Range-wide genetic diversity in natural populations of Larix principis-rupprechtii Mayr.

Prince Rupprecht’s larch(Larix principis-rupprechtii Mayr.),a deciduous conifer,widely grows in middle and high elevations of Northern China.Its natural distribution has sharply decreased and has become fragmented,which may have resulted in the loss of genetic variation.In this study,ten natural populations across the entire range of this species were analyzed using amplifi ed fragment length polymorphism markers.A total of 309 loci were detected from 225 individuals of these populations,of which 261(84.5%)were polymorphic.At the species level,the genetic diversity was high(average of the Nei’s genetic diversity H e=0.2602,and Shannon’s information index I=0.3967).The results of molecular variance analysis showed that 90.71%of the genetic diversity occurred within populations.The genetic diff erentiation among populations was moderate as a whole(F ST=0.0929,G ST=0.1510),which is consistent with the moderate level of gene fl ow among populations(N m=2.8116).Based on the unweighted pair group method with arithmetic mean and STRU CTU RE analysis,these populations were grouped into three genetically distinct clusters.The degree of inter-population diff erentiation(G ST=0.1338)for the south group was larger than that for the north group(G ST=0.0915).There was a signifi cant correlation between genetic distance and geographic distance across the species range(r=0.316,P<0.05).Genetic diversity was signifi-cantly associated with longitude but not elevation or climatic factors.The populations with high genetic diversity from each cluster are therefore recommended for future conservation and management of this species.

Effect of thinning intensity on the stem CO_(2) efflux of Larix principis-rupprechtii Mayr

Background:Stem CO_(2) efflux(E_(S))plays a critical role in the carbon budget of forest ecosystems.Thinning is a core practice for sustainable management of plantations.It is therefore necessary and urgent to study the effect and mechanism of thinning intensity(TI)on E_(S).Methods:In this study,five TIs were applied in Larix principis-rupprechtii Mayr 21-,25-,and 41-year-old stands in North China in 2010.Portable infrared gas analyzer(Li-8100 A)was used to measure ES and its association with environmental factors at monthly intervals from May to October in 2013 to 2015.In addition,nutrients,wood structure and nonstructural carbon(NSC)data were measured in August 2016.Results:The results show that ES increased with increasing TI.The maximum ES values occurred at a TI of 35%(3.29,4.57 and 2.98μmol·m^(-2)·s^(-1))and were 1.54-,1.94-and 2.89-fold greater than the minimum E_(S) value in the CK stands(2.14,2.35 and 1.03μmol·m^(-2)·s^(-1))in July for the 21-,25-and 41-year-old forests,respectively.The E_(S) of the trees in low-density stands was more sensitive to temperature than that of the trees in high-density stands.Soluble sugars(SS)and temperature are the main factors affecting ES.When the stand density is low enough as 41-year-old L.principis-rupprechtii forests with TI 35%,bark thickness(BT)and humidity should be considered in addition to air temperature(T_(a)),wood temperature(T_(w)),sapwood width(SW),nitrogen concentration(N)and SS in the evaluation of ES.If a change in stand density is ignored,the CO_(2) released from individual 21-,25-and 41-year-old trees could be underestimated by 168.89%,101.94% and 200.49%,respectively.CO_(2) release was estimated based on the stem equation in combination with the factors influencing ES for reference.Conclusions:We suggest that it is not sufficient to conventional models which quantify ES only by temperature and that incorporating the associated drivers(e.g.density,SS,SW and N)based on stand density into conventional models can improve the accuracy of ES estimates.

Mayr电弧模型下GIS中快速暂态过电压的仿真分析

SF6气体绝缘封闭组合开关(GIS)中隔离开关进行分合母线时,产生快速暂态过电压(VFTO),幅值高且上升速率极快,威胁GIS及相邻设备的绝缘。选取某800 kV GIS隔离开关分合母线的试验电路为研究对象,采用电磁暂态程序(EMTP/ATP)进行建模仿真,隔离开关燃弧时采用Mayr电弧模型,分析其对VFTO的影响,得出考虑Mayr电弧模型时操作隔离开关、断路器侧隔离开关及变压器侧隔离开关的电压波形,并与考虑时变电阻模型的VFTO进行对比。对VFTO波形进行离散傅里叶分析,得到过电压频率、幅值的变化特征,研究结果为GIS绝缘设计提供参考。

