A DENDROGEOMORPHOLOGICAL ANALYSIS OF SNOW AVALANCHES IN THE COLORADO FRONT RANGE,USA     

Shelly A. Rayback 《自然地理学》2013,34(6):502-515

Despite the growing risk of avalanche-related death and property damage associated with the burgeoning tourist industry in the Colorado Front Range, no dendro-geomorphological studies have been conducted to assess avalanche history in this region. In this study, dendrogeomorphological techniques are used to develop avalanche event chronologies and to reconstruct past slide magnitude at two sites located near Loveland Pass. At Mount Bethel, historical data compiled by the Colorado Department of Transportation (CDOT) and the Westwide Data Network for the period between 1974 and 1996 corroborate four of eight dendrochronologically dated event years. At Grizzly Peak, four of five dendrochronologically determined event years occurring between 1981 and 1996 are supported by historical data kept by CDOT, the Westwide Data Network and the Arapaho Basin Ski Patrol. Avalanche path reconstruction and the examination of vegetative indicator species reveal periodic fluctuations in slide magnitude at both sites, suggesting that larger avalanches have run outside the present tracks multiple times. The chronicling and assessment of each path's slide history informs of past occurrences and alerts us to future risks. [Key words: avalanche, dendrogeomorphology, Colorado Front Range.]  相似文献   

Winter Leaf Conductance Rates of Pinus Strobus L. (Eastern White Pine)     

《自然地理学》2013,34(5):474-482

Our knowledge of winter leaf conductance and transpiration rates during the winter and early spring is especially weak for Pinus strobus L. (eastern white pine). Hence, the present study was conducted to: (1) measure and examine the winter leaf conductance and transpiration rates among 10 P. strobus trees to supply preliminary data for an understudied tree species; and (2) investigate whether observed leaf conductance and transpiration rates are large enough to merit incorporation into existing water balance models. The fieldwork was conducted at the Fair Hill Natural Resources Management Area in northeastern Maryland (39°42'N, 75°50'W) using a Li-Cor 1600M Steady State Porometer. Meteorological data were acquired from a continuously recording meteorological station on-site. Meteorological data were recorded at five-minute intervals to ensure that weather conditions could be temporally sequenced with porometer readings. The 10 co-occurring P. strobus sample trees were of similar age and health on uniform soils in an open field. Winter and early spring leaf conductance values of the selected trees reached 20 mmol m^-2 s^-1, whereas transpiration reached 0.13 mmol m^-2 s^-1. Results of the study indicate that there is statistically significant differences in leaf conductance rates among co-occurring P. strobus trees (H = 16.74, p = .05). Since the upper winter leaf conductance and transpiration rates measured in this study overlap with growing season leaf conductance and transpiration values reported by others, it is suggested that winter leaf conductance of and transpiration from P. strobus trees are significant enough to incorporate into water balance calculations.  相似文献   

Impact of Pleistocene–Holocene climate shifts on vegetation and fire dynamics and its implications for Prearchaic humans in the central Great Basin,USA     

Sandra Olivia Brugger  David Rhode 《第四纪科学杂志》2020,35(8):987-993

The effects of climate change during the Terminal Pleistocene–Early Holocene transition on ecosystems and early Prearchaic hunter-gatherers in the central Great Basin of North America are not well understood. We present a palynological reconstruction of regional vegetation and fire history in Grass Valley, central Nevada, from ~14 to ~7.5k cal a BP showing that Pinus-dominated woodlands were replaced by dry-adapted steppe and desert vegetation accompanied by an increase in regional fire activity at the beginning of the Holocene, in response to summer warming and a drying climate. Following a severe drought period peaking ~10.2–9.3k cal a BP, Pinus woodlands partially recovered contemporaneously with the 8.2k cal a BP climate anomaly. Local wetlands provided important resource patches for human foraging societies, and periodic declines of wetlands in response to changing local hydrological conditions may have necessitated adjustments in subsistence and settlement practices and technology.  相似文献   

