Aggregate-associated Organic Carbon Research Articles

Effects of combined organic manure and mineral fertilization on soil aggregation and aggregate-associated organic carbon in two agricultural soils

The effect of organic manure and inorganic fertilizer on soil aggregate size distribution and stability, and associated carbon (C) within aggregates varies greatly in previous studies because of the differences in soil conditions, cropping systems, and management practices. This study was conducted as two field fertilization experiments, with different cropping systems, under a subtropical climate in China. The two field experiment sites were located in Jinhua (established in April 2011) in the Jinqu basin in Zhejiang province and Jintan (established in October 2010) in the low-middle Yangtze River plain in Jiangsu province. Both experiments consisted of four treatments, including unfertilized (CK), mineral fertilizer nitrogen (N)–phosphorus (P)–potassium (K) (NPK), NPK plus straw (NPK + SR), and NPK plus cattle manure (NPK + FYM) or half NPK plus cattle manure (1/2NPK + FYM). Water stable aggregate size classes (>5, 2–5, 1–2, 0.5–1, 0.25–0.5, and <0.25 mm) and associated soil organic C (SOC) at 0–15 cm depth were measured. The mean weight diameter (MWD), geometric mean diameter (GMD), and water stable aggregates (WSA) > 0.25 mm were also determined. The results showed that aggregate-size distribution varied with soil types. Combined application of NPK and organic matter (straw residue or cattle manure), unlike the CK and NPK treatments, significantly increased the WSA >0.25 mm, MWD, and GMD, while obviously reducing the proportion of <0.25 mm aggregates. However, no differences in WSA >0.25 mm, MWD, GMD, and associated C were observed between CK and NPK at both sites. The addition of FYM to the NPK treatment yielded the highest SOC contents in bulk soil, and showed significantly higher associations of C within all size aggregates at both sites. In contrast, NPK + SR significantly increased SOC within aggregate classes (2–5 mm, 0.5–1 mm, 0.25–0.5 mm, and <0.25 mm) at Jinhua and (>5 mm and 1–2 mm) at Jintan compared to the CK and NPK treatments. Overall, the combined application of FYM and mineral NPK was the best sustainable management practice for the improvement of aggregate stability and SOC sequestration.

Soil aggregate-associated organic carbon dynamics subjected to different types of land use: Evidence from 13C natural abundance

The technique of 13C natural abundance provides new information that can be applied to study carbon (C) incorporation into soil aggregates and to improve our understanding of the aggregate hierarchy theory. The organic matter (OM) in soil undergoes microbial decomposition, which preferentially removes the lighter 12C isotope, enriching the remaining soil in the heavier 13C isotope. We hypothesized that the soil aggregate turnover would gradually lead to C isotope fractionation, and changes in the 13C natural abundance are closely linked to C turnover that, in turn, is influenced by aggregates turnover. We examined how land use affects soil organic carbon (SOC) dynamics in soil aggregate with the following objectives: (1) evaluate the influence of land uses (woodland, orchard, paddy and upland) on aggregate-associated C isotope compositions and the distribution of new and old SOC in the Danjiangkou Reservoir area of central China, and (2) propose an extended scheme of C transfers between the aggregate size classes. The results showed that SOC content in aggregates generally increased with increasing aggregate size but the δ13C values of aggregates decreased. The SOC contents in bulk soil decreased in the order of paddy > woodland > upland > orchard. The most negative δ13C values in bulk soil and aggregates were observed in the paddy and woodland soils, whereas maximum δ13C values were obtained in the orchard and upland soils. The stable C isotope results suggest that SOC sequestration of fresh OM generally starts in macro-aggregates (>0.25 mm), and, after disaggregation processes and microbiological consumption, the resulting degraded OM is sequestered in micro-aggregates (<0.25 mm). This general trend is consistent with the concept of SOM stabilization by association with aggregate hierarchy theory. We conclude that different land uses and management practices significantly affect C incorporation in the aggregate system and C transfer in soil aggregates was considerably greater in the orchard and upland soils than in the woodland and paddy soils. These findings help improve the theory of soil aggregates.

