低覆盖度不同配置灌丛内风流结构与防风效果的风洞实验   总被引：4，自引：9，他引：4  

杨文斌  卢琦  吴波  杨红艳  赵爱国  王晶莹  胡小龙 《中国沙漠》2007,27(5):791-796

 低覆盖度灌木群丛是干旱、半干旱区广泛分布且具有重要意义的植被，也是人工修复沙地应遵从的植被。通过风洞试验模拟了覆盖度在20%左右的三种水平配置格局的灌木群丛内风流结构与防风固沙效果。结果表明：①水平配置格局不同，低覆盖度灌木群丛的防风效果差异显著，行带式模式具有非常显著的阻碍和降低风速的作用（风速降低36%~43%）;等株行距模式次之，风速降低7%~28%;随机不均匀配置模式内局部有风速抬升现象，② 行带式模式内形成规整的随灌丛带波动的流场结构，而随机不均匀配置模式内形成由多个风影区和风速加速区组合的非常复杂的流场结构，等株行距模式居于二者之间。③ 带间宽度在56 cm和64 cm时的防风效果较带宽为32 cm和40 cm好。说明覆盖度降低到11%~13%，行带式模式的防风效果仍然不会降低。④两行一带配置均表现防风效果优于单行配置，且随试验风速的增大防风效果更好。  相似文献   

Plant functional types and climate along a precipitation gradient in temperate grasslands, north-east China and south-east Mongolia   总被引：1，自引：0，他引：1  

Jian Ni 《Journal of Arid Environments》2003,53(4):501-516

Using data from three field surveys along a precipitation gradient of temperate grasslands in north-east China (the Northeast China Transect, NECT) and south-east Mongolia, the spatial distribution of six plant functional types (PFTs): C₃ species, C₄ species, grasses, shrubs, forbs and succulents and their relationships with climate were analysed. The spatial distribution of different PFTs varies in different regions and in different grassland types of the study area. The species richness in each PFT also has different relationships with climate (significantly or not). Generally, the number of C₃ species, C₄ species, grasses and forbs have positive relationships with precipitation and aridity. Shrubs have negative relationship with precipitation and aridity. Succulents were found to have no relationship with precipitation and aridity. Shrubs, grasses and forbs have stronger relationships with precipitation than C₃ and C₄ species. The relationships between C₃ species, forbs and aridity are more significant than with precipitation. On a regional basis, the combined effect of precipitation and temperature, the aridity, is more significantly correlated with the distribution of C₃ species and forbs, which are more dominant in the study area, than with C₄ species, grasses and succulents.  相似文献   

High-resolution images reveal rate and pattern of shrub encroachment over six decades in New Mexico, U.S.A.     

S. C. Goslee  K. M. Havstad  D. P. C. Peters  A. Rango  W. H. Schlesinger 《Journal of Arid Environments》2003,54(4):755-767

Encroachment of the shrub Prosopis glandulosa Torr. (honey mesquite) into semi-arid grasslands is a serious concern in the south-western United States, yet little is known about the long-term dynamics of the invasion process. We used ten high-resolution aerial and satellite images taken from 1936 to 1996 to track the population dynamics and spatial pattern of all P. glandulosa greater than 2 m in diameter on a 75 ha area in southern New Mexico.Shrub cover and patch numbers increased from 1936 to the 1970s, then stabilized at 43% cover and 83 patches ha⁻¹. Individual patches were extremely persistent: 95% of the area occupied by shrub patches in 1936 was still occupied in 1996. Recruitment into the 2 m size class was more variable: 0·6–5·2% year⁻¹ (mean 0·8% year⁻¹). Patch-shape complexity increased from 1936 to 1983 as adjacent shrubs merged, and then declined as those clusters filled in and became rounder. Spatial pattern of shrubs showed a distinct trend over time: strongly clustered in 1936 at lag distances up to 250 m, then random arrangement at all scales, and by 1983 pattern was regular at lag distances greater than 100 m. There was no clear relationship with precipitation.The use of remote sensing imagery allowed us to examine one site over time, and revealed patterns in population dynamics and spatial pattern that would not have been visible otherwise. Comparison of field estimates collected in 2001 with 1996 image data suggest that the canopy cover estimates were accurate, but shrub densities were seriously underestimated in the satellite photographs, which do not show shrubs smaller than 2 m diameter. As long as limitations of the imagery are understood, these methods can be applied over a larger and more heterogeneous area to examine environmental correlates of invasion success.  相似文献   

Short-term effects of shrub control on two different plant communities in Argentina     

