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Study of impacts of land uses on spatiotemporal dynamics of soil water content (SWC) is of great significance for understanding the performance characteristics of regional water cycling under changing environment. Based on long-term located field observations, this paper explored the temporal dynamics of soil water in 0-15 m soil profile under four land use types on the Loess Tableland from September 2012 to December 2015. Results showed that the annually averaged SWCs over the 0-15 m soil profile for alfalfa field, fallow field, fertilized cropland and unfertilized cropland were 15.1%, 22.0%, 19.6% and 21.1%, respectively. Soil water contents along the shallow soil profile exhibited seasonal and annual wetting and drying cycle from March to June and July to October, and the profile depths were 0-2, 0-4.6, 0-3 and 0-4.2 m, respectively. Soil water contents along the deep soil profiles had better temporal stability and were influenced by land-use types. Du-ring the observation years, the yield and water consumption in alfalfa field increased, which caused the increase of deep soil desiccation, the 2-10 m soil profile had become stable dry layer, blocking the way of precipitation recharge.As for the soil water balance in other three land use types, it was negative in cropland and fallow field during winter wheat growing season, however, during spring maize growing season, it was negative in fertilized cropland but positive in unfertilized cropland and fallow field. During the fallow period, it was positive in the three land use types. The crop water use efficiency in the fertilized cropland was increased by more than 3 times than the unfertilized cropland.

The analysis of the characteristics and footprint climatology of farmland water and heat fluxes has great significance to strengthen regional climate resource management and improve the hydrothermal resource utilization in the region of red soil. Based on quality controlled data from large aperture scintillometer and automatic meteorological station in hilly region of red soil, this paper analyzed in detail the characteristics of farmland water and heat fluxes at different temporal scales and the corresponding source area distribution of flux measurement in the non-rainy season and crop growth period in hilly region of red soil. The results showed that the diurnal variation of water and heat fluxes showed a unimodal trend, but compared with the sunny day, the diurnal variation curves fluctuated more complicatedly on cloudy day. In the whole, either ten-day periods or month scale, the water and heat fluxes were greater in August than in September, while the net radiation flux was more distributed to latent heat exchange. The proportion of net radiation to latent heat flux decreased in September compared to August, but the sensible heat flux was vice versa. With combined effects of weather conditions (particularly wind), stability, and surface condition, the source areas of flux measurement at different temporal scales showed different distribution characteristics. Combined with the underlying surface crops, the source areas at different temporal scales also had different contribution sources.

This paper proposed a vegetation health index (VHI) to rapidly monitor and assess vegetation health status in soil and water loss region based on remote sensing techniques and WorldView-2 imagery. VHI was constructed by three factors, i.e., the normalized mountain vegetation index, the nitrogen reflectance index and the reflectance of the yellow band, through the principal component transformation, in order to avoid the deviation induced by subjective method of weighted summation. The Hetian Basin of Changting County in Fujian Province, China, was taken as a test area to assess the vegetation health status in soil and water loss region using VHI. The results showed that the VHI could detect vegetation health status with a total accuracy of 91%. The vegetation of Hetian Basin in good, moderate and poor health status accounted for 10.1%, 49.2% and 40.7%, respectively. The vegetation of the study area was still under an unhealthy status because the soil was poor and the growth of newly planted vegetation was not good in the soil and water loss region.

In order to monitor soil water and salt content of saline soil conveniently and quickly, this paper took the typical salinization irrigation district of Xinjiang as the research object, obtained the spectral curve of soil water and salt content by using portable spectrometers based on the hyperspectral technology, transformed the original spectra of soil using the first order differential, second order differential and continuum removal methods. The results showed that the transformation of the original spectral data was beneficial to fingerprint band extraction of soil properties, and the method was not same in soils with different textures. In loam soil, continuum removal analysis was the best method for extraction of characteristic bands when the soil water content was 0% and 10%, first order differential equations were the best method when the soil water content was 15%, and second order differential equations were the best method when the soil water content was 19%. In sandy soil, continuum removal analysis was the best method for extraction of characteristic bands when the soil water content was 0%, whereas second order differential equations were the best method when soil water content was 10%, 15% or 19%. The transformed data were screened for inversion models of soil water and salt content by using the partial least squares regression method. When thesalinity was < 6.38 mS·cm -1 in loam soil and < 5.94 mS·cm -1 in sandy soil, the decision coefficients (R cal 2 ), internal cross validation (R cv ) were greater than 0.65 (P<0.05). When the soil moisture content was less than 16% in loam soil and 12% in sandy soil, the inversion accuracy of model was higher. The results would provide a reference threshold for si-multaneously monitoring soil water and salt content in salinized areas.2 ), and external validation (R val 2 ) were greater than 0.65 (P<0.05). When the soil moisture content was less than 16% in loam soil and 12% in sandy soil, the inversion accuracy of model was higher. The results would provide a reference threshold for si-multaneously monitoring soil water and salt content in salinized areas.

Land use change has an important role in hydrological processes and utilization of water resources, and is the main driving force of water yield function of ecosystem. This paper analyzed the change of land use from 1990 to 2013 in Nansi Lake Basin, Shandong Province. The future land use in 2030 was also predicted and simulated by CLUE-S model. Based on land use scenarios, we analyzed the influence of land use change on ecosystem function of water yield in nearly 25 years through InVEST water yield model and spatial mapping. The results showed that the area of construction land increased by 3.5% in 2013 because of burgeoning urbanization process, but farmland area decreased by 2.4% which was conversed to construction land mostly. The simulated result of InVEST model suggested that water yield level of whole basin decreased firstly and increased subsequently during last 25 years and peaked at 232.1 mm in 2013. The construction land area would increase by 6.7% in 2030 based on the land use scenarios of fast urbanization, which would lead to a remarkable growth for water yield and risk of flowing flooding. However, the water yield level of whole basin would decrease by 1.2 % in 2013 if 300 meter-wide forest buffer strips around Nansi Lake were built up.

Soil moisture is an important component of the soil-vegetation-atmosphere continuum (SPAC). It is a key factor to determine the water status of terrestrial ecosystems, and is also the main source of water supply for crops. In order to estimate soil moisture at different soil depths at a station scale, based on the energy balance equation and the water deficit index (WDI), a soil moisture estimation model was established in terms of the remote sensing data (the normalized difference vegetation index and surface temperature) and air temperature. The soil moisture estimation model was validated based on the data from the drought process experiment of summer maize (Zea mays) responding to different irrigation treatments carried out during 2014 at Gucheng eco-agrometeorological experimental station of China Meteorological Administration. The results indicated that the soil moisture estimation model developed in this paper was able to evaluate soil relative humidity at different soil depths in the summer maize field, and the hypothesis was reasonable that evapotranspiration deficit ratio (i.e., WDI) linearly depended on soil relative humidity. It showed that the estimation accuracy of 0-10 cm surface soil moisture was the highest (R 2 =0.90). The RMAEs of the estimated and measured soil relative humidity in deeper soil layers (up to 50 cm) were less than 15% and the RMSEs were less than 20%. The research could provide reference for drought monitoring and irrigation management.

