Data from: Nitrogen addition reduces soil respiration but increases the relative contribution of heterotrophic component in an alpine meadow

1. Disentangling the relative response sensitivity of soil autotrophic
(Ra) and heterotrophic respiration (Rh) to nitrogen (N) enrichment is
pivotal for evaluating soil carbon (C) storage and stability in the
scenario of intensified N deposition. However, the mechanisms underlying
differential sensitivities of Ra and Rh and relative contribution of Rh to
soil respiration (Rs) with increasing N deposition remains elusive. 2. A
manipulative field experiment with multi‐level N addition rates was
conducted over three years (2015–2017) in an alpine meadow to explore the
relative impact of N enrichment on Ra and Rh and the response of Rh/Rs
ratio to the gradient of N addition. 3. Soil respiration components had
different sensitivities to N enrichment, with Ra decreasing more than Rh,
leading to a higher Rh/Rs ratio as a function of increasing N addition
rates. Ra and Rh decreased nonlinearly as N addition rates increased, with
a critical load of 8 g N m−2 yr−1 above which N enrichment significantly
inhibited them. Ra and Rh were controlled by different abiotic and biotic
factors and the regulation of controlling factors on soil respiration
components varied over time. N induced reduction in the relative abundance
of forb significantly affected Ra and this effect was mainly evident in
the second and third year. Nitrogen enrichment significantly changed Rh in
the third year and the decreased Rh under high doses of N addition could
be attributed to the changes in microbial biomass C, soil substrate
quality, and microbial composition. 4. Our study highlights the leading
role of Ra in regulating Rs responses to N enrichment and the enhancement
of Rh/Rs ratio with increasing N addition. We also emphasize that N
induced shifts in plant community composition play a vital role in
regulating Ra instead of Rh. The changing drivers of Ra and Rh with time
suggests that long‐term experiments with multiple levels of N addition are
further needed to test the nonlinear responses and underlying mechanisms
of soil respiration components in face to aggravating N deposition.