中国西北C-3植物的碳同位素组成与年降雨量关系初探   总被引：2，自引：0，他引：2  

王国安  韩家懋 《地质科学》2001,(4):494

 本文对不同年降雨量环境下生长的藜、独行菜、魁蓟和平车前这4种常见C-3植物的δ¹³C进行了分析,发现这4种C-3植物的δ¹³C组成都表现出随年降雨量减少而变重的趋势,其中藜和独行菜的碳同位素组成对降水变化的响应相对要较其它2种植物强烈得多。藜、独行菜和魁蓟的δ¹³C组成与年降雨量有显著的线性关系,平车前碳同位素组成与年降雨量没有显著的相关性,表明藜、独行菜和魁蓟的δ¹³C组成可作为年降雨量的替代性指标,平车前的δ¹³C组成不能作为年降水的替代性指标。  相似文献   

云南白水台钙华水池中水化学日变化及其生物控制的发现   总被引：11，自引：0，他引：11  

刘再华  李强  孙海龙  汪进良  吴孔运 《水文地质工程地质》2005,32(6):10-15

为弄清云南白水台泉及其下游钙华水池中水化学的日变化,选取1号泉及其流经的两个钙华水池(6号和10号)作为研究对象并对其水温、pH值和电导率进行了自动监测。根据Ca2 、HCO3-与电导率存在的线性关系,用WATSPAC软件计算了水中方解石的饱和指数和PCO2。监测发现:泉水不存在显著的水化学日动态变化,而两个钙华水池表现出显著的日动态变化。其中10号钙华水池在白天温度较高时水中的CO2大量逸出并通过水下水生植物的光合作用加速了水中碳酸钙的沉积。6号钙华水池水生植物生长茂盛,其叶片和部分枝干露出水面,因而光合作用主要发生在空中,所以此处水化学表现为白天pH值降低和电导率升高的反常现象,即由温度主导的根呼吸作用,在白天释放更多的CO2进入水体而使沉积下来的碳酸钙重新溶解。  相似文献   

Above and belowground phenology of four Mediterranean sub-shrubs. Preliminary results on root–shoot competition     

S. Palacio  G. Montserrat-Martí 《Journal of Arid Environments》2007,68(4):522-533

Above and belowground phenology are critical aspects for plant life in areas of seasonal climate like Mediterranean regions. However, fine root growth phenology is rarely considered in most phenological studies. In this article we describe the above and belowground phenology of four species of Mediterranean sub-shrubs growing along a gradient of temperature and water availability, with special attention at the relationship between both processes. Observations were conducted monthly over a minimum of 12 months per species. Fine root growth varied significantly throughout the year, being higher in autumn than in spring and minimum in summer. In the species growing in cold areas, root growth was also reduced during winter. Shoot growth was maximum in spring for the four study species, buts its beginning was related to the site temperature, being earlier in those species growing in warmer sites. The species displaying a short vegetative period tended to separate root and shoot growth processes throughout the year. These results emphasize the importance of water availability and winter cold on fine root growth. A trade-off appears to exist between the duration of the vegetative period and the overlap between root and shoot growth processes.  相似文献   

Comparison of traditional wild plant knowledge between aboriginal communities inhabiting arid and forest environments in Patagonia, Argentina     

A. Ladio  M. Lozada  M. Weigandt 《Journal of Arid Environments》2007,69(4):695-715

The Mapuche people have a deeply rooted tradition of wild plant use for their subsistence. In this study we evaluated whether plant selection by the Mapuche is influenced by environmental constraints. Selection patterns of wild plant richness were compared in two Mapuche communities sharing the same traditions and beliefs but inhabiting different environments. Similarities and differences in the use patterns of wild medicinal and edible plants were quantitatively analyzed by using concepts derived from ecological theory. The Cayulef community is settled in the NW Patagonian (herbaceous) steppe while the Curruhuinca community is established near the Andean temperate forest, 100 km away from each other. Free-listing and semi-structured interviews were conducted with 32 families in Cayulef and 39 in Curruhuinca corresponding to 80% and 40% of each population, respectively. Data were analyzed by means of the Jaccard similarity index and statistical tests. The main results of this study showed that the home environment is a determinant factor that influences which plant species are utilized, as is the anthropic environment (with its high exotic species richness) in each community. However, similar patterns were found with respect to plant families, ways of utilization, plant parts and life forms utilized irrespective of where the communities are settled. In addition, in both populations, wild plant richness was significantly higher for medicinal than for edible species. Our results showed that the use of wild plants is primarily based on the utilization of species belonging to the nearest ecological environments that have both therapeutic and dietary functions.  相似文献   