Family selection and evaluation of Larix gmelinii var.principis-rupprechtii(Mayr.)Pilger based on stem analysis data at multiple sites

Larix gmelinii var.principis-rupprechtii(Mayr.)Pilger is an important native tree species in North China with advantages of fast growth,straight trunk,and good wood properties.The multi-year and multi-site breeding research of families of the species has not been reported previously.Based on diameter at breast height(DBH),height and volume of 25 families on four experimental sites,we calculated variance components,genetic parameters,juvenile and mature trait correlations and made genotype main effect plus genotype×environment interaction effect(GGE)biplot based on the breeding values estimated using the method of best linear unbiased prediction(BLUP).Compared with height,DBH and volume had higher heritability and larger variation coefficients,making them the more suitable traits for family selection and evaluation.Based on these,GGE biplots containing 20 combinations of site×age were drawn using data at 13 to 17 years when the interactions between family and location were strong.Test sites classifications based on DBH,and volume were inconsistent,with two categories for DBH and one for volume.The Guyuan site was the most suitable with strong discriminating ability,high representativeness and stability among tree ages.Integrating the ranking results of DBH and volume,families 66,76,82 and 111 were high-yielding and stable,families 78 and96 were high-yielding with above average stability,families72 and 79 were high-yielding with below average stability,whereas stability of family 100 was inconsistent between DBH and volume.Early selection based on DBH was convenient and reliable,and can be made at seven years.This study provides support for the selection of Larix gmelinii var.principis-rupprechtii families in Hebei province and an example for the application of stem analysis data from multiple sites in tree breeding.

270V直流开断特性研究与耗散功率变化的Mayr模型仿真分析

为了优化航空270V直流接触器结构设计以及预期接触器的开断容量,采用一种以栅片和磁吹系统相结合的直流接触器,进行典型负载类型下的开断性能实验,得到了感性负载情况下开断难度最大,且随着回路电感值的增大,燃弧时间和电弧熄灭时过电压峰值增加。主触点间并联RC支路虽然会增加整个燃弧时间,但能有效限制过电压的数值,且过电压峰值随并联支路电容C的增加而减小。假设燃弧过程中电弧具有对称性,并对电弧进行受力分析,提出横向磁场中电弧运动速度和消散功率的计算方法,得到一种Mayr电弧修正模型。在不同等级的阻性负载情况下,分别对燃弧过程进行数值仿真,经仿真与实验结果对比,所提Mayr电弧修正模型能够准确描述电极分断过程中电弧电压及运动速度的变化情况,为航空直流接触器的设计提供有效的参考。

基于Mayr模型的低压配电线路故障电弧研究

针对故障电弧研究需要搭建专门的实验环境来分别模拟串联故障电弧、并联故障电弧和接地故障电弧而存在费用较高、实际操作比较困难的问题,提出了一种能在Matlab7软件中工作的Mayr电弧模型的设计方案;介绍了Mayr电弧模型方程的物理意义,采用Mayr电弧模型封装子系统对低压交流线路发生的串联故障电弧进行了仿真,并根据仿真电路,模拟了低压交流线路发生串联故障电弧的实验。仿真及实验结果表明,Mayr电弧模型的故障电弧电流与实验采集到的故障电弧电流比较接近,采用Mayr电弧模型用于低压交流线路故障电弧仿真具有一定的可行性。

More tree growth reduction due to consecutive drought and its legacy effect for a semiarid larch plantation in Northwest China

Extreme climate has increasingly led to negative impacts on forest ecosystems globally,especially in semiarid areas where forest ecosystems are more vulnerable.However,it is poorly understood how tree growth is affected by different drought events.In 2006–2009,the larch plantations in the semiarid areas of Northwest China were negatively affected by four consecutive dry years,which was a very rare phenomenon that may occur frequently under future climate warming.In this study,we analyzed the effect of these consecutive dry years on tree growth based on the data of the tree rings in the dominant layer of the forest canopy on a larch plantation.We found that the tree-ring width index(RWI)in dry years was lower than that in normal years,and it experienced a rapidly decreasing trend from 2006 to 2009(slope=-0.139 year^(-1),r=-0.94)due to water supply deficits in those dry years.Drought induced legacy effects of tree growth reduction,and consecutive dry years corresponded with greater growth reductions and legacy effects.Growth reductions and legacy effects were significantly stronger in the third and fourth consecutive dry years than that of single dry year(p<0.05),which might have been due to the cumulative stress caused by consecutive dry years.Our results showed that larch trees experienced greater tree growth reduction due to consecutive dry years and their legacy effect,and the trees had lower recovery rates after consecutive dry years.Our results highlight that consecutive dry years pose a new threat to plantations under climate warming,and thus,the effect of climate extremes on tree growth should be considered in growth models in semiarid areas.