The precipitation exiguity and water deficiency are the major factors limiting crop growth in dry farming regions of northern China. Dual-mulching of ridges and furrows, which have been widely concerned both domestically and internationally, could increase the utilization efficiency of precipitation and crop yield. In this paper, we reviewed the concept and model of dual-mulching of ridges and furrows, its supporting farm machinery and implements as well as its ecological effects on soil and crops. Based on the current research progress of cultivation techniques using harvested rainfall in ridge and furrow, priority of future research aspects of the dual-mulching of ridges and furrows were suggested as follows: 1) to establish the suitable ridge-furrow ratios for different crops in different types of dry farming regions of northern China; 2) to pay more attention to the study of coupling effects of soil moisture with temperature, fertility and other factors; 3) to explore better environment-friendly mulching materials; 4) to enhance the research on technical evaluation and popularization, and the design of supporting farm machinery and implements.

Based on the data of soil moisture content and indoor soil surface spectral reflectance from five sampling sites of coastal saline soil, this paper analyzed the relationship between soil moisture content and soil spectrum in wavelength 350-2500 nm. We determined spectral parameters under ratio spectral index (RSI), normalized difference spectral index (NDSI) and difference spectral index (DI), and established the quantitative model of soil moisture content. The results showed significant negative correlation between spectral reflectance and soil moisture content, and the maximum negative correlation was near 1930 nm (r=0.86). By comparison of the regression equation of RSI, NDSI and DI, it was found that the regression equation of exponential function (y=0.00001e9.7203x) built by soil moisture content based on RSI (R1407, R1459) presented the maximum R2 (0.780) and the minimum SE (0.016). The established model based on RSI (R1407, R1459) could be used to monitor soil moisture content accurately in Jiangsu coastal saline soils.

This paper investigated soil moisture in alfalfa (Medicago sativa) cropland with different growth years (1, 3, 8, 12 and 14 years) and discussed the optimum growth years of alfalfa on the Loess Plateau of central Gansu. The results showed that the soil moisture along 0-300 cm soil profile of alfalfa croplands with different growth years was obviously lower than that of the local soil stable moisture. The soil water contents in croplands with alfalfa that had grown for 12 and 14 years were only 9.2% and 7.1% of local soil stable moisture, respectively, which were even lower than the lower limit of alfalfa growth. The average soil dryness indexes along 0-300 cm soil profile in 1, 3, 8, 12 and 14 years alfalfa croplands were 125.4%, 30.5%, 18.4%, -34.2% and -83.3% respectively. The results indicated that soil dryness occurred to varying degrees with different growth years except croplands with alfalfa grown for 1 year. With the increase of growth years of alfalfa, the soil dryness intensity increased and the soil dryness rate decreased. According to the soil moisture and alfalfa productivity results in this study, it could be concluded that the optimum growth years of alfalfa are 8-10 years in semiarid areas of the Loess Plateau.

Interaction between carbon and water in forest ecosystem is a coupling process in terrestrial ecosystem, which is an indispensable aspect for the study of forest carbon pool, ecohydrological processes and the responses to global change. In the context of global change, the interaction and coupling of carbon and water in forest ecosystem has attracted much attention among scientists. In this paper, we reviewed the process mechanism of forest carbon and water relationships based on previous studies, which consisted of advance in forest water use efficiency, carbon and water interactions at different scales, scaling, and model simulation. We summed up the factors affecting for- est water and carbon interaction, including water condition, carbon dioxide enrichment, warming, nitrogen deposition, ozone concentration variation, solar radiation, and altitudinal gradients. Finally, we discussed the problems in the previous studies, and prospected the possible future research fields, among which we thought the inherent dynamics mechanism and scaling of forest carbon and water interactions should be enhanced.

In this paper, the spring wheat (cv. Xihan No. 2) was taken as research material to investigate the dynamic changes of the non-structural carbohydrates (NSC) in flag leaves, stems and leaf sheaths and activities of carbon-metabolizing enzymes (SSS, GBSS) in grains during wheat development process under various water stresses by water stress and re-watering treatment methods. The results indicated that various water stresses had no significant effects on the sucrose contents in flag leaves, stems, leaf sheaths and other organs of wheat. With the increase of water stress, the content of starch in flag leaves was significantly increased within 12-18 d after flowering. Water stress shortened the starch accumulation period in stems and sheaths after flowering and inhibited the transformation and distribution of starch in wheat stems. The accumulation of starch in sheath also gradually increased, which was early terminated under moderate water stress. At the beginning of the water stress, the contents of NSC in vegetative organs were listed as: flag leaves > stems > leaf sheaths. With the increase of water stresses, the NSC contents in vegetative organs were listed as: stems > flag leaves > leaf sheaths. We could conclude that the changes in main NSC (sugar, starch) distribution and carbon-metabolism enzyme activities was a kind of physiological regulation response of wheat to water stresses.

Melt water erosion is one of the important soil erosion forms caused by the melt water from glacier and snow in high altitude cold areas of China. This paper investigated the influencing factors of deposition caused by melt water erosion in Naqu region. Alluvial fan ratio was presented as an index to characterize the degree of the deposition induced by melt water erosion. Minimum polygon was determined based on spatial overlay technology of Geographic Information System (GIS). The regression equation between the deposition index and the influencing factors was established through the stepwise regression analysis based on minimum polygon. Key influencing factors were identified according to the stepwise regression equation. The results showed that large amounts of alluvial fan were observed in Naqu region; extensive alluvial fans were centered at gentle slope areas in the central part of Naqu region with great spatial differences; alluvial fans were mainly distributed at valley exits, most of which were at large scale with vast differences in area and thickness. Wind speed, normalized difference vegetation index (NDVI), K value of soil erodibility, annual temperature range and the steep slope area ratio were identified as the key influencing factors on the deposition induced by melt water erosion in the studied area. Index of deposition was positively correlated with the wind speed and NDVI, and showed negative relationships with the K value of soil erodibility, the annual temperature range and steep slope area ratio.

Making clear the effects of biochar addition on soil water infiltration process can provide the scientific basis for the evaluation of the influence of biochar application on soil hydrology in semi-arid region. In this paper, through the soil column simulation method in laboratory, the effects of biochar of three sizes (1-2 mm, 0.25-1 mm and ≤ 0.25 mm) at 4 doses (10, 50, 100 and 150 g x kg(-1)) on the cumulative infiltration, the permeability and the stable infiltration rate of two different soils (anthrosol and aeolian sandy soil) were studied. The results showed that the infiltration capacity of the anthrosol was obviously increased compared to the control, however, the one in the aeolian sandy soil was decreased due to the biochar addition. At 100 minutes after infiltration starting, the averaged cumulative infiltration was increased by 25.1% in the anthrosol with comparison to the control. Contrarily, the averaged cumulative infiltration was decreased by 11.1% in the aeolian sandy soil at 15 minutes after infiltration starting. When the dose was the same, biochar with different particle sizes improved the infiltration for the anthrosol, but for the different dose treatments, the particle size of biochar which showed the greatest improvement was different. As for the aeolian sandy soil, the infiltration increased at the dose of 10 g x kg(-1) after the addition of biochar with different particle sizes, while decreased at the higher dose of 50, 100 and 150 g x kg(-1). The cumulative infiltration of the aeolian sandy soil was decreased with the increase in addition amount of biochar with the same particle size, while it was not so for the anthrosol. The determination coefficient fitted by the Philip infiltration model ranged from 0.965 to 0.999, suggesting this model was suitable for the simulation of soil water infiltration process after biochar application. Statistical analysis of main effects showed that the biochar particle size, the biochar addition amount, and the interactive effect had statistically significant effect on the soil permeability and stable infiltration rate in the two soils. In conclusion, the biochar had different effects on the soils with different textures, moreover, there was a positive correlation relationship between the impact and the addition amount.

