不同放牧强度下荒漠草原土壤氮矿化季节性动态研究

放牧是中国北方主要的草地利用方式。放牧强度通过影响群落结构和土壤的理化性状以及土壤微生物活性对草地生态系统的养分循环产生显著影响。以位于内蒙古四子王旗的荒漠草原长期放牧控制试验平台为研究对象,通过设置四个放牧强度,即对照(CK)、轻度放牧(LG)、中度放牧(MG)和重度放牧(HG),探讨了放牧强度对土壤无机氮库和氮矿化过程季节变化的影响。根据该地区气候特点和植物生长季节,将一年划分为3个时期,分别为生长季初期(5-6月)、生长季盛期(7-9月)和非生长季(10月至次年4月)。结果表明,(1)在生长季初期,放牧抑制了土壤氮矿化作用,土壤温度与土壤无机氮含量呈显著负相关。(2)在生长季盛期,放牧促进了土壤净氮矿化作用,其中LG区的净氮矿化速率和净硝化速率显著高于对照区均较高;土壤净氮矿化和净硝化速率与土壤温度和含水量均呈显著正相关关系。(3)在非生长季,放牧抑制了土壤氮矿化作用,对照区不放牧处理的土壤净氮矿化速率显著高于放牧区;土壤含水量与土壤无机氮含量呈显著正相关,而与净氮矿化速率和净硝化速率均呈显著负相关关系。综上,高强度放牧抑制了土壤氮矿化过程,可能会进一步加剧净初级生产力的氮素限制。同时,放牧对土壤氮素转换过程的影响存在显著的季节性差异。     

天山东部西伯利亚落叶松径向生长对气候的响应及其物候模拟

运用树轮气候学方法,探讨天山东部不同海拔西伯利亚落叶松(Larix sibirica)径向生长与气候因素和气候生态指标的关系,并借助VS-oscilloscope模型对落叶松的生长季物候进行模拟研究.结果显示:(1)上限树木径向生长与3月降水呈显著正相关,与7、8月气温呈显著负相关(P 0.05),下限树木径向生长与8、9月气温呈显著负相关(P 0.05),与降水相关性不显著.(2)上下限树木生长与春季降水和夏季气温的相关性分别呈显著正相关和显著负相关(P 0.05),与湿润指数的相关性呈显著正相关(P 0.05).(3)VS-oscilloscope模型模拟结果显示:上下限落叶松平均每年生长季开始都提前了0.39 d,生长季结束都推迟了0.21 d,生长季长度都延长了0.60 d,上下限树木径向生长与生长季开始和结束的相关性分别是0.361(P 0.01)和0.318(P 0.05).(4)上下限树木生长季开始时间大多与气温呈负相关,而结束时间大多与气温呈正相关,降水对树木生长季物候的影响并不显著(P 0.05).本研究表明海拔差异明显影响树木径向生长对单月气候的响应,而对季节性气候因子和气候生态指数的响应影响不明显;温度对树木生长季物候的影响较为明显,且海拔差异不能影响温度对树木生长季物候的限制;本研究结果有助于更加深入地了解气候变化对森林生态系统的影响,可为天山地区气候因子重建提供一定生理背景支持.(图8表5参48)     

华北落叶松不同林型土壤理化性质差异

在河北塞罕坝机械林场的华北落叶松3个不同类型人工林设立典型样地,研究落叶松白桦混交林、落叶松樟子松混交林、落叶松纯林的土壤理化性质和林地凋落物现存量等17项指标,分析这些指标在0-50 cm共5个土层间的差异情况.结果表明:(1)在土壤剖面上随土层加深,3种林型土壤容重均逐渐增加;土壤水分、有机质、全氮、全磷、碱解氮、有效磷、速效钾、电导率呈减小的趋势;孔隙度和全钾变化不显著.(2)在同一土层,土壤容重和p H总体表现为落叶松白桦混交林最低,落叶松纯林最高;林地凋落物现存量、土壤水分、有机质、氮、磷、钾、电导率均表现为落叶松白桦混交林最高,落叶松纯林和落叶松樟子松混交林无显著差异.(3)相关性分析表明容重与土壤水分、孔隙度、全钾、速效钾呈极显著负相关,与非毛管孔隙度、有机质、有效磷呈显著负相关;有机质、氮、磷、钾元素之间均有显著正相关关系,全氮、全磷、全钾与凋落物未分解层现存量都呈显著正相关.因此认为在3种林型中,落叶松白桦针阔混交林土壤理化性质明显优于落叶松樟子松混交林、落叶松纯林;结果可为合理利用森林土壤、科学营造华北落叶松人工林提供依据.     

