Aridity/humidity status of land surface in China during the last three decades

To clarify aridity/humidity status of land surface is helpful for studying environmental background and regional differences, seeking causes of environmental change, and providing a scientific basis for researches on climate change in the future. In this paper, the authors calcu- lated potential evapotranspiration of China using data from 616 meteorological stations during the period of 1971―2000 with the Penman-Monteith model recommanded by FAO in 1998. Vy- sothkii’s model was used to calculate aridity/humidity index. Then the calculated results of sta- tions were interpolated to land surface using ArcGIS. Results show that the annual average po- tential evapotranspiration is 400―1500 mm in the whole country, 600―800 mm in most parts of it; and 350―1400 mm in growing season (April―Octobor), which is nearly 200 mm less than the annual average. According to the aridity/humidity indexes of 1.0, 1.5 and 4.0, the aridity/humidity status is categorized to four types, namely, humid, subhumid, semiarid and arid. A majority of stations (76%) are more humid in growing season than the annual average. Results of com- prisons between the distribution map of aridity/humidity index with that of precipitation and vegetation indicate a good consistence of aridity/humidity status with natural environment. Therefore potential evapotranspiration calculated with modified FAO’s Penman-Monteith model in combination with aridity/humidity index that considers water balance can more reasonably explain the actual land surface aridity/humidity status of China.

Spatial distribution of air temperature and relative humidity in the greenhouse as affected by external shading in arid climates

The effect of external roof shading on the spatial distribution of air temperature and relative humidity in a greenhouse(Tin and RHin) was evaluated under the arid climatic conditions of Riyadh City, Saudi Arabia. Two identical, evaporatively-cooled, single-span greenhouses were used in the experiment. One greenhouse was externally shaded(Gs) using a movable black plastic net(30% transmissivity), and the other greenhouse was kept without shading(Gc). Strawberry plants were cultivated in both greenhouses. The results showed that the spatial distribution of the Tin and RHin was significantly affected by the outside solar radiation and evaporative cooling operation. The regression analysis showed that when the outside solar radiation intensity increased from 200 to 800 W m–2, the Tin increased by 4.5℃ in the Gc and 2℃in the Gs, while the RHin decreased by 15% in the Gc and 5% in the Gs, respectively. Compared with those in the Gc, more uniformity in the spatial distribution of the Tin and RHin was observed in the Gs. The difference between the maximum and minimum Tin of 6.4℃ and the RHin of 10% was lower in the Gs than those in the Gc during the early morning. Around 2℃ difference in the Tin was shown between the area closed to the exhausted fans and the area closed to the cooling pad with the external shading. In an evaporatively-cooled greenhouse in arid regions, the variation of the Tin and RHin in the vertical direction and along the sidewalls was much higher than that in the horizontal direction. The average variation of the Tin and RHin in the vertical direction was 5.2℃ and 10% in the Gc and 5.5℃ and 13% in the Gs, respectively. The external shading improved the spatial distribution of the Tin and RHin and improved the cooling efficiency of the evaporative cooling system by 12%, since the transmitted solar radiation and accumulated thermal energy in the greenhouse were significantly reduced.

Spatial-temporal characteristics and influencing factors of relative humidity in arid region of Northwest China during 1966–2017

Playing an important role in global warming and plant growth,relative humidity(RH)has profound impacts on production and living,and can be used as an integrated indicator for evaluating the wet-dry conditions in the arid and semi-arid area.However,information on the spatial-temporal variation and the influencing factors of RH in these regions is still limited.This study attempted to use daily meteorological data during 1966–2017 to reveal the spatial-temporal characteristics of RH in the arid region of Northwest China through rotated empirical orthogonal function and statistical analysis method,and the path analysis was used to clarify the impact of temperature(T),precipitation(P),actual evapotranspiration(ETa),wind speed(W)and sunshine duration(S)on RH.The results demonstrated that climatic conditions in North Xinjiang(NXJ)was more humid than those in Hexi Corridor(HXC)and South Xinjiang(SXJ).RH had a less significant downtrend in NXJ than that in HXC,but an increasingly rising trend was observed in SXJ during the last five decades,implying that HXC and NXJ were under the process of droughts,while SXJ was getting wetter.There was a turning point for the trend of RH in Xinjiang,which occurred in 2000.Path analysis indicated that RH was negatively correlated to T,ETa,W and S,but it increased with increase of P.S,T and W had the greatest direct effects on RH in HXC,NXJ and SXJ,respectively.ETa was the factor which had the greatest indirect effect on RH in HXC and NXJ,while T was the dominant factor in SXJ.

