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1.
Using China's ground observations, e.g., forest inventory, grassland resource, agricultural statistics, climate, and satellite data, we estimate terrestrial vegetation carbon sinks for China's major biomes between 1981 and 2000. The main results are in the following: (1) Forest area and forest biomass car- bon (C) stock increased from 116.5×106 ha and 4.3 Pg C (1 Pg C = 1015 g C) in the early 1980s to 142.8×106 ha and 5.9 Pg C in the early 2000s, respectively. Forest biomass carbon density increased form 36.9 Mg C/ha (1 Mg C = 106 g C) to 41.0 Mg C/ha, with an annual carbon sequestration rate of 0.075 Pg C/a. Grassland, shrub, and crop biomass sequestrate carbon at annual rates of 0.007 Pg C/a, 0.014― 0.024 Pg C/a, and 0.0125―0.0143 Pg C/a, respectively. (2) The total terrestrial vegetation C sink in China is in a range of 0.096―0.106 Pg C/a between 1981 and 2000, accounting for 14.6%―16.1% of carbon dioxide (CO2) emitted by China's industry in the same period. In addition, soil carbon sink is estimated at 0.04―0.07 Pg C/a. Accordingly, carbon sequestration by China's terrestrial ecosystems (vegetation and soil) offsets 20.8%―26.8% of its industrial CO2 emission for the study period. (3) Considerable uncertainties exist in the present study, especially in the estimation of soil carbon sinks, and need further intensive investigation in the future.  相似文献   

2.
The projected changes in carbon exchange between China terrestrial ecosystem and the atmosphere and vegetation and soil carbon storage during the 21st century were investigated using an atmos-phere-vegetation interaction model (AVIM2). The results show that in the coming 100 a, for SRES B2 scenario and constant atmospheric CO2 concentration, the net primary productivity (NPP) of terrestrial ecosystem in China will be decreased slowly, and vegetation and soil carbon storage as well as net ecosystem productivity (NEP) will also be decreased. The carbon sink for China terrestrial ecosystem in the beginning of the 20th century will become totally a carbon source by the year of 2020, while for B2 scenario and changing atmospheric CO2 concentration, NPP for China will increase continuously from 2.94 GtC·a?1 by the end of the 20th century to 3.99 GtC·a?1 by the end of the 21st century, and vegetation and soil carbon storage will increase to 110.3 GtC. NEP in China will keep rising during the first and middle periods of the 21st century, and reach the peak around 2050s, then will decrease gradually and approach to zero by the end of the 21st century.  相似文献   

3.
Based on the regional water resources character, the concept of soil water resources is first redefined, and then associated with their transfer relationship in the hydrological cycle, Evapotranspiration (ET)-based consumption structure and consumption efficiency of soil water resources are analyzed. According to ET’s function in productivity, the consumption efficiency of soil water resources is divided into three classes: high efficient consumption from vegetation transpiration, low efficient consumption from soil evaporation among plants with high vegetation coverage and inefficient consumption from soil evaporation among plants with low vegetation coverage and bare soil evaporation. The high efficient and low efficient consumption were further classified as productive consumption. The inefficient consumption is considered non-productive consumption because it is significant in the whole hydrological cycle process. Finally, according to these categories, and employing a WEP-L distributed hydrological model, this paper analyzes the consumption efficiency of soil water resources in the Yellow River Basin. The results show that there are 2078.89×108 m3 soil water resources in the whole basin. From the viewpoint of consumption structure, the soil water resources are comprised of 381.89×108 m3 transpiration consumption from vegetation and 1697.09×108 m3 evaporation consumption from soil among plants and bare soil. From the viewpoint of consumption efficiency, soil water resources are composed of 920.11×108 m3 efficient consumption and 1158.86×108 m3 of inefficient consumption. High efficient consumption accounts for 41.5 percent of the total efficient consumption of the whole basin, low efficient for 58.5 percent. Furthermore, consumption efficiency varies by region. Compared with ET from different land use conditions, the whole basin appears to follow the trend of having the greatest proportion of consumption as inefficient consumption, followed by low efficient consumption, and then the least proportion as high efficient consumption. The amount of inefficient consumption in some regions with vegetation is less than in other regions without vegetation. The amount of inefficient consumption in grasslands is much greater than in forestlands. However, the proportion of low efficient consumption is the greatest in crop fields. The amount of high efficient consumption in grasslands and forelands is similar to the corresponding low efficient consumption. However, the low efficient consumption in grasslands is larger than in the forelands. Therefore, when adjusting the utilization efficiency of soil water resources, vegetation coverage and plant structure should be modulated in terms of the principle of decreasing inefficient consumption, improving low efficiency ET and increasing high efficiency ET according to area character. Supported by the Project of the National 973 Program of China (Grant Nos. 2006CB403404 and G1999043602), the Project of the National Science Research for the 11th Five-Year Plan (Grant No. 2006BAB06B06), and the Innovation Team Project of the National Natural Science Foundation of China (Grant No.50721006)  相似文献   

