Tree Legumes as Sustainable Ecosystem Services in Livestock Systems

Arboreal legumes provide multiple uses in pastures and rangelands. Trees directly and indirectly feed, house, doctor, and warm humans at minimal environmental cost through forage (fodder), timber, biofuel, medicines, as well as edible leaves, pods, and seeds. Leguminous trees, because they foster biological nitrogen fixation (BNF) and acquire deep-soil nutrients and moisture, compete less with herbaceous plants for shallow-horizon soil moisture and nutrients. Their ecosystem services (ES) are generally less obvious and quantifiable. These include converting CO2 to sequestered C and released O2 in N-poor soils where trees without BNF do not thrive. Other ES include shade for animals (including humans), plants, and soil microorganisms that would not otherwise survive in direct sunlight, in dry seasons, or under human mismanagement (overgrazing). Arboreal legumes in semi-arid and arid environments also provide habitat and nutrition to insects (pollinators), mammals, and birds during crucial drought seasons and years, facilitating repopulation to the ecosystem when rainfall returns. Additional ES include crucial ecosystem biological diversity, climatic stability, as well as aesthetic and cultural values. Humans have long recognized their value in natural semi-arid and arid ecosystems such as rangelands but have been slower to incorporate them into cultivated pastures where herbaceous monocultures dominate. Incorporating arboreal legumes with greater regularity into restored rangelands or cultivated pastures would not only increase overall productivity by adding non-herbaceous aerial and deep-soil root biomass but also provide ES that herbaceous species cannot match