Effects of freeze-thaw cycles on aggregate-associated organic carbon and glomalin-related soil protein in natural-succession grassland and Chinese pine forest on the Loess Plateau

Glomalin-related soil protein (GRSP) is a hydrophobic glycoprotein that can protect soil organic carbon (SOC) from decomposition by promoting the formation of soil aggregates. Few studies, however, have evaluated the response of aggregate-associated SOC and GRSP to freeze-thaw cycles (FTs) under different patterns of vegetation restoration. Soil samples were collected from three typical natural-succession grasslands (dominated by Artemisia capillaris, A. sacrorum, and Bothriochloa ischaemum) and a Chinese pine (Pinus tabuliformis) forest before and after natural FTs during a winter-spring season on the Loess Plateau in China. The soil aggregate stability and concentrations of SOC, easily extractable GRSP (EE-GRSP) and total GRSP (T-GRSP) in different aggregate fractions were measured. The FTs decreased the proportion of >5.0 mm wet-sieved fractions, increased the proportion of <0.25 mm wet-sieved fractions, and decreased the mean weight diameters by 8.7, 9.5, 2.9, and 9.4% in the soils of A. capillaris, A. sacrorum, B. ischaemum, and P. tabuliformis, respectively. The SOC, T-GRSP, and EE-GRSP concentrations in each aggregate fraction generally decreased after FTs in the four vegetation types. The SOC, T-GRSP, and EE-GRSP concentrations did not differ significantly in the larger aggregate fractions before the FTs in the soils for B. ischaemum and P. tabuliformis, but their concentrations were significantly higher for B. ischaemum than P. tabuliformis after FTs. The SOC and GRSP concentrations were significantly and linearly correlated in most aggregate fractions both before and after the FTs. These results indicated that the FTs decreased SOC by decreasing the GRSP concentration in each aggregate fraction and that SOC was more sensitive to FTs in forest than in natural-succession grassland.

Effect of community-based soil and water conservation practices on soil glomalin, aggregate size distribution, aggregate stability and aggregate-associated organic carbon in northern highlands of Ethiopia

BackgroundLand degradation is a major and widespread problem causing losses of ecosystem services in Ethiopia. Extensive utilization of the land resources for centuries resulted in severe land degradation in the Tigray region of northern Ethiopia. To reverse the problem, land restoration activities have been carried out for the past three decades. This study was initiated to determine the effect of community-based soil and water conservation interventions on soil glomalin, aggregate size distribution, water stable aggregates (WSA) and aggregate-associated organic carbon.MethodsSoil samples were collected from exclosures + terraces, exclosures alone, stone terraces and non-conserved grazing lands using systematic sampling based on slope positions.ResultsBoth easily extractable glomalin and total glomalin were significantly (p < 0.05) higher in exclosures compared to terraces and non-conserved grazing lands. The macroaggregate fraction of all SWC measures ranged 21.91–32.41%, where the lowest was in non-conserved grazing lands, while the highest was in exclosures with terraces. The micro-aggregate fraction ranged 19.9–26.66%, where the lowest was in exclosures, while the highest was in non-conserved grazing lands. The results also indicated that exclosures had significantly (p < 0.05) higher percent of WSA compared to terraces and non-conserved grazing lands. Mean weight diameter (MWD) was also significantly (p < 0.05) higher in exclosures. The WSA and MWD decreased in the order of exclosures with terraces > exclosures alone > terracess > non-conserved communal grazing lands. Comparison of aggregate-associated organic carbon (AAOC) showed relatively higher organic carbon in macroaggregates than in micro-aggregates. Besides, both macro- and micro-aggregate-associated SOC was higher in exclosures than in terraces and non-conserved grazing lands. The AAOC of both macro- and micro-aggregates follows the order exclosures alone > exclosures + terraces > terraces > non-conserved communal grazing lands.ConclusionExclosures and terraces are important strategies for rehabilitation of degraded lands through improving glomalin content, aggregate structure and stability, and aggregate-associated organic carbon.

Responses of soil and aggregate-associated organic carbon mineralization to throughfall reduction in a Pinus massoniana plantation.

To examine the effects of altered precipitation pattern on the mechanism of forest soil carbon (C) emission under climate change scenarios, we established plots with 50% reduction in throughfall in a subtropical Pinus massoniana plantation. The effects of throughfall reduction on the mineralization of both soil and aggregate-associated organic C were quantified by laboratory incubation at constant temperature. The results showed that the cumulative mineralization of organic C in the 1-2 mm aggregates was higher than that in other sizes of aggregates. In the dry and wet seasons, the surface soil water content in the throughfall reduction plots was 82.1% and 82.7% of that in the control, but the mass fractions of 0.106-0.25 mm soil aggregates in the throughfall reduction plots increased by 1.8% and 4.2% than the control, respectively. The throughfall reduction treatment significantly reduced the mineralization rate of labile C pools (k1) of soil and micro-aggregates in the dry season, increased the mineralization rate of recalcitrant C pool (k2) of soil and <1 mm aggregates, and had no significant effects on the cumulative mineralization of soil organic C. Results from the correlation analyses revealed significant and positive correlations between k1 of soil and that of the micro-aggregates and between k2 of soil and that of the 0.25-1 mm aggregates. Under the influence of aggregate structure, water condition and soil organic carbon content, the throughfall reduction suppressed the mineralization of labile organic C while stimulated that of recalcitrant organic C.

