黄土丘陵区雨养梨枣树生长对初始土壤含水率的响应

以6年生矮化密植梨枣树(Ziziphus jujuba Mill.)为试材,在雨养条件下,设置4种不同初始土壤体积含水率水平(1区,15.17%;2区,14.33%;3区,11.34%;4区,8.61%),测定并分析土壤水分变化、枣树生长、枣树耗水及其产量。结果表明:在雨养条件下,随着时间的推进,4个小区的土壤体积含水率不断接近,由最初的有显著差异变为没有显著差异;梨枣林地在低土壤水分情况下,可以通过自然降雨修复干层;4个小区的生物量和产量都是随着初始土壤含水率的减小在减小,且小区之间产量差异显著;4种初始土壤水分条件下,4个小区获得的产量分别为21 744.9、18 648.0、12 354.3 kg·hm~(-2)和6 660.0 kg·hm~(-2),说明即使在初始土壤水分亏缺情况下,在平水年也可以得到一定的产量;高度为0.9~1.2 m,冠幅为0.5~0.9 m的梨枣树,产量却达到最高21 744.9 kg·hm~(-2),说明梨枣获得高产不需要高大的树体,所以矮化密植具有很大潜力。     

Response of soil water dynamics to precipitation years under different vegetation types on the northern Loess Plateau,China

Implementation of the Grain-for-Green project has led to rapid land cover changes and resulted in a significantly increased vegetation cover on the Loess Plateau of China during the past few decades. The main objective of this study was to examine the responses of soil water dynamics under four typical vegetation types against precipitation years. Soil water contents(SWCs) were measured in 0–4.0 m profiles on a hillslope under the four vegetation types of shrub, pasture, natural fallow and crop in a re-vegetated catchment area from April to October in normal(2010), dry(2011), wet(2014) and extremely wet(2013) years. The results indicated that precipitation and vegetation types jointly controlled the soil water temporal dynamics and profile characteristics in the study region. SWCs in 0–4.0 m profiles of the four vegetation types were ranked from high to low as cropfallowpastureshrub and this pattern displayed a temporal stability over the four years. In the extremely wet year, SWC changes occurred in the 0–2.0 m layer under shrub and pasture while the changes further extended to the depth of 4.0-m deep layers under fallow and crop. In the other three years, SWCs changes mainly occurred in the 0–1.0 m layer and kept relatively stable in the layers deeper than 1.0 m for all the four vegetation types. The interannual variation in soil depth of SWCs was about 0–2.0 m for shrub and pasture, about 0–3.4 m for fallow and about 0–4.0 m for crop, respectively. The dried soil layers formed at the depths of 1.0, 0.6, 1.6 and 0.7 m under shrub, and 1.0, 1.0, 2.0 and 0.9 m under pasture, respectively in 2010, 2011, 2013 and 2014. The infiltrated rainwater mostly stayed in the 0–1.0 m layer and hardly supplied to soil depth 1.0 m in normal, dry and wet years. Even in the extremely wet year of 2013, rainwater recharge depth did not exceed 2.0 m under shrub and pasture. This implied that soil desiccation was difficult to remove in normal, dry and wet years, and soil desiccation could be removed in 1.0–2.0 m soil layers even in the extremely wet year under shrub and pasture. The results indicated that the natural fallow was the best vegetation type for achieving sustainable utilization of soil water and preventing soil desiccation.     

