Distinct Climate Effects on Dahurian Larch Growth at an Asian Temperate-Boreal Forest Ecotone and Nearby Boreal Sites

Enzai Du,Yang Tang

doi:10.3390/f13010027

Abstract

Climate change is exerting profound impacts on the structure and function of global boreal forest. Compared with their northern counterparts, trees growing at the southern boreal forest and the temperate-boreal forest ecotone likely show distinct responses to climate change. Based on annual basal areal increment (BAI) of Dahurian larch (Larix gmelinii Rupr.) plantations with similar ages, tree densities and soil nutrient conditions, we investigated the tree growth responses to inter-annual climate variations at an Asian temperate-boreal forest ecotone and nearby boreal sites in northeast China. Annual BAI changed nonlinearly with cambial age in the form of a lognormal curve. The maximum annual BAI showed no significant difference between the two bioregions, while annual BAI peaked at an elder age at the boreal-temperate forest ecotone. After eliminating the age associated trend, conditional regression analyses indicate that residual BAI at the boreal sites increased significantly with higher growing-season mean nighttime minimum temperature and non-growing-season precipitation, but decreased significantly with higher growing-season mean daytime maximum temperature during the past three decades (1985–2015). In contrast, residual BAI at the boreal-temperate forest ecotone only showed a positive and weak response to inter-annual variations of growing-season precipitation. These findings suggest distinct effects of inter-annual climate variation on the growth of boreal trees at the temperate-boreal forest ecotone in comparison to the southern boreal regions, and highlight future efforts to elucidate the key factors that regulate the growth ofthe southernmost boreal trees.

Highlights

Boreal forest is experiencing strong climate change that results in profound impacts on tree growth and ecosystem function [1,2,3,4]
Showed a significant response to inter-annual variation of growing-season temperatures at the boreal sites, while no significant role of temperature associated variables was found during other periods (Figure 4a), implying that climate warming at the non-growing season likely exert limited effects on tree growth in the southern boreal region
Using data on annual basal areal increment (BAI) of Dahurian larch plantations with similar cambial ages, tree densities, and soil nutrient conditions, we investigated the tree growth characteristics and their responses to inter-annual climate variations at a temperate-boreal forest ecotone and nearby boreal sites in northeast China

Summary

Introduction

Boreal forest is experiencing strong climate change that results in profound impacts on tree growth and ecosystem function [1,2,3,4]. Climate warming has been found to alleviate the limitation of cold temperature and favor tree growth in some northern boreal forests [5,6]. The southernmost boreal trees growing at the boreal-temperate forest ecotone may even respond negatively to climate warming due to an exceedance of the optimal growth temperature [8]. Moisture stress is predicted to aggravate under warmer climate and may suppress tree growth in southern boreal forest [4]. These effects may jointly result in a decline in the dominance of boreal trees and a poleward shift of the southern boreal boundaries over time [1,9]. Understanding the climate effects on the growth of the southernmost boreal trees has important implications for the projection of future boreal forest dynamics, whereas relevant studies at the boreal-temperate forest ecotone are rare in literature [8,10]

Methods

Results

Discussion

Conclusion