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The Lithosphere-Asthenosphere Boundary (LAB) beneath oceanic plates is generally imaged as a sharp seismic velocity reduction, suggesting the presence of partial melts. However, the fate of a melt-rich LAB is unclear after these plates descend into the mantle at subduction zones. Recent geophysical studies suggest its persistence with down-going old and cold slabs, but whether or not it is commonly present remains unclear, especially for young and warm slabs such as in the Cascadia subduction zone. Here we provide evidence for its presence at Cascadia in the form of a large (9.8 ± 1.5 % ) decrease in shear-wave velocity over a very small (<3 km) depth interval. Similarly large and sharp seismic velocity reduction at the bottom of both old and young slabs, as well as along the base of oceanic plates before subduction, possibly represents widespread presence of melts. The melt-rich sub-slab LAB may strongly influence subduction dynamics and viscoelastic earthquake cycles. This study provides seismic evidence for the presence of partial melts along the base of Cascadia's subducting slab, with implications to lithosphere-asthenosphere decoupling that potentially influences subduction dynamics and earthquake cycles. [ABSTRACT FROM AUTHOR]

Spatial and environmental processes are two ecological processes that have attracted considerable attention in plant community assembly, depending on sampling scale and life history. However, the processes that determine community assembly have not been studied in the karst region of southwest China. In this study, a 25-ha (500 m × 500 m) monitoring plot within the subtropical climax forest in the karst region was established and canonical correspondence analysis was used to reveal the effects of topography and soil on the spatial patterns of tree community assembly. Our study suggests that spatial processes dominate species composition and the combined effects of spatial and environmental processes play an important role. Overall interpretation rate increases with enlarging the sampling scale. However, the pattern of variation partitioning was similar in different life stages. Environmental variables significantly affected species composition at different sampling sizes and life histories and had a higher interpretation rate of species composition on larger sampling sizes. Topographic wetness index was the most important variable to explain species composition of the environmental variables. These results suggest that it is necessary to consider the relative importance of environmental and spatial factors on community assembly to better understand, conserve, and manage subtropical karst forests. [ABSTRACT FROM AUTHOR]

Prevalent PET imaging reconstructs 2γ-photon pairs emitted after an annihilation from para-positronium (p-Ps) and rejects 3γ events from ortho-positronium (o-Ps) as noises. The 3γ/2γ decay ratio is ~ 3/7 in human body theoretically but in fact significantly lower due to pick-off process, hence PET imaging quality is well controlled. In a PET-MR hybrid unit, the MR magnetic field alters positronium decay patterns through magnetic quenching: all o-Ps and excited p-Ps states are split into finer quantum states under strong magnetic field, thus transitions between some triplet and singlet finer states (mz = 0) were no longer forbidden, thus some o-Ps converts to p-Ps spontaneously by emitting hyperfine split (HFS) photons, which also drops 3γ/2γ ratio hence helps PET imaging quality. However, inverse magnetic quenching might also occur if any external source of HFS frequencies is nearby, thus many p-Ps convert to o-Ps by absorbing those HFS photons (induced HFS transitions). This will dramatically increase 3γ/2γ ratio and hence degrade PET imaging quality instantaneously. The HFS spectrum lies in a broad range of microwaves, from 0.02 to 200 GHz. To prevent inverse magnetic quenching, it is necessary to block external microwave sources outside the hybrid vault, by adding a thin metal layer at all directions of the vault. This could be achieved by adopting the metallic Faraday Cage, which was originally for MR shielding, with possible amendment if necessary. The frequencies of excitation pulses in MR imaging overlap with HFS spectrum, however, the chance for mutual interference during hybrid imaging is small, hence there seems no need to veto each other during hybrid scans. [ABSTRACT FROM AUTHOR]

Asymbiotic N2 fixation (ANF) is a major nitrogen (N) input pathway to terrestrial ecosystems. However, there is considerable uncertainty about how lithology affects ANF. Here, we measured ANF rates in soil, litter, and moss in forests underlain by limestone (limestone forest), dolomite (dolomite forest), and clasolite (clasolite forest), respectively, in southwest China. Effects of lithology on soil ANF rate varied seasonally. The rate was highest in the dolomite forest during the wet season, but was highest in the limestone forest during the dry season. The overall soil ANF rate was significantly higher in the limestone forest than in the clasolite forest. Litter ANF rate was significantly higher in the limestone forest and dolomite forest than in the clasolite forest regardless of season. There was no significant difference in moss ANF rate among the three types of forests in both seasons. The annual N2 fixation rate was highest in the limestone forest (1.72 ± 0.27 kg N ha−1 y−1) but lowest in the clasolite forest (0.70 ± 0.08 kg N ha−1 y−1). In the wet season, the variation of ANF rates was best explained by soil nitrate and available iron for soil, and by litter N and calcium content for litter. In the dry season, the variation of ANF rates was best explained by soil water content, ammonia and total phosphorus for soil, and by litter water content and calcium content for litter. No strong explanatory variables were identified for ANF in moss during the wet or dry season. Our findings suggest that lithology significantly affected ANF in soil and litter, but not in moss, and hence should be considered in Earth system models to facilitate better prediction of N inputs via biological N2 fixation under global change. [ABSTRACT FROM AUTHOR]

Aims: Slope position affects soil nutrients and plant diversity, thereby altering arbuscular mycorrhizal fungi (AMF) communities. However, the effect of slope position on the relationship between plant diversity, soil nutrients, and AMF communities remains unclear. Methods: We characterized soil physicochemical properties, plant diversity, and the colonization, diversity, and composition of AMF on the upper, middle, and lower slopes of karst shrub ecosystems. Results: A lower slope increased the availability of soil nutrients such as available nitrogen, phosphorus, and potassium in the rainy and warm seasons. Slope position influenced AMF colonization and plant diversity. Specifically, plant richness was higher on lower and middle slopes than on upper slopes. AMF colonization intensity was higher on the lower and middle slopes than on the upper slope, and increased in the rainy and warm seasons compared to the that in the dry and cool seasons. Greater nodes and edges among AMF taxa caused more connection and complexity in the co-occurrence networks on lower and middle slopes than on upper slopes. The lower slope had relatively high available nutrients, soil thickness, and strong water capacity that improved plant growth, which in turn enhanced AMF colonization because of the mutually beneficial relationship between AMF and plants. Conclusions: Our results demonstrated that lower and middle slopes increase AMF colonization and interactions among AMF taxa by inducing plant growth with high diversity under rich soil nutrient conditions. Therefore, strengthening the colonizing strategies of AMF may substantially improve nutrient uptake and transfer during the recovery of abandoned agricultural lands. [ABSTRACT FROM AUTHOR]

At the northern Cascadia subduction zone, the subducting Explorer and Juan de Fuca plates interact across a transform deformation zone, known as the Nootka fault zone (NFZ). This study continues the Seafloor Earthquake Array Japan Canada Cascadia Experiment to a second phase (SeaJade II) consisting of nine months of recording of earthquakes using ocean-bottom and land-based seismometers. In addition to mapping the distribution of seismicity, including an MW 6.4 earthquake and aftershocks along the previously unknown Nootka Sequence Fault, we also conducted seismic tomography, which delineates the geometry of the shallow subducting Explorer plate (ExP). We derived hundreds of high-quality focal mechanism solutions from the SeaJade II data. The mechanisms manifest a complex regional tectonic state, with normal faulting of the ExP west of the NFZ, left-lateral strike-slip behaviour of the NFZ, and reverse faulting within the overriding plate above the subducting Juan de Fuca plate. Using data from the combined SeaJade I and II catalogs, we have performed double-difference hypocentre relocations and found seismicity lineations to the southeast of, and oriented 18° clockwise from, the subducted NFZ, which we interpret to represent less active small faults off the primary faults of the NFZ. These lineations are not optimally oriented for shear failure in the regional stress field, which we inferred from averaged focal mechanism solutions, and may represent paleo-configurations of the NFZ. Further, active faults interpreted from seismicity lineations within the subducted plate, including the Nootka Sequence Fault, may have originated as conjugate faults within the paleo-NFZ. [ABSTRACT FROM AUTHOR]

