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1.
The Grain to Green Program in China which began in 1999 led to the conversion of 0.64 million ha of cropland to grassland on steep sloping landscapes. However, the pattern of natural vegetation succession following cropland has not been well represented in previous regional syntheses of land use change effects on soil organic carbon (SOC). A chronosequence study focusing on the vegetation succession and soil carbon stocks was conducted in the center of the Loess Plateau. The chronosequence included fields of 0, 2, 5, 8, 9, 10, 12, 15 and 25 years of self‐restoration after cropland abandonment, as well as a natural grassland reference. Plant coverage, species richness and plant biomass increased significantly with time of cropland abandonment. Over time, the species composition more nearly resembled a natural grasslands community. Cropland abandonment replenished SOC stocks by 3.6 kg C m−2 during the 25‐year self‐restoration, but the SOC accumulation was restricted to the upper soil profiles (0–60 cm). SOC accumulation rate was 88 g C m−2 y−1 in 0–30 cm and 55 g C m−2 y−1 in 30–60 cm soil depth, respectively. These carbon stocks were still significantly lower than those found in the natural grassland soil. Our results suggest that the recovery of plant communities and SOC stocks appears to be slow in this semiarid environment without revegetation effort along with appropriate field management, although the post‐agricultural soils have a high potential for carbon sequestration. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

2.
Soil plays an important role in the global carbon cycle, and carbon sequestration in soil is important for mitigating global climate change. Historically, soil erosion led to great reductions of soil organic carbon (SOC) storage in China. Fortunately, with the economic development and remarkably effective soil erosion control measures in subtropical China over the past 20 years, soil erosion has been greatly decreased. As a result, soil organic carbon sequestration has gradually increased due to the rapid recovery of vegetation in the area. However, little information exists concerning the potential of soil carbon sequestration in the area. This paper introduces a case study in Xingguo County, Jiangxi Province, China, which used to be a typical area with significant soil loss in subtropical China. This work represents a systematic investigation of the interrelations of carbon sequestration potential with soil erosion types, altitudes, soil types and soil parent materials. In this study, 284 soil samples were collected from 151 sampling sites (51 are soil profile sites) to determine soil physicochemical properties including organic carbon content. Soil organic carbon distribution maps of the surface layer (0–20 cm) and whole profile (0–100 cm) were compiled by linking soil types to the polygons of digital soil maps using GIS. Assuming that SOC was lost following the destruction of native vegetation, these lands hold great promise for potentially sequestering carbon again. The potential of soil carbon sequestration in the study area was estimated by subtracting the organic carbon status in eroded soils from that in non-eroded soils under undisturbed forest. Results show that the potential of SOC in the surface layer is 4.47 Tg C while that in the whole profile is 12.3 Tg C for the entire county. The greatest potential for carbon sequestration (3.72 Tg C) is found in severely eroded soil, while non-eroded soil has the smallest potential. Also, soil carbon sequestration potential decreases with increasing altitude. Soils at altitudes of <300 m show the greatest potential (5.01 Tg C), while those of >800 m have the smallest potential (0.25 Tg C). Among various soil types, red earths (Humic Acrisols) have the greatest potential of carbon sequestration (5.32 Tg C), and yellow earths (Ferralic Cambisols) have the smallest (0.15 Tg C). As for soils derived from various parent materials, soils derived from phyllite possess the greatest carbon sequestration potential, and soils from Quaternary red clays have the smallest.  相似文献   

