Subtropical Monsoon Climate Region Research Articles

How to alleviate seasonal limitations on water quality in farmland ditches? The importance of plant selection and configuration

In subtropical monsoon climate regions, traditional plants in constructed wetlands such as farmland ditches underperform in cold months, detracting from both purification capacity and esthetic appeal. To alleviate this weakness, this study introduced Phalaris arundinacea, a species with strong adaptability and cold tolerance, into a plant community dominated by Phragmites australis, constructing an ingenious composite plant community for year‐round water quality restoration and enhancement of attractiveness. First, laboratory simulations revealed significant seasonal differences in the removal rates of ammonia nitrogen (NH3‐N), total nitrogen (TN), and total phosphorus (TP) by the P. arundinacea community and P. australis community under different pollutant loads. Phragmites australis showed superior NH3‐N and TN removal capabilities from May to October, whereas P. arundinacea excelled in the rest of the months throughout the year. For TP removal, P. australis outperformed P. arundinacea from July to October, while P. arundinacea was more effective from January to May. We then verified this in rear farmland ditches, where P. australis were strategically partial substituted with P. arundinacea (Partial Replacement Treatment [PRT]), and compared it with unchanged farmland ditches (Control Treatment). We found that PRT enhanced decontamination efficiency over the year, especially significantly improving the water quality during colder months. Hence, this study advocates a novel strategy for effective annual decontamination and maintenance of wetlands such as farmland ditches, highlighting the importance of seasonally adaptive plant communities for water restoration. This transformative approach dramatically advances the field of wetland management, insisting on the important role of cold‐resistant species for year‐round ecosystem service optimization.

Predictive Control Modeling of Regional Cooling Systems Incorporating Ice Storage Technology

Due to the hot climate, energy consumption for refrigeration is significantly higher in the subtropical monsoon climate region. Combined with renewable energy and ice-storage technology, a model predictive control model of the regional cooling system was proposed, which was conducive to improving the flexibility of the regional cooling system and the ability of peak shifting and valley filling. In this model, an artificial bee colony (ABC) optimized back propagation (BP) neural network was used to predict the cooling load of the regional cooling system, and the model parameter identification method was adopted, combining utilizing a river-water-source heat pump and ice-storage technology. The results showed that the load prediction algorithm of the ABC-BP neural network had a high accuracy, and the variance coefficient of load prediction root-mean-square error (RMSE) was 16.67%, which was lower than BP, support vector regression (SVR), and long short-term memory (LSTM). In addition, compared with the three control strategies of chiller priority, ice-storage priority, and fixed proportion, the operation strategy optimized by the comprehensive model can reduce the average daily cost by 19.20%, 4.45%, and 5.10%, respectively, and the maximum daily energy consumption by 30.02%, 18.08%, and 8.90%, respectively.

Assessing GNSS hydrological monitoring capability across different climatic settings in China

Vertical position changes of ground-based Global Navigation Satellite System (GNSS) stations have been used to study regional terrestrial water storage (TWS) changes. However, the feasibility is still unclear in many areas due to diverse local effects. This study aims to evaluate the capability of GNSS vertical displacements in monitoring hydrological variations in four climate settings over Chinese mainland. The spatial and temporal variations of hydrological load-induced (HYDL) vertical displacements at 208 GNSS sites during 2011–2020 were analyzed by comparing with Gravity Recovery and Climate Experiment (GRACE)/GRACE Follow-On (GFO) and Global Land Data Assimilation System (GLDAS) derived TWS changes. The results indicate that GNSS vertical positions show different capabilities in capturing seasonal and non-seasonal hydrological dynamics in different climate regions. Among the four climatic settings, the subtropical monsoon climate (SMC) region, with the largest deformation fluctuation (the regional mean root mean square (RMS) is 7.97 mm), has the highest regional mean HYDL-GRACE and HYDL-GLDAS anti-correlation coefficients (CCs) of −0.47 and −0.45 at the seasonal scale, respectively. For the individual GNSS site, the number of the sites with CC <−0.40 between HYDL and GRACE/GLDAS-derived TWS changes accounts for 55.1% and 55.1% (SMC), 13.0% and 7.4% (temperate monsoon climate, TMC), 6.7% and 13.3% (temperate continental climate, TCC), 32.3% and 38.7% (plateau climate, PC), respectively. For the non-seasonal term, although the proportion with CC <−0.40 in each climate type decreases mainly due to the influence of local geodynamic and human activities, especially in the SMC and PC regions, GNSS site vertical deformations still show good capability in monitoring hydrological extremes. The results provide valuable information for better application of GNSS to hydrology.

