Moving Dynamics of Nitrate Nitrogen in Soil of Maize Field on Meadow Soil of Daling River Valley in Liaoning and Its Fertilization Controlling

The moving dynamics of nitrate nitrogen（NO3-N）in soil of maize field on meadow soil of Daling river valley in Liaoning and its rational fertilization controlling were discussed in this study by the designing of different kinds of N application methods.The results showed that the content of NO3-N in soil was increased with the amount of nitrogen fertilizer;At the same amount of nitrogen fertilizer,the content of NO3-N in soil showed a trend of chemical fertilizerstraw treatmentslow controlled release fertilizer.Based on the requirement of roots in different growth stages to nutrition,the migration directions of NO3-N could be regulated by each layer of soil.In the early growth stage,the NO3-N would move upward,while it moved downward in the late growth stage.Straw returning treatment could improve the keeping ability of soil to NO3-N and avoid the downward migration of NO3-N,as well as reduce the damage of groundwater pollution.The use of slow controlled release fertilizer had achieved the continuing releasing of nutrition.Moreover,the peak of nutrition releasing had been delayed for 30 d,which had met the requirement of nutrient supply in maturing stage.The yield of slow controlled release fertilizer treatment was the highest with the least accumulation of NO3-N and less negative influence on environment.The yield of straw returning treatment and chemical fertilizer treatment was closed to each other.

Accurate Quantification of Grassland Cover Density in an Alpine Meadow Soil Based on Remote Sensing and GPS

The principles of remotely estimating grassland cover density in an alpine meadow soil from space lie in the synchronous collection of in situ samples with the satellite pass and statistically linking these cover densities to their image properties according to their geographic coordinates. The principles and procedures for quantifying grassland cover density from satellite image data were presented with an example from Qinghai Lake, China demonstrating how quantification could be made more accurate through the integrated use of remote sensing and global positioning systems (GPS). An empirical model was applied to an entire satellite image to convert pixel values into ground cover density. Satellite data based on 68 field samples was used to produce a map of ten cover densities. After calibration a strong linear regression relationship (r2 = 0.745) between pixel values on the satellite image and in situ measured grassland cover density was established with an 89% accuracy level. However, to minimize positional uncertainty of field samples, integrated use of hyperspatial satellite data and GPS could be utilized. This integration could reduce disparity in ground and space sampling intervals, and improve future quantification accuracy even more.

Studies on Fast Remediation of Soda Meadow Alkaline Soil

Researches on models of remediation quickly in soda meadow alkaline soil, and dynamic variation of water-salt in saline soil of Zhaozhou County were studied systematically from 2001 to 2006. Realize the vegetation cover of those years through the artificial planting, mixed seeding lyme grass （Elymus dahuricus Turcz） and melilot in the mode of rotary tillage and deep loosening in lower and medium saline soils. The results showed that there was remarkable relationship between net evaporation （difference of precipitation and evaporation） and total salt content in the soil. The net evaporation could be used as a new method to forecast the dynamics variation of salt to ensure the pasture optimum sowing time. Realize the autumnal vegetation cover of those years through direct planting on the bourgeon layer of soda meadow alkaline soil, on the other hand, the covered pasture made the function of restraining salt and alkaline content to realize the biology reverse succession quickly. Forage seeds were seeded directly on the seeding bed of soda alkaline meadow at the end of July. In fall of the same year, a certain amount of biomass was obtained. The model, which has remarkable economical efficiency and use widely, represented the innovative model for the fast vegetation restoration on the soda alkaline meadow soil.

Variation of Soil CO_2 Flux and Carbon Density in Three Apline Meadows

Three alpine meadows were chosen from the eastern margin of the Qilian Mountain：Polygonum viviparum meadow（P）,Stipa capillata grassland（S）and Rhododendron simsii shrub meadow（R）;LI-8100 A soil CO2 flux auto-monitoring system and lab analysis were applied to analyze the soil organic carbon density,dynamics of carbon flux,and their relationship with environmental factors.The results showed that different vegetations varied greatly in soil organic carbon density：R 〉 S 〉 P,and the soil carbon density reduced with the increasing depth;soil CO2flux：S 〉 P 〉 R,and sample plot P and S showed unimodal changes.The peak values appeared at 14：00-15：00 p.m.;soil CO2 flux was negatively correlated with near-ground air humidity and carbon content,positively correlated with soil temperature and near-ground air temperature,and showed no obvious correlation with soil moisture.

