BOSQUE 20(1): 9-21, 1999
Productivity and sustainability of
plantation forests*
Productividad y sustentabilidad de las plantaciones forestales
E.K. SADANANDAN NAMBIAR
CSIRO Forestry and Forest Products, PO Box E4008, Kingston, ACT 2604, Australia.
RESUMEN
El autor identifica una serie de objetivos generales en las plantaciones forestales y discute algunos de sus aspectos
relacionados con: el creciente papel de ellas en la obtención de beneficios económicos y ambientales, las tendencias
de su productividad a largo plazo, los conflictos que causan por las demanda y necesidades de suelo y la estimación
de su sustentabilidad.
Lo medular en la sustentabilidad de plantaciones es la producción rentable y permanente de madera cuidando
simultáneamente el medio ambiente. A pesar de la creciente preocupación, en la mitad de los años 60, sobre la
disminución del rendimiento de las plantaciones forestales, existen claras evidencias que demuestran que en las
zonas templadas frías y cálidas del mundo la productividad de las plantaciones ha aumentado durante las últimas
décadas, lo que constituye un punto a favor de la ciencia y el manejo forestal. Al evaluar la sustentabilidad de la
productividad se debe reconocer que no existe un punto de referencia inamovible al cual se pueda recurrir para
calibrarla, es decir, los índices de productividad sólo pueden dar una información puntual en el tiempo. Los
conocimientos básicos para lograr una mejor evaluación y satisfacción de las expectativas de sustentabilidad, con
las correspondientes obligaciones que ello implica, requieren de una actualización permanente del conocimiento, a
través de su aplicación en terreno y ajuste permanente.
En la medida en que las plantaciones forestales se expanden, entran en conflicto con otros usos de la tierra. Un
ejemplo de lo anterior es el impacto de las plantaciones sobre el recurso agua, también requerido para otros usos.
La solución a estos conflictos requiere de investigación y estrategias de comunicación para incorporar a la comunidad
en forma constructiva en esta problemática.
La sustentabilidad no sólo es de importancia comercial, es también una obligación nacional e internacional. Nociones
simplistas de criterios e indicadores para lograr la sustentabilidad sólo aportan poco. Sin embargo, la utilización de
conocimientos científicos, ponderando adecuadamente los objetivos medulares de las plantaciones forestales, permitirá
el desarrollo de oportunidades crecientes para la industria basada en ellas.
Palabras claves: productividad, sustentabilidad, plantaciones.
ABSTRACT
I have identified a set of generic goals for plantation forestry and discussed some of their aspects in relation to the
expanding role of plantation forests for economic and environmental benefits, the trends in long-term productivity,
conflicting demands and needs in land use values, and assessment of sustainability.
Profitable and sustained wood production with environmental care is at the heart of sustainable plantation forestry.
Despite the rising concern, in the mid 1960s, about the decline in yield of plantation forests, there is a substantial
amount of evidence to show that in temperate and warm temperate areas of the world, plantation productivity has
increased during the last decades; a credit to forest science and management. In evaluating sustained productivity
we need to recognise that there is no immutable reference point against which productivity can be bench-marked,
and indices of productivity may only provide a snap-shot in time. The base knowledge required to achieve this and
to accommodate the inevitable and diverse obligations and expectations of sustainability requires continuous updating of this knowledge through its application in the field, as well as appropriate feedback.
* Trabajo presentado en X Silvotecna. IUFRO Conference. Site Productivity Improvement.
9
E. K. SADANANDAN NAMBIAR
As plantation forestry expands, it comes into conflict with other land-use values. A striking example is the
widespread concern about the impact of plantations on water resources available for other purposes. The solution
of these conflicts requires sound research results and communication strategies to constructively engage the
community.
Sustainability is not only important commercially, it is a national and international obligation. Simplistic notions of
criteria and indicators for assessing sustainability may achieve little, but scientifically based assessments with
appropriate weighting given to the core goals of plantation forestry could further advance the growing opportunities
of plantation based forest industries.
Key words: productivity, sustainability, plantations.
INTRODUCTION
Plantation forestry is steadily expanding around
the world, under diverse bio-physical, social and
e c o n o m i c e n v i r o n m e n t s , and is providing a range
of products and services. Plantations have increasingly b e c o m e private business enterprises for econ o m i c benefits, whether m a n a g e d by small farmers or multinational corporations. Native forests
are still cleared to establish plantation forests in
s o m e countries, but this practice is rapidly declining globally. In m a n y countries such forest conversion is now heavily regulated or outlawed. Thus
plantation forestry, with s o m e exceptions, is substantially a land use system based either on successive rotation of plantations or on ' n e w forests'
established on land often d e g r a d e d by other activities including agriculture. Plantation forests are not
natural assets in the same sense as native forests;
they are assets deliberately g r o w n , often described
as tree farms, for one or m o r e specific purpose.
P l a n t a t i o n forestry has a c o m m e r c i a l focus.
H o w e v e r , m a n a g e m e n t goals for plantations are
diverse and strongly interactive with economic,
environmental and social values. Therefore their
links in the broader concept of sustainable develo p m e n t e v o k e m a n y expectations and conflicting
values. It is important to have clearly stated goals
relevant to national, regional and local contexts to
achieve sustainability in a practical sense, as well
as for the ongoing realisation of the full potential
of plantation forestry. A core set of generic goals
include ( N a m b i a r 1996a,b):
•
•
•
There may be other goals, for e x a m p l e , land
care and bio-diversity values that m a y be a c c o m modated or even enhanced d e p e n d i n g on the ecosystem that is being m a n a g e d . T h e e m p h a s i s on
any one or set of goals is a matter of local decision. Although, in reality we can rarely give equal
weighting to all goals, it is not acceptable to singlemindedly pursue any one goal (including a commercial goal) while disregarding other values.
In this paper I would like to discuss s o m e aspects of these goals. I wish to focus on the expanding role of plantation forests; trends in longterm productivity; interaction between productivity and landscape values; and, h o w sustainability
m a y be assessed. T h e continued and sustained
growth of plantation forestry is an ongoing challenge for all of us. It can only be met through
establishing partnerships between forest scientists,
managers, policy m a k e r s and the c o m m u n i t y .
EXPANDING ROLE OF PLANTATION
FORESTS
Increased
wood production.
