基于高通量测序的黄河三角洲4种人工林土壤细菌结构及多样性研究

为研究黄河三角洲不同人工林土壤细菌群落特征,应用高通量测序技术,比较分析了刺槐、榆树、白蜡、臭椿4种人工林土壤细菌结构及多样性,并结合土壤理化性质进行相关性分析。结果表明:人工林土壤中共有31门细菌;4种人工林土壤中酸杆菌门、变形菌门、放线菌门细菌以及刺槐、臭椿人工林土壤中硝化螺旋菌门细菌是土壤中的优势群落。不同人工林土壤中酸杆菌门、变形菌门、硝化螺旋菌门、芽单胞菌门、拟杆菌门、广古菌门、泉古菌门、蓝藻菌门细菌丰度差异显著。刺槐人工林土壤细菌多样性最高;白蜡人工林土壤细菌多样性最低。土壤pH、含水量、有机质含量与酸杆菌门细菌丰度呈显著负相关关系,土壤pH与变形菌门、硝化螺旋菌门、芽单胞菌门细菌丰度呈极显著正相关关系;土壤pH、有效磷含量与人工林细菌多样性呈显著正相关关系。以上研究结果表明,黄河三角洲不同人工林土壤细菌群落存在一定差异,土壤pH、含水量、有机质、有效磷含量是影响土壤细菌结构和多样性的主要土壤因素。     

转几丁质酶和葡聚糖酶双价基因棉花对土壤细菌种群多样性的影响

以转几丁质酶和葡聚糖酶双价基因棉花为研究对象,非转基因受体棉花为对照,通过比较可培养细菌数量和基于16S rRNA克隆文库细菌种群分析,评价外源双价基因的导入在苗期、蕾期、花铃期和吐絮期对棉花根际细菌群落多样性的影响。结果表明,可培养细菌的数量不受外源双价基因的影响,随着棉花生育期的交替而变化,以代谢旺盛的花铃期最多。构建的转基因和非转基因不同生育期根际土壤细菌16S rRNA文库容量为2400个克隆,涵盖了细菌的283个属。其中,Acidobacterium是最大优势类群,共包括624个克隆,其次为未知细菌种群和Flavisolibacter。比较转基因和非转基因棉花根际土壤细菌的种群结构,结果显示,同一生育期内前者种群的多样性显著低于后者,二者的共有类群随着生长发育的进行而增多。研究结果说明几丁质酶基因和葡聚糖酶基因对棉花根际细菌种群多样性有着不同程度的削减作用,但是随着种植时间的延长,该差异呈现逐渐缩小的趋势。     

Autotoxic potential of cucurbit crops

Soil sickness is often observed in cucurbit crops such as Citrullus lanatus, Cucumis melo and Cucumis sativus, but not in cucurbit crops such as Cucurbita moschata, Lagenaria leucantha and Luffa cylindrica. Results showed that root aqueous extracts of Citrullus lanatus, Cucumis melo and Cucumis sativus were autotoxic, but those of Cucurbita moschata, Momordica charantia and Luffa cylindrica were less autotoxic to the radicle elongation of respective species. Plant growth of Citrullus lanatus, Cucumis melo and Cucumis sativus were greatly inhibited by autotoxic substances released from powered root tissue at a rate of 1 g per seedling. Root exudates of Citrullus lanatus, Cucumis melo and Cucumis sativus were autotoxic to radicle elongation and seedling growth of respective species. However, root exudates of Citrullus lanatus did not inhibit radicle elongation of Cucurbita ficifolia, which is commonly used as rootstock for the grafting of Citrullus lanatus, Cucumis melo and Cucumis sativus to decrease soil-borne diseases in commercial production. It seems possible to overcome autotoxicity in cucurbit crops by grafting on Cucurbita ficifolia. This revised version was published online in June 2006 with corrections to the Cover Date.     

子午岭植被恢复对土壤饱和导水率的影响

通过对子午岭林区不同植被的土壤性质进行实验室测定和野外调查,对饱和土壤水分运动的重要参数之一土壤饱和导水率(Ks)及其相关因子进行了多元分析和通径分析,揭示了植被恢复提高土壤水分传输性能的机理,主要结论如下:土壤有机质是子午岭林区九种植被下土壤饱和导水率提高的主要驱动因子.不同植被下的土壤饱和导水率均随深度的增加而迅速降低,尽管草地和先锋草地在5～10cm深度有一强透水层.土壤饱和导水率在剖面上的平均值,从辽东栎、早期森林、灌丛、先锋草地、弃耕地到草地依次降低.灌丛与草地、弃耕地的差异达到显著水平,辽东栎顶级群落的饱和导水率最高,植被的恢复明显提高了土壤饱和导水率.土壤容重、毛管孔隙度、>0.25mm团聚体含量及粘粒含量直接影响土壤饱和导水率.土壤有机质含量的提高能够改善容重、毛管孔隙度、团聚体含量等物理性质.     

