科尔沁沙地樟子松人工林土壤粒径分布特征          下载免费PDF全文

陈宇轩  张飞岳  高广磊  丁国栋  张英  刘雪锋 《干旱区地理》2020,43(4):1051-1058

为揭示科尔沁沙地不同林龄沙地樟子松人工林对风沙土粒径分布特征的影响,以中龄、近熟和成熟沙地樟子松人工林风沙土为研究对象,以裸沙地风沙土为实验对照,采用激光衍射技术测定土壤样品粒度组成,计算分析土壤粒度参数特征,绘制土壤粒配曲线。结果显示：（1） 科尔沁沙地樟子松人工林风沙土以砂粒为主,其次是粉粒,黏粒含量最少。随林龄的增长,土壤黏粒、粉粒含量呈增加趋势,砂粒含量呈减少趋势。裸沙地风沙土砂粒含量多高于同层林地土壤。（2） 科尔沁沙地樟子松人工林风沙土质地较粗,分选性较差,偏度值多为正偏度,峰度值多为尖窄,0~10 cm和10~20 cm风沙土分形维数分别为2.18~2.43和1.98~2.17。裸沙地风沙土质地更粗,分选性更好,分形维数更小。（3） 科尔沁沙地樟子松人工林风沙土的粒度频率分布曲线均为双峰型。随林龄的增长,10~20 cm风沙土的土壤颗粒细化滞后于0~10 cm。林地悬移组分的含量高于裸沙地,裸沙地跃移组分的分选性高于林地。科尔沁沙地不同樟子松人工林风沙土粒径分布特征存在显著差异,本研究结果可为科尔沁沙地土地沙漠化防治及生态修复提供理论依据。  相似文献   

无人机遥感影像林地单株立木信息提取   总被引：2，自引：1，他引：1  

董新宇  李家国  陈瀚阅  赵磊  张黎明  邢世和 《遥感学报》2019,23(6):1269-1280

针对无人机遥感技术在提取单株立木信息的限制性问题，提出一种新的自动单株立木信息提取方法。对原始无人机影像进行光谱信息增强处理以突出局部细节特征；通过引入DBI指数自动化确定K-means聚类方法的最优聚类数目，进而对影像像素进行标记；通过利用高斯马尔可夫随机场模型进一步对影像进行分割；使用数学形态学算子等方法对分割结果进行后处理得到单株立木树冠信息，通过图像几何矩原理计算得到单株立木位置以作为其识别的依据。结果表明，应用该提取方法，油松林区和樟子松林区单株立木识别总体精度分别为89.52%和95.65%、单木树冠提取精度分别为81.90%和95.65%，均具有较好地适用性。该方法不需要大量的人工干预和先验知识的输入，大大提高提取方法的自动化程度。  相似文献   

Pine stumps in Irish peats: is their occurrence a valid proxy climate indicator?          下载免费PDF全文

ALWYNNE H. MCGEEVER  FRASER J.G. MITCHELL 《第四纪科学杂志》2015,30(5):489-496

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Reconstructing a cultural fire regime in the Pennsylvania Anthracite Region     

Thomas Saladyga 《自然地理学》2013,34(5):404-422

Abstract

Fire history reconstructions provide fire managers with valuable information regarding historical fire regime dynamics. Yet, in the Central Hardwood Forest Region (CHF), there is an absence of dendroecological studies where frequent wildfires have persisted into the twenty-first century. This study presents the first documented tree-ring reconstruction of fire history in the Pennsylvania anthracite coal-producing region. An approximately 150-year fire chronology was developed from fire-scarred pitch pine (Pinus rigida) and sassafras (Sassafras albidum) collected on Spring Mountain in Schuylkill County. Principal component analysis and k-means cluster analysis were used to identify four fire regime clusters based on interacting fire and non-fire parameters. Results indicate that fires occurred under a variety of moisture conditions and that a mid-twentieth century increase in fire activity on Spring Mountain was associated with the collapse of the regional anthracite industry and possibly amplified by the 1960s drought. Fires continue to burn on Spring Mountain in the twenty-first century, contrary to the dominant pattern of fire exclusion across the CHF. Future research needs are highlighted regarding historical fire regime dynamics and cultural ties to landscape burning in the Pennsylvania Anthracite Region.  相似文献   

