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1. chinaXiv:201912.00005 [pdf]

Natural vegetation restoration of Liaodong oak (Quercus liaotungensis Koidz.) forests rapidly increased the content and ratio of inert carbon in soil macroaggregates

SUN Lipeng; HE Lirong; WANG Guoliang; JING Hang; LIU Guobin
Subjects: Environmental Sciences, Resource Sciences >> Basic Disciplines of Environmental Science and Technology

The lack of clarity of how natural vegetation restoration influences soil organic carbon (SOC) content and SOC components in soil aggregate fractions limits the understanding of SOC sequestration and turnover in forest ecosystems. The aim of this study was to explore how natural vegetation restoration affects the SOC content and ratio of SOC components in soil macroaggregates (>250 ?m), microaggregates (53–250 ?m), and silt and clay (<53 ?m) fractions in 30-, 60-, 90- and 120-year-old Liaodong oak (Quercus liaotungensis Koidz.) forests, Shaanxi, China in 2015. And the associated effects of biomasses of leaf litter and different sizes of roots (0–0.5, 0.5–1.0, 1.0–2.0 and >2.0 mm diameter) on SOC components were studied too. Results showed that the contents of high activated carbon (HAC), activated carbon (AC) and inert carbon (IC) in the macroaggregates, microaggregates and silt and clay fractions increased with restoration ages. Moreover, IC content in the microaggregates in topsoil (0–20 cm) rapidly increased; peaking in the 90-year-old restored forest, and was 5.74 times higher than AC content. In deep soil (20–80 cm), IC content was 3.58 times that of AC content. Biomasses of 0.5–1.0 mm diameter roots and leaf litter affected the content of aggregate fractions in topsoil, while the biomass of >2.0 mm diameter roots affected the content of aggregate fractions in deep soil. Across the soil profiles, macroaggregates had the highest capacity for HAC sequestration. The effects of restoration ages on soil aggregate fractions and SOC content were less in deep soil than in topsoil. In conclusion, natural vegetation restoration of Liaodong oak forests improved the contents of SOC, especially IC within topsoil and deep soil. The influence of IC on aggregate stability was greater than the other SOC components, and the aggregate stability was significantly affected by the biomasses of litter, 0.5–1.0 mm diameter roots in topsoil and >2.0 mm diameter roots in deep soil. Natural vegetation restoration of Liaodong oak forests promoted SOC sequestration by soil macroaggregates.

submitted time 2019-12-06 From cooperative journals:《Journal of Arid Land》 Hits3065Downloads327 Comment 0

2. chinaXiv:201912.00014 [pdf]

Effects of recovery time after fire and fire severity on stand structure and soil of larch forest in the Kanas National Nature Reserve, Northwest China

LIU Xiaoju ; PAN Cunde
Subjects: Environmental Sciences, Resource Sciences >> Basic Disciplines of Environmental Science and Technology

Forest recovery may be influenced by several factors, of which fire is the most critical. However, moderate- and long-term effects of fire on forest recovery are less researched in Northwest China. Thus, the effects of different forest recovery time after fire (1917 (served as the control), 1974, 1983 and 1995) and fire severities (low, moderate and high) on larch (Larix sibirica Ledeb.) forest were investigated in the Kanas National Nature Reserve (KNNR), Northwest China in 2017. This paper analyzed post-fire changes in stand density, total basal area (TBA), litter mass, soil organic carbon (SOC) and soil nutrients (total nitrogen, total phosphorus and total potassium) with one-way analyses of variance. Results indicate that litter mass, TBA, SOC and soil nutrients increased with increasing recovery time after fire and decreasing fire severity, while the stand density showed an opposite response. The effects of fire disturbance on SOC and soil nutrients decreased with increasing soil depth. Moreover, we found that the time of more than 43 a is needed to recover the litter mass, TBA, SOC and soil nutrients to the pre-fire level. In conclusion, high-severity fire caused the greatest variations in stand structure and soil of larch forest, and low-severity fire was more advantageous for post-fire forest stand structure and soil recovery in the KNNR. Therefore, low-severity fire can be an efficient management mean through reducing the accumulation of forest floor fuel of post-fire forests in the KNNR, Northwest China.

submitted time 2019-12-06 From cooperative journals:《Journal of Arid Land》 Hits2221Downloads216 Comment 0

3. chinaXiv:201909.00009 [pdf]