C. B. Passera  O. Borsetto  L. I. Allegretti 《Journal of Arid Environments》1996,34(4):415-420

The aim of this work was to study the effect of controlling jarilla (Larreaspp.), nonforage shrubs for livestock, on two plant communities with different forage production in the arid mid-west of Argentina. Total vegetation cover, forage species cover and carrying capacity were determined during three growing seasons, for cleared and uncleared plots. At the end of the study, significant differences were found in theLarrea cuneifoliacommunity, where average forage species cover increased by 156% over the control, and greater carrying capacity (129%) was also obtained from the cleared treatment. No significant differences were found in theLarrea divaricatacommunity. Data lead us to recommend shrub control as an improvement practice only in areas with low forage species cover and poor carrying capacity.  相似文献   

灌丛对流动沙地土壤特性和草本植物的影响   总被引：28，自引：16，他引：12  

赵哈林  苏永中  张华  赵丽娅  周瑞莲 《中国沙漠》2007,27(3):385-390

通过对流动沙地灌丛内外土壤特性、土壤养分含量、土壤种子库和草本植物群落特征的差异性调查,分析了灌丛对沙地土壤特性和林下草本植被的影响。结果表明,在流动沙地0—20 cm土壤中细沙、极细沙、粘粉粒、有机质、总氮和总磷、有效磷和土壤水分含量,小叶锦鸡儿灌丛下分别较灌丛外高17.3%、4.4%、 49.5%、43.8%、40.0%、23.1%、16.3%和10.8%,黄柳灌丛下较灌丛外分别高3.5%、21.3%、0.0%、20.0%、16.7%、8.3%、10.6%和28.1%。小叶锦鸡儿、差不嘎蒿和黄柳灌丛下凋落物蓄积量要比灌丛外分别高18.3倍、365.2倍和15.5倍。差不嘎蒿灌丛下土壤种子库密度较灌丛外高10.9倍。原为半固定、半流动沙地优势种的多年生草本植物白草,不仅能在流动沙地灌丛下存活,而且具有较高的密度、高度、盖度和地上生物量。结果还表明,从灌丛中心到灌丛边缘,凋落物产量、土壤种子库密度、草本植物密度、盖度、生物量均存在明显的递减梯度,在灌丛外不远处消失。这些结果说明,在流动沙地,灌丛具有明显的“肥岛”效应和“保种”作用。  相似文献   

Patterns of shrub species richness and abundance in relation to environmental factors on the Alxa Plateau: Prerequisites for conserving shrub diversity in extreme arid desert regions     

XinRong Li  HuiJuan Tan  MingZhu He  XinPing Wang  XiaoJun Li 《中国科学D辑(英文版)》2009,52(5):669-680

Shrub species are considered the dominant plants in arid desert ecosystems, unlike in semiarid steppe zones or in grassland ecosystems. On the Alxa Plateau, northern China, sparse vegetation with cover ranging from 15% to 30% is characterized mainly by multifarious shrubs because herbaceous species are strongly restricted by the extreme drought climate, wind erosion, overgrazing and sand burial. Patterns in shrub species richness and species abundance in relation to environmental conditions were examined by DCA (detrended correspondence analysis) and interpreted by a biplot. The relationships between species diversity and environmental factors were examined using regression analyses. Our results show that the distributions of the shrub species in response to environmental conditions can be grouped into four ecological types, corresponding with the biological traits of the shrubs and their responses to the gradients of soil texture and soil water content. Patterns in species richness and species abundance were mainly determined by the deeper soil water content, instead of the soil texture as hypothesized by numerous studies in semiarid grasslands. With exception of the deeper soil water content, soil organic matter and total N content were positively correlated with species abundance, while pH was negatively correlated with it. These findings imply that it is vital for current shrub diversity conservation to reduce agricultural water use in the middle reaches of the Heihe River, which supplies water for the lower reaches in the western parts of the plateau, and to reduce the amount of groundwater exploitation and urban and oasis water use, to increase the water supply from Helan Mountain to the eastern desert of the Alxa Plateau. Supported by National Key Technology R & D Program (Grant Nos. 2007BAD46B03, 2006BAD26B0201) and National Natural Science Foundation of China (Gant No. 40825001)  相似文献   

Gender-related differences of shrubs in stands of Atriplex canescens with different histories of grazing by cattle     

Andres F. Cibils  David M. Swift  Richard H. Hart 《Journal of Arid Environments》2000,46(4):383

