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Radial profile of sap flow velocity in mature Xinjiang poplar(Populus alba L. var. pyramidalis) in Northwest China

Journal of Arid Land 2014年第5期6卷 612-627页

作者： HongZhong DANG TianShan ZHA JinSong ZHANG Wei LI shizeng liu Institute of Desertification Studies Chinese Academy of Forestry School of Soil and Water Conservation Beijing Forestry University Research Institute of Forestry Chinese Academy of Forestry Gansu Desert Control Research Institute

Estimation of the transpiration rate for a tree is generally based on sap flow measurements within the hydro-active stem xylem. In this study, radial variation of sap flow velocity（Js） was investigated at five depths of the xylem（1, 2, 3, 5 and 8 cm under the cambium） in three mature Xinjiang poplar（Populus alba L. var. pyramidalis） trees grown at the Gansu Minqin National Studies Station for Desert Steppe Ecosystem from May to October 2011. Thermal dissipation probes of various lengths manufactured according to the Granier＇s design were installed into each tree for simultaneous observation of the radial patterns of Js through the xylem. The radial patterns were found to fit the four-parameter GaussAmp equation. The peak Js was about 27.02±0.95 kg/（dm2？d） at approximately 3 to 5 cm deep from the cambium of the three trees,and the lowest Js appeared at 1 cm deep in most of the time. Approximately 50% of the total sap flow in Xinjiang poplar occurred within one-third of the xylem from its outer radius, whereas 90% of the total sap flow occurred within two-fifth of the xylem. In addition, the innermost point of the xylem（at 8-cm depth）, which appeared as the penultimate sap flow in most cases during the study period, was hydro-active with Js,8 of 7.55±3.83 kg/（dm2？d）. The radial pattern of Js was found to be steeper in midday than in other time of the day, and steeper diurnal fluctuations were recorded in June, July and August（the mid-growing season）. Maximum differences between the lowest Js（Js,1 or Js,8） and the highest Js（Js,3 or Js,5） from May through October were 12.41, 17.35, 16.30, 18.52, 12.60 and 16.04 g/（cm2？h）, respectively. The time-dependent changes of Js along the radial profile（except at 1-cm depth） were strongly related to the reference evapotranspiration（ET0）. Due to significant radial variability of Js, the mean daily sap flow at the whole-tree level could be over-estimated by up to 29.69% when only a single probe at depth of 2 cm was used. However, t

关键词： sap flow radial pattern Populus alba L.var.pyramidalis reference evapotranspiration(ET0) Granier method

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Effects of sand-fixing and windbreak forests on wind flow:a synthesis of results from field experiments and numerical simulations

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Journal of Arid Land 2017年第1期9卷 1-12页

作者： ZHAN Kejie liu shizeng YANG Zihui FANG Etian ZHOU Lanping HUANG Ning Key Laboratory of Mechanics on Western Disaster and Environment in China(Ministry of Education) Department of MechanicsLanzhou UniversityLanzhou 730000China Minqin National Station for Desert Steppe Ecosystem Studies Minqin 733000China

Sand-fixing and windbreak forests are widely used to protect or/and improve the ecological environments in arid and semi-arid regions. A full understanding of wind flow characteristics is essential to arranging the patterns of these protective forests for enhancing the effectiveness. In this study, the wind velocity over the underlying surface with sand-fixing forests and windbreak forests at the heights of 1–49 m was monitored from two 50-m high observation towers in an oasis of Minqin, Gansu Province of China. The wind velocities were simulated at different locations over these protective forests between those two towers by a two-dimensional Computational Fluid Dynamics（CFD） model. The results showed that at the heights of 1–49 m, the wind velocity profiles followed a classical logarithm law at the edge of the oasis and a multilayer structure inside the oasis. With increasing number of sand-fixing forest and windbreak forest arrays, the wind velocity at the heights of 1–49 m generally decreased along the downstream direction of the prevailing wind. Specifically, below the height of windbreak forests, the wind velocity decelerates as the airflow approaches to the windbreak forests and then accelerates as the airflow passes over the windbreak forests. In contrast, above the height of windbreak forests, the wind velocity accelerates as the airflow approaches to the windbreak forests and then generally decelerates as the airflow passes over the windbreak forests. Both the array number and array spacing of sand-fixing and windbreak forests could influence the wind velocity. The wind protection effects of sand-fixing forests were closely related to the array spacing of windbreak forests and increased with the addition of sand-fixing forests when the array of the forests was adequately spaced. However, if the array spacing of windbreak forests was smaller than seven times of the heights of windbreak forests, the effects were reduced or completely masked by the effects of