Effects of different tillage and straw retention practices on soil aggregates and carbon and nitrogen sequestration in soils of the northwestern China

WU Jun
Subjects: Geosciences >> Geography

Soil tillage and straw retention in dryland areas may affect the soil aggregates and the distribution of total organic carbon. The aims of this study were to establish how different tillage and straw retention practices affect the soil aggregates and soil organic carbon (SOC) and total nitrogen (TN) contents in the aggregate fractions based on a long-term (approximately 15 years) field experiment in the semi-arid western Loess Plateau, northwestern China. The experiment included four soil treatments, i.e., conventional tillage with straw removed (T), conventional tillage with straw incorporated (TS), no tillage with straw removed (NT) and no tillage with straw retention (NTS), which were arranged in a complete randomized block design. The wet-sieving method was used to separate four size fractions of aggregates, namely, large macroaggregates (LA, >2000 μm), small macroaggregates (SA, 250–2000 μm), microaggregates (MA, 53–250 μm), and silt and clay (SC, <53 μm). Compared to the conventional tillage practices (including T and TS treatments), the percentages of the macroaggregate fractions (LA and SA) under the conservation tillage practices (including NT and NTS treatments) were increased by 41.2%–56.6%, with the NTS treatment having the greatest effect. For soil layers of 0–5, 5–10 and 10–30 cm, values of the mean weight diameter (MWD) under the TS and NTS treatments were 10.68%, 13.83% and 17.65%, respectively. They were 18.45%, 19.15% and 14.12% higher than those under the T treatment, respectively. The maximum contents of the aggregate-associated SOC and TN were detected in the SA fraction, with the greatest effect being observed for the NTS treatment. The SOC and TN contents were significantly higher under the NTS and TS treatments than under the T treatment. Also, the increases in SOC and TN levels were much higher in the straw-retention plots than in the straw-removed plots. The macroaggregates (including LA and SA fractions) were the major pools for SOC and TN, regardless of tillage practices, storing 3.25–6.81 g C/kg soil and 0.34–0.62 g N/kg soil. Based on the above results, we recommend the NTS treatment as the best option to boost soil aggregates and to reinforce carbon and nitrogen sequestration in soils in the semi-arid western Loess Plateau of northwestern China.

submitted time 2019-08-30 From cooperative journals:《Journal of Arid Land》 Hits8899Downloads377 Comment 0

4. chinaXiv:201809.00170 [pdf]

Hierarchical responses of soil organic and inorganic carbon dynamics to soil acidification in a dryland agroecosystem, China

JIN, Shaofei; TIAN, Xiaohong; WANG, Hesong
Subjects: Geosciences >> History of Geosciences

Soil acidification is a major global issue of sustainable development for ecosystems. The increasing soil acidity induced by excessive nitrogen (N) fertilization in farmlands has profoundly impacted the soil carbon dynamics. However, the way in which changes in soil pH regulating the soil carbon dynamics in a deep soil profile is still not well elucidated. In this study, through a 12-year field N fertilization experiment with three N fertilizer treatments (0, 120, and 240 kg N/(hm2?a)) in a dryland agroecosystem of China, we explored the soil pH changes over a soil profile up to a depth of 200 cm and determined the responses of soil organic carbon (SOC) and soil inorganic carbon (SIC) to the changed soil pH. Using a generalized additive model, we identified the soil depth intervals with the most powerful statistical relationships between changes in soil pH and soil carbon dynamics. Hierarchical responses of SOC and SIC dynamics to soil acidification were found. The results indicate that the changes in soil pH explained the SOC dynamics well by using a non-linear relationship at the soil depth of 0–80 cm (P=0.006), whereas the changes in soil pH were significantly linearly correlated with SIC dynamics at the 100–180 cm soil depth (P=0.015). After a long-term N fertilization in the experimental field, the soil pH value decreased in all three N fertilizer treatments. Furthermore, the declines in soil pH in the deep soil layer (100–200 cm) were significantly greater (P=0.035) than those in the upper soil layer (0–80 cm). These results indicate that soil acidification in the upper soil layer can transfer excess protons to the deep soil layer, and subsequently, the structural heterogeneous responses of SOC and SIC to soil acidification were identified because of different buffer capacities for the SOC and SIC. To better estimate the effects of soil acidification on soil carbon dynamics, we suggest that future investigations for soil acidification should be extended to a deeper soil depth, e.g., 200 cm.

