Forest Soil Respiration: What Don't We Know?

More than half of the globe's total soil respiration comes from forests and woodlands, which cover about 40% of the Earth's land surface. Forests range from tropical to boreal latitudes, from sea level to over 3000 m elevation. They occur on all soil types and under a broad range of moisture conditions. They may be needle-leaved or broad-leaved, deciduous or evergreen, natural or planted, young or old, fertile or starved, diverse or simple. And as a result of many studies by many fine scientists on all forest-growing continents, we know quite a lot about soil respiration rates in forests, and the factors that control them. Or do we?