Litterfall Production Along Successional and Altitudinal Gradients of Subtropical Monsoon Evergreen Broadleaved Forests in Guangdong, China

Evaluation of litterfall production is important for understanding nutrient cycling, forest growth, successional pathways, and interactions with environmental variables in forest ecosystems. Litterfall was intensively studied during the period of 1982–2001 in two subtropical monsoon vegetation gradients in the Dinghushan Biosphere Reserve, Guangdong Province, China. The two gradients include: (1) a successional gradient composed of pine forest (PF), mixed pine and broadleaved forest (MF) and monsoon evergreen broadleaved forest (BF), and (2) an altitudinal gradient composed of Baiyunci ravine rain forest (BRF), Qingyunci ravine rain forest (QRF), BF and mountainous evergreen broadleaved forest (MMF). Mean annual litterfall production was 356, 861 and 849 g m⁻² for PF, MF and BF of the successional gradient, and 1016, 1061, 849 and 489 g m⁻² for BRF, QRF, BF and MMF of the altitudinal gradient, respectively. As expected, mean annual litterfall of the pioneer forest PF was the lowest, but rapidly increased over the observation period while those in other forests were relatively stable, confirming that forest litterfall production is closely related to successional stages and growth patterns. Leaf proportions of total litterfall in PF, MF, BF, BRF, QRF and MMF were 76.4%, 68.4%, 56.8%, 55.7%, 57.6% and 69.2%, respectively, which were consistent with the results from studies in other evergreen broadleaved forests. Our analysis on litterfall monthly distributions indicated that litterfall production was much higher during the period of April to September compared to other months for all studied forest types. Although there were significant impacts of some climate variables (maximum and effective temperatures) on litterfall production in some of the studied forests, the mechanisms of how climate factors (temperature and rainfall) interactively affect litterfall await further study.     

Ten years primary succession on a newly created landfill at a lagoon of the Mediterranean Sea (Lake Burullus RAMSAR site)

This study was carried out on the transported bed soil dredged from the outlet of Lake Burullus to the Mediterranean Sea and deposited nearby, forming by this way new land that underwent a primary plant succession. The multi-methodological approach comprised floristic inventories, vegetation sampling and soil composition analyses of the study site in order to detect the crucial parameters controlling the plant resettlement on recently deposited soil as related to time, local micro-topography and substrate characteristics. Floristic composition was assessed for the first 10 years of primary succession (2001–2010) on 18 stands of the area, distributed on basement, slope stands and plateau of the landfill, respectively. Vegetation surveys were the basis of multivariate analyses of the vegetation and soil data using TWINSPAN, DCA and CCA. Relationships between the edaphic gradients, floristic composition and species diversity were assessed.     

Biochemical characterization of indole prenyltransferases: filling the last gap of prenylation positions by a 5-dimethylallyltryptophan synthase from Aspergillus clavatus

The putative prenyltransferase gene ACLA_031240 belonging to the dimethylallyltryptophan synthase superfamily was identified in the genome sequence of Aspergillus clavatus and overexpressed in Escherichia coli. The soluble His-tagged protein EAW08391 was purified to near homogeneity and used for biochemical investigation with diverse aromatic substrates in the presence of different prenyl diphosphates. It has shown that in the presence of dimethylallyl diphosphate (DMAPP), the recombinant enzyme accepted very well simple indole derivatives with L-tryptophan as the best substrate. Product formation was also observed for tryptophan-containing cyclic dipeptides but with much lower conversion yields. In contrast, no product formation was detected in the reaction mixtures of L-tryptophan with geranyl or farnesyl diphosphate. Structure elucidation of the enzyme products by NMR and MS analyses proved unequivocally the highly regiospecific regular prenylation at C-5 of the indole nucleus of the simple indole derivatives. EAW08391 was therefore termed 5-dimethylallyltryptophan synthase, and it filled the last gap in the toolbox of indole prenyltransferases regarding their prenylation positions. K(m) values of 5-dimethylallyltryptophan synthase were determined for L-tryptophan and DMAPP at 34 and 76 μM, respectively. Average turnover number (k(cat)) at 1.1 s(-1) was calculated from kinetic data of L-tryptophan and DMAPP. Catalytic efficiencies of 5-dimethylallyltryptophan synthase for L-tryptophan at 25,588 s(-1)·M(-1) and for other 11 simple indole derivatives up to 1538 s(-1)·M(-1) provided evidence for its potential usage as a catalyst for chemoenzymatic synthesis.     

Plants and insects in early old-field succession: comparison of an English site and an American site

The plant and insect communities of early, secondary succession beginning with bare ground in an Old World site (southern Britain) and a New World site (Iowa, U.S.A.) shared a number of characteristics. Both sites showed similar temporal patterns of plant species cover and species richness, although overall richness was greater at the Old World site. Annuals dominated at both sites during the first year of succession and were largely replaced by perennials in the second year. Monocotyledons were more abundant at the Old World site, especially in the second year. The two sites differed markedly in the contribution of native and introduced plant species, with the Old World site dominated by natives and the New World site by alien plant species. Insect herbivore load was greater at the Old World site, when expressed in terms of structural complexity of the vegetation, suggesting that there may be major differences in the influence of herbivores on the direction and rate of succession at the two sites.     

