Timber harvesting can contribute to the problem because the calcium removed with the trees would otherwise be recycled within the ecosystem as 
(Timber harvesting; can contribute; to the problem; because the calcium removed with the trees would otherwise be recycled within the ecosystem as) (the calcium; removed; with the trees) (the calcium removed with the trees; would otherwise be recycled; L:within the ecosystem)
Timber harvesting the calcium the calcium removed with the trees
can contribute removed would otherwise be recycled
to the problem because the calcium removed with the trees would otherwise be recycled within the ecosystem as
with the trees
L:within the ecosystem