甘蓝型油菜polCMS育性恢复位点的全基因组关联分析

【目的】甘蓝型油菜波里马细胞质雄性不育(pol CMS)在中国已被广泛应用于杂交种育种,其育性恢复程度表现出受1对主效基因的控制,并受微效修饰基因的影响。通过全基因组关联分析方法挖掘育性恢复位点,并对候选基因进行比较分析。【方法】通过芸薹属60K SNP芯片对308份甘蓝型油菜自然群体进行基因型分型,并用pol CMS系301A作母本,与上述材料分别进行杂交得到308份F1,每份F-_1分别于2013年和2014年进行种植,每年2次重复,于始花期根据花粉育性和花蕊发育情况调查F1植株的育性等级,同时对测交父本自然群体进行群体结构分析和亲缘关系评估,并结合测交父本的基因型分型结果和F_1的育性等级进行全基因组关联分析(GWAS)。从GWAS分析中显著的SNP左右100 kb区间或与显著SNP处于同一单体型块(R~20.5)的区间内预测候选基因,并对候选基因进行QTL比较分析和单体型或等位基因的效应分析。【结果】方差分析结果显示,两年F_1的育性等级存在显著差异(P0.01),但相关分析发现,两年的育性等级存在显著的正相关(r=0.52,P0.001)。群体结构分析显示,所有测交父本被分为3个亚群(冬性、春性和半冬性),亲缘关系分析发现,任何2个材料之间平均亲缘关系值为0.072,73%的任意材料间亲缘关系值小于0.1,其中,约53%的材料亲缘关系值为0。GWAS分析共检测到13个与育性恢复程度显著关联的SNP,构成了6个候选区间,分别位于A01、A09、C03、C06和C08 5条染色体上,单个SNP解释的表型变异介于2.53%—9.96%。从中共预测到6个与育性恢复位点相关的候选基因,其中4个编码的蛋白含有恢复基因特有的PPR保守基序。共线性分析发现,4个候选基因中的2个(Bna A09g46700D和Bna C08g40710D)位于A09和C08染色体部分同源区间,且与已克隆的pol CMS育性恢复位点ORF2同源。另外2个新鉴定到的候选基因(Bna C03g45840D和Bna C06g13000D)连锁的SNP等位基因或单体型变化都与育性等级显著相关(P0.001)。【结论】通过GWAS分析鉴定到多个与油菜育性恢复有关的候选基因,开发基于与这些基因连锁位点或SNP的功能标记将有助于对该不育系统进行恢复系和保持系的筛选。     

A potential solution for food security in Kenya: implications of the Quzhou model in China

Poor soil fertility due to low nutrient inputs is a major factor limiting grain production in Kenya. Increasing soil fertility for crop productivity in China has implications for food security in Kenya. The purpose of this study was therefore to investigate the historical patterns of grain production, nutrient inputs, soil fertility and policies in Quzhou, a typical agricultural county on the North China Plain, and to compare grain production in Quzhou County and Kenya to identify a potential approach for increasing grain production in Kenya. Grain yields in Quzhou increased from 1 to 3 t·ha⁻¹ between 1961 and 1987 by increasing manure application accompanied by small amounts of chemical fertilizer after soil desalinization. There was a further increase from 3 to 5 t·ha⁻¹ up to 1996 which can be mainly attributed to chemical fertilizer use and policy support. Hence, a beneficial cycle between soil fertility and plant growth in Quzhou grain production was developed and strengthened. In contrast, there was only a slight increase in grain yields in Kenya over this period, resulting from low soil fertility with limited external nutrient inputs, a consequence of poor socioeconomic development. It is suggested that grain yields in Kenya would likely be boosted by the development of a self-reinforcing cycling between soil fertility and plant growth with manure and chemical fertilizer use if supported by policy and socioeconomic development.     

