Assessing early-stage natural regeneration and reforestation after wildfires using Cistus ladanifer (rockrose) as an indicator species

Wildfires pose an increasing threat to many ecosystems worldwide. While part of Mediterranean ecosystems, fire frequency and severity have been drastically increasing, necessitating assisted reforestation and regeneration. Success of these efforts is difficult to quantify, as many facets of ecosystem regeneration must be measured, such as survival of planted species and native vegetation cover. We propose gum rockrose (Cistus ladanifer) as an early stage bioindicator of post-fire ecosystem recovery by relating some of its ecophysiological and allometric traits to reforestation success with native tree species and patterns of natural regeneration. Specifically, we (i) quantify traits of rockrose in different treatments; (ii) relate them to survival rates of planted species and indicators of natural regeneration and (iii) develop allometric biomass models to assess fuel load and competitive pressure. After 12 months, rockrose height was 20.5 cm in the vegetation removal treatment, increasing to 28.5 where swales were applied and nearly doubling if swales were filled with woodchip or compost (38.3 and 35.3 cm, respectively). Survival rates of planted species increased in a similar way (13.6% in the swales and 46.9% in the compost treatment) while natural regeneration decreased (463.1 g/m2 for vegetation removal and 175.1 g/m2 in the compost treatment). Our results demonstrate that rockrose is a promising candidate to serve as an indicator species and especially some of its ecophysiological parameters such as leaf area, plant height and abundance deserve further attention as simple variables to estimate overall ecosystem response.