Desert Highway Research Articles

灌溉对三种荒漠植物蒸腾耗水特性的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 灌溉对三种荒漠植物蒸腾耗水特性的影响 DOI: 10.5846/stxb201108011125 作者: 作者单位: 甘肃农业大学林学院,甘肃农业大学林学院,中国科学院新疆生态与地理研究所,甘肃农业大学林学院 作者简介: 通讯作者: 中图分类号: 基金项目: 国家国际科技合作专项(2012DFR30830);中国科学院知识创新工程重要方向性项目(KZCX3-SW-342-02);科技部农业科技成果转化资金项目(2009GB2G100375) Effects of different irrigation regimes on characteristics of transpiring water- consumption of three desert species Author: Affiliation: College of Forestry,Gansu Agricultural University,College of Forestry,Gansu Agricultural University,Xinjiang Institute of Ecology and Geography,College of Forestry,Gansu Agricultural University Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:利用热平衡式茎流计和压力室对塔里木沙漠公路防护林不同灌溉量条件下3种荒漠植物多枝柽柳 (Tamarix ramosissima)、梭梭 (Haloxylon ammodendron)和乔木状沙拐枣(Calligonum arborescens)的液流变化、水势进行了测定。研究结果表明:(1) 茎干液流速率因灌溉量和物种的不同而异,同一灌溉量条件下不同物种间表现为多枝柽柳＞乔木状沙拐枣＞梭梭,不同灌溉量条件下3种荒漠植物的茎干液流速率均随灌溉量的减少而显著降低。3种荒漠植物的夜间蒸腾占有一定比例,表现为梭梭(18.68%)＞乔木状沙拐枣(17.48%)＞多枝柽柳(12.82%),表明3种灌木均可通过夜间液流以补充植物体白天的水分消耗,表现出较强的抗旱性,但梭梭形成的叶片-冠-根的水势差相对较大,夜间补偿流较多,表现出更强的抗旱性。多枝柽柳和乔木状沙拐枣茎干液流日变化趋势基本相同, 在灌溉量为35 kg·株-1·次-1和28 kg·株-1·次-1时均呈单峰曲线,液流速率较高且变化幅度较大,而灌溉量为17.5 kg·株-1·次-1时呈双峰曲线,液流速率较低;梭梭在不同灌溉量条件下其变化均呈单峰曲线,即当灌溉量降低到17.5 kg·株-1·次-1时多枝柽柳和乔木状沙拐枣可能出现了水分亏缺,通过调节气孔张开度或部分关闭降低蒸腾来适应其胁迫条件,但该灌溉条件下梭梭并没有出现水分亏缺,表明出较强的抗旱性。(2)相同时间不同灌溉量条件下,3种荒漠植物的清晨水势和午后水势均随着灌溉量的减少而降低;整个生长季相同时间同一灌溉量条件下,3种防护林植物的清晨、午后水势表现为乔木状沙拐枣＞多枝柽柳＞梭梭,表明3种荒漠植物在相同的灌溉条件下梭梭因保持较低的水势表现出较强的抗旱性。(3)相同时间不同灌溉量条件下,3种荒漠植物单株日耗水量均随着灌溉量的减少而减少,整个生长季各处理日平均耗水量的动态变化趋势均为单峰型,7月份耗水量最大,表明在塔克拉玛干沙漠腹地最炎热的7月份,3种防护林植物可以通过增加其蒸腾耗水量来适应干旱的环境条件。 Abstract:The sap flow velocity and leaf water potential of three desert shrubs (Tamarix ramosissima, Haloxylon ammodendron, and Calligonum arborescens), grown under three different volumes of irrigation water in the Tarim Desert Highway shelterbelt,which is located at Taklimakan Desert of China, were measured using a heat-balance stem flow gauge and press chamber. The sap flow velocity differed among the species and among the irrigation volume treatments. Under the same irrigation volume, the sap flow velocity of the three species followed the rank order T. ramosissima > C. arborescens > H. ammodendron. The sap flow velocity of the same species decreased significantly with reduction in irrigation volume. The night-time transpiration of the three species as a proportion of total diurnal transpiration followed the order H. ammodendron (18.68%) > C. arborescens (17.48%) > T. ramosissima (12.82%). These results indicate that the water consumption of the three species during the day can be supplemented through the sap flow at night, which results in increased drought resistance. The water potential of leaf-canopy-root of H. ammodendron was higher, and the compensatory sap flow at night was higher, than that of the other species and thus conferred stronger drought resistance. The diurnal variations in sap flow velocity of T. ramosissima and C. arborescens were similar. In both species, the diurnal variation in sap flow velocity was represented by a single-peaked curve, the sap flow velocity values were higher and the extent of variation was wider under irrigation volumes of 35 and 28 kg·plant-1·time-1. With an irrigation volume of 17.5 kg·plant-1·time-1 the diurnal variation in sap flow velocity was represented by a two-peaked curve and the sap flow velocity values were lower than those of the other treatments. The diurnal variation in stem sap flow velocity of H. ammodendron showed a single-peaked curve under each of the irrigation volume treatments. These results indicate that water deficit occurs in T. ramosissima and C. arborescens when irrigation volume decreased to 17.5 kg·plant-1·time-1, and the species adapt to drought stress by adjustment of stomatal conductance. However, water deficit is not found in H. ammodendron at an irrigation volume of 17.5 kg·plant-1·time-1 and this species exhibits greater drought resistance. With decreasing irrigation volume, the predawn and midday water potentials of the three species gradually decreased at the same sampling time. The rank order of the three species in terms of their predawn and midday water potential under the same irrigation volumes applied simultaneously was C. arborescens > T. ramosissima > H. ammodendron, which indicated H. ammodendron possessed stronger drought resistance because of its lower water potential. With decreasing irrigation volume, the daily water consumption of the three species decreased gradually at the same sampling time. The dynamics of variation in average daily water consumption showed a single curve during the growth period for each species and maximal water-consumption values were recorded in July. These results indicate that the three species can increase their water consumption in July in the hinterland of the Taklimakan Desert, and thus adapt to the arid conditions. 参考文献 相似文献 引证文献

