Reconstructing the annual precipitation variation since 1899 based on tree-ring width in the western Hedong sandy land of Ningxia

Based on the analysis of the correlation between the tree-ring width of Pinus tabulaeformis and the climate factors in the western Hedong sandy land of Ningxia, a conversion equation between the annual precipitation and the tree-ring width since 1899 was reconstructed. The results of cross verification indicated that the conversion equation is stable and the reconstructed results are reliable. The result of reconstructed annual precipitation showed the remarkable fluctuation of precipitation and dry-to-wet variation before the 1940s. The smaller fluctuation and high frequent changes of precipitation occurred during the period of 1940s-1980s and after the 1980s the change trend of the precipitation became high periodic extent and low frequent. The study found that there were some coincidences with the climate change in Changling Mountains, Helan Mountains and the east of Qilian Mountains. The relatively dry periods in the beginning of 20th century, 1920s to 1930s, the end of the 20th century and 2004 to 2006 in the western Hedong sandy land of Ningxia accelerated the desertification, while the relatively humid period during the periods of the 1910s-1920s, 1930s-1940s and 1990s is favorable to prevent and control the desertification, and to weaken the climate warming and drying. The periods of annual precipitation variation in the western Hedong sandy land of Ningxia since 1899 are approximately 2-4 years, 5-7 years and 10 years.

CHARACTERISTICS OF ZONAL ANOMALY OF ANNUAL PRECIPITATION IN THE NORTHEASTERN CHINA

The characteristics of zonal anomaly and change rule of temporal distribution of annual precipitation in the northeastern China are revealed in this paper with EOF (Empirical Orthogonal Function) and REOF (Rotated Empirical Orthogonal Function) methods and results are drawn in the standard relief maps with GIS technology for practical application. Data used in the study were obtained from 208 meteorological stations over the northeastern China from 1961 to 2001. EOF results show that the first 3 loading vectors could give entire spatial anomaly structure of annual precipitation. In the Northeast Plain including the Songneng Plain and the Liaohe Plain, there is a regional compatibility (whether wet or dry) of annual precipitation change and this precipitation pattern has occurred since the late 1980s to the present. There also exist annual precipitation patterns of wet (or dry) in south and dry (or wet) in north and wet (or dry) in east and dry (or wet) in west. REOF results display 8 principal precipitation anomaly areas by the first 8 rotated loading vectors: the west plain, the Liaodong hills, the Sanjiang Plain, the Liaoxi hills, the Changbai Mountains, the Hulun Buir Plateau, the southwest plateau and the Liaodong Peninsula.

The Application of Superimposed Marcov Chain for Prediction of Annual Precipitation

[Objective] The aim was to predict the annual precipitation using the method of Superimposed Marcov Chain.[Method] Based on annual precipitation in Xiaojin station on western Sichuan Plateau during 1961-2010,the Superimposed Marcov Chain method was applied to predict annual precipitation from 2001 to 2010.The prediction based on the Superimposed Marcov Chain method was compared with the observed data.[Result] For the ten years (2001-2010),the relative error in 7 years was less than 10%,even less than 5% in 4 years,which proved that Superimposed Marcov Chain can predict annual precipitation.But this method had certain defect in prediction in the extreme dry or extreme wet years,and that needs to be improved in the following study.[Conclusion] The Superimposed Marcov Chain method had clear concept,was convenient to calculate,and provided a way to explore the improvement of precipitation prediction.

Study on Correlation between Increment of Larix gmelinii and Annual Precipitation

Through the study on data of analytic tree, the fitting empirical equation for tree growth was obtained, i.e. , the function with increment as variable and annual precipitation as the independent variable. The threshold value of annual precipitation for tree growth was obtained through mathematical operation including derivation. It was concluded that Larix gmelinii grows the fast under the annual precipitation of about 545.1 mm, and negative growth would occur if the annual precipitation is lower than 349 mm and higher than 1 132.8 mm. Furthermore, the application value, research direction and matters needing attention were pointed out.