Historically
many
countries have planted forests, mostly of exotic
species, to supplement w o o d obtained from native
forests for the local timber industry. In m a n y cases,
this has not been sufficient to avoid a m i s m a t c h
between supply and d e m a n d . Estimates of wood
d e m a n d vary greatly for a variety of reasons. A c cording to A p s e y and Reed (1995), the predicted
global supply gap in 2 0 1 0 will be 5 5 0 million m 3 ,
to ensure that the trend in plantation productiv-
increasing to 675 million m 3 by 2020. T h e E u r o -
ity is non-declining over successive harvests;
pean Forest Institute (EFI A n n u a l Report 1996)
to protect and if possible e n h a n c e the quality of
projected that by the year 2050, 'with a higher
soil and water in the plantation environment;
G D P constant p r i c e ' scenario, world c o n s u m p t i o n
to p r o m o t e innovation and profit of g r o w i n g
will reach about 3 billion m 3 per year and that
and utilising w o o d for the business;
under a 'lower G D P , 0.5 % per year price in-
to i m p r o v e the e c o n o m i c and social benefits to
crease' it will reach about 2 billion m per year.
the c o m m u n i t y .
F u e l w o o d shortage is endemic in many develop-
3
•
10
PRODUCTIVITY, SUSTAINABILITY, PLANTATIONS
ing countries. If the rate of deforestation for fuel
under plantation forestry d o u b l e d from 85 million
w o o d continues at the current pace until the year
ha in 1980 to 180 million ha in 1995. By the year
2 0 2 0 , the loss of about 2 3 % of the forest cover in
2 0 1 0 this figure is expected to d o u b l e again ( F A O
the w o r l d today could occur (Apsey and R e e d
1997). While the scope appears promising for large-
1995), exacerbating the shortage of w o o d and e c o -
scale development of plantation forestry in the trop-
logical degradation. There are great disparities in
ics, their long-term success will d e p e n d on sound
w o o d c o n s u m p t i o n between p o o r and rich coun-
land use decisions and sustainable m a n a g e m e n t
tries. F o r example, according to F A O figures for
( N a m b i a r and B r o w n 1997a).
1993, global timber consumption ranges from (a
m e r e ) 5 m 3 t o 6 0 0 m 3 per 1000 people. Regardless
of the variations in estimates of c o n s u m p t i o n and
production, all information leads to the conclusion
that a serious w o o d deficit will occur in the future.
Such increasing d e m a n d s for industrial wood,
fuelwood and charcoal cannot be met by native
Environmental benefits. Although plantations are
mainly intended to p r o d u c e w o o d on a c o m m e r cial basis there is an increasing recognition of the
value of plantations as a form of land use to enhance environmental benefits ( N a m b i a r 1997, Kile
et al. 1998).
forests. Sustainably m a n a g e d plantation forests
offer a great opportunity and, the only feasible
m e a n s , for meeting future w o o d d e m a n d (eg: Shepherd 1993, B r o w n et al. 1997). Kuusipolo (1996)
e x a m i n e d the sustainability and rehabilitation of
forestry in Indonesia and suggested that the conversion of 1% of imperata grassland back to a
productive plantation forest state, with the help of
fast-growing trees, would be e n o u g h to provide
the w o o d supply for a 500 0 0 0 ton pulp mill, and
consequently, would save approximately an equal
area of natural forest from m a x i m a l exploitation.
Indonesia has embarked on large-scale developm e n t of fast-growing plantations
of Acacia and
Eucalyptus and plans to progressively shift its w o o d
c o n s u m p t i o n requirements from native forest harvest to plantation-grown wood. T h e w o o d products industry in India argues that India has s o m e
130 million ha of degraded forest land, and if they
are allowed to g r o w plantations in s o m e 1% of
this land, the current 'raw material crises' in India
Mitigation of land degradation. F a r m forestry
plantings are being promoted for the dual p u r p o s e
of growing w o o d and i m p r o v i n g soil and water
quality of agriculturally degraded land. A successful e x a m p l e is the integrated p r o g r a m to c o m b a t
wide spread soil-water salinity in Western Australia (Shea and Hewett 1997). Tree planting can
also improve the physical e n v i r o n m e n t and biodiversity in farms. For Australia, the estimated nonm a r k e t benefits from trebling its plantation resource, primarily through farm forestry, are considerable (CIE 1997). T h e s e include a 6 0 % increase in e m p l o y m e n t in s o m e regions, a halt in
farm decline with up to 2 0 % increase in i n c o m e ,
savings up to $85 h a - 1 by repairing soil degradation and a contribution to carbon sequestration
equivalent to carbon tax offsets of $13 h a - 1 . A l though these are only forward estimates, they do
indicate the opportunities that are ahead for A u s tralia.
can be met. They also hold that they can do so
with d u e e n v i r o n m e n t a l and social c a r e (India
Report, M a r c h 1996).
Climate change. The rising CO 2 levels and predicted changes in climate are major global issues.
In several countries (e.g. : Brazil, Chile and
T h e potential of plantations to sequester a t m o -
N e w Zealand), plantation forestry already has a
spheric carbon and thus contribute to m a n a g e m e n t
g r o w i n g role in economy and e m p l o y m e n t . In N e w
of this issue is m u c h debated. Estimates of the
Zealand, the forestry industry n o w contributes 6%
a m o u n t of carbon that can be sequestrated in this
of G D P ( O ' L o u g h l i n 1995), and with planned ex-
way, in comparison with the a m o u n t that is emit-
pansion, it is poised to b e c o m e the largest export
ted and the overall carbon budget vary consider-
earner. Ambitious programs to expand plantations
ably, for any geographical location. Because CO 2
and farm forestry are being p r o m o t e d in countries
will be both sequestered (depending on growth
as diverse as Australia, China, India and Uruguay.
rates) and released (by decomposition and burn-
A u s t r a l i a has e m b a r k e d u p o n a n a t i o n a l v i s i o n
ing) during the life cycles of plantations, the role
- Plantations for Australia: the 2 0 2 0 Vision - which
of plantations as a carbon ' s i n k s ' and their envi-
sets the stage for trebling the area under planta-
r o n m e n t a l impact d e p e n d s upon the d y n a m i c s of
tions by the year 2020. At a global level, areas
plantation
establishment,
management
and
11
E. K. SADANANDAN NAMBIAR
utilisation. For e x a m p l e in 1990 in N e w Zealand,
the fossil fuel - carbon emissions totalled 8 Mt yr -1
and the rate of carbon sequestered by forests was
3.5 Mt y r - 1 , or about 4 4 % of the emission. In comparison the emission in U S A was 1300 Mt yr - 1
against a forest sequestration of 80 Mt y r 1 , or
only 6% of the emission (Brown 1995). By comparison, a sustained plantation d e v e l o p m e n t program of 1.6 million ha over 40 years is estimated
to m a k e a contribution of about 10% in reducing
Australia's net CO 2 emissions (Barson and Gifford
1990). Plantation forests can be important sinks in
s o m e cases (Apps and Price 1996) and some analyses show them a m o n g the relatively low cost options for carbon sequestration (Sedjo 1996).
productive and can be a major source of w o o d
production in relatively small areas. T h e primary
role of plantations regardless of the size of the
investment,
tal
is
wood production
with
environmen-
care.
