分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2018-02-28 合作期刊: 《干旱区科学》
摘要: Cross-regional locality research reflects the influences of natural environment and the human activities due to the abundant land types and the multiple landscape combinations in related regions. The Chinese farming-pastoral ecotone is a typical large-scale region but few studies were conducted. This research contributed to the understanding of cross-regional locality of the Chinese farming-pastoral ecotone from different scales, including national, sectional, and provincial administrative units by utilizing geotagged photos (GTPs) obtained from the Panoramio website. The major results were as follows: (1) the locality elements of the Chinese farming-pastoral ecotone included 52 free nodes classified into 8 types of scene attributes; (2) there were huge differences between locality elements of different regions, and there was a negative correlation between the similarity degree of elements of different provinces and their spatial distances; (3) the Chinese farming-pastoral ecotone could be divided into the northern, central and southern sections, whose localities had differences in element constitution, association structure and the strength of elements, system stability and the anti-interference capability; and (4) the evolution of the localities of the northern and central sections was mainly influenced by human activities, while the locality of southern section retained more natural features. On a theoretical level, this research aimed to establish the research methodology of locality from the perspective of open data on the web with strong operability and replicability. On a practical level, this research could enrich the structuring recognition of the locality of the Chinese farming-pastoral ecotone and the comprehension of its dynamic mechanism. The results provide a reference for locality differentiation protection and the development of a cross-regional scale.
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2018-02-28 合作期刊: 《干旱区科学》
摘要: Field experiments were conducted from 2012 to 2015 in an arid region of Northwest China to investigate the effects of planting density on plant growth, yield, and water use efficiency (WUE) of maize for seed production. Five planting densities of 6.75, 8.25, 9.75, 11.25 and 12.75 plants/m2 were conducted in 2012, and a planting density of 14.25 plants/m2 was added from 2013 to 2015. Through comparison with the AquaCrop yield model, a modified model was developed to estimate the biomass accumulation and yield under different planting densities using adjustment coefficient for normalized biomass water productivity and harvest index. It was found that the modified yield model had a better performance and could generate results with higher determination coefficient and lower error. The results indicated that higher planting density increased the leaf area index and biomass accumulation, but decreased the biomass accumulation per plant. The total yield increased rapidly as planting density increased to 11.25 plants/m2, but only a slight increase was observed when the density was greater than 11.25 plants/m2. The WUE also reached the maximum when planting density was 11.25 plants/m2, which was the recommended planting density of maize for seed production in Northwest China.
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2018-02-28 合作期刊: 《干旱区科学》
摘要: Researching into changes in thermal growing season has been one of the most important scientific issues in studies of the impact of global climate change on terrestrial ecosystems. However, few studies investigated the differences under various definitions of thermal growing season and compared the trends of thermal growing season in different parts of China. Based on the daily mean air temperatures collected from 877 meteorological stations over northern China from 1961 to 2015, we investigated the variations of the thermal growing season parameters including the onset, ending and duration of the growing season using the methods of differential analysis, trend analysis, comparative analysis, and Kriging interpolation technique. Results indicate that the differences of the maximum values of those indices for the thermal growing season were significant, while they were insignificant for the mean values. For indices with the same length of the spells exceeding 5°C, frost criterion had a significant effect on the differences of the maximum values. The differences of the mean values between frost and non-frost indices were also slight, even smaller than those from the different lengths of the spells. Temporally, the starting date of the thermal growing season advanced by 10.0–11.0 days, while the ending dates delayed by 5.0–6.0 days during the period 1961–2015. Consequently, the duration of the thermal growing season was prolonged 15.0–16.0 days. Spatially, the advanced onset of the thermal growing season occurred in the southwestern, eastern, and northeastern parts of northern China, whereas the delayed ending of the thermal growing season appeared in the western part, and the length of the thermal growing season was prolonged significantly in the vast majority of northern China. The trend values of the thermal growing season were affected by altitude. The magnitude of the earlier onset of the thermal growing season decreased, and that of the later ending increased rapidly as the altitude increased, causing the magnitude of the prolonged growing season increased correspondingly. Comparing the applicability of selected indices and considering the impacts of frost on the definitions are important and necessary for determining the timing and length of the thermal growing season in northern China.
