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1.
利用高程辅助进行土壤有机质的随机模拟   总被引:8,自引:1,他引:7       下载免费PDF全文
为了探讨在条件模拟计算环境下,是否可以利用高程数据辅助提高土壤有机质空间变化的预测精度及相应的预测不确定性模拟的准确性,该文在北京市平谷区内选取研究样区,以土壤有机质作为目标变量,一方面利用序贯高斯模拟法对土壤有机质的空间分布进行模拟,另一方面以高程作为辅助信息,利用序贯高斯协模拟法对土壤有机质的空间分布进行模拟,然后对两种方法的模拟结果进行对比分析。结果表明,在土壤有机质的空间预测精度、模拟预测结果的局部不确定性和模拟预测结果的空间不确定性三方面,通过将高程数据考虑进有机质条件模拟过程中,准确性都得到了提高。这对于农业可持续发展以及全球碳平衡研究都具有十分重要的意义。  相似文献   

2.
土壤有机质含量是反映土壤肥力的重要特征,利用高光谱技术对耕层土壤有机质(OM)含量进行定量化反演可为土壤信息化管理和精准施肥提供重要的依据。本文利用ASD FR 2500高光谱仪在室内条件下测定了风干土壤样品的可见近红外光谱,分析了东北平原不同土壤类型土壤光谱反射率曲线形状变化及土壤有机质含量的光谱反演模型,结果表明,根据土壤光谱反射率曲线变化特点可以初步将东北平原的几种土壤类型划分为三类,其主要区别在于460~1350nm范围内曲线斜率变化的差异。通过相关分析进一步确定了土壤有机质敏感波段为650~750nm,建立了不同土壤类型的有机质含量回归预测模型,并且对不同模型的回归系数和截距进行了方差同质性检验。结果显示,黑土和黑钙土、黑土和暗棕壤的模型没有显著差异,即可以分别构建同质性模型来简化有机质的预测,但是预测精度有所降低。  相似文献   

3.
微生物残体在土壤中的积累转化过程与稳定机理研究进展   总被引:3,自引:0,他引:3  
张彬  陈奇  丁雪丽  何红波  张旭东 《土壤学报》2022,59(6):1479-1491
近年来,关于微生物残体在土壤有机质积累和转化过程中的作用越来越受到研究者的关注。土壤有机质中微生物残体的数量和组成比例变化与土壤有机质的形成、容量大小及周转特征密切相关。对目前土壤微生物残体研究方面的相关进展进行了梳理和总结,在明确土壤微生物残体的来源及其重要性的基础上,介绍了土壤微生物残体定量和转化的表征方法,阐述了微生物残体在土壤有机质积累转化过程中的作用及其主要影响因素,探讨了微生物残体在土壤中的稳定机制,提出了微生物通过同化代谢作用驱动细胞残体积累进而促进土壤有机质积累和稳定过程中亟待探讨的科学问题。期望为进一步探究陆地生态系统土壤有机质周转与微生物过程的相互作用机理提供一定的思考。  相似文献   

4.
分析了生物地球化学循环中植物—土壤生态系统的有机物动态,土壤有机质(SOM)主要库类——土壤C,N,P,S循环特点;阐述了土壤有机质的生物地球化学循环模型CENTURY结构。利用CENTURY模型模拟土地利用变化情形下内蒙古草原生态典型区土壤有机质动态。由数值模拟结果分析看,CENTURY对自然和人为活动影响下生态系统的土壤有机质动态有良好的模拟能力,同时又可有效地反映土地利用类型变化对生态环境和土壤侵蚀的影响。  相似文献   

5.
基于BP神经网络的土壤水力学参数预测   总被引:8,自引:1,他引:7  
为了获取区域土壤水分和溶质运移模拟所需的土壤水力学参数,利用黄淮海平原曲周县的试验资料建立基于BP神经网络的土壤转换函数模型。本文采用土壤粒径分布、容重、有机质含量等土壤基本理化性质,来预测土壤饱和导水率Ks、饱和含水量sθ、残余含水量θr、以及van Genuchten公式参数α、n的对数形式ln(α)和ln(n),并与多元线性逐步回归方法进行比较。t检验结果表明,BP神经网络训练和预测得到的模拟值与实测值之间吻合很好,该方法具有较高的预测精度。通过对平均相对误差的比较,得出在粒径分布的基础上增加容重、有机质含量等输入项目,可以提高部分土壤水力学参数的预测精度,而有些参数的预测精度反而降低。以误差平方和为标准的比较结果表明,BP神经网络模型的预测效果总的来看要优于多元线性回归法。  相似文献   