Soil erosion along a long slope in the gentle hilly areas of black soil region in Northeast China     

CUI Ming  CAI Qiangguo  ZHU Axing  FAN Haoming 《地理学报》2007,17(3):375-383

Characteristics of soil erosion change along a long slope in the gentle hilly areas in black soil region in Northeast China are discussed. A simplified slope model based on seg-ments was used to analyze the runoff data and soil erosion data observed between 2003 and 2004 over 10 field plots with different slope length in Heshan Farm, Heilongjiang Province. We found that soil erosion rate over long slopes in the black soil region changed alternatively along the slope and creates alternative zones of intensive erosion and week erosion.The exact place of each zone is different for different rainfall conditions. In a year with less and mild precipitation, rill cannot happen within the top 50 m, while in a year with large and inten-sive precipitation, rill can be formed starting even at 15 m from the top of the slope.  相似文献   

森林地下碳分配(TBCA)研究进展     

陈光水  杨玉盛  刘乐中  李熙波  赵月彩  袁一丁 《福建地理》2007,(1)

森林地下碳分配(TBCA)是森林碳循环的重要通量,对森林碳吸存有十分重要作用.TBCA是森林生态系统GPP中一个最大的汇,可占GPP的21%～61%,土壤呼吸的2/3来自TBCA.目前国际上常用的TBCA测定方法为碳平衡法,在假定地下碳库处于稳定状态时,TB-CA可由土壤呼吸减去凋落物量获得,但该方法存在一系列问题.影响森林TBCA的因素有生产力、森林类型、树龄和森林演替阶段、土壤养分和水分有效性、林分密度和树种组成、气候变化因素等.TBCA中各个组成部分均较难以测定和量化,通常假定TBCA中根系呼吸与根系生产力各约占50%,而TBCA中菌根菌和根系分泌物的贡献则仍不清楚.有关TBCA各组分去向及影响机理的研究亦很少.TBCA未来的研究应致力于揭示TBCA的根本驱动因子和其对全球变化的响应机理,以及TBCA转化为土壤新碳的效率及控制因素;同时应提高TBCA测定方法的确定性,特别是应将碳同位素法、微根管法及碳平衡法三者相结合.  相似文献   

天山南麓山前平原土壤盐分空间异质性对植物群落组成及结构的影响   总被引：1，自引：1，他引：1  

赵振勇  王让会  尹传华  王雷 《干旱区地理》2007,30(6):839-845

将轮台天山南麓山前平原中下部自北至南分为4个地貌带:洪水剥蚀带、溢出带、三角洲带及两河交汇区带。并以土壤电导作为积盐程度的指标,分析了天山南麓山前平原4个地貌带土壤盐的分布特征:溢出带和三角洲带土壤盐分含量高,两端洪水剥蚀带和两河交汇区带盐分含量低。物种多样性及物种组成分析结果表明,自北至南物种多样性及物种数量都在下降,洪水剥蚀带主要为柽柳群落、琵琶柴群落,溢出带主要为柽柳群落、盐节木群落、盐角草群落,三角洲带及两河交汇区均为柽柳群落。通过相关性分析,土壤盐分与群落物种多样性相关性不显著。但是,土壤盐渍化的变化明显影响到植物群落物种组成的变化、群落类型的空间分布和演替。  相似文献   

Impact of root architecture on the erosion‐reducing potential of roots during concentrated flow     

