Soil water response to precipitation in different microtopographies on the semi-arid Loess Plateau,China

Soil water is an important factor restricting afforestation on the semi-arid Loess Plateau.The microtopography of the loess slope has changed the distribution pattern of soil water on the slope.To improve water utilization efficiency and optimize afforestation configuration patterns,the relationship between soil water and precipitation at micro-topographic scale must be studied.We used time series analysis to study the temporal variation of soil water and its response to precipitation in four kinds of micro-topographies and undisturbed slope on loess slopes.Micro-topographies significantly influenced soil water distribution and dynamics on the slopes.Soil water stored in the platform,sinkhole,and ephemeral gully influenced subsequent soil water for 4 weeks,whereas soil water stored in the scarp and undisturbed slope could influence soil water for 2 weeks.It took 12 weeks,10 weeks,18 weeks,6 weeks,and 12 weeks for precipitation to reach the deeper soil layer in the platform,sinkhole,scarp,ephemeral gully,and undisturbed slope,respectively.These soil water characteristics in different micro-topographies are vital factors that should be taken into consideration when undertaking afforestation on the Loess Plateau.

Afforestation using micro-catchment water harvesting system with microphytic crust treatment on semi-arid Loess Plateau： A preliminary result

Water harvesting is one of main measures to solve water shortage resulting from less precipitation and erratically seasonal dis- tribution in arid and semi-arid areas. Different types of anti-infiltration treatments including mechanical and chemical to micro-catchment and their runoff efficiencies had been reported. This paper, through 5 years experiment from 1992 to 1996, is aimed at studying the im- pacts of microcatchment water-harvesting system (MCWHS) with microphytic crust treatment on afforestation on semi-arid Loess Plateau. The results showed that after 3 years of crust inoculation, crust had covered majority of MCWHS and the function of water harvesting had also been demonstrated partially, there were significant difference in soil moisture of shallow soil layer in three typical spring stages be- tween crust cover and control treatments (0.05 level), and about 0.9%-6.04% increase of monthly mean soil moisture within 1m soil layer in spring of late 3 years. The impact of severe spring drought can be alleviated effectively. In the meanwhile, as crust developed on the treated surface, there are significant differences (0.05 level) for tree height (H), diameter at breast height (DBH) and diameter at ground level (DGL) at the end of the study period (1996) with the increases by 22.38%, 17.34%, and 20.49% respectively compared with the con- trol treatment. Microphytic crust, as one of biological infiltration-proof materials, may become the optimized option for revegetation in Chinese Great West Development Strategy due to its self-propagation, non-pollution to water qualities, long use duration and relatively cost effective. Further work should be focused on the selection of endemic crust species and their batch-culture in arid environment.

An Overview of the Semi-arid Climate and Environment Research Observatory over the Loess Plateau

Arid and semi-arid areas comprise about 30% of the earth＇s surface. Changes in climate and climate variability will likely have a significant impact on these regions. The Loess Plateau over Northwest China is a special semi-arid land surface and part of a dust aerosol source. To improve understanding and capture the direct evidence of the impact of human activity on the semi-arid climate over the Loess Plateau, the Semi-Arid Climate and Environment Observatory of Lanzhou University （SACOL） was established in 2005. SACOL consists of a large set of instruments and focuses on： （1） monitoring of long term tendencies in semiarid climate changes; （2） monitoring of the aerosol effect on the water cycle; （3） studies of interaction between land surface and the atmosphere; （4） improving the land surface and climate models; and （5） validation of space-borne observations. This paper presents a description of SACOL objectives, measurements, and sampling strategies. Preliminary observation results are also reviewed in this paper.

