The critical role of soil moisture in compound hazards

It is of great significance to clarify the influence of soil temperature and moisture on soil respiration rate and its characteristics in ecologically fragile regions under the background of climate change for the accurate assessment and prediction of carbon budgets in this region. The average CO2 concentration and soil temperature and moisture at different soil depths (10, 50, and 100 cm) were measured using a CO2 analyzer and temperature and moisture sensors. The soil respiration rate was calculated using Fick's first diffusion coefficient method. The dynamic characteristics of soil temperature, soil moisture, and soil respiration rate in different soil depths were explored, and the response of soil respiration rate to soil temperature and moisture were further analyzed. The results showed that the diurnal variation in soil respiration rate decreased significantly with the increase in soil depth (P<0.05), and the peak time lagged behind. Soil respiration rate in adjacent soil depths (10, 50, and 100 cm) lagged 1 h from top to bottom. The monthly variation in soil respiration rate was a multi-peak curve, in which the maximum soil respiration rates of 10, 50, and 100 cm soil depths were on July 25th, August 6th, and August 10th, reaching 13.96, 2.96, and 1.47 μmol·(m2·s)-1, respectively. The effect of soil temperature on soil respiration rate decreased with the increase in soil depth. Soil temperature at 50 cm and below had no significant effect on soil respiration rate (P>0.05). The fitting index of 10 cm soil depth was the best (R2=0.96), but the fitting indexes of 50 cm and 100 cm soil depths were poor (R2=0.00 and R2=0.01, respectively). The temperature sensitivity coefficient Q10 decreased with the increase in soil depth. Soil moisture in different soil depths had significant effects on soil respiration rate (P<0.05), and the quadratic fitting indicated that 50 cm (R2=0.35)>10 cm (R2=0.22)>100 cm (R2=0.31). The combined effects of soil temperature and moisture in different soil depths could explain 96%, 6%-50%, and 22%-24% of soil respiration rate, respectively. In summary, the effects of soil temperature and moisture at different soil depths of the Caragana korshinskii plantation in the loess-hilly region on soil respiration rate differed. The soil respiration rate of the 10 cm soil depth was affected by the comprehensive effect of soil temperature and moisture; however, the relative contribution of soil temperature was higher, and soil moisture at and below a soil depth of 50 cm was the key factor. These results could help improve predictions on the impact of future climate change on the carbon cycle of terrestrial ecosystems in the region and provide a theoretical basis for greenhouse gas regulation in the future.

The rate of carbon (C) cycling in soils is controlled by an array of processes and conditions. It has been widely accepted that an increase in temperature would accelerate microbial decomposition of soil organic matter (SOM) and provide a positive feedback to global warming, other factors being equal. However, soil moisture has received little attention in C cycle studies. In this project, we developed a technique for sampling soil‐respired CO2 for isotopic measurements and a model that relates the radiocarbon (14C) content of soil respired CO2 to the rate of C cycling in soils. We measured soil CO2 flux, carbon isotopic content (both 13C and 14C) of soil‐respired CO2, soil temperature, and soil moisture on a monthly basis along an elevation transect in the Sierra Nevada in an attempt to determine the relationship between the rate of soil C cycling and soil environmental conditions. Both soil CO2 flux and its 14C content displayed significant variations (spatially and temporally), which reflect natural variations in the rate of SOM decomposition and in the relative amount of SOM‐derived CO2 versus root‐respired CO2 caused by seasonal changes in soil temperature, moisture, and plant activity. The relative contribution of SOM decomposition to total soil CO2 production changed throughout the year from ∼20–50% at the peak of the growing season to close to 100% in the nongrowing season. The apparent decay rate of SOM determined from the 14C content of soil‐respired CO2 varied from ∼0.2 yr−1 in the spring to ∼0.01 yr−1 in the fall at the lowest‐elevation site and from 0.1 yr−1 in the summer to ∼0.01 yr−1 in the late fall at the highest‐elevation site. It appears that the apparent decay rate of SOM increased with increasing temperature when soil moisture was adequate but decreased with increasing temperature when soil moisture became limited. The apparent decay rate of SOM also varied with soil moisture. Higher soil moisture content accelerated decomposition of SOM until it reached an optimal level of ∼14–25 wt % water content and then inhibited decomposition when more pores in soils became saturated with water and perhaps oxygen availability (for microbes) became limited. Although the rate of SOM decomposition varied throughout the year in response to fluctuations in soil temperature and moisture, the maximum apparent decay rate was higher at the low‐elevation site (i.e., maximum apparent decay rate = 0.22 yr−1) than at the high‐elevation sites (i.e., maximum apparent decay rate = 0.10 yr−1). Litter decomposition simulated by measuring changes in mass of litter in litter bags placed in the field also showed a similar decomposition pattern with decreasing decomposition rate with elevation. Multivariable regression analyses including various terms of soil temperature, moisture, and site variability suggest that soil moisture was a major factor, but not the only factor, controlling the rate of SOM decomposition and soil CO2 flux in the Sierra Nevada soils. Both decay rate and total soil CO2 flux are related significantly to soil moisture, temperature, and site effects.

