Co-occurrence Patterns of Above-ground and Below-ground Mite Communities in Farmland of Sanjiang Plain, Northeast China

One of the fundamental questions in community ecology is whether communities are random or formed by deterministic mechanisms. Although many efforts have been made to verify non-randomness in community structure, little is known with regard to co-occurrence patterns in above-ground and below-ground communities. In this paper, we used a null model to test non-randomness in the structure of the above-ground and below-ground mite communities in farmland of the Sanjiang Plain, Northeast China. Then, we used four tests for non-randomness to recognize species pairs that would be demonstrated as significantly aggregated or segregated co-occurrences of the above-ground and below-ground mite communities. The pattern of the above-ground mite commu- nity was significantly non-random in October, suggesting species segregation and hence interspecific competition. Additionally, species co-occurrence patterns did not differ from randomness in the above-ground mite community in August or in below-ground mite com- munities in August and October. Only one significant species pair was detected in the above-ground mite community in August, while no significant species pairs were recognized in the above-ground mite community in October or in the below-ground mite communities in August and October. The results indicate that non-randomness and significant species pairs may not be the general rule in the above-ground and below-ground mite communities in farmland of the Sanjiang Plain at the fine scale.

Assembly and co-occurrence patterns of rare and abundant bacterial sub-communities in rice rhizosphere soil under short-term nitrogen deep placement

Nitrogen(N)deep placement has been found to reduce N leaching and increase N use efficiency in paddy fields.However,relatively little is known how bacterial consortia,especially abundant and rare taxa,respond to N deep placement,which is critical for understanding the biodiversity and function of agricultural ecosystem.In this study,lllumina sequencing and ecological models were conducted to examine the diversity patterns and underlying assembly mechanisms of abundant and rare taxa in rice rhizosphere soil under different N fertilization regimes at four rice growth stages in paddy fields.The results showed that abundant and rare bacteria had distinct distribution patterns in rhizosphere samples.Abundant bacteria showed ubiquitous distribution;while rare taxa exhibited uneven distribution across all samples.Stochastic processes dominated community assembly of both abundant and rare bacteria,with dispersal limitation playing a more vital role in abundant bacteria,and undominated processes playing a more important role in rare bacteria.The N deep placement was associated with a greater influence of dispersal limitation than the broadcast N fertilizer(BN)and no N fertilizer(NN)treatments in abundant and rare taxa of rhizosphere soil;while greater contributions from homogenizing dispersal were observed for BN and NN in rare taxa.Network analysis indicated that abundant taxa with closer relationships were usually more likely to occupy the central position of the network than rare taxa.Nevertheless,most of the keystone species were rare taxa and might have played essential roles in maintaining the network stability.Overall,these findings highlighted that the ecological mechanisms and co-occurrence patterns of abundant and rare bacteria in rhizosphere soil under N deep placement.

Spatio-Temporal Variations in Co-Occurrence Patterns of Fish Communities in Haizhou Bay, China: Null Model Analysis

Co-occurrence pattern of fish species plays an important role in understanding the spatio-temporal structure and the stability of fish community.Species coexistence may vary with time and space.The co-occurrence patterns of fish species were examined using the C-score under fixed-fixed null model for fish communities in spring and autumn over different years in the Haizhou Bay,China.The results showed that fish assemblages in the whole bay had non-random patterns in spring and autumn over different years.However,the fish co-occurrence patterns were different for the northern and southern fish assemblages in spring and autumn.The northern fish assemblage showed structured pattern,whereas the southern assemblage were randomly assembled in spring.The co-occurrence patterns of fish communities were relatively stable over different years,and the number of significant species pairs in northern assemblage was more than that in the southern assemblage.Environmental heterogeneity played an important role in determining the distributions of fish species that formed significant species pairs,which might affect the co-occurrence patterns of northern and southern assemblages further in the Haizhou Bay.

