浙江九龙山青冈林的数值分类

用等级聚合分类方法中的组平均法对浙江省九龙山以６种青冈分别组成的典型常绿阔叶林进行数值分类。结果表明，主要有７个类型（群系）：青冈栎常绿阔叶林，云山青冈常绿阔叶林，褐叶青冈常绿阔叶林，小叶青冈常绿阔叶林，细叶青冈常绿阔叶林，多脉青冈常绿阔叶林及多脉青冈落叶阔叶混交林。并对其组成和分布进行了论述。     

放牧对明油子-扭黄茅灌草丛生物多样性的影响

2005年，在云南元谋干热河谷采用样方调查法及生物多样性分析法研究了放牧干扰对明油子Dodonaea viscosa-扭黄茅Heteropogon contortus灌草丛生物多样性的影响。结果表明，无放牧干扰的明油子-扭黄茅灌草丛植物和节肢动物种类最丰富，节肢动物群落优势度最低，而多样性和均匀度最高，优势种为扁平虹臭蚁Iridomyrmex anceps；曾经过度放牧的明油子-扭黄茅灌草丛植物种类和节肢动物种类最贫乏，灌木-草本层节肢动物多样性最低；长期存在一定放牧干扰的明油子-扭黄茅灌草丛植物种类和节肢动物种类比较丰富，但节肢动物群落优势度最高而均匀度最低；经受或存在放牧干扰的明油子，扭黄茅灌草丛林下以刺吸类昆虫占优势，地表以迈氏小家蚁Monomorium mayri占优势。过度放牧导致明油子-扭黄茅灌草丛种类组成发生变化，生物多样性大大降低，群落趋于不稳定，栖息环境出现退化。放牧干扰对地表节肢动物群落的影响比对灌木-草本层节肢动物群落的影响突出。表6参21     

广州白云山几种森林群落生物量和持水性能

对白去山风景区主要森林群落的生物量进行了测定，并对乔木层，灌草层，枯落物层和土壤层的持水状况进行了初步研究。结果表明，乔木层及灌草层生物量大小顺序均为马占相思＋木荷群落＞马尾松群落＞马占相思群落＞藜蒴群落＞加勒比松群落：枯落物层现存量为马尾松群落＞藜蒴群落＞马占相思＋木荷群落＞马占相思群落＞加勒比松群落；5个群落各层的自然持水量为土壤层＞乔木层＞灌草层＞枯落物层＞枯落物层（马尾松群落为灌草层＞乔木层）；群落各层总的自然持水量顺序为马占相＋木荷＞马占相思＞马尾松＞加勒比松＞藜蒴。     

重金属复合污染下土壤微生物群落功能多样性动力学特征

用碳素利用法对浙江省天台铅锌银尾矿区重金属复合污染土壤微生物群落功能多样性动力学特征进行了初步探讨。研究结果表明 ,矿区重金属复合污染降低了供试土壤的微生物群落代谢剖面 ,且群落代谢剖面值与培养时间之间呈非线性关系 ,其变化过程符合微生物种群生长动态模型 (S形 )。随着重金属复合污染程度的加剧 ,土壤微生物群落功能多样性动力学参数K和r值越低 ,参数s值所需的时间则越长。上述动力学参数与群落代谢剖面各自的主成分分析结果显示 ,微生物群落功能多样性的动力学参数K值和s值能够很好地区分矿区土壤重金属污染程度 ,并且其区分效果比微生物群落代谢剖面值好。土壤微生物群落功能多样性动力学特征的变化可以较好地显示矿区重金属复合污染土壤微生物群落对碳源利用模式的差异 ,反映矿区特定生境土壤微生物群落功能多样性的变化 ,在一定程度上揭示重金属胁迫下环境微生物种群作用机理。     