3.
Soil organic carbon and nitrogen are key elements of sustainable agriculture. Converting forest land and grassland to arable land is known to decrease the content of soil organic carbon (SOC), whereas converting land under annual crops into perennial grasslands has the potential to increase organic C and N sequestration, an assumption tested in this study. Compared to the levels in reed meadows, SOC and total nitrogen (TN) stocks in the top layer of 2489 Mg soil ha−1 (about 0–15 cm depth) significantly increased 3 years after the conversion, despite a slight decrease numerically in the first year following the conversion. And the mass of light fraction organic carbon (LFOC), total extractable carbon (TEC), humic acid carbon (HAC), and fulvic acid carbon (FAC) stocks all decreased significantly in the first year in the top layer but recovered after 3 years. In the deeper layer of 2549 Mg soil ha−1 (about 15–30 cm depth), however, the levels of SOC and heavy fraction organic carbon (HFOC) stocks began increasing from the first year itself. During the period of 1–10 years after the conversion, the degree of humification rate (HR) for the deeper layer were consistent, averaging 30%, whereas the same parameters in the top layer stabilized after 3 years at 33%. After 10 years of conversion, the soil recorded higher levels of SOC and TN stocks, used as indicators in this study, than those that had prevailed in the reed meadows, demonstrating the positive combined effects of the conversion on the retention of atmospheric C-CO2 in the soil. This study suggests that proper management of alfalfa fields can maintain or even improve chemical and physical quality of converted reed meadows soils.  相似文献   

4.
Poplar plantations are an important resource in China, which possess significant potential to offset carbon (C) emissions through the sequestration of atmospheric carbon dioxide (CO2) within biomass and soil. The traditional rotation age of poplar plantations is determined by maximizing the economic return from timber production. However, the optimal rotation age that results in the highest level of carbon sequestration within the soil remains unclear. In this study, we examined the total C, nitrogen (N) and microbial biomass (SMB) content of soils, as well as other properties in 0–10, 10–25 and 25–40 cm soil profiles along a 0‐ to 20‐yr chronosequence in a coastal region of Eastern China. Soil C stocks were determined for 1 m soil profiles, and the stand biomass in poplar plantations of different ages was investigated. We found that C concentrations within soils increased with plantation age, primarily in the topsoil layers. The periodic annual increment of C in soils peaked between stand ages of from 6 to 10 yr (0.71 t/ha/yr) and then decreased considerably at 17.5 yr, while the mean annual increment of C in soils was the highest at 15 yr (0.573 t/ha/yr). Soil C accumulation (i.e. soil C sequestration) was positively correlated with poplar biomass, soil N and SMB, and negatively correlated with soil potassium (K), calcium (Ca), magnesium (Mg) and sodium (Na), but not with sulphur (S) or phosphorus (P). Our results suggest that a rotation age of 15 yr is optimal for the sequestration of atmospheric CO2 in poplar plantations in the coastal region of Eastern China. The C sequestration capacity of soil was primarily controlled by poplar biomass, soil N and SMB.  相似文献   

5.

Purpose

Land use changes have a significant impact on soil carbon emission and sequestration worldwide. Accurate evaluation of the effect of land use change (cultivation and abandonment) on soil carbon content of subalpine meadows is required to monitor the soil carbon dynamics of rangeland ecosystems in China.

Materials and methods

Based on collection of soil cores and vegetation, investigations of four types of land use (undisturbed natural meadow, land cultivated for 20?years, land abandoned for 3?years following cultivation, and land abandoned for 10?years following cultivation) were undertaken in the headwater area of the Heihe River in northwest China. Three soil carbon fractions [soil organic carbon (SOC), light fraction organic carbon (LFOC), and microorganism biomass carbon (MBC)] were determined in the laboratory, and the relative abundances of LFOC/SOC and MBC/SOC were calculated.

Results and discussion

Repeated cultivation by ploughing reduced the carbon content of the top soil layer, resulting in more uniform vertical distribution of soil organic matter. Ten years after cessation of cultivation, the organic carbon content within the top 10-cm soil layer (0?C10?cm) had reached 90?% of the content in native meadows, equivalent to a mean annual sequestration rate of 1.73?t?C?ha?1. The rate of LFOC restoration was faster than that of SOC restoration. The variation in the ratio of MBC to SOC (0.91?C1.07?%) was small.

