Plant Area Index and microclimate underneath shrub species from a Chilean semiarid community     

Y. Tracol  J.R. Gutiérrez  F.A. Squeo 《Journal of Arid Environments》2011,75(1):1-6

In drylands, environmental conditions under shrub canopy differ from those found in open sites. We should expect that microclimate conditions under shrubs with distinct canopy architecture should also be different. Plant Area Index (PAI) of the three most abundant shrubs species (Porlieria chilensis, Adesmia bedwellii and Proustia cuneifolia) in Bosque Fray Jorge National Park, north-central Chile was measured using a Plant Canopy Analyzer. During two years (2004-2005), we recorded the Relative Humidity and Air Temperature underneath and away from the canopy of the shrubs.The three shrub species showed significant differences in PAI. Microclimate at 30 cm and 2 m above the soil in the open conditions were drier and warmer than underneath shrub canopies. Vegetation patches generate moderate microclimate conditions.Canopy structure can buffer climatic variability, contributing to high herbaceous productivity as well as shrub recruitment. Reflecting shrub architecture and observed PAI values, the lowest microclimate variations were observed under the canopies of P. chilensis, followed by P. cuneifolia and finally A. bedwellii. We bring a novel approach quantifying the Plant Area Index instead of the Plant cover and using a low cost method that integrates the distribution of leaves and may be derived from remote sensing products.  相似文献   

Thermal utility of desert vegetation for the Egyptian tortoise and its conservation implications     

《Journal of Arid Environments》2013

We examined the monthly shrub use and the thermal utility of the desert shrub, Artemisia monosperma, by the globally endangered Egyptian tortoise, Testudo kleinmanni, in Sinai, Egypt. A. monosperma is a common desert shrub that is often used by the Egyptian tortoise as a refuge. Egyptian tortoises had the highest mean carapace temperature and lowest carapace temperature range during summer months, which coincided with the aestivation period and the Egyptian tortoise's use of larger shrubs. Our results suggest that the thermal characteristics of larger shrubs are important to the microhabitat use of the Egyptian tortoise and likely long-term survival. Larger shrubs were effective as thermal refuges that ameliorated and stabilized micro-climatic variation. Smaller shrubs were not an adequate thermal refuge in the summer because the mean temperature, and its fluctuation range beneath them was too high to offer adequate refuge during aestivation. The tortoises used the smaller shrubs in the fall, winter, and spring seasons for basking, thermoregulation, and concealment and used shrubs with a cover diameter greater than one meter during the aestivation season. The future conservation of the Egyptian tortoise should focus on protecting and restoring existing habitat by maintaining large perennial shrubs for refuge and aestivation sites.  相似文献   

Soil erosion rates in rangelands of northeastern Patagonia: A dendrogeomorphological analysis using exposed shrub roots     

Marcelo Pablo Chartier  Csar Mario Rostagno  Fidel Alejandro Roig 《Geomorphology》2009,106(3-4):344-351

Soil erosion is an important process of land degradation in many rangelands and a significant driver of desertification in the world's drylands. Dendrogeomorphology is an alternative to traditional methods for determining soil erosion rate. Specifically, the vertical distance between the upper portion of exposed roots and the actual soil surface can be used as a bioindicator of erosion since plant establishment. In this study, we determined (i) the soil erosion rate from exposed roots of the dwarf shrub Margyricarpus pinnatus [Lam.] Kuntze in two ecological sites in the northeastern rangelands of Patagonia and (ii) the relationship between shrub age and upper root diameter. We selected two ecological sites, a pediment-like plateau and a flank pediment, where the dominant soils were Xeric Haplocalcids and Xeric Calciargids, respectively. The soil erosion rates in the pediment-like plateau and in the flank pediment were 2.4 and 3.1 mm yr^− 1, respectively. Data clearly indicate a high rate of soil erosion during the mean 8-year life span of the dwarf shrubs in degraded patches, which represent ~ 10% of surface cover in the study area. Simple linear regression analysis yielded a highly significant predictive model for age estimation of M. pinnatus plants using the upper root diameter as a predictor variable. The measurement of ground lowering against datable exposed roots represents a simple method for the determination of soil erosion rates. In combination with other soil surface features, it was used to infer the episodic nature of soil erosion. This approach could be particularly useful for monitoring the effects of land management practices on recent soil erosion and for the establishment of records in regions where historical data regarding this process are scarce or absent.  相似文献   

喀斯特石漠化概念演绎及其科学内涵的探讨   总被引：252，自引：26，他引：226  

王世杰 《中国岩溶》2002,21(2):101-105

通过喀斯特石漠化概念、演绎过程的介绍,深入探讨了喀斯特石漠化的科学内涵。喀斯特石漠化是指在亚热带脆弱的喀斯特环境背景下,受人类不合理的社会经济活动的干扰破坏,造成土壤严重侵蚀,基岩大面积出露,土地生产力严重下降,地表出现类似荒漠景观的土地退化过程。喀斯特石漠化是土地荒漠化的主要类型之一,它以脆弱的生态地质环境为基础,以强烈的人类活动为驱动力,以土地生产力退化为本质,以出现类似荒漠景观为标志。   相似文献   

Effects of biological soil crusts on water infiltration and evaporation Yanchi Ningxia,Maowusu Desert,China   总被引：4，自引：0，他引：4  