Effects of vegetation types on soil water dynamics during vegetation restoration in the Mu Us Sandy Land,northwestern China

The arid and semi-arid northwestern China has been undergoing ecological degradation and the efforts to reverse the ecological degradation have been undertaken for many years. Some shifting dunes have been fixed and the vegetation has been partially recovered in certain areas and the Mu Us Sandy Land in the Ordos Plateau is an example of the success. The present study attempts to reveal the relationships between the vegetation restoration and ecohydrology in the Mu Us Sandy Land. We continuously measured soil water content at 10-min intervals under three vegetation types(i.e., shifting dune, shrub-dominated community, and herb-dominated community) in the Mu Us Sandy Land from April 2012 to October 2013. The results show the infiltration coefficient increased with increased rainfall amount and eventually reached a stable value. Infiltration coefficients were 0.91, 0.64, and 0.74 in the shifting dune, in the shrub-dominated community, and in the herb-dominated community, respectively. Cumulative infiltration and soil texture are two vital factors affecting the depths of rainfall penetration. Only rainfall events larger than 35.0 mm could recharge soil water at the 60–80 cm layer in the herb-dominated community. Our results imply that the expected forward succession of restored vegetation may be destined to deterioration after reaching the climax simply because of following two facts:(1) soil water is mainly retained at shallower layer and(2) plant fine roots mainly distribute in deeper layer in the herb-dominated community.     

半干旱区草地土壤动物多样性的季节变化及其与温湿度的关系

在中国科学院奈曼沙漠化研究站附近选择不同程度封育草地为研究样地,通过调查不同季节降雨、温度、土壤温度和水分以及土壤动物特征,分析了土壤动物季节变化及其对降雨和温度的响应特征。结果表明:研究样地共获得土壤动物11目13个类群,螨类和鞘翅目幼虫为优势类群,存在于3个季节中;常见类群随季节变化发生更替。夏季大型土壤动物个体数多,种类丰富,多样性较高,而春季和秋季均较低。中小型土壤动物密度表现为春季>夏季>秋季,Shannon指数和均匀度指数表现为夏季较高,而春季和秋季均较低。相关分析表明,土壤含水量季节变化是影响大型土壤动物群落个体数季节分布的主要因素,而中小型土壤动物个体数、类群数、Shannon指数和均匀度指数与土壤含水量和温度间均无显著相关关系(P>0.05)。说明夏季"雨热同季"对大型土壤动物多样性影响较大,而对中小型土壤动物多样性影响相对较小。     

不同留茬覆盖模式对土壤蒸发和表层土壤含水量的影响

秸秆覆盖模式可显著影响土壤蒸发量和土壤含水量。本研究根据小麦机械收获的特点,设置不同的小麦留茬高度和覆盖量,研究了不同留茬高度和覆盖量组合对冬小麦收获后土壤表层含水量和土壤蒸发量的影响。试验结果显示冬小麦留茬高度0~35 cm对表层土壤含水量和土壤蒸发影响较小,而覆盖会明显改善土壤含水量和降低土壤蒸发量。当留茬高度为0~15 cm、田间剩余秸秆覆盖量为0.348~0.470 kg/m2时,试验期间(31 d)土壤累积蒸发量较无覆盖减少了16%~51%。考虑机收特点,建议小麦留茬高度为5~15 cm,其余残留碎杆覆盖在土壤表面,以减少土壤蒸发和提高水分利用效率。     

季节性冻融期覆砂对太谷农田土壤含水率时空变化的影响

研究了冻融期砂层覆盖对剖面土壤含水率的影响。野外试验于2016年11月—2017年3月在山西省太谷均衡实验站进行,主要监测3种地表处理剖面0~100 cm土壤含水率,各处理分别为无覆盖（LD）、0.5~1.5 mm粒径（XS）和1.5~2.0 mm粒径砂层覆盖（CS）。结果表明：冻融期砂层覆盖及土壤水分冻融使得XS和CS处理土壤剖面出现两个水分高值区,即近地表（15.40%~21.79%）和剖面20~40 cm间（15.99%~19.94%）;砂层覆盖对近地表有储水效果,储水效果随土壤深度增加而逐渐减小。覆砂处理对地表处储水效果最佳,平均土壤含水量较LD处理高8.45%~10.94%。覆砂对剖面0~40 cm有明显的储水效果,平均土壤含水率较LD处理高1.56%~1.62%。 40 cm以下3种处理土壤含水率相差较小,平均土壤含水率差值为0.09%~0.40%;砂层覆盖储水效果还与砂层粒径有关,XS处理0~5 cm储水效果优于CS处理,其土壤含水率高于CS处理0.57%~2.39%;地表砂层覆盖可以平抑地表土壤含水率变化,覆砂处理地表土壤含水率变幅较LD处理低约4.42%。     

