外来种互花米草对江苏省潮间带生物地球化学过程的影响研究

Spartina alterniflora Loisel, a species vegetating in intertidal flats along the eastern coast of the United States, was introduced in China almost 30 years ago and has become an urgent topic due to its invasiveness in the coastal zone of China. The impacts of this alien species S. alterniflora on intertidal ecosystem processes in the Jiangsu coastland were investigated by comparing the sediment nutrient availability and trace element concentration characteristics in a mud flat and those of a four-year old Spartina salt marsh that had earlier been a mudflat. At each study site, fifteen plots were sampled in different seasons to determine the sediment characteristics along the tidal flats. The results suggested that Spartina salt marsh sediments had significantly higher total N, available P, and water content, but lower pH and bulk density than mudflat sediments. Sediment salinity, water content, total N, organic C, and available P decreased along a seaward gradient in the Spartina salt marsh and increased with vegetation biomass. Furthermore, the concentrations of trace elements and some metal elements in the sediment were higher under Spartina although these increases were not significant. Also, in the Spartina marsh, some heavy metals were concentrated in the surface layer of the sediment. The Spartina salt marsh in this study was only four years old; therefore, it is suggested that further study of this allen species on a longer time frame in the Jiangsu coastland should be carried out.     

非饱和土壤热质运移的数学模型

A system atic study of coupled heat and mass transfer in unsaturated soils under complex boundary conditions was carried out and a mathematical model of heat and mass transfer in unsaturated soils was established by non-equilibrium thermodynamic theory. The gradient of volumetric moisture content, the gradient of temperature, the salt mass concentration and vapor pressure were the primary driving forces influencing the process of heat and mass transfer in unsaturated soils. Based on the thermodynam ic analysis and the mass and energy conservation principles, a set of mass and energy equations were developed. The initial and boundary conditions of soil column for one dimension were also given out.     

互花米草入侵潮滩沼泽本土C4植物后土壤有机碳的动态变化

Invasion of an exotic C_4 plant Spartina alterniflora has been shown to increase soil organic carbon(SOC) concentrations in native C_3 plant-dominated coastal wetlands of China. However, little is known about the effects of S. alterniflora invasion on SOC concentrations and fractions in tidal marshes dominated by native C_4 plants. In this study, a field experiment was conducted in a tidal marsh dominated by the native C_4 plant Cyperus malaccensis in the Minjiang River estuary, China. Concentrations of SOC and liable SOC fractions, dissolved organic carbon(DOC), microbial biomass carbon(MBC), and easily oxidizable carbon(EOC),were measured in the top 50-cm soils of the C. malaccensis community, as well as those of three S. alterniflora communities with an invasion duration of 0–4 years(SA-4), 4–8 years(SA-8), and 8–12 years(SA-12), respectively. Results showed that both SOC stocks in the 50-cm soils and mean SOC concentrations in the surface soils(0–10 cm) of the C. malaccensis community increased with the duration of S. alterniflora invasion, whereas SOC concentrations in the 10–50-cm soils decreased slightly during the initial period of S. alterniflora invasion, before increasing again. The pattern of changes in labile SOC fractions(DOC, MBC, and EOC) with invasion duration was generally similar to that of SOC, while the ratios of labile SOC fractions to total SOC(DOC:SOC, MBC:SOC, and EOC:SOC) decreased significantly with the duration of S. alterniflora invasion. The findings of this study suggest that invasion of the exotic C_4 plant S. alterniflora into a marsh dominated by the native C_4 plant C. malaccensis would enhance SOC sequestration owing to the greater amount of biomass and lower proportion of labile SOC fractions present in the S. alterniflora communities.     

