Underestimated ecosystem carbon turnover time and sequestration under the steady state assumption: A perspective from long‐term data assimilation

It is critical to accurately estimate carbon (C) turnover time as it dominates the uncertainty in ecosystem C sinks and their response to future climate change. In the absence of direct observations of ecosystem C losses, C turnover times are commonly estimated under the steady state assumption (SSA), which has been applied across a large range of temporal and spatial scales including many at which the validity of the assumption is likely to be violated. However, the errors associated with improperly applying SSA to estimate C turnover time and its covariance with climate as well as ecosystem C sequestrations have yet to be fully quantified. Here, we developed a novel model‐data fusion framework and systematically analyzed the SSA‐induced biases using time‐series data collected from 10 permanent forest plots in the eastern China monsoon region. The results showed that (a) the SSA significantly underestimated mean turnover times (MTTs) by 29%, thereby leading to a 4.83‐fold underestimation of the net ecosystem productivity (NEP) in these forest ecosystems, a major C sink globally; (b) the SSA‐induced bias in MTT and NEP correlates negatively with forest age, which provides a significant caveat for applying the SSA to young‐aged ecosystems; and (c) the sensitivity of MTT to temperature and precipitation was 22% and 42% lower, respectively, under the SSA. Thus, under the expected climate change, spatiotemporal changes in MTT are likely to be underestimated, thereby resulting in large errors in the variability of predicted global NEP. With the development of observation technology and the accumulation of spatiotemporal data, we suggest estimating MTTs at the disequilibrium state via long‐term data assimilation, thereby effectively reducing the uncertainty in ecosystem C sequestration estimations and providing a better understanding of regional or global C cycle dynamics and C‐climate feedback.     

Temporal shifts in the relative importance of climate and leaf litter traits in driving litter decomposition dynamics in a Chinese transitional mixed forest

Plant and Soil - To assess the direction and strength of climate and leaf litter trait effects on decomposition dynamics throughout the litter decomposition process. We performed a three-year-long...     

Poliovirus 2A(pro) induces the nucleic translocation of poliovirus 3CD and 3C' proteins

Poliovirus genomic RNA replication, protein translation, and virion assembly are performed in the cytoplasm of host cells. However, this does not mean that there is no relationship between poliovirus infection and the cellular nucleus. In this study, recombinant fluorescence-tagged poliovirus 3CD and 3C' proteins were shown to be expressed mainly in the cytoplasm of Vero cells in the absence of other viral proteins. However, upon poliovirus infection, many of these proteins redistributed to the nucleus, as well as to the cytoplasm. A series of transfection experiments revealed that the poliovirus 2A(pro) was responsible for the same redistribution of 3CD and 3C' proteins to the nucleus. Furthermore, a mutant 2A(pro) protein lacking protease activity abrogated this effect. The poliovirus 2A(pro) protein was also found to co-localize with the Nup153 protein, a component of the nuclear pore complexes on the nuclear envelope. These data provide further evidence that there are intrinsic interactions between poliovirus proteins and the cell nucleus, despite that many processes in the poliovirus replication cycle occur in the cytoplasm.     

Functionally orthologous viral and cellular microRNAs studied by a novel dual-fluorescent reporter system

Recent research raised the possibility that some viral microRNAs (miRNAs) may function as orthologs of cellular miRNAs. In the present work, to study the functional orthologous relationships of viral and cellular miRNAs, we first constructed a dual-fluorescent protein reporter vector system for the easy determination of miRNA function. By expressing the miRNAs and the indicator and internal control fluorescent proteins individually from a single vector, this simple reporter system can be used for miRNA functional assays that include visualizing miRNA activity in live cells. Sequence alignments indicated that the simian virus 40 (SV40) encoded miRNA sv40-mir-S1-5p contains a seed region identical to that of the human miRNA hsa-miR423-5p. Using the new reporter system, it was found that sv40-mir-S1-5p and hsa-miR423-5p downregulate the expression of common artificial target mRNAs and some predicted biological targets of hsa-miR423-5p, demonstrating that they are functional orthologs. The human immunodeficiency virus 1 (HIV-1) encoded hiv1-miR-N367 also contains a seed sequence identical to that of the human miRNA hsa-miR192. Functional assays showed that hiv1-miR-N367 and hsa-miR192 could downregulate common artificial and predicted biological targets, suggesting that these miRNAs may also act as functional orthologs. Thus, this study presents a simple and universal system for testing miRNA function and identifies two new pairs of functional orthologs, sv40-mir-S1-5p and hsa-miR423-5p as well as hiv-1-miR-N367 and hsa-miR192. These findings also expand upon our current knowledge of functional homology and imply that a more general phenomenon of orthologous relationships exists between viral and cellular miRNAs.     