-
T h e ideas of carbon tax and carbon credits are
being canvassed as a way of apportioning responsibility to those w h o contribute to emissions or
p r o m o t e sequestration as a part of an overall strategy to deal with carbon emission. T h e idea of 'carbon credits' requires well defined actions by industry to increase carbon sequestration through
increasing plantation forests, and these would be
accounted as 'offsetting credits' against the emission caused by other industrial e c o n o m i c activities. This idea has captured the attention of nonforest industries based on fossil fuel, and m a y lead
to n e w opportunities for plantation forestry.
Biodiversity. Recent research has provided new
possibilities for restoring native species richness
on d e g r a d e d land by first planting monoculture of
exotic species selected to m a t c h site conditions. In
turn, they foster an environment conducive to the
regeneration of a variety of native species (Parrotta
1992, L u g o 1996). Recent results from c o m m e r cially m a n a g e d h o o p pine plantations in Queensland (Australia) s h o w that numerous native species have re-established as understorey (Co-operative Research Centre for Tropical Ecology, A n nual report 1996). These results seem a paradox,
but, along with research from elsewhere they question the validity of the assertion (sometimes) m a d e
that plantations are 'biological deserts'. Thus industrial plantations, farm forests, w o o d lots for
fuel, and plantations established primarily for environmental
protection
(land
rehabilitation,
biodiversity rejuvenation, or catchment protection)
are all inalienable links in a continuum of sustainable land use. Several types of plantation developm e n t to suit one or m o r e land use objectives are
possible. Plantations, if m a n a g e d well are highly
12
PRODUCTIVITY
IMPROVEMENT IN THE
LONG-TERM
A central element of sustainability is historical
knowledge, and m a n a g e m e n t of long-term productivity. Site productivity is represented and m e a sured in a variety of w a y s (e.g.: net primary production, above ground biomass, merchantable stem
wood) and there is a plethora of m a n a g e m e n t and
research indices used to describe potential and
realised production: site index, site quality, site
potential, site carrying capacity and others. An
analysis of the relative merits of these indices is
not within the scope of this paper.
In plantation forestry, few site characteristics
have been monitored over the long-term. E v e n
when some changes in long-term trends are found,
it is difficult, if not impossible, to explain such
trends in terms of biophysical processes and their
interactions. Nevertheless, it is important to review the trends in production of s o m e ecosystems,
where data are available. T h e s e can help us to
relate to what is known about the basic principles
that govern productivity.
Figure 1 shows the c h a n g e in productivity of
Pinus radiata achieved by application of improved
m a n a g e m e n t practices (improved planting stock
and site m a n a g e m e n t ) by a private forest owner in
Australia (Leishout et al. 1996). T h e authors used
volume growth of all plantations established before 1971 as the unimproved base line for compiling these data. The lack of balanced 'control plots'
was partly compensated by stratification of data
by soil types, and the availability of over 10,000
plots systematically positioned throughout the estates. Results show a big and continuing improvement across all 14 soil types within the three m a j o r soil groups, with average increases of 7 7 % on
uniform sand, 5 5 % on Duplex soil and 5 3 % on
clay loam. Leishout and colleagues e x a m i n e d the
realised gain since 1988, and point out that u s i n g
pre-1971 v o l u m e growth as a base line, the gain
was 4 9 % in 1988, 5 1 % in 1993 and 6 3 % in 1995
(Fig. 2), showing a steady u p w a r d trend. Furtherm o r e , plantings until 1971 (base line) were en-
PRODUCTIVITY, SUSTAINABILITY, PLANTATIONS
tirely on first rotation sites, whereas b e t w e e n 1980-
the same sites at the c o m p a r t m e n t level mirrors
84, 5 7 - 7 8 % of the area planted was second rota-
this pattern of site quality u p g r a d i n g ( N a m b i a r
tion sites (2R - pine after pine). T h e progressive
1996b). This is a r e m a r k a b l e l o n g - t e r m i m p r o v e -
increase in M A I leading to 6 6 % by the 1980-84
m e n t in site productivity.
planting over the 1971 base line shows h o w imp r o v e d m a n a g e m e n t has increased productivity of
successive crops.
F i g u r e 2 s h o w s the pattern of v o l u m e g r o w t h of
plantations established b e t w e e n 1950 to 1984. T h e
a n n u a l fluctuations are c a u s e d b y p r o p o r t i o n a l
planting across various soil types and seasonal
variations. T h e overall trend is positive increasing
from about 7 m 3 ha - 1 yr - 1 to 15 m 3 ha - 1 y r - 1 . T h e
substantial i m p r o v e m e n t since the late 1970s has
b e e n s o m e w h a t d a m p e n e d by a large reduction in
the early 1980s following a severe drought period.
P l a n t a t i o n s of P.
radiata e s t a b l i s h e d in the
south-east of South Australia and western Victoria
contribute with a significant proportion of the w o o d
p r o d u c e d in Australia. L o c a l industry is entirely
d e p e n d e n t on w o o d g r o w n locally, on second and
third rotation sites. L o n g - t e r m research and its
systematic application has p r o d u c e d profitable silvicultural options to not only to maintain yield but
also to e n h a n c e it over extensive areas ( B o a r d m a n
1988). Forestry (South Australia), the largest custodian of plantations in the region, assessed growth
on their s e c o n d and third-rotation sites in 1994
according to a Site Quality Scale ( S Q VII: low) to
Figure 1. Realised gains in Mean Annual Increments
(MAI) measured at age 11 years for Pinus radiata from
improvements in silviculture and tree breeding since early
1970's. Sites in Gippsland, Australia. Individual histograms within the major soil groups represent different
soil types (Leishout et al. 1996).
