Seasonal Index Research Articles

Spatio‐temporal rainfall variability and trend analysis in the Tekeze‐Atbara river basin, northwestern Ethiopia

AbstractSpatial and temporal rainfall variability analysis at a basin scale is essential to understand water availability for sustainable water resource management. This study investigated the spatial distribution and temporal rainfall trend in the Tekeze river basin using daily rainfall data collected from 43 meteorological stations with records from 1960 to 2019. Coefficient of variation, seasonality index (SI) and trend index were used to evaluate monthly, seasonal and annual rainfall variability in the basin. The non‐parametric Mann‐Kendall's test was used to understand any rainfall trends. Results showed that there is moderate annual rainfall variability in the basin. Rainfall variability is higher in the Tsedey, Bega and Belg than kiremt season. SI results showed that majority of the Tekeze river basin is categorized as seasonal, most of the rain occurring in less than 3 months. Overall, Mann‐Kendall's test result revealed that there is no significant annual rainfall trend in the basin except for four stations. The seasonal rainfall characteristics and short duration of rain in the basin indicate that there is a need to implement water harvesting measures during the wet season for use in the dry periods.

Flood Season Staging and Adjustment of Limited Water Level for a Multi-Purpose Reservoir

A reasonable flood season delineation can effectively implement staged reservoir scheduling and improve water resource efficiency. Therefore, this study is aimed at analyzing the flood period segmentation and optimizing the staged flood limit water levels (FLWLs) for a multi-purpose reservoir, the Longtan Reservoir, China. The rainfall seasonality index (SIP) and the runoff seasonality index (SIR) are used to evaluate the feasibility and rationality of the flood period staging. The fractal method is then used to segment the flood season. Finally, the design flood is carried out to optimize the staged FLWLs. The results show that the SI is an effective indicator for judging the feasibility and verifying the rationality of flood segmentation. The flood period can be segmented into the pre-flood season (12 April–29 May), the main flood season (30 May–3 September), and the post-flood season (4 September–9 November). The FLWLs in the main flood and the post-flood season can be raised by 2.05 m and 3.45 m, and the effective reservoir capacity is increased by 5.810 billion m3 and 6.337 billion m3, according to the results of the flood season division.

Mangrove Growth Monitoring Based on Camera Visible Images—A Case Study on Typical Mangroves in Guangxi

Mangroves are an important coastal wetland ecosystem, and the high-throughput visible light (RGB) images of the canopy obtained by the ecological meteorological station can provide basic data for quantitative and continuous growth monitoring of mangroves. However, as for the mangroves that are subject to periodic seawater submersion, some key technical issues such as image selection, vegetation segmentation, and index applicability remain unsolved. With the typical mangroves in Beihai, Guangxi, as the object in this study, we used canopy RGB images and tidal data to find out the screening methods for high-quality nontidal submerged images, as well as the vegetation segmentation algorithms and RGB vegetation index applicability, so as to provide technical reference for the use of RGB images to monitor mangrove growth. The results showed that: 1) The critical tide levels can be determined according to the periodic changes of submersion in the mangroves, and critical tidal levels and image brightness can be used to quickly screen high-quality images of mangroves that are not submerged by seawater. 2) Machine learning and NLM filtering are effective strategies to obtain high-precision mangrove segmentation results. The machine learning algorithm has superiority in the segmentation of mangrove vegetation with a segmentation accuracy of higher than 80%, and the nonlocal mean filtering can effectively optimize the segmentation results of various algorithms. 3) The seasonal index VEG and antiseasonal index CIVE can be used as the optimal indices for mangrove growth monitoring, and the compound sine function can better simulate the change trend of various RGB vegetation indices, which is convenient for quickly judging mangrove growth changes. 4) Mangrove RGB vegetation indices are sensitive to meteorological factors and can be used to analyze the influence of meteorological conditions on mangrove growth.