Canadian fire weather index system (FWI) is the most widely used fire weather index system in the world. Its fuel moisture prediction is also a very important research method. In this paper, litter moisture contents of typical forest types in Tahe Forestry Bureau of Northeast China were successively observed and the relationships between FWI codes (fine fuel moisture code FFMC, duff moisture code DMC and drought code DC) and fuel moisture were analyzed. Results showed that the mean absolute error and the mean relative error of models.established using FWI moisture code FFMC was 14.9% and 70.7%, respectively, being lower than those of meteorological elements regression model, which indicated that FWI codes had some advantage in predicting litter moisture contents and could be used to predict fuel moisture contents. But the advantage was limited, and further calibration was still needed, especially in modification of FWI codes after rainfall.

Wind and water are the two dominant erosion agents that caused soil and water losses in the wind-water alternate erosion region on the Loess Plateau. It is meaningful to study the impact of wind-water alternate erosion on the characteristics of soil particles for understanding the response of soil quality and environment to erosion. Through wind tunnel combined rainfall simulation, this paper studied the characteristics of the erosive sediment particles under the effect of wind-water alternate erosion. The results showed that the particles of 0-1 cm soil were coarsened by wind erosion at the wind speeds of 11 and 14 m x s(-1) compared with no wind erosion. Soil fine particles (< 0.01 mm) decreased by 9.8%-10.8%, and coarse particles (> 0.05 mm) increased by 16.8%-20.8%. The physical property of surface soil was changed by the wind erosion, which, in turn, caused an increase in finer particles content in the sediment. Compared with no wind erosion, fine particles (< 0.01 mm) in sediment under the water-wind alternate erosion increased by 2.7%-18.9% , and coarse particles (> 0.05 mm) decreased by 3.7%-9.3%. However, the changing trend of erosive sediment particles after the wind erosion at wind speeds of 11 and 14 m x s(-1) was different along with the rainfall intensity and duration. The erosive sediment particles at the rainfall intensities of 60, 80, 100 mm x h(-1) changed to greater extents than at the 150 mm x h(-1) rainfall intensity with longer than 15 min runoff flowing.

Soil moisture products derived from microwave remote sensing data are commonly used in the studies of large-scale water resources or climate change. However, the spatial resolutions of these products are usually too coarse to be used in regional- or watershed-scale studies. Therefore, it is necessary to spatially downscale the coarse-resolution soil moisture products for use in regional- or watershed-scale studies. The UCLA method is one of the methods for spatially downscaling soil moisture products. In this method, the spatial indices (Ts/VI indices) calculated from land surface temperature and vegetation index are used as auxiliary variables for spatial downscaling. In this paper, we compared the performance of the UCLA method for spatially downscaling the coarse-resolution AMSR-E soil moisture products, using three Ts/VI indices as auxiliary variables, i. e., the soil wetness index (SW), temperature vegetation dryness index (TVDI), and vegetation temperature condition index (VTCI). These auxiliary variables were calculated from the products of MODIS land surface temperature (MYD11A1) and MODIS vegetation index (MYD13A2). The downscaled results using the three Ts/VI indices were all reasonable. However, the downscaled results using TVDI and VTCI were better than using SW. Therefore, we concluded that TVDI and VTCI are more suitable than SW to be used as the auxiliary variable when applying the UCLA method for downscaling soil moisture products. Finally, we discussed the error sources of applying the UCLA method, such as measurement errors of coarse resolution soil products, calculation errors from spatial indices, and errors from the UCLA method itself, and we also discussed the potential improvements of future research.

Weedy rice is an important germplasm source of rice, which has the characteristics of cold-, drought-, and barren tolerance. Taking 88 accessions of weedy rice and 4 varieties of cultivated rice in northern China as test materials, this paper studied the photosynthetic characteristics (photosynthetic rate, transpiration rate, and stomatal conductance), water physiological characteristics, and their interrelationships of weedy rice in northern China. There existed greater differences in the photosynthetic and water physiological characteristics among the weedy rice accessions, possessing abundant diversity. The photosynthetic rate of the accessions was from 12.47 micromol CO2 x m(-2) x s(-1) to 28.67 micromol CO2 X m(-2) x s(-1), and the instantaneous water use efficiency was from 1.39 mg x g(-1) to 3.40 mg x g(-1). Among the photosynthetic parameters, intercellular CO2 concentration had the smallest variable coefficient, while stomatal conductance had the largest one. The photosynthetic rate had significant conic relationships with transpiration rate and stomatal conductance, and had a linear relationship with intercellular CO2 concentration. The significant conic relationships also existed between the instantaneous water use efficiency and the transpiration rate and stomatal conductance. The excellent features of weedy rice could be used to improve the cultivated rice varieties.

This paper studied the effects of different mulching modes on the soil moisture in a semi-arid rainfed area of Loess Plateau, Northwest China. Seven treatments were installed, i. e., mulching plastic film in summer (T1), mulching plastic film in autumn (T2), mulching 5 cm long wheat straw in summer (T3), mulching whole wheat straw in summer (T4), mulching plastic film in summer plus wheat straw (T5), mulching used plastic film after harvest (T6), and un-mulching (CK). In T6, the soil moisture in different layers at different crop growth stages was all higher than that in CK. In the other five mulching treatments, the soil moisture in 0-90 cm layer before flowering stage was obviously higher, but that in 0-90 cm layer after flowering stage and in 90-200 cm layer during the whole growth season was lower than that of CK. The soil moisture in 0-200 cm layer in T6 during the whole growth period was significantly higher than that in CK, with a difference of 0.9%, but the soil moisture in 0-200 cm layer in other mulching treatments was lower. As compared with plastic film mulching, straw mulching increased the soil moisture in 0-200 cm layer. The soil moisture under mulching with used plastic film after harvest was higher than that under mulching with new plastic film. As compared to CK, the grain yield of winter wheat with plastic film mulching was increased by 20.3%-29.0%, and that With straw mulching was increased by 5.0%-16.7%. There was a significant positive correlation between the crop productivity and the soil water consumption during the growth period (r = 0.77*).

Model simulation and in situ observation are the two most important means in studying the water and carbon cycles of terrestrial ecosystems, but have their own advantages and shortcomings. To combine these two means would help to reflect the dynamic changes of ecosystem water and carbon fluxes more accurately. Data assimilation provides an effective way to integrate the model simulation and in situ observation. Based on the observation data from the Harvard Forest Environmental Monitoring Site (EMS), and by using ensemble Kalman Filter algorithm, this paper assimilated the field measured LAI and remote sensing LAI into the Biome-BGC model to simulate the water and carbon fluxes in Harvard forest area. As compared with the original model simulated without data assimilation, the improved Biome-BGC model with the assimilation of the field measured LAI in 1998, 1999, and 2006 increased the coefficient of determination R2 between model simulation and flux observation for the net ecosystem exchange (NEE) and evapotranspiration by 8.4% and 10.6%, decreased the sum of absolute error (SAE) and root mean square error (RMSE) of NEE by 17.7% and 21.2%, and decreased the SAE and RMSE of the evapotranspiration by 26. 8% and 28.3%, respectively. After assimilated the MODIS LAI products of 2000-2004 into the improved Biome-BGC model, the R2 between simulated and observed results of NEE and evapotranspiration was increased by 7.8% and 4.7%, the SAE and RMSE of NEE were decreased by 21.9% and 26.3%, and the SAE and RMSE of evapotranspiration were decreased by 24.5% and 25.5%, respectively. It was suggested that the simulation accuracy of ecosystem water and carbon fluxes could be effectively improved if the field measured LAI or remote sensing LAI was integrated into the model.

