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1.
The proportional differences in soil organic carbon (SOC) and its fractions under different land uses are of significance for understanding the process of aggregation and soil carbon sequestration mechanisms. A study was conducted in a mixed vegetation cover watershed with forest, grass, cultivated and eroded lands in the degraded Shiwaliks of the lower Himalayas to assess land‐use effects on profile SOC distribution and storage and to quantify the SOC fractions in water‐stable aggregates (WSA) and bulk soils. The soil samples were collected from eroded, cultivated, forest and grassland soils for the analysis of SOC fractions and aggregate stability. The SOC in eroded surface soils was lower than in less disturbed grassland, cultivated and forest soils. The surface and subsurface soils of grassland and forest lands differentially contributed to the total profile carbon stock. The SOC stock in the 1.05‐m soil profile was highest (83.5 Mg ha−1) under forest and lowest (55.6 Mg ha−1) in eroded lands. The SOC stock in the surface (0–15 cm) soil constituted 6.95, 27.6, 27 and 42.4 per cent of the total stock in the 1.05‐m profile of eroded, cultivated, forest and grassland soils, respectively. The forest soils were found to sequester 22.4 Mg ha−1 more SOC than the cultivated soils as measured in the 1.05‐m soil profiles. The differences in aggregate SOC content among the land uses were more conspicuous in bigger water‐stable macro‐aggregates (WSA > 2 mm) than in water‐stable micro‐aggregates (WSA < 0.25 mm). The SOC in micro‐aggregates (WSA < 0.25 mm) was found to be less vulnerable to changes in land use. The hot water soluble and labile carbon fractions were higher in the bulk soils of grasslands than in the individual aggregates, whereas particulate organic carbon was higher in the aggregates than in bulk soils. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

2.
The effect of soil management and land use change are of interest to the sustainable land management for improving the environment and advancing food security in developing countries. Both anthropogenic changes and natural processes affect agriculture primarily by altering soil quality. This paper reviews and synthesizes the available literatures related to the influence of soil management and land use changes on soil carbon (C) stock in Ethiopia. The review shows that topsoil C stock declines approximately 0–63%, 0–23%, and 17–83% upon land use conversion from forest to crop land, to open grazing, and to plantation, respectively. An increase of 1–3% in soil C stock was observed within 10 years of converting open grazed land to protected enclosures. However, there was a little change in soil C stock below 20 cm depth. There is a large potential of increasing SOC pool with adoption of land restorative measures. Total potential of soil C sequestration with the adoption of restoration measures ranges 0·066–2·2 Tg C y−1 on rain‐fed cropland and 4·2–10·5 Tg C y−1 on rangeland. Given large area and diverse ecological conditions in Ethiopia, research data available in published literature are rather scanty. Therefore, researchable priorities identified in this review are important. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

3.
In the northern highlands of Ethiopia, establishment of exclosures to restore degraded communal grazing lands has been practiced for the past three decades. However, empirical data on the effectiveness of exclosures in restoring degraded soils are lacking. We investigated the influence of exclosure age on degree of restoration of degraded soil and identified easily measurable biophysical and management‐related factors that can be used to predict soil nutrient restoration. We selected replicated (n = 3) 5‐, 10‐, 15‐, and 20‐year‐old exclosures and paired each exclosure with samples from adjacent communal grazing lands. All exclosures showed higher total soil nitrogen (N), available phosphorus (P), and cation exchange capacity than the communal grazing lands. The differences varied between 2·4 (±0·61) and 6·9 (±1·85) Mg ha−1 for the total N stock and from 17 (±3) to 39 (±7) kg ha−1 for the available P stock. The differences in N and P increased with exclosure age. In exclosures, much of the variability in soil N (R2 = 0·64) and P (R2 = 0·71) stocks were explained by a combination of annual average precipitation, woody biomass, and exclosure age. Precipitation and vegetation canopy cover also explained much of the variability in soil N (R2 = 0·74) and P (R2 = 0·52) stocks in communal grazing lands. Converting degraded communal grazing lands into exclosures is a viable option to restore degraded soils. Our results also confirm that the possibility to predict the changes in soil nutrient content after exclosure establishment using regression models is based on field measurements. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

