Dead wood is an important structure for conservation purposes and for maintaining biodiversity. In this context, snags were studied under different conditions in silver fir ancient forests of the southern French Alps. The impact of management status and developmental phases were estimated on both quantity and quality of this material. SDT volume averaged 64.6 +/- 19.8 m(3) • ha(-1) and 15.8 +/- 6.0 m(3) • ha(-1) in unmanaged and managed ancient forests, respectively. SDT volume varied according to the point in the silvicultural cycle and silvigenesis cycle ranging from 4.3 +/- 3.4 m(3) • ha(-1) in early aggradation phase of managed forests to 202.3 +/- 48.6 m(3) • ha(-1) in degradation phase of unmanaged forest. Large SDT significantly belonged to the degradation phase of unmanaged forests. Our research showed that SDT density in this ancient forests was mainly governed by natural processes. An average of 9 large SDT per ha has been proposed to preserve the ecological processes.