甘肃文县珙桐群落优势种的种间联结性测定

根据２×２联列表,应用Ｏｃｈｉａｉ指数、Ｄｉｃｅ指数和Ｊａｃｃａｒｄ指数等技术,测定甘肃文县珙桐群落的８个优势种群间的联结性,以半矩阵图表达测定结果。研究表明,珙桐群落种间联结较复杂。群落的８个优势种２８个种对间有１０对存在显著的正联结（Ｉ０＞０．４）。其中珙桐与生态习性相似的包果石栎、千金榆表现为极显著正联结,白桦与亮叶桦亦为极显著正联结。群落中１５个种对存在显著的负联结（Ｉ０＜０.７）,约占总种对数的５４％反映出该区域珙桐群落的次生性和年青性。珙桐、包果石栎、青冈与白桦、青冈与亮叶桦生态习性差异较大,表现为极显著的负联结。表明生态习性相似、对环境要求相似、亲缘关系较近的植物种相伴随出现的几率较大。     

Use of oral contraception in the United States, 1965. In only 5 years oral contraception has become a major means of regulating fertility

This is the first report from the Na-tional Fertility Study, 1965, a survey of the reproductive behavior of a national sample of married women, under the age of 55, living with their husbands. The report presents basic data on the use of oral contraception by women under the age of 45, in relation to age, parity, education, race, and religion. The study leads to certain conclusions, as follows. Present, past, and prospective use vary inversely with the age of the woman and directly with the number of years of schooling; the majority of young women with college training have already used the oral contraceptive. Use by Negroes is somewhat less extensive than use by whites, particularly for ages below 25; some of this difference is explainable by concomitant racial differences in educational level. Negroes seem less likely than whites to use oral contraception for timing early births, and more likely, when they do use it, to be attempting to terminate their fertility. The same observation holds for white Catholics in relation to white non-Catholics. Although the extent of use may be lower among Catholics than non-Catholics, the proportion of Catholics who report use is substantial indeed in view of the persisting theological controversy. The prospects for increased use of oral contraception seem very good at present, but they may be limited by further developments in the technology of fertility regulation. Meanwhile the birth rate has declined substantially. Although much sophisticated analysis of other data from the survey will be required to determine the extent of the contribution of oral contraception to this decline, the findings presented here suggest that the contribution is substantial for young married couples. The major effect on the couple's eventual number of children may be less than the effect on the time pattern of childbearing; in any event, both lower eventual parity and delayed fertility contribute to a decline in the numbers of births from year to year. Whatever the intent may be, it is apparent that young American couples have adopted a new means for achieving their reproductive goals.     

粗糙集理论在土壤肥力评价指标权重确定中的应用

【目的】土壤肥力是土壤诸多基本特性的综合反映,科学、合理、实用地评价土地肥力将为指导农业生产、土地利用规划和管理提供理论依据。其评价过程是一个无决策属性的多属性决策过程,而解决多属性决策问题的重要前提是各属性权重分配问题。【方法】确定指标权重的方法主要有主观赋权法和客观赋权法,然而,主观赋权法往往需要大量的先验知识,评价结果有一定的主观随意性,而且较少考虑评价指标之间的依赖关系;客观赋权法没有充分考虑到各参评因素对评价的重要度不同,统计数据有相关性也并不意味着两个事件具有因果联系。综合考虑主、客观赋权法各自的优缺点,利用粗糙集理论中知识约简和相对正域理论在消除冗余信息和处理不确定性信息等方面的优势,探究土壤肥力评价过程中一种主观和客观相结合的权重确定方法,并利用作物产量对评价结果进行验证。【结果】粗糙集理论在土壤肥力评价中的具体赋权思路包括：数据的离散化、土壤肥力综合等级的初步确定、属性值约简、等价类划分、属性重要度的计算和指标权重计算等步骤。以北京大兴区农田土壤样点的肥力评价对上述赋权思路进行实例分析,对比传统特尔斐法和粗糙集理论赋权结果发现,特尔斐法确定的土壤有机质、全氮、有效磷和速效钾等指标的权重分别为0.300、0.250、0.250和0.200,利用其评价得到的土壤综合肥力指数（IFI）与产量显著线性相关,R2为0.77,均方根误差（RMSE）为1.25;而粗糙集理论确定的土壤有机质、全氮、有效磷和速效钾等指标的权重依次为0.455、0.111、0.111和0.333,利用其评价得到的IFI与产量也显著线性相关,R2达0.83,RMSE为1.09,精度均较特尔斐法有了提高,其中RMSE相对精度提高值达12.80%。【结论】粗糙集理论在土壤肥力评价中的具体赋权思路基本是可行的,且相对于特尔斐法其确定出各指标权重更为合理、准确,可为土壤肥力评价及相关领域的评价提供一个有益的思路。     