4.
Abstract

Soil organic carbon (SOC) and nutrient stocks in the soil profile (0–80 cm) in four dominant land uses [forest, upland maize and millet (Bari), irrigated rice (Khet), and grazed systems)] and 0–15 cm depth along elevation gradient 1000 to 3000 m, and aspects in the Mardi watershed were measured. Soil properties at 0–15 cm depth were also measured in undisturbed forest, forest with free grazed system, managed forest, and grassland to compare the soil quality index (SQI) of topsoils. The SOC and nutrient concentration decreased with increasing profile depth. The SOC and N contents in the 0–15 cm depth of forest soils were significantly greater than the corresponding depth in upland maize and millet, irrigated rice, and grazed systems. On the other hand, available P and K concentrations at the same depth were significantly greater in upland maize and millet compared to irrigated rice, grazed system, and forest land uses. The SOC and N stocks (0–15 cm) increased from agricultural land at the valley bottom at about 1000 m above mean sea level (a.s.l.) (24 and 3 Mg ha?1) compared to undisturbed forest (74 and 5.9 Mg ha?1) at 2600 m a.s.l, demonstrating the effects of cover and elevation. Both SOC and N stocks decreased sharply in grassland (54 and 4.5 Mg ha?1) at elevations of 2600 to 2800 m a.s.l. compared with undisturbed forest. Above 2800 m a.s.l. the cover type changed from grass to coniferous forest, and the SOC and N stocks steadily increased at the summit level (3200 m a.s.l.) to 65 and 6.9 Mg ha?1, respectively. Slope and aspect significantly affected SOC with the northwest aspect having significantly higher concentrations (46 g kg?1) than other aspects. Similarly, SOC concentration at the lowest slope position (39 g kg?1) was significantly higher than the middle or upper positions (25 and 13 g kg?1). Integrated soil quality index (SQI) values varied from 0.17 to 0.69 for different land uses, being highest for undisturbed forest and lowest for irrigated rice. The SQI demonstrated the degradation status of land uses in the following ascending order: irrigated rice?>?grazed system?>?forest with free grazing?>?upland maize and millet?>?managed forest?>?grass land?>?undisturbed forest. The irrigated rice, grazed system, upland maize and millet, and freely grazed forestlands need immediate attention to minimize further deterioration of soil quality in these land uses.  相似文献   

5.
Agricultural soils are considered to have great potential for carbon sequestration through land‐use change. In this paper, we compiled data from the literatures and studied the change in soil organic carbon (SOC) following the ‘Grain‐for‐Green’ Programme (GGP, i.e., conversion from farmland to plantation, secondary forests and grasslands) in China. The results showed that SOC stocks accumulated at an average rate of 36·67 g m−2 y−1 in the top 20 cm with large variation. The current SOC storage could be estimated using the initial SOC stock and year since land use transformation (Adjusted R2 = 0·805, p = 0·000). After land use change, SOC stocks decreased during the initial 4–5 years, followed by an increase after above ground vegetation restoration. Annual average precipitation and initial SOC stocks had a significant effect (p < 0·05) on the rate of change in SOC, while no significant effects were observed between plantation and natural regeneration (p > 0·05). The ongoing ‘Grain‐for‐Green’ project might make significant contribution to China's carbon sequestration. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

6.
Temporal changes in soil chemical and nutritional properties were evaluated in a long-term experiment conducted on Alfisols in West Africa. Effects of land use and cropping duration on soil chemical properties at 0–5 cm and 5–10 cm depths were evaluated for five treatments: (1) alley cropping with Leucaena leucocephala established on the contour at 4-m intervals; (2) mucuna (Mucuna utilis) fallowing for 1 year followed by maize (Zea mays)-cowpea (Vigna unguiculata) cultivation for 2 years on severely degraded land; (3) fallowing with mucuna on moderately degraded soils; (4) ley farming involving growing improved pastures for 1 year, grazing for the second year, and growing maize-cowpea for the third year on severely degraded land; (5) ley farming on moderately degraded soils. Soil chemical properties were measured once every year from 1982 through 1986 during the dry season, and included pH, soil organic carbon (SOC), total soil nitrogen (TSN), Bray-P, exchangeable cations, and effective cation exchange capacity (CEC). Regardless of the cropping system treatments, soil chemical quality decreased with cultivation time. The rate of decrease at 0–5 cm depth was 0·23 units year−1 for pH, 0·05 per cent year−1 for SOC, 0·012 per cent year−1 for TSN, 0·49 cmol kg−1 year−1 for Ca2+, 0·03 cmol kg−1 year−1 for Mg2+, 0·018 cmol kg−1 year−1 for K+, and 0·48 cmol kg−1 year−1 for CEC. Although there was also a general decrease in soil chemical quality at 5–10 cm depth, the trends were not clearly defined. In contrast to the decrease in soil properties given above, there was an increase in concentration at 0–5 cm depth of total acidity with cultivation time at the rate of 0·62 cmol kg−1 year−1, and of Mn3+ concentration at the rate of 0·081 cmol kg−1 year−1. Continuous cropping also increased the concentration of Bray-P at 0–5 cm depth due to application of phosphatic fertilizer. Trends in soil chemical properties were not clearly defined with regards to cropping system treatments. In general, however, soil chemical properties were relatively favorable in ley farming and mucuna fallowing treatments imposed on moderately degraded soils. Results are discussed in terms of recommended rates of fertilizer use, in view of soil test values, expected yields, and critical limits of soil properties.  相似文献   

