Abstract
Short rotation coppices play an increasing role in providing wooden biomass for energy. Mixing fast-growing tree species in short rotation coppices may result in complementary effects and increased yield. The aim of this study was to analyze the effect on mortality of eight different poplar genotypes (Populus sp.) in mixed short rotation coppices with three different provenances of the N-fixing tree species black locust (Robinia pseudoacacia L.). Pure and mixed stands were established at two sites of contrasting fertility. Survival of poplar was assessed for each tree two times a year, for a period of three years. In the first two years, high variation in mortality was observed between the genotypes, but no significant differences between pure and mixed stands were identified. However, three years after planting, higher mortality rates were observed in the mixtures across all poplar genotypes in comparison to pure stands. The expected advantage on growth of combining an N-fixing tree with an N-demanding tree species, such as poplar, was overshadowed by the Robinia’s dominance and competitiveness.
Highlights
Wood is a renewable source of energy with great potential as a fossil fuel substitute [1]
We explored whether the poplar genotypes and the mixture types differed in seedling survival across sites
Interspecific hybridization, and cloning, poplar has been genetically improved to enhance its efficiency in intensive monocultures [35]
Summary
Wood is a renewable source of energy with great potential as a fossil fuel substitute [1]. Besides forest stands, short rotation coppices on arable lands are increasingly important as sources of wood biomass for energy [2]. To avoid rivalry between areas for food and wood production, short rotation plantations are often established on marginal lands where soil nitrogen and water are limiting [3]. The yield and fitness of Populus sp., the genus most commonly used for short rotation wood production in Germany, are highly correlated with nitrogen and water availability [4,5]. An alternative to the use of fertilizer may be the simultaneous planting of legumes. Due to their ability to fix nitrogen, these plants can potentially increase soil fertility without chemical fertilization [9,10,11]. Oliveira et al [16] and Rédei et al [17] were
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