-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

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Legumes contribute to pasture sustainability through symbiotic N2 fixation, which may increase primary productivity and animal performance in low‐input systems. Litterfall is the main way of cycling nutrients from tree legumes. We quantified gliricidia [Gliricidia sepium (Jacq.) Kunth ex Walp.] and sabiá (Mimosa caesalpiniifolia Benth) litter deposition, along two 336‐d cycles, in a signalgrass (Brachiaria decumbens Stapf.) pasture. Litterfall was produced throughout the year but concentrated in the dry season. Sabiá produced slightly greater (P < 0.0001) litterfall amounts in the two cycles (10,790 kg ha−1) than gliricidia (10,420 kg ha−1) but the overall average N concentration of gliricidia (21.5 g kg−1) was greater than that of sabiá (18.8 g kg−1). Nitrogen amounts cycled through the litter were greater for gliricidia in both cycles (105 and 109 kg N ha−1) than for sabiá (87 and 98 kg N ha−1). The proportions of litter N that were derived from the atmosphere by symbiotic fixation were similar (P ≥ 0.05) in both species (55%) and varied little along the two cycles. Lignin concentration, which influences decomposition, was similar in both species, averaging 238 and 214 g kg−1 in the two cycles for gliricidia and 233 and 246 g kg−1 for sabiá. Greater N concentration, lower C/N ratio and lower lignin concentration indicate that gliricidia litter may have a faster cycling rate than sabiá litter. Sabiá could be a more promising species for soil cover and protection because of its slower litter decomposition rate.Core Ideas Litter deposition was an important pathway of N return in warm‐climate silvopasture systems. Tree legumes added significant amounts of biological nitrogen fixation to silvopasture systems. Gliricidia litter presented better quality than Mimosa litter. Proportion of litter N derived from atmosphere was significant.

The objective was to evaluate the effect of three stocking rates (2, 3.9, and 5.8 animal units ha −1) and three fertilization levels (0, 150, and 300 kg N ha −1 yr −1) on herbage mass and nutritive value of elephantgrass (Pennisetum purpureum Schum.) cv. IRI-381. The experiment was conducted from May to August of 2009 and 2010 in Itambé, PE, Brazil, during the rainy season. Treatments were allocated in a split-plot arrangement in a completely randomized block design. The variables measured included leaf mass (pre-and post-grazing), botanical composition, soil cover, leaf area index, light interception, leaf angle, and concentrations of dry matter, organic matter, N, and in vitro digestible dry matter. When fertilized with 300 kg N ha −1 yr −1 , leaf mass reached 18,560 kg ha −1. Leaf area index decreased with increasing stocking rate. The relationship between sward height and light interception was R 2 = 0.0126. Increased stocking rate resulted in greater contribution of signalgrass [Brachiaria decumbens (Stapf.) R.D. Webster] in the botanical composition, with a contribution up to 29% in 2010. Elephantgrass nutritive value is directly affected by the fertilization levels and stocking rate, with highest nutrient concentrations observed with 2 AU ha −1 and 300 kg N ha −1 yr −1 .

Silvopasture systems enhance the use efficiency of natural resources by diversifying vegetation structure and function. However, shading from trees may affect the production and quality of herbaceous forages and, consequently, the animal performance. The objective of this research was to evaluate regrowth and development of tree legumes as well as productivity and nutritive value of signalgrass [Brachiaria decumbens (Stapf) R.D. Webster] subjected to shading from the tree legumes gliricidia [Gliricidia sepium (Jacq.) Steud] and sabiá (Mimosa caesalpiniifolia Benth.). Herbage responses were evaluated every 56 d. Trees were evaluated every 120 d to assess morphological responses and forage nutritive value. Response variables included in vitro digestible organic matter (IVDOM), concentrations of N, and stable isotopes (δ 15 N) in grass and legume leaves. Greater herbage accumulation occurred for signalgrass submitted to full sun (57 kg ha -1 d -1 ) than under shade (27 kg ha -1 d -1 ) (p = .0006). Morphometric measurements of tree regrowth did not show differences for total leaf mass (p = .8603) and mass of thick stems (p = .6157) between tree legume species. Gliricidia leaf IVDOM was greater (504 g kg -1 ) than sabiá leaf IVDOM (315 g kg -1 ) (p < .0001).Nitrogen concentration was greater in leaves (p = .0007), fine stems (p = .0050), and thick stems (p = .0333) of gliricidia throughout the evaluated period when compared to the same fractions of sabiá. Both tree species, at the densities employed in this study, affected negatively and to a similar extent the herbage accumulation of signalgrass.Abbreviations: BD, base diameter; BHD, breast height diameter; ID, intermediate diameter; IVDOM, in vitro digestibility organic matter; TLM, total leaf mass; TMFS, total mass of fine stems; TMTS, total mass of thick stems.

O experimento foi realizado com o objetivo de avaliar fatores relacionados à eficiência de pastejo de cinco genótipos de Pennisetum sp. (CE 08 A.D., Venezuela, HV-241, Elefante B e Hexaplóide) no período seco do ano na Zona da Mata de Pernambuco. Os genótipos foram manejados sob lotação rotacionada (44 dias de descanso e quatro dias de pastejo) ao longo de dois ciclos de pastejo. Adotou-se delineamento experimental em blocos ao acaso, com parcelas subdivididas (os genótipos representaram as parcelas e os ciclos de pastejo, as subparcelas) e quatro repetições. As massas de lâmina foliar total, verde e senescente pré-pastejo foram analisadas em seis repetições. O acúmulo e a eficiência de pastejo de lâmina foliar verde foram avaliados em delineamento em blocos casualizados, com quatro repetições. Os genótipos CE 08 A.D. e Elefante B apresentaram maiores massas de lâmina foliar total (1.374 kg de MS/ha) e verde pré-pastejo (737 kg de MS/ha) e maior acúmulo (654 kg de MS/ha/44 dias) e eficiência de pastejo de lâmina foliar verde (80%). No HV-241, a alta eficiência de pastejo (100% do acúmulo lâmina foliar verde) esteve associada ao baixo acúmulo de lâmina foliar verde (155 kg de MS/ha/44 dias). A menor eficiência de pastejo foi observada no Hexaplóide (59% do acúmulo de lâmina foliar verde), possivelmente em virtude das altas perdas sob pastejo (30% da massa de lâmina foliar total pré-pastejo). A massa de lâmina foliar verde diminuiu mais acentuadamente até o segundo dia de pastejo, enquanto as perdas de lâmina foliar total foram maiores no 2º e 3º dias de pastejo. Os genótipos CE 08 A.D. e Elefante B têm potencial para serem utilizados em sistemas de lotação rotacionada na Zona da Mata pernambucana.