油菜主花序角果密度及其相关性状的全基因组关联分析

【目的】油菜高产是育种工作的主要研究目标之一。角果密度、主花序有效角果数等性状与产量都有显著或极显著的正相关关系,是油菜高产育种考查的主要性状。为揭示油菜角果密度及其相关性状的遗传机理和分子机制奠定基础。【方法】以不同遗传背景和地理来源的213份甘蓝型油菜品种（系）构成的自然群体为研究对象,利用芸薹属60K Illumina Infinium SNP芯片对该群体进行基因型分型。分别于2015年和2016年在成熟期调查该群体主花序有效长和主花序有效角果数,计算主花序角果密度。利用Structure 2.3.4软件对该群体进行群体结构分析,Tassel 5.1.0软件分析亲缘关系和染色体连锁不平衡的衰减;然后基于最优模型对主花序角果密度及其相关性状进行全基因组关联分析（genome-wide association analysis,GWAS）,依据关联SNP位点的LD区间序列,预测与性状相关的重要关联候选基因。【结果】群体结构分析显示,213份甘蓝型油菜分为P1和P2亚群,P1亚群包含50份材料（23.5%）,P2亚群包含163份材料（76.5%）,基本上和油菜的地理栽培属性一致;亲缘关系发现约89.74%材料之间的亲缘关系值小于0.2,其中约有59.91%材料的亲缘关系值为0。总体来看,整个自然群体材料之间的亲缘关系比较远。对A、C基因组进行连锁不平衡分析发现,A和C基因组的r2随着遗传距离的增加而下降,A基因组的衰减距离整体比C基因组的衰减距离小。GWAS分析两年数据共检测到17个SNP位点与主花序角果密度及其相关性状关联。其中与主花序角果密度和主花序有效长相关的SNP标记分别有7个和9个,并分别解释11.34%—15.96%和9.67%—13.10%的表型变异;与主花序有效角果数相关联的标记有1个,解释11.56%的表型变异。通过分析关联SNP位点的LD区间与甘蓝型油菜对应的区间序列,找到22个与主花序角果密度及其相关性状有关的候选基因,其中BnaA01g16940D、BnaC01g38800D和BnaA04g09170D等主要通过调控赤霉素和生长素等内源激素的合成和信号转导来控制主花序角果密度及其相关性状;BnaA01g16970D、BnaA03g29180D、BnaA03g29810D、BnaC01g39680D和 BnaC03g32770D通过对分生组织的调控来改变表型;BnaC09g18690D和 BnaC09g09210D等主要通过控制细胞分裂生长等过程改变表型。【结论】检测到17个SNP标记与油菜主花序角果密度、主花序有效长和主花序有效角果数关联,筛选出22个与主花序角果密度及其相关性状有关的候选基因。     

杉木连栽地营造不同混交林后的土壤生化特性及土壤肥力的研究

本文通过对杉木连栽多代林地及连栽地营造不同类型混交林后林地的上壤化学性状和土壤生化特性的比较研究,探讨杉木连栽多代的林地营造不同混交林后土壤酶活性及化学性状的变化趋势,土壤酶活性与土壤养分含量之间的相关性。试验结果表明:在杉木连栽多代后营造不同类型混交林,土壤的营养元素含量有显著的增加,以有机质增加最为显著,土壤的生化活性除了个别的酶外,不同类型的混交林显著比多代的杉木纯林高,其中以柳杉×薄姜木为最佳;各种土壤酶活性与土壤化学性状关系密切,单相关系数可达0.3452—0.9745,复相关系数0.8710—0.9745,可用土壤酶活性作为评价杉木连栽林地土壤改良中土壤肥力变化的指标之一;综合土壤酶活性及土壤化学性状进行聚类分析,表明杉木连栽后营造成不同类型的混交林,均能提高土壤肥力,有良好的改土作用,本研究中,以柳杉×薄姜木最为理想。     

