Temperate Agroforestry Research: Considering Multifunctional Woody Polycultures and the Design of Long-Term ﬁeld Trials

Agroforest Syst DOI 10.1007/s10457-017-0087-4 Temperate agroforestry research: considering multifunctional woody polycultures and the design of long-term field trials Sarah Taylor Lovell . Christian Dupraz . Michael Gold . Shibu Jose . Ronald Revord . Erik Stanek . Kevin J. Wolz Received: 3 October 2016 / Accepted: 15 March 2017 Ó Springer Science+Business Media Dordrecht 2017 Abstract The many benefits of agroforestry are well- on agroforestry emphasizing tree crops. Critical aspects documented, from ecological functions such as biodi- of long-term agroforestry experiments are summarized, versity conservation and water quality improvement, to and two existing well-documented research sites are cultural functions including aesthetic value. In North presented as case studies. A new long-term agroforestry American agroforestry, however, little emphasis has trial at the University of Illinois, ‘‘Agroforestry for been placed on production capacity of the woody plants Food,’’ is introduced as an experiment designed to test themselves, taking into account their ability to trans- the performance of increasingly complex woody plant form portions of the landscape from annual monocul- combinations in an alley cropping system with produc- ture systems to diversified perennial systems capable of tive tree crops. This trial intends to address important producing fruits, nuts, and timber products. In this themes of food security, climate change, multifunc- paper, we introduce the concept of multifunctional tionality, and applied solutions. The challenges of woody polycultures (MWPs) and consider the design of establishing, maintaining, and funding long-term agro- long-term experimental trials for supporting research forestry research trials are discussed. S. T. Lovell (&) R. Revord Department of Crop Sciences, Institute for Sustainability, Department of Crop Sciences, Institute for Sustainability, Energy, and Environment, Plant Science Lab, University Energy, and Environment, University of Illinois at of Illinois at Urbana-Champaign, 1201 S. Dorner Drive, Urbana-Champaign, Urbana, IL, USA Urbana, IL, USA e-mail: [email protected] E. Stanek Department of Crop Sciences, University of Illinois at C. Dupraz Urbana-Champaign, Urbana, IL, USA Institut National de la Recherche Agronomique (INRA), UMR System, Montpellier, France K. J. Wolz e-mail: [email protected] Program in Ecology, Evolution and Conservation Biology, Institute for Sustainability, Energy, and M. Gold Á S. Jose Environment, University of Illinois at Urbana- School of Natural Resources, The Center for Champaign, Urbana, IL, USA Agroforestry, University of Missouri, Columbia, MO, USA e-mail: [email protected] S. Jose e-mail: [email protected] 123 Agroforest Syst Keywords Agroecology Á Multifunctional Background on multifunctional woody polyculture landscape Á Sustainable agriculture Á Permaculture Á Polyculture Despite broad recognition of the extensive conservation benefits of agroforestry (Jose 2009; Rigueiro- Rodriguez et al. 2009; Schoeneberger 2009; Udawatta and Jose 2012), these systems have not been widely Introduction adopted in many regions of the U.S. where annual monoculture crops dominate the landscape (Valdivia Over the years, various researchers have advocated et al. 2012). There are several reasons underlying slow for diversifying or transitioning some land areas to adoption of agroforestry. One reason is a lack of agroforestry with ‘‘tree crops’’ to simultaneously emphasis placed on the capacity of the woody plants to produce food and other environmental benefits produce edible crops themselves (Molnar et al. 2013; (Leakey 2014; Molnar et al. 2013; Smith 1950). Rhodes et al. 2016). Yet, the viability of agroforestry Despite compelling arguments for such a transition, is substantially undervalued when the productive particularly on land that is marginal or not well- potential of tree crops is not fully explored. The suited for row crops (e.g., fertile yet highly erodi- integration of fruit and nut species, especially of those ble), we have seen little support for the concept in with short juvenile periods, offers the opportunity to the United States (U.S.). Land use policy often improve agroforestry systems’ revenue potential and separates production and conservation, creating a rate of return, enhancing their appeal for prospective situation in which agroforestry is primarily pro- adopters. Multifunctional Woody Polyculture systems moted as a supplier of regulating services, but with intend to broaden the extent to which agroforestry’s very little consideration of commercial production ecological benefits are realized, by expanding the of tree crops such as fruits and nuts. The research adoption potential through the