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2018-02-28 合作期刊: 《干旱区科学》
摘要: In developing countries such as Ethiopia, research to develop and promote soil and water conservation practices rarely addressed regional diversity. Using a water-balance approach in this study, we used runoff plots from three sites, each representing a different agro-ecological environment, e.g., high, mid and low in both elevation and rainfall, in the Upper Blue Nile Basin of Ethiopia to examine the runoff response and runoff conservation efficiency of a range of different soil and water conservation measures and their impacts on soil moisture. The plots at each site represented common land use types (cultivated vs. non-agricultural land use types) and slopes (gentle and steep). Seasonal runoff from control plots in the highlands ranged 214–560 versus 253–475 mm at midlands and 119–200 mm at lowlands. The three soil and water conservation techniques applied in cultivated land increased runoff conservation efficiency by 32% to 51%, depending on the site. At the moist subtropical site in a highland region, soil and water conservation increased soil moisture enough to potentially cause waterlogging, which was absent at the low-rainfall sites. Soil bunds combined with Vetiveria zizanioides grass in cultivated land and short trenches in grassland conserved the most runoff (51% and 55%, respectively). Runoff responses showed high spatial variation within and between land use types, causing high variation in soil and water conservation efficiency. Our results highlight the need to understand the role of the agro-ecological environment in the success of soil and water conservation measures to control runoff and hydrological dynamics. This understanding will support policy development to promote the adoption of suitable techniques that can be tested at other locations with similar soil, climatic, and topographic conditions.
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2018-02-28 合作期刊: 《干旱区科学》
摘要: In Hebei Province of North China, forest was recovered with natural recruitment in plantations with large area of clear-cutting Chinese pine (Pinus tabuliformis). This study was aimed to demonstrate the dynamic characteristics of recruits during the natural recruitment. Both plot survey and the spatial point-pattern analysis were performed. Five developmental stages of natural recruitment were selected and studied, including 1 year before and 2, 5, 8, and 11 years after clear-cutting. Different slope aspects were also included. Natural recruitment was always dominated by Chinese pine with a proportion of higher than 90%. For plots of 1 year before clear-cutting on east- and north-facing slopes, recruit densities were 7886 and 5036 stems/hm2, the average heights were 0.78 (±0.85) and 1.06 (±1.15) m, and the average diameters at breast height (DBH) were 3.21 (±1.38) and 2.91 (±1.38) cm, respectively. After clear-cutting, recruit density was initially increased, then it was gradually declined with time; however, the variation of average DBH was contrary to that of recruit density. Both of them were no longer varied between 8 and 11 years after clear-cutting. The average height of recruits continued to increase after clear-cutting. For the plots of 11 years after clear-cutting on east- and north-facing slopes, average heights of recruits reached 2.00 (±1.14) and 2.24 (±1.20) m, respectively. The statuses of recruits on north-facing slopes were better than those on east-facing slopes after clear-cutting. Meanwhile, recruits on east-facing slopes were always aggregated at small scales, while spatial pattern of recruits varied with time on north-facing slopes. Moreover, forest was recovered more quickly by natural recruitment than by artificial afforestation after clear-cutting. The structural diversity was higher in naturally regenerated forests than in plantations of the same age. Our results demonstrated that clear-cutting of Chinese pine plantations recovered by natural recruitment has the potential to be an effective approach for establishing multifunctional forest.
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2018-02-28 合作期刊: 《干旱区科学》
摘要: Hydrological models are often linked with other models in cognate sciences to understand the interactions among climate, earth, water, ecosystem, and human society. This paper presents the development and implementation of a decision support system (DSS) that links the outputs of hydrological models with real-time decision making on social-economic assessments and land use management. Discharge and glacier geometry changes were simulated with hydrological model, water availability in semi-arid environments. Irrigation and ecological water were simulated by a new commercial software MIKE HYDRO. Groundwater was simulated by MODFLOW. All the outputs of theses hydrological models were taken as inputs into the DSS in three types of links: regression equations, stationary data inputs, or dynamic data inputs as the models running parallel in the simulation periods. The DSS integrates the hydrological data, geographic data, social and economic statistical data, and establishes the relationships with equations, conditional statements and fuzzy logics. The programming is realized in C++. The DSS has four remarkable features: (1) editable land use maps to assist decision-making; (2) conjunctive use of surface and groundwater resources; (3) interactions among water, earth, ecosystem, and humans; and (4) links with hydrological models. The overall goal of the DSS is to combine the outputs of scientific models, knowledge of experts, and perspectives of stakeholders, into a computer-based system, which allows sustainability impact assessment within regional planning; and to understand ecosystem services and integrate them into land and water management.
