| Dendroecology refers to the application of dated tree-ring information to ecological investigations, with particular emphasis on the reconstruction or identification of specific ecological events, past forest disturbances and climatic conditions by using the variations in ring structure. In general, semi-arid climates in the typical steppe are unfavorable for the natural growth and survival of most trees. However, one patch of Meyer spruce (Picea Meyeri) forest, a climatically remnant community from the early Holocene, appears in the Xilin River Basin. Meyer spruce forest is currently restricted to wet and cold mountainous regions in north-central China, and is clearly out-of-phases with semi-arid climates in the Xilin River Basin. Therefore, this relict coniferous forest provides a unique site to exploit the ecological adaptation of natural forest in the typical steppe. Using dendroecological methods together with wood anatomy technology, meteorological data and historical records, we evaluated climate-growth relationships of Meyer spruce on a sandy substrate, the stand disturbance history, tree-grass growth relationships, the forest response to global change in the typical steppe. The main results are briefly summarized as follows:1) A 65-year tree-ring standardized chronology ranging from 1930 to 1994 was developed. Statistical analysis of the chronology showed a mean series inter-correlation of 0.47, a signal-to-noise ratio of 14.44, and a mean sensitivity of0.18. Correlation function and response function analyses indicated that radial growth was positively correlated with precipitation in February and May of the current year, and in September of the preceding year.2) Light rings are characterized by one or very few latewood-cell layers, showing a lighter color under the microscope. By means of tree-ring analysis coupled with wood anatomy technology, we observed the occurrence of light rings in 1966, 1968 and 1972.3)Tree-ring analysis showed that the existing Meyer spruce was recruited in the late 1920s or early 1930s. In addition, strong correlation was found between Meyer spruce (XLPI) chronology with other three tree-ring chronologies from Korean spruce (Picea koraiensis) (BYAB), and Chinese pine (Pinus tabulaeformis ) (JGB and HHT), as reported by other investigators. The comparatively synchronized growth decline of JGB, HHT, and BYAB was also observed in the 1920s4) Chinese leymus (Leymus chinensis) displayed significantly positive growth response to May precipitation (P < 0.05) and the sum of current July and August precipitation (P<0.05). Moreover, two predominant collinear relationships was detected between above-ground biomass of Chinese leymus and ring width of Meyer spruce, each being corresponded to different precipitation patterns in this region. Furthermore, grass production from 1955 to 1979 was primarily reconstructed using tree-ring width of Meyer spruce and two models derived from tree-grass growth relationships with reference to seasonal precipitation patterns.5) The recorded meteorological data demonstrated that the increases in temperature were synchronous with slight decreases in precipitation during the recent 40 yeas. Correlation function analysis indicated the annual mean temperature and accumulated temperature (above 5癈, 10癈) respectively showed no significant correlation with the spruce growth relative to summer mean temperature, which displayed strong coherence with tree growth (P<0.01). The mean temperature in May showed significantly negative correlation with spruce growth (P<0.05). Furthermore, it was revealed that the negative influence of May temperature was due to the monthly mean maximum temperature (Tmax) (P<0.01) other than the monthly meanminimum temperature (Tmin) values (P<0.1). With this, it was speculated that extreme maximum temperature in May and June might impose the most detrimental influence on the growth of Meyer spruce in the Xilin River Basin.From all the data combined, we may safely conclud that Meyer spruce in this sta...
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