Effect of Temperature on Frost-Free Days and Length of Crop Growing Season across Southern Ontario

Climate change has an impact on various climatic variables. In this study our focus is mainly on temperature characteristics of climate parameter. In temperate and humid regions like southern Ontario, the effect of climate change on Frost-free days in winter is distinctive. The average annual temperature is going upward but the extreme increase is in the winter temperature. Winter average temperature is going up by about 2˚C. However, extreme daily minimum temperature is going up by more than 3˚C. This climate effect has a great impact on the nature of precipitation and length of frost-free days. The snowfall over winter months is decreasing and the rainfall is increasing. However, the number of frost-free days during late fall months, early winter months, late winter months and early spring months are increasing. This result reveals an increase in length of the growing season. This research focuses on the effect of change in climatic variables on Frost-free days in Southern Ontario. Therefore, special attention should be given to the effect of change in climate Frost-free conditions on length of crop growing in winter season for potential investigation.

Temporal and Spatial Variation Characteristics of Precipitation during Crop Growing Season in Northeast China

[Objective] The aims were to understand variation characteristics of water resources and provide theoretical guidance for the formulation of agricultural irrigation methods.[Method] Taking the precipitation records during crop growing season（from April to September）observed by 177 weather stations from 1971 to 2008 in the three provinces of Northeast China（Heilongjiang,Jilin and Liaoning）as research data,annual change and spatial distribution characteristics of precipitation during crop growing season were analyzed by means of small grid interpolation and climatic trend rate.[Result] The precipitation during crop growing season general exhibited the decreasing trend and the precipitation trend rate was-8.6 mm/10a in Northeast China.In addition,there was lack of rain from 1971 to 1980 and relatively abundant of rain during 1981 and 1990 respectively.Moreover,the precipitation obviously exhibited decreasing trend from 1991 to 2008.But the decreasing trend was inconsistent in spatial distributions,that was,the precipitation slightly increased in relatively rainless areas and obviously decreased in relatively rainy areas.[Conclusion] The areas with obvious decreasing trend of precipitation during crop growing season are the main grain producing zones in Northeast China,so the problem of food production security caused by the precipitation changes should be paid enough attention.

Climatic Change Characteristics in Growing Season in Rice Producing Area of Liaoning over the Past 50 years

Based on the conventional meteorological data of temperature,accumulated temperature,precipitation,sunshine,frozen soil and frost-free period from five stations(including Liaozhong,Kaiyuan,Dawa,Donggang and Zhuanghe)in Liaoning Province from April to September during 1960-2009,the climatic changes in growing season in rice producing area of Liaoning Province were analyzed.The results showed that average temperature,frost-free period and accumulated temperature showed increase trend in growing season in rice producing area over the past 50 years,while average maximum depth of frozen soil,precipitation and sunshine duration went down with fluctuation.

Variations of the thermal growing season during the period 1961–2015 in northern China

Researching into changes in thermal growing season has been one of the most important scientific issues in studies of the impact of global climate change on terrestrial ecosystems. However, few studies investigated the differences under various definitions of thermal growing season and compared the trends of thermal growing season in different parts of China. Based on the daily mean air temperatures collected from 877 meteorological stations over northern China from 1961 to 2015, we investigated the variations of the thermal growing season parameters including the onset, ending and duration of the growing season using the methods of differential analysis, trend analysis, comparative analysis, and Kriging interpolation technique. Results indicate that the differences of the maximum values of those indices for the thermal growing season were significant, while they were insignificant for the mean values. For indices with the same length of the spells exceeding 5°C, frost criterion had a significant effect on the differences of the maximum values. The differences of the mean values between frost and non-frost indices were also slight, even smaller than those from the different lengths of the spells. Temporally, the starting date of the thermal growing season advanced by 10.0–11.0 days, while the ending dates delayed by 5.0–6.0 days during the period 1961–2015. Consequently, the duration of the thermal growing season was prolonged 15.0–16.0 days. Spatially, the advanced onset of the thermal growing season occurred in the southwestern, eastern, and northeastern parts of northern China, whereas the delayed ending of the thermal growing season appeared in the western part, and the length of the thermal growing season was prolonged significantly in the vast majority of northern China. The trend values of the thermal growing season were affected by altitude. The magnitude of the earlier onset of the thermal growing season decreased, and that of the later ending increased rapidly as the altitude increased, causing the magnitude of the prolonged growing season increased correspondingly. Comparing the applicability of selected indices and considering the impacts of frost on the definitions are important and necessary for determining the timing and length of the thermal growing season in northern China.