Aumentos obtenidos en el incremento medio anual de Pinus
radiata a los 11 años de edad, con medidas de mejoramiento
silviculturales y genéticos, al principio de los años 70, en sitios
de Gippsland, Australia. Los histogramas individuales, dentro
de los grupos de suelos indicados, representan diferentes tipos
de suelos (Leishout et al. 1996).
( S Q I: high) and c o m p a r e d the results with yield
assessments m a d e in earlier years. T h e assessment
techniques w e r e b a s e d on well established inventory m e t h o d s w h i c h allowed reliable predictions
of yield over a full rotation, from m e a s u r e m e n t s at
a g e 10 years, if stands were m a n a g e d according to
p r e s c r i b e d thinning r e g i m e s . T h e result of that
evaluation is s h o w n in Figure 3. To simplify the
presentation, I h a v e aggregated the data into three
groups to indicate high, m e d i u m and l o w p r o d u c tivity classes. T h e results s h o w that in the early
1960s, about 7 0 % of the total plantation area w a s
in the r a n g e SQ V - V I ( M A I 18 to 13 m 3 ha - 1 yr - 1
at the m a x i m u m M A I a g e of 36 to 37 years). T h e
g r o w t h trends of subsequent plantations, planted
in 1984 ( m e a s u r e d in 1994) on p r e d o m i n a n t l y seco n d - and third-rotation sites h a v e p r o v i d e d a basis
for u p g r a d i n g m a n y sites to SQ I-III ( M A I 33 to
25 m 3 ha - 1 yr - 1 at the m a x i m u m M A I age of 29 to
32 years). At present, the organisation has less
than 1 0 % of their total estate classified in t h e l o w
productivity class SQ V - V I . A c o m p a r i s o n of p r o ductivity of first- and second-rotation stands within
Figure 2. Long-term trends in MAI across many sites,
soil types and planting year spanning 34 years. MAI
was measured at age 11 years, the last set of measurement being in 1995 (planted in 1984) (Leishout et al.
1996).
Tendencia de largo plazo del IMA, en representación de muchos
sitios, tipos de suelo y años de plantación para un período de
34 años. El IMA fue medido en plantaciones de 11 años y el
último set de mediciones fue efectuado en 1995 (plantación de
1984) (Leishout et al. 1996).
13
E. K. SADANANDAN NAMBIAR
and l o n g - t e r m inventory system w i t h s o u n d stratification to represent landscape, soil and silvicultural v a r i a t i o n s is n e c e s s a r y to o b t a i n r e l i a b l e
m e a s u r e s of realised gain. F u r t h e r m o r e , c h a n g e s
in yield m e a s u r e d by various m a n a g e m e n t inputs
(e.g.: potential benefits of tree breeding, g r o w t h
r e s p o n s e to silviculture etc.) are from small plots
under conditions designed to maximise the response
to applied treatments and often lack the reality of
the large-scale operational plantations. T h i s has
required the careful adjustment of gains from r e search plots d o w n w a r d , to ensure representation
Figure 3. Long-term trends in the area classified in
various Site Quality classes of second- and third-rotation plantations of Pinus radiata on podzolised sandy
soils in South Australia. (Forestry (S. Australia), 1995,
personal communication).
Tendencias de largo plazo de la superficie ocupada por clases
de sitio para Pinus radiata, en segunda y tercera rotación,
sobre suelos arenosos podsolizados en el Sur de Australia (Forestry (S. Australia), 1995, comunicación personal.
W i t h scientifically b a s e d m a n a g e m e n t , o n g o i n g
overall i m p r o v e m e n t in w o o d yield from plantations are being achieved across a r a n g e of soil and
e n v i r o n m e n t a l conditions in Australia (Figs. 1, 2
a n d 3) ( N a m b i a r 1995, B o r s c h m a n n 1995, L o n g
1997). G o n ç a l v e s et al. (1997) discussed several
soil a n d s t a n d m a n a g e m e n t i s s u e s critical for
achieving sustained productivity of short-rotation,
fast-growing eucalyptus plantations in Brazil. An
inventory of productivity of plantations in Brazil
showed that productivity increased steadily by 4 0 %
in w o o d yield, and by 7 5 % in p u l p yield from
1980 to 1995 (see N a m b i a r 1997 b a s e d on a report
b y A B E C E L 1995).
A s s e s s m e n t of long-term realised gains in w o o d
p r o d u c t i o n over b r o a d areas is not easy for several
reasons w o r t h briefly e x a m i n i n g here. First, scientific a n d technical i m p r o v e m e n t s and their application in forestry h a v e s e l d o m b e e n characterised
by spectacular j u m p s (unlike advances in the use
of d r u g s for disease control); i m p r o v e m e n t s are
incremental, and trends are influenced by m a n y
biophysical variations and investment decisions.
Second, productivity during one g r o w t h rotation
alone c a n be dramatically influenced by weather,
especially distribution a n d quantity of rainfall.
Third, since it is difficult to include strict biological controls against w h i c h continuous i m p r o v e m e n t s c a n be m e a s u r e d in space and time, a large
14
o v e r forest m a n a g e m e n t u n i t s ( L e i s h o u t et al.
1996). D e s p i t e these constraints, s y s t e m a t i c a l l y
collected, adequately stratified, l o n g - t e r m g r o w t h
data is invaluable not only for u n d e r s t a n d i n g longt e r m c h a n g e s in productivity and sustainability in
a true sense but also for m a k i n g critical m a n a g e m e n t decisions. T h e overall global trend indicates
that productivity of intensively m a n a g e d plantation forests is increasing ( N a m b i a r 1997).