保幼激素类似物饵料防治印度大头蚁Pheidole indica Mayr研究

通过保幼激素类似物和饵料对印度大头蚁防效的筛选,选出有效保幼激素类似物 ZR_(777)、ZR_(515)、ZR_(512)和最佳饵料熟鱼肉。0.06%的 ZR_(512)能杀灭蚁巢,0.6%效果更佳。在2.0×π×0.725cm^3的蚁巢中,用 ZR_(512)含量为0.06%、0.6%、1.5%的熟鱼肉作饵料时(每巢有4个蚁后,隔天加水并换饵0.40g),根绝蚁群所需时间分别为48.25天、34.75天和33.00天。经 ZR_(512)处理蚁巢的,蚁后卵巢萎缩、体积变小、卵巢管少,一般只有少数临产的卵,有些甚至没有卵或卵母细胞。

基于改进Mayr模型的弓网离线电弧仿真分析

弓网离线电弧对受电弓滑板和接触网导线具有烧饬作用,严重危害列车的运行安全。首先介绍Mayr电弧模型,并基于能量平衡理论和横向吹弧理论,对弓网离线电弧弧柱的能量过程进行数学分析,研究高速气流对电弧耗散功率的影响。确立电弧耗散功率Ploss和车速v、电流I和离线间距l之间的函数关系,对Mayr电弧模型进行改进。然后运用Simulink仿真软件,搭建改进的Mayr电弧模型。最后对比分析弓网离线电弧仿真波形和实验波形,验证搭建的弓网离线电弧模型的合理性。结论如下:随着列车运行速度提高和离线间距的增大,气流对电弧的吹弧作用更加显著,电弧耗散功率增加,燃弧尖峰电压和熄弧尖峰电压增大。

保幼激素类似物ZR－512的简便合成及其对印度大头蚁（PheidoleindicaMayr）的有效性

本文报导了ＺＲ－５１２的简便合成方法，总收率为４９％，并发现ＺＲ－５１２对印度大头蚁ＰｈｅｉｄｏｌｅｉｎｄｉｃａＭａｙｒ具有极显著的活性。

基于组合Mayr和Cassie电弧模型的弧光接地故障仿真及分析

弧光接地故障在配电网中发生的概率较大,其动态特性对于检测电弧故障起着十分重要的作用。Mayr、Cassie模型是研究电弧接地故障两种经典模型,适用于描述电弧不同的物理特性。文中以电弧电流为变量建立过渡函数,构造了一种Mayr-Cassie组合模型,该模型综合考虑了电弧对流散热和径向传导散热。在PSCAD/EMTP平台上搭建了单相电弧接地故障模型,分析了电弧电压、电流、电阻的动态特征,并进一步将该模型用于10kV配电网故障分析中,结果表明该模型可准确反映电弧特性。

爪哇扁头猛蚁(Ectomomyrmex javanus(Mayr))觅食活动规律研究

为了研究爪哇扁头猛蚁(Ectomomyrmex javanus(Mayr))的觅食活动规律及其食性,探查其觅食活动与环境温湿度的相互关系,采用陷阱诱集法统计不同季节、不同时段外出觅食工蚁的数量,分析环境温湿度与其觅食活动季节动态和日动态的相关性,并通过分析其捕获食物种类确定其食性。结果表明,爪哇扁头猛蚁觅食的季节动态与环境温度、湿度均显著相关(P<0.01),夏季是其觅食的高峰时期,秋季开始下降,冬季停止外出觅食,4月再次开始觅食活动;其觅食的日动态在一定范围内与环境温度显著相关(P<0.01),但与湿度相关性不显著;一天中8:00是其工蚁外出觅食的高峰期,随着环境温度的上升,其觅食活动开始减少,直到傍晚温度降低时,其觅食活动开始增加。爪哇扁头猛蚁主要取食节肢动物尸体,表现为肉食性。

