贵州山区3种木本植物无机碳利用特性的比较

以生长在喀斯特高原地区玉舍国家森林公园内的成熟银鹊树（Tapiscia sinensis）、白栎（Quercus fabri）和亮叶桦（Betula luminifera）为实验材料,通过对光合作用、叶绿素含量、叶绿素荧光参数、羧化效率（CE）、呼吸速率（Resp）、碳酸酐酶活性（WA）以及稳定碳同位素组成（δ13 C）等指标的测定,分析3种植物不同的无机碳利用特性,为该区生态环境修复选择合适的建群植物种提供依据。结果显示：（1）银鹊树、白栎和亮叶桦分布都较为广泛,银鹊树生长的最佳土壤pH是4.5~5.5,而白栎更倾向于中性到弱酸性土壤,肥沃的酸性土壤则更有益亮叶桦生长;白栎和亮叶桦都能忍受干旱和贫瘠,但是银鹊树不能忍受干旱和高温。（2）银鹊树叶片的Pn、Tr和Gs显著大于白栎和亮叶桦,亮叶桦和白栎的Pn、Tr和Gs分别是银鹊树的69.5%、48.2%、66.7%和28.6%、21.7%、22.2%;亮叶桦叶绿素含量均为银鹊树和白栎的2倍,但3种植物间的WUE则无显著差异。（3）3个树种叶片净光合速率均随着CO2浓度升高呈持续上升的趋势,但它们之间的CO2补偿点和饱和点明显不同。其中,银鹊树和亮叶桦的CO2补偿点均低于50μmol·mol-1,而白栎的则在250~300μmol·mol-1之间;银鹊树的CO2饱和点在1 200μmol·mol-1左右,亮叶桦则在2 300μmol·mol-1左右,而白栎的CO2饱和点明显高于2 300μmol·mol-1。（4）3个树种的CE、Resp和WA均为银鹊树〉亮叶桦〉白栎;而δ13 C值则以银鹊树最低,亮叶桦和白栎较高。其中,白栎和亮叶桦的CE、Resp、WA分别为银鹊树的5.1%、25.7%、4.0%和45.3%、54.6%、6.8%,且树种间差异显著;白栎和亮叶桦的δ13 C值显著高于银鹊树。研究表明,银鹊树能够吸收大气中的CO2或者在高活性碳酸酐酶作用下转化利用细胞内的HCO3-,它拥有较高的CO2利用能力及无机碳同化效率,因而能够拥有较高的产能;亮叶桦只能获取大气中的CO2作为无机碳源,但它对CO2的利用能力也较高,其产能仅次于银鹊树;白栎同样只能获取大气中的CO2作为无机碳源,同时它对大气中CO2的捕获、利用能力均低于银鹊树和亮叶桦,因而白栎生长非常缓慢,造成其本身对无机碳的需求也最低,所以其产能最低。

The influence of three mangrove species on the distribution of inorganic nitrogen and phosphorus in the Quanzhou Bay estuarine wetland soils

This study aims to investigate the effects of region and three regional dominated mangrove species(Avicennia marina, Aegiceras corniculatum and Kandelia candel) on the distribution of inorganic nitrogen and phosphorus. Measurement of the inorganic nitrogen and phosphorus and enzymatic activities was carried out in soils covered by three mangrove species in the Quanzhou Bay estuarine wetlands, a typical coastal wetland in China.Species with a higher biomass in upstream and midstream absorb more nitrogen from soils, and the retention of the available phosphorus in the soils of different regions causes the regional variation of phosphorus. In areas dominated by A. marina, nitrate nitrogen is lower while available phosphorus is higher. Meanwhile, nitrate nitrogen and available phosphorus are higher in the soils covered by K. candel.Moreover, all three species affect the elemental and enzymic stoichiometry. The mangrove species influences the diversity of the elemental and enzymic stoichiometric relationship through differential microenvironments, which induce the biodiversity of wetland ecosystems. Thus, this study may facilitate a better understanding of the transformation ability of mangroves to nitrogen and phosphorus and will therefore be beneficial for providing a basis for the ecological restoration of estuarine wetlands.