耕作方式对东北雨养区玉米光合与叶绿素荧光特性的影响

在东北地区设置大田试验,研究不同耕作方式下玉米全生育期耕层土壤温度、土壤含水量、叶片光合性能及叶绿素荧光参数的变化特征.结果表明:耕作方式对土壤水热性能的影响主要体现在播种-拔节阶段,2010-2011年平地播种中耕起垄(PL)和全生育期平作(PP)处理0～40 em土层土壤体积含水量在出苗期、苗期和拔节期比传统垄作(LL)处理平均提高5.6％和5.2％、4.6％和7.3％及3.9％和4.8％,苗期5 cm土壤最低温度分别比LL处理高1.4和1.3℃.由于土壤水热条件的改善,拔节期PL和PP处理的叶片净光合速率(Pn)、蒸腾速率(Tr)等指标显著高于LL处理,而PSⅡ潜在活性(Fv/Fo)和PSⅡ最大光化学效率(Fv/Fm)无显著差异,表明气孔导度和气孔限制值等气孔因素是导致光合作用差异的主要原因;灌浆期叶片Pn和Tr则以LL和PL处理显著高于PP处理,这主要是由于PP处理在强降雨时期经历了涝渍灾害,光合作用受到抑制.可见PL处理通过改善土壤水热条件增强了玉米光合性能,进而提高了籽粒产量.     

Global‐scale patterns of nutrient density and partitioning in forests in relation to climate

Knowledge of nutrient storage and partitioning in forests is imperative for ecosystem models and ecological theory. Whether the nutrients (N, P, K, Ca, and Mg) stored in forest biomass and their partitioning patterns vary systematically across climatic gradients remains unknown. Here, we explored the global‐scale patterns of nutrient density and partitioning using a newly compiled dataset including 372 forest stands. We found that temperature and precipitation were key factors driving the nutrients stored in living biomass of forests at global scale. The N, K, and Mg stored in living biomass tended to be greater in increasingly warm climates. The mean biomass N density was 577.0, 530.4, 513.2, and 336.7 kg/ha for tropical, subtropical, temperate, and boreal forests, respectively. Around 76% of the variation in biomass N density could be accounted by the empirical model combining biomass density, phylogeny (i.e., angiosperm, gymnosperm), and the interaction of mean annual temperature and precipitation. Climate, stand age, and biomass density significantly affected nutrients partitioning at forest community level. The fractional distribution of nutrients to roots decreased significantly with temperature, suggesting that forests in cold climates allocate greater nutrients to roots. Gymnosperm forests tended to allocate more nutrients to leaves as compared with angiosperm forests, whereas the angiosperm forests distributed more nutrients in stems. The nutrient‐based Root:Shoot ratios (R:S), averaged 0.30 for R:S_N, 0.36 for R:S_P, 0.32 for R:S_K, 0.27 for R:S_Ca, and 0.35 for R:S_Mg, respectively. The scaling exponents of the relationships describing root nutrients as a function of shoot nutrients were more than 1.0, suggesting that as nutrient allocated to shoot increases, nutrient allocated to roots increases faster than linearly with nutrient in shoot. Soil type significantly affected the total N, P, K, Ca, and Mg stored in living biomass of forests, and the Acrisols group displayed the lowest P, K, Ca, and Mg.     

4种温带森林非生长季土壤二氧化碳、甲烷和氧化亚氮通量

中高纬度森林土壤在漫长的非生长季中对重要温室气体——二氧化碳(CO2)、甲烷(CH4)和氧化亚氮(N2O)的释放或吸收在碳氮年收支中作用很大,但目前研究甚少。采用静态暗箱-气相色谱法,比较研究东北东部4种典型温带森林土壤表面CO2、CH4和N2O通量在非生长季中的时间动态及其影响因子。结果表明:4种森林土壤在非生长季中整体上均表现为CO2源、N2O源和CH4汇的功能。红松林、落叶松林、蒙古栎林、硬阔叶林的非生长季平均土壤表面CO2通量分别为(65.5±8.1)mgm-2h-1(平均值±标准差)、(70.5±10.2)mgm-2h-1、(77.1±8.0)mgm-2h-1、(80.5±23.5)mgm-2h-1;CH4通量分别为(-17.2±4.6)μgm-2h-1、(-15.4±4.2)μgm-2h-1、(-31.5±4.5)μgm-2h-1、(-23.6±4.1)μgm-2h-1;N2O通量分别为(19.3±5.1)μgm-2h-1、(11.5±2.5)μgm-2h-1、(16.4±4.0)μgm-2h-1、(14.4±5.4)μgm-2h-1;其中非生长季土壤表面CO2总排放量分别为143.4gm-2、162.8gm-2、189.9gm-2、252.7gm-2,分别占其年通量的7.3%、10.6%、8.4%和8.5%。所有林型非生长季土壤表面CO2通量在春季土壤解冻前均维持在较低水平;在解冻进程中随温度升高而增大。土壤表面CO2通量与5cm深土壤温度(T5)呈极显著的指数函数关系。在隆冬时节出现CH4净释放现象,但释放强度及其出现时间因林型而异,其中以红松林的释放强度较大,高达43.6μgm-2h-1。土壤表面CH4通量与T5呈显著的负相关。土壤表面N2O通量的时间动态格局在林型间的分异较大,但在春季土壤解冻阶段均释放出N2O,而释放峰值和出现时间因林型而异。土壤表面N2O通量与0—10cm深土壤含水量呈显著的正相关(红松林除外)。研究展示了不同温带森林类型的土壤水热条件对其非生长季土壤CO2、CH4和N2O通量的重要影响,但这3种温室气体的林型间分异的生物学机理尚需进一步研究。     