Effects of long-term tillage systems on aggregate-associated organic carbon in the eastern Mediterranean region of Turkey

The stability of aggregates plays a vital role in preserving and long term storing of soil organic carbon (SOC). In this study, the long-term (2006-2014) effects of six tillage systems on aggregate-associated SOC were investigated in a field experiment conducted under Mediterranean conditions. The tillage treatments were; c onventional tillage with residue incorporated in the soil (CT1), conventional tillage with residue burned (CT2), reduced tillage with heavy tandem disc-harrow (RT1), reduced tillage with rotary tiller (RT2), reduced tillage with heavy tandem disc harrow fallowed by no-tillage (RNT) for the second crop, and no tillage (NT). The most frequently encountered aggregates in all tillage systems were at 4.0-2.0 mm size and the least frequently found aggregates were 1.0-0.5 mm. The mean weight diameter (MWD) value increased in the NT compared to the conventional tillage practices at the rates of 137% and 204%, respectively at 0-15 cm soil depth. Aggregate-associated SOC contents in 0-15 cm depth were higher under conservation tillage systems. However, the highest SOC at 15-30 cm depth were greater mainly in conventional tillage systems as 9.4% for both CT1 and CT2. The results indicated that conservation tillage systems had greater aggregation and carbon storage at the soil surface.

Thermal stability of organic carbon in soil aggregates as affected by soil erosion and deposition

Knowledge about the stability of soil organic carbon (SOC) after erosion is essential for understanding the water erosion-induced organic carbon (OC) exchanges between soil and atmosphere. However, this issue has suffered from a shortage of focused studies and consensus results due to the complex processes and the use of various methods. The objective of the study was to estimate the stability of SOC in soil aggregates post-deposition by using thermogravimetric and differential scanning calorimetry (TG-DSC) techniques. Soils in eroded and depositional transects in subtropical China were collected and studied. To obtain the maximum difference in SOC along the transects based on the distributions of SOC concentrations along soil profiles, soils at depths of 0–5, 5–10, 20–30 and 120–150cm were selected to represent the transects. Water-stable aggregate distributions and the thermal stability of the aggregate SOC in the selected soils were determined. The study results showed that significant differences in edaphic properties and aggregate-associated OC thermal indices were only found at depth of 0–5 and 5–10cm (P<0.05). The distributions of soil aggregates indicate that soils at the depositional site had a better aggregate structure than those at the eroded site. The TG-T50 (the temperature resulting in 50% of SOM loss) and DSC-T50 (the temperature at which half of energy release occurred) values indicated that the eroded SOC was more stable than deposited SOC, and the thermal labile fractions (Exo1/Exotot) suggested that the eroded SOC had a higher decomposition rate. In spite of this, the deposited soils retained higher amounts of SOC. We attributed these results to the protection provided by macroaggregates. For the soils deeper than 20cm, there was no significant difference in soil aggregation, SOC content and SOC thermal stability between the soils at the two sites (P>0.05). Burial does not promote the formation of macroaggregates. The study results suggested that the quantity and quality of SOC are the primary factors controlling soil aggregation. Therefore, it is concluded that the protection provided by macroaggregates is an important mechanism for SOC stability.

Soil aggregation and aggregate-associated organic carbon under typical natural halophyte communities in arid saline areas of Northwest China