7.
This study assessed the soil organic C (SOC) and soil nutrients in smallholding home garden, woodlot, grazing land, and cropland at two soil depths and two sites in Wolaita Zone, southern Ethiopia. The results showed that soil properties were significantly influenced by land use. The home garden had significantly higher (p < 0.05) SOC and soil nutrients when compared to the cropland. When the home garden was compared to the woodlot and grazing land uses, it had significantly higher (p < 0.05) values except in SOC, total N (TN), cation exchange capacity (CEC), and exchangeable Ca. Cropland, in comparison with grazing land and woodlot, had a non‐significant difference except TN. The SOC stock (0–40 cm) in the home garden, woodlot, grazing land and cropland was 79.5, 68.0, 65.0, and 58.1 Mg ha?1, respectively. Home garden significantly differed (p ≤ 0.05) in SOC only from cropland, and this was attributed not only to the relatively higher organic input in the home garden but also to the little organic matter input and frequently tillage of the cropland. The similar SOC among the home garden, woodlot and grazing lands may imply that the balance between inputs and outputs could be nearly similar for the land uses. Soil TN and CEC had a nearly similar pattern of difference as in SOC among the land uses because of their close relationship with SOC. In general, the land use influence on soil nutrients can be in the order: home garden > wood land ≈ grazing land ≈ cropland, with home garden showing the least difference from the woodlot and the greatest from the cropland. In the agroecosystem, in general, the influence of smallholding home garden on SOC and soil nutrient was marginally different from Eucalyptus woodlot and grazing lands but evidently different from cropland.  相似文献   

8.
Cultivation of irrigated desert soils in Central Iran is one way of utilizing under‐exploited land to produce more food. This study explores the value of soil quality indicators as measures when converting desert to croplands. Soil samples from unfarmed desert, wheat and alfalfa sites in the Abarkooh Plain (Central Iran) were taken from 0–10, 10–20 and 20–30 cm depths. Soil quality indicators including organic carbon, total nitrogen, carbohydrate, particulate organic carbon (POC) in aggregate fractions, and aggregate water‐stability were determined. The desert soils contained organic carbon of 0·26–0·56 g kg−1, total nitrogen of 0·05–0·08 g kg−1 and carbohydrate of 0·03–0·11 g kg−1 at 0–30 cm depth. Across this depth, the contents of organic carbon, total nitrogen and carbohydrate in wheat were about 3–7, 2–3 and 6–26‐times higher than those of desert soils, respectively. These values for alfalfa were 5–12, 3–4 and 7–35 times, respectively. The POC (near zero in desert soils) and generally other soil quality indicators showed greater improvement in alfalfa than in wheat fields. The results indicated a significant decrease in proportion of the fraction <0·05 mm in cultivated soils, whereas the proportion of the large aggregate size classes (2–4 and 1–2 mm) was increased by irrigation and cultivation. A significant improvement in aggregate water‐stability was observed in cultivated soils. At all depths, a large portion of the total soil organic carbon was stored in the fractions <0·05 mm for desert and macroaggregates (0·25–2 mm) for cultivated soils. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