Impact of Sino-US Trade Friction on Import and Export Trade Pattern of Soybean in Heilongjiang

Under the background of Sino-US trade friction,soybean,as an important variety in the important and export trade of agricultural products,has become a key bargaining chip. After the Ministry of Commerce of China announced the counter list of agricultural products including soybean,the price fluctuations of domestic soybean and related agricultural products are rapidly expanding. Under the background of SinoUS trade friction,taking the soybean-producing areas in Heilongjiang as an example,the impact of Sino-US trade friction on the important and export pattern of soybean in Heilongjiang was explored to provide a certain theoretical basis for the development of soybean industry in Heilongjiang.

Technological Content of the Import of Services and the Transformation of Growth Patterns of China's Industrial Economy

Based on the latest approach for measuring technology content of import of services and with the contribution of total factor productivity(TFP) to gross industrial output as the indicator for measuring the growth pattern of China's industrial economy,this paper provides an empirical study on the effect of import technology content of trade in services on the development pattern of China's industrial economy between 2004 and2011.Result of econometric test reveals that the technology content of import of services has a significant positive effect on transforming the growth pattern of China's industrial economy.Moreover,import of new types of trade in services with high technology such as computer and information services has a much stronger positive effect compared with import of traditional trade in services with relatively low technology content such as transport.In terms of different industrial sectors,technology content of import of services has the greatest effect on transforming the development pattern of China's technologyintensive industrial sectors,followed by capital-intensive,resource-intensive and laborintensive sectors respectively.Transformation of the development pattern of China's industrial economy cannot be isolated from the system of global division of work.Against the backdrop of global service sector fragmentation,China should take the important opportunities in the development of global trade in services and give more attention to improving the quality of import of services in the interest of transforming the development pattern of its industrial economy.

Importance Sampling Strategy for Oscillatory Stochastic Processes

This paper contributes to the structural reliability problem by presenting a novel approach that enables for identification of stochastic oscillatory processes as a critical input for given mechanical models. Identification development follows a transparent image processing paradigm completely independent of state-of-the-art structural dynamics, aiming at delivering a simple and wide purpose method. Validation of the proposed importance sampling strategy is based on multi-scale clusters of realizations of digitally generated non-stationary stochastic processes. Good agreement with the reference pure Monte Carlo results indicates a significant potential in reducing the computational task of first passage probabilities estimation, an important feature in the field of e.g., probabilistic seismic design or risk assessment generally.

“双循环”格局下中国饲料粮进口稳定性研究

“双循环”格局下适度进口已成为缓解国内饲料粮供需矛盾的现实选择。在有效利用国际饲料粮市场的同时,降低饲料粮进口的稳定性风险,既重要且必要。在对国内饲料粮供需形势精准判断的基础上,综合分析饲料粮进口的可获性与可供性,并采用香农熵指数法对饲料粮的进口来源稳定性进行评估。结果表明:国内饲料粮供需格局趋紧并呈现常态化发展趋势,供需缺口不断扩大,适度进口饲料粮是大势所需。总量上,世界饲料粮的供应潜力巨大;时点上,我国与国际饲料粮生产波动的相关性较弱。因此,利用国际市场弥补国内饲料粮的供需缺口是可行的。1992—2020年,我国饲料粮进口的稳定程度整体处于较低水平,其中,玉米、麦麸和大麦的变动幅度较大,大豆的波动幅度较小。在新一轮高水平开放格局下,亟须完善政策体系、优化进口结构、提高进口稳定性,构建“双循环”新发展格局下开放型的国家饲料粮安全保障体系。

Clustering-Inverse: A Generalized Model for Pattern-Based Time Series Segmentation

Patterned-based time series segmentation (PTSS) is an important task for many time series data mining applications. In this paper, according to the characteristics of PTSS, a generalized model is proposed for PTSS. First, a new inter-pretation for PTSS is given by comparing this problem with the prototype-based clustering (PC). Then, a novel model, called clustering-inverse model (CI-model), is presented. Finally, two algorithms are presented to implement this model. Our experimental results on artificial and real-world time series demonstrate that the proposed algorithms are quite effective.

