North China Plain(NCP) is the primary winter wheat production region in China, characterized by smallholder farming systems. Whereas the winter wheat average yield of smallholder farmers is currently low, the yield po...North China Plain(NCP) is the primary winter wheat production region in China, characterized by smallholder farming systems. Whereas the winter wheat average yield of smallholder farmers is currently low, the yield potential and limiting factors driving the current yield gap remain unclear. Therefore, increasing the wheat yield in NCP is essential for the national food security. This study monitored wheat yield, management practices and soil nutrient data in 132 farmers’ fields of Xushui County, Baoding City, Hebei Province during 2014–2016. These data were analyzed using variance and path analysis to determine the yield gap and the contribution of yield components(i.e., spikes per hectare, grain number per spike and 1 000-grain weight) to wheat yield. Then, the limiting factors of yield components and the optimizing strategies were identified by a boundary line approach. The results showed that the attainable potential yield for winter wheat was 10 514 kg ha^–1. The yield gaps varied strongly between three yield groups(i.e., high, middle and low), which were divided by yield level and contained 44 farmers in each group, and amounted to 2 493, 1 636 and 814 kg ha^–1, respectively. For the three yield components, only spikes per hectare was significantly different(P<0.01) among the three yield groups. For all 132 farmers’ fields, correlation between yield and spikes per hectare(r=0.51, P<0.01), was significantly positive, while correlations with grain number per spike(r=–0.16) and 1 000-grain weight(r=–0.10) were not significant. The path analysis also showed that the spikes per hectare of winter wheat were the most important component to the wheat yield. Boundary line analysis showed that seeding date was the most limiting factor of spikes per hectare with the highest contribution rate(26.7%), followed by basal N input(22.1%) and seeding rate(14.5%), which indicated that management factors in the seeding step were the most important for affecting spikes per hectare. For desired spikes per hectare(>6.598×10^6 ha^–1),the seeding rate should range from 210–300 kg ha^–1, seeding date should range from 3th to 8th October, and basal N input should range from 90–180 kg ha^–1. Compared to these reasonable ranges of management measures, most of the farmers’ practices were not suitable, and both lower and higher levels of management existed. It is concluded that the strategies for optimizing yield components could be achieved by improving wheat seeding quality and optimizing farmers’ nutrient management practices in the NCP.展开更多
In order to investigate the effect of meteorological factors on the yield and quality of special rice during the filling stage, an experiment was conducted with 10 special rice varieties which were planted in three di...In order to investigate the effect of meteorological factors on the yield and quality of special rice during the filling stage, an experiment was conducted with 10 special rice varieties which were planted in three different regions during spring 2017. The results showed that the quality traits and yields from different regions of the same variety were different, which reached up to a significant level in most varieties. Among the quality traits, the grain chalkiness rate and chalkiness degree were the most sensitive to different climatic factors, and changes were found among them in different regions, while minor variation was found between brown rice rate and white rice rate. The parameters that were severely affected by temperature were gel consistency, gelatinization temperature, brown rice rate and yield during the filling stage. The critically affected factors by heat were brown rice rate, protein content, essential amino acid and amylose content while brown rice rate, chalkiness rate and gelatinization temperature were substantially affected by water factors. Grain yield and quality were closely related to meteorological factors on different stages after heading. Our results revealed that yield and quality of special rice were significantly influenced by meteorological factors during the grain filling stage.展开更多
In recent years, the role of human activities in changing sediment yield has become more apparent for the construction of hydraulic engineering and water conservation projections in the Upper Yangtze River, but it has...In recent years, the role of human activities in changing sediment yield has become more apparent for the construction of hydraulic engineering and water conservation projections in the Upper Yangtze River, but it has not been evaluated at the macro scale. Taking Sichuan Province and Chongqing City as an example, this paper studies the relationship between socio-economic factors and sediment yield in the Upper Yangtze River based on section data in 1989 and 2007. The results show that sediment yield is significantly correlated with population density and cultivated area, in which the former appears to be more closely related to sediment yield. Moreover, in the relation of sediment yield vs. population density, a critical value of population density exists, below which the sediment yield increases with the increase of population