A Microwave Radiometer Residual Inversion Neural Network Based on a Deadband Conditioning Model

Microwave radiometers are passive remote sensing devices that are widely used in marine atmospheric observations. The accuracy of its inversion of temperature and humidity profiles is an important indicator of its performance. Back Propagation (BP) neural networks are widely used in the study of microwave radiometer inversion problems. However, the BP network which is carried by the radiometer inversion suffers from profile data collapse. To address this, this study introduced a residual network to improve the accuracy of water vapor vertical profiles. Aiming at the problem of large inversion temperature error due to the effect of turbulence on the light-travel phase induced by stationary fronts along the seashore in the subtropical monsoon climate region, we used historical data to establish the seasonal a priori mean profile and design a dead-zone residual adjustment model. The accuracy of the residual network and the deadband-adjusted residual network was verified using the meteorological records of the Taizhou region from 2013–2018, with the experimental data and BP hierarchical network as the comparison term. We found no data collapse in the temperature and humidity profile inversion results of the residual network. Relative to the initial BP hierarchical algorithm, where the error of water vapor in the range 6–10 km was reduced by 80%, the dead zone residual adjustment model in the inverse-temperature phenomenon reduced the sum of squares error by 21%, compared with the ordinary residual network inversion results. Our findings provide new insights into the accuracy improvement of radiometer remote sensing.

Surface Runoff and Diffuse Nitrogen Loss Dynamics in a Mixed Land Use Watershed with a Subtropical Monsoon Climate

The surface hydrology and diffuse pollution loading is hypothesized based on the unique characteristics under different rainfall types in watersheds with a subtropical monsoon climate. This study evaluated the effects of different rainfall event intensity on surface runoff and diffuse nitrogen loss in a subtropical watershed located in the latitude range between 22.5° north and 25° north in southern China by adapting the hydrological model SWAT (Soil and Water Assessment Tool). The rainfall events were classified into four categories including light rainfall (LR), moderate rainfall (MR), intense rainfall (IR), and extreme rainfall (ER). Our results showed that the ER events had the lowest occurrences of 7 days per year, but they contributed the most to total surface runoff (54.29%) and TN losses (57.63%) in the subtropical watershed researched. Although forests and pastures had a better effect on reducing diffuse pollution, their surface runoff and nitrogen loss were still proved to be serious under ER events. As for the nitrogen loss form, water-soluble nitrogen oxides nitrogen (ON-N) loss was the dominant form of total nitrogen (TN) loss, which accounted for 90% of the total loss in the simulated watershed in the subtropical monsoon climate region. Under LR events, however, nitrate nitrogen (NO3-N) accounted for 74.54% and 55.59% of TN losses from paddy fields and dry lands, respectively. The effects of antecedent soil water content (ASW) on surface runoff and TN loss were higher under ER events. The surface runoff and TN loss in the high-ASW condition were 1.17–3.86 times and 1.34–1.76 times higher, respectively, than in the low-ASW condition. These findings highlighted the important influence of ER events on diffuse pollution and have significant implications for controlling diffuse pollution under different rainfall types. This conclusion proved that extra attention and efforts are required in handling non-point-source pollution in subtropical monsoon watersheds than the watersheds in cooler regions because the natural systems including forest and pastures are no longer effective enough in controlling surface runoff and TN loss during ER.

Excessive use of chemical fertilizers in catchment areas raises the seasonal pH in natural freshwater lakes of the subtropical monsoon climate region

