高原传统农区土地利用功能演变及其生态环境效应

为探究高原传统农区不同梯度上土地利用功能演变及其对生态环境影响特征的差异性,选取云南省昌宁县作为研究区,基于2000年、2010年、2020年3期土地利用数据,采用土地利用转移矩阵、区域生态环境质量指数等方法对研究区土地利用功能演变特征及其生态环境效应进行了分析。结果表明:(1)高原农区垂直梯度上土地利用功能格局多样,近20 a来研究区土地利用功能结构变化表现为生活用地、生态用地分别增加2784.18,2561.29 hm^(2),而生产用地减少5345.47 hm^(2),生态用地主要集中在中、高起伏地貌区,生产、生活用地主要集中在低起伏地貌区。(2)高原农区生态环境效应空间差异明显,研究区土地利用功能演变对生态环境质量的影响总体平稳,生态环境质量指数总体维持在0.5982的良好水平,尤其在北部和中部的中、高起伏地貌区,坡耕地、低效园地等农业生产用地转入以林地为主的生态用地,促进区域生态环境稳定向好发展;而由于人口集聚、土地承载和利用过度,在中南部的低起伏地貌区,农业结构调整以及城镇化占用耕地、林地和草地等现象多发,致使局部生态环境质量呈退化趋势。总体而言,伴随人口压力的转移和利用程度的减弱,高原农区土地利用整体格局趋于优化,土地利用功能可持续性增强,区内生态环境质量向好发展。

高原主要农区气候资源动态变化

统计分析了高原主要农区近三十年的气候资源的动态变化,结果表明:生长季气候变暖表现在夏季,尤其6月份增温明显,夏季平均最高气温、冬季平均最低气温有持续增高的趋势;生长季延长,积温增高;无霜期确有缩短的趋势.受气候变化的影响沿江一线、昌都降水逐年代递减的趋势较为明显,尤以6月的减少最为突出;东南部年降水、7—9月降水量有递增的趋势.

高原作物:南美藜

南美藜是一种很有潜力的高原作物,最适宜在海拔3000米左右的干旱、少雨、凉爽无霜期短的高原农区生长。抗逆性强、对土壤要求不严,其蛋白质等营养物质的含量高于目前人类广泛种植的所有粮食作物。

欧洲不同良种肉牛杂交利用青海黄牛后代生长发育试验研究

为了研究青海省肉牛杂交改良效果,筛选适应高寒地区肉牛最佳杂交组合,从而为今后开展肉牛杂交工作提供有力的依据,通过6年的试验研究,测定分析了蓝本、皮本、利本、夏本、德本F1牛和青海黄牛的初生,3月龄,6月龄,12月龄,18月龄体重及体尺指标及杂交后代对青海高原高寒气候的适应性观察。结果显示:五个杂交组合F1代不同年龄的生长速度和体尺指标均明显优于青海黄牛(P<0.01)说明良种肉牛改良效果显著,在不同杂交组合后代的比较中,蓝本F1牛生长发育最快,各阶段体重及体尺指标显著高于青海黄牛,比皮本、利本、夏本、德本F1牛也有明显提高。

Analysis of Land Use Change in Western Yunnan Plateau——Taking Midu County as an example

The research of land use/land cover change （LUCC） is the core content of global environmental change research and an important part of the sustainable development research. Taking the Midu County of western Yunnan Plateau as the example, GIS technology was used to make the spatial overlay with the land use database in 2009 and land change survey database in 2014 of Midu County, so as to analyze the changes of land use of the county, and reveal the law of land use change, with the aim to provide the basis for further rational utilization of land resources.

The Influence of Gender and Other Characteristics on Rural Laborers' Employment Patterns in the Mountainous and Upland Areas of Sichuan,China

This study examines gender differences in rural laborers‘ employment patterns in the mountainous and upland areas of Sichuan, China. The analysis employs both representative survey data of 400 households and geographical data. Multinomial logistic regression models are used to analyze the influences of gender, among other factors, on employment decisions of rural males and females, where the factors considered include personal, household, community natural environmental characteristics. Dividing laborers into four categories, we find that the proportions of males who participating in on-farm, pluriactive, and off-farm work, and unemployment were 24.41%, 28.64%, 46.27%, and 0.68% respectively, while that of females who participating in on-farm, pluriactive, and offfarm work, and unemployment were 43.20%, 13.95%, 30.95%, and 11.90% respectively. As to individual characteristics, age(AGE) and physical condition(PHY) effects appeared to be more pronounced for men, while education(EDU) and marital status(MAR)effects appeared to be more pronounced for women. Regarding household and community characteristics, the effects of the presence in the household of children aged 6-(CHI), number of persons in the household(POP), and labor force(LAB), per capitaincome in village(INCV), and the development status of village enterprises(ENT) on women were greater than that on men. In addition, the presence in the household of elderly individuals aged 65+(OLD) and time to reach the nearest township(TIME) are shown to have opposite impacts on men and women. While the presence in the household of pupils(PUP) and per capital gross value of industrial output(GVIO) was found to be irresponsive to men and women taking pluriavtivity and off-farm job. With respect to natural environments characteristics, the effects on men were opposite of those on women. Unemployment of women was found to be particularly responsive to household characteristics. A multinomial regression approach is undertaken to analyze rural males‘ and females‘ decisions of the four employment patterns considered, an approach that reveals considerable heterogeneity that is concealed by the dichotomous approach employed in most previous studies. The study thus contributes to our understanding of rural employment patterns and gender difference in mountainous and upland areas.