Purpose: Changes in climate and land use may disrupt the soil carbon (C), nitrogen (N), and phosphorus (P) cycles, which affect the availability of essential nutrients differently, including soil organic carbon (SOC), total nitrogen (TN), and total phosphorus (TP). Nevertheless, lithologic impact on soil C:N:P stoichiometry over a broad climatic gradient remains largely unknown. We aimed to determine the variation in nutrient limitations between karst and non-karst forests and croplands across a climate gradient. Materials and methods: This study investigated soil C:N:P stoichiometry in mature forest (MF) and nearby cropland rotation (CR) (as a control) soils on limestone (karst) and clastic rock (non-karst) throughout a climatic gradient in southwest China through analysis of soil samples. Result and discussion: The SOC and TN contents in the karst MF were 1.3 and 1.6 times greater, respectively, than that in the non-karst MF. Consequently, the karst MF had a lower C:N ratio than did the non-karst MF. The SOC and TN contents were considerably higher in the MF than they were in the CR under both lithologies, leading to higher C:P and N:P ratios in the MF compared to those in the CR. The increasing temperature resulted in a shift from TN and TP to SOC limitation, due to the increased decomposition of SOC by microbes with an increase in temperature. Soil pH and Ca content are controlled by the lithology, and they were closely related to C:N:P stoichiometry in this study, whereas a combination of lithology and temperature controlled soil microbial activity and plant growth. Importantly, the magnitude of lithology-induced changes in the stoichiometry was greater as temperature increased, which was more pronounced in the non-karst than it was in the karst. Conclusions: These findings highlight the responses of soil C, N, and P to climate warming in relation to stoichiometry, and soil-microorganism-plant response strategies may be the key to the mitigating the effect of temperature increase on nutrient cycles in karst ecosystems. [ABSTRACT FROM AUTHOR]

This research presents two unique techniques for engineering system reliability analysis of multi-dimensional non-linear dynamic structures. First, the structural reliability technique works best for multi-dimensional structural responses that have been either numerically simulated or measured over a long enough length to produce an ergodic time series. Second, a novel extreme value prediction method that can be used in various engineering applications is proposed. In contrast to those currently used in engineering reliability methodologies, the novel method is easy to use, and even a limited amount of data can still be used to obtain robust system failure estimates. As demonstrated in this work, proposed methods also provide accurate confidence bands for system failure levels in the case of real-life measured structural response. Additionally, traditional reliability approaches that deal with time series do not have the benefit of being able to handle a system's high dimensionality and cross-correlation across several dimensions readily. Container ship that experiences significant deck panel pressures and high roll angles when travelling in bad weather was selected as the example for this study. The main concern for ship transportation is the potential loss of cargo owing to violent movements. Simulating such a situation is difficult since waves and ship motions are non-stationary and complicatedly non-linear. Extreme movements greatly enhance the role of nonlinearities, activating effects of second and higher order. Furthermore, laboratory testing may also be called into doubt due to the scale and the choice of the sea state. Therefore, data collected from actual ships during difficult weather journeys offer a unique perspective on the statistics of ship movements. This work aims to benchmark state-of-the-art methods, making it possible to extract necessary information about the extreme response from available on-board measured time histories. Both suggested methods can be used in combination, making them attractive and ready to use for engineers. Methods proposed in this paper open up possibilities to predict simply yet efficiently system failure probability for non-linear multi-dimensional dynamic structure. [ABSTRACT FROM AUTHOR]

The power conversion efficiency (PCE) and stability of perovskite solar cells (PSCs) are affected by the presence of Pb-I antisite and I vacancy defects. Here, we propose a strategy for synchronous passivation of defects by Lewis bases D-Tryptophan methyl ester hydrochloride (D-TMe·HCl). The results show that the amino and carboxyl groups in D-TMe·HCl could synchronously passivate the Pb-I antisite and I vacancy defects through ionic and hydrogen bonding. In addition, the inhibition of ion migration of Pb2+ and I− effectively suppresses charge recombination and promotes interfacial carrier extraction. As a result, the PCE of the device with D-TMe·HCl increased to 20.59% with a fill factor of 79.8%. Furthermore, the introduction of D-TMe·HCl promotes the crystallinity of the perovskite and obtains a more dense and uniform film, thus the stability of the device is enhanced. The device with D-TMe·HCl retains more than 94% of its initial PCE after aging in a glovebox for 500 h under nitrogen conditions. This work opens up a new avenue for achieving efficient and stable PSCs by forming high-quality films, synchronously passivating defects, and inhibiting ion migration. [ABSTRACT FROM AUTHOR]

An ex-situ 15 N–18O tracing experiment with soils collected from the valley and slope, respectively, of a subtropical secondary karst forest with three N addition levels, i.e., 0, 50, and 100 kg N ha−1 year−1 for each topographic position to investigate N2O production pathways. Autotrophic nitrification pathways (ammonia oxidation, nitrifier denitrification, and nitrification-coupled denitrification) accounted for > 70% of total N2O production, but denitrification pathways (heterotrophic denitrification and co-denitrification) were the minor source of N2O at both topographic positions. In the valley, chronic N addition stimulated ammonia oxidation-derived N2O, which was paralleled by increased ammonia-oxidizing archaea (AOA) amoA gene transcript abundance, but inhibited nitrifier denitrification- and nitrification-coupled denitrification–derived N2O along with suppressed ammonia-oxidizing bacteria (AOB) amoA gene transcript abundance and stimulated nosZII gene transcript abundance, respectively. On the slope, chronic N addition stimulated ammonia oxidation-derived N2O along with increased AOB amoA gene transcript abundance, and enhanced nitrifier denitrification-derived N2O congruent with increased AOB amoA and decreased nirK gene transcript abundances. In addition, chronic N addition reduced the relative contribution of heterotrophic denitrification to N2O production but had no significant influence on heterotrophic denitrification-derived N2O on the slope. Overall, our results provide a comprehensive view in terms of how topography-driven soil properties regulate N2O production and its pathways in a subtropical forest. [ABSTRACT FROM AUTHOR]

