108 Reynolds, P. E., Simpson, J. A., Thevathasan, N. V., & Gordon, A. M. (2007). Effects of tree competition on corn and soybean photosynthesis, growth, and yield in a temperate tree‐based agroforestry intercropping system in southern Ontario, Canada. Ecological Engineering, 29, 362–371.
109 Rivest, D., & Vézina, A. (2015). Maize yield patterns on the leeward side of tree windbreaks are site‐specific and depend on rainfall conditions in eastern Canada. Agroforestry Systems, 89, 237–246.
110 Robin, C., Hay, M. J. M., Newton, P. C. D., & Greer, D. H. (1994). Effect of light quality (red:far‐red ratio) at the apical bud of the main stolon on morphogenesis of Trifolium repens L. Annals of Botany, 74, 119–123.
111 Root, R. (1973). Organization of a plant–arthropod association in simple and diverse habitats: The fauna of collards (Brassica oleracea). Ecological Monographs, 43, 95–124.
112 Sanchez, P. A. (2002). Soil fertility and hunger in Africa. Science, 295, 2019–2020.
113 Schroth, G. (1999). A review of belowground interactions in agroforestry, focusing on mechanisms and management options. Agroforestry Systems, 43, 5–34.
114 Seiter, S., Ingham, E. R., William, R. D., & Hibbs, D. E. (1995). Increase in soil microbial biomass and transfer of nitrogen from alder to sweet corn in an alley cropping system. In J. H. Ehrenreich, D. L. Ehrenreich, & H. W. Lee (Eds.), Growing a sustainable future (pp. 56–158). Boise, ID: University of Idaho.
115 Shainsky, L. J., & Radosevich, S. R. (1992). Mechanisms of competition between Douglas‐fir and red alder seedlings. Ecology, 73, 30–45.
116 Sharrow, S. H. (1999). Silvopastoralism: Competition and facilitation between trees, livestock, and improved grass–clover pastures on temperate rainfed lands. In L. E. Buck, J. Lassoie, & E. C. M. Fernandez (Eds.), Agroforestry in sustainable agricultural systems (pp. 111–130). Boca Raton, FL: CRC Press.
117 Silva‐Pando, F. J., Gonzalez‐Hernandez, M. P., & Rozados‐Lorenzo, M. J. (2002). Pasture production in a silvopastoral system in relation with microclimate variables in the Atlantic coast of Spain. Agroforestry Systems, 56, 203–211.
118 Singh, R. P., Ong, C. K., & Saharan, N. (1989). Above and below ground interactions in alley cropping in semiarid India. Agroforestry Systems, 9, 259–274.
119 Smil, V. (1999). Nitrogen in crop production: An account of global flows. Global Biogeochemical Cycles, 13, 647–662.
120 Smil, V. (2000). Phosphorus in the environment: Natural flows and human interferences. Annual Review of Energy and the Environment, 25, 53–88.
121 Smith, M. W., Arnold, D. C., Eikenbary, R. D., Rice, N. R., Shiferaw, A., Cheary, B. S., & Carroll, B.L. (1996). Influence of ground cover on beneficial arthropods in pecan. Biological Control, 6, 164–176.
122 Smith, M. W., Wolf, M. E., Cheary, B. S., & Carroll, B. L. (2001). Allelopathy of bermudagrass, tall fescue, redroot pigweed, and cutleaf evening primrose on pecan. HortScience, 36, 1047–1048.
123 Söderström, B., Svensson, B., Vessby, K., & Glimskär, A. (2001). Plants, insects and birds in semi‐natural pastures in relation to local habitat and landscape factors. Biodiversity & Conservation, 10, 1839–1863. https://doi.org/10.1023/A:1013153427422
124 Thevathasan, N. V., & Gordon, A. M. (2004) Ecology of tree intercropping systems in the north temperate region: Experiences from southern Ontario, Canada. Agroforestry Systems, 61, 257–268. https://doi.org/10.1023/B:AGFO.0000029003.00933.6d
125 Thevathasan, N. V., Gordon, A. M., & Voroney, R. P. (1998). Juglone (5‐hydroxy‐1,4 napthoquinone) and soil nitrogen transformation interactions under a walnut plantation in southern Ontario, Canada. Agroforestry Systems, 44, 151–162.
