排序方式： 共有44条查询结果，搜索用时 15 毫秒
1.
基于东北三省1981−2017年气候资料,明确不同区域不同耕作阶段（全年、休耕期和播前1个月）不同等级日最大风速发生的变化规律;结合考虑降水影响下的起动风速指标,解析不同区域各阶段风蚀发生天数的时空规律,为各区域提出相适应的土壤保护耕作措施提供科学依据。结果表明：东北三省全年0−3级、4−6级和7级及以上日最大风速年均出现频率分别为48.5%、50.4%和1.1%,研究期内,全年、休耕期和播前1个月0−3级日最大风速出现频率均呈增加趋势,而4级及以上风速出现频率呈减少趋势。研究区域全年风蚀发生天数比例为35.0%,而播前一个月发生风蚀天数占该时期总天数的比例高于全年均值,达57.0%。大部分地区各个时期风蚀发生天数呈减少趋势。辽河平原区和三江平原区休耕期和播前1个月风蚀发生天数均较多,应重视风蚀对土壤的影响。松嫩平原区虽然休耕期土壤风蚀发生频率较低,但播前1个月风蚀发生较多,该区域应倡导免耕技术以降低土壤风蚀。 相似文献
2.
3.
土地集约利用受土地报酬递减规律作用,呈现先增长后降低的发展趋势,由此可判断各地区所处土地集约利用阶段及水平,结合资源发展潜力等因素,作为土地集约利用分区和差别化政策的依据.该研究对安徽省16个市的经济发展和土地集约利用数据进行分析,得出安徽省土地集约利用发展曲线拐点发生在人均GDP 71 050元时;结合2009 ～2013年安徽省各市存量建设用地总量数据,将安徽省划分为4类土地集约利用管控区域——土地集约利用提升区、土地集约利用优化区、土地集约利用挖潜区、土地集约利用滞后区,并从土地供应数量投放、土地供应强度门槛、存量建设用地挖潜、城乡建设用地互动等方面提出各区土地集约利用的差别化政策建议. 相似文献
4.
5.
黑龙江省农作物冷害气候区划 总被引：7，自引：1，他引：6
在调查研究和科学实验的基础上,分析出符合黑龙江省实际的窕作物冷害指标和霜冻指标。延迟型冷害指标是随各地温度水平不同而改变的动态值,障碍型冷害是以水稻抽前第９天至第１１天,日平均气温连续３ｄ低于１８℃为指标。霜冻指标是以各地日平均气温稳定通过１０℃终日的８０％保证率日期为标准,用日最低气温≤０℃的初日去衡量,后者小于前者时测定义为早霜冻日期。为了有针对性的防御冷害,将黑龙江省划分为８个不同程序的冷害 相似文献
6.
7.
The modifiable areal unit problem has significant implications for ecological research that involve investigating and analyzing
the spatial heterogeneity of plant community. In this paper, semivariance analysis was used to evaluate the spatial characteristics
of plant community in the␣transitional zone between oasis and desert. The spatial structures of the plant community were characterized
using exponent model variogram parameters, including nugget (C
0) range (A
0) and sill (C
0+C). Two methods were employed to determine the scale effect of spatial heterogeneity. (1) A constant grain size (10×10 m2) and variational plot areas have been used to analyze spatial heterogeneity of the plant community. (2) The grain size was
only changed to analyze spatial heterogeneity. In addition, the plot of 500×500 m2 was clustered into nested units of different shapes and different directions to analyze zoning effect. Finally, using semivariance
analysis, we obtained a suitable plot area and zoning approach to weaken the scale and zoning effects. The results showed
that the effects of scale on different variogram parameters had significant difference. For example, C
0 and C
0+C were very sensitive at small scales, A
0 was influenced significantly by plot area at larger scales, and C
0 and A
0 were relatively sensitive to different zoning approaches. In order to get more representative characteristic of spatial heterogeneity
of the plant community, the sampling area should be more than 200×200 m2 for Nitraria sphaerocarpa populations, 100×100 m2 for Reaumuria soongorica populations, and a grain size from 20×20 m2 to 30×30 m2 for both populations. 相似文献
8.
以乡镇(街道)为风险评估单元,以人口和社会经济作为承灾体,根据联合国人道主义事务部的风险表达式,利用自然灾害风险指数法建立风雹灾害风险评估模型;利用指标体系法评估承灾体的脆弱性状态,根据加权综合评分法建立脆弱性评估模型,分析15个乡镇(街道)短时大风、冰雹灾害的危险性、承灾体的脆弱性,对风雹灾害风险进行评估,利用系统聚类方法对风险评估结果进行区划.结果表明,通州短时大风风险高值区在宋庄、潞城、漷县,低值区在西集镇、于家务乡、新华街道;冰雹风险高值区在潞城、西集镇,低值区在北苑、新华、玉桥街道及梨园、马驹桥、于家务乡(镇);风雹灾害风险高值区在宋庄、潞城、济县,低值区在新华、玉桥街道、马驹桥镇、于家务乡(镇). 相似文献
9.
Vanessa Hull Weihua Xu Wei Liu Shiqiang Zhou Andrés Viña Jindong Zhang Mao-Ning Tuanmu Jinyan Huang Marc Linderman Xiaodong Chen Yan Huang Zhiyun Ouyang Hemin Zhang Jianguo Liu 《Biological conservation》2011,144(12):3028-3037
Protected areas worldwide are facing increasing pressures to co-manage human development and biodiversity conservation. One strategy for managing multiple uses within and around protected areas is zoning, an approach in which spatial boundaries are drawn to distinguish areas with varying degrees of allowable human impacts. However, zoning designations are rarely evaluated for their efficacy using empirical data related to both human and biodiversity characteristics. To evaluate the effectiveness of zoning designations, we developed an integrated approach. The approach was calibrated empirically using data from Wolong Nature Reserve, a flagship protected area for the conservation of endangered giant pandas in China. We analyzed the spatial distribution of pandas, as well as human impacts (roads, houses, tourism infrastructure, livestock, and forest cover change) with respect to zoning designations in Wolong. Results show that the design of the zoning scheme could be improved to account for pandas and their habitat, considering the amount of suitable habitat outside of the core zone (area designated for biodiversity conservation). Zoning was largely successful in containing houses and roads to their designated experimental zone, but was less effective in containing livestock and was susceptible to boundary adjustments to allow for tourism development. We identified focus areas for potential zoning revision that could better protect the panda population without significantly compromising existing human settlements. Our findings highlight the need for evaluating the efficacy of zoning in other protected areas facing similar challenges with balancing human needs and conservation goals, not only in China but also around the world. 相似文献
10.
农业生产景观自然适宜性研究是新农村建设中农业景观规划和土地整治的基础。本文在界定农业景观内涵和提取出农业生产景观类型的基础上,构建农业生产景观自然适宜性评价指标体系,利用GIS栅格技术与自然适宜性综合评价模型进行农业生产景观自然适宜性评价,将湖南省金井镇农业生产景观类型划分为高度适宜类、中度适宜类和低度适宜3个等级。在此基础上,将金井镇农业生产景观划分为粮菜生产区、经济园林生产区、农业生产限制区,进而提出其相应的发展调控模式。研究结果为区域农业生产景观规划和农业土地综合整治提供有力的技术手段和科学支撑。 相似文献