红树叶片衰老过程中活性氧和保护酶活性的变化

测定了红树植物木榄(Bruguiera gymnorrhiza)和秋茄(Kandelia candel)幼叶、成熟叶和老叶间活性氧和三种细胞保护酶活性的变化。结果表明,在叶片衰老过程中,丙二醛和H2O2含量显著提高,超氧化物自由基产生速率加快,表明红树叶片衰老中膜脂过氧化作用增强,并且与H2O2和超氧化物自由基含量的上升相关。在3种细胞保护酶中,超氧化物歧化酶(SOD)活性逐渐降低,过氧化物酶(POD)活性显著提高,过氧化氢酶(CAT)活性在叶片成熟过程中增高,随着衰老而急剧降低,细胞保护酶酶活的变化直接影响了叶片衰老过程中活性氧代谢的平衡。     

运用动态谐波回归模型对MODIS叶面积指数时间序列产品的分析与预测

运用动态谐波回归模型(Dynamic Harmonic Regression,DHR)对MODIS的长时间序列的LAI产品进行分析,可以从中分离出LAI随时间变化的多年趋势、季节变化及残差等主要成分,通过建立的模型实现LAI年间变化的短时预测。本文将所述DHR模型分析方法试用于遥感数据产品随时间变化的信息提取,对LAI年间变化的预测结果证明该方法用于遥感像元尺度LAI产品的时间序列分析与预测的效果良好。     

苹果树叶片全氮含量高光谱估算模型研究

采用Field-Spec Pro便携式光谱仪,测定了不同苹果品种叶片的光谱反射率及对应的全氮含量,采用相关性及单变量线性与非线性拟合分析技术,对全氮含量与原始光谱反射率、一阶微分光谱、高光谱参数之间的关系进行了分析。研究确立叶片全氮含量的定量监测模型,以期为遥感技术在苹果氮素营养诊断中的实际应用提供理论依据。结果表明:全氮含量与原始光谱在715nm处具有最大负相关系数(r=?0.817),并且基于此波长所构建的对数关系估算模型明显优于线性模型;光谱反射率一阶微分值在723nm处具有最大正相关系数(r=0.87),并且基于此波长所构建的线性和非线性模型的拟合效果接近;对于所选取的3类高光谱特征变量,全氮含量除了与黄边位置及由红边位置和黄边面积所构建的比值植被指数和归一化植被指数的相关性较弱外,与其余变量均呈极显著相关,说明这些变量对苹果叶片全氮含量进行估算具有可行性。对所建立的各类方程进行检验,最终筛选确定在723nm处的光谱反射率一阶微分值所构建的指数模型作为苹果叶片全氮含量的预测模型最为理想。     

A first Holocene leaf wax isotope-based paleoclimate record from the semi-humid to semi-arid south-eastern Caucasian lowlands

The Holocene paleoclimate of the Caucasus region is rather complex and not yet well understood: while existing studies are mainly based on pollen records from high-altitude and humid lowland regions, no records are available from the semi-humid to semi-arid south-eastern Caucasian lowlands. Therefore, this study investigated compound-specific δ²H and δ¹³C isotopes of leaf wax biomarkers from Holocene floodplain soils in eastern Georgia. Our results show that the leaf wax δ²H signal from the paleosols mostly reflects changes in the moisture source and its isotopic composition. Depleted δ²H values before ~8 cal ka bp change towards enriched values after ~5 cal ka bp and become again depleted after ~1.6 cal ka bp. This trend could be caused by Holocene changes of the isotopic compositions of the Black and eastern Mediterranean Sea, and/or by varying contribution of both moisture sources linked with the North Atlantic Oscillation. The leaf wax δ¹³C signal from the paleosols directly indicates varying local water availability and drought stress. Depleted δ¹³C values before ~8 and after ~5 cal ka bp indicate wetter local conditions with higher water availability, whereas more enriched values during the middle Holocene (~8 until at least 5 cal ka bp ) indicate drier conditions with increased drought stress.     