盐沼湿地中植物根围土壤细菌群落结构和多样性的16S rDNA分析

The structure and diversity of the bacterial communities in rhizosphere soils of native Phragmites australis and Scirpus rnariqueter and alien Spartina alterniflora in the Yangtze River Estuary were investigated by constructing 16S ribosomal DNA （rDNA） clone libraries. The bacterial diversity was quantified by placing the clones into operational taxonomic unit （OTU） groups at the level of sequence similarity of 〉 97%. Phylogenetic analysis of the resulting 398 clone sequences indicated a high diversity of bacteria in the rhizosphere soils of these plants. The members of Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, and Deltaproteobacteria of the phylum Proteobacteria were the most abundant in rhizobacteria. Chao 1 nonpaxametric diversity estimator coupled with the reciprocal of Simpson＇s index （l/D） was applied to sequence data obtained from each library to evaluate total sequence diversity and quantitatively compare the level of dominance. The results showed that Phragmites, Scirpus, and Spartina rhizosphere soils contained 200, 668, and 382 OTUs, respectively. The bacterial communities in the Spartina and Phragraites rhizosphere soils displayed species dominance revealed by 1/D, whereas the bacterial community in Scirpus rhizosphere soil had uniform distributions of species abundance. Overall, analysis of 16S rDNA clone libraries from the rhizosphere soils indicates that the changes in bacterial composition may occur concomitantly with the shift of species composition in plant communities.     

印度西部卡奇沼泽地沉积物中微生物活性和人工培养细菌多样性的研究

The Great Rann of Kachchh, a vast expanse of salt desert in Western India is a unique hostile ecosystem posing an extreme environment to life forms due to high salt content, hyper-axid climate, seasonal water logging and extremes of temperature. In the virtual absence of natural vegetation, soils and sediments of Rann of Kachchh axe microbially dominated ecosystems. In the present study microbial activity and the diversity of cultivated heterotrophic bacteria were investigated in the sediments collected along a 5-m exposed section at Khadir Island in the Great Rann of Kachchh. Microbial activity （as an index of sediment enzymes） was found to be high in the middle of the section （200-280 cm）. Dehydrogenase （DHA）, substrate-induced DHA and alkaline phosphatase activities revealed the oligotrophic nature of the basal portion （320-480 cm）. Abundant bacterial isolates obtained from different depths were found to be clustered in 12 different phylogenetic groups by amplified ribosomal DNA restriction analysis. 16S rRNA gene sequencing revealed the dominant bacterial ribotypes to be affiliated to Firmicutes （Families Bacillaceae and Staphyloeoccaeeae） and Aetinobaeteria （Family Brevibaeteriaceae） with minor contribution of Proteobacteria （Families Phyllobacteriaeeae and Bartonellaceae）, pointing their endurance and adaptability to environmental stresses. Statistical analysis indicated that sediment organic carbon, salinity, total available nitrogen and total available phosphorous are most likely critical determinants of microbial activity in the Khadir Island sediments.     

植被覆盖和雨强对附着在沉积物上的养分流失, 泥沙颗粒组成及体积分形维数的影响

Vegetation and rainfall are two important factors affecting soil erosion and thus resulting in nutrient loss in the Chinese Loess Plateau.A field experiment was conducted to investigate the effects of rainfall intensities(60,100 and 140 mm h-1) and vegetation(Caragana korshinskii) coverages(0%,30% and 80%) on soil loss,nutrient loss,and the composition and volume fractal dimension of eroded sediment particles under simulated rainfall conditions.The results showed that vegetation cover,rainfall intensity and their interaction all had significant effects on sediment transport and the sedimentbound nutrient loss.Higher rainfall intensity and lower coverage led to higher sediment and nutrient losses.Positive linear relationships were observed between soil loss and nutrient loss.The treatments showed more significant effects on the enrichment ratio(ER) of nitrogen(ERN) than organic matter(EROM) and phosphorus(ERP).Compared with the original surface soil,the eroded sediment contained more fine particles.Under the same coverage,the clay content significantly decreased with increasing rainfall intensity.The ER of sediment-bound nutrients was positively correlated with that of clay,suggesting that the clay fraction was preferentially eroded and soil nutrients were mainly adsorbed onto or contained within this fraction.There were increments in the fractal dimension of the sediment particles compared to that of the original surface soil.Moreover,the fractal dimension was positively correlated with clay,silt,and sediment-bound OM,N,and P contents,whereas it was negatively correlated with sand content.This study demonstrated that fractal dimension analysis can be used to characterize differences in particle-size distribution and nutrient loss associated with soil erosion.     

