In the current alteration of temperature and snow cover regimes, the impacts of winter climate have received considerably less attention than those of the vegetation period. In this study, we present the results demonstrating the influence of the winter climate conditions on the Mountain pine (Pinus mugo Turra) communities in High Tatra Mts (Western Carpathians). The changes in greenness in 2000–2020 were represented by the inter-annual differences of satellite-derived Normalized Difference Vegetation Index (NDVI). The winter climate conditions were characterized by climate indices calculated from the temperature and snow cover data measured at Skalnaté Pleso Observatory (1778 m a.s.l.) over the period between 1941–2020. Areas with P. mugo were classified into two density classes and five altitudinal zones of occurrence. The partial correlation analyses, which controlled the influence of summer climate, indicated that winter warm spells (WWS) caused a significant decrease in the greenness of the P. mugo thickets growing in the dense class D2 (R = −0.47) and in the altitudinal zones A2 (1600–1700 m a.s.l.) and A3 (1700–1800 m a.s.l.) with R = −0.54 for each zone. The changes in greenness were related to the average snow depth (ASD) as well, particularly in the dense class D2 (R = 0.45) and in the altitudinal zone A2 (R = 0.50). Here, in the summers following winters with the incidence of WWS or low ASD, we found decreased greenness following the injury of P. mugo shrubs, but NDVI after winters with higher ASD indicated more greenness. At lower altitudes, injuries may result in the loss of competition capacity of P. mugo near the timberline, where taller mountain tree species can utilize the conditions of warmer climate for expansion. We also found a significant positive effect of warmer winter seasons in the sparse P. mugo thickets (D1) with R = 0.50 and at higher altitudes (R = 0.49 in A4—1800–1900 m a.s.l.; R = 0.53 in A5—1900–2000 m a.s.l.). The increased temperatures in December correlated significantly with the increase of the greenness in all P. mugo pixels (R = 0.47), with the most pronounced effect in the sparse class D1 (R = 0.57) and in altitudinal zones A4 (R = 0.63) and A5 (R = 0.44), creating advantageous conditions for the thermophilisation of the alpine zone by P. mugo.

中文翻译：

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与冬季气候相关的亚高山带山松（Pinus mugo Turra）的绿色变化

在当前温度和积雪状况的变化中，与植被期相比，冬季气候的影响受到的关注要少得多。在这项研究中，我们提供的结果证明了冬季气候条件对高塔特拉山（西部喀尔巴阡山脉）的松树（Pinus mugo Turra）社区的影响。2000年至2020年绿色的变化以卫星衍生的归一化植被指数（NDVI）的年际差异表示。冬季气候条件的特征在于，气候指数是根据1941-2020年期间SkalnatéPleso天文台（1778 m asl）测得的温度和积雪数据计算得出的。P. mugo的地区分为两个密度等级和五个垂直出现区域。偏相关分析控制了夏季气候的影响，表明冬季暖季（WWS）导致在密集的D2级（R = -0.47）和海拔高度上生长的P. mugo灌丛的绿色度显着下降。每个区域的区域A2（1600-1700 m asl）和A3（1700-1 800 m asl），R = −0.54。绿度的变化也与平均积雪深度（ASD）有关，特别是在密集的D2类（R = 0.45）和垂直区域A2（R = 0.50）中。在这里，在以下的冬天与WWS或低ASD发病率的夏天，我们发现了受伤后下降绿色P. mugo灌木，但冬季ASD较高的NDVI表示绿色度更高。在较低的海拔高度，受伤可能会导致林线附近的P. mugo失去竞争能力，而较高的山林树种可以利用气候变暖的条件来进行扩张。我们还发现，在稀疏的P. mugo灌木丛（D1）中，R = 0.50和更高的海拔（A4–1800–1900 m asl中的R = 0.49； A5–1900–900 R中的R = 0.53）对冬季变暖具有明显的积极作用。2000 m asl）。12月气温升高与所有P. muggo的绿度增加显着相关像素（R = 0.47），在稀疏类别D1（R = 0.57）以及在垂直区域A4（R = 0.63）和A5（R = 0.44）中效果最明显，为高山区域的高温化创造了有利条件由P. mugo撰写。