Interspecific variation in growth responses to tree size, competition and climate of western Canadian boreal mixed forests

Xinyu Jiang; Jian-Guo Huang; Jiong Cheng; Andria Dawson; Kenneth J Stadt; Philip G Comeau; Han Y H Chen

doi:10.1016/j.scitotenv.2018.03.099

Interspecific variation in growth responses to tree size, competition and climate of western Canadian boreal mixed forests

Sci Total Environ. 2018 Aug 1:631-632:1070-1078. doi: 10.1016/j.scitotenv.2018.03.099. Epub 2018 Mar 16.

Authors

Xinyu Jiang¹, Jian-Guo Huang², Jiong Cheng³, Andria Dawson⁴, Kenneth J Stadt⁵, Philip G Comeau⁶, Han Y H Chen⁷

Affiliations

¹ Key Laboratory of Vegetation Restoration and Management of Degraded Ecosystems, Guangdong Provincial Key Laboratory of Applied Botany, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou 510650, China; Guangdong Key Laboratory of Integrated Agro-environmental Pollution Control and Management, Guangdong Institute of Eco-environmental Science & Technology, Guangzhou 510650, China.
² Key Laboratory of Vegetation Restoration and Management of Degraded Ecosystems, Guangdong Provincial Key Laboratory of Applied Botany, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou 510650, China. Electronic address: huangjg@scbg.ac.cn.
³ Guangdong Key Laboratory of Integrated Agro-environmental Pollution Control and Management, Guangdong Institute of Eco-environmental Science & Technology, Guangzhou 510650, China.
⁴ Department of Geosciences, University of Arizona, Tucson, AZ 85721, USA.
⁵ Forest Management Branch, Sustainable Resource Development, Edmonton, Alberta, Canada.
⁶ Department of Renewable Resources, University of Alberta, Edmonton, Alberta, Canada.
⁷ Faculty of Natural Resources Management, Lakehead University, 955 Oliver Road, Thunder Bay, ON, Canada.

PMID: 29727933
DOI: 10.1016/j.scitotenv.2018.03.099

Abstract

Tree growth of boreal forest plays an important role on global carbon (C) cycle, while tree growth in the western Canadian boreal mixed forests has been predicted to be negatively affected by regional drought. Individual tree growth can be controlled by many factors, such as competition, climate, tree size and age. However, information about contributions of different factors to tree growth is still limited in this region. In order to address this uncertainty, tree rings of two dominant tree species, trembling aspen (Populus tremuloides Michx.) and white spruce (Picea glauca (Moench.) Voss), were sampled from boreal mixed forest stands distributed across Alberta, Canada. Tree growth rates over different time intervals (10years interval, 1998-2007; 20years interval, 1988-2007; 30years interval, 1978-2007) were calculated to study the effects of different factors (tree size, competition, climate, and age) on tree growth. Results indicated that tree growth of two species were both primarily affected by competition or tree size, while climatic indices showed less effects on tree growth. Growth of trembling aspen was significantly affected by inter- and intraspecific competition, while growth of white spruce was primarily influenced by tree size, followed by competition. Positive relationship was found between growth of white spruce and competition index of coniferous group, suggesting an intraspecific mutualism mechanism within coniferous group. Our results further suggested that competition driven succession was the primary process of forest composition shift in the western Canadian boreal mixed forest. Although drought stress increased tree mortality, decline of stem density under climate change released competition stress of surviving trees, which in turn sustained growth of surviving trees. Therefore, climatic indices showed fewer effects on growth of dominant tree species compared to other factors in our study.

Keywords: Boreal mixed forest; Climate change; Competition; Tree growth; Tree size.