Hey,
On "The Stalkers" page (p.7), there is a section that talks about experience and how it is gained, on the next page - "Stalker moves", there is a move called "Take a rest", it states: "During the rest, each stalker can also spend 10 XP to acquire 1 new talent, up to 10 talents max."
If you're asking if there is an automatic improvement system, when you "level up" and your basic stats become higher - there is no such mechanic. All improvements are linked to aquiring new talents.