density and over which the sediment yield increases with the decrease of population density. The phenomenon essentially reflects the influence of natural factors, such as topography, precipitation and soil property, and some human activities on sediment yield. The region with a higher population density than critical value is located in the east of the study area and is characterized by plains, hills and low mountains, whereas the opposite is located in the west and characterized by middle and high mountains. In the eastern region, more people live on the lands with a low slope where regional soil erosion is slight; therefore, sediment yield is negatively related with population density. In contrast, in the western region, the population tends to aggregate in the areas with abundant soil and water resources which usually lead to a higher intensity of natural erosion, and in turn, high-intensity agricultural practices in these areas may further strengthen local soil erosion. It is also found that population tends to move from the areas with bad environment and high sediment yield to the areas with more comfortable environment and less sediment yield. The natural factors have greater influence on sediment yield of western region than that of eastern region. Generally, the natural factors play a dominant role on sediment yield in the Upper Yangtze River.展开更多
The mechanism of action of ecological factors affecting crop growth and development was complicated. In order to study the relationships between ecological factors and the indexes of yield property equation and determ...The mechanism of action of ecological factors affecting crop growth and development was complicated. In order to study the relationships between ecological factors and the indexes of yield property equation and determine the main ecological factors affecting yield, using 3-yr field experimental results for different yielding spring maize （Zea mays L.） populations and the relative meteorological observation data in Huadian of Jilin Province in China, and analyzing on the base of the yield property equation （MLAI × D × MNAR × HI = EN × GN × GW）, the main ecological factors were screened, and further mechanisms of action affecting yield were analyzed. Stepwise regression analysis showed that yield was affected mainly by effective accumulated temperature, daily mean minimum temperature, daily mean maximum temperature in July, the ratios of growth days, and the sunshine hour before and after silking. In yield property equation, four indexes of MLAI, growth days, ear number and grain number （total grain number） affected principally yield, the ecological factors affecting predominantly yield were effective accumulated temperature, daily mean temperature, daily mean minimum temperature, daily mean maximum temperature in July, the ratios of growth days, rainfall, accumulated temperature, and sunshine hours before and after silking. Combined with the two analytical methods, it could be deduced that the temperature and the allocated ratios before and after silking of ecological factors were the key factors to achieve high yield. Therefore, appropriate sowing data should be adjusted to achieve the suitable temperature indexes during the whole growth stage and the rational allocated ratios of ecological factors before and after silking.展开更多
There are numerous factors which can affect the lymph node(LN) yield in colon cancer specimens.The aim of this paper was to identify both modifiable and nonmodifiable factors that have been demonstrated toaffect colon...There are numerous factors which can affect the lymph node(LN) yield in colon cancer specimens.The aim of this paper was to identify both modifiable and nonmodifiable factors that have been demonstrated toaffect colonic resection specimen LN yield and to summarise the pertinent literature on these topics.A literature review of Pub Med was performed to identify the potential factors which may influence the LN yield in colon cancer resection specimens.The terms used for the search were:LN,lymphadenectomy,LN yield,LN harvest,LN number,colon cancer and colorectal cancer.Both nonmodifiable and modifiable factors were identified.The review identified fifteen non-surgical factors:(13 nonmodifiable,2 modifiable) which may influence LN yield.LN yield is frequently reduced in older,obese patients and those with male sex and increased in patients with right sided,large,and poorly differentiated tumours.Patient ethnicity and lower socioeconomic class may negatively influence LN yield.Pre-operative tumour tattooing appears to increase LN yield.There are many factors that potentially influence the LN yield,although the strength of the association between the two varies greatly.Perfecting oncological resection and pathological analysis remain the cornerstones to achieving good quality and quantity LN yields in patients with colon cancer.展开更多
