Freeze-thaw process induced by increased precipitation affects root growth of alpine steppe on the Tibetan Plateau

The response of vegetation productivity to precipitation is becoming a worldwide concern.Most reports on responses of vegetation to precipitation trends are based on the growth season.In the soil freeze/thaw process,the soil water phase and heat transport change can affect root growth,especially during the thawing process in early spring.A field experiment with increased precipitation(control,increased 25%and increased 50%)was conducted to measure the effects of soil water in early spring on above-and below-ground productivity in an alpine steppe over two growing seasons from June 2017 to September 2018.The increased 50%treatment significantly increased the soil moisture at the 10 cm depth,there was no difference in soil moisture between the increased 25%treatment and the control in the growing season,which was not consistent in the freeze/thaw process.Increased soil moisture during the non-growing season retarded root growth.Increased precipitation in the freezing-thawing period can partially offset the difference between the control and increased precipitation plots in both above-and below-ground biomass.

基于ISM和MICMAC分析的国际物流与供应链人才胜任力研究

文章从个人和环境因素两个方面构建了国际化物流与供应链人才胜任力的影响因素模型。通过问卷调查和专家访谈,借助解释结构模型确定了各个影响因素之间的相互关系,并运用交叉影响矩阵相乘分析法识别出了各因素的驱动性和依赖性。研究结果表明,物流与供应链知识、商业知识/技能、人员管理技能、流程管理技巧、行为技巧和决策能力为影响国际物流与供应链人才的直接因素;数字与信息化能力为间接影响因素;自我概念、个人特质和动机为关键因素;合作人才培养模式创新为基础因素;国家政策为根源因素;其中,数字与信息化能力、个人内隐因素和环境因素对系统中其他因素驱动力较强,是需要重点管理和干预的对象。因此,建议完善国家政策,拓展高校、企业、行业协会和国际合作人才培养创新模式。在人才培养的过程中需要注重个人内在素质培养,构建人才综合能力培养新体系,重视理论与实践相结合,在精神和物质上给予激励;个人应当重视各项能力均衡发展。

C:N:P stoichiometry of perennial herbs’ organs in the alpine steppe of the northern Tibetan Plateau

The patterns of C:N:P stoichiometry across ecosystems are important in understanding biogeochemical processes. The stoichiometry of nutrients at the leaf and root level have been reported previously, but relationships of other plant organs, such as stems and the reproductive organs, remain unclear. We collected 228 samples of leaves, roots, stems and reproductive organs from 11 common plant species at 25 sites on the Tibetan Plateau to explore the relationships of C:N:P stoichiometry both within and across plant organs. The average C concentrations in the roots, leaves, stems and reproductive organs were 427.32, 410.51, 421.11 and 416.72 mg g-1, respectively. The shoot tissues(leaves, stems and reproductive organs) had significantly higher N and P concentrations than the roots. The N and P concentrations had a significant positive correlation within the same organ. The nutrient concentrations(N and P) and nutrient ratios(C:N, C:P and N:P) were significantly correlated across all pairwise organ combinations. Our data suggest that alpine perennial herbs share similar evolutionary histories and have constrained patterns of covariation for C concentrations, with differential patterns for N and P stoichiometry across organs. Our data also indicate that covarying sets of nutrient traits are consistent across environments and biogeographical regions and demonstrate convergent evolution in plant nutritional characteristics in extreme alpine environments.

Impacts of warming on root biomass allocation in alpine steppe on the north Tibetan Plateau

Biomass is an important component of global carbon cycling and is vulnerable to climate change. Previous studies have mainly focused on the responses of aboveground biomass and phenology to warming, while studies of root architecture and of root biomass allocation between coarse and fine roots have been scarcely reported in grassland ecosystems. We conducted an open-top-chamber warming experiment to investigate the effect of potential warming on root biomass and root allocation in alpine steppe on the north Tibetan Plateau. The results showed that Stipa purpurea had significantly higher total root length, root surface area and tips than Carex moocroftii. However,there were no differences in total root volume, mean diameter and forks for the two species. Warming significantly increased total root biomass(27.60%), root biomass at 0–10 cm depth(27.84%) and coarse root biomass(diameter > 0.20 mm, 57.68%) in the growing season(August). However, warming had no significant influence on root biomass in the non-growing season(April). Root biomass showed clear seasonalvariations: total root biomass, root biomass at 0–10 cm depth and coarse root biomass significantly increased in the growing season. The increase in total root biomass was due to the enhancement of root biomass at 0–10 cm depth, to which the increase of coarse root biomass made a great contribution. This research is of significance for understanding biomass allocation, carbon cycling and biological adaptability in alpine grassland ecosystems under future climate change.