KNOWLEDGE BASE AND SILVICULTURAL
DECISIONS FOR MANAGING PRODUCTIVITY
Site-stand management. T h e productivity of successive crops over (the) a long-term can be influenced positively or negatively, by site and stand
m a n a g e m e n t operations at any stage during the
rotation. H o w e v e r , in general, the m o s t intensive
impacts on the soil and site e n v i r o n m e n t o c c u r
during the inter-rotation management period
through operations w h i c h include harvesting, site
preparation, vegetation m a n a g e m e n t and other early
silvicultural practices. D u r i n g this period sites m a y
be heavily disturbed and e x p o s e d to degradation
processes (e.g. soil erosion, loss of organic matter
and nutrients through fire, leaching and displacem e n t s ) w h i c h can also c a u s e adverse off-site impacts (e.g. pollution of streams). M a n a g e m e n t strategies b a s e d on practices including genetically imp r o v e d planting stock, site preparation practices
that conserve site resources and i m p r o v e availability of water and nutrients, and control of c o m petition are critical elements for increasing p r o ductivity. T h e r e is a substantial b o d y of information on the process associated with inter-rotation
m a n a g e m e n t practices, and there are m a n y technological solutions that can be a d a p t e d to suite
site-specific conditions and p r o d u c t i o n goals (e.g.
B o a r d m a n 1988, N a m b i a r and S a n d s 1 9 9 3 , B e e t s
PRODUCTIVITY, SUSTAINABILITY, PLANTATIONS
et al.
1994,
N a m b i a r 1996b, Fife and N a m b i a r
1997, G o n ç a l v e s et al. 1997).
T h e r e are indeed m a n y m o r e challenges to overc o m e . A c o m p r e h e n s i v e r e v i e w of those issues are
not within the scope of this paper. H o w e v e r , let
me illustrate two cases especially related to
P. radiata silviculture as e x a m p l e s . In Australia,
P.
radiata is g r o w n u n d e r winter rainfall - dry
s u m m e r e n v i r o n m e n t s c o m m o n l y leading to large
w a t e r deficit. G r o w t h of stands is predominantly
influenced by available water (Fig. 2). F o r m a k i n g
s o u n d investments in silviculture, m a n a g e r s n e e d
tice. F o r e x a m p l e , w e d o k n o w that g r o w t h re-
Figure 4. Variation in annual photosynthetic carbon fixation over long-term, estimated by BIOMASS model for
two sites with contrasting Site Index in Australian Capital Territory (Snowdon et al. in press).
s p o n s e to the application of fertilisers to late-age
Variación anual de la fijación fotosintética de carbono en el
stands is d e p e n d e n t u p o n several soil (e.g. rates of
largo plazo, estimada por el modelo BIOMASS, para dos sitios
mineralisation, available soil water), and stand-eco-
con índices de sitio diferentes en el territorio de la capital de
tools to predict t h e nature and extent of g r o w t h
r e s p o n s e obtainable for a given m a n a g e m e n t prac-
physiological attributes including L A I (e.g. Carlyle
Australia (Snowdon et al. en prensa).
1995, in press ). Interaction b e t w e e n nutrients and
w a t e r is often the k e y to productivity ( N a m b i a r
1 9 9 0 / 9 1 , K i m m i n s 1994, Carlyle in press).
T h e nature and degree of the influence of clim a t i c factors o n p r o d u c t i o n c a n b e e x a m i n e d
t h r o u g h p r o c e s s - b a s e d m o d e l s . S n o w d o n et al. (in
press) u s e d a process-based m o d e l , B I O M A S S , to
estimate variation in photosynthesis by (in) several stands. T h e y u s e d a simplified non-varying
c a n o p y structure, a fixed L A I value and c r o w n
configuration, physiological p a r a m e t e r for P. radiata and soil moisture characteristics appropriate
to the sites (Fig. 4). Simulations w e r e carried out
using daily data for rainfall, m a x i m u m and minim u m temperature. T h e results s h o w e d that the 4 8 year average for the climate index varied from
17.3 a n d 29.9 C t h a - 1 . On a w e t site (long-term
annual rainfall, 1120 m m ) annual variation w a s
about 15 t C h a
- 1
,a n d on a dry site (long-term
annual rainfall, 6 4 6 m m ) it w a s about 9 t C h a - 1 .
These large variations in photosynthesis would lead
to equally large variation in g r o w t h b e t w e e n sites
a n d g r o w i n g seasons. Estimates and prediction of
yield usually do not take into account the e n d e m i c
vagaries of climatic factors and therefore can suffer from significant bias and inaccuracies d e p e n d ing u p o n the n a t u r e of the climatic variation itself
( S n o w d o n et al. in press). B e c a u s e of this, s h o r t t e r m yield forecasts b a s e d on empirical g r o w t h
m o d e l s a n d l o n g - t e r m average rainfall for a region, a c o m m o n practice in m o s t yield estimates,
are p r o n e to a h i g h degree of bias a n d inaccuracy
( S n o w d o n et al. in press).
B e c a u s e mid-rotation fertiliser application is an
economically attractive proposition for increasing
w o o d yield in a relatively short time (5-10 years),
efficient tools to predict the probability, size and
longevity of the g r o w t h response to fertiliser a p plication at a m a n a g e m e n t unit level is a very attractive area for research. F i g u r e 5 s h o w s the r e sults of a survey of mid-rotation fertiliser experim e n t s on P. radiata in Australia and N e w Zealand.
T h e probability and size of the response d e p e n d s
on the element applied and m a n y site and stand
characteristics. The proportion of experiments
w h i c h give zero response are c o m m o n if only N
or P alone are applied. T h e size and probability of
response increases w h e n N a n d P are applied together (Fig. 5). If g r o w t h is simultaneously limited by N and P, application of one e l e m e n t alone
is likely to be a w a s t e of m o n e y . In large-scale
operations, wide variations in growth response will
lead to unpredictable o u t c o m e s and return from
investments. Simple, traditional foliar analysis has
b e e n useful in the past to identify areas of gross
nutrient deficiency. As the overall quality of sitestand m a n a g e m e n t has i m p r o v e d (Fig. 2 and 3),
marginal deficiencies are m o r e c o m m o n than acute
ones. In a n u m b e r of circumstances the availability of water w o u l d h a v e an overriding influence
on the size and longevity of r e s p o n s e ( N a m b i a r
1990/91). T h e a b o v e e x a m p l e s illustrate that despite the fact that there are i m p r o v e d t e c h n o l o g i e s
available for increasing production, m o r e opportunities await for further i m p r o v e m e n t s by linking
15
E. K. SADANANDAN NAMBIAR
in genetic gain over successive generations dep e n d u p o n the quality a n d precision with w h i c h
tree breeding p r o g r a m s are i m p l e m e n t e d . T h e n e e d
to maintain the b a l a n c e b e t w e e n these c o m m e r c i a l
objectives, ecological risks and sustainability h a v e
b e e n discussed e l s e w h e r e ( N a m b i a r 1996a).
