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Volume 57, Issue 7, June 2009 ISSN: 0943-0105 (Print) 1866-6299 (Online) From Vol. 6 (1984) to Vol. 20 (1992), this journal was published as Environmental Geology and Water Sciences. As of Volume 59 this journal is published as Environmental Earth Sciences.
In this issue (22 articles) Original Article
Geochemical distribution and removal of As, Fe, Mn and Al in a surface water system affected by acid mine drainage at a coalfield in Southwestern China Pan Wu, Changyuan Tang, Congqiang Liu, Lijun Zhu, TingQuan Pei…
Pages 1457-1467
Original Article
Estimation of potential pollution from mine tailings in the San Pedro River (1993–2005), Mexico–US border Agustín Gómez-Alvarez, Diana Meza-Figueroa…
Pages 1469-1479
Original Article
Rocky desertification and its causes in karst areas: a case study in Yongshun County, Hunan Province, China Y. J. Xiong, G. Y. Qiu, D. K. Mo, H. Lin, H. Sun, Q. X. Wang…
Pages 1481-1488
Original Article
Well site conditions associated with nitrate contamination in a multilayer semiconfined aquifer of Buenos Aires, Argentina L. I. Carbó, M. C. Flores, M. A. Herrero
Pages 1489-1500
Original Article
Spatial and seasonal variation of salt ions under the influence of halophytes, in a coastal flat in eastern China Yanyou Wu, Rongcheng Liu, Yuguo Zhao, Pingping Li, Congqiang Liu
Pages 1501-1508
Original Article
A laboratory study on groundwater quality and mass movement occurrence Jen-Chen Fan, Che-Hsin Liu, Chih-Hsiang Yang, Hsiao-Yu Huang
Pages 1509-1519
Original Article
Spatial relationship of groundwater arsenic distribution with regional topography and water-table fluctuations in the shallow aquifers in Bangladesh M. Shamsudduha, L. J. Marzen, A. Uddin, M.-K. Lee, J. A. Saunders
Pages 1521-1535
Original Article
CO2 source-sink matching in the lower 48 United States, with examples from the Texas Gulf Coast and Permian Basin W. A. Ambrose, C. Breton, M. H. Holtz, V. Núñez-López…
Pages 1537-1551
Original Article
History of landslide susceptibility and a chorology of landslide-prone areas in the Western Ghats of Kerala, India Sekhar L. Kuriakose, G. Sankar, C. Muraleedharan
Pages 1553-1568
Original Article
Groundwater vulnerability assessment in shallow aquifer of Kathmandu Valley using GIS-based DRASTIC model Dhundi Raj Pathak, Akira Hiratsuka, Isao Awata, Luonan Chen
Pages 1569-1578
Original Article
Impact of fertilizer application and urban wastes on the quality of groundwater in the Cambrai Chalk aquifer, Northern France Hani Serhal, Daniel Bernard, Jamal El Khattabi…
Pages 1579-1592
Original Article
Natural and anthropogenic influences in the northeastern coast of the Nile delta, Egypt Mahmoud M. El Banna, Omran E. Frihy
Pages 1593-1602
Original Article
Slope stability analysis on a regional scale using GIS: a case study from Dhading, Nepal R. L. Ray, F. De Smedt
Pages 1603-1611
Original Article
Geological and environmental management of ceramic clay quarries: a review T. Sanfeliu, M. M. Jordán
Pages 1613-1618
Original Article
Behaviour of chromium VI in a multilayer aquifer in the industrial zone of Annaba, Algeria H. Khérici-Bousnoubra, N. Khérici, E. F. Derradji, C. Rousset…
Pages 1619-1624
Original Article
A survey of oil and gas wells in the Texas Gulf Coast, USA, and implications for geological sequestration of CO2 Jean-Philippe Nicot
Pages 1625-1638
Original Article
Numerical modeling of the development of a preferentially leached layer on feldspar surfaces Changbing Yang, Javier Samper, Chen Zhu, Scott B. Jones
Pages 1639-1647
Original Article
Geochemical baseline of trace elements in the sediment in Dexing area, South China Yanguo Teng, Shijun Ni, Jinsheng Wang, Ligen Niu
Pages 1649-1660
Original Article
Modeling diagnosis of suspended sediment transport in tidal estuarine system Wen-Cheng Liu, Chun-Hsien Lee, Chin H. Wu, Nobuaki Kimura
Pages 1661-1673
Original Article
