[目的]现有的作物估产模型通常在灾害气候条件下的估产精度不高,本研究提出一种基于干旱天气指数减产率模型的改进分层线性模型(Improved Hierarchical Linear Model,IHLM),旨在提高在干旱条件下作物产量估算的精度。[方法]采用最大值...[目的]现有的作物估产模型通常在灾害气候条件下的估产精度不高,本研究提出一种基于干旱天气指数减产率模型的改进分层线性模型(Improved Hierarchical Linear Model,IHLM),旨在提高在干旱条件下作物产量估算的精度。[方法]采用最大值的增强植被指数-2(Maximum Enhanced Vegetation Index 2,EVI2max)和每年3月~5月降水量,辐射量和气温等气象数据和2018—2021年山东省160个农情调查基点的冬小麦实测产量数据构建冬小麦产量预测基础分层线性模型(Hierarchical Linear Model,HLM)。考虑到气象因素的变异程度是影响作物生长的关键障碍因子,首先将气象因子相对性计算进行模型改进,并对改进的HLM模型与随机森林(Random Forest,RF)模型、支持向量回归(Support Vector Regression,SVR)模型和极端梯度提升(Extreme Gradient Boosting,XGBOOST)模型进行精度对比。然后引入农业保险行业的干旱天气指数减产率模型,对改进的HLM模型进一步优化,从而更加适应干旱条件下的作物估产。为了验证IHLM模型的迁移性,本研究将其应用于河南省进行对比分析,以评估该模型在不同地理和气候条件下的表现。[结果和讨论]基于相对气象因子(Relative Meteorological Factors,rMF)改进的HLM模型精度相比于RF、SVR和XGBOOST更高,验证精度皮尔逊相关系数r为0.76,均方根误差(Root Mean Square Error,RMSE)为0.60 t/hm^(2),归一化均方根误差(Normalized Root Mean Square Error,nRMSE)为11.21%。在干旱条件数据集中,利用冬小麦干旱天气指数和冬小麦减产率的关系对模型进行了改进,改进之后RMSE减少了0.48 t/hm^(2),nRMSE减少了28.64个百分点,提高了IHLM模型在干旱条件下的精度。[结论]该研究对冬小麦产量HLM模型进行改进,提高了模型精度,在干旱情况下模型精度和稳定性有一定提升,相比于RF、SVR、XGBOOST模型,IHLM模型更适合对冬小麦产量预测。展开更多
During the initial impoundment period of a canyon-shaped reservoir,the water body fluctuated violently regarding water level,hydrological condition,and thermal stratification.These variations may alter the structure o...During the initial impoundment period of a canyon-shaped reservoir,the water body fluctuated violently regarding water level,hydrological condition,and thermal stratification.These variations may alter the structure of phytoplankton community,resulting in algal blooms and seriously threatening the ecological security of the reservoir.It is of great significance to understand the continuous changes of phytoplankton in the initial impoundment period for the protection of reservoir water quality.Therefore,a two-year in-situ monitoring study was conducted on water quality and phytoplankton in a representative canyonshaped reservoir named Sanhekou and the interannual changes of phytoplankton community and its response to environmental changes during the initial impoundment period were discussed at taxonomic versus functional classification levels.The results showed that the total nitrogen and permanganate index levels were relatively high in the first year due to rapid water storage and heavy rainfall input,and the more stable hydrological conditions in the second year promoted the increase of algae density and the transformation of community,and the proportion of cyanobacteria increased significantly.The succession order of phytoplankton in the first year of the initial impoundment periodwas Chlorophyta-Bacillariophyta-Chlorophyta,or J/F/X1-P/MP/W1-A/X1/MP,respectively.And the succession order in the second year was Cyanobacteria/Chlorophyta-Bacillariophyta-Chlorophyta,or L_(M)/G/P-P/A/X1-X1/J/G.Water temperature,relativewater column stability,mixing depth,and pHwere crucial factors affecting phytoplankton community succession.This study revealed the interannual succession law and driving factors of phytoplankton in the initial impoundment period and provided an important reference for the operation management and ecological protection of canyon-shaped reservoirs.展开更多
基金supported by the National Key R&D Program of China(No.2022YFC3203602)the Natural Science Foundation of China(No.52370018)+1 种基金Shaanxi Provincial Youth Innovation Team Project(No.22JP040)Shaanxi Provincial Key Scientific and Technological Innovation Team(No.2023-CX-TD-32).
文摘During the initial impoundment period of a canyon-shaped reservoir,the water body fluctuated violently regarding water level,hydrological condition,and thermal stratification.These variations may alter the structure of phytoplankton community,resulting in algal blooms and seriously threatening the ecological security of the reservoir.It is of great significance to understand the continuous changes of phytoplankton in the initial impoundment period for the protection of reservoir water quality.Therefore,a two-year in-situ monitoring study was conducted on water quality and phytoplankton in a representative canyonshaped reservoir named Sanhekou and the interannual changes of phytoplankton community and its response to environmental changes during the initial impoundment period were discussed at taxonomic versus functional classification levels.The results showed that the total nitrogen and permanganate index levels were relatively high in the first year due to rapid water storage and heavy rainfall input,and the more stable hydrological conditions in the second year promoted the increase of algae density and the transformation of community,and the proportion of cyanobacteria increased significantly.The succession order of phytoplankton in the first year of the initial impoundment periodwas Chlorophyta-Bacillariophyta-Chlorophyta,or J/F/X1-P/MP/W1-A/X1/MP,respectively.And the succession order in the second year was Cyanobacteria/Chlorophyta-Bacillariophyta-Chlorophyta,or L_(M)/G/P-P/A/X1-X1/J/G.Water temperature,relativewater column stability,mixing depth,and pHwere crucial factors affecting phytoplankton community succession.This study revealed the interannual succession law and driving factors of phytoplankton in the initial impoundment period and provided an important reference for the operation management and ecological protection of canyon-shaped reservoirs.
