Soil chronosequence derived from landslides on the upper reach of Minjiang River,western China

Soil chronosequences derived from landslides with certain time series are the great avenue to elevate our understanding on the processes of pedogenesis,nutrient dynamics,and ecosystem evolution.However,the construction of reliable soil chronosequence from historical landslides remains intricate.Here,we presented a 22,000-year soil chronosequence from multiple landslides on the upper reach of Minjiang River,western China.The variation in a variety of pedogenesis indices and soil nutrients verified the reliability of the chronosequence.The silica-alumina ratio and silica sesquioxide ratio decreased significantly with soil age.This reflected the enrichment of Al/Fe/Ti oxides but the depletion of Si oxides with the soil development.Meanwhile,the values of the Chemical Index of Weathering and the Chemical Index of Alteration increased significantly with soil age,especially from 5 to 89 years.These variations were attributed to the soil weathering,which led to the destruction of soil minerals with the rapid loss of most of cations(e.g.,K,Na,Ca,and Mg)during the soil development.The concentrations of carbon and nitrogen in topsoil increased with soil age,and the carbon accumulation rate slowed significantly from 5,500 to 22,000 years.The total phosphorus concentrations decreased with soil age,suggesting the gradual loss of soil phosphorus with soil development.The results indicate that the landslide chronosequence established on the upper reach of Minjiang River is reliable and delineates a long-term soil development process,which will provide a great platform for further improvement of biogeochemical theories and understanding sustainable vegetation restoration.

Changes in soil organic carbon and aggregate stability following a chronosequence of Liriodendron chinense plantations

The objectives for this study were to determine changes in soil organic carbon(SOC)components and water-stable aggregates for soil profi les from diff erent ages of plantations of Liriodendron chinense and to clarify which organic carbon component is more closely associated with the formation and stability of soil aggregates.Three layers of soil(depths 0–20 cm,20–40 cm,40–60 cm)were collected from young,half-mature and mature stages of L.chinense.SOC,readily oxidizable organic carbon,chemically stable organic carbon and aggregate composition were determined.Intermediate stable organic carbon,the microbial quotient and aggregate stability(mean weight diameter)were calculated.SOC and aggregate stability in the L.chinense plantation did not increase linearly with an increase in L.chinense age;rather,they fi rst decreased,then increased with increasing age of L.chinense.The microbial quotient had a negative eff ect on the level of organic carbon and the stability of aggregates,while chemically stable organic carbon had a positive eff ect,which explained 55.0%and 19.3%of the total variation,respectively(P<0.01).Therefore,more attention should be paid of these two indicators in the future.

Changes in Soil Composition and Floral Coverage on a Glacial Foreland Chronosequence in Southern Iceland

The land surface in front of the Skaftafellsj?kull in southern Iceland, exposed by ice recession commencing about the start of the twentieth century, constitutes a foreland with a maximum age of about 100 years and a more distal outwash plain. The ages of different surfaces within this sequence are constrained by moraines of known or estimated ages. Across this chronosequence, we measured at various sites the extent of floral coverage of the surface, the soil carbon and nitrogen contents of the substrate and the soil CO2 flux rate. All measured parameters exhibit values increasing with distance from the ice front, which correlates approximately with age. The strongest correlations are seen between distance and the carbon and nitrogen concentrations of the soil. Marked horizonation of the soil is observed only on the oldest surfaces (100+ years).

Carbon stock in Korean larch plantations along a chronosequence in the Lesser Khingan Mountains, China

Carbon （C） dynamics are central to understanding ecosystem restoration effects within the context of Grain for Green Project （GGP）. GGP stared in China since 2003 to improve the environment. Despite its importance, how total forest ecosystem C stock （FECS） develops fol- lowing land-use changes from cropland to plantation is poorly under- stood, in particular the relationship of C allocation to pools. We quanti- fied C pools in a chronosequence ranging from 0 to 48 years, using com- plete above- and below-ground harvests based on detailed field inventory Stands were chosen along a succession sequence in managed plantations of Korean larch （Larix olgensis Henry.）, a native planting species in the Lesser Khingan Mountains, Northeast of China. The FECS of Korean larch plantation （KLP） were dynamic across stand development, chang- ing from 88.2 Mg.ha-1 at cropland, to 183.9 Mg.ha·-1 as an average of forest C from 7- through 48-year-old plantation. In a 48-year-old mature KLP, vegetation comprises 48.63% of FECS and accounts for 67.66% of annual net C increment （ANCI）. Soil is responsible for 38.19% and 13.53% of those, and with the remainders of 13.18% and 18.81% in down woody materials. Based on comparisons of our estimate to those of others, we conclude that afforestation of Korean larch plantation is a valid approach to sequester carbon.

