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1.
Spatio-temporal patterns of agricultural expansion and its effect on watershed degradation: a case from the mountains of Nepal 总被引:1,自引:1,他引:0
K. C. Krishna Bahadur 《Environmental Earth Sciences》2012,65(7):2063-2077
Expansion of agricultural at the cost of forested land is a common cause of watershed degradation in the mountain zones of
developing countries. Many studies have been conducted to demonstrate land use changes in such regions. However, current knowledge
regarding the changes, driving forces and implications of such change within the context of watershed development is limited.
This study analyses changes in spatial patterns of agricultural land use and their consequences for watershed degradation
during the 1976–2000 period along an altitude gradient in a watershed in Nepal, by means of remote sensing, GIS and the universal
soil loss equation. Estimated soil loss ranged from 589 to 620 t ha−1 y−1, while areas of extreme hazard severity (>100 t ha−1) increased from 9 to 14.5% from 1990 to 2000. Spatial distribution of soil loss in 2000 was characterized by 88% of total
soil losses being from upland agricultural areas. The study determined that without considering other forms of land degradation,
only water erosion was responsible for erosion of a substantial area in a short timeframe. Areas under upland cultivation
are in an extremely vulnerable state, with these areas potentially no longer cultivable within a period of 6 years. As sustainability
of the watershed is dependent on forests, continued depletion of forest resources will result in poor economic returns from
agriculture for local people, together with loss of ecosystem services. Thus, in order to achieve the goal of watershed development,
remaining forest lands must be kept under strict protection. 相似文献
2.
E. C. Milbrandt J. M. Greenawalt-Boswell P. D. Sokoloff S. A. Bortone 《Estuaries and Coasts》2006,29(6):979-984
Although hurricane disturbance is a natural occurrence in mangrove forests, the effect of widespread human alterations on
the resiliency of estuarine habitats is unknown. The resiliency of mangrove forests in southwest Florida to the 2004 hurricane
season was evaluated by determining the immediate response of mangroves to a catastrophic hurricane in areas with restricted
and unrestricted tidal connections. The landfall of Hurricane Charley, a category 4 storm, left pronounced disturbances to
mangrove forests on southwest Florida barrier islands. A significant and negative relationship between canopy loss and distance
from the eyewall was observed. While a species-specific response to the hurricane was expected, no significant differences
were found among species in the size of severely impacted trees. In the region farthest from the eyewall, increases in canopy
density indicated that refoliation and recovery occurred relatively quickly. There were no increases or decreases in canopy
density in regions closer to the eyewall where there were complete losses of crown structures. In pre-hurricane surveys, plots
located in areas of management concern (i.e., restricted connection) had significantly lower stem diameter at breast height
and higher stem densities than plots with unrestricted connection. These differences partially dictated the severity of effect
from the hurricane. There were also significantly lower red mangrove (Rhizophora mangle) seedling densities in plots with restricted connections. These observations suggest that delays in forest recovery are possible
in severely impacted areas if either the delivery of propagules or the production of seedlings is reduced by habitat fragmentation. 相似文献
3.
Estimation of soil erosion using RUSLE in a GIS framework: a case study in the Buyukcekmece Lake watershed,northwest Turkey 总被引:4,自引:3,他引:1
This study was aimed at predicting soil erosion risk in the Buyukcekmece Lake watershed located in the western part of Istanbul, Turkey, by using Revised Universal Soil Loss Equation (RUSLE) model in a GIS framework. The factors used in RUSLE were computed by using different data obtained or produced from meteorological station, soil surveys, topographic maps, and satellite images. The RUSLE factors were represented by raster layers in a GIS environment and then multiplied together to estimate the soil erosion rate in the study area using spatial analyst tool of ArcGIS 9.3. In the study, soil loss rate below 1 t/ha/year was defined as low erosion, while those >10 t/ha/year were defined as severe erosion. The values between low and severe erosion were further classified as slight, moderate, and high erosion areas. The study provided a reliable prediction of soil erosion rates and delineation of erosion-prone areas within the watershed. As the study revealed, soil erosion risk is low in more than half of the study area (54%) with soil loss <1 t/ha/year. Around one-fifth of the study area (19%) has slight erosion risk with values between 1 and 3 t/ha/year. Only 11% of the study area was found to be under high erosion risk with soil loss between 5 and 10 t/ha/year. The severe erosion risk is seen only in 5% of the study area with soil loss more than 10 t/ha/year. As the study revealed, nearly half of the Buyukcekmece Lake watershed requires implementation of effective soil conservation measures to reduce soil erosion risk. 相似文献
4.
