Post-fire management treatment effects on soil properties and burned area restoration in a wildland-urban interface, Haifa Fire case study

Lea Wittenberg; Hilde van der Wal; Saskia Keesstra; Naama Tessler

doi:10.1016/j.scitotenv.2019.135190

Post-fire management treatment effects on soil properties and burned area restoration in a wildland-urban interface, Haifa Fire case study

Sci Total Environ. 2020 May 10:716:135190. doi: 10.1016/j.scitotenv.2019.135190. Epub 2019 Nov 22.

Authors

Lea Wittenberg¹, Hilde van der Wal², Saskia Keesstra³, Naama Tessler⁴

Affiliations

¹ Department of Geography and Environmental Studies, University of Haifa, Israel.
² Department of Geography and Environmental Studies, University of Haifa, Israel; Wageningen Environmental Research, Team Soil, Water and Land Use, Droevendaalsesteeg 3, 6708PB Wageningen, Netherlands.
³ Wageningen Environmental Research, Team Soil, Water and Land Use, Droevendaalsesteeg 3, 6708PB Wageningen, Netherlands; Civil, Surveying and Environmental Engineering, The University of Newcastle, Callaghan 2308, Australia.
⁴ Hanoch Borger Agronomy Ltd., Kibbutz Yagur 3006500, Israel.

PMID: 31837883
DOI: 10.1016/j.scitotenv.2019.135190

Abstract

In November 2016, the urban dry streams (wadis) of the city of Haifa in Northern Israel were on fire. However, it was not just the fire that was threatening urban areas. Post-fire precipitation could turn into urban floods, further aggravating the fire damages. Several months after the fire a considerable restoration effort was initiated to restore the burned areas and mitigate future events. For urban forests the rehabilitation strategy was planned and implemented according to the topographic structure of the burned site and anticipated soil erosion. Accordingly, various post-fire management techniques were used: salvage-logging, afforestation, log erosion barriers and coconut fibre-webs. This study aimed to look at the effects of these methods on soil properties, namely, gravimetrical soil moisture, soil organic matter content, pH, electrical conductivity, hydraulic conductivity and soil water repellency. Results indicate that the control (burned, non-managed) site was the highest in soil moisture, organic matter and electrical conductivity compared to all other sites, however, the existence of ash cover made the response to precipitation unpredictable. The hydraulic conductivity (K) of the black ash (24.1 ± 8.6 mm/h), the white ash (19.0 ± 10.7 mm/h) and the disturbed (mixed) ash (11.7 ± 3.7 mm/h) were significantly higher than the underlying soil (3.3 ± 0.7 mm/h). As a result of these differences in K value, precipitation only infiltrates through the ash layers and then flows along the interface of the ash and the soil, triggering soil erosion. Most of the sites that were salvage logged showed signs of erosion. The log barriers were only effective for downstream areas. The afforestation could help to homogenise the soil, but the vegetation cover would be less dense and stable than after natural reforestation. Furthermore, the coconut fibre webs helped to improve the soil water retention and decreased the direct impact of rainfall.

Keywords: Ash; Post-fire management; Soil; Water repellency; Wildland-urban interface.