油菜耐盐相关性状的全基因组关联分析及其候选基因预测

【目的】通过对甘蓝型油菜耐盐相关性状进行全基因组关联分析,寻找可能与油菜耐盐性相关的SNP位点,发掘与油菜耐盐性有关的候选基因。【方法】以1.2%NaCl溶液作为培养液,去离子水为对照,对307个不同品系的甘蓝型油菜进行发芽试验。播种后7 d测定幼苗根长、鲜重及发芽率,计算盐胁迫下各性状相对值,并作为评价耐盐的指标。结合油菜60K SNP芯片,利用SPAGeDi v1.4软件对该群体307份甘蓝型油菜进行亲缘关系分析,并计算亲缘关系值的矩阵。利用软件STRUCTURE v2.3.4对关联群体进行了群体结构分析。为有效排除假关联的影响,将群体结构和材料间的亲缘关系考虑进关联分析中,同时进行了PCA+K模型、Q+K模型以及K模型3种混合线性模型分析和比较,根据所有SNP的–lg(P)观察值和期望值,确定每个性状GWAS分析的最优模型。采用TASSEL 5.0软件,在最优模型下对307份材料耐盐各性状的相对值分别与SNP标记进行全基因组关联分析。利用油菜基因组数据库,在显著SNP位点侧翼序列200 kb范围内提取基因。根据拟南芥中已经明确功能的耐盐相关基因,筛选出目标基因组区段内与耐盐相关的油菜同源基因。【结果】全基因组关联分析共检测到164个与根长显著关联的SNP位点,23个与鲜重显著关联的SNP位点,38个与发芽率显著关联的SNP位点。其中与根长、鲜重、发芽率最显著关联的SNP位点分别位于染色体A08、A02和A06,贡献率分别为23.84%、18.59%和31.81%。在这些显著SNP位点侧翼序列200 kb范围内发掘出可能与油菜耐盐性有关的50个候选基因。这些候选基因主要包括转录因子MYB、WRKY、ABI1、b ZIP、ERF1、CZF1、XERICO等以及一些下游受转录因子调控的不同功能基因NHX1、PTR3、CAT1、HKT、CAX1、ACER、STH、STO等。在根长和发芽率2个不同耐盐性状的分析结果中均筛选出位于A03染色体上的耐盐基因BnaA03g14410D。另外,这些耐盐候选基因中包含两组串联重复基因,分别是位于A03染色体上的BnaA03g18900D和BnaA03g18910D,位于C09染色体上的BnaC09g19080D、BnaC09g19090D和BnaC09g19100D。除此之外,耐盐候选基因中还包含2个距离非常近(中间只间隔2个基因)的重复基因BnaC02g39600D和BnaC02g39630D。【结论】共检测到225个与耐盐性状显著关联的SNP位点,筛选出50个可能与油菜耐盐性有关的候选基因。     

坡地土壤酶流失规律初探

采用人工室内降雨方法就河北内邱县岗底坡地褐土酶活性流失规律进行了初步探讨。结果表明:流失泥沙中单位土体酶活性随坡度增大而减小,除脲酶外流失泥沙均高于土壤中酶活性,有明显富集,呈现出高肥力土壤高流失,低肥力土壤低流失的基本规律;土壤酶流失总量与坡度呈指数变化关系,符合MC=atb预测模型;流失四种酶(过氧化氢酶、脲酶、蔗糖酶、磷酸酶)之间呈显著正相关,水土流失引起酶总体的损失;土壤酶和养分流失之间呈现出一定的相关关系,土壤蔗糖酶和磷酸酶活性可作为土壤侵蚀度的分级指标。     

