Widely observed inertia of forest communities contrasts with climate change projections that suggest dramatic alterations of forest composition for the coming decades. Disturbances might be a key process to catalyse changes in tree species composition under environmental change by creating opportunities for ‘new’ species to establish. To test this assumption, we compared two assessments (1993–1995, 2009–2017) from the Swiss National Forest Inventory to evaluate which forests were opened by natural canopy disturbance (that is, wind, insect outbreaks, fire and drought) and if these disturbances altered tree species composition both in terms of species-specific basal area and recruitment densities. Natural disturbances affected 14% of the Swiss forests within 25 years, with wind and insect outbreaks being the most frequent (75%) and fire and drought being rare (< 1.5%). Disturbances led to a shift from conifer to broadleaf tree species at low elevation, in particular in dense Picea abies stands, but no change was observed at higher elevations. The composition of undisturbed sites persisted during the same period. Our results demonstrate that undisturbed forests widely resist changes in tree species composition as an effect of direct ingrowth by stand-forming species. Disturbance events seem necessary to create opportunities for climatically ‘better suited and site-adapted’ species to (re-)establish and therefore potentially catalyse tree species turnover under environmental changes. We detected a reduction of tree species that were—centuries ago—cultivated outside their primary natural range, in particular P. abies, or depended on traditional management practices (Pinus sylvestris, Castanea sativa), which may inform us on how the projected increase in disturbance frequency and severity might filter tree species composition and hereby alter forest structure.

广泛观察到的森林群落的惯性与气候变化预测形成对比，气候变化预测表明未来几十年森林组成将发生巨大变化。通过创造“新”树种的建立机会，干扰可能是在环境变化下催化树木树种组成变化的关键过程。为了检验这一假设，我们比较了瑞士国家森林清单的两次评估（1993-1995年，2009-2017年），以评估哪些自然林冠层扰动（即风，虫害暴发，火灾和干旱）打开了哪些森林，以及是否扰动改变了树种的组成，无论是树种的特定基础面积还是募集密度。自然扰动在25年内影响了14％的瑞士森林，风和昆虫暴发最为频繁（75％），火灾和干旱很少见（<1.5％）。干扰导致低海拔地区从针叶树种转向阔叶树种，特别是在茂密的树种中云杉云杉站立，但在高海拔处未观察到变化。在同一时期内，未受干扰的站点的组成持续存在。我们的结果表明，未受干扰的森林广泛地抵抗林分组成物种直接向内生长的影响，从而改变了树种组成。扰动事件似乎是必要的，以便为气候上的“更合适和更适合地点”的物种创造机会，以（重新）建立并因此潜在地促进环境变化下的树木物种更新。我们发现，几个世纪前在其原始自然范围之外种植的树种减少了，特别是长柄假单胞菌，或者依赖于传统的管理方法（樟子松，栗木），这可能会告诉我们预计的干扰频率和严重性增加将如何过滤树种组成并由此改变森林结构。