中国典型山地温冰川水化学空间分布特征与近期冰川动态

从我国玉龙雪玉典型温水王白水１号冰川不同区段表面融水,新近积雪和冰川初给河水采样分析结果表明,雪线以下降水中的稳定同位素的离子含量比雪线以下为高,低海拔河水比高海拨融水的氧同浓度为低,可能在来源上存在着差异,这种分布特征说明本温冰川区局部大气环流情况高度而不同,有可能存在季气候区所特有的“降水量效应”或“季节性效应”。冰川不同水体内离子浓度变化说明,冰川融水与地壳表面接触时间越久,其中的可融性离了     

Woody buffer effects on water temperature: The role of spatial configuration and daily temperature fluctuations

Water temperature is a key driver for riverine biota and strongly depends on shading by woody riparian vegetation in summer. While the general effects of shading on daily maximum water temperature T_max are well understood, knowledge gaps on the role of the spatial configuration still exist. In this study, the effect of riparian buffer length, width, and canopy cover (percentage of buffer area covered by woody vegetation) on T_max was investigated during summer baseflow using data measured in seven small lowland streams in western Germany (wetted width 0.8–3.7 m). The effect of buffer length on T_max differed between downstream cooling and heating: T_max approached cooler equilibrium conditions after a distance of 0.4 km (~45 min travel-time) downstream of a sharp increase in canopy cover. In contrast, T_max continued to rise downstream of a sharp decrease in canopy cover along the whole 1.6 km stream length investigated. The effect of woody vegetation on T_max depended on buffer width, with changes in canopy cover in a 10 m wide buffer being a better predictor for changes in T_max compared to a 30 m buffer. The effect of woody vegetation on T_max was linearly related to canopy cover but also depended on daily temperature range T_range, which itself was governed by cloudiness, upstream canopy cover, and season. The derived empirical relationship indicated that T_max was reduced by −4.6°C and increased by +2.7°C downstream of a change from unshaded to fully shaded conditions and vice versa. This maximum effect was predicted for a 10 m wide buffer at sunny days in early summer, in streams with large diel fluctuations (large T_range). Therefore, even narrow woody riparian buffers may substantially reduce the increase in T_max due to climate change, especially in small shallow headwater streams with low baseflow discharge and large daily temperature fluctuations.     

1990—2010年长白山温带针阔叶混交林生长季及积温的变化

长白山温带针阔叶混交林作为典型的温带森林生态系统,对气候变化的反应比较敏感,其生长季及积温的变化是准确评价该我国东北林区气候变化的重要依据。本研究采用中国科学院长白山森林生态系统定位站获取的1982-2010年气温目值观测资料,分析了近20a该地区生长季长度及积温的变化,结果标明长白山温带针阔叶混交林29a的平均温度为3．6℃,29a中该地区气温有较弱的上升趋势;长白山温带针阔叶混交林1990-2010年生长季长度的平均值为174d,近20a中生长季长度呈弱增长趋势;长白山温带针阔叶混交林1990～2010年生长季起始日期变化较稳定,生长季终止日期有推后的趋势;长白山温带针阔叶混交林1990-2010年≥5℃的活动积温和有效积温平均值分别为2616．9℃、1744．8℃。近20a中,≥5℃活动积温和有效积温都有着缓慢升高的趋势。     

WorldView-2纹理的森林地上生物量反演

使用高空间分辨率卫星WorldView-2的多光谱遥感影像,构建植被指数和纹理因子等遥感因子与森林地上生物量的关系方程,并计算模型估测精度和均方根误差,探索高分辨率数据的光谱与纹理信息在温带森林地上生物量估测应用中的潜力。以黑龙江省凉水自然保护区温带天然林及天然次生林为研究对象,通过灰度共生矩阵(GLCM)、灰度差分向量(GLDV)及和差直方图(SADH)对高分辨率遥感影像进行纹理信息提取,并利用外业调查的74个样地地上生物量与遥感因子建立参数估计模型。提取的遥感因子包括6种植被指数(比值植被指数RVI、差值植被指数DVI、规一化植被指数NDVI、增强植被指数EVI、土壤调节植被指数SAVI和修正的土壤调节植被指数MSAVI)以及3类纹理因子(GLCM、GLDV和SADH)。为避免特征变量个数较多对估测模型造成过拟合,利用随机森林算法对提取的遥感因子进行特征选择,将最优的特征变量输入模型参与建模估测。采用支持向量回归(SVR)进行生物量建模及验证,结果显示选入模型的和差直方图均值(sadh_mean)、灰度共生矩阵方差(glcm_var)和差值植被指数(DVI)等遥感因子对森林地上生物量有较好的解释效果;植被指数+纹理因子组合的模型获得较精确的AGB估算结果(R2=0.85,RMSE=42.30 t/ha),单独使用植被指数的模型精度则较低(R~2=0.69,RMSE=61.13 t/ha)。     