PDF HTML阅读 XML下载 导出引用 引用提醒 天山北坡积雪消融对不同冻融阶段土壤温湿度的影响 DOI: 10.5846/stxb201901040044 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 自治区重点实验室课题(2018D04024);国家自然科学基金项目(U1603342,41961002) The influence of snowmelt on soil temperature and moisture in different freezing-thawing stages on the north slope of Tianshan mountain Author: Affiliation: Fund Project: The National Natural Science Foundation of China (General Program, Key Program, Major Research Plan) 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:积雪作为一种特殊的覆被,直接影响着土壤温度、土壤水分分布及其冻结深度、冻结速率等,影响当地的生态水文过程。利用2017年11月1日至2018年3月31日天山北坡伊犁阿热都拜流域的土壤含水率资料,划分土壤不同冻融阶段,结合积雪不同阶段,进而分析积雪消融对季节性冻土温湿度的影响。结果表明:在整个土壤冻融期间,土壤温湿度的变化取决于积雪深度、大气温度和雪面温度的高低,且与其稳定性有关。土壤冻结阶段,土壤温湿度持续下降,表层土壤温湿度受气温影响较大,且波动明显,而深层土壤的温湿度变化平缓;土壤完全冻结时,有稳定积雪覆盖,由于积雪的高反射性、低导热性,影响着地气之间的热量传递,因此土壤的温湿度变化较为平稳,积雪有一定的保温作用;冻土消融阶段,气温回升,积雪消融,地表出露,各层土壤温度随气温变化而变化,且越靠近地表,土壤温度越高,变幅越大,与冻结期完全相反。由于融雪水的下渗,土壤湿度快速增加。进一步分析积雪与土壤温湿度的相关性得出,积雪对土壤温湿度的影响分不同时期,对土壤温度的影响主要在积雪覆盖时,对土壤湿度的影响主要是在积雪消融时期,这对于研究该地生态水文循环及后续融雪性洪水的模拟与预报具有一定的参考价值。 Abstract:As a special cover, snow cover directly affects soil temperature, soil moisture distribution, freezing depth and freezing rate, and affects the local eco-hydrological processes. The existence of snow can affect the frozen soil, the interaction of surface-atmosphere, and change the energy exchange and temperature transfer between the soil and the atmosphere. The freezing-thawing process of soil has an important impact on soil water content. It is of great significance for the effective utilization of frozen soil resources, the guidance of irrigation water, the study of soil evaporation, groundwater recharge and local eco-hydrological cycle. In this paper, meteorological data, soil temperature and moisture data and snow cover data were used to analyze the characteristics of seasonal frozen soil temperature and moisture changes in the study area. Based on the data of soil water content from November 1, 2017 to March 31, 2018 in the Alatobe Basin, Ili, on the northern slope of Tianshan Mountains, the different freezing-thawing stages of soil were divided, and the effects of snow melting on the temperature and moisture of seasonal frozen soil were analyzed. The results show that snow melting has a great influence on the temperature and moisture of seasonal frozen soil. The soil was frozen beginning in November in Alatobe Basin, and the soil freezing time lagged with the increase of soil depth. The soil freezing process is one-way, starting from the surface, while the melting process is two-way, starting from both the surface and the bottom. During the whole freezing-thawing period, the change of soil temperature and moisture depends on the depth of snow cover, atmospheric temperature and snow surface temperature. And it mainly affects the surface soil temperature. The deeper the soil depth is, the more slightly the change of soil temperature and moisture is. During the soil freezing stage, the soil temperature and moisture continued to decline, the surface soil temperature and moisture were greatly affected by temperature, and the fluctuation was obvious, while the deep soil temperature and moisture changed slightly. When the soil was completely frozen, there was stable snow cover. Because the high reflectivity and low thermal conductivity of snow affected the heat transfer of surface-atmosphere, the change of soil temperature and moisture was relatively stable, and the snow cover had a certain degree. During the thawing stage, the temperature rises, the snow melts and the surface exposes. The soil temperature varies with the change of temperature. The closer to the surface, the higher the soil temperature, the larger the change range, which is completely contrary to the freezing period. Soil moisture increases rapidly due to the infiltration of snowmelt water. Further analysis of the correlation between snow cover and soil temperature and moisture shows that the influence of snow cover on soil temperature and moisture can be divided into different periods. The influence on soil temperature is mainly in snow cover, and the influence on soil moisture is mainly in snow melting period, which has a certain reference value for the study of the eco-hydrology cycle and the simulation and prediction of subsequent snowmelt flood in this area. 参考文献 相似文献 引证文献