Relationship between Species Diversity of Herbaceous Plants in the Shelterbelt and Environment Factors

Many researchers have focused on the close relationship between species diversity and ecosystem stability. The Taklimakan Desert is a mobile desert with various dunes. Climate in the desert is characterized by the extreme aridity,low vegetation coverage and a few survival salt-tolerant desert plants. So,herbaceous plants grow only in the bottom of dunes under the conditions of high temperature,drought and high saline environment. As the longest desert highway in the world,the Tarim Desert Highway in Xinjiang of China is 436 km in length and covers an area of 3 128 hm2. The shelterbelt along the highway with average width of 2-6 km is irrigated with salty groundwater. Shrubs of the shelterbelt are Haloxylon,Tamarix and Calligonum plants. Herbaceous plant species have been notably increased since the shelterbelt was planted,and the herbaceous plant coverage has been over 40% along some highway sections. A stable windbreak and sand-fixation system has been formed by the shrub layer and herbaceous plant layer. Previous researches focused on sand-fixing efficiency,micro-climate benefits,physical and chemical properties of soil,changes of plant growth and transpiration along the shelterbelt in the Taklimakan Desert. To date,there are no the papers focusing on the change of species diversity of the artificial ecosystem yet. In this paper,the spatial differentiation of herbaceous plants is researched,and the relationship between species diversity and environmental factors is analyzed. In the study,10 sample plots were delimited along the Tarim Desert Highway shelterbelt,3 sample lines,100 m in length and perpendicular to the highway,were set in each sample plot,and 10 to 14 sub-plots (5 m×5 m) were delimited between the sample lines. Number,coverage and richness of herbaceous plants and corresponding environment factors,such as groundwater level,groundwater electrical conductivity and mineralization,soil electrical conductivity,average range of tree crown of shrub layer and shade density,were recorded and surveyed comprehensively. Sample altitude was measured by GPS; groundwater level was measured with self-made electronic water level meter; shrub crown diameter was measured with steel tape; shade density of shrubs and coverage of herbaceous plants were measured by ocular estimate; groundwater samples in the study area were collected and analyzed in laboratory,their electrical conductivity and mineralization were measured by conductivity gauge; soil samples were collected at soil depths of 0-10 cm and 10-30 cm and analyzed in laboratory,and their conductivity was measured by conductivity gauge. Main indices included the richness index,important value index,average vegetation coverage in the plots,Shannon-wiener diversity index (H'),Simpson diversity index (D') and Sorensen similarity index. The results are as follows:(1) There were less herbaceous plants and their species in the Tarim Desert Highway shelterbelt; these herbaceous plants were composed of 13 species in 12 genera and 8 families. Most of the plants belonged to Chenopodiaceae and Compositae families,and many of them were perennial; (2) Some plant communities were consisted of the scarce species,but many ones are composed of single families; (3) Under different groundwater levels,the electrical conductivity of topsoil,distribution of herbs and species diversity were quite different; (4) The species diversity of herbaceous plants was closely correlated to groundwater level,groundwater electrical conductivity and topsoil electrical conductivity. The correlation coefficients between Shannon-Wiener index and groundwater level,groundwater electrical conductivity,electrical conductivity of soil at depth of 0-10 cm were 0.72,0.63 and 0.69,and those between Simpson index and groundwater level,groundwater electrical conductivity,topsoil electrical conductivity were 0.65,0.61 and 0.69,respectively. The coverage of herb community and the diversity index were increased with the raise of groundwater depth. Therefore,the study results can provide the basal information for conserving plant species diversity,improving the stability of the ecosystem,maintaining the unblocked desert highway traffic,and supplying the gap of herbaceous plant diversity in the shelterbelt along the desert highway.

Nationwide Desert Highway Assessment: A Case Study in China

The natural environment affects the construction of desert highways. Conversely, highway construction affects the natural environment and puts the ecological environment at a disadvantage. To satisfy the variety and hierarchy of desert highway construction and discover the spatio-temporal distribution of the natural environment and its effect on highway construction engineering, an assessment of the natural regional divisions of desert highways in China is carried out for the first time. Based on the general principles and method for the natural region division, the principles, method and index system for desert highway assessment is put forward by combining the desert highway construction features and the azonal differentiation law. The index system combines the dominant indicator and four auxiliary indicators. The dominant indicator is defined by the desert’s comprehensive state index and the auxiliary indicators include the sand dune height, the blown sand strength, the vegetation coverage ratio and the annual average temperature difference. First the region is divided according to the dominant indicator. Then the region boundaries are amended according to the four auxiliary indicators. Finally the natural region division map for desert highway assessment is presented. The Chinese desert highways can be divided into three sections: the east medium effect region, the middle medium-severe effect region, and the west slight-medium effect region. The natural region division map effectively paves the way for the route planning, design, construction, maintenance and ongoing management of desert highways, and further helps environmental protection.

Experimental Studies on Wind Erosion Mechanism of Aeolian Soils Subgrade Slope for Desert Highway

