Composición nutricional de seis gramíneas tropicales del estado de Jalisco, México

El objetivo de este estudio fue evaluar la composición química de seis gramíneas forrajeras para el trópico húmedo y seco mexicano: Andropogon gayanus, Andropogon gerardii, Cenchrus ciliaris, Chloris gayana, Megathyrsus maximus y Urochloa brizantha. Las muestras se colectaron en noviembre de 2019, en Tonaya, Jalisco, México. Se determinaron: materia seca, cenizas, proteína cruda (total e insoluble), extracto etéreo, fibra detergente neutro, fibra detergente ácido, hemicelulosa, lignina y celulosa. La evaluación se realizó en el Laboratorio de Nutrición Animal del Departamento de Zootecnia, Universidad Autónoma Chapingo, Texcoco, Estado de México. Cada gramínea se evaluó por triplicado y cada repetición se consideró como unidad experimental. Las medias de composición química fueron separadas mediante la prueba de Tukey (p < 0.05). La correlación entre cada par de variables (p < 0.05) se estimó mediante el coeficiente de Pearson (p < 0.05). A mayor porcentaje de proteína total (p < 0.05) menor porcentaje de extracto etéreo y mayores porcentajes de cenizas y de proteína insoluble. Además, a mayor porcentaje de proteína insoluble, menor porcentaje de lignina (p < 0.05). Probablemente, la proteína se concentra en su fracción insoluble a expensas del extracto etéreo y la lignina. Consecuentemente, gran-tallo-azul (Andropogon gerardii) mostró porcentajes altos de proteína total (10.27%) y cenizas (7.88%), y bajos de lignina (5.23%) y extracto etéreo (1.37%); pero su proteína insoluble no fue tan elevada (2.06%) como la de guinea (Megathyrsus maximus) (6.08%). Por tanto, A. gerardii tuvo el mejor contenido nutricional a los 35 días de rebrote.

Microanatomical traits track climate gradients for a dominant C4 grass species across the Great Plains, USA

Background and Aims Andropogon gerardii is a highly productive C4 grass species with a large geographic range throughout the North American Great Plains, a biome characterized by a variable temperate climate. Plant traits are often invoked to explain growth rates and competitive abilities within broad climate gradients. For example, plant competition models typically predict that species with large geographic ranges benefit from variation in traits underlying high growth potential. Here, we examined the relationship between climate variability and leaf-level traits in A. gerardii, emphasizing how leaf-level microanatomical traits serve as a mechanism that may underlie variation in commonly measured traits, such as specific leaf area (SLA). Methods Andropogon gerardii leaves were collected in August 2017 from Cedar Creek Ecosystem Science Reserve (MN), Konza Prairie Biological Station (KS), Platte River Prairie (NE) and Rocky Mountain Research Station (SD). Leaves from ten individuals from each site were trimmed, stained and prepared for fluorescent confocal microscopy to analyse internal leaf anatomy. Leaf microanatomical data were compared with historical and growing season climate data extracted from PRISM spatial climate models. Key Results Microanatomical traits displayed large variation within and across sites. According to AICc (Akaike’s information criterion adjusted for small sample sizes) selection scores, the interaction of mean precipitation and temperature for the 2017 growing season was the best predictor of variability for the anatomical and morphological traits measured here. Mesophyll area and bundle sheath thickness were directly correlated with mean temperature (annual and growing season). Tissues related to water-use strategies, such as bulliform cell and xylem area, were significantly correlated with one another. Conclusions The results indicate that (1) microanatomical trait variation exists within this broadly distributed grass species, (2) microanatomical trait variability appears likely to impact leaf-level carbon and water use strategies, and (3) microanatomical trait values vary across climate gradients, and may underlie variation in traits measured at larger ecological scales.

Competition Indices Identify Forb Species That Promote Overyielding of a Dominant Grass in Grassland Restoration

Overyielding is a common phenomenon. Overyielding of dominant grasses when in competition with common forbs during grassland restoration could lead to lower plant diversity. My objective was to characterize overyielding of Andropogon gerardii in competition with fcommon forbs. I collected soils representing different stages of restoration (0, 4, and 16 years restored) and conducted a pairwise competition experiment with a dominant grass, Andropogon gerardii, in competition with four subordinate forbs (Oligoneuron rigidum L., Liatris punctata Hook, Lespedeza capitata Michx., or Desmanthus illinoensis Michx.). Relative yield indices (RY) were calculated by comparison with a two-individual monoculture of A. gerardii with both per grass biomass and per grass net absolute tiller appearance rate (TAR). Overyielding of A. gerardii was in competition with Oligoneuron rigidum was indicated by RY values (greater than1) using both biomass and TAR measurements. These findings suggest that O. rigidum should be given low priority for inclusion in tallgrass prairie restoration seed mixes.