Sediment Delivery across Multiple Spatio-temporal Scales in an Agriculture Watershed of the Chinese Loess Plateau

There is a consensus that sediment delivery ratio in the Chinese Loess Plateau is close to 1at the inter-annual timescale. However, little information is available about the sediment delivery at finer timescales. We evaluated the sediment delivery from plots to watersheds at the event or intra-annual, annual, and inter-annual timescales within the Wudinghe river basin, a 30,261 km2 basin in the Loess Plateau. We calculated the ratio of sediment output to sediment input and presented the temporal change of the channel morphology to determine whether sediment deposition occurs.Although a single flood event frequently has a sediment yield exceeding 10,000 t km-2, sediment deposition rarely occurs except during some small runoff events(sediment yield < 5000 t km-2) or dry years(sediment yield < 10,000 t km-2) when moving from slopes up to the main channels of the Wudinghe River. This observation suggests a sediment delivery ratio close to 1 even at the event or intra-annual and the annual timescales, but not necessarily at the interannual timescale. Such a high sediment delivery ratio can be related to hyper-concentrated flows, which have very strong sediment transport capacity even at low flow strength. Because hyper-concentrated flows are well-developed in the whole Loess Plateau, a sediment delivery ratio close to 1 below the interannual timescale possibly remains true for other rivers in the Loess Plateau.

国外良种肉牛杂交利用青海黄牛的试验研究

为了研究青海省肉牛杂交改良效果,筛选适应高寒地区肉牛最佳杂交组合,为今后开展肉牛杂交工作提供有力的依据,通过6年的试验研究,测定分析了蓝本、皮本、利本、夏本、德本F1牛和青海黄牛的初生、3月龄、6月龄、9月龄、12月龄、18月龄体重、体尺指标及杂交后代对青海高原高寒气候的适应性观察。结果显示:5个杂交组合F1代不同年龄的生长速度和体尺指标均显著优于青海黄牛(P<0.01),说明良种肉牛改良效果显著。其中蓝本F1的杂交优势表现更为显著。

Effect of Rotational Tillage on Soil Aggregates, Organic Carbon and Nitrogen in the Loess Plateau Area of China

In rain-fed semi-arid agroecosystems, continuous conventional tillage can cause serious problems in soil quality and crop production, whereas rotational tillage （no-tillage and subsoiling） could decrease soil bulk density, and increase soil aggregates and organic carbon in the 0-40 cm soil layer. A 3-year field study was conducted to determine the effect of tillage practices on soil organic carbon （SOC）, total nitrogen （TN）, water-stable aggregate size distribution and aggregate C and N sequestration from 0 to 40 cm soil in semi-arid areas of southern Ningxia. Three tillage treatments were tested： no-tillage in year 1, subsoiling in year 2, and no-tillage in year 3 （NT-ST-NT）; subsoiling in year 1, no-tillage in year 2, and subsoiling in year 3 （ST-NT-ST）; and conventional tillage over years 1-3 （CT）. Mean values of soil bulk density in 0-40 cm under NT-ST-NT and ST-NT-ST were significantly decreased by 3.3% and 6.5%, respectively, compared with CT, while soil total porosity was greatly improved. Rotational tillage increased SOC, TN, and water-stable aggregates in the 0-40 cm soil, with the greatest effect under ST-NT-ST. In 0-20 and 2（}-40 cm soils, the tillage effect was confined to the 2-0.25 mm size fraction of soil aggregates, and rotational tillage treatments obtained significantly higher SOC and TN contents than conventional tillage. No significant differences were detected in SOC and TN contents in the 〉 2 mm and 〈 0.25 mm aggregates among all treatments. In conclusion, rotational tillage practices could significantly increase SOC and TN levels, due to a fundamental change in soil structure, and maintain agroecosystem sustainability in the Loess Plateau area of China.