Height growth and dry woody biomass production were studied on Populustrichocarpa × deltoides (Beaupré) coppiced at 1-, 2-, and 3-year intervals on a converted woodland in central France. For each rotation, two different planting densities were studied, ranging from 2000 to 20 000 cuttings per hectare. The experiment, which lasted for 6 years, allowed comparisons between establishment and subsequent coppice cycles on relatively large treatment plots (400 stools per plot). The highest planting densities yielded fewer shoots per stool and reduced height and diameter growth. Individual stool biomass was reduced by high stool densities; however, total biomass per unit area was higher, resulting from the greater number of stools. Height growth was greatly influenced by climatic variability, principally rainfall. Biomass production was greater after coppicing than during the establishment phase for the 2- and 3-year rotations, in spite of low water availability. Biomass production decreased in the 1-year rotation during 3 years, but was subsequently followed by a higher production, in strong relation with water availability. At the planting density of 5000 per hectare, total biomass yield was higher for the longest rotations. There was no evidence of ageing of the stumps even after six 1-year rotations.
Summary — In order to study the effects of extremely short rotations, the growth of hybrid poplar cuttings coppiced biannually over a period of 4 years, in summer and in winter, was compared with growth of cuttings coppiced annually in winter. The biannual treatment led to a progressive decrease in height growth and in total biomass production, and to high stool mortality. Some aspects of the physiology of coppicing are discussed.growth / coppice / short rotation / Populus Résumé — Production de biomasse et mortalité des souches de peuplier hybride recépé deux fois par an. Des boutures de peuplier hybride interaméricain recépées deux fois par an pendant 4 ans ont été comparées à des boutures recépées annuellement, dans le but d'étudier les effets d'un stress physiologique important sur la croissance des rejets de taillis. Le recépage bisannuel a entraîné une forte mortalité des souches et une baisse de la croissance en hauteur. Une diminution de la production de biomasse sèche par unité de surface peut être attribuée à la fois à une baisse de production en biomasse des souches vivantes et à la mortalité. Différents aspects du fonctionnement des arbres traités en taillis sont discutés.
We report on a series of 7- and 8-year-old genetic trials of red alder (Alnusrubra Bong.) planted in France as an initial exploration of its growth potential and genetic needs. Red alder is native to the Pacific Northwest coast of North America. Seed for the French plantings was collected in four Pacific Northwest river drainages (Santiam, Nisqually, Nooksack, and Hoh), which cover a wide latitudinal and elevational range.Of the four sites at which the red alder seed was planted, the best growth was observed at Rouvray in northwestern France, a site with deep sandy soil and adequate summer precipitation. Growth here was above average for red alder in its native habitat. Poor soil drainage at the other three test sites resulted in much poorer performance. Trees from Santiam River seed sources were generally the poorest performers at all test sites; the source river(s) for the best performing trees, however, varied by test site. Comparing performance of trees from the same source drainage, elevation of seed collection location correlated at best only weakly with growth; the level of nonsys-tematic variation was high. Regression on principal components derived from seed collection location environmental variables indicated that the best growth performance was associated with seed sources from warmer areas with low moisture demands. In general, this combination of climate conditions exists in low-elevation coastal areas; in this study, all seed collection locations fitting this description were in northwestern Washington state.
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