Above- and belowground carbon inputs affect seasonal variations of soil microbial biomass in a subtropical monsoon forest of southwest China

Soil microbial activity drives carbon and nutrient cycling in terrestrial ecosystems. Soil microbial biomass is commonly limited by environmental factors and soil carbon availability. We employed plant litter removal, root trenching and stem-girdling treatments to examine the effects of environmental factors, above- and belowground carbon inputs on soil microbial C in a subtropical monsoon forest in southwest China. During the experimental period from July 2006 through April 2007, 2 years after initiation of the treatments, microbial biomass C in the humus layer did not vary with seasonal changes in soil temperature or water content. Mineral soil microbial C decreased throughout the experimental period and varied with soil temperature and water content. Litter removal reduced mineral soil microbial C by 19.0% in the ungirdled plots, but only 4.0% in girdled plots. Root trenching, stem girdling and their interactions influenced microbial C in humus layer. Neither root trenching nor girdling significantly influenced mineral soil microbial C. Mineral soil microbial C correlated with following-month plant litterfall in control plots, but these correlations were not observed in root-trenching plots or girdling plots. Our results suggest that belowground carbon retranslocated from shoots and present in soil organic matter, rather than aboveground fresh plant litter inputs, determines seasonal fluctuation of mineral soil microbial biomass.     

亚热带地区蔬菜地甲烷净交换通量研究

农田土壤是大气甲烷(CH_4)的重要源和汇,以往关于农田CH_4净交换通量的研究多关注水稻、小麦、玉米等作物,而蔬菜地的观测研究不足。本研究采用静态暗箱-气相色谱法对亚热带地区一块种植包菜的典型露天蔬菜地开展将近1年的田间原位CH_4通量观测,以揭示蔬菜地CH_4净交换通量的周年变化特征及其影响因素,估算CH_4年累积净交换通量,并定量评估CH_4净交换通量的误差。本试验在包菜地的垄上和垄间同时布设观测点进行CH_4通量观测,并对环境因子进行同步测量,观测期为2016年1月1日至12月8日。结果表明,所研究的蔬菜地为大气CH_4的微弱汇,年平均通量为(-9.9±7.0)μg(C)×m~(-2)×h~(-1),全年累积通量为-0.84kg(C)×hm~(-2),较高的土壤水分条件和高施氮量可能是导致本研究蔬菜地CH_4吸收较弱的主要原因。全年CH_4累积通量的总体误差为-48%~-16%,其中,由于通量计算方法引起的系统误差会使估算的通量偏低32%,年尺度上的随机误差大小为16%,主要来自CH_4通量的空间差异,因此可适当增加空间重复,以减小空间随机误差。研究还发现垄上的CH_4吸收通量显著高于垄间(P0.01),因此在开展农田温室气体通量观测时应兼顾垄上和垄间、种植行和行间等农田管理措施存在显著差异的区域,均布设观测点,避免对通量观测结果造成系统性偏差。     

夏季对流层上空东风带扰动的结构演变特征及其影响西太副高短期东退的机制分析

针对东风带扰动影响西太副高短期异常东退的过程进行了分析。首先给出以下事实:位于西太副高南侧的东风带扰动与西风带扰动接近同经度时,西太副高出现异常东退。10年的统计结果表明,此现象出现的频数很高。挑选典型个例进行合成分析表明:东风带扰动具有垂直尺度深厚,上暖下冷的特征,冷区贯穿对流层中低层;垂直运动与经向风的分布取决于周围环境场;东风带扰动与西风带扰动相向移动到同经度时,南北冷区打通,在纬向上形成暖-冷-暖的温度梯度,从而引发的经向风变化是导致西太副高异常东退的原因。用热力学方程对此温度梯度的形成进行讨论,结果表明,东风带扰动西侧与西风带扰动东侧的变温联接成的负变温带造成了该温度梯度;东风带扰动西侧负变温的形成主要来自温度平流项与绝热加热项的作用;西风槽东侧负变温主要来自绝热加热项与余差项的作用。     

北太平洋亚热带海域大眼金枪鱼秋季摄食习性的初步研究

中国金枪鱼延绳钓渔业观察员于2018年9-12月在北太平洋亚热带水域(150°W-164°W,30°N-37°N)采集了146尾大眼金枪鱼(Thunnus obesus)样品,并对其胃含物组成进行了研究。结果表明,大眼金枪鱼胃含物中共鉴别出36种饵料种类,隶属于28科,优势饵料为帆蜥鱼(Alepisaurus ferox)、发光柔鱼(Eucleoteuthis luminosa)、魣蜥鱼(Lestidium prolixum)和眶灯鱼(Diaphus sp.),其相对重要性指数百分比(IRI%)分别为25.65%、14.48%、7.56%和6.77%。大眼金枪鱼在叉长为100~110 cm范围内的摄食强度最高,在性腺成熟度Ⅲ期的摄食强度也最高,而Ⅴ期的摄食强度最低,此外,在150~250 m水层中的摄食强度较高。研究结果有助于提高对大眼金枪鱼生物学特征和摄食习性的认识,及进一步了解其在生态系统和食物网结构中所扮演的重要角色。     

Impacts of elemental S applied under various temperature and moisture regimes on pH and available P in acidic, neutral and alkaline soils