Pensacola Bay, Florida, was in the strong northeast quadrant of Hurricane Ivan when it made landfall on September 16, 2004
as a category 3 hurricane on the Saffir-Simpson scale. We present data describing the timeline and maximum height of the storm
surge, the extent of flooding of coastal land, and the magnitude of the freshwater inflow pulse that followed the storm. We
computed the magnitude of tidal flushing associated with the surge using a tidal prism model. We also evaluated hurricane
effects on water quality using water quality surveys conducted 20 and 50 d after the storm, which we compared with a survey
14 d before landfall. We evaluated the scale of hurricane effects relative to normal variability using a 5-yr monthly record.
Ivan's 3.5 m storm surge inundated 165 km2 of land, increasing the surface area of Pensacola Bay by 50% and its volume by 230%. The model suggests that 60% of the Bay's
volume was flushed, initially increasing the average salinity of Bay waters from 23 to 30 and lowering nutrient and chlorophylla concentrations. Additional computations suggest that wind forcing was sufficient to completely mix the water column during
the storm. Freshwater discharge from the largest river increased twentyfold during the subsequent 4 d, stimulating a modest
phytoplankton bloom (chlorophyll up to 18 μg l−1) and maintaining hypoxia for several months. Although the immediate physical perturbation was extreme, the water quality
effects that persisted beyond the first several days were within the normal range of variability for this system. In terms
of water quality and phytoplankton productivity effects, this ecosystem appears to be quite resilient in the face of a severe
hurricane effect. 相似文献
5.
An assessment of soil erosion probability and erosion rate in a tropical mountainous watershed using remote sensing and GIS 总被引:1,自引:1,他引:0
H. Vijith M. Suma V. B. Rekha C. Shiju P. G. Rejith 《Arabian Journal of Geosciences》2012,5(4):797-805
Remote sensing data and Geographical Information System (GIS) has been integrated with the weighted index overlay (WIO) method and E 30 model for the identification and delineation of soil erosion susceptibility zones and the assessment of rate of soil erosion in the mountainous sub-watershed of River Manimala in Kerala (India). Soil erosion is identified as the one of the most serious environmental problems in the human altered mountainous environment. The reliability of estimated soil erosion susceptibility and soil loss is based on how accurately the different factors were estimated or prepared. In the present analysis, factors that are considered to be influence the soil erosion are: land use/land cover, NDVI, landform, drainage density, drainage frequency, lineament frequency, slope, and relative relief. By the WIO analysis, the area is divided into zones representing low (33.30%), moderate (33.70%), and high (33%) erosion proneness. The annual soil erosion rate of the area under investigation was calculated by carefully determining its various parameters and erosion for each of the pixels were estimated individually. The spatial pattern thus created for the area indicates that the average annual rate of soil erosion in the area was ranging from 0.04 mm yr−1 to 61.80 mm yr−1. The high soil erosion probability and maximum erosion rate was observed in areas with high terrain alteration, high relief and slopes with the intensity and duration of heavy precipitation during the monsoons. 相似文献
6.
《Quaternary Science Reviews》2007,26(9-10):1313-1331
In this paper, we describe mapping of palaeo-ice streams in the Foxe/Baffin sector of the Laurentide Ice Sheet by means of geomorphological interpretation of high-resolution satellite images. Our interpretations were guided by a glaciological inversion scheme, aided by digital elevation models, publicly available sonar surveys and field studies. As a result, we produced a map depicting the location, geometry and relative temporal changes of palaeo-ice streams and analysed their palaeoglaciological implications for the Foxe/Baffin sector. We conclude that in the period between the Last Glacial Maximum and approximately 7.0 kyr BP, the Foxe/Baffin sector was largely drained by topographically controlled outlet glaciers and ice streams, which were organized in a relatively stable pattern. During this time, large areas of Melville Peninsula and central Baffin Island were subject to cold-based conditions. Between 7.0 and 6.0 kyr BP, the Foxe/Baffin sector collapsed catastrophically in the Foxe Basin, after which its remnant portion became confined to Baffin Island. During this collapse, rapid successions of small transient ice streams occurred along wide, loosely defined topographical corridors in two sectors of Baffin Island. The presently available landform archive on emerged land is not sufficient to conclusively support the existence of fully scaled ice streams along the whole length of Hudson Strait. As an alternative solution, we propose that topographically controlled ice streams might have occurred along the deepest parts of Hudson Strait, with attendant cold-based ice zones on marginal areas and islands at the head of the strait. 相似文献
7.
