Tropical rain forests tend to have a lot of humus, but the soil in those biomes retain little of it because of leaching. what is leaching?

Natural process by which water soluble substances (such as calcium, fertilizers, pesticides) are washed out from soil or wastes. These leached out chemicals (called leachites) cause pollution of surface and sub-surface water.

To provide education in rural schools

Humid continental climate is found in the interior of continents between the 30 and 60 degrees latitude, but usually above the 40 degree line.   40 degrees north of the equator means less direct sunlight and therefore less warmth.   this climate is mainly found in the northern hemisphere since there are no major landmasses in the southern hemisphere.  if you live in northern indiana, you know all about humid continental because that is the climate type you have!