Grant: Strategic Projects - Group

The Canadian boreal forest plays an important role in global carbon (C) sequestration. Species mixtures are common in natural forests and it has been hypothesized that mixtures are more productive than single-species stands because they may use resources differently (niche separation hypothesis) and less competitively (competition reduction hypothesis). Empirical evidence of wood volume production gain in mixedwoods is, however, scarce and controversial. To our knowledge, there is no reported study to examine the role mixedwoods play in the context of C sequestration. The objective of the proposed research is to assess if the commonly occurring trembling aspen and spruce mixtures store and sequester more C than their respective single-species stands by addressing: (i) Do mixedwoods have a higher ecosystem biomass, total C pool, and net primary productivity (NPP) than their respective single-species stands? (ii) Do mixedwoods have a smaller rate of soil heterotrophic respiration (SHR)? (iii) How does time since fire influence the mixture effect if it exists? We will focus our effort on three signature areas: western Ontario, eastern claybelt, and Lake Duparquet of the eastern-central boreal shield. We will use an experimental approach to sample naturally established forest stands in combination with ecosystem modelling to 1) determine species mixture effects on ecosystem biomass, C pool, NPP, and SHR and 2) model these effects at the forest and regional levels using the Carbon Budget Model of the Canadian Forest Sector (CBM-CFS3). The proposed research will be conducted by a team of accomplished researchers and will train 7 highly qualified personnel. The results will be published in various media including peer-reviewed journal articles, theses, conferences, and workshops. It will also be used in modelling C budget for the purpose of forest certification. This project will lead to a significant improvement in understanding the role of the Canadian boreal mixedwoods in carbon sequestration. As the result, better forest management practices can be recommended and a more accurate accounting of carbon sequestration can be realized for the Canadian boreal mixedwoods.