关键词： wind velocity sand-fixing forest windbreak forest computational simulation Minqin

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Hyper-spectral characteristics of rolled-leaf desert vegetation in the Hexi Corridor, China

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Journal of Arid Land 2019年第3期11卷 332-344页

作者： WEI Huaidong YANG Xuemei ZHANG Bo DING Feng ZHANG Weixing liu shizeng CHEN Fang College of Geography and Environment Science Northwest Normal UniversityLanzhou 730070China State Key Laboratory Breeding Base of Desertification and Aeolian Sand Disaster Combating Gansu Desert Control Research InstituteLanzhou 730070China Key Laboratory of Remote Sensing of Gansu Province Northwest Institute of Eco-Environment and ResourcesChinese Academy of SciencesLanzhou 730000China

Desert plants survive harsh environment using a variety of drought-resistant structural modifications and physio-ecological ***-leaf plants roll up their leaves during periods of drought,making it difficult to distinguish between the external structures of various types of plants,it is therefore necessary to carry out spectral characteristics analysis for species identification of these rolled-leaf *** on hyper-spectral data measured in the field,we analyzed the spectral characteristics of seven types of typical temperate zone rolled-leaf desert plants in the Hexi Corridor,China using a variety of mathematical transformation *** results show that:(1)during the vigorous growth period in July and August,the locations of the red valleys,green peaks,and three-edge parameters,namely,the red edge,the blue edge,and the yellow edge of well-developed rolled-leaf desert plants are essentially consistent with those of the majority of terrestrial vegetation types;(2)the absorption regions of liquid water,i.e.,1400-1500 and 1600-1700 nm,are the optimal bands for distinguishing various types of rolled-leaf desert plants;(3)in the leaf reflectance regions of 700-1250 nm,which is controlled by cellular structure,it is difficult to select the characteristic bands for differentiation rolled-leaf desert vegetation;and(4)after processing the spectral reflectance curves using a first-order differential,the envelope removal method,and the normalized differential ratio,we identify the other characteristic bands and parameters that can be used for identifying various types of temperate zone rolled-leaf desert plants,i.e.,the 510-560,650-700 and 1330-1380 nm regions,and the red edge *** general,the mathematical transformation methods in the study are effective tools to capture useful spectral information for species identification of rolled-leaf plants in the Hexi Corridor.

关键词： rolled-leaf desert vegetation spectral characteristics mathematical transformation vegetation identification Hexi Corridor

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Spatial-temporal dynamics of desert vegetation and its responses to climatic variations over the last three decades:a case study of Hexi region in Northwest China

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Journal of Arid Land 2016年第4期8卷 556-568页

作者： YANG Xuemei liu shizeng YANG Taibao XU Xianying KANG Caizhou TANG Jinnian WEI Huaidong Mihretab G GHEBREZGABHER LI Zhiqi State Key Laboratory Breeding Base of Desertification and Aeolian Sand Disaster Combating Gansu Desert Control Research Institute Institute of Glaciology and Ecogeography College of Earth and Environmental SciencesLanzhou University Eritrea Institute of Technology College of Education Wuwei Natural Protection Station the Management Bureau of Gansu Qilianshan National Nature Reserve

Analysis of spatial-temporal variations of desert vegetation under the background of climate changes can provide references for ecological restoration in arid and semi-arid areas. In this study, we used the Global Inventory Modeling and Mapping Studies （GIMMS） NDVI data from 1982 to 2006 and Moderate Resolution Imaging Spectroradiometer （MODIS） NDVI data from 2000 to 2013 to reveal the dynamics of desert vegetation in Hexi region of Northwest China over the past three decades. We also used the annual temperature and precipitation data acquired from the Chinese meteorological stations to analyze the response of desert vegetation to climatic variations. The average value of NDVImax （the maximum NDVI during the growing season） for desert vegetation in Hexi region increased at the rate of 0.65x10-3/a （P〈0.05） from 1982 to 2013, and the significant increases of NDVImax mainly appeared in the typical desert vegetation areas. Vegetation was significantly improved in the lower reaches of Shule and Shiyang river basins, and the weighted mean center of desert vegetation mainly shifted toward the lower reaches of the two basins. Almost 95.32% of the total desert vegetation area showed positive correlation between NDVImax and annual precipitation, indicating that precipitation is the key factor for desert vegetation growth in the entire study area. Moreover, the areas with non-significant positive correlation between NDVImax and annual precipitation mainly located in the lower reaches of Shiyang and Shule river basins, this may be due to human activities. Only 7.64% of the desert vegetation showed significant positive correlation between NDVImax and annual precipitation in the Shule River Basin （an extremely arid area）, indicating that precipitation is not the most important factor for vegetation growth in this basin, and further studies are needed to investigate the mechanism for this phenomenon.

