土壤有机磷研究进展

土壤有机磷在农业生态系统的物质循环过程中具有重要作用．研究土壤有机磷,对深入了解土壤-植物系统中磷的营养循环特征具有重要意义．结合国内外已有成果和最新研究进展,从土壤有机磷含量及其影响因素、土壤有机磷的形态和测定方法、土壤有机磷的分组和施肥的影响、土壤有机磷的矿化等几个方面综述了国内外土壤有机磷的研究现状,并提出了目前在土壤有机磷研究中存在的一些问题以及今后研究的热点．     

渭北旱塬苹果种植分区土壤水分特征

在区域尺度和定位观测的基础上,探讨了渭北塬区不同苹果种植分区的土壤水分特征．结果表明,渭北旱塬苹果种植分区土壤水分特征主要受降水和蒸散量的影响．在区域尺度上,苹果地潜在蒸散量是台塬东部区>高原沟壑区>台塬西部区．3种类型区苹果地土壤水分都存在亏缺现象,台塬东部区苹果地平均土壤水分亏缺量为390．9mm．最大亏缺量为674．6mm,最小亏缺量为186．3mm;高原沟壑区苹果地水分平均亏缺量、最大亏缺量分别为264．4和441．2mm,偶尔也出现水分盈余的现象;台塬西部区总体上表现为亏缺。但苹果地出现水分盈余的现象较高原沟壑区普遍,最大盈余量达151．8mm．渭北旱塬苹果地水分储存量也存在区域分异,在全生育期2m土层水分储存量台塬西部区>高原沟壑区>台塬东部区．这种变化特性与降水量的时空变化、果树对土壤水分的消耗量及降水年型有关;具体表现为苹果地耗水量以台塬东部区最大,高原沟壑区次之,台塬西部区最小,干旱年苹果全生育期耗水量低于丰水年．在干旱年份,苹果树耗水量除来源于生育期问的有效降水外,还有相当一部分依赖于3m以下土层贮水,形成土壤干层。影响果业持续发展．     

土壤微生物多样性研究方法

概述了研究土壤微生物多样性的主要方法．传统上,土壤微生物群落的分析依赖于培养技术,使用各种培养基最大限度地培养各种微生物群体,但仍只能培养和分离出一小部分土壤微生物群落．使用Biolog分析、磷脂脂肪酸分析和核酸分析等方法,可研究和表征那些现在还不能够被培养的土壤微生物。从而获取关于土壤微生物群落多样性的更多和更完整的信息．     

砷对土壤脲酶活性影响的研究

采用模拟方法对As污染土壤脲酶特征进行了研究．结果表明,土壤中As浓度在0～200mg·kg^-1浓度范围内,反应初期脲酶活性变化无明显规律;一年后砷激活土壤脲酶活性,二者达到显著或极显著正相关．随As浓度增加,土壤脲酶Km值基本不变或略有增加,Vmax增大,从机制上揭示出As加速脲酶-尿素复合物的解离．厩肥和无肥土样脲酶对As的反应类似,只是变化幅度有所差异．     

不同人工林生态系统林地土壤质量评价

利用定位研究方法,综合比较了第2代连栽杉木纯林、杉木与阔叶树混交林以及阔叶纯林3种人工林生态系统对林地土壤质量的影响．结果表明,与连栽杉木纯林相比,在杉阔混交和阔叶树轮栽两种经营模式下,土壤养分含量增加,物理性状改善,土壤生物活性提高．利用土壤质量评价体系在对土壤功能评价的基础上,直观评价了3种经营模式的土壤质量状况．在研究区内,杉木与阔叶树混交以及阔叶树轮栽的水分有效性、养分有效性和根系适宜性以及最终的土壤质量指数均处于中等水平,而连栽杉木林的水分有效性、养分有效性和根系适宜性较差,土壤质量指数处于较低水平．总有机C、阳离子交换量和微生物生物量C与其它土壤理化性质和生物学性质之间明显相关,可将其作为研究区土壤质量的指示指标;土壤微生物生物量C、N、P与土壤总有机C、土壤全N、土壤全P含量之间也存在较好的相关性。     

黄土半干旱区坡地土壤水分、养分及生产力空间变异

通过田问取样,分析黄土半干旱丘陵区陡坡面土壤水分、养分及其生产力空间变异性及其相关关系．结果表明,坡面0～20cm土层土壤各养分含量均不同程度地高于20～40cm土层,但变异程度却明显低于20～40cm土层,且除全磷外,土壤养分变异程度均明显高于水分．20～40cm土层土壤养分沿坡面向下逐渐增大,而0～20cm沿坡面纵向差异较小．坡面浅沟沟槽处的土壤水分、养分条件最优,但其地上生物量却低于坡顶．虽然纵向坡度(35°～45°)明显大于横向(5°～10°),但横向坡位对土壤养分的影响却明显大于纵向(除20～40cm土层速效磷含量除外),而对水分的影响纵向大于横向．相关分析表明,0～120cm土壤水分与20～40cm土壤养分以及土壤养分之间(0～20cm速效磷除外)均呈极显著相关．坡位对土壤水分、养分及地上生物量有很大影响,但土壤水分、养分对生物量影响不显著．     