巴山冷杉的种实特性及其种子萌发力

对我国特有树种巴山冷杉(Abies fargesi)的球果长、球果宽、球果重量、单果出种量等球果特征和种子长、种子宽、种子厚和种子重等种子特性进行了分析,通过发芽实验测定了种子萌发能力.结果表明,巴山冷杉球果平均长5.37±0.75cm,球果宽3.01±0.32cm,球果重量18.93±6.06g,单果出种量59-567粒,种子长1.08-8.68mm,种子宽1.16-6.42mm,种子厚0.6-3.48mm,千粒重7.30g.各项球果特征指标和种子特征指标在种群内和种群间均存在显著差异,单果出种量在不同种群的频数分布格局不同.不同母树的种子发芽率和发芽势不等,且萌发速率也不相同.巴山冷杉种子败育率高,参试种子的空粒率75.79%.     

固定化微生物降解土壤中菲和芘的研究

1　引　　言固定化微生物技术是 2 0世纪 70年代兴起的一种新型生物技术 ,目前已成为国内外学者的研究热点[8] ,现被广泛应用于处理化学工业废水 .其优点是可以大幅度提高参加反应微生物浓度 ;减少活性污泥数量 ;微生物被高分子材料包埋 ,耐环境冲击 ;根据需要选择有效微生物 ,可降低二次污染等特点 ,因而受到越来越多的关注[4,6 ,10 ] .包埋法是固定化技术最为普遍的使用方法 ,包埋载体的选择是固定化微生物的关键 ,理想的载体具有对微生物无毒性 ,传质性能好 ,性质稳定 ,不易被微生物分解 ,强度高寿命长和价格低廉等优点[2 ] .迄今 ,国内…     

Density and Stability of Soil Organic Carbon beneath Impervious Surfaces in Urban Areas

Installation of impervious surfaces in urban areas has attracted increasing attention due to its potential hazard to urban ecosystems. Urban soils are suggested to have robust carbon (C) sequestration capacity; however, the C stocks and dynamics in the soils covered by impervious surfaces that dominate urban areas are still not well characterized. We compared soil organic C (SOC) densities and their stabilities under impervious surface, determined by a 28-d incubation experiment, with those in open areas in Yixing City, China. The SOC density (0–20 cm) under impervious surfaces was, on average, 68% lower than that in open areas. Furthermore, there was a significantly (P<0.05) positive correlation between the densities of SOC and total nitrogen (N) in the open soils, whereas the correlation was not apparent for the impervious-covered soils, suggesting that the artificial soil sealing in urban areas decoupled the cycle of C and N. Cumulative CO₂-C evolved during the 28-d incubation was lower from the impervious-covered soils than from the open soils, and agreed well with a first-order decay model (C _t = C ₁+C ₀(1-e ^-kt)). The model results indicated that the SOC underlying capped surfaces had weaker decomposability and lower turnover rate. Our results confirm the unique character of urban SOC, especially that beneath impervious surface, and suggest that scientific and management views on regional SOC assessment may need to consider the role of urban carbon stocks.     

中国特有植物银杉林的现状和未来

银杉是我国特有的珍稀植物,仅在四川、贵州、湖南和广西四省区残存。其地理分布可归结为大娄 山、越城岭、八面山和大瑶山等4个集积地。现有的银杉林全部为混交林．主要有7个类型：银杉-甜槠混交林、银杉-石栎混交林、银杉-亮叶桦混交林、银杉- 广东五针松混交林、银杉- 长苞铁杉混交林、银杉- 大明松 混交林及银杉- 南方铁杉- 福建柏混交林。银杉处于优势地位、群落相对稳定,但银杉更新不良。在自然演替 中,阔叶树种的入侵对银杉构成严重威胁,最终将会取代银杉。为了保护银杉,在林地对阔叶树进行透光伐,在林窗人工移植银杉幼苗幼树是必要的。     

Distribution of shrublands in relation to soil and climate in mid-subtropical China

Aims Understanding relationships between vegetation and environments is of importance for ecosystem restoration and management. However, information on how environments influence the floristic patterns of shrublands is lack, especially in the subtropical China. In this study, we explored how environments regulate species composition of shrublands at landscape scale in mid-subtropical China.Methods We investigated species composition and measured the climate and soil environments for 207 shrubland plots in mid-subtropical China (24°39′–30°08′N, 108°47′–114°15′E). We applied a hierarchical cluster analysis and indicator species analysis based on the Bray–Curtis similarity index to identify the main shrubland types and employed principal coordinate analysis (PCoA) to explore the relationship between floristic composition and environment.Important findings We identified four shrubland types occurring in different environmental conditions. Montane shrubland, dominated by species suitable for cool climates (e.g. Rhododendron simsii), were distributed in steep areas at comparatively high altitudes; foothill shrubland, dominated by mesophilous species (e.g. Loropetalum chinense), were distributed in low mountains and hills; pioneer shrubland, dominated by fast grow and short-life cycles species (e.g. Rhus chinensis), were distributed at low altitudes with dense population; and finally, limestone shrubland, dominated by calcicole plants (e.g. Coriaria nepalensis), were distributed in the extensive karst areas. Communities occurring in high pH soils were completely separated from those in low pH soils according to the hierarchical cluster analysis. PCoA ordination associated the four types with distinct edaphic and climatic gradients. Soil pH explained 63.3% of variation in PCoA, followed by soil depth and soil bulk density.