Kinship categories across languages reflect general communicative principles

Languages vary in their systems of kinship categories, but the scope of possible variation appears to be constrained. Previous accounts of kin classification have often emphasized constraints that are specific to the domain of kinship and are not derived from general principles. Here, we propose an account that is founded on two domain-general principles: Good systems of categories are simple, and they enable informative communication. We show computationally that kin classification systems in the world's languages achieve a near-optimal trade-off between these two competing principles. We also show that our account explains several specific constraints on kin classification proposed previously. Because the principles of simplicity and informativeness are also relevant to other semantic domains, the trade-off between them may provide a domain-general foundation for variation in category systems across languages.     

玉米单倍体雌穗育性自然恢复研究

为了对玉米单倍体雌穗育性恢复能力进行系统遗传分析,本研究以22个玉米自交系诱导产生的单倍体为材料对雌穗自然恢复能力进行观察,通过分类比较的方法分析单倍体雌穗平均结实株率、平均结实籽粒数和2个雌穗育性恢复指标自然恢复的遗传特点。结果表明,不同自交系的单倍体雌穗平均结实株率为89.54%,变异范围为73.56%~99.18%;单倍体雌穗平均结实籽粒数为15.4粒,变异范围为2.67~59.82粒。单倍体雌穗结实株率的广义遗传力为0.67,平均结实籽粒数的广义遗传力为0.86。22个自交系材料中,B73的单倍体雌穗育性恢复能力较其他试验材料强,单倍体雌穗平均结实株率为99.18%,平均结实籽粒数为59.82粒,基因型在单倍体雌穗育性自然恢复过程中起主要作用。通过对单倍体雌穗育性恢复与雄穗育性恢复性状进行相关性分析发现单倍体雌穗育性恢复与雄穗育性恢复是2个相对独立的过程。     

Male fertility and sex ratio at birth in red deer

Efforts to test sex ratio theory have focused mostly on females. However, when males possess traits that could enhance the reproductive success of sons, males would also benefit from the manipulation of the offspring sex ratio. We tested the prediction that more-fertile red deer males produce more sons. Our findings reveal that male fertility is positively related to the proportion of male offspring. We also show that there is a positive correlation between the percentage of morphologically normal spermatozoa (a main determinant of male fertility) and the proportion of male offspring. Thus, males may contribute significantly to biases in sex ratio at birth among mammals, creating the potential for conflicts of interest between males and females.     

土壤肥力和灌水组合对小麦植株-土壤系统氮素平衡的影响

采用15N示踪技术,在池栽群体条件下,研究了三种土壤肥力和两种灌水量组合对冬小麦生产系统氮素平衡的影响,结果表明:(1)不同处理氮肥的当季吸收利用率变化在39.08%￣53.08%,土壤残留率在21.80%￣33.59%之间,损失率变化幅度为18.81%￣34.62%,植株吸收积累氮素中的29.88%￣47.55%来自肥料;证明,采用不同土壤肥力和灌水量组合来调控小麦生产系统的氮素平衡具有较大的空间。(2)随土壤肥力的提高,植株吸收的总氮和土壤氮量显著增加,但营养体滞留量增加,向子粒的分配比例减少;而对肥料氮的吸收量则表现为中肥>高肥>低肥;氮肥损失率表现为低肥>高肥>中肥,残留率无明显变化,说明土壤肥力达到本实验的中等水平后再继续提高,会给肥料氮的吸收利用带来不利影响,但可有效降低对肥料氮的依赖。(3)增加灌水量在不同土壤肥力条件下均可促进对总氮的吸收量,但对土壤氮吸收的促进作用远高于肥料氮,同时也提高了肥料氮的损失率、降低了土壤残留率和向子粒的分配率。(4)提高土壤肥力和增加灌水量均可提高小麦的经济产量、生物产量和土壤A值,降低收获指数;子粒蛋白质含量随肥力的提高而增加,随灌水的增加而下降。     