Wind erosion mechanism is studied through interior wind erosion wind tunnel experiment for desert highway. The anti-wind erosion ability of Aeolian soil subgrade slope is equivalent to the variation of microstructure characteristics and shearing strength of Aeolian soil. Microstructure characteristics will be quantified analysis through scanning electron microscope and image analysis software for subgrade slope, and microstructure parameters are picked-up for wind erosion fore-and-aft. Aeolian soil’s Shearing strength and wind erosion depth are investigated at different position of windward slope during a long-time wind-blown. Then, wind erosion mechanism of Aeolian soils subgrade slope is clarified from two aspects of micro and macro, wind erosion influence depth is determined for certain environmental condition. Taking desert highway subgrade as an example, the results indicate that: the disturbance to the flow field enhances with the increase of slope ratio and subgrade height, wind erosion of the windward slope is severe. The anti-wind erosion ability on windward slope is weak obvious with the decreasing of soil’s water containing, the increasing of wind velocity and the blow time prolong. Shearing strength of Aeorian soil is gradually decreased from slope surface to its interior, from bottom to top of windward slope. According to environmental condition local, when average wind velocity is 11m/s and natural water containing is 2%, wind erosion depth is about 15mm on the top of slope which is 1/11 of subgrade height, relative to 10mm on the mid of slope. The conclusions drawn from micro and macro are proved the wind erosion mechanism of Aeolian soils subgrade slope perfectly.

Numerical Study on Aeolian Sand Ripples Forming and Moving Process in Desert Highway

In this paper, the sand break into highway problem in desert, which is caused by the sand flow blown by wind, is studied. The mathematical models are introduced by considering the fixed, semi-fixed and free sand desert fields based on the fluid dynamics and the sand particle dynamics. Different kinds of numerical models are made by changing the desert highway height, wind flow direction and its uniformity. The weak coupling method is used due to spatial relationships between air flow field and the sand flow field. Finally, by coupling the airflow field and sand flow field with desert highway, the numerical simulations of sand forming process on desert highway are conducted. The numerical results shown, that the wind blown sand breaks into highway easier when wind direction perpendicular highway and if the highway height higher than the range size of the sand surface the wind blown sand break into highway is more difficult.

Research on the Hydrochemical Characteristics of Groundwater at the Southern Edge of Taklimakan Desert and along the Southern Desert Highway, China

In this paper, the characteristics of chemical components of groundwater were analyzed by means of investigating and collecting groundwater samples and hydrochemical analyses in the lower reaches of Niya river, Yatonggusi river and Andier river, the south edge of Taklimakan desert and along the southern desert highway in Tarim basin. It indicates that the total dissolved solids (TDS) in shallow groundwater are respectively 2.14-4.97g•L-1, 5.79-7.71g•L- 1 and 1.21-38.85g•L-1 in Niya river, Yatonggusi river and Andier river. The partial correlationships of groundwater TDS with HCO3-, SO42-, Cl-, and Na+ ions are extremely obvious, the relative coefficients ranging from 0.9598 to 0.9874, and quite obvious to Mg2+, Ca2+ ions with the coefficients of 0.8508 and 0.7771 in the lower reaches of Andier river. For the groundwater TDS along the southern desert highway, its partial correlationships to SO42-, HCO3- and Cl- ions are extremely obvious, with the relative coefficients ranging from 0.9171 to 0.9686, and quite obvious to Na+ and Ca2+ ions with the coefficients of 0.7873 and 0.6322. In the lower reaches of Andier river, there are some spatial correlations on the aspects of K+ and HCO3- contents in groundwater, and the spatial correlation distances in latitude and longitude are 0.03° and 0.21°. Based on the established semivariogram models, isograms of the distribution of ion contents in groundwater were plotted by using Kriging and IDW methods. The results show that the spatial distribution characteristics of chemical components in groundwater are consistent with that of ions contents changing along the latitude from south to north.

Historical evolution and the effects of ecological management in Tarim Basin, China

The Tarim Basin, in northwestern China, is the largest continental basin in the world, and hosts desert landscapes as well as extensive oasis agriculture. Many horticultural products come from this basin. However, since the 1950s, frequent river flow interruptions have occurred in the lower reaches of the Tarim River. Thus, the natural ecology of the basin has undergone significant changes because of recent human economic and social activities. In particular, water resource development and utilization along with climate changes have had a significant impact on the area. To prevent further deterioration of the environment, the Central Government implemented a water conveyance project in 2000. Based on this project, Chinese scientists, together with those from overseas, have conducted extensive research on the historical evolution of the area, and the physiological and ecological responses of the natural vegetation around the Tarim Desert Highway. Progress has been made in the areas of environmental protection and ecological conservation.