Forest ecosystems in northeastern China play an important role in both local and national carbon budgets because of their large area extent and huge amount of carbon storage. The spatial and temporal changes in soil surface CO_2 flux (R_S), the major CO_2 source to the atmosphere from terrestrial ecosystems, directly influence the local and regional carbon budgets. However, few data on R_S were available for this region. In this study, we used an infrared gas exchange analyzer (LI_COR 6400) to measure the R_S and related biophysical factors, and examined soil temperature and moisture effects on soil respiration for six secondary temperate forest ecosystem types: Mongolian oak (dominated by Quercus mongolica), poplar_birch (dominated by Populus davidiana and Betula platyphylla), mixed_wood (no dominant tree species), hard_wood forests (dominated by Fraxinus mandshurica, Juglans mandshurica and Phellodendron amurense), Korean pine (Pinus koraiensis) and Dahurian larch (Larix gmelinii) plantations. Our specific objectives were to: 1) compare the soil temperature, soil moisture, R_S, and Q_ 10 (temperature coefficient) of the six forest types; 2) quantify the seasonality of R_S and related environmental factors; and 3) determine the environmental factors affecting the R_S, and construct models of R_S against the related environmental factors. Soil temperature, soil moisture and their interactions significantly (p 0.01) influenced the R_S, but their effects depended on forest type and soil depth. These factors could explain 67.5%-90.6% of the variations in the R_S data. During the growing season, the soil temperature at 10 cm depth in the different forest types did not differ significantly but soil moisture did. The R_S for the oak, pine, larch, hardwood, mixed_wood, and poplar_birch stands varied from 1.89-5.23, 1.09-4.66, 0.95-3.52, 1.13-5.97, 1.05-6.58, and 1.11-5.76 μmol CO_2·m~ -2 ·s~ -1 , respectively; the Q_ 10 values for those stands were 2.32, 2.76, 2.57, 2.94, 3.55 and 3.54, correspondingly. The seasonality of R_S was driven mainly by soil temperature and moisture, and was roughly consistent with that of soil temperature. The broad_leaved forests had a higher soil respiration rate than those of coniferous forests probably because of a more suitable soil thermal and moisture regimes and other biological factors. The temperature sensitivity coefficient of soil respiration (Q_ 10 ) showed a convex_type curve along a soil moisture gradient. The Q_ 10 tended to increase when soil moisture increased from 30.19 to 40.7, and then declined probably because the extremely high soil moisture content in the hardwood forest may impede activities of soil microbes and plant roots, and thus decrease decomposition rates and soil CO_2 emission. Our study strongly recommended that estimation of soil surface CO_2 flux from forest ecosystems should consider the comprehensive effects of both soil temperature and moisture on soil respiration so as to reduce uncertainties of ecosystem carbon budget studies in this region.

Soil temperature and moisture are important factors affecting vegetation growth and drought in desert steppe environments. These factors also strongly influence grassland ecosystems. This study interpreted long-term (2009–2019) ground observation data on soil temperature, soil moisture, and meteorological factors from a study area in Inner Mongolia. The monitoring station collected soil moisture, soil temperature, and precipitation data. Covarying relationships indicated how soil properties influence each other throughout the year. Soil temperature was clearly affected by atmospheric changes, solar radiation, and freeze/thaw processes. The surface soil layers showed the greatest degree of variation, while middle and lower layers showed less seasonal variation and smaller differences between daily highs and lows. Surface soil moisture correlates strongly with the vertical temperature decline in soil. Time series revealed major variation in soil moisture throughout the year with lower soil layers showing obvious hysteresis effects. Multi-year soil moisture data allowed for subdivision of the year into seven intervals based maximum and minimum values. Soil temperature showed unique patterns of covariation with soil moisture during different time periods. Differences in soil moisture cause more rapid changes in temperature during soil thawing relative the moisture-induced temperature changes observed 1 month after soil freezing. When soil temperature was greater than 0 °C (32 ℉), soil temperature and soil moisture showed inverse correlation. A dependency of evapotranspiration on soil temperature can explain its effect on soil moisture. When soil temperature fell below 0 °C(32 ℉), soil temperature and soil moisture showed a positive correlation. During an interval defined as the summer fluctuation (SF), precipitation and soil moisture showed a significant positive correlation. During other periods, soil moisture did not clearly covary with precipitation.

