Significant Exponential Correlation Research Articles

Spatiotemporal Variation of Snow Cover and Its Response to Climate Change in the Source Region of the Yangtze River, China

In the context of global warming, snow cover changes have an extremely important impact on the hydrological cycle and the redistribution of water resources in arid and semi-arid regions. In this paper, based on the daily cloud-free snow area remote sensing product data in the source region of Yangtze River (SRYR) from 2000 to 2019, the snow phenology variables such as the snow cover day (SCD), snow onset date (SOD), snow end date (SED), and snow duration day (SDD) were extracted separately for each hydrological year, and the vertical distribution of snow cover area (SCA) in the SRYR was analyzed by combining with the digital elevation model (DEM). In addition, we also combined climate factors and land cover types to further explore the spatiotemporal variation characteristics of snow phenology in response to different influencing factors, in order to reveal the spatiotemporal variation patterns of snow cover in the SRYR. The results showed that: (1) The SCA in the SRYR has a more obvious vertical distribution, with the maximum SCA reaching 61.58% at high elevation, while at low elevation, the SCA is mostly below 20%. The distribution of SCD in the study area showed a significant exponential correlation with DEM (R2 = 0.87). (2) The area of SOD in the SRYR showed an advanced trend of about 63.37%, while the area of SED showed a delayed trend of about 69.59%, and the area which showed significant trends is 4.29% and 4.36%, respectively. Therefore, the trends of both SOD and SED showed insignificant changes. (3) Temperature change is the main factor affecting the change of snow cover in the SRYR. Among them, 90.9% of the regions showed a significant positive correlation between temperature and SCD, while precipitation showed a significant negative correlation with SCD in about 75.3% of the total area of SRYR. Under the stable snow area (SCD > 60), the land cover type is glacial or permanent snow about 1.5 × 103 km2, which covers almost the entire glacial or permanent snow of the SRYR.

Optical instrument for the study of time recovery from total disability glare vision.

Disability glare is defined as the loss of contrast sensitivity of the retinal image due to intraocular straylight originated from the presence of an intense and broad bright light in the field of vision. This loss of vision can range between vision loss at high spatial frequencies or total temporal blindness. If the extreme case occurs, the recovery time is crucial in night driving conditions or those professional activities in which maximum visual acuity is required at any moment. The recovery time depends mainly on the intensity and glare angle of the light source, ocular straylight, and the photoreceptor response at the retina. The recovery time can also be affected by ocular pathologies, aging, or physiological factors that increase ocular straylight. The aim of this work is to develop a new optical instrument based on psychophysical methodology as well as to investigate the recovery time from total disability glare (photobleaching) as a function of the contrast of the visual target and the glare angle of the source in healthy volunteers. Results showed significant exponential correlation between recovery time and contrast of the visual target and linear correlation between contrast sensitivity and the glare angle. Those findings allowed to obtain an empirical expression to compute the recovery time required to restore contrast sensitivity baseline vision after photobleaching. Finally, a statistical dependence of recovery time with age was found for short glare angles that disappear as the glare angle increases.

Litter quality mediated the effect of nitrogen addition and precipitation reduction on the release and immobilization of plant litter nitrogen and phosphorus

A long-term field litterbag manipulation experiment was conducted to examine the effects of reduced precipitation (−30% of through-fall), nitrogen (N) addition (50 kg N·ha−1·yr−1), and their combination (−30% of through-fall and 50 kg N·ha−1·yr−1) on the release and immobilization of N and phosphorus (P) in four litter types (Pinus koraiensis (PK), Tilia amurensis (TA), Quercus mongolica (QM), and their mixture (MIX)). The results showed that N addition did not significantly stimulate litter decomposition, whereas precipitation reduction and the interaction significantly inhibited litter decomposition. N immobilization was significantly enhanced by N addition and reduced precipitation in the PK, QM, and MIX litters but was significantly inhibited in the TA litter. N addition, reduced precipitation, and their combination significantly increased the final P concentration of the litter in each sampling period. Furthermore, interestingly, there was a significant exponential correlation between the remaining N and final P concentration in the PK litter and a significant linear correlation for the QM and MIX litters, but no significant correlation for the TA litter, indicating that the dynamic relationship between the remaining N and final P concentration in the litter depended on the litter type. These results suggest that the forest litter layer may alleviate the effects of N deposition by increasing litter N immobilization and aggravating soil P limitation by inhibiting litter P release following N deposition. Reduced precipitation may further affect biogeochemical cycles by inhibiting the release of litter N and P.