大麦过氧化物体膜上的抗坏血酸过氧化物酶拟南芥的耐盐机制

Ascorbate peroxidases （APX）, localized in the cytosol, peroxisome, mitochondria, and chloroplasts of plant cells, catalyze the reduction of H2O2 to water by using ascorbic acid as the specific electron donor. To determine the role of peroxisomal type ascorbate peroxidase （pAPX）, an antioxidant enzyme, in protection against salt-induced oxidative stress, transgenic Arabidopsis thaliana plant carrying a pAPX gene （HvAPX1） from barley （Hordeum vulgate L.） was analyzed. The transgenic line pAPX3 was found to be more tolerant to salt stress than the wild type. Irrespective of salt stress, there were no significant differences in Na^＋, K^＋, Ca^2＋, and Mg^2＋ contents and the ratio of K^＋ to Na^＋ between pAPX3 and the wild type. Clearly, the salt tolerance in pAPX3 was not due to the maintenance and reestablishment of cellular ion homeostasis. However, the degree of H2O2 and lipid peroxidation （measured as the levels of malondialdehyde） accumulation under salt stress was higher in the wild type than in pAPX3. The mechanism of salt tolerance in transgenic pAPX3 can thus be explained by reduction of oxidative stress injury. Under all conditions tested, activities of superoxide, glutathione reductase, and catalase were not significantly different between pAPX3 and the wild type. In contrast, the activity of APX was significantly higher in the transgenic plant than in wild type under salt stress. These results suggested that in higher plants, HvAPX1 played an important role in salt tolerance and was a candidate gene for developing salttolerant crop plants.     

土壤盐－水动力学: V.土壤剖面盐平衡

Salt balance in simulated soil coulumns was calculated on the basis of a large amount of long term observation data.The results showed that under the climate conditions of semi-arid region of the Huang-Huai-Hai Plain,the soils in the columns were under salt accumulation conditions when the groundwater depth was controlled at less than 2.0m,and under desalinization conditions when at larger than 2.5m.In the soil columns with clay soil and silty loam soil intercalated with a clay layer,the amount of salt accumulated was far less than that in the soil column with silty loam soil throughout the whole profile.Under no irriagtion conditions crop planting may increase groundwater evaporation and hence salt accumulation in soil,making the soil columns under desalinization be under salt accumulation conditions.     

滇池沉积物的功能: 磷源还是磷库?

Dianchi Lake is a highly eutrophic lake in southwestern China where phosphorus (P) is the limiting element for eutrophication and where lake sediments play an important role in the P cycle. One hundred and eighteen sites were sampled throughout Dianchi Lake in 2002 to investigate the P loading of the lake sediments, while fresh surface sediments were studied in the laboratory to clarify its role for phosphorus. The results showed that concentrations of total phosphorus (TP) in sediments were very high, with a maximum value of 6.66 g kg^-1, and decreased with sediment depth. P adsorption on surface sediments was rapid with adsorption amounts higher in acidic than in alkaline conditions. The release experiments showed that P release increased as pH rose from 7.0 to 10.5. Additionally, compared with aerobic conditions, P release was much higher under anaerobic: conditions, especially with low P content in the lake water. At present, the sediments in Dianchi Lake still function as a sink for phosphorus at high P levels in lake water. However, if the external P load was reduced and P content in lake water became low, the sediment would have a large potential for P release under anaerobic conditions.     

Lake Sediments from Dianchi Lake： A Phosphorus Sink or Source？

Dianchi Lake is a highly eutrophic lake in southwestern China where phosphorus (P) is the limiting element for eutrophication and where lake sediments play an important role in the P cycle. One hundred and eighteen sites were sampled throughout Dianchi Lake in 2002 to investigate the P loading of the lake sediments, while fresh surface sediments were studied in the laboratory to clarify its role for phosphorus. The results showed that concentrations of total phosphorus(TP) in sediments were very high, with a maximum value of 6.66 g kg^-1, and decreased with sediment depth. P adsorption on surface sediments was rapid with adsorption amounts higher in acidic than in alkaline conditions. The release experiments showed that P release increased as pH rose from 7.0 to 10.5. Additionally, compared with aerobic conditions, P release was much higher under anaerobic conditions, especially with low P content in the lake water. At present, the sediments in Dianchi Lake still function as a sink for phosphorus at high P levels in lake water. However, if the external P load was reduced and P content in lake water became low, the sediment would have a large potential for P release under anaerobic conditions.     