Information on the effects of halophyte communities on soil organic carbon (SOC) is useful for sequestrating C in arid regions. In this study, we identified four typical natural halophyte communities in the Manasi River Basin in Xinjiang Province, Northeast China, namely, Karelinia caspia (Pall.) Less., Bassia dasyphylla (Fisch. et C. A. Mey.) Kuntze, Haloxylon ammodendron (C. A. Mey.) Bunge, and Tamarix ramosissima Lour. We compared soil aggregation and aggregated-associated SOC under these communities. The aggregate fraction of 0.053–0.25 mm accounted for 47%–75% of the total soil mass, significantly more than the > 0.25 and < 0.053 mm fractions, under all the halophyte communities. Significant differences in soil aggregate size distribution were observed among the plant communities, with the H. ammodendron and B. dasyphylla communities showing the highest proportions of > 0.25 mm aggregates (13.3%–43.8%) and T. ramosissima community having more < 0.053 mm aggregates (14.1%–27.2%). Aggregate-associated SOC concentrations were generally the highest in the > 0.25 mm fraction, followed by the < 0.053 mm fraction, and were the lowest in the 0.053–0.25 mm fraction; however, because of their large mass, 0.25–0.053 mm aggregates contributed significantly more to the total SOC. Total SOC concentrations (0–60 cm depth) decreased in the order of H. ammodendron (5.7 g kg−1) > T. ramosissima (4.9 g kg−1) > K. caspia (4.2 g kg−1) > B. dasyphylla (3.4 g kg−1). The H. ammodendron community had the highest total SOC and aggregate-associated SOC, which was primarily because aggregate-associated SOC content at the 0–10 and 10–20 cm depths under this community were higher than those under other plant communities. The H. ammodendron community could be beneficial for increasing SOC in saline soils in the arid region.

Effects of slope position and land use on the stability of aggregate-associated organic carbon in calcareous soils

Topography and land use affect soil organic carbon (SOC) storage, stabilization, and turnover, through several biogeochemical processes. This study investigated the aggregate composition and SOC content of bulk soils and aggregates at different slope positions under different land uses in a typical karst catchment of southwestern China. Our results show that the proportion of macro-aggregates and the SOC content of bulk soils and aggregates at different slope positions decreased from the upper to the lower slope. The SOC content generally increased with an increase in the mean weight diameter and proportion of macro-aggregates under different land uses. Our results indicate that macro-aggregates in forest and grassland soils make a greater contribution to both aggregate composition and SOC content than that in arable land soils. Therefore, converting farmland to forest or grassland can facilitate the accumulation of macro-aggregates as well as the storage of SOC.

Carbon sequestration and mineralization of aggregate-associated carbon in an intensively cultivated Anthrosol in north China as affected by long term fertilization

Understanding organic carbon (OC) sequestration in aggregates and OC stability under different fertilization practices is of key importance in improving soil quality and crop productivity and in mitigating the causes of climate change. A long-term field experiment established in 1990 was used to assess the influence of organic and inorganic fertilizers on aggregate-associated OC and its mineralization and on the SOC stock at a soil depth of 0–20cm under an intensive wheat-maize cropping system on Anthrosol in North China. The study involved three treatments: CK, control without fertilization; NPK, nitrogen (N), phosphorus (P) and potassium (K) fertilizers; MNPK, manure (M) combined with N, P and K fertilizers. Soil samples were collected and analyzed to determine the size distribution of aggregates, which were separated by dry sieving; the concentrations of OC and N in aggregates (>2, 0.25–2 and <0.25mm) and bulk soils; and respiration from aggregates and bulk soils in the 0–10 and 10–20cm layers after 21years. Fertilization did not affect the size distribution of aggregates in the surface soil layer, but there was a significant change in the subsurface layer in response to manure addition. Application of NPK and MNPK significantly and evenly augmented OC and N sequestration in the three aggregate classes tested. However, the OC mineralization rate was substantially higher in micro- than in macro-aggregates. Application of NPK and MNPK considerably increased OC mineralization in both aggregates and bulk soils; MNPK yielded the highest values. OC mineralization rates in bulk soils were comparable among the three treatments for the surface layer, but they increased in the subsurface layer because of adding manure. Overall, soils treated for 21years with NPK and MNPK showed increases in the OC pools in the top 20cm of 7.42 and 22.83MgCha−1, respectively, compared with the control treatment, and had average sequestration rates of 353 and 1087kgCha−1yr−1 respectively. Thus, appropriate application of NPK, alone or in combination with manure, can lead to improved OC sequestration by evenly augmenting aggregate-associated OC and providing the same degree of protection for OC in both macro-aggregates and micro-aggregates under a winter wheat-summer maize rotation on Anthrosol.

