The Llanos (Spanish Los Llanos, "The Plains"; ) is a vast tropical grassland plain situated to the east of the Andes in Colombia and Venezuela, in northwestern South America. It is an ecoregion of the tropical and subtropical grasslands, savannas, and shrublands biome. Geography The Llanos occupy a lowland that extends mostly east and west. The Llanos are bounded on the west and northwest by the Andes, and on the north by the Venezuelan Coastal Range. The Guiana Highlands are to the southeast, and the Negro-Branco moist forests are to the southwest. To the east the Orinoco wetlands and Orinoco Delta swamp forests occupy the Orinoco Delta. The Llanos' main river is the Orinoco, which runs from west to east through the ecoregion and forms part of the border between Colombia and Venezuela. The Orinoco is the major river system of Venezuela. Climate The ecoregion has a tropical savanna climate that grades into a tropical monsoon climate in the Colombian Llanos. Rainfall is highly seasonal, with a rainy season from April to November, and a dry season between December and March. The wettest months are typically June and July. Rainfall varies across the ecoregion, from up to per year in the southwest, in Apure State, and per year in the Llanos of Monagas State in the northeast. Mean annual temperature is , and the average monthly temperature varies little throughout the year; the lowest-temperature months (June, July, December, and January) are only cooler than the hottest months. Flora The plant communities in the Llanos include open grasslands, savannas with scattered trees or clumps of trees, and small areas of forest, typically gallery forests along rivers and streams. There are seasonally flooded grasslands and savannas (llano bajo) and grasslands and savannas that remain dry throughout the year (llano alto). The llano alto grasslands and savannas are characterized by grasses and shrubs 30–100 cm high, forming tussocks 10 to 30 cm apart. Soils are typically sandy and nutrient-poor. Llano alto covers approximately two-thirds of the Venezuelan llanos, and is also widespread in the Colombian llanos. Grasses of genus Trachypogon are predominant, and species include Trachypogon plumosus, T. vestitus, Axonopus canescens, A. anceps, Andropogon selloanus, Aristida spp., Leptocoryphium lanatum, Paspalum carinatum, Sporobolus indicus, and S. cubensis, and sedges in the genera Rhynchospora and Bulbostylis. Shrubs and herbs are most commonly legumes in the genera Mimosa, Cassia, Desmodium, Eriosema, Galactia, Indigofera, Phaseolus, Stylosanthes, Tephrosia,