Influence of land cover changes on the physical and chemical properties of alpine meadow soil

Taking the alpine cold meadow grassland in the southeastern part of the Qinghai-Tibetan Plateau as an ex-ample, this research deals with the characteristics of alpine meadow soil property changes, including soil nutrients, soil physical properties and soil moisture content under different land coverage conditions. With the degradation of grassland vegetation and the decline of vegetation coverage, soil com-pactness reduces, gravel content increases and bulk density increases. The originally dense root-system layer is gradually denuded, making the soil coarse and gravel. The change of the organic matter contents with the vegetation coverage change in the surface soil layer (0—20 cm) has shown an obvious cubic polynomial curve process. The organic matter contents increase rapidly when land coverage is above 60%, contrarily decreases on a large scale when land coverage is below 30%. Between 30%—60% of land coverage the or-ganic matter contents remain stable. The total N and organic matter contents in soil have shown quite similar change regularity. Following this the mathematic equations are de-rived to describe such change processes. Moisture content in soil changes sharply with the vegetation coverage change. Soil moisture content change with the vegetation coverage change has shown a quadratic parabola process. Results have shown that organic matter content and the total N con-tent of the alpine meadow soil decrease by 14890 kg/hm2 and 5505 kg/hm2 respectively as the vegetation coverage reduces from 90% to less than 30%. The heavy changes of soil physical and chemical properties with grassland degradation have made the recovery of alpine meadow ecological system impossible. The protection of alpine meadow vegetation is of vital importance to the maintenance of the regional soil en-vironment and the regional ecological system.

Warming effects on plant biomass allocation and correlations with the soil environment in an alpine meadow,China

Alpine meadow ecosystem is fragile and highly sensitive to climate change.An understanding of the allocation of above-and below-ground plant biomass and correlations with environmental factors in alpine meadow ecosystem can result in better protection and effective utilization of alpine meadow vegetation.We chose an alpine meadow in the Qinghai-Tibetan Plateau of China as the study area and designed experimental warming plots using a randomized block experimental design.We used single-tube infrared radiators as warming devices,established the warming treatments,and measured plant above- （AGB） and below-ground biomass （BGB） during the growing seasons （May to September） in 2012 and 2013.We determined the allocation of biomass and the relationship between biomass and soil environment under the warming treatment.Biomass indices including above-ground biomass,below-ground biomass and the ratio of root to shoot （R/S） ,and soil factors including soil moisture and soil temperature at different depths were measured.The results showed that （1） BGB of the alpine meadow had the most significant allometric correlation with its AGB （y=298.7x~ （0.44） ,P〈0.001） ,but the relationship decreased under warming treatment and the determination coefficient of the functional equation was 0.102 which was less than that of 0.188 of the unwarming treatment （control） ; （2） BGB increased,especially in the deeper soil layers under warming treatment （P〉0.05） .At 0–10 cm soil depth,the percentages of BGB under warming treatment were smaller than those of the control treatment with the decreases being 8.52% and 8.23% in 2012 and 2013,respectively.However,the BGB increased 2.13% and 2.06% in 2012 and 2013,respectively,at 10–50 cm soil depths; （3） BGB had significant positive correlations with soil moisture at 100 cm depth and with soil temperature at 20–100 cm depths （P〈0.05） ,but the mean correlation coefficient of soil temperature was 0.354,greater than the 0.245 of soil moisture.R/S ratio had a significant negative correlation with soil temperature at 20 cm depth （P〈0.05） .The warmer soil temperatures in shallow layers increased the biomass allocation to above-ground plant parts,which leading to the increase in AGB;whereas the enhanced thawing of frozen soil in deep layers causing by warming treatment produced more moisture that affected plant biomass allocation.

