桂西北喀斯特区域植被变化趋势及其对气候和地形的响应

基于1999—2010年的SPOT NDVI数据,分析了河池市植被变化趋势及空间差异,并结合气象和地形数据分析了植被与气候、地形的关系。结果表明:(1)桂西北喀斯特地区植被变化总体上呈恢复趋势,年均气候因子对植被变化的作用不明显;(2)200—500m的海拔范围内植被恢复显著,但400—500m的海拔范围内有小面积植被退化现象,随着海拔增加,植被变化趋于稳定;(3)6—15°的坡度范围内植被恢复最显著,而2—6°及大于25°坡度范围存在植被退化的现象;(4)不同坡向上的植被恢复差异不明显,但随着坡向由阴坡转阳坡,植被总体恢复呈减小趋势。喀斯特地区人类生态建设取得一定成效,但由于人类活动的负面影响,在海拔400—500m、坡度大于25°的阳坡区域仍存在植被减少的现象。     

山区夏季地表温度的影响因素——以泰山为例

以泰山为例,应用夏季的Landsat 5的TM6为基本数据源,基于单窗算法定量反演了泰山地表面温度(LST),在此基础上首先探讨了LST与地形因子的关系,然后比较了归一化水汽指数(NDMI)和归一化植被指数(NDVI)在表达山区LST上的效力,最后利用逐步回归分析法,构建出LST与地形因子、NDMI的回归方程,应用偏相关系数,得出各个因子对LST的影响程度。结果表明:1)在地形因子中,影响LST的主要因素是海拔,随海拔升高呈自然对数形式降低,相比而言,坡度、坡向以及太阳入射能量的影响则很小;2)在没有水体时,NDVI与NDMI都能有效地表达山区的LST,LST与NDVI间是二次项负相关关系,与NDMI间是线性负相关关系,在表达LST上NDMI比NDVI更有效;3)综合分析表明,地表水汽特征是其表面温度最主要的影响因素,其次是海拔。研究结果将为山区地表温度空间分异性特征及形成机制的研究提供科学的参考。     

Projecting future grassland productivity to assess the sustainability of potential biofuel feedstock areas in the Greater Platte River Basin

This study projects future (e.g., 2050 and 2099) grassland productivities in the Greater Platte River Basin (GPRB) using ecosystem performance (EP, a surrogate for measuring ecosystem productivity) models and future climate projections. The EP models developed from a previous study were based on the satellite vegetation index, site geophysical and biophysical features, and weather and climate drivers. The future climate data used in this study were derived from the National Center for Atmospheric Research Community Climate System Model 3.0 ‘SRES A1B’ (a ‘middle’ emissions path). The main objective of this study is to assess the future sustainability of the potential biofuel feedstock areas identified in a previous study. Results show that the potential biofuel feedstock areas (the more mesic eastern part of the GPRB) will remain productive (i.e., aboveground grassland biomass productivity >2750 kg ha^?1 year^?1) with a slight increasing trend in the future. The spatially averaged EPs for these areas are 3519, 3432, 3557, 3605, 3752, and 3583 kg ha^?1 year^?1 for current site potential (2000–2008 average), 2020, 2030, 2040, 2050, and 2099, respectively. Therefore, the identified potential biofuel feedstock areas will likely continue to be sustainable for future biofuel development. On the other hand, grasslands identified as having no biofuel potential in the drier western part of the GPRB would be expected to stay unproductive in the future (spatially averaged EPs are 1822, 1691, 1896, 2306, 1994, and 2169 kg ha^?1 year^?1 for site potential, 2020, 2030, 2040, 2050, and 2099). These areas should continue to be unsuitable for biofuel feedstock development in the future. These future grassland productivity estimation maps can help land managers to understand and adapt to the expected changes in future EP in the GPRB and to assess the future sustainability and feasibility of potential biofuel feedstock areas.     

Non-destructive stereological method for estimating the length of rigid root systems

A non-destructive method of total vertical projections for estimating the length of rigid root systems, not introduced yet in plant sciences, is described. It is demonstrated on measuring less and more dense root systems of seedlings of Zea mays grown at hypoxic or control conditions. Photographs of six vertical projections (30° apart) of each root system were taken and evaluated. The method being based on proved mathematical formula offers unbiased estimation of the length of a rigid root system, curved in three-dimensional space, by non-destructive means. Thus, it is applicable during ongoing experimentation on plants grown in a solution culture. It was shown that less than 120 intersections between the root projection and test lines in one photograph ensured sufficient precision of the method and that the observer subjectivity could be overcome by presented instructions. This revised version was published online in July 2006 with corrections to the Cover Date.     

