Soil Spatial Heterogeneity Research Articles

Improving risk management by using the spatial interaction relationship of heavy metals and PAHs in urban soil.

Identifying combined pollution risk areas is difficult because of the complex pollutant sources and heterogeneous soil properties in urban systems. This study used bivariate local Moran's I to analyze the spatial interaction between heavy metals and PAHs, revealed the causes of spatial interaction patterns through PMF, and proposed a risk zoning approach for combined pollution in urban areas. The results showed that both heavy metals and PAHs had high spatial heterogeneity in urban soil. Bivariate LISA maps revealed the spatial interactions between heavy metals and PAHs. The historical area was the hotspot of combined pollution. The overlay of pollutant sources and sinks was responsible for the spatial interaction patterns of combined organic and inorganic pollution. Coal consumption was the main emission source for heavy metal and PAHs pollution, accounting for 31% and 21%, respectively. We used bivariate LISA as the auxiliary variable to reduce the uncertainty of identification combined pollution risk zones. More than 11% of the total area clustered significantly where concentration of both heavy metals and PAHs ware in excess of the risk threshold. This study indicates that we can provide better decision-making support for soil risk management based on the knowledge derived from spatial interaction analysis.

Coupling gas transport measurements and X-ray tomography scans for multiscale analysis in silty soils

Scale is a key issue in soil studies. The idea that a sample must be of adequate size to embody a specific physical property comes from the representative elementary volume (REV) concept that defines minimum sample size for consistent results. Other approaches to describe soil spatial heterogeneity rely on the fractal dimension concept (FDC), which assumes structure changes with scale continuously, and the discrete hierarchy concept (DHC), which assumes change occurs discretely. This study considered using gas transport measurements combined with X-ray computed micro-tomography (μCT) for multi-scale analyses. Specifically, 24 large (“L cores”, 628.3 cm3) core volume samples were collected from two farms and two soil depths (3–11 cm and 20–28 cm) in northeast Italy. Gas transport parameters, such as air-filled porosity, air permeability, and gas diffusivity, were measured on the original cores and on successively sub-sampled medium (“M cores”, 100.4 cm3) and small (“S cores”, 4.7 cm3) cores. X-ray μCT–derived porosity indices were calculated for the two smaller scales. Soil core sub-sampling resulted in reduced soil gas transport property measurements, especially in the deepest depth when related to large and continuous bio-pore decreases in root channels and wormholes. In small core volumes, the pore network was dominated by small isolated pores, which might obstruct gas diffusion at that scale. All three concepts named above could be reconciled with our data. The limited numbers of samples and observation scales hindered identifying which model described soil spatial heterogeneity best. Finally, our results suggested the importance of considering scale effects on soil physical properties and their measurement consistency.

Soil C:N:P stoichiometry responds to vegetation change from grassland to woodland

Woody encroachment has been a major land cover change in dryland ecosystems during the past century. While numerous studies have demonstrated strong effects of woody encroachment on soil carbon (C), nitrogen (N), and phosphorus (P) storage, far less is known about the plasticity of soil C:N:P stoichiometry in response to woody encroachment. We assessed landscape-scale patterns of spatial heterogeneity in soil C:N:P ratios throughout a 1.2 m soil profile in a region where grassland is being replaced by a diverse assemblage of subtropical woody plants dominated by Prosopis glandulosa, an N2-fixing tree. Woody species had leaf and fine root C:N:P ratios significantly different from grasses. Variation in soil C:N ratios in both horizontal and vertical planes was remarkably smaller than that of soil N:P and C:P ratios. Spatial patterns of soil C:N ratio throughout the profile were not strongly related to vegetation cover. In contrast, spatial patterns of soil N:P and C:P ratios displayed a strong resemblance to that of vegetation cover throughout the soil profile. Within the uppermost soil layer (0–5 cm), soil N:P and C:P ratios were higher underneath woody patches while lower within the grassland; however, this pattern was reversed in subsurface soils (15–120 cm). These results indicate a complex response of soil C:N:P stoichiometry to vegetation change, which could have important implications for understanding C, N, and P interactions and nutrient limitations in dryland ecosystems.