分类: 其他 >> 综合 提交时间: 2018-02-26 合作期刊: 《中国科学院院刊》
分类: 其他 >> 综合 提交时间: 2018-02-26 合作期刊: 《中国科学院院刊》
分类: 其他 >> 综合 提交时间: 2018-02-26 合作期刊: 《中国科学院院刊》
分类: 其他 >> 综合 提交时间: 2018-02-26 合作期刊: 《中国科学院院刊》
摘要: 中科院环江喀斯特生态系统观测研究站面向我国西南喀斯特区域石漠化综合治理与生态服务提升和民生改善的重大需求,系统开展了喀斯特生态系统野外观测、试验与示范研究,发现了喀斯特坡地地表-地下二元水土流失特征,地表侵蚀产沙一般低于50 t/(km2·a),但人为干扰加剧地表侵蚀;揭示了人类活动对喀斯特退化生态系统的影响及其作用机理,阐明了喀斯特景观格局与关键生态过程的相互作用机理,研发了喀斯特退化生态系统适应性修复技术体系,开展了生态工程背景下喀斯特区域生态系统服务变化评估,提出了喀斯特景观保护的优化管控措施,构建了喀斯特生态脆弱区科技扶贫模式,形成了喀斯特生态系统服务优化调控的理论与技术体系,为我国西南地区石漠化治理与区域脱贫提供了重要科技支撑。
分类: 其他 >> 综合 提交时间: 2018-02-26 合作期刊: 《中国科学院院刊》
摘要: 我国东北黑土地是世界上最肥沃的土壤,土壤环境质量良好,适合优质农产品生产。黑土地开垦时间约200年,但是土壤肥力发生了巨大变化。开垦后大约经历了30年有机质含量快速下降期,使土壤中氮、磷和钾的比例更适合作物生长且肥力不断的提高;此后,土壤有机质呈现缓慢下降的趋势,土壤肥力也随之下降,这部分土壤有机质流失导致了黑土地退化。政府先后采取了多项黑土保护措施,获得了初步成效。建议进一步深化黑土地的科学技术研究;强化黑土保护政策的可持续性;建立可靠的野外监测网络,积累有价值的基础数据;实行黑土地保护的科技-管理-生产三位一体方式,实现全民保护黑土地。
分类: 其他 >> 综合 提交时间: 2018-02-26 合作期刊: 《中国科学院院刊》
摘要: 我国土壤侵蚀类型多样、侵蚀过程复杂,相应的水土保持措施丰富。文章对国内外土壤侵蚀及其阻控研究进行了分析,总结了我国复杂环境下土壤侵蚀理论和实践的研究成果;回顾了我国土壤侵蚀防治由优化坡面措施,到小流域综合整治,再到区域生态经济协同发展与优化布局的演变历程。在此基础上,提出了现阶段治理重心应从遏制面积扩张转向生态功能提升为主,治理手段应从综合治理转向生态调控,变对抗为利用,变控制为调节,寻求土壤侵蚀防治与农业高效生产和环境可持续发展的协同途径,以期为国家生态文明建设提供科学依据。
分类: 其他 >> 综合 提交时间: 2018-02-26 合作期刊: 《中国科学院院刊》
摘要: 土壤有机碳作为土壤肥力形成的基础,不但影响土壤质量、功能和粮食产量,而且在全球气候变化中扮演重要角色。在我国土壤资源同时面临保障粮食安全、发挥生态系统服务功能和应对气候变化等多重挑战的背景下,准确把握中国农田土壤固碳潜力及速率,对于实现土壤资源合理利用和农业可持续发展具有重要意义。文章首先介绍了对中国农田土壤有机碳变化速率和土壤固碳潜力的基本认识以及研究中面临的挑战,而后从基础研究、土壤信息平台、方法体系及研究成果与国家农业管理决策支撑方面提出了研究建议。
分类: 其他 >> 综合 提交时间: 2018-02-26 合作期刊: 《中国科学院院刊》
