Climate Change Impacts and Adaptation Strategies in Northwest China

Climate change resulted in changes in crop growth duration and planting structure,northward movement of planting region,and more severe plant diseases and insect pests in Northwest China.It caused earlier seeding for spring crop,later seeding for autumn crop,accelerated crop growth,and reduced mortality for winter crop.To adapt to climate change,measures such as optimization of agricultural arrangement,adjustment of planting structure,expansion of thermophilic crops,and development of water-saving agriculture have been taken.Damaging consequences of imbalance between grassland and livestock were enhanced.The deterioration trend of grassland was intensified;both grass quantity and quality declined.With overgrazing,proportions of inferior grass,weeds and poisonous weeds increased in plateau pastoral areas.Returning farmland to grazing,returning grazing to grassland,fence enclosure and artificial grassland construction have been implemented to restore the grassland vegetation,to increase the grassland coverage,to reasonably control the livestock carrying capacity,to prevent overgrazing,to keep balance between grassland and livestock,and to develop the ecological animal husbandry.In Northwest China,because the amount of regional water resources had an overall decreasing trend,there was a continuous expansion in the regional land desertification,and soil erosion was very serious.A series of measures,such as development of artificial precipitation(snow),water resources control,regional water diversion,water storage project and so on,were used effectively to respond to water deficit.It had played a certain role in controlling soil erosion by natural forest protection and returning farmland to forest and grassland.In the early21st century,noticeable achievements had been made in prevention and control of desertification in Northwest China.The regional ecological environment has been improved obviously,and the desertification trend has shown sign of under control.

Regional features of the temperature trend in China based on Empirical Mode Decomposition

By the Empirical Mode Decomposition method, we analyzed the observed monthly average temperature in more than 700 stations from 1951-2001 over China. Simultaneously, the temperature variability of each station is calculated by this method, and classification chart of long term trend and temperature variability distributing chart of China are obtained, supported by GIS, 1 kmxl km resolution. The results show that： in recent 50 years, the temperature has increased by more than 0.4~C/10a in most parts of northern China, while in Southwest China and the middle and lower Yangtze Valley, the increase is not significant. The areas with a negative temperature change rate are distributed sporadically in Southwest China. Meanwhile, the temperature data from 1881 to 2001 in nine study regions in China are also analyzed, indicating that in the past 100 years, the temperature has been increasing all the way in Northeast China, North China, South China, Northwest China and Xinjiang and declining in Southwest China. An inverse ‘V-shaped’ trend is also found in Central China. But in Tibet the change is less significant.

Structural Variation of an Atmospheric Heat Source over the Qinghai-Xizang Plateau and Its Influence on Precipitation in Northwest China

NCEP/NCAR reanalysis data and a 47-year precipitation dataset are utilized to analyze the relationship between an atmospheric heat source （hereafter called 〈 Q1 〉） over the Qinghai-Xizang Plateau （QXP） and its surrounding area and precipitation in northwest China. Our main conclusions are as follows： （1） The horizontal distribution of 〈 Q1 〉 and its changing trend are dramatic over QXP in the summer. There are three strong centers of 〈 Q1 〉 over the south side of QXP with obvious differences in the amount of yearly precipitation and the number of heat sinks predominate in the arid and semi-arid regions of northwest China （NWC）, beside the northern QXP with an obvious higher intensity in years with less precipitation. （2） In the summer, the variation of the heat source＇s vertical structure is obviously different between greater and lesser precipitation years in eastern northwest China （ENWC）. The narrow heat sink belt forms between the northeast QXP and the southwestern part of Lake Baikal. In July and August of greater precipitation years, the heating center of the eastern QXP stays nearly over 35°N, and at 400 hPa of the eastern QXP, the strong upward motion of the heating center constructs a closed secondary vertical circulation cell over the northeast QXP （40~ 46~N）, which is propitious to add precipitation over the ENWC. Otherwise, the heating center shifts to the south of 30°N and disappears in July and August of lesser precipitation years, an opposite secondary circulation cell forms over the northeast QXP, which is a disadvantage for precipitation. Meanwhile, the secondary circulation cell in years with more or less precipitation over the ENWC is also related to the heat source over the Lake Baikal. （3） The vertical structure of the heat source over the western QXP has obvious differences between greater and lesser precipitation years in western northwest China in June and July. The strong/weak heat source over the western QXP produces relatively strong/weak ascending motion and correspondingly constructs a secondary circulation cell in lesser/greater precipitation years.