喀斯特山区先锋植物叶片解剖特征及其生态适应性评价--以贵州花江峡谷区为例

通过研究贵州西南部典型喀斯特植被退化区花江峡谷植被现状,选取具一定经济价值和推广价值的先锋植物,采用生物显微制片技术与数理统计方法相结合,报导了6科10种分属不同生活型的植物叶片的解剖结构特征,并进行了比较和解剖因子分析。结果表明研究区喀斯特先锋植物叶片在不同种类之间具有明显差异,这些差异除受遗传因子控制外,环境因子(主要为光照和水分)也有重要作用;生活型不同对先锋植物叶片特征有一定影响,但未表现出规律性。根据叶片适应特征的差异,10种先锋植物可分为3种类型,即旱生或阳生叶类型的构树(Broussonetia papyrifera)、火棘(pyracantha fortuneana)、刺槐(Robinia pseudoacacia)、白三叶(Trifolium repens);偏中生叶类型(香椿的Toona sirensis)、顶坛花椒(Zanthaxylum pinum var．dingtanensis)、黔滇木蓝(In-digofera esquirolii)、忍冬(Lomicera japonica)、紫云英(Astragalus sinicus);偏阴生叶类型的繁缕(Stellaria media)。     

黑龙江省东部山地灌木林地的静态持水能力

从森林涵养水源的角度,对黑龙江省东部山地5种次生演替灌木林类型的土壤和枯落物的持水性能进行了调查和分析。结果表明：与当地的阔叶红松林相比灌木林在水源涵养方面也有着不可忽视的作用,5种灌木林类型的枯落物最大持水量和有效持水量分别在20．90～33．48t／hm^2间和12．83～25．07t／hm^2间,其土壤的最大持水量和有效持水量也分别为1927．12～2816．55t／hm^2间和505.09～865．15t／hm^2间。对5种次生演替灌木林地的持水能力的各项指标进行综合比较分析,其静态持水能力的大小依次为胡枝子灌丛、珍珠梅灌丛、接骨木灌丛、榛子灌丛和绣线菊灌丛。     

Is the Montreal Protocol a model that can help solve the global marine plastic debris problem?

The impacts of plastic debris on the marine environment have gained the attention of the global community. Although the plastic debris problem presents in the oceans, the failure to control land-based plastic waste is the primary cause of these marine environmental impacts. Plastics in the ocean are mainly a land policy issue, yet the regulation of marine plastic debris from land-based sources is a substantial gap within the international policy framework. Regulating different plastics at the final product level is difficult to implement. Instead, the Montreal Protocol may serve as a model to protect the global ocean common, by reducing the production of virgin material within the plastics industry and by regulating both the polymers and chemical additives as controlled substances at a global level. Similar to the Montreal Protocol, national production and consumption of this virgin content can be calculated, providing an opportunity for the introduction of phased targets to reduce and eliminate the agreed substances to be controlled. The international trade of feedstock materials that do not meet the agreed minimum standards can be restricted. The aim of such an agreement would be to encourage private investment in the collection, sorting and recycling of post-consumer material for reuse as feedstock, thereby contributing to the circular economy. The proposed model is not without its challenges, particularly when calculating costs and benefits, but is worthy of further consideration by the international community in the face of the global threats posed to the ocean by plastics.     