In recent years, the pH of some oligotrophic natural freshwater lakes in the subtropical monsoon climate region has generally reached an extremely high level of approximately 9.0 during the summer and autumn. It has not been proven that the explanation for why carbon assimilation in productive lakes exceeds carbon supply and causes a rise in pH also applies to oligotrophic freshwater lakes. Regardless, this may have been caused by changes in the solute composition of inflowing rivers as a result of changes in land use in catchment areas. Beimiao Reservoir in Baoshan City, Yunnan Province, where pH has increased significantly in summer and fall over the past few years, was chosen for this research in order to verify this hypothesis. This paper evaluates the status quo of water quality and nutrition in this reservoir. In addition, this paper analyzes the effects of water temperature, the metabolism of aquatic organisms, and river input on the horizontal and vertical spatial differences, diurnal variations, seasonal changes, and annual changes in the pH of the reservoir. It was discovered that one of the primary causes of the pH increase in natural freshwater lakes in the subtropical monsoon climate region during summer and autumn can be summarized as follows: A large amount of nitric acid and sulfuric acid are produced in the soil when chemical fertilizers are overused in runoff areas, particularly during intensive horticultural crop cultivation. Therefore, the subtropical monsoon climate region's soil loses calcium and magnesium ions, whose combined equivalent concentrations significantly exceed those of bicarbonate ions. The combined equivalent concentrations of calcium ions and magnesium ions in the inflowing rivers in summer and autumn are also significantly higher than those in the lake, resulting in the depletion of free carbon dioxide caused by calcium carbonate precipitation and an increase in pH. The conclusion of this research casts new light on the preservation and treatment of the ecological environment of lake water with similar issues.

Performance of the WRF model in simulating convective rainfall events in the humid subtropical monsoon climate region—Poyang Lake basin

Performance of the WRF model in simulating convective rainfall events in the humid subtropical monsoon climate region—Poyang Lake basin

Effect of replacing synthetic nitrogen fertilizer with animal manure on grain yield and nitrogen use efficiency in China: a meta-analysis.

To reduce reliance on synthetic nitrogen (N) fertilizer and sustain food production, replacing synthetic N fertilizer with animal manure as an effective method is widely used. However, the effects of replacing synthetic N fertilizer with animal manure on crop yield and nitrogen use efficiency (NUE) remain uncertain under varying fertilization management practices, climate conditions, and soil properties. Here, we performed a meta-analysis of wheat (Triticum aestivum L.), maize (Zea mays L.), and rice (Oryza sativa L.) based on 118 published studies conducted in China. Overall, the results indicated that substituting synthetic N fertilizer with manure increased yield by 3.3%-3.9% for the three grain crops and increased NUE by 6.3%-10.0%. Crop yields and NUE did not significantly increase at a low N application rate (≤120 kg ha-1) or high substitution rate (>60%). Yields and NUE values had higher increases for upland crops (wheat and maize) in temperate monsoon climate/temperate continental climate regions with less average annual rainfall (AAR) and lower mean annual temperature (MAT), while rice had higher increases in subtropical monsoon climate regions with more AAR and higher MAT. The effect of manure substitution was better in soil with low organic matter and available phosphorus. Our study shows that the optimal substitution rate was 44% and the total N fertilizer input cannot be less than 161kg ha-1 when substituting synthetic N fertilizer with manure. Moreover, site-specific conditions should also be considered.

Quantifying the contributions of climate factors and human activities to variations of net primary productivity in China from 2000 to 2020

Net primary productivity (NPP) plays a vital role in the globe carbon cycle. Quantitative assessment of the effects of climate changes and human activities on net primary productivity dynamics is vital for understanding the driving mechanisms of vegetation change and sustainable development of ecosystems. This study investigates the contributions of climatic factors and human activities to vegetation productivity changes in China from 2000 to 2020 based on the residual trend analysis (RESTREND) method. The results showed that the annual average net primary productivity in China was 325.11 g C/m2/year from 2000 to 2020 and net primary productivity showed a significantly increasing trend (p&amp;lt;0.05) at a rate of 2.32 g C/m2/year. Net primary productivity increased significantly (p&amp;lt;0.05) across 40.90% of China over the study period, while only 1.79% showed a significantly declining trend (p&amp;lt;0.05). The contributions of climatic factors and human activities to net primary productivity increase were 1.169 g C/m2/year and 1.142 g C/m2/year, respectively. Climate factors contributed positively mainly in Sichuan Basin, the Loess Plateau, the Mongolian Plateau, and Northeast China Plain. Positive contributions of human activities to net primary productivity mainly occurred in the Loess Plateau, Central China, and the Greater Khingan Mountains. The effects of climatic factors and human activities on net primary productivity changes varied among sub-regions. In Tropical Monsoon Climate Region and Subtropical Monsoon Climate Region, human activities had greater impacts on net primary productivity increase than climate factors, while climate factors were the dominant factor for net primary productivity recovery in other sub-regions. In addition, during 2000–2020, net primary productivity was dominated by both climate factors and human activities in 49.84% of China, while areas dominated solely by climate factors and human activities accounted for 13.67% and 10.92%, respectively. Compared to changed land cover types, the total net primary productivity as well as the increase of total net primary productivity in China was mostly contributed by unchanged land cover types, which contributed more than 90%.

