Variation of the Moisture Index from March to August during Rece...
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中国科技论文在线
Variation of the Moisture Index from March to August
during Recent 100 Years Indicated by Tree Ring of Luoshan
Mountains
#
Wang Yajun
1
, Ma Yuzhen
2
, Lu Ruijie
2
, Sang Yanli
2
, Meng Hongwei
2**
Foundations: Under the auspices of National Natural Science Foundation of China (No. 40801004, No.
40671184), and the Research Fund for the Doctoral Program of Higher Education (20070027019)
Brief author introduction:Wang Yajun, (1973-), Female, Associate Professor, environment change research
Correspondance author: Lu Ruijie, (1980-), Female, Associate Professor, Environment evolution and
desertification control. E-mail: ruijielu@bnu.edu.cn
(1. the Resource College of Hebei University of Engineering, HeBei HanDan 056038;
2. Key Laboratory of Environmental Changes and Natural Disaster,MOE ,Beijing Normal
University, Beijing 100875)
Abstract: The tree-ring width of Pinus Tabulaeformis from Luoshan Mountains correlates positively
with the monthly precipitation and negatively with the monthly temperature during the growing season.
There is a more significant relation between tree-ring width and the moisture index (P/T): the
simultaneous influence of precipitation and temperature. The reconstructed equation of the moisture
index from March to August is developed using the tree-ring width, with a correlation coefficient of
0.621, and reaches 0.001 significent level. The reconstructed moisture index shows that there is a
markable change of humid and dryness during recent 100 years, The reconstructed moisture index
lower than average reflects the drought years recorded in historical documents; By constrasting with
other areas, the dry period from 1923 to 1931 is correspondent with the period of high temperature and
low precipitation during the 1920s’ and 1930s’ at Northwest, North China and Yangtze River Basin in
China. Moreover, the humid period from 1939 to 1944 corresponds well with those of Qilianshan
Mountains, the south Plateau of Qinghai and the East Tianshan Mountains, etc, and also with the period
of low temperature and high precipitation after 1940s’ at Northwest, North China and Yangtze River
Basin in China. After primary analysis we conclude that the moisture index within 100 years of
Luoshan records the dry and wet change of Northwest at least and may be close with the climatic
change in large range.
Keywords:tree ring; Luoshan Mountains; Moisture index
0 Introduction
Many studies about environmental changes in recent several hundred years have been done in
desert areas of China. However, most of these studies were not ideal to reflect recent desert
climatic variations because the lower resolution and inherent deficiency of proxies. Tree rings
have advantages of absolute dating and high resolution，and can clearly reflect extreme climatic
events
[1-9]
. Luoshan Mountain, near to the Tengger Desert and the Mu Us Desert, has a large
natural forest and few human disturbances. Based on the tree ring of Pinus tabulaeformis from
Luoshan Mountain, this study provided high resolution climatic changes in the last l00 years,
which is a good complementarity to the basic data of climatic changes in desert area.
1 Study area
Luoshang reserve (Fig. 1) is located in inland, one of the three natural forest regions in
Ningxia. Luoshan is as famous as Helan Mountains and Liupan Mountains. Luoshan vegetation
distributes clearly. With the increasing of altitude, decreasing of temperature and improving of
moisture condition, the vegetation is desert steppe, shrub, broadleaf forest, mixed wood and
coniferous forest in turn. Picea Crassifolia and P. tabulaeformis, as the representative of typical
forest ecosystems, have been protected principally. The forest of Luoshan is the water
conservation forest of central Ningxia and the effective barrier to protect the regional ecological
environment. Luoshan lies in the natural reserve with few disturbs, the sampling site are in
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