North American Agroforestry. Группа авторов

Agroforestry practices exploit additional field scale niches including border areas, marginal sites (rocky, infertile, too wet or dry) and steep slopes.

      Departures from Traditional Agroforestry Nomenclature

      There is obvious inconsistency in the nomenclature used to describe the six categories of agroforestry practices. In the United States, Canada and abroad, efforts have been made to clarify definitions and nomenclature in agroforestry (Table 2–1). Mantau et al. (2007) offer a thorough discussion of the concepts of classification and nomenclature with regard to non‐timber forest products while Sinclair (1999) proposes a general classification of agroforestry practices. In the United States and Canadian nomenclature, two of the practices are named on the basis of function (windbreaks, and riparian and upland buffers), the names of two are based on the adoption of popularized names (forest farming, urban food forests).

      As previously discussed, the nomenclature also departs from the systems terminology developed for tropical agroforestry and temperate agroforestry in other countries. Growing trees, crops, and animals in mixtures is a long‐standing tradition of tropical farmers. Tropical agroforestry evolved from these age‐old customs as well as more recent tropical agriculture paradigms of the 1960’s and 1970’s known as “cropping systems” and later as “farming systems” (Hildebrand, 1990). Subsequently, the nomenclature of tropical agroforestry tree, crop, and animal combinations was defined by the International Center for Research on Agroforestry (Lundgren and Raintree, 1982). During this definition phase for tropical agroforestry, a great deal of effort went into development of classification methodology. Classification and descriptive criteria were based on the situation and intended purpose to which agroforestry was being applied (Sinclair, 1999). The history of agroforestry classification has been reviewed and the five approaches to classify tropical agroforestry have been summarized (Nair, 1993; Atangana et al., 2013).

      Nature of Components

      Agrisilviculture describes crop–tree combinations, silvopasture describes tree–livestock combinations, and agrosilvopasture, describes crop–tree–livestock combinations.

      Arrangement of Components

      This criterion denotes whether the components exist simultaneously, overlap during part of a rotation, or follow in a prescribed sequence.

      Functional Role

      The primary use, production or conservation, is a common approach to classifying tropical agroforestry.

      Agroecological Zone

      The use of agroecological zones to classify agroforestry is based upon a characterization of climate, vegetation, and land‐use capability, usually a region within a country, for example, humid lowlands, arid or semi‐arid lands, or highlands.

      Social and Economic Features

      This approach uses scale of production and level of technology, for example, subsistence, intermediate, or commercial to classify agroforestry.

      Perspectives on U.S. and Canadian Agroforestry

      Finally, one must recognize that there are two distinct perspectives on agroforestry in the United States and Canada, and it is important to distinguish them from a nomenclature standpoint.

      Agroforestry at the Practice Level

      For field practitioners and landowners to understand, accept, and use agroforestry, it must be as pragmatic, market‐focused, and adoptable as possible. Complex “systems terminology” is not acceptable. Consequently, a simple agroforestry nomenclature has been developed to make agroforestry practices compatible with, and complementary to, agricultural practices. The bottom line for agroforestry to succeed over most of North America is that it must be accepted and used within the agriculture community.

      Agroforestry at the Science Level

      Within the scientific community, agroforestry concepts have much in common with sustainable agriculture, agroecology, regenerative agriculture, and agroforestry in the rest of the world. Common goals are to conserve the natural resources upon which agriculture depends, minimize the environmental impacts of agriculture, maintain productivity and profitability, and provide for people’s economic and social needs (Fig. 2–1). At the science level, it is more important to focus on agroforestry concepts and their underlying process level functions, and less important to debate nomenclature.

      Aside from differences in nomenclature, the concepts of agroforestry over most of North America are not very different from those in the rest of the world. Agroforestry has emerged as a science‐based practice and is increasingly finding its place in our agencies and educational institutions (Nair, 2007; USDA, 2017; Munsell and Chamberlain, 2019). However, the success of agroforestry science will ultimately be determined by the accomplishment of interdisciplinary research, development, and applications between forestry and natural resources and agriculture and livestock communities working in close cooperation with specialists in rural sociology, community development, applied economics, and marketing. The final measure of success will be agroforestry practices adapted to local conditions and seamlessly integrated into mainstream agriculture production systems in all regions of temperate North America.

Agroforestry Concepts

      The effects of integrating trees into production agriculture systems are far‐reaching, and address not only on‐farm needs, but also numerous agriculturally‐related problems causing increasing concern around the world. Growing trees in combination with crops and livestock has been shown to enhance crop yields (Kort, 1988; Dupraz et al., 2018b), improve animal health (Brunetti, 2006; Pent et al., 2022) and reduce losses, conserve soil and recycle nutrients, and reduce environmental impacts of agriculture (Udawatta et al., 2002; Blanco‐Canqui et al., 2004; Dosskey et al., 2007; Lerch et al., 2017; Schulte et al., 2017), while producing various tree and specialty products (Gold et al., 2004; Mori et al., 2018). The postulated effects of agroforestry in the United States and Canada are presented in the form of verifiable agroforestry concepts (Table 2–3). Increasing amounts of data exist to support and prove these concepts. Current research and on‐the‐ground practices will continue to confirm and modify these concepts in the coming years.

Fundamentally, as the definition of agroforestry implies, the benefits from agroforestry are derived from the biophysical interactions created when trees and/or shrubs are combined with crops and/or livestock. Interactions refer to the influence of one component on the performance of the other components, and on the system as a whole. We seek to optimize these interactions to favor mutualism and commensalism and minimize competition and predation. Interactions include both above‐ground and below‐ground effects. Although the dynamics of component interactions is a complex research challenge (Jose and Holzmueller, 2022), the net effect of interactions is of practical significance, and creates the biophysical success or failure of an agroforestry practice. The observable net effects of component interactions are expressed by the terms complementary, supplementary, and competitive (Anderson and Sinclair, 1993; Ong et al., 2015; Jose and Holzmueller, 2022). Component interactions represent processes at the tree–crop interface and tree–crop–animal interface. These interactions can be positive (e.g., stress reduction, yield enhancement, soil retention, water capture) or negative (e.g., competition, allelopathy, pest enhancement) (Jose et al., 2004; Jose and Holzmueller, 2022). Consequently, it is imperative that agroforestry practices be properly designed and managed to optimize desired positive interactions and minimize