Structural and Economical Effect of Over Weight Trucks on Asphalt Pavement

The general authority of road, bridges, and land transportation (GARBLT) specify the limitation of truck loads that run on Egyptian highways. Many trucks violate these limits by loading additional weights to decrease the transportation unit cost. This behavior causes severe deterioration to the pavement. Such violating trucks are charged by eventually little penalties compared to the damage they cause to the pavement. The objectives of this study is to evaluate the effect of increasing axle load, due to overloaded trucks, on the pavement life and to estimate a critical load that makes a boundary between penalized loads and the unallowable loads by developing a relationship between the number of load repetition to failure and axle load. The research used the KENPAVE software to calculate the horizontal tensile strain occurring at the bottom of the asphalt layer and the vertical compressive strains occurring at the top the subgrade soil due to the different axle loads. The calculated strains are then utilized to estimate the number of load repetitions to failure due to fatigue cracking using the Asphalt Institute (AI) method. Finally, relationships relating the predicted numbers of load repetitions with axle load and tire pressure were developed using regression analysis. In this study, Cairo-Alexandria desert highway was used as a case study.

Characteristics of the soil microbial population in forest land irrigated with saline water in the desert area

The study of soil microbial populations and diversity is an important way to understanding the soil energy process.In this study we analyzed the characteristics of soil microbial populations of the Tarim Desert Highway shelter-forest,by identifying microbial fatty acids and using methods of conventional cul-tivation.The results illustrated that the amount of soil microbial activity and the diversity of soil microbial fatty acid increased significantly with the plantation age of the shelter-forest;the soil microbial population was dominated by bacteria.The fatty acids of C14︰0,C15︰0,C16︰0,C17︰0,C18︰1ω9,C18︰0,C18︰2ω6 and C21︰0 were found to be dominant soil microbial fatty acids in the shelter-forest soil.Prin-cipal analysis and regression analysis showed that(1) concentrations of fatty acids of C14︰0,C16︰0 and C18︰0 could be used as indicators of total soil microbial population;(2) soil bacteria and actinomycetes populations were closely correlated with the amount of fatty acids of C15︰0 and C17︰0;and(3) soil fungi were closely correlated with the amount of fatty acids of C18︰1ω9 and C18︰2ω6.

EVALUATION OF SAND BITUMEN AS A BASE LAYER FOR DESERT ROADS

ABSTRACT In Libya, the cost of gravel and crushed stone rises as existing sources become exhausted and suitable supplies have been overly exploited. Sand in Libya is the most prevailing available material for constructions. It is suggested that economic benefit could be derived from the rational use of stabilized sand in road construction. A main desert highway was constructed in Libya using in-place sand mix base. The main objective of this paper is to document and characterize the sand bitumen mix which was successfully used in this road. The work completed in this paper included field investigation, laboratory work and analysis of results. The field investigation was conducted to evaluate the pavement surface condition of the existing road in Libya. Core samples were obtained through this phase of study and tested for aggregates gradation and optimum MCO%. Results of work conducted in this research showed that sand bitumen mix could be used successfully as a base layer in desert roads. The average MCO content was found to be 2.82%. Future work should be conducted to check the response of sand bitumen mix under repeated traffic loads and to establish sand mix design criteria.

Analysis on Properties of Topsoil Salinity along the Shelterbelts of the Tarim Desert Highway