Spatio-temporal assessment of agro[sbnd]climatic indices and the monsoon pattern in the Banas River Basin, India

Climate change has intense environmental and socioeconomic consequences. It is a major challenge for farmers which directly affects the development of agriculture productivity through climatic factors like monsoon variability which is mainly involved in rain-fed agriculture. To analyze climate change in relation to agriculture, a wide variety of agro-climatic indices has been proposed by the scientific community. The trend of agro-climatic indices and changes in monsoon patterns were investigated using historical grid data in the Banas River basin, India. For this study, 43 years of gridded historical datasets of temperature and precipitation were collected from the India Meteorological Department (IMD) from 1971 to 2013. For climatic indices, trend analysis and test of significance using the Mann-Kendall method were performed. Rainfall deciles, standard precipitation index (SPI), and reconnaissance drought index (RDI) were analyzed to understand the spatio-temporal changes in the agroclimatic indices in the study basin. The results show that SPI and RDI had significantly decreased, whereas a non-significant rise was observed in the aridity index and the seasonality index. Further, the onset and offset of monsoons were also studied for two different historical periods to understand the changing patterns over the last few decades. It was observed that there is an increase in the monsoon duration in 1996–2013, as compared to the period of 1971–1995. The seasonality index (SI) and aridity index (AI) has increased in the north-eastern and south-western of the river basin in the last 43 years. Overall, it can be concluded from the study that the change in precipitation and temperature has put an impact on agro-climatic indices. Therefore, depending on the future climatic condition, if this trend continues, it can affect the cropping pattern of the region both negatively and positively. The present study can also help in predicting the future aspects and impacts of the changes in agro-climate indices based on past trends.

25(OH)D levels are decreased in patients with difficult-to-treat depression

ObjectivesThe aims of the study are i) to compare 25-hydroxyvitamin D (25(OH)D) levels between clinically depressed individuals with insufficient treatment response and healthy controls and ii) to test the association between 25(OH)D levels and different affective disorder diagnoses (i.e., major depressive disorder (MDD) single episode, MDD recurrent episode, chronic MDD, and dysthymia), as well as grade of suicidal ideation. MethodWe quantified serum 25(OH)D in 202 individuals with difficult-to-treat depression (DTD) and 41 healthy controls. Patients were diagnosed according to the Diagnostic and Statistical Manual of Mental Disorders, 4th Edition (DSM-IV-TR). ANCOVA was used to test differences in mean 25(OH)levels between depressed and controls, adjusting for sex, age, smoking, sampling season, ethnicity, somatic illness, and body mass index (BMI). Binary logistic regression models were used to test the association between depression and 25(OH)D levels. ResultsPatients with difficult-to-treat depression had significantly lower levels of 25(OH)D compared to healthy controls (ANCOVA, F = 4.89; p = 0.03). Thirty percent of the depressed patients were 25(OH)D deficient (<50 nmol/L) compared to 5% of the controls (Chi-squared test, χ2 = 11.38; p < 0.01). The odds for being depressed decreased significantly with 17% per 10 nmol/L increase of 25(OH)D (Binary logistic regression, p < 0.05). LimitationsThe cross-sectional design of the study precludes any conclusions about causality. A large part of the patients took psychotropic drugs and/or had somatic illnesses, which might have affected the results. ConclusionThe results of the present study add to the body of evidence linking 25(OH)D deficiency and depression. Further investigations are warranted to better understand any clinical implications of this association.

Assessment of Seasonal Drought Impact on Potato in the Northern Single Cropping Area of China

Drought is one of the key limiting factors for potato yield in the northern single cropping area (NSCA) in China. To analyze the impact of drought on potato yield in the NSCA, this study first analyzed the variation of dry/wet conditions in the plantable areas on a seasonal scale using the standardized precipitation evapotranspiration index (SPEI). Secondly, the changes in yield structure in the last 36 years were systematically analyzed and divided the total yield change into planting area contribution and climate yield contribution. Finally, a regression model of the seasonal drought index and contributing factors of total yield change in different administrative regions was constructed. The results showed that the main factors affecting the total potato yield of the NSCA began to change from yield to planting area in the 1990s, while the barycenter of the output structure and population moved to the southwest, with grassland being the main source; dry/wet conditions (year i) had varying degrees of effect on contributing factors (year i, year i + 1) of total yield change in different administrative regions that were not limited to the growing season; the non-overlap of high-yield area, high-adaptability area and planting area was the urgent problem to be solved for the NSCA. The results of this study can provide a scientific basis for NSCA crop management and communication with farmers, providing new ideas for sustainable production in other agricultural regions in the world.