Levels of Germinable Seed in Topsoil and Yak Dung on an Alpine Meadow on the North-East Qinghai-Tibetan Plateau

In order to clarify the interactive mechanism between grazing yak and alpine meadow on the Qinghai-Tibetan Plateau,our study assessed seed density（by species） in the topsoil of alpine meadow with different grazing intensities in the Tianzhu area,north-eastern margins of the Qinghai-Tibetan Plateau and their rates of occurrence in yak dung.Seed density in the topsoil of the lightly grazed,moderately grazed,heavily grazed and extremely grazed alpine meadows in November,2010 were 1 551,1 692,2 660 and 1 830 grains m-2,while in the same meadows in April,2011 densities were 1 530,2 404,2 530 and 2 692 grains m-2,respectively.In the cold season pasture,mean seed density in yak dung from November to April in the lightly grazed,moderately grazed,heavily grazed and extremely grazed sites were 121,127,187,and 120 grains kg-1of dry yak dung.The proportion of total seed numbers in yak dung to soil seed bank in lightly grazed,moderately grazed,heavily grazed and extremely grazed alpine meadow was 1.40,2.62,0.69,and 0.90%.12 species out of the 47 were not found in topsoil but were found in yak dung,10 species out of 45 were not found in yak dung but were found in the topsoil.Endozoochorous dispersal by yaks is therefore very important for soil seed bank and plant biodiversity and population dynamics in alpine meadows.

Effects of warming and clipping on plant and soil properties of an alpine meadow in the Qinghai-Tibetan Plateau, China

Climate warming and livestock grazing are known to have great influences on alpine ecosystems like those of the Qinghai-Tibetan Plateau （QTP） in China. However, it is lacking of studies on the effects of warming and grazing on plant and soil properties in these alpine ecosystems. In this study, we reported the related research from manipulative experiment in 2010-2012 in the QTP. The aim of this study was to investigate the individual and combined effects of warming and clipping on plant and soil properties in the alpine meadow ecosystem. Infrared radiators were used to simulate climate warming starting in July 2010, while clipping was performed once in Octo- ber 2011 to simulate the local livestock grazing. The experiment was designed as a randomized block consisting of five replications and four treatments： control （CK）, warming （W）, clipping （C） and warming＋clipping combination （WC）. The plant and soil properties were investigated in the growing season of the alpine meadow in 2012. The results showed that W and WC treatments significantly decreased relative humidity at 20-cm height above ground as well as significantly increases air temperature at the same height, surface temperature, and soil temperature at the depth of 0-30 cm. However, the C treatment did not significantly decrease soil moisture and soil temperature at the depth of 0-60 cm. Relative to CK, vegetation height and species number increased significantly in W and WC treatment, respectively, while vegetation aboveground biomass decreased significantly in C treatment in the early growing season. However, vegetation cover, species diversity, belowground biomass and soil properties at the depth of 0-30 cm did not differ significantly in W, C and WC treatments. Soil moisture increased at the depth of 40-100 cm in W and WC treatments, while belowground biomass, soil activated carbon, organic carbon and total nitrogen increased in the 30-50 cm soil layer in W, C and WC treatments. Although the initial responses of plant and soil properties to experimental warming and clipping were slow and weak, the drought induced by the down- ward shift of soil moisture in the upper soil layers may induce plant belowground biomass to transfer to the deeper soil layers. This movement would modify the distributions of soil activated carbon, organic carbon and total nitrogen However, long-term data collection is needed to further explain this interesting phenomenon.

Relations between the Underground Biomass and Soil Organic Carbon and Nitrogen of the Alpine Meadow at the Eastern Margin of the Qinghai-Tibet Plateau

This article, by combining field investigation with laboratorial analysis, studies diverse alpine meadow at the Eastern Margin of the Qinghai-Tibet Plateau for the underground biomass dynamics, vertical distribution of the content of soil carbon and nitrogen, the connection between the biomass and the content of carbon and nitrogen. The studies show that underground biomass in the herb layer of upland meadow is more than that in the terrace meadow, while underground biomass in the upland shrubland is the most. The vertical distribution of underground biomass of each type is obvious as in shape of＂T＂. As to the distribution of the content of soil organic carbon in the three sample grounds, it showed that the deeper the soil the less the content of soil organic carbon. In May, unlike at terrace meadow, the underground biomass and the content of soil organic carbon in positive proportion, such revelation at upland meadow and upland shrubland is not apparent. In July, at upland meadow and terrace meadow the underground biomass and the content of soil total nitrogen in positive proportion, such revelation at upland shrubland is not apparent either.