S. De Baets  J. Poesen  A. Knapen  P. Galindo 《地球表面变化过程与地形》2007,32(9):1323-1345

Many studies focus on the effects of vegetation cover on water erosion rates, whereas little attention has been paid to the effects of the below ground biomass. Recent research indicates that roots can reduce concentrated flow erosion rates significantly. In order to predict this root effect more accurately, this experimental study aims at gaining more insight into the importance of root architecture, soil and flow characteristics to the erosion‐reducing potential of roots during concentrated flow. Treatments were (1) bare, (2) grass (representing a fine‐branched root system), (3) carrots (representing a tap root system) and (4) carrots and fine‐branched weeds (representing both tap and fine‐branched roots). The soil types tested were a sandy loam and a silt loam. For each treatment, root density, root length density and mean root diameter (D) were assessed. Relative soil detachment rates and mean bottom flow shear stress were calculated. The results indicate that tap roots reduce the erosion rates to a lesser extent compared with fine‐branched roots. Different relationships linking relative soil detachment rate with root density could be established for different root diameter classes. Carrots with very fine roots (D < 5 mm) show a similar negative exponential relationship between root density and relative soil detachment rate to grass roots. With increasing root diameter (5 < D < 15 mm) the erosion‐reducing effect of carrot type roots becomes less pronounced. Additionally, an equation estimating the erosion‐reducing potential of root systems containing both tap roots and fine‐branched roots could be established. Moreover, the erosion‐reducing potential of grass roots is less pronounced for a sandy loam soil compared with a silt loam soil and a larger erosion‐reducing potential for both grass and carrot roots was found for initially wet soils. For carrots grown on a sandy loam soil, the erosion‐reducing effect of roots decreases with increasing flow shear stress. For grasses, grown on both soil types, no significant differences could be found according to flow shear stress. The erosion‐reducing effect of roots during concentrated flow is much more pronounced than suggested in previous studies dealing with interrill and rill erosion. Root density and root diameter explain the observed erosion rates during concentrated flow well for the different soil types tested. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Use of high spectral resolution remote sensing to determine leaf palatability of eucalypt trees for folivorous marsupials     

Steve Dury  Brian Turner  Bill Foley  Ian Wallis 《International Journal of Applied Earth Observation and Geoinformation》2001,3(4):328

In this study we assess the feasibility of remotely measuring canopy biochemistry, and thus the potential for conducting large-scale mapping of habitat quality. A number of studies have found nutrient composition of eucalypt foliage to be a major determinant of the distribution of folivorous marsupials. More recently it has been demonstrated that a specific group of secondary plant chemicals, the diformylphloroglucinols (DFPs), are the most important feeding deterrents, and are thus vital determinants of habitat quality. We report on the use of laboratory spectroscopy to attempt to identify one such DFP, sideroxylonal-A, in the foliage of Eucalyptus melliodora, one of the few eucalypt species browsed by folivorous marsupials. Reflectance spectra were obtained for freeze-dried, ground leaves using near infrared spectroscopy (NIRS) and for both oven-dried and fresh whole leaves using a laboratory-based (FieldSpec) spectroradiometer. Modified partial least squares (MPLS) regression was used to develop calibration equations for sideroxylonal-A concentration based on the reflectance spectra transformed as both the first and second difference of absorbance (Log 1/R). The predictive ability of the calibration equations was assessed using the standard error of calibration statistic (SECV). Coefficients of determination (r²) were highest for the ground leaf spectra (0.98), followed by the fresh leaf and dry leaf spectra (0.94 and 0.87, respectively). When applied to independent validation sub-sets, sideroxylonal-A was most accurately predicted from the ground leaf spectra (r² = 0.94), followed by the dry leaf and fresh leaf spectra (0.72 and 0.53, respectively). Two spectral regions, centred on 674 nm and 1394 nm, were found to be highly correlated with sideroxylonal-A concentration for each of the three spectral data sets studied. Results from this study suggest that calibration equations derived from modified partial least squares regression may be used to predict sideroxylonal-A concentration, and hence leaf palatability, of Eucalyptus melliodora trees, thereby indicating that the remote estimation of habitat quality of eucalypt forests for marsupial folivores is feasible.  相似文献   

应用Landsat ETM数据估算鄱阳湖湿生植被生物量   总被引：35，自引：1，他引：35  

李仁东  刘纪远 《地理学报》2001,56(5):532-540

利用2000年的Landsat ETM数据,首次采用全数字化遥感定量方法对鄱阳湖湿生植被的生物量及其分布进行调查研究.首先,用该时相卫星数据制作假彩色合成图象,以该图象为主要依据之一,设计了野外生物量采样路线与样点,并在地形图和GPS的帮助下,实时地开展了湿生植被生物量的野外实地采样.然后,在室内将采样点坐标和Landsat ETM图象坐标进行几何纠正和匹配,将坐标统一转换为等积圆锥投影.再逐个坐标点比较采样数据与ETM4波段数据和NDVI、DVI和第一主成分数据之间的线性相关关系.统计分析的结果表明,采样数据与ETM 4波段数据有最好的正相关,其相关系数达到0.86.采样数据与DVI、NDVI数据的相关系数分别为0.83、0.80.采样数据与第一主成分数据之间的相关关系不显著,仅0.40.基于这一比较,建立了采样数据与ETM 4波段数据的线性相关模型.据此,用ETM 4波段计算出鄱阳湖4月份湿生植被的总生物量为3.8×109 kg,并编制了整个湖泊生物量的分布图.  相似文献