Forest Trees - Bioenergy Crop Plants - page 376

on 3-5 year rotations. Most of the European studies of short rotation poplars were still at traditional
wide spacings (Louden 1976).
Ceulemans and Deraedt (1999) reviewed the potential of poplars grown under short rotation
culture for bioenergy. They outline that the way to optimize biomass productivity is to optimize
plant genotype or cultural management regime, or the interaction between both. Their review com-
pares many poplar clones, spacings and climates under coppicing (Ferm and Kauppi 1990) and
noncoppicing regimes. They found that there are clonal differences in biomass yields under differ-
ent coppicing regimes and reported yields of 20-30 mt/ha per year. In some cases the noncoppiced
clones yielded more than the coppiced (Proe et al. 2002). Cannell and Smith (1980) concluded that
the “working maximum” for short rotation forests was theoretically 10-12 mt/ha per year with a
possible increase of 10-20% with coppicing. At the time, this upper limit seemed reasonable with
existing clones. We know now that yields can be increased further with genetically improved mate-
rial and coppicing. For example, Pontailler et al. (1999) reported biomass yields of 4 poplar clones
at 0.8 m spacings over 5 coppices and found the highest biomass yield was over 30 mt/ha per year!
Improved genetic material does make a difference (Ceulemans 2004). Benetka et al. (2007) found
that native P. nigra clones produced much less than an NE U.S. hybrid. However, in some regions
the use of native plant material is required. They cited disease resistance as an important factor in
biomass yield.
R. Ceulemans and co-workers conducted a series of studies in the late 1990s to identify cop-
picing differences in biomass production in short rotation poplar (Ceulemans 2004). Laureysens
et al. (2003, 2004) reported results of the first rotation coppice study in Belgium. After 6 years
the biomass production of 17 poplar clones varied with clone; mortality of stools was also clone
related. Biomass production was 1.6-10.8 mt/ha per year (Table 15.5). The “best” clone was a T × D
hybrid. Laureysens et al. (2005) reported results of the second rotation of short rotation coppice
culture of poplar of the above study. Notably the results of the second rotation were significantly
different than the first. The P. nigra had biomass yields at 9.7 mt/ha per year, but the first rotation
“best” T × D clones performed poorly. Melampsora rust played an important part in determining

taBle 15.5
chronological synthesis of Poplar Biomass Production Field studies and
Plantations by location in europe

clone/
speciesa

age
(years)

spacing
(m)

Productivity
(mt/ha per year) location reference

United Kingdom T 5 0.5 9-10 Cannell and Smith (1980)

Finland B 6 0.7-1.4 4.2 Ferm et al. (1989)

France TD 2-3 Multiple 0.6-3.5 Auclair and Bouvarel (1992)

United Kingdom T, TD 4 1.0-2.0 13.6 Armstrong et al. (1999)

Belgium TD Multiple 0.8 30 Pontailler et al. (1999)

United Kingdom B 5 1.5 10.2-16.2 Proe et al. (2002)

Belgium Multiple 6 0.75-1.5 10.8 Laureysens et al. (2003)

Belgium Multiple 4 1.0 2.8-11.4 Laureysens et al. (2004)

Belgium Multiple Multiple 1.0 9.7 Laureysens et al. (2005)

Sweden T,TD 13 1.2 8.0 Christersson (2006)

Czech Republic N,MT 4-7 2.1 7.6-9.4 Benetka et al. (2007)

Belgium Multiple 3 0.75-1.5 2.8-9.7 Al Afas et al. (2007)

Belgium Multiple 11 0.75-1.5 13.3-14.6 Al Afas et al. (2008)

a B, P. balsamifera ; D, P. deltoides ; N, P. nigra , T, P. trichocarpa , DN, D × N; TD, T × D; M, P. maximowiczii ;
MT, M × T.