Soil hydrological process and migration mode influenced by the freeze-thaw process in the activity layer of permafrost regions in Qinghai-Tibet Plateau

It hasn't yet fully understood the influence of freeze-thaw action on hydrological processes in the active layer of permafrost regions. So this article investigated one permafrost cross-section at the northern slope of Bayan Har Mountains in the Source Area of the Yellow River in Qinghai-Tibet Plateau. According to the data of field monitoring, seasonal variability of soil hydrological processes in the active layer of permafrost regions was studied and simulated by the freeze–thaw module of HYDRUS-1D software. The results show that: 1) The soil moisture and the suprapermafrost water-level are divided into four stages based on the freeze-thaw process. Rainfall infiltration is the main driving force of soil hydrological processes, and the freeze-thaw front are the main limiting factors. 2) The active layer thickness (ALT) is greater on the upslope than that on the downslope due to the influence of terrain slope. It leads to that the change variation of the soil moisture and the suprapermafrost water-level on the upslope is also more gently than that on the downslope. 3) Temperature is the key factor that affects soil hydrologic process of the active layer in permafrost regions. Soil temperature and soil moisture showed a significant exponential linear correlation at different depths. The relationship between soil temperature and suprapermafrost water level shows Boltzmann function relations. 4) Soil moisture has a downward migration trend after a freeze-thaw cycle. It will result in the formation of underground ice near the permafrost table. Driven by the temperature gradient, the unfrozen water in the active layer moves from bottom to top during the freezing stage.

Effects of Adding Straw and Biochar with Equal Carbon Content on Soil Respiration and Microbial Biomass Carbon and Nitrogen

In order to investigate the response of soil respiration, soil microbial biomass carbon and nitrogen, and hydrothermal factors to the addition of biochar and straw, we used an LI-8100 soil carbon flux meter (LI-COR, Lincoln, USA) to study changes in soil respiration and microbial biomass under four treatments:conventional fertilization (CK), conventional fertilization +2.25t·hm-2 biochar-C (T1), conventional fertilizer +2.25t·hm-2 straw-C (T2), and conventional fertilizer +2.25t·hm-2 (biochar-C+straw-C), biochar-C:straw-C=1:1 (T3). The results showed that:① the addition of biochar and straw significantly increased the soil respiration rate and total CO2 emissions, with the largest increase in T3 and the smallest increase in T1. The effect of T1 on soil respiration was promoted in the early stage and later inhibited. ② The microbial biomass carbon and nitrogen and the number of functional bacterial colonies increased significantly with biochar and straw amendments. T1 had a significant promotion effect on nitrogen-fixing bacteria, while T2 had no significant effect on the number of fungi, and T3 showed a positive interaction effect. Soil respiration rates were significantly and positively related to soil microbial biomass carbon and nitrogen as well as to the number of bacteria and actinomycetes. ③ The 5 cm soil temperature of T3 significantly increased by 4.53%. The soil respiration rate and soil temperature showed a significant exponential correlation. To sum up, adding straw and biochar with equal carbon content can significantly increase the soil respiration rate and microbial biomass, and the interaction effect between biochar and straw is positive. Compared with that of the straw treatments, the application of biochar can reduce carbon mineralization to a certain extent, and the effect of carbon sequestration is better.

Normal age-related quantitative CT values in the pediatric lung: from the first breath to adulthood

ObjectiveTo characterize the normal progression of quantitative CT parameters in normal children from birth to adulthood. Materials and methodsPatients aged 0–18 years with non-contrast-enhanced chest CT and evidence of normal lung parenchyma were included. Patients with respiratory symptoms, incomplete anthropometric measurements, or sub-optimal imaging technique were excluded. Segmentation was performed using an open-source software with an automated threshold segmentation. The following parameters were obtained: mean lung density, kurtosis, skewness, lung volume, and mass. Linear and exponential regression models were calculated with age and height as independent variables. A p-value of <0.05 was considered significant. Results220 patients (111 females, 109 males) were included. Mean age was 9.6 ± 5.9 years and mean height was 133.9 ± 35.1 cm. Simple linear regression showed a significant relationship between mean lung density with age (R 2 = 0.70) and height (R 2 = 0.73). Kurtosis displayed a significant exponential correlation with age (R 2 = 0.70) and height (R 2 = 0.71). Skewness showed a significant exponential correlation with age (R 2 = 0.71) and height (R 2 = 0.73). Lung mass showed a correlation with age (R 2 = 0.93) and height (R 2 = 0.92). Exponential regression showed a significant relationship between lung volume with age (R 2 = 0.88) and height (R 2 = 0.93). ConclusionQuantitative CT parameters of the lung parenchyma demonstrate changes from birth to adulthood. As children grow, the mean lung density decreases, and the lung parenchyma becomes more homogenous.