4.
Assessments of the impacts of land use and land cover changes(LUCC) on the terrestrial carbon budget, atmospheric CO2 concentration, and CO2-related climatic change are important to understand the environmental effects of LUCC and provide information about the effects of historical carbon emissions. Using regional land cover reconstructions from historical records, with a bookkeeping model, we estimated the carbon sink changes caused by historical cropland expansion in Northeast China during the past 300 years. The conclusions are as follows:(1) There was a dramatic land reclamation of cropland during the past 300 years in Northeast China. Approximately 26% of the natural land was cultivated, and 38% of the grassland and 20% of the forest and shrubland were converted to cropland.(2) The carbon emission induced by cropland expansion between 1683 and 1980 was 1.06–2.55 Pg C, and the estimation from the moderate scenario was 1.45 Pg C. The carbon emissions of the soil carbon pool was larger than that from the vegetation carbon pool and comprised more than 2/3 of the total carbon emissions.(3) The carbon emissions of the three provinces in Northeast China were different. Heilongjiang Province had the largest carbon emissions, and Jilin Province had the second largest emissions.(4) The primary source of carbon emissions was forest reclamation(taking 60% of the total emissions in the moderate scenario), the secondary source was grassland cultivation(taking 27%), and the tertiary sources were shrubland and wetland reclamation(taking 13%). Examination on the data accuracy revealed that the high-resolution regional land cover data allowed the carbon budget to be evaluated at the county level and improved the precision of the results. The carbon emission estimation in this study was lower than those in previous studies because of the improved land use data quality and various types of land use change considered.  相似文献   

5.
High-resolution sampling, measurements of organic carbon contents and 14C signatures of selected four soil profiles in the Haibei Station situated on the northeast Tibetan Plateau, and application of 14C tracing technology were conducted in an attempt to investigate the turnover times of soil organic carbon and the soil-CO2 flux in the alpine meadow ecosystem. The results show that the organic carbon stored in the soils varies from 22.12×104 kg C hm−2 to 30.75×104 kg C hm−2 in the alpine meadow ecosystems, with an average of 26.86×104 kg C hm−2. Turnover times of organic carbon pools increase with depth from 45 a to 73 a in the surface soil horizon to hundreds of years or millennia or even longer at the deep soil horizons in the alpine meadow ecosystems. The soil-CO2 flux ranges from 103.24 g C m−2 a−1 to 254.93 gC m−2 a−1, with an average of 191.23 g C m−2 a−1. The CO2 efflux produced from microbial decomposition of organic matter varies from 73.3 g C m−2 a−1 to 181 g C m−2 a−1. More than 30% of total soil organic carbon resides in the active carbon pool and 72.8%281.23% of total CO2 emitted from organic matter decomposition results from the topsoil horizon (from 0 cm to 10 cm) for the Kobresia meadow. Responding to global warming, the storage, volume of flow and fate of the soil organic carbon in the alpine meadow ecosystem of the Tibetan Plateau will be changed, which needs further research. Supported by the National Natural Science Foundation of China (Grant Nos. 40231015, 40471120 and 40473002) and the Guangdong Provincial Natural Science Foundation of China (Grant No. 06300102)  相似文献   

