Facing up to the paradigm of ecological intensification in agronomy: Revisiting methods, concepts and knowledge

TL;DR: Five additional avenues that agronomic research could follow to strengthen the ecological intensification of current farming systems are proposed, assuming that progress in plant sciences over the last two decades provides new insight of potential use to agronomists.

About: This article is published in European Journal of Agronomy.The article was published on 2011-05-01 and is currently open access. It has received 433 citations till now. The article focuses on the topics: Agroecology & Biological regulation.

Summary

1. Introduction

• Many articles have been published on biological regulation in agroecosystems, mostly under the heading -agroecology‖, and new papers are continuing to appear.
• Research on this topic remains highly necessary, and is probably a challenge for most agronomists familiar with individualphysical and/or chemical aspects of agroecosystems.
• Agronomists have, until recently, relied essentially on their own scientific output.
• Prototyping (e.g. Vereijken, 1997; Lançon et al., 2007; Debaeke et al., 2009) and the model-based design of agricultural systems (e.g. Rossing et al., 1997; Bergez et al., 2010) are fed by results processed through simulation studies, statistical hypothesis testing and group analysis,from research groups working mostly at experimental stations.
• The diversification of knowledge sources may include (i) making use of recent advances in plant sciences, (ii) learning lessons from the functioning of natural ecosystems, guiding the design and management of acroecosystems and (iii) embracing local farmers' knowledge.

2.1 -Mobilizingadvances in plant sciences

• There has been tremendous progress in plant sciences in recent decades, with detailed elucidation of the genetic and environmental determinism of plant development, growth and reproduction.
• This progress was made possible, in particular, by increases in their ability todissect cellular and molecular processes, supported by exponential progress in laboratory techniques and the capacity to analyse masses of genomic data (e.g. Tardieu & Tuberosa, 2010) .
• This knowledge about the highly complex life of plants has often been developed in a simplified environment, far removed from the reality of farmers' fields.
• This has led to a widening of the gap between the research objectives of plant scientists and agronomists.
• The authors highlight briefly, with a few examples,ways in which agronomists could make use of advances in plant sciencesto designecologically intensive cropping systems.

2.1.1.A new look at the basics

• Agronomists involved in the design and evaluation of cropping systems often make use of a simplified crop description (Monteith 1977) ,despite the availability of more mechanistic models simulating canopy photosynthesis (Spitters et al., 1986; Spitters 1986; Depury & Farquhar, 1997) .
• Moreover, the more sophisticated representations of the basic processes of plant life implemented in more complex models do not necessarily improvethe ability of crop models to predict behaviour in a range of fluctuating conditions.
• Plant scientists have investigated in detail the exchanges of nitrogen between roots and their environment (Jackson et al., 2008) .
• Glass (2003) summarised the factors decreasing nitrogen absorption efficiency, on the basis of molecular knowledge and empirical data.
• They also provide us with opportunities to improve nitrogen management in the soil.

2.1.2. The cultivated plant and its biological environment

• These findings are promising for genetic engineering approaches, provided that the genetic basis of the metabolic pathways can be identified (Dudareva & Pichersky, 2008) .
• Cropping system may also play a role, as the expression of the metabolic pathways involved in direct or indirect defence probably depends on interactions between genotype and environment (Le Bot et al., 2009) .
• Moreover, it may be possible to elicit some of these pathways deliberately, with appropriate techniques.

2.1.3. Ways to improve the use of plant sciences for ecological intensification

• Finally, there are many different drivers of change in ecological intensification (see introduction and subsequent sections).
• Innovative systems that have already been developed in the domain of ecological intensification, such as the use of mixtures of cultivars or species, agroforestry andno-tillage systems, would certainly benefit from the knowledge provided by plant sciences.
• These systems will themselves raise new questions and issue new challenges to plant science.
• Plant sciences results are still often obtained in highlysimplified systems and therefore cannot easily be translated to multispecies systems.
• Above-ground competition for light and below-ground competition for water are major processes inecological intensification that require study in systems including facilitation between plants (Long & Nair, 1999; Zhang et al., 2008; Malézieux et al., 2009) .