黄土高原沟壑区果园还耕对土壤水分的影响

在黄土高原沟壑区王东沟小流域,在塬面、梁地和坡地三种地貌类型上,分别选取了盛果期果园、老果园和退耕还田等3种土地利用与管理方式,测定土壤0～400 cm(塬面0～600 c m)水分含量分布,研究果园的利用管理方式变化对土壤剖面中水分含量变化的影响.结果表明,梁地和坡地上,盛果期果园、老果园土壤水分含量均接近作物凋萎湿度(10%);塬面上,盛果期果园、老果园土壤水分含量为15%.退果4年的耕地、坡地0～400 cm土层土壤储水量显著增加,梁地和塬面虽有增加但与老果园相比,剖面储水量并没有达到显著水平;退果4年耕地、坡地和梁地剖面中的60～140 cm和220～400 cm含水量提高最显著,塬面上22 0～600 cm土层中水分提高显著.     

黄土高原南部植被恢复对土壤理化性状与土壤酶活性的影响

利用退耕区域不同植被恢复类型为试点,研究不同植被恢复年限、不同恢复类型土壤理化性状和土壤酶活性动态变化。结果表明,随着恢复年限增加,土壤容重先增加后逐渐下降;pH降低,降幅为1.47%~5.52%;土壤有机质、全氮逐渐增加,增幅分别为9.76%~71.54%、17.39%~62.32%;全磷含量除30 a刺槐比对照增加了12.92%外,其它植被类型均低于对照;速效养分略有增加,趋势不明显;酶活性逐渐增强,尿酶、过氧化氢酶、碱性磷酸酶、蔗糖酶增幅分别为39%~229%、34%~96%、25%~149%、74%~250%。相关性分析表明,各种酶活性与有机质及全氮含量显著相关。因此,实施退耕还林植被恢复有利于土壤理化性状改善,酶活性增强。     

保护性耕作对黄土高原旱地表土容重和水分入渗的影响

通过在陇中黄土高原半干旱区进行保护性耕作的定位研究,探讨了保护性耕作对土壤容重以及渗透性能的影响。结果表明:与传统耕作(T)、免耕无覆盖(NT)、传统耕作结合秸秆还田(TS)相比,试验的前2～3a免耕覆盖(NTS)使得土壤容重增大,而后保持稳定状态不再持续增加。通过对渗吸率、宏观毛管长度、有效孔径以及饱和导水率等指标的比较发现,免耕覆盖(NTS)对土壤的渗透性能有显著的改善作用。     

气候变化对内蒙古兴安盟半干旱农区土壤水分的影响

根据兴安盟重点农区突泉县1961～2006年气象资料和1982～2006年土壤水分资料,采用统计及相关分析方法,分析了近46年来气候变化及其对当地主要农区土壤水分的影响,以及未来气候变化将对土壤水分的可能影响.结果表明,近46年来,内蒙古兴安盟半干旱农区温度呈上升趋势,21世纪以来有加速升温的趋势;降水量变化趋势不明显,存在年代间差异和季节差异,但21世纪以来降水量减少趋势明显;近25年来各季节土壤水分呈下降趋势,并且有加速下降的趋势.环境气象因子对土壤水分的影响以温度和降水量的影响最明显,春季以温度的影响为主,而夏、秋季以降水量的影响为主导.未来气候变化将导致兴安盟半干旱农区土壤水分趋于减少,农业干旱将趋于严重,农业水资源将更加紧张.     

