黄土丘陵区草地土壤微生物C、N及呼吸熵对植被恢复的响应

以野外样地调查和室内分析法研究了黄土丘陵区不同植被恢复年限下草地土壤微生物C、N及土壤呼吸熵的变化.结果表明,土壤微生物量碳明显地随着植被恢复年限的增加而增加.在恢复前23a, 土壤微生物量碳在0～20 cm土层年增加率为24.1%;20～40 cm为104.4%.植被恢复23a后,0～20 cm土层增长率为0.83%,20～40 cm为0.19%.土壤微生物量N表现为在植被恢复的初期略有下降,3a后,开始出现明显增加.0～20 cm土层年增长率为20.14%,20～40 cm为15.11%.在植被恢复23a后,0～20 cm土层的年增长率为0.14%,20～40 cm变化不大.土壤微生物呼吸强度随着恢复年限的增加逐渐加强;土壤呼吸熵随植被封育时间的增加而呈对数降低趋势.土壤呼吸熵(qCO2)在反映土壤的生物质量变化时,显得更加稳定,受植物生长状况影响较小.相关分析表明,土壤微生物量和土壤微生物活性与土壤有机质、碱解氮和粘粒含量显著正相关;与土壤粉粒含量明显负相关;表层土壤pH值对其也有明显影响.草地植被自然恢复过程可增加土壤微生物活性,有利于土壤质量的提高.     

A common genetic basis to the origin of the leaf economics spectrum and metabolic scaling allometry

Many facets of plant form and function are reflected in general cross‐taxa scaling relationships. Metabolic scaling theory (MST) and the leaf economics spectrum (LES) have each proposed unifying frameworks and organisational principles to understand the origin of botanical diversity. Here, we test the evolutionary assumptions of MST and the LES using a cross of two genetic variants of Arabidopsis thaliana. We show that there is enough genetic variation to generate a large fraction of variation in the LES and MST scaling functions. The progeny sharing the parental, naturally occurring, allelic combinations at two pleiotropic genes exhibited the theorised optimum ¾ allometric scaling of growth rate and intermediate leaf economics. Our findings: (1) imply that a few pleiotropic genes underlie many plant functional traits and life histories; (2) unify MST and LES within a common genetic framework and (3) suggest that observed intermediate size and longevity in natural populations originate from stabilising selection to optimise physiological trade‐offs.     

Evaluation of Microbial Biomass and Activity in Different Soils Exposed to Increasing Level of Arsenic Pollution: A Laboratory Study

Soil contamination with arsenic is a widespread phenomenon in many parts of the world and it is well known that it may affect the soil microbial community. A laboratory experiment was performed to evaluate the acute toxicity effect of different As concentrations (0, 0.1, 1.0, 10, 100, and 200 mg/kg) on soil biological parameters like microbial biomass carbon (MBC), active microbial biomass carbon (AMBC), basal soil respiration (BSR), fluorescein diacetate hydrolase activity (FDA), and dehydrogenase activity (DHA) under three different soil types (Inceptisol, Vertisol, and Entisol). Soil enzyme activities, microbial biomass, and respiration were significantly decreased by arsenic exposure. The soil metabolic quotient increased with increasing As concentration, the maximum being observed for Entisol followed by Vertisol and Inceptisol. Except for soil enzyme activities, the majority of which started to decrease after the addition of 10 mg/kg arsenic, all other parameters decreased at arsenic dose ≥0.1 mg/kg. The decrease of AMBC/MBC ratio showed that acute arsenic stress affected the active microorganisms more than the dormant component of total microbial biomass. Among the three soils studied, Vertisol was comparatively more tolerant to As exposure in terms of soil enzymes and biomass, followed by Inceptisol and Entisol. MBC has evolved as a distinct parameter in cluster analysis, while some others, such as DHA and AMBC, and FDA and BSR, appeared essentially redundant.     

