GO WIDE TO GO DEEP: AFFORDABLE, REPLICABLE ROBOTIC MINIRHIZOTRON SAMPLING FOR PHENOLOGY STUDIES

Minirhizotrons (paired camera systems and buried observatories) are the best current method to make repeatable measurements of fine roots in the field. Automating the technique is also the only way to gather high resolution data necessary for comparison with phenology-relevant above-ground remote sensing, and, when appropriately validated, to assess with high temporal resolution belowground biomass, which can support carbon budgets estimates. Minirhizotron technology has been available for half a century but there are many challenges to automating the technique for global change experiments. Instruments must be cheap enough to replicate on field scales given their shallow field of view, and automated analysis must both be robust to changeable soil and root conditions because ultimately, image properties extracted from minirhizotrons must have biological meaning. Both digital photography and computer technology are rapidly evolving, with huge potential for generating belowground data from images using modern technological advantages. Here we demonstrate a homemade automatic minirhizotron scheme, built with off-the-shelf parts and sampling every two hours, which we paired with a neural network-based image analysis method in a proof-of-concept mesocosm study. We show that we are able to produce a robust daily timeseries of root cover dynamics. The method is applied at the same model across multiple instruments demonstrating good reproducibility of the measurements and a good pairing with an above-ground vegetation index and root biomass recovery through time. We found a sensitivity of the root cover we extracted to soil moisture conditions and time of day (potentially relating to soil moisture), which may only be an issue with high resolution automated imagery and not commonly reported as encountered when training neural networks on traditional, time-distinct minirhizotron studies. We discuss potential avenues for dealing with such issues in future field applications of such devices. If such issues are dealt with to a satisfactory manner in the field, automated timeseries of root biomass and traits from replicated instruments could add a new dimension to phenology understanding at ecosystem level by understanding the dynamics of root properties and traits.

Deep soil ploughing for afforestation: a review of potential impacts on soil and vegetation

Deep ploughing—which inverts, covers, or mixes soil organic layer (forest floor) and surface mineral A horizon into the mineral subsoil, burying the upper soil horizon in deeper layers, and disrupting pedogenic processes—is a debatable topic in forest plantation management. Overall, this review article aimed to identify the impacts of deep ploughing on the properties of forest plantations, adapting experiences from the agricultural sector. This paper examines the main impacts of deep ploughing technology on soil physical, chemical, and biological properties, ground vegetation, and tree aboveground and belowground biomass in afforested former agricultural land. Analysis of the published literature shows that deep ploughing can be used under different climatic and soil conditions, but it induces site-specific changes in soil properties and vegetation. Mechanical site preparation during afforestation and reforestation should follow the requirements of sustainable soil management, in order to avoid negative effects on the environment and biodiversity. Based on this analysis, we suggest key indicators that may be specific to deep ploughing responses in afforested sites and can contribute to risk assessment, aimed at achieving sustainable forest management. To date, most studies on mechanical site preparation for forest plantation have been performed using a few conifer tree species; therefore, it is important to expand empirical studies.

Systematic Approach for Remote Sensing of Historical Conflict Landscapes with UAV-Based Laserscanning

In order to locate historical traces, drone-based Laserscanning has become increasingly popular in archaeological prospection and historical conflict landscapes research. The low resolution of aircraft-based Laserscanning is not suitable for small-scale detailed analysis so that high-resolution UAV-based LiDAR data are required. However, many of the existing studies lack a systematic approach to UAV-LiDAR data acquisition and point cloud filtering. We use this methodology to detect anthropogenic terrain anomalies. In this study, we systematically investigated different influencing factors on UAV-LiDAR data acquisition. The flight parameters speed and altitude above ground were systematically varied. In addition, different vegetation cover and seasonal acquisition times were compared, and we evaluated three different types of filter algorithms to separate ground from non-ground. It could be seen from our experiments that for the detection of subsurface anomalies in treeless open terrain, higher flight speeds like 6m/s were feasible. Regarding the flight altitude, we recommend an altitude of 50–75m above ground. At higher flight altitudes of 100–120m above ground, there is the risk that terrain characteristics smaller than 50cm will be missed. Areas covered with deciduous forest should only be surveyed during leaf-off season. In the presence of low-level vegetation (small bushes and shrubs with a height of up to 2m), it turned out that the morphological filter was the most suitable. In tree-covered areas with total absence of near ground vegetation, however, the choice of filter algorithm plays only a subordinate role, especially during winter where the resulting ground point densities have a percentage deviation of less than 6% from each other.

