Increased high‐latitude photosynthetic carbon gain offset by respiration carbon loss during an anomalous warm winter to spring transition

Arctic and boreal ecosystems play an important role in the global carbon (C) budget, and whether they act as a future net C sink or source depends on climate and environmental change. Here, we used complementary in situ measurements, model simulations, and satellite observations to investigate the net carbon dioxide (CO₂) seasonal cycle and its climatic and environmental controls across Alaska and northwestern Canada during the anomalously warm winter to spring conditions of 2015 and 2016 (relative to 2010–2014). In the warm spring, we found that photosynthesis was enhanced more than respiration, leading to greater CO₂ uptake. However, photosynthetic enhancement from spring warming was partially offset by greater ecosystem respiration during the preceding anomalously warm winter, resulting in nearly neutral effects on the annual net CO₂ balance. Eddy covariance CO₂ flux measurements showed that air temperature has a primary influence on net CO₂ exchange in winter and spring, while soil moisture has a primary control on net CO₂ exchange in the fall. The net CO₂ exchange was generally more moisture limited in the boreal region than in the Arctic tundra. Our analysis indicates complex seasonal interactions of underlying C cycle processes in response to changing climate and hydrology that may not manifest in changes in net annual CO₂ exchange. Therefore, a better understanding of the seasonal response of C cycle processes may provide important insights for predicting future carbon–climate feedbacks and their consequences on atmospheric CO₂ dynamics in the northern high latitudes.     

Fluorescence characterization and microbial degradation of dissolved organic matter leached from salt marsh plants in the Yellow River Delta

盐沼植被是沿海水体中溶解有机物(Dissolved Organic Matter, DOM)的重要贡献者。然而,不同盐沼植物释放DOM的动力学特征尚缺乏系统研究和比较。黄河三角洲湿地是中国东海岸面积最大,保护最完善的沿海生态系统之一。本论文研究了2016年10月从黄河三角洲(Yellow River Delta, YRD)盐沼中采集的三种常见沼泽植物(芦苇(Phragmites australis),碱蓬(Suaeda salsa)和獐茅(Aeluropus littoralis)的DOM释放过程。通过测定溶解有机碳(Dissolved Organic Carbon, DOC)和溶解氮(Dissolved Nitrogen, DN)发现,植物叶片释放的DOM浓度远高于其根和茎。在27天的培养期内,平均有15%的生物碳和30%的生物氮以DOC和DN的形式通过植物叶片释放。从植物中释放的DOM非常不稳定,在27天的培养期内,细菌共消耗了92.4%–98.1%的DOC和88.0%–94.6%的DN。植物释放DOM的荧光特性表明,发色溶解的有机物(Chromophoric Dissolved Organic Matter, CDOM)是DOM的主要组分,而类蛋白组分是植物释放CDOM的主要组分。细菌的降解作用改变了DOM的荧光性质和化学组成。上述的室内研究结果得到了实地调查的充分支撑,表明在深秋时期黄河口湿地有大量DOM溢出。本研究结果表明,盐沼植物释放的DOM是沼泽和沿海水域DOC和DN的重要来源,而且易降解DOC和DN为黄河口湿地和邻近沿海水域中的微生物群落提供了重要的食物来源。     

耐盐碱促生菌的筛选及性能

盐分是影响作物生长最重要的因素,使用能促进植物生长的耐盐碱促生菌减轻盐胁迫引起的损害是一种农业上的有效方法。文中从盐碱地筛选得到7株耐盐细菌,并考察筛选菌株的产胞外聚合物(EPS)能力、降碱能力和产吲哚-3-乙酸(IAA)能力。经综合评价选出1株优势菌株DB01,菌株DB01产EPS能力为0.21 g/g,降碱能力为8.7%,产IAA的能力为8.97 mg/L。菌株经16S rRNA鉴定为海水盐单胞菌Halomonas aquamarina,并且有抑制香蕉枯萎病、番茄早疫病、大豆疫霉病、小麦纹枯病病原菌的能力,同时能够在盐胁迫下促进小麦幼苗的发芽率和根长。海水盐单胞菌Halomonas aquamarina DB01可为土壤微生物资源开发利用和盐碱地改良提供理论依据。     

神经递质的可视化荧光检测技术研究进展

神经递质是神经系统中至关重要的组成部分,神经递质释放的时间和空间变化是神经网络中信息处理的核心,可视化监测神经递质的生物传感器是探究各类生理和病理活动的重要工具。文中综述了近年来具有较高时间和空间分辨率的监测神经递质时空分布变化技术的研究进展,介绍了对谷氨酸、多巴胺、γ-氨基丁酸和乙酰胆碱这4类重要的神经递质的检测方法,并归纳总结了各类检测方法的基本原理和优缺点,为设计具有高时空分辨率的神经递质传感器提供一个较为系统的参考。     