Emergent Properties of Microbial Activity in Heterogeneous Soil Microenvironments: Different Research Approaches Are Slowly Converging, Yet Major Challenges Remain.

Over the last 60 years, soil microbiologists have accumulated a wealth of experimental data showing that the bulk, macroscopic parameters (e.g., granulometry, pH, soil organic matter, and biomass contents) commonly used to characterize soils provide insufficient information to describe quantitatively the activity of soil microorganisms and some of its outcomes, like the emission of greenhouse gasses. Clearly, new, more appropriate macroscopic parameters are needed, which reflect better the spatial heterogeneity of soils at the microscale (i.e., the pore scale) that is commensurate with the habitat of many microorganisms. For a long time, spectroscopic and microscopic tools were lacking to quantify processes at that scale, but major technological advances over the last 15 years have made suitable equipment available to researchers. In this context, the objective of the present article is to review progress achieved to date in the significant research program that has ensued. This program can be rationalized as a sequence of steps, namely the quantification and modeling of the physical-, (bio)chemical-, and microbiological properties of soils, the integration of these different perspectives into a unified theory, its upscaling to the macroscopic scale, and, eventually, the development of new approaches to measure macroscopic soil characteristics. At this stage, significant progress has been achieved on the physical front, and to a lesser extent on the (bio)chemical one as well, both in terms of experiments and modeling. With regard to the microbial aspects, although a lot of work has been devoted to the modeling of bacterial and fungal activity in soils at the pore scale, the appropriateness of model assumptions cannot be readily assessed because of the scarcity of relevant experimental data. For significant progress to be made, it is crucial to make sure that research on the microbial components of soil systems does not keep lagging behind the work on the physical and (bio)chemical characteristics. Concerning the subsequent steps in the program, very little integration of the various disciplinary perspectives has occurred so far, and, as a result, researchers have not yet been able to tackle the scaling up to the macroscopic level. Many challenges, some of them daunting, remain on the path ahead. Fortunately, a number of these challenges may be resolved by brand new measuring equipment that will become commercially available in the very near future.

The ecosystem engineering role of the Neotropical crab Cardisoma guanhumi on mangrove soil properties

The land crab Cardisoma guanhumi is one of the most common species in mangroves of the American Atlantic coast and Caribbean islands however, studies of its effects on the physical and chemical soil properties are scarce. This study compares specific physicochemical properties of soil between C. guanhumi burrows (B) and adjacent zones (AZ), and provides the first insights on their role as an ecosystem engineer in mangroves. The study was conducted in an estuarine system dominated by Rhizophora mangle, located at the Rio Chico estuary, Miranda state of Venezuela. Random soil samples were taken digging each burrow until reaching the bottom and at the same depth for AZ. Data analysis was carried out using Bayesian inference. Credible mean differences between B and AZ, were found for sand (B = 26.53 ± 10.76, AZ = 17.25 ± 5.7%), silt (B = 73.16 ± 10.77, AZ = 82.42 ± 5.69%), pH (B = 8.71 ± 0.36, AZ = 9.12 ± 0.30), soil organic matter (SOM, B = 0.43 ± 0.21, AZ = 0.17 ± 0.06%), total N (TN, B = 786 ± 232, AZ = 529 ± 107 µg g−1), Mg (B = 4.42 ± 0.60, AZ = 3.48 ± 0.71 cmolc kg−1) and K (B = 0.12 ± 0.05 AZ = 0.06 ± 0.02 cmolc kg−1). Chemical variables as SOM, K, Mg and TN showed the highest values of effect size (> 1.4). With the exception of the pH, all chemicals variables—which were different between B and AZ—showed strong and decisive evidences of correlations with SOM. When SOM variable was controlled, the relationships between pH–TN, TN–K and Mg–K decreased, even though the correlation evidence between each pair remained. Differences in chemical contents found in B respect to AZ suggest that the activities of C. guanhumi (feeding, moulting, excretion and defecation) within their burrows promote the spatial heterogeneity of mangrove soils.

