艾比湖湿地不同盐渍化土壤粒度组成及可蚀性研究

为了研究内陆干旱区不同盐渍化土壤的粒径组成及其可蚀性的空间分布,在不同盐渍化程度上探讨其与土壤中盐分含量的相互关系,本研究以新疆维吾尔自治区艾比湖湿地为研究靶区,利用2015年5月获取的66个表层土壤样品,对土壤的粒度组成、含盐量、分形维数和可蚀性因子K值进行了研究。结果表明:样品中盐土占比达到59.09%,平均含盐量达131.59 g/kg,研究区内盐渍化现象既普遍又严重;土壤颗粒以粉粒和砂粒为主,随着盐渍化程度的加剧黏粒含量不断增加,砂粒含量则相反;土壤颗粒的分形维数D值介于2.14~2.60,平均值为2.45;随着盐渍化程度加剧,分形维数逐渐变大,K值也随之逐渐增大,盐土的K值最大达0.093;土壤可蚀性因子K值与含盐量的相关性较高(r=0.596**),在一定程度上可以说明,土壤的含盐量水平越高,K值越大,越容易被侵蚀。     

原子力显微镜表征土壤中的纳米胶体

以平均粒径和多分散性指数为参数、采用原子力显微镜(AFM)表征了不同地区三种土壤纳米胶体的粒径与形貌,研究了pH及重金属离子对纳米胶体粒径和形貌的影响。结果表明,江苏九华(JH-4)土壤纳米胶体主要为形状规则的黏土矿物粒子,并部分被有机质包裹或覆盖,平均粒径为21.5nm(n=98),多分散性程度高(PI=1.9);浙江富阳(FY-1)土壤纳米胶体主要是无规则形状的有机质包裹的粒子,平均粒径为20.3nm(n=133),多分散性程度高(PI=2.0);江西德兴(DX-9)土壤纳米胶体主要是球状或近球状的无机粒子,平均粒径为56.3nm(n=147),多分散性程度较低(PI=1.3)。pH及重金属铜离子的存在对纳米胶体粒径和形貌会产生或分散或团聚的影响,这种影响可能与土壤纳米胶体的电荷性质、有机质含量等因素有关,形貌变化较为复杂。这种复杂性对理解和研究胶体在环境过程中的行为具有指导意义。     

冰雪灾后广东杨东山十二度水保护区森林大型土壤动物功能类群

对冰雪灾害后杨东山十二度水省级自然保护区的森林大型土壤动物功能群和生态特性进行了调查。结果表明:在海拨700～1000m的常绿与落叶阔叶混交林中,膜翅目、鞘翅目昆虫为数量上的优势类群。从生物量来看,优势类群为蚯蚓、鞘翅目昆虫、双翅目和鳞翅目幼虫。将研究区的大型土壤动物划分为腐食性、植食性和捕食性动物3个功能类群,其中腐食性动物的生物量所占比例最大,而植食性动物的数量占优势,捕食性动物两者所占比例较小。     

退化高寒草地浅层土壤理化性质Meta分析

青藏高原生态地位显著,草地退化影响区域生态安全,针对退化高寒草地土壤理化性质的研究众多但结果存在较大异质性。通过检索纳入79篇与退化高寒草地土壤理化性质相关的文献,采用整合分析方法用于定量述评不同退化程度高寒草地浅层土壤主要理化性质的效应及变化规律。结果表明：高寒草甸0～10 cm、10～20 cm土层内随着退化加剧土壤容重、pH上升,土壤含水量、有机碳、全氮、全磷、全钾、速效氮、速效磷、速效钾下降;高寒草原0～10 cm、10～20 cm土层内随退化加剧,土壤容重上升,pH、含水量、有机碳、速效钾下降。总体反映出不同退化程度对高寒草地土壤主要理化性质产生较大负面影响,研究结果可为青藏高原高寒草地生态保护提供依据。     

不同浸泡处理对破除那曲不同退化草甸草地土壤种子库种子休眠的影响研究

[目的]研究不同浸泡处理对破除那曲不同退化草甸草地土壤种子库种子休眠的影响。[方法]采用不同浓度的H2SO4、GA3、KNO3浸泡不同退化草甸草地土壤种子库种子,并测定其发芽数。[结果]60％、70％、80％。90％H2SO4浸泡土壤库种子时,种子发芽个数均为0,种子发芽均受到抑制;用GA3浸泡土壤库种子时,种子发芽数随着GA3浓度的增加而增加,当浓度增大至0．1％时,种子发芽个数受到抑制;用0．2％KNO3浸泡土壤库种子时,种子发芽个数较空白对照均有所提高。[结论]在中度退化草地和重度退化草地土壤种子库中,种子留存数较多;而轻度退化草地和极度退化草地中种子较少。     

武夷山土壤形成特点与系统分类

选取武夷山土壤垂直带中 6个代表性剖面 ,研究了土壤的形成条件和特点 ;按照《中国土壤系统分类 (修订方案 )》 ,鉴定了诊断层和诊断特性 ,检索了土壤系统分类名称 ;随海拔由低到高 ,依次为湿润富铁土—湿润淋溶土—常湿淋溶土—常湿雏形土等亚纲 ;并与发生学分类、美国土壤系统分类 (USST)以及世界土壤资源参比基础 (WRB)等不同分类系统中的土壤类别归属作了参比     

Rhizospheric and heterotrophic respiration of a warm-temperate oak chronosequence in China