Global patterns in above-ground net primary production and precipitation-use efficiency in grasslands

The above-ground net primary production(ANPP) and the precipitation-use efficiency(PUE) regulate the carbon and water cycles in grassland ecosystems, but the relationships among the ANPP, PUE and precipitation are still controversial. We selected 717 grassland sites with ANPP and mean annual precipitation(MAP) data from 40 publications to characterize the relationships ANPP–MAP and PUE–MAP across different grassland types. The MAP and ANPP showed large variations across all grassland types, ranging from 69 to 2335 mm and 4.3 to 1706 g m^(-2), respectively. The global maximum PUE ranged from 0.19 to 1.49 g m^(-2) mm^(-1) with a unimodal pattern. Analysis using the sigmoid function explained the ANPP–MAP relationship best at the global scale. The gradient of the ANPP–MAP graph was small for arid and semi-arid sites(MAP <400 mm). This study improves our understanding of the relationship between ANPP and MAP across dry grassland ecosystems. It provides new perspectives on the prediction and modeling of variations in the ANPP for different grassland types along precipitation gradients.

Variation in carbon,nitrogen and phosphorus partitioning between above-and belowground biomass along a precipitation gradient at Tibetan Plateau

Precipitation is a potential factor that significantly affects plant nutrient pools by influencing biomass sizes and nutrient concentrations. However, few studies have explicitly dissected carbon(C), nitrogen(N) and phosphorus(P) pools between above- and belowground biomass at the community level along a precipitation gradient. We conducted a transect(approx. 1300 km long) study of Stipa purpurea community in alpine steppe on the Tibet Plateau of China to test the variation of N pool of aboveground biomass/N pool of belowground biomass(AB/BB N) and P pool of aboveground biomass/P pool of belowground biomass(AB/BB P) along a precipitation gradient. The proportion of aboveground biomass decreased significantly from mesic to drier sites. Along the belt transect, the plant N concentration was relatively stable; thus, AB/BB N increased with moisture due to the major influences by above- and belowground biomass allocation. However, P concentration of aboveground biomass decreased significantly with increasing precipitation and AB/BB P did not vary with aridity because of the offset effect of the P concentration and biomass allocation. Precipitation gradients do decouple the N and P pool of a S. purpurea community along a precipitation gradient in alpine steppe. The decreasing of N:P in aboveground biomass in drier regions may indicate much stronger N limitation in more arid area.

可供性理论视角下制造业数字创新的驱动机制

党的二十大报告就加快建设数字中国作出新部署,而制造业的数字创新是完成这一艰巨任务的关键。本文基于可供性理论,构建以“基础—转型—创新”为主线的理论框架,分析组织环境和数字技术影响数字创新的内在机理,考察业务流程与商业模式的中介效应以及外部市场环境的调节效应。研究发现:企业内部组织环境对数字创新而言更为重要;外部市场环境动态性会对数字技术与组织环境的作用产生不同方向的调节效果。本文通过探究制造业数字创新过程的“黑箱”,能够为改善企业数字化转型效果,提升创新效率做出一定贡献。

基于数据融合的长江经济带城市建成区时空格局研究

在"共抓大保护,不搞大开发"导向下,准确识别长江经济带城市建成区,并揭示其演化规律对于优化流域国土空间格局具有重要意义。基于Landsat数据和夜间灯光数据,构建融合算法提取长江经济带城市建成区,并采用位序-规模、核密度、空间自相关等方法探索了其时空格局特征。结果表明:(1)长江经济带城市规模存在明显的位序-规模分布格局,分形特征显著;(2)建成区规模呈现"东高西低"、"轴线高两端低",建成区密度呈"一个中心,两个次中心"的格局特征;(3)城市由点源聚集增长向轴线式扩张转变,国土空间"T"型增长格局逐渐显现;(4)建成区增长表现出空间集聚特征,区域内三大城市群为主要热点区。研究结果能够为流域国土空间"保护"与"开发"权衡提供定量参考和决策依据。