Post fire ground vegetation development over 25 years

Fire has been a part of natural disturbance regime in boreal and to some extent also hemiboreal forests, affecting soil and light conditions, seedbanks, trees and ground vegetation. The most significant factors affecting occurrence, severity and size of forest fires are anthropogenic, weather and the environment, all of which are changing due to human-caused climate change. This paper discusses medium term (25 years) vegetation development in five different biotopes after fire disturbance. Sample plots were established in Slitere Reserve (now National park) in north-western Latvia on areas affected by large fire in 1992. Data were collected in 1993, 2002 and 2017. The aim of the study was to characterize the regeneration and succession of ground vegetation after the fire. In 1993, species such as bog-rosemary (Andromeda polifolia), heather (Calluna vulgaris) and cloudberry (Rubus chamaemorus) were observed in the ground vegetation a year after the fire. In 2002 liverworts appeared, indicating that the bog has acquired more stable and wetter conditions, but in 2017, liverwort mosses were no longer present and the percentage cover of Rubus chamaemorus decreased significantly and Calluna vulgaris, sphagnum sp., and Betula pendula were present in large quantities in the bog. Comparing these studied years, it can be concluded that all these years the biotopes and species have continuously developed and are regenerating.

Estimation of litter input in hemi-boreal forests with drained organic soils for improvement of GHG inventories

Assessments of net greenhouse gas (GHG) emissions in forest land with drained organic soils conducted within the scope of National GHG inventories requires reliable data on litter production and carbon (C) input to soil information. To estimate C input through tree above-ground litter, sampling of above-ground litter was done in 36 research sites in Latvia representing typical forests with drained organic soils in hemiboreal region. To estimate C input through tree below-ground litter and litter from ground vegetation, modelling approach based on literature review and data on characteristics of forest stands with drained organic soils in Latvia provided by National Forest Inventory (NFI) was used. The study highlighted dependence of C input to soil through litter production from the stand characteristics and thus significant differences in the C input with litter between young and middle age stands. The study also proves that drained organic soils in middle age forests dominated by Silver birch, Scots pine and Norway spruce may not be the source of net GHG emissions due to offset by C input through litter production. However, there is still high uncertainty of C input with tree below-ground litter and ground vegetation, particularly, mosses, herbs and grasses which may have crucial role in C balance in forests with drained organic soils. Key words: forests, drained organic soils, litter production, carbon input, National GHG inventory

Analysis of the influence of types of spatial structures of public gardens of the Orel city on the architectural and ecological sustainability of urbanized landscapes

Introduction. A public garden or park improvement project should arise from a scientifically grounded study of the territory and proceed from the further development of this object. The aim of the study is to analyze the territory of public gardens in the city of Orel to determine the influence of types of spatial structures on the features of the functioning of a landscape object, to predict the stability of the studied landscape and to assess the dynamics of urban ecosystems based on the state of tree vegetation. Tasks: to analyze the placement and ratio of types of spatial structures on the objects under study; to make an aesthetic and sanitary-hygienic assessment of the landscape; to monitor the state of woody vegetation at the facilities. Materials and methods. For the development of scientifically based design of sustainable urban ecosystems and the reconstruction of urban objects of landscape architecture, a method is proposed for studying the territory of squares along the selected contours of types of spatial structures (TPS), which allows us to identify positive and negative factors affecting the development of design solutions. When analyzing the TPS of the investigated squares, satellite images of objects were used. Results. As studies of the type of spatial structure have shown, in most of the investigated squares, indoor TPS prevails; on average, this type of spatial structure is established on 41.8 % of the square of squares. The location of open and semi-open TPS is haphazard and random. The lowest aesthetic score was established for the closed TPS-21.9 points, which is due to the difficulty of identifying species points in such spaces, poor visibility, inhibition of the growth of not only trees, but also the ground vegetation cover, which in most cases is represented by a sparse grass stand with poor species diversity. When conducting a sanitary and hygienic assessment of various TPSs, it was found that a closed TPS also corresponds to the worst grade (2.5 class), which is associated with a decrease in the suitability for performing sanitary and hygienic functions in weakened and damaged plants. Conclusions. For the majority of public gardens in the city of Orel with a plant age close to the maximum in urban conditions, a closed type of spatial structure is characteristic. The closed type of spatial structure led to a decrease not only in attractiveness, but also in the performed sanitary and hygienic role of landscape architecture objects.