The hydrological conditions of river-connected lakes are complex primarily owing to their considerable water-level fluctuations (WLFs). Water quality in such lakes varies with hydrodynamic variations; however, their relationship is not clear. To identify the unique relationship between water level and water quality in river-connected lakes, we used the comprehensive pollution index (CPI) and regression analysis to analyze the spatiotemporal variation in water quality in Dongting Lake from 2015 to 2018 and the effects of water level on water quality. Four water quality parameters were selected: total nitrogen (TN), total phosphorus (TP), permanganate index (CODMn), and chlorophyll a (Chl-a). The results showed significant spatial variation in the lake water quality, with relatively high concentrations of TN, TP, CODMn, and Chl-a in East Dongting Lake. TN and TP decreased by 12.15% and 37.61%, respectively, from 2015 to 2018, whereas CODMn increased from 1.781 to 2.009 mg/L. Seasonally, TN and TP concentrations were low in the summer and autumn, with high concentrations in the winter and spring. In contrast, CODMn and Chl-a concentrations exhibited opposite trends. The pollution level in Dongting Lake ranged between slightly and moderately polluted, with a CPI ranging from 0.76 to 1.32 across all sampling sites during 2015–2018. The water level in Dongting Lake initially increased and, then, decreased in a year, with marked WLFs owing to seasonal shifts in precipitation and human activities. The water level had significant negative relationships with TN and TP concentrations and a significant positive relationship with CODMn concentration (p < 0.05). Based on the results, strict control of excessive external nutrient loading should be actively implemented in Dongting Lake, in addition to hydrological regulation for effective lake water quality management. [ABSTRACT FROM AUTHOR]

Purpose: Soil nitrogen (N) availability plays an important role in determining ecosystem structure and function. However, the variation patterns of soil N availability under different vegetation restoration strategies along climatic gradients in the ecologically fragile karst region of China have been poorly understood. Methods: Soil N variables, including total N (TN), inorganic N [ammonium (NH4+) and nitrate (NO3-)], and rates of net N mineralization and nitrification were measured following managed (plantation forest) and natural (spontaneous regeneration) vegetation restoration along a climatic gradient in the karst region of southwestern China. Results: Compared to that in the cropland, soil TN and NH4+ concentrations significantly increased in both vegetation restoration strategies after 15 years of cropland abandonment. The net N mineralization and nitrification rates were lower in both vegetation restoration strategies compared with those in cropland and secondary forest. There were no significant differences in the soil N variables between the two vegetation restoration strategies. Furthermore, soil NO3− was positively correlated with mean annual temperature (MAT) following vegetation restoration, whereas the net nitrification rate was negatively correlated with MAT. Generally, soil pH was the main factor affecting soil inorganic N, whereas elevation, soil microbial abundance, SOC or C:N, and climatic factors mainly affected soil net N mineralization and nitrification rates. Conclusion: Vegetation restoration was beneficial to soil N accumulation and is likely to decrease the risk of N loss in warmer regions given the reduced potential nitrification rate with increased MAT in the karst region of Southwest China. [ABSTRACT FROM AUTHOR]

For assessing tsunami hazard in northernmost Cascadia, there is an urgent need to define tsunami sources due to megathrust rupture. Even though the knowledge of Cascadia fault structure and rupture behaviour is limited at present, geologically and mechanically plausible scenarios can still be designed. In this work, we use three-dimensional dislocation modelling to construct three types of rupture scenarios and illustrate their effects on tsunami generation and propagation. The first type, buried rupture, is a classical model based on the assumption of coseismic strengthening of the shallowest part of the fault. In the second type, splay-faulting rupture, fault slip is diverted to a main splay fault, enhancing seafloor uplift. Although the presence or absence of such a main splay fault is not yet confirmed by structural observations, this scenario cannot be excluded from hazard assessment. In the third type, trench-breaching rupture, slip extends to the deformation front and breaks the seafloor by activating a frontal thrust. The model frontal thrust, based on information extracted from multichannel seismic data, is hypothetically continuous along strike. Our low-resolution tsunami simulation indicates that, compared to the buried rupture, coastal wave surface elevation generated by the splay-faulting rupture is generally 50-100% higher, but that by trench-breaching rupture is slightly lower, especially if slip of the frontal thrust is large (e.g. 100% of peak slip). Wave elevation in the trench-breaching scenario depends on a trade-off between enhanced short-wavelength seafloor uplift over the frontal thrust and reduced uplift over a broader area farther landward. [ABSTRACT FROM AUTHOR]

Purpose: Changes in soil organic carbon (SOC) stock have major impacts on global terrestrial carbon cycling. However, their responses to land use conversions are poorly characterized for karst areas with extremely fragile geology and intensive human disturbance. Methods: To investigate the effects of soil type and land use on SOC stock in a typical karst region of southwestern China, 0–15 cm topsoil samples were randomly collected in 2015. Furthermore, in the same locations as the sites in 1983, 0–100 cm stratified profile soil samples (0–10, 10–20, 20–30, 30–50, 50–70, and 70–100 cm) were collected to evaluate the changes in SOC stock as affected by land use conversions from 1983 to 2015. Results: The current SOC stock in 0–15 cm differed significantly between Calcisols and Ferralsols, and was highest in the secondary forest, followed by shrubland, grassland, plantation forest, and cropland. Changes in the stratified SOC stock (both recalculated to 0–20, 20–40, 40–60, 60–80, and 80–100 cm intervals in 1983 and 2015) varied among different land use conversions. Average stratified SOC stock decreased after forest degradation and reclamation, except in 80–100 cm. After reforestation, it had decreases in 0–20 and 20–40 cm, whereas it increased in subsoil (40–60, 60–80, and 80–100 cm). However, compared with the cropland in which soil was exposed to continuous conventional tillage, average stratified SOC stock increased in all soil layers after reforestation. Conclusion: The increases in SOC stock after reforestation and re-cultivation (short-term reuse in abandoned croplands) indicated the positive role of agricultural abandonment in increasing terrestrial SOC stock. [ABSTRACT FROM AUTHOR]

In this paper, a low-cost high-performance axial flux Vernier machine (AFVM) with soft magnetic composite (SMC) cores and ferrite magnet is proposed, analyzed and optimized. By cooperating with spoke magnet rotor configuration and 3D magnetic flux stator structure, the proposed AFVM can output higher torque compared with the traditional permanent magnet machine though low-cost low-energy-density ferrite magnet and low-permeability SMC material are adopted. The main electromagnetic topology and operation principle of the proposed AFVM are introduced; then, its main dimensions are investigated and optimized by using sequential optimization method. Moreover, a new multilevel Taguchi design optimization which is an improvement of multilevel optimization is proposed for the torque and power factor optimization. Lastly, its main performance of AFVM optimized by the sequential optimization method and multilevel Taguchi design optimization method has been compared with a normal axial flux machine in terms of torque ability, power factor and efficiency based on 3D finite element method. [ABSTRACT FROM AUTHOR]

Context: South China karst is undergoing large scale land-use conversions driven by reforestation projects aiming at combating land degradation. However, the spatial extent of these human induced land-use changes is largely unknown. Objectives: This study aims at quantifying land use changes in South China karst in the context of large scale restoration and reforestation projects. Results: We apply an extensive field survey on land-use mapping and find that 45,406 km2 of farmland have been converted to forest, while 41,811 km2 have been deforested (likely due to timber harvest), which corresponds to a forest expansion of 6%, and an 8% contraction of farmlands. We find that the converted areas agree well with satellite observed greening trends, explaining why South China karst is considered a global hot-spot of vegetation cover increase. In total, 43% of the farmland to forest conversions have taken place on sloping hills steeper than 25° and predominantly at larger distances from settlements. However, 19,464 km2 of the steep sloping areas were still farmland in 2016, which is 15% of the total farmland in South China karst. Conclusions: Large scale forest dynamics are observed on sloping hills. Given the low agricultural productivity but high erosion risk, considerations regarding loss of crop production and local food security must be balanced against gains in expected provisioning of ecosystem services (e.g. carbon sequestration, timber production). [ABSTRACT FROM AUTHOR]