Interactions between Vegetation and Climatic Factors in Typical Arid and Humid Regions of China Based on NDVI

According to the distribution of arid and humid regions in China,the typical arid region (Erjina),the typical semi-arid/semi-humid region (Guanzhong basin/Loess Plateau) and the typical humid region (Poyang Lake basin) were selected as the study areas.Based on NDVI data from 1982 to 2000 and meteorological observing data of three study areas from 1981 to 2000,the interactions between vegetation NDVI and climatic factors (temperature and precipitation) in typical arid and humid regions were discussed in this study.The results showed that in the responses of vegetation to climatic factors,vegetation in the typical arid region (Erjina) was more sensitive to precipitation,while vegetation in the typical semi-arid/semi-humid region (Guanzhong basin/Loess Plateau) was more sensitive to both temperature and precipitation,and vegetation in the typical humid region (Poyang Lake basin) was more sensitive to temperature.As for effects of vegetation on climatic factors,there was a remarkable negative correlation between vegetation NDVI in the past winter and temperature in the present summer,and also a significant positive correlation between vegetation NDVI in the past winter and precipitation in the present summer.However,in the typical semi-arid/semi-humid region (Guanzhong basin/Loess Plateau),there was a significant positive correlation between vegetation NDVI in the present spring and temperature in the present summer.

甘肃省植被时空动态变化及其归因分析

甘肃省作为中国西部生态安全屏障的重要组成部分,其植被覆盖变化直接关系中国西部的生态安全。采用2000-2020年植被覆盖度(FVC)数据,并从自然和人文影响方面选取16个影响因子,涵盖气候、地形地貌、土壤、人类活动,利用趋势分析法、地理探测器模型和偏最小二乘结构方程建模(PLS-SEM),从甘肃省不同干湿区、不同时间节点的角度探究其植被覆盖的变化特征及驱动力。结果表明,1)2000-2020年,甘肃省FVC整体持续改善,高植被覆盖度显著增加,其中陇东高原、陇中高原和疏勒河南部地区改善最为明显。2)不同干湿区的植被覆盖变化差异显著。干旱和半干旱区植被改善较慢,受降水量波动和土地利用方式影响大;而半湿润和湿润区植被改善明显,得益于良好的气候条件、生态工程的推动以及土壤有机碳含量的增加。3)降水和土地利用对FVC解释力最大,“退耕还林工程”对FVC的增加起到积极作用,但不合理的土地利用和城市化等也引起植被退化。随着时间推移,气候对FVC的影响一直在积极增加,不合理人类活动对FVC的负面影响相对稳定且较大,部分抵消了退耕还林的正面效果。此外,土壤有机碳含量对FVC的影响显著下降,且间接受到气候的正向影响。4)利用PLS-SEM模型,可有效分离自然与人为因素对植被覆盖的驱动作用,也可探究因素间的作用强度与途径。该研究增强了对区域植被动态变化规律的理解,也为生态恢复和环境管理提供了科学支持。

Regional difference of aridity/humidity conditions change over China during the last thirty years

The meteorological data of 616 stations in China were used to calculate the potential evapotranspira-tion and aridity/humidity index by applying the modified FAO-Penman-Monteith model. Regional difference of trends in precipitation, potential evapotranspiration and arid-ity/humidity index over China and their interdecadal varia-tions were analyzed from 1971 to 2000. The results show that all the four climatic factors trends have obvious regional difference and interdecadal variations. Annual precipitation during the 30-year period shows an increasing trend over most regions of China, with decreasing trends in potential evapotranspiration and aridity/humidity index. Most regions in China become more humid, especially significant in northern Xinjiang, eastern Tibet, western Sichuan, and northern Yunnan. The average value over China would mask the regional difference of climate change because of the com-plex environmental condition in China. Therefore regional difference should be analyzed to further understand climate change and its impacts. Both water supply and demand need to be considered when attempting to study regional arid-ity/humidity conditions.

