What is Jims view of the inside of the stockade? Why is it so depressing?

From the text:

The slopes of the knoll and all the inside of the stockade had been cleared of timber to build the house, and we could see by the stumps what a fine and lofty grove had been destroyed. Most of the soil had been washed away or buried in drift after the removal of the trees; only where the streamlet ran down from the kettle a thick bed of moss and some ferns and little creeping bushes were still green among the sand. Very close around the stockade--too close for defence, they said--the wood still flourished high and dense, all of fir on the land side, but towards the sea with a large admixture of live-oaks. Chapter 19