The care and cultivation of forest trees.
Silviculture involves controlling the health and composition of the forest to promote specific goals; usually, the growing and tending of forest crops. The term 'forestry' is similar, but tends to be used for larger areas, while silviculture tends to apply to individual stands of trees.
Etymology: 1800s, French, from (Latin) silva, wood, + culture, cultivation.
My friend purchased a patch of untended woodland; among other things it's full of spindly trees reaching for the sun - and falling over. One option is to thin the woods - fewer trees means the remaining ones will have a chance to become sturdier.
When helping Mom write up the family history, I learned there was a history of silviculture in the family: a strong appreciation for "taking care" of woodland. My grandfather purchased 10 acres of virgin forest in the early 1900s - it was still there and owned by my aunt when I was growing up (and getting to be a very rare thing in Iowa). I would often hear Mom talk about her dad working in the woods, and I have many childhood memories of playing in our own neatly-tended patch of woods.