9.
Abstract

Plantation establishment using exotic species on disturbed cultivated and undisturbed primary forest soils is common in Gambo district, southern Ethiopia, but their effects on soil properties are not fully known. This study investigated the effects of plantation species on major soil physical and chemical properties and further evaluated the soil quality under different land uses. Soil samples in triplicates, collected under different plantations, were analysed for their physical and chemical properties. Based on these soil properties, an integrated soil quality index was determined. The soil bulk density (BD) varied from 0.72 to 0.80 cm?3 in plantations established on primary forest land and natural forest and from 0.86 to 1.14 g cm?3 in those plantations established on cultivated soils. Also significantly lower pore volume and infiltration rate were observed under plantations established on cultivated lands than those on primary forest soils. Higher water volume (% at ?1500 kPa matric potential) was obtained in soils under Juniperus procera and natural forest compared with that under the rest of the plantations investigated. The concentration of soil organic carbon (SOC) varied from 3.4 to 10.2%, N from 0.3 to 1.0% and Av.P from 1.5 to 7.0% in soils under plantations and natural forest. Exchangeable cations generally showed a decreasing trend with depth in all land use types with minor exceptions. The concentrations of exchangeable Ca+2 varied from 6.5 to 22.7 cmol kg?1 and were significantly higher under Juniperus procera than under Eucalyptus species. The soil under plantations on previously cultivated lands showed soil quality index below 0.5 (the baseline value), while those established on undisturbed forest soil were generally above that value. The study results suggest that selecting species such as Juniperus procera and prolonging the harvesting period would improve and maintain the quality of soil properties.  相似文献   

10.
Storage of soil organic carbon (SOC) is an essential function of ecosystems underpinning the delivery of multiple services to society. Regional SOC stock estimates often rely on data collected during land‐use‐specific inventory schemes with varying sampling depth and density. Using such data requires techniques that can deal with the associated heterogeneity. As the resulting SOC assessments are not calibrated for the local scale, they could suffer from oversimplification of landscape processes and heterogeneity. This might especially be the case for sandy regions where typical historical land use practices and soil development processes determine SOC storage. The aims of this study were (a) to combine four land‐use‐specific SOC stock assessments to estimate the total stock in Flanders, Belgium, and (b) to evaluate the applicability of this regional‐scale estimate at the local scale. We estimated the SOC stock in the upper 100 cm of the unsealed area in Flanders (887,745 ha) to be 111.67 Mt OC, or 12.6 ± 5.65 kg OC m?2 on average. In general, soils under (semi‐) natural land‐use types, for example forests, store on average more organic carbon than under agriculture. However, overall agricultural soils store the largest amounts of SOC due to their vast spatial extent. Zooming in on a sandy location study (13.55 km2) revealed the poor performance of the regional estimates, especially where Histosols occurred. Our findings show that a greater spatial sampling density is required when SOC stock estimates are needed to inform carbon‐aware land management rather than to provide for regional reporting.  相似文献   

11.
Lynchets represent a traditional landscape element in agricultural landscapes having multiple functions in soil material redistribution, water retention, biodiversity and landscape character. They act as a barrier to translocated soil matter, and they can store a significant amount of soil material and soil organic carbon. Lynchets developed in many regions during formation of agriculture landscape as field boundaries or path networks. Further management led to unleveling of the fields and development of lynchets. During the 20th century, a large number of lynchets disappeared in Central and Western Europe due to land consolidation, intensification and industrialization of agriculture. This study was performed at a large agricultural study plot with dissected relief (Central Czechia) with the aim of assessing the influence of former but now completely levelled lynchets on actual soil stratigraphy, depth, soil organic carbon stocks and structure of soil units. The soil profiles in 20‐m‐long transects perpendicular to former lynchets were analysed, and statistical relationships between the positions above, in and below the former lynchets were assessed. The results showed high variability of studied soil characteristics in the areas of former lynchets. Statistically significant greater A horizon thickness (50–100 cm) and SOC stock (12.7 kg/m2) were observed in the location of a former lynchet, where colluvial soils were identified. Other areas of accumulation were identified below a lynchet, at the former break‐in‐slope. The strip above a lynchet was identified as a sediment delivery area, having a partly truncated soil profile. SOC concentration and SOC stock in A horizon did not differ significantly in the positions in, above or below a lynchet.  相似文献   

