DataSheet1_Effects of litter chemical traits and species richness on soil carbon cycling changed over time.docx

Litter decomposition is the main driver of nutrient cycling process in terrestrial ecosystems. Afforestation completely altered vegetation composition and litter species, disrupting the long-term carbon balance in grassland ecosystem. However, there is a lack of understanding of how litter mixing effect (LME) affects soil carbon cycling in afforested ecosystem. Here, we investigated the effects of litter richness and quality of tree, shrub, and grass species and their litter mixture on soil CO2 fluxes. The results showed that cumulative soil CO2 flux in the early stage (1–28 days) was 1.75 times higher than that in the late stage (29–113 days), indicating litter decomposition was intensive at first and then decreased with time. Soil carbon flux changed with decomposition stages. In the early-stage of decomposition, soil CO2 flux increased with the concentrations of litter carbon, nitrogen and condense tannin. In the late phase of decomposition, all litter chemical traits were negatively related to the soil carbon flux. Additionally, plant litter richness was negatively correlated to early-stage soil CO2 flux, whereas it was positively related to late-stage soil carbon flux. Our results provide evidence that long-term carbon balance in grassland ecosystems was interrupted by afforestation, and the dominant litter chemical traits that controlling soil carbon cycling changed over time.</p

Spatial pattern of soil organic carbon and total nitrogen, and analysis of related factors in an agro-pastoral zone in Northern China

<div><p>The spatial pattern of soil organic carbon (SOC) and total nitrogen (TN) densities plays a profound important role in estimating carbon and nitrogen budgets. Naiman Banner located in northern China was chosen as research site, a total of 332 soil samples were taken in a depth of 100 cm from the low hilly land in the southern part, sandy land in the middle part and an alluvial plain in the northern part of the county. The results showed that SOC and TN density initially decreased and then increased from the north to the south, The highest densities, were generally in the south, with the lowest generally in the middle part. The SOC and TN densities in cropland were significantly greater than those in woodland and grassland in the alluvial plains and for Naiman as a whole. The woodland SOC and TN density were higher than those of grassland in the low hilly land, and higher densities of SOC and TN in grassland than woodland in the sandy land and low hilly land. There were significant differences in SOC and TN densities among the five soil types of Cambisols, Arenosols, Gleysols, Argosols, and Kastanozems. In addition, SOC and TN contents generally decreased with increasing soil depth, but increased below a depth of 40 cm in the Cambisols and became roughly constant at this depth in the Kastanozems. There is considerable potential to sequester carbon and nitrogen in the soil via the conversion of degraded sandy land into woodland and grassland in alluvial plain, and more grassland should be established in sandy land and low hilly land.</p></div

Parameters of the variogram models for the soil organic carbon (SOC) and total nitrogen (TN) densities to a depth of 100 cm in Naiman Banner.

<p>Parameters of the variogram models for the soil organic carbon (SOC) and total nitrogen (TN) densities to a depth of 100 cm in Naiman Banner.</p

Differences in the soil organic carbon (SOC) and total nitrogen (TN) densities to a depth of 100 cm for all sites combined in Naiman Banner and for the three land use types.

<p>For a given parameter, bars labeled with different letters differ significantly (P < 0.05, one-way ANOVA followed by LSD test). Values are means ± SE.</p

Mean values of the soil organic carbon (SOC) and total nitrogen (TN) densities to a depth of 100 cm in the alluvial plains, sandy land, and low hills of Naiman Banner.

<p>Mean values of the soil organic carbon (SOC) and total nitrogen (TN) densities to a depth of 100 cm in the alluvial plains, sandy land, and low hills of Naiman Banner.</p

Spatial pattern of soil organic carbon and total nitrogen, and analysis of related factors in an agro-pastoral zone in Northern China - Fig 7

<p><b>Vertical distribution of the (a) soil organic carbon (SOC) density and (b) total nitrogen (TN) density to a depth of 100 cm. Data points were plotted at the bottom of each soil layer.</b> Values are means ± SE.</p

Differences in the soil organic carbon (SOC) and total nitrogen (TN) densities to a depth of 100 cm among the five soil types.

<p>For a given element, bars labeled with different letters differ significantly (one-way ANOVA followed by LSD test, P < 0.01). Values are means ± SE.</p

Location of the study area and sampling sites.

<p><b>Reprinted from [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0197451#pone.0197451.ref027" target="_blank">27</a>] under a CC BY license, with permission from [Jie LIAN], original copyright [2017].</b> (a) Naiman Banner is located in the southern part of the Horqin Sandy Land (HSL). The northern and central areas of Naiman Banner belong to the national ecological function protected area (EFPA); the southern part belongs to the Source Region of the West Liaohe River (WLR). (b) The research area is located in the southeastern part of Inner Mongolia, in northern China. The region has been divided into three zones (AP, alluvial plains; SL, sandy land; LH, low hills) based on the soil and land use characteristics and Landsat ETM+ imagery from (c) June 2010 and (d) July 2015.</p

Statistical characteristics of the soil organic carbon (SOC) and total nitrogen (TN) densities (kg m^-2 to a depth of 100 cm) in Naiman Banner of northeastern China (n = 332 sample sites).

<p>Statistical characteristics of the soil organic carbon (SOC) and total nitrogen (TN) densities (kg m^-2 to a depth of 100 cm) in Naiman Banner of northeastern China (n = 332 sample sites).</p

The distribution of soil types in Naiman banner.

<p><b>Reprinted from [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0197451#pone.0197451.ref030" target="_blank">30</a>] under a CC BY license, with permission from [Wang Guoguang], original copyright [1984].</b> There are six soil types in Naiman Banner according to the second national soil survey: Arenosols cover 58.2% of the total area, Cambisols cover 20.0%, Argosols cover 12.1%, Kastanozems cover 8.4%, Gleysols cover 1.2%, and Solonchaks cover 0.1%.</p