Simulation of Spatial Distribution of Annual Average Precipitation in Shandong Province

Based on DEM data and conventional data of precipitation at 114 meteorological stations in Shandong Province during 1971 -2010, the statistical model of annual average precipitation in Shandong Province was established using SPSS software; DEM data and raster data of latitude and longitude were substituted into the statistical model, and the spatial distribution of annual average precipitation in Shandong Province based on the statistical model was obtained with the aid of ArcGIS software. Afterwards, the difference between actual value of precipitation at stations used in interpolation and simulated value was interpolated using Kriging interpolation method to obtain residual error of precipitation. Finally, the raster da- ta of annual average precipitation based on the regression model were overlaid with residual error of precipitation to obtain the spatial distribution map of annual average precipitation in Shandong Province. It is verified that the simulation result has high accuracy and can reflect the spatial distri- bution of precipitation in Shandong Province.

Some Annual Variation Characteristics for the Northern Hemispheric Monthly Mean Precipitation Fields

By the utilization of monthly precipitation data from all stations in the Northern Hemisphere annexed to the 'World Survey of climatology, Vol. 1-15', the distributions of the maximum precipitation months (MPM), the annual relative precipitation (ARP) and the monthly relative precipitation (percent of annual) in January and July are respectively mapped. Moreover the distributions of intermonthly relative precipitation variabilities from January to December are plotted as well. From these figures, the precipitation in the Northern Hemisphere may be classified into three types(continental, oceanic and transitional types) and 17 regions. The precipitation regime may also be divided into two patterns, the global and regional patterns. The global pattern consists of planetary front system and ITCZ and its inter-monthly variation shows the north-and-south shift of the rain belt; the regional pattern consists of the sea-land monsoon and plateau monsoon regime, in which the inter-monthly variation of rain belt shows a east-and-wcst shift.

Spatial and temporal relationships between precipitation and ANPP of four types of grasslands in northern China

Precipitation is considered to be the primary resource limiting terrestrial biological activity in water-limited regions. Its overriding effect on the production of grassland is complex. In this paper, field data of 48 sites （including temperate meadow steppe, temperate steppe, temperate desert steppe and alpine meadow） were gathered from 31 published papers and monographs to analyze the relationship between above-ground net primary productivity （ANPP） and precipitation by the method of regression analysis. The results indicated that there was a great difference between spatial pattern and temporal pattern by which precipitation influenced grassland ANPP. Mean annual precipitation （MAP） was the main factor determining spatial distribution of grassland ANPP （r^2 = 0.61, P 〈 0.01）; while temporally, no significant relationship was found between the variance of AN PP and inter-annual precipitation for the four types of grassland. However, after dividing annual preeipitation into monthly value and taking time lag effect into account, the study found significant relationships between ANPP and precipitation. For the temperate meadow steppe, the key variable determining inter-annual change of ANPP was last August-May precipitation （r^2 = 0.47, P = 0.01）; for the temperate steppe, the key variable was July precipitation （r^2 = 0.36, P = 0.02）; for the temperate desert steppe, the key variable was April-June precipitation （r^2 = 0.51, P 〈 0.01）; for the alpine meadow, the key variable was last September-May precipitation （r^2 = 0.29, P 〈 0.05）. In comparison with analogous research, the study demonstrated that the key factor determining inter-annual changes of grassland ANPP was the cumulative precipitation in certain periods of that year or the previous year.

Variation of net primary productivity and its drivers in China’s forests during 2000-2018

Background:Net primary productivity(NPP)in forests plays an important role in the global carbon cycle.However,it is not well known about the increase rate of China’s forest NPP,and there are different opinions about the key factors controlling the variability of forest NPP.Methods:This paper established a statistics-based multiple regression model to estimate forest NPP,using the observed NPP,meteorological and remote sensing data in five major forest ecosystems.The fluctuation values of NPP and environment variables were extracted to identify the key variables influencing the variation of forest NPP by correlation analysis.Results:The long-term trends and annual fluctuations of forest NPP between 2000 and 2018 were examined.The results showed a significant increase in forest NPP for all five forest ecosystems,with an average rise of 5.2 gC·m-2·year-1 over China.Over 90%of the forest area had an increasing NPP range of 0-161 gC·m-2·year-1.Forest NPP had an interannual fluctuation of 50-269 gC.m-2·year-1 for the five major forest ecosystems.The evergreen broadleaf forest had the largest fluctuation.The variability in forest NPP was caused mainly by variations in precipitation,then by temperature fluctuations.Conclusions:All five forest ecosystems in China exhibited a significant increasing NPP along with annual fluctuations evidently during 2000-2018.The variations in China’s forest NPP were controlled mainly by changes in precipitation.