12.
The industrial emission of carbon (C) in China in 2000 was about 1 Pg yr−1, which may surpass that of the United States (1ċ84 Pg C) by 2020. China's large land area, similar in size to that of the United States, comprises 124 Mha of cropland, 400 Mha of grazing land and 134 Mha of forestland. Terrestrial C pool of China comprises about 35–60 Pg in the forest and 120–186 Pg in soils. Soil degradation is a major issue affecting 145 Mha by different degradative processes, of which 126 Mha are prone to accelerated soil erosion. Total annual loss by erosion is estimated at 5ċ5 Pg of soil and 15ċ9 Tg of soil organic carbon (SOC). Erosion‐induced emission of C into the atmosphere may be 32–64 Tg yr−1. The SOC pool progressively declined from the 1930s to 1980s in soils of northern China and slightly increased in those of southern China because of change in land use. Management practices that lead to depletion of the SOC stock are cultivation of upland soils, negative nutrient balance in cropland, residue removal, and soil degradation by accelerated soil erosion and salinization and the like. Agricultural practices that enhance the SOC stock include conversion of upland to rice paddies, integrated nutrient management based on liberal use of biosolids and compost, crop rotations that return large quantities of biomass, and conservation‐effective systems. Adoption of recommended management practices can increase SOC concentration in puddled soil, red soil, loess soils, and salt‐affected soils. In addition, soil restoration has a potential to sequester SOC. Total potential of soil C sequestration in China is 105–198 Tg C yr−1 of SOC and 7–138 Tg C yr−1 for soil inorganic carbon (SIC). The accumulative potential of soil C sequestration of 11 Pg at an average rate of 224 Tg yr−1 may be realized by 2050. Soil C sequestration potential can offset about 20 per cent of the annual industrial emissions in China. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

13.
The organic carbon pool in agricultural land‐uses is capable of enhancing agricultural sustainability and serving as a potential sink of atmospheric carbon dioxide. A study was carried out to estimate and map carbon stock of different agricultural land‐uses in a sub‐watershed of Thailand and to assess the land‐use sustainability with respect to carbon management. A quadrat sampling methodology was adopted to estimate the biomass and its carbon content of 11 different land‐uses in the study area. Existing soil data were used to calculate the soil carbon. GIS was used for integrating biomass carbon, soil carbon and carbon stock mapping. Roth carbon model was used to project the soil carbon of present land‐uses in the coming 10 years and based on which the sustainability of land‐uses was predicted. The total carbon stock of agricultural land‐uses was estimated to be 20·5 Tg, of which 41·49 per cent was biomass carbon and 58·51 per cent was soil carbon. Among the land‐uses, para rubber had the highest average biomass C (136·34 Mg C ha−1) while paddy had the lowest (7·08 Mg C ha−1). About four‐fifths of agricultural land‐uses in the watershed are sustainable in maintaining the desired level of soil carbon in coming 10 years while one‐fifths are unstable. Such information on carbon stock could be valuable to develop viable land‐use options for agricultural sustainability and carbon sequestration. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

14.
Soil organic carbon tends to respond more sensitively to climate change and land use intensification in ecologically fragile and economically marginal regions of mountainous areas. This study aims to evaluate the soil organic carbon stock dynamic across various land uses at different altitudes in the Bagrot valley, Northern Karakoram, Gilgit-Baltistan, Pakistan. Soil samples from 0–20, 20–40 and 40–60 cm depth were collected from three land uses: pasture, forest, and adjacently located arable land at different altitude (ranging from 2100–4163 m). The variables investigated were soil bulk density (BD), soil organic carbon concentration (SOC), soil organic carbon stock (SOCS) and pH. A significant variation in all tested variables were found across the land uses and altitudes. Likewise, soil under forest had significantly higher values of SOCS (59.35?Mg ha?1) than pasture (42.48?Mg ha?1) and arable land (23.63?Mg ha?1). Similarly, SOCS increased with increasing altitude and decreased with soil depth in all land uses. In addition, SOCS had a negative relationship with BD and pH. Overall results indicated that the land use intensification and climate change (increase in temperature and decrease in precipitation) were associated with declining SOCS. These results suggest restoration of degraded agricultural land to the forest, especially at higher altitude, and decrease in intensity of land use could increase SOCS in the study area as well as other similar mountainous regions.  相似文献   