T h e realised and expected g a m in stem g r o w t h
(volume) of P. radiata by using seeds from first
generation seed orchards r a n g e from 15 to 3 0 %
over u n i m p r o v e d seeds ( M a t h e s o n et al.
Johnson
Figure 5. Relative basal area response to phosphorus,
nitrogen and phosphorus + nitrogen measured in a range
of experiments in New Zealand and Australia (Carlyle,
personal communication).
Respuesta del área basal a fertilizaciones de fósforo, nitrógeno
y nitrógeno + fósforo, expresada en porcentaje, en vanos
e x p e r i m e n t o s de N u e v a Z e l a n d a y Australia (Carlyle,
comunicación personal).
1991).
1986,
Advanced-generation breeding
strategies i n v o l v i n g c o n t r o l - p o l l i n a t e d b r e e d i n g
populations and clone p r o p a g a t i o n are estimated
to p r o v i d e further genetic a d v a n t a g e (based on
estimates of realised breeding values) ranging from
14 to 2 0 % (in basal area) over the previous generation (White et al, in press). T h e Southern T r e e
B r e e d i n g Association ( S T B A ) , a C o - o p e r a t i v e of
plantation growers in Australia, estimated that t h e
genetic gain achieved by open-pollinated and c o n trol-pollinated seed options w o u l d increase from
n e w information on soil based parameters and stand
p h y s i o l o g y . T h e d e v e l o p m e n t o f progressive m a n a g e m e n t practices is d e p e n d e n t on t w o critical factors: research directed at the fundamental factors
which determine productivity, and an organisation's
ability and determination to i m p l e m e n t research
findings.
about 1 2 % obtained i n 1980 t o 2 6 and 3 8 % , r e spectively, b y year 2 0 0 0 ( S T B A 1997).
M o s t analyses of genetic g a m are b a s e d on ' e s timated g a i n ' ; m e a s u r e d values of real gain o b tained from broad, operational plantings are rare.
In m o s t breeding p r o g r a m s , the selection a n d testing of genotypes for e c o n o m i c traits are c o m m o n l y
carried out u n d e r conditions w h e r e the inherent
Genetic
improvements
for
high
productivity.
c o n s t r a i n t s ( s t r e s s ) at a site a r e r e m o v e d or
C o n t i n u o u s i m p r o v e m e n t s in the genetic m a k e up
m i n i m i s e d by soil and stand m a n a g e m e n t p r a c -
of planting stock h a v e b e e n an integral part of the
tices. T h e r e are m a n y i m p e d i m e n t s to capture the
a d v a n c e s in plantation forestry. T r e e i m p r o v e m e n t
'estimated' genetic gain in an operational scale
p r o g r a m s designed to support this are based on
and it is important to be cautious a n d conservative
inter-related activities that include m a t c h i n g g e n o -
w h e n projecting the benefits of b r e e d i n g research
types to a site, recurrent cycles of breeding (in-
(Haines 1995, N a m b i a r 1996a).
c l u d i n g hybridisation) to m a x i m i s e the c o m b i n a -
T r e e b r e e d i n g is not a p a n a c e a , and use of g e -
tion of g e n e s affecting e c o n o m i c a l l y i m p o r t a n t
netically i m p r o v e d planting stock without a p p r o -
traits (growth of w o o d quality, resistance to pests
priate site-soil m a n a g e m e n t will m o s t l y lead to
and diseases) and d e v e l o p i n g propagation m e t h -
little (small) benefits. It should also be n o t e d that,
ods for large-scale production of planting stock of
in g e n e r a l , r e g a r d l e s s of t h e b r e e d i n g strategy
elite genotypes.
adopted, higher productivity requires h i g h e r levels
C o m m o n aims of tree breeding strategies are:
of resource inputs and intensity of m a n a g e m e n t .
( N a m b i a r 1996a) (1) to develop genotypes (breeds)
T h e a m o u n t of water transpired by P. radiata is
that h a v e h i g h harvest index (measured as stem
directly p r o p o r t i o n a l to s t e m size ( T e s k e y a n d
v o l u m e ) and p r o d u c e w o o d of the quality required
Sheriff 1996) and a m o u n t s of nutrients r e m o v e d
for manufacturing specific products, and (2) to
in logs is directly proportional to stem v o l u m e
r e d u c e the interval b e t w e e n generations so that the
regardless of family variation in g r o w t h ( N a m b i a r
genetic gain per unit t i m e can be m a x i m i s e d and
1996a). Productivity of m o s t plantation areas is
planting stock u p g r a d e d at each (shorter) harvest-
limited by m o r e than o n e site r e s o u r c e . Further-
ing cycle. It is also c o n c e r n e d with reducing the
m o r e , the genetic correlation b e t w e e n traits m a y
cost of b r e e d i n g and propagation. I m p r o v e m e n t s
be positive or negative, and from a practical p o i n t
16
PRODUCTIVITY, SUSTAINABILITY, PLANTATIONS
Figure 6.
I n t e r a c t i v e v a r i a b l e s a n d their a l i g n m e n t in relation to r i s k s ,
a s s e s s m e n t o f sustainability (Criteria a n d Indicators) and c o n t i n u o u s
i m p r o v e m e n t in m a n a g e m e n t ( N a m b i a r 1996, N a m b i a r 1997).
Variables interactivas y su ordenamiento en relación a riesgos, a la sustentabilidad
(criterios e indicadores) y al continuo mejoramiento del manejo (Nambiar 1996,
Nambiar 1997).
of view the addition of every trait to b r e e d i n g
objectives adds c o m p l e x i t y and cost to breeding
p r o g r a m s and their application.
I h a v e not addressed the issue of log and w o o d
quality, w h i c h has a great i m p a c t on profitability
a n d increasingly, on competitiveness in the market. R e s e a r c h on tree breeding, nutrient m a n a g e m e n t and stand m a n a g e m e n t offers opportunities
for i m p r o v i n g quality of w o o d and its suitability
for specific e n d p r o d u c t s .
S U S T A I N A B I L I T Y A N D ITS A S S E S S M E N T
Interacting variables.
T h e nature of investments
in and o w n e r s h i p of plantations, their intended use,
and the strong c o m m e r c i a l focus of m a n a g e r s will
i m p a c t o n m a n a g e m e n t practices i n m a n y w a y s .
