Assessment of the State of Forests Based on Joint Statistical Processing of Sentinel-2B Remote Sensing Data and the Data from Network of Ground-Based ICP-Forests Sample Plots

The research was carried out on the territory of the Karelian Isthmus of the Leningrad Region using Sentinel-2B images and data from a network of ground sample plots. The ground sample plots are located in the studied territory mainly in a regular manner, laid and surveyed according to the ICP-Forests methodology with some additions. The total area of the sample plots is a small part of the entire study area. One of the objectives of the study was to determine the possibility of using the k-NN (nearest neighbor method) to assess the state of forests throughout the whole studied territory by joint statistical processing of data from ground sample plots and Sentinel-2B imagery. The data of the ground-based sample plots were divided into 2 equal parts, one for the application of the k-NN method, the second for checking the results of the method application. The systematic error in determining the mean damage class of the tree stands on sample plots by the k-NN method turned out to be zero, the random error is equal to one point. These results offer a possibility to determine the state of the forest in the entire study area. The second objective of the study was to examine the possibility of using the short-wave vegetation index (SWVI) to assess the state of forests. As a result, a close statistically reliable dependence of the average score of the state of plantations and the value of the SWVI index was established, which makes it possible to use the established relationship to determine the state of forests throughout the studied territory. The joint use and statistical processing of remotely sensed data and ground-based test areas by the two studied methods make it possible to assess the state of forests throughout the large studied area within the image. The results obtained can be used to monitor the state of forests in large areas and design appropriate forestry protective measures.

Variable retention forestry in European boreal forests in Russia

We explored whether,and to what extent,variable retention(VR)forestry has been applied in European boreal forests in northwestern Russia.Our survey revealed VR since 1910.Between 1910 and the 1960s,the statistics showing how much was retained are largely missing.However,for example,in the 1950s,on a large scale in the Republic of Karelia,up to 200-ha-sized harvesting areas,18–33%,were retention patches with a mean growing stock of 30–40m3 ha−1.In the fellings defined as“incomplete clear fellings,”which were the most common final felling type at that time,11–40%of the growing stock was left.Between the 1960s and the early 1990s,with more efficient harvesting and skidding techniques,conventional clear fellings with a much lower amount of retention were practiced.Concern about the regeneration of harvested areas gradually led to smaller(maximum 50 ha)harvesting areas and the increase of silvicultural activities.Until now,to ensure natural regeneration,patches of understory and 20–25 seed trees(i.e.,ca.15–25m3)per ha have been left permanently in harvesting areas.Landscape-scale retention for protecting ecosystem functions and biodiversity was legislated in 1978 by preserving key biotopes up to 1000 ha in size.Since 2001,promoted by forest certification,the key biotopes,such as paludified forest patches,buffers around water bodies,and habitats of red-listed species,have also been retained in harvesting areas,together with a dispersed retention of different elements.Quantitative estimates of the amount of key biotopes are largely missing.However,estimates of 1–13%in harvesting areas and 23%in whole managed landscapes have been given.VR applied during the last century has emulated natural disturbances and created diverse uneven-aged forest structures with high amounts of diverse coarse woody debris.We conclude that an analysis of past and current retention practices is essential for estimating the global role of Russian forestry.Further decisions on the general direction of Russian forestry and,specifically,retention practices are important to address the global challenges of biodiversity loss and climate change.

Research on retention forestry in Northern Europe

Retention approaches in forest management are today common in several North European countries,integrated into the clearcutting practice as a way to promote biodiversity and maintain ecosystem functions.Individual green trees and retention patches(tree groups)are retained at final harvest,and deadwood is left at site or created.Here,we review research on retention in Sweden,Finland,Norway,the Baltic States,and NW Russia,with special focus on biodiversity.Following the first publication in 1994,about 180 peer-reviewed articles have been published.We present results from a systematic search of the retention literature,separated into the following topics:buffer zones,retention patches,high stumps,other types of deadwood,European aspen Populus tremula,and cost-efficiency.Russian literature is synthesized separately since studies from this region have so far almost exclusively been published in the Russian language.Furthermore,we describe six ongoing large-scale,replicated experiments with varying retention levels,five in Finland and one in Sweden,and summarize their main results.Among main conclusions for practice from the literature and experiments are that retention patches as large as 0.5 ha and 10-mwide buffers to watercourses are not enough to maintain pre-harvest species composition but survival of forest species is still larger than on conventional clearcuts.Deadwood on clearcuts may present important habitats to saproxylic species,including rare and red-listed ones and a prioritization of tree species per stand is recommended.We identify several important future research directions including switch of focus towards the landscape as well as the species population level.Surveys in parts of European Russia where retention has been unintentionally implemented already for a century would indicate possible future trajectories of biodiversity and their drivers in other regions of Northern Europe.A stronger link to ecological theory would help in study designs and in the formulation of predicted outcomes.

Correction to: Variable retention forestry in European boreal forests in Russia

Correction to:Ecol Process https://doi.org/10.1186/s13717-019-0183-7 In the original publication of this article(Shorohova et al.,2019),the figure captions of Figs.2,3 and 4 are incorrect.They should be changed to:‘Fig.2 The share of different forest management categories in different regions of NW Russia(Regional 2017,2018).Red lines denote the borders between the states.Gray lines denote the borders between vegetation zones(Bonh et al.2000,2003).NB northern boreal zone,MB middle boreal zone,SB southern boreal zone,HB hemiboreal zone.