Interpretation of important environmental geological indicators

According to the above environmental geological indicators of desertification investigation and monitoring, the environmental geological indicators of desertification are introduced in the form of international geological indicators interpretation.

I formation and activation of sand dunes

Name: Formation and Activation of Dunes

Introduction: Dunes and sand mats are formed under the influence of various climatic and environmental control factors, including wind speed and direction, humidity and accumulation. The sand dune system and sand mat in continental environment are formed by sediments transported or re-transported by wind. The newly formed sand dunes are caused by the reactivation of sediments caused by climate change and/or human interference. It originated from the migration of sand dunes on the edge of many deserts and the activation of semi-fixed and fixed sand dunes in temperate regions (such as the southeast edge of Taklimakan Desert and Mu Us Sandy Land). The change of sand dune shape or position can indicate the change of drought degree, wind speed and direction (see wind erosion and sandstorm effect) or human disturbance. Using drought index and sand dune activity index (sand dune activity index refers to the ratio of existing wind energy to precipitation-potential evaporation ratio), the change of sand dune can be related to climate change.

Significance: Moving sand dunes may bury houses and sites and hinder flexibility. Dune activities in semi-arid and semi-humid areas reduce the arable land of pasture and agriculture. They are also good indicators of drought change. Sand dunes control the increase and decrease of organisms by providing landforms and hydrology, and play an important role in many ecosystems (northern ecology, semi-arid areas and desert areas).

Man-made or natural reasons: the change of dune morphology and dune movement may be caused by the change of drought degree (drought cycle). Changes in wind patterns and human activities may also lead to extensive changes, such as vegetation destruction caused by overgrazing and unreasonable agricultural production and lifestyle.

Applicable environment: Sand dunes are widely distributed in arid, semi-arid, semi-humid deserts and sandy areas at mid-latitude, and scattered in the ancient river development zone in the basin.

Monitoring site types: active dune edge, semi-fixed dune and fixed dune with stable vegetation.

Spatial scale: block to landscape/regional scale.

Measurement method: The change of the size, shape and position of sand cushion and sand dune area can be monitored by repeated ground surveys, while the measurement of movable sand dunes, fixed sand dunes and residual sand dunes can be monitored by aerial photography or satellite images.

Measurement frequency: the measurement frequency for monitoring the changes of sand dunes related to drought cycle should be once every 5 ~ 10 years, and the monitoring frequency should be increased when movement is found.

Limitations of data and monitoring: there is usually a lack of climate records, especially wind information.

Past and future applications: records of sand dune activities in arid, semi-arid and semi-humid areas in the past 50 years can be established, which can be linked with temperature and precipitation records. The ancient records of Quaternary residual dunes (including ancient wind direction) can evaluate the potential impact of future climate change on aeolian sand system.

Possible critical value: dune activity index M & gt50. Other critical values may be based on the allowable limit of active dune area to agricultural cultivated land and related groundwater level.

Main references:

/kloc-sand from active dunes on the American great plains in the 0 th and 9 th centuries: evidence calculated by early explorers. Quaternary research, 43:118-124.

Desert geomorphology. London: UCL Press.

Dune landform. London: Rutledge.

Cook, Warren and Gaudi. Desert landform. London: USL Press.

Lancaster number 1995. Desert dune landform. London: Rutledge.

Muhs, D.R. and V.T.Holliday, 1995. /kloc-active dune sand on the great plains in the 0 th and 9 th centuries: evidence from the accounts of early explorers. Ternary research, 43:118-124.

Nordstorn, K.E., N.Psuty and B.Carter, 1990. Coastal dunes: form and process. John Wiley & sons.

Other sources: Agriculture and Environment Agency, Geological Survey, Desert Research Institute, International Quaternary Research Union.

International Association of Geomorphologists (IGA).

Related environmental and geological problems: mobile sand dunes may occupy and destroy agricultural production farmland and affect traffic trunk lines. Humans have tried to stabilize sand dunes. The movement of sand particles can reduce the surface evaporation and affect the shallow groundwater level.

Overall evaluation: Sand dunes are extremely important indicators of surface morphology and environmental changes in arid, semi-arid and semi-humid areas.