Effects of environmental factors such as climate,topography,vegetation and soil in shelter forests in Three Gorges Reservoir Region on runoff and sediment yields were monitored to identify dominant environmental facto...Effects of environmental factors such as climate,topography,vegetation and soil in shelter forests in Three Gorges Reservoir Region on runoff and sediment yields were monitored to identify dominant environmental factors controlling runoff and sediment yields in 15 runoff plots in study area by soil sampling,laboratory analysis,stepwise regression analysis and path analysis,and to establish the main control environmental factors that affect runoff and sediment yields. The results showed that soil bulk density,herbaceous cover,slope,and canopy density were the significant factors controlling runoff,and the direct path coefficient of each factor was ranked as canopy closure(-0. 628) > litter thickness(-0. 547) > bulk density( 0. 509) > altitude( 0. 289). The indirect path coefficient was ranked as soil bulk density( 0. 354) >litter thickness(-0. 169) > altitude( 0. 126) > canopy closure(-0. 104). Therefore,canopy closure and litter thickness mainly had direct effects on runoff,while soil bulk density mainly had indirect effects through their contributions to other factors. Herbaceous cover,litter thickness,slope,canopy density,and altitude were the significant factors controlling sediment yields. The direct path coefficient of each factor was ranked as herbaceous cover(-0. 815) > litter thickness(-0. 777) > canopy closure(-0. 624) > slope( 0. 620). The indirect path coefficient was ranked as slope( 0. 272) > litter thickness(-0. 131) > canopy closure(-0. 097) > herbaceous cover(-0. 084). Therefore,herbaceous cover and litter thickness mainly had direct effects on sediment yields,while slope mainly had indirect effects through their contributions to other factors. All the selected environmental factors jointly explained 85. 5% and 78. 3% of runoff and sediment yield variability,respectively. However,there were large values of remaining path coefficients of other factors influencing runoff and sediment yields,which indicated that some important factors are not included and should be taken into account.展开更多
Abiotic stresses like salinity and drought directly affect plant growth and water availability, resulting in lower yield in rice. So, a combination of stress tolerance along with enhanced grain yield is a major focus ...Abiotic stresses like salinity and drought directly affect plant growth and water availability, resulting in lower yield in rice. So, a combination of stress tolerance along with enhanced grain yield is a major focus of rice breeding. It was reported earlier that loss in function of the drought and salt tolerance (DST) gene results in increase in grain production through downregulating Gn1a/OsCKX2 expression. Moreover, dst mutants also showed enhanced drought and salt tolerance in rice by regulating genes involved in ROS homeostasis. In the present study, we proceeded to test these reports by downregulating DST using artificial microRNA technology in the commercial but salt sensitive, high-yielding, BRRIdhan 28 (BR28). This cultivar was transformed with DST_artificial microRNA (DST_amiRNA) driven by the constitutive CaMV35S promoter using tissue culture independent Agrobacterium mediated in planta transformation. DST_amiRNA transgenic plants were confirmed by artificial microRNA specific PCR. Transformed plants at T0 generation showed vigorous growth with significantly longer panicle length and higher primary branching resulting in higher yield, compared to the wild type (WT) BR28. Semi-quantitative RT PCR confirmed the decrease in DST expression in the BR28 transgenic plants compared to WT. T1 transgenic plants also showed improvement in a number of physiological parameters and greater growth compared to WT after 14 days of 120 mM salt (NaCl) stress at seedling stage. Therefore, DST downregulated transgenic plants showed both higher stress tolerance as well as better yields. Furthermore, stable inheritance of the improved phenotype of the DST_amiRNA transgenics will be tested in advanced generations.展开更多
针对青海高原及高寒地区小麦生产氮肥施用量高、温室气体排放量大等问题,探究绿肥不同还田方式及小麦季不同施氮量对小麦农田温室气体排放和产量的影响,为该区小麦可持续生产提供理论依据和技术支撑。试验于2023—2024年在青海大学农林...针对青海高原及高寒地区小麦生产氮肥施用量高、温室气体排放量大等问题,探究绿肥不同还田方式及小麦季不同施氮量对小麦农田温室气体排放和产量的影响,为该区小麦可持续生产提供理论依据和技术支撑。试验于2023—2024年在青海大学农林科学院试验站进行,采用裂区试验设计,主区为小麦季3个施氮水平:常规施氮(225kg hm^(–2), N2)、减施氮肥30%(158 kg hm^(–2), N1)和不施氮(0 kg hm^(–2), N0);裂区基于上一年度绿肥设置3种还田方式:地上部移除仅根茬还田(RR)、地上部过腹联合根茬还田(SDRR)、地上部及根茬全量还田(RROS)。结果表明,减氮30%结合绿肥过腹+根茬还田(N1SDRR)处理显著降低温室气体排放:CO_(2)排放总量较减氮30%全量还田(N1RROS)降低4.2%;N_(2)O排放总量、CH4吸收总量较N1RROS降低19.1%、提升15.8%;全球增温潜势(GWP)较N1RROS降低5.0%。N1SDRR处理小麦籽粒产量较N1RROS提高4.1%,温室气体排放强度(GHGI)较N1RROS降低14.6%,实现减排稳产。此外, N1SDRR处理土壤有机质、铵态氮含量较N1RROS提升9.1%、22.8%,土壤硝态氮含量较N1RROS降低10.0%;土壤蔗糖酶、脲酶活性较N1RROS分别提高3.2%、7.8%,但土壤亚硝酸还原酶、硝酸还原酶活性分别降低11.9%、5.7%,表明该模式通过提升土壤有机质、调控铵/硝态氮平衡同步降低温室气体排放并维持生产力。随机森林模型进一步表明,土壤蔗糖酶、籽粒产量及土壤有机质是调控温室气体排放强度的关键因子,优化施氮与绿肥还田方式会对土壤碳、氮含量产生影响,可显著降低单位产量碳排放。因此,氮肥减施30%结合绿肥地上部过腹联合根茬还田可改善土壤理化因子和酶活性,有效降低温室气体排放,稳定小麦籽粒产量,是青海高原及高寒地区小麦农田稳产减排的适宜管理措施。展开更多
产水量是生态系统服务功能中表征水资源供给能力的指标之一,对生态系统评价具有重要意义。本文采用InVEST模型中Annual Water Yield(年产水量)模块,利用GIS空间分析技术,对泰安市产水量变化规律及其对多源因素(降水量、潜在蒸散量、土...产水量是生态系统服务功能中表征水资源供给能力的指标之一,对生态系统评价具有重要意义。本文采用InVEST模型中Annual Water Yield(年产水量)模块,利用GIS空间分析技术,对泰安市产水量变化规律及其对多源因素(降水量、潜在蒸散量、土地利用类型、净初级生产力、温度)的响应进行研究。研究结果表明:时间上,1990-2022年,泰安市平均产水量为234.92 mm,产水量以2.1 mm/yr的趋势增加,产水量变化主周期为25年,且在2018年存在突变。空间上,泰安市94.1%的地区产水量呈增加趋势,集聚模式为高值集聚;热点多集中于泰安市东部和城区,冷点多集中于西部和山地区。不同土地利用类型的产水能力由强到弱依次为建设用地、草地、耕地、林地、水域。多源因素中,泰安市产水量与降水量呈极强正相关性,且具有极显著性,两者在全时域、全时间尺度下都表现出强相干特征,产水量与潜在蒸散量、净初级生产力及温度相关性较弱。未来变化环境下,随着降水量的增加及城市用地的扩张,产水量呈增加趋势。研究结果对泰安市生态系统评价及水资源时空管理具有一定指导意义。展开更多