Effects on catchment water balance from the management of Pinus plantations on the coastal lowlands of south‐east Queensland,Australia     

Ken A. Bubb  James T. Croton 《水文研究》2002,16(1):105-117

A paired catchment study was conducted over a 10‐year period on the hydrology of an exotic Pinus plantation in the coastal lowlands of south‐east Queensland, Australia. Each catchment was instrumented with a stream monitoring station, tipping bucket rain gauge, and a network of piezometers to monitor the shallow perched water table. After a 6‐year calibration period a harvest treatment was imposed on one catchment (Review): clearfelling approximately 90% of the catchment area, which contained a mature (44‐year‐old) Pinus elliottii plantation. This subsequently was re‐established with a second rotation plantation of a hybrid of P.elliottii × P.caribaea var. hondurensis. The control catchment (Crayfish) contained a P. elliottii plantation similar to that clearfelled at Review. The post‐harvest period was monitored for a further 4 years. Evapotranspiration was found to be the major output flux, with stream flow only a minor component of the study catchments' water budget. Areas with gleyed podzolic soils were found to remain waterlogged for periods up to 7 months following the seasonally high summer rainfall period, with other soils having water logging periods of only a few months. Little change was observed in waterlogging characteristics following harvesting, in contrast to stream flow which increased for 3 years but with evidence of a decline after 5 years. The perched‐watertable piezometric surface indicated that its lateral drainage differs from that of surface flows; the perched‐watertable drainage fluxes from the study catchments seem minor and off‐site movement of solutes (e.g. nutrients and contaminants) via them would be limited. It was identified that the interaction between the perched and deep aquifers was poorly understood, as well as the relative importance of the soil moisture storage of the aquitard clay layer between them. It was concluded that there is a need to undertake more detailed analysis using modelling, and to obtain additional field data on soil‐layer properties and piezometric levels of the deep aquifer. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

Development of a Neolithic pine tree‐ring chronology for northern Scotland     

Andy Moir 《第四纪科学杂志》2012,27(5):503-508

The peatlands of northern Scotland (one of the largest and most intact areas of blanket bog in the world) contain a rare widespread horizon of subfossil pine in stratigraphic context. Eighteen bog pine from three new sites are incorporated into a mean Neolithic pine chronology now composed of subfossil pine from 12 sites, which is tree‐ring‐dated against Irish bog pine chronologies to span 3198–2757 BC. Germination and peaks of radial growth infer drier conditions between 3199 and 3130 BC. Dying‐off phases and depression of growth reflect a change to wetter conditions between 3023 and 3002 BC and a terminal decline of pine between 2809 and 2782 BC. The close synchronization of germination/die‐off phases and major ring‐width variations between sites across this region indicates that the environmental changes are probably triggered by climate change. Twenty‐four bog pine samples remain unmatched. Future multi‐discipline research into this important example of climatic change at the Neolithic/Bronze Age transition is recommended. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

小陇山国家级自然保护区油松种群更新及生存   总被引：1，自引：0，他引：1  

巨天珍  米彩燕  师贺雄  宋小伟  张彦文  张宋智 《山地学报》2012,(1):36-40

以种群生命表及生存分析理论为基础,以林木径级结构代表年龄结构,采用分段匀滑技术,编制小陇山自然保护区油松种群特定时间生命表,绘制死亡率曲线、消失率曲线、存活曲线、生存函数曲线,分析种群数量动态特征,并对其年龄跟胸径进行线性回归。结果表明:1.油松种群年龄结构表现为稳定型。2.油松种群死亡率和消失率曲线变化趋势基本一致,存活曲线趋于Deevey-Ⅱ型。4个生存函数曲线表明,油松种群具有前期稳定、中后期锐减和末期衰退的特点。3.油松年龄与其胸径线性相关。  相似文献   

On modelling the effects of afforestation on acidification in heterogeneous catchments at different spatial and temporal scales     

