Semi-arid China Research Articles

Peach yield and fruit quality is maintained under mild deficit irrigation in semi-arid China

We conducted a two-year study of deficit irrigation impact on peach yield and quality in semi-arid northwest China. Over two years, four-year-old peach trees were irrigated at 100, 75, 50 and 25% of peach evapotranspiration (ETc), here, ETc= Coefficient (Kc)×Local reference evapotranspiration (ETo). During the April–July fruit production season we measured root zone soil water depletion, sap flow velocity, net photosynthetic rate (Pn), transpiration rate (Tr), stomatal conductance (Gs), water use efficiency (WUE=Pn/Tr), fruit quality, and yield under a mobile rain-out shelter. Increased soil water depletion reasonably mirrored decreasing irrigation rates both years, causing progressively greater water stress. Progressive water stress lowered Gs, which in turn translated into lower Tr as measured by sap flow. However, mild deficit irrigation (75% ETc) constricted Tr more than Pn. Pn was not different between 100 and 75% ETc treatments in both years, and it decreased only 5–8% in June with higher temperature than that in May with cooler temperature. Concurrently under 75% ETc treatment, Tr was reduced, and WUE was up to 13% higher than that under 100% ETc treatment. While total fruit yield was not different under the two treatments, because 75% ETc treatment had fewer but larger fruit than 100% ETc trees, suggesting mild water stress thinned fruit load. By contrast, sharply decreased Tr and Pn of the driest treatments (50 and 25% ETc) increased WUE, but less carbon uptake impacted total fruit yield, resulting 13 and 33% lower yield compared to that of 100% ETc treatment. Irrigation rates affected fruit quality, particularly between the 100 and 75% ETc trees. Fewer but larger fruit in the mildly water stressed trees (75% ETc) resulted in more soluble solids and vitamin C, firmer fruit, and improved sugar:acid ratio and fruit color compared to the 100% ETc treatment. Overall, trees deficit irrigated at 75% ETc maintained yield while improving fruit quality and using less water.

Plastic-Film Mulching for Enhanced Water-Use Efficiency and Economic Returns from Maize Fields in Semiarid China.

Film mulch has gradually been popularized to increase water availability to crops for improving and stabilizing agricultural production in the semiarid areas of Northwest China. To find more sustainable and economic film mulch methods for alleviating drought stress in semiarid region, it is necessary to test optimum planting methods in same cultivation conditions. A field experiment was conducted during 2013 and 2014 to evaluate the effects of different plastic film mulch methods on soil water, soil temperature, water use efficiency (WUE), yield and revenue. The treatments included: (i) the control, conventional flat planting without plastic film mulch (CK); (ii) flat planting with maize rows (60 cm spacing) on plastic film mulch (70 cm wide); (iii) furrow planting of maize (60 cm spacing), separated by consecutive plastic film-mulched ridges (each 50 cm wide and 15 cm tall); (iv) furrow planting of maize (60 cm spacing), separated by alternating large and small plastic film-mulched ridges (large ridges: 70 cm wide and 15 cm tall, small ridges 50 cm wide and 10 cm tall); and (v) furrow-flat planting of maize (60 cm spacing) with a large plastic film-mulched ridge (60 cm wide and 15 cm tall) alternating with a flat without plastic film-mulched space (60 cm wide). Topsoil temperature (5–25 cm) was significantly (p < 0.05) higher in field plots with plastic film mulch than the control (CK), and resulted in greater soil water storage (0–200 cm) up to 40 days after planting. Maize grain yield and WUE were significantly (p < 0.05) higher with the furrow planting methods (consecutive film-mulched ridges and alternating film-mulched ridges) than the check in both years. Maize yield was, on average, 29% (p < 0.05) greater and 28% (p < 0.05) greater with these furrow planting methods, while the average WUE increased by 22.8% (p < 0.05) with consecutive film-mulched ridges and 21.1% (p < 0.05) with alternating film-mulched ridges. The 2-year average net income increased by 1559, 528, and 350 Chinese Yuan (CNY) ha−1 with the consecutive film-mulched ridges, furrow-flat planting and alternating film-mulched ridges, respectively, compared with the control (CK). We conclude that the consecutive film-mulched ridge method was the most productive and profitable for maize in this semi-arid area with limited and erratic precipitation.