6.
王茵茵  齐雁冰  陈洋  解飞 《土壤学报》2016,53(2):342-354
遥感数据已经在数字土壤制图中得到广泛应用,并且可以一定程度上提高土壤属性预测的精度。本文以榆阳区的黄土丘陵和风沙滩地两种地貌区为例,利用不同分辨率的专题制图仪(thematic mapper,TM)、先进宽视场传感器(advanced wide field sensor,AWIFS)和中等分辨率成像仪(Moderate resolution imaging spectroradiometer,MODIS)的遥感影像数据(分辨率分别为30 m、56 m和250 m)和基于高级热量散射和反射辐射仪全球数字高程模型(advanced spaceborne thermal emission and reflection radiometer global digital elevation model,ASTER GDEM)的地形衍生数据,结合其他影响土壤有机质分布的辅助因子,用随机森林算法(random forest,RF)对表层土壤有机质进行模拟预测,并通过实测数据的百分比抽样对预测结果进行了验证。结果表明,在榆阳区的黄土丘陵区,基于TM数据的土壤有机质预测结果较好;在风沙滩地区,基于AWIFS数据的土壤有机质预测结果较好。基于RF的土壤有机质预测在榆阳区的黄土丘陵区结果较好,三个分辨率下的平均绝对误差在1.27~1.57 g kg-1之间,在风沙滩地区预测精度较低,平均绝对误差在1.46~2.08 g kg-1之间。高程、地理位置和植被是影响黄土丘陵区土壤有机质预测的主要因素,在风沙滩地区,植被、高程和离水源地的距离是影响有机质预测的主要因素。可见,在地貌相对简单的地区进行土壤有机质含量的预测时可以使用较低分辨率的数据代替较高分辨率的数据,同时,RF算法在复杂地貌区的土壤有机质预测更有效。  相似文献   

7.
基于多元地统计的土壤有机质含量空间格局反演   总被引:4,自引:2,他引:2  
为了提高土壤有机质含量的空间预测精度,该文采用了一种多元地统计方法来构建遥感定量反演模型。考虑到回归误差在空间上具有一定程度的聚类,该文提出了基于局部变化均值的普通克里金方法,然后用其构建土壤有机质含量遥感定量反演模型。对四川省西南部土壤有机质含量进行空间预测试验,并与普通克里金、普通遥感定量反演、基于回归克里金的遥感定量反演等方法相比较。结果表明:该文提出方法的空间预测结果最优,其原因为该方法通过空间统计来建立采样数据与地表反射率间的联系,充分考虑了数据间的空间相关性,因此可以更精确地获得土壤有机质含量的遥感反演模型;相比基于回归克里金的遥感定量反演方法,基于局部变化均值的普通克里金假设回归误差在局部邻域内的均值也不一定为零,更符合实际情况。该方法为农田养分管理及区域农业的可持续发展提供科学依据。  相似文献   

8.
基于EPO算法去除水分影响的土壤有机质高光谱估算   总被引:2,自引:0,他引:2       下载免费PDF全文
洪永胜  于雷  朱亚星  吴红霞  聂艳  周勇  Feng QI  夏天 《土壤学报》2017,54(5):1068-1078
野外进行土壤有机质的光谱快速预测时需考虑土壤含水量的影响。在室内设计人工加湿实验分别获取9个土壤含水量梯度(0~32%,间隔4%)的土壤光谱数据,分析土壤含水量变化对光谱的影响,再利用外部参数正交化法(external parameter orthogonalization,EPO)进行湿土光谱校正,并结合偏最小二乘回归和支持向量机回归分别建立土壤有机质预测模型。结果表明,土壤光谱反射率随着土壤含水量的增加呈非线性降低趋势,偏最小二乘回归模型的预测偏差比为1.16,模型不可用;经EPO算法校正后,各土壤含水量梯度之间的光谱差异性降低,能实现土壤有机质在不同土壤含水量梯度的有效估算,偏最小二乘回归和支持向量机回归模型的预测偏差比分别提高至1.76和2.15。研究结果可为田间快速预测土壤有机质提供必要参考。  相似文献   