Changes in aggregate-associated organic carbon and nitrogen after 27 years of fertilization in a dryland alfalfa grassland on the Loess Plateau of China

Changes in the distribution of soil aggregate sizes and concentrations of aggregate-associated organic carbon （OC） and nitrogen （N） in response to the fertilization of grasslands are not well understood. Understanding these changes is essential to the sustainable development of artificial grasslands. For understanding these changes, we collected soil samples at 0-20 and 20-40 cm depths from a semi-arid artificial alfalfa grassland after 27 years of applications of phosphorus （P） and nitrogen＋phosphorus＋manure （NPM） fertilizers on the Loess Pla- teau of China. The distribution of aggregate sizes and the concentrations and stocks of OC and N in total soils were determined. The results showed that NPM treatment significantly increased the proportions of 〉2.0 mm and 2.0-0.25 mm size fractions, the mean geometric diameter （MGD） and the mean weight diameter （MWD） in the 0-20 cm layer. Phosphorous fertilizer significantly increased the proportion of 〉2.0 mm size fractions, the MGD and the MWD in the 0-20 cm layer. Long-term application of fertilization （P and NPM） resulted in the accumulation of OC and N in soil aggregates. The largest changes in aggregate-associated OC and N in the 0-20 cm layer were found at the NPM treatment, whereas the largest changes in the 20-40 cm layer were found at the P treatment. The results suggest that long-term fertilization in the grassland leads to the accumulation of OC and N in the coarse size fractions and the redistribution of OC and N from fine size fractions to coarse size fractions.

Vegetation and environmental changes in western Chinese Loess Plateau since 13.0 ka BP

Pollen records from the Chinese Loess Plateau revealed a detailed history of vegetation variation and associated climate changes during the last 13.0 ka BP. Before 12.1 ka BP, steppe or desert-steppe vegetation dominated landscape then was replaced by a coniferous forest under a generally wet climate （12.1-11.0 ka BP）. The vegetation was deteriorated into steppe landscape and further into a desert-steppe landscape between 11.0 and 9.8 ka BP. After a brief episode of a cool and wet climate （9.8-9.6 ka BP）, a relatively mild and dry condition prevailed during the early Holocene （9.6-7.6 ka BP）. The most favourable climate of warm and humid period occurred during mid-Holocene （7.6-4.0 ka BP） marked by forest-steppe landscape and vegetation alternatively changed between steppe and desert-steppe from -4.0 to -1.0 ka BP.

Desert-steppe migration on the Loess Plateau at about 450 kaBP

According to the field investigation, observation by an electronic microscope and x-ray identification and chemical analysis, desert-steppe migration in the Loess Plateau at about 450 kaBP was studied. The data show that gypsum illuvial horizon indicating the desert-steppe environment developed in the early stage of the formation of the fifth layer loess in Shaoling tableland in Chang'an and Bailu tableland in Xi'an of Shaanxi are situated in the southern Loess Plateau. This indicates that remarkable drying occurred, a large-scope migration of desert steppe took place toward south and the climate zone migrated 5 degrees in latitude to south which is the largest migration range indicated by geochemical indexes. The desert-steppe and more wild environment distributed widely on the Loess Plateau at that time. The development of gypsum also indicates that the climate changed at 450 kaBP from monsoon climate to nonmonsoon climate in the Loess Plateau, and the region was not affected by summer monsoon and was in the cold and dry environment of nonmonsoon climate. Annual mean precipitation was about 200 mm, 400 mm less at that time than at present.