Changes in Local Growing Season Indices in Shanghai Due to Urbanization during 1873–2013

The contribution of urbanization to the changes in growing season indices(e.g.,the start date of the growing season,Ds)in Shanghai,eastern China,for the period 1873–2013 is assessed.The urban-related Ds advancement(referred to as the urbanization contribution,UC)is reconstructed based on the changing urban-land fraction within a grid box around Shanghai for 1873–2013.After removing the UC from the raw Ds time series,the secular trend(ST)representing the long-term climatic warming and multidecadal variability(MDV)representing an oscillatory component with a period of several decades are obtained by using the Ensemble Empirical Mode Decomposition(EEMD)method.Results show that the UC is comparable with the contribution of the ST for the period 1873–2013,when Ds exhibits an advancing rate of about 0.44 days per decade.MDV plays an important role in regulating changes in Ds on the decadal timescale,e.g.,with a contribution of about 56.1%for1981–2013.

Observed Climatic Variations in the Growing Season of Field Crops in Northeast China from 1992 to 2012

To determine the potential effects of climate change on crop phenological development and productivity, an integrated analysis was conducted based on the observed climatic and phenological records of Northeast China from 1992 to 2012. A set of quality assurance procedures, including repeated record checks, agro-meteorological station selection, internal consistency checks, temporal outlier checks, spatial outlier checks, and interpolation of missing data, were designed and applied to the phenology datasets of spring maize and paddy rice. Our results indicated that almost all phenological dates of spring maize and paddy rice became increasingly delayed from 1992 to 2012, The duration of the growing season was prolonged, particularly for the grain-filling stage （GS3）. The prolonged growing season was beneficial to productivity. For spring maize, the average precipitation during GS3 decreased at a rate of 27.46 mm/decade, and the annual accumulated temperature over 10℃ increased at a rate of 31.07℃/ decade. Farmers initiatively adjusted crop cultivars and selected drought-resistant crops to cope with the challenges of drought.

Soil Respiration Characteristics and Its Relationship with Environmental Factors of Different Vegetation Types during Growing Season in Dongting Lake

In order to ascertain the soil carbon flux characteristics of poplar plantations and crop communities in the Dongting Lake area during the growing season and their correlation with hydrothermal conditions,soil respiration rate was monitored at fixed sites and time points with an LI-8100 A automated soil flux system.Meanwhile,the surface temperature and soil temperature and humidity were measured. The soil respiration variation in the two different vegetation types and its correlation with environmental factors were analyzed. The results showed that in the growing season,the diurnal variation curves of soil respiration rate in the two different vegetation types showed a single peak variation,but there was certain difference in the appearance time of the peak. The peak of the crop appeared around11: 00 am,while the peak of soil respiration in the poplar appeared around 13: 00. The soil respiration rate of the poplar was also significantly higher than that of the crop,and the average difference of soil respiration rate between the two was 3. 09 and 3. 55 μmol/( m^2·s) in April and August,respectively. Temperature and soil moisture were the main factors affecting soil respiration of the poplar plantation and crop community. Temperature had a greater effect on the soil respiration of the crop community,and soil humidity had a greater impact on soil respiration in the poplar plantation,showing a correlation coefficient reaching 0. 952.

Projections of the Advance in the Start of the Growing Season during the 21st Century Based on CMIP5 Simulations

It is well-known that global warming due to anthropogenic atmospheric greenhouse effects advanced the start of the vegetation growing season （SOS） across the globe during the 20th century. Projections of further changes in the SOS for the 21st century under certain emissions scenarios （Representative Concentration Pathways, RCPs） are useful for improving understanding of the consequences of global warming. In this study, we first evaluate a linear relationship between the SOS （defined using the normalized difference vegetation index） and the April temperature for most land areas of the Northern Hemisphere for 1982-2008. Based on this relationship and the ensemble projection of April temperature under RCPs from the latest state-of-the-art global coupled climate models, we show the possible changes in the SOS for most of the land areas of the Northern Hemisphere during the 21st century. By around 2040-59, the SOS will have advanced by -4.7 days under RCP2.6, -8.4 days under RCP4.5, and -10.1 days under RCPS.5, relative to 1985-2004. By 2080-99, it will have advanced by -4.3 days under RCP2.6, -11.3 days under RCP4.5, and -21.6 days under RCP8.5. The geographic pattern of SOS advance is considerably dependent on that of the temperature sensitivity of the SOS. The larger the temperature sensitivity, the larger the date-shift-rate of the SOS.

