Canadian Forest Service Publications
Coppice growth responses of two North American willows in acidic clay soils on coal mine overburden. 2014. Mosseler, A.; Major, J.E. Canadian Journal of Plant Science 94: 1269-1279.
Issued by: Atlantic Forestry Centre
Catalog ID: 36313
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Acid-generating mine spoils with low pH are a major problem for revegetation and site reclamation. We compared growth responses of 15 genotypes from two widespread willow species, Salix discolor Muhl. (DIS) and S. eriocephala Michx. (ERI), native to eastern and central North America on two adjacent coal mine spoil sites that differed strongly in both pH (3.6 vs. 6.8) and soil texture. Despite significantly poorer growth responses for several coppice biomass traits on a highly acidic clay deposit compared with adjacent shale overburden, these willow clones demonstrated a surprising tolerance for extremely acidic soil conditions. Analysis of survival and growth uncovered genotype-environment interactions, indicating that both species and genotypic differences within species could be used to select better-adapted genotypes for extreme conditions. Most ERI and DIS clones grew comparatively better on the shale overburden site, but two of eight ERI clones and one of seven DIS clones grew significantly better on the acidic clay site, indicating the possibility for clonal selection for specific site adaptations within a species. Allometric relationships between coppice height and basal stem diameter were constant at both the species and site levels. However, there was a divergence of height and diameter in their relationship with green mass yields on the two different site types.
Plain Language Summary
This study aimed to understand relationships between biomass yield and various coppice growth traits in two native North American willow species, Salix discolor and S. eriocephala, established together in clonally replicated common garden field tests on three sites (Montreal, QC, Fredericton, NB, and Minto, NB) of differing quality but similar climates. These willows are widely distributed across eastern and central Canada and were selected for use in biomass production plantations for bio-energy and for emerging biomass-based chemicals and materials industries. Biomass yield was strongly and positively related to site quality and could be used in the same way that stem height at a specific age has been used for single stemmed trees to define site quality (site index) in forest timber production. Plant stem length and basal stem diameter measurements on up to 20 stems per plant indicated that measurements based on the average of the three longest stems per plant had the strongest relationship to biomass yield and provided a useful, non-destructive means for estimating biomass yield. Selected clones of these two willows can be cost-effectively established using unrooted stem cuttings and short-rotation biomass crops based on 2-year-old coppice growth can produce high quantities of biomass on site types of widely varying quality.