Effects of Hall Current on MHD Boundary Layer Second-Order Viscoelastic Fluid Flow Induced by a Continuous Surface with Heat Transfer

Effects of Hall current on heat transfer and magnetohydrodynamic (MHD) boundary layer flow induced by a continuous surface in a parallel free stream of a second-order viscoelastic fluid are studied for uniform suction/injection by taking viscous dissipation into account. Complex nonsimilar solutions to the stream function and temperature are developed by means of an elegant technique, known as homotopy analysis method (HAM). Convergence of the solutions is ensured with the help of -curves. Graphical and tabular results for the effects of Hall current reveal that it has a significant influence on: complex velocity, complex temperature, magnitude of the shear stress at the surface, magnitude of the rate of heat transfer at the surface and on boundary layer thickness.

Plant-soil feedback during biological invasions:effect of litter decomposition from an invasive plant(Sphagneticola trilobata)on its native congener(S.calendulacea)

Plant invasions can affect soil properties in the invaded habitat by altering the biotic and abiotic nature of soils through positive or negative plant–soil feedback.Litter decomposition from many invasive species enhanced soil nutrients,thereby decreasing native plant diversity and leading to further plant invasions.Here,we examined the impact of litter decomposition from an invasive plant(Sphagneticola trilobata)in a range of soils at varying depths on growth and physiology of its native congener(Sphagneticola calendulacea).We added litter from S.trilobata to each soil type at different depths(0,2,4 and 6 cm).Plants of S.calendulacea were grown in each treatment,and morphological and physiological parameters were measured at the end of the growing period.All soils treated with litter displayed increases in soil nutrients at depths of 2 and 4 cm;while most growth traits,leaf chlorophyll and leaf nitrogen of S.calendulacea decreased at the same soil depths.Therefore,litter decomposition from invasive S.trilobata resulted in a positive plant–soil feedback for soil nutrients,and a negative plant–soil feedback for growth in native S.calendulacea.Our findings also suggest that the effects of litter decomposition from an invasive plant on soils and native species can vary significantly depending on the soil depth at which the litter is deposited.Future studies should focus on plant–soil feedback for more native and invasive species in invaded habitats,and the effects of invasive litter in more soil types and at greater soil depths.

Warming and elevated nitrogen deposition accelerate the invasion process of Solidago canadensis L.

Background:Invasive species can threaten native diversity and alter ecosystem processes while interacting with other components of global environmental change.Invasive plants are becoming increasingly problematic and this can be stimulated by changes in the environment.However,existing studies have primarily investigated the effects of environmental change on a specific stage of plant invasion rather than the continuous invasion process.Methods:A space-for-time substitution experiment was performed to investigate how warming and nitrogen deposition affects the invasion process of a plant.Specifically,different ratios of invasive Solidago canadensis L.to native Artemisia argyi Levl.et Van were employed as a proxy to represent successive levels of invasion.A total of seven treatments were applied in the experiment:ambient(CK),N addition(+5,+12 g m^(−2)year^(−1)),warming(+1.15,+1.86℃)and their interaction(5 g N m^(−2)year^(−1)+1.15℃,12 g N m^(−2)year^(−1)+1.86℃).The growth performance and competitiveness of S.canadensis were investigated.Results:The competitiveness of Solidago canadensis decreased linearly with its invasion degree(p<0.05).Non-linear regression showed that S.canadensis invasion levels of 53%,53%,68%,55%and 58%were the critical thresholds for shifting the direction or magnitude of chlorophyll,leaf nitrogen,leaf shape index,diameter,and root/shoot ratio,respectively.Compared with the ambient treatment(CK,no warming and no N addition),the diameter,height,bio-mass and relative competitiveness of S.canadensis were each limited by warming,to a certain extent,whereas these and the above parameters were significantly increased by nitrogen deposition.The interaction of increased temperature and nitrogen deposition led to significant increases in the growth and competitiveness of S.canadensis,and this effect was detected in every stage of the invasion,throughout the invasion process.Conclusions:Environmental change might have a continuous,progressive,and augmentative effect on the phenotypic traits of S.canadensis.This study provides fairly robust evidence that environmental change promotes the invasion process of S.canadensis in general,not simply in specific stages.In the future,rather than focusing on specific stages,experimental studies should consider examining invasion on a broader scale.