Dynamic Simulation of the Crown Net Photosynthetic Rate for Young Larix olgensis Henry Trees

Numerical integration of the instantaneous net photosynthetic rate (An) is a common method for calculating the long-term CO2 uptake of trees, and accurate dynamic simulation of the crown An has been receiving substantial attention. Tree characteristics are challenging to assess given their aerodynamically coarse crown properties, spatiotemporal variation in leaf functional traits and microenvironments. Therefore, the variables associated with the dynamic variations in the crown An must be identified. The relationships of leaf temperature (Tleaf), the vapor pressure deficit (VPD), leaf mass per area (LMA) and the relative depth into the crown (RDINC) with the parameters of the photosynthetic light-response (PLR) model of Larix olgensis Henry were analyzed. The LMA, RDINC and VPD were highly correlated with the maximum net photosynthetic rate (Amax). The VPD was the key variable that mainly determined the variation in the apparent quantum yield (AQY). Tleaf exhibited a significant exponential correlation with the dark respiration rate (Rd). According to the above correlations, the crown PLR model of L. olgensis trees was constructed by linking VPD, LMA and RDINC to the original PLR equation. The model performed well, with a high coefficient of determination (R2) value (0.883) and low root mean square error (RMSE) value (1.440 μmol m−2 s−1). The extinction coefficient (k) of different pseudowhorls within a crown was calculated by the Beer–Lambert equation based on the observed photosynthetically active radiation (PAR) distribution. The results showed that k was not a constant value but varied with the RDINC, solar elevation angle (ψ) and cumulative leaf area of the whole crown (CLA). Thus, we constructed a k model by reparameterizing the power function of RDINC with the ψ and CLA, and the PAR distribution within a crown was therefore well estimated (R2 = 0.698 and RMSE = 174.4 μmol m−2 s−1). Dynamic simulation of the crown An for L. olgensis trees was achieved by combining the crown PLR model and dynamic PAR distribution model. Although the models showed some weakened physiological biochemical processes during photosynthesis, they enabled the estimation of long-term CO2 uptake for an L. olgensis plantation, and the results could be easily fitted to gas-exchange measurements.

Optimal positioning of storage systems in microgrids based on complex networks centrality measures

We propose a criterion based on complex networks centrality metrics to identify the optimal position of Energy Storage Systems in power networks. To this aim we study the relation between centrality metrics and voltage fluctuations in power grids in presence of high penetration of renewable energy sources and storage systems. For testing purposes we consider two prototypical IEEE networks and we compute the correlation between node centrality (namely Eigenvector, Closeness, Pagerank, Betweenness) and voltage fluctuations in presence of intermittent renewable energy generators and intermittent loads measured from domestic users. We show that the topological characteristics of the power networks are able to identify the optimal positioning of active and reactive power compensators (such as energy storage systems) used to reduce voltage fluctuations according to the common quality of service standards. Results show that, among the different metrics, eigenvector centrality shows a statistically significant exponential correlation with the reduction of voltage fluctuations. This finding confirms the technical know-how for which storage systems are heuristically positioned far from supply reactive nodes. This also represents an advantage both in terms of computational time, and in terms of planning of wide resilient networks, where a careful positioning of storage systems is needed, especially in a scenario of interconnected microgrids where intermittent distributed energy sources (such as wind or solar) are fully deployed.

Alpine wetland ecosystem carbon sink and its controls at the Qinghai Lake

Wetland ecosystems play an important role in regulating the Earth’s climate. This paper presents the results of a study on the alpine wetland ecosystem CO2 fluxes at the Qinghai Lake at different vegetative development stages and CO2 controlling factors measured by eddy covariance system. The results showed that the alpine wetland ecosystem at the Qinghai Lake area was a carbon sink on the whole year basis. The average net ecosystem CO2 exchange (NEE) amount was −904.42 g CO2/m2; the average amount of the ecosystem reparation (Re) was 1450 g CO2/m2; the average gross primary productivity (GPP) was 2354.42 g CO2/m2 from July 2011 to June 2013 year. The NEE, Re and GPP amounts were the maximum during the growing stage of the whole year. There were significant negative linear correlations between monthly NEE amount and monthly average total solar radiation (SR) (R 2 = 0.27, p < 0.05), incident photosynthetically active radiation (PAR) (R 2 = 0.28, p < 0.05), ambient vapor pressure deficit (VPD) (R 2 = 0.38, p < 0.01), monthly total precipitation (P) (R 2 = 0.65, p < 0.0001), monthly mean leaf area index (LAI) (R 2 = 0.85, p < 0.0001) and enhanced vegetation index (EVI) (R 2 = 0.84, p < 0.0001). Extreme significant polynomial nonlinear negative correlations were found between NEE amounts and monthly average air temperature (T a ) (R 2 = 0.84, p < 0.0001), soil temperature at 0–5 cm depth (T s ) (R 2 = 0.90, p < 0.0001) and air relative humidity (RH) (R 2 = 0.76, p < 0.0001). The monthly Re amount of alpine wetland ecosystem at the Qinghai Lake at different stages showed significant nonlinear positive correlations with all the identified affecting factors except for monthly mean EVI, which showed a linear relationship (R 2 = 0.72, p < 0.0001). The monthly GPP amount at different vegetative development stages showed a significant exponential correlation with monthly average T a (R 2 = 0.92, p < 0.0001), a power function with VPD (R 2 = 0.24, p < 0.05), quadratic polynomial ones with monthly average T s (R 2 = 0.93, p < 0.0001), RH (R 2 = 0.74, p < 0.0001) and monthly P (R 2 = 0.55, p < 0.05). Extremely significant linear correlations of the monthly GPP amount at different developing stages with monthly average LAI (R 2 = 0.85, p < 0.0001) and EVI (R 2 = 0.92, p < 0.0001) were also found.