15.
When tropical forests are felled, subsequent land uses affect surface runoff, soil erosion, and soil compaction. In some cases, they can markedly change the hydrology of a region with disastrous effects on human life. The objective of this paper is to investigate the effect of rainfall on stream hydrology due to conversion of primary forests to agriculture. Near surface water dynamics were compared for three land uses on the steep hillsides in the Talgua River Watershed in Honduras: degraded grass‐covered field; traditional coffee plantation; and primary forest. Infiltration and surface runoff rates were measured using several methods. A clear difference was observed in hydraulic conductivity between the degraded and non‐degraded lands. The degraded grass‐covered hillslopes developed a surface restrictive layer with a low saturated hydraulic conductivity of 8 to 11 mm/hr, resulting in more frequent overland flow than traditional coffee plantation and primary forest. Soils under the latter two land‐use types maintained high infiltration capacities and readily conducted water vertically at rates of 109 and 840 mm/hr, respectively. Dye tests confirmed that the coffee plantation and primary forest both maintained well‐connected macropores through which water flowed readily. In contrast, macropores in the degraded soil profile were filled by fine soil particles. Soils in the degraded grass‐covered field also showed more compaction than soils in the coffee plantation. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

16.
以不同土地利用方式下（疏林荒草地、荒草地、林地和耕地）第四纪古红土和埋藏第四纪古红土剖面为研究对象,测定古红土各发生层全土及各粒级团聚体的有机碳含量,比较不同土地利用方式下第四纪古红土剖面及团聚体的有机碳分布特征。结果表明:（1）埋藏古红土有机碳含量较低,随深度分布均一,各粒级团聚体内有机碳含量随团聚体粒径减小而降低;（2）埋藏古红土出露地表后,由于受到人为活动影响,表层全土有机碳及各粒级团聚体有机碳含量均增加,呈现林地 > 耕地 > 疏林荒草地 > 荒草地 > 埋藏古红土的特征,其中,林地显著高于其他土地利用方式,说明林地是古红土分布区的一种较合理的土地利用方式;（3）耕地0 ~ 10 cm土层粒径 > 1 mm和 < 0.25 mm团聚体的有机碳含量均随团聚体粒径减小而逐渐增加,1 ~ 0.25 mm团聚体有机碳含量随团聚体粒径减小逐渐降低。其余土地利用方式下古红土均呈现 > 0.25 mm团聚体的有机碳含量随着团聚体粒径减小而逐渐降低,< 0.25 mm团聚体的有机碳含量随团聚体粒径减小而逐渐增加。  相似文献   

17.
In order to assess the potential of soils as C reservoir at regional scale, accurate estimates of soil organic carbon (SOC) are required, and different approaches can be used. This study presents a method to assess and map topsoil organic carbon stock (Mg ha−1) at regional scale for the whole Emilia Romagna plain in Northern Italy (about 12 000 km2). A Scorpan Kriging approach is proposed, which combines the trend component of soil properties as derived from the 1:50 000 soil map with geostatistical modeling of the stochastic, locally varying but spatially correlated component. The trend component is described in terms of varying local means, calculated taking into account soil type and dominant land use. The resulting values of SOC, sand, silt, and clay contents are retained for calculating topsoil SOC stocks, using a set of locally calibrated pedotransfer functions (PTFs) to estimate bulk density. The maps of each soil attribute are validated over a subset of 2000 independent and randomly selected observations. As compared to the standard approach based on the mean values for delineation, results show lower standard errors for all the variables used for SOC stock assessment, with a relative improvement (RI) ranging from 4 per cent for SOC per cent to 24 per cent for silt. The total C stock (0–30 cm) in the study area is assessed as 73·24 ± 6·67 M t, with an average stock of 62·30 ± 5·55 Mg ha−1. The SOC stock estimates are used to infer possible SOC stock changes in terms of carbon sequestration potential and potential carbon loss (PCL). Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

18.
An experiment to evaluate the impact of water erosion and cultivation on the soil carbon dynamic and carbon stock in a semiarid area of South-East Spain was carried out. The study was performed under three different land use scenarios: (1) forest; (2) abandoned agricultural field; and (3) non-irrigated olive grove. Experimental erosion plots (in olive grove and forest) and sediment traps (in the abandoned area) were used to determine the carbon pools associated with sediments and runoff after each event occurring between September 2005 and November 2006.

