Abstract: To understand the effects of long-term drought on the growth of Mongolian pine (Pinus sylvestris var. mongolica) shelterbelts in Zhangbei County, Hebei Province, China, differences of healthy and declining trees in response to meteorological factors were evaluated based on tree-ring widths and wood anatomical traits. The results showed that the tree-ring width and basal area increment of declining trees were significantly different from those of healthy trees (P<0.01). Except for the mean tracheid area of earlywood, the tracheid number, total tracheid area, and mean tracheid area of the earlywood, latewood, and whole wood of declining trees were significantly lower than those of healthy trees (P<0.05). The earlywood of healthy trees was mainly affected by the meteorological factors in the previous year, whereas the earlywood of declining trees was affected by the meteorological factors in the previous year and the current year. The growth and anatomical characteristics of the latewood were more strongly correlated with the meteorological factors in the current year. At the annual scale, the anatomical traits of the earlywood and whole wood of healthy trees were significantly correlated with the meteorological factors in the previous year, whereas those of the latewood were significantly correlated with meteorological factors in the current year (P<0.05). A significant correlation between mean tracheid area and vapor pressure deficit (VPD) was detected only for the whole wood of declining trees, indicating a decrease in the responsiveness of the growth and wood anatomy to meteorological factors. The relative contributions of precipitation and standardized precipitation evapotranspiration index in the previous year were greater to the growth of healthy Mongolian pine, while the minimum temperature and mean temperature contri-buted more to the growth of declining trees. Relative humidity and maximum temperature contributed more to the anatomical traits of healthy trees, while VPD and minimum temperature contributed more strongly to the anatomical traits of declining trees. The results provide a reference for optimization of the planting layout and structure of Mongolian pine shelterbelts.

Key words: Mongolian pine, climate change, radial growth, xylem, wood anatomy