Study on potential evapotranspiration and wet-dry condition in the seasonal frozen soil region of northern Tibetan Plateau

This study was based on the CEOP/CAMP-Tibet observed data at AWS （Automatic Weather Station） of MS3478 in the seasonal frozen soil region of northern Tibetan Plateau from March 2007 to February 2008. The variation characteristics of PE （potential evapotransph＇ation） were analyzed based on the Penman-Monteith method recommended by FAO （the Food and Agriculture Organization of the United Na- lions）. The contributions of dynamic, thermal and water factors to PE were discussed, and the wet-dry condition of the plateau region was further studied. The results indicated that daily PE was between 0.52 mm and 6.46 mm for the whole year. Monthly PE was over 107 mm from May to September, but decreased to less than 41 mm from November to February. Annual PE was 1,037.8mm. In the summer, thermal PE was significantly more than dynamic PE, but conversely in the winter. Annual variation of thermal PE was of sine wave pattern. In addition, drought and semi-drought climate lasted for a long time while semi-humid climate was short. The effect of water and dynamic factors on PE varied considerably with the seasons. Annual variation of thermal PE was of sine wave pattern.

Relationship between Temperature Variation in Winter of China and Arctic Oscillation

[Objective] The study aimed to discuss the relationship between temperature variation in winter of China and arctic oscillation. [Method] By using the NCEP/NCAR reanalysis data, AO index series and monthly temperature data from 160 stations of China, the variation characteris- tics of temperature in winter and AO index series as well as their relationship from 1951 to 2007 were studied. [Result] Temperature in winter of Chi- na correlated positively with AO index series. Both arctic oscillation and winter temperature in China had two major periods of 8 and 18 years. ⅠWTr and ⅠAO series, which had obvious inter-annual and inter-decadal variations, presented the almost same rising trend and had close relationship on an inter-decadal scale. Compared with AO, the Siberia high had more distinguished influences on inter-annual variations of temperature in winter of China. AO might affect changes in the Siberian high and thereby influence temperature in winter of China. AO had a greater influence on tempera- ture in winter of China than the Siberia high on an inter-decadal scale. When the East Asian through was weak, temperature in winter of China and AO index were low, while they were high as it was strong. The impact of AO index on an inter-decadal scale was more significant than the impact on an inter-annual scale. [ Condusien] The research could make the effects of AO on winter temperature of China clear.

Characteristics of Wind Speed Profiles under Complex Terrain Conditions in Loess Plateau

To reveal the changing characteristics of wind speed with altitude in under complex terrain conditions in Loess Plateau in Northern Shaanxi, based on the complete data of wind speed profiles of six wind towers in the region in a year, the diurnal, monthly, and seasonal variations of wind shear index of the wind towers as well as the changes of wind shear index with wind speed under complex terrain conditions were studied. The results showed that the wind shear index of each wind tower was positive, showing that wind speed tended to increase with the rising of altitude in most areas of Loess Plateau in Northern Shaanxi; terrain had obvious effects on wind speed profiles. The wind shear index of the wind towers was small during the day and large at night; the differences between day and night in the wind shear index of various wind towers were different; there were obvious seasonal variations in the wind shear index of the wind towers under different terrain conditions. With the increase of wind speed, the wind shear index of each wind tower increased firstly and then decreased, but the peaks of wind shear index of various wind towers ap- peared in different wind speed ranges. When wind speed varied from 3 to 12 m/s, wind shear index was larger than the comprehensive wind shear index of the wind towers, which is beneficial to the improvement of power generation of a wind power plant. Wind shear index can be used to assess wind resources of a wind power plant.

