Abstract
Salvage logging is the commonest post-fire emergency action, but has unclear ecological effects. In the Mediterranean Basin, drought periods and fire regimes are changing and forest management should be adapted. In summer 2009, a mid-high severity fire burned 968 ha of Aleppo pine (Pinus halepensis Mill.) forest in southeast Spain, which was submitted to salvage logging six months later. In spring 2010, plots were set in untreated and logged areas to monitor the recruitment and survival of the main tree species and three companion species: Stipa tenacissima L. (resprouter), Cistus clusii Dunal and Rosmarinus officinalis L. (obligate seeders). We evaluated responses to different scenarios in relation to intensification of summer droughts and forest management to obtain differences in water stress, growth, and gas exchange to cope with summer drought. Drought was induced by using rain-exclusion shelters and recorded ecophysiological characteristics were obtained with a portable gas exchange system. The main tree species recruitment was poor, but companion species showed a high survival ratio. Lower water stress was found for obligate seeder seedlings, which was higher in logged areas with induced drought. The initial post-fire stage was similar for the studied areas. However, after two drought periods (2010 and 2011), significant differences were found in the morphological and ecophysiological responses. In the unmanaged area, the biggest size of individuals due to the most marked increases in height and coverage were observed mainly in resprouter S. tenacissima. In the area submitted to salvage logging, the growth ratios in plots with induced drought were lower, mainly for seeders. Greater productivity was related to higher transpiration, stomatal conductance, and net photosynthetic ratio, but lower water use efficiency was found in obligate seeders with no drought induction, and S. tenacissima obtained higher values in untreated areas. Our results confirm that both forest management and intensification of summer droughts influenced the resilience and productivity of the ecosystems in the short term. Adaptive forest management after fire can imply successful survival and recovery of plant communities in the mid to long term. This study provide a scientific basis to develop tools for the post-fire restoration of serotinous pine forests occurring in low-altitudinal areas of the Mediterranean Basin, prone to summer droughts and fire events.
Highlights
According to IPCC projections for the Mediterranean Basin, climate change will increase dryness and aridity due to warmer temperatures and reduced precipitation, mainly in summer [1,2] which will induce changes in fire regimes [3] and increase the distribution of resilient species [4]
The abrupt insolation increase promoted by salvage logging increased summer mortality and reduced the growth of survival Aleppo pine (Pinus halepensis Mill.) seedlings [12], altered the plant-animal interaction [13], and reduced carbon sequestration [14] which could increase restoration costs [15]
From the recordings obtained in the linear transects, we found a low P. halepensis seedling survival ratio in the UNCUT area (
Summary
According to IPCC projections for the Mediterranean Basin, climate change will increase dryness and aridity due to warmer temperatures and reduced precipitation, mainly in summer [1,2] which will induce changes in fire regimes [3] and increase the distribution of resilient species [4]. Emergency actions and post-fire management are implemented to recover ecosystems and landscapes, and salvage logging is one of the commonest tools implemented in Spain [6], and worldwide [7,8]. Several studies pointed to negative effects on the ecosystem, such as reducing growth and performance of regenerating Maritime pine Aiton) seedlings related to water stress and reduction of nutrient availability for plants [11]. The abrupt insolation increase promoted by salvage logging increased summer mortality and reduced the growth of survival Aleppo pine (Pinus halepensis Mill.) seedlings [12], altered the plant-animal interaction [13], and reduced carbon sequestration [14] which could increase restoration costs [15]
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