Conclusions

The activity of cultivation reduced all indicators of soil carbon status, which were not completely restored to the level of natural meadow, even after abandonment of cultivation for 10?years. Nevertheless, abandonment of cultivation is a practical, even if long-term, means of improving carbon sequestration in subalpine meadow of China.  相似文献   

6.
西南喀斯特地区是我国主要的生态脆弱区之一,石漠化严重,旱涝灾害频发。植被恢复是提升脆弱生态系统土壤碳氮固持的有效方式,但该区不同植被恢复方式土壤碳氮动态监测的研究还很缺乏。本研究以典型喀斯特峰丛洼地为对象,选取人工林、牧草地、人工林+牧草地、撂荒地自然恢复4种最主要的植被恢复方式为研究对象,以耕地作为对照,对比分析退耕前(2004年)、退耕10年(2014年)和13年后(2017年)土壤碳氮储量动态变化特征。其中2004—2014年研究区未发生极端内涝灾害, 2014—2017年连续发生2次极端内涝灾害事件。研究结果表明,退耕10年后, 4种恢复方式下土壤有机碳(SOC)储量均显著增加,但退耕13年后,除撂荒地SOC持续增加外,其他3种恢复方式下SOC表现出下降趋势。植被恢复后土壤全氮(TN)储量提升相对缓慢,退耕10年仅牧草地显著增加,退耕13年后人工林+牧草和撂荒地TN增加,且撂荒地在退耕后呈持续增加趋势。相关性分析结果表明,土壤交换性Ca~(2+)与SOC、TN均呈显著正相关关系,且与2014年相比, 2017年不同植物恢复方式下土壤交换性Ca~(2+)均显著下降,这可能与研究区2015年和2016年连续内涝灾害有关。以上结果说明,不同恢复方式均能显著提升喀斯特地区土壤碳氮固持,并以自然恢复最佳,其生态系统能有效抵御极端气候灾害带来的负面影响。  相似文献   

7.
Soils are the third biggest sink of carbon on the earth. Hence, suitable land uses for a climatic condition are expected to sequester optimum atmospheric carbon in soils. But, information on how climatic conditions and land uses influence carbon accumulation in the soils on the Himalayan Mountains is not known. This study reports the impact of four climatic conditions (sub-tropical, altitude: 500–1200 m; temperate 1200–2000 m; lower alpine 2000–3000 m; upper alpine, 3000–3500 m) and four land uses (forest, grassland, horticulture, agriculture) on the concentrations and stocks of soil organic carbon (SOC) in upper (0–30 cm) and deeper (30–100 cm) soil depths on the western Himalayan Mountains of India. The study also explored the drivers which influenced the SOC stock build up on the mountains. Rainfall and soil moisture showed quadratic relations, whereas temperature declined linearly with the altitude. SOC stock as well as concentration was the highest (101.8 Mg ha− 1 in 0–30 cm, 227.97 Mg ha− 1 in 0–100 cm) in temperate and the lowest in sub-tropical climate (37 Mg ha− 1 in 0–30 cm, 107.04 Mg ha− 1 in 0–100 cm). Pattern of SOC stock build up across the altitude was: temperate > lower alpine > upper alpine > sub-tropical. SOC stocks in all land uses across the climatic conditions, except agriculture in lower alpine, was higher (0.7 to 41.6%) in the deeper than upper soil depth. SOC stocks in both the depths showed quadratic relations with soil temperature and soil moisture. Other factors like fine soil particles, land-use factor and altitude influenced positively whereas slope and pH, negatively to the SOC stocks. In all climatic conditions, other than temperate, SOC stocks were greater in natural ecosystems like forests and pastures (112.5 to 247.5 Mg ha− 1) than agriculture (63 to 120.4 Mg ha− 1). In temperate climate, SOC stock in agriculture (253.6 Mg ha− 1) on well formed terraces was a little higher than forest (231.3 Mg ha− 1) on natural slope. These observations, suggest that land uses on temperate climate may be treated as potential sinks for sequestration of the atmospheric carbon. However, agriculture in subtropical climate need to be pursued with due SOC protection measures like the temperate climate for greater sequestration of the atmospheric carbon.  相似文献   