宁夏黄土区稀疏带状山杏人工林土壤湿度动态与影响因素

【目的】以宁夏南部黄土丘陵区带状山杏人工林为例,揭示林带内与带间的不同深度处土壤湿度的时空变化及其关键环境影响因素,为半干旱区林草植被科学管理及雨水资源高效利用提供依据。【方法】2020—2022年,在宁夏彭阳县山杏人工林带内和带间各布设1套200 cm测深的智墒传感器,分层逐时监测土壤体积含水量和土壤温度变化,同时布设1台气象站连续监测近地面降水、气温、空气湿度等气象条件,采用相关分析探究土壤湿度对前1日土壤湿度、土壤温度和气象因子的响应规律。【结果】2020年和2021年为平水年,降水量分别为467.4和440.8 mm;2022年为枯水年,降水量为354.8 mm;土壤体积含水量平均值为平水年(2021年,17.0%)显著高于枯水年(2022年,14.3%)。土壤体积含水量随土层加深呈近线性增加,其斜率表现为林带间高于林带内,平水年高于枯水年。在0~120 cm土层的土壤体积含水量为林带内(15.3%)高于林带间(14.0%),但在120~200 cm土层为林带间(17.6%)高于林带内(16.8%)。在0~60 cm土层的土壤体积含水量变异系数为林带间(42.9%)高于林带内(37.8%),但在60~200 cm土层为林带内(23.2%)高于林带间(19.1%)。土壤湿度变化的季节格局为:相对稳定期(3—4月)、耗损期(5—8月)、恢复期(9—11月)和衰退期(12月—次年2月),最大值多出现在4月,最小值出现在8月(平水年)和12月(枯水年);土壤湿度变化的垂直空间格局为:速变层(0~50 cm)、活跃层(50~90 cm)、次活跃层(90~170 cm)、相对稳定层(170~200 cm)。相关分析发现,土壤湿度日变化相关性最强的环境因子为正相关的前1日土壤湿度和负相关的土壤温度,月变化相关性最强的环境因子为负相关的土壤温度。【结论】宁夏黄土区稀疏带状山杏人工林林带内和林带间土壤湿度在季节和剖面上均表现出较大波动,枯水年比平水年波动的层次更深。综合分析发现前1日土壤湿度、土壤温度、气象因子均是影响枯水年和平水年日及月尺度各剖面层次土壤湿度变化的要素。其中,前1日土壤湿度和土壤温度为主要影响因子;在0~120 cm土层内的土壤湿度为林带内高于林带间。本研究结果对宁夏半干旱黄土区水平沟整地后退化植被科学恢复及土壤水分高效利用有很好的指导意义。

榆林野生地被植物资源的园林绿化应用评价

为了扩充陕北旱区园林绿化地被植物种类,采用样方法对榆林市横山县、绥德县、佳县野生地被植物资源展开调查,采用层次分析法构建了野生地被植物评价体系。结果表明,榆林市黄土旱区共有野生地被植物47种,以禾本科(14种)与菊科(7种)居多;评价体系准则层由园林观赏价值(权重值为0.334)、生态适应性(权重值为0.525)和防护功能(权重值为0.141)组成,要素层包括17个评价指标,其中权重值较高的分别是抗逆性(0.219)、繁殖难易度(0.141)、生长势(0.101)、生育期(0.077)、根系生长(0.071)、分布范围(0.064);最终评选出Ⅰ级优等地被植物9种,Ⅱ级良好地被植物12种,Ⅲ级一般地被植物13种,Ⅳ级较差地被植物13种。该评价体系能够准确反映榆林野生地被植物资源特点,为当地地被植物资源的筛选应用提供参考。

Effects of urban grass coverage on rainfall-induced runoff in Xi'an loess region in China

In this study, laboratory rainfall simulation experiments were conducted to investigate the regulatory effects of grass coverage on rainfallrunoff processes. A total of 80 grass blocks planted with well-grown manilagrass, together with their root systems, were sampled from an eastern suburban area of Xi'an City in the northwest arid area of China and sent to a laboratory for rainfall simulation experiments. The runoff and infiltration processes of a slope with different grass coverage ratios and vegetation patterns were analyzed. The results show that the runoff coefficient decreases with the increase of the grass coverage ratio, and the influence of grass coverage on the reduction of runoff shows a high degree of spatial variation. At a constant grass coverage ratio, as the area of grass coverage moves downward, the runoff coefficient, total runoff,and flood peak discharge gradually decrease, and the flood peak occurs later. With the increase of the grass coverage ratio, the flood peak discharge gradually decreases, and the flood peak occurs later as well. In conclusion, a high grass coverage ratio with the area of grass coverage located at the lower part of the slope will lead to satisfactory regulatory effects on rainfall-induced runoff.