Landuse impacts on soil organic carbon fractions in different rainfall areas of a subtropical dryland

ABSTRACTLanduse can alter soil organic carbon (SOC) fractions by affecting carbon inflows and outflows. This study evaluated changes in SOC fractions in response to different landuses under variable rainfalls. We compared cropland, grassland and forest soils in high rainfall (Islamabad ~1142 mm) and low rainfall (Chakwal ~667 mm) areas of Pothwar dryland, Pakistan. Forest soils in both rainfall areas had highest SOC (11.32 g kg−1), particulate organic carbon (POC, 1.70 g kg−1), mineral-associated organic carbon (MOC, 7.17 g kg−1) and aggregate-associated organic carbon (AOC, 7.86 g kg−1). However, in rangeland and cropland soils, these varied with rainfall. Under high rainfall, SOC and MOC were 12% and 17% higher in rangeland than in cropland while POC and AOC were equal. Under low rainfall, SOC and MOC were higher in rangeland than in cropland by 7.21 and 1.79 g kg−1 at 0–15 cm and equal at 15–30 cm depth. POC and AOC were higher in rangeland than in cropland, in both depths. Averagely, SOC, POC, MOC and AOC were 26%, 68%, 76% and 30% higher in high rainfall than in low rainfall soils. Sensitivity of SOC fractions to landuses observed under different rainfalls could provide useful information for soil management in subtropical drylands.

Temporal changes in soil organic carbon and aggregate-associated organic carbon after reclamation of abandoned, salinized farmland

SUMMARYA field experiment was conducted to quantify changes in soil aggregation and aggregate-associated soil organic carbon (SOC) concentration 1, 3, 5 and 10 years after abandoned, salinized land in the Manasi River Basin was reclaimed for cotton (Gossypium hirsutum L.). Results showed that reclamation significantly increased SOC concentrations and SOC stocks. Specifically, 10 years of cotton production increased SOC concentrations by 45% in the 0–60 cm depth and SOC stocks by 35%. The SOC concentrations and stocks decreased as soil depth increased. Reclamation time, season and soil depth had significant interaction effects on SOC. The SOC concentrations were significantly and positively correlated with available soil nitrogen and available soil phosphorus. Compared with abandoned farmland, macro-aggregate-associated (&gt;250 µm) SOC concentrations in the 0–60 cm depth increased by 47% after 5 years of cotton production and by 53% after 10 years of cotton production. The contribution of macro-aggregate-associated SOC to total SOC in the 0–60 cm depth increased by 87% after 5 years of cotton production and by 69% after 10 years of cotton production. The findings indicate that soil aggregates were more stable after abandoned, salinized farmland was reclaimed for cotton production. Furthermore, cotton production can increase SOC concentrations and sequester C in this arid area.

The role of poorly crystalline iron oxides in the stability of soil aggregate-associated organic carbon in a rice–wheat cropping system

The stability of the soil organic carbon (SOC) in a rice–wheat rotation paddy soil has been of interest because of the global emission of greenhouse gases from the soil and the sequestration of atmospheric carbon dioxide in the soil, as well as in terms of soil fertility in subtropical Asia. The purpose of this study was to explore the relationship between poorly crystalline iron oxides (Feo) and SOC in bulk soil and soil aggregates. Soil samples were collected after a wheat harvest in June 2014 and after a rice harvest in October 2014 and were separated into large macroaggregates, small macroaggregates, microaggregates, and silt and clay by wet-sieving. The long-term (5-year) application of pig manure compost plus chemical fertilizer (NPKM) increased the SOC content more efficiently than other treatments. The specific carbon mineralization rate (SCMR, rate per unit SOC) increased in the following order: microaggregate<macroaggregate<silt and clay, suggesting that SOC in the microaggregates is more stable than in the silt and clay fraction. The Feo concentration was significantly positively correlated with the SOC content in the bulk soil (P<0.001) and the soil aggregates (P<0.001), but negatively correlated with the SCMR (P<0.001). Compared with chemical fertilization alone (NPK), NPKM not only significantly improved soil aggregation but also efficiently activated the iron oxides as indicated by an increase in the aggregate mean-weight diameter (MWD) and the Feo content. Therefore, we suggested that the seasonal variation of wetting and drying drives the redox transformation of iron oxides and the mobility of Feo, and then affects the distribution of Feo in soil aggregates, which may endow paddy soil with a physico-chemical protection of SOC while application of organic fertilizers enhances this protection.