《国际泥沙研究》2016,(4):311-323

Biological soil crusts serve as a vanguard for improving the ecological environment in arid, semi-arid desertification areas. It is a good indicator of the level of improvement which the local ecological environment is undertaking. In desert areas, water condition is a key factor of improving the ecological environment. As a first layer protection, biological crusts play an important role in local vegetation succession due to their abilities to conserve and maintain moisture. Using Maowusu desert in Yanchi of Ningxia province as an example, after three years of research, this paper chooses three kinds of biological crusts including lichen, moss and cyanobacterial which are under the cover of Artemisia ordosica as research objects. The results of this study indicate that, the closer biological crusts are to Artemisia ordosica vegetation, the thicker they become. In the same position of Artemisia ordosica vegetation, the thickness of moss crusts is the highest, followed by lichen crusts, and the thickness of cyanobacterial crusts is the lowest. Biological soil crusts coverage protects the natural water content of soil layers from 0 to 5 cm. Also, it effects falling water to infiltrate deeper, and cannot prevent the surface water content from evaporating effectively. The effect of biological crusts blocking water infiltration decreases with the increase of rainfall. At the same rainfall level, moss crusts provide the strongest water infiltration blockage, followed by lichen crusts and cyanobacterial crusts. With the increase of rainfall, the depth of water infiltration increases. At the same rainfall level, the relationship of water infiltration depth is as follows: cyanobacterial crusts 4 lichen crusts 4 moss crusts. With the increase of biological crusts thickness, they blocking water infiltration capacity is stronger, and the depth of water infiltration is smaller. Analysis on the characteristic of simulated rainfall process on biological crusts shows that sandy land can be fixed by applying appropriate artificial biological crusts to build a sustainable forest pro-tection system and to create a stable ecosystem in desertification area.  相似文献   

利用遥感和GIS研究塔里木河下游阿拉干地区土地沙漠化   总被引：66，自引：0，他引：66  

王让会  樊自立 《遥感学报》1998,2(2):137-142

新疆塔里木河流域受人类活动的影响,特别是由于水资源利用的不合理,不同区域出现了一系列生态环境问题,下游地区普遍存在的沙漠化现象表现得尤为突出。通过应用多时相（１９５９年、１９８３年、１９９２年）、多波段、多平台的遥感信息,在野外调研的基础上编制阿拉干地区不同年代沙漠化类型图,并在ＡＲＣ／ＩＮＦＯ软件支持下,对图件进行编辑处理,制作沙漠化动态图;通过ＧＩＳ数据库提供的资源环境定量数据,应用系统论、信息论及控制论的观点分析阿拉干地区沙漠化的演化过程,并借助于ＧＭ（１,１）模型,预测阿拉干地区土地沙漠化的发展趋势。  相似文献   

福建省长汀县河田镇的水蚀荒漠化及其治理   总被引：2，自引：0，他引：2  

陈志清 《地理科学进展》1998,17(2):67-72

福建省长汀县河田镇的水蚀荒漠化是我国南方花岗岩丘陵地区的一个典型代表,严重的水蚀荒漠化主要由两个因素造成：在自然因素方面,一方面由于地表物质主要由风化强烈的花岗岩组成,为水蚀荒漠化的发展提供了物质基础,另一方面丰沛且集中的降水增加了水蚀荒漠化的强度;在社会因素方面,人口剧增加大了对土地的压力,几次大规模乱砍滥伐又使植被大量破坏。中华人民共和国成立以来,采取了科学试验研究与群众治理实践相结合的方针,开展了水蚀荒漠化的防治工作,使治理区生态环境得到明显改善。  相似文献   

松辽平原区荒漠化形成与发展的地质基础   总被引：1，自引：0，他引：1  

赵福岳  路云阁  姜德仁  陈树旺  姜琦刚 《国土资源遥感》2008,19(3):90-93

利用卫星数据,结合实地地质调查、光释光（Optically Stimulated Luminecence, OSL）测年及孢粉数据,从地层、新构造和沉积环境等角度阐述了松辽平原晚更新世晚期湖积环境的形成与变化,提出了松辽平原晚更新世晚期湖积环境或湖积物质是区内荒漠化形成与发展的地质基础。  相似文献   

基于地表定量参数的沙漠化遥感监测方法     

曾永年  冯兆东  向南平 《国土资源遥感》2005,16(2):40-44

利用野外沙漠化调查的定位数据和ETM+ 遥感数据，在实验分析的基础上，探讨了沙漠化程度与地表参数之间的定量关系，即沙漠化与植被指数（NDVI）、地表辐射温度（LST）之间的关系，提出了综合反映沙漠化土地生物物理特征的遥感监测指数——沙漠化遥感监测差值指数（DDI），为沙漠化遥感监测提供有效的定量化方法。  相似文献   

Recent trends in vegetation dynamics in the African Sahel and their relationship to climate   总被引：26，自引：1，他引：26  

Stefanie M. Herrmann  Assaf Anyamba  Compton J. Tucker   《Global Environmental Change》2005,15(4):394-404

Contrary to assertions of widespread irreversible desertification in the African Sahel, a recent increase in seasonal greenness over large areas of the Sahel has been observed, which has been interpreted as a recovery from the great Sahelian droughts. This research investigates temporal and spatial patterns of vegetation greenness and rainfall variability in the African Sahel and their interrelationships based on analyses of Normalized Difference Vegetation Index (NDVI) time series for the period 1982–2003 and gridded satellite rainfall estimates. While rainfall emerges as the dominant causative factor for the increase in vegetation greenness, there is evidence of another causative factor, hypothetically a human-induced change superimposed on the climate trend.  相似文献