1.2. New issues
Faced with the critical situation of intensive monocultures,
new conceptual ways of constructing sustainable agroecosystems
are being sought (Malézieux and Moustier, 2005, b).
Several agronomists recently proposed that traditional multispecies
systems could be used as models for designing sustainable
cropping systems (Gliessman, 2001; Altieri, 2002).
Jackson (2002) proposed imitating the structure of the prairie
ecosystem, composed of a number of species of different functional
groups, to achieve resilience to changes in climate and
water supplies, and to pests and other natural disturbances.
Ewel (1999) enhanced the role of woody perennial species in
the sustainability of ecosystem functioning in the humid tropics
and proposed forest-like agroecosystems. Such systems are
usually complex, as they are based on several species, and may
involve combinations of perennial and annual,woody and nonwoody
plants.
Agricultural research now has an adequate tool-box of
methods and models for technology development in monospecific
cropping systems, but its suitability for more complex
systems is unsure. Methods for designing multispecies systems
barely exist. Systemic agronomy concepts (crop management
sequences, cropping system), and especially the tools
derived from that discipline, scarcely deal with the complexity
of multispecies systems. In particular, the modelling tools
widely used today in agronomy are not well adapted to simulating
them. New models are required to represent, assess and
design sustainable multispecies cropping systems.
This article addresses those questions, reviews concepts
suitable for use in dealing with multispecies systems and attempts
to identify shortcomings in terms of tools, thereby
proposing new avenues of research. It is based on a wide range
of systems, such as simple or complex, uniform or heterogeneous
and intercropped species, such as annual and perennial,
herbaceous and woody, etc. The article is structured in 3 parts,
focusing successively on the following issues: (i) the reasons
for mixing species, i.e. benefits and drawbacks, (ii) the concepts
and tools used for understanding and designing cropping
systems with mixed species, and (iii) the models existing and
needed for simulating multispecies cropping systems.
1.2. New issuesFaced with the critical situation of intensive monocultures,new conceptual ways of constructing sustainable agroecosystemsare being sought (Malézieux and Moustier, 2005, b).Several agronomists recently proposed that traditional multispeciessystems could be used as models for designing sustainablecropping systems (Gliessman, 2001; Altieri, 2002).Jackson (2002) proposed imitating the structure of the prairieecosystem, composed of a number of species of different functionalgroups, to achieve resilience to changes in climate andwater supplies, and to pests and other natural disturbances.Ewel (1999) enhanced the role of woody perennial species inthe sustainability of ecosystem functioning in the humid tropicsand proposed forest-like agroecosystems. Such systems areusually complex, as they are based on several species, and mayinvolve combinations of perennial and annual,woody and nonwoodyplants.Agricultural research now has an adequate tool-box ofmethods and models for technology development in monospecificcropping systems, but its suitability for more complexsystems is unsure. Methods for designing multispecies systemsbarely exist. Systemic agronomy concepts (crop managementsequences, cropping system), and especially the toolsderived from that discipline, scarcely deal with the complexityof multispecies systems. In particular, the modelling toolswidely used today in agronomy are not well adapted to simulatingthem. New models are required to represent, assess anddesign sustainable multispecies cropping systems.This article addresses those questions, reviews conceptssuitable for use in dealing with multispecies systems and attemptsto identify shortcomings in terms of tools, therebyproposing new avenues of research. It is based on a wide rangeof systems, such as simple or complex, uniform or heterogeneousand intercropped species, such as annual and perennial,herbaceous and woody, etc. The article is structured in 3 parts,focusing successively on the following issues: (i) the reasonsfor mixing species, i.e. benefits and drawbacks, (ii) the conceptsand tools used for understanding and designing croppingsystems with mixed species, and (iii) the models existing andneeded for simulating multispecies cropping systems.
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