Compressing soil structural information into parameterized correlation functions     

Marina V. Karsanina  Efim V. Lavrukhin  Dmitry S. Fomin  Anna V. Yudina  Konstantin N. Abrosimov  Kirill M. Gerke 《European Journal of Soil Science》2021,72(2):561-577

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Prediction of topsoil organic matter and clay content from measurements of spectral reflectance and electrical conductivity     

Niels H Broge  Anton G Thomsen  Mogens H Greve 《Acta Agriculturae Scandinavica, Section B - Plant Soil Science》2013,63(4):232-240

Soil organic matter (SOM) and clay content of a soil characterized as a coarse sandy loam were modelled using hyperspectral reflectance data acquired with a spectrometer and soil electrical conductivity (SEC) data acquired with an EM38 instrument manufactured by Geonics Ltd. The partial least squares (PLS) regression method was applied and the results validated using cross validation. First, the models were calibrated using only spectral reflectance data; then EM38 data were included in the X-matrix of predictors. Although SEC is significantly correlated with clay content, the results showed that EM38 data did not improve model performance for the estimation of soil organic matter content and clay content, despite the fact that EM38 showed significant correlation with clay content.  相似文献   

Indexing Soil Conservation     

《Journal of Sustainable Forestry》2013,32(2):63-85

Abstract

Soil erosion poses economic and environmental concerns in many tropical uplands. Agroforestry has been proposed as a sustainable land use that can mitigate soil erosion and promote the economic welfare of small farmers. To evaluate such claims, we must (a) develop a composite measure of effectiveness, such as a soil conservation index, and (b) define it in terms understood by the farmers who ultimately choose to adopt and implement agroforestry. We construct an empirical soil conservation index as a weighted average of farmer perceptions of four soil attributes and develop a statistical model of soil conservation benefits of agroforestry by using survey data from the Philippines. Accounting for self-selection bias, we evaluate the soil conservation benefits by testing the correlation between the index and the level of agroforestry adoption. Our estimated model shows that agroforestry can generate 15-20 percent soil conservation for the typical small farmer. We offer several methodological, practical, and policy insights. Because many farmers in developing countries face informational and capital constraints, our study suggests that public policies should support smallholder agroforestry, a type of “natural investment” in soil capital, to generate private and public benefits.  相似文献   

杂交稻有序机抛增密减肥处理对产量及肥料偏生产力的影响     

石楠  高志强  胡海燕  陈崇怡  文双雅 《作物杂志》2021,37(5):128-1345

研究全程机械化条件下有序机抛技术增密减肥处理对杂交稻主要生育期地上部干物质积累、肥料偏生产力以及产量的影响。以水稻品种晶两优华占为试验材料,采用有序机抛技术,设置常规密度（D0：16万穴/hm²）、中密度（D1：19万穴/hm²）和高密度（D2：24万穴/hm²）3个移栽密度以及常规施肥处理（N0）和减量施肥处理（N1：常规施肥基础上减肥26.56%）2个施肥水平。结果表明,移栽密度和施肥量对水稻主要生育期地上部干物质积累、肥料偏生产力和产量均存在显著影响;与D0N0处理相比,D2N1处理有利于维持千粒重,协调穗、粒矛盾,且有效提高主要生育期地上部干物质量、肥料利用率（42.44%）及产量（4.47%）。相关分析表明,产量与移栽密度显著相关（r=0.53^*）,说明在减施肥料条件下,移栽密度对产量产生较大影响。在常规施肥基础上减施肥料26.56%,移栽密度24万穴/hm²,能提高水稻产量以及肥料偏生产力,为增密减肥的最佳处理。  相似文献   

基于偏相关分析的区域植被覆盖变化     

李强 《安徽农业科学》2012,40(25):12596-12598,12693

利用西北地区植被数据(GIMMS-NDVI),以绿度变化率和偏相关分析法为基础,分析了西北地区不同生态分区NDVI的年际变化,并研究了植被覆盖变化对气候要素在空间上的响应。结果表明,西北地区的东部和西北部植被覆盖较好,研究区的西部盆地区和西南部的高寒区,植被覆盖较差;不同生态分区NDVI的变化与气温的相关性明显高于与降水的相关性,但降水是限制性因子,决定着ND-VI与降水相关的密切程度;水热条件较好的区域主要分布在西北地区中东部,NDVI与水热要素的相关性由草原、草甸、阔叶林向荒漠逐步减弱,极端干旱荒漠区相关性最小。  相似文献   

基于偏最小二乘回归的黑龙江省大豆生产安全预警分析     

祁雪莲  柏继云  张战国 《安徽农业科学》2012,40(23):11915-11916

为消除先行警兆指标之间的多重相关性,引入偏最小二乘回归方法,建立黑龙江省大豆生产警情指标与滞后若干年的先行警兆指标的模型,利用警兆指标的先行值得到警情指标的未来值,并确定警限进行预警分析。结果表明,与一般的多元回归相比,偏最小二乘回归方法避免了自变量之间多重相关性带来的问题,能够得到与实际经验相符合的模型,保证了预警结果的准确性。  相似文献   

