Limited natural regeneration of unique Scalesia forest following invasive plant removal in Galapagos

More than 60% of the flora of the Galapagos Islands is introduced and some of these species have become invasive, severely altering ecosystems. An example of an affected ecosystem is the Scalesia forest, originally dominated by the endemic giant daisy tree Scalesia pedunculata (Asteraceae). The remnant patches of this unique forest are increasingly being invaded by introduced plants, mainly by Rubus niveus (blackberry, Rosaceae). To help large-scale restoration of this ecologically important forest, we seek to better understand the natural regeneration of S. pedunculata after invasive plant control. We monitored naturally recruited S. pedunculata saplings and young trees over five years in an area where invasive plant species are continuously being removed by manual means. We measured survival, height and growth of S. pedunculata saplings and young trees along permanent transects. Percent cover of surrounding plant species and of canopy shade directly above each S. pedunculata individual were determined, as well as distance to the next mature S. pedunculata tree. We identified potential factors influencing initial sapling survival and growth by applying generalized linear models. Results showed a rapid growth of saplings and young trees of up to 0.45 cm per day and a high mortality rate, as is typical for pioneer species like S. pedunculata. Sapling survival, growth and mortality seemed to be influenced by light availability, surrounding vegetation and distance to the next adult S. pedunculata tree. We concluded that natural regeneration of S. pedunculata was high only five months after the last herbicide application but that 95% of these recruits had died over the 5-year period. Further studies are needed to corroborate whether the number of surviving trees is sufficient to replace the aging adult trees and this way maintain remnants of the Scalesia forest. Urgent action is needed to help improve future restoration strategies to prevent further degradation of this rapidly shrinking threatened forest ecosystem.

Biophysical Settings that Influenced Plantation Survival During the 2015 Wildfires in Northern Rocky Mountain Moist Mixed-Conifer Forests

Fire suppression and the loss of western white pine (WWP) have made northern Rocky Mountain moist mixed-conifer forests less disturbance resilient. Although managers are installing hundreds of plantations, most of these plantations have not experienced wildfire since establishment. In 2015, wildfires burned through one hundred WWP plantations in this region, providing an opportunity to evaluate the effects of wildfires on sapling survival. A Weibull distribution approach was used to characterize the variation of fire severity pixels, as indicated by the differenced normalized burn ratio. The distribution parameters provided a method to identify the biophysical setting and plantation characteristics influencing fire severity and sapling survival. Plantations located on lower slope positions were more resistant to wildfires than plantations located midslope or close to the ridges. Snow water equivalent was positively correlated with wildfire resistance and resilience. Results will help focus reforestation efforts and identify locations where future plantations can potentially survive wildfires. Study Implications This study examined wildfire effects on western white pine plantations, with the intention to inform managers where to locate plantations that will be more resistant to wildfires and determine which plantations may require postfire reforestation. Plantations were more resilient and resistant to wildfires when they occurred on lower slopes, even when steep, indicating these places may be better suited for future plantations. Plantations located on upper slopes and ridges are vulnerable to wildfire even when located on moist habitat types and will likely need reforestation.

Changes in Woody Vegetation over 31 Years in Farmed Parkland of the Central Plateau, Burkina Faso

Farmed parklands of the Central Plateau, Burkina Faso, integrate native woody vegetation with managed cropland. However, sapling survival in the parklands is increasingly threatened. This study characterized woody vegetation abundance along a 2.7 km long transect in the Doulou Basin, Boulkiemdé Province, Central West Region, to assess changes in vegetation composition since 1984. In addition, a householder survey was conducted to gain insight into tree uses and preferences and residents’ knowledge of regulations. In total, 4999 individuals from 26 tree species were recorded, including 123 individuals (11 species) with stem DBH ≥ 5 cm, and 4876 individuals (21 species) with stem DBH < 5 cm. The three species with the highest importance value index provided fruit for sale or self-consumption. Tree abundance was associated with soil type and topography; highest abundance was on Lixisol soils along the lower transect. Soil degradation and preference changes among residents since 1984 may have influenced tree abundance. Certain beneficial species (e.g., Vitellaria paradoxa) have declined in abundance, and certain exotics (Azadirachta indica and Eucalyptus camaldulensis) have expanded in distribution. Respondents expressed strongest interest in three species, including V. paradoxa, that show high versatility. These results supported the recorded tree composition. The respondents generally understood forest conservation regulations. Dissemination of regreening technology and awareness promotion among residents is essential for sustainable tree use in farmed parklands.

Effect of proximity of buloke (Allocasuarina luehmannii) trees on buloke early sapling survival in a semiarid environment

Agricultural intensification has led to the dramatic decline of buloke (Allocasuarina luehmannii) and the plant communities it dominates in southern Australia. Conservation of remnant buloke woodlands and revegetation of agricultural land are both required for the persistence and improved ecological function of this threatened community. We examined the effect of proximity of mature buloke trees on early sapling survival, to provide guidelines for revegetation aimed at enhancing degraded remnants. We planted buloke saplings at different distances from the base of remnant mature trees at a site in western Wimmera, Victoria, with and without herbaceous competition. Mature buloke trees altered most soil nutrients (positively), soil water content (negatively) and soil conductivity (positively) at different gradients from the tree base, depending on the factor measured. Mature buloke trees had a strong negative effect on conspecific sapling survival in the first summer after planting in both the presence and absence of an herbaceous understorey, possibly because of the strong effect of trees on soil moisture. Competition from mature buloke was high nearest to the trees (up to 9 m from tree base), but competition from the native understorey also appeared important for saplings in the tree gaps, as evidenced by their improved survival when the understorey was removed. We suggest that to establish buloke saplings in areas where mature trees already occur (i.e. enhancement plantings around isolated paddock trees), planting tubestock outside the canopy of mature buloke is necessary to enhance establishment success.