Responsess of Digitaria sanguinalis (L.) Scop growth and soil respiration dynamics to ash content in a burned area

Abstract Background Global warming has significantly increased the frequency and scale of wildfires. However, the effects of fire residues on soil CO₂ emissions and the germination of pioneer species in burned areas have been insufficiently studied. Understanding these impacts is crucial for post-fire ecosystem recovery. This study examined the effects of wildfire ash from Liangshan Yi Autonomous Prefecture, China, on the germination of Digitaria sanguinalis (L.) Scop and soil respiration ( R s). Results Within the applied ash gradient (0.00, 0.58, 1.16, 1.73 kg m −2 ), final germination of Digitaria sanguinalis was not significantly affected by ash, whereas precipitation exerted the dominant control. In contrast, early seedling growth showed a significant ash × precipitation interaction: under normal to moderately wet conditions, intermediate ash loading (≈0.58 and 1.16 kg m −2 ) promoted plant height, but this effect disappeared under the driest or wettest scenarios. Across all precipitation regimes, R s increased with ash loading and showed an early rise, a mid-term peak, and a later stabilization or decline as ash-derived substrates were depleted. R s was strongly related to 5 cm soil temperature, whereas, no significant monotonic association between Rs and 5 cm soil moisture was detected within the moisture conditions maintained by the precipitation treatments, suggesting that temperature explained more of the short-term variability in Rs. The temperature sensitivity ( Q 10 ) of R s also increased with ash addition, with values of 1.30, 1.82, 2.18, and 2.34 for the four ash treatments. Conclusions Wildfire ash within a realistic post-fire range did not significantly inhibit the germination of the pioneer grass D. sanguinalis , which was mainly controlled by precipitation, but moderate ash loading (0.58, 1.16 kg m −2 ) supported early seedling growth under adequate moisture. At the same time, ash inputs enhanced R s and increased its apparent temperature sensitivity, with R s being predominantly driven by soil temperature and with moisture effects not emerging as a detectable monotonic trend within the experimental moisture window. These findings suggest that, in water-limited dry-valley ecosystems, complete removal of surface ash to avoid potential germination inhibition is unnecessary; instead, management should prioritize maintaining soil moisture while allowing moderate ash to remain on the surface to support early post-fire recovery and to improve the representation of ash effects in soil respiration models for fire-affected forests.