城乡交错带土壤氮素空间分布及其影响因素

PDF HTML阅读 XML下载 导出引用 引用提醒 城乡交错带土壤氮素空间分布及其影响因素 DOI: 10.5846/stxb201410081969 作者: 作者单位: 四川农业大学资源环境学院,四川农业大学资源环境学院,四川农业大学资源环境学院,四川农业大学资源环境学院,四川农业大学资源环境学院 作者简介: 通讯作者: 中图分类号: 基金项目: 国家"十二五"科技支撑计划项目(2012BAD14B18-2) Spatial distribution of soil nitrogen in an urban-rural fringe and its influencing factors Author: Affiliation: College of Resource and Environment of Sichuan Agricultural University,College of Resource and Environment of Sichuan Agricultural University,College of Resource and Environment of Sichuan Agricultural University,College of Resource and Environment of Sichuan Agricultural University,College of Resource and Environment of Sichuan Agricultural 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:城乡交错带土壤氮素是城乡生态系统中最重要的氮源与氮汇,但是城市化下的土壤氮素分布及其影响机制还不清楚,基于3S平台研究了土壤氮素在成都西郊城乡交错带的空间分布特征及城市化对土壤氮素的影响。结果表明,研究区内土壤全氮(STN)、硝态氮(NO3--N)和铵态氮(NH4+-N)含量均值分别为(1.46±0.06) g/kg、(50.04±3.59) mg/kg和(6.72±0.53) mg/kg。区内土壤氮素含量从近郊向远郊逐渐增高,STN和NO3--N含量为中部高于南北部,NH4+-N含量则由西北部和东南部向中部递增。方差分析表明,区内不同土地利用方式下STN、NO3--N和NH4+-N含量差异显著(P < 0.05)。回归分析显示STN含量与建筑密度(BD)、道路密度(RD)均呈现显著线性负相关(P < 0.05),NO3--N含量与道路密度呈极显著线性负相关(P=0.001),与建筑密度关系不明显(P=0.217)。土壤NH4+-N与建筑密度呈显著负线性相关(P=0.001),与道路密度呈显著指数相关关系(P=0.021)。研究结果显示城市发展使得城乡交错带土壤氮素含量降低,这种影响伴随着建筑面积的增加,道路长度的增加而加强。 Abstract:Urban-rural fringe is a special zone that evolved from the suburbanization accompanying intensified land use changes from agricultural to non-agricultural land. Nitrogen in the soil of urban-rural fringe is an important nitrogen source and sink for urban and suburban ecosystems. The nitrogen content changes not only affect greenhouse gas emissions, but also threaten plant nitrogen supply and water ecosystems. However, in suburb urbanization, the proportion of non-agricultural land, construction land, and road land exhibited a successive increase. Currently, the mechanism of spatial distribution of soil nitrogen, caused by an increase in non-agricultural land, remains unclear. In the present study, the 3S platform was used to investigate the spatial distribution of soil nitrogen and its influencing factors in the urban-rural fringe of the western suburbs of Chengdu. Results showed that the average contents of soil total nitrogen (STN), nitrate (NO3--N), and ammonium (NH4+-N) were (1.46±0.06) g/kg, (50.04±3.59) and (6.72±0.53) mg/kg, respectively. In the investigated region, average content of soil nitrogen gradually increased from the inner to the outer suburbs. The STN and NO3--N distribution in the inner suburbs were higher than those of the northern and southern areas. High STN(>1.5 g/kg) and soil NO3--N(> 62.2 mg/kg) values presented mass distribution in the eastern suburbs. In addition, NH4+-N in soil gradually increased from the northwest or southeast to the center, and the high values(> 8.5 mg/kg) presented irregular piece distribution in the eastern suburbs. Analysis of variance (ANOVA) showed that the difference of STN, NO3-N, and NH4+-N contents were significant under different land use patterns (P < 0.01). The STN content in vegetable fields was the highest (> 1.8 g/kg), followed by rape fields, gardens, and woodland (1.5-1.8 g/kg). Garlic fields and idle land were relatively moderate (1.0-1.5 g/kg), and residential land and urban green land were relatively low (< 1.0 g/kg). NO3--N content was ranked as residential land > vegetable field > garlic field > garden > rape field > idle field > woodland > urban green land. NH4+-N content was ranked as vegetable field > woodland > garden > rape field > garlic field > residential land > idle field > urban green land. Correlation analysis indicated that average STN content and building density (BD) showed a negative linear correlation (P <0.05), and similar linear correlation was also observed between STN and road density (RD) (P < 0.05). NO3--N content in soil and road density showed a negative correlation (P = 0.001). However, the correlation was not significant between NO3--N and the building density (P = 0.217) after being analyzed using different curve models. NH4+-N content and building density showed a significant negative linear correlation (P = 0.001), and a significant exponential correlation existed in NH4+-N content and the road density (P = 0.021). Therefore, a significant effect on the development of urban distribution of soil nitrogen was observed, that was potentially strengthened by increasing road lengths and building areas. It can be suggested that the monitoring and management of soil nitrogen should be enhanced, and the cycling of soil nitrogen, atmospheric nitrogen, and water nitrogen should be investigated in future studies. 参考文献 相似文献 引证文献