为揭示长江中游冬油菜主要气象因子及重要农艺性状对产量形成的影响机制,本研究以北纬30°为界,系统比较分析该纬度线南北两侧冬油菜生态适应性与产量主导因子的异同,旨在为优化区域品种选育与精准栽培管理提供理论依据与实践指导...为揭示长江中游冬油菜主要气象因子及重要农艺性状对产量形成的影响机制,本研究以北纬30°为界,系统比较分析该纬度线南北两侧冬油菜生态适应性与产量主导因子的异同,旨在为优化区域品种选育与精准栽培管理提供理论依据与实践指导。本研究选取2006—2007、2009—2010、2016—2017和2019—2020等4个气候条件差异显著、涵盖典型油菜生长季节气候类型(温暖干燥、偏冷湿润、气候波动强)的年份,作为代表性试验年度,在北纬30°以北与北纬30°以南共6个国家冬油菜区域试验站点,收集全部参试品种的重要农艺性状,并结合气象数据,通过多元统计方法,解析区域气象因子差异及其对产量的影响、重要农艺性状的差异及其与产量的协同关系。结果表明,北纬30°以北地区冬季气温更低、昼夜温差更大、降水量相对较少、日照时数前期较少后期较多;而北纬30°以南地区则相对温暖但后期多雨寡照,两地区气候差异显著。北纬30°以北地区平均产量比北纬30°以南地区高779.1 kg hm^(-2)(P<0.01),北纬30°以北地区单株产量和角果数显著高于北纬30°以南地区,但病害压力较大。逐步回归分析显示,北纬30°以北地区产量主要受4月份降水等因素影响;而北纬30°以南地区则主要受12月份日照时数和3月份降水量影响。北纬30°以北地区产量主要由单株产量和每角粒数直接决定;而北纬30°以南地区则更依赖单株产量与千粒重的协同作用,同时需控制分枝数与千粒重的负向效应。广适性品系0112、9ZYYP27、科乐油4号在南北两区均表现优异;而品系华68P25、渝华7号、越优577等则表现出明显的地域专适性。长江中游北纬30°两侧冬油菜生态区在气候资源、产量构成及主导性状上存在显著分化,区域光温水格局显著影响产量形成机制。北纬30°以北地区应注重苗期光照利用与后期排涝,优选耐渍、抗菌核病强、单株产量高、粒数粒重兼优的品种;北纬30°以南地区则应重视中后期光照利用,注意选育高光效、耐渍、单株产量高、粒数多、含油量高品种。建议构建“广适性+专适性”相结合的区域化品种推广体系,协同推进精准育种与高效栽培,以实现长江中游冬油菜高产、稳产与绿色可持续发展。展开更多
The impact of climate change on agriculture has received wide attention by the scientific community. This paper studies how to assess the grain yield impact of climate change, according to the climate change over a lo...The impact of climate change on agriculture has received wide attention by the scientific community. This paper studies how to assess the grain yield impact of climate change, according to the climate change over a long time period in the future as predicted by a climate system model. The application of the concept of a traditional ＂yield impact of meteorological factor （YIMF）＂ or ＂yield impact of weather factor＂ to the grain yield assessment of a decadal or even a longer timescale would be suffocated at the outset because the YIMF is for studying the phenomenon on an interannual timescale, and it is difficult to distinguish between the trend caused by climate change and the one resulting from changes in non-climatic factors. Therefore, the concept of the yield impact of climatic change （YICC）, which is defined as the difference in the per unit area yields （PUAY） of a grain crop under a changing and an envisaged invariant climate conditions, is presented in this paper to assess the impact of global climate change on grain yields. The climatic factor has been introduced into the renowned economic Cobb-Douglas model, yielding a quantitative assessment method of YICC using real data. The method has been tested using the historical data of Northeast China, and the results show that it has an encouraging application outlook.展开更多
The yield criterion parameters of the soil material change with different values of the cohesion and the angle of friction because of sustained rainfall infiltration. Based on the Mohr-Coulomb(M-C) and Drucker-Prager(...The yield criterion parameters of the soil material change with different values of the cohesion and the angle of friction because of sustained rainfall infiltration. Based on the Mohr-Coulomb(M-C) and Drucker-Prager(D-P) yield criteria, some reasonable yield criteria selections were discussed for quantitative analysis of unsaturated soil slope stability. Moreover, a critical point was found at the effective angle of friction equaling to 16.5° by transformation of parameters related to unsaturated soil under sustained rainfall. When the effective angle of friction more than 16.5° through parameter transformation of different yield criteria under natural condition, the calculation result of the safety factor was such that: f(DP1) > f(M-C) > f(equivalent M-C) > f(DP2) > f(DP3). While the effective angle of friction less than 16.5°, through parameter transformation, the safety factors were in the following order: f(DP1) > f(M-C) > f(DP2) > f(equivalent M-C) > f(DP3). The calculated results from a case study showed that the equivalent M-C yield criterion should be the best at evaluating soil slope stability before rainfall; the DP2 yield criterion should be selected to calculate the soil slope stability at the effective angle of friction less than 16.5° under sustained rainfall. The yield criterion should be selected or adjusted reasonably to calculate the safety factor of unsaturated soil slopes before and during sustained rainfall.展开更多
基金supported by the National Basic Research Program of China (2015CB150405)the Special Fund for Agro-scientific Research in the Public Interest, China (201103003)
文摘North China Plain(NCP) is the primary winter wheat production region in China, characterized by smallholder farming systems. Whereas the winter wheat average yield of smallholder farmers is currently low, the yield potential and limiting factors driving the current yield gap remain unclear. Therefore, increasing the wheat yield in NCP is essential for the national food security. This study monitored wheat yield, management practices and soil nutrient data in 132 farmers’ fields of Xushui County, Baoding City, Hebei Province during 2014–2016. These data were analyzed using variance and path analysis to determine the yield gap and the contribution of yield components(i.e., spikes per hectare, grain number per spike and 1 000-grain weight) to wheat yield. Then, the limiting factors of yield components and the optimizing strategies were identified by a boundary line approach. The results showed that the attainable potential yield for winter wheat was 10 514 kg ha^–1. The yield gaps varied strongly between three yield groups(i.e., high, middle and low), which were divided by yield