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Chudnova VI 《Soviet geography》1982,23(7):506-512
"The generalized results of a study of population growth in four territorial production complexes of Siberia are presented.... The study analyzed the contributions made over time by the two basic components of population formation--natural increase and net migration--in 13 industrial centers in the four complexes. Trends were found to differ between centers developing in sparsely settled northern regions and in more densely populated southern regions. In general, in-migration played a key role in the early stages of industrial development, with natural increase becoming more significant in later stages." 相似文献
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玉米生产在晋中地区具有战略性重要地位,但十年九旱的气候特征,使玉米生产几乎年年面临一个难过“三关”的问题,即春旱难过播种捉全苗关、抽雄叶丝期难过“卡脖子”伏旱关、灌浆期难过初霜冻危害关。本文通过对玉米生产中气象条件的分析,提出以适时旱播促使玉米生育期提前来避过“三关”夺取高产,这一科技措施已被晋中各地采用并证明为玉米生产过“三关”的最有效途径。 相似文献
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XU Weihua Andrés VIA QI Zengxiang OUYANG Zhiyun LIU Jianguo LIU Wei WAN Hui 《中国地理科学(英文版)》2014,24(1):60-70
Many nature reserves are established to protect the habitat needs of particular endangered species of interest but their effec-tiveness for protecting other species is questionable.In this study,this effectiveness was evaluated in a nature reserve network located in the Qinling Mountains,Shaanxi Province,China.The network of reserves was established mainly for the conservation of the giant panda,a species considered as a surrogate for the conservation of many other endangered species in the region.The habitat suitability of nine protected species,including the giant panda,was modeled by using Maximum Entropy(MAXENT) and their spatial congruence was analyzed.Habitat suitability of these species was also overlapped with nature reserve boundaries and their management zones(i.e.,core,buffer and experimental zones).Results show that in general the habitat of the giant panda constitutes a reasonable surrogate of the habitat of other protected species,and giant panda reserves protect a relatively high proportion of the habitat of other protected species.Therefore,giant panda habitat conservation also allows the conservation of the habitat of other protected species in the region.However,a large area of suitable habitat was excluded from the nature reserve network.In addition,four species exhibited a low proportion of highly suitable habitat inside the core zones of nature reserves.It suggests that a high proportion of suitable habitat of protected species not targeted for conservation is located in the experimental and buffer zones,thus,is being affected by human activities.To increase their conservation effectiveness,nature reserves and their management zones need to be re-examined in order to include suitable habitat of more endangered species.The procedures described in this study can be easily implemented for the conservation of many endangered species not only in China but in many other parts of the world. 相似文献