Not related. The suspected importance of savanna is more based on biodiversity than soil science. In these biomes, you have comparatively large amounts of anima

Not related. The suspected importance of savanna is more based on biodiversity than soil science. In these biomes, you have comparatively large amounts of animal and insect biomass. You have animals constantly eating the plants. This causes deep rooted plants which can regenerate quickly to dominate as they grow back intermittently. The sequestered carbon is mostly in the plants and animals as opposed to soil. Measuring biomass accumulation below ground is more difficult than above ground (counting trees is pretty easy). However some land use pattern studies have looked at which areas have historically been savanna normally show overlap with heavy agriculture regions as the soil is so good. In some cases these former oak savannas in the US will have dozens of feet of fertile topsoil. So there's some speculation that the high soil fertility in such biomes is due to compaction from grazing animals, which I guess is not related to the humus theory, but would be a similar idea about how so much carbon can accumulate.