Nutrient status of Populus euphratica growing in desert riparian forests of northwestern China

Seasonal and microhabitat variations of chemical constituents of foliar organic carbon （C）, total nitrogen （N）, total phosphorus （P）, and total potassium （K）, in Populus euphratica growing in desert riparian forests in northwestern China and their correlations were studied. Results show that ranges of C, N, P and K contents in the leaves ofP. euphratica were 39.08%-46.16%, 0.28%-2.81%, 0.05%-0.18% and 0.35%-2.03%, with means of 43.51%, 1.49%, 0.102% and 1.17%, respectively. The ratio of C/N, C/P and N/P changed from 16.26 to 146.61, from 258.08 to 908.67 and from 2.89 to 26.67; the mean was 37.24, 466.27 and 15.14, respectively. The mean N content was significantly lower than of deciduous trees in China, but the mean P content was nearly equivalent. The ratio of C/N was remarkably higher than of global land plants. The ratio of N/P indicated that growth ofP. euphratica was jointly limited by N and P nutrient deficiency. During the growth season, total trends of leaf C, N, P and K contents decreased. The max- imum appeared in May, and the minimum in September. Among microhabitats, C, N and K contents gradually increased from ri- parian lowland, flatland, sandpile, Gobi and dune, but C/N ratio was opposite, and P content was not apparent. Foliar C content was extremely, significantly and positively correlated with N and K contents, respectively. The relationships of N-K and P-K were both significantly positive.

基于网格水滴的汇流模拟计算方法

为探究网格水滴汇流方法的预报精度及物理性质,并验证其在缺资料或无资料地区的适用性,以蓄满产流为原理,结合网格新安江模型进行产流计算,构建了基于网格水滴的汇流模型。以湿润地区屯溪及其嵌套子流域和半湿润地区东湾及其嵌子套流域为研究对象,假设嵌套子流域为缺资料地区,在不重新率定参数情况下对屯溪和东湾内部嵌套子流域进行模拟验证。结果表明:相同流域内,基于网格水滴的汇流模型综合模拟精度随着子流域面积减小而降低;模型在屯溪流域模拟精度达到甲级,其嵌套子流域模拟精度基本满足需求;在东湾流域模拟精度达到乙级,其嵌套子流域模拟精度除洪峰合格率外均达丙级;模拟结果验证了网格水滴汇流模型在缺资料流域的适用性。

干旱大风环境下不同养护措施对桥梁混凝土性能的影响

干旱风环境作用加速桥梁结构混凝土内部水分传输与相对湿度的降低,使得混凝土在凝结硬化过程中易产生性能的劣化。本文通过试验研究模拟干旱多风环境下C50塔柱混凝土内养护及内外协同养护方式对结构混凝土内部湿度、强度与抗裂性的影响,并提出干旱大风环境下养护建议。①掺入15%的不同粒径沸石粉混凝土,5 d保湿养护后在20℃、相对湿度30%环境下继续放置至28 d,随着龄期的增长混凝土的内部相对湿度均呈现下降趋势,0~28 d龄期范围的掺入沸石粉内部湿度明显高于高比未掺入沸石粉混凝土,5 m/s风速下混凝土内部湿度进一步降低,而保湿养护5 d后表面喷涂养护剂协同养护可有效提高内部湿度;②掺入沸石粉对抗压强度有一定的降低,且随沸石粉平均粒径的减小,28 d强度呈降低趋势,劈裂抗拉强度的变化规律与抗压强度相同;掺入沸石粉可以降低5 m/s的风作用混凝土的28 d强度的损失,表面喷涂养护剂协同养护可有效提高28 d混凝土的抗压与抗拉强度;③圆环抗裂性能试验表明,干燥环境与风作用下未掺沸石粉混凝土收缩应力大,在11 d时产生裂缝释放应力,而掺入沸石粉、采取内掺沸石粉和表面涂刷养护剂协同养护可以有效降低混凝土内部收缩应力,未发生开裂现象,且采取内掺外涂刷协同养护的混凝土收缩应力更小。干旱多风环境下采取沸石粉内养护与外涂养护剂协同养护措施,可以在保证混凝土的强度的基础上,抑制结构混凝土的早期开裂。

跨季节与跨气候区的地表生态状况遥感评估方法

针对已有遥感生态指数存在植被稀疏区表现不力及不同季节稳健性不强,难以在冬春季节直接应用的难题,在遥感生态指数(remote sensing ecological index,RSEI)基础上,提出了一个可跨季节和气候区使用的全局遥感生态指数(global remote sensing ecological index,GRSEI),该指数由绿度、枯度、湿度、旱度和干度5项生态指标构成,采用CRITIC权重法和几何聚合法建模。在不同干湿气候区选取了5个案例区,对GRSEI、RSEI以及其他两个同名指数即地表生态状态综合指数(land surface ecological status composite index,LSESCI)和改进遥感生态指数(modified remote sensing ecological index,MRSEI)进行跨季节、跨气候区适用性检验。结果表明,GRSEI更契合季节变化规律和用地生态规律,模型生态含义明确,可用于各个季节和气候区的生态状况监测;RSEI夏秋季节表现较好,但在冬春季节使用受限;LSESCI和MRSEI异常值出现频次较多,不利于量化分析。

