Environmental changes following burning in a Songnen grassland, China

Grassland research plots in the Changling Provincial Natural Preserve, Jilin, China, were burned in early spring (5 April) or late spring (15 May) 1993, and their microclimates and soil physical properties were compared with those of unburned plots during the ensuing summer. In mid-August, burned plots exhibited 30–54% increases in soil surface hardness, with the early-burned plots showing more variation than the late-burned plots. At the end of the growing season, soil bulk density was 5% lower in the late-burned plots. Soil water content was 20% less in the early-burned plots than in the unburned. There was greater sunlight penetration of the canopy in the burned plots, leading to higher soil temperatures and a more extreme daily range of canopy temperatures. Comparison of illumination and biomass data suggests that well-replicated illumination index measurements could provide a useful alternative to destructive sampling for biomass assessment. A summary of the environmental effects of time of burning is presented; the optimum burning time for management purposes is just before the spring initiation of vegetation growth, although a later burn might have other ecological and economic benefits.