Grasshopper eggs overwinter in soil for almost half a year. Changes in soil temperature and moisture have a substantial effect on grasshopper eggs, especially temperature and moisture extremes. However, the combinatorial effect of temperature and moisture on the development and survival of grasshopper eggs has not been well studied. Here, we examined the effects of different soil moistures (2, 5, 8, 11, 14% water content) at 26°C and combinations of extreme soil moisture and soil temperature on the egg development and survival of three dominant species of grasshopper (Dasyhippus barbipes, Oedaleus asiaticus, and Chorthippus fallax) in Inner Mongolian grasslands. Our data indicated that the egg water content of the three grasshopper species was positively correlated with soil moisture but negatively correlated with hatching time. The relationship between hatching rate and soil moisture was unimodal. Averaged across 2 and 11% soil moisture, a soil temperature of 35oCsignificantly advanced the egg hatching time of D. barbipes, O. asiaticus, and C. fallax by 5.63, 4.75, and 2.63 days and reduced the egg hatching rate of D. barbipes by 18%. Averaged across 26 and 35°C, 2% soil moisture significantly delayed the egg hatching time of D. barbipes, O. asiaticus, and C. fallax by 0.69, 11.01, and 0.31 days, respectively, and decreased the egg hatching rate of D. barbipes by 10%. The hatching time was prolonged as drought exposure duration increased, and the egg hatching rate was negatively correlated with drought exposure duration, except for O. asiaticus. Overall, the combination of high soil temperature and low soil moisture had a significantly negative effect on egg development, survival, and egg hatching. Generally, the response of grasshopper eggs to soil temperature and moisture provides important information on the population dynamics of grasshoppers and their ability to respond to future climate change.

Soil respiration dynamics in Cinnamomum camphora forest and a nearby Liquidambar formosana forest in Subtropical China

Soil moisture is not only an essential component of the water cycle in terrestrial ecosystems but also a major influencing factor of regional climate. In the soil hydrothermal process, soil moisture has a significant regulating effect on surface temperature; it can drive surface temperature change by influencing the soil’s physical properties and the partitioning of the available surface energy. However, limited soil temperature and moisture observations restrict the previous studies of soil hydrothermal processes, and few models focus on estimating the impact of soil moisture on soil temperature. Therefore, based on the experiments conducted in Wuchuan County in 2020, this study proposes a soil water and heat coupling model that includes radiation, evaporation, soil water transport, soil heat conduction and ground temperature coupling modules to simulate the soil temperature and moisture and subsequently estimate the effects of soil moisture. The results show that the model performs well. The Nash–Sutcliffe coefficient (NSE) and the concordance index (C) of the simulated and measured values under each treatment are higher than 0.26 and 0.7, respectively. The RMSE of the simulation results is between 0.0067–0.017 kg kg−1 (soil moisture) and 0.43–1.06 °C (soil temperature), respectively. The simulated values matched well with the actual values. The soil moisture had a noticeable regulatory effect on the soil temperature change, the soil surface temperature would increase by 0.08–0.43 °C for every 1% decrease in soil moisture, and with the increase in soil moisture, the variation of the soil temperature decreased. Due to the changes in the solar radiation, the sensitivity of the soil temperature to the decline in soil moisture was the greatest during June–July and the least in September. Moreover, the contributions of soil moisture changes to temperature increase under various initial conditions are inconsistent, the increase in sunshine hours, initial daily average temperature and decrease in leaf area index (LAI), soil density and soil heat capacity can increase the soil surface temperature. The results are expected to provide insights for exploring the impact mechanism of regional climate change and optimizing the structure of agricultural production.