油松和侧柏常绿树种对典型污染物的吸滞与富集作用          下载免费PDF全文

褚建民  王燕  王琼  李少宁  胡守明  王叶红 《气象与环境学报》2012,28(3):15-20

以城市森林生态系统常绿树种为对象,测定了油松（Pinus tabuliformis）和侧柏（Platycladus orientalis）叶片对大气污染物（SO₂、Cl₂）和土壤重金属污染物（Cu、Zn、As、Hg和Pb、Cd和Cr）的吸滞作用与富集作用。结果表明：油松和侧柏具有较强吸滞污染物的作用,对污染物的吸滞能力受环境污染程度、不同生长季节的污染元素种类等因素的影响。其中,油松在秋季对S、Cu、Zn、Pb和Hg具有较高的吸附能力,针叶中S、Cu、Zn、Pb和Hg含量平均值分别为2158.75、6.31、31.46、4.05 mg·kg-1和0.08 mg·kg-1;侧柏在秋季对Cu、Zn、Hg和Cd具有较高的吸附能力,叶片中Cu、Zn、Hg、Cd含量平均值分别为4.47、22.47、0.09 mg·kg-1和0.20 mg·kg-1;在不同立地条件下,油松和侧柏对污染物的吸滞与富集量有所差异,其中在土壤污染较重的石景山松林园样地,油松对大气污染物SO₂有较强的吸附能力,侧柏则表现出对Cl₂有较强的吸附能力。对重金属污染物而言,油松和侧柏对Cu、Pb、Cr和As有较高的富集作用。  相似文献   

造林对沙地土壤微生物的数量、生物量碳及酶活性的影响     

王少昆  赵学勇  张铜会  李玉强  连杰  黄文达  云建英 《中国沙漠》2013,33(2):529-535

对科尔沁沙地流动沙丘中林龄为20年左右的樟子松（Pinus sylvestris var. mongolica）和小叶杨（Populus simonii）人工林表层土壤微生物数量、微生物生物量碳和酶活性进行了研究,流动沙丘作为对照。研究表明:樟子松和小叶杨人工林可以显著改善流动沙丘土壤性状,对沙丘土壤微生物活性具有显著的促进作用;土壤微生物数量、微生物生物量碳和酶活性均表现为小叶杨林>樟子松林>流动沙丘。樟子松和小叶杨林地土壤微生物总数分别是对照的50.16倍和72.48倍,三者差异显著;樟子松和小叶杨林地土壤微生物生物量碳分别是对照的23.67倍和33.34倍,林地与对照差异显著;两种林地土壤脱氢酶、过氧化物酶、蛋白酶、脲酶、纤维素酶活性分别是对照的19.00倍和27.54倍、4.78倍和9.89倍、4.05倍和8.67倍、29.93倍和37.46倍、9.66倍和13.42倍,林地与对照差异显著。在科尔沁沙地,人工种植适合当地气候特点的乔木,不仅可以改善流动沙丘土壤性状和微生物活性,而且还能起到固定流动沙丘的目的,樟子松和小叶杨是当地值得推广种植的防风固沙树种。土壤微生物量商（Cmic∶C）是一个衡量林地土壤稳定性和有效性较好的指标,从林地土壤养分有效性、林木稳定性和可持续性等方面综合考虑,樟子松比小叶杨更具优势。  相似文献   

樟子松碳汇价值的长时间尺度模拟分析（英文）     

裴厦  谢高地  张昌顺  刘春兰  李士美  张彩霞  陈龙 《资源与生态学报(英文版)》2015,6(1):37-43

森林生态系统具有重要的碳汇作用。目前,碳汇价格可以通过碳交易、碳税和固碳项目实际成本3种机制实现。本研究从森林植被碳汇功能发挥的过程出发,认为森林植被碳汇价值包括碳固定价值和碳蓄积价值两部分。在此基础上以樟子松(Pinus sylvestris var.mongolica)为例,采用固碳项目实际成本,模拟了森林植被在100年的生命历程中碳汇价值的动态变化过程。研究表明,单株樟子松碳固定的物理量和价值量动态过程曲线都呈倒"U"型;碳蓄积的物理量和价值量动态过程曲线都近似呈"S"型。在碳固定和碳蓄积价值叠加下,碳汇价值流量过程曲线近似呈"S"型,且逐渐趋近碳蓄积价值流量曲线。100年内,樟子松的碳汇总价值(资产价值)随着林龄逐渐增大,其中碳蓄积价值所占的比重逐渐增加。樟子松林分碳汇价值曲线与单株树木的曲线不完全相同,但是基本形态一致。  相似文献   

