Tropical Rainforest: Typically has the highest NPP due to abundant rainfall and year-round warm temperatures. It is one of the most productive ecosystems on earth.
Tropical Deciduous Forest: Also has high productivity, though generally lower than rainforests because it experiences a period of drought where trees lose their leaves.
Temperate Deciduous Forest: Has moderate productivity; these forests go through a dormant period in winter. Temperate Coniferous Forest: Generally has the lowest NPP among the four listed here because of cooler temperatures and lower nutrient availability. So, arranging these ecosystems in increasing order of their mean NPP (tons/ha/year) would be .

──────────────────────────────────────────────────────────────────────────────────────────