Tree legumes: an underexploited resource in warm-climate silvopastures

Abstract

-Tree legumes are an underexploited resource in warm-climate silvopastures. Perceived benefits of tree legumes include provisioning (browse/mast, timber, fuel, human food, natural medicines, and ornamentals), regulating (C sequestration, greenhouse gas mitigation, soil erosion control and riparian buffers, shade, windbreaks, and habitat for pollinators), supporting (biological N 2 -fixation, nutrient cycling, soil fertility and soil health, photosynthesis, and primary productivity), and cultural ecosystem services. Tree legumes, however, have not been assessed to the same extent as herbaceous legumes. Once tree legumes are established, they are often more persistent than most herbaceous legumes. There are limitations for extended research with tree legume silvopastures, but extensive research has been done in Africa and Australia and recent efforts have been reported in South America. Economic benefits must be demonstrated to land managers to increase adoption. These benefits are apparent in the research and successes already available, but more long-term research, including the livestock component is necessary. Other factors that reduce adoption include paucity of domesticated germplasm, lag in research/technology, challenges of multipurpose trees and management complexity, challenges to mechanization, dangers of invasive weeds, and social and cultural barriers. In the current scenario of climate change and the need to increase food security, tree legumes are a key component for the sustainable intensification of livestock systems in warm-climate regions.Key Words: biological N 2 fixation, ecosystem services, grassland, nutrient cycling, tropical Revista Brasileira de Zootecnia

Forage legumes in grass pastures in tropical Brazil and likely impacts on greenhouse gas emissions: A review

“…Tree legumes shown a high stability in mixed pasture due to the greater lifetime of these plants (main axis). Then, once they are established, tree legumes are usually more persistent than most crown-forming herbaceous legumes (Dubeux, Muir, et al, 2017). The wide adaptation potential of these legumes, ranging from semiarid to humid areas, increases the scope for their utilization (Dubeux, Muir, et al, 2017) At this same study site, the amount of N cycled through litter was greater for gliricidia then for sabiá (107 vs. 92.5 kg of N/ha for cycle respectively).…”

“…Then, once they are established, tree legumes are usually more persistent than most crown-forming herbaceous legumes (Dubeux, Muir, et al, 2017). The wide adaptation potential of these legumes, ranging from semiarid to humid areas, increases the scope for their utilization (Dubeux, Muir, et al, 2017) At this same study site, the amount of N cycled through litter was greater for gliricidia then for sabiá (107 vs. 92.5 kg of N/ha for cycle respectively). The proportion of the N in the litter that was derived from the atmosphere by symbiotic fixation was around of 55% in both species (Apolinário et al, 2016).…”

“…However, if only cattle performance is the goal, grass monoculture or the gliricidia systems were the best options. Thus, tree legumes are a tool for the sustainable intensification of livestock systems, in which perceived benefits are the provisioning, regulating, supporting and cultural ecosystem services (Dubeux, Muir, et al, 2017).…”

Value of endemic legumes for livestock production on Caatinga rangelands

“…In the initial 3 years of establishment, animal productivity is similar among SPS containing sabiá or gliricidia compared to Brachiaria decumbens monoculture (Costa et al, 2016). However, with the maturation of Sabiá trees, competition with herbaceous stratum vegetation may reduce the system's carrying capacity (Dubeux Jr. et al, 2017). Despite the reduction, sale of firewood and wood stakes compensates for the animal product loss and, in fact, can double the system's gross income.…”

“…Forage legumes provide a variety of environmental services including forage for ruminants, fuel, lumber, shade, BFN, forage for insect pollinators, C sequestration and stock, nutrient cycling and primary productivity in environments with N limitation (Dubeux Jr. et al, 2017). Tree legumes produce substantial biomass (above and below ground) which, depending on the management, are allocated to tissues such as twigs and trunks (in addition to roots), which have a low decomposition rate and a high half-life when compared to leaf tissue and leaf/stem of herbaceous vegetation.…”