关键词： desert vegetation NDVI global warming spatial-temporal variations Hexi region

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Progress and Problems of Development Research and Application of Sand Barriers

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Meteorological and Environmental Research 2018年第3期9卷 18-23,29页

作者： Chang Zhaofeng liu shizeng Wang Qi liu Shujuan Wang Fei Gansu Desert Control Research Institute Lanzhou 730070China

Due to the restrictions on the conditions for afforestation and sand control,the development research,and application of sand barriers have accelerated in recent years,but some problems that cannot be ignored have emerged in practice. In this paper,the functions of wind prevention,sand blocking and fixation,improving soil physical and chemical properties and increasing plant diversity of sand barriers,accretion coefficient and capacity between sand barriers,and mobile sand barriers were analyzed firstly,and then several issues that should be noted in the development and application of sand barriers were proposed. The results show that sand barriers can fix sand on the spot and maintain the stability of sand surface. As an auxiliary measure before afforestation on a mobile sand surface,they are practical and feasible. The biggest drawback of sand barriers is that they are easy to be saturated. Although they can increase plant diversity and surface roughness,they lose the function of blocking sand flow after being saturated,and their function of in-situ sand fixation also rapidly decreases with the degradation of sand barriers. Mobile sand barriers overcome the disadvantage of sand barriers being easy to be saturated to some extent,but the cost greatly increases. In terms of desertification prevention and control by plants,plants are used as sand barriers to study their functions of sand blocking and sand fixation in many researches and practices,but the more important ecological functions of adjusting temperature on sand surface and achieving surface thermodynamic equilibrium of plants are ignored.

关键词： Sand barriers Development research Progress Problems

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单排光伏板防风固沙功能的风洞模拟研究

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干旱区资源与环境 2022年第4期36卷 111-119页

作者：孙涛王祺刘世增孙得祥林官明尚雯甘肃省治沙研究所甘肃省荒漠化与风沙灾害防治重点实验室-省部共建国家重点实验室培育基地武威733000 甘肃省林业科学研究院兰州730030 甘肃省武威市石羊河林业总场民勤733399 北京大学环境科学与工程学院北京100871

为了阐明光伏板的防风固沙功能,在风沙环境风洞内模拟研究与主风向呈2种角度(β=45°、β=90°)的单排光伏板在4种不同风速条件(5m/s,8m/s,12m/s,16m/s)下的风速流场和防风效能,并采用在光伏板底部覆沙的方法研究其风蚀积量的变化过程... 详细信息

为了阐明光伏板的防风固沙功能,在风沙环境风洞内模拟研究与主风向呈2种角度(β=45°、β=90°)的单排光伏板在4种不同风速条件(5m/s,8m/s,12m/s,16m/s)下的风速流场和防风效能,并采用在光伏板底部覆沙的方法研究其风蚀积量的变化过程和固沙功能。结果表明:1)两种角度的单排光伏板对来流风速均具有分流减速作用,当风经过光伏板时,在板上部区域形成气流加速区,下部有狭管效应,板面上方0~2H区域内有风影区产生,其它区域均对风速产生阻滞减速作用。2)各观测位点风速廓线表明,β=90°光伏板风速廓线分布较分散,曲线倾斜度大,β=45°光伏板风速廓线分布紧密,曲线倾斜度小,平均风速降低趋势β=45°相比β=90°光伏板更平缓,波动小。3)随水平距离的增加,β=45°光伏板防风效能变化呈倒“V”型单峰曲线变化,变化平缓,而β=90°光伏板防风效能呈倒“W”型双峰曲线变化,波动剧烈。4)两种光伏板在不同部位风蚀积特征有差异,在光伏板前部均有积沙,β=90°呈单峰态,而β=45°呈双峰曲线变化;在光伏板中部,均有掏蚀作用发生,而在光伏板后部,β=45°随水平距离的增加呈风蚀积交替变化,而β=90°以风蚀为主。光伏板中部区域是防沙治沙的重点区域。

