Pearson’s correlation coefficients (<i>r</i>) between biotic or abiotic factors and decomposition rate (<i>k</i>).

<p>An asterisk (*) indicates significant difference at <i>P</i><0.05.</p><p>Abbreviations: FTCs = numbers of soil freeze-thaw cycles, MBC = microbial biomass carbon, MBN = microbial biomass nitrogen, MBP = microbial biomass phosphorus, and ACPA = acid (pH 6.5) phosphatase (ACP) activity.</p

Basic geography, vegetation and soil along the four subalpine and alpine forests in the Bipenggou Nature Reserve, Sichuan, China.

<p>Basic geography, vegetation and soil along the four subalpine and alpine forests in the Bipenggou Nature Reserve, Sichuan, China.</p

Concentrations of leaf litter carbon (A), nitrogen (B), phosphorus (C), potassium (D), lignin (E), C:N (F) and lignin:N (G) ratios at different elevations after every sampling date.

<p>Concentrations of leaf litter carbon (A), nitrogen (B), phosphorus (C), potassium (D), lignin (E), C:N (F) and lignin:N (G) ratios at different elevations after every sampling date.</p

Results of the two-way ANOVA for the effects of elevation and species treatments and their interactions on the leaf litter decomposition rate (<i>k</i>).

<p>Bold <i>P</i>-values indicate significant effects (<i>P</i><0.05).</p

Partitioning of deviance in the decomposition rate during each stage calculated with a partial regression method.

<p>In the figure, a and c are the independent components attributed to two groups of biotic factors (litter chemistry and microbe-related factors), respectively; b is the covariance in a component of the two groups; and d is the residual deviance. The group 1 consists of litter chemical variables, whilst the group 2 is the microbe-related factors. See details of these partial regressions in the Material and Methods section.</p

Percentage of biomass remaining of leaf litter (A) and the decomposition rate (<i>k</i>) during each stage of decomposition at the four elevations (B).

<p>Insert figure is the <i>k</i> values of the 2 year of decomposition (means ± SE, n = 5) and different letters denote significant differences at <i>P</i><0.05.</p

Variations of surface soil temperature (A), mean seasonal soil temperature (columns) and numbers of soil freeze-thaw cycles (FTCs) (dots) (B) during each stage of decomposition at the four study sites (elevations).

<p>Variations of surface soil temperature (A), mean seasonal soil temperature (columns) and numbers of soil freeze-thaw cycles (FTCs) (dots) (B) during each stage of decomposition at the four study sites (elevations).</p

Pearson’s correlation coefficients (<i>r</i>) between elevation and biotic or abiotic factors in decomposing litter.

<p>An asterisk (*) indicates significant difference at <i>P</i><0.05.</p><p>Abbreviations: FTCs = numbers of soil freeze-thaw cycles, MBC = microbial biomass carbon, MBN = microbial biomass nitrogen, MBP = microbial biomass phosphorus, and ACPA = acid (pH 6.5) phosphatase (ACP) activity. An asterisk (*) indicates statistically significant (<i>P</i><0.05).</p

Concentrations of leaf litter microbial biology, activity of sucrase and acid phosphatase at different elevations after every sampling date.

<p>Abbreviations: MBC = microbial biomass carbon (A), MBN = microbial biomass nitrogen (B), MBP = microbial biomass phosphorous (C), bacterial biomass (D), fungal biomass (E) sucrase A = Sucrase activity (F) and ACPA = acid (pH 6.5) phosphatase activity (G).</p

Data_Sheet_1_Effects of Organic Amendments on the Transformation of Fe (Oxyhydr)Oxides and Soil Organic Carbon Storage.PDF

Organic amendments from animal production are commonly used for promoting soil fertility, and their impacts on the residual soil organic carbon (SOC) are of both agricultural and environmental interest. Iron (Fe) in the form of (oxyhydr)oxides has been proposed to play a critical role in long-term SOC preservation by forming Fe-organic associations, though currently a comprehensive understanding of how these Fe-organic associations are regulated by long-term organic amendments is limited. Here, we synthesize information to link Fe (oxyhydr)oxides, SOC sequestration, and long-term organic inputs from both field and laboratory studies. The results show that vigorous Fe mobilization can be regulated by long-term application of organic amendments, and these organically amended soils contained significantly higher concentrations of poorly crystalline Fe that was closely related to SOC storage in both upland and paddy soils. Potential mechanisms are proposed as follows: (1) DOM from the organically amended soils is more likely to co-precipitate with poorly crystalline Fe, and DOM from the inorganically fertilized soils is to a larger extent adsorbed on poorly crystalline Fe. The co-precipitated Fe-OM complexes are more resistant to desorption than the adsorbed OM. (2) DOM extracts from soils treated with organic amendments exhibit a stronger inhibitory effect on the crystallization of poorly crystalline Fe than DOM from inorganically fertilized soils, which may be the consequence of increased numbers of aromatic functional groups. Organic acids in root exudates increased soil mineral availability and the formation of poorly crystalline minerals. Compared to inorganic fertilizers, organic amendments significantly increase (>20%, p < 0.05) the concentration of poorly crystalline minerals in the presence of actual roots. (3) Microbially mediated Fe cycling is strongly linked to the Fe mineralogy in soils, and regulated by long-term organic amendments. Greater consumption of poorly crystalline Fe was observed in inorganically fertilized soil than that in organically amended soil, due to a higher relative abundance of well-known Fe(III) reducers. Conversely, Fe(II) oxidizers, were more abundant, and produced higher levels of poorly crystalline Fe under organic amendments. In conclusion, continuous organic amendments initialize a positive feedback loop for the maintenance of poorly crystalline Fe in soils, which can contribute to enhanced SOC storage.</p