木材弦向导热系数的理论表达式

分析木材细胞结构形态,以长匣子形作为木材细胞模型,根据材料导热与导电规律的相似性,应用类比推理方法,从欧姆电阻定律推出材料导热的热阻公式;依据该细胞模型和热阻公式推导木材弦向导热系数的理论表达式,从而揭示木材弦向导热系数是木材孔隙率的函数。孔隙率越大的木材,导热系数越小,并实际计算了24种木材的弦向导热系数,与试验值比较,理论值的最大误差12.6%,平均误差小于6.4%。     

Ecophysiological and genetic variation in seedling traits and in first-year field performance of eight <Emphasis Type="Italic">Acacia senegal</Emphasis> provenances in the Blue Nile,Sudan

The genetic variation in seed weight, seed number per kg and seedling traits was compared among eight Acacia senegal provenances originating from the clay plain (east) and sand plains (west) of the gum belt in Sudan. The main objective of this study was to identify germplasm sources of A. senegal that have a good seed germination capacity and seedling traits suitable for reforestation in the clay-soil part of the dryland gum belt in the Blue Nile region in Sudan. A specific objective was to tentatively explore the adaptive strategy of A. senegal populations. Seventeen-week-old seedlings were planted in the field at spacing of 3 m × 3 m, giving 100 trees per plot and replication; within a randomized complete block design with four replications. The experimental site was in the clay plain region. Seed variables showed significant differences. Clay plain provenances showed considerable variation in seed weight and seed number. They had the smallest seed weight but the highest seed number, while the sand (western) provenances had the largest seed weight but lowest seed number. Seedling branch number, root length, root to shoot ratio and shoot dry weight differed significantly among the provenances 12 weeks after germination. Clay provenances had the highest branch number and shoot dry weight but the shortest roots and lowest root to shoot ratio. This was interpreted as showing better adaptation to the site in these local provenances in comparison to those originating from the western sandy soil regions. High positive correlations were observed between seedling variables, such as root nodule and branch numbers; this could be used for early selection. The variation was greater between provenance groups than within them, suggesting that especially selection among groups would yield genetic gain.     

以电导法评价12个石榴品种的抗寒性

冻害是目前石榴商业化生产中最重要的限制因子之一。为给抗寒石榴种质的挖掘与筛选、石榴抗寒机理的深入研究和抗寒石榴的栽培生产提供理论依据,使用电导法测定了12个石榴品种1年生休眠枝在不同低温处理下的相对电导率,并拟合Logistic方程,计算了其半致死温度。结果表明:随着处理温度的降低即低温胁迫的加强,枝条组织的相对电导率呈"S"型曲线增长,各处理温度下不同品种的相对电导率间有显著性差异;供试石榴品种的半致死温度范围为-7.59~-12.60℃;供试的12个石榴品种其抗寒性的强弱次序为:峄城三白甜峄城青皮岗榴临潼净皮甜宁津青皮酸峄城复瓣白宁津三白酸太行红峄城大青皮甜峄城青皮马牙甜峄城大红皮甜新疆和田甜突尼斯软籽。     

基于电磁感应数据的电导率反演模型研究

【目的】土壤盐渍化是限制新疆南部棉花高产的主要因子,准确获取区域尺度土壤剖面盐分信息。【方法】以南疆阿拉尔垦区为研究区,以田间尺度采集的30个不同盐渍化程度棉田的540个样点的0~0.375、0~0.750、0~1.000 m的土壤剖面电导率数据和对应的电磁感应数据为数据源,采用线性模型和非线性模型分别构建了田间尺度和区域尺度的土壤剖面电导率的电磁感应反演模型,并采用缩减建模样本量方法进一步检验了区域尺度模型的可靠性和稳定性。【结果】多元线性回归(MLR)、偏最小二乘回归(PLSR)和主成分回归(PCR)建模方法的田间尺度模型R²在0.88~0.95,而对应的区域尺度模型R²在0.34~0.53。基于随机森林(RF)、神经网络(NN)和支持向量机(SVM)非线性建模方法构建的土壤剖面电导率的区域尺度电磁感应反演模型R²在0.60~0.85,其中RF模型的精度最高。0~0.375、0~0.750、0~1.000 m土壤剖面电导率的RF反演模型R²分别为0.80、0.85和0.84,相较于线性建模方法的区域尺度模型精度有明显的提高。RF区域尺度模型的样本数量由540个缩减到240个,模型精度没有明显变化,表明采用区域尺度模型,可大幅度降低土壤剖面样本采集数量,从而可显著提高采样效率和降低采样成本。【结论】区域尺度下构建土壤剖面电导率反演模型时,随机森林建模方法效果较优,模型预测能力具有较高的可靠性。     

Developing a dynamic growth model for teak plantations in India

Background： Tectono grandis （teak） is one of the most important tropical timber species occurring naturally in India. Appropriate growth models, based on advanced modeling techniques, are not available but are necessary for the successful management of teak stands in the country. Long-term forest planning requires mathematical models and the principles of Dynamical System Theory provide a solid foundation for these.
Methods： The state-space approach makes it possible to accommodate disturbances and avarying environment. In this paper, an attempt has been made to develop a dynamic growth model based on the limited data, consisting of three annual measurements, collected from 22 teak sample plots in Karnataka, Southern India.
Results： A biologically consistent whole-stand growth model has been presented which uses the state-space approach for modelling rates of change of three state-variables viz., dominant height, stems per hectare and stand basal area. Moreover, the model includes a stand volume equation as an output function to estimate this variable at any point in time. Transition functions were fitted separately and simultaneously. Moreover, a continuous autoregressive error structure is also included in the modelling process. For fitting volume equation, generalized method of moments was used to get efficient parameter estimates under heteroscedastic conditions.
Conclusions： A simple model containing few free parameters performed well and is particularly well suited to situations where available data is scarce.     

