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1.
Ecosystem services evaluation aims at understanding the status of ecosystem services on different spatial and temporal scale. In this paper, we selected the middle reach of the Heihe River Basin (HRB), which is the second largest inland river basin in China, as one of the typical area to estimate the ecosystem services values (ESVs) corresponding to the land use changes. Based on the land use data and ecosystem service value coefficients, the total ecosystem services values (TESVs) of the middle reach of the HBR are quantitatively calculated, which were 9.244 × 108, 9.099 × 108, 9.131 × 108 and 9.146 × 108 USD in 1988, 2000, 2005 and 2008 respectively. During 1988–2008, the decrease of grassland, forest land, water area and unused land contributed 148.94%, 57.85%, 87.87% and 16.42% respectively to the net loss of TESVs, while the dramatic increase of cultivated land improved the TESVs with contribution of −211.08% to the net loss of TESVs. Expansion of cultivated land, which especially caused the loss of grassland and forest land, directly exerted negative impacts on the provision of ecosystem services in the study area. The findings of this research indicated that land use change was an important form of human activities, which had a strong impact on ecosystem services.  相似文献   

2.
In humid, forested mountain belts, bedrock landslides can harvest organic carbon from above ground biomass and soil (OCmodern) while acting to refresh the landscape surface and turnover forest ecosystems. Here the impact of landslides on organic carbon cycling in 13 river catchments spanning the length of the western Southern Alps, New Zealand is assessed over four decades. Spatial and temporal landslide maps are combined with the observed distribution and measured variability of hillslope OCmodern stocks. On average, it is estimated that landslides mobilized 7.6 ± 2.9 tC km?2 yr?1 of OCmodern, ~30% of which was delivered to river channels. Comparison with published estimates of OCmodern export in river suspended load suggests additional erosion of OCmodern by small, shallow landslides or overland flow in catchments. The exported OCmodern may contribute to geological carbon sequestration if buried in sedimentary deposits. Landslides may have also contributed to carbon sequestration over shorter timescales (<100 years). 5.4 ± 3.0 tC km?2 yr?1 of the eroded OCmodern was retained on hillslopes, representing a net‐carbon sink following re‐vegetation of scar surfaces. In addition, it was found that landslides caused rapid turnover of the landscape, with rates of 0.3% of the surface area per decade. High rates of net ecosystem productivity were measured in this forest of 94 ± 11 tC km?2 yr?1, which is consistent with rapid landscape turnover suppressing ecosystem retrogression. Landslide‐OCmodern yields and rates of turnover vary between river catchments and appear to be controlled by gradients in climate (precipitation) and geomorphology (rock exhumation rate, topographic slope). Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

3.
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   

4.
不同生活型水生植物对水环境的影响和碳固持能力不同,开展大尺度范围内不同生活型水生植物的时空分布和动态变化研究,是全面掌握湖泊水生态环境变化趋势、准确核算水生生态系统碳源/碳汇的前提。以长江中下游10 km2以上(共131个)的湖泊为研究对象,基于野外调查和先验知识,通过光谱分析,研发了不同生活型水生植物遥感高精度机器学习识别算法,解析了长江中下游湖泊群不同生活型水生植物的时空变化规律。研究表明,长江中下游湖泊群不同生活型水生植物遥感监测精度为0.81,Kappa系数为0.74;1986—2020年长江中下游湖泊群水生植物面积为2541.58~4571.42 km2,占湖泊总面积的15.99%~28.77%,沉水植物是优势类型(Max1995年=2649.21 km2,Min2005年=921.38 km2),其次是挺水植物(Max2005年=1779.44 km2,Min2020年=569.05 km2)和浮叶植物(Max2015年=685.68 km2,Min2000年=293.04 km2);水生植物主要分布在长江干流流域湖泊群,其次是鄱阳湖流域、洞庭湖流域、太湖流域和汉江流域;变化趋势上,1986—2020年长江中下游湖泊群水生植物面积呈现先增长(1986—1995年)、后下降(1995—2010年)、再增加(2010年后)的趋势。本研究可为长江中下游湖泊群生态环境调查及水环境管理提供重要参考。  相似文献   