level and contained 44 farmers in each group, and amounted to 2 493, 1 636 and 814 kg ha^–1, respectively. For the three yield components, only spikes per hectare was significantly different(P<0.01) among the three yield groups. For all 132 farmers’ fields, correlation between yield and spikes per hectare(r=0.51, P<0.01), was significantly positive, while correlations with grain number per spike(r=–0.16) and 1 000-grain weight(r=–0.10) were not significant. The path analysis also showed that the spikes per hectare of winter wheat were the most important component to the wheat yield. Boundary line analysis showed that seeding date was the most limiting factor of spikes per hectare with the highest contribution rate(26.7%), followed by basal N input(22.1%) and seeding rate(14.5%), which indicated that management factors in the seeding step were the most important for affecting spikes per hectare. For desired spikes per hectare(>6.598×10^6 ha^–1),the seeding rate should range from 210–300 kg ha^–1, seeding date should range from 3th to 8th October, and basal N input should range from 90–180 kg ha^–1. Compared to these reasonable ranges of management measures, most of the farmers’ practices were not suitable, and both lower and higher levels of management existed. It is concluded that the strategies for optimizing yield components could be achieved by improving wheat seeding quality and optimizing farmers’ nutrient management practices in the NCP.
文摘In order to investigate the effect of meteorological factors on the yield and quality of special rice during the filling stage, an experiment was conducted with 10 special rice varieties which were planted in three different regions during spring 2017. The results showed that the quality traits and yields from different regions of the same variety were different, which reached up to a significant level in most varieties. Among the quality traits, the grain chalkiness rate and chalkiness degree were the most sensitive to different climatic factors, and changes were found among them in different regions, while minor variation was found between brown rice rate and white rice rate. The parameters that were severely affected by temperature were gel consistency, gelatinization temperature, brown rice rate and yield during the filling stage. The critically affected factors by heat were brown rice rate, protein content, essential amino acid and amylose content while brown rice rate, chalkiness rate and gelatinization temperature were substantially affected by water factors. Grain yield and quality were closely related to meteorological factors on different stages after heading. Our results revealed that yield and quality of special rice were significantly influenced by meteorological factors during the grain filling stage.
基金Commonweal Special Project of the Minislry of Water Resources of China, No.2007SHZ0901034 National Natural Science Foundation of China, No.40971012 Acknowledgements We are grateful to Data Center for Resources and Environmental Sciences of Chinese Academy of Sciences for providing the data of soil and to China Meteorological Administration for providing the data of precipitation.
文摘In recent years, the role of human activities in changing sediment yield has become more apparent for the construction of hydraulic engineering and water conservation projections in the Upper Yangtze River, but it has not been evaluated at the macro scale. Taking Sichuan Province and Chongqing City as an example, this paper studies the relationship between socio-economic factors and sediment yield in the Upper Yangtze River based on section data in 1989 and 2007. The results show that sediment yield is significantly correlated with population density and cultivated area, in which the former appears to be more closely related to sediment yield. Moreover, in the relation of sediment yield vs. population density, a critical value of population density exists, below which the sediment yield increases with the increase of population density and over which the sediment yield increases with the decrease of population density. The phenomenon essentially reflects the influence of natural factors, such as topography, precipitation and soil property, and some human activities on sediment yield. The region with a higher population density than critical value is located in the east of the study area and is characterized by plains, hills and low mountains, whereas the opposite is located in the west and characterized by middle and high mountains. In the eastern region, more people live on the lands with a low slope where regional soil erosion is slight; therefore, sediment yield is negatively related with population density. In contrast, in the western region, the population tends to aggregate in the areas with abundant soil and water resources which usually lead to a higher intensity of natural erosion, and in turn, high-intensity agricultural practices in these areas may further strengthen local soil erosion. It is also found that population tends to move from the areas with bad environment and high sediment yield to the areas with more comfortable environment and less sediment yield. The natural factors have greater influence on sediment yield of western region than that of eastern region. Generally, the natural factors play a dominant role on sediment yield in the Upper Yangtze River.