黄土高原半干旱区覆膜和施磷对紫花苜蓿草地土壤磷组分的影响

在黄土高原半干旱区,较低的土壤磷(P)有效性限制了紫花苜蓿(Medicago sativa L.)的生长。阐明连续覆膜和施磷对紫花苜蓿草地土壤磷组分的影响对合理施磷和提高紫花苜蓿草地生产力具有重要意义。试验设置2个覆膜处理(不覆膜和覆膜)和4个磷肥梯度[0 kg(P)·hm^(−2)、9.7 kg(P)·hm^(−2)、19.2 kg(P)·hm^(−2)和28.8 kg(P)·hm^(−2)],研究了覆膜和施磷在不同处理年限(3年和9年)对紫花苜蓿草地不同活性土壤磷组分及其影响因素的影响。结果表明,与不覆膜相比,覆膜处理第3年紫花苜蓿地上部分磷吸收量显著增加52.4%,土壤Olsen-P、活性较高的NaHCO_(3)-Po和NaHCO_(3)-Pi以及中等活性的NaOH-Pi含量分别显著降低15.5%、20.2%、10.2%和27.9%;覆膜处理第9年土壤NaHCO_(3)-Po和NaHCO_(3)-Pi含量显著增加37.3%和24.3%,而地上部分磷吸收量、土壤Olsen-P和NaOH-Pi含量没有显著变化。与不覆膜相比,无论处理年限长短,覆膜均显著降低了活性较低的稀HCl-Pi含量,显著提高了土壤Na-OH-Po、浓HCl-Po和残留态磷(Residual-P)含量,而对浓HCl-Pi和全磷含量没有显著影响。与不施磷相比,除施磷处理第3年土壤残留态磷含量没有显著变化外,施磷处理第3年和第9年紫花苜蓿地上部分磷吸收量、土壤全磷、Olsen-P以及所有磷组分含量均显著增加。冗余分析显示,地上部分磷吸收量、土壤pH和碱性磷酸酶活性是影响土壤磷组分变化的主要因素。与不覆膜相比,覆膜处理在第3年和第9年显著增加了土壤碱性磷酸酶活性,在第9年显著降低土壤pH。与不施磷相比,施磷处理在第3年和第9年显著降低了土壤pH,在第9年显著降低了土壤碱性磷酸酶活性。综上,覆膜可通过降低土壤pH和提高磷酸酶活性促进低活性磷组分向中、高活性磷组分转化,所以将覆膜和施磷结合可有效提高紫花苜蓿草地土壤磷有效性和供磷潜力,且随着处理年限的延长,效果愈加明显。

黄土高原半干旱雨养农业区冬小麦气候适宜度评价——以通渭县为例

气候适宜度可以表征气候条件对作物生长发育的影响程度。利用黄土高原半干旱区通渭县近40 a气象资料和农业气象观测资料,基于模糊数学方法,根据冬小麦各发育时段对温度、水分、光照的需求,对黄土高原半干旱雨养农业区冬小麦全生育期气候适宜度进行评价。结果表明:通渭县近40 a冬小麦全生育期温度适宜度为0.58,停止生长—返青期的温度适宜度最高,达0.95,三叶期—停止生长的温度适宜度低,仅为-0.42,年际间差异小,全生育期温度适宜度以0.019/10 a的速率上升;水分适宜度为0.46,乳熟期—成熟期的水分适宜度最高,为0.66,其次为返青期—拔节期,为0.63,年际间差异大,全生育期水分适宜度以0.017/10 a的速率上升;光照适宜度为0.62,三叶期—停止生长和返青期—拔节期的光照适宜度最高,为0.68,乳熟期—成熟期最低,为0.51,全生育期光照适宜度以0.011/10 a的速率上升;综合适宜度为0.54,返青期—拔节期的综合适宜度最高,为0.70,三叶期—停止生长最低,为-0.36,全生育期综合适宜度以0.014/10 a的速率上升。冬小麦产量与抽穗期—乳熟期温度适宜度、乳熟期—成熟期水分适宜度、乳熟期—成熟期综合适宜度呈显著相关。气候适宜度能够较准确地反映出黄土高原半干旱雨养农业区冬小麦生育期内气象条件的优劣变化。