以树轮宽度重建公元1558年以来华山5～6月平均温度及20世纪中后期升温   总被引：3，自引：3，他引：0       下载免费PDF全文

刘禹  田沁花  宋慧明  孙军艳  Deliang Chen  蔡秋芳  他维媛  雷莺 《第四纪研究》2009,29(5):888-895

通过对秦岭东端华山地区油松树木年轮宽度序列的分析研究,探讨了华山地区油松对气候环境响应的敏感性,结果表明在华山地区油松对气温和降水的响应均高于华山松,与 5～6月平均温度相关较高,且通过了0.01显著性信度检验。在此基础上,我们重建了华山地区 1558～2006年间 5～6月的平均温度,重建序列的方差解释量达到41%。结果显示： 华山过去449年中,大部分年份 5～6月平均温度在平均值附近波动,变幅不大; 重建序列可与秦岭南五台 5～7月温度序列进行良好对比,其年际间相关系数达到了0.49(N＝246, p<0.0001)。华山地区20世纪 20～30年代初的暖期略偏低; 20世纪30年代中期至50年代是整个重建时段中低温持续时间较长的时段; 20世纪60年代之后,气温波动平缓; 从20世纪70年代开始快速升温,对全球变暖有较强响应。  相似文献   

长白山红松、水曲柳的能量与物质分析     

张郁  秦丽杰  吴东辉  周密 《山地学报》2002,20(2):241-245

通过对长白山地区典型样地的调查、测定和分析，以红松、水曲柳为代表树种，对其进行了能量与物质研究，得出红松和水曲柳的化学能模型以及物质含量变化图，从而为揭示森林生态系统中物质与能量的运动规律提供了科学依据。  相似文献   

云南上新世杜鹃属和松属化石木研究及其古气候意义          下载免费PDF全文

扆铁梅  李承森  姜笑梅  王宇飞 《古地理学报》2002,4(4):90-98

研究了云南西部龙陵县上新世的化石木。鉴定出两种木材类型。杜鹃花科杜鹃属的似腋花杜鹃Rhododendron cf. racemosum Franchet，其主要木材特征有散孔材，生长轮略明显，导管具多角形轮廓，螺纹加厚出现在整个导管壁上，梯状穿孔板，射线异形II型。松科华山松Pinus armandii Franchet的主要特征有交叉场纹孔窗格状，具正常轴向和纵向树脂道，且泌脂细胞壁薄，射线管胞内壁平滑或具稀疏的微锯齿。两种类型的化石木在我国均属首次报道。根据化石木结构和现代相应树种和植被的生境范围，当时植物生长于亚热带温凉湿润的山地环境，其海拔大约在1800米左右。  相似文献   

黄土丘陵区人工油松林地土壤水分动态的时间序列分析   总被引：10，自引：1，他引：10  

石辉  刘世荣  孙鹏森  李秧秧 《山地学报》2004,22(4):411-414

利用时间序列分析方法研究了黄土丘陵区人工油松林地土壤水分序列和降水序列之间的关系。在黄土丘陵区，降水时间序列不存在自相关关系，相反土壤贮水量之间存在自相关关系；这说明了前期降水对后期降水没有影响，而前期土壤含水量的高低影响了后期含水量的多少。降水时间序列与人工油松林地0～80cm土层总贮水量序列之间存在相关关系，同时油松林地贮水量与降水时间序列相比表现出1个滞后时间距(1月)，说明贮水量主要受当月和前一个月降水的影响。对于上部三个层次(0～10cm，10-20cm，20～40cm)的贮水动态与降水时间序列相关；而20cm以下的土层，与一个滞后时间距的降水时间序列相关系数增大；说明20cm以上土层的贮水量主要受当月降水的影响，20cm以下土层贮水量与当月和前一个月的降水有关。当月降水可以补充到40cm深土层。  相似文献