Landslide susceptibility mapping of vicinity of Yaka Landslide (Gelendost, Turkey) using conditional probability approach in GIS Adnan Ozdemir
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Pages 1675-1686
From Vol. 6 (1984) to Vol. 20 (1992), this journal was published as Environmental Environ Geol (2009) 57:1481–1488 Geology DOI 10.1007/s00254-008-1425-7
ORIGINAL ARTICLE
and Water Sciences. Prior to Volume 59 this journal was published as
Environmental Geology. As of Volume 59 this journal is published as Environmental Earth Sciences. IF=1.445 (2012)
Rocky desertification and its causes in karst areas: a case study in Yongshun County, Hunan Province, China Y. J. Xiong Æ G. Y. Qiu Æ D. K. Mo Æ H. Lin Æ H. Sun Æ Q. X. Wang Æ S. H. Zhao Æ J. Yin
Received: 30 May 2007 / Revised: 19 May 2008 / Accepted: 9 June 2008 / Published online: 27 June 2008 Ó Springer-Verlag 2008
Abstract Rocky desertification, a process of land degradation characterized by soil erosion and bedrock exposure, is one of the most serious land degradation problems in karst areas, and is regarded as an obstacle to local sustainable development. It is well known that human activities can accelerate rocky desertification; however, the effects of climate change on rocky desertification in karst areas are still unclear. This study focused on the effects of temperature and precipitation changes and human activities
Electronic supplementary material The online version of this article (doi:10.1007/s00254-008-1425-7) contains supplementary material, which is available to authorized users. Y. J. Xiong G. Y. Qiu (&) S. H. Zhao J. Yin College of Resources Science and Technology, Beijing Normal University, Xinjiekouwai St. 19th, 100875 Beijing, People’s Republic of China e-mail:
[email protected] Y. J. Xiong e-mail:
[email protected] G. Y. Qiu State Key Laboratory of Earth Surface Processes and Resource Ecology, Beijing Normal University, 100875 Beijing, People’s Republic of China D. K. Mo H. Lin H. Sun Research Center of Forestry Remote Sensing and Information Engineering, Central South University of Forestry and Technology, Shaoshan Road 498th, 410004 Changsha, Hunan, People’s Republic of China Q. X. Wang Asia Water Environment Section, National Institute for Environmental Studies, 16-2 Onogawa, 305-8506 Tsukuba, Japan
on rocky desertification in karst areas to determine the impacts of climate change and human disturbances on rocky desertification. Areas of different level of rocky desertification were obtained from Landsat TM (1987) and Landsat ETM+ (2000) images. The results show that, although the total desertification area increased by only 1.27% between 1987 and 2000, 17.73% of the slightly desertified land had degraded to a moderate or intense level, 2.01 and 15.71%, respectively. Meanwhile, between 1987 and 2000, the air temperature increased by 0.7°C, and precipitation increased by 170 mm. Statistical results indicate that the increase in precipitation was caused by heavy rainfall. In addition, under the interactive influences of heavy rainfall and temperature, the average karst dissolution rate was about 87 m3 km-2 a-1 during the 14 years in the study area. Further analysis indicated that rocky desertification was positively related with the increase in temperature and precipitation and especially with the heavy rainfall events. Climate change accelerated rocky desertification in the karst areas. Keywords Remote sensing Karst rocky desertification Temperature Heavy rainfall
Introduction Climate change refers to a statistically significant variation in either the mean state of the climate or in its variability, which persists for an extended period (Houghton et al. 2001). Climate exerts strong influences on the environment, especially precipitation and temperature, which are two key factors that determine the potential distribution of terrestrial vegetation and constitute principal factors in the genesis and evolution of soil (Sivakumar 2006).