Using the green purchase method to help farmers escape the poverty trap in semiarid China

People who live in ecologically fragile environments face both poverty and environmental degradation, which reinforce each other and create a “poverty trap.” Traditional ecological restoration projects focus only on ecological measures, and thus ignore the livelihoods of local residents. Those projects therefore fail to solve the poverty trap. In addition, project subsidies to residents typically end when the projects end, thus forcing residents to return to their old way of life and reversing the gains from the projects. To break this cycle, we performed a study in China’s Yanan City, in Shaanxi Province, to promote a new “green purchase” method for implementing sustainable economic activities that bring residents ongoing earnings without harming the environment. This method involves the construction of terraced fields, establishment of fruit tree orchards, implementation of grazing restrictions, and ecological migration. We found that the method was ecologically effective, as it increased Yanan’s vegetation cover by 0.89% annually since 1999, which is twice the rate for Shaanxi Province.

Isolating and Quantifying the Effects of Climate and CO2 Changes (1980–2014) on the Net Primary Productivity in Arid and Semiarid China

Although the net primary productivity (NPP) of arid/semiarid ecosystem is generally thought to be controlled by precipitation, other factors like CO2 fertilization effect and temperature change may also have important impacts, especially in the cold temperate areas of the northern China, where significant warming was reported in the recent decades. However, the impacts of climate and atmospheric CO2 changes to the NPP dynamics in the arid and semiarid areas of China (ASA-China) is still unclear, hindering the development of climate adaptation strategy. Based on numeric experiments and factorial analysis, this study isolated and quantified the effects of climate and CO2 changes between 1980–2014 on ASA-China’s NPP, using the Arid Ecosystem Model (AEM) that performed well in predicting ecosystems’ responses to climate/CO2 change according to our evaluation based on 21 field experiments. Our results showed that the annual variation in NPP was dominated by changes in precipitation, which reduced the regional NPP by 10.9 g·C/(m2·year). The precipitation-induced loss, however, has been compensated by the CO2 fertilization effect that increased the regional NPP by 14.9 g·C/(m2·year). The CO2 fertilization effect particularly benefited the extensive croplands in the Northern China Plain, but was weakened in the dry grassland of the central Tibetan Plateau due to suppressed plant activity as induced by a drier climate. Our study showed that the climate change in ASA-China and the ecosystem’s responses were highly heterogeneous in space and time. There were complex interactive effects among the climate factors, and different plant functional types (e.g., phreatophyte vs. non-phreatophyte) could have distinct responses to similar climate change. Therefore, effective climate-adaptive strategies should be based on careful analysis of local climate pattern and understanding of the characteristic responses of the dominant species. Particularly, China’s policy makers should pay close attention to climate change and ecosystem health in northeastern China, where significant loss in forest NPP has been triggered by drought, and carefully balance the ecological and agricultural water usage. For wildlife conservation, the drought-stressed grassland in the central Tibetan Plateau should be protected from overgrazing in the face of dramatic warming in the 21st century.

Effects of stubble and mulching on soil erosion by wind in semi-arid China.

Soil erosion is a growing challenge for agricultural production in Northern China. To explore the effect of variation in stubble height and mulching biomass on soil erosion caused by wind, we conducted a field experiment using a quadratic rotation combination design. Results showed that the quantity of straw mulch was the dominant factor affecting soil erosion, and stubble height was of secondary importance. The soil water content in stubble and straw mulching treatments was higher than in a control treatment at 0–20 cm soil, and the tendency in the amount of soil water content was opposite to the amount of wind erosion (r = −0.882, n = 10, p < 0.01). The change in soil water content observed in the stubble and mulch treatments at the 15–20 cm depth was higher than the change from 0–5 cm to 5–10 cm. Combined, the influence of a stubble height of 34 cm and mulch quantity of 4260 kg·ha−1 lowered the amount of erosion to 0.42 t·ha−1, and increased the corn yield to 11900 kg·ha−1. We determined that those were the most appropriate levels of stubble height and straw mulch for crop fields in the semi-arid regions of Northern China.

The combination of subsoil and the incorporation of corn stover affect physicochemical properties of soil and corn yield in semi-arid China

ABSTRACTThe main objective of this study was to investigate the effects of combining subsoil and incorporation of corn stover on soil profile, soil physicochemical properties, and corn yield. A five-year field trial was conducted that consisted of two treatments arranged in a completely random design and replicated three times. Two soil management operations were tested: subsoil + corn stover incorporation (plow construction [PC] treatment) and conventional rotary tillage (control check [CK] treatment). Compared with rotary tillage, it was found that combining subsoil and corn stover incorporation significantly affected corn grain yield in all seasons. Further, combining subsoil and corn stover incorporation significantly increased the thickness of the plow layer, quantity of plow layer soil, thickness of the plow pan and soil bulk density, as well as soil organic matter, available nitrogen, available phosphorus, and available potassium. Evidence indicates that reconstructing the soil plow layer through combination of subsoil and corn stover incorporation improved soil structure, nutrient content, and corn yield. It is of interest that farmers are now applying subsoil and returning crop straw instead of solely relying on rotary tillage.