Amylose Content and Starch Granule Size in Rice Grains are Affected By Growing Season

Amylose content and starch granule size in grains influence rice quality,which differs between the early(ES)and late season(LS).The objective of this study was to determine the variation of amylose content and starch granule size between seasons and find the main reasons(e.g.,temperature and solar radiation)for the observed variation.Field experiments with six rice varieties(three high and three low amylose content rice)planted in the ES and LS were conducted in 2016 and 2017,respectively.The mean temperatures during the filling stage were higher in ES,however,the daily temperatures at 7-10 days after flowering(DAF)in 2016,and at 5-10,13-14 DAF in 2017 were higher in LS.The results showed that amylose content in LS was lower than in ES with high amylose content rice varieties(HACV);the opposite trend occurred with low amylose content rice varieties(LACV).The mean starch granule diameter was higher in LS than ES in 2016,but the opposite result occurred in 2017 with all rice.Our results suggest that higher temperatures increased and decreased the amylose content in HACV and LACV,respectively.Temperatures at 5-15 DAF were important for the formation of starch granules:lower temperatures during 10-14 DAF increased the proportion of larger starch granules(d>6.21μm,some with d>13.3μm),and higher temperatures at 5-6 DAF increased the proportion of starch granules with diameter 4.24-6.21μm.

Non-growing season soil CO_2 efflux and its changes in an alpine meadow ecosystem of the Qilian Mountains,Northwest China

Most soil respiration measurements are conducted during the growing season.In tundra and boreal forest ecosystems,cumulative,non-growing season soil CO2 fluxes are reported to be a significant component of these systems＇ annual carbon budgets.However,little information exists on soil CO2 efflux during the non-growing season from alpine ecosystems.Therefore,comparing measurements of soil respiration taken annually versus during the growing season will improve the accuracy of estimating ecosystem carbon budgets,as well as predicting the response of soil CO2 efflux to climate changes.In this study,we measured soil CO2 efflux and its spatial and temporal changes for different altitudes during the non-growing season in an alpine meadow located in the Qilian Mountains,Northwest China.Field experiments on the soil CO2 efflux of alpine meadow from the Qilian Mountains were conducted along an elevation gradient from October 2010 to April 2011.We measured the soil CO2 efflux,and analyzed the effects of soil water content and soil temperature on this measure.The results show that soil CO2 efflux gradually decreased along the elevation gradient during the non-growing season.The daily variation of soil CO2 efflux appeared as a single-peak curve.The soil CO2 efflux was low at night,with the lowest value occurring between 02：00-06：00.Then,values started to rise rapidly between 07：00-08：30,and then descend again between 16：00-18：30.The peak soil CO2 efflux appeared from 11：00 to 16：00.The soil CO2 efflux values gradually decreased from October to February of the next year and started to increase in March.Non-growing season Q10 （the multiplier to the respiration rate for a 10℃ increase in temperature） was increased with raising altitude and average Q10 of the Qilian Mountains was generally higher than the average growing season Q10 of the Heihe River Basin.Seasonally,non-growing season soil CO2 efflux was relatively high in October and early spring and low in the winter.The soil CO2 efflux was positively correlated with soil temperature and soil water content.Our results indicate that in alpine ecosystems,soil CO2 efflux continues throughout the non-growing season,and soil respiration is an important component of annual soil CO2 efflux.

Precipitation Variation during the Crop Growing Season and Analysis of the Trend of Agricultural Drought and Flood in Dalian City in Recent 60 Years