Spatial heterogeneity in root litter and soil legacies differentially affect legume root traits

Background and AimsPlants affect the soil environment via litter inputs and changes in biotic communities, which feed back to subsequent plant growth. Here we investigated the individual contributions of litter and biotic communities to soil feedback effects, and plant ability to respond to spatial heterogeneity in soil legacy.MethodsWe tested for localised and systemic responses of Trifolium repens to soil biotic and root litter legacy of seven grassland species by exposing half of a root system to control soil and the other half to specific inoculum or root litter.ResultsSoil inoculation triggered a localised reduction in root length while litter locally increased root biomass independent of inoculum or litter species identity. Nodule formation was locally suppressed in response to soil conditioned by another legume (Vicia cracca) and showed a trend towards systemic reduction in response to conspecific soil. V. cracca litter also caused a systemic response with thinner roots produced in the part of the root system not directly exposed to the litter.ConclusionsSpatial heterogeneity in root litter distribution and soil communities generate distinct local and systemic responses in root morphology and nodulation. These responses can influence plant-mutualist interactions and nutrient cycling, and should be included in plant co-existence models.

Microscale Heterogeneity of Floodplain Meadows (Using the Example of the Delta of the Northern Dvina River)

This article provides a quantitative evaluation of aspects of the spatial heterogeneity of soil and vegetation cover of floodplains in relation to the microrelief using the example of floodplains of the Northern Dvina River delta. It is detected that the soil and vegetation cover of the floodplain meadows in the Northern Dvina Delta is a feature of a relief on a microlandscape level. This dependence displays itself in the specific structural features of some ingredients of the soil and vegetation cover. Due to the intrazonal localization of floodplain ecosystems, the results of a local survey, for example, in Arkhangelsk oblast of Russia, can be extrapolated to other regions of the country and the world. The relevance of the study of heterogeneity of soil and vegetation cover is based not only on fundamental aspects, but also on the needs of agricultural management.

Наукові основи точного механічного обробітку ґрунту і перспективи його впровадження в Україні

Precision mechanical tillage is a fundamentally new agricultural strategy of farming, which is based on the use of information technology and new technical means and involves the implementation of technological measures for the main and pre-sowing tillage, taking into account the spatial heterogeneity of the physical properties of the root-content layer as indicators of differentiation of field tillage. In the article were presented the main provisions and stages of the method of determining the soil spatial heterogeneity of the plot. It was characterized indicators of precision mechanical soil tillage and promising methods for measuring parameters for precision tillage, including technical and software. It was proposed the preliminary norms of the physical properties of the treated layer for substantiation of the intensity of the basic mechanical soil tillage. It was proposed the characteristic of the main stages of the transition to precision farming and the mechanisms that should ensure its effective functioning, it was calculated the expected economic efficiency of precision farming. In the article was analyzed the spatial heterogeneity of arable land of Ukraine in terms of basic physical characteristics (structure, bulk density and penetration resistance) in the crop layer and plow sole. Some general patterns of manifestation of the spatial heterogeneity of the investigated properties of the soil cover of the land plots and the crop in all natural zones of Ukraine are analyzed, it serving as the main argument for the transition from generalized zonal technologies to precision mechanical tillage. The baseline data for the technological substantiation of the development of precision tillage (according to the content of the blocks in the seed layer) was worked out. Prospects for the introduction of precision agriculture in Ukraine are considered, based on the successful experience of mastering precision farming systems. Key words: soil, precision tillage, spatial heterogeneity, physical properties.