Decomposition of Mongolian pine litter in the presence of understory species in semi-arid northeast China

The effects of understory plant litter on dominant tree litter decomposition are not well documented especially in semi-arid forests. In this study, we used a microcosm experiment to examine the effects of two understory species (Artemisia scoparia and Setaria viridis) litter on the mass loss and N release of Mongolian pine (Pinus sylvestris var. mongolica) litter in Keerqin Sandy Lands, northeast China, and identified the influencing mechanism from the chemical quality of decomposing litter. Four litter combinations were set up: one monoculture of Mongolian pine and three mixtures of Mongolian pine and one or two understory species in equal mass proportions of each species. Total C, total N, lignin, cellulose and polyphenol concentrations, and mass loss of pine litter were analyzed at days 84 and 182 of incubation. The chemistry of pine litter not only changed with the stages of decomposition, but was also strongly influenced by the presence of understory species during decomposition. Both understory species promoted mass loss of pine litter at 84 days, while only the simultaneous presence of two understory species promoted mass loss of pine litter at 182 days. Mass loss of pine litter was negatively correlated with initial ratios of C/N, lignin/N and polyphenol/N of litter combinations during the entire incubation period; at 182 days it was negatively correlated with polyphenol concentration and ratios of C/N and polyphenol/N of litter combinations at 84 days of incubation. Nitrogen release of pine litter was promoted in the presence of understory species. Nitrogen release at 84 days was negatively correlated with initial N concentration; at 182 days it was negatively correlated with initial polyphenol concentration of litter combinations and positively correlated with lignin concentration of litter combinations at 84 days of incubation. Our results suggest that the presence of understory species causes substantial changes in chemical components of pine litter that can exert strong influences on subsequent decomposition of pine litter.

Effect of straw incorporation on the temporal variations of water characteristics, water – use efficiency and maize biomass production in semi-arid China

Field experiments were conducted in 2008–2010 in the Loess Plateau of China to study the effects of straw incorporation on maize growth and biomass water use efficiency (WUE) under semi-arid condition in dark loessial soil. Low (LS 4.5tha−1), medium (MS 9.0tha−1), and high (HS 13.5 tha−1) levels of straw were incorporated into the surface soil combined with fixed levels of inorganic fertilizers (CK) as control. Straw incorporation compared with CK significantly improved biomass yield at the tasseling–maturity stage of maize and WUE at the jointing–ten leaf collar and the tasseling–grain filling stages. WUEs with LS and MS treatments were significantly lower than that with CK at the ten leaf collar–tasseling stage, although the WUEs with MS and HS treatments were significantly higher in the whole growth period. HS treatment compared with LS treatment significantly increased biomass yield at the ten leaf collar–maturity stage and WUE at the jointing–tasseling stage. Meanwhile, MS and HS treatments compared with LS treatment significantly increased the biomass yield at the late grow period. Straw incorporation significantly improved WUE at the sowing–jointing stage and soil organic carbon relative to CK. Biomass yield at the ten leaf collar stage and WUE in whole growth period with LS treatment were significantly higher compared with CK. WUE at the ten leaf collar–tasseling and the grain filling–maturity stages were significantly higher with HS treatment compared with CK. In the long term, the rational straw incorporation level in improving maize biomass yield and WUE was 9.0tha−1.