重金属复合污染下红壤微生物活性及其群落结构的变化

在室内培养条件下,应用4因素5水平二次正交回归旋转组合设计方案,对重金属复合污染红壤的微生物活性及群落功能多样性进行了研究。结果表明,在Cu、Zn、Pb、Cd复合污染生境中重金属的微生物毒性效应发挥主要由Cd、Cu两元素决定,其生物毒性顺序表现为:Cd>Cu>Zn>Ph,红砂泥中表现较为突出。与单一镉、单一铅污染处理相比,重金属复合污染对供试红壤微生物生物活性及其群落功能多样性的影响并非仅仅表现出简单的加和作用,同时还存在协同作用和拮抗作用。典型相关分析显示,红壤微生物活性与重金属含量之间关系密切,第一对典型变量的相关系数r达0.885 8、0.932 8,均达极显著水平(p<0.001), 说明重金属复合污染与红壤微生物间存在较为稳定的数量反馈机制,红壤总体微生物活性指标能较好地反映供试红壤重金属复合污染状况,可作为重金属污染红壤环境质量评价及量化分类的有效指标。     

Nano-scale secondary ion mass spectrometry — A new analytical tool in biogeochemistry and soil ecology: A review article

Soils are structurally heterogeneous across a wide range of spatio-temporal scales. Consequently, external environmental conditions do not have a uniform effect throughout the soil, resulting in a large diversity of micro-habitats. It has been suggested that soil function can be studied without explicit consideration of such fine detail, but recent research has indicated that the micro-scale distribution of organisms may be of importance for a mechanistic understanding of many soil functions. Current techniques still lack the adequate sensitivity and resolution for data collection at the micro-scale, and the question ‘How important are various soil processes acting at different scales for ecological function?’ is therefore challenging to answer. The nano-scale secondary ion mass spectrometer (NanoSIMS) represents the latest generation of ion microprobes, which link high-resolution microscopy with isotopic analysis. The main advantage of NanoSIMS over other secondary ion mass spectrometers is its ability to operate at high mass resolution, whilst maintaining both excellent signal transmission and spatial resolution (down to 50 nm). NanoSIMS has been used previously in studies focussing on presolar materials from meteorites, in material science, biology, geology and mineralogy. Recently, the potential of NanoSIMS as a new tool in the study of biophysical interfaces in soils has been demonstrated. This paper describes the principles of NanoSIMS and discusses the potential of this tool to contribute to the field of biogeochemistry and soil ecology. Practical considerations (sample size and preparation, simultaneous collection of isotopes, mass resolution, isobaric interference and quantification of the isotopes of interest) are discussed. Adequate sample preparation, avoiding bias due to artefacts, and identification of regions-of-interest will be critical concerns if NanoSIMS is used as a new tool in biogeochemistry and soil ecology. Finally, we review the areas of research most likely to benefit from the high spatial and high mass resolution attainable with this new approach.     

Frog communities and wetland condition: relationships with grazing by domestic livestock along an Australian floodplain river

Frogs are in decline worldwide, and are known to be sensitive indicators of environmental change. Floodplains of the Murray-Darling Basin in southeastern Australia have been altered in many ways by livestock grazing, by the introduction of exotic fish, and by changes to flooding regimes. These changes have led to declines in wetland condition and hence to the availability of habitat for wetland frogs. This study examined relationships between frogs, wetland condition and livestock grazing intensity at 26 wetlands on the floodplain of the Murrumbidgee River. Frog communities, species richness, and some individual species of frogs declined with increased grazing intensity. Wetland condition also declined with increased grazing intensity, particularly the aquatic vegetation and water quality components. There were clear relationships between frog communities and wetland condition, with several taxa responding to aquatic and fringing vegetation components of wetland condition. Thus, grazing intensity appeared to influence frog communities through changes in wetland habitat quality, particularly the vegetation. Reduced stocking rates may result in improved wetland condition and more diverse frog communities. River management to provide natural seasonal inundation of floodplain wetlands may also enhance wetland condition, frog activity and reproductive success.     