6.
The soil in the Rif, Morocco, is at serious risk because increasing anthropogenic pressures are gradually transforming large natural areas into farmland. The distribution of magnetic minerals within the soil profile can be used to assess soil development and degradation. The soils in the study area are severely eroded because of a combination of highly erodible soils, intense rainstorms and scarce vegetation cover. To sample of representative soil profiles, lithology, slope gradient and land use were considered. The ranges of magnetic susceptibility in the soil profiles distinguished between two primary soil groups. Magnetic susceptibility varied in the soil profile and along the soil toposequence, and the variations were related to the differences in the original magnetic composition and the influence of main erosion factors. Lithology is the main factor contributing to the variation in magnetic susceptibility. The magnetic susceptibility values in soils on Tertiary marls (χ = 13·5 × 10?8 m3 kg?1) differed significantly from those on Quaternary terraces (χ = 122·1 × 10?8 m3 kg?1). Slope affected the distribution of magnetic susceptibility because of the continuous loss of topsoil in some parts of the slope and the deposition of eroded soil in others. Elimination of the natural vegetation cover and a shift to cultivated land for cereals has had a negative impact on soil development and, on similar slopes and substrates, magnetic susceptibility decreased significantly in cultivated soils. The soils on steep slopes that had natural vegetation cover retained the magnetic minerals better than did those on gentler slopes that were under cultivation. Grazing, clearing and, especially, tilling has weakened the soil and made it much more vulnerable to erosion. An analysis of the main factors causing erosion will help to promote rational use of the land and to establish conservation strategies in such fragile agroecosystems. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

7.
Soil water depletion depth by planted vegetation on the Loess Plateau   总被引：4，自引：0，他引：4  
Evapotranspiration of much planted vegetation exceeds precipitation, and this can deplete soil water and cause a deep dry layer in the soil profile, which is a serious obstacle to sustainable land use on the Loess Plateau, China. This study aimed to determine water depletion depth of planted grassland, shrub, and forest in a semiarid area on the Loess Plateau. Soil moisture of five vegetation types was measured to >20 m in depth. The vegetation types were crop, natural grasse, seven-year-old planted alfalfa (Medicago sativa L.), 23-year-old planted caragana (Caragana microphylla Lam.) shrub, and 23-year-old planted pine (Pinus tabulaeformis L) forest land. Through comparing moisture of planted alfalfa grass, caragana shrub, and pine forest to crop and natural grassland, the depth and amount of soil water consumed by grassland, caragana brush and pine forest was determined. The depth of soil water depleted by alfalfa, caragana brush, and pine forest reached 15.5, 22.4 and 21.5 m, respectively. Supported by National Basic Research Program of China (Grant No. 2007CB407204) and National Natural Science Foundation of China (Grant No. 40471082)  相似文献   