Book review

“Fertility of the Sea”. J. D. Costlow (Ed.). 1971. 2 Volumes (Vol. 1, 320 pp.; Vol. 2, 326 pp.) Gordon & Breach, Science Publishers, 12 Bloomsbury Way, London. £14.60 the set.     

1900-2007年横断山区部分海洋型冰川变化

横断山区7条海洋型冰川近百年进退速度变化呈现出以退缩为总趋势的阶段性变化,具体表现为20世纪初至1930s的冰川稳定,1930s-1960s的冰川后退,1970s-1980s的冰川稳定或减速后退,20世纪80年代中期以来的冰川后退,这与我国、北半球及横断山区同期的气候变化呈明显对应,展现出冷干阶段冰川稳定或前进、暖湿阶段后退的态势,但各冰川的变化幅度因纬度位置、坡向、冰川规模、局地环境等而存在明显差异.1982/83年大、小贡巴冰川、海螺沟冰川冰舌段的消融水当量分别为2710mm、3139 mm和5281 mm,1990/91-97/98期间海螺沟冰川冰舌段的年均消融水当量为6157 mm,比1982/83年增加了876 mm.2002年夏季白水1号冰川的积雪消融量由于表碛覆盖较少表现出明显的随海拔升高而降低的特征,平均消融水当量为1086.25 mm,2008.9-19.10.13期间白水1号冰川物质平衡花竿的观测表明,花竿布设区域10月6号左右转入物质积累期.期间日均积累深为1cm,折合水当量5mm.     

Quantification of the effect of forest harvesting versus climate on streamflow cycles and trends in an evergreen broadleaf catchment

ABSTRACT

A new method known as Unobserved Components–Dynamic Harmonic Regression (UC-DHR) was applied to a 39-year record of rainfall and streamflow for three sub-catchments of the Sarukawa Experimental Watershed in southwestern Japan. Some 25% of the timber was harvested from one of the sub-catchments in May–July 1982 and the objective was to quantify the magnitude of this effect relative to the effects of climate cycles (e.g. Southern Oscillation Index). The observed effects of inter-annual climate cycles (i.e. 0.89–1.36 mm/d) were seen to be comparable (i.e. 0.70–1.17 mm/d) to the effects of harvesting 25% of the standing timber. This result underlines the importance of always quantifying the effect of climate on streamflow response when harvesting impacts are studied.

Editor D. Koutsoyiannis; Associate editor T. Okruszko     

Weakening of gneiss surfaces colonized by endolithic lichens in the temperate climate area of northwest Italy

