Wildfire frequency and extent is increasing throughout the boreal forest-tundra ecotone as climate warms. Overall, these results help link life history characteristics, such as reproductive maturity, to variation in post-fire recruitment of dominant serotinous conifers. We suggest that the higher reproductive efficiency of jack pine can explain the greater resilience of this species to wildfire compared with black spruce. We examined the reproductive efficiency i.e., the number of seedlings recruited per reproductive tree, linking pre-fire reproductive maturity of recently burned stands and post-fire seedling recruitment (recorded up to 4 years after the fires) and found that a reproductive jack pine can recruit on average three times more seedlings than a reproductive black spruce. Number of reproductive jack pine trees increased where soils were shallower. The number of reproductive black spruce trees increased with deeper soils, whereas the more » The harsh climatic conditions present at these higher latitudes, however, limited the recruitment of jack pine at the treeline ecotone. The number of reproductive trees per plot increased with stem density, basal area, and at higher latitudes (colder locations). Our results show that reproductive maturity was triggered by a minimum tree size threshold rather than an age threshold, with trees reaching reproductive maturity at smaller sizes where environmental conditions were more stressful. Presence or absence of female cones were recorded in approximately 15,000 individuals within old and recently burned stands in two distinct ecozones of the Northwest Territories (NWT), Canada.
Phillips ecotone drivers#
Here, we assessed the drivers of reproductive maturity in two dominant and widespread conifers, semi-serotinous black spruce and serotinous jack pine. Improved understanding of the drivers of reproductive maturity can provide important information about the capacity of these forests to self-replace following fire. For these forests, reductions in fire return interval could limit reproductive success, owing to insufficient time for stands to reach reproductive maturity i.e., to initiate cone production. In addition to climate, the effects of anthropogenic disturbances on subalpine forests should be considered in adaptive forest management and in projections of future forest changes.In boreal North America, much of the landscape is covered by fire-adapted forests dominated by serotinous conifers. In the future, broadleaved forests could expand more rapidly than evergreen needle-leaved forests under moderate warming scenarios. Shifts in these foundation species will have profound impacts on ecosystem functions and services. Thus, moderate disturbances shifted forest composition through a gradual loss of resilience of spruce-fir forests. By strongly altering site conditions, disturbances in concert with climate warming reshuffle community composition to warm-adapted broadleaf-pine species. Such a turnover in species composition mainly occurred in the 1994–1998 period. Based on the analysis of 3145 forest inventory plots at 4- to 5-year resolution, we found that spruce-fir forests shifted to pine and broadleaved forests since the early 1970s. Thus, they provide an excellent setting to test whether disturbances and climate warming led to changes in forest structure. Before the 1970s, subalpine forests on the southeastern Qinghai-Tibet Plateau mainly experienced logging and fire, but afterwards they were more impacted by climate warming. Despite vulnerability of subalpine forests to warming climate, little is known as to how their community composition has responded to disturbances and climate warming over decades. A better understanding of the structure and dynamics of disturbed forests is key for forecasting their future successional trajectories.
0 kommentar(er)
