华北地台早古生代竹叶状灰岩岩石特征及成因研究进展

砾屑灰岩在华北地台寒武系-奥陶系广泛发育,竹叶状灰岩只是其中一种,且所指范围界限模糊,常与其他类型的砾屑灰岩伴生在一起。古代陆表海提供了砾屑灰岩广泛发育的环境基础。潮坪和潮下开阔海是陆表海广泛发育的基本地貌单元,也是砾屑灰岩形成的重要场所。古板块运动表明,寒武纪华北地台处于低纬度地区,符合古风暴频发的要求。风暴及潮汐流是砾屑灰岩形成的主要动力。另外,成岩过程中的压实和固结脱水也是板条状砾屑的重要成因。条带状薄层灰泥石灰岩与泥岩及泥质灰岩的频繁互层是发生破碎并形成砾屑的物质基础。华北地台砾屑灰岩具有多种成因,可以按照砾屑的颜色特征、形态及磨圆程度、砾屑灰岩的支撑结构、充填物的类型等进行区分并进行成因分析。     

额济纳绿洲河岸胡杨(Populus euphratica)叶水势变化特征

利用WP4露点水势仪对额济纳绿洲胡杨(Populus euphratica)叶水势进行测定,研究了胡杨叶水势的日和月变化规律及其影响因子。结果表明:(1)胡杨叶水势日进程呈"V"形,最小值大都出现在13:00,日均值为-2.53±0.30MPa;月变化呈先上升后下降趋势,月均值为-2.43±0.30MPa。(2)树龄越小对应的叶水势越高;叶片着生部位越高,对应的水势越低;卵圆形叶水势整体稍高于披针形叶水势。(3)叶水势与气温、饱和水汽压差和蒸腾速率呈极显著线性负相关,相关系数依次为-0.87、-0.69和-0.88;与相对湿度和光合速率呈极显著二次多项式相关,相关系数分别为0.85和0.92。胡杨叶水势各方面的综合研究对于明晰胡杨的水分亏缺和抗旱机理有一定的理论指导意义。     

藏东南色季拉山林线物种方枝柏的叶寿命

作为叶经济学谱系中的一个关键指标,叶寿命是植物为了获得最大化光合碳收获的重要适应策略。由于很难鉴别越冬芽鳞痕以及区别不同叶龄叶片,鲜有研究关注柏科物种的叶寿命,使得我们对该类群的叶经济学谱系研究缺乏了解。基于此,我们对西藏东南部色季拉山不同海拔、不同冠层高度的方枝柏叶寿命和单位重量的叶氮含量(N;)开展了调查分析。结果表明,方枝柏平均叶寿命约为4.2±1.2年,总体上不同海拔间叶寿命差异不明显。随树冠高度的垂直变化,叶寿命总体上并未表现出明显的线性变化趋势。随叶寿命的增加,N;呈现降低趋势。进一步分析了叶寿命与对应绿色小枝长度的关系,发现二者关系不显著或解释度极低,表明小枝长度不能很好地预测叶寿命的变化。总的来说,在高山林线以及邻近的亚高山地区,海拔和冠高的变化对方枝柏叶寿命的影响较小,而叶寿命与叶氮含量的关系符合叶的经济学法则。     

Changes in Global Vegetation Distribution and Carbon Fluxes in Response to Global Warming: Simulated Results from IAP-DGVM in CAS-ESM2