9.
长期施肥条件下土壤碳氮循环过程研究进展   总被引:33,自引:1,他引:32  
李海波  韩晓增  王风 《土壤通报》2007,38(2):384-388
土壤是主要的陆地生态系统碳库,碳、氮通过大气-作物-土壤界面进行周转和协同转化。长期施肥通过改变土壤物理、化学和生物学性质,进而影响土壤有机碳、氮储量的稳定性。土壤有机质是评价土壤质量的重要指标,具有农艺和环境双重功能。有机-无机肥配施不仅可显著提高土壤肥力,并且可减少农田土壤温室气体排放,保持农田土地的可持续利用。本文就土壤碳、氮消长动态研究以及有机质周转的同位素示踪测试技术等作一简要综述。  相似文献   

10.
郭龙  张海涛  陈家赢  李锐娟  秦聪 《土壤学报》2012,49(5):1037-1042
选取宜昌市红花套镇作为研究区域,研究土壤pH、有机质、有效磷、速效钾、碱解氮与土壤属性指标变量之间的关系,选择与预测变量之间具有较高相关性的变量作为辅助变量用以提高预测精度,本文试图将地理加权回归模型应用于土壤属性空间模拟中,以此与协同克里格插值的预测结果进行对照,从而比较它们的预测精度以提出更适合土壤属性预测的模型。结果表明:协同克里格插值和地理加权回归模型对土壤属性的空间模拟均有较高的预测精度,在辅助变量较多的情况下地理加权回归模型具有比协同克里格插值更为简单的算法,并且比较预测值相对误差的范围跨度和标准差以及均方根误差等方面,地理加权回归模型在土壤属性指标预测方面具有更高的预测精度,也具有更大的优势。  相似文献   

11.
The net effect of increasing ultraviolet B radiation levels on ecosystems is unknown. Most of the relevant ecological research has focused on the responses of living plants and algae to ultraviolet B exposure, with little attention directed toward other groups. However, research in such diverse areas of study as the degradation of textiles, pigments, synthetic polymers, paper, cellulose, wood, and museum artifacts show that ultraviolet light is a significant factor in the decay of many organic compounds. In aquatic ecosystems, the photochemical degradation of recalcitrant, dissolved organic compounds is increased by ultraviolet B exposure, and similar reactions could make important contributions to organic matter turnover in terrestrial ecosystems. This hypothesis is supported by observed patterns of decomposition of exposed surface litter in arid and semi-arid environments. Since plant lignins are both photochemically reactive and form a significant component of soil organic matter, ultraviolet B-induced lignin degradation could alter material cycling in terrestrial ecosystems. However, results of a model simulating the potential effects of ultraviolet B-induced lignin degradation suggest that higher rates of litter turnover may have only slight effects on soil organic matter dynamics.  相似文献   

12.
The fate of global soil carbon stores in response to predicted climate change is a ‘hotly’ debated topic. Considerable uncertainties remain as to the temperature sensitivity of non-labile soil organic matter (SOM) to decomposition. Currently, models assume that organic matter decomposition is solely controlled by the interaction between climatic conditions and soil mineral characteristics. Consequently, little attention has been paid to adaptive responses of soil decomposer organisms to climate change and their impacts on the turnover of long-standing terrestrial carbon reservoirs. Using a radiocarbon approach we found that warming increased soil invertebrate populations (Enchytraeid worms) leading to a greater turnover of older soil carbon pools. The implication of this finding is that until soil physiology and biology are meaningfully represented in ecosystem carbon models, predictions will underestimate soil carbon turnover.  相似文献   

13.
The distribution in a New Zealand pasture soil of total organic carbon, of 13C/12C and 14C/12C ratios, up to a depth of l m and over a period of 15 yr, has been analysed to provide models for radiocarbon enrichment and organic matter turnover. For the enrichment model, the parameters of C input, rates of decomposition and diffusion down the soil profile, and turnover rates have been determined. Input rates are compatible with herbage productivity measurements; the turnover period is estimated as 63 yr, and the downward diffusivity of C is estimated at 13cm2 yr?1. The steady state model indicates that a small fraction of the soil organic C, about 16%, is relatively very old and uniformly distributed throughout the soil profile. Most of the remaining fraction of modern C, other than “bomb” C, is less than 100 yr old and decreases exponentially with increasing depth. The models provide a rational integration of empirical measurements of C input, rates of organic matter decomposition, diffusivity and turnover, enabling an unknown to be calculated from measured parameters. They also provide a rational and precise method for determining the age of soil organic matter from radiocarbon measurements and have been used to examine alternative hypotheses for the distribution of UC with depth.  相似文献   