基金supported by the National High-Tech Research and Development Program of China(2006AA10Z272)the National Basic Research Program of China (2006BAD02A13)
文摘The mechanism of action of ecological factors affecting crop growth and development was complicated. In order to study the relationships between ecological factors and the indexes of yield property equation and determine the main ecological factors affecting yield, using 3-yr field experimental results for different yielding spring maize （Zea mays L.） populations and the relative meteorological observation data in Huadian of Jilin Province in China, and analyzing on the base of the yield property equation （MLAI × D × MNAR × HI = EN × GN × GW）, the main ecological factors were screened, and further mechanisms of action affecting yield were analyzed. Stepwise regression analysis showed that yield was affected mainly by effective accumulated temperature, daily mean minimum temperature, daily mean maximum temperature in July, the ratios of growth days, and the sunshine hour before and after silking. In yield property equation, four indexes of MLAI, growth days, ear number and grain number （total grain number） affected principally yield, the ecological factors affecting predominantly yield were effective accumulated temperature, daily mean temperature, daily mean minimum temperature, daily mean maximum temperature in July, the ratios of growth days, rainfall, accumulated temperature, and sunshine hours before and after silking. Combined with the two analytical methods, it could be deduced that the temperature and the allocated ratios before and after silking of ecological factors were the key factors to achieve high yield. Therefore, appropriate sowing data should be adjusted to achieve the suitable temperature indexes during the whole growth stage and the rational allocated ratios of ecological factors before and after silking.
文摘There are numerous factors which can affect the lymph node(LN) yield in colon cancer specimens.The aim of this paper was to identify both modifiable and nonmodifiable factors that have been demonstrated toaffect colonic resection specimen LN yield and to summarise the pertinent literature on these topics.A literature review of Pub Med was performed to identify the potential factors which may influence the LN yield in colon cancer resection specimens.The terms used for the search were:LN,lymphadenectomy,LN yield,LN harvest,LN number,colon cancer and colorectal cancer.Both nonmodifiable and modifiable factors were identified.The review identified fifteen non-surgical factors:(13 nonmodifiable,2 modifiable) which may influence LN yield.LN yield is frequently reduced in older,obese patients and those with male sex and increased in patients with right sided,large,and poorly differentiated tumours.Patient ethnicity and lower socioeconomic class may negatively influence LN yield.Pre-operative tumour tattooing appears to increase LN yield.There are many factors that potentially influence the LN yield,although the strength of the association between the two varies greatly.Perfecting oncological resection and pathological analysis remain the cornerstones to achieving good quality and quantity LN yields in patients with colon cancer.
基金Supported by National Key Technology Research and Development Program of the Ministry of Science and Technology of China(2015BAD07B04)Key Science and Technology Program of Henan Province,China(152102110059)
文摘Effects of environmental factors such as climate,topography,vegetation and soil in shelter forests in Three Gorges Reservoir Region on runoff and sediment yields were monitored to identify dominant environmental factors controlling runoff and sediment yields in 15 runoff plots in study area by soil sampling,laboratory analysis,stepwise regression analysis and path analysis,and to establish the main control environmental factors that affect runoff and sediment yields. The results showed that soil bulk density,herbaceous cover,slope,and canopy density were the significant factors controlling runoff,and the direct path coefficient of each factor was ranked as canopy closure(-0. 628) > litter thickness(-0. 547) > bulk density( 0. 509) > altitude( 0. 289). The indirect path coefficient was ranked as soil bulk density( 0. 354) >litter thickness(-0. 169) > altitude( 0. 126) > canopy closure(-0. 104). Therefore,canopy closure and litter thickness mainly had direct effects on runoff,while soil bulk density mainly had indirect effects through their contributions to other factors. Herbaceous cover,litter thickness,slope,canopy density,and altitude were the significant factors controlling sediment yields. The direct path coefficient of each factor was ranked as herbaceous cover(-0. 815) > litter thickness(-0. 777) > canopy closure(-0. 624) > slope( 0. 620). The indirect path coefficient was ranked as slope( 0. 272) > litter thickness(-0. 131) > canopy closure(-0. 097) > herbaceous cover(-0. 084). Therefore,herbaceous cover and litter thickness mainly had direct effects on sediment yields,while slope mainly had indirect effects through their contributions to other factors. All the selected environmental factors jointly explained 85. 5% and 78. 3% of runoff and sediment yield variability,respectively. However,there were large values of remaining path coefficients of other factors influencing runoff and sediment yields,which indicated that some important factors are not included and should be taken into account.