The shelterbelts along the Tarim Desert Highway are faced with serious topsoil salinization and the adaptability of plants irrigated with high-saline water.Based on the field observation,some samples of topsoil and groundwater were collected along the Tarim Desert Highway.According to the analyzed results of 56 soil samples and 49 groundwater samples,in this paper the properties of topsoil salinity along the shelterbelts of the Tarim Desert Highway are discussed.The content,chemical components and spatial distribution of topsoil salinity are analyzed. The results are as follows:(1) The topsoil salinity along the shelterbelts of the Tarim Desert Highway is high because of the high evaporation and severe environment in the Taklimakan Desert;(2) The correlation between electric conductivity and salinity of groundwater is very significant(R~2=0.673).The linear correlation between soil electric conductivity and topsoil salinity is determined,and the dependent equation is developed;(3) High salt accumulation occurs in topsoil,and the total salt content is as high as 257.94 g/kg.The dominant anion from salt in soil is Cl~-,accounting for 54.12%～96.95%of the total anion,and then SO_4~(2-) and HCO_3~-;the dominant cation is Na~+,its proportion is as high as 77.41%～88.53%of the total cation,then Mg~(2+) and Ca~(2+) with proportions of 4.68%～11.90%and 1.08%～8.69%respectively.The correlation coefficient between Na~+ and Cl~-is 0.97 indicating that the dominant soluble salt is NaCl,and then Na_2SO_4,MgCl_2 and CaCl_2.There are high correlations between electric conductivity and concentrations of Cl~-,Na~+ and salt content in topsoil,and their correlation coefficients are 0.862,0.813 and 0.815 respectively;(4) The spatial variability of topsoil salinity,pH value and electric conductivity of topsoil shows that the variation of salinity and electrical conductivity of topsoil is moderate, the variation of pH value is rather weak,and the pH value of topsoil along the shelterbelts of the Tarim Desert Highway increases gradually from north to south.These results are expected to provide some scientific insights on the plant growth of the shelterbelts along the Tarim Desert Highway and the management of groundwater resources, and can also shed a light of the sustainability of shelterbelts along the Tarim Desert Highway.

Change in soil physical and chemical property in the Tarim Desert Highway shelterbelt under saline water drip-irrigation

Abstract The physical and chemical properties of drip-irrigated aeolian soil with highly saline groundwater in the shelterbelt along the Tarim Desert Highway were investigated. The results show that surface layer litter quantity increases with shelterbelt age. Soil compactness in crust, 0~5 cm, 5~15 cm and 15~30 cm soil layers also decreases with shelterbelt age. Soil organic matter content increases with the shelterbelt age, and on the other hand, gradually reduces from the top to deeper layer of the soil profile. Total salt content decreases with both shelterbelt age and soil depth. Individual ions content in crust layer decreases, that in 0~5 cm, 5~15 cm and 15~30 cm soil layers increases with shelterbelt age. Soil pH in crust, 5~15 cm and 15~30 cm layers decreases with shelterbelt age, while that in 0~5 cm soil layer increases with shelterbelt age. Key words Saline water drip-irrigation, Aeolian soil, Soil physical and chemical property, Tarim, Highway shelterbelt in desert, Taklimakan Desert (Received June 20, 2008; accepted Nov. 17, 2008)

Site type classification for the shelter-forest ecological project along the Tarim Desert Highway

Site types of the afforestation region of the shelter-forest ecological project along the Tarim Desert Highway were classified based on the natural conditions and windblown sand damages. The extremely severe environment, the irrigation with saline water, and large-scale linear project makes this classification of site types most unique and significant. It adopted a three-level classification system integrating the dominant factors and restrictive factors in regard to their impacts on plant survival and growth as well as on the protective property. Six site type districts were classified based on the medium-scale geomorphic unit, the windblown sand damages, and the major production facilities; 21 site type groups were obtained according to the small-scale geomorphic type, terrain, and wind regime; 36 site types were further classified based on the salt contents of the underground water and soil types. Especially, in this study, spatial distribution of the six site type districts along the desert highway is continuous, which is unique and different from that of most other classifications. In addition, the salt-stress tolerance threshold of the main afforestation plant species to underground water have been set to 8 g/L and 15 g/L according to selective breeding tests and the salinity spatial distribution of the underground water. Thus, the underground water with salinity lower than 8 g/L is defined as light saline water in this area.