Second, the surface rock and soil composition

Name: Composition of Surface Rock and Soil

Brief introduction: There are various rock and soil types exposed on the surface, among which loose deposits have the worst weathering resistance. Under the condition of less rain and windy in arid, semi-arid and partly semi-humid areas, the sediment yield of different rock and soil types is quite different. Generally speaking, the distribution areas of carbonate rocks and eruptive rocks (limestone, dolomite, basalt, rhyolite, etc.). ) are all non-sand producing areas; Semi-consolidated clastic rocks with poor weathering resistance in late Mesozoic and Tertiary are small sand-producing areas. Loose Quaternary sediments, especially the rich distribution area of the lakeside sediments of the late Quaternary rivers, are a large number of sand-producing areas of land desertification. Modern deserts and desertified land in China are mainly distributed in a large number of sand-producing areas and surrounding areas with fragile ecological environment.

Significance: The consolidation degree of surface rock and soil and the particle size composition of loose deposits are the basic environmental geological indicators to judge the occurrence and development of land desertification. Especially, the composition and physical characteristics of surface rocks and soil are of guiding significance in predicting areas where land desertification may occur.

Man-made or natural causes: natural causes.

Applicable environment: arid, semi-arid and partially semi-humid areas.

Monitoring site type: small sand-producing areas (Jurassic and Cretaceous stratigraphic distribution areas) such as central and northern Mu Us sandy land; Quaternary distribution area.

Spatial scale: block to landscape/mesoscale to regional scale.

Measurement method: Combined with the compilation of geological map, the weathering physical and chemical tests of "bran sand" on the surface of Jurassic and Cretaceous strata were carried out in the field.

Limitation of data and monitoring: the composition of the surface rock and soil is strongly influenced by nature and man-made, and the weathering intensity is difficult to monitor.

Past and future applications: when predicting future climate and environmental changes, key areas prone to land desertification and possible sand production.

Possible critical value: refers to the boundary of geological units of rock type.

Main references:

Dong Guangrong, Jin Jiong, Shen Jianyou, et al. 1990. Desertification process and its causes of terrestrial ecosystem in China since late Pleistocene. See: Edited by Liu Dongsheng. Quaternary geology of loess. Global change (Part II). Beijing: Science Press, 9 1- 10 1.

Fan, Ma Yingjun. 2002. Water resources utilization, ecological balance and land desertification in Tarim Basin. China History Theory Series, 17 (3): 27-32.

Gong jiadong, cheng, et al. 2002. Environment and evolution of Ejina area in the lower reaches of Heihe River. Progress in Earth Science, 17 (4): 49 1-496.

Wu Bo, Ci Long Jun. 1998b。 Development stages and causes of desertification in Mu Us sandy land. Science Bulletin, 43 (22): 2437-2440.

Xinjiang wasteland resources comprehensive investigation team. 1985. Rational utilization of wasteland resources in key areas of Xinjiang. Urumqi: Xinjiang People's Publishing House.

Zhao Harlem, Zhao, Zhang Tonghui, Wei Wu, et al. 2003. Desertification process and its recovery mechanism in Horqin sandy land. Beijing: Ocean Press.

China Academy of Sciences Taklimakan Desert Comprehensive Scientific Investigation Team. 1994. Soil and land resources in Taklimakan Desert. Beijing: Science Press.

Zhu Zhenda, Wang Tao. 1992. Theory and practice of desertification research in China. Quaternary research, (2): 97- 106.

Acton Food Company Gregoric (ed.) 1995. The health of our soil-sustainable agriculture in Canada. Land and Biological Resources Research Center, Ottawa: Canadian agriculture and agrifood.

Plant and soil water dynamics: a theoretical method of eco-hydrology for water control ecosystem. Cambridge: Cambridge University Press, 2003.

Related environmental geological problems: under the action of nature and human beings, soil erosion may occur.

Overall evaluation: the composition of surface rock and soil is the product of environment and human activities, and its change will affect the quality of surface and groundwater.

Third, the content of soil material components.

Name: Content of Soil Material Components

Introduction: From the geoscience point of view, the soil layer is not only the weathering crust produced by the weathering of surface sediments and biological action. It is also a geological sign reflecting environmental factors such as climate, moisture, vegetation and topography. The analysis of general soil material content mainly includes: physical clay and quantitative changes of organic matter, nitrogen and phosphorus. The practical work in Horqin Sandy Land in the east of China, Yikezhaomeng in Inner Mongolia and Shapotou in the southeast edge of Tengger Desert proved that the content of soil substance and its change index can be used to determine the development stage or degree of land desertification.