Evaluating the grassland net primary productivity of southern China from 2000 to 2011 using a new climate productivity model

Grassland is the important component of the terrestrial ecosystems. Estimating net primary productivity （NPP） of grassland ecosystem has been a central focus in global climate change researches. To simulate the grassland NPP in southern China, we built a new climate productivity model, and validated the model with the measured data from different years in the past. The results showed that there was a logarithmic correlation between the grassland NPP and the mean annual temperature, and there was a linear positive correlation between the grassland NPP and the annual precipitation in southern China. Al these results reached a very signiifcant level （P〈0.01）. There was a good correlation between the simulated and the measured NPP, withR2 of 0.8027, reaching the very signiifcant level. Meanwhile, both root mean square errors （RMSE） and relative root-mean-square errors （RRMSE） stayed at a relatively low level, showing that the simulation results of the model were reliable. The NPP values in the study area had a decreasing trend from east to west and from south to north, and the mean NPP was 471.62 g C m？2 from 2000 to 2011. Additionaly, there was a rising trend year by year for the mean annual NPP of southern grassland and the tilt rate of the mean annual NPP was 3.49 g C m？2 yr？1 in recent 12 years. The above results provided a new method for grassland NPP estimation in southern China.

Biomass Components and Environmental Controls in Ningxia Grasslands

Grassland plays an important role in the global carbon cycle and climate regulation. However, there are still large uncertainties in grassland carbon pool and also its role in global carbon cycle due to the lack of measured grassland biomass at regional scale or global scale with a unified survey method, particular for below-ground biomass. The present study, based on a total of 44 grassland sampling plots with 220 quadrats across Ningxia, investigated the characteristics of above-ground biomass （AGB）, below-ground biomass （BGB）, litter biomass （LB）, total biomass （TB） and root：shoot ratios （R：S） for six predominantly grassland types, and their relationships with climatic factors. AGB, BGB, LB and TB varied markedly across different grassland types, the median value ranging from 28.2-692.6 g m-2 for AGB, 130.4-2 036.6 g m-： for BGB, 9.2-82.3 g m2 for LB, and 168.0-2 681.3 g m-： for TB. R：S showed less variation with median values from 3.2 to 5.3 （excluding marshy meadow）. The different grassland types showed similar patterns of biomass allocation, with more than 70% BGB for all types. There is evidence of strong positive effects associated with mean annual precipitation （MAP） and negative effects associated with mean annual temperature （MAT） on AGB, BGB, and LB, although both factors have the opposite effect on R：S.

Zonal Differences in Correlation Patterns Between Soil Organic Carbon and Climate Factors at Multi-extent

Studying the relationship between climate factors and soil organic carbon （SOC） is vitally important. However, how SOC responses to climate （temperature and precipitation） at cohesive extents is poorly studied. Two transects of approximately the same length （transect P and transect T） were selected to examine the variation of SOC content in relation to mean annual temperature （MAT） and mean annual precipitation （MAP）. The coefficients of partial correlation between SOC density and MAT （Rt） and MAP （Rp） were determined to quantify the relationships between SOC density and the two climate factors. The results indicated that for transect T, Rt was statistically significant once the extent level was greater than or equal to two fundamental extent units, while for transect P, Rp showed statistical significance only at extent levels which were greater than two fundamental extent traits. At the same extent levels but in different transects, Rts exhibited no zonal difference, but Rps did once the extent level was greater than two fundamental extent units. Therefore, to study the relationship between SOC density and different climate factors, different minimum extent levels should be ex- amined. The results of this paper could deepen the understanding of the impacts that SOC pool has on terrestrial ecosystem and global carbon cycling.