Vegetation-Climate Relationship and Its Application in the Division of Vegetation Zone in China

Distribution of vegetation is closely coupled with climate; the climate controls distribution of vegetation and the vegetation type reflects regional climates. To reveal vegetation_climate relationships is the foundation for understanding the vegetation distribution and theoretically serving vegetation regionalization. Vegetation regionalization is a theoretical integration of vegetation studies and provides a base for physiogeographical regionalization as well as agriculture and forestry regionalization. Based on a brief historical overview on studies of vegetation_climate relationships and vegetation regionalization conducted in China, we review the principles, bases and major schemes of previous vegetation regionalization and discuss on several contentious boundaries of vegetation zones in the present paper. We proposed that, under the circumstances that the primary vegetation has been destroyed in most parts of China, the division of vegetation zones/regions should be based on the distribution of primary and its secondary vegetation types and climatic indices that delimit distribution of the vegetation types. This not only reveals the closed relationship between vegetation and climate, but also is feasible practically. Although there still are divergence of views on the name and their boundaries of the several vegetation zones, it is commonly accepted that there are eight major vegetation regions in China, i.e. cold temperate needleleaf forest region, temperate needleleaf and broadleaf mixed forest region, warm temperate deciduous broadleaf forest region, subtropical evergreen broadleaf forest region, tropical monsoon forest and rain forest region, temperate steppe region, temperate desert region, and Qinghai_Xizang (Tibetan) Plateau high_cold vegetation region. Analyzing characteristics of vegetation and climate of major vegetation boundaries, we suggested that: 1) Qinling Mountain_Huaihe River line is an important arid/humid climatic, but not a thermal climatic boundary, and thus can not also be regarded as the northern limit of the subtropical vegetation zone; 2) the northern limit of subtropical vegetation zone in China is along the northern coast of the Yangtze River, from Hangzhou Bay, via Taihu Lake, Xuancheng and Tongling in Anhui Province, through by southern slope of the Dabie Mountains, to Wuhan and its west, coinciding with a warmth index ( WI ) value of 130-140 ℃·month; 3) the tropical region is limited in a very small area in southeastern Hainan Island and southern edge of Taiwan Island; and 4) considering a significant difference in climates between the southern and northern parts of the warm temperate zone, we suggested that the warm temperate zone in China is divided into two vegetation regions, deciduous broadleaf woodland region and deciduous and evergreen broadleaf mixed forest region, the Qinling Mountain_Huaihe River line being as their boundary. We also claimed that the zonal vegetation in North China is deciduous broadleaf woodland. Finally, we emphasized the importance of dynamic vegetation regionalization linked to climate changes.

可可西里地区中新世湖相叠层石成因及其古气候意义

青藏高原北部可可西里地区新发现湖相叠层石,它们集中分布在中新世五道梁群地层中。这些叠层石形态以穹隆状最为常见,局部地区甚至形成叠层石藻丘礁,根据显微镜和扫描电镜观察,其纹层构造和显微结构与现代海洋叠层石和前寒武纪时期的叠层石十分相似。根据对采集的叠层石样品进行微量元素分析、碳氧同位素分析,并与藻团块灰岩、生物碎屑灰岩和泥质灰岩以及少量白云岩进行对比研究,结果表明:叠层石灰岩、藻团块灰岩具有相似的地球化学特点,表现为低Sr/Ba、高Fe/Mn的特点,判断这些叠层石碳酸盐沉积在低盐度湖泊环境,建造叠层石的蓝绿藻生长在滨浅湖地带。它们的δ18O值变化于-6.63‰^-7.63‰之间,接近一般湖相淡水灰岩的范围内,指示入湖水量增加、湖水向淡化方向发展。湖泊中蓝绿藻类繁盛和叠层石的出现指示高湖面湖泛事件,说明青藏高原中新世时期曾出现过气候异常湿润期,这为判别区域气候的干湿变化提供了一个沉积标识。