小麦物候期与主要农艺性状相关性的研究

通过对小麦物候期与主要农艺性状相关性的研究分析,结果表明：小麦物候期(挑旗期、抽穗期、开花期)与主要农艺性状之间存在着不同程度的相关。其中,挑旗期与抽穗期、开花期、小穗数、不孕小穗数、最高分蘖数呈显正相关;与旗叶长度负相关不显。抽穗期与开花期、小穗数呈极显正相关;与旗叶长度呈极显负相关;与倒三叶宽、倒三叶面积呈显正相关。开花期与小穗数呈极显正相关;与倒三叶宽、倒三叶面积呈显正相关;与旗叶长度呈极显负相关。     

北京八达岭地区土壤酶活性及其与土壤肥力的关系

为探讨土壤健康的生物学指标,该文对北京八达岭地区不同植被类型0～5 cm土层的土壤酶活性及其与土壤肥力状况的相关性进行了研究. 结果表明:不同植被类型的土壤酶活性有显著的区别,其中除过氧化物酶外,糠椴林的土壤酶活性均属最高水平,而灌草丛所有酶活性都属最低水平;灌木丛中脲酶和碱性磷酸酶活性显著高于杂木林; 华北落叶松林的磷酸酶和过氧化氢酶活性均高于油松林. 相关分析表明,脲酶、酸性磷酸酶、碱性磷酸酶、过氧化氢酶与土壤肥力状况的相关性较好;总磷酸酶活性与土壤肥力状况的相关性高于单项磷酸酶; 多酚氧化酶和过氧化物酶与土壤肥力状况的相关性较差.      

Effects of Vegetation Succession on Soil Fertility Within Farming-Plantation Ecotone in Ziwuling Mountains of the Loess Plateau in China

To further understand the relationship between vegetation succession and soil fertility within farming-plantation ecotone in Ziwuling Mountains of the Loess Plateau, nine kinds of widely distributed communities at different succession stages were selected, and the effects of vegetation succession on soil fertility were studied through the methods of comparing two hierarchical clustering （similarity index： B） and other multivariate analysis. The results showed that： （i） the similarity in clustering pattern of nine communities which classified by plant species and soil nutrients respectively showed a trend of B ^-overall plant-soil0-10cn〉B^-overall plant-soil 10-20 cm 〉B^- overall plant-soil 20-40 cm, and for the top soil, it showed a trend of B^- grass-soil 0-10 cm 〉 B^-shrub-soil 0-10 cm 〉 Btree-soil0-10 cm; （ii） soil fertility increased during the succession process from abandoned land to forest community, and the soil fertility of forest community showed an increased order of coniferous forest →mixed forest →broadleaf forest; （iii） during the process of vegetation succession, the variation of topsoil fertility was higher than that of the subsurface soil （coefficient of variation： CV0-10 cm 〉CV 10-20 cm 〉 CV20-40 cm）, and when the succession developed into the stages of shrub and forest communities, the top soil fertility had been improved significantly; and （iv） for the subsurface soil of the communities at the advanced succession stages, the soil fertility also increased to some extent. Our results suggested that the method of comparing two hierarchical clustering reflected the similarity level of different cluster patterns, therefore, it was helpful to study the relationship between vegetation succession and soil fertility. There was a corresponding relationship between the change process of soil fertility from the top soil to subsurface soil and the process of vegetation succession from the early stages to the advanced stage. The differentiations of soil fertility in vertical space and horizontal space were both caused by vegetation succession, which was significant for both the shrub and forest communities. The improved level of forest soil fertility was related to forest vegetation types and the improved fertility level of broad-leaved forest-soil community was higher than that of the coniferous forest soil. In the practice on soil fertility ecological restoration of the loess plateau, it is important to carry out reasonably artificial forestation so as to enhance the restoration and improvement of soil fertility.     