126 Tilman, D. (1980). A graphical‐mechanistic approach to competition and predation. The American Naturalist, 116, 362–393.
127 Tilman, D. (1982). Resource competition and community structure. Princeton, NJ: Princeton University Press.
128 Tilman, D. (1990). Constraints and tradeoffs: Toward a predictive theory of competition and succession. Oikos, 58, 3–15.
129 Tilman, D., Cassman, K. G., Matson, P. A., Naylor, R., & Polasky, S. (2002). Agricultural sustainability and intensive production practices. Nature, 418, 671–677.
130 Todhunter, M. N., & Beineke, W. F. (1979). Effect of fescue on black walnut growth. Tree Planters’ Notes, 30, 20–23.
131 Troeh, F. R., & Thompson, L. M. (1993). Soils and soil fertility (5th ed.) New York: Oxford University Press.
132 Tsonkova, P., Böhm, C., Quinkenstein, A., & Freese, D. (2012). Ecological benefits provided by alley cropping systems for production of woody biomass in the temperate region: A review. Agroforestry Systems, 85, 133–152.
133 van Noordwijk, M., Lawson, G., Soumaré, A., Groot, J. J. R., & Hairiah, K. (1996). Root distribution of trees and crops: Competition and/or complementarity. In C. K. Ong & P. Huxley (Eds.), Tree–crop interactions: A physiological approach (pp. 319–364). Wallingford, UK: CAB International.
134 Von Kiparski, G. R., Lee, L. S., & Gillespie, A. R. (2007). Occurrence and fate of the phytotoxin juglone in alley soils under black walnut trees. Journal of Environmental Quality, 36, 709–717.
135 Wanvestraut, R., Jose, S., Nair, P. K. R., & Brecke, B. J. (2004). Competition for water in a pecan–cotton alley cropping system. Agroforestry Systems, 60, 167–179.
136 Waring, H. D., & Snowdon, P. (1985). Clover and urea as sources of nitrogen for the establishment of Pinus radiata. Australian Forest Research, 15, 115–121.
137 Wojtkowski, P. (1998). The theory and practice of agroforestry design. Enfield, NH: Science Publishers.
138 Yang, L. L., Ding, X. Q., Liu, X. J., Li, P. M., & Egrinya Eneji, A. (2016). Impacts of long‐term jujube tree/winter wheat–summer maize intercropping on soil fertility and economic efficiency: A case study in the lower North China Plain. European Journal of Agronomy, 75, 105–117.
139 Zamora, D., Jose, S., & Nair, P. K. R. (2006). Interspecific interaction in a pecan–cotton alleycropping system in the southern United States: The production physiology. Canadian Journal of Botany, 84, 1686–1694.
140 Zamora, D., Jose, S., & Nair, P. K. R. (2007). Morphological plasticity of cotton roots in response to interspecific competition with pecan in an alleycropping system in the southern United States. Agroforestry Systems, 69, 107–116.
141 Zhang, W., Wang, B. J., Gan, Y. W., Duan, Z. P., Hao, X. D., Xu, W. L., & Li, L. H. (2018). Different tree age affects light competition and yield in wheat grown as a companion crop in jujube–wheat agroforestry. Agroforestry Systems, 93, 653–664.
Study Questions
1 Explain how the competitive exclusion principle and the unified neutral theory vary in explaining species coexistence.
2 How can we make use of physiological information such as photosynthetic pathway (e.g., C3 vs. C4) of component species in designing sustainable agroforestry systems?
3 Although shading is commonly associated with competition for light, shading can be beneficial in agroforestry systems. Describe the beneficial or facilitative role of shading with the help of examples.
4 What is meant by “safety‐net hypothesis” in an agroforestry context? Provide an example each from (a) alley cropping, (b) silvopasture, and (c) riparian buffer.
5 Agroforestry systems seem to have fewer pest problems than their monoculture counterparts.