全国干湿分布区动态变化研究

在全球气候变化的背景下,我国的干湿状况发生相应变化。本文主要研究过去60年全国干湿状况动态变化,以便于了解气候变化对我国干湿状况的影响。基于1951~2010年全国756个气象站点的气象数据,根据Penman-Monteith潜在蒸散量方法计算潜在蒸散发量,再结合降水量数据计算干燥度指数。利用干湿区划分阈值,划分1951~2010年不同干湿分区,主要有极端干旱区、干旱区、半干旱区、干性半湿润区、半湿润区、湿性半湿润区、湿润区分区,并研究1951~2010年10年年际动态变化。研究结果表明,全国在总体上趋向于干旱,尤其东北地区最为严重,而北疆地区趋向于湿润。不同年代呈现不同的干湿波动性规律,80年代为湿润时期,90年代为极端干旱时期,半干旱区范围明显增加并往东南移动。本研究对理解我国植被空间分布的变化和生态环境建设具有一定的指导意义。

近50年来西北半干旱区气候变化特征

选用西北半干旱区33个气象站1951-2004年温度、降水、相对湿度、风速、蒸发量等气象观测资料,分析主要气候要素变化规律,揭示了近50年来西北半干旱区气候变化的一些新特征。结果表明,西北半干旱区降水量近50年来年际变化趋势除个别地方外绝大多数地区呈下降趋势,降水量变化曲线线性拟合倾向率在-59.168～-1.143 mm/10 a之间,秋季降水量减少最多,春季次之,而夏季部分地区和冬季大部分地区降水量呈略增趋势。降水量存在3年、6～8年的周期振荡特征,3年周期振荡在1962-1966年为中心的局部时段内最强,之后逐渐减弱。6～8年振荡在1980-1985年为中心的局部时段内最强。气温距平呈上升趋势,气温距平变化曲线线性拟合倾向率在0.074～0.507℃/10 a之间,大部分地区呈先降后升型,转型时间为20世纪60年代后期至70年代前期。冬季气温增高最多,秋季、春季次之,夏季陕、甘、宁交界区及陇中地区气温增高而其余地区气温距平略呈下降趋势。相对湿度近50年来年呈波动变化。平均风速近50年来年际变化趋势除个别地方略增外,其余各地均呈下降趋势。蒸发量近50年来年际变化趋势除个别地方呈上升趋势外,其余各地蒸发量呈下降趋势。

近40a来青海湖地区的气候变化分析

选用青海湖流域天峻、刚察、共和、茶卡 4站 4 1a(195 8— 1998年 )的气象资料 ,运用主成分分析、趋势分析和相关分析对各气象要素的年、季平均值序列进行了分析。结果表明 :青海湖地区降水和日照时数的年际变化较大 ,但无明显的长期趋势 ;该地区的平均气温、平均最高、平均最低气温都明显升高 ,其中以平均最低气温上升最为明显 ;风速呈明显的下降趋势 ,2 0世纪 70年代最大 ,80年代最小 ,90年代又略有增加 ;该区 80年代相对湿度较大 ,而

中国东北近50年干旱发展及对全球气候变暖的响应

应用实测的降水、气温和土壤湿度资料,分析我国东北区(含黑龙江、吉林、辽宁三省和内蒙古自治区的东部)近50年干旱化的发展趋势.结果表明,用月平均气温和降水量的距平和均方差所构造的'大气干旱指数'以及土壤湿度都显示,近50年来整个东北区是向干旱发展的,1990年代中期以来这种干旱化趋势尤为明显;而东北西部亚干旱地区的干旱化相对更严重(特别是内蒙古东部的北半部).在亚干旱地区的气温和降水两个要素中,气温的升高对干旱化的作用可能更重要.在东北区的南部,近50年来的降水是略有增加,但仍有向干旱发展的趋势.这显然与全球气候变暖的大背景有关.为探讨东北区干旱的发展对全球气候变暖的响应,利用Jones等的1951～2000年全球平均气温资料和东北区25个站的大气干旱指数进行线性回归分析.结果表明,在全球平均温度上升1℃的情况下,中国东北区的干旱化程度要增加5～20%,最大的达到22%.这种形势应该引起我们的关注.