长白山北坡林线处岳桦年轮年表及其与气候的关系

运用相关函数及响应分析等树木年轮气候学方法,研究了长白山北坡林线处岳桦(Betula ermanii)径向生长及其与气候的关系.结果表明,林线处岳桦年轮宽度年表具有较强的气候敏感性.其径向生长与上年7月和当年3月的温度显著负相关(P<0.05),与上年9月和当年7月的温度显著正相关;同时与上年6月降水量显著正相关.与季节性气候因子的响应分析表明,岳桦径向生长与当年春季(1～3月)和当年生长季前(4、5月)的平均温度呈显著负相关,与当年生长季前的平均最高温度显著正相关,与降水量的相关关系不显著.利用多元逐步回归方法模拟了岳桦年轮宽度指数与气候因子间的关系,并据此预测在温度和降水增加的背景下,林线处岳桦径向生长将降低14.8%.     

山西芦芽山林线附近土壤水分空间分布特征及其影响因素

于2008年植被生长季,在芦芽山荷叶坪亚高山草甸及森林-草甸过渡带内布设观测样带,应用FDR土壤剖面水分测量仪测量10～40 cm深度土壤含水量,并分析其空间分布特征和影响因素。结果表明:(1)根据所处位置及地上植被状况可将样带分为林地样带和草甸样带,林地样带土壤含水量随深度增加呈先升高后降低的变化趋势,草甸样带则恰好相反。(2)10和40 cm深度为土壤含水量稳定层,20和30 cm深度为活跃层,且林地样带10 cm深度土壤含水量小于草甸样带,20、30和40 cm深度土壤含水量则大于草甸样带。(3)降雨发生后,阴坡上部树岛样带土壤含水量增幅最大,阳坡上、中、下部草甸样带土壤含水量增幅也较大;不同土层深度比较而言,10cm深度土壤含水量增幅最大,20、30和40 cm深度土壤含水量增幅较为接近,土壤含水量对降雨的响应存在1～2d的时滞。(4)10、20和30 cm土壤含水量变化值与坡度呈显著正相关,30、40 cm土壤含水量变化值与初始土壤含水量呈显著负相关,20、30 cm土壤含水量变化值与地形湿度指数呈显著负相关。研究区内土壤含水量空间分布格局及其动态变化受植被和降雨影响显著,初始土壤含水量、坡度以及地形湿度指数对其也有一定影响。     

华北落叶松不同林型土壤理化性质差异北大核心CSCD

在河北塞罕坝机械林场的华北落叶松3个不同类型人工林设立典型样地,研究落叶松白桦混交林、落叶松樟子松混交林、落叶松纯林的土壤理化性质和林地凋落物现存量等17项指标,分析这些指标在0-50 cm共5个土层间的差异情况.结果表明：（1）在土壤剖面上随土层加深,3种林型土壤容重均逐渐增加;土壤水分、有机质、全氮、全磷、碱解氮、有效磷、速效钾、电导率呈减小的趋势;孔隙度和全钾变化不显著.（2）在同一土层,土壤容重和p H总体表现为落叶松白桦混交林最低,落叶松纯林最高;林地凋落物现存量、土壤水分、有机质、氮、磷、钾、电导率均表现为落叶松白桦混交林最高,落叶松纯林和落叶松樟子松混交林无显著差异.（3）相关性分析表明容重与土壤水分、孔隙度、全钾、速效钾呈极显著负相关,与非毛管孔隙度、有机质、有效磷呈显著负相关;有机质、氮、磷、钾元素之间均有显著正相关关系,全氮、全磷、全钾与凋落物未分解层现存量都呈显著正相关.因此认为在3种林型中,落叶松白桦针阔混交林土壤理化性质明显优于落叶松樟子松混交林、落叶松纯林;结果可为合理利用森林土壤、科学营造华北落叶松人工林提供依据.     