Current Situation and Evolution of Drought and Flood in Fen-wei Plain

Based on the latest results and data of drought and flood in Fen-wei Plain, current situation and evolution of drought and flood in Fen-wei Plain were analyzed. The results show that in Fen-wei Plain drought and flood are natural disasters bringing about the most serious damage, and drought risk in east central Weihe Plain is serious. In Fen-wei Plain, precipitation tended to decrease, and temperature, drought days and intensity increased over the past 50 years. There were obvious differences between two decades in drought and flood. Drought was the severest in the 1990s, and flood was the most serious in Fenhe Plain in the 1960s and in Weihe Plain from the late 1970s to the early 1980s. Over the past ten years, precipitation and flood frequency increased, and temperature, drought days and intensity decreased. In Fen-wei Plain, temperature will rise and precipitation will increase slightly in next 20 -40 years. Monitoring and early warning capability of drought and flood in Fen-wei Plain have im- proved gradually, but some issues need to be paid more attention to and solved.

Statistical Reconstruction of the Antarctic Oscillation Index Based on Multiple Proxies

Based on multiple proxies from the Southern Hemisphere, an austral summer (December-January-February: DJF) Antarctic Oscillation Index (AAO) since 1500 A.D. was reconstructed with a focus on interannual to interdecadal variability (<50 a). By applying a multivariate regression method, the observational AAO-proxy relations were calibrated and cross-validated for the period of 1957 89. The regressions were employed to compute the DJF-AAO index for 1500 1956. To verify the results, the authors checked the explained variance (r 2 ), the reduction of error (RE), and the standard error (SE). Cross-validation was performed by applying a leave-one-out validation method. Over the entire reconstruction period, the mean values of r 2 , RE, and SE are 59.9%, 0.47, and 0.67, respectively. These statistics indicate that the DJF-AAO reconstruction is relatively skillful and reliable for the last ～460 years. The reconstructed AAO variations on the interannual and interdecadal timescales compare favorably with those of several shorter sea level pressure (SLP)-based AAO indices. The leading periods of the DJF-AAO index over the last 500 years are ～2.4, ～2.6, ～6.3, ～24.1, and ～37.6 years, all of which are significant at the 95% level as estimated by power spectral analysis.

Modeling habitat distribution of Cornus officinalis with Maxent modeling and fuzzy logics in China

Aims Predicting suitable habitat distribution is an effective way to protect rare or endangered medicinal plants.Cornus officinalis is a perennial tree growing in forest edge and its air-dried pericarp is one of the traditional Chinese medicines(TCM)with significant medicinal values.In recent years,C.officinalis has undergone severe degeneration of its natural habitat owing to growing market demands and unprecedented damage to the forests.Moreover,the degeneration of suitable habitat has threatened the supply of medicinal materials,and even led to the extinction of some engendered medicinal plant species.In this case,there is a great risk to introduce and cultivate medicinal plants if planners determine the suitable cultivation regions based on personal subjective experience alone.Therefore,predicting suitable potential habitat distribution of medicinal plants(e.g.C.officinalis)and revealing the environmental factors determining such distribution patterns are important to habitat conservation and environmental restoration.Methods In this article,we report the results of a study on the habitat distribution of C.officinalis using maximum entropy(Maxent)modeling and fuzzy logics together with loganin content and environmental variables.The localities of 106 C.officinalis in China were collected by our group and other researchers and used as occurrence data.The loganin content of 234 C.officinalis germplasm resources were tested by high-performance liquid chromatography(HPLC)and used as content data.79 environmental variables were selected and processed with multicollinearity test by using Pearson Correlation Coefficient(r)to determine a set of independent variables.The chosen variables were then processed in the fuzzy linear model according to the cell values(maximum,minimum)of localities with estimated loganin content.The SDMtoolbox was used to spatially rarefy occurrence data and prepare bias files.Furthermore,combined Maxent modeling and fuzzy logics were used to predict the suitable habitat of C.officinalis.The modeling result was validated using null-model method.Important Findings As a result,six environmental factors including tmin3,prec3,bio4,alt,bio12 and bio3 were determined as key influential factors that mostly affected both the habitat suitability and active ingredient of C.officinalis.The highly suitable regions of C.officinalis mainly distribute in a‘core distribution zone’of the east-central China.The statistically significant AUC value indicated that combined Maxent modeling and fuzzy logics could be used to predict the suitable habitat distribution of medicinal plants.Furthermore,our results confirm that ecological factors played critical roles in assessing suitable geographical regions as well as active ingredient of plants,highlighting the need for effective habitat rehabilitation and resource conservation.