Land use policies have turned southern China into one of the most intensively managed forest regions in the world, with actions maximizing forest cover on soils with marginal agricultural potential while concurrently increasing livelihoods and mitigating climate change. Based on satellite observations, here we show that diverse land use changes in southern China have increased standing aboveground carbon stocks by 0.11 ± 0.05 Pg C y−1 during 2002–2017. Most of this regional carbon sink was contributed by newly established forests (32%), while forests already existing contributed 24%. Forest growth in harvested forest areas contributed 16% and non-forest areas contributed 28% to the carbon sink, while timber harvest was tripled. Soil moisture declined significantly in 8% of the area. We demonstrate that land management in southern China has been removing an amount of carbon equivalent to 33% of regional fossil CO2 emissions during the last 6 years, but forest growth saturation, land competition for food production and soil-water depletion challenge the longevity of this carbon sink service. Forest management may play an important role in climate change mitigation. Here, Tong et al. combine remote sensing and machine learning modelling to map forest cover dynamics in southern China during 2002–2017, showing effects on carbon sequestration that are extensive but of uncertain longevity and possible negative impact on soil water. [ABSTRACT FROM AUTHOR]

Context: The karst region of southwestern China, one of the largest continuous karsts in the world, is known for its unique landscapes and rich biodiversity. This region has suffered severe environmental degradation (e.g., vegetation cover loss, soil erosion and biodiversity loss). In recent decades, Chinese governments at different levels have initiated several ecological programs (e.g., Green for Grain, Mountain Closure) to restore the degraded environment and to alleviate poverty. Objectives: This study summarizes landscape studies of karst landscapes patterns, their dynamics and interactions among landscape pattern, hydrological processes and ecosystem services (ES). Methods: We conducted a systematic literature review of science and land use policy to identify knowledge gaps and recommend future research and policy directions. Results: Karst landscapes have experienced rapid turnover in recent decades due largely to the overlap of intense human activity on the fragile karst ecosystems. Many studies have comprehensively examined hydrology, soil processes and ecosystem services (ES) and their relationships with landscape pattern. Most of these studies have found that karst ecosystems recover with improved ES. However, the importance of epikarst in hydrological and soil processes, intense anthropogenic disturbance and landscape heterogeneity in landscape models remains elusive. Conclusions: Future research should focus on in-depth examination and modelling of karst specific hydrological and soil processes, investigating relationships between climatic change, landscape change, ecological processes, and region-specific ES assessments. Results from such research should provide the necessary scientific support for a comprehensive, national karst rocky desertification treatment project (Stage II) and poverty alleviation initiatives. [ABSTRACT FROM AUTHOR]

Purpose: Tillage disturbance can significantly affect soil microbial metabolic activity and CO2 fluxes. Nevertheless, the influence of different tillage frequencies on microbial metabolic activity and short-term temporal changes of CO2 fluxes remains unclear. Materials and methods: We established an in situ experiment with the following treatments: no tillage (T0), semiannual tillage (T1), tillage every 4 months (T2), bimonthly tillage (T3), and monthly tillage (T4). The microbial metabolic activity (Biolog EcoPlate), short-term (hours to days) temporal changes in CO2 fluxes within 1 week, and soil properties were measured after 1 year of treatment. Results and discussion: The highest CO2 emissions occurred in the first 72 h after tillage treatment and were significantly higher in T3 and T4 than in T0, T1, and T2 within 1 week. Average well color development (AWCD) values reflect microbial metabolic activity and were significantly higher in the tillage treatments (T1, T2, T3, and T4) than under no tillage. There was no significant difference in the Shannon diversity index under all treatments. A higher Simpson diversity index was observed under high tillage frequency in T2, T3, and T4 compared with T0 and T1, while the highest was observed in T2. The highest utilization of carboxylic acids, amino acids, and polymers occurred in T3 and T4 soils, whereas T2 had the highest utilization of carbohydrates, amines, and miscellaneous carbon sources. AWCD values and short-term CO2 fluxes were significantly correlated with annual changes in soil organic carbon (△SOC), annual changes in dissolved organic carbon (△DOC), microbial biomass carbon (MBC), and large macroaggregates (> 1 mm). Conclusions: These results suggest that frequent tillage disturbance increases microbial metabolic activity, which can stimulate short-term CO2 emissions through changes in soil aggregates, SOC, DOC, and MBC. [ABSTRACT FROM AUTHOR]

Studying the influence of topography and litter and soil nutrients on soil enzymes and microbial biomass is important to the understanding of soil nutrient transformation and cycling, but these relationships in heterogeneous soils of karst ecosystem remains poorly understood. We determined environment factors influencing the urease (URS) and alkaline phosphatase (ALP) activity and microbial biomass C and N (MBC and MBN) with advancing vegetation succession. The results showed that ALP increased but URS decreased with the advancing vegetation succession. The MBC and MBN were highest in shrubland, but both were lowest in grassland. The URS was positively correlated with the surface cover of rock outcrops (SRO) but negatively correlated with litter N, and soil available N and pH. Conversely, ALP was positively correlated with litter N, soil organic carbon (SOC), and soil available N and pH, but negatively correlated with soil total N. The MBC was positively related to litter quantities and SOC but negatively related to soil pH; the MBN was positively related to slope gradient (SLG), SOC, and soil total P and available P. Additionally, the trends of the index URS/MBN were grassland > secondary forest > shrubland > primary forest, but the index ALP/MBN increased with advancing vegetation succession. It indicated that soil microorganism mainly exudate extracellular URS and ALP to soils. We also found the interactions of topography (SLG and SRO), litter (nutrients and quantity), and soil (nutrients and pH) explained 42.00, 87.00, and 66.00% of the variations in URS, ALP, and microbial biomass, respectively. Path analysis showed that the topography had a directly positive effect on litter nutrients and quantities, but not on soil nutrients; the litter nutrients and quantities had direct positive effect on soil nutrients, which had direct effect on soil enzymes and microbial biomass; the relationships (R2) between the independent variable and enzymes activities and microbial biomass increased with advancing successions. Thus, it suggested that high SLG and SRO are good for collecting litters back to soils and then the topography, litter, and soil factors increased its controlling effect on soil enzymes activities and microbial biomass with advancing successions in karst ecosystem. [ABSTRACT FROM AUTHOR]

Determining the effects of nitrogen (N) and phosphorus (P) application on arbuscular mycorrhizal fungi (AMF) communities is important for predicting AMF responses to nutrient deposition. The AMF parameters and soil properties were monitored in karst grassland after 2 years of N and P addition. Then, AMF abundance, diversity, and community composition significantly differed between seasons. AMF abundance was higher in July (summer) than in December (winter), whereas richness and Chao1 estimator values showed the opposite results. The numbers of the genera Funneliformis and Sclerocystis were significantly more abundant in December, but the proportions of Scutellospora, Redeckera, and Diversispora were significantly higher in July. N and NP treatments significantly increased AMF abundance; richness and Chao1 values in the P treatment were significantly higher than those of the control in July. AMF community composition changed substantially between December and July but did not respond to fertilization. AMF abundance was significantly correlated with total N (TN), while AMF richness was also significantly correlated with available P (AP) and pH. pH and nitrate N (NO3−-N) strongly affected AMF community composition. These results suggested that P became more limiting with N fertilization, AMF investment increased access to more P, and richness was lower when certain AMF taxa (Diversisporales) increased in abundance during the growing season and under more P-limiting conditions. These results also suggested that N and P addition have specifically different effects on AMF abundance and diversity, and consequently potential effect on long-term vegetation composition and productivity. [ABSTRACT FROM AUTHOR]