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Rocky desertification is defined as a process of land degradation (Kharin 1990) and is characterized by soil erosion and bedrock exposure that leads to low productivity and eventually these places become fragile eco-geo-environments. Karst terrain consists of mountainous limestone with barren soil, severe water–soil erosion, fragile ecosystems, and frequent droughts and flood disasters (Liu et al. 2005). The problems caused by rocky desertification in these karst areas tend to be much more serious than in other terrains (Xiong et al. 2002; Wang et al. 2004a, b). About 175,864 km2 of karst areas are distributed throughout southwest China (Wang et al. 2003). In China, many studies of the impacts of climate change on the environment, e.g., on agriculture (Smit and Cai 1996) and land degradation (Zhang et al. 2005), have been carried out, but studies on rocky desertification in karst areas in southwest China are scarce. While some studies have only described climate change as a factor of rocky desertification (Yao et al. 2001; Jing et al. 2003; Liao et al. 2004; Hu et al. 2004; Wang et al. 2004a, b), they had no quantitative analyses. Since the effects of climate change on rocky desertification in karst areas are still unclear, it is necessary to evaluate and quantify its impacts (UNCCD 2005; Sivakumar 2006). Therefore, this paper focuses on the effects of climate change on rocky desertification in karst areas to determine whether climate change can lead to rocky desertification. Study area The study area of Yongshun County, located at approximately 28°420 –29°270 N and 109°340 –110°240 E, is Fig. 1 Location map of Yongshun County and the locations of meteorological stations
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in Xiangxi Tujia and Miao Nationality Autonomous Prefecture, northwestern Hunan Province, China, and it has an area of 3,810.6 km2 (Fig. 1). Topographic features of this area include fluvial erosion landforms and karst landforms, characterized by hills, syncline valleys, and mountains. Elevations range from 162.6 to 1,437.9 m and mountains are predominant. The climate is a subtropical warm–moist climate, with a mean annual temperature of 16.4°C and mean annual precipitation of 1,357 mm.
Data and methodology Data In this study, Landsat images were adopted because of their continuous temporal and fine spatial resolution. In consideration of the availability and quality of the satellite data, one Thematic Mapper (TM) image (October 26th, 1987) and one Enhanced Thematic Mapper (ETM+) image (May 14th, 2000) from path 125 and row 40 were chosen (Figure 1, in Electronic Supplementary Material). The meteorological data, obtained from seven national meteorological stations (Fig. 1) with daily observed values for temperature, precipitation and other parameters from 1959 to 2000 were used. Socio-economic statistical data between 1987 and 2000 were also collected from the National Bureau of Statistics of China. Other data included topographical maps, slope data, forestry inventory data, and land-use maps.
Environ Geol (2009) 57:1481–1488
Methodology The processing steps of the study are shown in Fig. 2. First, the satellite data were preprocessed and combined to form false color images by displaying bands 4, 3, and 2 with red, green, and blue, respectively. Second, the images and other data were projected to the same coordinate system and spatial resolution. The images were then segmented and classified. The classification process included three stages (Mo et al. 2007): (a) image segmentation and feature extraction, which is based on a multi-scale segmentation technique and is an object-oriented image analysis method, rather than the traditional methods, which are based on individual pixels (Benz et al. 2004; Mo et al. 2006; Lathrop et al. 2006; Yu et al. 2006); (b) performing field surveys and establishing interpreted signs (the field survey data included two parts: one was the results of a forestry resources investigation performed by Central South Academy of Forest Inventory and Planning in 2000; the other was personal field surveys based on the adopted ETM+ image from May 10–15, 2002); and (c) sample training and
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classification. With the interpreted sign and extracted features, the segmented images were classified into nonrocky or rocky desertification areas. Thereafter, with the extracted features and auxiliary data, the rocky desertification areas were further classified into slight, moderate, and intense levels through visual human– computer interactive interpretation in a geographical information system according to vegetation cover rate, bedrock exposure rate, and slope, as shown in Table 1 (Wang et al. 2004a). When the attributes of a segment fall into one of the three criteria ranges, the level of rocky desertification can be confirmed. The results are shown in Figs. 3 and 4. Finally, the results of rocky desertification were quantitatively analyzed. Meanwhile, meteorological data obtained from seven meteorological stations around the study area (Fig. 1) were processed. The daily observed temperature and precipitation data from 1956 to 2000 were selected. Some missing observed data were excluded, and the mean annual temperature of each year was averaged. Mean precipitation was summed from 1956 to 2000. Then, the annual mean values of temperature and precipitation were calculated for
Fig. 2 Synopsis of the methodology
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Table 1 Classification standards of rocky desertification (revised from Wang et al. 2004a) Vegetation cover (%) Bedrock exposure (%) Slope (°) Slight
35–50
35–65
15–20
Moderate 20–34
66–85
21–25
[85
[25
Intense
10–19
each meteorological station. In addition, the data were interpolated for the study area by applying the inverse distance weight (IDW) interpolation method, which assumes that each input point has a local influence diminishing with distance. The results are shown in Figs. 5 and 6. Finally, the frequency of heavy rainfall, defined as precipitation more than 50 mm day-1, was calculated for each 14-year period from 1959 to 2000 (Fig. 7). Lastly, based on the results generalized from above and the statistical results from the socio-economic data (Figures 2, 3, 4, 5, in Electronic Supplementary Material), the likely driving factors that could result in rocky desertification development were elaborated in detail.