Preventive control of desert locusts is based on monitoring recession areas to detect outbreaks. Remote sensing has been increasingly used in the preventive control strategy. Soil moisture is a major ecological driver of desert locust populations but is still missing in the current imagery toolkit for preventive management. By means of statistical analyses, combining field observations of locust presence/absence and soil moisture estimates at 1 km resolution from a disaggregation algorithm, we assess the potential of soil moisture to help preventive management of desert locust. We observe that a soil moisture dynamics increase of above 0.09 cm3/cm3 for 20 days followed by a decrease of soil moisture may increase the chance to observe locusts 70 days later. We estimate the gains in early warning timing compared to using imagery from vegetation to be 3 weeks. We demonstrate that forecasting errors may be reduced by the combination of several types of indicators such as soil moisture and vegetation index in a common statistical model forecasting locust presence. Policy implications. Soil moisture estimates at 1 km resolution should be used to plan desert locust surveys in preventive management. When soil moisture increases in a dry area of potential habitat for the desert locust, field surveys should be conducted two months later to evaluate the need of further preventive actions. Remote sensing estimates of soil moisture could also be used for other applications of integrated pest management.

The boundary that separates the earth from the atmosphere is a crucial zone of study for meteorology and hydrology. Here, solar energy is partitioned into sensible heat which drives atmospheric circulation, latent heat needed for evaporation from the soil and transpiration of vegetation, and soil heat which warms the subsurface. Precipitation is partitioned into interception that evaporates directly into the atmosphere, surface runoff that discharges quickly into water courses and infiltration which resides longer in the subsurface. Soil moisture influences all these processes and is therefore considered a key variable in land-atmosphere interaction. In order to obtain a better understanding of the heat and water balance of topsoil, observations are key, but challenging with in situ point sensors. Recent rapid developments in remote sensing have tremendously increased our ability to observe the boundary between soil and atmosphere. Retrieving state variables such as soil temperature and moisture from remote sensing is far from trivial: detected signals originate not only from the soil, but also from the atmosphere and vegetation, the depth of the detection is a function of the soil moisture itself, and pixels are large and heterogeneous. Field validation is difficult, because of scale disparity between in situ point sensors and remote sensing pixels. Still, given the limitations, remote sensing provides an opportunity to improve understanding of heat and moisture transfer in the topsoil. The central question of this research is: What can be learnt from (remote sensing) observations about the heat and moisture balance of the topsoil? First a cross validation of different soil moisture products based on remote sensing was performed to investigate similarities and differences between these products. The differences were significant and could be attributed to differences in land use and vegetation, but not fully explained. This illustrated that retrieval algorithms for soil moisture are far from converged. One prerequisite for improving retrieval algorithms is ground truth, ground observations at scales relevant for remote sensing. Second, a field technique was developed that can potentially be used for bridging the observation gap between point sensors and remote sensing pixels. This technique uses Distributed Temperature Sensing (DTS) over horizontal extents up to kilometers to infer soil moisture at this intermediate scale. Propagation of variations in atmospheric temperature and radiation with depth is a function of soil moisture. By using DTS observations at three depths, it is possible to infer soil moisture, assuming that heat conduction is the dominant heat transfer mechanism. The heat diffusion equation is inverted to obtain estimates of soil heat diffusivity and soil moisture. Since this technique relies on observations of the passive thermal response of the soil to atmospheric temperature and radiation variations, this technique is called passive SoilDTS in contrast to active soil DTS, which relies on active heat pulses. The feasibility of passive SoilDTS for soil moisture estimation was asserted in a field experiment conducted in Monster in the Netherlands. The analysis of the experimental results of this feasibility study pointed out a number of technical and modeling issues that needed to be investigated further in order for passive SoilDTS to be used for soil moisture estimation and scaling. Some soil moisture estimates were not reasonable due to uncertainties in cable depths and heat transfer mechanisms. To separate the technical issue of cable depth from the modeling challenges, the same methodology used to infer soil moisture from passive SoilDTS was applied to profile data of temperature and soil moisture obtained with point sensors. The depth of these point sensors could be determined with far greater accuracy than the cable depth. Analysis of the point observations challenged the common assumption that conduction is the dominant heat transfer mechanism in soil. Evaporation seemed to play a dominant role in heat transfer on dry days. Yet evaporation rates found were higher than would be expected if mass diffusion would be the dominant transfer mechanism of water vapor. Vapor diffusion appeared to be enhanced. Enhancement of vapor diffusion is a long-studied phenomenon, subject to debate on the explanations of underlying mechanism. In an extensive literature review on vapor enhancement in soils, the plausibility of various mechanisms was assessed. We reviewed mechanisms based on (combinations of) diffusive, viscous, buoyant, capillary and external pressure forces including: thermodiffusion, dispersion, Stefan’s flow, Knudsen diffusion, liquid island effect, hydraulic