秸秆还田对中国农田土壤节肢动物数量及多样性影响的整合分析

PDF HTML阅读 XML下载 导出引用 引用提醒 秸秆还田对中国农田土壤节肢动物数量及多样性影响的整合分析 DOI: 10.5846/stxb202111053105 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 江苏省自然科学基金项目（BK20200552）；国家自然科学基金项目（32001181）；江苏省博士后基金项目（2020Z201）；南京农业大学中央高校基本业务费项目（KJQN202113） Impacts of straw returning on the number and diversity of soil arthropods in China: A meta-analysis Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:秸秆还田是提高土壤生物数量和多样性的有效手段，但土壤节肢动物对秸秆还田的响应尚未明确。搜集2005到2020年国内有关秸秆还田对农田土壤节肢动物数量及多样性影响的25篇田间试验文献，分别获得230对土壤节肢动物数量数据和112对土壤节肢动物多样性数据，并采用整合分析方法探究不同气候类型、土层深度、种植制度、秸秆还田量、还田方式及还田时间下秸秆还田对农田土壤节肢动物数量及多样性的影响。结果表明，与不还田相比，秸秆还田总体上显著增加了农田土壤节肢动物的数量，但在亚热带季风气候区或还田时间大于5 a时，秸秆还田对节肢动物数量的增加效应则不显著；此外，秸秆还田对土壤节肢动物数量的促进作用还受到节肢动物体型的影响，秸秆还田显著增加土壤中小型节肢动物的数量，特别是蜱螨目类土壤节肢动物，但是对大型土壤节肢动物的促进作用并不显著。秸秆还田总体上也提高了农田土壤节肢动物的多样性，特别是在温带季风气候、年均温小于5℃、年均降水量小于600 mm、秸秆还田量大于10000 kg/hm2、轮作以及还田时间大于5 a这些条件下，秸秆还田能显著提高土壤节肢动物的多样性。回归分析结果显示随着秸秆还田时间的增加，土壤节肢动物数量的增加率显著降低，而随着秸秆还田量的增加，节肢动物数量的增加率则显著升高；节肢动物多样性的增加率随着年均降水量的增加显著降低，而随着秸秆还田时间和还田量的增加显著升高。以上结果表明，秸秆还田有助于提高农田土壤节肢动物的数量和多样性，但此效应会受到气候因子及农田管理方式的影响。 Abstract:Straw returning is an effective way to enhance the number and diversity of soil organisms, but the responses of soil arthropods to straw returning are still unclear. In this study, we conducted a meta-analysis involving 230 comparisons of soil arthropod number and 112 comparisons of soil arthropod diversity collected from 25 related literatures during 2005-2020. The objectives of this study are to assess the effects of straw returning on the number and diversity of soil arthropods in agroecosystems of China, as well as the variation of these effects under different climates, soil depths, cropping systems, straw returning amounts, straw returning methods and time. The results showed that straw returning significantly increased the number of soil arthropods compared with no straw returning, except the studies conducted at subtropical monsoon climate regions, or the time of straw returning was more than 5 a. In addition, the promotional effect of straw returning on soil arthropod number was also affected by the size of arthropods, with straw returning significantly increasing the number of small and medium-sized soil arthropods, especially acari, rather than large soil arthropods. Straw returning also had a tendency to increase the diversity of soil arthropods, and this effect was significant under the conditions of temperate monsoon climates, mean annual temperature less than 5℃, mean annual precipitation less than 600 mm, rotation cropping, amount of straw returning more than 10000 kg/hm2 and straw returning time more than 5 a. The regression analysis showed that the increased rate of soil arthropod number under straw returning significantly decreased with straw returning time, but it significantly increased with straw returning amount; the increased rate of soil arthropod diversity under straw returning decreased significantly with mean annual precipitation, but it significantly increased with straw returning amount and time. Together, these results indicated that straw returning could improve the number and diversity of soil arthropods, which could be affected by climate factors and agricultural managements. 参考文献 相似文献 引证文献

On the Use of Recycled Asphalt and Trinidad Lake Asphalt (TLA) for the Preparation of High Modulus Asphalt Concrete