E x p e c t a t i o n s of p r o d u c t i o n are h i g h , - a policy of
sustaining p r o d u c t i o n at a static level is a lost
o p p o r t u n i t y - , and in c o m m e r c i a l forestry, m a n a g ers are not simply satisfied by m a i n t a i n i n g yield.
T h e balance b e t w e e n e n v i r o n m e n t a l a n d p r o d u c tion values is accounted for in terms of unit cost
of w o o d because, c o m p l i a n c e with m a n y environmental principles is seen as an a d d e d cost on p r o duction. Nevertheless, plantation forestry has to
be, for its long-term future, in h a r m o n y with the
societal n e e d s , awareness and expectations of sustainable development (Nambiar and B r o w n 1997b).
T h e risks to plantations and prospects for their
sustainability can be e x a m i n e d in t e r m s of the
degree of alignment of a set of core interactive
variables ( N a m b i a r and B r o w n 1997b, Fig. 6). T h e
ecological capacity of plantations is b o u n d by inh e r e n t soil a n d b i o p h y s i c a l constraints (especially
available water), the genetic potential of the species, and its ecological m a t c h with the site. M a n 17
E. K. SADANANDAN NAMBIAR
a g e m e n t systems which exceed these bounds can
lead to productivity loss and failed investments.
The intensity of m a n a g e m e n t applied to a site and
its impact on production, will change as our knowledge, expected o u t c o m e , and commercial realities
c h a n g e (Fig. 6). E c o n o m i c efficiency is dependent
on cost of production at the site and at the mill,
c o m b i n e d with product d e v e l o p m e n t and market
opportunities. T h e e n h a n c e m e n t of the productive
capacity of the soil, wherever possible, is a good
fundamental basis for sustainability. If soil properties are sustained through j u d i c i o u s m a n a g e m e n t
in situ adverse off-site impacts can be minimised.
Impacts on water resources. A striking example
of the way plantation forestry c o m e s into conflict
with the multiple use of land, can be seen in the
concern about the threat of e x p a n d i n g plantations
that w o u l d use up the available water for other
purposes. This concern has led to the opposition
to or negative perceptions of plantation forestry in
several countries.
South Africa has a forest industry providing
m a n y e c o n o m i c benefits for society based plantations of exotic species. Yet, the expansion of plantations has been severely restricted since the 1970s.
T h e predicted d e m a n d s for w o o d and water are
expected to increase in 10-20 years (Dye 1996), a
sensitive and delicate issue in a country where the
a m o u n t of available water per capita is very low.
A p a r t from the social issues related to the close
link b e t w e e n land tenure and access to water for
the population, there are t w o important biophysi-
cal considerations: (i) commercial forestry w h i c h
occupies about 2 . 5 % of the land area, is located
over the same limited area that receives the best
rainfall (>850 mm per year) and (ii) plantations
established on catchments which were under native vegetation have reduced the a m o u n t of water
that flows into the river system in an a m o u n t
equivalent to 100-200 mm y r - 1 of rainfall. On a
broad scale, this has caused an overall reduction
of about 3 0 % in available water (Scholes et al.
1995). T h e impact of forestry on stream How at the
catchment level can be severe, depending on the
hydrological process in the catchment, plantation
species, their growth rates, rotation length and
m a n a g e m e n t systems (Table 1). Apart from water,
other considerations of sustainability i n c l u d i n g
plantation scale and location, biodiversity, soil
values, aesthetic values, economic and social imp e r a t i v e s i n c l u d i n g labour, and the l o n g - t e r m
sustainability of plantation forestry are topics of
serious discussion and analysis in South Africa
(eg: Scholes et al. 1995, Versfeld 1996, Olbrich et
al. 1997).
T h e profound questions to be dealt with include
equity in access to water, based on fundamental
principles enshrined in the constitution, and criteria for costing the water as a national resource,
based on a balanced evaluation of its use for national benefit. T h e various options being considered will have major impact on the forest industry
and its ability to compete.
TABLE 1
Examples of the impact of plantations on catchment streamflow compared with streamflow from
unafforested catchments in South Africa (Scholes et al. 1995).
Ejemplos del impacto de plantaciones en los escurrimientos superficiales comparados
con cuencas no forestadas en Sudafrica.
Natural
Mean annual
Virgin mean
Species and
Reduction in
rainfall
annual runoff
extent of
streamflow
(mm)
(mm)
afforestation (%)
Age (yrs)
mm
Grassland
1634
880
P. patula - 75
0-29
360
Fynbos
1400
600
P. radiata - 57
0-23
200
Grassland
1150
250
E. grandis - 100
5
403
9
Dry
catchment
18
PRODUCTIVITY, SUSTAINABILITY, PLANTATIONS
Plantations of introduced species including eu-
g e n e r a l l y d e s c r i b e d as
'identified e l e m e n t s of
calyptus and acacias have b e c o m e a vital resource
sustainability - against which forest m a n a g e m e n t
for offsetting, at least partly, I n d i a ' s w o o d crisis.
can be assessed' (Prabhu et al. 1996). Criteria m a y
As in several other countries, such developments
deal with the extent and productivity of forests,
m e e t i n f o r m e d and uninformed opposition and
their attributes and function, environmental ben-
anxieties arising from conflicting d e m a n d s on the
efits and socio-economic goods and services d e -
land. T h e alleged impact of eucalyptus plantations
pendent on forests. O n e definition of an indicator
on water availability in Karnataka State in India,
is 'any variable or c o m p o n e n t of the forest e c o -
has caused n u m e r o u s arguments and conflicts, yet
system or the relevant m a n a g e m e n t system used
m a n y farmers continue to plant eucalyptus for their
to infer attributes of the sustainability of the re-
e c o n o m i c benefit. These concerns have stimulated
source and utilisation' (Landres 1992, P r a b h u et
c o m p r e h e n s i v e research p r o g r a m s to e x a m i n e the
al. 1996). E x a m p l e s of the indicators p r o p o s e d by
i m p a c t of plantations on the hydrological process
Prabhu et al. (1996) range from 'absence of ponding
in a tropical semi-arid region; c o m p r e h e n s i v e ac-
behind stream / river crossing' to 'there are assured
counts of this w o r k have been reported (e.g. Calder
compensation benefits in cases of accident'. T h e s e
et al. 1992, Calder 1994, Calder 1996).
e x a m p l e s show the extraordinary wide range of
R e s e a r c h in S o u t h Africa, India, Brazil and
S o u t h A u s t r a l i a s h o w s that with k n o w l e d g e it
should be possible to locate and successfully m a n -
indicators being considered. There can be several
indicators for any selected criterion.