内蒙古阿拉善地区气候区划研究

在 2 0世纪 60年代以来的历次阿拉善地区气候区划工作基础上 ,本文分析了大量气象数据并参照遥感技术对气候、地貌、土壤、植被等分类与分区研究成果 ,认为阿拉善地区具有中温带向暖温带过渡的明显特征 ,其中近一半的地区应属于暖温带。基于常规方法与遥感手段的结合 ,根据植被、土壤、地貌、等景观生态因素与气候相关的综合评定 ,制定了气候分类指标系统 ;采用插值方法 ,得到每个网格点的有关气象要素值 ,编制了气象要素等值线图 ,完成了综合反映下垫面多种要素的阿拉善气候区划方案。

干旱区荒漠灌木林地土壤呼吸及其影响因素分析

沿三工河流域山前丘陵、冲-洪积平原绿洲及北部荒漠的过渡区测定了灌(丛)木林地土壤呼吸及土壤理化性质,对干旱区灌(丛)木林地土壤呼吸与土壤因子及环境因子之间的相关性作了初步分析并得出二者沿流域的变化规律:(1)大气CO2浓度呈降低趋势,但不明显,土壤呼吸与大气相对湿度的变化趋势一致,沿流域降低,二者相关系数为0.97。在干旱区水分对土壤呼吸具有一定的影响;(2)相关性分析表明土壤碳酸钙与土壤呼吸间存在显著相关性,相关系数为0.93。有关干旱区土壤碳酸钙对土壤呼吸的作用机理有待于进一步深入研究。本文分析结果有助于人们更好的了解有关干旱区灌(丛)木林地的土壤呼吸,作为干旱区灌(丛)木林地土壤碳素研究的参考依据。

中国不同干湿区蒸发皿蒸发和实际蒸发之间关系的研究

利用降水量将中国划分为干旱、半干旱、湿润和半湿润4个区域,开展不同区域中蒸发皿蒸发和多个模式模拟的实际蒸发的集成结果对比研究,探讨和分析在不同干湿背景下蒸发皿蒸发和利用观测的气象数据驱动的陆面过程模型模拟的实际蒸发之间的关系,并对导致这种关系的原因进行了分析,表明结果:(1)实际蒸发在中国整体上表现为下降趋势,这与湿润和半湿润区的变化趋势一致,而在干旱和半干旱区,实际蒸发表现为上升的变化趋势;(2)对比不同干湿区域的结果发现,在干旱和半干旱区,蒸发皿蒸发和实际蒸发表现为相反的变化趋势,在半湿润和湿润区,蒸发皿蒸发和实际蒸发表现为相同的变化趋势,在中国整体上蒸发皿蒸发和实际蒸发在总体上也具有一致的变化趋势;(3)单站分析的结果表明,中国东南大部分站点蒸发皿蒸发和实际蒸发表现为相同的变化趋势,而在西北地区大部分站点两者之间是相反的关系,这与区域平均的结果是一致的;(4)蒸发皿蒸发和实际蒸发之间在各个地区存在不同的关系主要是由于不同的干湿背景下实际蒸发变化的主要制约因子不同造成的。

不同根型苜蓿根颈变化特征分析

在甘肃省3个不同生态区(天水半湿润区、兰州半干旱区和武威干旱区),应用Marquez-Ortiz法和Johnson法对根茎型"清水"苜蓿(Medicago sativa L.cv."Qingshui")、根蘖型野生黄花苜蓿(native M.falcatamaterial)和"甘农2号"杂花苜蓿(M.varia Martin.cv."Gannong No.2")及直根型"陇东"苜蓿(M.sativa L.cv."Longdong")生长前3年的根颈特性进行了连续研究。结果表明,在3个生态区,不同根型苜蓿根颈特性差异显著,其中根茎型"清水"苜蓿根颈直径和分枝直径均较细,根颈入土深度较深,根颈分枝数较多;根蘖型野生黄花苜蓿和"甘农2号"杂花苜蓿的根颈直径和分枝直径均较粗,根颈入土深度相对较浅,根颈分枝数与根茎型"清水"苜蓿差异不显著;直根型"陇东"苜蓿的各项指标介于根茎型与根蘖型苜蓿之间,与根蘖型苜蓿更接近。根茎型、根蘖型苜蓿的水平伸展特性在不同生态区和不同土壤质地生长当年和生长第2年均未表现,生长第3年根茎/根蘖性状在3个生态区均得到表达,但根茎率/根蘖率不同。根茎率在天水半湿润区最高,武威干旱区最低;根蘖率在武威干旱区和兰州半干旱区较高,天水半湿润区较低,且根茎率/根蘖率随生育时期的延长呈增加趋势。结荚期根茎型"清水"苜蓿在天水半湿润区根茎率为76.7%,兰州半干旱区、武威干旱区分别为43.5%和39.0%。根蘖型黄花苜蓿和"甘农2号"杂花苜蓿的根蘖率在兰州半干旱区为61.2%和50.6%,在武威干旱区为58.7%和54.7%,在天水半湿润区为44.5%和36.3%。