全球中华鲎资源保护现状及对策建议

鲎是古老的海洋节肢动物。中华鲎(Tachypleus tridentatus)是世界现存4种鲎中体型最大的一种, 是河口生态系统的标志物种, 同时其血液被用于生产医用检验试剂――鲎试剂。中华鲎的自然地理分布范围相当狭窄, 仅局限于日本濑户内海向南延伸至印度尼西亚爪哇岛北岸以北的太平洋西岸海域, 其中在中国东岸和日本南部海域的历史产量较高。自20世纪50年代以来中华鲎种群数量出现了显著减少, 2019年中华鲎在IUCN红色名录中的濒危等级正式更新为濒危(EN), 明确了中华鲎资源呈现全球性衰退的状态, 究其原因可归纳为鲎生境破坏和过度捕捞两个方面。在开展鲎资源保护的实践工作中, 作者深刻反思当前鲎资源保护在海洋保护区划定、增殖放流及科普和野生动物保护法宣传中存在的问题并提出相应建议, 包括加快完善种群基线数据, 制定标准化种群和生境基线监测指南, 构建科学放流体系等, 以期推进全球范围内的中华鲎资源保护与科学管理。     

黑斑侧褶蛙蝌蚪断尾后的补偿生长和发育研究

动物在经历不利的生长条件或环境后往往出现补偿生长。研究了黑斑侧褶蛙(Pelophylax nigromaculatus)蝌蚪经历来自食蚊鱼(Gambusia affinis)捕食造成断尾损伤后的补偿生长模式、断尾损失对蝌蚪游泳能力以及变态时间与大小的影响。结果表明,经历捕食压力后,全尾组和1/3断尾组蝌蚪的体长显著大于1/2断尾组蝌蚪的体长,全尾组和1/3断尾组之间的蝌蚪体长差异不显著;第19天时,1/2断尾组蝌蚪经过补偿生长后体长显著大于全尾组蝌蚪,1/3断尾组与全尾组和1/2断尾组之间的蝌蚪体长差异均不显著;三个实验组之间蝌蚪尾长差异不显著;全尾组蝌蚪的疾游速显著大于1/2断尾组蝌蚪的疾游速,1/3断尾组蝌蚪的疾游速与全尾组和1/2断尾组之间差异不显著,表明严重断尾对蝌蚪疾游速产生了消极影响。三个实验组蝌蚪的变态时间和变态前后形态差异均不显著。黑斑侧褶蛙蝌蚪能够在变态前调整生长轨迹补偿早期捕食风险造成的生长损失,断尾损失并不影响变态时间与大小,断尾超过一半的蝌蚪经过补偿生长后仍要付出一定的运动代价。     

Energy–water and seasonal variations in climate underlie the spatial distribution patterns of gymnosperm species richness in China

Studying the pattern of species richness is crucial in understanding the diversity and distribution of organisms in the earth. Climate and human influences are the major driving factors that directly influence the large‐scale distributions of plant species, including gymnosperms. Understanding how gymnosperms respond to climate, topography, and human‐induced changes is useful in predicting the impacts of global change. Here, we attempt to evaluate how climatic and human‐induced processes could affect the spatial richness patterns of gymnosperms in China. Initially, we divided a map of the country into grid cells of 50 × 50 km² spatial resolution and plotted the geographical coordinate distribution occurrence of 236 native gymnosperm taxa. The gymnosperm taxa were separated into three response variables: (a) all species, (b) endemic species, and (c) nonendemic species, based on their distribution. The species richness patterns of these response variables to four predictor sets were also evaluated: (a) energy–water, (b) climatic seasonality, (c) habitat heterogeneity, and (d) human influences. We performed generalized linear models (GLMs) and variation partitioning analyses to determine the effect of predictors on spatial richness patterns. The results showed that the distribution pattern of species richness was highest in the southwestern mountainous area and Taiwan in China. We found a significant relationship between the predictor variable set and species richness pattern. Further, our findings provide evidence that climatic seasonality is the most important factor in explaining distinct fractions of variations in the species richness patterns of all studied response variables. Moreover, it was found that energy–water was the best predictor set to determine the richness pattern of all species and endemic species, while habitat heterogeneity has a better influence on nonendemic species. Therefore, we conclude that with the current climate fluctuations as a result of climate change and increasing human activities, gymnosperms might face a high risk of extinction.