Xi Wang Zhang Bing Fang Wu Xiao Song Li Shan Long Lu 《Environmental Earth Sciences》2012,65(1):221-229
The spatial pattern of soil erosion can provide valuable insights into the soil erosion processes that require a rapid assessment
in practical applications. Generally, quantitative technique is expensive and time-consuming. The objective of this paper
is to reveal the spatial pattern of erosion with a rapid assessment method. The affecting factors such as land cover, vegetation
fraction and slope gradient are integrated into this method using a qualitative means. Beijing-1 images in 2006 were used
to produce land-cover and vegetation fraction, and 1:50,000 topographic maps were used to calculate slope gradient. The study
area was classified into six grades. Results show that the upstream area of Guanting Reservoir, in general, is exposed to
a moderate risk; there are 17,740.33 km2 of land that suffered from water soil erosion in 2006, occupied 40.69% of the total area, and most of the soil erosion area
is on the light and moderate risk, which occupied 25.05 and 62.83% of the eroded area, respectively. Eight elevation zones
and six slope gradient zones were overlaid with the assessed risk. The analyzed results show that: (1) the areas above 2,000 m
have the lowest erosion risk, which is only 0.75% of the eroded area; 1,250–1,500 m elevation zone has the highest erosion
risk, which is 34.72% of the eroded area. (2) The slope gradient zone less than 5 degrees and greater than 35 degrees have
the lowest erosion risk, which is 0.02 and 0.75% of the eroded area, respectively; the slope gradient zone with 8–15 degrees
has the highest erosion risk, which is 36.40% of the eroded area. These results will be useful for water and soil conservation
management and the planning of mitigation measures. 相似文献
8.
We present here the first high-resolution pollen record of vegetation response to interactions of hurricane and fire disturbances over the past 1200 yr from a small lake in Alabama on the Gulf of Mexico coast. The paleotempestological record inferred from the overwash sand layers suggests that the Alabama coast was directly struck by Saffir-Simpson category 4 or 5 hurricanes twice during the last 1200 yr, around 1170 and 860 cal yr BP, suggesting an annual landfall probability of 0.17% for these intense hurricanes. The charcoal data suggest that intense fires occurred after each of these hurricanes. The pollen data suggest that populations of halophytic plants (Chenopodiaceae) and heliophytic shrubs (Myrica) expanded after the hurricane strikes, probably due to saltwater intrusion into the marshes and soil salinization caused by overwash processes. Populations of pines (Pinus sp.) decreased significantly after each intense hurricane and the ensuing intense fire, suggesting that repeated hurricane-fire interactions resulted in high tree mortality and probably impeded recruitment and recovery. Our data support the hypothesis that the likelihood and intensity of fire increased significantly after a major hurricane, producing responses by vegetation that are more complex and unpredictable than if the disturbance agents were acting singly and independently. 相似文献
9.