Pedotransfer Functions in Earth System Science: Challenges and Perspectives

AbstractSoil, through its various functions, plays a vital role in the Earth's ecosystems and provides multiple ecosystem services to humanity. Pedotransfer functions (PTFs) are simple to complex knowledge rules that relate available soil information to soil properties and variables that are needed to parameterize soil processes. In this paper, we review the existing PTFs and document the new generation of PTFs developed in the different disciplines of Earth system science. To meet the methodological challenges for a successful application in Earth system modeling, we emphasize that PTF development has to go hand in hand with suitable extrapolation and upscaling techniques such that the PTFs correctly represent the spatial heterogeneity of soils. PTFs should encompass the variability of the estimated soil property or process, in such a way that the estimation of parameters allows for validation and can also confidently provide for extrapolation and upscaling purposes capturing the spatial variation in soils. Most actively pursued recent developments are related to parameterizations of solute transport, heat exchange, soil respiration, and organic carbon content, root density, and vegetation water uptake. Further challenges are to be addressed in parameterization of soil erosivity and land use change impacts at multiple scales. We argue that a comprehensive set of PTFs can be applied throughout a wide range of disciplines of Earth system science, with emphasis on land surface models. Novel sensing techniques provide a true breakthrough for this, yet further improvements are necessary for methods to deal with uncertainty and to validate applications at global scale.

Data assimilation of soil water flow via ensemble Kalman filter: Infusing soil moisture data at different scales

This paper assesses the value of multi-scale near-surface (0∼5 cm) soil moisture observations to improve state-only or state-parameter estimation based on the ensemble Kalman filter (EnKF). To the best of our knowledge, studies on assimilating multi-scale soil moisture data into a distributed hydrological model with a series of detailed vertical soil moisture profiles are rare. Our analysis factors include spatial measurement scales, soil spatial heterogeneity, multi-scale data with contrasting information and systematic measurement errors. Results show that coarse-scale soil moisture data are also very useful for identifying finer-scale parameters and states given biased initial parameter fields, but it becomes increasingly difficult to recover the finer-scale spatial heterogeneity of soil property as the observation grids become coarser. In state-only estimation, near-surface soil moisture data result in improvement for shallow soil moisture profiles and degradation for deeper soil moisture profiles, with stronger influences from finer-scale data. With the decrease of background spatial heterogeneity of soil property, the value of coarse-scale data increases notably. Soil moisture data at two scales with contrasting information are found to be both useful. By updating spatially correlated soil hydraulic parameters, deviated observations still contain considerably useful information for finer-scale state-parameter estimation. Eventually, by presenting a difference information assimilation method based on EnKF we successfully extract useful information from soil moisture data containing systematic measurement errors. The current study can be extended to consider more complex atmosphere input and topography, etc.

Reply to: discussion on “Array-derived rotational seismic motions: revisited” by Basu et al.

Spatial variability of seismic ground motion is related to the difference in amplitude and phase of ground motion recorded over a given area. Spatial variability results from different contributions: the wave passage effect due to time delays in the arrival times of various seismic phases, the site response effect due to spatial soil heterogeneity, the attenuation along the ray path and the incoherence effects due to scattering of waves by local heterogeneities, the seismic rupture mechanism and, in near fields, the source directivity.

Lateral water flux in the unsaturated zone: A mechanism for the formation of spatial soil heterogeneity in a headwater catchment

AbstractMeasurements of soil water potential and water table fluctuations suggest that morphologically distinct soils in a headwater catchment at the Hubbard Brook Experimental Forest in New Hampshire formed as a result of variations in saturated and unsaturated hydrologic fluxes in the mineral soil. Previous work showed that each group of these soils had distinct water table fluctuations in response to precipitation; however, observed variations in soil morphology also occurred above the maximum height of observed saturation. Variations in unsaturated fluxes have been hypothesized to explain differences in soil horizon thickness and presence/absence of specific horizons but have not been explicitly investigated. We examined tensiometer and shallow groundwater well records to identify differences in unsaturated water fluxes among podzols that show distinct morphological and chemical differences. The lack of vertical hydraulic gradients at the study sites suggests that lateral unsaturated flow occurs in several of the soil units. We propose that the variations in soil horizon thickness and presence/absence observed at the site are due in part to slope‐parallel water flux in the unsaturated portion of the solum. In addition, unsaturated flow may be involved in the translocation of spodic material that primes those areas to contribute water with distinct chemistry to the stream network and represents a potential source/sink of organometallic compounds in the landscape.

