Growing season

Cold temperate steppe: Steppes tend to get their precipitation spread out over the whole year, so rains rarely build on each other. Biological productivity is much lower than tropical grasslands that get the same precipitation in a four-month summer growing season. On the cold steppe, cool temperatures and a short growing season also limit productivity.
 

Mild temperate steppe: Erratic and spread-out precipitation limit productivity. Mild temperatures create faster evaporation than on the cold steppe, further limiting usable moisture.
 

High rainfall tropical savanna: growing season. Abundant rainfall combines with warm temperatures to create terrific growing conditions and very high biological productivity. Plant growth is so fast during the rainy season that it's far more challenging to maintain pasture quality than to prevent overgrazing of plants.