An Improved Markov Chain Model Based on Autocorrelation and Entropy Techniques and Its Application to State Prediction of Water Resources

According to the relationships among state transition probability matrixes with different step lengths, an improved Markov chain model based on autocorrelation and entropy techniques was introduced. In the improved Markov chain model, the state transition probability matrixes can be adjusted. The steps of the historical state of the event, which was significantly related to the future state of the event, were determined by the autocorrelation technique, and the impact weights of the event historical state on the event future state were determined by the entropy technique. The presented model was applied to predicting annual precipitation and annual runoff states, showing that the improved model is of higher precision than those existing Markov chain models, and the determination of the state transition probability matrixes and the weights is more reasonable. The physical concepts of the improved model are distinct, and its computation process is simple and direct, thus, the presented model is sufficiently general to be applicable to the prediction problems in hydrology and water resources.

Responses of phreatophyte transpiration to falling water table in hyper-arid and arid regions,Northwest China

Quantitative assessment of the impact of groundwater depletion on phreatophytes in(hyper-)arid regions is key to sustainable groundwater management.However,a parsimonious model for predicting the response of phreatophytes to a decrease of the water table is lacking.A variable saturated flow model,HYDRUS-1D,was used to numerically assess the influences of depth to the water table(DWT)and mean annual precipitation(MAP)on transpiration of groundwater-dependent vegetation in(hyper-)arid regions of northwest China.An exponential relationship is found for the normalized transpiration(a ratio of transpiration at a certain DWT to transpiration at 1 m depth,T_(a)^(*))with increasing DWT,while a positive linear relationship is identified between T_(a)^(*)and annual precipitation.Sensitivity analysis shows that the model is insensitive to parameters,such as saturated soil hydraulic conductivity and water stress parameters,indicated by an insignificant variation(less than 20%in most cases)under±50%changes of these parameters.Based on these two relationships,a universal model has been developed to predict the response of phreatophyte transpiration to groundwater drawdown for(hyper-)arid regions using MAP only.The estimated T_(a)^(*)from the model is reasonable by comparing with published measured values.

Influence of Climate on Soil Organic Carbon in Chinese Paddy Soils

Soil organic carbon(SOC) is a major component of the global carbon cycle and has a potentially large impact on the greenhouse effect. Paddy soils are important agricultural soils worldwide, especially in Asia. Thus, a better understanding of the relationship between SOC of paddy soils and climate variables is crucial to a robust understanding of the potential effect of climate change on the global carbon cycle. A soil profile data set(n = 1490) from the Second National Soil Survey of China conducted from 1979 to 1994 was used to explore the relationships of SOC density with mean annual temperature(MAT) and mean annual precipitation(MAP) in six soil regions and eight paddy soil subgroups. Results showed that SOC density of paddy soils was negatively correlated with MAT and positively correlated with MAP(P < 0.01). The relationships of SOC density with MAT and MAP were weak and varied among the six soil regions and eight paddy soil subgroups. A preliminary assessment of the response of SOC in Chinese paddy soils to climate indicated that climate could lead to a 13% SOC loss from paddy soils. Compared to other soil regions, paddy soils in Northern China will potentially more sensitive to climate change over the next several decades. Paddy soils in Middle and Lower Yangtze River Basin could be a potential carbon sink. Reducing the climate impact on paddy soil SOC will mitigate the positive feedback loop between SOC release and global climate change.