8.
Mulching with forest residues has proved to be highly effective in reducing post-fire soil losses at the plot scale. However, its effectiveness has not been quantified at the application rates that are typically used in operational post-fire land management (2–3 Mg ha-1 using straw), as well as at scales larger than 100 m2. The present study compared post-fire erosion rates for six convergent hillslopes or swales of 500 to 800 m2, three of which were left untreated while the other three were mulched immediately after the fire with shredded eucalypt bark at a rate of 2.4 Mg ha-1. Erosion rates were monitored at irregular intervals during the first three post-fire years, whilst ground cover was assessed yearly. Selected topsoil properties (0–2 cm) such as organic matter content and aggregate stability were determined at a single occasion – two years after the wildfire, for three micro-environments separately: bare soil, and under mulch/litter and vegetation. Soil losses on the untreated swales decreased with post-fire year from 2.2 to 0.4 and 0.11 Mg ha-1 yr-1 (respectively for the first, second and third post-fire years), while the mulched swales produced 84%, 77% and 38% less soil losses than the untreated swales. Soil losses also depended on slope aspect, with the north-facing swales producing less erosion than the west-facing ones. This could be linked to their significant differences in bare soil, vegetation and stone cover, or a combination thereof. The type of micro-environment also played a significant role in topsoil properties (stone content, bulk density, resistance to penetration/shear stress, porosity and organic matter content). The present results add to the increasing evidence that forest residues should be duly considered for operational post-fire land management. Forest residues were highly effective in reducing erosion from swales at application rates as low as the typical 2 Mg ha-1 of post-fire straw mulch. © 2019 John Wiley & Sons, Ltd. © 2019 John Wiley & Sons, Ltd.  相似文献   

9.
The advanced process-based model, National Integrated Catchment-based Eco-hydrology (NICE)-BGC, which incorporates the whole process of carbon cycling in land, was modified to include the feedback between soil organic content and overland carbon fluxes. It is a crucial and difficult task to evaluate the balance of the terrestrial carbon budget including the effect of inland water robustly. To accomplish this purpose, NICE-BGC was applied to quantify the global biogeochemical carbon cycle closely associated with the complex hydrological cycle during the 36 years between 1980 and 2015. The model demonstrated that the inter-annual variations of carbon cycle have been greatly affected by the extreme weather patterns. In particular, spatial distribution of temporal trends in riverine carbon fluxes and their relation to soil organic carbon (SOC) were analysed between different biomes and major river basins. Although there was a positive relationship between SOC and riverine flux of dissolved organic carbon and particulate organic carbon in the northern boreal region, it is difficult to see this relation in other regions. Further, the evaluation of potential controlling factors of temporal trends in SOC and fluvial carbon exports was also helpful to quantify the inter-annual variation or temporal trend caused by the various effects. SOC was more influenced by temperature variations, whereas riverine carbon exports were mainly determined by precipitation variations. Finally, net land flux including inland water (−1.49 ± 0.50 PgC/year) showed a slight decrease in the carbon sink in comparison with previous values (−2.33 ± 0.50 PgC/year). These results help to distinguish the carbon cycle in different river basins and to re-evaluate carbon cycle change explicitly including the effect of inland water because this effect has been so far implicitly included within the range of uncertainty in the Earth's global carbon cycle comprising land, oceans, and atmosphere.  相似文献   

10.
The salinized sandy lands are the important reclaimable reserve wastelands in the south area of the Xinjiang Uygur Autonomous Region of China. But it is necessary that the ecological environment of the area is not destroyed by action of oasis development. The main factor to hinder oasis development is land salinization. Rational oasis establishment rebuilds wastelands with lower productivity and utilization efficiency for the growth of agriculture, forestry, and stock raising.The results of surveying sub-soil environment of Aimugaike-Awati oasis in Hotian County of the Xinjiang Uygur Autonomous Region show that the underground water and soil environment are not deteriorated under the rational management and administration, which could be coordinated for obtaining economic and environmental benefit. During the oasis establishment period from 1997 to 1999, the plowland area has reached 166.7 hm2, and the seed cotton yield per unit area has reached 2250 kg · hm?2, the area of timber forest and active sand break forest has reached 20 hm2, the area of fruit trees is 71.5 hm2; and the soil moisture has decreased from 22.07% to 18.12%. In the first year of oasis establishment, the soil type has changed salt soil into light salt soil, in the second year the soil has been out of salt harm; and the content of soil organic matter in topsoil has increased obviously.  相似文献   