中国亚热带不同菌根树种的根叶形态学性状特征与生长差异: 以江西新岗山为例

探究植物功能性状的种内和种间变异不仅有助于揭示植物对环境的适应, 也能够反映植物的生态策略, 但不同菌根类型树木生长过程中根叶形态学功能性状的适应策略仍有待探究。本研究依托中国亚热带森林生物多样性与生态系统功能实验研究平台(BEF-China)选取7种丛枝菌根(AM)树木和7种外生菌根(EM)树木的纯林, 测定各个树种的比叶面积、叶干物质含量、比根长、根系直径、树高生长速率、地径生长速率及细根生物量等根叶形态学功能性状和生长指标, 探讨了两种菌根类型树种间的根叶形态学特征的差异。结果表明: 与AM树种相比, EM树种具有较小的比叶面积、吸收根平均直径和生长速率, 但具有更大的叶干物质含量; 两种菌根树种之间的比根长和细根生物量无显著差异。比叶面积、叶干物质含量、树高生长速率、地径生长速率和细根生物量等功能性状及生长指标在不同菌根类型、树种及二者的交互作用中均存在显著差异; 且树种、根功能型、菌根类型及三者之间的交互作用均对根功能性状有显著影响。EM树种地上指标的种内变异均大于种间变异, 而AM树种地上指标的种内和种间变异程度类似; 但两种菌根树种细根生物量的种间变异均大于种内变异。尽管两种菌根树种地上部分生长速率较快通常表现为较低的叶干物质含量, 但AM树种通常拥有较高的吸收根比根长, 而EM树种拥有较粗的运输根平均直径。吸收根比根长越低, 两类菌根树种的细根生物量就越多。由此可见, 根叶功能性状对植物地上部分的生长具有一定的协同效应, 其中运输根主要在EM树种地上生长过程中发挥重要作用, 吸收根主要与AM树种的地上部分生长有关; 但两类菌根树种的地下细根生物量均与吸收根有关。     

喀斯特峰丛洼地土壤剖面微生物特性对植被和坡位的响应

选取广西环江县喀斯特峰丛洼地:草丛(T)、灌丛(S)、原生林(PF)(中坡位)不同植被类型,原生林上、中、下不同坡位,按土壤发生层采集淋溶层(A层,0-10 cm)、过渡层(AB层,20-30 cm,草丛和灌丛;30-50 cm,原生林)、淀积层(B层,70-100cm)样品,研究土壤微生物量碳、氮(Soil microbial biomass carbon (SMBC)、soil microbial biomass nitrogen (SMBN))、微生物碳熵、氮熵(ratio of SMBC to soil organic carbon (qMBC)、ratio of SMBN to soil total nitrogen (qMBN))、土壤基础呼吸(soil basic respiration (SBR))以及代谢熵(microbial metabolic quotient(qCO2))的剖面分异特征及其影响因素.结果表明,植被、土层深度显著影响土壤微生物量及基础呼吸,随植被恢复,SMBC、SMBN、SBR由草丛、灌丛、原生林依次上升,并随土壤发生层位的加深逐渐减少,qCO2在3种植被类型间差异显著:T＞PF＞S;原生林A层SMBC,SMBN在各坡位间均显著高于AB层、B层,SBR在A层由下坡位至上坡位递减,而在AB和B层的上、下坡位间无显著差异,qCO2坡位间无显著差异(P＞0.05);SMBC与SMBN之间存在显著正相关(r=0.825,P＜0.01,n=45),且SMBC、SMBN、SBR分别与有机碳、全氮、碱解氮均呈显著正相关.因此,随植被恢复,土壤质量明显改善,且坡位对A层土壤的影响较AB层和B层更显著,对于维持土壤微生物调节的土壤养分循环功能,调控土壤氮素营养与土壤有机质同等重要,这为合理制订喀斯特生态恢复措施提供了理论依据.     

A monoclonal antibody to (S)-abscisic acid: its characterisation and use in a radioimmunoassay for measuring abscisic acid in crude extracts of cereal and lupin leaves

A monoclonal antibody produced to abscisic acid (ABA) has been characterised and the development of a radioimmunoassay (RIA) for ABA using the antibody is described. The antibody had a high selectivity for the free acid of (S)-cis, trans-ABA. Using the antibody, ABA could be assayed reliably in the RIA over a range from 100 to 4000 pg (0.4 to 15 pmol) ABA per assay vial. As methanol and acetone affected ABA-antibody binding, water was used to extract ABA from leaves. Water was as effective as aqueous methanol and acetone in extracting the ABA present. Crude aqueous extracts of wheat, maize and lupin leaves could be analysed without serious interference from other immunoreactive material. This was shown by measuring the distribution of immunoreactivity in crude extracts separated by thin-layer chromatography (TLC) and high-performance liquid chromatography (HPLC), or by comparing the assay with physicochemical methods of analysis. Analysis of crude extracts by RIA and either, after TLC purification, by gas chromatography using an electron-capture detector or, after HPLC purification, by combined gas chromatography-mass spectrometry (GC-MS) gave very similar ABA concentrations in the initial leaf samples. However, RIA analysis of crude aqueous extracts of pea seeds resulted in considerable overestimation of the amount of ABA present. Determinations of ABA content by GC-MS and RIA were similar after pea seed extracts had been purified by HPLC. Although the RIA could not be used to analyse ABA in crude extracts of pea seeds, it is likely that crude extracts of leaves of several other species may be assayed successfully.Abbreviations ABA abscisic acid - DW dry weight - FW fresh weight - GC-ECD gas chromatography using an electron capture detector - GC-MS combined gas chromatographymass spectrometry - HPLC high-performance liquid chromatography - McAb monoclonal antibody - PVP soluble polyvinylpyrrolidone - RIA radioimmunoassay - TLC thin-layer chromatography