AUTHOR=Saulino Luigi , Rita Angelo , Stinca Adriano , Liuzzi Greta , Silvestro Roberto , Rossi Sergio , Saracino Antonio 

TITLE=Wildfire promotes the invasion of Robinia pseudoacacia in the unmanaged Mediterranean Castanea sativa coppice forests

JOURNAL=Frontiers in Forests and Global Change

VOLUME=6

YEAR=2023

URL=https://www.frontiersin.org/journals/forests-and-global-change/articles/10.3389/ffgc.2023.1177551

DOI=10.3389/ffgc.2023.1177551

ISSN=2624-893X

ABSTRACT=<p>In the Mediterranean region of southern Europe, <italic>Castanea sativa</italic> Mill. (<italic>Castanea</italic>) coppice stands are being invaded by non-native pioneer tree species due to recurrent coppicing and wildfire disturbances. There is a need to control the spread of non-native tree species in <italic>Castanea</italic> coppices due to their pivotal socio-economic role, however, to facilitate this, further research into invasive strategies and their interactions with disturbances is required. The non-native <italic>Robinia pseudoacacia</italic> L. (<italic>Robinia</italic>) has widely colonized the overaged and unmanaged <italic>Castanea</italic> coppice forests in Vesuvius National Park, which were disturbed by the low-severity fires in the summer of 2017. Here, we aimed to assess the functional traits conferring a competitive advantage to the <italic>Robinia</italic> over <italic>Castanea</italic> and the changes in spatial stand patterns driven by wildfire disturbance. To achieve this we assessed the spatial stem patterns, regeneration strategies, and conducted field-assessments and remote sensing of the spring leaf phenology of both <italic>Castanea</italic> and <italic>Robinia</italic> in five 300–600 m<sup>2</sup> plots. After the 2017 wildfire, root suckers constituted 72% (±12) of the <italic>Robinia</italic> vegetative living sprouts and occurred up to a distance of 10 m from the adult parent trees under the canopy of the <italic>Castanea</italic> trees. NDVI-based estimates at the start of the growing season (<italic>sos</italic>) in <italic>Castanea</italic> occurred over a 7 day period, from DOY 118–124, increasing at a rate (<italic>rsp</italic>) of 0.10–0.16, in agreement with the field-based assessment of spring leaf phenology. In <italic>Robinia</italic>, the <italic>sos</italic> estimated at DOY 109 from the NDVI seasonal trajectory disagreed with the field-based observations, which started later than <italic>Castanea</italic>, after approximately DOY 133. Here, the high percentage cover (∼90%) of the understory species influenced NDVI-based estimates of <italic>Robinia</italic> leaf spring phenology. The results suggest that low-severity wildfires increased the invasiveness of <italic>Robinia</italic>, and that vegetative regeneration strategies, rather than earlier spring phenology, conferred a competitive advantage in the fire-disturbed <italic>Castanea</italic> coppice stands. The results thus suggest that appropriate management of invasive <italic>Robinia</italic> trees to conserve the continuous canopy cover of <italic>Castanea</italic> stands should guide nature-based solutions to control the spread of non-native tree species.</p>