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蔬菜废弃物中温厌氧发酵酸化失稳预警指标筛选
No full text厌氧消化是一种可以较好地将有机废弃物处理和能源回收结合的生物技术,它是多种厌氧微生物共同参与、分阶段有序进行的复杂串联代谢过程。其中产甲烷菌对环境最敏感、代谢速率最慢,产甲烷阶段往往是厌氧消化系统的瓶颈,水解酸化与产甲烷两阶段不能较好地匹配,极易受到抑制。针对蔬菜废弃物厌氧发酵易酸化的特点,该试验旨在筛选发酵体系酸化失稳预警指标,采用自行设计的70 L反应装置,在中温35℃条件下进行蔬菜废弃物厌氧发酵的连续冲击负荷试验。通过对发酵过程中的气相及液相指标监测,该研究筛选出4类失稳预警指标,分别为:1)甲烷与二氧化碳的比值。当CH_4/CO_20.4时,系统提前13、12和12 d做出酸化预警指示,此时发酵体系缓冲性能较差,系统极易出现挥发性脂肪酸的累积进而导致系统酸化失稳;4)氧化还原电位和pH值在整个厌氧消化过程中均持续微弱变化,利用其绝对值很难做出失稳判断,利用其相对变化值可做出失稳判断,骤变分别发生在产气彻底停止前第5天和第4天,预警能力较弱。在工程实际应用中,相比液相指标而言,气相指标的监测更容易实现,建议CH_4/CO_2作为预警指标
Utilization of a Wheat660K SNP array-derived high-density genetic map for high-resolution mapping of a major QTL for kernel number
No full textIn crop plants, a high-density genetic linkage map is essential for both genetic and genomic researches. The complexity and the large size of wheat genome have hampered the acquisition of a high-resolution genetic map. In this study, we report a high-density genetic map based on an individual mapping population using the Affymetrix Wheat660K single-nucleotide polymorphism (SNP) array as a probe in hexaploid wheat. The resultant genetic map consisted of 119 566 loci spanning 4424.4 cM, and 119 001 of those loci were SNP markers. This genetic map showed good collinearity with the 90 K and 820 K consensus genetic maps and was also in accordance with the recently released wheat whole genome assembly. The high-density wheat genetic map will provide a major resource for future genetic and genomic research in wheat. Moreover, a comparative genomics analysis among gramineous plant genomes was conducted based on the high-density wheat genetic map, providing an overview of the structural relationships among theses gramineous plant genomes. A major stable quantitative trait locus (QTL) for kernel number per spike was characterized, providing a solid foundation for the future high-resolution mapping and map-based cloning of the targeted QTL
不同LED光质对迭鞘石斛生理及品质的影响
No full text设置6种光质,自然光(对照,N5)、100%红光+0%蓝光(R5)、100%蓝光+0%红光(B5)、80%红光+20%蓝光[RB(4:1)]、60%红光+40%蓝光[RB(3:2)]、40%红光+60%蓝光[RB(2:3)],测定不同处理时间迭鞘石斛的生理指标以及多糖、黄酮的含量.结果显示光质对迭鞘石斛生理及品质有较为明显的影响.B5处理组的超氧化物歧化酶含量最高;R5处理组的丙二醛含量最高.RB(3:2)处理组的叶绿素含量最高,RB(2:3)处理组的可溶性糖、可溶性蛋白、多糖含量都最高;N5处理组的黄酮含量最高.R5处理组的叶绿素、可溶性糖、可溶性蛋白、多糖和黄酮含量都较低,说明纯红光并不利于迭鞘石斛生长.此外,不同处理天数下丙二醛、可溶性蛋白、可溶性糖、多糖和黄酮含量整体上呈现上升趋势;超氧化物歧化酶活力整体下降趋势;叶绿素含量整体上呈现先下降后上升的趋势.本研究说明红蓝光配比有利于迭鞘石斛生长发育和次生代谢物质积累,对迭鞘石斛组培苗的光控培养和品质改良具有生产上的指导意义
清远地区麻竹笋地下害虫的危害特征及防治措施
No full text采用抽样调查的方法,研究了麻竹笋地下害虫的危害特征及防治措施。结果表明,麻竹笋地下害虫的种类较多,其中危害较大的是沟金针虫、阔胫鳃金龟、毛黄脊鳃金龟、小黄鳃金龟、黑绒鳃金龟。体型较大的沟金针虫在麻竹笋土壤中的分布为聚集分布,而金龟子类害虫则为随机分布,采用多种防治措施均可有效防治麻竹笋地下害虫
Near-zero methane emission from an abandoned boreal peatland pasture based on eddy covariance measurements
No full textAlthough estimates of the annual methane (CH4) flux from agriculturally managed peatlands exist, knowledge of controls over the variation of CH4 at different time-scales is limited due to the lack of high temporal-resolution data. Here we present CH4 fluxes measured from May 2014 to April 2016 using the eddy covariance technique at an abandoned peatland pasture in western Newfoundland, Canada. The goals of the study were to identify the controls on the seasonal variations in CH4 flux and to quantify the annual CH4 flux. The seasonal variation in daily CH4 flux was not strong in the two study years, however a few periods of pronounced emissions occurred in the late growing season. The daily average CH4 flux was small relative to other studies, ranging from -4.1 to 9.9 nmol m(-2) s(-1) in 2014-15 and from -7.1 to 12.1 nmol m(-2) s(-1) in 2015-16. Stepwise multiple regression was used to investigate controls on CH4 flux and this analysis found shifting controls on CH4 flux at different periods of the growing season. During the early growing season CH4 flux was closely related to carbon dioxide fixation rates, suggesting substrate availability was the main control. The peak growing season CH4 flux was principally controlled by the CH4 oxidation in 2014, where the CH4 flux decreased and increased with soil temperature at 50 cm and soil water content at 10 cm, but a contrasting temperature-CH4 relation was found in 2015. The late growing season CH4 flux was found to be regulated by the variation in water table level and air temperature in 2014. The annual CH4 emission was near zero in both study years (0.36 +/- 0.30 g CH4 m(-2) yr(-1) in 2014-15 and 0.13 +/- 0.38 g CH4 m(-2) yr(-1) in 2015-16), but fell within the range of CH4 emissions reported for agriculturally managed peatlands elsewhere