文摘Abiotic stresses like salinity and drought directly affect plant growth and water availability, resulting in lower yield in rice. So, a combination of stress tolerance along with enhanced grain yield is a major focus of rice breeding. It was reported earlier that loss in function of the drought and salt tolerance (DST) gene results in increase in grain production through downregulating Gn1a/OsCKX2 expression. Moreover, dst mutants also showed enhanced drought and salt tolerance in rice by regulating genes involved in ROS homeostasis. In the present study, we proceeded to test these reports by downregulating DST using artificial microRNA technology in the commercial but salt sensitive, high-yielding, BRRIdhan 28 (BR28). This cultivar was transformed with DST_artificial microRNA (DST_amiRNA) driven by the constitutive CaMV35S promoter using tissue culture independent Agrobacterium mediated in planta transformation. DST_amiRNA transgenic plants were confirmed by artificial microRNA specific PCR. Transformed plants at T0 generation showed vigorous growth with significantly longer panicle length and higher primary branching resulting in higher yield, compared to the wild type (WT) BR28. Semi-quantitative RT PCR confirmed the decrease in DST expression in the BR28 transgenic plants compared to WT. T1 transgenic plants also showed improvement in a number of physiological parameters and greater growth compared to WT after 14 days of 120 mM salt (NaCl) stress at seedling stage. Therefore, DST downregulated transgenic plants showed both higher stress tolerance as well as better yields. Furthermore, stable inheritance of the improved phenotype of the DST_amiRNA transgenics will be tested in advanced generations.
文摘针对青海高原及高寒地区小麦生产氮肥施用量高、温室气体排放量大等问题,探究绿肥不同还田方式及小麦季不同施氮量对小麦农田温室气体排放和产量的影响,为该区小麦可持续生产提供理论依据和技术支撑。试验于2023—2024年在青海大学农林科学院试验站进行,采用裂区试验设计,主区为小麦季3个施氮水平:常规施氮(225kg hm^(–2), N2)、减施氮肥30%(158 kg hm^(–2), N1)和不施氮(0 kg hm^(–2), N0);裂区基于上一年度绿肥设置3种还田方式:地上部移除仅根茬还田(RR)、地上部过腹联合根茬还田(SDRR)、地上部及根茬全量还田(RROS)。结果表明,减氮30%结合绿肥过腹+根茬还田(N1SDRR)处理显著降低温室气体排放:CO_(2)排放总量较减氮30%全量还田(N1RROS)降低4.2%;N_(2)O排放总量、CH4吸收总量较N1RROS降低19.1%、提升15.8%;全球增温潜势(GWP)较N1RROS降低5.0%。N1SDRR处理小麦籽粒产量较N1RROS提高4.1%,温室气体排放强度(GHGI)较N1RROS降低14.6%,实现减排稳产。此外, N1SDRR处理土壤有机质、铵态氮含量较N1RROS提升9.1%、22.8%,土壤硝态氮含量较N1RROS降低10.0%;土壤蔗糖酶、脲酶活性较N1RROS分别提高3.2%、7.8%,但土壤亚硝酸还原酶、硝酸还原酶活性分别降低11.9%、5.7%,表明该模式通过提升土壤有机质、调控铵/硝态氮平衡同步降低温室气体排放并维持生产力。随机森林模型进一步表明,土壤蔗糖酶、籽粒产量及土壤有机质是调控温室气体排放强度的关键因子,优化施氮与绿肥还田方式会对土壤碳、氮含量产生影响,可显著降低单位产量碳排放。因此,氮肥减施30%结合绿肥地上部过腹联合根茬还田可改善土壤理化因子和酶活性,有效降低温室气体排放,稳定小麦籽粒产量,是青海高原及高寒地区小麦农田稳产减排的适宜管理措施。
文摘产水量是生态系统服务功能中表征水资源供给能力的指标之一,对生态系统评价具有重要意义。本文采用InVEST模型中Annual Water Yield(年产水量)模块,利用GIS空间分析技术,对泰安市产水量变化规律及其对多源因素(降水量、潜在蒸散量、土地利用类型、净初级生产力、温度)的响应进行研究。研究结果表明:时间上,1990-2022年,泰安市平均产水量为234.92 mm,产水量以2.1 mm/yr的趋势增加,产水量变化主周期为25年,且在2018年存在突变。空间上,泰安市94.1%的地区产水量呈增加趋势,集聚模式为高值集聚;热点多集中于泰安市东部和城区,冷点多集中于西部和山地区。不同土地利用类型的产水能力由强到弱依次为建设用地、草地、耕地、林地、水域。多源因素中,泰安市产水量与降水量呈极强正相关性,且具有极显著性,两者在全时域、全时间尺度下都表现出强相干特征,产水量与潜在蒸散量、净初级生产力及温度相关性较弱。未来变化环境下,随着降水量的增加及城市用地的扩张,产水量呈增加趋势。研究结果对泰安市生态系统评价及水资源时空管理具有一定指导意义。
文摘为揭示长江中游冬油菜主要气象因子及重要农艺性状对产量形成的影响机制,本研究以北纬30°为界,系统比较分析该纬度线南北两侧冬油菜生态适应性与产量主导因子的异同,旨在为优化区域品种选育与精准栽培管理提供理论依据与实践指导。本研究选取2006—2007、2009—2010、2016—2017和2019—2020等4个气候条件差异显著、涵盖典型油菜生长季节气候类型(温暖干燥、偏冷湿润、气候波动强)的年份,作为代表性试验年度,在北纬30°以北与北纬30°以南共6个国家冬油菜区域试验站点,收集全部参试品种的重要农艺性状,并结合气象数据,通过多元统计方法,解析区域气象因子差异及其对产量的影响、重要农艺性状的差异及其与产量的协同关系。结果表明,北纬30°以北地区冬季气温更低、昼夜温差更大、降水量相对较少、日照时数前期较少后期较多;而北纬30°以南地区则相对温暖但后期多雨寡照,两地区气候差异显著。北纬30°以北地区平均产量比北纬30°以南地区高779.1 kg hm^(-2)(P<0.01),北纬30°以北地区单株产量和角果数显著高于北纬30°以南地区,但病害压力较大。逐步回归分析显示,北纬30°以北地区产量主要受4月份降水等因素影响;而北纬30°以南地区则主要受12月份日照时数和3月份降水量影响。北纬30°以北地区产量主要由单株产量和每角粒数直接决定;而北纬30°以南地区则更依赖单株产量与千粒重的协同作用,同时需控制分枝数与千粒重的负向效应。广适性品系0112、9ZYYP27、科乐油4号在南北两区均表现优异;而品系华68P25、渝华7号、越优577等则表现出明显的地域专适性。长江中游北纬30°两侧冬油菜生态区在气候资源、产量构成及主导性状上存在显著分化,区域光温水格局显著影响产量形成机制。北纬30°以北地区应注重苗期光照利用与后期排涝,优选耐渍、抗菌核病强、单株产量高、粒数粒重兼优的品种;北纬30°以南地区则应重视中后期光照利用,注意选育高光效、耐渍、单株产量高、粒数多、含油量高品种。建议构建“广适性+专适性”相结合的区域化品种推广体系,协同推进精准育种与高效栽培,以实现长江中游冬油菜高产、稳产与绿色可持续发展。