Results Rocky desertification Based on the results of rocky desertification (Fig. 3), numerical statistical data could be calculated (Fig. 4). Figure 3 shows the levels of desertification from 1987 and 2000. Since data from both Landsat 5 TM and Landsat 7 ETM+ have the same spectral resolution and spatial resolution from band 1 to band 7 (spatial resolution of band 6 is an exception, Table 2), there is no difference between the band width and spatial resolution of the two satellite platforms. Therefore, for the purpose of this study, the results are completely comparable. Between 1987 and
Fig. 3 Maps of different levels of rocky desertification extracted from Landsat data a for 1987 and b for 2000
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2000, the area of rocky desertification increased by 1.27% (Fig. 4). Though the total desertification area expanded only a small amount, 17.73% of the slightly desertified land had degraded to the moderate or intense level, 2.01% for the former and 15.71% for the latter. In general, rocky desertification in Yongshun County was getting worse, and the affected areas have increased in the past decade, especially those of intense rocky desertification. Climate change Figures 5 and 6 suggest that climate change in Yongshun County is occurring, as both temperature and precipitation rose from 1987 to 2000, during which time, the temperature increased by 0.7°C and precipitation increased by 170 mm on average. The rising temperature trend in the study area is similar to the universal trend of the global average surface temperature, which has increased by 0.6 ± 0.2°C since the late nineteenth century (Houghton et al. 2001). To find out why precipitation has increased, annual precipitation was divided into two parts: heavy rainfall (precipitation more than 50 mm day-1) and common precipitation (precipitation less than 50 mm day-1). The two types of precipitation of the study area were then interpolated with meteorological data according to daily rainfall amounts (Fig. 8), leading to the conclusion that the increase in precipitation was caused by heavy rainfall events. Figure 8 shows that the tendency of common precipitation decreased slightly, whereas that of heavy rainfall increased. Figure 7 confirms that the frequency of heavy rainfall has continued to increase since the 1960s. Other researchers, such as Tang et al. (2006) in China and Karl and Knight (1998) in the U.S., have also reported that total precipitation has increased because of the heavy rainfall events in the past century. Since water power is mainly related to the splash power of precipitation and rainfall has the greatest direct erosive
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Fig. 5 Variations and linear trend of mean annual precipitation in Yongshun County
Fig. 4 Degradation trends of rocky desertification a for 1987 and b for 2000 (the numbers indicate the percentage of areas of each kind of rocky desertification in the study area)
Table 2 Spatial and spectral characteristics of Landsat 5 TM and Landsat 7 ETM+ Band
Spectral range (lm)
Pixel resolution (m)
1
0.450–0.515
30
2
0.525–0.605
30
3
0.630–0.690
30
4
0.750–0.900
30
5
1.550–1.750
30
7
2.080–2.350
30
6
10.400–12.500
120 (TM only) 60 (ETM+ only)
8
0.520–0.900
15 (ETM+ only)
power, especially the intensity of precipitation (FavisMortlock and Guerra 1999; Pruski and Nearing 2002; Michaela et al. 2005; Nearing et al. 2005), changes in the frequency and intensity of precipitation caused by climate change affect soil erosion processes. The heavier the rainfall is, the more serious are the effects of splash erosion. The powerful impacts caused by heavy rainfall can wash soil away directly, thus enhancing soil erosion. Pruski and Nearing (2002) found that, for every 1% increase in total rainfall, the erosion rate increases by only 0.85% if there was
Fig. 6 Variations and linear trend of mean annual temperature in Yongshun County
Fig. 7 Periodical changes of heavy rainfall in every 14-year period from 1959 to 2000 in Yongshun County (frequency: the times heavy rainfall occurred)
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Environ Geol (2009) 57:1481–1488 Table 3 Land use and land change in Yongshun Land use type
Fig. 8 Trend of heavy rainfall and common precipitation from 1987 to 2000
no corresponding increase in rainfall intensity; however, if both rainfall amount and intensity change together in a statistically representative manner, the predicted erosion rate increases by 1.7% for every 1% increase in total rainfall. Thus, the increase in heavy rainfall and its frequency in the study area was the most likely natural driving factor that resulted in the development of rocky desertification.
