Microbial carbon use efficiency along an altitudinal gradient

Soil microbial carbon-use efficiency (CUE), described as the ratio of growth over total carbon (C) uptake, i.e. sum and respiration, is a key variable in all soil organic matter (SOM) models critical to ecosystem C cycling. However, there still lack consensus on CUE when estimated using different methods. Furthermore, significance many fundamental drivers remains largely unknown inconclusive, especially for tropical ecosystems. For these reasons, we determined indicators nutrient availability seven forest soils along an altitudinal gradient (circa 900–2200 m a.s.l) occurring at Taita Hills, Kenya. We used this study (N P) its relation estimates. assessing availability, both bulk stoichiometric ratios (soil C:N, C:P N:P), well SOM degradation related enzyme activities. two methods: substrate independent 18O-water tracing 13C-glucose method. Based approaches, uptake added glucose versus native SOM, with latter defined by C:N stoichiometry, studied did not reveal N limitation. P limitation increased slightly elevation. Additionally, based extracellular activities, decreased The 13C-CUE change altitude indicating that was efficiently taken up microbes. On other hand, 18O-CUE, which reflects microbes growing clearly declined increasing associated indicators. our results, higher elevations invested more energy scavenge nutrients from complex whereas lower may have been readily available.