Significance: The change of soil material component content is an important symbol of land desertification process and an important information reflecting environmental changes in desert areas. Physical clay is the dividing line between soil plasticity and water-holding capacity, and its high content means good soil physical properties and high water and fertilizer retention capacity. On the one hand, soil organic matter reflects the nutrient returning ability of plant residues, on the other hand, it also reflects the growth of ground plants. Therefore, soil organic matter and physical clay play an important role in evaluating the characteristics of desertification soil.

When studying the problem of wind erosion and desertification, by studying the material content of desertification soil, we can deeply and comprehensively understand the development law of desertification process and the evolution process of desertification soil degradation, understand the harm of desertification, and provide reliable scientific basis for predicting the development trend of desertification and taking corresponding control measures.

Man-made or natural reasons: the content of soil material components is the result and expression of natural phenomena such as human land transformation or wind erosion and water erosion.

Applicable environment: arid, semi-arid and semi-humid sandy land in different natural zones.

Monitoring site type: non-desertification and desertification land. The content of non-desertified soil material components can be used as background value.

Spatial scale: regional scale/small scale.

Measurement methods: routine physical analysis and chemical analysis.

Measurement frequency: 3 ~ 5 years.

Limitations of data and monitoring: The background values of native soil nutrients are not the same in different regions, so the soil indicators of various types of desertification land in different regions cannot be the same, and it is difficult to quantitatively determine the soil indicators of various development stages of desertification.

Limitation of data and monitoring: Hu (199 1) sorted out the single-factor grading index of land desertification in Horqin area according to the statistical data of a large number of field investigation points: taking Naiman Banner in Inner Mongolia in Horqin desert area as the experimental point, the soil nutrient content decreased obviously after desertification, regardless of grassland or dry land (Table 3- 14). Soil nutrient is the material guarantee of crop growth and reproduction, and its content is directly related to its biomass. Obviously, the deterioration of soil nutrient environment after land desertification is one of the important reasons that hinder the growth, development and reproduction of plants (crops).

Table 3- 14 Changes of Soil Nutrient Content in Grassland and Dryland during Desertification

Liu Yuping (1998) has also successfully completed the evaluation of soil profile by using soil material content index and soil texture in the experimental study of Mu Us sandy grassland.

Yao Honglin (2002) believes that in the process of land desertification, the change of soil indicators is not single, but multiple indicators are at work. The main indicators are soil organic matter and physical clay particles less than 0.01mm. The basic characteristics of soils with different desertification degrees are as follows:

Mobile sandy land: 0.02% ~ 0.08% of soil organic matter, 0.003% ~ 0.00 1% of total nitrogen, 0.8 ~ 2.14 ppm of available nitrogen and 0.0 16% ~ 0.02% of total phosphorus. 64.5% ~ 83.5% of sand particles are 0.25 ~ 0.05 mm, 0.8% ~ 2.4% of physical clay particles are less than 0.0 1 mm, and 0.6% ~ 1.5% of clay particles are less than 0.00 1 mm.

Semi-fixed sandy land: 0.39% ~ 0.84% of soil organic matter, 0.0 1 1% ~ 0.033% of total nitrogen, 2.08 ~ 2.93 ppm of available nitrogen, 0.028% ~ 0.04% of total phosphorus and 0/5.7 ~ of available phosphorus. 67.2% ~ 75.5% of sand particles are 0.25 ~ 0.05 mm, 3.25% ~ 5.58% of physical clay particles are less than 0.0 1 mm, and 1.35% ~ 4.35% of clay particles are less than 0.00 1 mm.

Fixed sandy land: soil organic matter 1.8 1% ~ 3.52%, total nitrogen 0.0 1% ~ 0.047%, available nitrogen 1. 14 ~ 3.57 ppm and total phosphorus 0.029%. 56.6% ~ 76.6% of sand particles are 0.25 ~ 0.05 mm, 2.85% ~ 10.3% of physical clay particles are less than 0.0 1 mm, and 1.4% ~ 6.6% of clay particles are less than 0.00/kloc-.

Possible critical value: physical clay-clay with diameter less than 0.001mm.

Main references:

Guan Youzhi. 1992. Elements, clay minerals and sedimentary environment in Horqin sandy land of China desert,12 (1): 9-15.

Hu. 199 1. Quantitative index of land desertification classification in Horqin. China desert, 1 1 (3): 57-6 1.

