RECENT CASE NOTES

<p><i>Notes</i>: H-sites and L-sites refer to high-tide-zone sites and low-tide-zone sites, respectively.</p><p>Results of <i>t</i>-test for effects of different stands on aboveground net primary production (ANPP), soil pH, total carbon (TC), organic and inorganic carbon (SOC and SIC, 0–100 cm), and SMBC.</p

The temperature sensitivity of soil organic carbon decomposition is not related to labile and recalcitrant carbon

<div><p>The response of resistant soil organic matter to temperature change is crucial for predicting climate change impacts on C cycling in terrestrial ecosystems. However, the response of the decomposition of different soil organic carbon (SOC) fractions to temperature is still under debate. To investigate whether the labile and resistant SOC components have different temperature sensitivities, soil samples were collected from three forest and two grass land sites, along with a gradient of latitude from 18°40’to 43°17’N and elevation from 600 to 3510 m across China, and were incubated under changing temperature (from 12 to 32 ^oC) for at least 260 days. Soil respiration rates were positively related to the content of soil organic carbon and soil microbial carbon. The temperature sensitivity of soil respiration, presented as <i>Q</i>₁₀ value, varies from 1.93 ± 0.15 to 2.60 ± 0.21. During the incubation, there were no significant differences between the <i>Q</i>₁₀ values of soil samples from different layers of the same site, nor a clear pattern of <i>Q</i>₁₀ values along with the gradient of latitude. The result of this study does not support current opinion that resistant soil carbon decomposition is more sensitive to temperature change than labile soil carbon.</p></div

Variation in <i>Q</i>_<i>10</i> values (mean ± SD) along with incubation.

<p>Variation in <i>Q</i>_<i>10</i> values (mean ± SD) along with incubation.</p

SOC decomposition rates (at 20 ^oC) declined over incubation times.

<p>(DF: deciduous forest; TM: temperate meadow; RF: tropical rainforest; EF: evergreen forest; SG: semi-arid grassland).</p

The <i>Q</i>_<i>10</i> value of each ecosystem coupled with SOC content.

<p><b><i>Q</i></b>_{<b><i>10</i></b>}<b>value is the average <i>Q</i></b>_{<b><i>10</i></b>}<b>value over the whole incubation of each surface soil.</b> (DF: deciduous forest; TM: temperate meadow; RF: tropical rainforest; EF: evergreen forest; SG: semi-arid grassland).</p

Variation in SOC decomposition rates, <i>Q</i>_<i>10</i> values and soil carbon pools with increasing incubation time.

<p><b>Values are average of four replications and normalized by initial values</b>. (DF: deciduous forest; TM: temperate meadow; RF: tropical rainforest; EF: evergreen forest; SG: semi-arid grassland).</p

Relationship between SOC decomposition rates and incubating temperatures for soil samples from different sites.

<p>(DF: deciduous forest; TM: temperate meadow; RF: tropical rainforest; EF: evergreen forest; SG: semi-arid grassland).</p

Study sites characteristics.

<p>Study sites characteristics.</p

Chemical characteristics of soils from different sites.

<p>Chemical characteristics of soils from different sites.</p

The variation of <i>Q</i>₁₀ values calculated with two different models along with incubation time.

<p><i>Q</i>₁₀(20) was the <i>Q</i>₁₀ value calculated at 20 ^oC and <i>Q</i>₁₀(10) was the Q₁₀ value calculated at 10 ^oC by the O’connel model, while <i>Q</i>₁₀ was the <i>Q</i>₁₀ value calculated by first–ordered exponential model. (DF: deciduous forest; EF: evergreen forest; SG: semi-arid grassland).</p