submitted time 2018-09-18 From cooperative journals:《Journal of Arid Land》 Hits1938Downloads465 Comment 0

5. chinaXiv:201807.00032 [pdf]

Characteristics of soil organic carbon and total nitrogen under various grassland types along a transect in a mountain-basin system in Xinjiang, China

BI Xu; LI Bo; NAN Bo; FAN Yao; FU Qi; ZHANG Xinshi
Subjects: Biology >> Ecology

Soil organic carbon (SOC) and soil total nitrogen (STN) in arid regions are important components of global C and the N cycles, and their response to climate change will have important implications for both ecosystem processes and global climate feedbacks. Grassland ecosystems of Funyun County in the southern foot of the Altay Mountains are characterized by complex topography, suggesting large variability in the spatial distribution of SOC and STN. However, there has been little investigation of SOC and STN on grasslands in arid regions with a mountain-basin structure. Therefore, we investigated the characteristics of SOC and STN in different grassland types in a mountain-basin system at the southern foot of the Altai Mountains, north of the Junggar Basin in China, and explored their potential influencing factors and relationships with meteorological factors and soil properties. We found that the concentrations and storages of SOC and STN varied significantly with grassland type, and showed a decreasing trend along a decreasing elevation gradient in alpine meadow, mountain meadow, temperate typical steppe, temperate steppe desert, and temperate steppe desert. In addition, the SOC and STN concentrations decreased with depth, except in the temperate desert steppe. According to Pearson's correlation values and redundancy analysis, the mean annual precipitation, soil moisture content and soil available N concentration were significantly positively correlated with the SOC and STN concentrations. In contrast, the mean annual temperature, pH, and soil bulk density were significantly and negatively correlated with the SOC and STN concentrations. The mean annual precipitation and mean annual temperature were the primary factors related to the SOC and STN concentrations. The distributions of the SOC and STN concentrations were highly regulated by the elevation-induced differences in meteorological factors. Mean annual precipitation and mean annual temperature together explained 97.85% and 98.38% of the overall variations in the SOC and STN concentrations, respectively, at soil depth of 0–40 cm, with precipitation making the greatest contribution. Our results provide a basis for estimating and predicting SOC and STN concentrations in grasslands in arid regions with a mountain-basin structure.

submitted time 2018-07-05 From cooperative journals:《Journal of Arid Land》 Hits2976Downloads688 Comment 0

6. chinaXiv:201804.02344 [pdf]

grassland degradation; semi-arid grassland; greenhouse gases; CO2; CH4; N2O; Inner Mongolia

JIN Dongyan; Phil J MURRAY; XIN Xiaoping; QIN Yifei; CHEN Baorui; QING Gele; ZHANG Zhao; YAN Ruirui
Subjects: Physics >> General Physics: Statistical and Quantum Mechanics, Quantum Information, etc.

The variation in soil organic carbon density (SOCD) has been widely documented at various spatial and temporal scales. However, an accurate method for examining the attribution of explanatory factors for change in SOCD is still lacking. This study aims to attribute and quantify the key climatic factors, anthropogenic activities, and soil properties associated with SOCD change in the native grasslands of Inner Mongolia, China, by comparing data between the 1960s and the 2010s. In 2007 and 2011, we resampled 142 soil profiles which were originally sampled during 1963–1964 in the native grasslands of Inner Mongolia. SOCD was determined in A horizon (eluvial horizon) of the soil. We selected the explanatory factors based on a random forest method, and explored the relationships between SOCD change and each of the explanatory factors using a linear mixed model. Our results indicated that the change in SOCD varied from the east to the west of Inner Mongolia, and SOCD was 18% lower in the 2010s than in the 1960s. The lower SOCD in the 2010s may primarily be attributed to the increasing in mean annual water surface evaporation, which explained approximately 10% and 50% of the total variation and explainable variation in the change in SOCD, respectively. The sand content of the soil is also a significant explanatory factor for the decrease in SOCD, which explained about 4% and 21% of the total variation and explainable variation in the change in SOCD, respectively. Furthermore, the collection of quantitative information on grazing frequency and duration may also help to improve our understanding of the anthropogenic factors that govern the change in SOCD.

submitted time 2018-04-24 From cooperative journals:《Journal of Arid Land》 Hits1294Downloads421 Comment 0

7. chinaXiv:201804.00020 [pdf]

Film-mulched continuous ridge-furrow planting improves soil temperature, nutrient content and enzymatic activity in a winter oilseed rape field, Northwest China

GU, Xiaobo; LI, Yuannong; DU, Yadan
Subjects: Physics >> General Physics: Statistical and Quantum Mechanics, Quantum Information, etc.