Atriplex canescens is a relatively common dioecious shrub in western North America. It is considered a valuable forage resource for both wild and domestic herbivores. Sex ratios and shrub dimensions were recorded in stands of tetraploid A. canescens that had been either protected from cattle grazing or summer- or winter-grazed by cattle for at least 20 years. Stem diameter and crown shape were used as surrogates for shrub age which could not be estimated by counting growth rings. Shrub sex ratios in exclosures were significantly more female biased than the empirically derived ratio for tetraploid A. canescens (55 female:35 male: 10 monecious). Conversely, shrub sex ratios in grazed pastures were not significantly different from the empirical ratio. Proportion of female shrubs in exclosures was significantly higher than in grazed pastures. Proportion of male shrubs, on the other hand, was similar in exclosures and grazed pastures. Winter-grazed shrub stands were apparently younger than both summer-grazed and protected shrubs. Protected shrubs appeared to be the oldest. Grazed female shrubs were apparently younger than grazed males, however, shrub ages of protected male and female shrubs were apparently not different. Cattle-grazing may have affected female shrubs more negatively at this site, causing gender-based differential mortality, and/or sex-shifting. Such processes could account for the differences in sex ratios, and for the apparent gender-related differences in shrub age that were observed.  相似文献   

石羊河下游白刺灌丛演替发育过程的土壤呼吸及其影响因素分析   总被引：5，自引：0，他引：5  

靳虎甲  马全林  张有佳  曾新德 《中国沙漠》2012,32(1):140-147

对不同类型土壤呼吸及其影响因素的研究有助于了解区域生态过程和全球气候变化。在石羊河下游,根据白刺灌丛生长及其生境状况,选择了初期发育、稳定、衰退、严重衰退的白刺灌丛植被,采用Li-8100土壤碳通量监测系统,研究了白刺灌丛演替过程的土壤呼吸日变化。结果表明,各发育阶段的白刺灌丛土壤呼吸最大值均出现在12:00,呼吸速率均值大小顺序为:稳定阶段＞初期发育阶段＞衰退阶段＞严重衰退阶段。各发育阶段不同坡位土壤呼吸日变化动态存在差异,但平均值都表现为迎风坡＞背风坡＞丘间地。建立各因素与土壤呼吸之间的模型发现,白刺的生长状况与土壤呼吸之间的相关性达到极显著,表层土壤含水量对土壤呼吸的影响大于深层土壤,而二次函数较其他模型能更好地表达地下10 cm温度与土壤呼吸之间的关系,且两者之间相关性达到极显著。  相似文献   

祁连山东段山地典型灌丛枯落物及土壤水源涵养功能研究   总被引：2，自引：0，他引：2  

杨晓霞  赵锦梅  张雪  樊宇航  张斌  王婧楠  张碧艳 《干旱区地理》2022,45(1):197-207

为探讨高寒地区灌丛枯落物层及土壤层的水源涵养功能,以祁连山东段6种典型灌丛的枯落物和土壤为研究对象,采用野外调查与室内浸泡相结合的方法,对枯落物及土壤水文特征进行了研究.结果表明:(1)6种灌丛枯落物的蓄积量范围为0.23～3.61 t·hm-2,大小排序为山生柳>硬叶柳>绣线菊>金露梅>头花杜鹃>千里香杜鹃.(2)枯...  相似文献   

几种旱生灌木种子萌发特性及化学成分     

李茜  任运涛  牛得草  张宝林  赵慧  傅华 《中国沙漠》2015,35(2):345-351

研究了旱生灌木白沙蒿(Artemisia sphaerocephala)、红砂(Reaumuria soongorica)、梭梭(Haloxylon ammodendron)、羊柴(Hedysarum mongdicum)、霸王(Zygophyllum xanthoxylum)、白刺(Nitraria tangutorum)、沙冬青(Ammopiptanthus mongolicus)、柠条(Caragana korshinskii)种子的化学成分、适宜发芽条件下的吸水发芽特性及两者之间的关系,测定和计算了其发芽率、吸水率,淀粉、脂肪、蛋白质、碳(C)、氮(N)、磷(P)含量及C:N、C:P、N:P值,并分析了这些指标间的相关性,以期归纳出西北干旱荒漠区植物种子萌发适应干旱环境的基本特性。结果表明:脂肪含量、蛋白质含量、氮含量与种子的最低萌发需水量之间呈显著正相关,而种子的单一化学成分及C:N、C:P、N:P值并没有对发芽率形成显著影响。8种植物种子萌发对环境的适应机制大致可分为两类:需要外界较高水分供应,萌发迅速而集中;不需要外界较高水分的供应,萌发持续而分散。  相似文献