much of the rest of the country makes up the central asian southern desert ecoregion, which includes the karakum desert, the southern part of the kyzylkum desert and other areas with rolling dunes, sandy plateaus and alluvial plains. this area receives practically no rain during the summer and the extreme heat means that little grows at this time of year. in the winter, some precipitation with much cooler temperatures occurs, and grasses such as "bromus" and vascular plants such as "malcolmia", "koelpinia" and "amberboa" sprout. in march and april, ephemeral plants appear, including fox-tail lilies, "rheums", tulips and stars of bethlehem, but by the end of may these have given way to the summer drought. communities of "salsola" grow on the alluvial flats along with asafoetida, "ephedra strobilacea", black saxaul and white saxaul. the sand acacia and several species of "calligonum" grow among the dunes.