Purpose: Information on root-zone soil water content (SWC) is essential for vegetation restoration, irrigation scheduling, and hydrological modeling. However, measurements of SWC within a variety of land uses may be time-consuming and labor-costing. This study tested whether SWC at a depth of a land use can be used to predict profile SWC of other land uses in terms of temporal stability analysis at a karst depression area in southwest China.Materials and methods: A total of 30 datasets of root-zone SWC from 0.1- to 0.5-m depths were collected by time domain reflectometry probes for three typical land uses from March 12 to November 8, 2015.Results and discussion: Results showed that the profile mean SWC and its associated standard deviation (SDP) and coefficient of variation (CVP) differed significantly (P < 0.05) among the grassland, farmland, and forestland. The profile SWC was more temporally stable according to the apparently lower CVT in comparison with CVP. The similarities of the vertical patterns of SWC were strong for the same land uses, while were relatively weak between the different land uses. The SWC measurements of the most temporally stable depth can be used to accurately predict profile SWC for both the same land use and other land uses.Conclusions: This study further expands the application of the temporal stability analysis and can aid water resource management in areas with diverse land uses. [ABSTRACT FROM AUTHOR]

Purpose: Cultivation can affect soil microbial activities, with consequences for microorganisms that metabolize soil organic carbon and release CO2 to the atmosphere. Nevertheless, there is limited understanding of the short-term effects that tillage disturbance, maize planting, or their interactions exert on microbial biomass and metabolic function in a typical karst calcareous soil. A 1-year simulation experiment quantified the impacts of tillage disturbance and maize planting on soil microorganisms.Materials and methods: Four treatments (2 × 2 m plot size), comprising conventional tillage with (CTM) and without maize (CT), and non-tillage with (NTM) and without (NT) maize, were conducted. Microbial biomass carbon (MBC), carbon metabolic function (Biolog profiles), CO2 flux, soil organic carbon (SOC), and dissolved organic carbon (DOC) were measured after 1-year tillage disturbance and maize planting.Results and discussion: DOC was significantly lower in CTM, NTM, and CT than in NT, but SOC was slightly higher in NTM than in CTM and NT. Annual cumulative CO2 fluxes were significantly higher in CTM and NTM than in CT, which in turn was significantly higher than NT. Principal component analysis (PCA) suggests microbial community catabolic function differs in all treatments. CT showed significantly decreased MBC compared with NT, but significantly increased microbial metabolic activity and Simpson index (D). Compared with NT, NTM showed significantly increased microorganism metabolic activity, Shannon index (H), and D, but no significant difference in MBC. The interactions between maize planting and tillage disturbance had no significant effect on MBC or metabolic function diversity.Conclusions: Microbial biomass appears sensitive to tillage disturbance, while microbial metabolic activity is sensitive to maize planting. Maize planting with no tillage would increase CO2 emissions through enhanced microbial activity, but, at the same time, mitigate SOC loss due to an increase in C input by crop residues and roots left in the soil. [ABSTRACT FROM AUTHOR]

The responses of spatiotemporal variation of ecosystem service values (ESVs) to landscape pattern from 1985 to 2005 in a typical Karst area of the northwest Guangxi Zhuang Autonomous Region, China, were examined using remote sensing and geographic information system techniques in this paper. The total ecosystem service values declined significantly from 1985 to 1990, and then increased slowly from 1990 to 2005, almost equaled to the 1985 level. The ecosystem service values tended to decline from the west to the east and from mountainous regions to peak-cluster depression areas in 1985, 1990, 2000 and 2005 respectively. During the period from 1985 to 2005, the ecosystem service values have increased in the middle and eastern parts of the study area. Landscape pattern indices, such as total area, largest patch index, contagion, aggregative index, effective mesh and proportion of like adjacencies, are significantly correlated with ecosystem service values. This suggests that ecosystem service values tend to increase with the growth of patch area and patch connectivity. However, there are negative correlations between ecosystem service values and landscape pattern indices, such as division index and patch richness. It indicates that ecosystem service values decrease with patch fragmentation and patch size shrinkage. The ecosystem conditions in the typical Karst area have been improved because of the control measures of rocky desertification. It is important to protect key landscape types, such as woodland, shrub and grassland, and to increase patch size and connectivity to avoid further fragmentation. Furthermore, it is necessary to reduce disturbances to ensure the growth of ecosystem service values and to facilitate the sustainable development in this region. [ABSTRACT FROM AUTHOR]

Key message: Soil nitrogen and phosphorus are the most important factors influenced the leaf N:P ratios across plant functional groups in the karst region of southwestern China, and plant diversity are also important to certain groups. Abstract: Leaf nitrogen:phosphorus (N:P) stoichiometry, which affects plant growth, nutrient cycling, and primary production in terrestrial ecosystems, is influenced by soil N and P, among other factors. However, it remains unclear how biotic and abiotic factors influence leaf N and P stoichiometry of different plant functional groups in the karst ecosystem of southwest China. We measured the leaf N and P of different plant functional groups, as well as soil total nitrogen (TN), total phosphorus (TP), available nitrogen (AN), and available phosphorus at 0-15 cm depth under each plant functional group. The linear mixed models (LMMs) results showed that the leaf N, P, and N:P ratios were characterized by functional groups. Higher leaf P, but lower leaf N and N:P ratios, were found in grasses than in shrubs and trees. The leaf N was higher in trees than that in shrubs. Additionally, the leaf N and N:P ratios were higher in legumes than that in nonlegumes. The LMMs results showed that the Shannon-Wiener diversity indexes ( H′), soil TN, and TP significantly impacted the leaf N:P ratios (with grass-shrub-tree group as random factor), and Simpson diversity indexes (DS), soil TN, AN, and TP significantly impacted the leaf N:P ratios (with nonlegume-legume group as random factor). It suggested that soil TN and TP had major effects on the leaf N:P ratios of all the studied functional groups in the karst region, while DS and H′ diversity indexes, and soil AN significantly impacted the leaf N:P ratios in several specific groups. [ABSTRACT FROM AUTHOR]

In karst regions, the spatial heterogeneity of soil mineral oxides and environmental variables is still not clear. We investigated the spatial heterogeneity of SiO, AlO, FeO, CaO, MgO, PO, KO, and MnO contents in the soils of slope land, plantation forest, secondary forest, and primary forest, as well as their relationships with environmental variables in a karst region of Southwest China. Geostatistics, principal component analysis (PCA), and canonical correlation analysis (CCA) were applied to analyze the field data. The results show that SiO was the predominant mineral in the soils (45.02%-67.33%), followed by AlO and FeO. Most soil mineral oxide components had a strong spatial dependence, except for CaO, MgO, and PO in the plantation forest, MgO and PO in the secondary forest, and CaO in the slope land. Dimensionality reduction in PCA was not appropriate due to the strong spatial heterogeneity in the ecosystems. Soil mineral oxide components, the main factors in all ecosystems, had greater influences on vegetation than those of conventional soil properties. There were close relationships between soil mineral oxide components and vegetation, topography, and conventional soil properties. Mineral oxide components affected species diversity, organic matter and nitrogen levels. [ABSTRACT FROM AUTHOR]