integration of commer- funding portfolio is similar, offering very different cially proven fruit and nut species. programs for agriculture versus environmental The potential for MWPs to produce a wide range of health, with few resources available for transforma- commercial products and materials has grown recently tive solutions in the ‘‘applied research’’ realm that due to continued germplasm collection and the genetic consider both services. improvement of edible fruit and nut species that have Indeed, long-term research supporting the inte- been historically underutilized in the Midwest U.S. gration of food-producing woody crops into agro- For several important tree and shrub species (e.g., forestry systems is underdeveloped. Very limited chestnut, hazelnut, black currant, and elderberry), information exists on the productive potential of breeding objectives such as increased productivity, diverse tree crops established within agroforestry disease resistance, and broader environmental adapt- systems. We will refer to this system as Multifunc- ability have been achieved. Considering these species, tional Woody Polyculture (MWP), where the term many new selections have recently been transitioned ‘‘multifunctional’’ captures the production potential into replicated performance trials in regions through- (as in ‘‘multifunctional landscapes’’ that integrate out the U.S. to identify new varieties or assess the ecological, cultural, and production functions) adaptability of varieties to different regions (Anag- (Brandt and Vejre 2004; Lovell and Johnston nostakis 2012; Capik et al. 2013; Dale and Galic 2014; 2009), ‘‘woody’’ reflects the type of species as trees Fulbright et al. 1983; Hummer and Dale 2010; Molnar and shrubs, and ‘‘polyculture’’ references the mixing and Capik 2012; Molnar et al. 2007). This pre- of different species within the system. The object of breeding work has been formative in developing first this paper is to introduce MWP as a concept generation MWPs, allowing a broader collection of relevant to agroforestry, as well as to facilitate the commercially suited fruit and nut species to be adoption of long-term MWP trials through review of considered when conceptualizing plant assemblages. design concepts and discussion of where trials may The improved varieties of tree crops have the be implemented. Lessons learned from case studies potential to boost the overall performance of the of selected long-term trials of temperate agroforestry system, particularly when integrated into a polycul- systems are also presented to aid this objective. ture. Figure 1 shows how MWPs might compare to 123 Agroforest Syst Fig. 1 Tradeoffs in performance along a spectrum of common land use types demonstrating the typical trajectory of decreasing production with increasing resilience and biodiversity other land use types considering tradeoffs in perfor- (Macdaniels and Lieberman 1979; Molnar et al. 2013), mance along a continuum of ecological complexity. particularly considering systems with har- MWPs integrate multiple species that grow in differ- vestable products other than timber (Malezieux et al. ent layers of the tree canopy, much like the structure of 2009). Yield estimates from improved tree and shrub a natural woody plant community. A key goal is to cultivars planted orchard-style can provide a baseline optimize the system for greater productivity, without for forecasting (Hunt et al. 2005; Molnar and Capik substantial loss of other ecosystem services. 2012; Thomas et al. 2015; Wright et al. 1990), but we In addition to recognizing the tradeoffs in allocation do not have information on the impact of combining of resources, we also appreciate that the concept of different species into a polyculture system with polyculture systems with multiple canopy layers is not multiple canopy layers. The benefits of mixing species new, and we can draw from examples in permaculture in agroforestry systems will also depend on the and tropical homegardens. These systems demonstrate specific interactions between crops, providing com- the potential for greater productivity with increasing plementarity of resource capture (Cannell et al. 1996). diversity of plants when species occupy different A clear need exists to better understand the interspeci- niches, canopy layers, and below-ground rooting fic interactions including new species combinations zones (Ferguson and Lovell 2014, 2015;Meńdez and site-specific conditions (Jose 2011; Jose et al. et al. 2001; Mollison et al. 1981). These relationships, 2004). Without the valuable long-term data on the however, have been studied little at the scale of performance of different MWPs under a variety of commercial farming in temperate zones. conditions, growers are unlikely to take on the risk of establishing them

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