适用于低压串联故障电弧的Mayr改进模型

电气火灾中由串联故障电弧引起的占很大一部分比例,所以串联故障电弧分析具有很重要的意义。在Mayr模型的基础上提出了一种改进型的串联故障电弧模型,弥补了经典电弧模型在阻性负载和阻感性负载下丢失一些原本电弧所具有的特征。将电弧看成一个时变阻抗的黑盒模型,将零休时期的电弧模型等效为RLC串联电路,用MATLAB/Simulink仿真出的电弧电流波形和实际试验的电弧电流波形比经典模型更加接近,验证了模型的可行性。

Age–age correlations and early selection for growth traits in 40 half-sib families of Larix principis-rupprechtii

Larix principis-rupprechtii Mayr is a dominant species in coniferous forests of North China.However,early selection of L.principis-rupprechtii for growth traits is poorly characterised.To explore the optimal selection age for this species,heights(HT)and diameters at breast(DBH)of 40 half-sib families were measured at ages 3,12,22,and 28 years in a progeny test population established in the town of Kangjiahui,Shanxi Province.Age trends in heritability,age–age genetic correlations,and early selection efficiency for height and DBH were analysed.The individual heritability of these growth traits varied over time,and maximized at different ages(0.55 at age 12 for HT and 0.48 at age 28 for DBH).The age–age genetic correlations were always positive,and the majority were high(0.790–0.953)between the juvenile and mature ages for HT and DBH.For the same pairs of measurements,HT demonstrated higher age–age genetic correlations than DBH,and both age–age genetic correlation data sets were described well by the linear relationship with the logarithm of the age ratio(r2[0.90).The regression slope for DBH was lower than that for HT.Based on the early selection efficiency estimates,the optimal selection age could be as early as age 6 for DBH and 8–9 years for HT.The results of this study provide information that can be used to assist early selection practices in L.principis-rupprechtii improvement programs in Shanxi Province.

基于MAYR电弧模型的船舶直流配电系统熔断器仿真研究

大功率变频器和储能设备的接入,对船舶直流配电系统在各种工况下的安全运行提出了考验。由于针对船舶直流配电系统专门搭建实验环境模拟短路故障实验复杂且代价高昂,因此提出了一种基于MAYR电弧模型熔断器的仿真选型方案。在MATLAB/SIMULINK平台进行模拟短路故障仿真,能够较精确地复现短路故障熔断器状态。结合短路故障实际工况,搭建系统故障模型进行仿真。结果表明,基于MAYR模型的熔断器在短路故障发生时可以有效保护网络组件,能对熔断器和断路器的选型提供更可靠的参考依据。

Variations in stem radii of Larix principis-rupprechtii to environmental factors at two slope locations in the Liupan Mountains,northwest China

Relationships between stem growth and climatic and edaphic factors,notably air temperatures and soil moisture for different slopes,are not completely understood.Stem radial variations were monitored at the bottom and top slope positions in a Larix principis-rupprechtii plantation during the 2017 and 2018 growing seasons.Total precipitation during the growing season in 2017 and 2018 was 566 mm and 728 mm,respectively.Stem contractions typically occurred after mid-morning followed by swelling in the late afternoon in both plots,reflecting the diurnal cycle of water uptake and loss.Trees at the two locations showed the same growth initiation(mid-May)because of the small differences in air and soil temperatures.There were no significant differences in cumulative stem radial growth between the bottom plot(1.57±0.34 mm)and the top plot(1.55±0.26 mm)in 2018.However,in 2017,the main growth period of the bottom plot ceased 17 days earlier than in the top plot,while cumulative seasonal growth of the bottom plot(1.08±0.25 mm)was significantly less than the top plot(1.54±0.43 mm).Maximum daily stem shrinkage was positively correlated with air and soil temperatures,solar radiation,vapor pressure deficits,and negatively correlated with volumetric soil moisture content.The maximum daily shrinkage reflected transpiration rates as affected by environmental factors.Daily radial stem increment was correlated with precipitation and volumetric soil moisture in both years,but with air temperatures only in 2017.The seasonal growth of L.principis-rupprechtii Mayr thus shows interannual dynamics,while precipitation constitutes a key driving factor.