Liu Yuping, Ci Long Jun. 1998. Study on evaluation index system of grassland desertification in Mu Us sandy land [J]. China Desert, 18 (4): 366-372.

Shen Jianyou, Dong Guangrong, Li Changzhi, et al. Desertification and the change of soil material content. China desert, 12 (1): 40-48.

Wang, Wang, Wang. 2004. Study on evaluation index system of desertification land. Resources and Environment in Arid Areas, 18 (4): 23-28.

Wang Tao, Wei Wu, Zhao, et al. 2004. Analysis on driving factors of modern desertification in Horqin area. China desert, 24 (5): 5 19-528.

Yao Honglin. 2002. Study on Evaluation Index of Desertification Land in Inner Mongolia [J]. Forestry Science and Technology in Inner Mongolia, (3): 19-23.

Zhu Zhenda, Liu Nu, Di Xingmin. 1989. Desertification and its control in China. Beijing: Science Press.

Related environmental and geological problems: the change of soil material content may lead to the death of vegetation.

Overall evaluation: Soil material content is a sensitive indicator of environment and human activities: changes will affect land quality and vegetation growth. Monitoring the change of soil substance content is helpful to predict the future soil desertification and its value to agriculture and forestry.

Four. Groundwater level and hydrochemistry

Name: groundwater level, hydrochemistry

Introduction: Groundwater is the most precious ecological resource in arid, semi-arid and partially semi-humid areas. The change of water level depth affects the growth of surface plants and the process of land desertification. On the other hand, the quality of groundwater, especially the salt content and salinity of water, has a great influence on the hydrochemical composition of soil and the survival and growth of surface plants. The correlation between vegetation and groundwater quality in Tarim River basin shows that Populus euphratica begins to wither when the groundwater salinity is 5 ~ 6g/L, all Populus euphratica dies when the salinity is > 30g/l, and sparse red willows can be seen when the salinity is > 70g/L. ..

Man-made or natural reasons: the groundwater level can change naturally due to climate change, and the change of its buried depth can be used as an indirect index to predict the surface environment and plant growth environment. In addition, over-exploitation by human beings has led to a sharp drop in groundwater level and desertification of surface land. The vegetable planting area in the local greenhouse in Bashang, Hebei Province, absorbed a large amount of groundwater, which led to the drying up of lakes and the desertification of large areas of land.

Applicable environment: any place where groundwater is pumped for human drinking, irrigation and industrial use, or an area that affects the ecosystem.

Spatial scale: from block to landscape/regional scale.

Type of monitoring point: it can represent wells, wells or springs in a specific aquifer.

Determination method: manually measure the depth of groundwater level and monitor it with automatic water level recorder or pressure sensor. Standard hydrogeological methods are used to calculate water balance. When calculating the actual recharge rate, we must consider the climate change and surface ecosystem change in recent decades.

Measurement frequency: the minimum interval used to reflect seasonal and annual changes is month. The time interval for evaluating the state of ancient aquifers should be about 5 years.

Limitations of data and monitoring: in order to determine the overall trend, it is necessary to measure the water level seasonally every year for decades. The total accuracy of manual method is about 65438±0cm, but the accuracy can be improved by using automatic method.

Past and future applications: Ancient water bodies can be used as "archives" of past climate change.

Possible critical value: when the pumping rate exceeds the recharge rate, the sustainable renewable resources become non-renewable and weak after crossing a certain limit. When the pumping speed of the well exceeds the lateral inflow speed, the well will dry up and cross a certain limit, although the situation itself can be reversed when the pumping stops or the recharge increases.

Main references:

Groundwater. Cleaves, Englewood, NJ: prentiss Hall Press.

Introduction to groundwater. London: Allen and Unwin Publishing House.

Quantitative geology. New york Academic Press.

Study on critical index system of groundwater ecological environment and rational utilization of deep confined water in northwest China. Report on 96-9 12-0 1-03S, a key scientific and technological project of the Ninth Five-Year Plan.

deMrsily，G. 1986。 Quantitative hydrology. New york: Academic Press.

Freeze R&D and J.A.Cherry 1979. Groundwater. Ingwald Cliff, New Jersey: prentiss Hall.

Price, M. 1985. Introduce groundwater. London: Allen and Unwin.

Other sources: Environment, Water/Hydrological Company, Geological Survey, International Union of Hydrogeologists, International Association of Hydrological Sciences (IAHS), International Hydrological Programme (IHP) and World Health Organization (WHO).

