This is the 2008 CSP SIR data from a subset of 12 CSPs representing the age gradient. Samples were analyzed over the depth profile of each CSP (see detailed methods below) and analyzed for basal respiration, substrate induced respiration, and the quotient CO2, which represent the heterotrophic microbial biomass and ecophysiological capacity of the microbial community. The point of this study was to characterize the microbial community of the CSPs, as well as to determine which factors most influence microbial community dynamics, including forest age and other factors.

A subset of 12 CSPs were selected according to an successional age and a diversity gradient; based on the original age classifications which were later changed: young (CSPs 16,17,25,26), medium (CSPs 1,5,8,9) and old (CSPs 2,4,12,13). At each CSP, samples were originally taken by SP6 at 5 cm intervals down to 50 cm, and then combined according to soil horizons. For each depth, samples were taken from all 9 subplots then combined into one pooled sample.

The Gutianshan National Nature Reserve (NNR) is located in the western part of Zhejiang Province (29º8'18" – 29º17'29" N, 118º2'14" – 118º11'12" E, Fig. 1). The Gutianshan NNR has an area of approximately 81 km2 and was initially established as a National Forest Reserve in 1975 and became a National Nature Reserve in 2001. The NNR comprises a large portion of broad-leaved forests of advanced successional stages (Hu & Yu 2008), which have not been managed since the beginning of the 1990ies, as well as young successional stages and conifer plantations, mainly of Cunninghamia lanceolata and Pinus massoniana. --- The vegetation is composed of different types of subtropical evergreen and mixed broad-leaved forests (Yu et al. 2001). Most of the stands are secondary forests, evidenced by maximum tree ages of 180 years, by agricultural terraces in almost all plots and by the presence of charcoal in almost all soil profiles. Around the Gutianshan NRR extensive deforestation has occurred during the Great Leap Forward in the 1950s, as in most parts of Southeast China. However, due to prevailing steep slopes, the Gutianshan area was only marginally usable for agricultural activities, and thus an exceptionally intact forest cover has been preserved. --- The climate at Gutianshan NNR is warm and temperate with a short dry season in November and December and with warm summers (Fig. 2). The climatic conditions are characteristic for the subtropics with an annual average temperature of 15.1°C, January minimum temperatures of -6.8°C, July maximum temperatures of 38.1°C and an accumulated temperature sum (≥ 5°C) of 5221.5 degree days.

Samples were taken in August and September 2008 from the CSPs, taken to Germany, and analyzed in the laboratory afterward (over the next several months). Cmic was estimated with 25 g oven-dry equivalent of field-moist soil by substrate induced respiration. Before analyzing, frozen samples were completely thawed and adjusted to an appropriate moisture content. All samples were pre-incubated at 20 ˚C for at least 48 h. Later the analysis was also carried out at 20 ˚C. Basal respiration (BR) was first measured for 24 hours without amendment, followed by addition of glucose and talcum to measure substrate induced respiration (Cmic). The CO2 production of each sample was measured with an automatic infrared gas analyzer (Type 225 MK3) in an air flushed incubation device. The CO2 production was then averaged over four internal replicates of each sample. This CO2 production can be used to estimate the microbial biomass and to calculate two microbial ecophysiological indicators, the metabolic quotient (qCO2) and the Cmic/ Corg ratio. The qCO2 was determined as the ratio of BR (μg g soil-1 hr-1 CO2-C) to Cmic (μg g soil-1). The Cmic/ Corg ratio was calculated by dividing Cmic (μg) by percent soil organic carbon (Corg).

No specific organisms were analyzed here, but this data can represent the total microbial heterotrophic biomass

The parameters of interest were the basal respiration (BR, soil CO2 production with no ammendments), substrate induced respiration (SIR, soil CO2 production after addition of glucose and talc), and the quotient CO2 (qCO2, the ratio of BR/SIR). Data were then analyzed in R using multivariate (NMDS) or univariate (co-variate regressions and ANOVA) methods. The columns of CSP name, depth, and horizon name are explanitory variables, the response columns are the BR, SIR, and qCO2 --- note that the age classes analyzed here are not the most current age classes. They were changed, but analysis was already deep underway on the paper at that point.