人水共生理念下传统窑洞聚落景观理水智慧研究——以陕北地区为例

中国传统聚落景观营建素有将人水共生作为古人聚居选址及农耕生产的理念和举措。因此,在聚落选址之初,古人对自然山水环境的寻找、观察及借用的用心程度甚至超过聚落后期的建设过程。为了更好地保护和传承半干旱区传统窑洞聚落景观理水智慧,避免本土理水营建技术的消失与断代,以陕北黄土高原区传统窑洞聚落为研究对象,从人水共生哲学思想出发,结合DIKW层次结构模型,构建传统聚落理水智慧解析路径与方法。从聚落选址布局理水智慧、人居营建理水智慧、农耕生产理水智慧和自然生态理水智慧4个方面,开展陕北传统窑洞聚落景观理水智慧的提取与体系构建。以期为当前我国半干旱地区乡村聚落生态人居景观营建和水基础设施建设提供理论与经验借鉴。

黄土旱区炭氮配施对大豆生理特性和生物量积累分配的影响

为了探究黄土旱区炭氮配施对大豆光合产物运移、干物质积累分配的影响,以大豆品种中黄13为试验材料,设置单施氮肥(210(CK)、420(N1)、630(N2)、840(N3)kg/hm^(2))以及氮肥与稻壳炭配施(氮肥420 kg/hm^(2),稻壳炭999 kg/hm(²C1N1),氮肥630 kg/hm^(2)和稻壳炭1998 kg/hm(²C2N2),氮肥840 kg/hm^(2)和稻壳炭2997 kg/hm^(2)(C3N3))共7个处理,研究大豆叶片生理功能和干物质积累分配的调控机制。连续2 a分析结果表明,炭氮配施处理(C1N1、C2N2、C3N3)与单施氮肥处理(N1、N2、N3)相比,2022年大豆花期和结荚期的叶面积指数分别增加49.57%~159.08%、32.08%~110.20%,2023年仅花期叶面积指数增加12.82%~92.60%;叶日积指数在2022年分别增加77.40%~198.04%、13.38%~67.99%,在2023年分别增加2.87%~80.41%、18.95%~64.72%;总干物质量在2022、2023年分别增加0.66%~20.87%、4.70%~23.62%。其中,炭氮配施的C2N2处理与C1N1和C3N3处理相比,叶面积指数在2022年结荚期增幅最大,分别增加46.59%、55.31%;叶日积指数在2022年花期增幅最大,分别增加10.72%、171.22%;叶绿素含量在2023年结荚期增幅最大,分别增加10.90%、14.28%;内在水分利用效率在2022年花期增幅最大,分别增加87.37%、41.56%;羧化速率在2022年结荚期增幅最大,分别增加29.14%、36.75%;总干物质量在2023年鼓粒期增幅最大,分别增加21.63%、32.02%。综上,氮肥630 kg/hm^(2)和稻壳炭1998 kg/hm^(2)的施肥配比能够作为大豆栽培的新培肥技术推荐使用。

