Northern Tibet lies within the remote regions of the Tibetan Plateau, features a dry and cold climate, and forms a broad strip of land sensitive to global warming. Meadows are the largest and most important ecosystems in northern Tibet.Alpine meadows are extensively distributed in the northern Tibetan Plateau and are typical features of the region. The alpine meadow soil type in the study area is seasonally frozen. We chose three representative plant communities as samples areas, which we identified as Potentilla spp. , Kobresia pygmaea, and Kobresia littledalei based on the dominant species of each community to study soil nematode communities. The plots are situated at Dejixiangdaga village at N31毅31忆38义-31毅32忆02义, http: / / www. ecologica. cn E92毅04忆03义-92毅04忆16义 in Naqu County in the Naqu region of the Tibet Autonomous Region, China.Soil nematode communities in the upper 0-30 cm soil were investigated in three typical plant communities in alpine meadows of northern Tibet from May to November 2011. The soil nematodes were collected using the shallow basin method.The following soil chemical properties were tested: pH, potentiometry, soil water content ( oven drying method) , and electricity conductivity. The trophic composition, c鄄p group structure and functional structure index, as well as the characteristic values between trophic groups, c鄄p groups and soil properties, were analyzed to understand the effect of cold alpine conditions on soil nematode functional diversity. A total of 33038 nematodes, which were classified to nematode phylum, 2 classes, 6 orders, 51 families and 93 genera, were collected during the surveys. Average individual density was 847 nematodes per 100g dry soil. The results were mostly within the scope of previous reports, and nematodes obviously appeared to aggregate in the upper soil layers. The research indicated soil nematode tropic composition varied from one plant community to another in alpine meadows. Herbivorous and bacterivorous nematodes were the major nematode communities in the area. The relative abundance of herbivorous to omnivorous and / or predatory nematodes obviously varied in different plant communities. An analysis of the constitution of the c鄄p groups showed all cp2 groups were the predominant groups in all three plant communities, and all c鄄p groups were mainly r鄄strategists. Kobresia pygmaea was the most common food source for nematodes. Kobresia littledalei had the lowest nematode density, possibly because limited food availability limits the reproduction of cp1 and cp2 nematodes. The result of analysis of the plant parasite index indicated the Potentilla community was easier for nematodes to populate when compared to the other two vegetation types, whereas the data from the maturity index ( MI) , PPI / MI and cp5 demonstrated nematode stability in Potentilla was highest among three vegetation types. The fungal to bacterial feeder ratio and Nematode Channel Ratio showed bacterial decomposition was the major decomposition pathway in the soil organic substance decom...
Earthworms perform a number of essential functions in soil and are ideal indicators of soil pollution and declines in soil quality. The effects of pollutants on earthworm biomarkers are often investigated to assess the risk of soil pollution. The aim of this review is to explore whether the currently known earthworm biomarkers can be used in practice to assess soil pollution risk. In this paper, we review four aspects of earthworm biomarkers based on studies published in the past two decades and especially in the most recent 10 years. 1) The role of earthworm biomarkers in soil pollution risk assessment was first discussed, leading to the conclusion that although earthworm biomarkers cannot replace conventional chemical analytical methods, they offer a good complement for the flaws of chemical analysis, and may provide more comprehensive and straightforward information about soil pollution risk. Therefore, earthworm biomarkers may be very useful for primary screens in large鄄scale soil pollution surveys. 2) The earthworms tested in previous studies represented many different species and all three ecological categories (epigeic, anecic, and endogeic) , but most studies involved Eisenia fetida / andrei (epigeic). Earthworm biomarkers could be classified into different groups: physiological鄄biochemical, individual behavior, morphological, molecular genetic and immunological. However, most researchers have focused on the anti鄄oxidant defense system, metallothionein (MT) , avoidance response, lysosomal fragility (neutral red retention assay) , and the comet assay. http: / / www.ecologica.cn In addition, the range of exposure medium, exposure time, other components in the experimental design, and differences in the results were critically reviewed. We concluded that earthworm biomarker studies have been carried out mainly at the laboratory scale, that many biomarkers have been screened, and that the response mechanisms of typical earthworm biomarkers to typical pollutants and to combined pollutants have been elucidated to some extent. However, in the future, studies should focus on the feasibility of using earthworm biomarkers in real soil conditions. 3) Published studies vary greatly in experimental design and results, including the range of biomarkers and the response level in earthworms, and therefore are not directly comparable. This fact may pose a challenge to inferring broadly reliable conclusion and might limit the practical applications of this research. To elucidate the problems, we discuss the varying responses of superoxide dismutase, an important component of the antioxidant enzyme system in different earthworm studies; the results varied by three orders of magnitude which is confusing because the change of physiological鄄biochemical level should not be so large even in spiked earthworms. As a result, standard protocols for earthworm biomarker assays may be needed to aid comparisons among studies. 4) We recommend a set of research guidelines (such as the earthworm species to be tested, exposure times, types ...
摘要:通过室内培养试验,研究了赤子爱胜蚓(Eisenia foetida) 和威廉环 毛蚓(Metaphire guillelmi) 对土壤氨基酸组分及含量的影 响,并探讨了两种不同生活型蚯蚓作用效果的异同。 结果表明:蚯蚓活动可显著改变土壤氨基酸含量,爱胜蚓作用下土壤酸解 氨基酸和游离氨基酸分别增加 5.08 g / kg 和 7.72 mg / kg,环毛蚓作用下土壤酸解氨基酸和游离氨基酸分别增加 3.86 g / kg 和 4.44 mg / kg。 各处理酸解氨基酸均以中性氨基酸所占比例为最大(平均 51.9%) ,酸性氨基酸次之(平均 23.3%) ,而含硫氨基酸(平 均 14.4%) 及碱性氨基酸最少(平均 10.4%) 。 各处理游离氨基酸同样以中性氨基酸为主,平均 54.4%,而以碱性氨基酸含量最
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