Functional and phylogenetic diversity determine woody productivity in a temperate forest

Understanding the relationships between biodiversity and ecosystem productivity has become a central issue in ecology and conservation biology studies, particularly when these relationships are connected with global climate change and species extinction. However, which facets of biodiversity (i.e. taxonomic, functional, and phylogenetic diversity) account most for variations in productivity are still not understood very well. This is especially true with regard to temperate forest ecosystems. In this study, we used a dataset from a stem‐mapped permanent forest plot in northeastern China exploring the relationships between biodiversity and productivity at different spatial scales (20 × 20 m; 40 × 40 m; and 60 × 60 m). The influence of specific environmental conditions (topographic conditions) and stand maturity (expressed by initial stand volume and biomass) were taken into account using the multivariate approach known as structural equation models. The variable “Biodiversity” includes taxonomic (Shannon), functional (FDis), and phylogenetic diversity (PD). Biodiversity–productivity relationships varied with the spatial scales. At the scale of 20 × 20 m, PD and FDis significantly affected forest biomass productivity, while Shannon had only indirect effects. At the 40 × 40 m and 60 × 60 m scales, biodiversity and productivity were weakly correlated. The initial stand volume and biomass were the most important drivers of forest productivity. The local environmental conditions significantly influenced the stand volume, biomass, biodiversity, and productivity. The results highlight the scale dependency of the relationships between forest biodiversity and productivity. The positive role of biodiversity in facilitating forest productivity was confirmed at the smaller scales. Our findings emphasize the fundamental role of environmental conditions in determining forest ecosystem performances. The results of this study provide a better understanding of the underlying ecological processes that influence specific forest biodiversity and productivity relationships.     

稳定同位素化学标记结合质谱技术在定量蛋白质组学中的应用

传统的蛋白质组定量策略主要是通过双向凝胶电泳来进行相对定量。由于该方法不能对相对分子质量极高或极低、等电点极酸或极碱和含量低的蛋白质以及膜蛋白质等进行有效分离和检测,所以已不能适应目前蛋白质组研究深入发展的需要。近年来,定量蛋白质组学的发展主要是以同位素亲和标签试剂为代表的、以质谱检测为核心的稳定同位素化学标记方法。稳定同位素化学标记结合质谱技术,使定量蛋白质组的分析更趋简单、准确和快速,具有良好的发展前景。本文对稳定同位素化学标记结合质谱技术在定量蛋白质组学中的研究进展进行了评述。     

黄土高原典型植物根际对土壤微生物生物量碳、氮、磷和基础呼吸的影响

选择黄土高原7种典型植物的根际与非根际土壤为研究对象,对土壤的养分含量、微生物生物量碳、氮、磷和基础呼吸的影响进行了初步研究。结果表明,7种不同植物根际土壤与非根际土壤的养分含量、微生物生物量和基础呼吸均存在显著差异;除冷蒿的土壤微生物生物量磷以外,其他各种植物的根际土壤的养分含量、微生物生物量和基础呼吸均比非根际土壤的高;土壤有机碳、全氮与土壤微生物生物量碳、氮及基础呼吸之间均具有极显著或显著相关关系,表明了土壤微生物生物量碳、氮可以作为判断土壤肥力状况的生物学指标,同时也可为提高土壤肥力水平和土壤培肥效果提供依据。     

高寒草甸不同植被土壤微生物数量及微生物生物量的特征

用稀释平板法和氯仿熏蒸法研究了藏嵩草草甸、小嵩草草甸、矮嵩草草甸、禾草草甸、杂类草草甸及金露梅灌丛土壤的微生物数量、生物量及有机质的变化特征.结果表明:0～40 cm土层细菌和放线菌数量、微生物生物量碳和土壤有机质含量均以藏嵩草草甸最高,其微生物生物量及土壤有机质显著高于其它5种植被;真菌数量以金露梅灌丛最高;由表层到深层,随着土壤深度的增加以上各项指标均呈下降趋势.通径分析表明:土壤各生物环境因子之间存在着不同程度的相关性;土壤微生物数量、生物量及土壤有机质含量均与土壤水分含量存在显著的相关关系,说明土壤水分是调节高寒草甸生态系统土壤微生物代谢及物质转化的关键因子.     

Effects of Plant Species Diversity and Composition on Nitrogen Cycling and the Trace Gas Balance of Soils

Experiments addressing the role of plant species diversity for ecosystem functioning have recently proliferated. Most studies have focused on plant biomass responses. However, microbial processes involved in the production of N₂O and the oxidation of atmospheric CH₄ could potentially be affected via effects on N cycling, on soil diffusive properties (due to changes in water relations and root architecture) and by more direct interactions of plants with soil microbes. We studied ecosystem-level CH₄ and N₂O fluxes in experimental communities assembled from two pasture soils and from combinations of 1, 3, 6, 8 or 9 species typical for these pastures. The soils contrasted with respect to texture and fertility. N₂O emissions decreased with diversity and increased in the presence of legumes. Soils were sinks for CH₄ at all times; legume monocultures were a smaller sink for atmospheric CH₄ than non-legume monocultures, but no effect of species richness per se was detected. However, both the exchange of CH₄ and N₂O strongly depended on plant community composition, and on the interaction of composition with soil type, indicating that the functional role of species and their interactions differed between soils. N₂O fluxes were mainly driven by effects on soil nitrate and on nitrification while soil moisture had less of an effect. Soil microbial C and N and N mineralisation rates were not altered. The driver of the interactive soil type×plant community composition-effects was less clear. Because soil methanotrophs may take longer to respond to alterations of N cycling than the 1/2 year treatment in this study, we also tested species richness-effects in two separate 5-year field studies, but results were ambiguous, indicating complex interactions with soil disturbance. In conclusion, our study demonstrates that plant community composition can affect the soil trace gas balance, whereas plant species richness per se was less important; it also indicates a potential link between the botanical composition of plant communities and global warming.     