关键词：光伏板风洞模拟风速流场防风效能生态效应

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Ecological Effects of Accumulated Sand-belts along the Oasis Fringe in Hexi of Gansu

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Animal Husbandry and Feed Science 2014年第3期6卷 107-112页

作者： Chang Zhaofeng Zhang Jianhui Wang Qiangqiang Zhu Shujuan Zhang Dabiao Fan Baoli Tang Jinnian liu shizeng Gansu Key Laboratory of Desertification Combating Minqin National Station for Desert Steppe Ecosystem Studies Gansu Desert Control Research Institute

The accumulated sand-belts have formed along the oasis fringe, especially at the upwind areas of the desert area in Gansu Hexi of China during the process of desert control in recent 60 years. The accumulated sand-belt is a byproduct of desertifieation combating through afforestation and barriers-setting. This pa- per analyzed the data （ including wind velocity/direction） of 21 sites on the accumulated sand-belt to evaluate its stability and ecological effects. The results showed that the accumulated sand-belt is in a stable state. It plays a significant role in weakening wind and this effect is enhanced with the increase of wind velocity. The height of accumulated sand-belt is an important factor characterizing its windproof function. When the wind velocity is higher than 2 m/s, the windproof area in the downwind places is 20 times greater than the height of the accumulated sand-beh. When the wind velocity is higher than 8 m/s, the wind velocity on the top of the accumulated sand-belt is less than that in the upwind open areas. When the air flow reaches the windward slope, its energy is released and reduced by uplifting along the slope and diversion towards the two wings. Wind deflector reduces the velocity of the prevailing wind on the windward slope.

关键词： Height of accumulated sand-belt Stability Protective effects Gansu Hexi

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两种云杉种子萌发和幼苗生长对环境因子的适应性

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生态学报 2019年第2期39卷 611-619页

作者：刘有军刘世增康才周满多清甘肃省治沙研究所甘肃省荒漠化与风沙灾害防治国家重点实验室培育基地兰州730070

青海云杉是我国沙区通过种子育苗引种成功的物种。通过对不同储藏时间青海云杉和沙地云杉种子生活力测定、种子萌发对温度、光照、水盐胁迫以及幼苗生长对水盐胁迫和沙埋的响应实验,比较两种种子萌发和幼苗生长对环境因子适应性,为沙地... 详细信息

青海云杉是我国沙区通过种子育苗引种成功的物种。通过对不同储藏时间青海云杉和沙地云杉种子生活力测定、种子萌发对温度、光照、水盐胁迫以及幼苗生长对水盐胁迫和沙埋的响应实验,比较两种种子萌发和幼苗生长对环境因子适应性,为沙地云杉在我国沙区广泛引种提供参考。结果表明:1)在2年的储藏过程中,沙地云杉和青海云杉种子生活力分别由79%和72%下降了19%和5%; 2)沙地云杉和青海云杉种子适宜萌发温度分别为15—30℃和10—30℃,最适萌发温度分别为25℃(72%)和25/15℃(69%),除10℃和10/30℃外,两种种子萌发率在各温度下没有显著差异; 3)沙地云杉种子萌发光照条件为14 h光照/8 h黑暗交替(67%),青海云杉为24 h光照(61%)或24 h黑暗(61%); 4)水势在-2.7—0 MPa时,2种云杉的IGR(初始萌发率)、RGR(恢复萌发率)、ISL(初始幼苗长度)和RSL(恢复幼苗长度)均没有显著差异; 5) NaCl浓度在200 mmol/L和250 mmol/L,青海云杉种子IGR显著大于沙地云杉,NaCl浓度在0—450 mmol/L,青海云杉和沙地云杉种子RGR没有显著差异,当NaCl浓度为50 mmol/L和100 mmol/L,青海云杉ISL显著大于沙地云杉; 6)在0.5—2.0 cm沙埋深度时,青海云杉出苗率显著高于沙地云杉,沙地云杉最适沙埋深度0.5 cm,青海云杉为0.5—1.5 cm。因此,青海云杉种子萌发和幼苗生长比沙地云杉有更强的环境适应性,但只要采取合理的播种时间、播种深度和水分管理等措施,沙地云杉会和青海云杉一样在我国沙区大面积引种育苗。

