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1.
为弥补光学遥感在煤矿区资源与生态环境监测中应用的不足, 研究应用全极化SAR图像有效提取煤矿区土地覆盖信息的方法具有重要意义。针对全极化SAR图像极化信息丰富、斑点噪声多、局部异质性大等特点, 提出采用面向对象的影像分类方法对其进行分层土地覆盖信息提取。以徐州市西南部的煤矿区为研究区, 选取Radarsat-2的全极化SAR图像, 分析了研究区内全极化SAR图像中典型地物的灰度特征, 提出面向对象分类方法所涉及的最优分割尺度选择法, 给出全极化SAR图像分割对象后向散射特征的计算方法。对研究区的SAR图像进行试验, 首先对SAR图像进行多尺度分割, 选择各土地覆盖类型的最优分割尺度, 然后在该尺度下计算出土地覆盖类型的后向散射特征指数, 最后采用模糊逻辑分类法分层提取出研究区内的土地覆盖信息。结果表明: 在适于各土地覆盖类型提取的最优分割尺度下, 充分利用分割对象的灰度、形状、纹理以及类间相关特征, 并综合应用隶属函数法和最邻近分类法, 能有效地提取煤矿区的农田、道路、塌陷地、建筑物、山林这5类土地覆盖信息。与最大似然分类法相比, 该方法能够较好地消除"椒盐现象", 各种土地覆盖类型的提取精度都有所提高, 其总体分类精度可提高38.3%。  相似文献   

2.
基于极化分解和集成学习的PolSAR影像分类   总被引:1,自引:1,他引:0  
肖艳  王斌  姜琦刚  闻雅 《农业工程学报》2020,36(16):134-141
为实现Pol SAR数据极化信息的充分利用,以进一步改善分类效果,该研究提出了一种基于极化分解和集成学习的Pol SAR影像分类方法。该方法首先利用多种极化分解方法从Pol SAR影像中提取极化参数;将提取的极化参数组合成一幅多通道影像;然后对多通道影像进行分割和特征提取,分别提取出各目标极化分解方法所对应的特征;并进行特征选择和分类,得到各目标极化分解方法的分类结果;最后利用集成学习技术对各分类结果进行集成。该研究以吉林省长春市部分区域为研究区,Radarsat2影像为数据源,将提出的方法应用于土地覆被分类中,取得了较好的分类效果,总体精度和Kappa系数分别达到了92.49%和0.90。此外,该研究还将提出方法与其他基于多种极化分解的分类方法进行比较,对比方法的总体精度和Kappa系数分别为90.74%和0.88,比提出方法分别低1.75%和0.02,对比结果进一步证明了提出方法的优越性。  相似文献   

3.
及时掌握农作物类型、时空分布和结构信息,是合理调整农业结构的重要科学依据。针对光学遥感依赖于太阳辐射,在农作物生长周期内常受制于云雾的影响而无法获取到光学遥感数据的问题,本文采用全天时全天候、不受云雾等天气影响的合成孔径雷达(synthetic aperture radar,SAR)影像,探讨典型农作物的后向散射特性和纹理特征,为采用合成孔径雷达影像实现高精度农作物大面积监测提供科学依据。以吉林省农安县为例,利用12景Sentinel-1B双极化SAR影像数据,经影像预处理和统计分析,研究不同极化的农作物后向散射特性和纹理信息。结果表明:3种作物(大豆、玉米、水稻1和水稻2)同极化(VV)的SAR后向散射系数在生长周期内均高于交叉极化(VH),农作物植株形态改变极化方式的能力为-25~-15 dB。3种作物在整个生长期内,后向散射系数呈现较大波动,各阶段后向散射特征差异明显。在生长初期,土壤对后向散射特征起主要作用,在SAR图像上表现为暗色调;随着作物生长,冠层散射叠加土壤散射作用占据主要位置,散射值随作物生长呈现逐渐增加的趋势,在SAR图像上表现为亮色调;拔节(分枝)后(7月10日后)作物的后向散射信号除冠层散射作用外,还主要受到土壤含水量及其与作物相互作用的影响,因此拔节后两种水稻后向散射系数下降幅度较大。水稻对雷达波的吸收强于玉米和大豆,整体上后向散射系数第2种水稻<第1种水稻<玉米<大豆,尤其在VH极化方式下表现更明显。对作物SAR纹理信息的研究表明纹理信息的均值、方差和协同性对于农作物的SAR识别更有效,最佳纹理信息为VH极化均值,有利于识别3种作物;VV极化方差和VV协同性有助于区分两种水稻;SAR影像识别作物的最佳时相为5月23日至7月10日。  相似文献   