Spatial heterogeneity of soil salinization and its influencing factors in the typical region of the Mu Us Desert-Loess Plateau transitional zone, Northwest China

Studies on the spatial heterogeneity of saline soil in the Mu Us Desert-Loess Plateau transition zone are meaningful for understanding the mechanisms of land desertification. Taking the Mu Us Desert-Loess Plateau transition zone as the study subject, its spatial heterogeneity of pH, electrical conductivity (EC) and total salt content were analyzed by using on-site sampling followed with indoor analysis, classical statistical and geostatistical analysis. The results indicated that: 1) The average values of pH, EC and total salt content were 8.44, 5.13 mS·cm-1 and 21.66 g·kg-1, respectively, and the coefficient of variation ranged from 6.9% to 73.3%. The pH was weakly variable, while EC and total salt content were moderately variable. 2) Results of semivariogram analysis showed that the most fitting model for spatial variability of all three indexes was spherical model. The C0/(C0+C) ratios of three indexes ranged from 8.6% to 14.3%, which suggested the spatial variability of all indexes had a strong spatial autocorrelation, and the structural factors played a more important role. The variation range decreased in order of pH <total salt < EC. The Kriging interpolation showed that pH, EC and total salt content distributed in a striped pattern with good continuity. The pH value increased with increasing terrain slope, while EC and total salt content decreased. 3) In terms of vertical distribution, the salt aggregated on surface in the area with severe salinization. In the area with light salinization, the vertical distribution of salinity was firstly decreased and then increased. In general, the heterogeneity of soil salinization in the Mu Us Desert-Loess Plateau transition zone was influenced by climate, landscape, plant distribution, especially affected by geological conditions, topography and hydrogeological conditions. This study provided a theoretical basis for future land engineering and ecosystem restoration programs.

Adapting HYDRUS‐1D to Simulate Overland Flow and Reactive Transport during Sheet Flow Deviations

Core Ideas HYDRUS‐1D code was adapted to solve the diffusion wave equation for overland flow. The modified code can simulate transport and fate of many different kinds of solute. The model can simulate physically nonequilibrium overland flow and transport processes. Surface runoff is commonly described in numerical models using either the diffusion wave or kinematic wave equations, which assume that surface runoff occurs as sheet flow with a uniform depth and velocity across the slope. In reality, overland water flow and transport processes are rarely uniform. Local soil topography, vegetation, and spatial soil heterogeneity control directions and magnitudes of water fluxes. These spatially varying surface characteristics can generate deviations from sheet flow such as physical nonequilibrium flow and transport processes that occur only on a limited fraction of the soil surface. In this study, we first adapted the HYDRUS‐1D model to solve the diffusion wave equation for overland flow at the soil surface. The numerical results obtained by the new model produced an excellent agreement with an analytical solution for the kinematic wave equation. Additional model tests further demonstrated the applicability of the adapted model to simulate the transport and fate of many different solutes (non‐adsorbing tracers, nutrients, pesticides, and microbes) that undergo equilibrium and/or kinetic sorption and desorption and first‐ or zero‐order reactions. HYDRUS‐1D includes a hierarchical series of models of increasing complexity to account for both uniform and physical nonequilibrium flow and transport, e.g., dual‐porosity and dual‐permeability models, up to a dual‐permeability model with immobile water. This same conceptualization was adapted to simulate physical nonequilibrium overland flow and transport at the soil surface. The developed model improves our ability to describe nonequilibrium overland flow and transport processes and our understanding of factors that cause this behavior.

It is elemental: soil nutrient stoichiometry drives bacterial diversity.

It is well established that resource quantity and elemental stoichiometry play major roles in shaping below and aboveground plant biodiversity, but their importance for shaping microbial diversity in soil remains unclear. Here, we used statistical modeling on a regional database covering 179 locations and six ecosystem types across Scotland to evaluate the roles of total carbon (C), nitrogen (N) and phosphorus (P) availabilities and ratios, together with land use, climate and biotic and abiotic factors, in determining regional scale patterns of soil bacterial diversity. We found that bacterial diversity and composition were primarily driven by variation in soil resource stoichiometry (total C:N:P ratios), itself linked to different land uses, and secondarily driven by other important biodiversity drivers such as climate, soil spatial heterogeneity, soil pH, root influence (plant-soil microbe interactions) and microbial biomass (soil microbe-microbe interactions). In aggregate, these findings provide evidence that nutrient stoichiometry is a strong predictor of bacterial diversity and composition at a regional scale.

