基于生态系统服务簇的深圳市生态系统服务时空演变轨迹研究

明晰生态系统服务的演变特征,有助于针对性的提出区域生态系统服务提升决策,对于维持和改善人类福祉、促进城市可持续发展具有重要意义。以深圳市为例,选取11种生态系统服务,以街道为基本空间单元,对生态系统服务结构特征进行分类,进而探究生态系统服务的长时序演变轨迹。结果表明,深圳市生态系统服务簇有6种类型,分别为水文调节主导型、文化支持潜力型、服务枯竭型、水文调节控制型、水源消耗型、生态保育型;1980—2015年深圳市大部分地区的生态系统服务簇结构稳定,变化明显的地区大多毗邻香港;生态系统服务簇的时空演变轨迹类型有8种,以持续型轨迹为主;生态系统服务簇的时空演变轨迹与城市扩张具有一定的一致性,表明城市扩张对生态系统结构和功能影响的主导性。     

生境梯度影响下的天然红松种群空间格局与种内关联

为理清生境梯度下天然红松种群空间分布规律,以黑龙江省凉水国家级自然保护区内自坡底至坡顶的四种生境(生境Ⅰ,谷地平坡潮湿生境;生境Ⅱ,坡下缓坡潮湿生境;生境Ⅲ,坡上斜坡半湿润生境;生境Ⅳ,坡顶陡坡半干旱生境)类型中建群种红松种群为研究对象。分析不同林层(主林层、亚林层、演替层、更新层)红松种群的数量特征,并基于O-ring函数,在重复采样条件下评价了红松种群空间分布格局。结果表明:(1)下坡位生境(生境Ⅰ、Ⅱ)红松更新层种群数量显著大于上坡位(生境Ⅲ、Ⅳ)(P0.05),演替层中差异不显著;自坡底至坡顶的生境梯度上,主林层和亚林层中红松株数比例增加,红松种群年龄结构结构由倒J型向J型转变。(2)下坡位原始红松林更新层和演替层中红松种群聚集规模与聚集强度均高于上坡位,坡顶(生境Ⅳ)原始红松林更新层中红松种群聚集规模与聚集强度高于坡上(生境Ⅲ)。(3)四类生境的原始红松林中主林层与更新层中红松种群总体表现为空间独立,在个别尺度上表现出微弱的空间正关联或负关联;在0—5 m尺度上,下坡位红松林原始林内演替层与主林层红松种群表现为空间负关联,而上坡位生境林分对应林层间空间关系则为空间正关联;四类生境中,亚林层与主林层中红松种群在全部研究尺度上均表现为空间独立。可以认为,造成上坡位生境的原始红松林中幼树、幼苗聚集规模与强度弱于下坡位的原因是上坡位更新与演替层中种群数量较少;而随坡位上升,更现层、演替层与主林层中红松种群间的空间关系由空间负关联向空间正关联转变是生物与非生物因子共同作用的结果。研究结果为阔叶红松林的经营管理与生态修复提供了理论依据。     

青岛地区COVID19流行病学特征分析

目的分析青岛地区新型冠状病毒肺炎(COVID-19)的流行病学特征。方法纳入青岛市自2020年1月21日至3月3日所有COVID-19确诊病例(n=60),收集患者基本信息和流行病学资料,分析易感人群、传播模式、基本繁殖数、疫情进展及其与防控措施的相关性。结果 60例确诊患者包括27例输入性病例和33例本地感染病例。本地感染者以女性为主,占69.7%,显著高于输入性病例(37.0%)(χ~2=6.400,P=0.011)。本地共发生三代传播,发病例数逐代减少。青岛地区总病例R0值为1.49。本地一代、二代和三代的R0值分别为1.38、1.53、1.56。传播模式由家庭聚集性向密切接触转换。结论青岛地区本地传播病例女性易感,日新增病例总体呈波浪式下降趋势,目前疫情已基本得到控制,应进一步做好分区分级精准防控,加强对外来人员的隔离观察,防止出现疫情反弹。     