Spatiotemporal Characteristics of Droughts and Their Propagation during the Past 67 Years in Northern Thailand

Droughts grow concurrently in space and time; however, their spatiotemporal propagation is still not fully studied. In this study, drought propagation and spatiotemporal characteristics were studied in northern, northeastern, and central Thailand (NNCT). The NNCT is an important agricultural exporter worldwide, and droughts here can lead to considerable pressure on the food supply. This study investigated meteorological drought and soil drought in northern Thailand and identified 70 meteorological drought events and 44 soil drought events over 1948–2014. Severe droughts (droughts with long trivariate return periods) mainly occurred after 1975 and were centered in northern and northeastern Thailand. Meteorological drought and soil drought that occurred during 1979–1980 had the longest trivariate return periods of 157 years and 179 years, respectively. The drought centers were mainly located in the Chao Phraya River basin and the Mun River basin. The mean propagation ratios of all drought parameters (duration, area, severity) were lower than 1, indicating that the underlying surface can serve as a buffer to alleviate water deficits. Most of the probability distribution coefficients and all drought propagation ratios of the three drought parameters were found to change significantly based on a moving-window method, indicating that the drought parameters and propagation from meteorological drought to soil drought were non-stationary. Significant increasing trends were detected in mean values of most drought parameters, ranging from 2.4%/decade to 16.6%/decade. Significant decreasing trends were detected in coefficients of skewness (Cs) of all drought parameters and coefficients of variation (Cv) of most drought parameters, ranging from −3.3 to −12.4%/decade, and from −5.5 to −19.4%/decade, respectively. The propagation ratios of all drought parameters showed significant increasing trends, indicating that the function of the underlying surface as a buffer has become weaker. The drought propagation ratios were found to be positively related to two climate indices, the phase index (PI) and the climate seasonality index (CSI). These findings will help to develop a better understanding and management of water resources in Thailand.

Improvement of Extreme Value Modeling for Extreme Rainfall Using Large-Scale Climate Modes and Considering Model Uncertainty

Extreme value modeling for extreme rainfall is one of the most important processes in the field of hydrology. For the improvement of extreme value modeling and its physical meaning, large-scale climate modes have been widely used as covariates of distribution parameters, as they can physically account for climate variability. This study proposes a novel procedure for extreme value modeling of rainfall based on the significant relationship between the long-term trend of the annual maximum (AM) daily rainfall and large-scale climate indices. This procedure is characterized by two main steps: (a) identifying significant seasonal climate indices (SCIs), which impact the long-term trend of AM daily rainfall using statistical approaches, such as ensemble empirical mode decomposition, and (b) selecting an appropriate generalized extreme value (GEV) distribution among the stationary GEV and nonstationary GEV (NS-GEV) using time and SCIs as covariates by comparing their model fit and uncertainty. Our findings showed significant relationships between the long-term trend of AM daily rainfall over South Korea and SCIs (i.e., the Atlantic Meridional Mode, Atlantic Multidecadal Oscillation in the fall season, and North Atlantic Oscillation in the summer season). In addition, we proposed a model selection procedure considering both the Akaike information criterion and residual bootstrap method to select an appropriate GEV distribution among a total of 59 GEV candidates. As a result, the NS-GEV with SCI covariates generally showed the best performance over South Korea. We expect that this study can contribute to estimating more reliable extreme rainfall quantiles using climate covariates.

Factors Influencing the Seasonal Flux of the Varved Sediments of Kusai Lake on the Northern Tibetan Plateau During the Last ∼2280 years

The varved sediments of Kusai Lake on the northern Tibetan Plateau are rhythmically laminated with the interaction of dark and light layers formed during winter and summer within a year. This provides opportunities to explore the seasonal fluxes of varves and, thus, assess the potential for annual-resolution climate reconstruction. Here, we define a season index (SI) based on the difference in thickness between the light and dark layers, to evaluate the factors influencing the seasonal flux of varved Kusai Lake sediments. A positive SI represents more summer flux, and a negative SI indicates more winter flux. The results showed that the summer flux was higher than the winter flux in most of the last 2280 years. The summer flux had periodicities of approximately 2.3–2.9, 27, and 99 years at the 99% confidence level and approximately 15–16, 36 and 285 years at the 95% confidence level, indicating that summer flux is affected mainly by solar activity (Gleissberg and 350 unnamed cycle) at centennial scales, by the Pacific Decadal Oscillation (Pacific Decadal Oscillation with a period of 15–25 years) at decadal scales, and by the Quasi-biennial Oscillation (Quasi-biennial Oscillation with a period of 2–3 years) at interannual scales. Noticeable increasing spikes of high winter flux corresponded well to lower solar activity and stronger Siberian high pressure (SH). The periods of high and low winter flux are generally related to the negative and positive phases of the North Atlantic Oscillation and Atlantic Multidecadal Oscillation respectively, during the last 1000 years.