Film mulching system is a widely employed agricultural practice worldwide. However, the effects of different planting and mulching patterns on soil nutrient content and enzymatic activity have not been well documented. In this study, we examined the impact of four planting and mulching patterns (including control, flat planting without mulching; M1, flat planting with film mulching; M2, ridge-furrow planting with film mulching on both ridges and furrows; and M3, ridge-furrow planting with film mulching on continuous ridges) on the seed yield of winter oilseed rape, soil moisture, soil temperature, soil organic carbon (SOC) content, soil nutrient content, and soil enzymatic activity over three growing seasons from 2012 to 2015 in a winter oilseed rape field in the semi-arid area of Northwest China. Seed yield of winter oilseed rape, soil moisture, soil temperature, enzymatic activities, and contents of nitrate-nitrogen, available phosphorus, and available potassium were all significantly higher in mulching treatments (M1, M2 and M3) than in control treatment over the three growing seasons, whereas SOC content was significantly lower in mulching treatments than in control treatment during 2013–2014 and 2014–2015. Among the three mulching treatments (M1, M2 and M3), the M3 treatment showed consistently higher seed yield, SOC content, nutrient contents, and enzymatic activities than the other two treatments. Seed yield of winter oilseed rape was 41.1% and 15.0% higher in M3 than in M1 and M2, respectively. SOC content and soil enzymatic activities in the top 0–20 cm soil layers and nitrate-nitrogen content in the top 0–30 cm soil layers were all significantly higher in M3 than in M1 and M2. Therefore, we advise the ridge-furrow planting with film mulching on continuous ridges (i.e., M3) as an efficient planting and mulching pattern for sustainably improving the seed yield of winter oilseed rape and preserving soil fertility in the semi-arid area of Northwest China.

submitted time 2018-04-03 From cooperative journals:《Journal of Arid Land》 Hits1446Downloads463 Comment 0

8. chinaXiv:201802.00449 [pdf]

Carbon storage in a wolfberry plantation chronosequence established on a secondary saline land in an arid irrigated area of Gansu Province, China

MA Quanlin; WANG Yaolin; LI Yinke; SUN Tao; Eleanor MILNE
Subjects: Agriculture, Forestry,Livestock & Aquatic Products Science >> Soil Science

Carbon (C) storage has received significant attention for its relevance to agricultural security and climate change. Afforestation can increase C storage in terrestrial ecosystems, and has been recognized as an important measure to offset CO2 emissions. In order to analyze the C benefits of planting wolfberry (Lycium barbarum L.) on the secondary saline lands in arid areas, we conducted a case study on the dynamics of biomass carbon (BC) storage and soil organic carbon (SOC) storage in different-aged wolfberry plantations (4-, 7- and 11-year-old) established on a secondary saline land as well as on the influence of wolfberry plantations on C storage in the plant-soil system in an arid irrigated area (Jingtai County) of Gansu Province, China. The C sequestration and its potential in the wolfberry plantations of Gansu Province were also evaluated. An intact secondary saline land was selected as control. Results show that wolfberry planting could decrease soil salinity, and increase BC, SOC and litter C storage of the secondary saline land significantly, especially in the first 4 years after planting. The aboveground and belowground BC storage values in the intact secondary saline land (control) accounted for only 1.0% and 1.2% of those in the wolfberry plantations, respectively. Compared to the intact secondary saline land, the SOC storage values in the 4-, 7- and 11-year-old wolfberry plantations increased by 36.4%, 37.3% and 43.3%, respectively, and the SOC storage in the wolfberry plantations occupied more than 92% of the ecosystem C storage. The average BC and SOC sequestration rates of the wolfberry plantations for the age group of 0–11 years were 0.73 and 3.30 Mg C/(hm2?a), respectively. There were no significant differences in BC and SOC storage between the 7-year-old and 11-year-old wolfberry plantations, which may be due in part to the large amounts of C offtakes in new branches and fruits. In Gansu Province, the C storage in the wolfberry plantations has reached up to 3.574 Tg in 2013, and the C sequestration potential of the existing wolfberry plantations was 0.134 Tg C/a. These results indicate that wolfberry planting is an ideal agricultural model to restore the degraded saline lands and increase the C sequestration capacity of agricultural lands in arid areas.