Estimating canopy closure density and above-ground tree biomass using partial least square methods in Chinese boreal forests     

Cheng-liang Lei  Cun-yong Ju  Ti-jiu Cai  Xia Jing  Xiao-hua Wei  Xue-ying Di 《林业研究》2012,23(2):191-196

Boreal forests play an important role in global environment systems. Understanding boreal forest ecosystem structure and function requires accurate monitoring and estimating of forest canopy and biomass. We used partial least square regression (PLSR) models to relate forest parameters, i.e. canopy closure density and above ground tree biomass, to Landsat ETM+ data. The established models were optimized according to the variable importance for projection (VIP) criterion and the bootstrap method, and their performance was compared using several statistical indices. All variables selected by the VIP criterion passed the bootstrap test (p<0.05). The simplified models without insignificant variables (VIP <1) performed as well as the full model but with less computation time. The relative root mean square error (RMSE%) was 29% for canopy closure density, and 58% for above-ground tree biomass. We conclude that PLSR can be an effective method for estimating canopy closure density and above-ground biomass.  相似文献   

Precision Fire Hazard Divisions for Collective Forest in Southern China     

Xu Aijun  Huang Xiaoyin  Jiang Guangyu  Shao Jianlong 《中国林业科技(英文版)》2012,(3):55-56

This paper focuses on how to build the model of precision fire hazard divisions in the level of forest resources sub-compartment.Based on 3D GIS technology and characteristics of forest fires in collective forest of southern China,this study utilized Lin’an City,Zhejiang Province as the experimental area.Forest fire factors were divided into 11 indexes from the three categories(social and economic factors,forestry characteristics,and meteorological characteristics) and weighted for analysis.Next,three eigenvectors(one for each category) were created to build a nonlinear mathematical model called precision fire hazard divisions for forests.Then,the model was used to optimize and test forest fire hazard divisions with the least squares.Results showed that experimental and theoretical values of error were less than 0.1. Thus,in the experimental area this model and the fire occurrence history matched.  相似文献   

A multivariate approach to automatic grading of Pinus sylvestris sawn timber     

《Scandinavian Journal of Forest Research》2012,27(2):167-174

Abstract

The objective of this study was to create an easier way to handle the often complicated and intricate situations with which the operator of an automatic grading system is faced each time a change to the grading rules is proposed. The scope of the study was the possibility of a holistic method of automatic appearance grading of sawn wood similar to manual grading and based on multivariate statistics. The study was based on 90 Scots pine (Pinus sylvestris L.) sawlogs. The logs were sawn and the boards were scanned and manually graded. The result of the manual grading was defined as the true grade. Models for prediction of board grade based on aggregated defect variables were calibrated using partial least squares regression. The classification based on the multivariate models resulted in 80–85% of the boards being correctly graded according to the manual grading. In conclusion, this paper shows that a multivariate statistical approach for grading timber is a possible way to simplify the process of grading and to customize the grading rules when using an automatic grading system.  相似文献   

Chemical characteristics of saponins from Paris fargesii var. brevipetala and cytotoxic activity of its main ingredient, paris saponin H     

Wen F  Yin H  Chen C  Liu X  Xue D  Chen T  He J  Zhang H 《Fitoterapia》2012,83(4):627-635

More attention was paid to the anti-tumor activity of Rhizoma Paridis (RP) recently, of which the wild resource was decreased significantly. This study was aimed to elucidate the chemical characteristics of Paris fargesii var. brevipetala (PFB) that may be administrated as alternate resource of legal RP. A HPLC-ELSD method was established to characterize the steroid saponins in rhizomes of PFB and two legal Paris species [Paris polyphylla var. chinensis (PPC) and P. polyphylla var. yunnanensis (PPY)] in Chinese Pharmacopoeia (CP). Ten saponins (paris saponins I, II, V, VI, VII, H, gracillin and other three paris saponins) were involved as standards. The results indicated that PFB contained pennogenyl saponins as the main components with small amounts of diosgenin saponins. The total contents of the detected saponins in PFB ranged from 9.12mg/g to 85.33mg/g. Nine of the twelve PFB samples own a total content of paris saponins I, II, VI, and VII more than 6.0mg/g (meeting the standard of CP 2010 edition). Principal Component Analysis (PCA) and Partial Least Squares-Discriminate Analysis (PLS-DA) both confirmed the fact that saponin profiles of PFB, PPC and PPY were different from each other. In addition, paris saponin H (Ps H), the predominant saponin of PFB (>50%), was tested in vitro to evaluate its cytotoxic activities on HepG2, A549, RPE and L929 cells with a positive control of Cisplatin. Ps H showed a remarkable cytotoxic activity on A549 cells with an IC(50) value of 1.53±0.08μg/mL.  相似文献