Rutting of asphalt pavement occurs earlier and is more serious under the increasingly heavy traffic load conditions that can be found in subtropical monsoon climate regions. High modulus asphalt concrete (HMAC) with excellent anti-rutting and anti-fatigue properties is generally used to mitigate this issue. Given the relatively high cost of the additives used in this type of asphalt, in this study the feasibility of using recycled asphalt mixture (RAP) and Trinidad lake asphalt (TLA) for the preparation of HMAC is considered. The mineral composition of the RAP is first analyzed, then the TLA modified asphalt with different levels of RAP content is used to assess the effect of RAP on the performance of the mixture. Finally, the high-temperature rheological properties of extracted bitumen and the adhesion characteristic between mineral and bitumen are analyzed. The results show that after RAP combustion, the yellowish and greyish minerals display different alkalinity values, while the greyish mineral exhibits an improved ability to combine with bitumen. Thus, RAP can significantly enhance the high-temperature rutting resistance of TLA modified asphalt mixtures. The aged bitumen in RAP makes the mixed binder harder and improves its rheological properties at high temperatures.

Highway performance prediction model of International Roughness Index based on panel data analysis in subtropical monsoon climate

Pavement performance prediction is the crucial basis for decision-making of Pavement Management Systems (PMS). Pavement roughness is not only related to safety and comfort but also a vital index to evaluate highway performance. Therefore, it is of great significance to develop a prediction model for pavement roughness. The International Roughness Index (IRI) is the most commonly used index to represent pavement roughness in the worldwide. Many deterministic models based on time series data have been developed, but there are still few researches based on panel data to study IRI. This paper aims to investigate the rich information of panel data and develop a prediction model of IRI for semi-rigid asphalt pavements in subtropical monsoon climate. With the data from the PMS of Guizhou Province, the data matrix was built from 2017 to 2020. For the independent variables, the internal and external factors affecting IRI were considered, including climate, road age, traffic, and pavement structure. The random-effects model was employed for panel data analysis and the obtained model yielded a coefficient of determination (R2) value of 0.8858. This model can be applied to the highways which are designed, constructed, and qualified under the same standard and are located in the subtropical monsoon climate region. The predicted values in 2021 were compared with the measured values of highways in Guizhou Province. The average error is 12.7%. It shows that the model has better prediction accuracy and generalization performance with good robustness to the interference of geographic region and climate.

Optimizing Water and Nitrogen Management for Green Pepper (Capsicum annuum L.) under Drip Irrigation in Sub-Tropical Monsoon Climate Regions

Green pepper (Capsicum annuum L.) is one of the major vegetables cultivated in sub-tropical monsoon climate regions. However, with the unreasonable use of water and nitrogen (N) fertilizer, efficient water and N fertilizer management systems need to be identified. The goal of this project was to investigate the coupling effects of different amounts of water and N on green pepper yield, water use efficiency (WUE), as well as N use efficiency (NUE) in sub-tropical monsoon climate regions. The optimum combination of water and N inputs was determined for multi-objective optimization through the multiple regression analysis and the combinations of likelihood functions. The pot experiment was conducted during the green pepper growing seasons (May–September) of 2019 and 2020 in a greenhouse at Nanchang, Jiangxi of China that included three water deficit levels, i.e., mild deficit (W1: 95~80%θFC, %θ field capacity simplified as %θFC), moderate deficit (W2: 80~65%θFC), and severe deficit (W3: 65~50%θFC), and four levels of nitrogen application (Napp) rate, i.e., 6.0 (N1), 3.0 (N2), 1.5 (N3), and 0.0 g plant−1 (N4), for a total of twelve treatments (i.e., 3 × 4) with six replications. Results show that water levels have an extremely significant effect (p &lt; 0.01) on green pepper yield and WUE, but no effect on NUE (p &gt; 0.05). N treatments have significant effects on green pepper yield, WUE, and NUE. Meanwhile, the effects of water levels and N treatment interaction on WUE and NUE were extremely significant (p &lt; 0.01), but varied on yield between the two years. The maximum yields (576.26 and 619.00 g plant−1) occurred when the water level and Napp rate were 80~65%θFC and 6.0 g plant−1. While the water level and Napp rate were 80~65%θFC and 3.0 g plant−1, the WUEs and NUEs reached the maximum, which were 20.14 and 17.71 g L−1, 76.54, and 77.73 g−1 in 2019 and 2020. The dualistic and quadric regression equations of irrigation amount and Napp rate indicated that the yield, WUE and NUE cannot reach the maximum at the same time. By establishing a multiobjective optimization model using combinations of likelihood functions, it was concluded that the water level shall be controlled in 80~65%θFC and the Napp rate is 3.78 g plant−1, which can be used as the suitable strategy of water and N management for the maximum comprehensive benefits of yield, WUE, and NUE for green pepper. The obtained optimum combination of water and N inputs can provide a scientific basis for irrigation and fertilization optimization and management in sub-tropical monsoon climate regions.

