Complex sentence: Tree growth, which would otherwise take over the land, is kept down partly through grazing by sheep, goats, cattle and horses, and partly through felling of upcoming trees, as well as felling of established wooded areas.
Split into simpler sentences: Tree growth, which would otherwise take over the land, is kept down. Partly through grazing by sheep, goats, cattle and horses, and partly through felling of upcoming trees, as well as felling of established wooded areas.