基金This work was supported by the National Natural Science Foundation of China under Grant No. 40231006 the National Key Program for Developing Basic Sciences under Grant No. 2006CB400503the Knowledge Innovation Project of the Chinese Academy of Science under Grant No. KZCX- SW-218.
文摘The impact of climate change on agriculture has received wide attention by the scientific community. This paper studies how to assess the grain yield impact of climate change, according to the climate change over a long time period in the future as predicted by a climate system model. The application of the concept of a traditional ＂yield impact of meteorological factor （YIMF）＂ or ＂yield impact of weather factor＂ to the grain yield assessment of a decadal or even a longer timescale would be suffocated at the outset because the YIMF is for studying the phenomenon on an interannual timescale, and it is difficult to distinguish between the trend caused by climate change and the one resulting from changes in non-climatic factors. Therefore, the concept of the yield impact of climatic change （YICC）, which is defined as the difference in the per unit area yields （PUAY） of a grain crop under a changing and an envisaged invariant climate conditions, is presented in this paper to assess the impact of global climate change on grain yields. The climatic factor has been introduced into the renowned economic Cobb-Douglas model, yielding a quantitative assessment method of YICC using real data. The method has been tested using the historical data of Northeast China, and the results show that it has an encouraging application outlook.
基金sponsored by the Zhejiang Provincial Natural Science Foundation of China(Grant No.LY13E080008)the Natural Science Foundation of China(Grant No.51108293)the Science and Technology Fund of Yunnan Provincial Communication Department of China(Grant No.2010(A)06-b)
文摘The yield criterion parameters of the soil material change with different values of the cohesion and the angle of friction because of sustained rainfall infiltration. Based on the Mohr-Coulomb(M-C) and Drucker-Prager(D-P) yield criteria, some reasonable yield criteria selections were discussed for quantitative analysis of unsaturated soil slope stability. Moreover, a critical point was found at the effective angle of friction equaling to 16.5° by transformation of parameters related to unsaturated soil under sustained rainfall. When the effective angle of friction more than 16.5° through parameter transformation of different yield criteria under natural condition, the calculation result of the safety factor was such that: f(DP1) > f(M-C) > f(equivalent M-C) > f(DP2) > f(DP3). While the effective angle of friction less than 16.5°, through parameter transformation, the safety factors were in the following order: f(DP1) > f(M-C) > f(DP2) > f(equivalent M-C) > f(DP3). The calculated results from a case study showed that the equivalent M-C yield criterion should be the best at evaluating soil slope stability before rainfall; the DP2 yield criterion should be selected to calculate the soil slope stability at the effective angle of friction less than 16.5° under sustained rainfall. The yield criterion should be selected or adjusted reasonably to calculate the safety factor of unsaturated soil slopes before and during sustained rainfall.