2.2 -Learninglessons from the functioning of natural ecosystems

• Strategies for agroecosystem design and management may be derived from the observation of natural ecosystems, guiding alternative agronomic practices (Malézieux, 2011) .
• Several authors (e.g. Ewel, 1999; Altieri, 2002; Jackson, 2002; Vandermeer, 2003) have already suggested that natural ecosystems may provide appropriate models for agroecosystem design to achieve both environmental and social goals while ensuring long-term sustainability.
• This idea is basedon the assumption that natural ecosystems are adapted to local constraints, due to a long process of natural selection (Dawson & Fry, 1998; Ewel, 1999) .
• These features are particularly useful for dealing with pest outbreaks (Trenbath, 1993) and increasing energy efficiency in a context of the depletion of fossil fuels (Hatfield, 1997) .
• In natural ecosystems, the various animal and plant species interact through population dynamics and trophic networks, providing the final ecosystem with services, such as pollination.

2.2.1 What does -Mimicking natural ecosystems‖ mean?

• Moreover, interesting properties may arise from the spatial and temporal organisation of the species rather than purely from their number.
• Finally, approaches based on mimicking natural ecosystems will inevitably be confronted with the -aim problem‖.
• Natural ecosystems provide many services but are not targeted.
• Such as the removal of the minerals contained in agricultural products.
• Some insight may be gained from regarding agroecosystems as complex systems with many simultaneous feedback loops including a dimension absent from natural ecosystems: human agency.

2.2.2 Agroecosystems as complex socio-ecological systems

• A wider definition of agroecosystem diversification, more compatible with the socioecological nature of complex agroecosystems, must consider not only species diversity, but also the diversity of agricultural practices and rural knowledge adapted to/derived from local pedoclimatic conditions.
• These lie at the core of human agency and represent new sources of knowledge for agronomic research (see below).
• Agroecosystem diversification in its broadestsense thus concerns the diversity of livelihood strategies ata certain location, diverse land use, management and marketing strategies, the integration of production activities (e.g. crop-livestock interactions), spatial and temporal associations of crops and crop cultivars, and the maintenance of genetic agrobiodiversity in the system.
• New avenues for agronomy to strengthen agroecological intensification should go beyond the cultivated field or the mixture of species in a given landscape.
• They should explore desirable properties and mechanisms that operate at the scale of complex socio-ecological systems i.e.that take into account sociological and ecological dynamics and interactions in agroecosystems.

2.3 -Farmers' knowledge and lay expertisevalorisation and integration into scientific knowledge

• Farmers can observe not only their own production systems, but also other systems (both agricultural and natural) and interactions between these systems.
• They can also gainexperimental knowledge in their own systems.
• They are often willing to do so and therefore carry out experiments in the operation of their own agroecosystem, evaluating the response of the system to their decisions.
• Farmers' knowledge is not only of value for application and for the adaptation of agronomic knowledge to a particular case.
• The authors will defend this point and discuss the various issues it raises below.

2.3.2 Qualification and validation of lay expertise and knowledge expression

• The qualification of lay expertise has been shown to be a necessary step in approaches aiming to combine this expertisewith scientific knowledge.
• Going beyond the issues of the domain of validity, certainty and precision, there is the question of validation of the new knowledge obtained.
• To validate the greenhouse management rules formalised from expert knowledge, Tchamitchian et al. (2006) used a two-step method rather than a direct validation of the rules themselves, which was not possible.
• The first step involved checking that the application of these rules really did result in the desired pattern of behaviour in the greenhouse (as expressed when building the rules), without questioning the agronomic validity of this behaviour.
• It would not have been possible to designthe rule from this identified scientific knowledge, generally because the scopes of the scientific knowledge and that of the lay expertise yielding the rule were different.

3. Methods for synthesizing information

• Thedata generated are then processed, mostly byclassical methods,such as simulation studies, single-experiment data analysis, or group analysis.
• These methods could probably be complemented with two other methods: meta-analysis, involving the statistical synthesis of results from a series of studies, and comparative analyses of agroecosystems, involving the use of large-scale comparisons similar to those used in ecology (e.g. Fortunel et al., 2009) .

vi.

