standard deviations in the case of broadleaved leaf type. Larger differences in optical leaf properties of spruce needles collected with the CP and ISs are implicated from the different measurement procedure due to needle-like leaf where shoots with spatially oriented needles were measured with the CP and individual needles with the IS. The study shows that a direct comparison between the spectra collected with two devices is not advisable as spectrally dependent offsets may likely exist. We propose that the future studies shall focus on standardisation of measurement procedures so that open access spectral libraries could serve as a reliable input for modelling of optical properties on a leaf level.

The map of lakes and selected glacier-related landforms in Huascarán National Park was created describing their spatial distribution and selected properties related to their development. This work presents additional information on previous lake inventories that was not available prior to its completion despite the fact that some of the newly collected information is important for glacial lake flood hazard assessment. The ongoing environmental changes documented in the national park are affecting the number, size, spatial distribution and development of the glacial lakes. Many of the lakes are also filled with sediment, as well as subject to outburst floods. The lake typology is based on the character of their dam, whilst moraine ridge types are defined with specific geomorphological features that affect their stability. Over 1250 moraine ridges (longer than 200 m) were mapped and classified along with 2370 lakes each with a specific dam type. This represents the most detailed inventory which can be used for future statistical analysis or hazard assessment.

This paper presents a snow avalanche hazard map of the most avalanche-prone mountain range in the Czech Republic, the Krkonoše Mountains. The map was prepared using historical records of 1132 avalanches which occurred over the last 54 years and state-of-the-art modelling of avalanche propagation and the spatial distribution of potential avalanche source areas. The map provides not only reliable and easy to understand information for the Mountain Rescue Service of the Czech Republic and mountain tourists, but also for land use managers to identify areas where new avalanche paths may develop under favourable conditions, including the total removal of forest cover.

Forests have always been a major concern for public authorities given their significant role as a resource for timber production, as well as for climate regulation. The infestation of bark beetles poses a challenging problem in forests, causing tree mortality, reduced timber quality, and ecosystem disruption. Multispectral imagery (MS) captured from unmanned aerial vehicles (UAVs) are increasingly employed for forest health assessment and have been extensively used to map the tree mortality caused by bark beetles. However, its utilisation for the identification of the initial stage of infestation known as "green attack" when infested trees do not display any visible symptoms yet, is still uncertain. This study is innovative in the ways it works with so far rare dense and comprehensive time series of MS UAV imagery starting in the initial month prior to the infestation and before the development of the Bark Beetle (BB) infestation visual symptoms, aiming to evaluate the detectability of bark beetle (Ips typographus L.) green attack. The study area predominantly covered by Norway spruce (Picea abies (L.) Karst.) is located in the Krkonoše Mountains National Park, in the Czech Republic. From May to August 2022, a total of nine MS UAV datasets were acquired with a DJI Phantom 4 MS sensor. The research question is whether infested trees exhibit significantly different changes in the spectra compared to healthy trees at an early stage. The detectability of green attacks was statistically investigated along with the underlying factors (flowering, growth of new shoots) that can affect the accuracy of detection. The results showed a distinct reduction in tree vitality of the infested trees in the late summer season and later stages of infestations. Based on our findings, we conclude that the proposed methods using UAV MS images can be employed to map local infestations and evaluate the tree vitality throughout the season, but the early detection of the green attack stage (in the absence of visible symptoms at the crown level) of Bark Beetle infestation from UAV MS data remains unfeasible. The precision of the detection using statistical methods can be further investigated using a time series of UAV hyperspectral images that offer a higher spectral resolution.