A role of lithobionts in geomorphological processes is increasingly argued, but the spatio‐temporal scale of their impact is largely unexplored in many ecosystems. This study first characterizes in the temperate zone (northwest Italy) the relationships between lithobiontic communities including endolithic lichens and the hardness of their siliceous rock substrate (Villarfocchiardo Gneiss). The communities are characterized, on humid and xeric quarry surfaces exposed for decades and natural outcrops exposed for centuries, in terms of lichen and microbial constituents, using a combined morphological and molecular approach, and with regard to their development on and within the gneiss. A lichen species belonging to Acarosporaceae (Polysporina‐Sarcogyne‐Acarospora group, needing taxonomic revision) chasmoendolithically colonizes both the humid and xeric quarry surfaces, on which epilithic cyanobacterial biofilms and epilithic pioneer lichens respectively occur. Light and electron microscopic observations show the development of the endolithic thalli within rock microcracks and the hyphal penetration along crystal boundaries down to depths of 1 to 3 mm, more pronounced within the humid surfaces. Such colonization patterns are likely related to biogeophysical deterioration, while no chemical alteration characterizes minerals contacted by the endolithic lichen. By contrast, on natural outcrops, where the endolithic colonization is negligible, a reddish rind below epilithic lichens indicates chemical weathering processes. Schmidt Hammer measurements highlight that the endolithic lichens deeply affect the hardness of the gneiss (down to ?60% with respect to fresh controls and surfaces only colonized by cyanobacteria), exerting a significantly higher weakening effect with respect to the associated epilithic lithobionts. The phenomenon is more remarkable on humid than on xeric quarry surfaces and natural outcrops, where epilithic lichens are likely involved in long‐term hardening processes supporting surface stabilization. Endolithic lichens are thus active biogeomorphological agents at the upper millimetric layer of siliceous rocks in temperate areas, exerting their weakening action during the early decade‐scaled stages of surface exposure. Copyright © 2015 John Wiley & Sons, Ltd.     

Seasonal evolution of the englacial and subglacial drainage systems of a temperate glacier revealed by hydrological analysis

Englacial and subglacial drainage systems of temperate glaciers have a strong influence on glacier dynamics, glacier-induced floods, glacier-weathering processes, and runoff from glacierized drainage basins. Proglacial discharge is partly controlled by the geometry of the glacial drainage network and by the process of producing meltwater. The glacial-drainage system of some alpine glaciers has been characterized using a model based on proglacial discharge analysis. In this paper, we apply cross-correlation analysis to hourly hydro-climatic data collected from China＇s Hailuogou Glacier, a typical temperate glacier in Mt. Gongga, to study the seasonal status changes of the englacial and subglacial drainage systems by discharge-temperature （Q-T） time lag analy-sis. During early ablation season （April-May） of 2003, 2004 and 2005, the change of englacial and subglacial drainage system usually leads several outburst flood events, which are also substantiated by observing the leakage of supraglacial pond and cre-vasses pond water during field works in April, 2008. At the end of ablation season （October-December）, the glacial-drainage net-works become less hydro-efficient. Those events are evidenced by hourly hydro-process near the terminus of Hailuogou Glacier, and the analysis of Q-T time lags also can be a good indicator of those changes. However, more detailed observations or experi-ments, e.g. dye-tracing experiment and recording borehole water level variations, are necessary to describe the evolutionary status and processes of englacial and subglacial drainage systems evolution during ablation season.     

Isotopic and chemical analyses of a temperate firn core from a Chinese alpine glacier and its regional climatic significance

Mt. Yulong is the southernmost currently glacier-covered area in Eurasia, including China. There are 19 sub-tropical temperate glaciers on the mountain, controlled by the south-western monsoon climate. In the summer of 1999, a firn core, 10. 10 m long, extending down to glacier ice, was recovered in the accumulation area of the largest glacier, Baishui No. 1. Periodic variations of climatic signals above 7. 8 m depth were apparent, and net accumulation of four years was identified by the annual oscillations of isotopic and ionic composition. The boundaries of annual accumulation were confirmed by higher values of electrical conductivity and pH, and by dirty refreezing ice layers at the levels of summer surfaces. Calculated mean annual net accumulation from 1994/1995 to 1997/1998 was about 900 mm water equivalent. The amplitude of isotopic variations in the profile decreased with increasing depth, and isotopic homogenization occurred below 7. 8 m as a result of meltwater percolation. Variations of δ18O above 7. 8 m showed an approximate correlation with the winter climatic trend at Li Jiang Station, 25 km away. Concentrations of Ca2+ and Mg2+ were much higher than those of Na+ and K+ , indicating that the air masses for precipitation were mainly from a continental source, and that the core material accumulated during the winter period. The close correspondence of C1- and Na+ indicated their common origin. Very low concentrations of SO2-4 and NO3- suggest that pollution caused by human activities is quite low in the area. The mean annual net accumulation in the core and the estimated ablation indicate that the average annual precipitation above the glacier's equilibrium line is 2400 - 3150 mm, but this needs to be confirmed by long term observation of mass balance.