A Method for Temporary Water Scarcity Analysis in Humid Region Under Droughts Condition

Water scarcity in China has long been discussed and studied, mostly in arid and semi-arid Northern China. However, temporary water scarcity caused by seasonal droughts hasn’t drawn enough attention still, while some humid regions in South China are readily to be encountered with seasonal droughts, especially in the background of climate change. In this study, a method based on System Dynamics (SD) and mathematical optimization is developed to analyze the situation of temporary water scarcity and optimize the water allocation under seasonal droughts, considering rapid urbanization, industrialization, and increasing food demand. And a case study in Nanchang Municipality, a typical humid region in Southern China, is presented. The simulation results show that conventional management scenarios including enforcing demand reduction strategies and increasing local water supply will not fill the water shortage gap, and the total water shortage rate will retain more than 9.0 % in special drought condition. Thus, we examine the water transfer scenario, and it proves to be effective in coping with the water shortage gap. The optimization results indicate that the water transferred from Ganjiang River to Fuhe River Water Demand Subsystem may account for 50.21 % of the total fresh water supply of Fuhe River Water Demand Subsystem, in September, under a certain drought condition. In addition, the current situation reveals fierce competition between social economic water needs and eco-environmental water requirements in local scale in dry condition. The situation argues that management of the distribution of water in space must be involved, and the simulation of the inter-basin transfer scenario proves it a necessary and effective countermeasure.

Intrinsic water use efficiency in wet and dry years at young and old plantations of Pinus sylvestris var. mongolica in semiarid China

Rainfall is the most important factor influencing the growth and survival of Mongolian pine (Pinus sylvestris var. mongolica), but the responses of these trees to extremes of rainfall are still poorly understood. Intrinsic water use efficiency (iWUE, as proxied by δ13C), specific leaf area, dry matter content, soil water content and groundwater level were measured in 18-year-old and 38-year-old Mongolian pine stands (young and old) during two conservative years with extreme rainfalls (280 mm, 2009; and 580 mm, 2010). The results indicated that young trees displayed higher δ13C values of current-year-old needles in 2009 than in 2010, but no difference was detected in old trees. For both age groups of trees, no significant differences were observed in the specific leaf area and dry matter content of current-year-old needles between the two years. These results suggested that the iWUE of young trees was more sensitive to the extreme rainfall than that of the old trees. The groundwater level remained within vertical root distributions for old trees. In 2009, the mean δ13C value of the current-year-old needles was higher in young trees than in old trees, but this pattern was reversed in 2010. In conclusion, young trees improved iWUE to acclimate to extremely low rainfall, whereas old trees maintained a lower iWUE, possibly because of the uptake of groundwater.

Whole-farm economic and risk effects of conservation agriculture in a crop-livestock system in western China

Researchers advocate using conservation agriculture as a tool to improve farmer livelihoods, with crop residue retention being an integral component of conservation agriculture. Crop residues are used for mulch, livestock feed, and fuel material in crop-livestock farming systems. In this article, we conducted long-term simulation modelling to compare the economic effects of different crop residue retention practices for a crop-livestock agricultural household in semi-arid China. We calculated the average profit and net present value (and associated variability) of different crop residue retention practices using planning horizons of 3, 6, 10, and 20 years. Crop residue retention increased grain production, reduced forage production leading to smaller livestock flock sizes, and increased family heating and cooking costs. The net effect was that retaining minimal crop residues gave the highest profits using the three year planning horizon.Full crop residue retention provided the highest profit when the planning horizon exceeded 10 years. Relatively flat economic payoffs associated with changing crop residue usage around the maximum economic payoff existed. Calls for comprehensive crop residue retention are unlikely to be attractive when farmers discount future profits, and when crop residues have significant value as a fuel and feed source. The economic benefits of crop residue retention can take numerous years to eventuate and retaining crop residues also increased simulated ground cover and this positive environmental impact extends beyond individual farm boundaries. Because of these time lags and external environmental benefits, providing financial incentives to retain crop residues during the initial transition years could be a policy option.

Groundwater recharge and evolution of water quality in China’s Jilantai Basin based on hydrogeochemical and isotopic evidence

We investigated major ions, stable isotopes, and radiocarbon dates in a Quaternary aquifer in semi-arid northwestern China to gain insights into groundwater recharge and evolution. Most deep and shallow groundwater in the Helan Mountains was fresh, with total dissolved solids <1,000 mg L−1 and Cl− <250 mg L−1. The relationships of major ions with Cl− suggest strong dissolution of evaporites. However, dissolution of carbonates, albite weathering, and ion exchange are also the major groundwater process in Jilantai basin. The shallow desert groundwater is enriched in δ18O and intercepts the local meteoric water line at δ18O = −13.4 ‰, indicating that direct infiltration is a minor recharge source. The isotope compositions in intermediate confined aquifers resemble those of shallow unconfined groundwater, revealing that upward recharge from intermediate formations is a major source of shallow groundwater in the plains and desert. The estimated residence time of 10.0 kyr at one desert site, indicating that some replenishment of desert aquifers occurred in the late Pleistocene and early Holocene with a wetter and colder climate than at present.