阿维菌素在土壤中的微生物降解研究

运用恒温培养法研究了阿维菌素在土壤中的降解动力学．结果表明,非生物+微生物降解、非生物降解及微生物降解的半衰期分别为34．8、277．3和49．9d,说明阿维菌素在土壤中的降解主要由微生物引起．从试验土壤中分离到1株高效降解阿维菌素的菌株,经16S rDNA鉴定为嗜麦芽寡养单胞菌(Stenotrophomonas maltrophilia)．从该降解菌中提取的粗酶液米氏常数(Km)为6．78nmol·ml^-1,最大降解速率为81．5nmol·min^-1·mg^-1。     

南京城市土壤重金属含量及其影响因素

研究了南京城市土壤重金属含量、来源及其与土壤性质的关系。结果表明,南京城市土壤中,Fe、Ni、Co、V污染不明显,但受到了不同程度的Mn、Cr、Cu、Zn、Pb污染,其中：Pb污染非常严重;重金属在土壤剖面分布没有规律性;Fe、Ni、Co、V元素主要来源于原土壤物质,Cu、Zn、Pb、Cr元素主要来源于人为输入,Mn可能在不同的土壤中来源不同;Fe、Cr、Ni、Co、V元素含量之间均呈极显著正相关,Cu、Zn、Pb、Cr元素含量之间均呈极显著正相关。Fe、Co、V、Ni含量与粘粒含量、CEC呈极显著正相关;Cu、Zn、Pb含量与粘粒含量呈极显著负相关;Cu、Zn、Pb、Cr含量与有机碳呈极显著正相关,Pb含量与pH呈极显著正相关。     

广义Schumacher模型的改进及其应用

通过对前人提出的生长方程的具体分析,提出了一种改进的Schumacher生长方程．该模型包含了Gompenz函数、Schumacher方程及广义Schumacher方程,具有很强的自适应性和实用性．采用遗传算法。利用该模型对珍稀植物长苞铁杉和侧柏生长资料分别进行了拟合．结果表明,改进的Schumacher方程的拟合精度明显优于Schumache,方程和广义Schumacher方程,也优于经典的Logistic模型和李新运等自适应模型。可以在林木生长动态模拟及种群增长动态研究中广泛应用．     

金沙江干热河谷人工植被土壤水环境

金沙江干热河谷异常干热的气候特点,普遍存在水分亏缺问题,人工植被土壤水环境问题比其它干旱、半干旱地区更加突出．在干热河谷典型地段——元谋的试验观测表明,现有的乔木林明显表现出“土壤干化”的特点,土壤水分持续长时间亏缺,雨季结束之后的11月份。2m土层内的土壤含水量只有15％(相当于田间持水量的35％)左右,之后持续下降,直到5月份达到最低点(9％左右),几乎接近林木的凋萎湿度(元谋表蚀燥红壤的凋萎湿度为9．O％)．由此而导致林木生长缓慢．车桑子(Radonaea wiscosa)灌木林同层土壤含水率相对比乔木林高42．68％,自然草坡的土壤水分明显优于乔木和灌木林,分别比乔木林和灌木林高34．36％和22．22％．这种人工乔木林的“土壤干化”问题在干热河谷地区的植被恢复中还没有引起重视,将极大地制约人工植被的可持续发展．     

森林流域非饱和土壤水与饱和土壤水转化研究进展

阐述了森林流域几种土壤水分运动方式(入渗、潜水蒸发、潜水补给以及壤中流)中非饱和土壤水与饱和土壤水之间转化的研究进展,并对土壤水分运动参数中的土壤水分特征曲线、非饱和导水率和饱和导水率的研究现状作以简要介绍,最后提出了未来的发展方向.     

The effects of stubble retention and tillage practices on surface soil structure and hydraulic conductivity of a loess soil

The current cropping system of excessive tillage and stubble removal in the northwestern Loess Plateau of China is clearly unsustainable. A better understanding of tillage and stubble management on surface soil structure is vital for the development of effective soil conservation practices in the long term. Changes in surface soil structure and hydraulic properties were measured after 4 years of stubble management (stubble retained vs. stubble removed) under contrasting tillage practices (no-tillage vs. conventional tillage) in a silt loam soil (Los Orthic Entisol) in Dingxi, Gansu, the northwestern Loess Plateau, China. Our results indicated that after 4 years small but significant changes in soil properties were observed amongst the different tillage and stubble treatments. Surface soil (0–5 cm) under no-tillage with stubble retention had the highest water stability of macroaggregates (>250 μm), soil organic carbon (SOC) and saturated hydraulic conductivity. Significant correlation was found between water stable macro-aggregates and soil organic carbon content, indicating the importance of the latter on soil structural stability. The improvement in soil structure and stability was confirmed by higher soil hydraulic conductivity measurements. Consistently higher K_sat was detected in the no tillage with stubble retained soil compared to other treatments. Therefore, no-tillage with stubble retention practice is an effective management technique for improving physical quality of this fragile soil in the long term.     