lift, free convection, double diffusive convection and forced convection. The analysis of the order of magnitude of the mechanisms based on first principles clearly distinguishes between plausible and implausible mechanisms. Thermodiffusion, Stefan’s flow, Knudsen effects, liquid islands do not significantly contribute to enhanced evaporation. Double diffusive convection seemed unlikely due to lack of experimental evidence, but could not be completely excluded from the list of potential mechanisms. Hydraulic lift, the mechanism that small capillaries lift liquid water to the surface where it evaporates, does significantly contribute to enhanced evaporation from soils, also from dryer soils. The experimental evidence for and the theoretical underpinnings of this mechanism are convincing. However, we sought mechanisms that both explain enhanced evaporation and steep temperature gradients in the soil during the daytime. These often observed gradients consist of a sharp decrease of temperature with a depth up to the depth of the evaporation front. Hydraulic lift cannot explain this because the evaporation front is located at the surface. One remaining mechanism is forced convection due to atmospheric pressure fluctuations, also referred to as wind pumping. Wind pumping causes displacement and flow velocities too small for significant convective and too small for significant dispersive transport, when steady state dispersion formulations are used. However, experiments do indicate significant dispersive transport that can be explained by dispersion under unsteady flow conditions. Forced convection due to pressure fluctuations seems to be the only mechanism that can explain both enhanced evaporation and the steep temperature gradients. We investigated under which conditions wind pumping can enhance water vapor transfer from the soil to the atmosphere and which mechanisms are responsible for this enhancement in a modeling study. Previous models of wind pumping relied on enhanced transfer due to enhanced mixing described with empirical macroscopic dispersion coefficients with weak physical foundations. We searched for better understanding of physical mechanisms driving enhanced mixing. With combination of order of magnitude analysis, phenomenological, empirical and analytical models, mechanisms were investigated. A model for surface pressure fluctuations was coupled with a pressure diffusion model, a pore flow velocity model and a dispersion model. Based on this coupled model, we propose that the enhancement is caused by mixing at the pore level due to flow instabilities. Fast pressure fluctuations at the soil-air interface make vortices in the soil unstable. Instabilities arise when the timescale of the pressure fluctuations is close to the timescale of viscous dissipation which is related to the pore size. In this case, vortices in the soil cannot increase, decrease and turn direction, in phase with the pressure fluctuations and instabilities occur in the form of ejections. The ejections of vortices enhance mixing and transport. Timescales of wind induced pressure fluctuations and pore sizes are such that this mechanism is considered likely in soils. Further research is needed to prove this mechanism and quantify it. The developed model is a hypothesis and should be tested with numerical and laboratory experiments. For estimating the effect of this vapor enhancement on the soil heat budget, a coupled heat and moisture transfer model should be developed. Such a model could also shed light on the relative importance of hydraulic lift and wind pumping for evaporation rates. Perhaps, because the topsoil forms the boundary between land and atmosphere, but also between two disciplines meteorology and hydrology, there are still many questions that remain about heat and moisture transfer in the upper few centimeters of the soil. Remote sensing soil moisture retrievals force the scientific community to revisit our understanding of the topsoil. As a result, remote sensing presents not only a challenge for ground validation, but also an opportunity for hydrological and meteorological model improvement. Observation is the beginning of most learning.

Rainfall depth fluctuates, which increases the uncertainty of soil erosion and moisture dynamics in sloping cropland. Soil and water conservation practices affect soil erosion and moisture infiltration. However, the responses of runoff and soil moisture to time‐course rainfall patterns under soil and water conservation practices are not fully understood. Based on the distribution of concentrated rainfall depth, we classified 122 natural rainfall events in Southern China from 2019 to 2022 into advanced, intermediate, delayed, and uniform patterns. We used 12 runoff plots to observe runoff and soil moisture dynamics in sloping cropland under soil and water conservation practices (i.e., bare land, no‐till, conventional tillage, conventional tillage with straw mulch, conventional tillage with polyacrylamide, and cross‐slope ridge tillage). The results demonstrate that the advanced and intermediate rainfall patterns were the most prevalent in South China, occurring up to 82.79% of the frequency and contributing to 88.27% of the total runoff depth. Soil moisture increment and growth rate were maximum for the advanced pattern and minimum for the uniform pattern, and decreased with increasing soil depth, but soil moisture increment per unit of rainfall depth was maximum for the delayed pattern. Soil moisture increment and pre‐rainfall soil moisture content were negatively correlated under advanced, intermediate, and delayed patterns but were positively correlated under the uniform pattern. Additionally, the applied soil and water conservation practices reduced annual runoff depth by 69%–79% and significantly increased long‐term soil moisture content. The combined effect of the practices on runoff and soil moisture indicates that ploughing in conjunction with straw mulching is a more suitable practice for sloping land in Southern China. The findings can enhance our comprehension of runoff generation and soil moisture infiltration processes in red soil hilly regions and furnish guidance for improving regional soil and water conservation strategies.