Evolution and significance of soil magnetism of basalt-derived chronosequence soils in tropical southern China

Soil samples were collected from eight basalt- derived chronosequence soils with the ages of 0.01, 0.58, 0.92, 1.33, 2.04, 3.04, 3.76 and 6.12 Ma respectively from Leizhou Peninsula and northern Hainan Island of tropical southern China. Magnetic parameters of magnetic susceptibility (MS), percentage of frequency-dependent magnetic susceptibility (FDS%), anhysteretic remanent magnetization (ARM), saturation isothermal remanent magnetization (SIRM), soft and hard isothermal remanent magnetization (IRMs and IRMh) of the collected samples were measured to study the evolution and the significance of the magnetism with soil age. The results show that the magnetic parameters changed fast from Primosols to Ferrosols (0.01 ~ 0.92 Ma) but slowly at Ferralosols stage (1.33 Ma~), it suggests a stable phase occurred for soil magnetism at Ferralosols, the existence of this phase could be supported by the little changes in the contents of clay, Fet and Fed. Obvious differences existed in the values of magnetic parameters between Ferralosols and other soil types (Primosols and Ferrosols), FDS%: Ferralosols > 10%, Primosols and Ferrosols –8· SIm3·kg–1, Primosols and Ferrosols > 8000 × 10–8 SIm3·kg–1, thus, it is possible to differentiate Ferralosols from other soil types in tropical region by using magnetic indices.

Soil chronosequence and biosequence on old lake sediments of the Burdur Lake in Turkey

The Burdur Lake is located in the southwest of Turkey,and its area has decreased by 40% from 211 km^(2) in 1975 to 126 km^(2) in 2019.In this study,we investigated how the soil has changed in the lacustrine material.Three soil profiles were sampled from the former lakebed(chronosequence profiles:P1,2007;P2,1994;and P3,1975),and three soil profiles under different land use types(biosequence profiles:P4,native forest vegetation;P5,agriculture;and P6,lakebed)were sampled.The chronosequence and biosequence soil profiles represented various distances from the Burdur Lake and showed different stages of lacustrine evolution.Soil electrical conductivity(EC;18.1 to 0.4 dS m^(-1)),exchangeable Na^(+)(34.7 to 1.4 cmol kg^(-1))and K^(+)(0.61 to 0.56 cmol kg^(-1)),and water-soluble Cl^(-)(70.3 to 2.1 cmol L^(-1))and SO_(4)^(2-)(275.9 to 25.0 cmol L^(-1))decreased with increasing distance from the Burdur Lake,whereas the A horizon thickness(10 to 48 cm),structure formation(0 to 48 cm),gleization-oxidation depth(0 to 79 cm),and montmorillonite and organic matter(OM;25.9 to 46.0 g kg^(-1))contents increased in the chronosequence soil profiles.The formation of P3 in the chronosequence and P5 in the biosequence soil profiles increased due to longer exposure to pedogenic processes(time,land use,vegetation,etc.).Changes in EC,exchangeable cation(Na^(+) and K^(+))and water-soluble anion(Cl^(-) and SO_(4)^(2-))concentrations of the salt-enriched horizon,OM,gleization-oxidation depth,A horizon thickness,and structure formation of the chronosequence and biosequence soil profiles(especially the topsoil horizon)were highly related to the distance from the Burdur Lake,time,and land use.

