Effects of Pre-Fire Land Use on Recovery of Soil Chemical Properties After a Prescribed Fire: A Short-, Medium- and Long-term Case Study in the NE Iberian Peninsula

Rural land abandonment means that some rural areas fall into disuse or are taken over by forest stands. In this context, prescribed burning is a widely used forest management tool, but few studies have analyzed the influence of pre-burn land use on post-burn soil recovery. This study seeks to determine the impact of prescribed burning on soil chemical properties and to examine any differences in these parameters based on prior land use. The study is conducted in two plots – one, a forest plot (TV2); the other an abandoned agricultural terrace (TV3) – located in Tivissa (southern Catalonia), both dominated by Pinus halepensis Mill. and Quercus ilex L., and situated on Lithic Calcixerept soils. The plots, located 3 km apart, share a similar topography, exposure, and vegetation structure. Low-intensity prescribed burns were conducted in 2001, and soil samples (0–5 cm depth) were collected in five campaigns: just before the fire (BPF), immediately after the fire (APF), and at 1-, 3-, and 13-years post-burn (1YAPF, 3YAPF, and 13YAPF, respectively). In each sampling period, 30 samples were collected from an experimental plot of 72 m2 (4 x 18 m). The soil properties analyzed included total carbon (TC), total nitrogen (TN), pH, electrical conductivity (EC), and extractable calcium (Ca), magnesium (Mg), potassium (K), and available phosphorus (P) concentrations. In TV2 soil, TC and TN increase at short and medium term, soil pH increases after fire and decreases gradually, EC decreases at short and medium term, and increases at long-term, and extractable major cations increase until medium term and are reduced at long-term. In TV3 soil TC decreases and TN increases gradually over time, pH increases at short and decreases at long-term, EC decreases from short to long-term with a slight increase at medium-term, and extractable major cations (except P which decrease over time) increase until long-term. Changes caused by different pre-fire land use and consequently differences caused by different vegetation cover minor over time. Despite differences in soil properties in the short and medium term due to land use prior to prescribed fire, after 13 years, soil conditions had largely stabilized, and there was no evidence of horizontal or vertical continuity in plant fuel. These findings suggest that prescribed burning does not result in long-term soil degradation and, thus, remains a viable tool for sustainable forest management under different land uses.