Interannual variation in methane emissions from tropical wetlands triggered by repeated El Nino Southern Oscillation
No full textMethane (CH4) emissions from tropical wetlands contribute 60%-80% of global natural wetland CH4 emissions. Decreased wetland CH4 emissions can act as a negative feedback mechanism for future climate warming and vice versa. The impact of the El Nino-Southern Oscillation (ENSO) on CH4 emissions from wetlands remains poorly quantified at both regional and global scales, and El Nino events are expected to become more severe based on climate models' projections. We use a process-based model of global wetland CH4 emissions to investigate the impacts of the ENSO on CH4 emissions in tropical wetlands for the period from 1950 to 2012. The results show that CH4 emissions from tropical wetlands respond strongly to repeated ENSO events, with negative anomalies occurring during El Nino periods and with positive anomalies occurring during La Nina periods. An approximately 8-month time lag was detected between tropical wetland CH4 emissions and ENSO events, which was caused by the combined time lag effects of ENSO events on precipitation and temperature over tropical wetlands. The ENSO can explain 49% of interannual variations for tropical wetland CH4 emissions. Furthermore, relative to neutral years, changes in temperature have much stronger effects on tropical wetland CH4 emissions than the changes in precipitation during ENSO periods. The occurrence of several El Nino events contributed to a lower decadal mean growth rate in atmospheric CH4 concentrations throughout the 1980s and 1990s and to stable atmospheric CH4 concentrations from 1999 to 2006, resulting in negative feedback to global warming
Consistent profile pattern and spatial variation of soil C/N/P stoichiometric ratios in the subalpine forests
No full textPurpose The vertical patterns of soil carbon (C), nitrogen (N), and phosphorus (P) stoichiometry are still controversial, and relative contribution of their controlling factors also is rarely understood for the whole soil profile. This study aimed to assess the vertical variation of both C/N, N/P, C/P ratios and their determining factors along soil profiles in subalpine forests of the eastern Tibetan Plateau. Materials and methods Soil samples at five depths (0-10, 10-20, 20-30, 30-50, and 50-100 cm) were collected from 132 forest sites to evaluate the vertical distribution of soil C/N, N/P, and C/P ratios. Eleven relevant environmental factors (e.g., altitude, latitude, longitude, soil pH, soil bulk density, relative stone contents, soil order, slope, position, forest type, and dominant tree species) were measured to examine their relative contribution on stoichiometric ratios within each soil layer using boosted regression tree (BRT) analysis. Result and discussion Soil C/N, N/P, and C/P ratios consistently decreased with increasing soil depth. BRT models accurately predicted the soil C/N, N/P, and C/P ratios in the upper four layers (R (2) = 49-97 %). For soil C/N and N/P ratios, altitude associated with latitude had the highest contribution across five soil layers, while the contributions of soil pH and bulk density were significant within soil layers closer to the surface. Independently, soil bulk density and altitude were the most important factors of C/P ratios in 0-30- and 30-100-cm soil layers. Conclusion This study indicated that soil C/N/P stoichiometric ratios, and the relative importance of their controlling factors, shifted within soil profiles across Tibetan Plateau forests. Further research will be needed to understand the regulatory mechanism of soil stoichiometry and biogeochemistry in response to environmental change at whole soil profiles