水相中氢气浓度检测方法的建立

近年来,研究表明氢分子具有广泛的生物学效应,饮用富氢水（hydrogen-rich water,HRW）是其主要的摄取方法,但目前对于水相中氢气浓度检测方法的研究甚少。为了建立适用于测定水相中氢气浓度的检测方法,利用纯水氢气发生器制备饱和富氢水。然后,利用氢气微电极直接测定水相中的氢气浓度,结果表明,在不同氢气浓度范围内（0～1.620 0 mg·L-1和0～0.202 5 mg·L-1）,氢气浓度与微电极信号值均呈现良好的线性关系,方法检出限（method detection limit,MDL）为4.3×10-3 mg·L-1。同时,采用顶空方式将水相中的氢气转移到气相中,通过气相色谱法测定氢气的浓度,结果表明,在不同氢气浓度范围内（0～1.620 0 mg·L-1和0～0.202 5 mg·L-1）,氢气浓度与气相色谱峰面积均具有良好的线性关系,MDL为8.7×10-4 mg·L-1。研究结果表明,氢微电极法和气相色谱法均可用于水相中氢气浓度的精确定量,即成功建立了采用氢气微电极及顶空气相色谱测定水相中氢气含量的检测方法。     

多杀菌素对天敌昆虫白蛾周氏啮小蜂的毒力评估

[目的] 生物防治与化学防治相结合是害虫综合防治的重要策略,蛹寄生蜂白蛾周氏啮小蜂是一种重要的天敌昆虫,在美国白蛾的生物防控中起关键作用。本研究旨在评估农林生产中常用的广谱、低毒杀虫剂多杀菌素对白蛾周氏啮小蜂的安全性。[方法] 采用药膜法检测多杀菌素对小蜂的毒力,并检测亚致死浓度多杀菌素处理后,小蜂体内解毒酶活性的变化。[结果] 多杀菌素对小蜂无短期（1 h）触杀作用,但随施药时间延长,其对小蜂的毒杀作用增强,25 mg·L^-1多杀菌素施药2 h后,可诱导约18.67%小蜂个体死亡。施药4 h后,不同浓度多杀菌素对小蜂的毒杀作用差异最明显,低浓度（5 mg·L^-1）多杀菌素可诱导11.33%小蜂死亡,而中、高浓度多杀菌素（≥ 15 mg·L^-1）可诱导77.33%~88.00%个体死亡。施药6 h后,LC₅₀值达7.44 mg·L^-1,安全系数为0.31,属高风险性农药。此外,亚致死浓度多杀菌素可明显诱导小蜂羧酸酯酶活性提高,对乙酰胆碱酯酶与谷胱甘肽-S-转移酶活性具有剂量效应。[结论] 多杀菌素对白蛾周氏啮小蜂的毒力作用较强,在美国白蛾生防区需慎用。     

DNA methylation and demethylation link the properties of mesenchymal stem cells: Regeneration and immunomodulation

Mesenchymal stem cells (MSCs) are a heterogeneous population that can be isolated from various tissues, including bone marrow, adipose tissue, umbilical cord blood, and craniofacial tissue. MSCs have attracted increasingly more attention over the years due to their regenerative capacity and function in immunomodulation. The foundation of tissue regeneration is the potential of cells to differentiate into multiple cell lineages and give rise to multiple tissue types. In addition,the immunoregulatory function of MSCs has provided insights into therapeutic treatments for immune-mediated diseases. DNA methylation and demethylation are important epigenetic mechanisms that have been shown to modulate embryonic stem cell maintenance, proliferation, differentiation and apoptosis by activating or suppressing a number of genes. In most studies, DNA hypermethylation is associated with gene suppression, while hypomethylation or demethylation is associated with gene activation. The dynamic balance of DNA methylation and demethylation is required for normal mammalian development and inhibits the onset of abnormal phenotypes. However, the exact role of DNA methylation and demethylation in MSC-based tissue regeneration and immunomodulation requires further investigation. In this review, we discuss how DNA methylation and demethylation function in multi-lineage cell differentiation and immunomodulation of MSCs based on previously published work. Furthermore, we discuss the implications of the role of DNA methylation and demethylation in MSCs for the treatment of metabolic or immune-related diseases.     

