So I see that animals respawn so hide is not an issue. Plants seem to respawn as well so hardwood and petals (leaves?) are not an issue. However crates do not seem to respawn. I am having a lot of trouble finding salvage parts because of this. I'm trying to upgrade all of my weapons prior to moving on to the Copper Mill area in the Soviet Installation Hub, but it seems like this is not doable since I can't find enough salvage. I am only upgrading Tier 1 as I have not found or purchased the upgrade tool.

BTW I've finished the game once on Seasoned Raider difficulty now I'm trying out Survivor. Maybe the respawning is due to the difficulty level. They did say resources would be more scarce, but as I stated it only seems to be these particular ones.