关键词：沙地云杉青海云杉种子萌发幼苗生长环境因子适应性

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Canonical Correlation Factors Causing the Formation of Accumulated Sand-belts along the Oasis Fringe in Hexi Corridor

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Animal Husbandry and Feed Science 2014年第5期6卷 279-284页

作者： Chang Zhaofeng Wang Qiangqiang Zhang Jianhui Tang Jinnian Zhu Shujuan Fan Baoli Zhang Dabiao liu shizeng Zhang Guozhong Li Aide Minqin National Station for Desert Steppe Ecosystem Studies Gansu Desert Control Research Institute

Accumulated sand-belts refer to those formed along the oasis fringe,especially at the upwind location,due to the accumulation of sand blocked by farmland windbreak. In the 60 years since the foundation of new China,a lot of trees have been planted for desertification combating in northwest and north China,thus,accumulated sand-belts were formed at the upwind location. The formation and the ecological effects of the accumulated sand-belts along the oasis fringe is a new scientific concern. To study the formation causes of these belts in Hexi corridor,21 samples were selected,and the height / width of the belts,as well as the vegetation,soil,soil moisture and climatic factors were investigated. This paper analyzed the correlation between the height / width of the belts and the vegetation,soil,soil moisture and climatic factors using the methods of variance analysis,correlation analysis and canonical correlation analysis. The results indicate that: the accumulated sand-belts take a trend of being high and wide in the east whereas low and narrow in the west,and most of the parts tend to be stable; the species on the belts are dominated by Tamarix austromongolica,the vegetation cover and the pure vegetation cover of different dominant species on the leeward slope of the accumulated sand-belts vary significantly. The canonical correlation analysis shows that: the height and width of accumulated sand-belt is the interaction of precipitation,distance to the sand source,leeward vegetation cover and annual average wind speed. Moreover,the height of accumulated sand-belts are negatively correlated to the soil moisture at the depth of 30- 50 cm,air humidity and leeward vegetation cover,and the width of the belts is also negatively correlated with the distance to the sand source. The ecological effects of the accumulated sand-belts are both positive( stopping sands from moving into farmland,protective role as an obstacle)and negative( when the belts decay and activate one day,th

关键词： Height of accumulated sand-belt Width of accumulated sand-belt Climatic and environmental factors Canonical correlation factors Ecological effects Hexi of Gansu

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潮湿环境下支柱绝缘子聚氨酯芯体的吸湿吸水特性研究

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高压电器 2022年第6期58卷 64-69,76页

作者：刘世增马义刚付致玮管兮远吴焱松梅红伟王黎明中国南方电网有限责任公司超高压输电公司大理局云南大理671000 三峡大学电气与新能源学院湖北宜昌443002 清华大学深圳国际研究生院广东深圳518055

灌注式支柱绝缘子内部使用聚氨酯材料填充,聚氨酯芯体特性是支柱绝缘子绝缘问题研究的重点。水分侵入会降低其绝缘强度,危害支柱绝缘子的运行可靠性。文中通过试验研究了潮湿环境下聚氨酯芯体的吸湿特性、吸水特性和水分在聚氨酯中的渗... 详细信息

灌注式支柱绝缘子内部使用聚氨酯材料填充,聚氨酯芯体特性是支柱绝缘子绝缘问题研究的重点。水分侵入会降低其绝缘强度,危害支柱绝缘子的运行可靠性。文中通过试验研究了潮湿环境下聚氨酯芯体的吸湿特性、吸水特性和水分在聚氨酯中的渗透特性。研究结果表明,水分在聚氨酯芯体中的渗透特性符合Langmuir模型;聚氨酯材料吸湿过程呈现出饱和曲线;水分在聚氨酯芯体中的渗透路径是聚氨酯的高分子网架,渗水质量与时间成线性正关系;聚氨酯B料比例增大时样品的吸湿能力、吸水能力、渗水速度都将提高;聚氨酯样品厚度与水分的渗透速率成反比;绝缘子良好的密封性能可以提高其使用寿命。

关键词：灌注式支柱绝缘子聚氨酯吸湿特性吸水特性渗水特性

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