Change in land use from forest to cultivated enhanced the risk of erosion (total soil loss in olive cropland seven-fold higher than in the forest area) and reduced the soil carbon stock (in the top 5 cm) by about 50%. Mineral-associated organic carbon (MOC) represented the main C pool in the three study areas although its contribution to soil organic carbon (SOC) was significantly higher in the disturbed areas (78.91 ± 1.81% and 77.29 ± 1.21% for abandoned and olive area, respectively) than in the forest area (66.05 ± 3.11%). In both, the olive and abandoned soils, the reduction in particulate organic carbon (POC) was proportionally greater than the decline in MOC.

The higher degree of sediment production in the olive cropland had an important consequence in terms of the carbon losses induced by erosion compared to the abandoned and forest plots. Thus, the total OC lost by erosion in the sediments was around three times higher in the cultivated (5.12 g C m−2) than the forest plot (1.77 g C m−2). The abandoned area displayed similar OC losses as a result of erosion as the forest plot (in the measurement period: 2.07 g C m−2, 0.63 g C m−2 and 0.65 g C m−2 for olive, forest and abandoned area, respectively). MOC represented the highest percentage of contribution to total sediment OC for all the events analysed and in all uses being, in general these values higher in Olive (74–90%) than in the other two areas (55–80%). The organic carbon lost was basically linked to the solid phase in the three land uses, although the contribution of DOC to total carbon loss by erosion varied widely with each event.

Data from this study show that the more labile OC fraction (POC) lost in soil in the cultivated area was mainly due to the effect of cultivation (low overall biomass production and residue return together with high C mineralization) rather than to water erosion, given that the major part of the OC lost in sediments was in the form of MOC.  相似文献   


19.
李雪 《水土保持通报》2016,36(3):136-140
[目的]分析土地利用变化对土壤有机碳分布的影响,为科学评估区域生态系统碳储量的变化提供依据。[方法]利用遥感影像获取滨海新区1979与2013年土地利用变化数据,针对不同土地利用类型均匀布设样点采集2013年表层土壤,试验监测土壤有机碳含量。结合第二次土壤调查数据,计算分析研究区1979—2013年土壤有机碳储量的变化及其空间分布变化。[结果]研究期内土地利用变化明显,耕地、滩涂、未利用地等土地利用类型大量转变为建设用地,同时土壤有机碳密度和储量均相应降低,其中土壤有机碳储量从1979年的1．23×107 t 减少到2013年的9．97×106 t 。[结论]随着人类对土地利用程度的加强,碳储量空间分布由高碳储量分布为主转变为低碳储量分布为主的碳储量分布格局。  相似文献   

20.
城郊土壤不透水表面有土壤机碳转化及其相关性质的研究   总被引：2，自引：0，他引：2  
Installation of impervious surface in urban area prevents the exchange of material and energy between soil and other environmental counterparts, thereby resulting in negative effects on soil function and urban environment. Soil samples were collected at 0-20 cm depth in Nanjing City, China, in which seven sites were selected for urban open soils, and fourteen sites with similar parent material were selected for the impervious-covered soils, to examine the effect of impervious surface on soil properties and microbial activities, and to determine the most important soil properties associated with soil organic carbon （SOC） transformation in the urban soils covered by impervious surfaces. Soil organic carbon and water-soluble organic carbon （WSOC） concentrations, potential carbon （C） and nitrogen （N） mineralization rates, basal respiration, and physicochemical properties with respect to C transformation were measured. Installation of impervious surface severely affected soil physicochemical properties and microbial activities, e.g., it significantly decreased total N contents, potential C mineralization and basal respiration rate （P 〈 0.01）, while increased pH, clay and Olsen-P concentrations. Soil organic carbon in the sealed soils at 0-20 cm was 2.35 kg m-2, which was significantly lower than the value of 4.52 kg m-2 in the open soils （P 〈 0.05）. Canonical correlation analysis showed WSOC played a major role in determining SOC transformation in the impervious-covered soil, and it was highly correlated with total N content and potential C mineralization rate. These findings demonstrate that installation of impervious surface in urban area, which will result in decreases of SOC and total N concentrations and soil microbial activities, has certain negative consequences for soil fertility and long-term storage of SOC.  相似文献   

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