Earthworm Invasion as the Driving Force Behind Plant Invasion and Community Change in Northeastern North American Forests

Abstract:  Identification of factors that drive changes in plant community structure and contribute to decline and endangerment of native plant species is essential to the development of appropriate management strategies. Introduced species are assumed to be driving causes of shifts in native plant communities, but unequivocal evidence supporting this view is frequently lacking. We measured native vegetation, non-native earthworm biomass, and leaf-litter volume in 15 forests in the presence and absence of 3 non-native plant species ( Microstegium vimineum, Alliaria petiolata, Berberis thunbergii ) to assess the general impact of non-native plant and earthworm invasions on native plant communities in northeastern United States. Non-native plant cover was positively correlated with total native plant cover and non-native earthworm biomass. Earthworm biomass was negatively associated with cover of native woody and most herbaceous plants and with litter volume. Graminoid cover was positively associated with non-native earthworm biomass and non-native plant cover. These earthworm-associated responses were detected at all sites despite differences in earthworm species and abundance, composition of the native plant community, identity of invasive plant species, and geographic region. These patterns suggest earthworm invasion, rather than non-native plant invasion, is the driving force behind changes in forest plant communities in northeastern North America, including declines in native plant species, and earthworm invasions appear to facilitate plant invasions in these forests. Thus, a focus on management of invasive plant species may be insufficient to protect northeastern forest understory species.     

不同土壤类型中外源汞对白符跳(Folsomia candida)的毒性

参考国际标准化组织(ISO)颁布的跳虫毒性测试方法 ISO11267,分析了汞(Hg)在我国9种典型土壤中对白符跳(Folsomia candida)的急性毒性及繁殖毒性。发现Hg在不同类型土壤中对白符跳的半数致死浓度(LC50)变化为(0.92~1.94)mg·kg-1,而对白符跳繁殖产生影响的半数效应浓度(EC50)变化范围为(0.98~2.43)mg·kg-1,产生10%影响的浓度(EC10)变化范围为(0.29~1.40)mg·kg-1。将土壤的主要理化性质(p H、OM、CEC)与Hg对白符跳的EC50进行相关性回归分析,发现土壤CEC与EC50呈显著正相关关系(r=0.8624,p0.01),随着土壤CEC的增大,Hg的EC50值也趋于升高。因此,土壤CEC可能是导致不同类型土壤中汞对白符跳毒性差异的主要因素。本研究结果可为制定基于我国土壤类型的生态筛选值提供基础参考数据。     

不同土壤类型中外源汞对白符跳（Folsomia candida）的毒性研究

参考国际标准化组织(ISO)颁布的跳虫毒性测试方法 ISO11267,分析了汞(Hg)在我国9种典型土壤中对白符跳(Folsomia candida)的急性毒性及繁殖毒性。发现Hg在不同类型土壤中对白符跳的半数致死浓度(LC₅₀)变化为(0.92～1.94) mg·kg^-1,而对白符跳繁殖产生影响的半数效应浓度(EC₅₀)变化范围为(0.98～2.43) mg·kg^-1,产生10%影响的浓度(EC10)变化范围为(0.29～1.40) mg·kg^-1 。将土壤的主要理化性质(pH、OM、CEC)与Hg对白符跳的EC₅₀进行相关性回归分析,发现土壤CEC与EC₅₀呈显著正相关关系(r=0.8624,p<0.01),随着土壤CEC的增大,Hg的EC₅₀值也趋于升高。因此,土壤CEC可能是导致不同类型土壤中汞对白符跳毒性差异的主要因素。本研究结果可为制定基于我国土壤类型的生态筛选值提供基础参考数据。     

Optimization of methyl orange removal from aqueous solution by response surface methodology using spent tea leaves as adsorbent

The effective disposal of redundant tea waste is crucial to environmental protection and comprehensive utilization of trash resources. In this work, the removal of methyl orange （MO） from aqueous solution using spent tea leaves as the sorbent was investigated in a batch experiment. First, the effects of various parameters such as temperature, adsorption time, dose of spent tea leaves, and initial concentration of MO were investigated. Then, the response surface methodology （RSM）, based on Box- Behnken design, was employed to obtain the optimum adsorption conditions. The optimal conditions could be obtained at an initial concentration of MO of 9.75 mg·L-1, temperature of 35.3℃, contact time of 63.8 min, and an adsorbent dosage 3.90 g· L-1. Under the optimized condi- tions, the maximal removal of MO was 58.2%. The results indicate that spent tea leaves could be used as an effective and economical adsorbent in the removal of MO from aqueous solution.     

Environmental Pollution Due to Natural Factors: A Case Study in A Volcanic Area (Vulcano Island,Italy)

A major influence on the environment of active volcanic areas is expected from continuous input of chemical species pertaining to fumarolic activities occurring during inter-eruptive intervals.

The systematic investigations carried out during thirteen years in the island of Vulcano (Italy) showed also substantial contributions to phreatic waters and soils of minor constituents and trace metals from volcanic rocks with no negligible influence on growing crops.

Greater extents of these phenomena have been observed for products of hydromagmatic volcanic activity or of long-lasting weathering processes.     

Trends and Seasonality in the Nitrate Concentrations and Loads of the Bere Stream (Dorset) for the Period 1966-1986

Neutron activation analysis was used for the determination of the elemental composition of different plants and soils. Variations in concentrations of elements during the day were found. Mean concentrations, standard deviations and relationships between elements in soils and different parts of plants were studied. It was shown that the behaviour of chemical elements in samples from urban and unpolluted areas have significant differences.     