14.
黏粒阳离子交换量估测模型的优化研究   总被引:1,自引:0,他引:1       下载免费PDF全文
为了优化土壤黏粒阳离子交换量估测模型,提升估测结果准确性,为土壤系统分类检索提供可靠数据支持,以江西省土壤为主要研究对象,根据有机质、粉粒阳离子交换量对现有估测模型的影响,将有机质含量低于6 g·kg-1的土壤样本定为低有机质样本,高于6 g·kg-1的土壤定为高有机质样本开展分类建模。高有机质样本中主要误差因子为有机质,按照土壤质地不同开展分类建模;低有机质样本中主要误差因子为粉粒CEC7,在实测粉粒CEC7的同时根据pH、年均气温、纬度估测粉粒CEC7大小,建立低有机质样本间接估测模型。分类优化后的黏粒CEC7估测模型的估测值更加接近实测值,提升了土壤系统分类检索的准确度。  相似文献   

15.
Physical fractionation is used increasingly to study the turnover of organic matter in soil. This essay links the methods of fractionation to concepts of turnover by defining levels of structural and functional complexity that refer to experimentally verifiable pools of organic matter in the soil. Physical fractionation according to size and density of soil particles emphasizes the importance of interactions between organic and inorganic soil components in the turnover of organic matter. It allows the separation of free and occluded uncomplexed organic matter and of primary and secondary organomineral complexes. This methodological approach recognizes that the overall regulation of decomposer activity is through the structure of soil, which determines gas exchange, the availability of substrates and water, and the transport of solutes. Results from physical fractionations suggest three levels of structural and functional complexity in the turnover of organic matter in soil. Primary organomineral complexes isolated from fully dispersed soil account for the primary level of complexity. The clay‐, silt‐ and sand‐sized complexes are seen as the basic units in soil, surface reactions between substrates, organisms and minerals being the main regulatory mechanisms. Secondary complexes reflect the degree of aggregation of primary organomineral complexes and refer to the second level of complexity. Physical protection of uncomplexed organic matter and soil organisms and the creation of gas and moisture gradients are emergent features regulating the turnover at this level of complexity. The structurally intact soil (the soil in situ) constitutes the third level of complexity. This integrates the effects of primary and secondary complexes. Emergent structural features associated with this level are resource islands, macropores, roots, mesofauna, tillage and soil compaction, the corresponding functional features being related to the transport and exchange of solutes and gases, and the spatial distribution and comminution of litter and uncomplexed organic matter. Thus, a thorough understanding of the turnover and storage of organic matter in soil can be acquired only by considering all levels of complexity in the decomposition subsystem.  相似文献   

16.
A novel computer model is presented which describes the flow of C and N in the soil. It employs a structure with conceptual compartments. Organic matter is represented by seven different compartments, two for added matter, two for soil microbial biomass, one for microbial residues, one for native (‘humified’) organic matter, and one for inert organic matter. The latter pool represents both truly inert matter, and matter with negligible turnover in a time-span of decades to a century. This paper describes the parameterisation and performance of this model on selected long-term field carbon and radiocarbon data from United Kingdom, Sweden and Denmark. Previously unpublished radiocarbon data series from Denmark are included. Statistical methods were employed to estimate parameters, and obtain proximate confidence intervals for these parameters. Simulations in good agreement with measured values could be achieved, using the same set of parameters on all sites. It was demonstrated that the inert pool might constitute any amount between approx. 10 and 50% of total soil C, so that modelling cannot be used as a tool to obtain narrow estimates for this pool.  相似文献   

17.
Based on a literature review including 201 surface soils from wet, mild, mid-latitude climates and 290 soils from the Lower Saxony soil monitoring programme (Germany), we investigated the relationship between soil clay content and soil organic matter turnover. The relationship was then used to evaluate the clay modifier for microbial decomposition in the organic matter module of the soil-plant-atmosphere model DAISY. A positive relationship was found between soil clay content and soil microbial biomass (SMB) C. Furthermore, a negative relationship was found between soil clay content and metabolic quotient (qCO2) as an indicator of specific microbial activity. Both findings support the hypothesis of a clay dependent capacity of soils to protect microbial biomass. Under the differing conditions of practical agriculture and forestry, no or only very weak relationships were found between soil clay content and non-living soil organic matter C (humus C). It is concluded that the stabilising effect of clay is much stronger for SMB than for humus. This is in contrast to the DAISY clay modifier assuming the same negative relationship between soil clay content, on the one hand, and turnover of SMB and turnover of soil humus on the other. There is a positive relationship between SMB and microbial decomposition activity under steady-state conditions (microbial growth≈microbial death). The original concept of a biomass-independent simulation of organic matter turnover in the DAISY model must therefore be rejected. In addition to the original modifiers of organic matter turnover, a modifier based on the pool size of decomposing organisms is suggested. Priming effects can be simulated by applying this modifier. When using this approach, the original modifiers are related to specific microbial activity. The DAISY clay modifier is a useful approximation of the relationship between the metabolic quotient (qCO2) as an indicator of specific microbial activity and soil clay content.  相似文献   