Terrestrial ecosystems are an important part of Earth systems, and they are undergoing remarkable changes in response to global warming. This study investigates the response of the terrestrial vegetation distribution and carbon fluxes to global warming by using the new dynamic global vegetation model in the second version of the Chinese Academy of Sciences (CAS) Earth System Model (CAS-ESM2). We conducted two sets of simulations, a present-day simulation and a future simulation, which were forced by the present-day climate during 1981–2000 and the future climate during 2081–2100, respectively, as derived from RCP8.5 outputs in CMIP5. CO₂ concentration is kept constant in all simulations to isolate CO₂-fertilization effects. The results show an overall increase in vegetation coverage in response to global warming, which is the net result of the greening in the mid-high latitudes and the browning in the tropics. The results also show an enhancement in carbon fluxes in response to global warming, including gross primary productivity, net primary productivity, and autotrophic respiration. We found that the changes in vegetation coverage were significantly correlated with changes in surface air temperature, reflecting the dominant role of temperature, while the changes in carbon fluxes were caused by the combined effects of leaf area index, temperature, and precipitation. This study applies the CAS-ESM2 to investigate the response of terrestrial ecosystems to climate warming. Even though the interpretation of the results is limited by isolating CO₂-fertilization effects, this application is still beneficial for adding to our understanding of vegetation processes and to further improve upon model parameterizations.     

Mapping saltcedar (Tamarix ramosissima) and other riparian and agricultural vegetation in the Lower Colorado River region using multi-spectral Landsat TM imagery

Saltcedar (Tamarix ramosissima), an invasive shrub species, has successfully invaded large extents of several riparian zones in the western United States and northern Mexico. Mapping the distribution and abundance of saltcedar over these large areas through a multi-seasonal, cost-effective monitoring approach using satellite remote sensing is very essential. Ground truth surveys were conducted at 79 locations where the spectral reflectance measurements of vegetation, type of plant species, plant heights, soil samples and GPS co-ordinates were recorded. All the sampling was designed to coincide with the satellite overpass period. The Landsat TM colour-composite spectral ratio image (normalized difference vegetative index (NDVI), R _1,5 and R _1,7 as green, blue and red) can clearly identify and map the areas infested with saltcedar. The Landsat image analysis shows that these spectral ratios can be applied to multiple satellite overpasses for monitoring the seasonal progression of the saltcedar growth over time.     

Identifying saltcedar with hyperspectral data and support vectormachines

Saltcedar (Tamarix spp.) are a group of dense phreatophytic shrubs and trees that are invasive to riparian areas throughout the United States. This study determined the feasibility of using hyperspectral data and a support vector machine (SVM) classifier to discriminate saltcedar from other cover types in west Texas. Spectral measurements were collected with a ground-based hyperspectral spectroradiometer (spectral range 350–2500 nm) in December 2008 and April 2009. Spectral data consisting of 1698 spectral bands (400–1349, 1441–1789, 1991–2359 nm) were subjected to a support vector machine classification to differentiate saltcedar from other vegetative and non-vegetative classes. For both dates, a linear kernel model with a C value (error penalty) of 100 was found optimum for separating saltcedar from the other classes. It identified saltcedar with accuracies ranging from 95% to 100%. Findings support further exploration of hyperspectral remote sensing technology and SVM classifiers for differentiating saltcedar from other cover types.     

Impact of episodic herbivory by the tamarisk leaf beetle on leaf litter nitrogen and stem starch content: A short communication

Tamarisk (Tamarix spp.) has in recent decades come to dominate riparian corridors throughout much of the western U.S. The implementation of biological control, utilizing the tamarisk leaf beetle (Diorhabda spp., particularly Diorhabda carinulata), has focused attention and research on this method for Tamarix suppression. Researchers are just beginning to understand how herbivory by Diorhabda affects Tamarix physiology and nutritional dynamics. The purpose of this study was to investigate whether herbivory by D. carinulata altered leaf litter nitrogen and stem starch content, and if so, how such alteration varied across a gradient of herbivory chronosequence. Leaf litter and stem analysis showed significantly higher levels of both nitrogen and stem starch content in trees that had experienced herbivory by the leaf beetle. However, there were no significant differences in nitrogen or stem starch content based on years of beetle herbivory. Higher levels of nitrogen in leaf litter from beetle-affected trees may be a result of herbivory-induced desiccation and foliar mortality prior to the translocation of nitrogen back into plant reserves. Additionally, higher stem starch may be a result of either phloem damage reducing the translocation of photoassimilates, or an increase in the shunting of carbohydrates to the site of new leaf growth. Finally, the lack of correlation between years of herbivory and both leaf litter nitrogen and stem starch may indicate that as of yet there have not been sufficient defoliation events to yield anticipated host plant impact.     