哀牢山湿性常绿阔叶林木质藤本植物地上部分生物量及其对人为干扰的响应

 木质藤本植物是森林, 尤其是热带和亚热带森林中的重要组分。由于野外调查的困难, 对其生态学的研究相对较少。对哀牢山原生山地湿性常绿阔叶林和4类次生林中的藤本植物进行了调查, 利用48株藤本植物样木实测数据, 采用样本回归分析法, 选取藤本植物的不同参数作为自变量, 分别对冠层和林下两类藤本混合种生物量模型进行了拟合比较, 结合样地内长度≥50 cm的所有藤本植物的调查资料估算了各森林群落藤本植物地上部分生物量, 探讨了原生林中藤本植物地上部分生物量的组成与分布特征, 以及人为干扰对藤本植物地上部分生物量的影响。结果表明: 1)以藤本基径为自变量建立幂函数回归模型, 其相关系数较高, 具有较高的实用价值; 2)该区山地湿性常绿阔叶林中藤本植物地上部分生物量为9.82×10³ kg·hm^–2, 其中冠层藤本(基径≥1.0 cm, 长度≥5.0 m)生物量占藤本植物总生物量的99.70%, 林下藤本(基径<1.0 cm, 长度<5.0 m)的地上部分生物量很低; 3)人为干扰后林下藤本植物的生物量相对增加, 而冠层藤本植物的地上部分生物量显著减少; 经过约100年恢复演替的老龄栎类萌生林藤本植物地上部分生物量才达到接近原生林的水平。     

Comparison of SHF and SSF processes for the bioconversion of steam-exploded wheat straw

Two processes for ethanol production from wheat straw have been evaluated — separate hydrolysis and fermentation (SHF) and simultaneous saccharification and fermentation (SSF). The study compares the ethanol yield for biomass subjected to varying steam explosion pretreatment conditions: temperature and time of pretreatment was 200°C or 217°C and at 3 or 10 min. A rinsing procedure with water and NaOH solutions was employed for removing lignin residues and the products of hemicellulose degradation from the biomass, resulting in a final structure that facilitated enzymatic hydrolysis. Biomass loading in the bioreactor ranged from 25 to 100 g l⁻¹ (dry weight). The enzyme-to-biomass mass ratio was 0.06. Ethanol yields close to 81% of theoretical were achieved in the two-step process (SHF) at hydrolysis and fermentation temperatures of 45°C and 37°C, respectively. The broth required addition of nutrients. Sterilisation of the biomass hydrolysate in SHF and of reaction medium in SSF can be avoided as can the use of different buffers in the two stages. The optimum temperature for the single-step process (SSF) was found to be 37°C and ethanol yields close to 68% of theoretical were achieved. The SSF process required a much shorter overall process time (≈30 h) than the SHF process (96 h) and resulted in a large increase in ethanol productivity (0.837 g l⁻¹ h⁻¹ for SSF compared to 0.313 g l⁻¹ h⁻¹ for SHF). Journal of Industrial Microbiology & Biotechnology (2000) 25, 184–192. Received 02 December 1999/ Accepted in revised form 20 July 2000     

西双版纳热带季节雨林的生物量及其分配特征

 根据3块1 hm² 样地的调查资料,利用123株样木数据建立以胸径(D)为单变量的生物量预测方程。采用样木回归分析法(乔木层、木质藤本)和样 方收获法(灌木层、草本层), 获取西双版纳热带季节雨林的生物量,并分析了其组成和分配特征。结果表明,西双版纳热带季节雨林的总生物 量为423.908±109.702 Mg•hm^－2(平均值±标准差,n=3) ,其中活体植物生物量占95.28%,粗死木质残体占4.07%,地上凋落物占 0.64%。在 其层次分配方面：乔木层优势明显,占98.09%±0.60%;其次为木质藤本,占0.83%±0.31%;灌木层和草本层生物量均小于木质藤本的生物量; 附生植物最低,仅为0.06%±0.03%。总生物量的器官分配以茎所占比例最高,达68.33%;根、枝、叶的比例分别为18.91%、11.07%和1.65 %。 乔木层生物量的径级分配主要集中于中等径级和最大径级。大树(D＞70 cm)具有较高的生物量,占整个乔木层的43.67%±12.67%。树种分配方 面,生物量排序前10位的树种占乔木层总生物量的63.43%±4.09%,生物量集中分配于少量优势树种。西双版纳热带季节雨林乔木层叶面积指数 为6.39±0.85。西双版纳热带季节雨林乔木层的地上生物量位于世界热带湿润森林的中下范围。