线虫群落结构对外源添加不同浓度铜污染物的响应

通过盆栽模拟试验的方法研究外源添加铜对土壤线虫群落结构的影响,试验添加Cu浓度分别为50 mg kg-1,100 mg kg-1,200 mg kg-1,400 mg kg-1干土和不施加污染物的对照处理,在小麦的生长关键期取样。试验结果表明:线虫不同营养类群对铜污染物的响应在小麦拔节期比较明显,拔节期捕食/杂食线虫的数量在外源添加400 mg kg-1Cu处理中显著低于对照,而不同浓度铜对食细菌线虫和食真菌线虫的影响则表现为低浓度促进高浓度抑制。线虫的生态指数对不同浓度铜污染物反映比较敏感,在小麦苗期和拔节期,与对照相比,不同浓度铜处理中线虫多样性降低,而优势度增加;自由生活线虫成熟度指数对不同浓度铜反映相对滞后,只在小麦成熟期表现出差异,即高浓度铜处理中线虫成熟度指数显著低于对照。     

不同种植年限黄瓜温室土壤线虫群落结构及多样性的比较

【目的】针对土壤连作障碍问题,以土壤线虫群落结构和多样性为研究重点,分析不同种植年限土壤生态系统间的差异,进而探讨不同种植年限温室土壤的健康状况。 【方法】采集 8 年、10 年、13 年和 16 年温室黄瓜土壤,以1年露地土壤为对照,采用线虫形态学鉴定方法,分析不同种植年限土壤线虫群落结构及多样性的变化规律。 【结果】不同种植年限共观测到土壤线虫属 21 个,全部为优势属和常见属;线虫总数和植物寄生线虫数量在不同种植年限的分布依次为 10 年 > 16 年 > 13 年 > 8 年 > 1 年,线虫总数种植年限之间差异显著,范围为每 100 g 干土 61～437 条;线虫群落生态指数对种植年限有不同的响应,土壤线虫群落多样性指数 H′ 在不同种植年限土壤中的分布为 16 年 > 13 年 > 1 年 > 8 年 > 10 年,均匀度指数 J 为 13 年 > 16 年 > 1 年 > 8 年 > 10 年,而优势度指数 λ 的分布则为 10 年 > 16 年 > 13 年 > 8 年 > 1 年,5 种不同种植年限土壤的 NCR 指数在 0.6～9.8 之间,WI 分布为 1 年 > 8 年 > 13 年 > 16 年 > 10 年;线虫成熟指数 MI 在种植 16 年的温室土壤中最小,相反 PPI/MI 值则在种植 16 年的土壤中最大;丰富度指数 SR 随种植年限呈先升高后降低,10 年的最低;线虫区系分布结果显示,除种植 10 年黄瓜土壤的样点落在第 Ⅳ 象限外,其余种植年限黄瓜土壤的样点均落在第 Ⅰ 象限。 【结论】综合分析得出,连续种植会使土壤变得贫瘠,健康状况变差,受干扰程度变大,种植 10 年土壤线虫多样性、稳定性最差,土壤环境已受胁迫。     

Assessment of nematode biodiversity using DGGE of 18S rDNA following extraction of nematodes from soil

Soil nematodes are both taxonomically and functionally diverse, respond quickly to soil perturbation and have much potential as indicators of soil health. However, because of the perceived difficulty of identifying nematodes to species level morphologically, they are frequently neglected in soil ecological studies. Recently, extraction of soil DNA, amplification of 18S rDNA genes using nematode consensus primers and subsequent separation by denaturing gradient gel electrophoresis (DGGE) has been used to estimate nematode diversity in soil. Here, we investigate an alternative approach whereby nematodes are first extracted from the soil prior the 18S rDNA gene amplification using universal primers. We used this system to estimate nematode species richness in 10 soil samples—five from Scotland and five from the Netherlands. There was no direct correlation between species richness as estimated morphologically and by the PCR-DGGE method. However, inspection of the data suggested that the samples fell into two discrete groups, which was confirmed by canonical and stepwise discriminant function analysis; the values for the Shannon and equitability indices being important discriminators. Further analysis revealed a significant relationship between morphological species richness and DGGE estimates for species that represented greater than 1% of the sample biomass.     