Based on the 1959-2008 meteorological data from 249 meteorological stations in southern China, and by using crop water deficit index (CWDI) as the agricultural drought index, this paper calculated the drought frequency and drought stations ratio in this region, and analyzed the spatiotemporal distribution characteristics of drought for spring maize and summer maize during their growth periods. As for the spatial pattern of drought frequency, the drought for spring maize was more severe in the north of Huaihe River, northern Yunnan, and southern South China, but was lighter in the other regions. Except that the drought for summer maize at its late developmental stage was more severe in the middle-lower reaches of Yangtze River, northern South China, and eastern Southwest China, the drought for summer maize at its other developmental stages within southern China was lighter. As for the variation trend of drought intensity and drought area, the drought intensity of spring maize from its seven-leaf stage to jointing stage in the middle-lower reaches of Yangtze River increased obviously, while the drought intensity and drought area of the spring maize from its late spinning stage to milky maturity stage presented a decreasing trend. The drought of summer maize from its late jointing stage to tasseling stage and from late spinning stage to milky maturity stage all showed a decreasing trend. In Southwest China, the drought intensity and drought area for spring maize and summer maize had no clear trend. From the viewpoint of the inter-annual and decadal variability of drought intensity and drought area, there was a larger variation for the summer maize in the middle-lower reaches of Yangtze River, but less difference in Southwest China.

By the methods of classical statistics and geostatistics, this paper studied the spatial heterogeneity of surface soil (0-20 cm layer) moisture and salt contents under three kinds of artificial vegetation in coastal salt land in Chongming Dongtan of Shanghai. The soil moisture content in different plots was in order of Cynodon dactylon > Taxodium distichum > Nerium indicum, and the coefficient of variation was 13.9%, 13.4% and 12.9%, respectively. The soil electric conductivity was in the order of N. indicum > C. dactylon > T. distichum, and the coefficient of variation was 79.2%, 55.4% and 15. 9%, respectively. Both the soil moisture content and the salt content were in moderate variation. The theoretical models of variogram for the soil moisture and salt contents in different plots varied, among which, the soil electric conductivity fitted better, with R2 between 0.97 and 0.99. When the artificial vegetation varied from N. indicum to T. distichum and then to C. dactylon, the spatial heterogeneity of soil moisture content changed from weak to strong, in which, the variability was random under N. indicum. When the vegetation varied from C. dactylon to T. distichum and to N. indicum, the spatial heterogeneity of soil electric conductivity changed from moderate to strong. Under different vegetations, the soil electric conductivity was mostly in positive correlation, whereas the soil moisture content was in negative correlation. The spatial pattern of soil moisture and salt contents under T. distichum was in striped distribution, that under C. dactylon was in large plaque and continuous distribution, whereas under N. indicum, the spatial pattern of soil moisture content was in small breaking plaque distribution, and that of soil salt content was in striped distribution.

By using the equilibrium moisture content-time lag methods of Nelson and Simard and the meteorological element regression method, this paper studied the dynamics of the moisture content of ground surface fine dead fuels under a Larix gmelinii stand on the sunny slope in Daxing' anling with a time interval of one hour, established the corresponding prediction models, and analyzed the prediction errors under different understory densities. The results showed that the prediction methods of the fuels moisture content based on one-hour time step were applicable for the typical Larix gmelinii stand in Daxing' anling. The mean absolute error and the mean relative error of Simard method was 1.1% and 8.5%, respectively, being lower than those of Nelson method and meteorological element regression method, and close to those of similar studies. On the same slopes and slope positions, the fuel moisture content varied with different understory densities, and thus, it would be necessary to select the appropriate equilibrium moisture content model for specific regional stand and position, or establish the fuel moisture content model based on specific stand when the dynamics of fuel moisture content would be investigated with a time interval of one hour.

Taking the two-year old potted Prunus sibirica seedlings as test materials, and using CIRAS-2 photosynthetic system, this paper studied the CO2 response process of P. sibirica photosynthesis in semi-arid loess hilly region under eight soil moisture conditions. The CO2 response data of P. sibirica were fitted and analyzed by rectangular hyperbola model, exponential equation, and modified rectangular hyperbola model. Meanwhile, the quantitative relationships between the photosynthesis and the soil moisture were discussed. The results showed that the CO2 response process of P. sibirica photosynthesis had obvious response characteristics to the soil moisture threshold. The relative soil water content (RWC) required to maintain the higher photosynthetic rate (P(n)) and carboxylation efficiency (CE) of P. sibirica was in the range of 46.3%-81.9%. In this RWC range, the photosynthesis did not appear obvious CO2 saturated inhibition phenomenon. When the RWC exceeded this range, the photosynthetic capacity (P(n max)), CE, and CO2 saturation point (CSP) decreased evidently. Under different soil moisture conditions, there existed obvious differences among the three models in simulating the CO2 response data of P. sibirica. When the RWC was in the range of 46.3%-81.9%, the CO2 response process and the characteristic parameters such as CE, CO2 compensation point (see symbol), and photorespiration rate (R(p)) could be well fitted by the three models, and the accuracy was in the order of modified rectangular hyperbola model > exponential equation > rectangular hyperbola model. When the RWC was too high or too low, namely, the RWC was > 81.9% or < 46.3%, only the modified rectangular hyperbola model could well fit the CO2 response process and the characteristic parameters. It was suggested that when the RWC was from 46.3% to 81.9%, the photosynthetic efficiency of P. sibirica was higher, and, as compared with rectangular hyperbola model and exponential equation, modified rectangular hyperbola model had more applicability to fit the CO2 response data of P. sibirica photosynthesis under different soil moisture conditions.

To study the surface soil moisture spatial variability and its scale effect is of significance to understand the real variability of soil moisture and to objectively provide a reference for constructing a logical sampling scheme. By using "re-sampling" method, this paper studied the scale-dependency of the spatial variability of soil surface moisture in the woodland and farmland in the oasis ecological system in the middle reaches of Heihe River. The results showed that the variation degree of the surface soil moisture in the test woodland and farmland increased with increasing soil moisture content, and the coefficient of variation (CV) became closer to the true value when the sampling scale increased. Under both dry and moist conditions, and when the sampling amplitude increased within a definite range, the CV, Moran's I index, nugget, and sill of soil moisture in the woodland and farmland as well as the variation range in the woodland all increased, while the variation range in the farmland under arid condition did not show a stable regular pattern. When the sampling density increased within a definite range, the nugget and variation range increased, but the CV, Moran's I index, and sill showed less change.

Evapotranspiration (ET) is an important component of water cycle, but its measurement in high altitude mountainous region is quite difficult, inducing the insufficient understanding on the actual ET in high altitude mountainous region and the effects of ET on this region' s water cycle. In this paper, two small type weighing mini-lysimeters were applied to measure the daily ET in a piece of grassland in a high altitude mountainous region of the Heihe River basin from July 1st, 2009 to June 30th, 2010. Based on the measured data, the methods of FAO-56 Penman-Monteith (F-P-M), Priestley-Taylor (P-T), and Hargreaves-Samani (H-S) were employed to estimate the ET to analyze the applicability of the three methods for the mountainous region, and the pan coefficient at the measurement spots was discussed. During the measurement period, the total annual ET at the measurement spots was 439.9 mm, accounting for 96.5% of the precipitation in the same period, and the ET showed an obvious seasonal distribution, being 389. 3 mm in May-October, accounting for 88. 5% of the annual value. All the three methods could be well applied to estimate the summer ET but not the winter ET, and their applicability followed the sequence of P-T > F-P-M > H-S. At the measurement spots, the daily pan coefficient in summer was 0.7-0. 8, while that in winter was quite variable.