Possible Influences on the Interpretation of Functional Domain (FD) Near-Infrared Spectroscopy (NIRS): An Explorative Study.

The influence of subcutaneous adipose tissue (ATT) and oxygen (O2) delivery has been poorly defined in frequency domain (FD) near-infrared spectroscopy (NIRS). Therefore, the aim of this study was to investigate the possible influence of these variables on all FD NIRS responses using a reliable protocol. Moreover, these influences were also investigated when using relative oxy- and deoxyhemoglobin and -myoglobin (oxy[Hb + Mb] and deoxy[Hb + Mb]) values (in %). A regression analysis was carried out for ATT and maximal-minimum oxy[Hb + Mb], deoxy[Hb + Mb], oxygen saturation (SmO2), and total hemoglobin (totHb) amplitudes during an incremental cyclic contraction protocol (ICCP) in a group of 45 participants. Moreover, the same analysis was carried out between subcutaneous ATT and the relative oxy- and deoxy[Hb + Mb] values (in %). In the second part of this study, a regression analysis was performed for peak forearm blood flow (FBF) during ICCP and the absolute and relative NIRS values in a group of 37 participants. Significant exponential correlation coefficients were found between ATT and deoxy[Hb + Mb] (r = 0.53; P < 0.001), oxy[Hb + Mb] (r = 0.57; P < 0.001), and SmO2 amplitudes (r = 0.57; P < 0.001). No significant relations were found between ATT and relative oxy[Hb + Mb] (r = 0.37; P = 0.07) and deoxy[Hb + Mb] (r = 0.09; P = 0.82). Significant positive correlation coefficients were found between force at exhaustion and maximal FBF (r = 0.66; P < 0.001), maximal differences in deoxy[Hb + Mb] (r = 0.353; P = 0.032) and totHb (r = 0.512; P = 0.002) while no significant correlation coefficients were found between these maximal force values and maximal differences in oxy[Hb + Mb] (r = -0.267; P = 0.111) and SmO2 (r = -0.267; P = 0.111). Significant linear correlation coefficients were found between FBF and deoxy[Hb + Mb] (r = 0.51; P = 0.001), oxy[Hb + Mb] (r = -0.50; P = 0.001), SmO2 (r = -0.54; P = 0.001), and totHb amplitude (r = 0.61; P < 0.001). No significant correlations were found when using relative oxy[Hb + Mb] (r = -0.01; P = 0.957) and deoxy[Hb + Mb] (r = -0.02; P = 0.895). Based on these findings, caution is advised when using NIRS values, as subcutaneous ATT and O2 delivery significantly influence NIRS measurements. To eliminate these influences, use of relative deoxy[Hb + Mb] is advised, especially in clinical settings or in people with a higher subcutaneous ATT layer.