不同植被类型对土壤理化性质和土壤呼吸的影响

不同植被类型影响地表覆盖和土壤特性,进而可能会改变生态系统碳循环。为了揭示植被类型对土壤理化性质和土壤呼吸碳排放的影响,本文通过测定并分析大兴安岭南段蒙古栎(Quercus mongolica)林、林缘草地、华北落叶松(Larix pricepis-ruprechtii)人工林、山杏(Armeniaca sibirica)灌丛和山荆子(Malus baccata)林5种植被类型的土壤理化性质和土壤碳通量,探讨了不同植被类型中土壤特性和土壤呼吸的变化。结果表明,土壤全氮、速效磷和有机碳均表现为山荆子林显著高于其他植被类型。生长季的土壤温度呈单峰趋势,在8月份达到最高;土壤含水量呈先升高后下降再升高的趋势,其范围在0.77~1.18 cm~3·cm~(-3)之间;土壤呼吸速率与土壤温度的变化趋势一致,各植被类型均在8月份达到峰值,以山杏灌丛的土壤呼吸速率最大(9.778μmol·m~(-2)·s~(-1)),分别是山荆子林、林缘草地、蒙古栎林和华北落叶松人工林的1.25、1.37、1.84和1.87倍。单因素方差分析表明,生长季的各个月份的土壤呼吸速率在不同植被类型间有显著差异;华北落叶松人工林生长季土壤呼吸的排放量最低;生长季土壤呼吸速率与土壤温度和含水量均呈显著正相关关系。因此,大兴安岭南段的不同植被类型是影响生长季土壤碳排放的主要生物因子,而土壤温度是其主要的非生物因子。该研究可为植被类型的科学管理提供科学依据,对植被碳排放的进一步理解具有一定的意义。     

冀北山地3种森林植被恢复类型对土壤质量的影响

森林植被恢复对土壤质量的改善是森林可持续经营的重要条件。为研究冀北不同森林植被恢复类型对土壤质量的影响差异,以小五台山自然保护区46年生华北落叶松(Larixprincipis-rupprechtii)、白桦(Betulaplatyphylla)、华北落叶松-白桦混交林为研究对象,分层测定了3种植被类型的土壤物理性状、持水能力和养分特征,采用土壤质量指数评价法对3种植被恢复类型土壤质量进行了综合评价。结果表明,(1)华北落叶松-白桦混交林对中下层(20～60 cm)土壤物理性状的改善作用较大,其浅层土壤(0～20cm)物理性质与华北落叶松和白桦纯林差异不明显。(2)华北落叶松-白桦混交林对土壤持水能力的改善作用较大,特别是对最大持水量和田间持水量的改善作用明显大于华北落叶松和白桦纯林;对20 cm以下土层毛管持水量和土壤含水量有明显的改善作用。(3)3种植被恢复类型中,土壤养分状况表现为华北落叶松-白桦混交林华北落叶松林白桦林。(4)土壤质量综合评价结果表明,不同植被恢复类型对土壤质量的改善作用表现为华北落叶松-白桦混交林华北落叶松林白桦林,改善作用最明显的是中下层土壤(20 cm以下)。综上,森林植被恢复对土壤质量的改善作用是由浅及深的过程,随着林龄增大,其对土壤质量的改善作用逐渐深入到土壤中下层。     

海北高寒草甸返青期土壤温度与水分动态变化

分析青藏高原高寒草甸返青期土壤水分和温度的变化以及相互关系是理解高寒草甸生态系统变化的重要基础。为明晰青藏高原祁连山东部高寒草甸返青期的土壤温度与水分变化规律,选择祁连山东部海北高寒草甸为试验区,以实地测试与方差、相关及回归分析相结合的方法研究了海北高寒草甸返青期土壤分层水分和温度的动态变化。结果表明:(1)观测期内,高寒草甸整个返青期表层0 cm及地表以下5、15、30、60和120 cm土壤各层平均温度分别为10.47、4.11、3.28、1.76、0.80和0.51℃,表层0 cm地温受气温变化影响最为显著;返青早期各层土壤温度均稳定于0℃左右,返青中期各层土壤温度迅速增加,返青中后期自上而下不同土壤层温度逐渐降低;(2)表层、中层和深层土壤平均含水量分别为17.3%、20.6%和20.9%,中层和深层土壤水分含量较小;表层土壤含水量波动剧烈,在整个返青期呈逐渐下降趋势,中层和深层土壤含水量连续增加,波动范围小;(3)高寒草甸土层0~15 cm的土壤体积含水量与土壤温度呈显著负相关,随土壤平均温度增加,土壤体积含水量逐渐降低;15~30、30~45和45~60 cm较深层土壤含水量与土壤平均温度呈显著正相关,随土壤深度增加其相关性也随之增强。该研究可为理解青藏高原高寒草甸生态系统的变化规律和变化过程提供参考依据,对高寒草甸的保护及可持续利用也具有重要意义。     