摘要: 南美洲古老农业文明孕育的暗色肥沃土壤引发了全球生物质炭研究热潮。将农业生产过程中产生的有机废弃物经过低温热裂解技术转化为生物质炭并施用于农田土壤中,是一种新的土壤可持续管理途径,且服务于生物质废弃物治理与生态农业。我国生物质炭工业化生产技术及炭基肥制备与施用技术已经形成,土壤增碳与农业增产、减肥、增效潜力显著。大规模生物质炭工业化生产的推广催生了一个新兴的科技领域——生物质科技与工程。该科技服务于中国巨大的生物质废弃物治理和土壤改良、化肥减量及绿色农业等需求,这一学科领域尚待系统整合和提升。文章提出,研究生物质炭的有机质组分、结构、性质与功能的表征与有机质-矿物-微生物相互作用的基础研究是未来土壤可持续管理中的重要研究方向。这些问题将揭示生物质炭对于农业生命的系统健康及绿色农业的巨大价值,也进一步彰显了土壤学服务于中国农业可持续管理与生物质产业融合的巨大价值。
分类: 其他 >> 综合 提交时间: 2018-02-26 合作期刊: 《中国科学院院刊》
摘要: 我国是世界上最大的化学氮肥消耗国,总用量达到了全球总量的33%。但是氮肥的过量施用并没有带来持续的作物高产,反而造成了一系列的环境问题。文章综述了我国近30年来农田土壤氮素的收支和利用率情况,分析了我国农田土壤氮素的去向及其环境影响,重点论述了如何通过氮肥合理管理来实现粮食安全和环境可持续发展的双重目标。
分类: 其他 >> 综合 提交时间: 2018-02-26 合作期刊: 《中国科学院院刊》
摘要: 农业面源污染正成为我国地表水体的主要污染负荷来源,威胁水生态健康和水环境安全。文章分析了农业面源污染的特征及其主要的形成原因,总结了当前主流的防控技术与策略,重点阐述了从全局防控农业面源污染的“源头减量(Reduce)—过程阻断(Retain)—养分再利用(Reuse)—生态修复(Restore)”策略(简称“4R策略”)。深入剖析了当前农业面源污染防控存在的问题,并从深化基础研究、强化生态系统服务功能与促进区域联控,以及农业面源污染防控技术的物化方面进行了展望。
分类: 其他 >> 综合 提交时间: 2018-02-26 合作期刊: 《中国科学院院刊》
摘要: 我国南方日趋严重的农田土壤酸化不仅导致农作物大幅度减产甚至绝收,而且促进重金属等有害物质在农产品中吸收累积,威胁国家粮食安全和民众健康。但因酸性土壤分布详情不清,作物酸害阈值不明,土壤酸化预测的研究不足,酸化防治技术严重缺乏,红壤酸化没有得到有效控制。采取有效措施改良酸化农田土壤、遏制土壤的持续酸化,将热带和亚热带地区的土壤酸度维持在较低水平,对我国农业可持续发展和乡村振兴战略的实施具有重要意义。
分类: 其他 >> 综合 提交时间: 2018-02-26 合作期刊: 《中国科学院院刊》
摘要: 我国农田土壤重金属污染形势严峻,已对粮食安全构成威胁。文章针对我国农田土壤和粮食作物重金属超标现状,强调把粮食作物区域划分为禁产、限产和宜产3种类型;通过采用重金属低积累粮食作物品种、重金属钝化与阻隔技术及农艺管理等措施,实现中轻度重金属污染农田的安全利用,为粮食安全生产提供技术保障;并明确提出了重金属动态监测、低积累作物品种资源库、钝化剂市场准入、超标农田的轮作休耕、高重金属含量秸秆的处置、粮食安全生产保障体系与政策等是今后我国农田土壤安全利用的关键环节。
分类: 其他 >> 综合 提交时间: 2018-02-26 合作期刊: 《中国科学院院刊》
摘要: 我国已实行分类、分级的土壤环境监管工作,但尚未融合分区治理修复策略。自然地球化学异常或人为污染物空间排放差异可使土壤环境污染具有区域性特征。实行区域土壤污染的分区治理符合土壤污染的客观性和人为性。文章在分析土壤污染的自然与人为成因基础上,提出了基于土壤污染区域差异性的分区治理修复策略。建议积极推进制定地方土壤污染防治法,允许地方制修订土壤环境质量标准,以及加强支持土壤污染的分区治理修复与安全利用的科技创新,包括加大区域土壤污染与修复基础研究和技术发展,区域土壤污染治理与修复技术示范先行区建设,区域土壤污染治理与修复科技创新能力建设,以及区域土壤污染治理与修复科技成果转化工作。文章还建议建立健全我国区域土壤环境质量综合监管与改善技术体系,构建土壤污染分区防治体系,支持区域土壤环境监管,确保区域土壤环境安全与可持续健康发展。