5.
Measurements made on the floors of the temporarily-drained Glenfarg and Glenquey Reservoirs indicate that sediments with wet volumes of 63.94 × 103 m3 and 12.64 × 103 m3 were deposited in 56 and 73 years respectively. These figures represent 2.5 per cent and 1.1 per cent losses of original storage capacity. When corrected for water, organic, and diatom skeleton contents, and reservoir trap efficiency inorganic sediment yields of at least 31.3 tonnes km?2 yr?1 and of 9.0 tonnes km?2 yr?1 are suggested. The difference is probably related to contrasts of land use.  相似文献   

6.
We measured soil, stem and branch respiration of trees and shrubs, foliage photosynthesis and respiration in ecosystem of the needle and broad-leaved Korean pine forest in Changbai Mountain by LI-6400 CO2 analysis system. Measurement of forest microclimate was conducted simultaneously and a model was found for the relationship of soil, stem, leaf and climate factors. CO2 flux of different components in ecosystem of the broad-leaved Korean pine forest was estimated based on vegetation characteristics. The net ecosystem exchange was measured by eddy covariance technique. And we studied the effect of temperature and photosynthetic active radiation on ecosystem CO2 flux. Through analysis we found that the net ecosystem exchange was affected mainly by soil respiration and leaf photosynthesis. Annual net ecosystem exchange ranged from a minimum of about ?4.671 μmol·m?2·s?1 to a maximum of 13.80 μmol·m?2·s?1, mean net ecosystem exchange of CO2 flux was ?2.0 μmol·m?2·s?1 and 3.9 μmol·m?2·s?1 in winter and summer respectively (mean value during 24 h). Primary productivity of tree, shrub and herbage contributed about 89.7%, 3.5% and 6.8% to the gross primary productivity of the broad-leaved Korean pine forest respectively. Soil respiration contributed about 69.7% CO2 to the broad-leaved Korean pine forest ecosystem, comprising about 15.2% from tree leaves and 15.1% from branches. The net ecosystem exchange in growing season and non-growing season contributed 56.8% and 43.2% to the annual CO2 efflux respectively. The ratio of autotrophic respiration to gross primary productivity (R a:GPP) was 0.52 (NPP:GPP=0.48). Annual carbon accumulation underground accounted for 52% of the gross primary productivity, and soil respiration contributed 60% to gross primary productivity. The NPP of the needle and broad-leaved Korean pine forest was 769.3 gC·m?2·a?1. The net ecosystem exchange of this forest ecosystem (NEE) was 229.51 gC·m?2·a?1. The NEE of this forest ecosystem acquired by eddy covariance technique was lower than chamber estimates by 19.8%.  相似文献   

7.
The majority of the world's mangrove forests occur on mostly mineral sediments of fluvial origin. Two perspectives exist on the biogeomorphic development of these forests, i.e. that mangroves are opportunistic, with forest development primarily driven by physical processes, or alternatively that biophysical feedbacks strongly influence sedimentation and resulting geomorphology. On the Firth of Thames coast, New Zealand, we evaluate these two possible scenarios for sediment accumulation and forest development using high‐resolution sedimentary records and a detailed chronology of mangrove‐forest (Avicennia marina) development since the 1950s. Cores were collected along a shore‐normal transect of known elevation relative to mean sea level (MSL). Activities for lead‐210 (210Pb), caesium‐137 (137Cs) and beryllium‐7 (7Be), and sediment properties were analysed, with 210Pb sediment accumulation rates (SARs), compensated for deep subsidence (~8 mm yr?1) used as a proxy for elevation gain. At least four phases of forest development since the 1950s are recognized. An old‐growth forest developed by the late‐1970s with more recent seaward forest expansion thereafter. Excess 210Pb profiles from the old‐growth forest exhibit relatively low SARs near the top (7–12 mm yr?1) and bottom (10–22 mm yr?1) of cores, separated by an interval of higher SARs (33–100 mm yr?1). A general trend of increasing SAR over time characterizes the recent forest. Biogeomorphic evolution of the system is more complex than simple mudflat accretion/progradation and mangrove‐forest expansion. Surface‐elevation gain in the old‐growth forest displays an asymptotic trajectory, with a secondary depocentre developing on the seaward mudflat from the mid‐1970s. Two‐ to ten‐fold increases in 210Pb SARs are unambiguously large and occurred years to decades before seedling recruitment, demonstrating that mangroves do not measurably enhance sedimentation over annual to decadal timescales. This suggests that mangrove‐forest development is largely dependent on physical processes, with forests occupying mudflats once they reach a suitable elevation in the intertidal. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