By using polyethylene glycol (PEG-6000) solution to regulate the water potential of tomato (Lycopersicon esculentum) rhizosphere to simulate water stress, this paper studied the dynamic changes of net photosynthetic rate, dark respiratory rate and CO2 compensatory concentration of detached tomato leaves in the process of photosynthetic induction. Under 1000 micromol m-2 s-1 of light induction, the time required to reach the maximum net photosynthetic rate of water-stressed tomato leaves was shortened by 1/3, while the stomatal conductance was increased by 1.5 times, as compared to the non-stress control. Also, the light saturation point (LSP) of water-stressed tomato leaves was lowered by 65% to 85%, and the light compensation point (LCP) was increased by 75% to 100%, suggesting that the effective range of light utilized by tomato leaves was reduced. Furthermore, water stress decreased the maximum photosynthetic capacity of tomato leaves by 40%, but increased the dark respiration rate by about 45% . It was suggested that rapid water stress made the stomata of tomato leaves quickly opened, without initial photosynthetic induction stage. In conclusion, water stress could induce the decrease of plant light-energy use efficiency and potential, being the main reason for the decrease of plant productivity, and stomatal regulation could be the main physiological mechanism of tomato plants to adapt to rapid water stress.

By the method of field experiment combined with laboratory analysis, this paper studied the ecological significance of hygroscopic and condensate water on the biological soil crusts in the vegetation sand-fixing area in Shapotou region of China. In the study area, 90% of hygroscopic and condensate water was within the 3 cm soil depth, which didn' t affect the surface soil water content. The hygroscopic and condensate water generated at night involved in the exchange process of soil surface water and atmosphere water vapor, made up the loss of soil water due to the evaporation during the day, and made the surface soil water not reduced rapidly. The amount of the generated hygroscopic and condensate water had a positive correlation with the chlorophyll content of biological soil crusts, indicating that the hygroscopic and condensate water could improve the growth activity of the biological soil crusts, and thus, benefit the biomass accumulation of the crusts.

Taking the 11-, 15-, 20-, and 43 years old apple orchards on the Luochuan highland of Shaanxi, Northwest China as test objects, this paper measured the moisture content in 0-1500 cm soil layer and the organic matter and total and available nitrogen, phosphorous, and potassium contents in 0-300 cm soil layer, with the soil moisture and nutrient regimes as well as their variation characteristics with apple tree age and soil depth analyzed. The moisture content in 0-1500 cm soil layer in 11-, 15-, 20-, and 43 years old apple orchards was averagely 18.6%, 13.7%, 17.0%, 11.5%, and 13.1%, respectively, and decreased with apple tree age. Soil desiccation did not occurr in the orchards with supplementary irrigation, but a slight or medium soil desiccation occurred in the rainfed orchards. Nevertheless, the moisture content in 0-300 cm soil layer in the rainfed orchards was still higher than that in wheat field. The contents of organic matter and total and available nitrogen in 0-300 cm soil layer in the five apple orchards were less than 10 g.kg-1, 0.75 g. kg-1, and 50 mg.kg-1, respectively, all at shortage level, whilst the content of available phosphorous in 0-300 cm soil layer was 3.30-6.42 mg.kg-1, being moderate in upper soil layer and scarce in deep soil layer. The content of available potassium in 0-300 cm soil layer was 78.09-98.31 mg.kg-1, presenting abundant. The contents of nutrients were all higher in 0-100 cm soil layer than in 100-300 cm soil layer. The soil organic matter and total and available nitrogen contents and the soil nutrient index (SNI) all presented a trend of decrease after an initial increase with the increasing apple tree age. The contents of the test nutrients except total potassium in 0-100 cm soil layer all decreased rapidly with soil depth, while those in deeper soil layers kept relatively stable. There existed significant correlations between the contents of soil organic matter, total nitrogen, available nitrogen, total phosphorous, available phosphorous, and available potassium, but no significant correlations between the contents of soil total potassium and other nutrient factors.

This paper studied the threshold value of the water use of Nitraria tanturorum shrubs at the southeast edge of Baddain Jiran Desert. From the early May to late September in 2009, an irrigation simulating increased precipitation was conducted once every month. Three ratios of increased precipitation (0, 50% and 100%) were designed, based on the local mean annual precipitation (115 mm). On the 1 day before irrigation and the 1, 3 and 7 days after irrigation in May, July and September, the deltaD in the xylem water of N. tangutorum, the soil water at the depths 10 and 30 cm, and the well water and natural rainfall, and the variations of the soil water content were measured. Under natural condition, the N. tangutorum mainly utilize ground water in May and September, and utilize the soil water at the depths 10 and 30 cm in July. After irrigation, the ground water use rate of the N. tangutorum decreased, while the soil water use rate increased. In the treatment of 100% increased precipitation, the deltaD ratio of the water in N. tangutorum xylem was affected significantly, and the water use of the N. tangutorum in May, July and September increased. In the treatment of 50% increased precipitation, the soil water condition in May and July was improved, but the water use rate had little improvement. Only when the increased precipitation reached 100% of the local mean annual precipitation, could the water use rate of the N. tangutorum have an obvious increase.

This paper studied the community characteristics of two sand-fixing plants (Artemisia ordosica and Caragana korshinskii) under different configuration modes (1 m x 1 m and 2 m x 2 m) in the Shapotou region of Northwest China as well as the water relation, gas exchange, and their adjustment mechanisms of the plants under natural and artificial precipitation conditions. With the variation of soil water content, the physiological water consumption and growth characteristics of A. ordosica differed from those of C. korshinskii. A. ordosica presented obvious fluctuation in the stomatal conductance, water potential, transpiration rate, photosynthetic rate, and rapid growth, and had higher water consumption than C. korshinskii. However, the variations of the above-mentioned indices of C. korshinskii were relatively slow and more constant. The C. korshinskii had a lower photosynthetic rate but a very high accumulated biomass over years than A. ordosica. The response procedures and adjustment mechanisms of the two plants under water stress differed, with a water-conserving mechanism for A. ordosica and a water-saving mechanism for C. korshinskii. In extremely drought years, the C. korshinskii had stronger capabilities of water-saving and stress tolerance than A. ordosica. It was suggested that the selection of sand-fixing plants should have a view to the benefits in water saving and sand fixation, and also, to the stability of sand-fixing forest.

Based on a long-term experiment of using hedgerow to control soil and water loss, this paper studied the composition and stability of soil aggregates in a hedgerow-crop slope land. Compared with those under routine contour cropping, the contents of > 0.25 mm soil mechanical-stable and water-stable aggregates under the complex mode hedgerow-crop increased significantly by 13.3%-16.1% and 37.8% -55.6%, respectively. Under the complex mode, the contents of > 0.25 mm soil water-stable aggregates on each slope position increased obviously, and the status of > 0.25 mm soil water-stable aggregates being relatively rich at low slope and poor at top slope was improved. Planting hedgerow could significantly increase the mean mass diameter and geometric mean diameter of soil aggregates, decrease the fractal dimension of soil aggregates and the destruction rate of > 0.25 mm soil aggregates, and thus, increase the stability and erosion-resistance of soil aggregates in slope cropland. No significant effects of slope and hedgerow types were observed on the composition, stability and distribution of soil aggregates.