Plot trenching and root decomposition experiments were conducted in a warm-temperate oak chronosequence (40-year-old, 48-year-old, 80-year-old, and 143-year-old) in China. We partitioned total soil surface CO₂ efflux (R_S) into heterotrophic (R_H) and rhizospheric (R_R) components across the growing season of 2009. We found that the temporal variation of R_R and R_H can be well explained by soil temperature (T₅) at 5 cm depth using exponential equations for all forests. However, R_R of 40-year-old and 48-year-old forests peaked in September, while their T₅ peaks occurred in August. R_R of 80-year-old and 143-year-old forests showed a similar pattern to T₅. The contribution of R_R to R_S (RC) of 40-year-old and 48-year-old forests presented a second peak in September. Seasonal variation of R_R may be accounted for by the different successional stages. Cumulative R_H and R_R during the growing season varied with forest age. The estimated R_H values for 40-year-old, 48-year-old, 80-year-old and 143-year-old forests averaged 431.72, 452.02, 484.62 and 678.93 g C m⁻², respectively, while the corresponding values of R_R averaged 191.94, 206.51, 321.13 and 153.03 g C m⁻². The estimated RC increased from 30.78% in the 40-year-old forest to 39.85% in the 80-year-old forest and then declined to 18.39% in the 143-year-old forest. We found soil organic carbon (SOC), especially the light fraction organic carbon (LFOC), stock at 0-10 cm soil depth correlated well with R_H. There was no significant relationship between R_R and fine root biomass regardless of stand age. Measured apparent temperature sensitivity (Q₁₀) of R_H (3.93 ± 0.27) was significantly higher than that of R_R (2.78 ± 0.73). Capillary porosity decreased as stand age increased and it was negatively correlated to cumulative R_S. Our results emphasize the importance of partitioning soil respiration in evaluating the stand age effect on soil respiration and its significance to future model construction.     

不同采伐、集材方式对林地土壤理化性质影响的研究

选择５种不同集材方式的皆伐作业与采伐强度为３０％的择伐作业,进行土壤理化性质指标变化程度的比较。在考虑各种作业的集材量和集材道面积的情况下,经主成分分析得出不同采伐、集材方式对林地土壤理化性质的干扰程度。认为,以皆伐作业手扶拖拉机集材为最大,其次为皆伐作业土滑道集材,其余依次为皆伐作业半悬索道集材,皆伐作业手拉板车集材,皆伐作业全悬索道集材,最低为择伐作业人力集材。     

Whole tree harvesting can reduce second rotation forest productivity

The practice of harvesting forest residues is rapidly increasing due to rising demand for renewable energy. However, major concerns have been raised about the sustainability of this practice and its net impact on productivity, in particular through negative effects on the growth of subsequent tree crops. We measured height, diameter at breast height (DBH) and tree spacing density on 23-year-old second rotation stands of Sitka spruce (Picea sitchensis), following whole tree harvesting (WTH—of all above ground biomass, by cable crane) or conventional stem-only harvesting (CH) of the first rotation crop. Overall, WTH reduced tree DBH by 10.3% (p = 0.017), with weaker evidence that it may have reduced height (by 8.2%, p = 0.164) and stand basal area (by 15.3%, p = 0.101). However, treatment effects differed greatly between individual blocks and, analysed separately by block, significant differences (WTH plot trees smaller than CH plot trees) were most notable in the two more exposed south-facing blocks (where, in both cases, p < 0.01 for height and p < 0.05 for basal area). Variation in productivity between the experimental plots cannot simply be attributed to preharvesting site environment – no correlation was found between first rotation and second rotation productivity – nor was treatment effect explained by differences in tree spacing density. Treatment effects can be attributed to the removal of three to four times larger quantities of N, P and K in the tree biomass by WTH than by CH of the first rotation crop, combined with greater competition with tree natural regeneration and other vegetation in WTH plots during the early stages of the second rotation. Soil moisture was higher in WTH plots but there was no evidence that WTH increased soil acidity or aluminium mobility nor that it decreased soil organic matter. The results also highlight the complexities of predicting the effect of harvesting treatment on future productivity, even within single-age, single-species forests. The study demonstrates the risk that WTH can reduce second rotation productivity of conifer forests in acidic upland sites, and that this practice will only be sustainable with appropriate interventions to overcome shortage of nutrients and high levels of vegetation competition.     

牧草间作对桉树人工林下土壤酶活性的影响

[目的]研究牧草间作对桉树人工林下土壤酶活性的影响。[方法]试验地内以桉树人工林林龄2年为第一代林,选用5种牧草种植区的土壤样品作为人工林地间供试材料,行带内杂草地土样作为对照,采用随机区组设计,在每个区组中选3个取样点,每个取样点挖剖面,测定土壤含水量、蔗糖酶、过氧化物酶和脲酶活性。[结果]桉树人工林地间作牧草以后,有效提高了林下土壤含水量;蔗糖酶活性测定中糖蜜草样地的蔗糖酶活性提高幅度最大,达到73．92％;网脉臂形草样地的次之,为46．85％;脲酶活性测定中网脉臂形草样地的脲酶活性提高到19．11％,GC1581柱花草和糖蜜草样地的也有显著提高,分别是10．07％和8．43％。[结论]牧草间作能有效改善桉树人工林地土壤理化性状,提高土壤肥力,有效减缓土壤衰退。