Rafael da Rosa Couto Luiz Carloz Pittol Martini Luciano Colpo Gatiboni Paulo Belli Filho Sérgio Roberto Martins Cleiton Junior Ribeiro Lazzari Vilmar Müller Júnior Jucinei José Comin Paul John Anthony Withers Ricardo Bergamo Schenato Gustavo Brunetto 《Environmental Earth Sciences》2018,77(4):144
The application of phosphorus (P)-index methodology to assess the risk of water pollution from agriculture in river basins usually takes time and expends a great amount of resources. This study adapted the P-index methodology using digital mapping of key basin risk criteria for P loss in reference areas to evaluate the wider vulnerability to P loss in a zero-order basin with an intense concentration of pigs and with a history of pig slurry additions to the soil. The P content of eleven reference areas, where ten areas have received various applications of pig slurry and one area has no history of addition, was extrapolated to a zero-order basin using principal component analysis and analysis of hierarchical groupings. Estimated loss of soil and the distance between the P source and the watercourse were mapped using satellite images and in situ evaluations. The methodology of extrapolating was well correlated with a survey of P concentrations in land runoff and provides the potential to improve land management of those areas that are most vulnerable. Principal component analysis and hierarchical clustering analysis proved to be useful tools for the separation of areas with different slurry application times. Our results suggest that the P loss risk could be reduced through the adoption of soil conservation techniques such as reduced-tillage incorporating slurry and crop residue management to provide adequate soil protection, reduce the impact of raindrops and reduce erosion risk and transport of chemical pollutants to water bodies. 相似文献
10.
Michela Izzo Pietro Patrizio Ciro Aucelli Yudith Javier Caridad Pérez Carmen Maria Rosskopf 《Natural Hazards》2010,53(1):139-158
In the period between the end of October and the beginning of November 2007, the Dominican Republic was hit by the tropical
storm Noel, then turned into hurricane in its movement toward the Californian coasts. The passage of Noel was accompanied
by huge precipitation especially in the south-western part of the country. In some areas, the rainfall registered in 6 days
exceeded 700 mm, i.e., more than two-thirds of the mean annual precipitation. The return periods calculated for this rainfall
event vary greatly from region to region: while they locally reach 200 years, such as in San José de Ocoa (50 km west of Santo
Domingo), in other areas, as for instance in the territory of the capital Santo Domingo, return periods do not exceed 20 years.
The tropical storm caused huge damage both in terms of human victims and economic losses, related to diffused inundations
and landslide phenomena, which may be attributed only partially to the exceptionality of the event. As a matter of fact, in
many regions, the inadequate answer of the territory—widely characterized by serious problems of land degradation and an almost
complete lack of territorial planning—appears to be the major responsible for the occurred negative effects. The impact assessment,
based on the calculation of an Impact Index, confirms this statement. 相似文献
11.
Changes in soil physico-chemical and microbiological properties during natural succession on abandoned farmland in the Loess Plateau 总被引:3,自引:1,他引:2
The re-establishment of natural species-rich heath lands on abandoned farmland is one of the main measures in soil erosion
control in the Loess Plateau of China. So, it is important to understand how the vegetation and soil properties develop after
land abandonment. The objective of this study was to determine how physico-chemical properties, microbial biomass, and enzyme
activities changed for abandoned farmland with an age sequence of 0, 1, 5, 7, 10, 15, 20, 25, 30, 40 and 50 years in Zhifanggou
watershed (8.27 km2), Shaanxi Province, NW China. The results of this study indicate that species succession after land abandonment in the Zhifanggou
watershed on the Loess Plateau resulted in a significant improvement in soil chemical and microbiological properties. Soil
organic C, total N, available N and K, soil microbial biomass C, N and P, as well as alkaline phosphatase, catalase, saccharase,
and cellulase activity increased with time since plantation establishment increased. In contrast, soil bulk density, pH, and
polyphenol oxidase activity decreased after farmland abandonment. Urease and α-amylase decreased until 15 years at the early
phase of species succession, and then increased. However, there was no significant change in total P and available P during
the restoration. Results only implied the tendency that the herbage was developing toward shrub. Although secondary succession
plays an important role which improved soil properties after farmland abandonment, the values of these parameters were still
much lower than native forest in 50 years. Thus, vegetation recovery after farmland abandonment in a semi-arid environment
would be slow and the improvement of soil properties in the Loess Plateau is likely to require a considerably long period
of time. 相似文献
12.
