forester not vic papel and jug free professor clemons 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 pearson is old spruce forest they examine the soil to a depth of one and a half metres. of them as you can scoop in 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 winterkorn 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 petal planted 25 year