Responses of root exudation and nutrient cycling to grazing intensities and recovery practices in an alpine meadow: An implication for pasture management
No full textThe rhizosphere priming effect is caused by root carbon (C) exudation into the rhizosphere; the role of this effect in nutrient cycling and ecosystem recovery of natural grasslands as affected by different grazing intensities is still unknown. The objective of the present study was to investigate the relationships among root C exudation, rhizospheric microbial activity, and their influences on plant nutrient uptake during grazing and recovery periods. Field experiments were conducted in the Hongyuan Alpine Meadow to measure root exudation rate and nutrient cycling processes of the dominant species Elymus nutans. Three grazing intensities (an ungrazed control, moderate grazing and heavy grazing) were introduced for two months, following which all treatments received a recovery practice (no grazing for 21 days). Heavy grazing significantly decreased root exudation rate, soil nitrogen (N) mineralization rate, beta-1,4-glucosidase (BG) activity, and foliar C concentration, while moderate grazing had no influence on these parameters compared to the control. After the 21 days of recovery, all these parameters, except N mineralization rate and foliar C concentrations in the heavy grazing treatment, returned to similar levels as in the control, whereas root exudation rate and BG activity rose to even higher levels. Meanwhile, moderate grazing significantly promoted root exudation rate, soil inorganic N concentration, net soil N mineralization rate, and beta-N-acetylglucosaminidase (NAG) activity during the recovery stage as compared to the control. Foliar quality was also improved by the recovery practice, indicating that the high availability of N and P is a consequence of the positive root-microbe feedback and will ultimately benefit grazers. The flush of labile C released to the rhizosphere by grazed plants stimulated extracellular enzyme activities, enhanced soil N mineralization, and increased plant nutrient uptake. These results imply that reasonable (i.e. moderate) grazing followed by a recovery practice can effectively restore and strengthen grassland vegetation, and contribute to the sustainable use of alpine meadows such as Hongyuan
Two Ultraviolet Radiation Datasets that Cover China
No full textUltraviolet (UV) radiation has significant effects on ecosystems, environments, and human health, as well as atmospheric processes and climate change. Two ultraviolet radiation datasets are described in this paper. One contains hourly observations of UV radiation measured at 40 Chinese Ecosystem Research Network stations from 2005 to 2015. CUV3 broadband radiometers were used to observe the UV radiation, with an accuracy of 5%, which meets the World Meteorology Organization's measurement standards. The extremum method was used to control the quality of the measured datasets. The other dataset contains daily cumulative UV radiation estimates that were calculated using an all-sky estimation model combined with a hybrid model. The reconstructed daily UV radiation data span from 1961 to 2014. The mean absolute bias error and root-mean-square error are smaller than 30% at most stations, and most of the mean bias error values are negative, which indicates underestimation of the UV radiation intensity. These datasets can improve our basic knowledge of the spatial and temporal variations in UV radiation. Additionally, these datasets can be used in studies of potential ozone formation and atmospheric oxidation, as well as simulations of ecological processes