Mismatch between species distribution and climatic niche optima in relation to functional traits

Background:Forecasts of climate change impacts on biodiversity often assume that the current geographical distributions of species match their niche optima.However,empirical evidence has challenged this assumption,suggesting a mismatch.We examine whether the mismatch is related to functional traits along temperature or precipitation gradients.Methods:The observed distributions of 32 tree species in northeast China were evaluated to test this mismatch.Bayesian models were used to estimate the climatic niche optima,i.e.the habitats where the highest species growth and density can be expected.The mismatch is defined as the difference between the actual species occurrence in an assumed niche optimum and the habitat with the highest probability of species occurrence.Species’functional traits were used to explore the mechanisms that may have caused the mismatches.Results:Contrasting these climatic niche optima with the observed species distributions,we found that the distribution-niche optima mismatch had high variability among species based on temperature and precipitation gradients.However,these mismatches depended on functional traits associated with competition and migration lags only in temperature gradients.Conclusions:We conclude that more relevant research is needed in the future to quantify the mismatch between species distribution and climatic niche optima,which may be crucial for future designs of forested landscapes,species conservation and dynamic forecasting of biodiversity under expected climate change.

The partitioning patterns of nutrients between pods and seeds of Zanthoxylum fruits impacted by environmental factors

The nutritive quality in plant organs is related to the different partitioning patterns of nutrient resources among the organs under various environmental conditions.This study examined the relationship between the nutritive quality of pods and seeds in Zanthoxylum and environmental factors, such as temperature and preciptation by using numerous samples collected from Southwest China to the East China of Shandong peninsula. The increasing accumulations of N, P and C in seeds implied that the nutritive quality in seeds was higher at the regions with relative higher mean annual temperature(MAT) and mean annual precipitation(MAP), while that in pods was on the contrary. By contrast, pod nutritive content was relatively high, but seed nutritive content was relatively low at the regions with relative high MAT and MAP. In addition, C:N ratio in pods was significantly and negatively correlated with MAT and MAP, while that in seed was significantly and positively correlated with MAT and MAP. The partitioning patterns of N-compounds between pods and seeds reflected different nitrogen translocations in the plant organs under various climate condition. The N:P ratios were negatively correlated with MAP, implying a higher proportional allocation of P to seeds than that of N in the areas with a relative high MAP. Therefore, the strategies to assess pod nutritional quality should be taken into accountfor nutritive translocation under various environmental conditions.

Changes in the relationship between species richness and belowground biomass among grassland types and along environmental gradients in Xinjiang, Northwest China

The association between biodiversity and belowground biomass(BGB) remains a central debate in ecology.In this study, we compared the variations in species richness(SR) and BGB as well as their interaction in the top(0–20 cm), middle(20–50 cm) and deep(50–100 cm) soil depths among 8 grassland types(lowland meadow, temperate desert, temperate desert steppe, temperate steppe desert, temperate steppe, temperate meadow steppe, mountain meadow and alpine steppe) and along environmental gradients(elevation, energy condition(annual mean temperature(AMT) and potential evapotranspiration(PET)), and mean annual precipitation(MAP)) based on a 2011–2013 survey of 379 sites in Xinjiang, Northwest China.The SR and BGB varied among the grassland types.The alpine steppe had a medium level of SR but the highest BGB in the top soil depth, whereas the lowland meadow had the lowest SR but the highest BGB in the middle and deep soil depths.The SR and BGB in the different soil depths were tightly associated with elevation, MAP and energy condition;however, the particular forms of trends in SR and BGB depended on environmental factors and soil depths.The relationship between SR and BGB was unimodal in the top soil depth, but SR was positively related with BGB in the middle soil depth.Although elevation, MAP, energy condition and SR had significant effects on BGB, the variations in BGB in the top soil depth were mostly determined by elevation, and those in the middle and deep soil depths were mainly affected by energy condition.These findings highlight the importance of environmental factors in the regulations of SR and BGB as well as their interaction in the grasslands in Xinjiang.

The Annual Modes of Tropical Precipitation Simulated by the LASG/IAP Coupled Ocean-Atmosphere Model FGOALS_s1.1