Effects of soil nutrients and climate factors on belowground biomass in an alpine meadow in the source region of the Yangtze-Yellow rivers, Tibetan Plateau of China

Improving our knowledge of the effects of environmental factors （e.g. soil conditions, precipitation and temperature） on belowground biomass in an alpine grassland is essential for understanding the consequences of carbon storage in this biome. The object of this study is to investigate the relative importance of soil nutrients and climate factors on belowground biomass in an alpine meadow in the source region of the Yangtze and Yellow rivers, Tibetan Plateau. Soil organic carbon （SOC）, total nitrogen （TN） and total phosphorous （TP） contents and belowground biomass were measured at 22 sampling sites across an alpine meadow on the Tibetan Plateau. We analyzed the data by using the redundancy analysis to determine the main environmental factors affecting the belowground biomass and the contribution of each factor. The results showed that SOC, TN and TP were the main factors that influenced belowground biomass, and the contribution of SOC, TN and TP on biomass was in the range of 47.87%-72.06% at soil depths of 0-30 cm. Moreover, the combined contribution of annual mean temperature （AMT） and mean annual precipitation （MAP） on belowground biomass ranged from 0.92% to 4.10%. A potential mechanism for the differences in belowground biomass was caused by the variations in soil nitrogen and phosphorous, which were coupled with SOC. A significant correlation was observed between MAP and soil nutrients （SOC, TN and TP） at the soil depth of 0-10 cm （P〈0.05）. We concluded that precipitation is an important driving force in regulating ecosystem functioning as reflected in variations of soil nutrients （SOC, TN and TP） and dynamics of belowground biomass in alpine grassland ecosystems.

Study on Soil Respiration Characteristics and Carbon Balance of <i>Kobresia pygmaea</i>Meadow in Qinghai-Tibet Plateau, China

Although soil respiration is the largest contributor to C flux from terrestrial ecosystems to the atmosphere, our understanding of its characteristics and carbon budget in alpine meadow is rather limited because of extremely geographic situation. This study was designed to examine soil CO2 efflux characteristics of diurnal and seasonal variation, thus obtaining estimates of carbon balance of Kobresia pygmaea meadow in Qinghai-Tibet plateau. The results showed that the soil respiration of diurnal and seasonal rate changed little in growing season and was mainly affected by temperature, and single peak curve that showed afternoon appeared. Composite model which was set by soil respiration rate, soil moisture content and temperature (atmospheric temperature and soil temperature) could explain better the variations of soil respiration rate. The variation range of Q10 ranged from 1.28 to 2.34, which was sensitive to temperature in green-up period and late growth stage, and decreased in growth peak period. Meanwhile, during the growing seasons the observed amount of annual carbon fixation via primary production for Kobresia pygmaea meadow ecosystem was about 120.21 g C·m-2·a-1. The carbon dioxide output via soil heterotrophic respiration was about 37.54 g C·m-2·a-1. So carbon budget had more input than output. The Kobresia pygmaea meadow ecosystem has stronger potential to absorb carbon dioxide, it was a sink of atmospheric CO2, and the plant community had a net carbon gain of 82.67 g C·m-2·a-1.

高寒草地退化对土壤碳氮磷及酶活性的影响

【目的】土壤碳氮磷元素是支撑高寒草地生态系统的关键,高寒草甸退化会改变土壤养分含量及分布规律,明确高寒草甸退化对土壤关键养分碳氮磷含量及其与酶活性之间相关性的影响可为退化高寒草甸的恢复提供理论依据。【方法】以东祁连山围封草地(FG)为对照,对轻度(LD)、中度(MD)和重度(SD)退化高寒草甸土壤有机碳、全氮、有效氮、全磷、有效磷含量,以及土壤碳氮磷转化相关的过氧化氢酶、脲酶、碱性磷酸酶活性进行研究。【结果】相比FG,退化基本导致高寒草甸土壤的有机碳含量升高,SD 0~10 cm土层有机碳含量最高,为82.1 g/kg;退化导致过氧化氢酶活性表现出下降的趋势,围封草地20~30 cm土层的过氧化氢酶活性最高,为23.35 mg/g,LD 10~20 cm土层的过氧化氢酶活性最低,为20.90 mg/g。退化导致土壤全氮含量降低,有效氮含量和脲酶活性显著升高,SD草地有效氮含量和脲酶活性均最高,分别为649 mg/k和3.47 mg/g,脲酶活性在FG和SD随土层加深而升高,但在MD和SD随土层加深而降低。4种类型草地全磷的变化范围为0.18~0.22 g/kg,退化对0~10 cm土层的全磷含量没有显著影响,而使0~10 cm土层,LD和MD的有效磷含量分别增加了152%和60%,而SD降低了32%,0~30 cm土层碱性磷酸酶活性升高,变化范围为0.52~0.62 mg/g。相关性分析表明,围封草地土壤有机碳与过氧化氢酶活性呈显著负相关,而轻度和重度退化未表现出有相关性;围封草地土壤全氮、有效氮含量与脲酶活性均没有相关性,而轻度和中度退化高寒草甸的脲酶活性与土壤有效氮含量存在显著正相关性;围封草地的土壤全磷、有效磷含量与碱性磷酸酶活性均成呈显著正相关,而退化草地未表现出明显的相关性。【结论】高寒草甸退化后改变了其关键养分与其相关酶活性之间的相关性,重度退化高寒草甸恢复中应考虑土壤磷素的投入。