兴安落叶松林土壤呼吸及组分的变化特征

采用挖壕法断根对兴安落叶松（Larix gmelinii）林土壤呼吸的组分进行分离,利用静态箱/碱液吸收法对土壤呼吸以及各组分的呼吸速率及10 cm土层的土壤温度和土壤含水量进行测定。研究兴安落叶松林土壤呼吸及其组分的日动态和季动态变化特征,阐明大兴安岭地区兴安落叶松林土壤呼吸及其组分的变化规律及其与土壤温度、土壤含水量两个影响因子之间的关系。研究结果显示,①兴安落叶松林土壤呼吸、异养呼吸和自养呼吸都呈现明显的日变化和季节变化规律,日变化曲线均呈单峰型,自养呼吸速率的日变化较平缓,其最大值与土壤呼吸、异养呼吸和土壤温度的时间比较出现滞后现象：在生长季土壤呼吸和异养呼吸月平均呼吸速率值的排列顺序依次为：7月>8月>9月>6月,而自养呼吸月平均呼吸速率值的排列顺序依次为：8月>7月>9月>6月。②兴安落叶松林中土壤呼吸速率、异养呼吸速率和自养呼吸速率与10 cm土壤温度之间均成指数相关关系,通过计算得出Q10值分别为1.69、1.97和1.24,与其他地区的研究结果相比温度敏感性偏低。土壤呼吸、异养呼吸和自养呼吸与土壤含水量有相关性但不显著。③异养呼吸和自养呼吸对土壤总呼吸的贡献率分别约为63％、37％,该地区土壤异养呼吸所占比例接近于自养呼吸的两倍。     

Applications of chitosan in food,pharmaceuticals, medicine,cosmetics, agriculture,textiles, pulp and paper,biotechnology, and environmental chemistry

Environmental Chemistry Letters - Chitosan is a biopolymer obtained from chitin, one of the most abundant and renewable materials on Earth. Chitin is a primary component of cell walls in fungi, the...     

Fragmentation of Phragmites Habitats, Minimum Viable Population Size, Habitat Suitability, and Local Extinction of Moths, Midges, Flies, Aphids, and Birds

Results from populations of insects and birds inhabiting Phragmites habitats were used to analyze effects of fragmentation. Flush-crash cycles of the stem-boring moth Archanara geminipuncta (Lepidoptera, Noctuidae) showed regionally concurrent, local extinctions despite an originally enormous population size (more than 180,000 adults), emphasizing the importance of metapopulation dynamics. Further, A. geminipuncta could be considered a keystone species, since shoot damage facilitated more than twenty species of herbivores, saprovores (of the caterpillars' feces), and their parasitoids. The gall midge Lasioptera arundinis could survive only in side shoots induced by shoot damage of A. geminipuncta .
Small Phragmites stands had thinner shoots (due to a water or nutrient deficiency) and shoots with more leaves (due to a better light supply) than large stands, thereby influencing species-specific demands for habitat suitability and nutritiousness of reed tissue. In other words significance of habitat fragmentation could not be assessed by area alone. For example, two chloropid flies depending on thin, yellowish shoots survived only in small habitats or in the unmown edges of large habitats.
Local persistence of Phragmites herbivores depended on much larger population sizes than could be expected from a population size sufficient to maintain genetic variation. At least 11,000 adults of the gall midge Giraudiella inclusa (or more than 84,000 galls) were necessary to avoid local extinction.
With regard to conservation management of reed habitats, nature reserves should consist of old and unmown reeds, have fewer disturbed (particularly, fewer mown) habitat edges, measure more than two hectares (priority should go to the largest remaining fragments), and be surrounded by nearby reed habitats providing reservoir populations and diverse shoot types.     

Metal passivity as mechanism of metal carcinogenesis: Chromium,nickel, iron,copper, cobalt,platinum, molybdenum

For the transition metals chromium, nickel, iron, copper, cobalt, platinum, and molybdenum, mechanisms of stable bonding in biochemistry (emphasis on carcinogenic mechanisms), chemistry, industrial chemistry, as well as epidemiological, occupational, orthopedic (implant devices) effects related to carcinogenesis, were reviewed. Hypothetically, the propensity to stable bonding (inertness), which ensures the metals’ performance capacity for consumers and industrial application, relates to their carcinogenicity. For chromium, a relationship between industrial/chemical and biological reactivity was noted for the tendency of Cr(III) ions to cause hydrolysis previous to stable bonding, as occurs during anodic passivation, leather tanning, and as indicated in biochemical studies pertaining to a mechanism of DNA condensation, which was suggested as a carcinogenic mechanism. The involvement of metal hydrolysis in both anodic passivation and biochemistry was noted also for nickel, iron, and platinum; the DNA interaction of platinum (cis-platin) is known to depend on hydrolysis. For nickel, issues of potential (V) were found important in both passivation and carcinogenicity. Comparably, the passivity behavior of cobalt and copper was found atypical, and their carcinogenicity yet unclear. Molybdenum, contained in passivated metallic implants, may relate to implant-associated carcinogenesis. Occupational carcinogenic effects were indicated for chromium, nickel, iron, and cobalt as caused by both reactive and passivated metal species. Exposure to acids and chronic respiratory irritation/infection/inflammation in workers were important cofactors in metal carcinogenesis. For wood and leather workers exposed to dust, the assumed presence in dust of metal particles abraded from alloys (sawing or cutting blades) may be a carcinogenic exposure hazard.     

