Calculation method for sunshine duration in canopy gaps and its application in analyzing gap light regimes

Understory light is essential to the growth and survival of plants, yet the light varies temporally and spatially within forest gaps. Measurement of understory light levels using light sensors is both time and labor intensive. Sunshine duration (SD) has a strong correlation with solar radiation and has been the variable most widely used for estimating solar radiation. The power of SD-based methods for estimating solar radiation lies in its ability to quickly estimate light levels. Although several calculation methods for SD within canopy gaps are available, all the methods oversimplify canopy gaps by classifying them as cylindrical or ellipsoid and thus have a relatively low level of accuracy. In this study we developed a calculation method for SD at any given point within natural canopy gaps and we used SD to estimate solar radiation within 12 canopy gaps on Mt. Taibai in China based on the Angström-Prescott model. We then evaluated the SD-based solar radiation by the total and direct solar radiation derived from a gap light index based on hemispherical photographs (HP). Finally, we analyzed the spatial-temporal characteristics of light levels within these 12 gaps by using the solar radiation derived from SD at hundreds of simulated points in each gap. Our results showed that (1) SD-based solar radiation was not statistically different from HP-based direct solar radiation and had a strong linear correlation with HP-based total solar radiation; (2) growing-season daily mean solar radiation within the 12 gaps varied from 0.08 to 13.28 MJ m⁻² day⁻¹ with an average of 4.13 MJ m⁻² day⁻¹; (3) solar radiation had a positive correlation with the ratio of the square root of the canopy gap area to the mean canopy height. This relationship was significant but solar radiation had no correlation with the canopy gap area; (4) among most gaps solar radiation was greatest in May while potential SD was longest in June 2008. From these results we can conclude that the SD-based method for estimating solar radiation developed in this study can quickly and accurately estimate light levels at any specified point within canopy gaps. SD-based solar radiation appears to be a good choice for studies on the spatial-temporal characteristics of gap light levels.     

洛阳孟津冬小麦生产潜力长周期定量模拟与评价

以洛阳孟津地区气象数据库、土壤数据库、作物数据库和多年田间试验数据库为基础, 应用DSSAT作物生长模型估算了当地冬小麦光温生产潜力和光温水生产潜力, 并对节水潜力及途径进行了分析.结果表明, 洛阳孟津地区46年冬小麦光温生产潜力为7 571～10 965 kg·hm-2, 平均9 209 kg·hm-2, 此值可作为当地补灌区产量的上限参考值; 光温水生产潜力为3 957～7 450 kg·hm-2, 平均5 510 kg·hm-2, 仅占光温生产潜力的59.8%, 此值可作为雨养冬小麦产量的上限参考值.冬小麦生育期内平均降水量为226.29 mm, 不及需水量的一半, 平均水分亏缺量占生育期降水量比例高达72.5%, 平均水分满足率为66.4%, 生育期水分亏缺成为影响洛阳孟津地区旱作冬小麦生产发展的首要障碍.不同土壤类型及不同降雨年型冬小麦潜在水分利用效率变幅较大, 波动范围为12.06～22.94 kg·hm-2·mm-1, 46年均值为16.94 kg·hm-2·mm-1.近8年旱作冬小麦现实水分利用效率仅占潜在水分利用效率的58.5%, 平均光温水生产潜力开发度为60.5%.结果表明, 洛阳孟津地区冬小麦节水潜力较大, 采用合理的节水农业措施, 加强农田建设, 改善地力, 增强土壤储水蓄水能力, 高效利用降水资源, 提高水分利用效率是今后提高冬小麦产量的重要途径.     

Chemical evaluation of waste from Thaumatococcus danielli (Benth) processing

Three different batches of Thaumatococcus danielli (Benth) fruits were collected at different fruiting seasons. The proximate compositions of the pericarp and seeds were determined on a dry weight basis. Partial characterization of the lipid extract was carried out and tannin content determined. The average moisture, ash and lipid contents of the pericarp were higher (89.2 ± 4.17%, 20.7 ± 1.10% and 11.6 ± 1.23%, respectively) than those of the seed (31.2 ± 4.66% 9.1 ± 0.71% and 8.2 ± 1.64%, respectively). Crude protein and total carbohydrate were, however, higher in the seed (9.5 ± 4.38% and 69.4 ± 11.52%, respectively) than in the pericarp (4.5 ± 2.21% and 6.3 ± 3.94%, respectively). The dietary fiber contents of both pericarp and seed were high. Starch content was very low in the pericarp (0.4 ± 0.0%) compared to the seed (66.28 ± 9.21%). Tannin content in the pericarp and seeds was 12.1 ± 1.52 mg/g and 21.9 ± 2.28 mg/g, respectively. The oil extracted from both pericarp and seeds was light-yellow in color and slightly solid at room temperature. Unsaturation level of T. danielli oil was low, while free fatty acids were high. The results obtained suggested that T. danielli waste could potentially be a raw material in livestock feed formulation.     

Bartonella species and their ectoparasites: selective host adaptation or strain selection between the vector and the mammalian host?

A wide range of blood-sucking arthropods have either been confirmed or are suspected as important vectors in Bartonella transmission to mammals, including humans. Overall, it appears that the diversity of Bartonella species DNA identified in ectoparasites is much broader than the species detected in their mammalian hosts, suggesting a mechanism of adaptation of Bartonella species to their host-vector ecosystem. However, these mechanisms leading to the fitness between the vectors and their hosts still need to be investigated.     