Due to the coupling effects of wind and water erosions in the wind-water erosion crisscross region of Loess Plateau, the slope erosion in the region was quite serious, and the erosion process was quite complicated. By using wind tunnel combined with simulated rainfall, this paper studied the sediment-yielding process and its mechanisms of slope erosion under the effects of wind-water alternate erosion, and quantitatively analyzed the efffects of wind erosion on water erosion and the relationships between wind and water erosions. There was an obvious positive interaction between wind and water erosions. Wind erosion promoted the development of microtopography, and altered the quantitative relationship between the sediment-yielding under water erosion and the variation of rainfall intensity. At the rainfall intensity of 60 and 80 mm x h(-1), the sediment-yielding without wind erosion decreased with the duration of rainfall and tended to be stable, but the sediment-yielding with wind erosion decreased to a certain valley value first, and then showed an increasing trend. At the rainfall intensity of 60, 80, and 100 mm x h(-1), the sediment-yielding with the wind erosion at speeds of 11 and 14 m x s(-1) increased by 7.3%-27.9% and 23.2%-39.0%, respectively, as compared with the sediment-yielding without wind erosion. At the rainfall intensity of 120 and 150 mm x h(-1) and in the rainfall duration of 15 minutes, the sediment-yielding with and without wind erosion presented a decreasing trend, but, with the increase of rainfall duration, the sediment-yielding with wind erosion showed a trend of decreasing first and increasing then, as compared with the sediment-yielding without wind erosion. The mechanisms of wind-water alternate erosion were complicated, reflecting in the mutual relation and mutual promotion of wind erosion and water erosion in the aspects of temporal-spatial distribution, energy supply, and action mode of erosion forces.

Based on the two successive years observation of the water content of ten representative shrub species in Maoershan Mountain region of Northeast China, this paper studied the dynamics of the water content of these shrub species during their growth period and related affecting factors, with the prediction models of the shrub water content established. For the ten shrub species, their minimal water content during growth period was higher than 100% , and most of the species had a water content higher than 200% within the period from the late phase of leaf-unfolding to early phase of leaf-falling. Euonymus verrucosus, Sorbaria sorbifolia, and Sambucus williamsii were incombustible in their whole growth period due to the extremely high water content, while Syringa reticulate, Philadelphus schrenkii, Euonymus verrucosus, Spiraea chamaedryfolia, Lonicera maackii, Lonicera ruprechtiana, and Rhamnus parvifolia were combustible only in the phases of budding and leaf-falling. Soil moisture content and daily maximum temperature had effects on the water content of most (7) of the ten shrubs, and canopy drought severity index affected the water content of 5 of the ten shrubs. The established 9 prediction models could explain more than 35% of the water content variance of the shrub species, with a mean MRE of 35.9% and a mean MRE of 13.4%.

The increasing demand of adaptive management of land, forest, and water resources under the background of global change and water resources crisis has promoted the comprehensive study of coupling ecosystem water and carbon cycles and their restrictive relations. To construct the water-carbon coupling model and to approach the ecosystem water-carbon balance and its interactive response mechanisms under climate change at multiple spatiotemporal scales is nowadays a major concern. After reviewing the coupling relationships of water and carbon at various scales, this paper explored the implications and estimation methods of the key processes and related parameters of water-carbon coupling, the construction of evapotranspiration model at large scale based on RS, and the importance of this model in water-carbon coupling researches. The applications of assimilative multivariate data in water-carbon coupling researches under future climate change scenarios were also prospected.

By using Box-Behnken design and response surface methodology, this paper studied the effects of three major environmental factors, i. e., water temperature (20-36 degrees C), salinity (0-16), and pH (5.5-8.5), on the sex differentiation of GIFT strain Nile tilapia (Oreochromis niloticus). It was observed that water temperature had highly significant linear and quadratic effects on the sex differentiation, water salinity and pH had non-significant linear and quadratic effects, and the two-factor interactions of the three factors were not significant. The analysis with response surface methodology showed that the male rate of the GIFT tilapia increased with increasing water temperature, and at water temperature 36 degrees C, salinity 8, and pH 8.5, the male rate reached the maximum (80%). A model equation about the relationships of the male rate with the three major environmental factors was established, and after eliminating the related non-significant factors, an optimal model equation about the relationship between the male rate and water temperature was attained, which could predict the variation of the GIFT tilapia male rate.

To understand the nighttime water recharge of tree through its sap flow is beneficial to the precise estimation of total transpiration and canopy stomatal conductance, and to the further understanding of the time lag between canopy transpiration and stem sap flow. By using Granier's thermal dissipation probe, this paper measured the stem sap flow of Schima superba, and synchronously measured the main environmental factors including air temperature, relative humidity, photosynthetically active radiation, and soil moisture content, and also analyzed the water recharge through nighttime stem flow of S. superba at daily and seasonal scales. The sap flow density of S. superba was lower at night than at daytime, and the nighttime sap flow density had a larger variation in dry season than in wet season. The water recharge at night generally started from sunset when radiation was approaching zero, and lasted up to midnight (18:00-22:00). No significant difference was observed in the nighttime water recharge among seasons, and no significant correlations were found between the nighttime water recharge and environmental factors, but the nighttime water recharge was well regressed with the diameter at breast height, tree height, tree canopy size, stem biomass, and canopy biomass, suggesting that tree form features and biomass could better explain the nighttime water recharge. The contribution of nighttime water recharge to the total transpiration varied significantly with seasons, and was obviously higher in dry season than in wet season.

Based on the multi-disciplinary researches, and in terms of the transformation efficiency of surface water to soil water, availability of cropland soil water, crop canopy structure, total irrigation volume needed on a given area, and crop yield, this paper discussed the water-saving mechanisms of intercropping system in improving cropland water use efficiency. Intercropping system could promote the full use of cropland water by plant roots, increase the water storage in root zone, reduce the inter-row evaporation and control excessive transpiration, and create a special microclimate advantageous to the plant growth and development. In addition, intercropping system could optimize source-sink relationship, provide a sound foundation for intensively utilizing resources temporally and spatially, and increase the crop yield per unit area greatly without increase of water consumption, so as to promote the crop water use efficiency effectively.

Based on the measurements of the foliar carbon content (Cmass, nitrogen content (Nmass), isotope abundance (delta13C and delta15N), and light response curve of 10 dominant plant species (Larix gmelinii, Quercus mongolica, Fraxinus mandshurica, Tilia amurensis, Acer mono, Pinus koraiensis, Cunninghamia lanceolata, Schima superba, Pinus massoniana, and Castanea henryi) in the main forests along the North-South Transect of Eastern China (NSTEC), this paper analyzed the differences and the relationships between the foliar water use efficiency and nitrogen use efficiency of the plant species. There existed significant differences in the foliar Nmass and delta15N among the plant species, manifesting as broadleaved species > coniferous species, and deciduous species > evergreen species. The maximum photosynthetic rate (Pn max) was coniferous species > broadleaved species, and deciduous species > evergreen species. Broadleaved and evergreen species tended to have higher foliar instantaneous water use efficiency (WUEi) and long-term water use efficiency (WUE), as compared to coniferous and deciduous species, but an opposite trend was observed in the foliar instantaneous nitrogen use efficiency (NUE) and long-term nitrogen use efficiency (NUE). Moreover, there was a significant difference in the foliar NUE between evergreen and deciduous species. No significant correlation was observed between WUEi and WUE, but a significant positive correlation existed between NUEi and NUE. There was a significant negative correlation between the foliar water use efficiency and nitrogen use efficiency at instantaneous or long-term time scales. In sum, the foliar water use efficiency and nitrogen use efficiency were dominated by plant life-form, and a trade-off existed between the two resources use efficiencies.