• In the context of ecological intensification, the meta-analysis framework constitutes an interesting alternative to dynamic crop models.
• A considerable body of experimental data is available for such purposes (e.g., Rochette & Janzen, 2005) .
• Such data could be reviewed, combinedand analysed withstatistical techniques, to rank cropping systems as a function of their impact on key environmental variables, such as water nitrate content, greenhouse gas emissions (e.g., N 2 O) and the presence/absence of species of ecological interest (e.g., earthworms, birds).
• Meta-analysis requires the use of appropriate techniques and the value of a meta-analysis may be greatly decreased if the six steps outlined above are not rigorously implemented.

3.2. Comparative analysis of agroecosystems

• Informationuseful for the ecological intensification of agroecosystems may be obtainedfrom comparative analyses of the structural and functional properties and performance of contrasting agroecosystems.
• These methods evaluateindicators relatingto the properties of agroecosystems, such as productivity, stability and resilience.
• These properties are often interdependent and, as pointed out by Marten (1988), they are not universal and must be redefined under each new set of conditions.
• As discussed above, studies of the local knowledge sustaining various mechanisms of indigenous resilience across contrasting agroecosystems, particularly at the scale of the landscape and its functionality (e.g., Birman et al., 2010) , are also a promising starting point for obtaining information useful for ecological intensification.

3.2.1 Comparative analysis based on multiple indicators

• In general, comparative analyses based on indicators providea static picture of the status of agroecosystems at one particular point in time, without considering the underlying feedback and system dynamics responsible for bringing the system to its current status and for any subsequent change to that status.
• Beyond comparing multiple indicators and the tradeoffs between them, the comparative analysis of agroecosystems should aim to distil the relationships between relevant properties; e.g., between performance on the one hand, and diversity, coherence and connectedness on the other.
• A common denominator ofthe indicators used in multi-criteria evaluations is their interdependence and their dependence on the structural diversity of the agroecosystem.
• Thisinterdependence results from the co-adaptation of agroecosystem components over time.
• The structural diversity ofagroecosystems,corresponding to the diversity of system components and their interrelationships, is only functional when organised in a specific way.

3.2.2 Analysing the structure and functioning of agroecosystems

• Manyof the properties of agroecosystems are often interdependent, together determining thevulnerability and adaptation capacity of these systems in the face of external shocks and stressors (Luers, 2005) .
• Far from being postulates of a new theory, these properties are discussed here as operational, working concepts.
• In practical terms, 'design' implies proposing alternative configurations for the organisation of energy, matter and information flows towards, within and from the system in space and time.
• The examples examined here indicate that, up to a certain critical level, an increase in the diversity of system components and interrelationships confers desirable properties onagroecosystems consistent with the paradigm of ecological intensification.
• These properties manifest themselves as patterns in space and time that become more evident at particular scales and are often described as variability and/or heterogeneity at other scales.

Figures

Table 1. Examples of recent results fromplant sciences useful in agronomy 905

Frequently asked questions

Q1. What contributions have the authors mentioned in the paper "Facing up to the paradigm of ecological intensification in agronomy: revisiting methods, concepts and knowledge" ?

The authors propose here five additional 32 avenues that agronomic research could follow to strengthen the ecological intensification of 33 current farming systems. The authors begin by assuming that progress in plant sciencesover the last 34 two decades provides new insight of potential use toagronomists. The authors then suggest that natural 37 ecosystems may also provide sources of inspiration for cropping system design, in terms of 38 theirstructure and function on the onehand, and farmers ‘ knowledge on the other. The authors 43 discuss ways in which this knowledge could be combined with, or fed into scientific 44 knowledge and innovation, and the extent to which this is likely to be possible. Potentially useful new 35 developments in plant science include advances in the fields of energy conversion by plants, 36 nitrogen use efficiency and defence mechanisms against pests. The authors suggest that agronomists make more use of meta46 analysis and comparative system studies, these two types of methods being commonly used in 47 other disciplines but barely usedin agronomy.