Changes in ecosystem carbon stocks in a grassland ash (Fraxinus excelsior) afforestation chronosequence in Ireland

Aims Government policy in Ireland is to increase the national forest cover from the current 10%to 18%of the total land area by 2020.This represents a major land use change that is expected to impact on the national carbon(C)stocks.While the C stocks of ecosystem bio-mass and soils of Irish grasslands and coniferous forests have been quantified,little work has been done to assess the impact of broad-leaf afforestation on C stocks.Methods In this study,we sampled a chronosequence of ash(Fraxinus excel-sior)forests aged 12,20,27,40 and 47 years on brown earth soils.A grassland site,representative of the pre-afforestation land use,was sampled as a control.Important Findings Our results show that there was a significant decline(P<0.05)in the carbon density of the soil(0-30 cm)following afforestation from the grassland(90.2 Mg C ha^(−1))to the 27-year-old forest(66.7 Mg C ha^(−1)).Subsequently,the forest soils switched from being a C source to a C sink and began to sequester C to 71.3 Mg C ha^(−1) at the 47-year-old forest.We found the amount of C stored in the above-and belowground biomass increased with age of the forest stands and offset the amount of C lost from the soil.The amount of C stored in the above-and belowground biomass increased on average by 1.83 Mg C ha^(−1) year^(−1).The increased storage of C in the biomass led to an increase in the total ecosystem C,from 90.2 Mg C ha^(−1) at the grassland site to 162.6 Mg C ha^(−1) at the 47-year-old forest.On a national scale,projected rates of ash afforestation to the year 2020 may cause a loss of 290752 Mg C from the soil compared to 2525936 Mg C sequestered into the tree biomass.The effects of harvesting and reforestation may further modify the development of ecosystem C stocks over an entire ash rotation.

Disparity in soil bacterial community succession along a short time-scale deglaciation chronosequence on the Tibetan Plateau

Global warming leads to deglaciations in high-elevation regions,which exposes deglaciated soils to microbial colonization.Disparity in year-to-year successional patterns of bacterial community and influencing factors in freshly deglaciated soils remain unclear.We explored the abundance of bacterial 16S rRNA gene and community succession in deglaciated soils along a 14-year chronosequence after deglaciation using qPCR and Illumina sequencing on the Tibetan Plateau.The results showed that the abundance of bacterial 16S rRNA gene gradually increased with increasing deglaciation age.Soil bacterial community succession was clustered into three deglaciation stages,which were the early(zero-year old),transitional(1-7 years old)and late(8-14 years old)stages.A significantly abrupt bacterial community succession occurred from the early to the transitional stage(P<0.01),while a mild succession(P=0.078)occurred from the transitional to the late stage.The bacterial community at the early and transitional stages were dominated by Proteobacteria,while the late stage was dominated by Actinobacteria.Less abundant(<10%)Acidobacteria,Gemmatimonadetes,Verrucomicrobia,Chloroflexi,Planctomycetes,unclassified bacteria dominantly occurred in the transition and late stage and Cyanobacteria in the early stage.Total organic carbon(24.7%),post deglaciation age(21%),pH(16.5%)and moisture(10.1%)significantly contributed(P<0.05)to the variation of bacterial community succession.Our findings provided a new insight that short time-scale chronosequence is a good model to study yearly resolution of microbial community succession.

Adsorption and desorption of Cu(Ⅱ) and Pb(Ⅱ) in paddy soils cultivated for various years in the subtropical China

The adsorption and desorption of Cu（Ⅱ） and Pb（Ⅱ） on upland red soil,and paddy soils which were originated from the upland soil and cultivated for 8,15,35 and 85 years,were investigated using the batch method.The study showed that the organic matter content and cation exchange capacity （CEC） of the soils are important factors controlling the adsorption and desorption of Cu（Ⅱ） and Pb（Ⅱ）.The 15-Year paddy soil had the highest adsorption capacity for Pb（Ⅱ）,followed by the 35-Year paddy soil.Both the 35-Year paddy soil and 15-Year paddy soil adsorbed more Cu（Ⅱ） than the upland soil and other paddy soils.The 15-Year paddy soils exhibited the highest desorption percentage for both Cu（Ⅱ） and Pb（Ⅱ）.These results are consistent with the trend for the CEC of the soils tested.The high soil CEC contributes not only to the adsorption of Cu（Ⅱ） and Pb（Ⅱ） but also to the electrostatic adsorption of the two heavy metals by the soils.Lower desorption percentages for Cu（Ⅱ） （36.7% to 42.2%） and Pb（Ⅱ） （50.4% to 57.9%） were observed for the 85-Year paddy soil.The highest content of organic matter in the soil was responsible for the low desorption percentages for the two metals because the formation of the complexes between the organic matter and the metals could increase the stability of the heavy metals in the soils.

