Advance Regeneration of Norway Spruce and Scots Pine in Hemiboreal Forests in Latvia

Didzis Elferts,Solveiga Luguza,Aris Jansons,Endijs Baders,Iveta Desaine,Guntars Snepsts,Janis Donis,Mara Kitenberga

doi:10.3390/f11020215

Abstract

Continuous cover forestry (CCF) aims to emulate small natural disturbances and take advantage of natural regeneration. To implement these management practices successfully, knowledge of advance regeneration under the canopy in different conditions is crucial. Therefore, the aim of this study was to assess the influence of stand inventory parameters of canopy layer (age, basal area, height, and density) on the probability and density of advance regeneration of the Norway spruce (Picea abies (L.) H. Karst.) and Scots pine (Pinus sylvestris L.) in hemiboreal forests in Latvia. The data were obtained from the National Forest Inventory, from a total of 879 plots. In the study, only Norway spruce or Scots pine dominated stands were used and the sampled stand age ranged from 21 to 218 years. The probability of advance regeneration differed between stands dominated by Scots pine versus Norway spruce. The probability and density of the advance regeneration of Norway spruce were positively linked to increased stand age, whereas the probability of the advance regeneration of Scots pine was negatively linked to the basal area of the stand. In stands dominated by Norway spruce and Scots pine on mesic soils, the advance regeneration of Norway spruce has a high density, whereas the advance regeneration of Scots pine is sporadic and scarce.

Highlights

A deeper ecological understanding of the structural and functional complexity of forest ecosystems has led to specific management implications and increasing awareness that forests should be governed as complex adaptive systems [1,2,3]
In stands dominated by Scots pine and Norway spruce, an average of 2000 trees of advance regeneration per hectare were observed in all age groups (Figure 2)
In stands dominated by Scots pine and Norway spruce, the probability of advance regeneration of Scots pine decreased with the increasing basal area (Figure 6)

Summary

Introduction

A deeper ecological understanding of the structural and functional complexity of forest ecosystems has led to specific management implications and increasing awareness that forests should be governed as complex adaptive systems [1,2,3]. The concepts of management approaches such as close-to-nature or continuous cover silviculture systems first appeared in the 18th and 19th century in Central Europe when overexploited monocultures failed to maintain forest vitality and soil fertility [5]. The first book in which small-scale group selection was suggested as way to maintained structural diversity of mixed stands by Karl Gayer was published at the end of 19th century [6]. Continuous cover forestry (CCF) aims to emulate the small-scale tree mortality pattern (gap/patch dynamics) to maintain forest stands, soil integrity, and productivity [5,13]. The CCF system relies on natural regeneration, Forests 2020, 11, 215; doi:10.3390/f11020215 www.mdpi.com/journal/forests

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