Related environmental and geological issues: There are a large number of "memoranda" on environmental issues related to groundwater reduction, including wetland drainage, geological stability and soil salinization (see groundwater quality). Groundwater pollution is a big problem in urban areas, which also reduces the total amount of water resources.

Overall evaluation: In areas where groundwater is used, groundwater level is a basic parameter.

Verb (abbreviation for verb) wind erosion and wind accumulation

Name: Wind Erosion and Aeolian Action

Brief introduction: Wind erosion is a complex natural-economic compound process formed by the interaction between atmosphere and PEDOSPHERE or lithosphere, and the interference between biosphere and human activities. Aeolian action is that in the process of wind-driven transportation, fine sand particles, mainly in the form of jumping or rolling transportation, begin to accumulate at specific stationary points, forming various types of sand dunes and sand mats. Wind-blown sand and wind erosion are near-surface phenomena of sandstorm movement, and they are important signs reflecting the geological process of denudation-accumulation in arid areas. Strong winds act on loose sediments and fragile rock formations on the surface, causing wind erosion and taking away fine particles in sediments and soil. The geological process of wind erosion mainly forms Ya Dan landform, wind erosion dry valleys and depressions; The process of wind erosion often exposes underground sediments and plant roots due to wind erosion, which reduces vegetation coverage. Because fine particles blow from the ground, soil nutrients are insufficient or vegetation is reduced. The aeolian process often leads to the formation and movement of sand dunes and grass mats on the surface, burying fields, blocking roads, or thickening the soil in a certain range, which reduces the natural biological yield of cultivated land and grassland.

Significance: The formation of wind erosion and wind accumulation and the landform changes accompanied by drought are important environmental geological characteristics to measure the formation of desert and the development of land desertification.

Man-made or natural reasons: wind erosion and wind accumulation are natural phenomena in arid and windy areas, and their action process often changes the micro-geomorphological characteristics of the surface, the organic combination of soil components and the living environment of vegetation. At the same time, the changeable wind erosion and aeolian surface morphology are very sensitive to human activities, especially human influences such as farming and overgrazing, which will lead to the decrease of vegetation.

Applicable environment: arid, semi-arid and partially semi-humid areas.

Monitoring site type: desert, sandy land in different natural zones and wind erosion and aeolian ground in fragile ecological environment areas.

Spatial scale: block to landscape/mesoscale to regional scale.

Survey method: Using aerial photos, the geological and geomorphological survey and general survey were carried out in typical areas within a certain range. A series of maps, aerial photographs, satellite images and ground verification methods in typical areas are used for large-scale monitoring. Measurement frequency: 5 ~ 20 years 1 time.

Limitations of data and monitoring: different types of rock and soil and landforms have different amounts of wind erosion, and the roughness (obstacle degree) of the ground is different, which leads to the difference of wind weakening near the ground and the difference of wind erosion intensity. Therefore, both wind erosion factors and the resulting wind erosion process are random in time and space, such as wind speed at all levels, so it is difficult to evaluate the erosion intensity of complex landscapes.

Past and future applications: Past wind erosion and aeolian deposits can be detected by studying buried soil layers and ancient sand dunes formed on ancient erosion surfaces.

Possible critical value: the erosion, transportation and accumulation of sediments occur in a specific wind speed range, which depends on particle size, degree of cementation and compaction, water content, vegetation and micro-landform morphology.

Main references:

Desert landform. London: UCL Press.

Geomorphology of desert environment. London: Chapman &; Hall press.

Wang Tao. Deserts and desertification in China. Shijiazhuang: Hebei Science and Technology Press, 2003.

Wang Xunming, Dong Zhibao, Shengzhi Wu, Chen Guangting. Stochastic model of soil wind erosion. Bulletin of soil and water conservation, 200 1, 2 1( 1).

Zheng Wu. Essays on aeolian geomorphology. Beijing: Ocean Press, 2004.

Abraham, A.D. & Parsons 1994. Geomorphology of desert environment. London: Chapman & Hall.

Cook Warren Company; Goody 1993. Desert geomorphology. London: UCL Press.

Woodruff, New Jersey, USA. Sidoway 1965. Proceedings of the American Conference of the Soil Science Society. 29(5):602-608。

Related environmental and geological problems: farmland, grassland degradation and desertification.

Overall evaluation: In arid and semi-arid areas, wind erosion and wind accumulation are valuable indicators of geological environment changes.