11.
Soil erosion is a severe problem hindering sustainable agriculture on the Loess Plateau of China. Plot experiments were conducted under the natural rainfall condition during 1995–1997 at Wangdongguo and Aobao catchments in this region to evaluate the effects of various land use, cropping systems, land slopes and rainfall on runoff and sediment losses, as well as the differences in catchment responses. The experiments included various surface conditions ranging from bare soil to vegetated surfaces (maize, wheat residue, Robinia pseudoacacia L., Amorpha fruticosa L., Stipa capillata L., buckwheat and Astragarus adsurgens L.). The measurements were carried out on hill slopes with different gradients (i.e. 0 ° to 36 °). These plots varied from 20 to 60 m in length. Results indicated that runoff and erosion in this region occurred mainly during summer storms. Summer runoff and sediment losses under cropping and other vegetation were significantly less than those from ploughed bare soil (i.e. without crop/plant or crop residue). There were fewer runoff and sediment losses with increasing canopy cover. Land slope had a major effect on runoff and sediment losses and this effect was markedly larger in the tillage plots than that in the natural grass and forest plots, although this effect was very small when the maximum rainfall intensity was larger than 58·8 mm/h or smaller than 2·4 mm/h. Sediment losses per unit area rose with increasing slope length for the same land slope and same land use. The effect of slope length on sediment losses was stronger on a bare soil plot than on a crop/plant plot. The runoff volume and sediment losses were both closely related to rainfall volume and maximum intensity, while runoff coefficient was mainly controlled by maximum rainfall intensity. Hortonian overland flow is the dominant runoff process in the region. The differences in runoff volume, runoff coefficient and sediment losses between the catchments are mainly controlled by the maximum rainfall intensity and infiltration characteristics. The Aobao catchment yielded much larger runoff volume, runoff coefficient and sediment than the Wangdongguo catchment. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

12.
Tropical river basins are experiencing major hydrological alterations as a result of climate variability and deforestation. These drivers of flow changes are often difficult to isolate in large basins based on either observations or experiments; however, combining these methods with numerical models can help identify the contribution of climate and deforestation to hydrological alterations. This paper presents a study carried out in the Tapaj?s River (Brazil), a 477,000 km2 basin in South‐eastern Amazonia, in which we analysed the role of annual land cover change on daily river flows. Analysis of observed spatial and temporal trends in rainfall, forest cover, and river flow metrics for 1976 to 2008 indicates a significant shortening of the wet season and reduction in river flows through most of the basin despite no significant trend in annual precipitation. Coincident with seasonal trends over the past 4 decades, over 35% of the original forest (140,000 out of 400,000 km2) was cleared. In order to determine the effects of land clearing and rainfall variability to trends in river flows, we conducted hindcast simulations with ED2 + R, a terrestrial biosphere model incorporating fine scale ecosystem heterogeneity arising from annual land‐use change and linked to a flow routing scheme. The simulations indicated basin‐wide increases in dry season flows caused by land cover transitions beginning in the early 1990s when forest cover dropped to 80% of its original extent. Simulations of historical potential vegetation in the absence of land cover transitions indicate that reduction in rainfall during the dry season (mean of ?9 mm per month) would have had an opposite and larger magnitude effect than deforestation (maximum of +4 mm/month), leading to the overall net negative trend in river flows. In light of the expected increase in future climate variability and water infrastructure development in the Amazon and other tropical basins, this study presents an approach for analysing how multiple drivers of change are altering regional hydrology and water resources management.  相似文献   