Long-term fertilization increases the temperature sensitivity of OC mineralization in soil aggregates of a highland agroecosystem

The mineralization of aggregate-associated organic carbon (OC) and the effect of long-term fertilization on its temperature sensitivity have not been addressed, but are critical for understanding OC sequestration and dynamics in agricultural soil. We measured the mineralization of OC in total soils and aggregates after 27years of application of various fertilizers in a highland agroecosystem in central China and calculated the temperature sensitivity of OC mineralization. Our objectives were to understand the effects of long-term fertilization on OC mineralization in aggregates and its temperature sensitivity, and to determine the contribution of each aggregate size class to OC mineralization in total soils. Long-term fertilization decreased cumulative mineralized OC (Cmin) in <0.053mm size class but increased Cmin in >2, 0.25–2, and 0.053–0.25mm aggregates. The increases were smaller in treatments with mineral fertilizers than with manure or manure combined with mineral fertilizer. The temperature sensitivity of OC mineralization was decreased in >2mm aggregate but increased in <2mm aggregates and total soils by fertilization treatments. The OC mineralization in <0.053mm size class accounted for 36% of the OC mineralization in total soils. Manure or manure combined with mineral fertilizer had a higher potential to change the contribution of aggregates to OC mineralization in total soils. Our results suggest that OC mineralization in total soils was determined mainly by mineralization in the <0.053mm size class of these highland agricultural soils, and long-term fertilization increased the temperature sensitivity of OC mineralization in total soils and <2mm aggregates.

Effects of iron-aluminium oxides and organic carbon on aggregate stability of bauxite residues.

In order to successfully establish vegetation on bauxite residue, properties such as aggregate structure and stability require improvement. Spontaneous plant colonization on the deposits in Central China over the last 20years has revealed that natural processes may improve the physical condition of bauxite residues. Samples from three different stacking ages were selected to determine aggregate formation and stability and its relationship with iron-aluminium oxides and organic carbon. The residue aggregate particles became coarser in both dry and wet sieving processes. The mean weight diameter (MWD) and geometry mean diameter (GMD) increased significantly, and the proportion of aggregate destruction (PAD) decreased. Natural stacking processes could increase aggregate stability and erosion resistant of bauxite residues. Free iron oxides and amorphous aluminium oxides were the major forms in bauxite residues, but there was no significant correlation between the iron-aluminium oxides and aggregate stability. Aromatic-C, alkanes-C, aliphatic-C and alkenes-C were the major functional groups present in the residues. With increasing stacking age, total organic carbon content and aggregate-associated organic carbon both increased. Alkanes-C, aliphatic-C and alkenes-C increased and were mainly distributed in macro-aggregates, whereas aromatic-C was mainly distributed in <0.05-mm aggregates. Organic carbon stability in micro-aggregates was higher than that in macro-aggregates and became more stable. Organic carbon contents in total residues, and within different aggregate sizes, were all negatively correlated with PAD. It indicated that organic materials had a more significant effect on macro-aggregate stability and the effects of iron-aluminium oxides maybe more important for stability of micro-aggregates.

Effects of vegetation restoration on the aggregate stability and distribution of aggregate-associated organic carbon in a typical karst gorge region

Abstract. Land use changes have a major impact on soil structure and soil nutrients. The influences of vegetation restoration on aggregate stability and soil carbon storage have been studied extensively, but the distribution of aggregate-associated carbon is not yet understood. The objective of this work was to study the influences of vegetation restoration on aggregate stability and distribution of soil organic carbon (SOC) associated with water-stable aggregates (WSAs) in a karst gorge region. The experiment was carried out in 2012 and included four land use types: bare land (BL), grassland (GL), shrubland (SL), and woodland (WL). Soil samples were collected from the 0–20, 20–40, and 40–60 cm depths, and aggregates were separated by a wet-sieving method. Aggregate stability and aggregated-associated SOC were determined, and the relationships between water-stable aggregation with SOC were examined. The results showed that total SOC and SOC associated with WSAs of various sizes were the highest at a soil depth of 0–20 cm. In addition, the SOC contents of the WSAs increased as the soil aggregate sizes decreased. The SOC contents of the WSAs &lt; 0.25 mm were highest except in the bare land, and the SOC contents of the aggregates &lt; 0.25 mm comprised the majority of the total aggregate SOC contents. The aggregates were dominated by particles with sizes &gt; 5 mm under dry-sieving treatment, while aggregates were predominantly comprised of WSAs &lt; 0.25 mm under wet-sieving treatment. At a soil depth of 0–60 cm, the mean weight diameter (MWD), geometrical mean diameter (GMD), and fractal dimensions (D) of the dry aggregates and water-stable aggregates in the different types of land were ranked, in descending order, as WL &gt; GL &gt; SL &gt; BL. The contents of WSAs &gt; 0.25 mm, MWD, and GMD increased significantly, in that order, and the percentage of aggregate destruction (PAD) and fractal dimensions decreased significantly as the soil aggregate stability improved. SOC contents increased after vegetation restoration, and the average SOC content of WL was 2.35, 1.37, and 1.26 times greater than that in the BL, GL, and SL, respectively. We conclude that woodland and grassland facilitated WSA stability and SOC protection; thus, promoting the natural restoration of vegetation by reducing artificial disturbances could effectively restore the ecology and prevent soil erosion in karst regions.