Spurious thermoluminescence characteristics of the Ediacaran Doushantuo Formation (ca. 635–551 Ma) and its implications for marine dissolved organic carbon reservoir

The Ediacaran Doushantuo Formation (ca. 635–551 Ma) deposited immediately after the last Neoproterozoic glaciations and recorded the most prominent negative excursions of carbonate carbon isotopic composition (δ13Ccarb). These excursions have been interpreted as a result of widespread remineralization of a large dissolved organic carbon (DOC) reservoir in the Ediacaran deep oceans. However, there is no direct evidence so far found in rocks for the proposed DOC reservoir, which devalues such an interpretation. Here, we conducted a detailed study on the glow-curves characteristics and signal origins of spurious thermoluminescence (TL) of the Doushantuo Formation at Jiulongwan in Yangtze Gorges area, South China, through sequential tests under CO2, N2 and air. Spurious TL intensities for test samples before and after removing soluble organic matter via accelerated solvent extraction (ASE) are nearly identical. Further, significant positive correlation between the spurious TL intensity and total inorganic carbon (TIC) content (R 2=0.7) indicate that the Doushantuo spurious TL with the characteristic peak at 393.5 °C from the sequential test is chemiluminescence (CL) which is derived from the oxidation of a type of non-volatile organic matter strongly associated with carbonate mineral lattice (termed as “X-OM”). A most likely explanation is that the X-OM is a type of dissolved organic matter which co-precipitated with carbonate minerals into sediments in the Ediacaran Doushantuo Ocean. Furthermore, a significant exponential negative correlation (R 2=0.55) is observed between the CL data and the isotopic difference between carbonate and coexisting bulk organic matter (i.e., Δ13Ccarb-org, a proxy for remineralization degree of DOC reservoir in proposed DOC hypothesis), suggesting that the X-OM was derived from the oxidation of the DOC reservoir in the Ediacaran Ocean. We thus propose that the X-OM and its CL detected in our study may have recorded the evolution of the possible DOC reservoir in the Ediacaran Doushantuo Ocean. If this is correct, the stratigraphic variations of the CL intensity in the Doushantuo Formation at Jiulongwan support the pulsed oxidation of the DOC reservoir in the Ediacaran Ocean. Our findings indicate that the CL derived from the oxidation of non-volatile organic matter which is strongly associated with carbonate mineral lattices in rocks may provide a feasible approach for probing the evolution of DOC reservoir in the ancient oceans, thus likely provide direct geological evidence for the development of oceanic DOC reservoir in geological times.

Annual ecosystem respiration variability of alpine peatland on the eastern Qinghai-Tibet Plateau and its controlling factors.

Peatlands are widely developed in the eastern Qinghai-Tibet Plateau, but little is known about carbon budgets for these alpine peatland ecosystems. In this study, we used an automatic chamber system to measure ecosystem respiration in the Hongyuan peatland, which is located in the eastern Qinghai-Tibet Plateau. Annual ecosystem respiration measurements showed a typical seasonal pattern, with the peak appearing in June. The highest respiration was 10.43 μmol CO2/m(2)/s, and the lowest was 0.20 μmol CO2/m(2)/s. The annual average ecosystem respiration was 2.06 μmol CO2/m(2)/s. The total annual respiration was 599.98 g C/m(2), and respiration during the growing season (from May to September) accounted for 78 % of the annual sum. Nonlinear regression revealed that ecosystem respiration has a significant exponential correlation with soil temperature at 10-cm depth (R (2) = 0.98). The Q 10 value was 3.90, which is far higher than the average Q 10 value of terrestrial ecosystems. Ecosystem respiration had an apparent diurnal variation pattern in growing season, with peaks and valleys appearing at approximately 14:00 and 10:00, respectively, which could be explained by soil temperature and soil water content variation at 10-cm depth.

Body Mass Exponential Index: An Age-Independent Anthropometric Nutritional Assessment

Background: Body mass index (BMI) is a squared-height power function. Nevertheless, some studies show a significant exponential weight-height correlation. Objectives: To demonstrate that the weight-height relationship from 2 to 20 years of age is better expressed by an exponential function. Design: 5th, 50th and 85th percentile weight-height curves according CDC 2000 Growth Charts. A theoretical curve was created with the data on the 50th percentiles of weight and height for each age, equivalent to the 50th percentile of the weight-for-height curve. The statistical analysis was performed applying regression analysis of the curve estimation in the power and exponential models. Results: The exponential model correlation coefficient is higher than the power model. The exponential model variable (1.9 in boys, 2 in girls) was standardized to 2 to establish the body mass exponential index (BMEI): weight/exp(2*height). Weight-for-age and exponential height-for-age fiftieth percentile curves show a stable age-independent ratio near 2. These ratios are 1.5 and 2.5 for the 5th and 85th percentiles, respectively. The shape of the well-known curve BMI-for-age is due to the disparity between a exponential curve and a power curve. Conclusions: An exponential function expresses the weight-height relationship during growth better than a power function. A BMEI of 2 with limits of 1.5 and 2.5 is useful for screening nutritional status during growth, and the weight-for-height chart is an ideal substitute for the BMI-for-age chart. The BMI-for-age curve shape and the disproportional BMI in taller children are mathematical artifacts without biological meanings.