有机物料还田对草甸土孔隙结构及玉米产量的影响

为了研究有机物料还田对草甸土孔隙结构及玉米产量的影响,优化草甸土耕作层结构、提高作物产量,2019年以吉林省公主岭市的草甸土为试验地,在玉米播种前设置了秸秆浅混还田(CT,0~15cm)、秸秆深混还田(STS,0~35cm)、秸秆和有机肥深混还田(STSM,0~35 cm)、无秸秆还田常规耕作(CK)4个处理。对玉米收获后的土壤进行取样分析,测定0~35 cm土层土壤物理性质和孔隙结构,并采用结构方程模式、Mantel test和随机森林方法分析土壤孔隙结构调控玉米产量的途径。结果表明,经CT、STS和STSM处理后的0~15 cm土层土壤容重与CK处理相比显著下降了5.2%~7.8%(P<0.05),而田间持水量和饱和导水率均呈现上升趋势,分别显著增加了7.8%~16.6%和77.5%~325%(P<0.05);STS和STSM处理进一步显著改变了>15~35 cm土层上述3个土壤物理性质。CT扫描结果显示,有机物料还田显著改善了相应土层土壤结构。与CK处理相比,CT、STS和STSM处理显著增加了0~15 cm土层>1000µm孔隙数量和孔隙度;与CT处理相比,STS和STSM处理>15~35 cm土层>1000µm孔隙数量和孔隙度分别显著增加了1.2倍~1.3倍和47.5%~58.9%(P<0.05)。有机物料还田增加了土壤孔隙的复杂性和连通性。与CK处理相比,CT、STS和STSM处理显著增加了0~15 cm土层的各向异性和分形维数,降低了欧拉数(P<0.05);STS和STSM处理显著改善了15~35 cm土层土壤孔隙结构。不同处理间玉米产量表现为STSM>STS>CT>CK。结构方程模型结果显示,0~15 cm土层土壤孔隙结构可以直接影响玉米产量或者通过影响容重和饱和导水率间接影响玉米产量,而15~35 cm土层土壤孔隙结构只能通过影响田间持水量间接影响玉米产量。0~35 cm土层土壤物理性质和孔隙结构能够解释玉米产量的81.9%,15~35 cm土层对玉米产量的贡献大于0~15 cm土层。有机物料深混还田通过改变0~35 cm土层草甸土物理性质和孔隙分布,增加孔隙结构的复杂性和连通性,优化耕层结构,具备提高玉米产量的潜力,其中秸秆和有机物配合施用的效果优于单独秸秆还田。如果草甸土分布区有机肥源充足,建议利用秸秆和有机肥料进行深混还田可建立良好的土壤肥力,可以有效增加玉米产量。