Forest succession in post-agricultural Larix olgensis plantations in northeast China

In order to understand the management of regional vegetation,numerical classification and ordination are widely used to investigate community distribution and vegetation features.In particular,two-way indicator-species analysis programs(TWINSPAN)classifies plots and species into different groups.De-trended correspondence analysis(DCA)and canonical correspondence analysis(CCA)reflects the relationship between community and site conditions.Afforestation with Larix olgensis Herry.Plantations is a suitable restoration strategy on post-agricultural fields in the Lesser Khingan Mountains.The results of this study show how these plantations develop over time to establish a reliable pathway model by measuring and clarifying the succession process.Twenty-eight L.olgensis plantations along a 48-year chronosequence of afforestation were investigated with a quadrat sampling method.Species composition,community structure attributes of diversity,and site conditions were analyzed.Communities were classified by TWINSPAN into five successional stages:immature,juvenile,mid-aged,nearmature and mature.Classifications were validated by DCA and CCA analysis.Site conditions such as soil and litter thickness,soil organic matter,soil density,and pH were measured.Successional stages varied in community composition and species population,accompanied by time from afforestation and a gradient of site conditions.This gradient showed changes in vegetation occurrence and diversity coinciding with changes in soil conditions.The study showed that L.olgensis plantations had marked predominance in growth and were associated with improved soil fertility and the formation of a stable plant community.

The establishment and development of Haloxylon ammodendron promotes salt accumulation in surface soil of arid sandy land

Haloxylon ammodendron, a representative C_4 succulent xerophyte and salt-secreting plant, is widely used in vegetation reestablishment programs to stabilize shifting sand, and is one of the dominant shrubs in the shelter belt used to control desertification in the desert-oasis ecotone in northwestern China. In this study, we collected soil samples in an age sequence of 0-, 2-, 5-, 13-, 16-, 31-, and 39-year-old H. ammodendron plantations to assess the effects of the shrub on soil fertility and salinity. Results show that SOC and total N concentrations increased significantly with increasing plantation age and increased 5.95-(in the interspaces) to 9.05-fold(under the canopy) and 6.15-to 8.46-fold at the 0-5 cm depth at the 39-year-old plantation compared with non-vegetated sandy land. Simultaneously, H. ammodendron establishment and development resulted in significant salt accumulation in the surface layer. On average, total soil salt content at the 0-5 cm and 5-20 cm depth increased 16.8-fold and 4.4-fold, respectively, compared with non-vegetated sandy land. The increase of total salt derived mostly from the accumulation of SO_4^(2-), Ca^(2+) and Na^+ with H. ammodendron development. The accumulation in salinity was more significant than the increase in fertility, suggesting that improved soil fertility did not limit the impact of salinization. The adverse effect of salt accumulation may result in H. ammodendron plantation degradation and impact community stability in the long run.

Assessing Spatial Patterns of Plant Communities at Varying Stages of Succession

There is a well known connection between the structural complexity of vegetative stands and ecosystem properties. Developing methods to quantify this structural complexity is an important goal for ecologists. We present an efficient and easily implemented field technique for calculating the shape of forest canopies, and the shape of forest stands as succession occurs, using fractal geometry. Fractal geometry can be used to describe complex, non-Euclidean objects that are common in natural systems. We tested the use of this tool in 22 vegetative and forested plots in Western New York State, USA. We found an asymptotic relationship for fractal dimension (D) as a function of basal area (BA;r2= 0.68). In a randomization test to investigate the robustness of D to different tree canopy shapes, we found that D was sensitive to canopy shape switching, suggesting that the method is able to differentiate among similar forests comprised of species having different shaped crowns. We conclude that the shape is conserved in vegetative areas as they progress from one stage of succession to the next (range of mean D: 2.56 to 2.68 across stages). Furthermore, we conclude that the shape filling properties—i.e., distribution of trunks and limbs in a forested area, measured as mean distance—are also conserved across vegetational chronosequences (F = 1.3189, df = 8, 3, p = 0.3341).