Application of an In Situ Electrical Resistivity Device to Monitor Water and Salt Transport in Shandong Coastal Saline Soil

In situ monitoring of water and salt transport in saline soil is a valuable tool for the rational exploitation and conservation of water and soil resources in coastal areas. In this paper, an automatic monitoring device was used to monitor the vertical variation of soil resistivity during leaching in laboratory and field experiments. The experimental results showed that the resistivity peak moved downwards and eventually disappeared during leaching. An equation describing the change in leaching speed over time was obtained. It was found that the desalination occurred from top to bottom and that the desalination depth was constant when the same volume of leaching fluid was applied. Resistivity indication and salinity content showed a significant exponential correlation (R (2) > 0.9). The field experiment demonstrated the stability of data transmission, and variations in apparent resistivity in one day and over a longer period were observed. Rainfall resulted in the downward migration of salt from surface soil, whereas evaporation led to migration of salt upward. The temporal and spatial resolution of this monitoring device can be adjusted to achieve dynamic monitoring, providing an easy means to manage soil and water conservation.

Evaluation of intereye corneal asymmetry in patients with keratoconus. A scheimpflug imaging study.

PurposeTo assess the correlation between keratoconus severity and intereye asymmetry of pachymetric data and posterior elevation values and to evaluate their combined accuracy in discriminating normal corneas from those with keratoconus.MethodsThis study included 97 patients: 65 subjects with bilateral normal corneas (NC) and 32 with keratoconus (KC). Central corneal thickness (CCT), thinnest corneal thickness (ThCT) and posterior elevation (PE) at the thinnest point of the cornea were measured in both eyes using Scheimpflug imaging. Intereye asymmetry and its correlation with keratoconus severity were calculated for each variable. The area under the receiver operating characteristic curve (AUROC) was used to compare predictive accuracy of different variables for keratoconus.ResultsIn normal eyes, intereye differences were significantly lower compared with the keratoconus eyes (p<0.001, for CCT, ThCT and PE). There was a significant exponential correlation between disease severity and intereye asymmetry of steep keratometry (r2 = 0.55, p<0.001), CCT (r2 = 0.39, p<0.001), ThCT (r2 = 0.48, p<0.001) and PE (r2 = 0.64, p<0.001). After adjustment for keratoconus severity, asymmetry in thinnest pachymetry proved to be the best parameter to characterize intereye corneal asymmetry in keratoconus. This variable had high accuracy and significantly better discriminating ability (AUROC: 0.99) for KC than posterior elevation (AUROC: 0.96), ThCT (AUROC: 0.94) or CCT (AUROC: 0.92) alone.ConclusionsThere is an increased intereye asymmetry in keratometry, pachymetry and posterior corneal elevation values in keratoconic patients compared to subjects with normal corneas. Keratoconus patients with more severe disease are also more asymmetric in their disease status which should be taken into account during clinical care.

Summertime CO2 fluxes and ecosystem respiration from marine animal colony tundra in maritime Antarctica

Net ecosystem CO2 exchange (NEE) and ecosystem respiration (ER) were investigated at penguin, seal and skua colony tundra and the adjacent animal-lacking tundra sites in maritime Antarctica. Net CO2 fluxes showed a large difference between marine animal colonies and animal-lacking tundra sites. The mean NEE from penguin, seal and skua colony tundra sites ranged from −37.2 to 5.2 mg CO2 m−2 h−1, whereas animal-lacking tundra sites experienced a larger net gain of CO2 with the mean flux range from −85.6 to −23.9 mg CO2 m−2 h−1. Ecosystem respiration rates at penguin colony tundra sites (mean 201.3 ± 31.4 mg CO2 m−2 h−1) were significantly higher (P < 0.01) than those at penguin-lacking tundra sites (64.0–87.1 mg CO2 m−2 h−1). The gross photosynthesis (Pg) showed a consistent trend to ER with the highest mean Pg (219.7 ± 34.5 mg CO2 m−2 h−1) at penguin colony tundra sites. When all the data were combined from different types of tundra ecosystems, summertime tundra NEE showed a weak or strong positive correlation with air temperature, 0–10 cm soil temperature or precipitation. The NEE from marine animal colony and animal-lacking tundra was significantly positively correlated (P < 0.001) with soil organic carbon (SOC), total nitrogen (TN) contents and C:N ratios. The ER showed a significant exponential correlation (P < 0.01) with mean 0–15 cm soil temperature, and much higher Q10 value (9.97) was obtained compared with other terrestrial ecosystems, indicating greater temperature sensitivity of tundra ecosystem respiration. Our results indicate that marine animals and the deposition of their excreta might have an important effect on tundra CO2 exchanges and ecosystem respiration, and current climate warming will further decrease tundra CO2 sink in maritime Antarctica.