4.
针对中国北方部分农区夏秋两季易受长时间云、雨、雾影响导致区域农用地信息难以实时准确获取的现状,在Freeman极化分解模型基础上,该文提出了一种三分量极化分解优化模型农用地合成孔径雷达(SAR)影像自动提取方法,并开展不同作物覆盖条件下农用地信息提取试验研究。该文首先通过引入体散射分量参数,二次散射分量参数和布拉格散射分量参数,对现有Freeman极化分解模型进行优化,使分解结果更符合农业区域不同地物散射特征;然后,在利用优化三分量极化分解方法提取极化分量基础上,结合模糊C均值聚类,实现农用地信息高精度自动提取。最后,该研究以中国重要黄淮海农业区河北衡水枣强县为试验区,以Radarsat-2影像为试验数据源,在作物全覆盖和作物部分覆盖2种条件下,通过将优化三分量-FCM分类和常用雷达分类方法 H-Alpha-Lambda分类的农用地提取结果与地面验证样方进行对比,完成该研究所提出SAR影像农用地提取方法的精度验证和评价。结果表明,在作物全覆盖条件下,利用优化三分量-FCM分类提取农用地信息的总体精度和Kappa系数分别为96.12%和0.857,较H-Alpha-Lambda分类方法分别提高了8.69个百分点和0.337;在作物部分覆盖条件下,利用优化三分量-FCM分类提取农用地信息的总体精度和Kappa系数分别为97.53%和0.902,较H-Alpha-Lambda分类分别提高了17.37个百分点和0.595。可见,无论在作物全覆盖还是部分覆盖条件下,优化三分量-FCM分类方法提取的农用地精度均优于H-Alpha-Lambda分类方法,证明了该算法提取农用地信息具有一定可行性和适用性,为SAR影像在农业遥感应用中的农用地信息提取提供了新的思路。  相似文献   

5.
地貌复杂性、地物多样性等特征使得全极化SAR(Synthetic Aperture Radar,SAR)数据的散射机制和散射强度相互交织,从而导致基于传统Wishart-H/α的全极化SAR数据难以实现喀斯特地区土地类型的有效划分。针对此问题,本文先用复Wishart距离测度对研究区土地类型样本进行聚类,同时利用H/α平面对研究区进行超盒聚类,然后根据超盒聚类结果平均相干矩阵与样本聚类结果平均相干矩阵间的复Wishart距离进行半监督分类,获得研究区土地类型划分的初步结果。在此基础上利用对建筑物与裸岩地敏感的极化总功率(Polarimetric-Total-Power,SPAN)和对林地、草地与耕地敏感的归一化植被指数(Normalized Differential Vegetation Index,NDVI)对初步结果继续进行划分,最终将研究区土地类型划分为水体、林地、草地、耕地、建筑地和裸岩地,总体分类精度为81.45%;采用另一地势相对平缓、地形相对单一的典型喀斯特地区全极化SAR数据进行验证,在实现该地区土地类型划分的同时总体分类精度为85.66%。说明gai该研究方法能够实现喀斯特地区土地类型的准确划分。  相似文献   

6.
小麦倒伏的雷达极化特征及其遥感监测   总被引:9,自引:6,他引:3  
研究探索了雷达遥感大面积监测小麦倒伏状况的潜力。利用覆盖整个小麦生育期的5景时间序列Radarsat-2全极化影像数据,对比分析了倒伏小麦与正常小麦在不同时间、不同极化的雷达后向散射动态响应规律,发现雷达极化特征对小麦倒伏十分敏感,基于此提出利用雷达极化指数监测小麦倒伏的方法。并利用内蒙古额尔古纳市上库力农场春小麦抽穗灌浆期的实地调查数据,对提出方法进行验证,结果表明该方法能有效辨识和监测小麦倒伏。为大面积监测小麦倒伏提供了一种简单、快速、有效的手段。  相似文献   