The effects of stubble retention and tillage practices on surface soil structure and hydraulic conductivity of a loess soil

The current cropping system of excessive tillage and stubble removal in the northwestern Loess Plateau of China is clearly unsustainable. A better understanding of tillage and stubble management on surface soil structure is vital for the development of effective soil conservation practices in the long term. Changes in surface soil structure and hydraulic properties were measured after 4 years of stubble management (stubble retained vs. stubble removed) under contrasting tillage practices (no-tillage vs. conventional tillage) in a silt loam soil (Los Orthic Entisol) in Dingxi, Gansu, the northwestern Loess Plateau, China. Our results indicated that after 4 years small but significant changes in soil properties were observed amongst the different tillage and stubble treatments. Surface soil (0–5 cm) under no-tillage with stubble retention had the highest water stability of macroaggregates (>250 μm), soil organic carbon (SOC) and saturated hydraulic conductivity. Significant correlation was found between water stable macro-aggregates and soil organic carbon content, indicating the importance of the latter on soil structural stability. The improvement in soil structure and stability was confirmed by higher soil hydraulic conductivity measurements. Consistently higher K_sat was detected in the no tillage with stubble retained soil compared to other treatments. Therefore, no-tillage with stubble retention practice is an effective management technique for improving physical quality of this fragile soil in the long term.     

土壤水势对水曲柳幼苗水分生态的影响

采用根区渗灌控水技术,将土壤水势长期控制在0～-20kPa(W1)、-20～-40kPa(W2)、-40～-60kPa(W3)、-60～-80kPa(W4)、-80～-160kPa(W5)范围内,系统地研究了不同土壤水势条件下水曲柳幼苗的蒸腾过程、吸水过程、根叶水势13动态过程及SPAC体系的水流阻力,结果表明,在亚饱和土壤水分状态下(W1),细根水势最高,水分由土壤进入细根的阻力最小,根系吸水速率最高,从而支持了13间强烈的蒸腾作用．在田间持水量土壤水分状态下(W2),细根吸水阻力成倍增加,吸水速率和蒸腾速率显著下降,但尚未改变蒸腾作用13动态过程的单峰模式．当土壤水分在田间持水量状态以下(W3-W5)时,随着土壤水势递降,细根吸水阻力急剧增加至几倍乃至几十倍,根系吸水速率过低,吸水与蒸腾矛盾加剧,叶水势降至很低,气孔关闭,蒸腾作用受到严重抑制,呈现明显的午休低谷．在实验范围内(0～-160kPa),土壤水分对水曲柳幼苗是非等效的,当土壤水分在田间持水量状态以下(<-40kPa)时,水曲柳全光苗发生显著的水分胁迫。     

黑河上游山区土壤非饱和导水率测定及其估算——以排露沟流域为例

黑河上游山区土壤水分表现为非饱和特征,准确估算该区域表层土壤非饱和导水率(K10)可提高山区生态水文模型的可靠性.本研究野外测定了黑河上游排露沟流域的K10,并利用土壤传递函数(PTFs)以土壤机械组成、容重及土壤平均粒径作为分析因子进行模拟估算,结果表明:排露沟流域森林、草地、退耕裸地的K10均值分别为(0.21±0...     

子午岭植被恢复对土壤饱和导水率的影响

通过对子午岭林区不同植被的土壤性质进行实验室测定和野外调查,对饱和土壤水分运动的重要参数之一土壤饱和导水率(Ks)及其相关因子进行了多元分析和通径分析,揭示了植被恢复提高土壤水分传输性能的机理,主要结论如下:土壤有机质是子午岭林区九种植被下土壤饱和导水率提高的主要驱动因子.不同植被下的土壤饱和导水率均随深度的增加而迅速降低,尽管草地和先锋草地在5～10cm深度有一强透水层.土壤饱和导水率在剖面上的平均值,从辽东栎、早期森林、灌丛、先锋草地、弃耕地到草地依次降低.灌丛与草地、弃耕地的差异达到显著水平,辽东栎顶级群落的饱和导水率最高,植被的恢复明显提高了土壤饱和导水率.土壤容重、毛管孔隙度、>0.25mm团聚体含量及粘粒含量直接影响土壤饱和导水率.土壤有机质含量的提高能够改善容重、毛管孔隙度、团聚体含量等物理性质.     