8.
Few studies have been conducted on the factors and distribution of soil organic carbon (SOC) in plantation forests in arid mountainous regions, especially in orchards. We aimed to unravel the SOC distribution among land-use types and the effects of altitude gradients and rock fragment content (RFC) on SOC accumulation and sequestration in the Upper Min River Arid Valley, China. The differences in SOC distribution among land-use types were quantified. The correlation analysis of SOC with various factors, such as altitude and RFC, was conducted. The variation percentage in SOC content and stocks was explained by the factors' contribution using mixed-effects models. SOC distribution was characterized by high content and low stocks in native forests and shrubs, high content and high stocks in eco-forest, and low content and high stocks in orchards. At the surface (0–30 cm), SOC content and stocks in orchards (cherry, plum, and apple) were significantly lower than those in eco-forests. There was a significant positive correlation between altitude and SOC content at the surface but not at the subsoil (30–60 cm). With RFC increased, the surface SOC content decreased in native forests, shrubs, and eco-forests, while it increased in orchards. Our results suggest that land management is the main factor controlling the variation in SOC distribution. Enhancing the surface SOC stability in orchards by land management is a priority for soil carbon pool management in the Arid Valleys.  相似文献   

9.
黄土高原丘陵区退耕还林地土壤碳氮库的动态变化(英文)   总被引：1，自引：1，他引：1  
为了揭示坡耕地退化土壤植被恢复后土壤中碳(C)、氮(N)运移规律,采用植被次生演替空间序列代替时间序列的方法,研究了黄土丘陵沟壑区纸坊沟流域不同植被恢复模式下的C、N库及其相互关系在土壤剖面的时空变化。结果表明退化农地的造林显著地促进了CO2的固存,恢复了土壤N的可获得性,进而降低了N不足对可持续的CO2固存的限制。植被恢复显著地促进了0~60 cm土壤有机碳(soil organic carbon,SOC)和总氮(total nitrogen,TN)的积累,而只有在高于一定的恢复时间阈值(如26 a)下,促进了SOC库和TN库间的线性相关性。在土壤剖面上,SOC和TN库、SOC/TN库比以及SOC-TN间的线性相关性均随着土壤深度的增加而降低。与自然恢复相比,人工林在短期内具有CO2固存的优势,但由于随着恢复时间的增加,SOC增幅越来越大于TN增幅的事实,表明造林对碳固存的可持续性需在一个较长的时段下来评估,尤其需要关注20 cm以下层土壤。研究结果为黄土高原的生态修复和减缓温室效应提供了理论依据。  相似文献   

10.
《Soil & Tillage Research》2005,80(1-2):201-213
Minimum tillage practices are known for increasing soil organic carbon (SOC). However, not all environmental situations may manifest this potential change. The SOC and N stocks were assessed on a Mollisol in central Ohio in an 8-year-old tillage experiment as well as under two relatively undisturbed land uses; a secondary forest and a pasture on the same soil type. Cropped systems had 51±4 (equiv. mass) Mg ha−1 lower SOC and lower 3.5±0.3 (equiv. mass) Mg ha−1 N in the top 30 cm soil layer than under forest. Being a secondary forest, the loss in SOC and N stocks by cultivation may have been even more than these reported herein. No differences among systems were detected below this depth. The SOC stock in the pasture treatment was 29±3 Mg ha−1 greater in the top 10 cm layer than in cultivated soils, but was similar to those under forest and no-till (NT). Among tillage practices (plow, chisel and NT) only the 0–5 cm soil layer under NT exhibited higher SOC and N concentrations. An analysis of the literature of NT effect on SOC stocks, using meta-analysis, suggested that NT would have an overall positive effect on SOC sequestration rate but with a greater variability of what was previously reported. The average sequestration rate of NT was 330 kg SOC ha−1 year−1 with a 95% confidence interval ranging from 47 to 620 kg SOC ha−1 year−1. There was no effect of soil texture or crop rotation on the SOC sequestration rate that could explain this variability. The conversion factor for SOC stock changes from plow to NT was equal to 1.04. This suggests that the complex mechanisms and pathways of SOC accrual warrant a cautious approach when generalizing the beneficial changes of NT on SOC stocks.  相似文献   

