Mortality of Different Populus Genotypes in Recently Established Mixed Short Rotation Coppice with Robinia pseudoacacia L.

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.

Hybrid and Environmental Effects on Gene Expression in Poplar Clones in Pure and Mixed with Black Locust Stands

“…The other site, Deppoldshausen, is characterized by the shallow (<60 cm deep) and stony soil with low ability to hold water of Calcaric Leptosol type (according to the FAO classification), a mean annual temperature of 9.0 • C and an average annual precipitation of 457 mm measured in 2016 by on-site station Adolf Thies GmbH & Co. KG (Goettingen, Germany). During the observation period 2015-2016, rainfall and mean annual temperature were lower in Deppoldshausen than in Reinshof (for the weather data see [35]). Four blocks (repetitions) were established at each study site (Figure S1).…”

“…Each of the four blocks (repetitions) at one site consisted of the same 40 plots with a random distribution within and between the rows. During the vegetation periods of 2014 and 2015, the growth and survival rates of all poplar clones and black locust provenances were measured [35].…”

“…For transcriptome analyses, four clones were selected: two clones "Hybride 275" and "Matrix 11" (P3 and P5, P. maximowiczii × P. trichocarpa) with an intermediate performance in terms of survival and growth, one "Max 1" (P7, P. nigra × P. maximowiczii) with the best performance, and one "Muhle Larsen" (P8, P. trichocarpa) with the worst performance [35]. Only stands with Robinia "HGK 81901" (R1) were selected.…”

“…Only stands with Robinia "HGK 81901" (R1) were selected. The black locust provenances "HKG81901" (R1) and "HKG81902" (R2) showed no significant differences in their performance in terms of mortality and growth [35], thus, they were handled as one provenance throughout the whole experiment. It was observed that bud burst of the P8 clone occurred about two weeks later in comparison to the three other clones.…”

“…In the present study, we report the first results for four Populus leaf transcriptomes. Experimental plots were established in two ecologically different sites to observe the influence of the clone, environmental conditions and mixed vs. monoculture cultivation on development of the stands [35]. The following hypotheses were tested in our study: (1) poplar clones respond differently to the planting design; (2) study site conditions influence the performance of stands; (3) the interaction between poplar and black locust trees is weak at the early stage of stand development.…”