The Sharm El-Sheikh/Ras-Nasrani area is one of the most attractive tourist resorts in Egypt particularly and in the world
in general. The area has been rapidly growing during the last few years. Many construction projects including villages, hotels,
beaches, and roads have recently been undertaken. The following study demonstrates the use of high-resolution satellite images,
QuickBird imagery, acquired on June 2nd, 2007 (0.61 m spatial resolution), for detailed mapping of the recent developments
and the slope instability hazard zones. The results were confirmed by field reconnaissance. Our findings indicate that there
are many development areas threatened by unstable zones. The hazard areas have been delineated and classified, and a final
slope instability hazard map has been established. Different factors were found to have a crucial impact on the slope instability,
some natural and others man-made. These unstable localities need to be remediated and/or monitored to avoid any loss in property
and/or lives. 相似文献
13.
基于遥感影像的决策树分类,结合土地利用图,将北京市农业地表覆盖划分为春玉米、冬小麦、果园、林木苗圃、牧草地、设施农业和畜禽饲养地。考虑海拔、坡度和土壤质地三个因子将北京市分成10个景观区,在景观分区和不同农业用地基础上划分出39类农业景观单元。利用基于遥感影像计算的归一化差异植被指数,结合实地调查验证,分类出北京市冬春季裸露农田。结合景观分类,分析了不同景观单元冬春季地表裸露情况。结果表明:2007—2008年冬春季裸露农田共8.05×104 hm2,主要分布在延庆盆地、密云水库北岸和城区边缘的近郊农业区;海拔和土地利用方式对裸露情况影响较大,其中山区春玉米和平原果园裸露情况绝对面积较大,分别占到总裸露农田面积的40%和17%,牧草地、林木苗圃与设施农业地裸露程度较高。基于不同景观单元裸露程度,结合绿肥种植、保护性耕作、生草覆盖等裸露农田治理方法,探讨了北京市农业产业和景观一体化建设策略。 相似文献
14.
First arrival times from P-wave refraction and reflection seismic surveys along Bear Creek Valley on the Oak Ridge Reservation,
Tennessee, were inverted to produce refraction tomographic velocity images showing seismic velocity variations within thinly
mantled karstic bedrock to a depth of approximately 20 m. Inverted velocities are consistent with two distinct bedrock groups:
the Nolichucky Shale (2,730–5,150 m/s) and Maynardville Limestone (3,940–7,575 m/s). Low-velocity zones (2,700–4,000 m/s)
in the tomographic images correspond to previously inferred cross-valley strike-slip faults; in places, these faults create
permeability barriers that offset or block groundwater flowing along Bear Creek Valley. These faults may also force groundwater
contaminants, such as dense non-aqueous phase liquids, to migrate laterally or downward, spreading contamination throughout
the groundwater system. Other, previously unmapped cross-valley faults may also be visible in the tomographic images. Borehole
logs suggest the low-velocity values are caused by low rigidity fractured and vuggy rock, water zones, cavities and collapse
features. Surface streams, including Bear Creek, tend to lie directly above these low-velocity zones, suggesting fault and
fracture control of surface drainage, in addition to the subsurface flow system. In some cases, fault zones are also associated
with bedrock depressions and thicker accumulations of unconsolidated sediment. 相似文献
15.
Mohamed E. Hereher 《Environmental Earth Sciences》2011,64(4):1117-1125
A set of six Landsat satellite images with 5–9 years apart was used in a post-classification analysis to map changes occurred
at Rosetta promontory between 1973 and 2008 due to coastal erosion. Spectral information were extracted from two multi-spectral
scanner (MSS) images (1973 and 1978), three thematic mapper (TM) images (1984, 1990, and 1999), and one enhanced thematic
mapper plus (ETM+) image (2008). To estimate the quantity of land loss in terms of coastal erosion, a supervised classification
scheme was applied to each image to highlight only two classes: seawater and land. The area of each class was then estimated
from the number of pixels pertaining to this class in every image. In addition, the shoreline position was digitized to address
retreat/advance pattern throughout the study period. Results showed that Rosetta promontory had lost 12.29 km2 of land between 1973 and 2008 and the shoreline withdrew southward about 3.5 km due to coastal erosion. Most land loss and
shoreline retreat occurred between 1973 and 1978 (0.55 km2/year and 132 m/year, respectively). Coastal protection structures were constructed successively at the promontory. These
structures have considerably contributed to reduce coastal erosion; however, they promoted downdrift erosion. 相似文献
16.