11.
Soil organic carbon (SOC) stocks and nutrient availability are key indicators of soil quality, and both can be influenced by land-use change. However, it is still unclear whether the impact of land-use change on SOC and nutrient stocks differs between ecoregions. Grasslands near the northeast border of the Qinghai-Tibetan Plateau (QTP) occur across several ecoregions that have recently been subjected to substantial land-use change. Based on long-term land-use history, we conducted a field investigation comparing soil C and nutrient stocks between natural grassland (NGL) and three types of converted grassland (agricultural grassland, AGL; farmland, FL; and abandoned farmland, AFL) in three ecoregions along a climate gradient: alpine meadow, temperate steppe and temperate desert. Compared with NGL, soil C stocks in converted grasslands were 22%–30% lower in the alpine meadow, but 60–82% higher in the temperate steppe and 6%–76% higher in the temperate desert. Converted grasslands also contained higher stocks of available nitrogen and phosphorus than NGL in the temperate steppe and desert. Soils (0–40 cm) in NGL contained 14.8 ± 0.1 kg C m−2 in alpine meadow, 6.7 ± 0.6 kg C m−2 in temperate steppe and 1.7 ± 0.3 kg C m−2 in temperate desert. Together, our results indicate that the responses of soil C and nutrients to grassland conversion differed between ecoregions. Thus, to optimize soil C sequestration rates and overall soil quality, we suggest that land-use policies in this area should take into account local environmental conditions.  相似文献   

12.
Concerns with rising atmospheric levels of CO2 have stimulated interest in C flow in terrestrial ecosystems and the potential for increased soil C sequestration. Our objectives were to assess land management effects on soil organic carbon (SOC) dynamics and SOC sequestration for long-term studies in the tallgrass prairie region of the US. Major losses of SOC following conversion of native prairie to arable agriculture at Sanborn Field and the Morrow Plots were rapid (20 to 40 yr), occurred in response to greatly reduced C inputs and accelerated C decay rates, and had largely abated by the mid-1900s. Losses of SOC occurred mainly in easily decomposable, labile C fractions. At Sanborn Field, modeled labile SOC was reduced to 4% of native prairie levels for treatments with low C inputs. A large capacity for soil C sequestration likely exists in the tallgrass prairie region, if labile C pools can be replenished. This agroecosystem has a strong C decomposition regime and increased sequestration of labile C will rely on management practices that increase C inputs (i.e., fertilization, returning crop residues) and stabilize labile C (i.e., perennial cropping, reduced tillage). The capacity for soil C sequestration, however, will vary considerably among sites and be dependent on initial levels of labile SOC and the ability of management practices to stabilize greater inputs of labile C.  相似文献   

13.
Agroforestry systems have the potential to increase sequestration of atmospheric carbon dioxide (CO2) as soil organic carbon (SOC) because of the increased rates of organic matter addition and retention. However, few studies have characterized the relative stability of sequestered SOC in soil. We characterized SOC storage in aggregate size and chemical stability classes to estimate the relative stability of SOC pools after the addition of Leucaena-KX2 pruning residues (mulch) from 2006 to 2008 in a shaded coffee agroforestry system in Hawaii. Soil samples were separated by microaggregate isolation, density flotation and dispersion, and acid hydrolysis, resulting in five distinct fractions that differed in relative stability: coarse particulate organic matter (POM), fine POM, microaggregate-protected POM, silt + clay hydrolyzable soil organic matter (SOM), and silt + clay non-hydrolyzable SOM. With mulch addition, the fine POM fraction increased. There was also a shift in the proportion of SOC to more stable silt + clay fractions. In the absence of mulch there was no significant change in SOC fractions. Given that the turnover time of SOC in silt + clay fractions is on the order of decades to centuries, the potential benefits of active shade management and mulching compensate for the loss of C sequestration in tree biomass from pollarding.  相似文献   

14.
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   

15.