高寒露天矿区渣土基质粒度组成及养分特征

以青海省木里与江仓露天煤矿区渣土为研究对象,采集了矿区渣土样品20个,未受人为扰动和污染的沼泽草甸土壤样品17个作为背景值。通过测试分析矿区渣土和沼泽草甸土壤的粒径组成,发现两个矿区渣土粒级组成与沼泽草甸土壤相同,含量由高到低依次为粉粒-砂粒-黏粒,但是在组成比例上存在差异,沼泽草甸土壤粉粒的含量更为丰富。根据土壤质地分类标准,木里矿区的渣土归属于粉壤土,江仓矿区的渣土归属于粉壤土和壤土,以粉壤土为主,沼泽草甸土壤兼具粉壤土与壤土的特性。同时,对矿渣土的pH、有机碳、全钾、全磷、全氮、碱解氮、速效氮、有效磷、速效钾等指标进行统计分析,结果表明两个矿区的渣土pH值偏碱性且有机质含量低,全量养分与沼泽草甸土壤存在差异,其中全氮的含量远低于沼泽草甸土壤,全钾的含量略高于沼泽草甸土壤。速效养分中的速效氮含量非常贫瘠,有效磷与速效钾的平均含量均高于沼泽草甸土壤,尤其是速效钾更明显。相关性分析显示矿区渣土的黏粒与所有养分均呈正相关,粉粒、砂粒与养分关系逐渐减弱,因此在土壤修复和重构过程中不仅要关注渣土养分的变化,还应该改善渣土基质粒径的结构比例,加速土壤熟化,完善土壤-植物-微生物体系,构建适应高寒矿区植被生长的土壤。

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.

不同龄级瑞香狼毒影响微尺度高寒草甸群落结构

通过样圆法群落调查探究不同龄级狼毒对微尺度草地群落结构和土壤化学计量特征的影响,结果表明:(1)狼毒能显著降低微尺度草地的群落盖度、群落加权平均高度、植物密度和地上生物量等指标,且影响程度随着狼毒龄级的增加而增大。(2)狼毒显著改变了草地的群落结构,降低了禾本科和莎草科植物的优势度,增加了杂草植物的优势度,随着狼毒龄级的增加,杂草的优势度逐渐增加。(3)狼毒的生长增加了退化草地物种多样性,但当狼毒龄级达到Ⅴ龄时,草地物种多样性逐渐降低。(4)随着狼毒龄级的增加,土壤全碳含量、全氮含量和全磷含量整体呈显著下降趋势,而碳磷比和氮磷比呈显著上升趋势。总之,狼毒对微尺度高寒草甸植物群落结构和土壤化学计量特征有显著影响,且与龄级有关,建议在修复狼毒型退化草地时,应及时进行人工干预,尤其在狼毒龄级达到Ⅴ龄之前,采取围栏封育、施氮肥和补播豆科优良牧草等措施,加强退化草地的生态修复。

牦牛放牧活动范围对高寒草甸冷季牧场植被群落结构和土壤理化性质的影响

【目的】揭示家畜放牧过程中植物群落格局的变化趋势及放牧家畜的选择性采食和游走规律对草地的干扰范围和程度,为草地管理和草牧业生产提供参考。【方法】在天祝高寒草甸研究了放牧牦牛冷季牧场出入口及其周围1 000 m范围内的植被演替规律和土壤变化情况。【结果】600 m以外的草地植被多样性显著高于牧场出入口200 m范围的草地植被多样性,平均草层高度以600~800 m的范围较低,以出入口周围200 m的草层高度最高,在400~600 m的范围内的地上生物量变化较大。随着放牧牦牛的活动范围距离出入口渐远,植被地下生物量和植被盖度显著增加,可食性牧草的种类和数量显著增加(P<0.05)。土壤以牧场出入口周围100 m内的容重最大,土壤水分、土壤渗透速率和土壤饱和持水量最低。土壤全效养分在家畜活动频繁的出入口具有较低的含量,而在家畜活动范围较远的区域具有较高的含量。土壤速效养分在100 m和>800 m的范围具有较高的含量。【结论】距离牧场出入口较近的草地受践踏和采食频度的影响较高,使得植被物种单一,土壤易被侵蚀,造成了牧场出入口及200 m附近的草地植被结构发生变化。高寒草地牧场出入口及附近的草地植被和土壤特性变化反映了植被和土壤对放牧强度的响应,在实际的牧场管理中可对出入口进行更换,或在出入口进行补播,以防止草地退化。