[Objective] The aim was to study the precipitation changes and agricultural flood and drought degree of crops in Dalian City in recent 60 years. [Method] The monthly precipitation and average temperature data from April to October during 1951-2010 in Dalian observation station were selected. By dint of linear regression, climate tendency rate and humidity index, the growth changes and agricultural flood and drought degree of crops in recent 60 years in Dalian City were expounded from the aspects of natural precipitation tendency changes and agricultural water satisfaction degree of crops in growth period. [Result] In recent 60 years, the precipitation of crops during growth period in Dalian City had decreasing tendency. The inclination rate was -15.888 m/10 a. Precipitation decreased 95.3 mm in recent 60 years; precipitation increased a little in spring and decreased a lot in summer, then decreased in autumn. The monthly precipitation in each month distributed unevenly. Precipitation in July and August increased, taking account of 53.8% of the total precipitation during the growth period of crops. The K value of humidity index during the growth period of crops in Dalian in recent 60 years was 0.90 in general. It was light drought climate. The humidity index was decreasing. Climate developed toward drought direction; the drought occurrence frequency was 59%. It was mild drought climate in spring and autumn. The climate was generally wet in summer. Seen from the yearly means, besides of July and August, it reached mild drought degree in other months. [Conclusion] The study provided reference for the regional agricultural production, agricultural structure adjustment and drought and flood disaster prevention.

Mid-West Growing Season Weather

An earlier discussion of the summer northward heat flux at ground level at one location in northwest Iowa, based on observing the winds there over 30 consecutive summers, is extended geographically west to the Rocky Mountains and southward. Also the time-scale is stretched well past 30 years. Evidence cited is the eastward increase in plant size and greenery at constant latitude starting at the mountains, which is easily noticed from Texas to North Dakota. One dynamical element, the Coriolis force, acting on the north and south winds over long time periods helps explain the observations. Conservation of mass is another important ingredient.

Plant community dynamics during the growing season of typical ecosystems on the Tibetan Plateau

The relationships between vegetation and environmental factors have always been a core concern of ecologists.The dynamic characteristics of plant communities during the growing season can directly reflect these relation-ships,so we examined this issue for three typical ecosystems on the Tibetan Plateau.During the growing season,the dominant species remained stable while non-dominant species changed significantly in the alpine meadow and alpine steppe and a mono-dominant community was found in the temperate desert shrub.Due to the seasonal variations of temperature and soil water content,plant species diversity varied significantly during the growing season.Patrick richness,Pielou evenness and Simpson diversity indices differed significantly in the alpine meadow and alpine steppe.The total biomass of these three ecosystems was the largest during the middle growing season.Biomass was greater in the alpine meadow than the alpine steeps or temperature desert.The root-to-shoot ratio was the lowest during the middle growing season for the alpine meadow and alpine steppe and largest during the early growing season for temperate desert shrub.RDA showed the belowground and total biomass were greatly affected by soil physicochemical factors.Multiple linear stepwise regression showed the above ground biomass was greatly affected by relative atmospheric humidity and belowground and total biomass were greatly affected by soil organic carbon,total nitrogen at 0-20 cm soil depth and pH at 10-20 cm soil depth.These findings pro-vide insights into understanding the relationships between vegetation and environmental factors and promote the sustainable utilization of local grasslands on the Tibetan Plateau.

Effect of seasonal snow on the start of growing season of typical vegetation in Northern Hemisphere

Under global warming, seasonal snow takes faster melting rate than before, which greatly changes the hydro-logical cycle. In this study, by targeting three typical seasonal snow-covered land types (i.e., open shrubland,evergreen needleleaf forest and mixed forest) in the Northern Hemisphere, the start of growing season (SGS) hasbeen found obviously advanced in the past years, greatly contributed by the faster melting rate of seasonal snow.It is manifested that significantly positive correlation has been found between SGS and May snow depth for openshrubs, March and April snow depth for evergreen needleleaf forests and March snow depth for mixed forests.However, such close association is not appeared in all the climate conditions of same vegetation. In the future,as the rate of melting snow becomes faster in the high emission of greenhouse gasses than the current situation,continuously advanced SGS will accelerate the change of vegetation distribution in the Northern Hemisphere.These findings offer insights into understanding the effect from seasonal snow on vegetation and promote thesustainable utilization of regional vegetation in the Northern Hemisphere.

Decoupling between Plant Productivity and Growing Season Length under a Warming Climate in Canada’s Arctic

Given the short duration of growing season in the Arctic, a strong correlation between plant productivity and growing season length (GSL) is conventionally assumed. Will this assumption hold true under a warming climate? In this study, we addressed the question by investigating the relationship between net primary productivity of leaves (NPPleaf) and GSL for various tundra ecosystems. We quantified NPPleaf and GSL using long-term satellite data and field measurements. Our results indicated that the relationship was not significant (i.e., decoupled) for 44% to 64% of tundra classes in the southern Canadian Arctic, but significant for all classes in the northern Canadian Arctic. To better understand the causes of the decoupling, we further decomposed the relationship into two components: the correspondence of interannual variations and the agreement of long- term trends. We found that the longer the mean GSL for a tundra class, the poorer the correspondence between their interannual variations. Soil moisture limitation further decoupled the relationship by deteriorating the agreement of long-term trends. Consequently, the decoupling between NPPleaf and GSL would be more likely to occur under a warming climate if the tundra class had a mean GSL > 116 (or 123) days with a dry (or moist) soil moisture regime.

