Abstract The arboreal communities of a silvopastoral agroecosystem play an important role in the arid and semiarid ecosystems of the country, by conserving the biodiversity and the development of the livestock activities that are of vital importance in the North of Mexico. With the objective of characterizing an arboreal community of a silvopastoral agroforestry system in a transition zone of tamaulipan thornscrub and mezquital in Nuevo Leon, five sampling sites of 2500 m2 were established; we made an inventory of all tree species with diameter at the height of 1.30 m (DBH) > 7.5 cm. The vertical and horizontal structure and composition were evaluated through vegetation analysis (relative abundance, relative frequency, relative dominance), importance value index, forest value index and models for the normal diameter - canopy cover variables. The main species from an ecological standpoint were Prosopis laevigata (Hump. & Bonlp., Ex.Will.) M. C. Johnst. and Ebenopsis ebano (Berland.) Barneby & J. W. Grimes; the community presented high density of individuals, high canopy cover and a vertical structure with a high proportion of individuals ≥ 6 m in height. The linear model showed the best adjustments by presenting an R2 = 0.621. Silvopastoral management has conserved and promoted the structural attributes of the native plant community.

Resumen Las comunidades arbóreas con sistemas silvopastoriles desempeñan un papel importante en los ecosistemas áridos y semiáridos del país, al conservar la biodiversidad y el desarrollo de las actividades ganaderas, que son de vital importancia en el norte de México. Con el objetivo de caracterizar una comunidad arbórea de un sistema silvopastoril en una zona de transición de matorral espinoso tamaulipeco y mezquital en Nuevo León, se establecieron cinco sitios de muestreo de 2500 m2, en los cuales se realizó un inventario de todas las especies arbóreas con diámetro a la altura de 1.30 m (DAP) igual o mayor que 7.5 cm. Se evaluaron composición y estructuras vertical y horizontal a través de parámetros estructurales de la vegetación (abundancia relativa, frecuencia relativa, dominancia relativa), índice de valor de importancia, índice de valor forestal y modelos para las variables diámetro normal - área de copa. Las especies principales desde un punto de vista ecológico fueron Prosopis laevigata (Hump. & Bonlp. ex. Willd.) M. C. Johnst. y Ebenopsis ebano (Berland.) Barneby & J. W. Grimes; la comunidad presentó alta densidad de individuos, alta cobertura de copa y una estructura vertical con alta proporción de individuos con altura mayor o igual a 6 m. El modelo lineal mostró los mejores ajustes al presentar un R2 = 0.621. El manejo silvo-pastoril ha conservado y promovido los atributos estructurales de la comunidad vegetal nativa.

Abstract: Elephant grass (EG) (Pennisetum purpureum Schum.) have great importance in tropical and subtropical climates, especially on dairy farms. Normally, EG is established alone under high fertilization levels. EG in organic production system can improve low production costs and environmental issues, are still little known. The aim of this research was to evaluate the performance of herbage yield, nutritive value, extraction/ export nutrient and forage yield and animal responses. Three production systems of EG were analyzed: (i) EG mixed spontaneous-growing species (SGE) in warm-season and ryegrass (R) in cool-season under organic production; (ii) EG mixed SGE + R under conventional system (positive control); and (iii) EG based under conventional production (control). Holstein cows were used in a rotational stocking. Forage samples were collected to evaluate the pasture and animal responses. Seven grazing cycles were performed during the experimental period (312 days). Herbage yield, forage intake, and stocking rate were 12548; 10270; 19168 kg ha-1 and 2.5; 2.6; 2.7% and 3.3; 2.1; 4.5 AU ha-1 day-1, respectively. Crude protein of EG was 17.9; 15.4; 16.4%, respectively. Mixed pastures, in conventional and organic production, had a better forage distribution throughout the seasons. Highest forage yield and extraction/ export nutrient was reported in pure EG within the conventional system.

RESUMOEsta pesquisa foi conduzida com o objetivo de avaliar a utilização da biomassa remanescente de pastagens de estação fria para produção de silagem e feno. As espécies testadas foram: aveia preta cv. Agro Zebu, azevém anual cv. Comum e trigo cv. BRS Tarumã. As forrageiras foram pastejadas por vacas em lactação da raça Holandesa, sob método de pastejo de lotação rotacionada. A silagem e o feno foram elaborados da biomassa remanescente das pastagens, 20 dias após o final do período de pastejo. O delineamento experimental foi o inteiramente ao acaso, em arranjo fatorial 3x2, com três repetições. Foram avaliados o rendimento de forragem, a composição botânica e a estrutural da forragem conservada, os parâmetros fermentativos da silagem e o valor nutritivo da silagem e do feno. O rendimento de forragem foi similar entre as espécies, e o material ensilado apresentou pequenos percentuais de lâminas foliares e grãos. A silagem apresentou características fermentativas desejáveis. A ensilagem apresentou menores perdas de componentes solúveis e proporcionou uma forragem com valor nutritivo mais elevado em relação à fenação, sendo a forma mais indicada para conservar a biomassa remanescente de pastagens de estação fria.

ABSTRACTThe aim of this research was to evaluate the use of cool season pastures' remaining biomass as conserved forage. The tested species were: Agro Zebu black oat, Common ryegrass and BRS Tarumã wheat. The pastures were grazed by Holstein dairy cows, in the rotating stocking grazing method. Hay and silage were done from the stubble of pasture, twenty days after the end of the grazing period. The experimental design was completely randomized, in a 3 x 2 factorial scheme, with tree replicates. Forage yield, structural and botanical composition of preserved forage, fermentative parameters and nutritive value of silage and hay were evaluated. Forage yield was similar among species, and ensiled material has small percentuals of leaf blades and grains. The silage presents desirables fermentation parameters. The silage had lower losses of soluble components, provides forage with a higher nutritional value compared to hay, and is the most appropriate way to conserve cool season remaining biomass.