南盘江流域细叶云南松次生林群落主要木本种群的种间联结

该研究运用方差比率法、χ~2检验、Pearson相关检验和Spearman轶相关检验,对广西雅长兰科植物国家级自然保护区南盘江流域的细叶云南松(Pinus yunnanensis Franch.var.tenuifolia Cheng et Law)次生林14个大树树种(DBH≥10cm)、15个小树树种(5cm≤DBH10cm)和19个幼树树种(1cm≤DBH5cm)进行定量分析,以揭示南盘江流域细叶云南松次生林群落中木本种群的关联性及其更新演替规律,为桂西北细叶云南松林管理保护、干热河谷地区植被恢复和生态重建提供参考依据。结果表明:(1)研究区内细叶云南松林大树和小树的总体关联性表现为不显著负关联,幼树及群落总体表现为不显著正关联;χ~2检验显示,大树和小树负关联种对占多数(分别为48.35%和46.67%),幼树的正关联或负关联种对占比基本持平(分别为40.35%和39.18%),群落整体无关联种对占比较大(41.13%)。(2)Pearson相关系数和Spearman秩相关系数检验显示,细叶云南松林的大树、小树、幼树和群落总体均表现为负关联种对较多,正关联次之。(3)群落大树和小树物种在资源竞争上较激烈,结构不稳定;群落幼树物种适应了林下荫蔽环境,对光照要求较低,种间关系已具有较低的稳定性,个别物种表现出独立性。研究认为,南盘江流域细叶云南松次生林群落物种间存在一定的关联性,但未能形成稳定的配置关系,群落结构尚不稳定,仍处于演替早期阶段。     

基于景观尺度过程模型的长白山地表径流量时空变化特征的模拟

运用已建立的景观尺度生态系统生产力过程模型EPPML对长白山自然保护区地表径流量的季节动态和空间分布特征进行了模拟,对其与环境因子间的相互关系进行了分析．模拟结果表明,长白山自然保护区地表径流量的季节进程表现出明显的三峰型,6月和9月出现低谷,8月达最大(2．58mm·d^-1),与土壤含水量的季节变化趋势十分相似．1995年地表径流量的模拟值平均为0．203m·年^-l,空间分布随海拔升高呈现明显增加的趋势,最高为高山流砾滩(0．619m·年^-1),最低为阔叶红松林(0．081m·年^-1)．年地表径流量与叶面积指数(LAI)呈极显著负相关指数关系(R^2＝0．857)．年地表径流量与气温和总辐射呈负相关关系(R^2分别为0．965和0．836),与降水量、相对湿度和风速呈正相关关系(R^2均大于0．950),还与土壤特性密切相关。     

Theories for ecological restoration in changing environment: Toward ‘futuristic’ restoration

Ecological restoration is one of the fastest growing fields in applied ecology providing new ideas and opportunities for biological conservation and natural resource management. Despite countless attempts in the past, large portions of restoration projects have been considered unsuccessful mainly due to: unrealistic goals; inadequate restoration plans based on an ad-hoc approach; lack of explicit and quantified evaluation criteria for restoration success; lack of ecological understanding; social, economic, and political constraints; or combinations of these factors. Existing ecological theories, particularly succession theories, may provide a conceptual framework for a restoration trajectory. However, projecting a desirable trajectory and outcome is often challenged by the unpredictability of ecological communities in the changing environment. Particularly, the sustainability of reconstructed historic ecosystems appears to be an unlikely goal in the ever-changing and unpredictable future environment. This paper calls for a shift in the restoration paradigm from historic to futuristic. A futuristic restoration is: (i) to set realistic and dynamic (instead of static) goals for future, instead of past, environment; (ii) to assume multiple trajectories acknowledging the unpredictable nature of ecological communities and ecosystems; (iii) to take an ecosystem or landscape approach, instead of ad-hoc gardening, for both function and structure; (iv) to evaluate the restoration progress with explicit criteria, based on quantitative inference; and (v) to maintain long-term monitoring of restoration outcomes. A theoretical framework for futuristic restoration, in terms of goals, trajectories, evaluation criteria, and monitoring, along with a historical perspective is presented in this paper.     

Marine actinobacteria: perspectives,challenges, future directions

In this paper we evaluate the current state of research on the biology and biotechnology of marine actinobacteria. The topics covered include the abundance, diversity, novelty and biogeographic distribution of marine actinobacteria, ecosystem function, bioprospecting, and a new approach to the exploration of actinobacterial taxonomic space. An agenda for future marine actinobacterial research is suggested based upon consideration of the above issues.     

Potential applications of natural origin polymer-based systems in soft tissue regeneration

Despite the many advances in tissue engineering approaches, scientists still face significant challenges in trying to repair and replace soft tissues. Nature-inspired routes involving the creation of polymer-based systems of natural origins constitute an interesting alternative route to produce novel materials. The interest in these materials comes from the possibility of constructing multi-component systems that can be manipulated by composition allowing one to mimic the tissue environment required for the cellular regeneration of soft tissues. For this purpose, factors such as the design, choice, and compatibility of the polymers are considered to be key factors for successful strategies in soft tissue regeneration. More recently, polysaccharide-protein based systems have being increasingly studied and proposed for the treatment of soft tissues. The characteristics, properties, and compatibility of the resulting materials investigated in the last 10 years, as well as commercially available matrices or those currently under investigation are the subject matter of this review.     

Pseudo-natural products and natural product-inspired methods in chemical biology and drug discovery

Through evolution, nature has provided natural products (NPs) as a rich source of diverse bioactive material. Many drug discovery programs have used nature as an inspiration for the design of NP-like compound classes. These concepts are guided by the prevalidated biological relevance of NPs while going beyond the limitations of nature to produce chemical matter that could have unexpected or novel bioactivities. Herein, we discuss, compare, and highlight recent examples of NP-inspired methods with a focus on the pseudo-NP concept.