Larvae of the Queensland fruit fly, Bactrocera tryoni, pupate in the soil, but the influence of soil variables on B. tryoni pupal mortality is not known. For other tropical tephritid species, soil moisture has been identified as a major pupal mortality factor. In the laboratory, we tested the effects of soil moisture and soil type on pupal survival through a factorial experiment which used three soil types (loamy sand, loam, sandy clay) and seven soil moisture levels (0%, 10%, 25%, 50%, 75%, 90% and 100%). Minor, but significant, differences in pupal mortality were observed between the soil types, but the most significant factor affecting pupae was extremes of soil moisture. Eighty‐five percent pupal mortality occurred at 0% soil moisture and 30% mortality at 100% soil moisture: very low levels of mortality occurred at all intermediate levels. We detected a significant interaction between soil type and moisture level but cannot explain it. In a follow‐up experiment, we demonstrated that prepupal wandering larvae of B. tryoni could discriminate between different moisture levels, with significantly greater pupation in loam soil at 75% soil moisture than at either 0% or 100% soil moisture. Results are used to modify a pupal mortality/soil moisture equation used in a recently published DYMEX model of B. tryoni population dynamics.

&amp;lt;p&amp;gt;&amp;lt;strong&amp;gt;Abstract:&amp;lt;/strong&amp;gt;&amp;amp;#160;The contrastive analysis of soil bulk density, moisture content, organic matter spatial heterogeneity karst hillslopes can serves as theoretical guidance for preventing&amp;amp;#160;soil degradation in Nandong subterranean stream basin. This study analysis the 0-20cm, 20-40cm soil bulk density, moisture and organic matter spatial heterogeneity Zhumashao depression basing on classical statistics and geostatistics methods. Research&amp;amp;#160;results&amp;amp;#160;showed that: the soil organic matter aberrance in Zhumashao depression is the largest, up to 70.62%, the variation of bulk density and water, respectively 15.25% and 11.29%. According to the statistical analysis of different types of land use, the soil moisture content can be ordered as follows,&amp;amp;#160;cultivated land &amp;amp;#65308;grassland&amp;amp;#65308;shrubs, and the bulk density&amp;amp;#160;can be ordered as&amp;amp;#160;shrubs &amp;amp;#65308;grassland&amp;amp;#65308;cultivated land, and organic matter content&amp;amp;#160;can be ordered as&amp;amp;#160;cultivated land&amp;amp;#65308;grassland&amp;amp;#65308;shrubs. The bulk density of the northern slope is higher than the southern slope, and the coefficient of variation is lower than the southern slope. The soil moisture and organic matter are lower than the southern slope, and the coefficient of variation is higher than the southern slope.&amp;amp;#160;It also showed a significant negative correlation between soil bulk density and soil moisture, as well as a significant negative correlation between soil bulk density and organic matter, and the correlation coefficients were -0.609&amp;amp;#160;and&amp;amp;#160;-0.581,&amp;amp;#160;respectively. In 0-20 cm, the soil moisture, bulk density, organic matter and the spherical model are fitter and fitting degree of R&amp;lt;sup&amp;gt;2&amp;lt;/sup&amp;gt;&amp;amp;#160;were 0.911, 0.977, and 0.922,&amp;amp;#160;respectively.&amp;amp;#160;In&amp;amp;#160;20-40&amp;amp;#160;cm, the soil moisture, bulk density, organic matter and Gauss model match better and fitting degree of R&amp;lt;sup&amp;gt;2&amp;lt;/sup&amp;gt;&amp;amp;#160;were 0.647, 0.730, and 0.881, respectively. The nugget coefficient shows that the spatial correlation of 0-20&amp;amp;#160;cm factors, 20-40&amp;amp;#160;cm is weak, which may be related to human activities in space. Through the analysis of normal kriging interpolation, soil bulk density in the south slope of the depression is less than those in the north slope, as well as the water and organic matter is more than those in the north slope.&amp;amp;#160;The soil moisture&amp;amp;#160;and organic matter at the bottom of the depression have the minimum value, while the bulk density has the maximum value. The water content and organic matter at the bottom and middle slope are the lowest, and the bulk density is the highest; the moisture and organic matter are higher on the downhill and uphill, and the bulk density is lower.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;&amp;lt;strong&amp;gt;Key words: &amp;lt;/strong&amp;gt;spatial heterogeneity; karst slope; land use, soil moisture, bulk density, organic matter&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;&amp;amp;#160;&amp;lt;/p&amp;gt;

