forrester look vic papel and jug free professor clemens geitner pay close attention to the forest floor and what lies beneath it holds the key to a healthy forest. they're going to explain to us the profound influence trees have on the quality of the soil. in a small piece in this old spruce forest they examined the soil to a depth of one and a half meters. of them as you can scooting proof you know we can see here the various layers on the surface there are spruce needles the stuff the trees shed it's a lot sometimes 5 or 6 centimeters deep sixed and. the needles decomposed to create a layer of humus which makes the soil more acidic the who took on the next layer down is the mineral soil with lots of tree roots spruces have very shallow roots and can't access the water or nutrients from lower down that is a disadvantage it means the roots don't loosen the soil or create channels for the humus to trickle down so the spruce can take advantage of the benefits of this good location and importance of. nearby is a mixed forest of coniferous and deciduous trees which look big battle planted 2