8.
Field observations suggest that burrowing activity is the primary mode of sediment transport currently active in a small grassland drainage basin in Marin County, California. Spatial concentrations of the 1150 gopher mounds surveyed vary from 0-16 mounds m?2 on interfluves to 0.32 mounds m?2 on sideslopes and in the topographic hollow, with localized concentrations of up to 2.88 mounds m?2 on the margins of the colluvial deposit. Simple models of sediment transport by burrowing activity yield estimates of between 0.91 and 2.33 cm3 cm?1 yr?1 for the basin as a whole, with absolute minimum and maximum rates of 0.48 and 631 cm3 cm?1 yr?1. These values are similar to those previously estimated for this area (Lehre, 1982) and are nearly an order-of-magnitude less than average long-term sediment transport rates at the same site (Reneau, 1988).  相似文献   

9.
The Mongolian Plateau (MP) steppe is one of the largest steppe environments in the world. To monitor the terrestrial vegetation dynamics on the MP and to ascertain what the driving forces, this study examined the vegetation dynamics in Republic of Mongolia (M) and the Inner Mongolia Autonomous Region (IM) of China from the period 1982 to 2011, based on the satellite-derived GIMMS NDVI3g (Normalized Difference Vegetation Index) data across three biomes (desert, grassland and forest). The results are as followed: (1) Vegetation coverage in IM was generally greater than that in M. Before 2002, time series of NDVI over the MP increased at an average rate of 0.05% yr−1. Additionally, after 2002, the NDVI increased at a rate of 0.21% yr−1. From 1982 to 2011, the area of IM and M with positive anomalies in the NDVI increased at a separate rate of 1.82% yr−1 and 1.76% yr−1, respectively. (2) At the biome scale, the inter-annual forest NDVI variation in IM and desert NDVI for the entire MP had a significant increasing trend (0.06% yr−1 and 0.04% yr−1, respectively). (3) Climate forcing was a dominant controlling factor affecting the vegetation, and the anthropogenic behavior exhibited no significant value in the whole region. However, overgrazing was the most important reason for the regional degradation, particularly in IM. (4) In the future, the forest biome will go to recovery, whereas both the grassland and desert biomes are predicted to degrade continuously.  相似文献   

10.
A whole rock U-Th-Pb study was carried out on eight granites from a suite previously dated at 177 ± 4my(λ = 1.39 × 10?11yr?1) by Rb-Sr methods. A U-Pb isochron was not obtained owing to recent leaching of U in the outcrop. Seven samples gave a Th-Pb isochron with age 184 ± 16my(λ = 4.99 × 10?11yr?1), (20/8Pb204Pb)0 = 39.2 ± 0.2 and MSWD 0.8. The eighth sample fell off the line and was rejected on geological grounds. Dissolving 5 g aliquots of the powdered rock markedly improved the reproducibility of U analyses but analysis of the variances suggests that inhomogeneities still might exist between duplicate dissolutions. Th-Pb geochronology needs further development to bring it to the level of precision of the Rb-Sr method.  相似文献   

11.
太湖河湖水系连通需求评价初探   总被引：3，自引：2，他引：1  
水系连通需求分析是河湖水系连通战略研究的重要内容.水系连通需求指人类社会经济发展对水资源调配、防洪排涝、改善生态环境等方面的需求及对河湖水系健康的维护,它源于水系能够提供各种水生态系统服务功能的生态学特性.通过分析水系连通需求、水生态系统服务功能和水系连通工程之间的内在关系,认为水系连通需求评价可转化为对水生态系统服务功能的评价.运用水当量评价方法,建立了河湖水系连通需求评价的方法体系,并以河网地区的典型代表——太湖为例,定量评价了太湖在水资源调配、调蓄洪水、水环境净化和维持生境等方面的连通需求.结果表明,太湖水系年均连通需求最大的是净化入湖废污水需水量,其次为水资源调配需水量,而太湖调蓄洪水的需求减少;湖水自身净化需水量较大,且为一次性需水.水环境净化的需求需要通过降低污染物入湖量,进行湖泊生态修复等主要措施以及引清水增加环境容量这一辅助连通措施共同完成.水系连通需求的定量评价可为水系连通战略及工程的规划设计提供理论基础.  相似文献   