Lead,cadmium, copper,zinc, iron,and calcium in human hair as a function of gender,age, smoking,and hair dyeing

Hair samples were collected randomly from 110 subjects (55 male and 55 female) ranging in age from (<15–60) years. Each subject was asked to complete a personal questionnaire describing his/her sex, age, general health, smoking, use of hair dyes, occupational area, and living habits. Concentrations of Pb, Cd, Cu, Zn, Fe, and Ca in human hair samples were evaluated using atomic absorption spectrometry. Results indicated that concentrations of Pb, Cd, Cu, and Zn in the hair of smokers were higher than those in the hair of non-smokers, whereas, Fe and Ca concentrations in hair of smokers were lower than those in hair of non-smokers. Moreover, the concentrations of these elements are higher in dyed hair compared with undyed hair.     

Concentrations of V,Cr, Mn,Fe, Ni,Co, Cu,Zn, As and Cd in mesopelagic crustaceans from the North East Atlantic Ocean

Specimens of oceanic decapods, mysids and euphausiids, collected from the North East Atlantic Ocean during July 1985, were analysed for V, Cr, Mn, Fe, Ni, Co, Cu, Zn, As and Cd. Measurement of the metals was carried out using two techniques: inductively-coupled plasma-source mass spectrometry (ICP-MS) and atomic absorption (AAS). With the exception of the iron data, good agreement was observed between the data from the two techniques. Baseline-metal data are presented for the species measured, along with any effects of animal size on metal concentration. The data presented for oceanic animals from different trophic levels are important in studies of metal fluxes and for the assessment of markers within the food web in the oceans.     

Research progress on distribution,sources, identification,toxicity, and biodegradation of microplastics in the ocean,freshwater, and soil environment

• Microplastics are widely found in both aquatic and terrestrial environments. • Cleaning products and discarded plastic waste are primary sources of microplastics. • Microplastics have apparent toxic effects on the growth of fish and soil plants. • Multiple strains of biodegradable microplastics have been isolated. Microplastics (MPs) are distributed in the oceans, freshwater, and soil environment and have become major pollutants. MPs are generally referred to as plastic particles less than 5 mm in diameter. They consist of primary microplastics synthesized in microscopic size manufactured production and secondary microplastics generated by physical and environmental degradation. Plastic particles are long-lived pollutants that are highly resistant to environmental degradation. In this review, the distribution and possible sources of MPs in aquatic and terrestrial environments are described. Moreover, the adverse effects of MPs on natural creatures due to ingestion have been discussed. We also have summarized identification methods based on MPs particle size and chemical bond. To control the pollution of MPs, the biodegradation of MPs under the action of different microbes has also been reviewed in this work. This review will contribute to a better understanding of MPs pollution in the environment, as well as their identification, toxicity, and biodegradation in the ocean, freshwater, and soil, and the assessment and control of microplastics exposure.     

Fractionation of trace metals (Mn,Zn, Cu,Pb) in Red Sea sediments,Gulf of Aden,Yemen

A sequential extraction technique was applied to estimate the chemical association of Mn, Zn, Cu and Pb in five chemical phases (exchangeable, carbonate, Fe–Mn oxides, organic matter and residual) in sediments of the Gulf of Aden, Yemen. The results indicated that a higher level of Mn was associated with the residual fraction (natural sources) than the non-residual fraction (anthropogenic sources). Zn fractionations revealed that it was associated more with Fe–Mn oxides and organic fractions than exchangeable and carbonate fractions. Most of the Cu was present in the residual form (60–72%) except for in the main port area (zone III), where it was associated with the organic phase (77% of the total Cu content, the organic matter content was 5%). Similarly, most Pb was bound in the residual fraction (56–71%) except the main port area where ～ 62% of the total Pb was bound in non-residual fractions. It was also found that the Pb concentration in the exchangeable fraction was very high compared with other metals. The risk assessment code for the metals showed a low risk for Zn and Cu, but low to medium risk for Mn. Fractionation of Pb showed medium risk at most of the regions except at the eastern area, which revealed a high risk for the aquatic environment.