Water-stable aggregates and aggregate-associated organic carbon and nitrogen after three annual applications of poultry manure and spent mushroom wastes

Water stable aggregates influence mechanisms for both water and fertility conservation and nutrient release in the soil. The effect of application of different organic amendments on aggregate stability and carbon-nitrogen storage within aggregates of a degraded soil was studied. The treatments were: control (P0S0), no amendments, 5tha−1 poultry manure (P5S0), 10tha−1 poultry manure (P10S0), 5tha−1 spent mushroom waste (P0S5), 10tha−1 spent mushroom waste (P0S10) and 5tha−1 each of poultry manure and spent mushroom waste (P5S5) applied in three consecutive years. These were arranged in randomized complete block design in five replicates. Soil samples were collected from the topsoil (0–20cm), air-dried and separated into 4.75–2.0, 2.0–1.0, 1.0–0.5, 0.5–0.25, and <0.25mm aggregate classes by dry sieving. Results showed that P5S5 increased macro aggregates >0.25mm and mean weight diameter (MWD) over other treatments. Saturated hydraulic conductivities (Ksat) were 17.55cmhr−1 and 16.28cmhr−1 in P5S0 and P0S10 amended soils, respectively. Generally, spent mushroom waste (SMW) and poultry manure (PM) significantly (p<0.05) reduced bulk density and increased total porosity, indicating positive effects of SMW and PM as soil amendments. Total nitrogen (N) concentrations in aggregate classes were significantly higher in soils amended with PM and SMW than the control. The P10S0 treatment had the highest concentrations of N (1.51gkg−1) in 1.0–0.5mm aggregates size class. Soil organic carbon (SOC) was preferentially higher in larger aggregates >2mm and in smaller aggregates <0.25mm irrespective of treatments, whereas, total N was higher in aggregates >0.5mm in PM amended soils. In all the treatments, SOC was enriched in larger aggregates than smaller aggregates. Poultry manure improved soil structure, aggregate-associated OC and total N than SMW. However, SMW has the potentials for use as soil amendment because it showed positive effects on soil structure and soil C-N storage.