黄土高原典型塬区土壤湿度特征分析

利用2005和2006年黄土高原陆气相互作用观测资料分析了不同下垫面的土壤湿度状况,并从土壤物理学的角度分析了造成各种下垫面湿度分布和变化不同的原因,得到如下结论:在近地层,各站的土壤湿度具有微弱的日变化特征;5cm层土壤含水量对降水比较敏感,随着降水的发生,土壤含水量迅速上升。随着深度的增大,土壤含水量上升的幅度逐渐减小,且滞后时间逐渐延长,但到了40cm深度处,土壤含水量就基本不受降水的影响了。从全年来说,该地区一年中可以区分出两个主要的水分时期,即蓄水期和失水期。蓄水期处于雨季,从6月到9月,10月开始到次年5月为失水期。冬春季节是土壤含水量最少的季节,从1月下旬一直持续到3月上旬,9月是土壤含水量最大的季节。土壤含水量变化规律可以分为两层,在25cm深度以上,冬春季节从上层到下层依次减小,夏秋季节从上到下依次增大;25cm到40cm土层全年都是从上层到下层依次增大;20cm土层附近相对于其余各层土壤含水量在全年都是最低的。     

Changes in soil microbial community response to precipitation events in a semi-arid steppe of the Xilin River Basin,China

In the context of climate change, precipitation is predicted to become more intense at the global scale. Such change may alter soil microbial communities and the microbially mediated carbon and nitrogen dynamics. In this study, we experimentally repackaged precipitation patterns during the growing season(from June to September) of 2012 in a semi-arid temperate steppe of the Xilin River Basin in Inner Mongolia of China, based on the 60-year growing season precipitation data. Specifically, a total amount of 240 mm simulated precipitation was assigned to experimental plots by taking the following treatments:(1) P6(6 extreme precipitation events, near the 1~(st) percentile);(2) P10(10 extreme precipitation events, near the 5~(th) percentile);(3) P16(16 moderate precipitation events, near the 50~(th) percentile); and(4) P24(24 events, 60-year average precipitation, near the 50~(th) percentile). At the end of the growing season, we analyzed soil microbial community structure and biomass, bacterial abundance, fungal abundance and bacterial composition, by using phospholipid fatty acid(PLFA), real-time quantitative polymerase chain reaction(RT-qPCR) and 16S rRNA gene clone library methods. The extreme precipitation events did not change soil microbial community structure(represented by the ratio of PLFA concentration in fungi to PLFA concentration in bacteria, and the ratio of PLFA concentration in gram-positive bacterial biomass to PLFA concentration in gram-negative bacterial biomass). However, the extreme precipitation events significantly increased soil microbial activity(represented by soil microbial biomass nitrogen and soil bacterial 16S rRNA gene copy numbers). Soil fungal community showed no significant response to precipitation events. According to the redundancy analysis, both soil microbial biomass nitrogen and soil ammonium nitrogen(NH_4-N) were found to be significant in shaping soil microbial community. Acidobacteria, Actinobacteria and Proteobacteria were the dominant phyla in soil bacterial composition, and responded differently to the extreme precipitation events. Based on the results, we concluded that the extreme precipitation events altered the overall soil microbial activity, but did not impact how the processes would occur, since soil microbial community structure remained unchanged.     

Long-term effects of mowing on plasticity and allometry of Leymus chinensis in a temperate semi-arid grassland,China

Mowing is an important land management practice for natural semi-arid regions.A growing body of empirical evidence shows that different mowing regimes affect the functioning of grassland ecosystems.However,the responses of plant functional traits to long-term mowing and their allometric scaling under long-term mowing are poorly understood.For a better understanding of the effects of mowing on grassland ecosystems,we analyzed the allometric traits of leaves and stems of Leymus chinensis(Trin.) Tzvel.,a dominant grass species in eastern Eurasian temperate grassland,at different mowing intensities(no clipping,clipping once every two years,once a year and twice a year).Experiments were conducted on plots established over a decade ago in a typical steppe of Xilinhot,Inner Mongolia,China.Results showed that most of the functional traits of L.chinensis decreased with the increased mowing intensity.The responses of leaves and stems to long-term mowing were asymmetric,in which leaf traits were more stable than stem traits.Also significant allometric relationships were found among most of the plant functional traits under the four mowing treatments.Sensitive traits of L.chinensis(e.g.leaf length and stem length) were primary indicators associated with aboveground biomass decline under high mowing intensity.In conclusion,the allometric growth of different functional traits of L.chinensis varies with different long-term mowing practices,which is likely to be a strategy used by the plant to adapt to the mowing disturbances.     