A comparison of molecular methods for monitoring soil nematodes and their use as biological indicators

Soil fauna, especially soil nematode communities may be used as indicators for monitoring soil biodiversity and ecological processes. A major drawback facing ecologists is the specialised taxonomic knowledge and labour intensive nature of the work required for traditional morphological identification of soil fauna. We review rapid molecular methods, including: DNA Barcoding or sequencing, PCR-DGGE, PCR-TRFLP and real-time PCR, which could enable an empirical assessment of soil nematode assemblages, in relation to their use as monitoring tools. Based on advantages of: high-throughput; ease of comparison between samples; and rapid data analysis, we argue that PCR-TRFLP is well suited to monitoring purposes.     

连作年限对香蕉园土壤线虫群落结构及多样性的影响

为研究连作对蕉园土壤生态系统的影响,以海南香蕉种植区为例,采集不同连作年限(l a、3 a、5 a、7a、10 a和15 a)蕉园土壤,采用线虫形态学鉴定方法,分析了不同连作年限蕉园土壤线虫群落结构及多样性的变化规律。结果表明:整个生育期不同连作年限地块共发现土壤线虫属45个。苗期随连作年限增加线虫总数、食细菌线虫数量和食真菌线虫数量逐渐降低(15 a除外);营养生长期随连作年限增加线虫总数、食细菌线虫数量和食真菌线虫数量先增加后降低;抽蕾期随连作年限增加线虫总数和食细菌线虫数量先增加后降低,食真菌线虫数量逐渐降低。整个生长季,随着连作年限增加植物寄生线虫数量先增加后降低。苗期、营养生长期和成熟期,随着连作年限增加捕食/杂食线虫数量逐渐降低。苗期和抽蕾期的线虫总数显著高于营养生长期和成熟期。苗期的食真菌线虫数量和营养生长期的植物寄生线虫数量显著低于其他各生长时期。苗期和营养生长期的捕食/杂食线虫数量显著低于抽蕾期和成熟期。苗期随连作年限增加,优势度指数(λ)先增加后降低,香农多样性指数(H)和植物寄生线虫成熟度指数(PPI)逐渐增加,瓦斯乐斯卡指数(WI)和通路指数(NCR)逐渐降低;营养生长期随连作年限增加,λ先增加后降低,NCR和PPI逐渐增加,H、自由生活线虫成熟度指数(MI)和WI逐渐降低;抽蕾期随连作年限增加,λ先增加后降低,NCR和PPI逐渐增加,H和WI逐渐降低;成熟期随连作年限增加,H和MI逐渐降低,PPI逐渐增加。从整个生育期来看,随生长时间推移,H逐渐增加,λ逐渐降低,苗期和营养生长期的MI低于抽蕾期和成熟期,苗期和成熟期的WI低于营养生长期和抽蕾期。本研究显示,土壤线虫群落结构可有效反映连作蕉园土壤的健康状况,土壤线虫可作为土壤中重要的指示生物。     

Body size is a sensitive trait-based indicator of soil nematode community response to fertilization in rice and wheat agroecosystems

Nematode body size is a trait that could be responsive to environmental changes, such as agricultural management practices, and adopted as a standard trait-based indicator in soil community analysis. Our study investigated how body size in the nematode community responded to fertilization in a double-cropping system with paddy rice and upland wheat. Four fertilizer treatments were examined: an unfertilized control (CK), chemical fertilizer (CF), manure plus chemical fertilizer (MCF) and manure plus straw plus chemical fertilizer (MSCF). The community-weighted mean (CWM) of body size was the trait-based indicator used for nematode community analysis. A trend of increasing body size in fertilized plots was observed for most genera, with a relatively small increase in the size of small-bodied bacterivores and fungivores and a relatively large increase in the size of large-bodied omnivores. Fertilized plots had significantly greater CWM of body size than the CK treatment, although total nematode abundance increased significantly in the MSCF treatment only. Discriminant and multiple regression analyses showed that CWM of body size was positively correlated with the soil organic C, total N, available P and available K concentrations, which responded to fertilizer inputs. In contrast, soil fertility was weakly related to total body size in the wheat phase and the following abundance-based indicators: Margalef's richness index, Shannon's diversity index, summed maturity index (∑MI) and enrichment index (EI) in both phases. Since fertilization resulted in larger body size but no other change in the nematode community (i.e. diversity and abundance were generally unaffected by fertilization), this implies that nematodes have a plastic growth habit that does not necessarily result in greater reproduction or fitness of offspring. We suggest that CWM of body size is a reliable trait-based indicator of the soil nematode community response to fertilization, but this requires further testing across a wider range of fertilized agroecosystems.     