Prairie Restoration Effects on Near-Surface Soil Nutrient Changes Over Time in the Ozark Highlands Region of Northwest Arkansas

The Ozark Highlands is a unique botanical transition zone where native prairie and forest once co-existed, but conversion to managed agricultural landuse has severely reduced the extent of native tallgrass prairie. Quantifying soil nutrient changes over time can contribute to improved understanding of the importance of soil fertility in prairie restoration success. The objective of this study was to evaluate the effects of prairie ecosystem [i.e., chronosequence of four prairie restorations and a native prairie (NP)] and soil moisture regime (SMR;aquic and udic) on the change in extractable soil nutrients over a 12-yr period from 2005 to 2017 in the Ozark Highlands region of northwest Arkansas. Soil Ca content decreased over time (P ≤ 0.05) in the 17-year-old-aquic and NP-udic combinations, which did not differ and averaged ?55.7 kg?ha?1?yr?1, but did not change over time in all other ecosystem-SMR combinations. Soil Na content also decreased over time (P ≤ 0.05) in the 17-year-old-aquic combination (?0.7 kg?ha?1?yr?1), but did not change over time in any of the other ecosystem-SMR combinations. Averaged across SMR, soil P content decreased over time (P ≤ 0.05) in the 17-year-old restoration (?1.6 kg?ha?1?yr?1), while did not change over time in the other three restorations and NP. Soil K, Mg, and Zn content changes over time did not differ (P > 0.05) among ecosystem or between SMRs. Soil nutrient changes are manifestations of soil organic matter dynamics over time and contribute to the inherent soil fertility status of an ecosystem, which needs to be balanced for proper ecosystem functioning and restoration success.

Structural and chemical changes in pyrogenic organic matter aged in a boreal forest soil

Pyrogenic organic matter(PyOM)is formed during wildfires and prescribed burnings or produced intentionally in the form of biochar for soil amendment purposes.It is attracting a growing scientific and practical interest due to its important role in the global carbon cycle and agronomic applications as a soil enhancer.Most of the studies on the physicochemical properties of PyOM have been conducted using fresh biochars even though the characteristics of PyOM are expected to alter due to aging processes in soil environment.In this paper,we report the results of a study that utilized X-ray microtomography and elemental analysis to investigate the chemical and structural changes in the PyOM formed during prescribed burning events and aged thereafter for 1–71 years in a boreal forest soil.Our results indicate that changes in elemental composition occurred at decadal timescales,and an apparent steady state was reached ca.30 years after PyOM formation and exposure to the environment.At such timescales,PyOM was able to retain its porous structure originating from the cellular structure of the initial wood tissues.However,structural analysis revealed several effects of aging on the pore structure,such as the formation of surface coating layers,pore fillings,and fractures.These changes may alter pore size distribution and accessibility of the pores and further alter the influence of PyOM on soil functions,such as the transfer and retention of water and nutrients in PyOM pores.

Is thirty-seven years sufficient for full return of the ant biota following restoration?

Introduction:An assessment of whether rehabilitated mine sites have resulted in natural or novel ecosystems requires monitoring over considerable periods of time or the use of space-for-time substitution(chronosequence)approaches.Methods:To provide an assessment of ecosystem recovery in areas mined for bauxite in 1975,the ant fauna of one area planted with Eucalyptus resinifera,one seeded with mixed native species,one topsoiled but unrestored,and a forest reference was subjected to a‘long-term’study by sampling monthly and latterly annually between 1976 and 1989 using pitfall traps.These plots were resampled in 2012.A companion‘short-term’chronosequence study was performed in 1979 in 28 bauxite mines of various ages and restored by a range of different methods,plus three forest references.In order to examine the assertion that the observed differences between restored areas and forest references will lessen with time,sampling using comparable methods was repeated in 2012 in seven of the original plots,representing progressive advances in rehabilitation technology:planted pines;planted eastern states eucalypts;planted native eucalypts;planted eucalypts over seeded understorey;and planted eucalypts on fresh,double-stripped topsoil,plus two forest reference sites.Results:Ant and other invertebrate richness in the long-term study was initially superior in the seeded plot,with little difference between the planted and unplanted plots.It was concluded that although composition of the ant fauna had converged on that of the forest over the 14-year period,differences still persisted.The 2012 resampling revealed that ant species richness and composition had deteriorated in the seeded plot,while values in the unplanted plot,which now supported naturally colonised trees and an understorey,had increased.Differences between all rehabilitated plots and forest still persisted.As with the long-term study,the rate of fauna return and the type of ants present in the short-term study plots differed with the method of rehabilitation used,and,in 1979,no plots had converged on the forest in terms of the ant assemblage.By 2012 ant richness increased,and more so with each advance in rehabilitation technology,except for seeding,in which the understorey had collapsed.Double-stripping of topsoil resulted in the greatest improvements in ant species richness,although none of the areas had converged on the forest reference areas in terms of assemblage composition or ant functional group profiles.Furthermore,assemblage composition in the forest had changed over time,possibly due to reductions in rainfall,which further complicates rehabilitation objectives.Conclusions:It is concluded that although rehabilitation can achieve its objective of restoring diversity,the original assemblage has still not been achieved after 37 years,suggesting that a degree of novelty has been introduced into these older-style rehabilitated areas.The company’s current rehabilitation practices reflect multiple advances in their approach,lending optimism that current restoration may achieve something close to the original ecosystem,an outcome that can only be verified by extended studies like the one described here.