Rain Fall Partition of the Forest Canopy beside Songhua River

Through field investigation and room experiment, the characteristics of the rainfall partition in the canopy layer of six forest types beside Songhua River were studied. The canopy interception of the rainfall was different in six forest types; from maximum to minimum was Quercus monglica forest, Pinus koraiensis plantation, Tilia mandshurica forest, Fraxinus mandshurica-Larix olgensis forest, Fraxinus mandshurica-Populus davidiana forest and Juglans mandshurica forest. There were significant linear correlation between through fall and precipitation and significant exponential correlation between canopy interception and precipitation in studied forest types; The stem flow ratio to gross rain fall ranged from 0.74% to 16.61% in six forest types, from maximum to minimum was Juglans mandshurica forest, Quercus monglica forest, Pinus koraiensis plantation, Fraxinus mandshurica-Larix olgensis forest, Fraxinus mandshurica-Populus davidiana forest and Tilia mandshurica Forest. In the same precipitation condition, the stem flow ratio to gross rain fall should be affected negatively by canopy size.

Soil respiration for different plant communities in an urban green-belt of Shanghai

The soil respiration rate of nine plant communities （Cinnamomum camphora，Torreya grandis-Ginkgo biloba，Cedrus deodara，Ginkgo biboba，Osmanthus fragrans，Cercis sp.，Lolium perenne-Cynodon dactylon，Zoysia japonica，and Cynodon dactylon） in Shanghai City were studied with a CFX-2 Soil Respiration Chamber，and the main influential factors were identified，and the aim was to evaluate correctly soil respiration of urban soil. The digital thermometer was used to test the air temperature，the soil temperature at 5 cm depth and the soil temperature at 10 cm depth. And all data were average of three replications，and a correlation analysis was also employed. Results showed that soil respiration rates varied by season with the maximum found from June to September and the minimum from December to the following March. Daily variation in the soil respiration rate under communities of trees and bushes was generally stable; whereas a lawn had a single-peaked curve. The maximum soil respiration rates （5.51 molm－2s－1） found under Cynodon dactylon and the minimum （2.76 times less） found under a Cercis sp. community. The soil respiration rate had a significant exponential correlation （P＜0.01） with the air temperature，the soil temperature at 5 cm depth，and the soil temperature at 10 cm depth. Soil water content had an effect on soil respiration under lawns，but it had a relatively small influence on tree and bush communities. The soil labile organic carbon content was ranked in the following order: light fraction organic carbon （LFOC） ＞ microbial biomass carbon （MBC） ＞ dissolved organic carbon （DOC），but MBC and DOC had the greatest influence on the soil respiration rate. The maximum released quantity of CO2 reached to 33.18 thm－2a－1 under lawns, which was 1.95 times that of trees and 2.12 times that of bushes.［Ch，3 fig. 6 tab. 30 ref］

Assessment of diffuse contamination of agricultural soil by copper in Aquitaine region by using French national databases

A long-term application of copper-based fungicides to fight against downy mildew has led to soil contamination by copper particularly in Aquitaine region where viticulture is important. This work aims to statistically validate the origin of diffuse contamination of Aquitaine agricultural soils and show that contamination is closely related to wine-growing in this region. For this purpose, several national databases have been used. From the French National Soil Monitoring Network (Réseau de Mesures de la Qualité des sols RMQS) data, an Exploratory Data Analysis (EDA) was performed to bring out the copper contamination. The French test soil database (Base de Données des Analyses de Terre BDAT) and the national census of agriculture (Recensement Général Agricole RGA) have been crossed. A statistical approach has been used to determine the relationship between the median concentration of copper extracted by Ethylene Diamine Tetra-acetic Acid (EDTA) referred to as CuEDTA in cultivated topsoils of the Aquitaine region and the ratio between winegrowing area (Svine) and the Used Agricultural Area (UAA) expressed as the form Svine/UAA. The results revealed a strongly significant exponential correlation between these two variables. They allow concluding that at cantonal scale, when vines cover more than 80% of the UAA, an overexposure of soils to the diffuse contamination by copper can occur.