Nitrogen fertilization effects on nitrogen balance and use efficiency for film-mulched maize in a semiarid region

Efficient nitrogen (N) applications are crucial for sustainable agricultural development. A three-year field study was conducted to evaluate the effects of N fertilization on soil NO3-N contents, N balance, grain yield, and N use efficiency of film-mulched maize (Zea mays L.) in the semiarid northwest China. Six N levels were examined: 0 (N0), 100 (N100), 200 (N200), 250 (N250), 300 (N300), and 400 (N400) kg N ha−1. Results showed that residual soil NO3-N contents after harvest and apparent N losses markedly increased with increased N fertilizer rate. High accumulations of soil NO3-N were detected in the 80–200 cm layers in the N300 and N400 treatments in 2010 and 2011, indicating that excessive N applications resulted in NO3-N leaching in this semiarid region. The N use efficiency decreased with increased N fertilizer rate, but insignificant differences in agronomic efficiency, apparent recovery efficiency, and physiological efficiency were observed between N100, N200, and N250 treatments. Maize grain yields increased with N fertilization, but it did not further increase when N application was higher than plant N requirements. A linear plateau relationship was observed between grain yield and N supply (fertilizer N plus initial soil NO3-N in the 0–100 cm layers). The minimal N supply rate required to obtain the maximum yield (13.9 Mg ha−1) was 279 kg N ha−1, which was similar to plant N uptake and simultaneously reduced apparent N losses. We conclude that N fertilizer recommendations which consider soil NO3-N contents can simultaneously provide sufficient N for high yields and improve N fertilization of film-mulched maize in the semiarid areas.

AEOLIAN TRANSPORT AND SANDY DESERTIFICATION IN SEMIARID CHINA: A WIND TUNNEL APPROACH

ABSTRACTBy using surface samples collected in areas under high desertification risk in semiarid China, the roles of aeolian transport and the surface characteristics on sandy desertification were analysed. The results show that vegetation cover may not play the key role in the aeolian processes. However, the content of silt and clay decrease the aeolian transport rates even when the surfaces are moderately crushed. The low moisture content of the surface soils (&lt;1%) did not play an important role in the aeolian transport rate. The intensity of aeolian transport was mainly determined by the availability of the erodible material. Considering that human activities may not result in the surfaces being completely crushed, moderate human activities may not trigger severe desertification. Copyright © 2013 John Wiley &amp; Sons, Ltd.

Effects of amount and frequency of precipitation and sand burial on seed germination, seedling emergence and survival of the dune grass Leymus secalinus in semiarid China

Aims Seed germination and seedling emergence are vulnerable to water stress in arid environments. When precipitation is low and unpredictable during the early growing season, seeds near the sand surface often suffer from hydration/dehydration during germination. We investigated the responses of seedling emergence and survival of a sand dune grass with high sand stabilization value to amount and frequency of precipitation and depth of burial in sand.

Spatial Variability of Agriophyllum squarrosum Across Scales and Along the Slope on an Active Sand Dune in Semi-Arid China

Spatial variability has been recognized as a critical issue in vegetation restoration, and this condition is favorable for understanding underlying ecological processes or mechanisms. To assess the potential effects of spatial scales and environmental factors on vegetation patterns on active sand dunes, a 0.25 ha (50 m × 50 m) sampling plot was selected on the windward slope of an active sand dune to analyze the spatial variability of annual psammophyte Agriophyllum squarrosum across scales and along the slope. The average density, coverage, and height of A. squarrosum seedlings at five grain sizes (from 1 m × 1 m to 25 m × 25 m) as well as along the slope were measured. In A. squarrosum community, density, coverage, and height had the highest values at fine scales, but the lowest values at coarse scales. The highest value decreased gradually as scale increased, which means spatial variability gradually decreased as grain size increased. The correlations between density and height as well as between density and coverage decreased with increasing spatial scale, whereas the correlations between height and coverage increased. In regards to the slope, the seedlings of A. squarrosum developed better on top, and the Pearson correlation coefficients between plant density and height, as well as between density and coverage decreased in a fluctuating manner from the top to the bottom. In conclusion, grain size is an important consideration in the analysis of vegetation variability. Moreover, disturbances in sand dunes, such as wind erosion, should be further considered and discussed in the study of vegetation restoration and biodiversity conservation in active sand dunes.