全球重要农业文化遗产桑基鱼塘时空格局演变和驱动因素

浙江省湖州市南浔区是目前桑基鱼塘保留最完整、规模最大的区域之一,该地的桑基鱼塘系统被列入全球重要农业文化遗产。随着社会经济发展、消费需求改变、农业现代化生产,桑基鱼塘系统的生产方式、经济及服务价值等发生了重大变化。本文利用遥感影像、社会经济等数据对1975—2019年南浔区桑基鱼塘的时空格局演变和驱动因素进行了研究,主要结果如下:1)从规模变化上看,鱼塘快速扩张,桑园明显减少,水田剧烈萎缩,桑基鱼塘规模明显减小,基塘比例严重降低;从形态变化上看,鱼塘呈集聚化、规模化趋势,桑园和水田呈破碎化趋势,且鱼塘逐渐脱离传统桑基鱼塘系统布局特色而独立存在。2)2012—2019年,鱼塘养殖的经济效益远高于蚕桑养殖和水稻种植,是导致桑园、水田明显萎缩及鱼塘大规模扩张的主要驱动力。因此,通过全球重要农业文化遗产的建立来进一步加强桑基鱼塘系统的保护与传承是非常必要的,也是支撑湖州市南浔区农业可持续发展的重要举措。

“双循环”新发展格局下我国饲料进出口贸易的新机遇与新路径

饲料进出口贸易高速发展是促进我国国民经济发展的内生动力,也是加快推进农业强国建设进程的重大举措。“双循环”新发展格局视域下,我国饲料进出口贸易已取得初步成效,表现为出口贸易增速高于进口贸易、进口来源和出口市场更具广泛性、饲料产业发展更具规模化和精细化。在“双循环”新发展格局持续推动下,我国饲料进出口贸易需把握政策支持力度逐渐加大、产品供给能力不断增强、科技支撑作用逐步扩大的机遇,充分培育新优势、激发新动能。因此,文章提出建立健全配套政策,优化市场监管机制,打造创新科技平台,实现智慧化降本增效,拓宽国际贸易渠道,掌握饲料进口主动权等实践路径,以期为饲料进出口贸易发展提供可行性参考。

生态安全视角下山地-平原型城市土地利用冲突区分级识别

山地—平原型城市的土地利用冲突区识别对于预防区域生态系统失稳至关重要。从生态安全视角出发,以西安市长安区为例,融合生态系统服务重要性-生态敏感性-景观连通性的多维评价方法构建生态安全格局;通过生态安全格局与人为活动区域(耕地、建设用地)的叠合分析识别冲突区,并据此制定管控策略。结果表明:1)长安区共识别生态源地79处(总面积867.57 km^(2)),潜在生态廊道178条(总长258.59 km);2)土地利用冲突类型被细分为12类,分布于秦岭北麓山前区域以及主要流域中下游;3)根据冲突区分级结果,划定不同级别的冲突管控区,即一级管控区(建设用地/耕地与生态源地等冲突)、二级管控区(与中安全缓冲区冲突)、三级管控区(与高安全缓冲区冲突)并制定相应级别的管控策略。因此,本研究在提升冲突区识别准确性的同时减少了土地利用冲突发生,这种差异化管理有助于管控实施的针对性和落地性。

基于平面赤足足迹轮廓的相似度计算研究

轮廓作为赤足足迹的一个重要特征,在同源与异源赤足足迹的检验鉴定中发挥着重要作用。针对赤足足迹的轮廓特征难以量化的问题提出一种相似度计算方法,以提高检验鉴定的科学性和准确性。首先收集920名志愿者的2120枚赤足足迹样本,经过图像预处理后利用形状上下文算法对赤足足迹脚趾区、跖前缘和跟后缘的轮廓相似度进行计算。借助偏最小二乘判别分析计算三个区域的变量投影重要性,经权重归一化后分别为0.41、0.42和0.17。将3个区域设置权重后计算总体轮廓相似度,在该相似度下同源、异源赤足足迹具有显著差异且模式识别正确率分别为83.0%和100.0%。最终建立了一个赤足足迹相似度评估体系,该体系可对赤足足迹检材与样本之间的相似度进行计算,实现对于同源与异源赤足足迹的有效区分,辅助检验鉴定工作。