Water Uptake Pattern by Coniferous Forests in Two Habitats Linked to Precipitation Changes in Subtropical Monsoon Climate Region, China

Variations in precipitation patterns under climate changes influence water availability, which has important implications for plants’ water use and the sustainability of vegetation. However, the water uptake patterns of the main forest species under different temporal spatial conditions of water availability remain poorly understood, especially in areas of high temporal spatial heterogeneity, such as the subtropical monsoon climate region of China. We investigated the water uptake patterns and physiological factors of the most widespread and coniferous forest species, Cunninghamia lanceolata L. and Pinus massoniana L., in the early wet season with short drought (NP), high antecedent precipitation (HP), and low antecedent precipitation (LP), as well as in the early dry season (DP), in edaphic and rocky habitats. The results showed that the two species mainly absorbed soil water from shallow layers, even in the short drought period in the wet season and switched to deeper layers in the early dry season in both habitats. It was noted that the trees utilized deep layers water in edaphic habitats when the antecedent rainfall was high. The two species showed no significant differences in water uptake depth, but exhibited notably distinct leaf water potential behavior. C. lanceolata maintained less negative predawn and midday water potential, whereas P. massoniana showed higher diurnal water potential ranges. Moreover, the water potential of P. massoniana was negatively associated with the antecedent precipitation amount. These results indicate that for co-existing species in these communities, there is significant eco-physiological niche segregation but no eco-hydrological segregation. For tree species in two habitats, the water uptake depth was influenced by the available soil water but the physiological factors were unchanged, and were determined by the species’ genes. Furthermore, during the long drought in the growing season, we observed probable divergent responses of C. lanceolata and P. massoniana, such as growth restriction for the former and hydraulic failure for the latter. However, when the precipitation was heavy and long, these natural species were able to increase the ecohydrological linkages between the ecosystem and the deep-layer system in this edaphic habitat.

Optimizing Shade Cultivation Method and Irrigation Amount to Improve Photosynthetic Characteristics, Bean Yield, and Quality of Coffee in a Subtropical Monsoon Climate.

Reasonable water and light management technology can improve economic benefits, coffee yield, and quality. We used cluster analysis and principal component analysis to evaluate and optimize the water and light management technology with high coffee yield, quality, and economic benefits in a subtropical monsoon climate region of China. The experiment was arranged in a randomized complete block design with two factors (3 irrigation levels × 4 shade cultivation treatments) replicated four times during 2016–2017. The irrigation levels consisted of full irrigation (FI) and two deficit irrigations (DIL: 75% FI, DIS: 50% FI). The shade cultivation treatments consisted of no shade cultivation (S0) and three shade cultivation modes (SL: intercropping with four lines of coffee and one line of banana; SM: intercropping with three lines of coffee and one line of banana; SS: intercropping with two lines of coffee and one line of banana). The results showed that the effects of irrigation level and shade cultivation mode on growth, crop yield, most of the photosynthetic characteristics, and nutritional quality were significant (p < 0.05). Regression analysis showed that the leaf radiation use efficiency (RUE) showed a significant negative exponential relation or logistic-curve variation with photosynthetically active radiation (PAR). The bean yield increased with an increase of the shade degree when water was seriously deficient, whereas it first increased and then decreased with an increase of the shade degree under FI and DIL. Based on both cluster analysis and principal component analysis, the FISS treatment resulted in the highest comprehensive quality of coffee, followed by the FISM treatment; the DISS0 treatment obtained the lowest quality. Compared with the FIS0 treatment, the FISM treatment increased the 2-year average bean yield and net income by 15.0 and 28.5%, respectively, whereas the FISS treatment decreased these by 17.8 and 8.7%, respectively. To summarize, FISS treatment significantly improved the nutritional quality of coffee, and FISM treatment significantly increased the dry bean yield and economic benefits of coffee. The results of the study could provide a theoretical basis for water-saving irrigation and shade cultivation management of coffee in a subtropical monsoon climate region of China.