12.
Total organic carbon fluxes of the Red River system (Vietnam)   总被引：1，自引：0，他引：1       下载免费PDF全文
Riverine transport of organic carbon from terrestrial ecosystems to the oceans plays an important role in the global carbon cycle. The Red River is located in Southeast Asia where river discharge, sediment loads and fluxes of elements (carbon, nitrogen and phosphorus) associated with suspended solids have been dramatically altered over past decades as a result of reservoir impoundment and land use, population, and climate change. Dissolved organic carbon (DOC) and particulate organic carbon (POC) concentrations were measured monthly at four stations of the Red River system from January 2008 to December 2010. The results reveal that POC changed synchronically with total suspended solids (TSS) concentration and with the river discharge, whereas no clear trend was observed for DOC concentration. The mean value of total organic carbon (TOC = DOC + POC) flux in the delta of the Red River was 31.5 × 1013 ± 4.0 × 1013 MgC.yr?1 (range 27.9–35.8 × 1013 MgC.yr?1 which leads to a specific TOC flux of 2012 ± 255 kgC.km?2.yr?1 during this 2008–2010 period. About 80% of the TOC flux was transferred to the estuary during the rainy season as a consequence of the higher river water discharge. The high mean value of the POC:Chl‐a ratio (1585 ± 870 mgC.mgChl‐a?1) and the moderate C:N ratio (7.3 ± 0.1) in the water column system suggest that organic carbon in the Red River system is mainly derived from erosion and soil leaching in the basin. The effect of two new dam impoundments in the Red River was also observable with lower TOC fluxes in 2010 compared with 2008. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

13.
The biosphere of the Earth is the material founda-tion of human survival and development.With the increasing problems of the resources,the environment and population,most countries in the world have paid special attention to the measurement and evaluation of ecological capital,which refers to the sum of the direct natural resources value and the indirect ecosystem services value.Ecological capital depends on not only the quality of the national ecological environment,butalso the social recogni…  相似文献   

14.
Among the different controls of erosion budget at basin level, the relative impact of dams and land management is yet to be investigated. In this paper, the impact of dams on sediment yield has been assessed by using a conceptual modelling framework which considers the gross erosion and the cascade of dams constructed on a river network. The sediment budget has been estimated based on the gross erosion, deposition of sediment in reservoirs, and sediment yields of 23 mainland river basins of India. The gross erosion of the country is estimated as 5.11 ± 0.4 Gt yr?1 or 1559 t km?2 yr?1, out of which 34.1 ± 12% of the total eroded soil is deposited in the reservoirs, 22.9 ± 29% is discharged outside the country (mainly to oceans), and the remaining 43.0 ± 41% is displaced within the river basins. The river basins of northern India contribute about 81% of the total sediment yield from landmass while the share of southern river basins is 19%. The components of revised sediment budget for India are prominently influenced by the sediment trapped in reservoirs and the treatment of catchment areas by soil and water conservation measures. Analysis of sediment deposition in 4937 reservoirs indicated the average annual percentage capacity loss as 1.04% though it varies from 0.8% to >2% per year in smaller dams (1–50 Mm3 capacity) and from <0.5% to 0.8% per year in larger dams (51 to >1000 Mm3 capacity). Siltation of smaller dams poses a serious threat to their ecosystem services as they cater to a wider population for domestic, agricultural, and industrial purposes. Amongst the environment controls, land use significantly impacts the gross erosion rate and specific sediment yield as compared to climatic and topographic parameters. However, to analyse their integrated effect on the complex processes of sediment fluxes in a basin, further research efforts are needed. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

