Social and economic evaluation of innovative alley coppice
systems mixing timber trees with bioenergy wood crops in
agroforestry systems
Tosi L2/6,Nahm M1, Paris P2,*, Pisanelli A.2, Douglas GC3, Morhart C4, Graves A5
*Correspondence author: piero.paris@ibaf.cnr.it
1
Forest Research Institute Baden-Württemberg (FVA), Freiburg, Germany; 2CNR-IBAF Porano, Italy; 3Teagasc Kinsealy Research
Centre, Dublin 17, Ireland; 4Chair of Forest Growth, Albert-Ludwigs-University of Freiburg, Germany, 5Centre for Environmental Risks
and Futures,Cranfield University, United Kingdom; 6DIBAF, Univ. of Tuscia, Viterbo, Italy.
Introduction
Alley coppice (AC) is an innovative agroforestry system where high value timber trees, or standard
trees,are planted in lines with bioenergy short rotation coppice (SRC) as intercrop. AC is a new studied
system whose rationale is based on already known tree based systems, like traditional coppice with
standards, and modern SRC, alley cropping and mixed plantations (Morhart et al. 2014). AC potentially
provides several benefits, in terms ofenvironment, increasing biodiversity and reducing soil erosion; wood
quality of standard trees, increasing their stem formand branching habit, as well as reducing pruningintensity
thanks to light competition between species; economically, providing an income to farmers due to the
biomass production during the standard trees growth. Being innovative, AC needs to be tested and assessed
in terms of social acceptability, as well as profitability. The objective of this paper is to: i) assess the farmers’
interest in AC systems; ii) evaluate the economic profitability of AC systems. The study has been carried out
within the framework of the AgroCop European project (www.agrocop.com).
Material
An on-farm survey was conducted with the aim to identify farmers who more likely would be
interested to test and adopt AC system on farm land, according to their socio-economic characteristics,
knowledge and awareness. A structured questionnaire was prepared and submitted to a sample of farmers
located in Italy. Farmers were chosen among those with experience in alley coppice or short rotation
coppice.
An economic simulation comparing AC (poplar SRC mixed with wild cherry) and monocultures of the
same species was run. For this purpose, we developed a database on costs and prices of timber and SRC
plantation forestry across Europe. AC systemwas simulated according to a standard scheme taken from
Morhart et al (2014). In both cases standard trees have to be thinned at the 9th and 20thyear, leaving the best
30 trees in AC system and the best 70 trees in monoculture. The site conditions are optimal in all three
cases, without the need for irrigation. According to our experience, we estimated an average biennial yield of
20 todt/ha of biomass for pure poplar, which decreases in AC system, due to the reduction of land used for
SRC and the light competition between species. For standard trees, we assume a final dimension of about
60 cm DBH and a total stem height of 28 m, with an average of 5 m of branch-free trunk for veneering or
sawing. During the first 20 years of the AC system, we assumed a SRC yield reduction equal to the area
Alley Coppice
Poplar SRC
2.5 x 0.5
4800 (planting time)
Tree species
Spacing (m)
Number of trees
W. Cherry
28 x 12
30 (at 60 years)
RotationCycle (year)
60
2 years x 20 years x 3 cycles
Cover Area %
Yield:
Timber in m3
Biomass in MgDM
22
78
1-20 years: 6 MgDM ha-1y-1
21-40 years: 5 MgDM ha-1y-1
41-50 years: 4.2 MgDM ha-1y-1
42.3 m3ha-1
16.8MgDM ha-1
SRC
Hybridpoplars
2.5 x 0.5
8000
(planting time)
2 years x 20 years x 3
cycles
100
1-60 years:
10 MgDMha-1y-1
PlantationForestry
W. Cherry
12 x 12
70 (at 60 years)
60
100
98.7 m3ha-1
39.2 MgDM ha-1
Tab. 2Main cultural characteristics of the compared tree systems for economic simulation
occupied by the standard trees. During the second 20 years, to the above mentioned yield reduction of SRC
we added a further -15%, equal to the standard tree canopy closure at age 30. For the third 20 years, a
further yield reduction of -40%, equal to the standard tree canopy closure at age 30. Finally, we estimate a
production of 1.41 m3/tree of valuable wood and 0.56MgDM/tree of firewood, sold as biomass for energy.