The Adaptive Marine Policy (AMP) toolbox: Supporting policy-makers developing adaptive policies in the Mediterranean and Black Sea

Adaptive management is essential to the practical application of the Ecosystem-Based Approach (EBA). Despite there are frequent assertions that adaptive management is being used, evidence on its success is still limited. Indeed, it is difficult to bring the different elements of adaptive management together in a robust way and to choose the appropriate tools to do it. Therefore, it is necessary to provide a practical framework for adaptive policy action, consistent with the EBA. Accordingly, to operationalize the design and implementation of adaptive policies on the basis of the EBA, the Adaptive Marine Policy toolbox has been developed. The objective of the toolbox is to provide policy-makers a practical framework to design and implement adaptive policies. To show the functionality of the toolbox, the guidelines and resources provided within the toolbox have been applied to the marine litter issue in the Mediterranean and Black Sea as an example. The example application has shown that the toolbox is a useful and operational framework to build a science-policy interface according to the EBA. Despite some resources could be missing from the toolbox, they provide a practical and useful starting point to support the application of the different steps and key activities.     

The replacement of native plants by exotic species may affect the colonization and reproduction of aquatic hyphomycetes

The tropical riparian zone has a high diversity of plant species that produce a wide variety of chemical compounds, which may be released into streams. However, in recent decades there has been an extensive replacement of tropical native vegetation by Eucalyptus monocultures. Our objective was to compare fungal colonization of Eucalyptus camaldulensis leaves with fungal colonization of native plant species from riparian zones in Brazilian Cerrado (savannah) streams. The fungal colonization and enzymatic activity significantly influenced leaf litter decomposition. Fungal sporulation rates from leaf litter varied significantly with leaf species, with E. camaldulensis showing the highest sporulation rate (1226 conidia mg⁻¹AFDM day⁻¹) and leaf mass loss (23.2 ± 0.9%). This species has the lowest lignin content and highest N concentration among the studied species. Among the studied native species, we observed the highest sporulation rate for Protium spruceanum (271 conidia mg⁻¹AFDM day⁻¹), Maprounea guianensis (268 conidia mg⁻¹AFDM day⁻¹) and Copaifera langsdorffii (196 conidia mg⁻¹AFDM day⁻¹). Overall, native plant species of the Brazilian Cerrado exhibited recalcitrant characteristics and a higher lignin:N ratio. Therefore, variations in the physical and chemical characteristics of the leaf litter could explain the higher decay rate and reproductive activity observed for E. camaldulensis. However, the detritus of this species were colonized almost exclusively by Anguillospora filiformis (99.6 ± 0.4%) and exhibited a reduction in aquatic hyphomycetes species diversity. Our results suggest that the disturbance in the composition of riparian vegetation and consequently, in the diversity of leaf litter input into streams, could change the patterns and rates of leaf litter utilization by microbial decomposers. These changes may have important consequences in the processing of organic matter and, consequently, in the functioning of freshwater ecosystems.     

Determinants of sediment properties and organic matter in beach and dune environments based on boosted regression trees

Grain size properties and the variation of organic matter in coastal beach and dune environments are assumed to be controlled by the intensity of aeolian processes, time and the sediment source. However, assumptions are based on relatively limited empirical studies. In this study, we examined which environmental variables are the main predictors of multiple topsoil properties. To achieve this, we analysed an extensive dataset systematically collected across all beach zones and a large geographical area at the Finnish Baltic Sea coast characterized by post‐glacial land uplift. We included a comprehensive set of predictors in the analysis and applied boosted regression trees, a modern modelling technique particularly suited for analysis without prior assumptions of the data model. The results suggest that mean grain size and sorting are mainly determined by northing and fetch. Northing, disturbance and fetch predicted the variation of soil organic matter while litter cover was strongly related to disturbance. Based on the analyses, we were able to identify the main drivers of multiple topsoil properties on land uplift beaches. Parent material is suggested to determine sediment textural properties, which largely masks the effects of transient processes. Mean grain size and sorting are highly interdependent: grains become finer and sorting improves with increasing shore exposure. The intensity of momentary geomorphic processes controls the accumulation of litter whereas the slower accumulation of organic matter in the soil is influenced also by the static exposure setting. Skewness and kurtosis of the grain size distribution are mainly influenced by unmeasured processes, potentially relating to the geomorphological origin of the sediment. Copyright © 2014 John Wiley & Sons, Ltd.