CO2 evasion from boreal lakes: Revised estimate,drivers of spatial variability,and future projections

Lakes (including reservoirs) are an important component of the global carbon (C) cycle, as acknowledged by the fifth assessment report of the IPCC. In the context of lakes, the boreal region is disproportionately important contributing to 27% of the worldwide lake area, despite representing just 14% of global land surface area. In this study, we used a statistical approach to derive a prediction equation for the partial pressure of CO₂ (pCO₂) in lakes as a function of lake area, terrestrial net primary productivity (NPP), and precipitation (r² = .56), and to create the first high‐resolution, circumboreal map (0.5°) of lake pCO₂. The map of pCO₂ was combined with lake area from the recently published GLOWABO database and three different estimates of the gas transfer velocity k to produce a resulting map of CO₂ evasion (FCO₂). For the boreal region, we estimate an average, lake area weighted, pCO₂ of 966 (678–1,325) μatm and a total FCO₂ of 189 (74–347) Tg C year^?1, and evaluate the corresponding uncertainties based on Monte Carlo simulation. Our estimate of FCO₂ is approximately twofold greater than previous estimates, as a result of methodological and data source differences. We use our results along with published estimates of the other C fluxes through inland waters to derive a C budget for the boreal region, and find that FCO₂ from lakes is the most significant flux of the land‐ocean aquatic continuum, and of a similar magnitude as emissions from forest fires. Using the model and applying it to spatially resolved projections of terrestrial NPP and precipitation while keeping everything else constant, we predict a 107% increase in boreal lake FCO₂ under emission scenario RCP8.5 by 2100. Our projections are largely driven by increases in terrestrial NPP over the same period, showing the very close connection between the terrestrial and aquatic C cycle.     

A review and meta‐analysis of the effects of climate change on Holarctic mountain and upland bird populations

Mountain regions are globally important areas for biodiversity but are subject to multiple human‐induced threats, including climate change, which has been more severe at higher elevations. We reviewed evidence for impacts of climate change on Holarctic mountain bird populations in terms of physiology, phenology, trophic interactions, demography and observed and projected distribution shifts, including effects of other factors that interact with climate change. We developed an objective classification of high‐elevation, mountain specialist and generalist species, based on the proportion of their breeding range occurring in mountain regions. Our review found evidence of responses of mountain bird populations to climate (extreme weather events, temperature, rainfall and snow) and environmental (i.e. land use) change, but we know little about either the underlying mechanisms or the synergistic effects of climate and land use. Long‐term studies assessing reproductive success or survival of mountain birds in relation to climate change were rare. Few studies have considered shifts in elevational distribution over time and a meta‐analysis did not find a consistent direction in elevation change. A meta‐analysis carried out on future projections of distribution shifts suggested that birds whose breeding distributions are largely restricted to mountains are likely to be more negatively impacted than other species. Adaptation responses to climate change rely mostly on managing and extending current protected areas for both species already present, and for expected colonizing species that are losing habitat and climate space at lower elevation. However, developing effective management actions requires an improvement in the current knowledge of mountain species ecology, in the quality of climate data and in understanding the role of interacting factors. Furthermore, the evidence was mostly based on widespread species rather than mountain specialists. Scientists should provide valuable tools to assess the status of mountain birds, for example through the development of a mountain bird population index, and policy‐makers should influence legislation to develop efficient agri‐environment schemes and forestry practices for mountain birds, as well as to regulate leisure activities at higher elevations.     

Characteristic glycopeptides associated with extreme human longevity identified through plasma glycoproteomics

Background

Glycosylation is highly susceptible to changes of the physiological conditions, and accordingly, is a potential biomarker associated with several diseases and/or longevity. Semi-supercentenarians (SSCs; older than 105?years) are thought to be a model of human longevity. Thus, we performed glycoproteomics using plasma samples of SSCs, and identified proteins and conjugated N-glycans that are characteristic of extreme human longevity.