7.
针对无控制点情况下星载SAR地面目标高精度定位问题,提出在整个成像条带中任选一景SAR影像,并基于全球DEM数据生成模拟的SAR影像,然后通过自动或半自动匹配方式寻找一个控制点,修正整个条带的轨道参数,从而消除了系统误差的影响,提高了整个SAR条带影像的定位精度。  相似文献   

8.
利用时序合成孔径雷达数据监测水稻叶面积指数   总被引:2,自引:0,他引:2  
为了确定全极化雷达数据监测水稻叶面积指数动态变化的精度,该文对水稻叶面积指数与后向散射系数进行了各生长阶段建模比较。采用广东雷州地区多时相多入射角精细全极化Radarsat-2数据,结合水稻全生育期地面样方实测数据,首先分析多入射角归一化后四极化(vertical-horizontal polarization,VH;vertical-vertical polarization,VV;horizontal-horizontal polarization,HH;horizontal-vertical polarization,HV)、比值极化HH/VV后向散射系数与水稻叶面积指数(leaf area index,LAI)随时间变化特征以及在营养生长阶段、生殖生长阶段和全生育期的相关关系,提取相关系数高于0.8的极化与生长阶段进行水云模型建模,最终生成多期水稻LAI反演分布图,并验证该数据反演水稻各生长阶段LAI的精度,探索SAR数据追踪区域尺度水稻长势的可行性。结果表明,在地形较为平坦的水稻集中连片种植区,VV、HH/VV后向散射系数与LAI在营养生长期、全生育期极显著相关(P0.01),相关系数均高于0.83。营养生长阶段VV、HH/VV水云模型拟合决定系数分别为0.77、0.87,全生育期VV、HH/VV水云模型拟合决定系数分别为0.73、0.8,营养生长阶段模型优于全生育期模型。精细四极化SAR数据监测区域尺度水稻LAI动态变化具有应用潜力,优选的极化模型为进一步的水稻长势监测提供依据。  相似文献   

9.
基于合成孔径雷达的农作物识别研究进展   总被引:13,自引:8,他引:5  
精准识别农作物对于及时准确估计农作物种植面积、产量等关键农情信息具有重要意义。合成孔径雷达(synthetic aperture radar,SAR)以其不受云雨天气影响,可全天时、全天候监测等优点已被广泛应用于农情遥感监测领域,为大区域尺度的农作物遥感识别提供了强有力的数据保障和技术支持。该文以雷达技术的发展进程为论述主线,对20余年来国内外农作物SAR识别研究与实践应用的新进展进行了系统总结,具体归纳为4个方面:早期研究(20世纪80年代末-2002年),特征是以单波段、单极化、多时相SAR数据为主;基于多极化、多波段SAR数据进行农作物识别与面积监测研究;利用SAR与光学遥感相结合提高农作物的识别精度与效率研究;农作物SAR分类算法研究。在今后农作物SAR识别研究中,对于复杂种植结构背景下的旱地作物识别,如何优化组合SAR系统工作参数(极化方式、频率及入射角等)及与光学遥感融合来提高农作物识别精度与时效性,发展机理性的农作物SAR分类算法将是需要重点解决的3个问题。  相似文献   

10.
土壤盐渍化不仅严重制约着干旱区农业可持续发展,并且对绿洲生态环境构成了重大威胁。该文提出将多种极化目标分解方法、绕封模型(wrapper feature selector, WFS)特征子集选择方法和支持向量机(support vector machine, SVM)结合起来(简称WFS-SVM),利用全极化合成孔径雷达(polarimetric synthetic aperture radar, PolSAR)数据实现对土壤盐渍化监测。以新疆干旱区典型绿洲--渭干河-库车河三角洲绿洲(渭-库绿洲)为研究区,对研究区四极化Radarsat-2数据进行多种极化目标分解处理,得到相应的特征参数和特征分量。采用WFS方法进行SVM最佳特征子集的选择,并选出最佳适应度的子集对 SVM进行训练。从而构建基于最佳特征子集和最优分类参数的WFS-SVM分类模型,对研究区进行不同程度盐渍地信息(包括重度盐渍地和中-轻度盐渍地)的提取,并结合野外实地考察验证数据,将分类结果与经典的Wishart监督分类方法和一般SVM分类方法进行了对比和验证。结果表明,该方法较大程度地提高了全极化PolSAR影像在干旱区盐渍地信息提取的精度,相比Wishart监督分类,该方法分类总精度和Kappa系数分别提高了14.12个百分点和0.18,证明了该文所提出的监测方法具有有效性和研究潜力。该成果也将促进PolSAR数据在干旱区盐渍化监测中发挥更大的作用。  相似文献   