Numerical simulation and experimental study on farmland nitrogen loss to surface runoff in a raindrop driven process

It has been widely recognized that surface runoff from agricultural field is an important non-point pollution source, which however, the chemical transfer amount in the process is very difficult to be quantified in field since some variables and natural factors are hard to control, such as rainfall intensity, temperature, wind speeds and soil spatial heterogeneity, which may significantly affect the field experimental results. Therefore, a physically based nitrogen transport model was developed and tested with the so called semi-field experiments (i.e., artificial rainfall was used instead of natural rainfall, but other conditions were natural) in this paper. Our model integrated the raindrop driven process and diffusion effect with the simplified nitrogen chain reactions. In this model, chemicals in the soil surface layer, or the ‘exchange layer’, were transformed into the surface runoff layer due to raindrop impact. The raindrops also have a significant role on the diffusion process between the exchange layer and the underlying soil. The established mathematical model was solved numerically through the modified Hydrus-1d source code, and the model simulations agreed well with the experimental data. The modeling results indicate that the depth of the exchange layer and raindrop induced water transfer rate are two important parameters for the simulation results. Variation of the water transfer rate, er, can strongly influence the peak values of the NO−3-N and NH+4-N concentration breakthrough curves. The concentration of NO−3-N is more sensitive to the exchange layer depth, de, than NH+4-N. In general, the developed model well describes the nitrogen loss into surface runoff in a raindrop driven process. Since the raindrop splash erosion process may aggravate the loss of chemical fertilizer, choosing an appropriate fertilization time and application method is very important to prevent the pollution.