By using an improved wet sieving method, this paper studied the water stability of biological soil crusts with different biological components and biomass in the hilly regions of Loess Plateau. The water stability of the biological soil crusts was related to the crusts' biological components. Moss-dominated crust had significantly higher water stability than cyanobacteria-dominated crust. After 390 shakings, the thickness- and mass losses of moss-dominated crust were only 47.3% and 40.1% of those of cyanobacteria-dominated crust, respectively. Moss-dominated crust had the highest water stability when the moss coverage was up to 60%, and the thickness- and mass losses were 22.7% and 28.6% of those of cyanobacteria-dominated crust (no moss coverage), respectively. The horizontal stability of the biological soil crusts was significantly higher than the vertical stability. After 390 shakings, the area loss of moss-dominated crust was only 6.4% of thickness loss. The biological soil crusts had a layer structure with strong stability in horizontal direction, which increased the crusts' resistance against wind- and water erosion.

Based on the 1961-2007 ground surface meteorological data from 558 meteorological stations in China, this paper analyzed the differences of agricultural climate resources in China different regions, and compared the change characteristics of the agricultural climate resources in 1961-1980 (period I) and 1981-2007 (period II), taking the year 1981 as the time node. As compared with period I, the mean annual temperature in China in period II increased by 0.6 degrees C, and the > or = 0 degrees C active accumulated temperature in the growth periods of chimonophilous crops and the > or = 10 degrees C active accumulated temperature in the growth periods of thermophilic crops increased averagely by 123.3 degrees C x d and 125.9 degrees C x d, respectively. In 1961-2007, the mean annual temperature increased most in Northeast China, and the > or = 10 degrees C active accumulated temperature in the growth periods of thermophilic crops increased most in South China. The whole year sunshine hours and the sunshine hours in the growth periods of chimonophilous crops and of thermophilic crops in period II decreased by 125.7 h, 32.2 h, and 53.6 h, respectively, compared with those in period I. In 1961-2007, the annual sunshine hours decreased most in the middle and lower reaches of Yangtze River, while the sunshine hours in the growth periods of chimonophilous crops and of thermophilic crops decreased most in North China and South China, respectively. In the whole year and in the growth periods of chimonophilous and thermophilic crops, both the precipitation and the reference crop evapotranspiration in this country all showed a decreasing trend, with the largest decrement in the precipitation in the whole year and in the growth periods of chimonophilous and thermophilic crops in North China, the largest decrement in the reference crop evapotranspiration in the whole year and in the growth periods of thermophilic crops in the middle and lower reaches of Yangtze River, and the largest decrement in the reference crop evapotranspiration in the growth periods of chimonophilous crops in Northwest China. In 1961-2007, the climate in China in the whole year and in the growth periods of thermophilic crops showed an overall tendency of warm and dry, and the climate in the growth periods of thermophilic crops became warm and dry in Southwest China, North China, and Northeast China, but warm and wet in the middle and lower reaches of Yangtze River, Northwest China, and South China, whereas the climate in the growth periods of chimonophilous crops became warm and dry in North China, but became warm and wet in Northwest China.

Transpiration is a major component of vegetation evapotranspiration, and a core in the study of plant water physiological ecology. Its measurement methods attracted extensive attention, among which, thermal dissipation is considered as an optimal method for measuring tree transpiration. Numerous studies showed that thermal dissipation method was relatively accurate in measuring individual tree transpiration and stand-scale water consumption. However, there exist potential errors between the true value and the measurements during measurement process. In this paper, the potential errors of thermal dissipation method in measuring sap flux density and of the temperature difference determination from single tree to stand-scale were reviewed, and the research prospects on the potential errors of thermal dissipation method in China were discussed. The corresponding solutions were also proposed.

By measuring the foliar delta13C values of 5 common shrub species (Rhamnus davurica, Pyracantha fortuneana, Rubus biflorus, Zanthoxylum planispinum, and Viburnum utile) growing in various microhabitats in Wangjiazhai catchment, a typical karst desertification area in Guizhou Province, this paper studied the spatial heterogeneity of plant water use at niche scale and the response of the heterogeneity to different karst rocky desertification degrees. The foliar delta13C values of the shrub species in the microhabitats followed the order of stony surface > stony gully > stony crevice > soil surface, and those of the majority of the species were more negative in the microhabitat soil surface than in the others. The foliar delta13C values decreased in the sequence of V. utile > R. biflorus > Z. planispinum > P. fortuneana > R. davurica, and the mean foliar delta13C value of the shrubs and that of typical species in various microhabitats all increased with increasing karst rocky desertification degree, differed significantly among different microhabitats. It was suggested that with the increasing degree of karst rocky desertification, the structure and functions of karst habitats were impaired, microhabitats differentiated gradually, and drought degree increased.

By using the site-specific observation data of oil flax growth and related meteorological records in semi-arid region of Loess Plateau, this paper studied the effects of climate change on the oil flax growth, and analyzed the relationships between the oil flax water use efficiency and meteorological condition. In this region, the annual precipitation displayed a decreasing trend, and its climatic trend rate was -15.80 mm (10 a)(-1), with an annual periodic change of 3 a and 6 a, whereas the annual air temperature had an increasing trend, and its climatic trend rate was 0.36 degrees C (10 a)(-1). In crop growth period, the aridity index displayed a marked increasing trend, its climatic trend rate was 0.12 (10 a)(-1), and the aridity tendency was more obvious from the beginning of 1990s to the year 2009. From sowing to maturation, oil flax needed 120-150 d, 1700-2100 degrees C d of > or = 0 degrees C accumulated temperature, 200-250 mm precipitation, and 1000-1300 h sunshine hours. The main meteorological factors affecting the oil flax growth in the region were air temperature and precipitation. The increase of air temperature shortened the prophase vegetative growth stage, whereas the increase of air temperature and the decrease of precipitation extended the reproductive growth stage, causing the extension of the whole growth period of the oil flax. The air temperature in the oil flax whole growth period except at seeding stage and maturing stage had negative effect on the yield formation, being more obvious at squaring stage, whereas the precipitation in the whole growth period except at blooming stage had positive effect on the yield formation, being more obvious at seeding stage. The water use efficiency of the oil flax was significantly positively correlated with the air temperature and sunshine hours at seeding stage as well as the aridity index from squaring stage to maturing stage, and negatively correlated with the precipitation from squaring stage to maturing stage. In the study region, the aridity index from May to July was the key factor affecting the water use efficiency of oil flax.