15.
Natural riparian forest wetlands are known to be effective in their ability to remove nitrate by denitrification and sediments with attached phosphorus via sedimentation. On the other hand, litter input and decomposition is a process of crucial importance in cycling of nitrogen and phosphorus in a forest ecosystem.In this study we investigated the amount of nitrogen and phosphorus entering the alder fen ecosystem through leaf litter and its decomposition and the removal capacity of nitrogen and phosphorus by measuring denitrification and sedimentation in the alder fen.We found an average input of leaf litter during fall 1998 of 226 g m−2 yr−1 DW with nutrient concentration of 0.17% P and 1.6% N. This means a yearly input of 0.4 g m−2 yr−1 P and 3.6 g m−2 yr−1 N. The decomposition of leaf litter using litter bags with small and large mesh size resulted in bags with macroinvertebrates (large mesh size) and without macroinvertebrates (small mesh size). After 57 days the litter bags with macroinvertebrates had a decomposition rate of 79%.Denitrification was measured in May and June of 1997 using the acetylene inhibition technique on intact soil cores and slurry-experiments. The average annual denitrification rate was 0.2 g m−2 yr−1 N using data from the core experiments. The denitrification rate was higher after addition of nitrate, indicating that denitrification in the riparian alder fen is mainly controlled by nitrate supply.The sedimentation rate in the investigated alder fen ranged from 0.47 kg m−2 yr−1 DW to 4.46 kg m−2 yr−1 DW in 1998 depending on the study site and method we used. Sedimentation rates were lower in newly designed plate traps than in cylinder traps. The alder fen also showed lower rates than the adjacent creek Briese. Average phosphorus removal rate was 0.33 g m−2 yr−1 P.Input sources for the surface water of the alder fen are sediment mineralization and decomposition of leaf litter; output sources are sedimentation and denitrification. This study showed that a nutrient input of 24.58 kg ha−1 yr−1 N, 8.8 kg ha−1 yr−1 P and 419 kg ha−1 yr−1 DOC into the surface water of the alder fen is possible. Alder fens cannot improve water quality of an adjacent river system. This is only true for a nearly pristine alder fen with the hydrology of 10 months flooded conditions and 2 months non-flooding conditions a year.  相似文献   

16.
Changes in the rate of soil erosion in lake catchments can be identified from changes in the rate of sediment accumulation in lakes. Here we compare recently afforested sites with non-afforested sites in the Galloway area of Southwest Scotland. We show that lakes with non-afforested catchments have slow, constant sediment accumulation rates, whereas lakes with recently afforested catchments have changes in accumulation that parallel the known history of afforestation. For Loch Grannoch the sediment accumulation rate increases from 0.1 cm yr?1 to over 2 cm yr?2 during the disturbance period. Data from L. Skerrow, however, suggest that the rate might decline to predisturbance levels after approximately 10 years as the forest canopy closes and drainage channels stabilize.  相似文献   

17.
Glacier recessions caused by climate change may uncover pro‐glacial lakes that form important sedimentation basins regulating the downstream sediment delivery. The impact of modern pro‐glacial lakes on fluvial sediment transport from three different Norwegian glaciers: Nigardsbreen, Engabreen and Tunsbergdalsbreen, and their long‐term development has been studied. All of these lakes developed in modern times in overdeepened bedrock basins. The recession of Nigardsbreen uncovered a 1.8 km long and on average 15 m deep pro‐glacial lake basin during 1937 to 1968. Since then the glacier front has been situated entirely on land, and the sediment input and output of the lake has been measured. The suspended sediment transport into and out of the lake averaged 11 730 t yr?1 and 2340 t yr?1 respectively. Thus, 20% remained in suspension at the outlet. The measured mean annual bedload supplied to the lake was 11 800 t yr?1, giving a total transport of 23 530 t yr?1 which corresponds to a specific sediment yield of 561 t km?2 yr?1. A 1.9 km long and up to 90 m deep pro‐glacial lake basin downstream from Engabreen glacier was uncovered during 1890 to 1944. The average suspended sediment load delivered from the glacier during the years 1970–1981 amounted to 12 375 t yr?1and the transport out of the lake was 2021 t yr?1, giving an average of 16% remaining in suspension. The mean annual bedload was 8000 t yr?1, thus the total transport was 20 375 t yr?1, giving a specific sediment yield of 566 t km?2 yr?1. For Tunsbergdalsbreen glacier, measurements in the early 1970s indicated that the suspended sediment transport was on average 44 000 t yr?1. From 1987 to 1993 the recession of the glacier uncovered a small pro‐glacial lake, 0.3 km long and around 9 m deep. Downstream from this, the suspended sediment load measured in 2009 was 28 000 t yr?1, indicating that as much as 64% remained in suspension. Flow velocity, grain size of sediment, and morphology of the lake are important factors controlling the sedimentation rate in the pro‐glacial lakes. A survey of the sub‐glacial morphology of Tunsbergdalsbreen revealed that there are several overdeepened basins beneath the glacier. The largest is 4 km long and 100 m deep. When the glacier melts back they will become lakes and act as sedimentation basins. Despite an expected increase in sediment yield from the glacier, little sediment will pass these lakes and downstream sediment delivery will be reduced markedly. Beneath Nigardsbreen there was only a small depression that may form a lake and the sediment delivery will not be significantly affected. © 2014 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd.  相似文献   