中国长江流域冬麦区小麦品种试验精确度回溯分析

为全面评价长江流域小麦品种区域试验精确度的发展水平,分析了2011—2021年度中国长江流域冬麦区单年单点和一年多点小麦区域试验的试验精确度和品种比较精确度,对产量、穗数、穗粒数、千粒重、生育期、株高、基本苗和最高茎数等性状的试验精确度差异进行了比较。结果表明,长江流域冬麦区单年单点品种试验精确度较好,试验误差变异系数(CEV)在5%和10%以下的试点数占比分别在60%和95%以上,但品种比较精确度(RLSD_0.05)在3%以下的试验比例不到10%,长江上游和中下游单点品种试验RLSD_0.05在10%以下的试点数分别占比约60%和90%。一年多点区域试验精确度和品种比较精确度显著优于单年单点试验,上游和中下游试验平均CEV分别在8%和5%以下。采用试点固定模型时,长江上游和中下游试验平均RLSD_0.05分别为2.19%和1.49%,符合国家小麦品种审定标准对品种比较精确度的要求;但采用试点随机模型时,小麦品种试验尚无法鉴别出品种间3%的产量差异。试验对生育期、株高、基本苗、千粒重和穗数的RLSD_0.05优于产量性状,而最高茎数和穗粒数的RLSD_0.05较低。     

Time dependence of hydraulic parameters estimation from transient analysis of mini disc infiltrometer measurements

The transient analysis of mini disc infiltrometer (MDI) measurements is an established method for characterising near-surface hydraulic characteristics of soils. The reliability of hydraulic characteristics obtained from transient analysis depends on the (1) adequacy of model, (2) adequacy of data, (3) measurement time and (4) measurement footprint. The measurement time dependence recommendations are reported only for a few soil textures, initially wet samples and tension infiltrometer (TI) with a higher measurement footprint than the MDI. This study investigated the adequacy of infiltration data (using cumulative linearization [CL] and differentiated linearization [DL]) and measurement time influence on the hydraulic parameters determined from the transient analysis of MDI measurements for six soil textures. The objective of the study is to identify suitable MDI measurement durations for different soil textures for the initially dry state, considering both adequacy of data and time fractionation (measurement time influence). The data adequacy time obtained from the DL (T_DL) was found to be 0.8 times less than the value obtained from CL (T_CL). The marginal difference in T_DL and T_CL had a significant influence on the determination of infiltration equation coefficient C₁ and negligible influence on coefficient C₂. The time fractionation procedure adopted for identifying adequate MDI measurement time (T_m) was found to be comparable based on sorptivity (S₀) and hydraulic conductivity (K₀). The average T_m was also comparable with T_DL and T_CL with a strong positive correlation. The C₂ values obtained based on T_m, T_DL, and T_CL were in better agreement than the corresponding C₁ values. The adequate MDI measurement times identified by considering T_m, T_DL, and T_CL were texture dependent, ranging from 45 min for silt to 120 min for silt loam and silty clay loam. For loamy sand, it was 50 min; for sand, it was 70 min, followed by 60 min for loam.     

不同含油量油菜品种LECl基因表达研究

[目的]揭示不同含油量油莱品种LECl基因的遗传多样性。[方法]测定不同含油量品种不同发育时期LECl基因的表达量及含油量。[结果]甘蓝型油菜LECl基因与含油量密切相关,其相对表达量在花期和角果期均与含油量呈显著正相关,且花期的相关系数大于角果期相关系数。[结论]该研究为选育高含油量油菜品种提供理论依据。     

高致病性禽流感与天气条件分析

利用全国气象观测资料、NCEP／NCAR日平均再分析数据资料集和我国高致病性禽流感疫情资料,分析高致病性禽流感发生的时空特征以及与天气条件的关系。结果表明,我国高致病性禽流感全年可以发生,疫情的分布范围广,大部分地区都有出现。发生和传播与环境气象条件有关,季节性明显,冬季和秋季为主要发病季节。冬季禽流感发生前高空500hPa以槽为主,冷空气活动频繁。发生日基本在高压系统的控制之下,地面流场呈辐散状,风速稳定少变。     

电导法对32个辣椒品种组合抗寒性的测定及配合力分析

为了比较辣椒品种的抗寒性,以32个线椒杂交组合为试材,在人工气候箱下进行低温处理,应用电导法测定叶片相对电导率(REC)。通过Logistic曲线方程拟合求出拐点温度(即半致死温度)(LT50),作为各试材抗寒性评价的参考指标,并将32个线椒组合的半致死温度(LT50)进行比较。结果表明:随处理温度的降低,相对电导率不断升高,变化过程呈"S"型曲线。32个线椒组合抗寒性顺序依次为:H2H13≈H28H31≈H1≈H23H24H26H30H8H27≈H19H5≈H12H21H3H18H15≈H14H22H17H7≈H29H4H11H10≈H16H20H6H9H25H32。配合力分析表明,相对电导率的GCA效应值以亲本P1和P2最低,SCA效应值以P1×P2最低。