11.
李聃枫  朱春梧 《土壤》2020,52(3):561-566
自20世纪60年代"绿色革命"以来,育种技术和农耕技术的发展促进了农作物产量的大幅提升,然而作物的营养品质出现下降趋势。在相似的遗传背景下,大气CO_2浓度升高会使单位体积农作物产品的营养元素含量下降,因此"绿色革命"至今,农作物产品的营养元素下降可能受大气CO_2浓度升高影响。通过植物生长箱模拟"绿色革命"初期和目前的大气CO_2浓度水平(310μmol/mol和400μmol/mol),针对主要C_3作物水稻、小麦和大豆,研究"绿色革命"以来大气CO_2浓度升高对其籽粒的C、N、Fe、Zn元素含量的影响,结果表明:CO_2浓度升高对3种作物籽粒的C元素含量几乎没有影响,变化幅度在±1.5%之间;籽粒的N、Fe、Zn元素含量普遍呈现下降趋势,但均未达到显著水平。  相似文献   

12.
Discovery and incorporation of genes from wild species provide means to sustain crop improvement, particularly when levels of resistance in the cultigens are low and virulent strains of pests and pathogens overcome the host plant resistance. The extent of utilization and the potential of the wild genepool for genetic enhancement were reviewed in five important food crops viz. sorghum, pearl millet, chickpea, pigeonpea and groundnut grown in the semi-arid tropics. Introgression from compatible wild germplasm in the primary gene pool resulted in transfer of new cytoplasmic male sterility systems in pearl millet and pigeonpea, development of high protein, cleistogamous flower and dwarf pigeonpea lines and foliar disease resistant groundnut cultivars. Utilization of wild species in secondary and tertiary gene pools has been generally limited due to sterility, restricted recombination or cross incompatibility. Nevertheless, these species are extremely important as they contain high levels of resistance to several important biotic and abiotic stresses. Several of them, like those belonging to the Parasorghum section and the rhizomatous Arachis species are sources of multiple resistances and hold great promise to sustain crop productivity.  相似文献   

13.
正The Center for Agricultural Resources Research(CARR),the Institute of Genetics and Developmental Biology(IGDB),Chinese Academy of Sciences,invites applicants for several research group leader positions.CARR is one of the research organizations in Chinese Academy of Sciences(CAS).We seek nominations and applications  相似文献   

14.
Nutrient distributions under no tillage (NT) compared with conventional disk-and-bed tillage (CT) management in the warm, humid region of the southeastern USA need to be assessed so that future placement, quantity, and type of fertilizers can be altered, if necessary, to efficiently match crop demands. We determined soil-profile distributions of pH, N, P, S, K, Ca, Mg, Na, Zn, Fe, Mn, and Cu to a depth of 0.9 m at the end of 8.5 years of continuous CT and NT management on a Weswood silty clay loam (fine, mixed, thermic Fluventic Ustochrept) in southcentral Texas. Most dramatic changes occurred within the 0–0.05 m depth, where soil under NT had lower pH, Fe, and Cu than under CT, but greater P, K, Zn, and Mn. Greater P and K under NT than under CT also occurred below the till-zone (0.15–0.3 m). At a depth of 0–0.3 m, soil under NT contained greater amounts of extractable P, K, Zn, Fe, Mn, and Cu than under CT. Nitrogen fertilization had little effect on nutrient distributions, except resulting in greater extractable K at 0–0.05 m and greater nitrate at 0–0.15 m. Few changes in soil-profile distributions were observed for extractable S, Ca, Mg, and Na. Long-term continuous use of NT on this fine-textured, high-fertility (except for N) soil had no apparent adverse effects on nutrient distributions relative to CT, but enhanced conservation and availability of P, K, Zn, Fe, Mn, and Cu near the soil surface where crop roots proliferate.  相似文献   