This paper studied the effects of habitats (riparian inter-dune and dry top dune) and years after rejuvenation pruning (1, 2, 3-4, and 5-6 years) on the leaf functional traits (gas exchange, water use efficiency, structural traits, and N and P contents) of Salix psammophila growing in the southern edge of Mu Us Sandy Land. In the habitat of riparian inter-dune, the leaf net photosynthetic rate, stomatal conductance, and instantaneous and long-term water use efficiencies were all higher, while the leaf N and P contents were lower, as compared with those in the habitat of dry top dune. No significant differences were observed in the leaf structural traits between the two habitats, suggesting that S. psammophila could survive in a dry habitat by the strategies of increasing nutrient uptake and decreasing photosynthesis and water use. With the increasing years after rejuvenation pruning, the leaf net photosynthetic rate and stomatal conductance decreased significantly, and the leaf N content and instantaneous water use efficiency also showed a decreasing trend, with a positive correlation between them. One-year after rejuvenation pruning, the leaf area was the highest, and the specific leaf mass and leaf dry matter content were the lowest. Thereafter, the leaf area and dry matter content had no obvious change, but the specific leaf mass increased with increasing years after rejuvenation pruning. There were no significant correlations between leaf structural traits and photosynthetic and nutrient traits, suggesting that the decreases of leaf photosynthetic capacity and N content were the major reasons for S. psammophila senescence with increasing years after rejuvenation pruning.

Taking Betula ermanii forests distributed at the altitudes 1800-2050 m on the northern slope of Changbai Mountains as test objects, and using leaf carbon isotope content (813 C) as an indicator of B. ermanii water use efficiency (WUE), this paper studied the effects of altitudinal gradient on the WUE of B. ermanji forests in the area. With the increase of altitude, the soil volumetric water content (VMC) and the leaf mass per area (LMA) of B. ermanji increased significantly, while the leaf water content (LWC) and soil temperature were in adverse. There was a significant positive correlation between leaf delta13 C and altitude, with the increment of leaf delta13 C being 1.013 % per hundred x (100 m)(-1), and the leaf delta13C was positively correlated with soil VWC and LMA but negatively correlated with soil temperature and LWC. Temperature was not the sole limiting factor for the distribution of treeline in Changbai Mountains, whereas the physiological drought of B. ermanii during its growing season caused by the different water and heat conditions and their interactions along the altitudinal gradient could be the other limiting factors.

Taking the artificial sand-fixing Salix psammophila shrubs with different plant density (0.2, 0.6, and 0.8 plants x m(-2)) in Mu Us Sandy Land as test objects, this paper studied the soil moisture dynamics and evapotranspiration during growth season. There existed obvious differences in the soil moisture dynamics and evapotranspiration among the shrubs. The soil moisture content changed in single-hump-shape with the increase of plant density, and in "S" shape during growth season, being closely correlated with precipitation. The evapotranspiration was the highest (114.5 mm) in the shrubs with a density 0.8 plants x m(-1), accounting for 90.8% of the total precipitation during growth season, and the lowest (109.7 mm) in the shrubs with a density 0.6 plants x m(-2) Based on the soil moisture dynamics and water balance characteristics, the appropriate planting density of S. psammophila shrubs in Mu Us Sandy Land could be 0.6 plants x m(-2).

Taking a 2-year-old tea garden in Qingdao of Shandong Province as test object, this paper studied the effects of different mulching modes on the soil water and nutrient dynamics and tea plant growth. Four treatments were installed, i.e., no mulching (CK), straw mulching (T1), plastic film mulching (T2), and straw plus plastic film mulching (T3). Comparing with CK, mulching could keep the soil water content at a higher level, and enhance the water use efficiency. In treatments T1 and T3, the tea growth water use efficiency and yield water use efficiency increased by 43%-48% and 7%-13%, respectively, compared with CK. Also in treatments T1 and T3, the contents of soil organic matter, available-N, nitrate-N, and ammonium-N increased significantly, with the soil fertility improved, and the leaf nitrate-N content and nitrate reductase activity increased, which promoted the tea growth and yield (12%-13% higher than CK) and made the peak period of bud growth appeared earlier. Considering the tea growth and yield, water and nutrient use efficiency, environment safety and economic benefit, straw mulching could be an effective ground surface mulching mode for young tea garden.

By the methods of direct measurement and regression analysis, this paper estimated the water storage capacity of Picea crassifolia forest canopy in Guantan in Qilianshan Mountains, based on the observed throughfall and the laboratory experimental data about the water storage capacity of various canopy components in 2008. Due to the impacts of various factors, differences existed in the canopy water storage capacity estimated by the two methods. The regression analysis was mainly impacted by the measurement approaches of the throughfall, the maximum water storage capacity estimated being 0.69 mm, whereas the direct measurement was mainly impacted by tree height, diameter at breast height, plant density, and leaf area index, with the estimated maximum water storage capacity being 0.77 mm. The direct measurement showed that the maximum water storage capacity per unit area of the canopy components of the forest was in the order of barks (0.31 mm) > branches (0.28 mm) > leaves (0.08 mm).

Based on the 1961-2007 ground observation data from 55 meteorological stations in arid and semi-arid region of Tibetan Plateau, and by using 5-day moving average method and ArcGIS-IDW module, this paper analyzed the spatiotemporal change characteristics and climatic trend rates of agricultural climate resources in the region in 1961-1980 (period I) and 1981-2007 (period II). In 1961-2007, the sunshine duration during the growth season of chimonophilous crops in the study region changed less, while that during the growth season of thermophilic crops increased but with little spatial change. Comparing with those in period I, the average value of accumulated temperature in period II showed an increasing trend, and the area with > or = 1500 degrees C x d during the growth season of thermophilic crops increased by 33.9%. The precipitation decreased gradually from southeast to northwest. During the growth season of chimonophilous crops, the precipitation in the southeast in the two periods reached 800 mm, but the climatic trend in other areas was positive or negative, and the change rate was small. The area with precipitation > or = 400 mm during the growth season of thermophilic crops in period II expanded by 40%, as compared in period I. The reference crop evapotranspiration (ET0) generally increased slightly, and shared the similar spatial distribution pattern with sunshine duration and accumulated temperature. During the growth season of thermophilic crops, the area with ET0 > or = 400 mm in period II expanded by 35.7%, compared with that in period I. In the study period, the heat and precipitation resources during crop growth seasons in Tibet Plateau increased in a certain degree, which was very beneficial to the agriculture-stock production. However, the increase of reference crop evapotranspitation indicated the increase of potential evaporation. Thereby, the researches about the possible effects of climate change on agriculture-stock production should be further strengthened.

To understand the dynamic variations of soil moisture in the root zone of original Haloxylon ammodendron land is of significance for further understanding the interactions between hydrological processes and vegetations in the Gurbantunggut Desert. By using TDR probes system, this paper measured the volumetric soil moisture content in H. ammodendron land in the southern edge of Gurbantunggut Desert, and analyzed the spatiotemporal distribution of soil moisture in the root zone of H. ammodendron in August 2007-July 2008. There existed 'wet island' effect in H. ammodendron root zone. The 0-60 cm soil water storage in the root zone was 1.49 times of that in bare land. Such a difference was greater in summer than in spring and after rainfall than before rainfall. The soil moisture content in the Desert was the richest in spring after snow melting and the lowest in winter, and its annual variation could be divided into three periods, i.e., quick supplement-consumption period in spring (from March to May), slow consumption period in summer and autumn (from June to September), and stable period in winter (form October to next February). Based on wavelet analysis, the soil moisture variation in H. ammodendron root zone and bare land had a short cycle of 43 and 40 days and a long cycle of 110 and 103 days, respectively. The relatively rich soil moisture content in H. ammodendron root zone could be mainly due to the stem flow water collection, tree canopy shading, and the better water percolating capacity in root zone.