This paper evaluates the performance of a coupled general circulation model FGOALS_s1.1 developed by LASG/IAP in simulating the annual modes of tropical precipitation.To understand the impacts of air-sea coupling on the annual modes,the result of an off-line simulation of the atmospheric component of FGOALS_s1.1,i.e.,LASG/IAP atmospheric general circulation model SAMIL,is also analyzed.FGOALS_s1.1 can reasonably reproduce major characteristics of the annual mean precipitation.Nonetheless,the coupled model shows overestimation of precipitation over the equatorial Pacific and tropical South Pacific,and underestimation of precipitation over the northern equatorial Pacific.The monsoon mode simulated by FGOALS_s1.1 shows an equatorial anti-symmetric structure,which is consistent with the observation.The bias of the coupled model in simulating monsoon mode resembles that of SAMIL,especially over the subtropics.The main deficiency of FGOALS_s1.1 is its failure in simulating the spring-fall asymmetric mode.This is attributed to the false phase of sea surface temperature anomaly（SSTA） annual cycle over the equatorial central-eastern Pacific and Indian Ocean,which leads to the bias of the Walker circulation over the equatorial Pacific and the anti-Walker circulation over the Indian Ocean in boreal spring and fall.In addition,the domains of the western North Pacific monsoon and Indian monsoon simulated by the coupled model are smaller than the observation.The study suggests that the bias of the fully coupled oceanatmosphere model can only be partly attributed to the bias of the atmospheric component.The performance of FGOALS_s1.1 in simulating the annual cycle of equatorial SST deserves further improvement.

Potassium isotopic signatures of modern offshore detrital sediments from different climatic regimes and the implications

Potassium isotopes are a novel tracer for continental weathering.Previous K isotope studies on chemical weathering generally targeted weathering profiles under a particular climate region,yet the effects of chemical weathering on K isotopes under different climatic backgrounds remain unclear.Moreover,little is known about the K isotope signatures of modern unconsolidated detrital sediments.Here,we report K isotopic data of surficial seafloor sediments from continental shelves along the east coast of China(ECC),as well as those around the tropical Hainan island in the northern South China Sea.The ECC sediments have a relatively narrow distribution ofδ^(41)K(with reference to NIST3141a)values,which range from(-0.40±0.01)‰to(-0.57±0.04)‰,with an average of(-0.51±0.09)‰.By contrast,δ^(41)K values of Hainan offshore sediments display a larger variation,ranging from(-0.28±0.07)‰to(-0.67±0.02)‰.Theδ^(41)K values of Hainan offshore sediments exhibit negative correlations with the chemical index of alteration(CIA),Al/K,Ti/K,and total iron(FeT),which underlines the control of chemical weathering on K isotopic signatures of detritus inputs into oceans.We also measured Mg isotope compositions for the same samples;interestingly,the variability inδ^(26)Mg of the samples is small(~0.24‰)for all ECC and Hainan offshore sediments,andδ^(26)Mg values do not show clear correlations with indexes of chemical weathering.Our study demonstrates the link between K isotopic variability of detrital sediments and climatic conditions including rainfall intensity,which indicates that K isotopes of the detrital component of marine sediments could be applied to study Earth’s climate in deep time.Theδ^(41)K values of the offshore detrital sediments are significantly less variable than those of pelagic marine sediments,highlighting the importance of distinguishing the effects of diagenesis and neoformation of clay minerals from continental weathering in attempts to study deep-time climate-weathering link by K isotopes in detrital sedimentary records.

STABILITY AND POTENTIAL PREDICTABILITY OF ANNUAL PERCIPITATION OVER CHINA

The precipitation is a primary element which directly affects the agricultural production of the country with one fifth of the world population.With the economic development the water resource stress is getting greater.In this paper,based on the data at 162 stations selected evenly over China from 1960 to 1991 the stability and potential predictability of annual precipitation have been stud- ied.The eastern and southern parts of the country having abundant precipitation enjoy more stable precipitation.The north and northwest parts of the country where the precipitations are deficient have unstable precipitations.The potential predictability approximates to the ratio of the estimated interannual variance to the climatic noise.Generally the annual precipitation over China is poten- tially predictable.In the area between the Huanghe River and Changjiang River and the east of northeastern China the potential predictability is the lowest in the country.In the north and north- west of the country the potential predictability is greater.The southeastern coast has relatively low values of potential predictability.Also,the method of estimating climatic noise of annual precipita- tion has been discussed from the idea of Yamamoto et al.(1985)in order to estimate the potential predictability.