干旱区典型盐生植物群落土壤团聚体组成及有机碳分布

PDF HTML阅读 XML下载 导出引用 引用提醒 干旱区典型盐生植物群落土壤团聚体组成及有机碳分布 DOI: 10.5846/stxb201405221057 作者: 作者单位: 石河子大学 石河子,石河子大学 石河子 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目(U1203282, 31360320); 教育部科学技术研究项目(213039A) Distribution of soil aggregates and aggregate-associated organic carbon from typical halophyte community in arid region Author: Affiliation: Shihezi University,Shihezi University;China Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:以干旱区玛纳斯河流域扇缘带为研究区,分析了花花柴(Karelinia caspia)、雾冰藜(Bassia dasyphylla)、梭梭(Haloxylon ammodendron)和柽柳(Tamarix ramosissima)4个典型盐生植物群落土壤团聚体的组成及有机碳分布。研究表明:不同植物群落土壤团聚体均以0.25-0.053 mm粒径为主,占了46.7%-74.6%,且与其他粒径差异显著(P < 0.05), > 0.25 mm和 < 0.053 mm粒径土壤团聚体含量较少,仅占7.8%-43%。梭梭群落 > 0.25 mm团聚体平均含量较高,达32%。不同植被群落土壤总有机碳介于2.01-8.73 g/kg之间,不同粒径团聚体有机碳介于1.70-13.68 g/kg之间。不同群落之间,梭梭和柽柳群落总有机碳和团聚体有机碳含量均相对较高,且随着土层深度下降而下降。不同粒径之间,有机碳含量在0.25-0.053 mm粒径最低,在 > 0.25 mm和 < 0.053 mm粒径中最高,呈现"V"型分布且差异显著(P < 0.05)。0.25-0.053 mm团聚体中有机碳含量的贡献率最高,达43.43%,而 < 0.053 mm粒级贡献率较低,但有机碳含量较高,说明了小粒径团聚体对有机碳保护能力较强。土壤有机碳含量与0.25-0.053 mm团聚体含量呈显著负相关(P < 0.05)。而从整体来看,梭梭群落 > 0.25 mm团聚体比例较高,且土壤有机碳和团聚体有机碳含量也较高,说明了在该研究区,梭梭群落聚集土壤养分能力较强,相对其他群落更有利于土壤有机碳的积累。 Abstract:Soil aggregates are organic-inorganic complexes and the basic unit of soil structure. Their formation and stability are closely related to soil organic carbon content. The distribution of aggregate-associated organic carbon determines the capacity for soil organic carbon storage and retention. Currently, research on soil aggregate-associated organic carbon mainly focuses on agricultural and artificial ecosystems; relatively few studies have focused on natural ecosystems. In particular, little is known about distribution of aggregate-associated organic carbon in halophyte communities in Xinjiang. In light of this, a field experiment was conducted on an alluvial fan in the Manasi River Basin to quantify changes in soil aggregation and aggregated-associated soil organic carbon associated with four halophytes (Karelinia caspia, Bassia dasyphylla, Haloxylon ammodendron, and Tamarix ramosissima). Our objective was to determine 1) the particle size that is most conducive to carbon retention and 2) which of the four halophytes is associated with the accumulation of the most soil organic carbon. The results showed: 1) 46.7% to 74.6% of the total soil mass comprised particles of intermediate diameter (0.25-0.053 mm). This was significantly greater (P < 0.05) than the other two classes of particle size defined in this study ( > 0.25 mm and < 0.053 mm). The > 0.25 mm or < 0.053 mm classes only comprised 7.8% to 43% of soil mass. The > 0.25 mm class was most abundant in the Haloxylon ammodendron community, accounting for 32% of soil mass. 2) Soil total organic carbon content was 2.01-8.73 g/kg, and aggregate-associated soil organic carbon content varied from 1.70 to 13.68 g/kg among communities. Total organic carbon and aggregate-associated organic carbon were greater in the Haloxylon ammodendron and Tamarix ramosissima communities than in the other communities studied. These measures decreased in all communities with depth. 3) The aggregate-associated organic carbon content was lowest in the 0.25-0.053 mm class, and significantly higher (P < 0.05) in the >0.25 mm and < 0.053 mm classes. 4) Because the 0.25-0.053 mm class was the most abundant, aggregate-associated organic carbon in this fraction contributed more to soil total organic carbon contained 43.43%. There was more aggregate-associated organic carbon in the < 0.053 mm class, but this contributed less to total soil organic carbon, indicating that these micro-aggregates have the greatest potential to retain soil organic carbon. There was a significant negative relationship between the abundance of 0.25-0.053 mm soil aggregate particles and soil organic carbon content.Total soil organic carbon, aggregate-associated soil organic carbon and abundance of >0.25 mm aggregate particles were highest in the Haloxylon ammodendron community, which implies that this community has the greatest potential to gather soil nutrients of the four communities studies, could be useful for accumulating soil organic carbon in arid areas. 参考文献 相似文献 引证文献

稻草覆盖和香根草篱对红壤水稳性团聚体组成及有机碳含量的影响

稻草覆盖和香根草篱对红壤水稳性团聚体组成及有机碳含量的影响

Dynamics of soil aggregate-associated organic carbon along an afforestation chronosequence

The objectives of this study were to determine the dynamics of aggregate-associated organic carbon (OC) along an afforestation chronosequence on abandoned farmland of China, and to examine the contributions of changes in aggregate-associated OC to changes in total soil OC. We investigated the dynamics of OC associated with aggregates along an afforestation chronosequence. Water-stable aggregates were isolated, and the OC concentrations in total soil and the aggregates were measured. Averaged across the entire chronosequence, afforestation led to 116, 128 and 108 % average increases in OC concentrations in macroaggregates, microaggregates and the <0.053 mm size class, respectively, in the top 20 cm of soil. The OC stocks in macroaggregates increased by averages of 651 and 473 % at 0–10 and 10–20 cm depths, respectively, mostly within the first 24 years. The OC stocks in microaggregates decreased during the first 35 years and then increased during 48–200 years of afforestation. Averaged across the entire chronosequence, the increases in OC stocks in macroaggregates accounted for 83 and 100 % of the total increase in OC stocks in soils at 0–10 and 10–20 cm depths, respectively. Our results indicated that the accumulation of OC in soils after afforestation on abandoned farmland was mainly due to the accumulation of OC in macroaggregates.