土壤水势对水曲柳幼苗水分生态的影响

采用根区渗灌控水技术,将土壤水势长期控制在0～-20kPa(W₁)、-20～-40kPa(W₂)、-40～-60kPa(W₃)、-60～-80kPa(W₄)、-80～-160kPa(W₅)范围内,系统地研究了不同土壤水势条件下水曲柳幼苗的蒸腾过程、吸水过程、根叶水势日动态过程及SPAC体系的水流阻力.结果表明,在亚饱和土壤水分状态下(W₁),细根水势最高,水分由土壤进入细根的阻力最小,根系吸水速率最高,从而支持了日间强烈的蒸腾作用.在田间持水量土壤水分状态下(W₂),细根吸水阻力成倍增加,吸水速率和蒸腾速率显著下降,但尚未改变蒸腾作用日动态过程的单峰模式.当土壤水分在田间持水量状态以下(W₃～W₅)时,随着土壤水势递降,细根吸水阻力急剧增加至几倍乃至几十倍,根系吸水速率过低,吸水与蒸腾矛盾加剧,叶水势降至很低,气孔关闭,蒸腾作用受到严重抑制,呈现明显的午休低谷.在实验范围内(0～-160kPa),土壤水分对水曲柳幼苗是非等效的,当土壤水分在田间持水量状态以下(<-40kPa)时,水曲柳全光苗发生显著的水分胁迫.     

The role of soil hydraulic conductivity on the spatial and temporal variation of root water uptake in drip-irrigated corn

A multiplexed TDR system and a heat-pulse system for stem sap flow measurements were used to determine the spatial and temporal pattern of root water uptake in field-grown corn. The TDR probes, 0.15 and 0.30 m in length, were buried vertically in the soil profile to a depth of 0.95 m below the soil surface and heat-pulse sensors were installed on the plant base. Nocturnal readings from TDR probes were used successfully to differentiate the two components of moisture change: root uptake and net drainage. The instantaneous rate of water extraction by the plant measured by the heat-pulse system agreed well with the integrated rate of root water uptake measured frequently (at half-hour or hourly intervals) by the TDR probes. This agreement enabled further exploration into the cause of the evolution of the spatial and temporal patterns of root water uptake during a drying cycle. The results indicated that right after irrigation in the well-watered soil profile, it is the spatial distribution of the roots that mainly determines the typical pattern of root extraction, in addition to the fact that the roots near the plant base are more effective than those farther away. The higher density and effectiveness of the roots near the plant base dry the soil rapidly so that soil hydraulic conductivity soon becomes a limiting factor for water uptake. Further analysis revealed that a decrease in root uptake occurs near the plant base under a given atmospheric demand when the relative bulk soil hydraulic conductivity decreases to 0.002K _r. This suggests that low conductivity (high resistance) in the soil near the plant base is the initial cause for downward and lateral shifting of the root uptake pattern. Note that this critical value of hydraulic conductivity is not universal since it depends on the soil type and atmospheric water demand during the period under observation. Therefore, prior to the application of moisture content or suction head as measures of water availability or to control irrigation scheduling, it is suggested that these parameters be calibrated by the soil K() or K() curves, respectively, for the expected atmospheric water demand for the specific crop and growing period.     

Assessing the impact of agro-industrial olive wastes in soil water retention: Implications for remediation of degraded soils and water availability for plant growth

Olive solid waste (OSW) is a toxic by-product of olive oil production. Disposal of OSW is a major problem in many Mediterranean countries leading to increased interest in its potential as an organic fertiliser. Relatively little is known regarding the impact of augmentation with OSW and olive solid waste compost (OSWC) on soil hydraulic properties. The effect of OSW and OSWC on the hydraulic characteristics of common agricultural soils with high sand but very different silt and clay contents was analysed. Increased organic inputs induced reductions in soil bulk density and increases in air capacity, hydraulic conductivity and the water content available for plant growth (AWC) in the Sandy Clay Loam (SCL) soil. Similar patterns were observed in Loamy Sand (LS) soil augmented with OSW, but OSWC caused reductions in hydraulic conductivity, air capacity and AWC. Nonetheless, over longer timescales OSWC may benefit the hydraulic properties of loamy sand soils as the compost becomes fully incorporated within the soil structure. Augmentation with organic olive waste induced the hydraulic parameters of the sandy clay loam soil to become identical to those loamy sand (LS) with a higher available water capacity; suggesting that soil augmentation with OSW and OSWC may be an effective tool in remediating and improving degraded or organic poor soils. In terms of the improvement of hydraulic parameters, application rates of 6–8% OSW/OSWC were most beneficial for both soil types.