15.
“Wicked” problems are those that are complex and that change when solutions are applied. Many conflicts in conservation fall into this category. The study approached the problem of how to constrain the apparent wickedness of a problem in the conservation management of a species by using simple empirical indicators to carry out iterative assessment of the risk to a population and to document how this risk evolves in relation to the addition of new data and the implementation of management actions. Effects of high levels of uncertainty within data and also concerning population structure were examined through stochastic simulation and by exploration of scenarios. Historical trends in the example used, the Steller sea lion, showed rapid declines in abundance in some regions during the 1980s. The current total population is 130,000-150,000 Steller sea lions through Alaska and British Columbia and this number has been stable since about 1990 in spite of regional differences in population dynamics. Regional differences in the sequence of changes in the number of pups and non-pups, suggested that an internal re-distribution of juveniles could have happened between 1980 and 1990. Current productivity also appears close to the long-term mean. Stochastic population projection using various scenarios showed that, based upon this history, the risk of extinction for the population has declined and is below reasonable thresholds for considering the population to be endangered. The trends in risk suggest that management actions taken since 1990 have probably been effective. Consequently, the conservation management objectives for the Steller sea lion are probably being met. The approach provides a mechanism, based upon experience and scenario analysis, for exploring future policy options and may help to constrain the debate amongst stakeholders about the cost-benefit trade-offs associated with different options.  相似文献   

16.
Despite a raising interest on turfs in Italy, all theavailable varieties of this kind in the Country are of foreign origin, and areoften poorly adapted to the prevailing climatic conditions. This prompted tobegin a collection activity of indigenous turfgrass species, with the ultimategoal of identifying promising materials for future breeding based on localgenetic resources. The collection was carried out in three areas of Italy, viz.the northern Po Plain, the coastal region of Liguria, and the island of Sardiniathat are characterised, respectively, by subcontinental, warm temperate, andtypical Mediterranean climate. Altogether, 141 sites were visited, yielding 226accessions belonging to eight species of potential interest for turfs:Poa pratensis, Poa trivialis,Festuca rubra, Festuca arundinacea,Lolium perenne, Agrostis stolonifera,Agrostis tenuis, and Cynodon dactylon,this last being a warm-season grass. Poa pratensis andCynodon dactylon were mostly collected in northern Italyand Sardinia, respectively, whereas Festuca arundinacea andLolium perenne were rather ubiquitous. The collection sitesranged from 0 to 1040 m asl, but sites over 750 m wereonly visited in the inner part of Sardinia. All the accessions, collected aswhole plants, were transplanted at Lodi, northern Italy, where they are beingevaluated. Their preliminary evaluation for traits of importance for turf use,such as sward colour and overall quality, highlighted the great variation andthe occurrence of interesting accessions in all species. Other characters wererecorded, bearing specific importance in individual species, and in all casespromising accessions were identified. The germplasm of Festucarubra, Festuca arundinacea, and Loliumperenne proved highly infected by endophytic (symbiotic) fungi of thegenus Neotyphodium.  相似文献   

17.
To evaluate the feasibility of long-term desert reforestation technology of mixed vegetation, cardon cactus (Pachycereus pringlei) seedlings from indoor and outdoor nurseries were planted in the field adjacent to one seedling of potential legume nurse trees: mesquite amargo (Prosopis articulata), yellow palo verde (Parkinsonia microphylla), and blue palo verde (Parkinsonia florida). Some of the planting holes were also supplemented with common dairy compost. Additionally, the combinations of legume tree–cactus were inoculated with either a consortium of desert arbuscular mycorrhizal (AM) fungi, plant growth promoting bacteria (PGPB; the diazotroph Azospirillum brasilense Cd, and the phosphate solubilizer Paenibacillus sp.), or a mixture of all. The field experiments were evaluated periodically during 30 months for survival and growth. Cardons reared in an outdoor screen house survived better in the field than those reared in a controlled growth chamber and hardened later outdoors. Association with any legume nurse tree increased survival and enhanced growth of untreated cardons. For cardons growing alone, application of either compost, AM fungi, and all the treatments combined increased survival. For these plants, no treatment affected plant growth during the first 3 months after transplanting. Later, all treatments, except for AM fungi, enhanced plant growth. However, only 2 years after transplanting the enhanced growth effect of AM fungi was also significant. In the presence of the legume nurse trees, transient positive effects on cardon growth were recorded. General evaluation after 30 months of cultivation showed that the treatments positively affected cardon growth when growing alone or in combination only with mesquite amargo but not with the other two legume trees. This study proposes that young legume trees have the capacity to enhance survival and growth of cardon cactus, depending on the legume cactus combination. Additional treatments such as compost or PGPB can either amplify the effect or else attenuate it.  相似文献   

