Abstract As climate warming is more obvious in high mountains, the spatial patterns of mountainous vegetation responding to climate warming are expected to become a new aspect in forest ecosystem research. However, we do not know how spatial patterns of vegetation in mountainous regions respond to climate warming, and we also do not know what will happen to the patterns when rainfall occurs. Here, we conducted warming experiments to explore the variation pattern of the response of the herbaceous community to experimental warming along latitudinal and altitudinal gradients in mountainous forests of the Loess Plateau. In low and high warming amplitudes, air temperature increased by a maximum of 0.86 °C and 2.83 °C, respectively; the response of air temperature was obviously affected by elevation, whereas air humidity was not sensitive to warming. When rainfall occurred, warming produced decreases in soil temperature by a maximum of 0.56 °C and 0.61 °C in low and high warming amplitudes, respectively; soil temperature was evidently affected by latitude; and soil moisture was insensitive to warming. That was, the corresponding responsiveness of air and soil temperature was dependent on elevation and latitude, and a sudden increase in soil moisture caused by rainfall influenced the effects of warming on soil temperature. Warming also increased plant height and coverage, but plant density and frequency did not respond to warming, thus leading to insignificant changes for importance values of grass, sedge, and forb. Moreover, plant richness and Simpson indices increased in low-amplitude warming and decreased in high-amplitude warming, but the Pielou index was insensitive to warming. The responsiveness of these plant factors decreased with latitude and increased with elevation. Correlations tended to be enhanced by warming among vegetation, temperature (air temperature and soil temperature), and moisture (air humidity and soil moisture); the correlation among vegetation, air humidity, and soil moisture increased relatively rapidly in response to warming. With soil moisture increasing, plant height diminished and species diversity enlarged in warming, demonstrating that moisture increase caused by rainfall modified warming effects on vegetation. In regions with water deficits as the Loess Plateau, warming reinforced the relationship of vegetation with water and thus promoted its dependence on water. Warming could be controlled in a certain range and thus exerted positive effects on vegetation and facilitated plant community development. In regions where water is the limiting factor, warming effects were largely influenced by rainfall; the moisture increment induced by rainfall might weaken warming effects on soil and its correlation with vegetation.

中文翻译：

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黄土高原山地森林植物草本群落响应气候变暖的空间变化格局沿纬度和海拔梯度

摘要 随着气候变暖在高山地区更为明显，山地植被响应气候变暖的空间格局有望成为森林生态系统研究的一个新方向。然而，我们不知道山区植被的空间格局如何响应气候变暖，我们也不知道降雨时这些格局会发生什么变化。在这里，我们进行了变暖实验，以探索黄土高原山地森林中草本群落对实验变暖沿纬度和海拔梯度的响应变化模式。在低升温幅度和高升温幅度下，气温最高分别增加了 0.86 °C 和 2.83 °C；气温响应受海拔高度影响明显，而空气湿度对增温不敏感。当降雨发生时，产生的变暖使土壤温度在低和高变暖幅度下分别降低了 0.56°C 和 0.61°C；土壤温度受纬度影响明显；土壤水分对变暖不敏感。也就是说，空气和土壤温度的相应响应取决于海拔和纬度，降雨引起的土壤水分突然增加会影响变暖对土壤温度的影响。变暖也增加了植物高度和覆盖率，但植物密度和频率对变暖没有反应，因此导致草、莎草和杂草的重要性值发生微不足道的变化。此外，植物丰富度和辛普森指数在低幅度变暖时增加，在高幅度变暖时减少，但皮尔卢指数对变暖不敏感。这些植物因子的响应性随纬度升高而降低，随海拔升高而升高。植被、温度（气温和土壤温度）和水分（空气湿度和土壤湿度）之间的变暖往往会增强相关性；随着气候变暖，植被、空气湿度和土壤湿度之间的相关性增加相对较快。随着土壤水分的增加，植物高度降低，物种多样性增加，表明降雨引起的水分增加改变了对植被的变暖效应。在黄土高原等缺水地区，气候变暖加强了植被与水的关系，从而促进了其对水的依赖。变暖可以控制在一定范围内，从而对植被产生积极影响，促进植物群落发展。在水是限制因素的地区，变暖效应主要受降雨影响；降雨引起的水分增加可能会减弱对土壤的增温效应及其与植被的相关性。