Differentiation of larch (Larix spp.) climatypes in the Central Siberian forest-steppe provenance trial

Abstract

Forest conservation is one of the main problems in world forestry. Numerous forest fires and widespread fungal pathogens and pests have led to a significant decline in forest areas and biodiversity and the disappearance of valuable populations. The problem of forest conservation and regeneration became especially relevant at the beginning of this century because of increasing wood harvesting. In this case, genetic collections of woody species, including provenance trials, established at different times play an important role in gene pool conservation of the main coniferous species - the forest-forming species in Russia - and in basic and applied problems in the context of climate change and the growing conditions in biogeocoenoses. The special interest in larch research is associated with a wide range of factors, such as inter- and intraspecific differentiation, capability to adapt to stressful growth conditions and the ability to successfully transfer seeds over large distances for creation of plantations with special purposes. The aim of this study was to assess inter- and intraspecific differences in height growth, crown area and length using the example of future generations of different larch species representing different provenances in the provenance trial. We obtained material for this study, located in the provenance trial research plot ‘Pogorelsky bor’ (56°22'06"N, 92°57'23"E) in the forest-steppe of Krasnoyarsk krai, in 2016. Live larch trees in the provenance trial were inventoried using the GIS complex ‘Field-Map’. The total number of inventoried trees was 1674. Nineteen provenances (climatic ecotypes) of various larch species (See Table and Fig. 1) were chosen for comparative analysis of height, crown area and crown length using a nonparametric method - the Kruskal-Wallis ANOVA test and Median test. The crown proportion of tree stems was assessed using median values. Trees with a diameter similar to that of the main sample (121-160 mm; 412 trees) and an alternative sample of trees with a wider diameter (181-220 mm; 291 trees) were chosen for comparative analysis. Such an approach enabled the assessment of different biometric traits of trees while accounting for diameter and similar growth conditions at the trial site. The number of trees in the main sample was 3 and 148 in the two provenances, whereas it ranged from 6 to 48 in the rest of the provenances. In this study, tree height (See Fig. 2) and tree crown length (See Fig. 4) differed between climatic ecotypes of different larch species in the forest-steppe provenance trial of the south Krasnoyarsk region. These differences were related to the origin of the climatypes. We found that larch climatypes from mountain regions showed lower tree height and crown length. We also found that descendants of larch that originated in climatically favourable areas or those connected to the hollows of southern Siberia and the Biryusa and Chuna river basins within the Pre-Sayan province, as well as representatives of the Dahurian larch (Larix gmelinii Rupr.) and Chekanowskii larch (L. czekanowskii Szafer) from Chita Oblast, had greater tree height and tree crown length in the provenance trial (See Fig. 2 and 4). Therefore, the exploitation of these provenances for reforestation of the Krasnoyarsk forest-steppe may be reasonable and rational. Although the results obtained for 10-year-old trees (Iroshnikov, 1977) indicated that the height growth of the Petrovsk-Zabaikalski climatype (Chekanowskii larch) was lower than that of the Siberian and Dahurian larches, by the age of 50 years, it achieved a similar diameter and may be regarded as equal in height growth to the majority of representatives of the latter two larches in the forest-steppe zone. Comparative analysis of samples with different diameters showed that, in general, climatypes were in the same tree height groups (See Fig. 1). Our results show that significant differences in tree height between climatypes are not an obligatory condition for differences in crown length. Tree crown length has its own separate developmental strategy, which is genetically associated with the environmental conditions of the place of origin. The climatype from the highlands with the lowest hydrothermal coefficient of place of origin (the Tes-Khem climatype from Tyva) had the shortest crown length. The ratio of crown to full stem length of the Tes-Khem climatype was 18%. High crown lengths were found for larch climatypes from the hollows of southern Siberia and for representatives of the Dahurian larch from Amur Oblast (the Zeya climatype). The northernmost climatype from the southern taiga (the Motygino climatype, Angara river basin) had a crown length lower than that of the representatives of the Dahurian larch. The crown length proportion of the Zeya climatype (38%, the highest median value of the samples compared) was 14% higher than that of the Motygino climatype (24%). Differences in crown proportion of more than 5%-10% were observed between a few larch climatypes. In general, natural differences between species could not be defined. In this study, significant differences between samples representing different larch species were only found for crown length. The Gmelin larch had a significantly higher crown length than the Siberian (p < 0.001) and Japanese (p < 0.05) larches. In contrast to the other traits studied, crown area did not significantly influence the difference between climatypes. The reasons for the absence of significant differences were the high variability of this trait in the majority of climatypes and the presence of extremes in some samples (See Fig. 3). The paper contains 4 Figures, 1 Table, and 26 References. Acknowledgements: The authors are grateful to Vladimir Kalashnikov (Head of the State Forest Inventory Department of “VOSTSIBLESPROJECT” branch of FSBD “ROSLESINFORG”) for his assistance in management and performance of the field work, and to Yana Semenuk for her contribution in the inventory data processing during the preparation of her bachelor thesis at Siberian Federal University. The Authors declare no conflict of interest.