覆膜对春小麦农田微生物数量和土壤养分的影响

研究了黄绵土区不同覆膜时期对旱作麦田土壤微生物数量及其与土壤碳、氮、磷含量的关系。丰水的 1 999年 ,土壤微生物数量增长早 ,延续时间长 ,覆膜 60 d微生物数量最高 (3 3 .93 8× 1 0 6 /g dry soil) ,其次为全程覆膜 (3 2 .2 5 9× 1 0 6 ) ;干旱的 2 0 0 0年微生物平均数量只有 1 999年的 3 6.5 % ,在后期有一定降水后微生物数量才出现高峰 ,以全程覆膜数量最高(1 4.83 6× 1 0 6 ) ,覆膜 60 d次之 (1 1 .5 2 9× 1 0 6 )。 1 999年各类群微生物数量同土壤有机碳之间均呈显著或极显著负相关。2 0 0 0年相关系数几乎全面下降 ,氨化细菌、硝化细菌和反硝化细菌 ,甚至微生物总量同土壤有机碳之间都已不再显著相关。 1 999年土壤全氮同氨化细菌、硝化细菌、亚硝化细菌、解磷细菌及微生物总量均呈显著或极显著负相关 ,2 0 0 0年只与氨化细菌、亚硝化细菌、微生物总数显著负相关。土壤速效磷含量在 1 999年与解磷细菌显著负相关 ,而在 2 0 0 0年相关已不再显著。两年试验结束后 ,全程覆膜处理有机质下降 2 1 .2 % ,覆膜 60 d处理下降 1 7.2 % ,覆膜 3 0 d和不覆膜处理下降相对较小 (4 .3 %和 6.7% )。由于施用化肥 ,土壤全氮有明显升高。速效磷在 1 999生长季和随后的休闲期都有升高 ,在干旱的 2 0 0 0?

黄土区地膜覆盖对麦田土壤微生物体碳的影响

研究了1999年(丰水年)和2000年(干旱年)旱地条件下不同时间覆膜(不覆膜、覆膜30 d、覆膜60d和全程覆膜)对春小麦(Triticum aestivum)农田土壤微生物体碳的影响。结果表明,1999年土壤微生物体碳平均为335.3 mg·kg^(-1)干土,2000年平均为259.3 mg·kg^(-1)干土,前者高出后者29.37％。2年中最高微生物体碳均出现在全程覆膜处理。1999年,土壤微生物体碳在覆膜60d时即接近最高值,该处理籽粒产量也最高。2000年,由于春小麦生育后期降水丰富,在整个生育期中,微生物体碳增长表现为“增长-平稳甚至出现下降-再增长”的梯形方式,到生育后期,各处理之间才出现显著差异,全程覆膜处理的微生物体碳后期大幅度增加,与1999年接近。2年中各处理的C/N处于7.732～9.042之间,远低于11.3的临界值,C/P处于300.8～719.6之间,均高于300的临界值,不利于土壤微生物体碳的增加,微生物和作物对土壤有效态氮和磷的吸收处于竞争状态,表明该农田生态系统有机质严重不足,已经构成了限制作物生产力发挥的重要因素,长期地膜覆盖和大量使用化肥将加剧这一问题的严重性。

半干旱黄土高原退化生态系统的修复与生态农业发展

首先分析了半干旱黄土高原区域生态系统的特点,指出:这里地带性植被极度退化,土壤质量严重恶化,治理难度大,可持续发展受到严重威胁。然后,进行生态系统退化关键驱动力的分析,认为,在不同时期,农民的利益驱动始终是土地利用格局和生态系统演化/退化的关键驱动力。在寻求分析退化生态系统修复的突破口时,认为提高作物产量和经济效益,解决农民的需求是具有可操作性的途径。而实现这一途径必须提高单产,以减轻更广大土地面积上的生产力需求压力。通过集水、覆盖等措施改善农田水分条件,再配合地膜、化肥,在对农田进行合理管理的情况下,粮食单产可获得持续大幅度的提高。在此基础上,提出了实现区域可持续发展的途径——集水型生态农业及其景观配置模式。在这一模式中,经济作物、粮食作物、人工草地和天然草地在一个完整的景观单元内合理配置,形成完整的景观复合生态系统。对这一模式的深入研究和正确实施将推动半干旱黄土高原退化生态系统的修复,并为西部开发中经济建设和生态建设并举提供理论与实践指导。