Scale‐dependent effects of neighborhood biodiversity on individual tree productivity in a coniferous and broad‐leaved mixed forest in China

The relationship between biodiversity and productivity has stimulated an increasing body of research over the past decades, and this topic still occupies a central place in ecology. While most studies have focused on biomass production in quadrats or plots, few have investigated the scale‐dependent relationship from an individual plant perspective. We present an analysis of the effects of biodiversity (species diversity and functional diversity) on individual tree growth with a data set of 16,060 growth records from a 30‐ha temperate forest plot using spatially explicit individual tree‐based methods. A significant relationship between species diversity and tree growth was found at the individual tree level in our study. The magnitude and direction of biodiversity effects varies with the spatial scale. We found positive effects of species diversity on tree growth at scales exceeding 9 m. Individual tree growth rates increased when there was a greater diversity of species in the neighborhood of the focal tree, which provides evidence of a niche complementarity effect. At small scales (3–5 m), species diversity had negative effects on tree growth, suggesting that competition is more prevalent than complementarity or facilitation in these close neighborhoods. The results also revealed many confounding factors which influence tree growth, such as elevation and available sun light. We conclude that the use of individual tree‐based methods may lead to a better understanding of the biodiversity‐productivity relationship in forest communities.     

Genetic diversity and population structure of Quercus fabri Hance in China revealed by genotyping‐by‐sequencing

Analysis of genetic diversity and population structure among Quercus fabri populations is essential for the conservation and utilization of Q. fabri resources. Here, the genetic diversity and structure of 158 individuals from 13 natural populations of Quercus fabri in China were analyzed using genotyping‐by‐sequencing (GBS). A total of 459,564 high‐quality single nucleotide polymorphisms (SNPs) were obtained after filtration for subsequent analysis. Genetic structure analysis revealed that these individuals can be clustered into two groups and the structure can be explained mainly by the geographic barrier, showed gene introgression from coastal to inland areas and high mountains could significantly hinder the mutual introgression of genes. Genetic diversity analysis indicated that the individual differences within groups are greater than the differences between the two groups. These results will help us better understand the genetic backgrounds of Q. fabri.     

Nitrogen economy of alpine plants on the north Tibetan Plateau: Nitrogen conservation by resorption rather than open sources through biological symbiotic fixation

Nitrogen (N) is one of the most important factors limiting plant productivity, and N fixation by legume species is an important source of N input into ecosystems. Meanwhile, N resorption from senescent plant tissues conserves nutrients taken up in the current season, which may alleviate ecosystem N limitation. N fixation was assessed by the ¹⁵N dilution technique in four types of alpine grasslands along the precipitation and soil nutrient gradients. The N resorption efficiency (NRE) was also measured in these alpine grasslands. The aboveground biomass in the alpine meadow was 4–6 times higher than in the alpine meadow steppe, alpine steppe, and alpine desert steppe. However, the proportion of legume species to community biomass in the alpine steppe and the alpine desert steppe was significantly higher than the proportion in the alpine meadow. N fixation by the legume plants in the alpine meadow was 0.236 g N/m², which was significantly higher than N fixation in other alpine grasslands (0.041 to 0.089 g N/m²). The NRE in the alpine meadows was lower than in the other three alpine grasslands. Both the aboveground biomass and N fixation of the legume plants showed decreasing trends with the decline of precipitation and soil N gradients from east to west, while the NRE of alpine plants showed increasing trends along the gradients, which indicates that alpine plants enhance the NRE to adapt to the increasing droughts and nutrient‐poor environments. The opposite trends of N fixation and NRE along the precipitation and soil nutrient gradients indicate that alpine plants adapt to precipitation and soil nutrient limitation by promoting NRE (conservative nutrient use by alpine plants) rather than biological N fixation (open sources by legume plants) on the north Tibetan Plateau.