Characterizing the potential distribution of the invasive Asian longhorned beetle (Anoplophora glabripennis) in Worcester County,Massachusetts

The Asian longhorned beetle (ALB) (Anoplophora glabripennis) is an invasive insect pest that has established populations in Worcester County, Massachusetts as of 2008. ALB predominantly targets red maple (Acer rubrum), sugar maple (Acer saccharum), which are prominent in New England hardwood forests, and Norway maple (Acer platanoides), which was planted in built environments as street trees in response to severe weather and invasive insect and pathogen disturbances. Mahalanobis Typicality models related presence locations of ALB presence-only locations in Worcester County towns from 2008 to 2012 to biotic, abiotic, and anthropogenic variables to predict the potential distribution of ALB and to determine locations most characteristic of infestation. k-fold cross-validation and a continuous Boyce Index were employed to validate model performance and to identify threshold values at which continuous models of typicality could be reclassified into categorical maps. Distance-to-roads (r² = 0.19) and probability of maple presence (r² = 0.13) were the most important predictor variables in the ALB model. Locations that were most consistently susceptible to ALB infestation had significant high maple presence (p < 0.001) and significant low distance-to-roads (p < 0.001) compared to the whole study area, suggesting that ALB in Worcester County, MA, prefers maple-dominant edge habitats at the current stage of invasion. The localized ALB potential distribution model was consistently accurate (Boyce Continuous Index = 0.84) despite the lack of absence locations and incomplete knowledge of ALB niche breadth in both native and invaded ranges. The results from this study could be used as a baseline for effective adaptive management policies that could help prioritize the need for early detection/eradication measures and address the potential ecological and social ramifications of the current ALB outbreak in Worcester County. It is hoped that the model employed could be further tested for future outbreaks as they are discovered in the USA.     

叶片辐射传输模型PROSPECT 理论研究

综述植物叶片辐射传输PROSPECT 模型的理论,并对其理论来源PLATE 模型作了扼要介绍。进一步研究叶片结构、叶片光学吸收参数和叶片反射率、透射率之间的非线性关系,给出如何用单层致密叶片迭代来表示多层非致密叶片的反射率、透射率。讨论了Stokes 光学系统理论及其在模型理论中的应用,并用复向量的方法证明其各向同性光学介质中反射率和透射率递推关系式。表明PROSPECT 模型基于良好的物理模型,在满足假设条件下,能够准确模拟叶片的反射率和透射率。     

基于高光谱数据的荔枝SPAD值快速估测

通过分析荔枝叶片的反射光谱曲线与荔枝秋稍老熟阶段叶片SPAD-502 叶绿素计读数（SPAD 值）之间的关系,探索高光谱数据进行荔枝叶片SPAD 值估算的能力。研究4 类光谱变量,第1 类变量是其他文献中提出的光谱指数,第2 类变量是基于波段迭代算法进行波段优化后的新指数,第3 类变量是蓝边、黄边和红边（“三边”）的面积、位置、斜率,第4 类变量是二阶导数光谱波峰、波谷区间区间内光谱曲线的面积、最值、最值处波长。结果表明：一阶导数的蓝边斜率和光谱二阶导数提取的490~520 nm 范围内光谱数值之和与SPAD 值的相关程度也很高（r 分别为-0.834 和-0.856）;对于3 种光谱数据处理形式SNV 光谱（Standard Normal Variate,SNV）、FD 光谱（First Derivative,FD）和SD 光谱（Second Derivative,SD）,波段迭代算法优化后的最佳四波段双差值指数与SPAD 值相关性最好,其中（FD516－FD474）－（FD684－FD660）与SPAD 值的相关系数最高达到0.875,预测模型的确定系数达到0.747,RMSECV 为2.375。利用高光谱数据监测荔枝叶片SPAD 值是可行的。