Purpose  

Although organic amendments have been recommended as one of the practices for crop production and soil carbon sequestration, little has been done to evaluate soil organic carbon (SOC) dynamics following long-term application of organic amendments. The objective of this research were to (1) assess the effect of long-term organic amendments on SOC dynamics in rice-based systems; (2) evaluate the relationship between soil carbon sequestration and carbon input based on various mineral and organic fertilization treatments.  相似文献   

16.
子午岭植被自然恢复过程中土壤有机碳密度的时空变化   总被引：11，自引：0，他引：11  
To probe the processes and mechanisms of soil organic carbon （SOC） changes during forest recovery, a 150-year chronosequence study on SOC was conducted for various vegetation succession stages at the Ziwuling area, in the central part of the Loess Plateau, China. Results showed that during the 150 years of local vegetation rehabilitation SOC increased significantly （P 〈 0.05） over time in the initial period of 55-59 years, but slightly decreased afterwards. Average SOC densities for the 0-100 cm layer of farmland, grassland, shrubland and forest were 4.46, 5.05, 9.95, and 7.49 kg C m^-3, respectively. The decrease in SOC from 60 to 150 years of abandonment implied that the soil carbon pool was a sink for CO2 before the shrubland stage and became a source in the later period. This change resulted from the spatially varied composition and structure of the vegetation. Vegetation recovery had a maximum effect on the surface （0-20 cm） SOC pool. It was concluded that vegetation recovery on the Loess Plateau could result in significantly increased sequestration of atmospheric CO2 in soil and vegetation, which was ecologically important for mitigating the increase of atmospheric concentration of CO2 and for ameliorating the local eco-environment.  相似文献   

17.
Mountainous peatlands are one of the most important terrestrial ecosystems for carbon storage and play an important role in the global carbon cycle. An insight into the carbon cycle of peat swamps located in mountainous regions can be obtained by studying the distribution of soil organic carbon (SOC) and its relationships with environmental factors. This study focused on the development conditions of peat swamps in the Gahai wetlands, located on the Zoigê Plateau, China, with four different altitudinal gradients as experimental sample sites. The distribution of SOC and its relationship with environmental factors were analysed through vegetation surveys and a generalized additive model (GAM). The results show that with increasing altitude, soil temperature decreased while the soil pH and bulk density initially decreased then increased. On the contrary, the topographic wetness index (TWI), SOC content, above-ground biomass and litter count initially increased then decreased. The SOC content of the 0–30 cm soil layer was in the range 226–330 g·kg−1 (coefficient of variation (CV) = 21.4%), and the 30–60 cm layer was 178–257 g·kg−1 (CV = 17.5%) and was significantly correlated (p < .05) with above-ground biomass and litter count. Meanwhile, the SOC content in the 60–90 cm soil layer was in the range 132–167 g·kg−1 (CV = 9.2%) with a significant correlation (p < .05) with soil temperature, pH, bulk density and topographic moisture index. The study showed that the SOC content exhibited more pronounced spatial patterns with increasing altitude, with the peak value in the shallow soil layer appearing in lower elevation areas compared with the deep soil layer. The level of variation changed from medium to low, reflecting the stable mechanism for maintaining SOC within the heterogeneous peat swamp environment.  相似文献   

18.
Climate, soil physical–chemical characteristics, land management, and carbon (C) input from crop residues greatly affect soil organic carbon (SOC) sequestration. According to the concept of SOC saturation, the ability of SOC to increase with C input decreases as SOC increases and approaches a SOC saturation level. In a 12‐year experiment, six semi‐arid cropping systems characterized by different rates of C input to soil were compared for ability to sequester SOC, SOC saturation level, and the time necessary to reach the SOC saturation level. SOC stocks, soil aggregate sizes, and C inputs were measured in durum wheat monocropping with (Ws) and without (W) return of aboveground residue to the soil and in the following cropping systems without return of aboveground residue to soil: durum wheat/fallow (Wfall), durum wheat/berseem clover, durum wheat/barley/faba bean, and durum wheat/Hedysarum coronarium. The C sequestration rate and SOC content were lowest in Wfall plots but did not differ among the other cropping systems. The C sequestration rate ranged from 0.47 Mg C ha−1 y−1 in Ws plots to 0.66 Mg C ha−1 y−1 in W plots but was negative (−0.06 Mg C ha−1 y−1) in Wfall plots. Increases in SOC were related to C input up to a SOC saturation value; over this value, further C inputs did not lead to SOC increase. Across all cropping systems, the C saturation value for the experimental soil was 57.7 Mg ha−1, which was reached with a cumulative C input of 15 Mg ha−1. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