The characteristics and trends of Hungarian outpatient antibiotic use (2010–2019)

Prudent antibiotic use is an important tool to preserve their effectiveness as well as reverse and confine antibiotic resistance. To evaluate the trends and characteristics of Hungarian outpatient antibiotic use. Crude, package level antibiotic sales data for the period 2010-2019 were converted into DDD (defined daily dose) and were standardized for 1000 inhabitants and per year (ATC-DDD index, version 2019). Internationally validated drug-specific quality indicators were used to evaluate antibiotic use. The scale of antibiotic use was stagnating with minimal fluctuation (min.: 12.9 DID, max.: 14.7 DID), and with high intra-year seasonality index. The ratio of the consumption of broad to narrow spectrum beta-lactams and macrolides increased gradually from year to year (2010: 13.3 vs. 2019: 71.6) and the relative consumption of fluoroquinolones is still remarkable (2010: 14.3%, 2019: 14.5%). Out of the twelve surveyed drug-specific quality indicators in the first and last year of analysis, we were ranked among the weakest European countries in the case of four and six indicators, respectively. The scale of Hungarian outpatient antibiotic use is not high, in European comperison, but has some reserve capacity for reduction. The pattern of Hungarian antibiotic use is suboptimal and had further decreased quality through the years. Based on the recorded data of antibiotic use and their interpretation, the development of national antibiotic strategy (including both professional and authority interventions) is a pressing moral obligation. Orv Hetil. 2021; 163(4): 140-149.

A background-free phenology index for improved monitoring of vegetation phenology

Accurate monitoring of vegetation phenology (e.g., the start and end of the growing season, SOS and EOS) is helpful for understanding the impacts of climate change on vegetation and the terrestrial carbon cycle. The remote sensing-based vegetation index (e.g., enhanced vegetation index, EVI) and remote sensing-based phenology index (e.g., normalized difference greenness index, NDGI) are the major data sources for phenology monitoring at regional and global scales. However, these remote sensing-based indices are vulnerable to the influences of backgrounds and their variations. As a result, it is difficult to obtain high-precision vegetation phenology by using only the remote sensing-based indices, especially for the EOS. In this study, we developed a background-free phenology index (BFPI) by coupling the remote sensing-based index and the meteorological factor-based normalized growing season index (calculated by the normalized daily minimum temperature, vapor pressure deficit, and photoperiod). The BFPIs (BFPIEVI and BFPINDGI) were constructed as products of the EVI/NDGI and normalized growing season index. The performances of the BFPIs in phenology monitoring were evaluated by using the gross primary production data from 64 carbon flux towers and green chromatic coordinate data from 57 PhenoCam sites in forests and grasslands in the Northern Hemisphere. The results showed that the BFPIs performed better than the remote sensing-based indices in phenology monitoring for both forests and grasslands. The BFPINDGI performed better than the BFPIEVI for SOS monitoring, and the two BFPIs had nearly equal performances for monitoring the EOS of grasslands. For forests, the BFPIEVI performed better than the BFPINDGI in phenology monitoring. Although the performances of the BFPIs were limited for EOS monitoring, the phenology monitoring accuracy based on BFPIs were still obviously higher than that based on the remote sensing indices. Overall, the newly-developed BFPI that integrates biological and meteorological factors not only improved the precision of phenology monitoring, but also provided a new perspective for multisource data-based phenology monitoring.

Temporal distribution patterns of metals in water, sediment, and components of the trophic structure in a tropical coastal lagoon of the Gulf of Mexico.

Trophic transfer and bioaccumulation of trace metals have a profound impact on the structure and function of coastal areas; however, the metal accumulation patterns in detritus-based food webs and the influence of climatic variability have not been thoroughly investigated. The Tampamachoco Lagoon (Gulf of Mexico) is a coastal system impacted by emissions from a thermoelectric plant. We evaluated the spatial-temporal distribution patterns of Al, Cd, Hg, Cr, Cu, and Pb in water, sediments, and in organisms categorized by trophic levels (TLs), trophic guilds, and habitat preferences. The sediments had the highest concentrations of metals with no significant differences between seasons. The indices of geo-accumulation and potential ecological risk classified sediments as "moderately contaminated", evidencing a threat to human health through consumption of detritivores and filter-feeders. The lowest TLs (filter-feeders and detritivorous) reached the maximum Metal Pollution Index in the rainy season. According to discriminant analyses of metals and species, omnivorous and zoobentivorous organisms were associated with Hg during the rainy and dry seasons; while Al, Cd, and Cu were related to low TLs, and seston was associated with Pb. Food web magnification factor analysis showed that: (a) Pb, Cu, and Cr were biodiluted as trophic levels increased; (b) Cd and Hg showed temporal biomagnification trends; (c) Al, Pb, Cu, and Cd showed significant biodilution from the lowest TL to intermediate TLs; and (d) Hg was transferred from the lowest to intermediate TLs with clear biomagnification effects.