Snow depth manipulation and its influence on soil frost and water dynamics in a northern hardwood forest

Climate change will likelyresult in warmer winter temperatures leading toless snowfall in temperate forests. Thesechanges may lead to increases in soil freezingbecause of lack of an insulating snow cover andchanges in soil water dynamics during theimportant snowmelt period. In this study, wemanipulated snow depth by removing snow for twowinters, simulating the late development of thesnowpack as may occur with global warming, toexplore the relationships between snow depth,soil freezing, soil moisture, and infiltration.We established four sites, each with two pairedplots, at the Hubbard Brook Experimental Forest(HBEF) in New Hampshire, U.S.A. and instrumentedall eight plots with soil and snow thermistors,frost tubes, soil moisture probes, and soillysimeters. For two winters, we removed snowfrom the designated treatment plots untilFebruary. Snow in the reference plots wasundisturbed. The treatment winters (1997/1998 and1998/1999) were relatively mild, withtemperatures above the seasonal norm and snowdepths below average. Results show the treatedplots accumulated significantly less snow andhad more extensive soil frost than referenceplots. Snow depth was a strong regulator ofsoil temperature and frost depth at all sites.Soil moisture measured by time domainreflectometry probes and leaching volumescollected in lysimeters were lower in thetreatment plots in March and April compared tothe rest of the year. The ratio of leachatevolumes collected in the treatment plots tothat in the reference plots decreased as thesnow ablation seasons progressed. Our data showthat even mild winters with low snowfall,simulated by snow removal, will result inincreased soil freezing in the forests at theHBEF. Our results suggest that a climate shifttoward less snowfall or a shorter duration ofsnow on the ground will produce increases insoil freezing in northern hardwood forests.Increases in soil freezing will haveimplications for changes in soil biogeochemicalprocesses.     

戈壁灌丛堆周边地表土壤颗粒的空间异质特征

研究戈壁地区单个灌丛及其下沙堆这一有机整体对周边土壤风蚀的抑制能力, 对加强相关地区的植被类型及其空间配置格局的防沙效应研究十分重要, 可为荒漠化监测的评价和制定科学的防治措施提供参考。该文利用数字图像处理技术, 获取吉兰泰盐湖北部戈壁上单个白刺(Nitraria tangutorum)灌丛沙堆和沙冬青(Ammopiptanthus mongolicus)灌丛沙堆周边地表不同土壤风蚀颗粒的百分含量; 并采用经典描述性统计及地统计学方法, 对各类土壤风蚀颗粒百分含量的水平空间异质性进行分析。结果表明: (1)灌丛基部和下风向是细物质积累区, 以灌丛堆为中心向外, <0.42 mm的细颗粒含量呈减少趋势; 而且细物质积累的最大值出现在白刺灌丛的迎风侧附近, 沙冬青样地则相反, 出现在灌丛的背风侧附近。在沙源物质有限的戈壁中, 白刺的防风固沙作用集中体现在灌丛附近, 其水平空间尺度范围不及沙冬青, 这亦是白刺样地粗粒化程度高于沙冬青样地的原因。(2)白刺和沙冬青灌丛附近地表中粒径>0.84 mm (不可蚀)、0.84-0.42 mm (半可蚀)及<0.42 mm (高度可蚀)颗粒的空间异质性尺度分别为17.80 m、66.63 m、8.41 m和9.82 m、15.33 m、14.91 m, 均超出了灌丛冠幅覆盖范围, 空间自相关部分比例C/(C₀ + C)在63.40%-99.96%之间, 由此推断灌丛沙堆附近的风沙流特征是造成相应尺度内土壤颗粒空间异质性的主要因子。(3)高度可蚀颗粒的空间异质性尺度略大于灌丛平均间距(8.77 m包括灌丛半径), 从防止土壤风蚀来看, 这说明研究区内的建群种灌丛间存在一定程度的相互促进关系, 有利于该区植被的稳定与发展。     

土壤病毒生态学研究方法

病毒是地球上最丰富的生物实体,每克土壤中可包含数以亿计的病毒,它不仅影响土壤中其它微生物的群落组成、土壤元素的生物地球化学循环,还会影响土壤微生物的物种进化,甚至影响植物、动物和人体健康。目前人们对土壤中病毒的种类及丰度、分布特征以及功能引起的生态环境效应还知之甚少。在概述病毒生态学研究方法的基础上,对土壤病毒的提取、纯化、定量及分子生态学方法等基本流程进行了比较分析,以期建立一套快速简便、高效稳定的适用于土壤病毒研究的方法,并用于研究土壤病毒的多样性及分布特征,探讨病毒在环境中的生存和传播机制,为土壤病毒的防控及开发利用提供支撑。