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滇西北的怒江、迪庆两州地处云南省高寒高山峡谷区,地形破碎而陡峻,耕地稀缺,陡坡种植业占有很高的比重。由于人口的增长,陡坡耕地仍将作为该地区的主要耕地长期存在。这种传统的耕种方式已对环境产生了深刻的负效应。本文根据其生存条件和利用现状就通过改良以取得持续利用的方向和途径作了初步探讨。 相似文献
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以糜子作物为例,分析了河曲县砖窑沟流域农地生产潜力的层次,以及影响生产潜力的主次因素等,计算了流域理想的生产潜力与实际生产潜力。通过分析计算,提出了提高农地增产潜力的途径,为提高本流域及晋西北地区农地的增产潜力提供了理论依据与实际应用范例。 相似文献
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通过地质勘探与生产勘探 ,生产勘探与开采所获地质资料进行对比分析 ,探讨三家厂铜矿床凤山矿段 2 9号矿体 10— 13中段勘探方法 ,验证勘探类型、网度和检查勘探程度的合理性 ,总结出可供借鉴的勘探经验 相似文献
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IINTRODUCTIONLanduse/coverisoneofthemostimportalfactorseffectingsoilandwaterloss.Researchonlanduse/coverandwaterandsoillosswithremotesensinghasbeendonemuchinthepast.Butremotelysensedimageryonlycarriestheinstantaneousandtwo-dimensionalinformationofitsprototypegeographicobjects(ChenandZhao,1990).Thereforemathematicalandphysicalprocessingonremotelysensedimageoftenproduceindefiniteandunreliableresult.Inordertoimprovetheprecisionofclassification,otherdatasetssuchastopographicmaps,thematicmaps… 相似文献
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Phytoplankton community structure defined by key environmental variables in Tagus estuary, Portugal 总被引:4,自引:0,他引:4
In this work, we analyze environmental (physical and chemical) and biological (phytoplankton) data obtained along Tagus estuary during three surveys, carried out in productive period (May/June/July) at ebb tide. The main objective of this study was to identify the key environmental factors affecting phytoplankton structure in the estuary. BIOENV analysis revealed that, in study period, temperature, salinity, silicate and total phosphorus were the variables that best explained the phytoplankton spatial pattern in the estuary (Spearman correlation, rho=0.803). A generalized linear model (GLM) also identified salinity, silicate and phosphate as having a high explanatory power (63%) of phytoplankton abundance. These selected nutrients appear to be consistent with the requirements of the dominant phytoplankton group, Baccilariophyceae. Apparently, phytoplankton community is adapted to fluctuations in light intensity, as suspended particulate matter did not come out as a key factor in shaping phytoplankton structure along Tagus estuary. 相似文献
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邬翊光 《云南地理环境研究》1990,2(2):1-7
本文对我国40年来生产力宏观布局几次大的变化,特别是60—70年代“西进”和近十年“东回”战略,进行了总体评价。作者肯定了“西进”战略决策的成绩,并就“东回”战略转移中存在的问题提出了自己的看法。指出在新的形势下认真总结我国生产力布局的历史经验和教训,具有重要的理论和现实意义。 相似文献
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Cyanobacterial blooms in water supply sources in both central Indiana USA (CIN) and South Australia (SA) are a cause of great concerns for toxin production and water quality deterioration. Remote sensing provides an effective approach for quick assessment of cyanobacteria through quantification of phycocyanin (PC) concentration. In total, 363 samples spanning a large variation of optically active constituents (OACs) in CIN and SA waters were collected during 24 field surveys. Concurrently, remote sensing reflectance spectra (Rrs) were measured. A partial least squares–artificial neural network (PLS–ANN) model, artificial neural network (ANN) and three-band model (TBM) were developed or tuned by relating the Rrs with PC concentration. Our results indicate that the PLS–ANN model outperformed the ANN and TBM with both the original spectra and simulated ESA/Sentinel-3/Ocean and Land Color Instrument (OLCI) and EO-1/Hyperion spectra. The PLS–ANN model resulted in a high coefficient of determination (R2) for CIN dataset (R2 = 0.92, R: 0.3–220.7 μg/L) and SA (R2 = 0.98, R: 0.2–13.2 μg/L). In comparison, the TBM model yielded an R2 = 0.77 and 0.94 for the CIN and SA datasets, respectively; while the ANN obtained an intermediate modeling accuracy (CIN: R2 = 0.86; SA: R2 = 0.95). Applying the simulated OLCI and Hyperion aggregated datasets, the PLS–ANN model still achieved good performance (OLCI: R2 = 0.84; Hyperion: R2 = 0.90); the TBM also presented acceptable performance for PC estimations (OLCI: R2 = 0.65, Hyperion: R2 = 0.70). Based on the results, the PLS–ANN is an effective modeling approach for the quantification of PC in productive water supplies based on its effectiveness in solving the non-linearity of PC with other OACs. Furthermore, our investigation indicates that the ratio of inorganic suspended matter (ISM) to PC concentration has close relationship to modeling relative errors (CIN: R2 = 0.81; SA: R2 = 0.92), indicating that ISM concentration exert significant impact on PC estimation accuracy. 相似文献