To assess progress towards sustainability, we
age plantations, taking into account the area planted
need meaningful
in relation to catchment size, species, growth rates,
progress can be evaluated. T h e difficulties in es-
'bench-marks'
against which
stand m a n a g e m e n t and overall e c o n o m i c and en-
tablishing such ' b e n c h - m a r k s ' , using potential soil
v i r o n m e n t a l benefits ( D y e 1996, C a l d e r 1994,
based indicators as examples, h a v e been discussed
L i m a et al. 1996, Versfeld 1996). T h e d e v e l o p -
previously (Nambiar 1996a, 1996c). Conclusions
m e n t of plantation forests which threaten the avail-
that we m a y draw on the net effects of plantations
ability of water for critical purposes will not be
on environment and soil sustainability d e p e n d on
sustainable.
the state of the ecosystem at the start. For example, for P. radiata plantations in Australia where
Assessment of sustainability.
Despite
the
many
the rates of production in second- and third-rota-
and diverse views on sustainability, there is a broad
tion crops are greater than those obtained for the
and shared understanding of the fundamental ele-
first-rotation (Fig. 2 and 3), should the ' b e n c h -
m e n t s (regarding) of sustainable forest m a n a g e -
m a r k ' soil used for comparison be in the retained
m e n t . H o w they should b e assessed, w h a t the
dry-sclerophyll native vegetation, part of w h i c h
agreed o u t c o m e should be, and what benefits there
has been cleared for various purposes over de-
are and w h o should get them are subjects for on-
c a d e s ? Should the comparison be with adjacent
going debates. T h e idea of Criteria and Indicators
agricultural land which has been cultivated over
( C & I ) has e m e r g e d as a basis for providing a com-
the s a m e period or should it be between IR - 2R
m o n understanding and an implicit definition of
- 3R pine plantation sites? Clearly, o u t c o m e s from
w h a t constitutes sustainable forest m a n a g e m e n t
m e a s u r e m e n t s of changes in soil properties de-
( G r a n h o l m et al. 1996). It is not an end in itself,
p e n d on the starting point. Furthermore, changes
but a tool for m a k i n g progress towards sustainable
in s o m e soil properties per se m a y have little rel-
m a n a g e m e n t and it is intended to foster a c o m m o n
evance for the continued productive use of that
understanding
of sustainability.
agement is
balancing
man-
land. Research narrowly directed to the discovery
act.
of sustainability indicators per se would not be a
T h e r e h a v e been several initiatives, both at in-
creative path for strengthening the k n o w l e d g e re-
ternational and regional levels, to develop C & I as
quired to improve sustainable practices. R e s e a r c h
a
Sustainable
for e x a m p l e initiatives by specific organisations
efforts for increasing w o o d production with envi-
(e.g. Forest Stewardship Council), by consortia of
ronmental care would b e c o m e m o r e r e w a r d i n g if
national g o v e r n m e n t s (e.g. Helsinki Process,
we continuously strengthened our understanding
M o n t r e a l Process), by an international research
of degradation, rejuvenation and e n h a n c e m e n t pro-
organisation ( C I F O R , see P r a b h u et al. 1996), and
cesses in the ecosystem in relation to plantation
by national g o v e r n m e n t s (e.g. France). Criteria are
m a n a g e m e n t practices. T h a t k n o w l e d g e should b e
19
E. K. SADANANDAN NAMBIAR
c o n t i n u o u s l y r e l a y e d in a practical and operational
c o n t e x t to m a n a g e r s t h r o u g h c o d e of practices for
m a n a g e m e n t (Fig
6), w h i c h should be a b i d e d by
all p l a n t a t i o n e n t e r p r i s e s
A l o n g with global a w a r e n e s s of sustainability
and international pressure for action, the m o v e for
C & I s w a s also p u s h e d b y the d e m a n d for ' e c o labelling'
and other
'certification and l a b e l l i n g '
ideas as a c o n d i t i o n for m a r k e t a c c e p t a n c e of exp o r t e d / i m p o r t e d w o o d by the E u r o p e a n - b a s e d
environmentalist
organisations?
The momentum
t o w a r d s C & I and labelling has as m u c h to do with
politics as it has to do with sustainability
T h e foregoing discussion and the relationship
b e t w e e n the d e g r e e of a l i g n m e n t and the level of
risk d e s c r i b e d in F i g u r e 6, e m p h a s i s e the d y n a m i c
n a t u r e of the c o n c e p t and practice of sustainability.
T h e a l i g n m e n t will n e v e r b e perfect, nor can w e
t a k e it for g r a n t e d that any low risk scenario will
persist,
once
achieved.
Plantation m a n a g e m e n t
s y s t e m s s h o u l d strive t o e n s u r e m a x i m u m alignment
of
the
core
goals
(minimum
risks
to
sustainability) as o p p o s e d to dysfunctions b e t w e e n
values (high risks to sustainability). T h e way ahead
for p l a n t a t i o n forestry is unlikely to be as straightf o r w a r d as the earlier foresters m a y h a v e anticip a t e d . T h e r e are g e n u i n e issues of equity, social
j u s t i c e and sustainability associated with plantations in s o m e r e g i o n s of the world and it is n e c e s sary for n a t i o n a l g o v e r n m e n t s to address t h e m locally in a socio-political context. Profitability of
i n d u s t r y and social j u s t i c e m a y not go h a n d - i n h a n d . H o w e v e r , e c o n o m i c viability, e n v i r o n m e n tal benefits and social goals are closely linked,
a n d it is so w i t h plantation forestry. Plantations in
m a n y c a s e s c o m p a r e favourably with other land
u s e s , i n c l u d i n g c r o p s and animal p r o d u c t i o n , in
t e r m s of costs and benefits.
ACKNOWLEDGEMENT
I t h a n k H e n r y L i e s h o u t ( A P Plantations Pty Ltd)
a n d R o g e r Pfitzner (Forestry S. Australia) for givi n g a c c e s s t o l o n g - t e r m g r o w t h data
C S I R O col-
l e a g u e s R o b i n C r o m e r and Peter S n o w d o n p r o v i d e d v a l u a b l e c o m m e n t s on the m a n u s c r i p t .
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