Species interactions implicate a complex balance of facilitation and competition, which may shift during community development, thus structuring the subalpine ecotone of Mediterranean mountain ranges through time and space. This study highlights that encroachment of grasslands and simultaneous downward/upward movement of forest tree species involve species interferences and environmental feedbacks, with differential effects on mountain pine and European beech, and the grassland communities of the Majella Massif. The transitional ecotone from the European beech closed forest to the mountain pine krummholz vegetation in the Majella Massif (Apennines, Italy) is a sensitive area to climate and land-use changes. Vegetation shifts in these ecotonal zones may cause a negative impact on the spatial distribution and survival of rare or endemic herbaceous species, thus influencing the appearance, structure, and productivity of the subalpine ecotone of the Majella National Park. We focused on determining the structures and dynamics of this Mediterranean tree line, and the climate–growth relationships of European beech and mountain pine. We investigated the upward and downward movement of pine into areas potentially suitable for beech expansion, and the concurrent beech encroachment upward. Growth dynamics and canopy cover of European beech closed forest and mountain pine krummholz vegetation were analyzed in relation to disturbances at four different sites. Spring and summer temperatures and summer precipitation affected stem radial growth of both species. In details, spring and summer temperatures negatively affected tree ring width (TRW) of European beech, except for the highest site, whereas spring temperatures affected positively and summer temperatures negatively TRW of mountain pine. Mountain pine expanded upward, encroaching formerly grazed pastures and harvested areas, especially where the soil is shallow and rocky; downward expansion is also occurring, following progressive abandonment of forest management practices. At the same time, European beech recruitment is moving upward, interspersed within mountain pine krummholz, taking advantage from canopy shelter and higher temperature. Climate and land-cover simultaneous changes induce species interactions and a complex balance of facilitation and competition, which may shift during community development and structure the subalpine European beech-mountain pine ecotone of the Majella Massif through time and space.

中文翻译：

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地中海山区山毛榉和木果松森林群落过渡时的气候-生长关系

物种相互作用意味着促进和竞争的复杂平衡，这可能会在社区发展过程中发生变化，从而在时间和空间上构建地中海山脉的亚高山交错带。这项研究强调了草原的侵占和森林树种同时向下/向上移动涉及物种干扰和环境反馈，对山松和欧洲山毛榉以及 Majella 地块的草原群落有不同的影响。从欧洲山毛榉封闭林到 Majella 地块（意大利亚平宁山脉）的山松 krummholz 植被的过渡交错带是气候和土地利用变化的敏感区域。这些生态带的植被变化可能会对稀有或地方性草本植物的空间分布和生存产生负面影响，从而影响马耶拉国家公园亚高山交错带的外观、结构和生产力。我们专注于确定这条地中海树线的结构和动态，以及欧洲山毛榉和山松的气候-生长关系。我们调查了松树向上和向下移动到可能适合山毛榉扩张的区域，以及同时向上侵占山毛榉的情况。分析了欧洲山毛榉封闭林和山松 krummholz 植被的生长动态和冠层覆盖与四个不同地点的干扰的关系。春夏气温和夏季降水影响了这两个物种的茎径向生长。具体而言，春季和夏季温度对欧洲山毛榉的树轮宽度 (TRW) 产生负面影响，但最高点除外，而春季温度对山松树的年轮宽度 (TRW) 产生积极影响，而夏季温度对 TRW 产生负面影响。山松向上扩张，侵占原先放牧的牧场和收获区，尤其是土壤浅层和多岩石的地方；在逐步放弃森林管理做法之后，向下扩展也在发生。与此同时，欧洲山毛榉的招募正在向上移动，散布在山松 krummholz 中，利用树冠遮蔽和更高的温度。气候和土地覆盖同时变化导致物种相互作用以及促进和竞争的复杂平衡，