Spatial variation characteristics of vegetation phenology and its influencing factors in the subtropical monsoon climate region of southern China.

Understanding the response mechanism of ecosystems to climate change and human disturbance can be improved by analyzing the spatial patterns of vegetation phenology and its influencing factors. Because the diverse phenological patterns are impacted by cloud cover contamination issues in the satellite observations, there are few remote sensing phenological research data in subtropical monsoon climate regions. To better understand the horizontal and vertical changes of vegetation phenology in these regions and how it may be affected by climatic factors and topographical features, we first extracted vegetation phenological information (such as start of growth season (SOS), end of growth season (EOS) and length of growth season (LEN)) from a reconstructed MODIS EVI time-series data. We then used geographic detectors to identify the influencing factors of phenology in different elevation zoning areas. We have found that in the Xiangjiang River Basin: 1) gradual changes in the longitudinal or latitudinal gradient of vegetation phenology were not obvious. Instead of horizontal changes, the variation pattern of phenology was similar to the striped river network of the Xiangjiang River. Earlier SOS mainly appeared in the areas far away from the river; later SOS appeared in the midstream and downstream reaches.2) Elevation played an important role in the regional differentiation of phenology. Boundaries at elevations of 320 m and 520 m distinctly separated the region into plain, hilly, and mountain vegetation phenological characteristics. 3) The impacts of climatic factors were quite different in the three vertical zoning areas. Precipitation was the most crucial factor affecting SOS both in plain and mountain areas. There was no significant factor affecting EOS in the plain area, but temperature had an essential effect on EOS in the mountain area. The hilly areas had a concentrated growth period with no significant factors affecting phenology. These findings highlight the importance of elevation in phenology at a watershed scale, enhance our understanding of the impact of climate changes on subtropical ecosystems, and provide a reference for further land-use change monitoring.

Temporal variations and evaporation control effect of the stable isotope composition of precipitation in the subtropical monsoon climate region, Southwest China

Stable hydrogen and oxygen isotopes in precipitation, which are sensitive to climate change and the water cycle, are widely used as natural tracers to investigate hydrological processes and paleoclimate reconstruction. High resolution event-based precipitation sampling was conducted in Guilin, a subtropical monsoon climate region in Southwest China, from 2010 to 2016 to identify the temporal variability of stable isotopes of precipitation and its dominant meteorological factors. The results showed that the stable isotopes of precipitation exhibited significant seasonal variability, with lower values in the wet season and higher values in the dry season, reflecting the changes in the character of precipitation in response to seasonal variability of the moisture sources and atmospheric dynamics. δ18O values were significantly negatively correlated with temperature and potential evapotranspiration (ET0) on the daily and monthly timescales; however, there was no significant correlation between monthly δ18O and the amount of rainfall. Multivariate regression analysis showed that when temperature, precipitation amount and ET0 were considered, 39% of the variability of the monthly oxygen isotope composition of precipitation was explained. Monthly mean temperature had a higher covariation with precipitation δ18O, indicating that the variations of precipitation isotope were more dependent on temperature, but not substantially dependent on the amount effect of rainfall. Howerver, the main influence of meteorological factors on the isotopic variations of precipitation varied seasonally. Temperature strongly influenced the isotopic composition of precipitation in summer, while the amount effect was prominent due to the enhanced convective activity characterized by more depleted δ18O values. Although evapotranspiration is a minor contributor of precipitation isotope variability, the impact of evapotranspiration on the enrichment of precipitation isotopes in autumn is a substantial control and should be considered, which makes a major contribution to compensate for the depletion in heavy isotopes of rainfall. The non-linear relationship between d-excess and ET0 was attributed to the variable contribution of large-scale convective moisture and local evaporation, as well as water vapor transfer processes. The response of precipitation stable isotopes to convective events was characterized by distinct stage patterns, associated with the water vapor sources and physical processes during rainout. The significant depletion of precipitation δ18O values during convective events was not due to the ‘amount effect’, but due to large-scale convection activity. These findings provide further insight into intraevent-scale isotopic variations associated with organized convection and their key influencing factors, which ultimately improves our interpretation of the paleoclimate records in subtropical monsoon regions.