Discussion of the causes of rocky desertification Human disturbances As is the case with the rest of China, the population in Yongshun is increasing, but the growth rate is around 5,000 year-1 and has been declining (Figure 2, in Electronic Supplementary Material). Since it is hard to evaluate the effects on rocky desertification caused by population increase, specific human activities were chosen to judge whether or not they resulted in rocky desertification. Over-reclamation was analyzed based on the area of farmland. Farmland is composed of paddy fields and dry farming fields. The statistics available since 1989 showed that both kinds of farmland decreased slightly, except for a rebound in 2000 (Figure 3, in Electronic Supplementary Material). This showed that, as the area of farmland decreased, reclamation was not impossible. Even if overreclamation occurred in 2000, rocky desertification could not seriously degrade in 1 year. Therefore, we inferred that the rocky desertification in Yongshun was not related to over-reclamation. Grazing was analyzed as a possible cause of desertification. Even though the number of livestock has increased since 1987, the maximum livestock density
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Percent (%) 1987
2000
Urban
0.06
0.13
Water
1.09
0.79
Forest
52.95
51.41
Shrub
36.15
34.50
Farmland
7.85
10.19
Bare area
1.90
2.98
was 30 capita km-2 in 1999 (Figure 4, in Electronic Supplementary Material). Xie and Wittig (2004) suggested that the ideal intensity of grazing activities should remain within 50–60 km-2 in Ningxia province, northern China. Considering that their study area was in a much more arid region than that of Yongshun, we interpreted that 30 livestock km-2 was far from over-grazing. Fuel wood collection has been forbidden in the study area since the early 1990s, and there is no wild Chinese medicine in Yongshun. Hence, the frequency of fuel wood and medicine collection, regarded as one of the main causes of anthropogenic land degradation, was most likely negligible. Economic development in this area could be considered collateral evidence to a low frequency of fuel wood collection as GDP and the average per capita net income of peasants has shown continued growth (Figure 5, in Electronic Supplementary Material). Good economic conditions are known to reduce fuel wood collection. Land use can also represent human activities that are the key factors in causing rocky desertification. Therefore, based on the classification results of the two images (Table 3), land use and land change (LUCC) were analyzed in Yongshun for the period of 1987–2000. The predominant land type was forest, followed by shrub, farmland, bare area, water, and urban areas. Among the six land types, half decreased in area while half increased. The area of forest lost was 1.54%, and 1.65% of shrub and 0.30% of water areas were lost. In contrast, the areas of farmland, bare area, and urban areas increased 2.34, 1.08, and 0.07%, respectively. Overlaying LUCC maps with the rocky desertification maps revealed that rocky desertification was often accompanied by a loss of vegetation, such as forest land changing into shrub or shrub to farmland and even from forest or shrub to bare areas. The decline of forest and shrub areas and the increase of farmland and bare areas accounted for land degradation in the study area. According to the results of analyzing the above driving factors, several effects of human activities could not be ignored, but the effects of over-reclamation and overgrazing could be excluded as the driving factors that result in rocky desertification. Furthermore, rapid urbanization
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and large scale logging were not found in the study area. In these cases, sudden changes of land use caused by human activities were not predominant. Changes of temperature and precipitation Because human disturbance was not the predominant factor for rocky desertification, gradual changes of land caused by natural driving factors could mostly account for rocky desertification. The interaction between natural factors and environmental evolution is often complex, dynamic, and nonlinear. Hence, the powerful driving force of nature should not be underestimated. Studies have found that increasing temperature affects soil erosion indirectly in several ways. Vegetation can