频率域反射仪测定土壤含水量的校正与田间验证

为了获得精确的土壤含水量测定数据,在室内和田间分别进行了频率域反射仪(FDR)测定土壤含水量的校正,并在田间运用土钻取样和烘干法对模型参数进行了验证。结果表明,室内试验获得了较好的模型参数,均方根误差平均达到了0.023 m3/m3,但是应用到田间条件下误差很大,均方根误差平均为0.066 m3/m3;田间条件下也间接获得了较好的模型参数,均方根误差的平均值为0.026 m3/m3,应用于田间时测定含水量的精确度较高,均方根误差的平均值为0.026 m3/m3。因此,对于构成复杂的城市或园林土壤,在不挖剖面或土钻取样破坏土壤的前提下,建议采用田间间接法进行校正。     

Effects of vegetation near-soil-surface factors on runoff and sediment reduction in typical grasslands on the Loess Plateau,China

Vegetation near-soil-surface factors can protect topsoil from erosion, however, their contributions to the reduction of soil erosion, especially under natural rainfall events, have not been systematically recognized. This study was performed to quantify the effects of near-soil-surface factors on runoff and sediment under natural rainfall events on grasslands dominated by Bothriochloa ischaemum(Linn.)Keng(BI grassland) and Artemisia gmelinii Thunb.(AG grassland) in two typical watersheds on the ...     

Effects of agriculture,climate, and policy on NDVI change in a semi-arid river basin of the Chinese Loess Plateau

In 1999, the Grain for Green Project was implemented by the Chinese government. Since then, the vegetation of Zuli River Basin, a semi-arid river basin of the Chinese Loess Plateau, has been greatly changed. Clearly understanding the impact of natural and artificial factors on vegetation change is important for policy making and ecosystem management. In this study, spatio-temporal variations in vegetation cover in Chinese Zuli River Basin during 1999–2016 were investigated using Landsat normalized difference vegetation index (NDVI) data. Analyses of several indicators, including changes in NDVI in different slopes and land use changes and the relationships between climatic factors and NDVI change, were presented to quantitatively evaluate the effects of agriculture, climate, and policy on NDVI change. The NDVI in the Zuli River Basin increased during the study period, and the main contributors to this change were forest in 1999–2011, cropland, abandoned farmland, and grassland in 2009–2016, and land with slopes ≤ 15°. Land with slope > 15°, where the “Project” was implemented, slightly contributed to the increase in regional NDVI. In 1999–2011, the project (?98.16%) combined with climate change (?68.18%) showed negative effects on the increase in NDVI in the Zuli River Basin, but agriculture (22.28%) played a positive role in increasing this index. In 2009–2016 and 1999–2016, the project (38.45% and 35.25%, respectively), the project combined with climate change (49.83% and 46.30%, respectively), agriculture (18.61% and 23.30%, respectively), promoted increases in NDVI in the basin.     

Streamflow responses to climate change and LUCC in a semi-arid watershed of Chinese Loess Plateau

Climate change and Land Use/Cover Change(LUCC) have been identified as two primary factors affecting watershed hydrological regime. This study analyzed the trends of streamflow, precipitation, air temperature and potential evapotranspiration(PET) from 1962 to 2008 in the Jihe watershed in northwestern Loess Plateau of China using the Mann-Kendall test. The streamflow responses to climate change and LUCC were quantified independently by the elasticity method. The results show that the streamflow presented a dramatic decline with a turning point occurred in 1971, while the precipitation and PET did not change significantly. The results also show that the temperature rose markedly especially since 1990 s with an approximate increase of 1.74°C over the entire research period(1962–2008). Using land use transition matrix, we found that slope cropland was significantly converted to terrace between 1970 s and 1990 s and that forest cover increased relatively significantly because of the Grain for Green Project after 2000. The streamflow reduction was predominantly caused by LUCC and its contribution reached up to 90.2%, while the contribution of climate change to streamflow decline was only 9.8%. Although the analytical results between the elasticity method and linear regression model were not satisfactorily consistent, they both indicated that LUCC(human activity) was the major factor causing streamflow decline in the Jihe watershed from 1962 to 2008.     