腐熟油菜秸秆、煤矸石组合的栽培基质重金属污染及蔬菜安全评价

以腐熟油菜秸秆、煤矸石等废弃资源为原料, 配制有机生态型无土栽培混合基质, 在人工光照室内以盆栽的方法栽培白菜、生菜、苋菜和菠菜, 采用尼梅罗综合污染指数和Hakanson 潜在生态风险指数法对5 种混合基质以及此基质中生长的 4 种蔬菜的重金属污染和潜在生态风险进行综合评价。结果表明: 5 种混合基质中, 煤矸石含量较少的T₁、T₂、T₃(即煤矸石与腐熟油菜秸秆的体积比分别为 2∶8、3∶7 和4∶6)基质的重金属污染程度较小, 潜在生态风险程度较低, 在这 3 种基质上栽种的蔬菜重金属综合污染评价等级为优良或安全, 符合蔬菜绿色食品标准。重金属对混合基质产生的污染中, Cd 和Hg 是主要的重金属污染及潜在生态风险因子, 其他重金属(Cr、Cu、Pb、Zn、As)的污染能力较低。此外, 影响混合基质重金属生物有效性的主要因子是有机质, 除Cd、As 外, 基质中的有机质含量与有效态重金属含量存在极显著负相关, 基质pH 对其影响较小。     

中美猪肉产业互补性对双边猪肉贸易的影响分析

中美两国猪肉产业资源禀赋和生产率存在显著差异,双边猪肉贸易不平衡,产业互补性和贸易潜力有待提升。为研究中美两国猪肉产业互补性问题,本文以双边猪肉产业互补性指数为核心解释变量,对两国猪肉贸易引力模型进行了估计。结果显示:中美两国猪肉产业互补性指数对双边猪肉贸易有着正的影响;中美两国猪肉贸易潜力巨大,双边猪肉贸易具有很大的提升空间。在中美贸易纠纷逐步解决的背景下两国应加强猪肉产业合作,提高双边猪肉贸易互补水平。     

土地整理潜力评价指标体系初探 ——以重庆市为例

旨在构建完整的土地整理潜力评价指标体系,为土地开发整理规划以及在实施土地整理中确定土地整理重点区域和重点项目奠定基础。分别采用了因果分析法、文献资料法、实证分析法等研究方法,从土地整理的目标、土地整理潜力以及影响因素等分析入手,以重庆市为例,构建了省级层次的耕地整理、农村居民点整理、废弃土地复垦、未利用土地开发潜力评价指标体系。     

河南省扶沟县农牧业全面发展的调查分析

 扶沟县养牛业发展很快，每5.6亩地一头牛，人均牛肉占有量比全国高1倍。由于牛种改良慢，出栏率还低，每头存栏牛产肉量仅为先进国家的40%，故潜力极大。猪、牛头数比为0.55∶1，猪、牛产肉比为2∶1，猪的饲料转化率较高，有必要提高牲猪出栏比例。扶沟县粮、棉人均占有量分别达470.3和71.1公斤，在全国也是先进的。但总肉品生产量过低。目前，扶沟县已形成了粮、棉、畜三元结构雏形。在粮草兼作，粮肉生产关系和畜牧业内部结构上还有待进一步合理化；农牧营养物质相互转化都在30%上下，宜进一步强化。     

山西高产氮高效玉米品种的筛选及其干物质氮素累积与分配

通过分析16个玉米品种在施氮(225 kg/hm²)和不施氮条件下的产量及其节氮潜力等筛选高产氮高效品种。结果表明,两年中晋玉18、登海605、先玉335增产潜力在5%以上,节氮潜力为15.48%~18.39%(2018年)和14.26%~29.47%(2019年)。根据供试品种在施氮和不施氮条件下的产量平均值作为分界线,将这16个品种划分为4种类型。通过对其生物量及氮素累积与转运特征的分析,表明高产氮高效品种具有较高的花后干物质累积量,在保证一般水平的花前氮素转运量的基础上有较高的花后氮素吸收量。     

气候变化条件下马尾松人工林潜在地理分布的诊断

基于186条中国马尾松分布记录和1931-1960年、1961-1990年、1991-2017年3个时期19个气候因子数据,利用最大熵模型(MaxEnt),研究过去近90a影响中国马尾松适生区分布的气候因子、适宜马尾松生长及分布的气候条件,以及马尾松在不同时期适生区分布变化情况,以期为中国南方人工林应对气候变化提供决策支持。结果表明：(1)影响马尾松适生区分布的主要气候因子为最冷季度降水量、最干燥月降水量、气温年较差、温度季节变化标准差、年降水量和最干季度平均温度。(2)1931-1960年适宜地区总面积和较适宜地区面积最大,分别约为184.88万km²和87.45万km²,1961-1990年完全适宜地区面积最大,约为52.71万km²,1991-2017年北侧边界较1931-1960年向北偏移约1°,南侧海南岛适宜区域减至0,雷州半岛分布边界较1931-1960年向北偏移约2°。(3)随着近90a来气候变化,马尾松潜在适生区整体向东向北偏移,原有西侧和南侧零散的适生区域减退,适宜地区总面积呈现先减少后增加的趋势,现状...