Fine structure and primary sensory projections of sensilla located in the sacculus of the antenna of Drosophila melanogaster

Sensilla lining the inner walls of the sacculus on the third antennal segment of Drosophila melanogaster were studied by light and transmission electron microscopy. The sacculus consists of three chambers: I, II and III. Inside each chamber morphologically distinct groups of sensilla having inflexible sockets were observed. Chamber I contains no-pore sensilla basiconica (np-SB). The lumen of all np-SB are innervated by two neurons, both resembling hygroreceptors. However, a few np-SB contain one additional neuron, presumed to be thermoreceptive. Chamber II houses no-pore sensilla coeloconica (np-SC). All np-SC are innervated by three neurons. The outer dendritic segments of two of these neurons fit tightly to the wall of the lumen and resemble hygroreceptor neurons. A third, more electron-dense sensory neuron, terminates at the base of the sensillum and resembles a thermoreceptor cell. Chamber III of the sacculus is divided into ventral and dorsal compartments, each housing morphologically distinct grooved sensilla (GS). The ventral compartment contains thick GS₁, and the dorsal compartment has slender sensilla GS₂. Ultrastructurally, both GS₁ and GS₂ are doublewalled sensilla with a longitudinal slit-channel system and are innervated by two neurons. The dendritic outer segment of one ofthe two neurons innervates the lumen of the GS and branches. On morphological criteria, we infer this neuron to be olfactory. The other sensory neuron is probably thermoreceptive. Thus, the sacculus in Drosophila has sensilla that are predominantly involved in hygroreception, thermoreception, and olfaction. We have traced the sensory projections of the neurons innervating the sacculus sensilla of chamber III using cobaltous lysine or ethanolic cobalt (II) chloride. The fibres project to the antennal lobes, and at least four glomeruli (VM₃, DA₃ and DL_2-3) are projection areas of sensory neurons from these sensilla. glomerulus DL₂ is a common target for the afferent fibres of the surface sensilla coeloconica and GS, whereas the VM₃, DA₃ and DL₃ glomeruli receive sensory fibres only from the GS.     

Foliar Nutrient Dynamics and Resorption in Naturalized Lonicera maackii (Caprifoliaceae) Populations in Ohio,USA

Foliar phosphorus (P) and nitrogen (N) concentrations and nutrient resorption in the forest understory shrub Lonicera maackii (Rupr.) Maxim (Caprifoliaceae) were measured along contiguous topographic gradients in two southwestern Ohio forests during 1992–1994. Mean summer foliar P varied significantly among topographic positions (but not sites or years), with uplands having greatest P concentrations and bottomlands exhibiting the lowest. Unlike for P, the mean summer foliar N concentrations varied little among sites, topographic positions, and years. Mean absolute and proportional P resorption ranged from 0.48 mg/dm² (33.7%) in slope positions to 0.80 mg/dm² (53.1%) in bottomland positions. Repeated-measures analysis of variance (RMANOVA) for P resorption indicated significant topographic and year effects, a site × year and a site × year × topographic interaction. Mean absolute and proportional foliar N resorption ranged from 6.82 mg/dm² (30.7%) in bottomlands to 8.41 mg/dm² (37.3%) in slope positions. RMANOVA indicated a significant topographic effect for both absolute and proportional N resorption and a significant year effect for absolute N resorption. These significant year effects for P and N stemmed from lowest resorption of nutrients in 1993. The results for P resorption support the hypothesis that foliar resorption is greater in forested sites with lower P fertility. However, resorption rates for N did not support the hypothesis clearly, as slopes with intermediate N availability had greater N resorption rates than did N-rich bottomlands.     

Topographic EEG mapping of the relaxation response

The purpose of this study was to assess the central nervous system effects of the relaxation response (RR) in novice subjects using a controlled, within-subjects design and topographic EEG mapping as the dependent measure. Twenty subjects listened to a RR and control audiotape presented in a counterbalanced order while EEG was recorded from 14 scalp locations. TheRR condition produced greater (p<.0164) reductions in frontal EEG beta activity relative to the control condition. No significant differences were observed for any other frequency band or scalp region. These findings suggest that elicitation of the RR produces significant reductions in cortical activation in anterior brain regions in novice subjects.