Grasslands

IUCN GET 2.0

T4 Savannas and grasslands

The savannas and grasslands biome is comprised these Ecosystem Functional Groups (EFG): Trophic savannas, Pyric tussock savannas, Hummock savannas, Temperate woodlands, Temperate subhumid grasslands. Ecological functions within the Savannas and grasslands biome are closely linked to a mostly continuous ground layer of grasses that contribute moderate to very high levels of primary productivity driven by strongly seasonal water surplus and deficit cycles. The timing of the seasonal cycle of productivity varies with latitude and becomes more variable inter-annually as total rainfall declines. The woody component of the vegetation may be completely absent or may vary to a height and stature that resembles that of a forest. In the tropics and subtropics, productivity peaks in the summer when high rainfall coincides with warm temperatures. At temperate latitudes, summer growth is suppressed by water deficits associated with high evapotranspiration, sometimes exacerbated by weakly seasonal (winter-maximum) rainfall, so that productivity peaks in spring when warming temperatures coincide with high soil moisture accumulated over winter. Co-existence between trees and grasses and between grasses and interstitial forbs is mediated by herbivory and/or fire. These agents are critical in the top- down regulation of grassy ecosystems and in some cases are involved in feedback mechanisms that mediate regime shifts between alternative stable states. Herbivory is the primary driver in highly fertile and productive systems, whereas fire is the primary driver in less fertile and lower productivity systems. Nutrient gradients are exacerbated volatilisation during fire and the loss of nutrients in smoke. The representation of grass species with C3 and C4 photosynthetic pathways varies with water availability and temperature over regional and continental climatic gradients. Grasses are rapid responders to seasonal pulses of elevated soil moisture and sustain a complex trophic web with large-bodied mammalian herbivores and their predators. The curing of grasses over the dry season is critical to flammability. Mammal diversity, trophic complexity, and the expression of physical and chemical defences against herbivory also vary with soil fertility.

ESVD

Grassland/Rangeland biome comprised of Savanna, Tropical grasslands, Temperate grasslands, Steppe (dry, cold grassland), Other (grassland)

FEMA ESV

Not defined as a land cover / ecosystem type. Referenced in Riparian, Urban Green Open Space and Rural Open Space.

Other

ESRI Land Cover “Rangeland”:

Dense Rangeland – Healthy, closely packed vegetation that is predominantly dense, short (under 5m) woody shrubs with very little to no mixed grass or bare ground cover. May contain small isolated trees. Within and around areas classified as built, this class can also include highly manicured lawns or fields. Defined as a rangeland prediction with a maximum NDVI value greater than or equal to a biome-specific threshold during the given time period.

Sparse Rangeland – Vegetation that is some mix of grasses and/or dispersed, short, woody scrub, with or without some bare ground cover. May contain small isolated trees. Defined as a rangeland prediction with a maximum NDVI value less than a biome-specific threshold during the given time period.

USGS “Herbaceous”:

Grassland/Herbaceous - areas dominated by gramanoid or herbaceous vegetation, generally greater than 80% of total vegetation. These areas are not subject to intensive management such as tilling, but can be utilized for grazing.

Sedge/Herbaceous - Alaska only areas dominated by sedges and forbs, generally greater than 80% of total vegetation. This type can occur with significant other grasses or other grass like plants, and includes sedge tundra, and sedge tussock tundra.

Lichens - Alaska only areas dominated by fruticose or foliose lichens generally greater than 80% of total vegetation.

Moss - Alaska only areas dominated by mosses, generally greater than 80% of total vegetation.

Dynamic World “Grass”

Natural grasslands, livestock pastures, and parks