划破草皮技术对退化高寒小嵩草草甸土壤及植被恢复的影响

【目的】明确不同土壤草皮划破技术对高寒小嵩草草甸土壤理化性质和植物群落地上生产力恢复的影响。【方法】以退化小嵩草草甸的不同土层深度(0~10、10~20、20~30、30~40 cm)土壤养分、水分、紧实度等特征及植物群落生长繁殖特性为评判指标,分析划破草皮(C_(1))、划破草皮+补播(C_(2))、划破草皮+施肥(C_(3))、划破草皮+补播+施肥(C_(4))4种草皮划破技术处理对土壤理化性质和植物群落地上生产力恢复的影响。【结果】4种草皮划破技术处理下土壤湿度分别比对照增加了0.09%、4.80%、3.58%和4.05%,对土壤碳、氮、磷和钾含量亦具有一定程度的提升效果。双因素方差分析结果表明,处理方式、土壤深度及两者的交互作用对土壤全碳和全氮含量存在极显著影响(P<0.01)。不同处理方式对植物群落及实生苗数量特征存在不同程度的提升效应(P<0.01),其中,C_(2)处理植物群落密度比对照增加了68.77株/m^(2)(P<0.05);双子叶植物数量与土壤无机碳含量存在极显著负相关关系(P<0.01),相关系数为-0.37。基于不同处理的土壤物理性质(土壤湿度、土壤温度、土壤紧实度)、全量养分(全氮、全碳)和速效养分(有效磷、速效钾、铵态氮)含量的标准化多维数据分析结果表明,单一划破草皮处理(C_(1))在短期内对土壤物理和化学性质的综合改善能力较弱,而在划破草皮之上辅以补播或施肥处理对土壤理化性质的改善和限制性养分的活化效果更优。【结论】采用划破草皮配合外源种库和外源养分添加的生态恢复措施可以在短期内提高退化小嵩草草甸生产能力和土壤限制性养分含量,在生态恢复实践中具有一定的应用前景。

施用生物炭对东北大豆草甸土理化性质及腐殖质组分的影响

为评价生物炭添加对土壤理化性质、腐殖质及其腐殖化程度的改良效果,以生物炭田间定位试验为基础,设置4个处理:空白对照(CK)、常规施肥(NPK)、单施生物炭(B1)和化肥配施生物炭(NPK+B1),通过连续2年的田间试验,研究了生物炭添加对土壤理化性质和土壤胡敏酸(HA)、富里酸(FA)和胡敏素(HM)以及大豆产量的影响。结果表明:施用生物炭可短期内有效提高土壤养分,增加土壤中腐殖物质含量,提高稳定性,并改善土壤质地,提高大豆产量。其中与CK相比,B1和NPK+B1处理的土壤理化性质提升效果较为明显,电导率(EC)提高3.50%—98.99%、有机碳(OC)含量提高18.01%—23.18%、碱解氮(AN)含量提高23.48%—37.15%、全氮(TN)含量提高14.93%—25.37%、有效磷(AP)含量提高8.33%—110.16%、全磷(TP)含量提高10.00%—45.00%、速效钾(AK)含量提高6.61%—20.76%、全钾(TK)含量提高13.24%—30.74%、大豆产量提高了54.34%—90.36%。与NPK处理相比,NPK+B1处理土壤HA、FA和HM含量分别提高了38.62%、26.76%和16.45%。且通过相关性分析和主成分分析表明,土壤pH、EC、AK、TK、TP、AN、TN、OC和大豆产量与腐殖质存在显著的正相关关系。因此,化肥配施生物炭处理可有效改善土壤理化特性,提高土壤腐殖质组分含量,为克服大豆连作障碍,提高大豆生产能力提供理论和技术支撑。

退化高寒草甸土壤真菌群落水平分布格局及驱动因子

为探讨退化高寒草甸土壤真菌群落水平分布格局及驱动因子,本研究采用嵌套式取样方法在1000 m×1000 m的中度退化草甸区域内,综合分析了土壤真菌群落在不同取样距离上物种多样性和功能组成的变化规律及驱动土壤真菌群落分布的主要环境因子。结果表明:在不同取样距离上,土壤真菌的α多样性和群落结构存在显著的差异,退化草甸环境异质性可导致真菌群落的变化。FunGuil功能预测表明草甸退化使得腐生型和病理性土壤真菌增加,草甸退化过程中地上植被群落的改变可导致土壤真菌营养型的变化。此外,土壤营养成分是驱动退化草甸土壤真菌群落水平分布格局的主要环境因子。因此,微生物多样性空间分布受控于不同的环境因素,而土壤营养成分的改变容易引起退化草地生态系统中微生物的空间分布变化。