Change trends for desertified lands in the Horqin Sandy Land at the beginning of the twenty-first century 总被引:2,自引:1,他引:1
Zhiwen Han Tao Wang Changzhen Yan Yubin Liu Lichao Liu Aimin Li Heqiang Du 《Environmental Earth Sciences》2010,59(8):1749-1757
The dynamics of desertification in the Horqin Sandy Land between 2000 and 2005 were analyzed using Landsat TM/ETM images and
the data-processing function of geographical information software. The results showed that the extent of desertified land
decreased at a rate of slightly more than 0.1 km2 year−1, from 22,423.1 km2 in 2000 to 22,422.4 km2 in 2005, indicating that desertification has been controlled in this area and that desert areas may be approaching a steady
state. The dynamics of desertification differed among land types. Desertification decreased most obviously in areas of previous
desert land. The area in which desertification was ameliorated was higher than the area that underwent further degradation,
but non-desertified land (113.3 km2) deteriorated at a rate of 22.7 km2 year−1 during this period. This significant change requires careful attention by managers in the study area. 相似文献
17.
Bihong Fu Pilong Shi Huadong Guo Satoshi Okuyama Yoshiki Ninomiya Sarah Wright 《Journal of Asian Earth Sciences》2011,40(4):805-824
The 12 May 2008 Ms 8.0 Wenchuan earthquake, China, was one of largest continental thrusting events worldwide. Based on interpretations of post-earthquake high-resolution remote sensing images and field surveys, we investigated the geometry, geomorphology, and kinematics of co-seismic surface ruptures, as well as seismic and geologic hazards along the Longmen Shan fold-and-thrust belt. Our results indicate that the Wenchuan earthquake occurred along the NE–SW-trending Yingxiu–Beichuan and Guanxian–Anxian faults in the Longmen Shan fold-and-thrust belt. The main surface rupture zones along the Yingxiu–Beichuan and Guanxian–Anxian fault zones are approximately 235 and 72 km in length, respectively. These sub-parallel ruptures may merge at depth. The Yingxiu–Donghekou surface rupture zone can be divided into four segments separated by discontinuities that appear as step-overs or bends in map view. Surface deformation is characterized by oblique reverse faulting with a maximum vertical displacement of approximately 10 m in areas around Beichuan County. Earthquake-related disasters (e.g., landslides) are linearly distributed along the surface rupture zones and associated river valleys.The Wenchuan earthquake provides new insights into the nature of mountain building within the Longmen Shan, eastern Tibetan Plateau. The total crustal shortening accommodated by this great earthquake was as much as 8.5 m, with a maximum vertical uplift of approximately 10 m. The present results suggest that ongoing mountain building of the Longmen Shan is driven mainly by crustal shortening and uplift related to repeated large seismic events such as the 2008 Wenchuan earthquake. Furthermore, rapid erosion within the Longmen Shan fold-and-thrust belt occurs along deep valleys and rupture zones following the occurrence of large-scale landslides triggered by earthquakes. Consequently, we suggest that crustal shortening related to repeated great seismic events, together with isostatic rebound induced by rapid erosion-related unloading, is a key component of the geodynamics that drive ongoing mountain building on the eastern Tibetan Plateau. 相似文献
18.
Guotao Dong Shengtian Yang Yunfei Gao Juan Bai Xuelei Wang Donghai Zheng 《Environmental Earth Sciences》2014,72(5):1643-1657
Riparian zones act as important buffer zones for non-point source pollution, thus improving the health of aquatic ecosystems. Previous research has shown that riparian zones play an important role, and that land use has an important effect, on phosphorus (P) retention. A spatial basin-scale approach for analyzing P retention and land use effects could be important in preventing pollution in riparian zones. In this study, a riparian phosphorus cycle model based on EcoHAT was generated with algorithms from soil moisture and heat models, simplified soil and plant phosphorus models, plant growth models, and universal soil loss equations. Based on remote sensing data, model performance was enhanced for spatial and temporal prediction of P retention in the riparian zone. A modified soil and plant P model was used to simulate the soil P cycle of a riparian zone in a temperate continental monsoon climate in northern China. A laboratory experiment and a field experiment were conducted to validate the P cycle model. High coefficients of determination (R 2) between simulated and observed values indicate that the model provides reliable results. P uptake variations were the same as the net primary productivity (NPP) trends, which were affected by soil temperature and moisture in the temperate continental monsoon climate. Beginning in June, the monthly content increased, with the maximum appearing in August, when the most precipitation and the highest temperatures occur. The spatial distribution of P uptake rates from March to September showed that areas near water frequently had relatively high values from May to August, which is contrary to results obtained in March, April, and September. The P uptake amounts for different land uses changed according to expectation. The average monthly P uptake rates for farmlands and grasslands were more than those for orchards and lowlands, which had moderate P uptake rates, followed by shrubs and forests. The spatial distribution of soil erosion demonstrated that the soil erosion came primarily from high-intensity agricultural land in the western and central areas, while the northern and eastern study regions, which were less affected by human activity, experienced relatively slight soil erosion. From the point of view of P pollution prevention, the spatial structure of riparian zones and the spatial distribution of land use around the Guanting reservoir are thus not favorable. 相似文献
19.