Impact of Climate Warming and Drying on Crop Growing Season in Northwestern Liaoning

Based on the observation data of the average temperature and precipitation of 8 national meteorological stations in the northwest region of Liaoning Province from April to October during 1961-2015,methods such as linear trend estimation,moving average,standard deviation and Mann-Kendall test are used to analyze the characteristics of average temperature and precipitation during the crop growing season in northwestern Liaoning.The results show that the average temperature during the crop growing season in the study area showed an upward trend,and the climate tendency rate was 0.193 ℃/10 a( P < 0.01).The largest contribution rate to temperature increase was in September,with a climate tendency rate of 0.27 ℃/10 a;the smallest contribution rate to the temperature increase was in July,with a climate tendency rate of 0.10 ℃/10 a.The warming trend was the most obvious in the second base year,with a climate tendency rate of 0.413 ℃/10 a( P < 0.01).The temperature was the lowest in the 1970s and the highest in the 2010s.The warming trend changed suddenly in 1996,and the sudden change reached a significant level of α = 0.05 after 2002.Precipitation was generally decreased,and the climate tendency rate was -7.68 mm/10 a.The decrease in precipitation was the most in July,and the climate tendency rate was -12.08 mm/10 a.The average temperature in the four base years failed to pass the correlation significance test.Among them,it showed an increasing trend in the second and third base year and a decreasing trend in the first and fourth base year.Rainfall was the highest in the 1960s and the lowest in the 1980s.After the abrupt change in 2002,precipitation decreased significantly.The research results provide reference for effective utilization of climate resources,rational adjustment of agricultural planting structure,and improvement of ecological environment quality.

Growing Season and Phenological Stages of Small Grain Crops in Response to Climate Change in Alaska

The climate change in Alaska has caused earlier spring snowmelt and the growing season expanded. However, the effect of climate change on crop phenological stages, heading (BBCH 55) and maturity (BBCH 85), is unknown. In this study, the trends of growing-season length (GSL), phenological stages of crops and climatic parameters, and the correlations between climatic parameters and the phenological stages were analyzed using the climate data and crop data over the period of 1978 to 2016. The longer GSL was found in Fairbanks (64.83˚N, 147.77˚W) and in Delta Junction (64.05˚N, 145.60˚W) but not in Palmer (61.60˚N, 149.11˚W). Sowing dates did not change significantly in three locations. The decreasing trends of heading and maturity of crops were observed but varied with location. Heading of barley and oat significantly advanced 3 and 3.1 d decade-1, respectively from 1989 to 2016 in Fairbanks while no change of heading was observed in Delta Junction and Palmer. Maturity of barley, oat and wheat significantly advanced 2.6, 3.8 and 3.9 d decade-1, respectively from 1978 to 2016 in Fairbanks (P < 0.05);maturity of oat and wheat significantly advanced 4.4 and 3.4 d decade-1 from 1978 to 2015, respectively in Delta Junction (P < 0.05). The increasing temperature trends and decreasing precipitation trends were found in Fairbanks and Delta Junction but varied with phenological stages of crops. Sowing was more important for heading than for maturity of crops. The effect of climate change on heading was less important than that on maturity. Earlier maturity of crops in Fairbanks may be attributed to increased temperatures, that in Delta Junction to both increased minimum temperature and decreased precipitation and that in Palmer to temperature and precipitation.