protect soil from erosion in three ways: (a) lessening the splash power of precipitation, (b) intercepting and capturing precipitation, and (c) functioning as an agent of anti-erosion. In Yongshun County, there was not enough soil for vegetation to live within the carbonate rock outcrop areas, which consequently led to less vegetation cover and less protection for the soil. In addition, under high temperatures, e.g., 30°C, soil evaporation and vegetation transpiration must increase, which can lessen soil moisture, further drying out the remaining soil and in some cases, leading to drought. Therefore, the environment becomes increasingly fragile to different erosions, such as water erosion. In addition, the frequency and intensity of heavy rainfall has been increasing, which has led to splash erosion directly in areas with little vegetation cover and which has reduced soil infiltration capacity due to decreased soil porosity from the splashed soil. As a result, with more rainfall, there is also much more overland flow that washes soil away. When comparing the rates of soil formation and soil erosion, the latter can occur in a very short time. In a case study in Jishou, the capital of Xiangxi Autonomous Prefecture, the results showed that it would take 28,000– 84,000 years to form residual soil with a depth of one meter (Wang et al. 1999). Soil erosion has been worsening for ages, resulting in soil loss and bedrock exposure and leading to gradual rocky desertification. When temperature and precipitation interact together, the impact on land surface is even more complex.
According to a study of Pulina given by Cao et al. (2005), when temperature is low, precipitation variation has little effect on karst dissolution rates, but, when temperature rises to 16–20°C, karst dissolution rates rise quickly as precipitation increases (Fig. 9). From 1987 to 2000 in the study area, the mean annual temperature ranged from 15.9 to 17.3°C (Fig. 5), and the mean annual precipitation ranged from 1,040 to 1,770 mm (Fig. 6). Karst dissolution rates were interpolated with the results from Pulina (Cao et al. 2005), and the average value was about 87 m3 km-2 a-1 in Yongshun County (Table 4). Table 4 shows that karst dissolution rates were positively correlated with the amount of precipitation when temperature ranged from 15.9 to 17.3°C. If annual precipitation was less than 1,200 mm, the maximum dissolution rate was only 68 m3 km-2 a-1, but, when the annual precipitation became more than 1,400 mm, the minimum dissolution rate increased to 86 m3 km-2 a-1. During the 14 years, there were nine years in which the karst dissolution rate was higher than 86 m3 km-2 a-1, which could be considered the best evidence of karst rocky desertification.
Fig. 9 The relation between precipitation, temperature and dissolution rate (revised from Cao et al. 2005)
Table 4 Karst dissolution rate during 1987–2000 Year
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
MAP (mm)
1,419
1,047
1,600
1,428
1,449
1,108
1,628
1,140
1,571
1,606
1,146
1,770
1,680
1,169
MAT (°C)
16.3
16.4
MAKDR (m3 km-2 a-1)
87
60
15.9 100
16.8
16.2
16.5
88
88
64
15.9 100
16.8
16.6
68
99
16.1 100
16.6 68
17.3 116
17.3 108
16.5 68
MAP mean annual precipitation, MAT mean annual temperature, MKDR mean annual karst dissolution rate
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Conclusions The conclusions of this study were that rocky desertification in Yongshun County was positively correlated to the increased precipitation and temperature in the past 14 years, especially the heavy rainfall, and that climate change accelerated the rocky desertification in the karst areas. Acknowledgments This study was supported by the National Science Foundation for Distinguished Young Scholars (Project 40425008) and by the Scientific Research Fund of Central South University of Forestry and Technology (Project 07005B). Thanks go to F. Che, X. P. Xue, H. Wang, Y. L. Sun, X. Li, Doctor C. Y. He, and Professor J. Chen, for their advice, to the Forestry Department of Hunan Province for providing forest inventory data of Yongshun County, to the China Meteorological Administration for providing meteorological data, to the National Bureau of Statistics of China for providing socio-economic data, and to the University of Maryland, for providing Landsat data.
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