Effect of the shelterbelt along the Tarim Desert Highway on air temperature and humidity

The temperature and humidity of the shelterbelt micro-climate on both horizontal and vertical scales in the extremely drought area were measured with multiple HOBO temperature and humidity automatic observation equipments in the hinterland of the Taklimakan Desert. The results show that the shelterbelt ecosystem of the desert highway plays typical micro-climate adjustment rolesin stabilizing surface air temperature and increasing air humidity, and so on. Solar radiation significantly affects both temperature and humidity of surface layers, and it has a positive correlation with the temperature but a negative correlation with the air humidity. When it is cloudy, the weather has a great impact on keeping temperature and humidity in the shelterbelt. The shelterbelt also significantly influences the environment, and the micro-climate in the belt has an obvious characteristic of cooling and humidification: compared with the original sand area, the temperature in the shelterbelt is always lower and the humidity is always higher. Moreover, the temperature range at the shelterbelt edge is greater than that in the sand area, but the humidity is always higher. Our conclusion is that the vertical-effect range of temperature of the shelterbelts is 4-10 m, and the humidity range is 6 to 8 m; the horizontal-effect range of temperature is 16 m and the humidity range is about 24 m.

Classification and regionalization of the forming environment of windblown sand disasters along the Tarim Desert Highway

Through the systematic field survey and observations, the factor quantification as well as setting the criteria, the sand disaster-forming environment along the Tarim Desert Highway can be divided into four grades by the classification and regionalization based on fuzzy mathematics. The length of the regions with significant sand disaster accounted for 37.1% of the total highway length. Particularly, the area along the Tarim Desert Highway, based on the sand disaster-forming environment classification as well as the difference in the five basic landform units along the highway, combined with the difference of wind regime, can be divided into five regions, in which the length of the regions suffering severe sand damage occupied 64.3% of the total highway length. In addition, the index of disaster formation grade along the highway decreased from north to south, showing a repeated spatial pattern in small length scales.

The effect of salt stress on the chlorophyll level of the main sand-binding plants in the shelterbelt along the Tarim Desert Highway

Based on the fact that only high saline water irrigated to the shelterbelt along the Tarim Desert Highway, the experiment about three species with six degree of salinity was carried out to analyze the relation between chlorophyll content and salt stress. The results show that: (1) the chlorophyll content of tree species decreases with aggravating the salt stress, which explains that salt stress can affect chlorophyll accumulation of three plants; (2) from chlorophyll content with different salinity, the chlorophyll content of three shrubs also has twice obvious decrease, which indicates that some plants adapt to salt stress. We divided salt resistance of the plant into three grades, namely the slight salt resistance, the heavy salt resistance and the extreme salt resistance; and (3) according to the experimental results, the salt stress of each plant was divided, which can provide theoretical guidance for constructing the shelterbelt along the Tarim Desert Highway.

Evaluation of soil fertility of the shelter-forest land along the Tarim Desert Highway

To study the changes of soil fertility of the shelter-forest land along the Tarim Desert Highway, soils from the forest land were collected at the layers of 0–10 cm, 10–20 cm, 20–30 cm. Different soil fertility parameters were measured, and quantitative evaluation of soil fertility was performed by the soil integrated fertility index (IFI). The main results show that the construction of the shelter forest along the Tarim Desert Highway improved the soil physical structure, increased soil porosity and enhanced water-holding capacity. With the increase of plantation time of the shelter forest, soil microbial biomass C, N, P and the activities of six types of enzyme were enhanced, which promoted the accumulation and transformation of soil nutrients of the forest land. Consequently, the soil nutrients in 12-year-old forest land were much higher than in the newer ones and drifting sand. However, soil salt content of the older forest land was higher owing to the drip-irrigation with salt water. Through the comprehensive evaluation, we found that soil fertility index in the forest land was enhanced with the forest age, and it had close correlations with the growth indices of the forest trees. In summary, construction of the shelterforest along the Tarim Desert Highway accelerated the improvement of aeolian soil in the forest land, and the soil fertility improved year by year. We conclude that the forest trees grow normally under the stress of the present drip-irrigation with salt water.