Forecasting earthquake and tsunami hazards along the southern Cascadia subduction zone is complicated by uncertainties in the amount of megathrust fault slip during past ruptures. Here, we estimate slip on hypothetical ruptures of the southern part of the megathrust through comparisons of late Holocene Cascadia earthquake histories derived from tsunami deposits on land and marine turbidites offshore. Bradley Lake in southern Oregon lies ~600 m landward of the shoreline and contains deposits from 12 tsunamis in the past 4600 years. Tsunami simulations that overtop the 6-m-high lake outlet, generated by ruptures with most slip south of Cape Blanco, require release of at least as much strain on the megathrust as would accumulate in 430-640 years (>15-22 m). Such high slip is inconsistent with global seismic data for a rupture ~300-km long and slip deficits over the past ~4700 years on the southern Cascadia subduction zone. Assuming slip deficits accumulated during the time intervals between marine turbidites, up to 8 of 12 tsunami inundations at the lake are predicted from a marine core site 170 km north of the lake (at Hydrate Ridge) compared to 4 of 12 when using a core site ~80 km south (at Rogue Apron). Longer time intervals between turbidites at Hydrate Ridge imply larger slip deficits compared to Rogue Apron. The different inundations predicted by the two records suggest that Hydrate Ridge records subduction ruptures that extend past both Rogue Apron and Bradley Lake. We also show how turbidite-based estimates of CSZ rupture length relate to tsunami source scenarios for probabilistic tsunami hazard assessments consistent with lake inundations over the last ~4600 years. [ABSTRACT FROM AUTHOR]

Infrared (IR) laser ablation was used to remove material from tissue sections mounted on microscope slides, with subsequent capture in a solvent-containing microcentrifuge tube. Experiments conducted with a 3200-bp double-stranded plasmid DNA template demonstrated IR-laser ablation transfer of intact DNA. The transfer efficiency and the molecular integrity of the captured DNA were evaluated using Sanger sequencing, gel electrophoresis, and fluorimetric analysis. The plasmid DNA was reproducibly transferred with an efficiency of 59 ± 3% at laser fluences of between 10 and 20 kJ/m at a wavelength of 3 μm. IR laser ablation sample transfer was then used to ablate and capture DNA from 50-μm-thick rat brain and kidney tissue sections. DNA was extracted from the captured material using five commercial DNA extraction kits that employed significantly divergent methodologies, with all kits recovering sufficient DNA for successful amplification by polymerase chain reaction (PCR). Four sets of primers were employed, targeting one region of the CYP 11b2 gene (376 bp) and three different regions of the Snn1g gene (298, 168, and 281 bp). The PCR results were not consistently reliable when using unpurified ablation samples; however, after extraction, all samples produced PCR products of the expected size. This work expands the sampling capabilities of IR laser ablation, demonstrating that DNA can be isolated from tissue samples for genomic assays. Due to the small size of the ablation regions (1 mm), this technique will be useful for sampling discrete cell populations from tissue sections. [ABSTRACT FROM AUTHOR]

Coarse root biomass (CRB) is an important store of carbon (C) and forest residue for renewable energy, but is often overlooked due to the lack of a simple and effective way to estimate its magnitude. In this study, we developed allometric equations for three functional groups using data from 133 tree samples, with a diameter at breast height (DBH) ranging from 2.6 to 52.0 cm. The functional groups included evergreen coniferous ( Pinus massoniana), deciduous broad-leaved ( Alniphyllum fortunei, Choerospondias axillaris, Liquidambar formosana and Quercus fabri) and evergreen broad-leaved ( Castanopsis carlesii, Cyclobalanopsis glauca, Litsea coreana and Schima superba) species. Allometric equations that related CRB to plot inventory data (e.g. DBH or tree height (H)) and their combinations significantly fitted ( P < 0.0001) for the functional groups and all tree species. The equations using DBH or DBH-H as predictor variables were the best fit ( R ≥ 0.90) and produced good predictions with little bias (less than 21%) for local sites and at regional scales. Allometric equations related to easily obtained remote sensing data (i.e. crown width (CW) and H) were also significantly fitted ( P < 0.0001, R ≥ 0.76), and predictions were close to the observed CRB, despite a high bias (larger than 98.0%). In conclusion, the use of these equations to estimate CRB is essential to the harvest process and helps to formulate new policies for managing the feedstock supply to bioenergy production in subtropical forests. [ABSTRACT FROM AUTHOR]

Episodic tremor and accompanying slow slip, together called ETS, is most often observed in subduction zones of young and warm subducting slabs. ETS should help us to understand the mechanics of subduction megathrusts, but its mechanism is still unclear. It is commonly assumed that ETS represents a transition from seismic to aseismic behaviour of the megathrust with increasing depth, but this assumption is in contradiction with an observed spatial separation between the seismogenic zone and the ETS zone. Here we propose a unifying model for the necessary geological condition of ETS that explains the relationship between the two zones. By developing numerical thermal models, we examine the governing role of thermo-petrologically controlled fault zone rheology (frictional versus viscous shear). High temperatures in the warm-slab environment cause the megathrust seismogenic zone to terminate before reaching the depth of the intersection of the continental Mohorovičić discontinuity (Moho) and the subduction interface, called the mantle wedge corner. High pore-fluid pressures around the mantle wedge corner give rise to an isolated friction zone responsible for ETS. Separating the two zones is a segment of semi-frictional or viscous behaviour. The new model reconciles a wide range of seemingly disparate observations and defines a conceptual framework for the study of slip behaviour and the seismogenesis of major faults. [ABSTRACT FROM AUTHOR]

Knowledge of the temporal variability of soil water content (SWC) at the hillslope scale is essential for guiding rehabilitation strategies and for optimizing water resource management in the karst region of southwest China. This study aimed to use temporal stability analysis to upscale point-scale measurements to represent mean areal SWC on two typical karst hillslopes. Based on a grid sampling scheme (10 m × 10 m) applied to two 90 m × 120 m plots located on two hillslops, the SWC at a depth of 0-16 cm was measured 11-12 times across 259 sampling points, using time domain reflectometry (TDR) from April 2011 to October 2012. Soil texture, bulk density (BD), saturated hydraulic conductivity ( K ), organic carbon (SOC), rock fragment content (RFC), and site elevation (SE) were also measured at these locations. Results showed the hillslope with more shrub cover was wetter than the hillslope with mixed grass-shrub cover. This difference was related to the differences in soil texture, soil hydraulic permeability, and topography. Through a comparison of values obtained with the Spearman correlation coefficient ( r ), standard deviation of mean relative difference (SDRD), and mean absolute bias error (MABE), we inferred that there is a higher degree of temporal stability for SWC in wet conditions than in drier conditions on the two hillslopes. Based on the values of the index of temporal stability (ITS), which combine the mean relative difference (MRD) and SDRD, the two locations were determined to be representative of mean SWC on both hillslopes. Moreover, these locations captured changes in mean SWC (NSCE = 0.69, and 0.65, and RMSE = 1.96, and 1.96 %, respectively). This demonstrates the feasibility of using the temporal stability of SWC to acquire mean SWC on karst hillslopes of southwestern China. The indirect method, which estimates mean SWC by considering the offset between the mean and the measurement value at a time-stable location, predicted mean SWC (NSCE = 0.86, and 0.76, and RMSE = 1.29, and 1.63 %, respectively) more precisely than the direct method (mean SWC directly measured at a time-stable location), because it eliminates deviation by introducing a constant offset (MRD). We recommended the use of the indirect method to acquire mean SWC values, when an allowable bias of 5 % for both MRD and SDRD can not be achieved. In addition, we found that soil texture, RFC, and elevation affect the pattern of SWC on the shrub hillslope. These results are expected to be useful for monitoring soil water dynamics on karst hillslopes, especially for restoration purposes. [ABSTRACT FROM AUTHOR]