进口扩大背景下中国玉米市场格局与议价能力演变

随着中国玉米供需缺口逐渐加大和国际外部环境不确定性的增加,如何提升中国在国际玉米市场上的议价能力具有重要现实意义。为测度中国在玉米国际贸易市场上的议价能力,本文基于双边随机前沿模型,从理论和实证两个方面对中国在国际玉米市场上的议价能力进行定性与定量分析。研究发现:①中国玉米进口数量上涨明显,对外依存度提高,且进口来源集中度较高;②中国在玉米国际市场上的议价能力长期低于玉米主要出口国,玉米进口价格高于理论进口价格;③长期以来,中国在与美国的玉米贸易中处于弱势地位,尤其是当中国进口来源过度集中于美国时,这种议价差距将进一步被放大。推动中国进口来源多元化,加快农业“走出去”步伐,建立可持续的粮食供应体系对提升中国在国际玉米市场的谈判能力和抵御风险能力大有裨益。

新形势下中国油气进口安全面临的挑战及应对建议

近年来,特别是乌克兰危机爆发以来,国际地缘政治局势急剧变化持续冲击油气市场,中东对全球石油市场的影响上升,美俄石油贸易流向出现变化;全球天然气市场正经历由非稳态向稳态转变的亚平衡阶段,美国加大天然气出口,俄罗斯天然气出口重心开始由欧洲转向亚洲市场。目前中国石油进口来源多元化得到明显提升,但储备能力尚不足,在战争等极端情况下存在断供风险;国际天然气市场尚处于亚平衡状态,供应稳定性较弱,而国内天然气基础设施建设滞后、储备能力不足,安全风险尤为突出,在短时冲击下存在断供或价格飙升风险。针对中国油气进口安全面临的问题,提出了保障国家能源安全的建议:一是加大勘探开发力度,二是选择差异化对外合作战略,三是优化进口油气资源结构,四是建好用好储备设施。

基于生态评价的国土空间生态修复分区研究——以甘肃省崇信县为例

国土空间生态修复分区是开展生态修复工作的空间指导与前提基础。为研究国土空间生态修复分区,以甘肃省崇信县为例,通过生态敏感性评价、生态系统服务价值计算、生态重要性评价等构建了崇信县生态安全格局,识别了崇信县生态修复重点区域,最终确定了崇信县国土空间生态修复分区。结果表明:(1)崇信县生态轻度敏感性、中度敏感性、高度敏感性和极敏感性面积分别为13021.25 hm^(2)、31405.57 hm^(2)、12670.73 hm^(2)和27805.28 hm^(2),分别占崇信县总面积的15.34%、36.99%、14.92%和32.74%。(2)崇信县生态系统服务价值为41159.21万元。从生态系统服务类型来看,维持生物多样性所占比重最高(15.53%);从土地利用类型来看,林地的生态系统所占比重最高(83.19%);低值区、中值区、高值区和极值区面积分别为53978.02 hm^(2)、14702.93 hm^(2)、13544.10 hm^(2)和2616.10 hm^(2),所占比重分别为63.62%、17.33%、15.96%和3.08%。(3)崇信县生态一般重要区、中等重要区、高度重要区、极重要区面积分别为33599.39 hm^(2)、12942.71 hm^(2)、20668.78 hm^(2)和17691.96 hm^(2),分别占崇信县总面积的39.57%、15.24%、24.34%和20.84%。(4)构建了“三蓝三绿四区一核心”的崇信县生态安全格局。生态源地面积为34927.91 hm^(2),3条绿廊总长度为7481.69 m。(5)崇信县生态核心区、生态提升区、生态修复区和生态控制区面积分别为2182.20 hm^(2)、11390.21 hm^(2)、24339.28 hm^(2)和46947.15 hm^(2),分别占崇信县总面积的2.57%、13.42%、28.68%和55.32%。