Lakeshore diversity and rarity relationships along interacting disturbance gradients: catchment area, wave action and depth

Diversity patterns of riparian plant communities have been associated with disturbance. Populations of a diversity of Atlantic Coastal Plain plants occur as disjuncts on shores of large catchment area lakes in Nova Scotia. These lakeshore communities contain rare plants with local, national and global rankings. The populations of rare plants are dynamic and their management requires an understanding of the relationship between disturbance and the survival of rare plants. This present study measured (overwinter wooden dowel removal) and observed disturbance along gradients of catchment area (CA), exposure and depth. In three separate experiments ranging from the landscape to the lake, to the single shoreline level, disturbance was linked to lake CA, exposure and depth, respectively. At all scales, disturbance was positively associated with the presence of rare species. The pattern of rare species richness over the river system was complex; at the within-lake level, the frequency of rare species per site was greatest in the intermediate CA lake while the pool of rare species was greatest in the largest CA lake. The findings focus field efforts on wide, exposed shorelines of large CA lakes where new rare plants continue to be discovered. In addition, the discrepancy between highest frequency of rare plants on intermediate CA lakes and highest species pools of rarities on large CA lakes, reinforces the need for larger protected area systems for the most naturally disturbed ecosystems which often support populations having a high turnover rate but a low site to site frequency.     

Functional and molecular responses of soil microbial communities under differing soil management practices

The effects of soil management on some microbiological properties and soil bacterial community structure were evaluated. Two field sites with the same soil type, located on the same geographic area adjacent to one other, have received different soil management practices and cultivation. One site has been subjected for 20 years to intensive horticulture under conventional tillage and irrigation with low quality salt-rich water; the second field site has been uncultivated for a long period and was turned to organic farming practices over the last 5 years and is currently cultivated with fruit orchard. Total bacterial counts, microbial ATP, microbial community metabolic (BIOLOG^®) profiles, and DNA fingerprinting by PCR-DGGE were determined. Two-way ANOVA revealed that total bacterial counts were not significantly (P>0.3) affected by the two different management practices; ATP content was consistently and significantly (P<0.001) lower in salt-water irrigated soil than in organic soil at the three sampling times. The cluster analysis of community level physiological profiles indicated that microbial communities were much more uniform in organic soil than in irrigated one, suggesting that salt-water irrigation could have affected the size of the microbial population, its metabolic activities, as well as its composition. Molecular patterns fitted the BIOLOG^® profile diversity. In particular, at any sampling time, PCR-DGGE patterns of bacterial DNA, extracted by an indirect method, significantly discriminated irrigated from organic soil samples. The PCR-DGGE patterns of total soil DNA, extracted by a direct method, showed a moderate to significant variation among irrigated and organic soil samples. Biochemical, microbiological and molecular data contributed to evidence a significantly different response of indigenous microflora to soil management by using saline water or organic farming.     

Surface and subsurface organic carbon, microbial biomass and activity in a forest soil sequence

The distribution of organic carbon, microbial biomass and activity, from the surface down to 70 cm, was investigated through three semiarid Mediterranean soils: (1) a Typic Calcixeroll covered with a native pinewood (NP), (2) a Typic Calcixerept under a mature pine plantation (PP) on abandoned agricultural terraces and (3) a Typic Haploxerept under a grassland (GS). NP and GS had the highest and lowest soil organic carbon (SOC) pools, respectively. Both of them had decreasing SOC contents with depth. PP, which held intermediate SOC levels, showed an increase in total organic C and humic substances C with depth due to their mineralization in the anciently ploughed topsoil layer. The soils were similarly ranked as regards their microbial biomass and activity: NP>PP>GS. In general, the microbial communities were less dense and active towards the deeper horizons. More specifically, PP and GS had a very populated and active top 20-cm layer, which was attributed to the dense root system of their grass cover. NP maintained high microbial biomass and activity levels from 0 to 70 cm, progressively diminishing along with shrub root density (e.g. microbial biomass C dropped from 2342 to 394 mg kg⁻¹ soil). The latter soil presented the sharpest drop of its microbial properties with depth, what was considered an indicator of its quality. Generally decreasing patterns of microbial biomass and activity were not always coincident with previously published gradients of microbial metabolic abilities and genetic structure. This reinforces the need of combining biomass, activity and biodiversity measurements if the ecosystem's functioning is to be fully understood and a real monitoring of degradation processes and restoration strategies is to be achieved.