19.
Nie  Xiuqing  Peng  Yunfeng  Li  Fan  Yang  Lucun  Xiong  Feng  Li  Changbin  Zhou  Guoying 《Journal of Soils and Sediments》2019,19(1):322-331
Purpose

Although large amounts of soil organic carbon (SOC) stored in the shrublands, information about SOC storage was little on the Tibetan Plateau. This study aims to evaluate the spatial patterns and storage of SOC in the shrublands and the relationships of climatic variables and soil pH on the Tibetan Plateau.

Materials and methods

We used 177 profiles of soil samples obtained from 59 shrubland sites on the northeast Tibetan Plateau from 2011 to 2013. Ordinary least squares regressions, curve estimation, and multiple linear regressions were used to evaluate controlling factors on SOC stock. Kriging interpolation was used to upscale sit-level measurements to the whole study area.

Results and discussion

We found that SOC storage in the northeast Tibetan shrublands was 1.36 Pg C in the top 1 m with an average SOC stock of 12.38 kg m?2. SOC stock decreased from east to west and south to north but generally increased significantly with the mean annual temperature (MAT) and the mean annual precipitation (MAP), and tended to decrease with soil pH. Although similar relationships were also observed in alpine shrublands, the trends among SOC stock, MAP, and MAT were not observed in desert shrublands. Our results indicate that a reduction in soil pH accelerates the C sequestration potential. Furthermore, global warming contributed to C sequestration in alpine shrublands, specifically, SOC stock increased 8.44 kg m?2 with an increased unit of MAT in alpine shrublands just considering temperature effects. Meanwhile, the C sequestration was different among different regions due to the uneven increases in precipitation. However, in desert shrublands, MAP and MAT did not significantly affect SOC stock.

Conclusions

The results indicate that though a reduction in soil pH could contribute to C sequestration, MAT and MAP have different effects on SOC stock in different Tibetan Plateau shrublands. Increased MAT and MAP were 0.05 °C and 1.67 mm every year on the Tibetan Plateau, which will increase C sequestration in alpine shrublands, but might have limited impacts on desert shrublands, which help us comprehend soil C cycling in the global climate change scenario.

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20.
Land-use change (LUC) is widely considered a major factor that affects soil organic carbon (SOC) sequestration. The impacts of four LUC types on soil properties, SOC, particulate organic carbon (POC) and labile organic carbon (LOC) at the 0–100 cm depth were examined in the west of Loess Plateau, northwest China. Bulk density at the 20–40 cm depth increased significantly after native grassland conversion to cropland, while artificial grassland establishment and abandonment on former cropland caused reverse change. Soil water content in the profile increased 60–230% after cultivation and decreased 32–49% after abandonment (p < 0.01). The particle size distribution also showed a response to LUC. Only artificial grassland establishment caused an SOC sink of 32% at the 0–10 cm depth as well as two labile fractions. SOC tended to increase after cultivation and after abandonment, with 6% and 20% at soil surface, respectively. There were increasing trends in POC and LOC. After afforestation on former native grassland, SOC tended to decrease (23%) at the 0–10 cm depth while POC and LOC tended to increase (33% and 6%, respectively). Principal component analysis was successful in separating LUC through soil property parameters. Carbon sequestration is largely ascribed to increased below-ground production and tillage elimination after perennial alfalfa (Medicago sativa L.) plantation. Irrigation and fertilization activities contribute to SOC accumulation after cultivation to some extent. The self-restoration dynamic depending on time since abandonment is important to SOC change. A lower proportion of stabilized carbon results in a slow rate of SOC accumulation after afforestation. It is necessary to investigate the long-term dynamic after LUC.  相似文献   

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