Edward Castañeda-Moya Robert R. Twilley Victor H. Rivera-Monroy Keqi Zhang Stephen E. DavisIII Michael Ross 《Estuaries and Coasts》2010,33(1):45-58
The distribution of mangrove biomass and forest structure along Shark River estuary in the Florida Coastal Everglades (FCE)
has been correlated with elevated total phosphorus concentration in soils thought to be associated with storm events. The
passage of Hurricane Wilma across Shark River estuary in 2005 allowed us to quantify sediment deposition and nutrient inputs
in FCE mangrove forests associated with this storm event and to evaluate whether these pulsing events are sufficient to regulate
nutrient biogeochemistry in mangrove forests of south Florida. We sampled the spatial pattern of sediment deposits and their
chemical properties in mangrove forests along FCE sites in December 2005 and October 2006. The thickness (0.5 to 4.5 cm) of
hurricane sediment deposits decreased with distance inland at each site. Bulk density, organic matter content, total nitrogen
(N) and phosphorus (P) concentrations, and inorganic and organic P pools of hurricane sediment deposits differed from surface
(0–10 cm) mangrove soils at each site. Vertical accretion resulting from this hurricane event was eight to 17 times greater
than the annual accretion rate (0.30 ± 0.03 cm year−1) averaged over the last 50 years. Total P inputs from storm-derived sediments were equivalent to twice the average surface
soil nutrient P density (0.19 mg cm−3). In contrast, total N inputs contributed 0.8 times the average soil nutrient N density (2.8 mg cm−3). Allochthonous mineral inputs from Hurricane Wilma represent a significant source of sediment to soil vertical accretion
rates and nutrient resources in mangroves of southwestern Everglades. The gradient in total P deposition to mangrove soils
from west to east direction across the FCE associated with this storm event is particularly significant to forest development
due to the P-limited condition of this carbonate ecosystem. This source of P may be an important adaptation of mangrove forests
in the Caribbean region to projected impacts of sea-level rise. 相似文献
20.
The relations between land use and karst rocky desertification in a typical karst area,China 总被引:13,自引:0,他引:13
Karst rocky desertification (KRD) is one major type of desertification which is under irrational human impact on the vulnerable
eco-geo-environment. In this study, Zhudong fengcong rocky desertification landscape was selected to investigate the land
use types distribution law in different rock types and the KRD land in different land use types. KRD data was determined by
user–computer interactive interpreting method from Aster images in 2004, according to the exposed ratio of rock, the coverage
of vegetation and soil in 0.2 km2 unit, integrating with land utilizing present situation map, hydrogeology map, relief map, vegetation map, soil distribution
map, as well as the practical investigation and the population census datum in 2002. Results showed that the occurrence ratio
of KRD land is different in land use types and rocky assemblages obviously; land cover has a strong impact upon KRD. The sloping
cropland distributed in homogenous limestone has a higher occurrence ratio of light KRD, secondly, is in the limestone interbedded
with clastic rock. Light KRD land was dominated by shrubland, and sloping cropland accounts for 11.67% of it, moderate KRD
land was dominated by moderate coverage grass slopes, strong and extremely strong KRD was dominated by rocky dry land which
is difficult to use. 相似文献