小麦基因组中与雌性育性关联标记的初步扫描

[目的]发掘与小麦雌性育性紧密关联的SSR分子标记,并估算其表型效应。[方法]选择遍布基因组的40个多态性标记,对包括小麦雌性不育系的261个小麦品种（系）组成的目标群体使用STRUCTRE软件进行群体结构评估,并利用TASSEL软件的GLM模型检测40个多态性标记与小麦雌性育性D.F.（国内法育性）和I.F.（国际法育性）2种表型值的关联程度,确定入选标记。[结果]群体结构评估表明,目标群体中存在3个亚群。基因组多态性标记关联分析结果显示,标记Xcfd36（2AS、2DS）和Xcfd88（4AL）与小麦雌性育性2种表型值相关联,2个标记对D.F.和I.F.的效应分别是0.1585、0.113和0.087、0.0596。[结论]2DS、4AL和2AS可能存在控制小麦雌性育性的QTL。与表型紧密关联的标记的鉴别对于小麦雌性育性遗传机制的研究具有重要的意义。     

Biological diversity, soils, and economics

Terrestrial biological diversity is supported by solar energy captured by plants growing in soil. This soil-based plant productivity also provides the foundation for human societies through production of food and renewable forms of energy. Variations in plant productivity, resulting from differences in inherent soil fertility, variations in climate and weather, and differences in chemical inputs and agricultural practices, produce patterns of biological diversity that are associated with the agricultural component of economic productivity. Ecological processes lead to a generally negative relation between the diversity of plant species and potential agricultural productivity at both local and global scales. One implication of this negative relation is that preservation of areas of high plant biodiversity does not require the sacrifice of productive agricultural lands.     

福建省几种土壤类型酶活性的研究

通过潴育性水稻土、淹育性水稻土及红壤旱地等12块不同土壤肥力水平及种植不同作物的土壤,研究了土壤水份含量,土壤肥力因素与土壤酶活性及后者与甘蔗产量的相互关系,以及土壤酶活性在土壤剖面中的分布规律。结果发现,由于土壤水份含量与土壤层次及土壤肥力的不同,土壤酶活性也存在着明显的差异,而且这种差异直接影响了蔗茎产量。经统计检验,土壤肥力因素与土壤中脱氢酶、过氧化氢酶、蛋白酶、磷酸酶、脲酶等酶活性有明显的正相关,供试六种土壤酶活性与蔗茎产量也呈明显的正相关,相关系数达显著或极显著水平。     

塞罕坝华北落叶松纯林和混交林土壤肥力质量评价

  目的  基于土壤质量指数（SQI）,研究华北落叶松林不同混交方式对土壤肥力质量的影响,为其合理经营和地力恢复提供理论依据。  方法  该研究以河北省塞罕坝林场华北落叶松纯林（落叶松纯林）、华北落叶松白桦混交林（落桦混交林）和华北落叶松樟子松混交林（落樟混交林）为研究对象,采集和分析0 ~ 20 cm土层的土壤进行土壤理化性质、生物性质的调查研究,利用SQI法进行土壤肥力质量评价。建立SQI包括3个步骤:采用主成分分析法筛选最小数据集（MDS）,利用非线性得分函数计算MDS指标得分,利用加权求和模型计算SQI。  结果  不同混交方式间土壤理化和生物性质存在不同程度的差异。与落叶松纯林相比,落桦混交林的土壤理化和生物性质有了明显改善;落樟混交林的土壤理化状况较差,土壤生物性质与落叶松纯林没有明显差异。在17个土壤肥力质量指标中,MDS由土壤微生物生物量氮、全磷、氨氮3个指标组成。不同混交方式间SQI差异显著,表现为落桦混交林（0.59） > 落叶松纯林（0.47） > 落樟混交林（0.39）。  结论  土壤肥力质量在不同混交方式下差异显著,塞罕坝机械林场落叶松白桦混交林有利于改善土壤肥力。利用指数法建立SQI进行土壤肥力质量评价,可为其他树种或其他地区的森林土壤质量评价提供借鉴。