Seasonal water use patterns of semi-arid plants in China

Water sources of woody plants in semi-arid or seasonally dry areas of China are little known. This study investigated the differences in water sources for plants due to seasonal changes (wet/transitional and dry seasons) in semi-arid areas. Stable isotope techniques were applied to determine plant water sources in different seasons. The results show that there is generally a switch of water sources from shallow depths in the rainy season to lower depths in the dry season. This study highlights how seasonal changes in climate in semi-arid China affect plant water uptake and suggests that further study with replicated systematic experiments are needed to better understand the responses in water use patterns to changes in environmental conditions in drought-prone areas.

Initiation and variation of the dune fields in semi-arid China – with a special reference to the Hunshandake Sandy Land, Inner Mongolia

Sedimentary sequences occurring in desert dunes reflect changes in desert systems, and as such may contain signals useful for recognizing spatial and temporal changes of deserts and their response to regional or even global climate fluctuations. Geomorphological and palaeoenvironmental studies within the dune fields of the Asian middle-latitudes have provided some solid evidence for interpreting the history of these sand seas. Using the Hunshandake (Otindag) Sandy Land, a sandy area covered primarily by stabilized dunes and located in the semi-arid zone of eastern Inner Mongolia, China (Fig. 1), as an example, we studied the initiation and variation in the dune landscape in the eastern portion of the desert belt in northern China. On the basis of physical and biochemical indicators in the sediments and OSL chronology, we herein argue that this dune system in the middle latitudes of eastern Asia is much younger than previously assumed and that it has responded sensitively to climate change during the late Quaternary. Geological evidence from the Sandy Land suggests that most of the current dunes are of late Pleistocene or even Holocene age. Palaeosols intercalated in the aeolian sequences and their OSL chronology show that the climate of the Hunshandake was much wetter than today between 9.6 ka and 3 ka. This resulted in stabilization of the dunes in the eastern and central portions of the Sandy Land. Epochs of reworking or stabilization of the dunes are broadly consistent with the fluctuations in northern hemisphere solar radiation although with an obvious time lag. Because the increase rate of annual precipitation was not sufficient to fully stabilize the dunes in more arid part of the region, some active dunes persisted even during this long-lasting wetter epoch. We conclude that periods of Holocene dune stabilization due to palaeosol formation varied along the climate gradients across the various sandy lands of northern China, and in general it began earlier and lasted longer in the east than in the west. The general nature of the sandy lands and their counterparts in the western portion of the desert belt during the LGM and mid-Holocene climate optimum is discussed in comparison with their current states.

Effects of grassland restoration programs on ecosystems in arid and semiarid China

We explored the ecological effects of grassland restoration programs using satellite imagery and field plots sampling data and analyzing the patterns and mechanisms of land cover change and vegetation activities in arid and semiarid China during the period from 1982 to 2008. The grassland cover in the 1980s, 2000 and 2005 was compared before and after the restoration programs. The variability of net primary production (NPP) and rain use efficiency (RUE) were analyzed as indicators of vegetation productivity. Our study showed that changes in grassland cover were closely related to the relative area of farmland, with increases in grassland being caused by returning farmland to grassland and decreases being caused by reclamation for agriculture. The results of NPP and RUE measurements over the past 30 years showed systematic increases in the area of grassland in most regions, especially from 2000 to 2008. This fact was reflected by intensified vegetation activity and cannot be completely explained by the warmer and wetter climate, which suggested a contribution from restored, ungrazed grasslands. Our analysis indicates that both vegetation activity and grassland cover increased in regions in which grassland and rangeland restoration programs were implemented.

Lake evaporation: A possible factor affecting lake level changes tested by modern observational data in arid and semi-arid China

Qinghai Lake and Zhuye Lake, ∼400 km apart, are located in the northwest margin of the Asian summer monsoon. Water of these two lakes mostly comes from the middle and eastern parts of the Qilian Mountains. Previous studies show that the Holocene climate changes of the two lakes implied from lake records are different. Whether lake evaporation plays a role in asynchronous Holocene climate changes is important to understand the lake records. In this paper, we used modern observations beside Qinghai Lake and Zhuye Lake to test the impact factors for lake evaporation. Pan evaporation near the two lakes is mainly related to relative humidity, temperature, vapor pressure and sunshine duration. But temperature has different impacts to lake evaporation of the two lakes, which can affect Holocene millennial-scale lake level changes. In addition, differences in relative humidity on the millennial-scale would be more significant, which also can contribute to asynchronous lake records.