18.
Modelling refractory soil organic matter   总被引:5,自引:0,他引:5  
Most models for the turnover of soil organic matter (SOM) include a compartment that is either considered inert, or has a very slow turnover time (refractory SOM; RSOM). The RSOM content of soils varies markedly between sites, and knowledge of its size and variability are essential for determining whether soils behave as sources or sinks of atmospheric CO2. It has also been suggested that the accurate specification of RSOM pools is essential to modelling studies, and that uncertainty in estimates of the size of RSOM pool could be a major source of error in modelling soil organic C. In this paper, current SOM models are reviewed, and approaches to modelling RSOM and its significance are discussed. Simulations of SOM turnover for the Rothamsted Broadbalk winter wheat experiment using the Rothamsted C model and CENTURY are presented as examples. Received: 13 July 1999  相似文献   

19.
荒漠土壤有机质含量高光谱估算模型   总被引:17,自引:6,他引:11  
为解决荒漠土壤有机质含量高光谱估算存在的困难,提高土壤有机质含量估算的精准性,该文对准噶尔盆地东部荒漠土壤进行采样、化验分析和光谱测量、处理,分析土壤光谱与有机质含量的相关性,确定敏感光谱波段,建立荒漠土壤有机质含量多种高光谱估算模型,旨在通过模型精度的比较,确定最优模型。结果表明:反射率、倒数对数光谱与荒漠土壤有机质含量相关性低,而经过一阶微分、二阶微分变换后,相关系数有所提高,部分波段的相关系数通过0.01显著水平的检验,可以用来荒漠土壤有机质含量的估算;一元线性回归建立的估算模型的精度低,不适用荒漠土壤有机质含量高光谱的估算。荒漠土壤有机质多元逐步回归模型的二阶微分、倒数对数二阶微分修正决定系数得到了较大提高,分别提高了0.22和0.31,均方根误差下降了0.66和0.80,建模精度高于一元线性回归模型。荒漠土壤有机质一阶微分、二阶微分光谱的最小偏二乘回归模型的决定系数比其多元逐步回归模型提高了0.07、0.04,一阶微分、二阶微分均方根误差都下降了0.11,二阶微分偏最小二乘法回归模型是该研究所建12个模型的最优估算模型。在多元逐步、偏最小二乘回归模型中,最优估算模型是二阶微分模型,因而用偏最小二乘法回归估算荒漠土壤有机质含量是个可行的方法。该研究的成果为荒漠土壤有机质高光谱遥感分析提供了支撑,实现荒漠土壤有机质监测的时效性、准确性,为区域生态环境的修复提供依据。  相似文献   

20.
The suitability of the DeNitrification-DeComposition (DNDC) model for simulating long-term changes in the content of soil organic carbon (SOC) was validated using 5 sites for long-term experiments related to Japanese paddy soils. Since the model could not simulate crop growth adequately, several crop growth parameters provided by the model as default were changed to adjust crop growth to the observation. Overall, the changes in the content of SOC with time simulated by DNDC using adjusted crop parameters, agreed well with the observation in 9 plots from 5 experimental sites during the 16 to 22-year period of the experiment. The good performance of the decomposition sub-model in the DNDC was verified in the long-term SOC decomposition in paddy soils as well as in upland soils reported in previous studies. However, the simulated SOC did not agree well with the observation in some plots, especially in soils with a very low SOC content, suggesting that care should be exercised when applying the model to soils with a very low SOC content. Moreover, careful tuning of crop growth parameters should be promoted for better simulation, and detailed information about farm management required for input parameters is often difficult to obtain, especially in long-term experiments. In conclusion, the DNDC model is an effective tool for simulating long-term SOC dynamics in paddy soils. The unique kinetic scheme "anaerobic balloon" in the model may play an important role in successful simulation of SOC dynamics in paddy soils that are water-logged during the rice cropping period. This scheme may be helpful for modifying the other turnover models of soil organic matter for use for paddy soils, too.  相似文献   

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