Spatial and temporal dynamics of growth of woody plant species (birch and willows) on the foreland of a retreating glacier in southern Iceland

Background:The forelands of retreating glaciers are invaluable natural laboratories in which to explore the processes of primary succession.Numerous studies have been conducted on foreland chronosequences to identify temporal and spatial trends of the successional communities.This study focused on the spatio-temporal distribution of three woody plant species on the foreland of a retreating glacier in southern Iceland where historical observations provide precise age control of the moraines.To evaluate colonization and successional trends,we examined which species increase in abundance with time and tested the role of proximity to a seed source in colonization.Additionally,we quantified the rate at which biomass carbon is added to the landscape.Results:The density of stems of Betula pubescens increases with moraine age across the foreland chronosequence while the density of stems of both Salix lanata and Salix phylicifolia decreases.We found low statistical significance to the relationship between the density of B.pubescens and distance from a forested ridge nor did we find a relationship between the lengths of the stems and the moraine ages.Woody biomass increased fastest during early successional stages and reached a maximum of 28.5 g C m^(−2) on the oldest moraine.Conclusions:Early colonization of moraines was controlled by environmental filters which favored both Salix species.Colonization by B.pubescens followed as environmental factors,e.g.,favorable soil properties,improved.We found no conclusive evidence that proximity to a potential source of B.pubescens propagules was a significant factor in controlling colonization.The assumption that the abundance of individuals increased with time through later successional stages proved valid for B.pubescens,but not for either species of Salix.These findings are consistent with the classical spatial successional model of community homogenization.Thus,general successional processes at the landscape scale control the temporal dynamics of individual species.

Changes in profile distribution and chemical properties of natural nanoparticles in paddy soils as affected by long-term rice cultivation

Systematic studies on the genesis,properties,and distribution of natural nanoparticles(NNPs)in soil remain scarce.This study examined a soil chronosequence of continuous paddy field land use for periods ranging from 0 to 1000 years to determine how NNPs in soil changed at the early stages of soil genesis in eastern China.Soil samples were collected from coastal reclaimed paddy fields that were cultivated for 0,50,100,300,700,and 1000 years.Natural nanoparticles were isolated and characterized along with bulk soil samples(<2-mm fraction)for selected physical and chemical properties.The NNP content increased with increasing soil cultivation age at 60 g m^(-2) year-1,which was related to decreasing soil electrical conductivity(172-1297μS cm^(-1))and NNP zeta potentials(from -22 to -36 mV)with increasing soil cultivation age.Changes in several NNP properties,such as pedogenic iron oxide and total organic carbon contents,were consistent with those of the bulk soils across the soil chronosequence.Notably,changes in NNP iron oxide content were obvious and illustrated active chemical weathering,pedogenesis,and potential impacts on the microbial community.Redundancy analysis demonstrated that the soil cultivation age was the most important factor affecting NNP properties,contributing 60.7% of the total variation.Cluster and principal component analysis(PCA)revealed splitting of NNP samples into age groups of 50-300 and 700-1000 years,indicating rapid evolution of NNP properties,after an initial period of desalinization(approximately 50 years).Overall,this study provides new insights into NNP evolution in soil during pedogenesis and predicting their influences on agriculture and ecological risks over millennial-scale rice cultivation.