Seasonality of cruise ship activity in neighboring regions

The continuous growth of the cruise industry has brought with it a series of threats. Among them is the management of the seasonality of cruise activity in order to address its negative effects. This study examines the monthly cruise passenger movement distribution among a group of harbors located in the northeast sector of the Atlantic Ocean and the Baltic Sea with the aim of determining the existence of seasonality patterns in cruise traffic and their relationship between different regions. A database of cruise passenger movements during the period from 2007 to 2019 among 24 harbors forms the backbone of the empirical analysis. First, the seasonal variation index of each harbor was calculated to determine the seasonality pattern. Second, a cluster analysis was performed to classify harbors into clusters with analogous seasonality patterns. The results reveal that seasonality of cruise activity in a consolidated region is explained by own factors of the region, but also by an induced seasonality imported from neighboring cruise regions.

Data mining assessment of Poaceae pollen influencing factors and its environmental implications

Poaceae pollen is highly allergenic, with a marked contribution to the pollen worldwide allergy prevalence. Pollen counts are defined by the species present in the considered area, although year-to-year oscillations may be triggered by different parameters, among which are weather conditions. Due to the predominant role of Poaceae pollen in the allergenicity in urban green areas, the aim of this study was the analysis of pollen trends and the influence of meteorology to forecast relevant variations in airborne pollen levels. The study was carried out during the 1993–2020 period in Ourense, in NW Iberian Peninsula. We used a volumetric Lanzoni VPPS 2000 trap for recording Poaceae airborne pollen grains, and meteorological daily data were obtained from the Galician Institute for Meteorology and Oceanography. The main indexes of the pollen season and their trends were calculated. A correlation analysis and ‘C5.0 Decision Trees and Rule-Based Models’ data mining algorithm were applied to determine the influence of meteorological conditions on pollen levels. We detected atmospheric Poaceae pollen during 139 days on average, mainly from April to August. The mean pollen grains amount recorded during the pollen season was 4608 pollen grains, with the pollen maximum peak of 276 pollen/m3 on 27 June. We found no statistically significant trends and slight slopes for the seasonal indexes, similarly to previous Poaceae studies in the same region. The calculated C5.0 model offered defined results, indicating that the combination of mean temperature above 17.46 °C and sunlight exposure higher than 12.7 h is conductive to significantly high pollen levels. The obtained results make possible the identification of risk moments during the pollen season for the activation of protective measures for sensitized population to grass pollen.

COMPARATIVE ANALYSIS OF THE US IMPORTATION SEASONALITY OF WOODEN MOLDINGS MADE OUT OF BRAZILIAN AND CHILEAN CONIFERS

Conifer wood moldings are classified as high value-added wood products and are used for several purposes in civil construction. Brazil is the world’s leading exporter of this product and the United States are its main destination market. It is very important to analyze the behavior of such importations and exportations to set strategies to obtain or increase the competitive advantage and improve the commercialization of these products. The objective of this study was to analyze the US importation seasonality of conifer wood moldings from Brazil and Chile, the main competitor of the Brazilian product in the US market. To write this paper, monthly data of the quantity of US importations of Brazilian and Chilean moldings from the period of 2011 to 2017 were collected from the database of the United States Department of Agriculture/Foreign Agricultural Service. The methodology proposed by Hoffman (2006) was employed to calculate the seasonal and seasonality indexes. The results indicated that the US importation of conifer wood moldings, both from Brazil and Chile, have a seasonal behavior, with great variation of the seasonal index.