Influence of moisture on the growth and biomass allocation in Haloxylon ammodendron and Tamarix ramosissima seedlings in the shelterbelt along the Tarim Desert Highway, Xinjiang, China

The authors studied the effects using three different levels of irrigation on the growth and biomass allocation in H. ammodendron and T. ramosissima seedlings in the shelterbelt along the Tarim Desert Highway. The three irrigation amounts were 35 (CK), 24.5 (treatment 1), and 14 (treatment 2) kg·ind. plant−1·once−1, respectively. The results show that (1) the vertical depth of the two seedlings’ root increased with lower levels of irrigation showing that the two species adapted to decreased irrigation by root elongation in the hinterland of the Taklimakan Desert, and the vertical root depth of H. ammodendron under treatment 2 was notably higher than CK. (2) Compared with CK, the belowground biomass of treatment 1 and 2 both showed a significant increase as follows: H. ammodendron seedlings increased by 14.51% and 37.03% under treatment 1 and 2, respectively, while T. ramosissima seedlings increased by 68.19% and 25.78% under treatment 1 and 2, respectively. This means that H. ammodendron seedlings were more adapted to the conditions in treatment 2 while T. ramosissima seedlings were better adapted to treatment 1 conditions. (3) When compared with CK, the fine root bomass of these two species all exhibited some increase under both treatments, and ANOVA analysis showed that the biomass of deep layer root of the two species under treatment 2 was notably higher than CK and treatment 1. This should help seedlings to more effectively absorb soil water from deep layers during dry conditions. (4) The root-shoot ratio was different for these two species. For H. ammodendron seedlings, the root-shoot ratio was less than 1, while for T. ramosissim seedlings it was larger than 1. The root-shoot ratio of H. ammodendron seedlings increased with decreasing levels of irrigation, and that of T. ramosissim seedlings also increased under treatment 2. (5) With decreasing levels of irrigation, due to the difference of species, the growth variation of aboveground indexes was also different, while compared with CK, it was not significant.

The salt accumulation at the shifting aeolian sandy soil surface with high salinity groundwater drip irrigation in the hinterland of the Taklimakan Desert

The EC analysis and water serial sampling was performed in the Tarim Desert Highway shelterbelt to explore the water and salt dynamics of the shallow aeolian sandy soil (0–30cm) under high salinity groundwater drip irrigation. It was found that in one irrigation cycle, the EC of the shallow shifting aeolian sandy soil (0–30cm) increased while the water content decreased. The EC of the surface aeolian sandy soil at the wetting front was far greater than that of the wetting area or the outside of the wetting area. During the irrigation cycle, the EC of the wetting front and the wetting area changed at a significant magnitude, whereas the EC of the outside of the wetting area remained largely steady. The horizontal influence distance of drip irrigation on the salt accumulation at the soil surface was about 100 cm, and the vertical influence depth was 5 cm. The three most abundant ions in the accumulated salt at the aeolian sandy soil surface were Na+, Cl− and SO4 2−. The salt accumulation at the soil surface was influenced by air temperature, wind speed, mineralization of irrigation water, sand burial thickness, soil texture, and litter content.

The vertical distribution of the root system of the desert highway shelterbelt in the hinterland of the Taklimakan Desert

In this work, the vertical distribution of the root system in the Tarim Desert Highway shelterbelt under high salinity water drip irrigation was investigated. The effect of site condition and shelterbelt age was studied. The root sample was collected by plant side soil column excavation. The root distribution was found to be dependent on soil texture, aspect, and plant age. In harden sand, the roots were mostly in the 0–40 cm soil. The root distribution is deep in flat sandy ground and ridge sand. In unit soil volume, the root weight of flat sandy ground was the highest. Compared with the shady slope, the sunny slope had much high total root weight, deeper root distribution, but less hair root. The root weight increased rapidly with the increase of the shelterbelt ages, and the most substantial increase was observed in the early years after forest implantation.