地中海农业生态系统中土壤自生线虫种群多样性及动态研究

To determine the effect of agricultural management on the dynamics and functional diversity of soil nematode communities in a carrot field at Kibbutz Ramat Hakovesh, Israel, soil samples from 0--10 cm and 10--20 cm depths were collected during the growing season of carrot. Indices were used to compare and assess the response of soil free-living nematode communities to agricultural management. Eighteen nematode families and 20 genera were observed during the growing period, with Cephalobus, Rhabditidae, Aphelenchus, Tylenchus, and Dorylaimus being the dominant genera/families. During the planting, mid-season and post-harvest periods the total number of nematodes at both depths was significantly lower (P < 0.01) in the carrot treatment than in the control plots, while during the harvest period at both depths total nematodes and bacterivores were significantly higher in the treatment plots (P < 0.01). The values of the maturity index (MI) at both depths were found to be significantly lower in the treatment plots than in the control plots during the pre-planting period (P < 0.05). Overall, WI, MI and PPI were found to be more sensitive indicators than other ecological indices for assessing the response of nematode communities to agricultural management in a Mediterranean agroecosystem.     

嘎隆拉山铁杉林土壤线虫群落结构与多样性研究

为了解西藏墨脱嘎隆拉山铁杉林土壤生态系统线虫群落的结构及多样性特征,采用种类组成、个体密度、多样性指数、功能性指数等特征值分析土壤线虫群落结构及多样性特点,并通过冗余分析及线性相关性分析探讨线虫群落与土壤理化性质间的关系.结果显示,嘎隆拉山铁杉林土壤线虫隶属于5目29科34属,个体密度介于0～1231条?100 g–1...     

Diversity of parasitic fungi from soybean cyst nematode associated with long-term continuous cropping of soybean in black soil

The soybean cyst nematode (SCN) is a major yield-limiting pest of soybean. In this study, experiments were conducted to examine the diversity of parasitic fungi from SCN associated with disease-suppressive soil fields in Northeast China. Soil samples were collected from three fields under different rotation systems that were established in 1991: (1) a continuous long-term cropping field with soybean (SSSS) that had been shown to be SCN-suppressive, (2) cycles of three-year rotation with corn, soybean, and wheat (WCS), and (3) continuous cropping field with three-year cycles of two years soybean and one-year corn (SSC). In the traditional method result, cyst densities of SCN declined as increase of parasitic fungi, and the percentage of parasitic fungi associated with cyst of SCN was higher in SSSS field than other two fields. Polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) also showed that parasitic fungi of SCN were also increased in SSSS field, compared with the other two fields. Principal component analysis based on PCR-DGGE data revealed that fungal communities on cysts could be divided into three groups: one group occurred in SSSS, and the other two groups were in WCS and SSC fields, respectively. Long-term cropping with soybean monoculture in the black soil field might increase parasitic fungi of SCN. These fungal communities may play an important role in the ecological suppression of SCN in disease-suppressive soil.     

棕壤线虫对尿素配施尿酶抑制剂和硝化抑制剂的响应研究

Effects of urea amended with urease and nitrification inhibitors on soil nematode communities were studied in a Hapli- Udic Argosol （Cambisol, FAO） in Liaoning Province of Northeast China. A completely random design with four treatments, i.e., conventional urea （CU）, slow-release urea amended with a liquid urease inhibitor （SRU1）, SRU1 ＋nitrification inhibitor dicyandiamide （SRU2）, and SRU1 ＋ nitrification inhibitor 3,5-dimethylpyrazole （SRU3） and four replicates were applied. Thirty-nine genera of nematodes were identified, with Cephalobus and Aphelenchus being dominant; and in all treatments, the dominant trophic group was bacterivores. In addition, during the growth period of spring wheat （Triticum aestivum L.）, soil urease activity was lower in SRUs than in CU. The numbers of total nematodes and bacterivores at wheat heading and ripening stages, and omnivores-predators at ripening stage were higher in SUR3 than in CU, SRU1 and SRU2 （P 〈 0.05）.