18.
Detailed karyotypes and 4C DNA amounts have been studied in five cultivars of Cajanus cajan and 20 species belonging to Cajanus, Rhynchosia, Dunbaria, Flemingia and Paracalyx. C. cajan shows intraspecific variability and its karyotype is most similar to that of C. cajanifolius (sect. Cajanus) in the morphology and number of satellite chromosomes and the lack of any correlation between chromosome size within the complement and asymmetry. Karyotypes of C. lineatus and C. sericeus belonging to sect. Atylia are similar with respect to maximum r-index and the ratio of longest and shortest chromosomes in their respective complements. C. acutifolius (sect. Frutocosa) is distinct in having a very low ratio (1.44) between the longest and the shortest chromosomes, while in C. albicans, C. goensis, C. scarabaeoides (sect. Cantharospermum) there is no chromosome pair with r-index >2.0. C. mollis and C. volubilis (sect. Volubilis) show similarity with regard to ratio between the longest and the shortest chromosomes and a distinct chromosome pair with an arm ratio of 2.7 and C. platycarpus is distinct (sect. Rhynchosoides) in having the smallest ratio (1.36) between the longest and the shortest chromosomes. 4C DNA amounts in Cajanus and Rhynchosia vary between 3.28 pg to 11.69 pg and 4.92 pg to 11.13 pg respectively, while in Dunbaria, Flemingia and Paracalyx these vary between 4.70 and 7:06 pg. In the genus Cajanus karyotypic features and 4C DNA amounts agree with the sectional classification and bring out a close relationship between C. cajan and C. cajanifolius. This is supported by studies based on seed protein patterns, isozyme analysis, trypsin and chymotrypsin inhibitor patterns, RFLP and RAPD data and crossability relationships. A clear relation between DNA amount and abnormalities effecting the extent of pairing and recombination in interspecific hybrids shows the importance of this study in developing future breeding programme involving C. cajan and its wild relatives that are of potential value.  相似文献   

19.
Several commercial fungicide seed treatments were evaluated for their possible effect on the survival of Bradyrhizobium japonicum on seeds and on the nodulation and yield of soybeans in a greenhouse and a field experiment. quinolate Pro (carbendazim and oxine copper), Vitavax 200FF (carboxin and thiram), and Monceren (pencycuron) had a small effect or no effect on the survival of B. japonicum and on the nodulation and yield of soybeans. They can thus be considered compatible with soybean seed inoculation. Germipro UFB (carbendazim and iprodione), Apron 35J (metalaxyl), and Tachigaren (hymexazol) decreased B. japonicum survival and the nodulation and yield of soybeans and thus cannot be considered compatible with soybean seed inoculation.  相似文献   

20.
Mineral element deficiencies and toxicities are common problems associated with sorghum [Sorghum bicolor (L.) Moench] production on acid soils. To better understand some of the mineral element problems and the analysis of plant tissue of sorghum plants grown on acid soils, four sorghum genotypes were grown on an acid Oxisol at Carimagua, Colombia limed with dolomite at 2 and 6 Mg ha‐1.

Samples for mineral element analyses were obtained from leaves at different positions on the four genotypes. Concentrations of P and Mg were highest in the flag leaf (Leaf No. 1) and decreased as the position on the plant declined from the top of the plant for plants grown at 2 Mg lime ha‐1. Similar decreases in P, Mg, K, and Zn concentrations occurred in plants grown with 6 Mg lime ha‐1. Concentrations of Ca, S, Si, Mn, Fe, Cu, and Al increased as leaf position declined from the flag leaf for plants grown at 2 and 6 Mg lime ha‐1. The higher lime supply enhanced Ca and reduced Mn and Fe concentrations in leaves. Differences in mineral element concentrations for the four genotypes used were fairly extensive. The elements to show the greatest range among genotypes were Al and Si and the elements to show the least range among genotypes were P, K, and S. Care should be used in collecting leaf samples for plant analysis and genotypic differences for accumulation of mineral elements should be considered in interpretation of results.  相似文献   

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