Impact of changes in climate and CO₂ on the carbon-sequestration potential of vegetation under limited water availability using SEIB-DGVM version 3.02

Documenting year-to-year variations in carbon-sequestration potential in terrestrial ecosystems is crucial for the determination of carbon dioxide (CO2) emissions. However, the magnitude, pattern and inner biomass partitioning of carbon-sequestration potential, and the effect of the changes in climate and CO2 on inner carbon stocks, remain poorly quantified. Herein, we use a spatially explicit individual based-dynamic global vegetation model to investigate the influences of the changes in climate and CO2 on the enhanced carbon-sequestration potential of vegetation. The modelling included a series of factorial simulations using the CRU dataset from 1916 to 2015. The results show that CO2 predominantly leads to a persistent and widespread increase in above-ground vegetation biomass carbon-stocks (AVBC) and below-ground vegetation biomass carbon-stocks (BVBC). Climate change appears to play a secondary role in carbon-sequestration potential. Importantly, with the mitigation of water stress, the magnitude of the above- and below-ground responses in vegetation carbon-stocks gradually increases, and the ratio between AVBC and BVBC increases to capture CO2 and sunlight. Changes in the pattern of vegetation carbon storage was linked to regional limitations in water, which directly weakens and indirectly regulates the response of potential vegetation carbon-stocks to a changing environment. Our findings differ from previous modelling evaluations of vegetation that ignored inner carbon dynamics and demonstrates that the long-term trend in increased vegetation biomass carbon-stocks is driven by CO2 fertilization and temperature effects that are controlled by water limitations.

Satellite monitoring of the state and dynamics of disturbed natural and technogenic landscapes in Siberia

A method for monitoring recovery process in post-fire and post-technogenic landscapes was proposed based on satellite data in wide spectral range including the infrared bands data. The spectral albedo in short-wavelength bands (MODIS band #1 and #2) was underestimated by 20–48% relative to the background in the first year after the wildfire and remained underestimated by 3–12% after 20 years of vegetation restoration. For the variant of post-technogenic plot with reclamation, the albedo value was corresponded to the dynamics in post-fire plots, while for post-technogenic dumps without reclamation the level of the albedo underestimation remained 45–60% throughout the observation period (> 60 years). A decrease in the spectral albedo of the surface in post-fire areas, due to destruction of on-ground vegetation, provokes excessive heating of surface and upper soil layer. Surface thermal anomalies were evaluated under conditions of changes in the heat-insulating properties of vegetation and ground cover. Temperature anomalies in post-fire plots (overestimation up to 30%) are typical for permafrost conditions of Siberia. Similar process was recorded for both natural (post-fire) and post-technogenic landscapes. Within 20 years of the fire, thermal insulation properties of the vegetation cover restore. Thus, the relative temperature anomaly has reached the background value of 3 ± 1%. In post-technogenic plots conditions are more “contrast” compared to the background, and restoration of the thermal regime takes significantly longer period (> 60 years). Forming “neo-technogenic ecosystems” are characterized with specific thermal regimes of soils compared to the background ones both for reclaimed and for non-reclaimed post-technogenic plots. In averaged, surface temperature has overestimated at least by 10–15% in post-technogenic plots.

Effects of overstory tree density, site preparation and ground vegetation on natural Scots pine seedling emergence and survival in northern boreal pine forests

Natural regeneration is commonly used forest regeneration method in Northern Finland. It is not known however, what would be the optimal overstory density and ground vegetation composition for seedling emergence and survival, and if site preparation is needed to accompany overstory density manipulation. We studied the effects of overstory density (unthinned control and thinning to 50, 150 and 250 trees ha-1) and ground vegetation removal (mechanical site preparation with disc trenching) on the number of naturally germinated pine seedlings and survival of individual seedlings during 8-11 years. Bare mineral soil was a superior seedbed compared to intact vegetation cover, even though also mortality rate was high on mineral soil. Greater cover of lingonberry, crowberry and slash had a negative effect on seedling number. Seedling mortality was initially high (60% died during the first two years) but decreased throughout the first five years. The mineral soil in the elevated part of disc trencher track showed twice the survival rate in the bottom part of the track. High coverage of small haired mosses was associated with poorer seedling survival. An overstory density of 50-150 trees ha-1 with site preparation seems to be an efficient treatment to promote regeneration under these circumstances.