Palm density and grazing effects on plant communities: implications for livestock management in a Butia palm grove.

Some grasslands in ecotones with forests tend to be encroached by woody species, because of changes in climate and land use. Such structural changes in vegetation can be facilitated when the grassland community presents an autochthonous arboreal component, like Butia palms. We aim to identify the responses of taxonomic and functional diversity on grassland community with the occurrence of arborescent/arboreal species (autochthonous and encroaching) to palm density and grazing intensity. The study was conducted in a Butia odorata palm grove under cattle management, in Southern Brazil. To assess the taxonomic and functional composition we performed ordinations analysis with the vegetational data and using path analysis we assessed the causal relationships between variables of interest. Density of Butia odorata and woody plants were strongly positive related, suggesting a facilitation process in the establishment of arborescent plants on the grassland matrix. The abundance of less palatable plants and grazing pressure were inversely related, indicating a selection process induced by higher grazing intensity. We suggest that the grazing intensity management must be based on the autochthonous tree density, applying higher grazing intensity in areas with higher density of encroaching plants, in addition to maintaining other regions conducive to Butia palm regeneration through fallows.

Phylogenetic patterns and phenotypic profiles of the species of plants and mammals farmed for food.

The origins of agriculture were key events in human history, during which people came to depend for their food on small numbers of animal and plant species. However, the biological traits determining which species were domesticated for food provision, and which were not, are unclear. Here, we investigate the phylogenetic distribution of livestock and crops, and compare their phenotypic traits with those of wild species. Our results indicate that phylogenetic clustering is modest for crop species but more intense for livestock. Domesticated species explore a reduced portion of the phenotypic space occupied by their wild counterparts and have particular traits in common. For example, herbaceous crops are globally characterized by traits including high leaf nitrogen concentration and tall canopies, which make them fast-growing species and proficient competitors. Livestock species are relatively large mammals with low basal metabolic rates, which indicate moderate to slow life histories. Our study therefore reveals ecological differences in domestication potential between plants and mammals. Domesticated plants belong to clades with traits that are advantageous in intensively managed high-resource habitats, whereas domesticated mammals are from clades adapted to moderately productive environments. Combining comparative phylogenetic methods with ecologically relevant traits has proven useful to unravel the causes and consequences of domestication.

Global patterns of leaf mechanical properties.

Leaf mechanical properties strongly influence leaf lifespan, plant-herbivore interactions, litter decomposition and nutrient cycling, but global patterns in their interspecific variation and underlying mechanisms remain poorly understood. We synthesize data across the three major measurement methods, permitting the first global analyses of leaf mechanics and associated traits, for 2819 species from 90 sites worldwide. Key measures of leaf mechanical resistance varied c. 500-800-fold among species. Contrary to a long-standing hypothesis, tropical leaves were not mechanically more resistant than temperate leaves. Leaf mechanical resistance was modestly related to rainfall and local light environment. By partitioning leaf mechanical resistance into three different components we discovered that toughness per density contributed a surprisingly large fraction to variation in mechanical resistance, larger than the fractions contributed by lamina thickness and tissue density. Higher toughness per density was associated with long leaf lifespan especially in forest understory. Seldom appreciated in the past, toughness per density is a key factor in leaf mechanical resistance, which itself influences plant-animal interactions and ecosystem functions across the globe.