Reduction in Precipitation Seasonality in China from 1960 to 2018

AbstractChanges in precipitation seasonality or the distribution of precipitation have important impacts on hydrological extremes (e.g., floods or droughts). Precipitation extremes have been widely reported to increase with global warming; however, the variability and mechanism of precipitation seasonality have not been well quantified in China. Here, we explore the multiscale variability in precipitation seasonality from 1960 to 2018 in China. A seasonality index of precipitation is defined to quantify the precipitation seasonality with a lower value indicating a more even distribution throughout a year. The seasonality index increases from southeastern to northwestern China, with a decrease in the annual mean precipitation, a later timing of the wet season, and a shorter wet season duration. The seasonality index decreases from 1960 to 2018 in China, accompanied by the increasing duration of wet season, especially in northern climate-sensitive basins, such as the Northwest River, Hai River, and Songliao River basins. In the Northwest River basin, for example, the observed significant decrease in the seasonality index (~0.02 decade−1) from 1960 to 2018 is consistent with a significant decrease in the ratio of annual maximum 10-day precipitation to annual precipitation, which is confirmed by their significant positive correlation (R= 0.72;p= 0). El Niño–Southern Oscillation (ENSO) dominates interannual fluctuations and spatial patterns of precipitation seasonality in China. In El Niño years, the precipitation seasonality index decreases across China except for the Yangtze River basin, with broad increases in annual precipitation.

黄土丘陵区优势造林树种水分来源对季节性干旱的响应

PDF HTML阅读 XML下载 导出引用 引用提醒 黄土丘陵区优势造林树种水分来源对季节性干旱的响应 DOI: 10.5846/stxb202106221657 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 山西省高等学校科技创新（2020L0141，2020L0146）；山西农业大学科技创新基金（博士科研启动）（2020BQ44）；山西省优秀博士来晋工作奖励（SXYBKY2020007） Responses of water source to seasonal drought of dominant afforestation tree species in the loess hilly region of China Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:黄土丘陵区处于季节性干旱生态脆弱地带，探明水分环境变化对区域优势造林树种水分来源的影响，对干旱区植物水分利用及其共生关系具有重要意义。以该地区广泛种植的沙棘（Hippophae rhamnoides）+油松（Pinus tabuliformis）、沙棘（H.rhamnoides）+刺槐（Robinia pseudoacacia）混交林（HrPt，HrRp）及沙棘（Hr）、油松（Pt）和刺槐（Rp）纯林为对象，测定其茎秆水、土壤水和降水稳定同位素组成，采用IsoSource模型量化水分来源，相似性比例指数（PS）定量分析共生植物间水分利用关系。结果表明：（1）旱季，同一树种纯林和混交林间吸水层位存在差异，纯林中主要利用0-100 cm土层土壤水，其中Hr和Rp对40-100 cm的利用率为46.8%和43.8%，Pt对0-40 cm为83.9%；混交林中则更倾向于利用40-200 cm，其中HrPt（沙棘）对100-200 cm为58.8%，HrPt（油松）对40-100 cm为47.4%；HrRp（沙棘）对100-200 cm为58.2%，HrRp（刺槐）对100-200 cm为65.3%。（2）湿润季，纯林和混交林中各树种主要利用0-100 cm土层土壤水，利用率均在70%以上。（3）旱季PS指数显著大于湿润季，且HrRp的PS指数最大，表明沙棘和刺槐之间存在水源竞争现象。综上，相比HrRp，HrPt中共生植物间主要通过水分利用空间上的差异应对季节性干旱，使其组成的生态系统更好地适应区域脆弱的生态环境。研究结果可为区域退化生态恢复与重建及干旱适应性措施体系构建等提供依据。 Abstract:The loess hilly region is located in an ecologically fragile area with seasonal drought. Clarifying the impact of changes in the water environment on the water source of regional dominant afforestation tree species is of great significance to the water use of plants and their symbiosis in arid areas. Therefore, two kinds of mixed forests (Hippophae rhamnoides + Pinus tabuliformis, HtPt, H. rhamnoides+Robinia pseudoacacia, HtRp), the pure forests of H. rhamnoides (Ht), P. tabuliformis (Pt), and R. pseudoacacia (Rp) were selected. The isotope composition of xylem water, soil water and precipitation were determined. The water use and the relationship among symbiotic plants were quantitatively analyzed by using the IsoSource model and the proportional similarity (PS) index. The results indicated that:(1) during the dry season, there were differences in water absorption layer between pure forest and mixed forest of the same tree species. The tree species in the pure forest mainly used soil water in the 0-100 cm. The utilization ratios of Hr and Rp to 40-100 cm were 46.8% and 43.8%, and Pt from 0-40 cm was 83.9%. While, in the mixed forests were more inclined to use 40-200 cm. Among them, the utilization rate of HrPt (H. rhamnoides) from 100-200 cm layer was 58.8%, HrPt (P. tabuliformis) from 40-100 cm was 47.4%. HrRp (H. rhamnoides) and HrRp (R. pseudoacacia) from 100-200 cm were 58.2% and 65.3%, respectively. (2) During the wet season, tree species in pure and mixed forests were mainly use soil water in the 0-100 cm, and the utilization rates was above 70%. (3) The PS index in the dry season was significantly greater than that in the wet season, and in the HrRp was the highest, indicating that there might be water competition between H. rhamnoides and R. pseudoacacia. In summary, compared with HrRp, symbiotic plants in HrPt mainly respond to seasonal droughts through spatial differences in water use, which made it much easier for this ecosystem to be adaptive to the fragile ecological environment in the region. The research results can provide a basis for the restoration and reconstruction of regional degraded ecology and the construction of drought-adaptive measures system. 参考文献 相似文献 引证文献