Spatial distribution of soil water content (SWC) plays an important role in soil hydrological processes. Karst areas are especially heterogeneous with respect to soil distribution and properties and have not been adequately studied. The purpose of this study was to characterize the surface SWC and to discuss its controlling factors in a small karst catchment in Guangxi, China. SWC was measured using the gravimetric method along seven line-transects crossing farmland, shrub-grassland, shrubland and forestland, as well as hillslopes and depressions. Soil bulk density, capillary porosity, macroporosity, rock fragment content (RC), soil organic carbon and soil texture of the soil samples were also determined. Regression and sensitivity analysis methods were used to analyze the influence of soil properties on SWC in both the wet and dry season. Generally, SWC was significantly higher in depressions than on hillslopes. In the shrub-grassland and shrubland, SWC decreased with increasing elevation, whereas in the forestland, no obvious trend along the transect was found. Soil porosity, RC and soil texture were three main soil properties that influenced SWC significantly. Moreover, the distribution of SWC along the line-transects were coincidence with that of these soil properties. The results document the spatial distribution of SWC in a karst catchment in southwest China, laying a foundation for a better understanding and modeling of hydrological processes in this complex landform. [ABSTRACT FROM AUTHOR]

The Integrated Environmental Monitoring (IEM) project, part of the Asia-Pacific Environmental Innovation Strategy (APEIS) project, developed an integrated environmental monitoring system that can be used to detect, monitor, and assess environmental disasters, degradation, and their impacts in the Asia-Pacific region. The system primarily employs data from the moderate resolution imaging spectrometer (MODIS) sensor on the Earth Observation System-(EOS-) Terra/Aqua satellite, as well as those from ground observations at five sites in different ecological systems in China. From the preliminary data analysis on both annual and daily variations of water, heat and CO2 fluxes, we can confirm that this system basically has been working well. The results show that both latent flux and CO2 flux are much greater in the crop field than those in the grassland and the saline desert, whereas the sensible heat flux shows the opposite trend. Different data products from MODIS have very different correspondence, e.g. MODIS-derived land surface temperature has a close correlation with measured ones, but LAI and NPP are quite different from ground measurements, which suggests that the algorithms used to process MODIS data need to be revised by using the local dataset. We are now using the APEIS-FLUX data to develop an integrated model, which can simulate the regional water, heat, and carbon fluxes. Finally, we are expected to use this model to develop more precise high-order MODIS products in Asia-Pacific region. [ABSTRACT FROM AUTHOR]

Soil nitrogen (N) dynamics are crucial for ecosystem development and carbon sequestration. However, N dynamics during post-agriculture succession have not been well understood. Here soil N dynamics during post-agriculture succession were investigated in a subtropical karst area, southwest China. The succession sequence includes grassland (~10 years), shrubland (~29 years), secondary forest (~59 years) and primary forest with cropland as reference. The soil is calcareous lithosols. Soil N stock (0-15 cm) in the cropland (335.2 ± 55.1 g N m) was not significantly different from that in the grassland, but was elevated by 120 to 221 % in the later three succession stages. Across the sequence, soil N accumulated with an average rate of 12.4 g N m yr. Soil N stock recovered to the primary forest level in about 67 years following agricultural abandonment. NO concentrations increased while NH concentrations decreased with years following agricultural abandonment. High NO concentrations (66.5-120.9 mg N kg) may imply N saturation in the shrubland, secondary forest and primary forest. Rates of net N mineralization and nitrification increased with succession. δN of soil, leaves and litter was significantly elevated in the later three succession stages relative to the grassland, indicating that the N cycle became more open with succession. N release from bedrock weathering was likely a potential N source in addition to atmospheric N deposition and biological N fixation. Our study suggests that N would not be the limiting nutrient for secondary succession and ecological restoration in the karst region of southwest China. [ABSTRACT FROM AUTHOR]

Anthropogenic activities have altered the climate and led to changes in the water cycle. Understanding the climate change and hydrological responses is critical to derive adaptive strategies for sustainable water resources management. In this study, we diagnosed the trends of primary climate elements and hydrological components during the past half century (1960-2009) for the humid Xiangjiang River Basin in central-south China at multiple temporal and spatial scales. The air temperature trend demonstrated an overall warming climate but with a quicker pace in recent years; however, the wind speed reduced significantly in the early period, and this downtrend had largely disappeared after the mid-1990s. Under such a shifting climate, the hydrological responses were not monotonic during the past 50 years: the evapotranspiration behaved in a decreasing trend in the early 35 years (1960-1994), followed by an uptrend in the later period (1995-2009). The stepwise analysis of soil water content and baseflow demonstrated a wetting trend followed by a drying one but with a steeper slope, indicating an accelerated drying trend which may cause a concern in stream water availability especially in the dry season. Spatial trend analysis showed that some areas experienced a downtrend (drying) in the dry season, but most areas had an uptrend (wetting) in the wet season for the whole study period. Overall, the analyses of temporal and spatial changes are useful for decision makers to deal with the continuing changes in climate and hydrology. This study also highlighted the necessity of climate change studies at multiple temporal and spatial scales. [ABSTRACT FROM AUTHOR]

Researchers recently proposed a model describing the trade-offs between the positive and negative effects of nitrogen (N) fertilization on biomass and/or abundance of soil biota. The positive effects presumably result from the bottom-up influences of fertilizer-enhanced plant growth and from the improved soil habitat for soil biota. The negative effects presumably result from degradation of soil physico-chemical properties (e.g., salt effect, aluminum toxicity, calcium or magnesium deficiency, soil pH decline, and soil carbon resource availability reduction). The magnitude of these effects determines the net effect (or trade-off) of N fertilization on the biomass and/or abundance of soil biota. Our understanding of how positive and negative effects generate different net effects with changes in the N fertilization level is inadequate. In this paper, we propose two patterns of positive and negative effects (i.e., S-shaped and linear curves when the effects are plotted on fertilization level) and consider the many possibilities for the trade-offs. Specifically, there were 7 possible trade-offs between S-shaped positive effects and linear negative effects, 9 possibilities of the trade-off between linear positive effects and linear negative effects, 20 possibilities of the trade-off between S-shaped positive effects and S-shaped negative effects, and 9 possibilities of the trade-off between linear positive effects and S-shaped negative effects. In addition, the net effect might change or remain neutral (±), positive (+), or negative (−) with increasing nitrogen application. The hypothetical model could help explain the inconsistent results of the impacts of fertilization on soil biota reported in previous studies and could increase our understanding of the responses of soil biota to fertilization and other environmental disturbances. [ABSTRACT FROM AUTHOR]