Estimation of leaf area index from high resolution ZY-3 satellite imagery in a catchment dominated by Larix principis-rupprechtii,northern China

Leaf area index(LAI) is a key factor that determines a forest ecosystem's net primary production and energy exchange between the atmosphere and land surfaces.LAI can be measured in many ways, but there has been little research to compare LAI estimated by different methods. In this study, we compared the LAI results from two different approaches, i.e., the dimidiate pixel model(DPM) and an empirical statistic model(ESM) using ZY-3 high-accuracy satellite images validated by field data. We explored the relationship of LAI of Larix principis-rupprechtii Mayr plantations with topographic conditions. The results show that DPM improves the simulation of LAI(r = 0.86,RMSE = 0.57) compared with ESM(r = 0.62, RMSE =0.79). We further concluded that elevation and slope significantly affect the distribution of LAI. The maximum peak of LAI appeared at an aspect of east and southeast at an elevation of 1700–2000 m. Our results suggest that ZY-3 can satisfy the needs of quantitative monitoring of leaf area indices in small-scale catchment areas. DPM provides a simple and accurate method to obtain forest vegetation parameters in the case of non-ground measurement points.

Rules of Changes in Soil Nutrients and Enzyme Activities of Larix principis-rupprechtii in Different Forest Ages

In this study,three different ages of Larix principis-rupprechtii forests in 5,10 and 20 years were selected as the research objects,and the changes in soil nutrient and soil enzyme activities in different growth stages were analyzed. The results showed that the contents of organic matter and available phosphorus in the soil of different growth stages showed a significant downward trend with the increase of soil depth.For different forest ages in the same soil layer,the soil available phosphorus content declined with the increase of the forest age. The organic matter content of 40-60 cm in 20 years of forest age was the lowest in July,which was 4. 17 g/kg,significantly lower than that in other soil layers. Besides,the soil available phosphorus content of 5 years of forest age reached the maximum in July,with an average of 4. 44 mg/kg,which was higher than the available phosphorus content in soil in May and September,but the difference between the three months was not significant. The changes in ammonium nitrogen and nitrate nitrogen content in soil with different forest ages were consistent with the changes in the soil depth,showing a downward trend. In the new leaf stage,the ammonium nitrogen content of the L. principis-rupprechtii forest land in5 years of age at 20-40 and 40-60 cm of the soil depth was 13. 47 and 9. 09 mg/kg,respectively,which was 46. 9% and 64. 2% lower than that at 0-20 cm( 25. 36 mg/kg) of the soil depth. The soil nitrate nitrogen content of 20 years of forest age was 19. 24 mg/kg,which was25. 8% lower than that of 10 years of forest age,showing significant difference( P < 0. 05). In addition,with the increase of the age of L. principis-rupprechtii,soil catalase( CAT),alkaline phosphatase( ALP) and urease( Ure) decreased,and the decline of ALP was slow,while CAT and Ure decreased significantly. In summary,it is concluded that the soil fertility of forest land declined with the increase of forest age on the basis of change trend of soil nutrient and soil enzyme activity in the surveyed forest age.

基于Mayr-Cassie的配电网络单相接地电弧建模及仿真研究

中低压配电网络中,单相接地故障发生的概率最大,能准确反映接地故障特征的相应数学模型是配电网故障分析的基础。基于弧隙平衡理论,分析了经典Mayr模型和Cassie模型的特点,建立了一种Mayr和Cassie合理结合的电弧模型,进一步研究了弧长参数对电弧特性的影响,反映出接地电弧的物理特性;最后,将此电弧模型用于某10kV配电网络,以间歇性电弧接地的故障形式进行模拟仿真,通过对结果的分析和与实际情况的比较,验证了该电弧模型的正确性,为下一步配电网故障分析打下良好基础。

直流可控避雷器用并联可控间隙电弧的维持规律

根据白鹤滩—江苏±800kV特高压直流输电工程提出的技术需求,针对系统过电压幅值较低情况下可控间隙动作时间隙无法维持导通状态至机械开关动作的情况,设计了可控避雷器用并联可控间隙并开展研究。通过补充的Mayr电弧模型对给定条件下触发器注入能量与间隙电弧维持时间的关系进行了分析和预测,并搭建实验平台研究了触发器提供的功率及能量对间隙电弧维持时间的影响,结果表明提高触发器的功率和能量都可以提高间隙电弧维持燃烧的时间;间隙主回路能量不足时,触发器提供的能量可以作为衡量间隙最低导通能力的标准。最终通过5路触发器间隔1ms接续触发的方式,使间隙在主回路没有能量注入时也能维持导通5ms,从而具备了与快速机械开关无缝时序配合的能力,为采用并联可控间隙的可控避雷器方案的推广提供了理论支持。