In the western United States, overgrazing, weed invasion and wildfire have resulted in the conversion of shrub-steppe to annual grasslands, with substantial effects on ecosystem function.
We found that 56% (15 620 km2) of grasslands in this region are burned less than every 3 yr and are therefore susceptible to conversion to shrub or tree dominance.
As the detection analysis results revealed this observed consistent expansion was attributed to the conversion of the wetland, shrub land, grass land and forest cover into cultivated and settlement land at different stages.
Our method is designed to characterize the main land cover changes associated with different drivers, including the conversion of forests to shrub and grassland primarily as a result of wildland fire and forest harvest, the vegetation successional processes after disturbance, and changes of surface water extent and glacier ice/snow associated with weather and climate changes.
Both analytical approaches show that the Dupont's lark favours flat areas characterized by small shrubs with bare ground, so that, for example, a conversion of dry crops to shrubs promoted by agri-environment schemes under CAP could increase the population size up to 80%.
Similarly the expansion of this LULC type in the second period (1986 2014) was due to the conversion of 251 ha of forest, 1465 ha of shrub land, 308 ha of grass land, 35 ha of bare land and 193 ha of wet land to cultivated and rural settlement land (Table 5).
What we are seeing in the Southwest is a fairly extensive conversion of forests into grasslands and shrubs, which are inherently more resistant to dry, warm conditions.
Similarly, reduction in grassland covers were mostly caused by conversion of its initial extent into shrubs by about 42% (3377.97 ha), and farmland and settlement by about 41.1% (3259.98 ha) despite some gains from other LULC classes.
The SOC in soil depth layers of 0 10, 10 20, 20 40, 40 60 and 60 80 cm were reduced with afforestation of grassland but not significantly (p > 0.05), while conversion of cropland to forests (trees or shrubs) increased SOC significantly for each soil depth layer up to 60 cm depth (p < 0.05).
In addition, shrinkage of shrubs were largely due to conversion of its original extent into farmlands and settlement by about 50.2% (3946.1 ha) despite some area gains were observed mainly from grasslands, and farmland and settlement by about 29.3% (2136.44 ha) and 36.48% (2660.21 ha), respectively.
The northern half of the country consists of a mix of shrub and tree steppes and shrub and tree savannas.