Juncus tenuis Willd. is a warm‐season, perennial weed of turfgrass. In wet and compacted soils, it is well documented, yet little is known regarding the interaction effects of compaction and soil moisture on its rooting and foliar growth. A greenhouse experiment examined the effects of soil compaction and moisture on the above‐ and belowground growth of J. tenuis. The experimental design was completely randomized with a 3 × 3 arrangement with four replications and two runs. Factors included soil compaction (bulk densities of 1.56, 1.77, and 2.00 g cm–3) and soil moisture (10.9, 27.9, and 59.6% volumetric water content). Juncus tenuis was transplanted into pots, acclimated for 7 d, and subjected to the treatments for a 10‐wk period. Foliar growth was harvested every 2 wk and root growth was destructively assessed. Cumulative foliar and root biomass varied in response to compaction and soil moisture; however, no significant soil moisture × compaction interactions were detected. The effect of compaction on foliar and root biomass accounted for 15 and 12% of the explained variation, respectively. Increasing the bulk density from 1.56 to 2.00 g cm–3 reduced foliar and root biomass by 29 and 40%, respectively. Soil moisture accounted for ≥84% of the variation in foliar and root biomass. Increasing the soil moisture from 10.9 to 59.6% increased foliar and root biomass by 150 and 230%, respectively. The results suggested that cultural practices that prioritize soil moisture modification while alleviating compaction may reduce the presence of J. tenuis within maintained turfgrass.

Fusarium solani FSSC 11 and F. tricinctum are important root rot pathogens of soybean in North Dakota. The roles of soil type, temperature, and moisture in disease development by both species are poorly documented. To assess the effect of soil type on disease, three types of soil (Glyndon sandy loam, La Prairie silt loam, and Fargo clay) that represent soils of the soybean production region in the Red River Valley were examined in greenhouse, microplot, and growth chamber studies. Disease incidence and lesion length on roots were evaluated at growth stages V3 and R6. Soil type significantly affected disease development, with higher severity in the lighter soils of Glyndon sandy loam and La Prairie silt loam compared with Fargo clay. Soil type also interacted with Fusarium species, in which the maximum severity was observed in Glyndon sandy loam for F. solani, and in La Prairie silt loam for F. tricinctum. In addition, the cumulative effects of soil type, temperature, and soil moisture were tested in a growth chamber. Emergence and disease on seedlings were evaluated at growth stage V3. Significant reductions in emergence occurred at 10°C in treatments with F. solani and F. tricinctum, but there was no significant difference among the three soils. Infection was visible at temperatures of 10 to 20°C for F. solani and 15 to 20°C for F. tricinctum. F. solani caused the greatest infection at 20°C in Glyndon sandy loam, while it was at 15°C in La Prairie silt loam for F. tricinctum. The isolates of the two Fusarium species caused root rot in soil moisture ranging from 20 to 100% water holding capacity (WHC). The greatest reduction in emergence caused by the Fusarium spp. was observed at 80% WHC in silt loam and clay soils and 40% WHC in sandy loam soil, when compared with the same WHC in noninfested soils. Ranges of soil moisture causing infection were negatively correlated with temperature. At the lower temperature there was a broader range of soil moistures resulting in infection compared with higher temperatures. At 18°C, most infection occurred at soil moistures of 20 to 80% WHC, while it was 40 to 80% WHC at 28°C. Disease caused by F. solani was favored by a temperature of 18°C with high soil moisture (60 to 80% WHC) or 28°C with low soil moisture (20 to 40% WHC), while F. tricinctum was favored by cooler temperature and lower soil moisture.