submitted time 2018-02-07 From cooperative journals:《Journal of Arid Land》 Hits10447Downloads986 Comment 1

9. chinaXiv:201605.00541 [pdf]

The priming potential of environmentally weathered pyrogenic carbon during land‐use transition to biomass crop production

Gary J. McClean; Will Meredith; Andrew Cross; Kate V. Heal; Gary D. Bending; Saran P. Sohi
Subjects: Biology >> Botany >> Plant ecology, plant geography

Since land-use change (LUC) to lignocellulosic biomass crops often causes a loss of soil organic carbon (SOC), at least in the short term, this study investigated the potential for pyrogenic carbon (PyC) to ameliorate this effect. Although negative priming has been observed in many studies, most of these are long-term incubation experiments which do not account for the interactions between environmentally weathered PyC and native SOC. Here, the aim was to assess the impact of environmentally weathered PyC on native SOC mineralization at different time points in LUC from arable crops to short rotation coppice (SRC) willow. At eight SRC willow plantations in England, with ages of 3–22 years, soil amended 18–22 months previously with PyC was compared with unamended control soil. Cumulative CO2 flux was measured weekly from incubated soil at 0–5 cm depth, and soil-surface CO2 flux was also measured in the field. For the incubated soil, cumulative CO2 flux was significantly higher from soil containing weathered PyC than the control soil for seven of the eight sites. Across all sites, the mean cumulative CO2 flux was 21% higher from soil incubated with weathered PyC than the control soil. These results indicate the potential for positive priming in the surface 5 cm of soil independent of changes in soil properties following LUC to SRC willow production. However, no net effect on CO2 flux was observed in the field, suggesting this increase in CO2 is offset by a contrasting PyC-induced effect at a different soil depth or that different effects were observed under laboratory and field conditions. Although the mechanisms for these contrasting effects remain unclear, results presented here suggest that PyC does not reduce LUC-induced SOC losses through negative priming, at least for this PyC type and application rate.

submitted time 2016-05-04 Hits7931Downloads406 Comment 0

10. chinaXiv:201605.00540 [pdf]

Evaluation of the ECOSSE model for simulating soil organic carbon under Miscanthus and short rotation coppice‐willow crops in Britain

Marta Dondini; Mark Richards; Mark Pogson; Edward O. Jones; Rebecca L. Rowe; Aidan M. Keith; Niall P. McNamara; Joanne U. Smith; Pete Smith
Subjects: Biology >> Botany >> Plant ecology, plant geography

In this paper, we focus on the impact on soil organic carbon (SOC) of two dedicated energy crops: perennial grass Miscanthus x Giganteus (Miscanthus) and short rotation coppice (SRC)-willow. The amount of SOC sequestered in the soil is a function of site-specific factors including soil texture, management practices, initial SOC levels and climate; for these reasons, both losses and gains in SOC were observed in previous Miscanthus and SRC-willow studies. The ECOSSE model was developed to simulate soil C dynamics and greenhouse gas emissions in mineral and organic soils. The performance of ECOSSE has already been tested at site level to simulate the impacts of land-use change to short rotation forestry (SRF) on SOC. However, it has not been extensively evaluated under other bioenergy plantations, such as Miscanthus and SRC-willow. Twenty-nine locations in the United Kingdom, comprising 19 paired transitions to SRC-willow and 20 paired transitions to Miscanthus, were selected to evaluate the performance of ECOSSE in predicting SOC and SOC change from conventional systems (arable and grassland) to these selected bioenergy crops. The results of the present work revealed a strong correlation between modelled and measured SOC and SOC change after transition to Miscanthus and SRC-willow plantations, at two soil depths (0–30 and 0–100 cm), as well as the absence of significant bias in the model. Moreover, model error was within (i.e. not significantly larger than) the measurement error. The high degrees of association and coincidence with measured SOC under Miscanthus and SRC-willow plantations in the United Kingdom, provide confidence in using this process-based model for quantitatively predicting the impacts of future land use on SOC, at site level as well as at national level.

submitted time 2016-05-04 Hits7531Downloads556 Comment 0

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