13.
Spatiotemporal dynamic simulation of grassland carbon storage in China   总被引：1，自引：0，他引：1  
Based on the Terrestrial Ecosystem Model(TEM 5.0), together with the data of climate(temperature, precipitation and solar radiation) and environment(grassland vegetation types, soil texture, altitude, longitude and latitude, and atmospheric CO2 concentration data), the spatiotemporal variations of carbon storage and density, and their controlling factors were discussed in this paper. The results indicated that:(1) the total carbon storage of China's grasslands with a total area of 394.93×104 km2 was 59.47 Pg C. Among them, there were 3.15 Pg C in vegetation and 56.32 Pg C in soil carbon. China's grasslands covering 7.0–11.3% of the total world's grassland area had 1.3–11.3% of the vegetation carbon and 9.7–22.5% of the soil carbon in the world grasslands. The total carbon storage increased from 59.13 to 60.16 Pg C during 1961–2013 with an increasing rate of 19.4 Tg C yr~(-1).(2) The grasslands in the Qinghai-Tibetan Plateau contributed most to the total carbon storage during 1961–2013, accounting for 63.2% of the total grassland carbon storage, followed by Xinjiang grasslands(15.8%) and Inner Mongolia grasslands(11.1%).(3) The vegetation carbon storage showed an increasing trend, with the average annual growth rate of 9.62 Tg C yr~(-1) during 1961–2013, and temperature was the main determinant factor, explaining approximately 85% of its variation. The vegetation carbon storage showed an increasing trend in most grassland regions, however, a decreasing trend in the central grassland in the southern China, the western and central parts of the Inner Mongolian grasslands as well as some parts on the Qinghai-Tibetan Plateau. The soil carbon storage showed a significantly increasing trend with a rate of 7.96 Tg C yr~(-1), which resulted from the interaction of more precipitation and low temperature in the 1980 s and 1990 s. Among them, precipitation was the main determinant factor of increasing soil carbon increases of China's grasslands.  相似文献   

14.
Understanding how land cover change will impact water resources in snow-dominated regions is of critical importance as these locations produce disproportionate runoff relative to their land area. We coupled a land cover evolution model with a spatially explicit, physics-based, watershed process model to simulate land cover change and its impact on the water balance in a 5.0 km2 headwater catchment spanning the alpine–subalpine transition on the Colorado Front Range. We simulated two potential futures both with greater air temperature (+4°C/century) and more precipitation (+15%/century, MP) or less precipitation (−15%/century, LP) from 2000 to 2100. Forest cover in the catchment increased from 72% in 2000 to 84% and 83% in 2050 and to 95% and 92% in 2100 for MP and LP, respectively. Surprisingly, increases in forest cover led to mean increases in annual streamflow production of 12 mm (6%) and 2 mm (1%) for MP and LP in 2050 with an annual control streamflow of 208 mm. In 2100, mean streamflow production increased by 91 mm (44%) and 61 mm (29%) for MP and LP. This result counters previous work as runoff production increased with forested area due to decreases in snow wind-scour and increases in drifting leeward of vegetation, highlighting the need to better understand the impacts of forest expansion on the spatial pattern of snow scour, deposition and catchment effective precipitation. Identifying the hydrologic response of mountainous areas to climate warming induced land cover change is critically important due to the potential water resources impacts on downstream regions.  相似文献   

15.
Terrestrial vegetation is one of the most important components of the Earth’s land surface. Variations in terrestrial vegetation directly impact the Earth system’s balance of material and energy. This paper describes detected variations in vegetation activity at a national scale for China based on nearly 30 years of remote sensing data derived from NOAA/AVHRR (1982–2006) and MODIS (2001–2009). Vegetation activity is analyzed for four regions covering agriculture, forests, grasslands, and China’s Northwest region with sparse vegetation cover (including regions without vegetation). Relationships between variations in vegetation activity and climate change as well as agricultural production are also explored. The results show that vegetation activity has generally increased across large areas, especially during the most recent decade. The variations in vegetation activity have been driven primarily by human factors, especially in the southern forest region and the Northwest region with sparse vegetation cover. The results further show that the variations in vegetation activity have influenced agricultural production, but with a certain time lag.  相似文献   

