Forested watershed

Sand Prairie is moderately-low to moderately vulnerable to climate change (when evaluated in low to high climate change emissions scenarios). The Sand Prairie environment is intrinsically hot and arid, plants are adapted to growing on infertile soils and thus the species that grow in this natural community are able to resist potential climate change threats such as drought and extreme heat. It’s possible that the frequency, intensity and timing of precipitation along with increased dry periods between rains may affect groundwater infiltration and increase drought stress.

Bracken Grassland is moderately low to moderately vulnerable to climate change (when evaluated in low to high climate change emissions scenarios). This natural community occurs on nutrient poor sites with a history of disturbance, where non-native species are dominant alongside native weedy species. These generalist species may prove to be hardy in the face of a changing climate. Changes in community structure are a significant threat, mainly due to increasing cover from trees and brush.

Precipitation in winter is projected to more often be rain or freezing rain than snow, further increasing the threat of runoff if rain falls on frozen ground. Nutrient enrichment and sedimentation are among the leading causes of degradation of wet and wet-mesic prairies, and may also negatively impact upland grasslands by favoring non-native invasive and aggressive native species. Erosion may occur on steep slopes during extreme storm events, especially after a prescribed burn.

Non-native invasive plants may increase in productivity with increasing atmospheric CO2, warmer temperatures, longer growing seasons, and milder winters, and may invade new areas during extreme flood events. For grasslands in lower landscape positions, agricultural run-off may also enhance growth of non-native invasive plants.

Prescribed fire is a very important tool for maintaining grasslands. The frequency, intensity, and timing of precipitation and drought will be major determinants of where and when managers can burn. Earlier and potentially wetter springs combined with rapid warm-up could reduce opportunities for prescribed burning. This could require a shift to burning at different times of year (if feasible).

Water is central to the region’s productivity. Projected increases in winter and spring precipitation in the Southern Plains may benefit productivity by increasing water availability through soil moisture reserves during the early growing season. The Southern Plains will remain vulnerable to periodic drought because much of the projected increase in precipitation is expected to occur in the cooler months while increasing temperatures will result in additional evapotranspiration.

The freeze-free season is defined as the period of time between the last spring frost (daily minimum temperature below 32 degrees F) and the first fall frost. The length of the annual freeze-free season has been increasing since the 1980s, and all climate models agree that it will continue to increase in the future. The largest increases are projected for southeastern Texas, where the freeze-free season could be 30 days longer.

By mid-century, summer precipitation is expected to decrease by 5-15% for much of Kansas, Oklahoma, and northern Texas, and increase by as much as 15% in central Texas. The means of several climate models indicate that winter and spring precipitation may increase by up to 10% percent by mid-century across most of the region, although southwest Texas may see decreases during these seasons. Under mild climate scenarios, changes are generally smaller than in more extreme climate scenarios.

The frequency and intensity of heavy precipitation events are anticipated to continue to increase, particularly under higher scenarios and later in the century. Most of the Southern Great Plains region is projected to experience 0 to 30% more days each year with more than an inch of precipitation by the middle of the century. Days with more than 2 inches, 3 inches, and 4 inches of precipitation are also expected to occur more regularly. Rare events, such as 100-year floods, may also become more common.