A. J. Wade  C. Neal  C. Soulsby  S. J. Langan  R. P. Smart 《Journal of Hydrology》2001,250(1-4):149-169

A modelling approach is presented for simulating and predicting future changes in streamwater Gran alkalinity throughout a large, heterogeneous river system. The methodology is based on integrating End Member Mixing Analysis (EMMA), the Model of Acidification of Groundwater in Catchments (MAGIC) and spatial data describing the catchment characteristics stored on a Geographical Information System (GIS). These are integrated within a Functional Unit Network (FUN) to predict the changes in Gran alkalinity resulting from possible future changes in atmospheric deposition and land use (low intensity afforestation) in the River Dee catchment, NE Scotland. Model results indicate that declining sulphate and constant nitrogen deposition, combined with low intensity Scots pine (Pinus sylvestris) afforestation are unlikely to contribute significantly to streamwater acidification.  相似文献   

Drought is the major limiting factor for tree-ring growth of high-altitude Canary Island pines on Tenerife   总被引：2，自引：0，他引：2  

Stig Jonsson  Björn Gunnarson  & Constantino Criado 《Geografiska Annaler: Series A, Physical Geography》2002,84(1):51-71

This is a detailed study of 50 wood cores sampled from 25 Canary Island pines ( Pinus canariensis ) growing in a subtropical climate close to the tree limit (at Lomo de Retamar, 2000–2100 m a.s.l.) on the southern, leeward side of Tenerife.
The Canary Island pines form tree-rings and, similarly to temperate pines, earlywood is formed during spring. But many pines fail to form tree-rings every year and one purpose for this paper has been to find a way to overcome this problem. Another purpose has been to see what correlations, if any, exist between the ring widths and meteorological data. Meteorological data have been collected since 1916 at the nearby Izaña meteorological observatory. It was also important to find the limiting factor for growth of Canary Island pines close to the tree limit.
Through cross-dating, missing rings were found to be typical for younger parts of older trees; in the same years younger trees instead had low growth. Some trees lacked more than 20 rings in a century. This study shows that it is possible to compensate for missing rings, at least when the number of missing rings is less than 10%.
Correlation studies showed that the growth of the tree rings was mainly due to the precipitation factor, particularly the annual precipitation one year before the ring formation, but also due to temperature. Strangely enough, multiple linear regression gave the highest correlation coefficient (0.50) for a combination of annual precipitation one year earlier and temperature four years earlier.  相似文献   

Response of needle dark respiration of Pinus koraiensis and Pinus sylvestriformis to elevated CO_2 concentra-tions for four growing seasons’ exposure     

ZHOU YuMei  HAN ShiJie  ZHANG HaiSen  XIN LiHua & ZHENG JunQiang Institute of Applied Ecology  Chinese Academy of Sciences  Shenyang  China  Shenyang Agricultural University  Shenyang  China 《中国科学D辑(英文版)》2007,(4)

The long-term effect of elevated CO2 concentrations on needle dark respiration of two coniferous spe- cies—Pinus koraiensis and Pinus sylvestriformis on the Changbai Mountain was investigated using open-top chambers. P. koraiensis and P. sylvestriformis were exposed to 700, 500 μmol·mol-1 CO2 and ambient CO2 (approx. 350 μmol·mol-1) for four growing seasons. Needle dark respiration was meas- ured during the second, third and fourth growing seasons’ exposure to elevated CO2. The results showed that needle dark respiration rate increased for P. koraiensis and P. sylvestriformis grown at elevated CO2 concentrations during the second growing season, could be attributed to the change of carbohydrate and/or nitrogen content of needles. Needle dark respiration of P. koraiensis was stimu- lated and that of P. sylvestriformis was inhibited by elevated CO2 concentrations during the third growing season. Different response of the two tree species to elevated CO2 mainly resulted from the difference in the growth rate. Elevated CO2 concentrations inhibited needle dark respiration of both P. koraiensis and P. sylvestriformis during the fourth growing season. There was consistent trend be- tween the short-term effect and the long-term effect of elevated CO2 on needle dark respiration in P. sylvestriformis during the third growing season by changing measurement CO2 concentrations. How- ever, the short-term effect was different from the long-term effect for P. koraiensis. Response of dark respiration of P. koraiensis and P. sylvestriformis to elevated CO2 concentrations was related to the treatment time of CO2 and the stage of growth and development of plant. The change of dark respiration for the two tree species was determined by the direct effect of CO2 and long-term acclimation. The prediction of the long-term response of needle dark respiration to elevated CO2 concentration based on the short-term response is in dispute.  相似文献