Assessment and calibration of MODIS precipitable water vapor products based on GPS network over China

The ground-based GPS provides a promising way to assess and calibrate precipitable water vapor (PWV) products from the Moderate-Resolution Imaging Spectrometer (MODIS) which has high spatial resolution and near global coverage. This study utilized PWV at about 260 ground-based GPS stations from the Crustal Movement Observation Network of China (CMONOC) from 2015 to 2018 to comprehensively assess the MODIS Near Infrared (NIR) PWV products as well as the latest ECMWF reanalysis, ERA5. Results reveal a general underestimate of MODIS PWV compared to GPS over China, with mean bias of 1.32 mm (GPS-MODIS), compared to −0.28 mm for ERA5 (GPS-ERA5). Taking GPS PWV as references, the average MODIS PWV error root mean square (RMS) is about 5.35 mm, with correlation coefficient (R) of ~90% between GPS and MODIS PWV, compared to the RMS of 1.73 mm and R of ~98% for ERA5. PWV differences between MODIS and GPS also show clear seasonal and climate type dependency over China. A refined linear MODIS PWV calibration model taking into account of climate region difference was then developed and examined. The calibrated MODIS PWV at more than 800 independent GPS stations from China Meteorological Administration (CMA) in the year of 2016 show obvious improvements, with RMS reduced by about 14.7, 17.7, 20.9, 2.5 and 11.3% in tropical monsoon (TM), subtropical monsoon (SM), midlatitude monsoon (MM), humid continental (HC) and plateau (PL) climate region, respectively. Compared to the unified calibration model which does not distinguish the climate regions, the RMS values after calibration using the refined model are reduced by 10.5, 8.3, 9.1, and 11.9% in TM, SM, MM and Plateau climate (PL) region, respectively. In addition, bias values are reduced from 2.01, 3.42, 1.50 and 0.84 mm to 1.64, 0.33, 0.68 and −0.06 mm in TM, SM, MM, PL region, respectively.

Energy Conservation and Consumption Reduction in Residential Quarters: Taking Cuihu Garden Residential District in Pingxiang City as an Example

This paper uses Auto-Revit for an energy assessment of Cuihu Garden Residential District located in Anyuan District, Pingxiang City, Jiangxi Province. Comparative analysis of building energy consumption before and after energy-saving renovation. Through simulation analysis, it can be concluded that replacing LED light sources, enhancing natural ventilation efficiency, and increasing green roof construction can effectively reduce building energy consumption. This article draws the following conclusions: Firstly, by replacing the LED light source, the energy of the residents in the community can be reduced by 65.2%; secondly, the combination of mechanical ventilation and natural shaft ventilation can reduce 73kWh of electricity in ten hours; finally, the green roof energy effectively alleviate temperature changes on the surface of the building, and indirectly reduce the power consumption of heating and air conditioning in the building. The research results can serve as a reference for the improvement of building energy efficiency in cities with subtropical monsoon climate regions represented by Pingxiang City. The direction of energy-saving improvement can be extended to inland small cities in the country and the world.

Evaluation of Different Roof Materials for the Mitigation of Urban Warming in a Subtropical Monsoon Climate

AbstractDifferent roof materials are deployed for mitigating the urban heat, which significantly affects our life. However, the answer to the question of which roof material has the best cooling performance in urban areas remains uncertain. We need to compare different roof materials together under a certain climate condition to find geographically appropriate mitigation strategies. This study performs field experiments using four different roof materials (gray, white, and grass surfaces, and rooftop solar panel) to evaluate their effectiveness on temperature reductions in a subtropical monsoon climate region from December 2017 to July 2018. The results show that the white surface reduced the average daily surface temperature by 3.37 °C. This cooling effect increased with the increase in surface albedo and incoming solar radiation. On the other hand, the average cooling effect of the grass surface was much lower (0.43 °C). This is attributable to the low soil moisture, which was influenced by the monsoon, thereby indicating that the adoption of grass roofs requires consideration of the availability of water resources even in humid regions. The solar panel reduced the daily surface temperature by 0.59 °C but exerted strong warming effect (7.36 °C) during midday and cooling effect (4.03 °C) during midnight because of its low albedo, low emissivity, and low heat capacity. Our results suggest that the grass roof with a native plant species is still not comparable with the white roof for mitigating urban heat in a subtropical monsoon climate under the present climatic conditions and especially for drier climates predicted for the future, and rooftop solar panels may heat the urban atmosphere by their warm surface during daytime.