Effects of nurse shrubs and biochar on planted conifer seedling survival and growth in a high-severity burn patch in New Mexico, USA

The synergistic effects of widespread high-severity wildfire and anthropogenic climate change are driving large-scale vegetation conversion. In the southwestern United States, areas that were once dominated by conifer forests are now shrub- or grasslands after high-severity wildfire, an ecosystem conversion that could be permanent without human intervention. Yet, the reforestation of these landscapes is rarely successful, with a mean planted seedling survival of just 25 %. Given these low rates, we carried out a planting experiment to quantify the impacts of biochar as a soil amendment and shrubs as nurse plants on planted conifer seedling survival and growth following high-severity wildfire. We planted 1200 seedlings of three species (Pinus ponderosa, P. strobiformis, and Pseudotsuga menziesii) in a 2-ha area within the footprint of the Las Conchas fire in New Mexico, USA. We used four treatments: under shrubs, or in the open and with or without biochar in a full-factorial design. We f..., In 2011, the Las Conchas fire burned approximately 63,130 ha in the Jemez Mountains of New Mexico, USA, ∼30 % of which was high-severity as defined by Eidenshink and colleagues, (2007). The Las Conchas fire burned over footprints from five previous wildfires (​Coop et al, 2016​). This repeated high-severity burning has led to a large-scale vegetation shift, from ponderosa pine-dominated forest to a Gambel oak (Quercus gambelii) and New Mexico locust (Robinia neomexicna) shrub-dominated landscape (​Coop et al., 2016; Kaufmann et al., 2016​). We selected a 2 ha area within the footprint of the Las Conchas fire for our planting experiment (lat: 35.785, long: -106.415), due to its location within an area classified as having experienced high-severity wildfire, its elevation, 2520 m above sea level, (close to the mean elevation of the Las Conchas fire footprint, 2541 m) and proximity to a road to enable planting efforts. We planted all 1200 seedlings during July 15–17 of 2019, between 2516 m...,