18.
Glacial erosion rates are estimated to be among the highest in the world. Few studies have attempted, however, to quantify the flux of sediment from the periglacial landscape to a glacier. Here, erosion rates from the nonglacial landscape above the Matanuska Glacier, Alaska are presented and compare with an 8‐yr record of proglacial suspended sediment yield. Non‐glacial lowering rates range from 1·8 ± 0·5 mm yr?1 to 8·5 ± 3·4 mm yr?1 from estimates of rock fall and debris‐flow fan volumes. An average erosion rate of 0·08 ± 0·04 mm yr?1 from eight convex‐up ridge crests was determined using in situ produced cosmogenic 10Be. Extrapolating these rates, based on landscape morphometry, to the Matanuska basin (58% ice‐cover), it was found that nonglacial processes account for an annual sediment flux of 2·3 ± 1·0 × 106 t. Suspended sediment data for 8 years and an assumed bedload to estimate the annual sediment yield at the Matanuska terminus to be 2·9 ± 1·0 × 106 t, corresponding to an erosion rate of 1·8 ± 0·6 mm yr?1: nonglacial sources therefore account for 80 ± 45% of the proglacial yield. A similar set of analyses were used for a small tributary sub‐basin (32% ice‐cover) to determine an erosion rate of 12·1 ± 6·9 mm yr?1, based on proglacial sediment yield, with the nonglacial sediment flux equal to 10 ± 7% of the proglacial yield. It is suggested that erosion rates by nonglacial processes are similar to inferred subglacial rates, such that the ice‐free regions of a glaciated landscape contribute significantly to the glacial sediment budget. The similar magnitude of nonglacial and glacial rates implies that partially glaciated landscapes will respond rapidly to changes in climate and base level through a rapid nonglacial response to glacially driven incision. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

19.
Sediment yields were calculated on the ?anks of Merapi and Semeru volcanoes in Java, Indonesia, using two different methods. During the ?rst year following the 22 November 1994 eruption of Merapi, a sediment yield in excess of 1·5 × 105 m3 km?2 yr?1 was calculated in the Boyong River drainage basin, based on the volumes of sediment that were trapped by ?ve check dams. At Semeru, sediment discharges were assessed in the Curah Lengkong River from direct measurements on the lahars in motion and on the most signi?cant stream?ows. The calculated rate of sediment yield during one year of data in 2000 was 2·7 × 105 m3 km?2 yr?1. Sediment yields are dominated by rain‐triggered lahars, which occur every rainy season in several drainage basins of Merapi and Semeru volcanoes, mostly during the rainy season extending from October to April. The return period of lahars carrying sediment in excess of 5 × 105 m3 is about one year in the Curah Lengkong River at Semeru. At Merapi, the volume of sediments transported by a lahar did not exceed 2·8 × 105 m3 in the Boyong River during the rainy season 1994–95. On both volcanoes, the sediments are derived from similar sources: pyroclastic‐?ow/surges deposits, rockfalls from the lava domes, and old material from the riverbed and banks. However, daily explosions of vulcanian type at Semeru provide a more continuous sediment supply than at Merapi. Therefore, sediment yields are larger at Semeru. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

20.
As one component of ChinaFLUX, the measurement of CO2 flux using eddy covariance over subtropical planted coniferous ecosystem in Qianyanzhou was conducted for a long term. This paper discusses the seasonal dynamics of net ecosystem exchange (NEE), ecosystem respiration (RE) and gross ecosystem exchange (GEE) between the coniferous ecosystem and atmosphere along 2003 and 2004. The variations of NEE, RE and GEE show obvious seasonal variabilities and correlate to each other, i.e. lower in winter and drought season, but higher in summer; light, temperature and soil water content are the main factors determining NEE; air temperature and water vapor pressure deficit (VPD) influence NEE with stronger influence from VPD. Under the proper light condition, drought stress could decrease the temperature range for carbon capture in planted coniferous, air temperature and precipitation controlled RE; The NEE, RE, and GEE for planted coniferous in Qianyanzhou are ?387.2 g C·m?2 a?1, 1223.3 g C·m?2 a?1, ?1610.4 g C·m?2 a?1 in 2003 and ?423.8 g C·m?2 a?1, 1442.0 g C·m?2 a?1, ?1865.8 g C·m?2 a?1 in 2004, respectively, which suggest the intensive ability of plantation coniferous forest on carbon absorbing in Qianyanzhou.  相似文献   

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