Water Productivity of Irrigated Tomatoes in Eastern Canada Based on AquaCrop Simulations

HighlightsMeasured field harvest index improved the performance of AquaCrop simulations.Optimal irrigated tomato yield can be achieved by maintaining available soil water depletion below 25%.Water productivity for tomatoes in humid regions can be suitably simulated using AquaCrop.Irrespective of the soil type, the water productivity was highest for fully irrigated fields compared to water limiting irrigated fields.Abstract. Methodologies to predict crop water requirements in arid and semi-arid regions are well known. Humid regions such as eastern Canada pose a challenge because irrigation is normally only required for short periods during the growing season to supplement rainfall. This study assessed the capability of the AquaCrop model to simulate the effects of different irrigation regimes on field-grown tomatoes (Solanum lycopersicum L.) in the humid region of eastern Canada. The experimental study was conducted at the Horticultural Research station of McGill University, Quebec, Canada. There were three irrigation treatments in 2017 and in 2019, that were based on the % depletion of available water content (AWC). The AquaCrop model was calibrated and verified with the 2017 and 2019 field data, respectively. The verified model was used to predict irrigation water requirements and fruit yield for the driest year (1993) and the average rainfall year (2001) of a 35-year historic weather dataset from 1986 to 2000, for three different soil types (silty clay, sandy loam, and heavy clay) under four irrigation regimes. Model performance was greatly improved when the seasonal harvest index (HI) measured from experimental data was used instead of the default model HI values. AquaCrop was suitable for estimating dry yield and total biomass with RMSE = 0.57 ton ha-1 and 0.89 ton ha-1, respectively, in the calibration phase, and RMSE = 0.28 ton ha-1 and 0.01 ton ha-1 for dry yield and total biomass, respectively, in the verification phase. These results indicate a very high accuracy of AquaCrop to estimate total above ground biomass and fruit yield in humid regions with seasonally adjusted HI values. The predictions showed that maintaining AWC depletion below 25% resulted in no significant decrease in crop yield and biomass, making it an optimum water management guideline for irrigated tomato production in Quebec. The findings of this study are useful to crop growers and water resource managers in eastern Canada, who seek better irrigation strategies to optimize productivity. Keywords: AquaCrop, Crop Modeling, Humid climate, Irrigation water requirement, Tomatoes, Yield.

The Recent Droughts of 2019/20 in Southern Africa and Its Teleconnection with ENSO Events

This study is motivated to highlight the variability of recent drought hotspots in the region of southern Africa in terms of the seasonal and annual rainfall regimes and their possible spatial linkage with the 1950-2020 seasonal El Niño/Southern Oscillation (ENSO). Some evidence is found on possible links between the occurrence of drought hotspots in the region in terms of seasonal and mean annual runoff and warm ENSO events. This was revealed by the existence of a strong and nearly-strong positive linear correlation between Seasonal and annual rainfall depths and the warm seasonal ENSO indices explained by the southern oscillation index represented by the sea level pressure (SLP) anomalies data obtained from the National Oceanographic and Aeronautics Administration (NOAA). Considering the entire southern African region, 41% of the surface areas exhibit moderate (r > 0.25) and strong (r > 0.5) correlation coefficients in terms of the December to February quarter rainfall and ENSO indices. Above 50% confidence interval in the correlation between seasonal rainfall and ENSO during DJF quarters is found in 74% of the surface area of the region of southern Africa. The high confidence interval of the positive correlation coefficients is an indication that substantial variance of precipitation during ENSO years is accounted for by the warm ENSO events. The areas with pronounced lower rainfalls and droughts associated with ENSO activity in the region include larger and some pockets of various countries in southern Africa, including but not limited to Angola, Botswana, Lesotho, Namibia, Zambia, Zimbabwe, South Africa and Mozambique. The recent drought events of 2019/2020, and previously in 2015/16 in this region with wider regional impacts can be explained by the ENSO phenomena.