16.
The range of relative sea level rise in the northwestern South China Sea since the Last Glacial Maximum was over 100 m. As a result, lowland regions including the Northeast Vietnam coast, Beibu Gulf, and South China coast experienced an evolution from land to sea. Based on the principle of reconstructing paleogeography and using recent digital elevation model, relative sea level curves, and sediment accumulation data, this paper presents a series of paleogeographic scenarios back to 20 cal. ka BP for the northwestern South China Sea. The scenarios demonstrate the entire process of coastline changes for the area of interest. During the late glacial period from 20 to 15 cal. ka BP, coastline slowly retreated, causing a land loss of only 1×104 km2, and thus the land-sea distribution remained nearly unchanged. Later in 15–10 cal. ka BP coastline rapidly retreated and area of land loss was up to 24×104km2, causing lowlands around Northeast Vietnam and South China soon to be underwater. Coastline retreat continued quite rapidly during the early Holocene. From 10 to 6 cal. ka BP land area had decreased by 9×104km2, and during that process the Qiongzhou Strait completely opened up. Since the mid Holocene, main controls on coastline change are from vertical crustal movements and sedimentation. Transgression was surpassed by regression, resulting in a land accretion of about 10×104km2. Supported by Key Laboratory of Marginal Sea Geology, Chinese Academy of Sciences (Grant No. MSGL0711), the Guangdong Natural Science Foundation (Grant No. 04001309) and Open Fund of the Key Laboratory of Marine Geology and Environment, Chinese Academy of Sciences (Grant No. MGE2007KG04)  相似文献   

17.
利用中国自主研制的全球首套30 m分辨率GlobeLand30地表覆盖产品调查全国定点形变台站周边5 km范围内的土地覆盖类型分布。应用地类面积/变化率、类型转入转出率等指标分析研究区各类型的转移规律,并辅以MODIS土地覆盖年数据集从全国和分区角度揭示2001—2018年间各土地类型时空变化格局,最后以垂直摆倾斜观测为例,探索台站周边土地覆盖变化总量与仪器观测背景噪声的关系。结果表明:(1)中国定点形变台站周边5 km范围内主要以耕地、森林为主。2000—2010年间,人造地表占比从11.8%升高至14.5%,而耕地和草地面积分别减少了2.2%和1.6%。研究区内耕地转为人造地表的面积最大,共计525 km~2。(2)中国大陆各地震区内台站周边土地覆盖变化格局不同,华北地震区的耕地降低和人造地表增长最为剧烈;新疆地震区以草地类型的降低和裸地类型的升高为主;东北地震区草地类型增长而人造地表稍有下降。(3)2001—2018年间,研究区森林面积在波动中缓慢升高;耕地面积则持续减少,尤其在2005—2016年间,减少幅度增大;人造地表类型则是逐年持续、稳定的增加。(4)2016年全国垂直摆倾斜仪观测背景噪声与台站周边全年的土地覆盖变化总量有一定的相关性,但华南地震区内台站由于受到海洋运动的影响,其仪器的噪声水平与周边环境变化不成正相关。  相似文献   

18.
Understanding land use/land cover (LULC) effects on tropical soil infiltration is crucial for maximizing watershed scale hydro-ecosystem services and informing land managers. This paper reports results from a multiyear investigation of LULC effects on soil bulk infiltration in steep, humid tropical, and lowland catchments. A rainfall simulator applied water at measured rates on 2 × 6 m plots producing infiltration through structured, granulated, and macroporous Ferralsols in Panama's central lowlands. Time-lapse electrical resistivity tomography (ERT) helped to visualize infiltration depth and bulk velocity. A space-for-time substitution methodology allowed a land-use history investigation by considering the following: (a) a continuously heavy-grazed cattle pasture, (b) a rotationally grazed traditional cattle pasture, (c) a 4-year-old (y.o.) silvopastoral system with nonnative improved pasture grasses and managed intensive rotational grazing, (d) a 7 y.o. teak (Tectona grandis) plantation, (e) an approximately 10 y.o. secondary succession forest, (f) a 12 y.o. coffee plantation (Coffea canephora), (g) an approximately 30 y.o. secondary succession forest, and (h) a >100 y.o. secondary succession forest. Within a land cover, unique plot sites totalled two at (a), (c), (d), (e), and (g); three at (b); and one at (f) and (h). Our observations confirmed measured infiltration scale dependency by comparing our 12 m2 plot-scale measurements against 8.9 cm diameter core-scale measurements collected by others from nearby sites. Preferential flow pathways (PFPs) significantly increased soil infiltration capacity, particularly in forests greater than or equal to 10 y.o. Time-lapse ERT observations revealed shallower rapid bulk infiltration and increased rapid lateral subsurface flow in pasture land covers when compared with forest land covers and highlighted how much subsurface flow pathways can vary within the Ferralsol soil class. Results suggest that LULC effects on PFPs are the dominant mechanism by which LULC affects throughfall partitioning, runoff generation, and flow pathways.  相似文献   