Co-influence of the start of thermal growing season and precipitation on vegetation spring green-up on the Tibetan Plateau

The climate in the Tibetan Plateau(TP)has undergone significant change in recent decades,mainly in thermal and water conditions,which plays a crucial role in phenological changes in vegetation spring phenology.However,how the start of the thermal growing season(SOS-T)and the start of the rainy season(SORS)as key climatic factors affect vegetation green-up remains unclear.Given that these factors characterize thermal and water conditions required for vegetation green-up,this study investigated changes in the SOS-T and SORS from 1961 to 2022,using observation-based datasets with long time series.We found that the SOS-T and SORS have advanced across the TP in 1961-2022 and have shown a spatial pattern of advancement in the east and delay in the west in 2000-2022.Further,the co-effect of temperature and precipitation change on the start of vegetation growing season(SOS-V)in 2000-2022 was observed.Averaged across TP,the SOS-V had an early onset of 1.3 d per decade during 2000-2022,corresponding to advanced SOS-T and SORS.Regionally,the SOS-V generally occurred nearly at the same time as the SOS-T in the high-altitude meadow region.A substantial delay in the SOS-V relative to the SOS-T was observed in the desert,shrub,grassland and forest regions and generally kept pace with the SORS.Furthermore,for 50%of the vegetated regions on the TP,inter-annual variation in the delay in the SOS-V relative to the SOS-T was dominated by precipitation change,which was profound in warm-climate regions.This study highlights the co-regulation of precipitation and temperature change in the SOS-V in different vegetation cover regions in the TP,offering a scientific foundation for comprehending the impact of climate change and prospects for vegetation phenology on the TP.

Unique genes carried by abundant species enhance CH_(4) emissions during the growing season at the Tibetan Plateau

CH_(4) emission rates followed an increased pattern during the growing season at Tibetan Plateau.•Unique genes carried by abundant species were positively correlated with CH_(4) emission rates.•Climate factors influenced CH_(4) emission rates by regulating microbial community and their genes.Microorganisms play pivotal roles in soil methane(CH_(4))emissions and their functional genes are origins of a key mechanism for soil CH4-cycling.However,understanding of the roles of specific genes(e.g.,unique or shared genes carried by species)underlying CH_(4)-cycling remains elusive.Here,we measured CH_(4) emission rates and investigated variations in microbial community and the abundance of genes carried by species during the growing season in alpine meadow on the Tibetan Plateau.We discovered that CH_(4) emission rates increased from 394.4,745.9,and 1092.7µg CH4 m−2 h−1,in April,June,and August,respectively,and had a positive correlation with unique genes carried by abundant species during the growing season.Moreover,we found that unique genes carried by abundant species involved in methanogenesis processes have a higher abundance than methanotrophic processes.Further analysis indicated that climate factors(i.e.,mean monthly temperature(MMT)and mean monthly precipitation(MMP))influenced microbial community and their functional genes,and therefore affected the CH_(4) emission rates.Overall,the present study provides a novel insight into the variation of soil CH4 emissions from a functional gene perspective,highlighting the important roles of unique genes carried by abundant species in CH4 emissions in the Tibetan Plateau under seasonal variation.

基于连续观测数据的毛乌素沙地生长季土壤水分动态及其对降雨的响应

水分是制约半干旱区沙地植物生长发育和生态建设的关键非生物因子。于2008—2010年和2018—2021年生长季(4—10月)对毛乌素沙地流动、半固定和固定沙地0~100cm深土壤水分进行了连续观测,系统分析了不同固定程度沙地土壤水分动态变化规律及其对降雨的响应。结果表明:(1)受降雨季节变化的影响,流动、半固定和固定沙地不同深度土壤水分季节变化一般呈∽型或双峰型,10 cm和30 cm深土壤水分含量波动较大,60 cm和100 cm深土壤水分含量波动较小。(2)3种固定程度沙地生长季土壤水分动态差异明显,总体来看,流动沙地土壤水分状况最好,且土壤水分含量变化相对平缓,固定沙地土壤水分状况最差,且土壤水分含量变化最为剧烈,半固定沙地居于二者之间;固定沙地10~30cm深土壤水分状况好于半固定沙地和流动沙地,30~100cm深土壤水分状况则相反。(3)降雨格局是形成土壤水分时空格局的主要原因,随降雨事件降雨量增加,降雨的入渗深度逐渐增加;但是固定沙地土壤水分的深层补充需较强的降雨和较长的时间。生长季降雨事件以小降雨事件为主,表层土壤水分波动更剧烈。生长季初期降雨较少且以小降雨事件为主,10cm以下土壤水分补充困难,土壤水分状况较差。流动沙地和半固定沙地10~30cm深土壤水分状况好于30~100cm深土壤,而固定沙地土壤水分状况则相反。研究结果可为半干旱区沙化土地近自然植被恢复与固沙植被稳定性维持提供科学依据。