The Loch Fleet Project in the Context of Acidification Reduction Measures

At Loch Fleet, and in other liming studies in similar environments, catchment liming is successful if an adequate amount of lime is added to hydrological source areas. Geochemical modelling demonstrates that the relatively late acidification of L. Fleet is consistent with the ameliorating effect of an alkaline groundwater input: the presence of this input implies that had the Loch not been limed in 1985 it would have recovered to conditions suitable for fish in about 20 years, given current commitments to sulphur emission reductions. Lakes without similar alkaline groundwater are not likely to recover as quickly. the different consequences of liming and emission reduction as methods of restoring acid waters are reviewed and contrasted. Restoration of waters by liming may result in some undesirable effects on the terrestrial catchment: these are discussed but it is concluded that catchment liming, used with discrimination, can be an acceptable management tool.     

Observations on metal trends in soil and vegetation samples collected in the vicinity of a hazardous waste incinerator under construction (1996–1998)

The temporal variation in metal concentrations in soil and vegetation samples collected in an area of Catalonia (Spain), which will be under the potential influence of a new hazardous waste incinerator was determined. In 1996 and again in 1998, As, Be, Cd, Cr, Hg, Mn, Ni, Pb, Sn, Tl and V were measured in 40 soil and 40 herbage samples collected at 250–4000 m from the facility at the same sampling points. Data of both surveys and the percentages of variation are here presented for all metals. Results are shown according to the main wind directions in the area, as well as distances from the new facility. During the period 1996–1998, a general decrease was noted for most metals. Only the levels of Hg were significantly increased during this period. The present results will be useful for future surveys aimed to evaluate the environmental impact of metals derived from emissions of the new plant.     

Deposition and resorption of organic aerosol constituents in the respiratory tract as calculated from particle size distribution data

Data on the particle size distributions of organic aerosol constituents were used as input for a study, designed to calculate the fractions of the particulate concentrations of these compounds, deposited into the respiratory tract. The known relation between the deposition probability and the particle size as described by the ICRP‐model was used. The organic constituents were from the classes of the aliphatic hydrocarbons, carboxylic acids, polycyclic and aza‐heterocyclic aromatic hydrocarbons. Aerosol samples were obtained by Hi‐Vol cascade impactor sampling at suburban, rural and sea shore background stations as well as in an industrial emission site (coke oven).

Our approach uses the measured concentrations, being average values within each impactor particle size interval, as well as the integrated average deposition probabilities. This procedure was validated experimentally for eight model distributions from the literature, for which an infinitesimal calculation of the deposited fractions was possible.

Dilution reduces total particulate concentrations in the remote areas and predominantly determines the total deposited pollutant concentrations. Of these, pulmonary and nasopharyngeal deposition are most significant and, as a first approximation, correspond largely to the relative importance of the accumulation and dispersion modes of the sampled aerosol. A particle size distribution shift toward larger particles within the accumulation mode occurs upon ageing of the aerosol and reduces the pulmonary deposited fraction of the measured compounds in the background sites, compared to the one in the suburb. The total deposited fraction, however, increases. The contributions of biogenic higher odd n‐alkanes and, to a lesser extent, of even carboxylic acids to the dispersion mode of the aerosol result in an increased nasopharyngeal deposition at the background sites mainly during summer.

Since little information on the bio‐availability of organic aerosol constituents is available in the literature, the fractions of the particulate pollutant concentrations, resorbed in the tissues from the deposited material, were calculated, assuming an average efficiency of 70% for pulmonary and of 10% for nasopharyngeal and tracheobronchial resorption. A nearly constant total resorbed fraction of 20±2% resulted, independent of the sampling station or the season chosen, in contrast with the total deposited fractions, for which significant differences were observed. The predominant pulmonary resorption as well as compensating effects of the nasopharyngeal resorption level out the relatively small differences in particle size distributions observed. Based on these data, a first estimate in nanogram of the daily intake by inhalation of the organic pollutants studied can be formulated as four times the particulate pollutant concentration, expressed in ngm^‐3.     

Distribution of metallic compounds between plants and soils∗

Distribution of metallic constituents between soil and aerial parts of wild plants has been discussed by using relative ionic impulsions, i/I, defined as functions of concentrations of metallics ions, being i = [M]^1/2M, z_M the oxidation state of considered metal and I = S i the summation of contribution of metals. For this calculation metals were divided into two groups leading to ^I macro (K, Na, Ca, Mg, and Mn, elements accumulated in aerial parts) and to I _Micro (Fe, Cu, Zn, Co and contaminants accumulated in roots). Relative ionic impulsions may be attributed to an electric potential gradient and show if an active or passive uptake is happening. For macroelements linear relationships were obtained for Mg‐K (global active uptake) and Na‐Mn‐Ca (global passive uptake) with inverse slopes. Passive ions seem to be used as counter ions for helping active assimilation. Calculated potential gradient was close to 20 mV. The same situation was found for microelements and pollutants, where Fe is taken passively helping assimilation of the rest (Cu, Zn, Co, Cd, Pb, Ni and Cr) with a potential gradient close to 13 mV. Influences of other ecological segments (rainfall, dry deposition, airborne dust and irrigation), as well as additions for amending contaminated soils are finally discussed.