North American Agroforestry. Группа авторов

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North American Agroforestry - Группа авторов


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Non‐solar energy inputs, MJ ha−1 (Mcal acre−1) 0 17.3 × 103 (1670) 0 Annual aboveground NPP, g m−2 300–700 983 597.6 Annual belowground NPP, g m−2 500–1200 177 950 Proportion of total NPP as seed or grain, % 6 45 2 Energy capture efficiency (%) 0.72‐1.09 0.74 1.08 Water use efficiency 1.8–2.18 1.87 2.07 Partitioning of aboveground NPP, % Herbivores 13–45 5 <0.2 Detritivores 55–87 50 99 Exported from the system 0 45 0 Nutrient cycling Avg. annual N inputs, g N m−2 1.0 8.2 2 Avg. annual N losses, g N m−2 0.26–0.6 2.2 2 Avg. annual N export in harvested crop, g N m−2 0 10.9 0 Belowground N, % of total >98 >98 92 Soil erosion, kg ha−1 yr−1 minimal 11,200 minimal Changes in soil SOM pool stable loss of ≥ 30% in first 30 yr of cultivation stable

      Note. SOM, soil organic matter; OM, organic matter; PAR, photosynthetically active radiation; NPP, net primary productivity.

      Eric J. Holzmueller

      Modern agricultural practices have allowed a dramatic increase in crop and livestock production during the past several decades; however, it has come at the expense of many environmental challenges and the loss of long‐term agricultural sustainability (Foley et al., 2011; Funabashi, 2018; Poore & Nemecek, 2018; Tilman, Cassman, Matson, Naylor, & Polasky, 2002). Agroforestry, the intentional incorporation of trees, agricultural crops, and/or animals into a single land‐use system, is one way to reduce the negative impacts of modern agriculture (Sanchez, 2002). By combining multiple components in the same system, there is potential to increase nutrient use efficiency; control subsurface water levels; improve soil, water, and air quality; provide favorable habitats for plant, insect or animal species; and create a more sustainable agricultural production system (Garrett, McGraw, & Walter, 2009; Garrity, 2004; Jose, 2009; Jose & Dollinger, 2019).

Image described by caption.

       (reprinted with permission from Jose et al., 2004).

      It is important to review the theoretical basis for species coexistence before discussing the biophysical interactions among them. The competitive exclusion principle (CEP), termed by Hardin (1960), also known as the competitive displacement principle, Grinnell’s axiom, the Volterra–Gause principle, or Gause’s law, has been a cornerstone in ecological thinking regarding species coexistence for decades. The CEP is based on Gause’s (1934) contention that two similar species competing for the same resources cannot stably coexist. Competition between species may lead to three outcomes:


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