Influences of 20th‐century warming at the upper tree line contingent on local‐scale interactions: evidence from a latitudinal gradient in the Rocky Mountains, USA

摘要: Aims  Twentieth-century climate, the spatial pattern of tree establishment and positive feedback influence upper line ecotones. Here, I investigate how these factors interact to gain a more holistic understanding broad-scale abiotic local-scale site conditions regulate within ecotones. Location  A latitudinal gradient (c. 35–45° N) in US Rocky Mountains. Study sites (n= 22) were located Bighorn (BH), Medicine Bow (MB), Front Range (FR) Sangre de Cristo (SDC) mountain ranges. Methods  Dendroecological techniques used reconstruct dates that compared with 20th-century climate data using correlation regime shift analyses. Spatial patterns analysed by Ripley's K determine interactions capable ameliorating inputs through feedback. Results  Significant correlations (P < 0.01) between confined FR, where was found summer (June–August) cool season (November–April) temperature range (Tmax−Tmin). These trees almost exclusively situated random pattern. Similar exist BH, yet their contingent on availability local shelter lee boulders. Trees MB SDC primarily clustered space had no significant climate. Considerable lag times changes towards favourable growing corresponding shifts all ranges except synchronous occurred early 1950s. Main conclusions  results suggest dynamics is related influences feedback. This research has important implications for vegetation communities will respond global change.