生态源地识别与生态安全格局构建研究——以福建省福清市为例

以福建省福清市为例,从生态系统服务重要性、景观斑块连通性、生态需求重要性3个层面综合评价生态重要性,基于生态重要性评价结果识别生态源地,利用城市兴趣点数据修正基础阻力面,并借助最小累积阻力模型提取生态廊道,最终构建生态安全格局。研究表明:福清市生态源地面积为154.77 km2,占总面积的8.20%,主要分布于西北部山区和东南部滩涂湿地,与现行生态保护区分布基本一致;福清市生态廊道网络全长391.75 km,其中核心廊道长度为220.02 km,潜在廊道长度为171.73 km,为城乡总体空间格局发挥生态屏障作用。以"源地-廊道"为模式构建生态安全格局,为福清市融入生态文明先行示范区建设提供科学依据与决策参考。

伏牛山自然保护区物种多样性分布格局

在伏牛山自然保护区典型地段设立样方,通过群落调查和多样性分析对物种多样性的垂直分布格局进行研究。发现:α多样性,乔木层在中海拔的落叶阔叶混交林带最高,灌木层随海拔升高稍呈上升趋势,草本层在低海拔次生林带和山顶矮林带物种多样性较高;β多样性总体上呈"～"型变化,在中海拔建群种发生更替的落叶阔叶混交林区最高,物种更替速率最快,其次是山顶附近。γ多样性大致沿海拔升高递减,以700m以下和过渡带落叶阔叶混交林区总物种丰富度最高。沿海拔梯度升高,水热组合发生变化,地带性植被总体上表现为由栓皮栎(Quercus variabilis)林向锐齿栎(Quercus aliena var.acuteserrata)林更替,在建群种发生更替的中海拔过渡带形成混交林带,短柄枹(Quercus glandulifera var.brevipetiolata)、槲栎(Quercus aliena)等夹杂其间在一些小生境中形成优势种群。总体上体现了过渡带具有高的物种多样性和更替速率,总物种丰富度隐含着沿海拔升高而降低的负相关关系。

中国受胁鸟类的分布与现状分析

参照《ThreatenedBirdsofAsia》(《亚洲受胁鸟类红皮书》) ,将其中记载的在中国有分布的物种与《中国濒危动物红皮书·鸟类》的物种进行比较。两者的物种组成有明显差异 ,仅 6 9种鸟同时出现在两个红皮书中 ;《亚洲受胁鸟类红皮书》中雀形目鸟类占比例最大 ,而《中国濒危动物红皮书·鸟类》中鸡形目鸟类占比例最大。两个红皮书中的受胁鸟类均以森林、湿地和灌丛为主要栖息生境 ,而导致物种受胁的主要原因是人为干扰所造成的栖息地破坏。在地理分布方面 ,应用Arcview 3.2的数据处理与叠加功能 ,发现西南山地亚区、东部丘陵平原亚区和黄淮平原亚区以及台湾亚区受胁鸟类物种丰富度较高 ,其中留鸟在西南山地亚区及其周边地区相对集中 ,迁徙鸟在东部丘陵平原亚区及其周边地区相对集中。在保护方面 ,中国的显著重要鸟区中有 5 1个是在自然保护区范围内 ,但还有 6个尚未建立保护区 ,建议予以保护和重视。作者认为西南山地和台湾、海南地区的受胁鸟类面临更大的灭绝威胁 。

时间序列异常检测

在k-近邻局部异常检测算法的基础上,结合时间序列的分割方法,提出了一种高效的时间序列异常检测算法。该算法首先把序列重要点作为数据的分割点,对时间序列数据进行高比例压缩;其次利用局部异常检测方法检测出时间序列中的异常模式。通过心电图(ECG)数据实验验证了算法的有效性和合理性。

基于关联规则重要性的产品购买序列模式发现

为了解决利用关联规则进行购物篮挖掘分析存在的两个问题:由于数据挖掘前的业务分析不足,不能有效的挖掘出想要的规则;按照传统的关联规则参数设置挖掘得到的关联规则太多,用户无法对其进行取舍.结合实例销售数据,对数据源进行了业务深层分析,构建了基于销售的主题数据仓库,保证了数据挖掘的有效性,同时用概率代替置信度进行参数设置,并引入关联规则"重要性"参数作为新的衡量标准,分析规则的有趣性,以筛选出更有价值的关联规则.将研究结果应用于某制造业产品销售实例,进行了基于关联规则的产品序列购买模式研究,得到了有效的产品销售关联规则,支持了市场决策.