图1 中国与欧洲的研究点分布。 A图中三角形表示位于青藏高原的气象站点, 圆点表示位于内蒙古的气象站点。B图中圆点表示欧洲地区木本植物物候观测点。

Fig. 1 Spatial distribution of study sites in China (A) and Europe (B). The triangles/dots in (A) are the distributions of meteorological stations in Qinghai-Xizang Plateau and in Nei Mongol, respectively. The points in (B) indicate the locations of phenological observation sites for woody plants in Europe.

图2 春季降水与气温对内蒙古草原、青藏高原草甸和欧洲地区木本植物返青期的影响。每一方框的上下横线分别表示样本统计量的四分位值即75%和25%的位点, 框内中央横线是中位数, 上下端短横线分别是统计量的90%和10%的位点, 圆点表示统计分布的特异最大或最小值。

Fig. 2 The changes in model coefficients of green-up date with spring precipitation and air temperature for the grasslands in Nei Mongol, meadows in Qinghai-Xizang Plateau, and woody plants in Europe. In these boxplots, the top and bottom values of the bars indicate the 25th and 75th percentiles, respectively; the black line within the box indicates the median; whiskers below and above the box indicate the 10th and 90th percentiles; and points indicate outliers. Letters on top of the whiskers are the results of an analysis of variance: different letters indicate statistically significant difference between the mean values (p < 0.01, t-test).

图3 内蒙古草原、青藏高原草甸和欧洲地区木本植物的Holdridge干燥度指数(HAI)的分布统计特征。统计变量的说明参见图2。

Fig. 3 Boxplots of the Holdridge aridity index (HAI) for the grasslands of Nei Mongol, meadows in Qinghai-Xizang Plateau, and woody plants in Europe. See Fig. 2 for explanations of the symbols.

图4 内蒙古草原、青藏高原草甸和欧洲地区木本植物降水与气温对返青期的影响强度与Holdridge干燥度指数(HAI)的关系。

Fig. 4 The changes in the model coefficient of precipitation and temperature with the Holdridge aridity index (HAI) for the grasslands of Nei Mongol,meadows in Qinghai-Xizang Plateau, and woody plants in Europe.

图5 在春季气温上升的3种情境下(+1、+2、+3 ℃)所研究生态系统返青期的变化。负值为返青期延后, 正值为返青期提前。A, 升温1、2和3 ℃情况下所有研究点返青期变化量的频数。B、C、D分别为升温1、2 和3 ℃时各个生态系统返青期变化量的频数。

Fig. 5 Predicted changes of green-up date under the three scenarios of elevated spring-temperature at 1, 2 and 3 °C for the target areas. Negative and positive dates indicate the delayed and advanced days of the green-up date, respectively. A, Predicted changes under all the three temperature scenarios. B, C, D, Predicted changes for each target area with the temperature increase of 1, 2 and 3 °C, respectively.

图6 在3种春季降水增加的情景下(+10、+20、+30 mm)所研究生态系统返青期的变化情况。负值表示返青期延后, 正值表示返青期提前。A, 增水10、20和30 mm情况下所有研究点返青期变化量的频数。B、C、D分别为增水10、20和30 mm时各个生态系统返青期变化量的频数。

Fig. 6 Predicted changes of green-up date under the three scenarios of elevated spring-precipitation at 10, 20 and 30 mm among each target area. Negative and positive dates indicate the delayed and advanced days of the green-up date, respectively. A, Predicted changes for all the three precipitation scenarios. B, C, D, Predicted changes for each target area with the precipitation increase at 10, 20 and 30 mm, respectively.

图7 利用线性回归模型计算的3个地区返青期气温敏感性。统计变量的说明参见图2。

Fig. 7 Boxplots of temperature sensitivity of green-up date from linear regression models for the three cases of the study. See Fig. 2 for explanations of the symbols.