Reconstruction of the Expansion of Siberian Larch into the Mountain Tundra in the Polar Urals in the 20th—Early 21st Centuries

Valery Fomin,Anna Mikhailovich,Dmitry Golikov,Egor Agapitov

doi:10.3390/f13030419

Abstract

This paper presents results of analyzing the second half of the 20th–early 21st century changes in lateral spatial structure of Larix sibirica Ledeb. population in the upper treeline ecotone located on the Rai-Iz massif (Polar Urals, Russia). The GIS layers characterizing distribution of Siberian larch trees and undergrowth together with their crowns was produced for a 7.32 square kilometer area based on aerial images recognition. Using statistical models, we assessed probabilities for assigning trees to age intervals of 1–10, 11–40, and 40+ years based on the average radius of tree crown projection. These maps and layer showing locations of trees that grew in the upper part of the ecotone, and died during the Little Ice Age, allow for assessing specifics of forest cover proliferation at different parts of upper treeline ecotone, and comparing current location of the trees with one from the past. The proposed method for probability-based recognition of Siberian larch tree generations in the upper treeline ecotone using average crown radius can be used to reconstruct time and spatial forest dynamics at the upper growth boundaries for time spans up to 100 years and more.

Highlights

IntroductionExtensive research demonstrates the fact that forests advancing to the upper parts of mountain massif slopes located in different regions of Earth can be attributed to improvement of climate conditions that occurred in the 20th century and at the beginning of the 21st century [1–14]
Vegetation at the upper tree line is a sensitive indicator for changes in regional climate
A map demonstrating location of individual larch trees (88,833 specimens) and the size of their crowns in the research area was created based on their recognition in aerial images captured from 50 m altitude with an unmanned aerial vehicle on a 7.32 square kilometer territory

Summary

Introduction

Extensive research demonstrates the fact that forests advancing to the upper parts of mountain massif slopes located in different regions of Earth can be attributed to improvement of climate conditions that occurred in the 20th century and at the beginning of the 21st century [1–14]. Mountain systems subject for the studies of climate-driven forest cover dynamics at the upper boundaries of the forest are used as areas for monitoring biota reactions to global and local climate changes [2,13–17]. Intensive developments in the field of obtaining and processing high-spatial resolution satellite images, and ultra-high resolution images obtained with small unmanned aerial vehicles extended the spectrum of available solutions for obtaining and analyzing data on spatial position of the trees, which, in turn, create new opportunities for retrospective analysis of temporal and spatial dynamics of forests based on the quantitative assessment of age and specific biometrical parameters for the trees [17]

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