Ecological restoration, which aims to restore disturbed ecosystems, has been an important approach to mitigate human pressures on natural ecosystems and to improve ecosystem services. Determination of the vegetation carbon effect requires the assessment of ecological restoration measures. In this study, the temporal-spatial characteristics of vegetation carbon services were analyzed using remote sensing data and weather parameters by using geographic information system in northwest Guangxi, China, a typical karst area covered by the ongoing China's Grain-to-Green Program and eco-environment immigration during 2000-2010. The results showed that ecosystem services of vegetation carbon sequestration showed an upward trend during the 11 years; approximately 21.14 and 18.09 % of the karst area showed significant changes in the net primary productivity (NPP) and net ecosystem productivity (NEP; P < 0.05), respectively. With regard to spatial distribution, NPP and NEP were higher for the western non-karst areas, and the greatest increase in these parameters was recorded in the eastern part of the restoration area of karst rocky desertification. Vegetation carbon sequestration was significantly affected by the impacts of vegetation coverage, vegetation species, and forest type. The results of this study suggested that rocky desertification control measures have positive impacts on the spatial distribution of vegetation carbon services in the typical karst area of northwest Guangxi, China. [ABSTRACT FROM AUTHOR]

Soil saturated hydraulic conductivity ( K) is one of the most important parameters that determine soil water redistribution. However, it is little known in a karst area with thin, discontinuous, and rocky soils. The purpose of this paper was to investigate the spatial variability of K and its influencing factors in a small karst catchment with high heterogeneity in southwest China. Undisturbed surface (0-10 cm) soil samples were collected with metal cylinders from an 80 m × 80 m grid for measuring K, bulk density (ρ), non-capillary porosity (NCP), and capillary porosity (CP). Disturbed surface samples were taken with a shovel to measure soil organic carbon (SOC) and rock fragment content (RC). Environmental factors including topographical location (slope and depression), land-use type (forestland, shrubland, shrub-grassland, and farmland), slope gradient, slope exposure, and elevation were investigated for each sampling point. The results showed that K value was relatively high (9.10 m/d) with a moderate variation, and had a strong spatial dependence (nugget/sill value = 0.06 %). NCP showed a very significantly ( p < 0.01) positive correlation but ρ showed a very significantly negative correlation with K. RC and SOC had significantly ( p < 0.05) positive correlations but CP had no obvious effect on K. This indicated that NCP and ρ were the dominant influencing factors of K in a karst area. The effects of topographical locations and land-use types on K were not significant ( p > 0.05), but their interaction effects were significant. This suggested that the influencing factors were more complex and they should be considered together in a karst area. The mean K value was the lowest in the forestland on the hillslope and in the farmland in the depression, indicating where the surface runoff may appear easily. Such results could help to better understand the soil hydrological processes and contribute to the building of hydrological models in small karst catchments. [ABSTRACT FROM AUTHOR]

Background and aims: Nitrogen (N) and/or phosphorus (P) limitation to primary productivity and other biological processes can change in a variety of ways as ecosystems develop. How N limitation and P limitation change from the early to the late stages of a secondary succession following farmland abandonment remains unclear in karst ecosystems in southwest China. Methods: We used community foliar N:P ratio, soil alkaline phosphatase activity (APA) and other indicators of nutrient status (soil organic carbon [SOC], total soil N [TN], and total soil P [TP], Alkali-hydrolyzable N [AN], and available soil phosphorus [AP] concentrations) to examine changes in N and P status during secondary vegetation succession. Four types of plant communities (grasslands, shrublands, secondary forest, and primary forest) represented the early, middle, late, and very late successional stages, respectively. Results: Community foliar N:P ratio, APA, and APA per unit SOC increased as succession proceeded from the grassland to the secondary and primary forest communities. Moreover, community foliar N:P ratios in the grassland were positively correlated with soil TN, while community foliar N:P ratios in the secondary forest and primary forest were negatively correlated with soil TP, but were not correlated with soil TN. Community foliar N:P ratios in the shrubland were not correlated with either soil TN or TP. Conclusions: Our results suggest that the grassland in the karst region of southwest China is N limited, that the secondary and primary forests are P limited, and that the shrubland is constrained by N and P together or by other nutrients. [ABSTRACT FROM AUTHOR]

Availability of high-resolution satellite rainfall products provides a great opportunity to monitor precipitation frequently over large and remote areas. However, the accuracies of these products need thorough assessment before they can be widely used. The objective of this study is to evaluate the accuracies of Tropical Rainfall Measuring Mission Multisatellite Precipitation Analysis 3B42 products (TMPA V6 and TMPA V7) using a network of 75 rain gauges over Southwestern China. The study region has a complex terrain, which makes it challenging for TMPA rainfall products to give reliable estimates. The results show that the TMPA products tend to underestimate the occurrences of rainfall events. Furthermore, TMPA V6 always underestimates the precipitation, while V7 generally overestimates rainfall in wet season and underestimates it in dry season. Under- and overestimation of rainfall by the two products can be mainly attributed to false alarm events. The overall accuracies of the two products depend heavily on the time scale. At the daily scale, these products may not be reliable; however, the overall accuracies are improved substantially when the time scale is extended from daily to monthly and seasonal scales. Reliability of the TMPA precipitation estimates is also dependent on the climate zones and elevation to some extent and shows clear seasonal variations. In the wet months from May to September, the estimates for TMPA 3B42 V6 and V7 tend to be more accurate. In comparison, the accuracy of V7 is improved slightly over V6. However, V7 still has some major limitations in reproducing precipitation in dry seasons and in high-elevation regions with complex terrains, suggesting that further improvements in TMPA precipitation retrieval algorithms are still needed for this type of regions. [ABSTRACT FROM AUTHOR]

After a large subduction earthquake, crustal deformation continues to occur, with a complex pattern of evolution. This postseismic deformation is due primarily to viscoelastic relaxation of stresses induced by the earthquake rupture and continuing slip (afterslip) or relocking of different parts of the fault. When postseismic geodetic observations are used to study Earth's rheology and fault behaviour, it is commonly assumed that short-term (a few years) deformation near the rupture zone is caused mainly by afterslip, and that viscoelasticity is important only for longer-term deformation. However, it is difficult to test the validity of this assumption against conventional geodetic data. Here we show that new seafloor GPS (Global Positioning System) observations immediately after the great Tohoku-oki earthquake provide unambiguous evidence for the dominant role of viscoelastic relaxation in short-term postseismic deformation. These data reveal fast landward motion of the trench area, opposing the seaward motion of GPS sites on land. Using numerical models of transient viscoelastic mantle rheology, we demonstrate that the landward motion is a consequence of relaxation of stresses induced by the asymmetric rupture of the thrust earthquake, a process previously unknown because of the lack of near-field observations. Our findings indicate that previous models assuming an elastic Earth will have substantially overestimated afterslip downdip of the rupture zone, and underestimated afterslip updip of the rupture zone; our knowledge of fault friction based on these estimates therefore needs to be revised. [ABSTRACT FROM AUTHOR]

The wave functions of the bound state of the charged kaon are obtained from Bethe-Salpeter equation with the phenomenological vector-vector-type flat-bottom potential. The physical spacelike electromagnetic form factor of the charged kaon is calculated from the wave functions. The radius of the kaon is given from the electromagnetic form factor. The decay constant f of the kaon is estimated by the relationship between the decay constant and the normalization factor derived from the axial-vector Ward identity. All calculated results give a good fit to the experimental values. [ABSTRACT FROM AUTHOR]

This paper focuses on migration occurrence as a result of environmental degradation and population growth. It briefly reviews previous practices in some less developed courtries and then considers the extent to which environmental factors have been and may be significant in initiating migration. A case study of the karst region of southwest China is used to illustrate the phenomenon, including root causes, restrictive factors, nature of the migration, desires of migrants, strategies of response and optional policies. It is argued that a comprehensive approach to the prevention of environmentally caused displacement should be developed. [ABSTRACT FROM AUTHOR]