晋北黄土丘陵区不同林草措施的蓄水保土和土壤水分效应研究

以设在山西省阳高县的大型径流观测场为依托,以2005-2009年的野外实测数据为依据,研究了晋北黄土丘陵区人工植被与鱼鳞坑配合的蓄水保土及土壤水分效应,并与荒坡、苜蓿地进行了对比。结果表明:在观测的5年内,柠条、沙棘、油松的蓄水保土能力随种植年限延长无明显增加趋势,但鱼鳞坑的蓄水能力和保土能力分别高达84.7%～96.0%和95.2%～99.7%;荒坡和苜蓿(Medicago sativa)第一年和第二年的蓄水保土能力较差,第三年和第四年随植被盖度增加能力急剧增强,第四年蓄水能力分别达82.8%和91.2%,保土能力达97.0%和98.0%;土壤水份分析结果表明:不同小区4～9月土壤水分变异系数为7.0%～19.1%,油松区变异系数最大,其次为沙棘、苜蓿和柠条区,荒坡区和裸坡区变异较小,不同小区土壤水分亏缺率为23.98%～52.66%,亏缺顺序为柠条区>苜蓿区>油松区>沙棘区>荒坡区>裸坡区;林草植被有效地减少了水土流失,亦增加了土壤水分的变异及亏缺程度,应注意林草植被的合理选择和配置。     

青海湖东沙地不同植被恢复措施下土壤水分变化特征

土壤水分是沙地植被格局和过程改变的主要驱动力,也是干旱半干旱区植物生长最大的限制因子.沙漠地区的土壤水分表现出明显的空间异质性.以高寒半干旱沙地青海湖东沙地为研究区,以栽植人工固沙植物(小叶杨、樟子松、沙棘和乌柳)的沙丘和自然固定沙丘(沙蒿为优势种)作为研究样地,探讨不同固沙植物影响下的沙丘不同地貌部位土壤水分变化特征...     

Effects of different mulching patterns on soil moisture,temperature, and maize yield in a semi-arid region of the Loess Plateau,China

A study was conducted in the semi-arid region of the Loess Plateau in China to identify an alternative material for use instead of plastic film under maize crops. Plastic film (PMW), straw (SMW), and biodegradable film (BMW) were used for mulching throughout the whole season (fallow and growth periods), in addition to straw for mulching (SMF) only during the fallow period. The results showed that PMW and BMW treatments retained 17 mm and 11 mm more water, respectively, than the mean value of both SMW and SMF treatments, and 53 mm and 38 mm more water than nonmulching (NM) treatment during the fallow period. PMW and BMW treatments increased the soil water and temperature during the early growth stage of maize and significantly improved the dry matter accumulation. Under PMW and BMW treatments, the yield improved by 4.6–6.4 Mg ha^?1 and 2.3–2.8 Mg ha^?1, and the net income increased by 1166 USD ha^?1 and 372 USD ha^?1 compared with NM treatment, respectively. SMW treatment led to poor growth and yield reductions of 3.7 Mg ha^?1 due to the lower temperature, whereas SMF treatment had no significant effects on the yield (P > 0.05). High water consumption with PMW treatment reduced the water supply capacity at the end of the season, and resulted in soil water deficit during 2015, indicating that high yields might not be sustained in the long-term. Therefore, BMW treatment is recommended as an effective method for increasing the maize yield and maintaining the balance of soil water in semi-arid areas.