喀斯特常绿落叶阔叶混交林土壤磷钾养分空间异质性

PDF HTML阅读 XML下载 导出引用 引用提醒 喀斯特常绿落叶阔叶混交林土壤磷钾养分空间异质性 DOI: 10.5846/stxb201611182348 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家重点研发计划（2016YFC0502405）；国家自然科学基金项目（31370485，31370623，31400412，31460135）；广西科技惠民项目（桂科转1599001-6）；广西重点研发计划（桂科AB16380255）；湖南省研究生科研创新项目（CX2015B231）；广西特聘专家项目 Spatial heterogeneity of soil phosphorus and potassium in a mixed evergreen and deciduous broad-leaved forest in karst region of southwest China Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:在木论国家级自然保护区内喀斯特常绿落叶阔叶混交林内建立500 m×500 m长期监测样地，采用经典统计学和地统计学方法研究喀斯特森林土壤磷钾养分含量及其空间变异特征。结果表明：研究区土壤全磷（TP）、全钾（TK）、速效磷（AP）、速效钾（AK）含量分别为（1.60±0.76）g/kg、（5.42±2.74）g/kg、（5.74±3.63）mg/kg、（5.20±2.96）mg/kg；磷钾养分含量均为中等变异，变异强度为AP > AK > TK > TP。研究区土壤TP、TK、AP、AK变异函数值的最佳拟合模型均为指数模型，决定系数均很高（0.671-0.995），TP、AP呈中等强度空间自相关，TK、AK呈弱空间自相关。TP、AP的变程较长，分别为336.00 m和373.50 m，空间连续性较好，TK、AK变程较短（33.30 m、64.50 m），空间依赖性较强。土壤TP表现为坡下（含洼地）含量高，坡上含量较低；AK表现为坡中含量高于洼地含量；AP、TK呈斑块破碎化分布。海拔、坡度和地面凹凸度是土壤磷钾养分空间异质性的主要影响因素。喀斯特常绿落叶阔叶混交林土壤磷钾养分存在不同空间异质性和空间关联性，这为小流域尺度上土壤养分管理、可持续利用策略、喀斯特退化生态系统生态恢复提供理论依据。 Abstract:The availability of soil nutrients, e.g. phosphorus (P) and potassium (K), and their spatial distribution are key factors controlling plant growth, community development, and ecosystem restoration. Karst is one of the main fragile habitat zones in China. In this study, we examined the soil P and K and their spatial heterogeneity in a 500 m×500 m long-term monitoring forest plot in the Mulun National Nature Reserve, Guangxi, using classical statistics and geostatistics methods. The results showed that the average contents of total phosphorus (TP), total potassium (TK), available phosphorus (AP), and available potassium (AK) in the studied area were (1.60 ±0.76) g/kg, (5.42 ±2.74) g/kg, (5.74 ±3.63) mg/kg, and (5.20 ±2.96) mg/kg, respectively. The variability of soil P and K at a moderate intensity level, and the order of which was AP > AK > TK > TP. Exponential model was best-fitted for the semivariogram of soil TP, TK, AP and AK, and the coefficients of determination are very high, ranging from 0.671 to 0.995. The contents of TP and AP showed moderate spatial autocorrelation, which indicated that the variations were caused by structural variation and random factors, whereas TK and AK had weak spatial autocorrelation. TP and AP had a relatively long autocorrelation distance (336.00 m and 373.50 m, respectively), indicating a relatively good spatial continuity. The autocorrelation distances of TK and AK (33.30 m and 64.50 m, respectively) were shorter than those of TP and AP, suggesting a strong spatial dependence. The distribution of TP in the soil was high on the toe slope (including depressions) and low on the upslope. AK content was higher on the slope than in depression. In addition, both AP and TK had patchy distributions. Elevation, slope, and convex topography were the main factors determining the spatial heterogeneity of soil P and K. Overall, soil P and K showed different patterns for spatial heterogeneity and spatial correlation in karst mixed evergreen and deciduous broad-leaved forest, which provides a reference for site-specific soil nutrients management and designing strategies for ecological restoration of degraded ecosystems in the karst region. 参考文献 相似文献 引证文献