For the economic comparison, we use Net Present Value (NPV):
𝑛
𝐶𝑡
𝑁𝑃𝑉 = ∑
(1 + 𝑖)𝑡
𝑡=0
Where n is cycle length (years), t is
year, C is cashflow (revenues – costs), i is
discount rate. NPV is an estimate of the
current value of all future incomes from an
investment.
A discount rate of 3% was
used.Considering the high uncertainly of
timber and biomass prices, and the
consequent difficulty to predict revenues for a
long period, a comparison was made between
three level prices at farmgate both for
biomass (40, 60, 100 €/tDM) and for valuable
woods (150, 300, 500 €/m 3). For costs, we
used data from German experimental fields of
the Agrocop project.
Expected benefit
Average score
economic benefits
4.27
social benefits
3.37
biodiversity conservation
4.33
landscape improvement
4.40
soil quality improvement
4.22
Table 2: Farmers’ evaluation of the most important expected benefits
from AC system. Farmers were asked to score from 1 (low) to 5 (high)
the expected benefits according to their experience and knowledge.
Results
A total amount of 20 questionnaires was completed and returned. Most of the interviewed farmers
are located in Northern Italy, in the Po Valley plain.
The survey evidenced that farmers have a great awareness and experience concerning plantation forestry.
Most of them, in fact, manage various typology of plantation forestry, combining different design and planting
scheme, planting several woody species. Among them, the most common are walnut and cherry as primary
species aimed producing timber;hornbeam, ash and oaks, as species aimed producing biomass or other
secondary products or services. Concerning the management aspects of these plantations, most of the
farmers claim that the weed control represents the main constraint. Nevertheless, farmers report satisfactory
tree growth rates.
Economic analysis are currently underway. From the very early results it seems that pure SRC
plantation should be the more profitable system, without considering the many risks over a 60 year period.
Discussion
The interviewed farmers appeared to be familiar with managing forest plantations as species
mixtures and with the value of fuelwood. However, the value of the timber and biomass produced during the
rotation appeared to be farmers’ main source of uncertainty, with no clear idea of what demand there would
be for both wood products, and they assigned a higher rank to the importance of environmental benefits
such as biodiversity, landscape, soil fertility improvement (tab. 2).Thus, farmers are interested on mixed
cultural models of plantation forestry, although the economic final objective is not very clear.
AC could be an innovative option for timber and bioenergy production, integrating some of the
advantages that are characteristic of agroforestry systems into mixed tree plantations.Economic simulations,
under optimal site conditions, will demonstrate the most profitable cultural option (AC vs SRC vs Plantation
forestry) under various scenarios of wood prices and discount rates. The SRC component has an important
role to play, not only producing biomass, but also increasing the quality of the valuable timber by improving
timber tree form, reducing the costs of management operations and for giving a revenue during the growth of
standard trees.SRC should be a continuous source of revenue for farmers during the growth of standard
trees, and should guarantee a profit even when the valuable wood price should be low. This is an important
issue, considering the uncertainty of timber wood price. However in our economic simulations we considered
only a moderate competition between tree species, assuming a loss of yield for SRC equal to reduction of
canopy closure. Further economic simulations should include possible realistic scenarios of the mutual
detrimental competitions.
References:
Morhart C., Douglas G., Dupraz C., Graves A., Nahm M., Paris P., Sauter U., Sheppard J., Spiecker H. (2014).Alley coppice –
a new system with ancient roots. In: Annals of forest science, article in press. DOI: 10.1007/s13595-014-0373-5