We evaluated the effect of elemental S (S⁰) under three moisture (40, 60, 120% water-filled pore space; WFPS) and three temperature regimes (12, 24, 36°C) on changes in pH and available P (0.5 N NaHCO₃-extractable P) concentrations in acidic (pH 4.9), neutral (pH 7.1) and alkaline (pH 10.2) soils. Repacked soil cores were incubated for 0, 14, 28 and 42 days. Application of S⁰ did not alter the trends of pH in acidic and neutral soils at all moisture regimes but promoted a decrease in the pH of alkaline soil under aerobic conditions (40%, 60% WFPS). Moisture and temperature had profound effects on the available P concentrations in all three soils, accumulation of available P being greatest under flooded conditions (120% WFPS) at 36°C. Application of S⁰ in acidic, neutral and alkaline soils resulted in the net accumulation of 16.5, 14.5 and 13 g P g^–1 soil after 42 days at 60% WFPS, but had no effect under flooded conditions. The greatest available P accumulations in the respective soils were 19, 19.5 and 20 g P g^–1 soil (equivalent to 38, 41, 45 kg P ha^–1) with the combined effects of 36°C, 60% WFPS and applied S⁰. The results of our study revealed that oxidation of S⁰ lowered the pH of alkaline soil (r=–0.88, P<0.01), which in turn enhanced available P concentrations. Also, considering the significant relationship between the release of sulphate and accumulation of P, even in acidic soil (r=0.92, P<0.01) and neutral soil (r=0.85, P<0.01) where the decrease in pH was smaller, it is possible that the stimulatory effect of sulphate on the availability of P was due to its concurrent desorption from the colloidal surface, release from fixation sites and/or mineralization of organic P. Thus, in the humid tropics and irrigated subtropics where high moisture and temperature regimes are prevalent, the application of S⁰ could be beneficial not only in alleviating S deficiency in soils but also for enhancing the availability of P in arable soils, irrespective of their initial pH.     

2013年夏季驻马店市一次强对流天气过程分析

利用天气图分析方法,通过MICAPS、自动站资料和多普勒雷达资料,对2013年8月1日驻马店的强天气过程进行分析。结果表明：该次强降水过程是在低槽东移、副高边缘的形势下,由中低层切变线、低空急流、地面横切、地面风场切变共同作用影响。强对流天气发生时段低层水汽辐合跃增,配合,在强对流区上空建立深厚的湿层。过程前期处在副高边缘,这为强降水的发生积聚了大量不稳定的能量。同时大的CAPE值和 K指数,也体现出较强的不稳定性。     

福建南靖虎伯寮亚热带雨林竹类植物热值的研究

在春季对福建省靖县虎伯寮亚热带雨林的竹类植物叶的灰分含量,干重热值和灰分热值进行了研究。结果表明：①竹类值物叶的灰分含量大小不同,在８．０３％～２０．３９％之间,灰分含量高。②竹类植物叶的干重热值在１６２２７．１～１９８８２．５Ｊ／ｇ之间,去灰分热值在１９２５７．７～２２０７１．２Ｊ／ｇ之间。③竹类植物叶的干重热值和灰分含量有极显著的线性相关,相关方程为Ｙ＝－２１０．１９Ｘ＋２０７９２,ｒ＝０．７     

利用贵州亚热带野生经济植物建设农业科技园区

贵州亚热带地区野生经济植物种质资源极为丰富。利用这些野生植物资源建立农业科技园区有其重要价值。选用野生果树、野生药用植物、野生观赏植物、野生蔬菜、野生香料和野生淀粉植物进行农业科技园区建设,走产学研综合之路,对促进科技进步,从而推进贵州亚热带地区农业现代化进程。     

提升福建南亚热区优势农产品竞争力的思考

阐述了提升福建热区优势农产品竞争力的必要性,提出必须抓好优化区域布局,确保质量安全,加强科技创新,扩大产品流通等环节的观点和当前工作重点。     

Detection of Bartonella sp. and a novel spotted fever group Rickettsia sp. in Neotropical fleas of wild rodents (Cricetidae) from Southern Brazil

The Neotropical region shows a great diversity of fleas, comprising more than 50 genera. The importance of the study of fleas is linked to their potential role as disease vectors. The aim of this study is to investigate the presence of Rickettsia spp. and Bartonella spp. in Neotropical fleas collected from wild rodents in Southern Brazil. From 350 rodents captured, 30 were parasitized by fleas. A total of 61 fleas belonging to two genera and six different species were collected (Craneopsylla minerva minerva, Polygenis occidentalis occidentalis, Polygenis platensis, Polygenis pradoi, Polygenis rimatus, and Polygenis roberti roberti). In 13 % of fleas of three different species (C. minerva, P. platensis, and P. pradoi) Rickettsia sp. DNA was found. Phylogenetic analysis of concatenated sequences of gltA, htrA, and ompA genes showed that Rickettsia sp. found in rodent fleas (referred as strain Taim) grouped together with Spotted Fever Group Rickettsia. In reference to Bartonella spp., five genotypes were identified in seven fleas of two species (C. minerva and P. platensis) and in five rodent spleens. Also, 207 frozen samples of wild rodents were screened for these pathogens: while none was positive for Rickettsia spp.; five rodent spleens were PCR-positive for Bartonella spp.. Herein, we show the detection of potential novel variants of Bartonella sp. and Rickettsia sp. in fleas collected of wild rodents from Southern Brazil. Further studies are needed to fully characterize these microorganisms, as well as to improve the knowledge on the potential role of Neotropical flea species as diseases vectors.