抚育对林地土壤碳释放的影响——基于Yasso07估算

PDF HTML阅读 XML下载 导出引用 引用提醒 抚育对林地土壤碳释放的影响——基于Yasso07估算 DOI: 10.5846/stxb201601270197 作者: 作者单位: 西北农林科技大学林学院,西北农林科技大学林学院 作者简介: 通讯作者: 中图分类号: 基金项目: 国家林业公益性行业科研专项（201304307） Effects of forest thinning on soil CO2 emissions in a pine-oak mixed stand in the Qinling Mountains based on the Yasso07 model estimate Author: Affiliation: college of forestry,Northwest ADdDdF University,Northwest AgriculturalDdDdForestry university Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:间伐是森林经营的有效措施之一，其能减少林木枯损，有利于林下植被生长和植物种群更新，但也可改变森林小气候，从而影响林地土壤碳释放。以秦岭火地塘林区松栎混交林为研究对象，运用Yasso07模型模拟了不同间伐强度和间伐残留物移除强度下林地土壤CO2释放。结果表明：（1）针叶树种（油松Pinus tabulaefomis、华山松Pinus armandi）和阔叶树种（锐齿栎Quercus aliena var. acutesrrata）叶凋落物化学组分有较明显差异，针叶树种酒精溶解性化合物（ESC）和水溶性化合物（WSC）含量明显低于阔叶树种，其不溶性化合物（NSC）含量明显高于阔叶树种；（2）凋落物化学组分对林地土壤CO2释放有显著的影响；（3）在研究两个控制因子中，间伐强度是影响林地土壤CO2释放的主导因子，间伐后林地土壤CO2释放量有升高趋势；当间伐强度为12.38%，间伐残留物移除强度为53.18%时，林地土壤CO2释放量最小，为15.318 Mg hm-2 a-1。 Abstract:Natural forest-protection programs have been implemented to increase stand volume and forest ecosystem diversity, and to improve forest resources. However, they have had some negative influences on forests, such as high stand density and poor growth, and these can easily lead to insect outbreaks and fire disasters. Forest thinning can effectively eliminate the negative influences caused by natural forest protection management. Forest thinning programs have been conducted for several years and these approaches have led to reduced tree mortality and accelerated natural regeneration. However, it has been demonstrated that forest micro-climates influence soil CO2 emissions. This study investigated the effects of forest thinning on soil CO2 emissions using the Yasso07 model to simulate a pine-oak mixed forest in the Huoditang forest zone area of the Qinling Mountains. The topography of the Qinling Mountains is complicated and fractured, so it is difficult to duplicate experimental plots in a randomized block design. Therefore, the quadratic general rotary design was applied, and thinning and residue-removed intensity were the factors in the experiment. Thirteen experimental plots were selected, including five control levels and nine treatment plots. Five litter-fall collection frames (1 m × 1 m) were laid in each experimental plot. The litter fall was collected each month from September 2012 to September 2014. The ethanol-soluble, water-soluble, acid-soluble, and non-soluble compound contents in the leaf litter fall were determined. Although the technology to measure soil CO2 emissions has continually improved, the soil spatial heterogeneity and strong soil carbon stability in undisturbed habitats has led to inaccuracies in the evaluation methods used in forest soil carbon dynamics research. Yasso07 is a soil-carbon decomposition model and is based on the assumption that there are four types of litter transformation. Yasso07 has been widely used in Europe and the United States because it can be operated easily; requires few parameters, which are easy to obtain; and the simulated results are reliable. However, there was no basis to determine if it could be applied in the Qinling Mountains. Therefore, this study validated the reliability of the Yasso07 model in this region. The soil CO2 emission traits under different thinning and residue-removed intensities were analyzed based on simulations by the model. The following results were obtained: (1) there was a significant difference between the conifer and broadleaf litter chemical compositions. The ethanol and water soluble compound contents were significantly higher in the conifer tree litter than in the broadleaf tree litter, and the non-soluble compound content was significantly lower in conifer litter than in broadleaf litter. (2) The chemical composition of the litter fall significantly affected soil CO2 emissions, and (3) thinning intensity was the key factor affecting CO2 emissions. Soil CO2 emissions increased after forest thinning, and when the thinning and residue-removed intensities were 12.38% and 53.18%, respectively, the soil CO2 emission fell to a minimum of -15.318 Mg hm-2 a-1. 参考文献 相似文献 引证文献

喀斯特小流域土壤有机碳空间异质性及储量估算方法

喀斯特小流域土壤有机碳空间异质性及储量估算方法

Dynamics of dissolved organic carbon in hillslope discharge: Modeling and challenges

Reliable quantitative prediction of water movement and fluxes of dissolved substances – specifically organic carbon – at both the hillslope and the catchment scales remains a challenge due to complex boundary conditions and soil spatial heterogeneity. In addition, microbially mediated transformations of dissolved organic carbon (DOC) are recognized to determine the balance of DOC in soils. So far, only few studies utilized stable water isotope information in modeling and even fewer linked dissolved carbon fluxes to mixing and/or transport models. In this study, stormflow dynamics of 18O/16O ratios in the water molecules (expressed as δ18O) and DOC were analyzed using a physically-based modeling approach. A one-dimensional dual-continuum vertical flow and transport model was used to simulate the subsurface transport processes in a forest hillslope soil over a period of 2.5years. The model was applied to describe the transformation of input signals of δ18O and DOC into output signals observed in the hillslope stormflow. To quantify uncertainty associated with the model parameterization, Monte Carlo analysis in conjunction with Latin hypercube sampling was applied. δ18O variations in hillslope discharge and in soil pore water were predicted reasonably well. Despite the complex nature of microbial transformations that caused uncertainty in model parameters and subsequent prediction of DOC transport, the simulated temporal patterns of DOC concentration in stormflow showed similar behavior to that reflected in the observed DOC fluxes. Due to preferential flow, the contribution of the hillslope DOC export was higher than the amounts that are usually found in the available literature.