19.
A sediment budget was developed for the 1.7 km2 Maluna Creek drainage basin located in the Hunter Valley, New South Wales, Australia, for the period 1971-86. the impact of viticulture, which commenced at Maluna in 1971, was studied using erosion plots, with caesium-137 as an indicator of both soil erosion and sedimentation. Two methods were used to estimate vineyard soil losses from caesium-137 measurements. Sediment output from the catchment was measured for three years, and extrapolated from readings taken at a nearby long-term stream flow gauging station for the remaining 13 years. Relative amounts of soil loss from forest (60 per cent basin area), grazing land (30 per cent) and vineyards (10 per cent) were calculated. Soil losses by rain splash detachment were ten times greater from bare/cultivated sufaces than from the forest. Erosion plots of area 2 m2 showed no significant differences in soil loss between forest and grassland but, under bare soil, losses were 100 times greater. the 137Cs method was employed to calculate net soil loss from all vineyard blocks using both a previously established calibration curve and a proportional model. the latter method gave estimates of soil loss which were 3-9 times greater than by the calibration curve, and indicated that average soil losses from the vineyard were equivalent to 62 t ha?1 y?1 (1971-86). It was estimated that the forest contributed 1-8 per cent, the grazing land 1.6 per cent, and the vineyard 96.6 per cent of the total soil loss during that period. Sediment storages within the fluvial system adjacent to the vineyard ws 9460 t for the period, whereas sediment output was equivalent to 215 t km?1 y?1. Independent measurements of soil erosion, storage, and output showed that 56 per cent of the eroded sediment remained in the catchment, and 34 per cent was transported out by Maluna Creek. the budget was able to be balanced to within 10 per cent.  相似文献   

20.
太湖上游低山丘陵地区不同用地类型氮、磷收支平衡特征   总被引：4，自引：4，他引：0  
不同用地类型的土壤氮、磷收支平衡决定了氮、磷在土壤的富集,进一步影响氮、磷的流失强度,分析该过程有助于揭示不同用地类型对区域的环境效应.以位于太湖上游低山丘陵地区的天目湖流域为研究区,采用农户调查问卷、土壤和植被生物量实验分析、文献调研和氮、磷表观平衡模型的方法,选择研究区的茶园、水田、马尾松林和竹林四种典型用地类型,系统分析了氮、磷的输入要素,包括肥料输入、大气沉降、秸秆返田/枯枝落叶、生物固氮、人畜排泄物返田,以及输出要素,包括植物生长吸收、氨挥发、反硝化,并比较不同用地类型氮、磷收支特征.在此基础上进一步与土壤表层氮、磷含量比较,揭示太湖流域上游丘陵山区主要用地类型的水环境效应.研究结果显示:土壤氮、磷盈余量大小顺序为茶园 > 水田 > 马尾松林 > 竹林,分别是648.6、248.9、115.5、53.6 kgN/(hm2·a)和319.9、29.7、1.2和-3.4 kgP/(hm2·a);氮、磷利用效率以竹林最高,茶园的氮、磷利用效率均最低,仅为15.0%和3.1%;土壤氮盈余量与表层氮含量未能呈现出一致的关系,土壤磷盈余量与表层磷含量比较类似,并由此得出竹林比马尾松林更有利于水环境保护,而茶园对水环境的不利影响超过水田.  相似文献   

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