半干旱黄土区苜蓿草地轮作农田土壤氮素变化

田间试验研究了多年生苜蓿草地轮作为农田后2年内土壤矿质氮和全氮的变化,结果表明,与苜蓿连作相比,土壤全氮在苜蓿翻耕后迅速下降,土壤硝态氮和铵态氮在耕作下层出现大量累积,土壤氮素有效性提高。不同轮作方式对土壤氮素变化有显著影响,轮作第2年种植玉米或马铃薯可以增加硝态氮在土壤中的累积,种植春小麦则增加了铵态氮和总矿质氮累积量,休闲土壤矿质氮变化幅度居中。与轮作春小麦相比,轮作玉米显著增加了对土壤全氮的消耗,因此多年生苜蓿草地轮作农田后应避免种植玉米等耗肥量较大的作物以维持土壤氮素平衡。

黄土高原半干旱区集雨补灌生态农业研究进展

黄土高原半干旱地区在中国旱作农业生产中占有重要地位。干旱缺水与水土流失并存是制约该区域经济发展的两大瓶颈因素。水保农业和径流农业两种旱作农业生产方式已趋于成熟,但对天然降水调控利用能力低下,难于实现农业生产的优质高产高效。集雨补灌生态农业是在继承水保农业和径流农业成功技术基础上,对降雨调控利用方式的进一步发展,它能在时间和空间两个方面实现降雨径流的富集叠加,能充分发挥环境资源与水肥光热因子的协同增效作用,大幅度提高农业生产力,实现同步缓解干旱缺水与水土流失双重目标。集雨补灌是黄土高原半干旱区农业可持续发展的一种综合模式和战略性措施,对黄土高原半干旱区生态型现代农业发展具有重要推动作用。

半干旱黄土丘陵沟壑区封禁流域植被枯落物分布规律研究

通过对陕北半干旱黄土丘陵沟壑区封育流域内不同立地条件下枯落物现存量的测定与分析,研究了枯落物的影响因子及分布规律。对60个样地调查研究结果表明:枯落物现存量与坡度呈二次回归关系,枯落物现存量最小值出现在坡度25.5°的位置;阴坡枯落物现存量比阳坡高25.1%,沟坡枯落物现存量比梁坡高41.7%;地表生物量与枯落物现存量呈显著的正相关性(P<0.05);土壤含水量与枯落物现存量呈正相关性;土壤含水量与地表生物量两者的共同作用对枯落物现存量影响明显。

黄土丘陵区不同土地利用方式土壤微生物功能多样性特征

土壤微生物是生态系统的重要组成部分,分析黄土丘陵区小流域不同土地利用方式土壤微生物功能多样性变化状况以及与土壤化学因子间的关系,以期为区域土壤微生物研究以及生态环境监测提供一定的参考依据。采集区域主要土地利用类型土样38份,采用生态板(Biolog-ECO)方法测定不同土地利用方式土壤微生物利用碳源的状况,利用主成分综合评价和相关系数等方法,分析不同土地利用方式土壤微生物功能多样性,以及平均吸光值、多样性指数、6类碳源和土壤化学因子的关系;结果表明:(1)土壤微生物平均吸光值随着培养时间的延长,微生物活性呈现直线增加趋势,土壤微生物功能多样性从表层到底层呈现递减趋势;(2)土壤微生物功能多样性总体趋势为林地>天然草地>耕地,苜蓿地土壤微生物功能多样性不同层次间变异大;(3)土壤全量氮、有机质、速效磷和速效氮对土壤微生物功能多样性具有显著影响。不同土地利用方式以及相同利用方式下不同措施土壤微生物功能多样性变化较大,Biolog-ECO技术可以作为生态环境监测的指标。