新疆三种独尾草的适宜分布及其对未来气候变化的响应

PDF HTML阅读 XML下载 导出引用 引用提醒 新疆三种独尾草的适宜分布及其对未来气候变化的响应 DOI: 10.5846/stxb202110152910 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（41561007，41261011）；新疆维吾尔自治区草原总站草原生态修复治理补助项目（XJCYZZ202007） Suitable distributions of three species of Eremurus in Xinjiang and their responses to future climatic changes 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:研究国内仅分布于新疆的3种短命植物阿尔泰独尾草（Eremurus altaicus）、粗柄独尾草（Eremurus inderiensis）和异翅独尾草（Eremurus anisopterus）的适宜分布及其对未来气候的可能响应，对新疆短命植物资源的分布、利用与科学保护具有重要意义。共收集了64个自然分布点，筛选了6个气候因子和2个地形因子数据，利用MaxEnt模型和地理信息系统ArcGIS软件模拟了当前气候情景下3种独尾草的生态适宜性，探讨影响3种植物分布的主导因子及其数值范围，预测3种独尾草的适宜分布对未来气候变化（2001-2040年、2041-2080年，基于温室气体中等排放情景：SSP2-4.5共享社会经济路径）的可能响应。结果表明：（1）基准气候下，3种独尾草在新疆的适宜分布存在较大差异：阿尔泰独尾草主要分布于伊犁河谷、天山北麓、阿尔泰山中段和准噶尔西部山地；两种沙生独尾草均分布于天山中段的绿洲-荒漠区过渡带，古尔班通古特沙漠西南部沙地；（2）最干月降水量（1-25mm）主要限制了阿尔泰独尾草的适宜分布；温度季节性变动指数（1150-1672）主要限制了两种沙生独尾草的适宜分布；（3）2001-2040年和2041-2080年，3种独尾草的适宜分布整体均呈缩减趋势：阿尔泰独尾草向天山北麓和准噶尔西部山地略微缩减；粗柄独尾草和异翅独尾草向古尔班通古特沙漠南缘略微缩减。 Abstract:In China,Eremurus altaicus,Eremurus inderiensis and Eremurus anisopterus are only distributed in Xinjiang.It is of great significance to the distribution, utilization and scientific protection of ephemeral plant resources in Xinjiang to study the suitable distributions of Eremurus altaicus, Eremurus inderiensis and Eremurus anisopterus and their possible responses to future climatic changes. A total of 64 natural distribution sites, 6 climate factors and 2 topographic factors were collected in this study. MaxEnt model and ArcGIS software were used to simulate the ecological suitability of the three species of Eremurus under current climate scenario. To investigate the dominant factors influencing the distribution of the three species and their numerical ranges, and to predict the possible responses of the suitable distribution of the three species to future climatic changes (2001-2040、2041-2080,the society is a medium greenhouse gas emission scenario:based on SSP2-4.5 shard socio-economic path).The research results show that:(1) Under the basic climate, there is great differences in the suitable distribution of the three species in Xinjiang:Eremurus altaicus is mainly distributed in Ili River Valley, northern foot of the Tianshan Mountain, middle of the Altai Mountain and the Western Junggar Mountains. Both of psammophytes are distributed in the oasis-desert transition zone in the central Tianshan Mountains and the sandy land in the southwest of Gurbantunggut Desert; (2) The maximum monthly precipitation (1-25mm) mainly limited the suitable distribution of Eremurus altaicus, the temperature seasonal variation index (1150-1672) mainly limited the suitable distribution of Eremurus inderiensis and Eremurus anisopterus; (3) During 2001-2040 and 2041-2080, the suitable distribution of the three species of Eremurus show a decreasing trend as a whole:the Eremurus altaicus is reduced slightly towards the northern foot of the Tianshan Mountain and the Western Junggar Mountains; Eremurus inderiensis and Eremurus anisopterus shrink slightly towards the southern edge of the Gurbantunggut Desert. 参考文献 相似文献 引证文献