Differences in C, N, δ13C and δ15N among plant functional types after a wildfire in a black spruce forest, interior Alaska

We measured differences in %C, %N,  13C and  15N of plant functional types 17 (PFTs) between burned and unburned ground surfaces soon after a wildfire on a north-18 facing slope in interior Alaska. The C and N were measured for 16 species and 19 Sphagnum litter.  13C differed among the PFTs and was low for trees and shrubs, 20 suggesting that woody stems slowed C dynamics or showed low water use efficiency. 21  15N concentrations suggested that the herbaceous plants depended less on the 22 mycorrhizal associations that became weak on the burned surfaces. The shrub leaves 23 showed the lowest  15N of PFTs and showed higher  15N on the burned surface, showing 24 that N transfer from the soils to the leaves in the shrubs was slowed by the wildfire. 25 Mosses showed the highest C/N ratio. Sphagnum litter decomposed faster on the burned 26 surface, and %N and  15N in the litter increased from the second to third year on both 27 burned and unburned surfaces, while %C changed little. In conclusion, the responses to 28 the wildfire differed among the PFTs as characterized by their C and N dynamics. 29 30 Key words: Burned and unburned ground surface, carbon (C) and nitrogen (N), Alaskan 31 taiga, plant functional type, stable isotope

Mammoth Ivory Rods in Eastern Beringia: Earliest in North America

The Holzman archaeological site, located along Shaw Creek in interior Alaska, contained two mammoth ivory rods, of which one is bi-beveled, within a stratigraphically sealed cultural context. Dated 13,600–13,300 cal BP, these are the earliest known examples of osseous rod technology in the Americas. Beveled ivory, antler, and bone rods and points share technological similarities between Upper Paleolithic Europe, Asia, eastern Beringia, and the Clovis tradition of North America and are important tool types in understanding the late Pleistocene dispersal of modern humans. The Holzman finds are comparable to well-known Clovis tradition artifacts from Anzick (Montana), Blackwater Draw (New Mexico), East Wenatchee (Washington), and Sherman Cave (Ohio). We describe these tools in the broader context of late Pleistocene osseous technology with implications for acquisition and use of mammoth ivory in eastern Beringia and beyond.

Sources and Sinks of Carbon in Boreal Ecosystems of Interior Alaska : A Review

Boreal ecosystems store large quantities of carbon but are increasingly vulnerable to carbon loss due to disturbance and climate warming. The boreal region in Alaska and Canada, largely underlain by discontinuous permafrost, presents a challenging landscape for itemizing carbon sources and sinks in soil and vegetation. The roles of fire, forest succession, and the presence/absence of permafrost on carbon cycle, vegetation, and hydrologic processes have been the focus of multidisciplinary research in boreal ecosystems for the past 20 years. However, projections of a warming future climate, an increase in fire severity and extent, and the potential degradation of permafrost could lead to major landscape and carbon cycle changes over the next 20 to 50 years. To assist land managers in interior Alaska in adapting and managing for potential changes in the carbon cycle, this paper was developed incorporating an overview of the climate, ecosystem processes, vegetation, and soil regimes. The objective is to provide a synthesis of the most current carbon storage estimates and measurements to guide policy and land management decisions on how to best manage carbon sources and sinks. We provide recommendations to address the challenges facing land managers in efforts to manage carbon cycle processes. The results of this study can be used for carbon cycle management in other locations within the boreal biome which encompasses a broad distribution from 45° to 83° north.

Assessing Wildfire Burn Severity and Its Relationship with Environmental Factors: A Case Study in Interior Alaska Boreal Forest

In recent years, there have been rapid improvements in both remote sensing methods and satellite image availability that have the potential to massively improve burn severity assessments of the Alaskan boreal forest. In this study, we utilized recent pre- and post-fire Sentinel-2 satellite imagery of the 2019 Nugget Creek and Shovel Creek burn scars located in Interior Alaska to both assess burn severity across the burn scars and test the effectiveness of several remote sensing methods for generating accurate map products: Normalized Difference Vegetation Index (NDVI), Normalized Burn Ratio (NBR), and Random Forest (RF) and Support Vector Machine (SVM) supervised classification. We used 52 Composite Burn Index (CBI) plots from the Shovel Creek burn scar and 28 from the Nugget Creek burn scar for training classifiers and product validation. For the Shovel Creek burn scar, the RF and SVM machine learning (ML) classification methods outperformed the traditional spectral indices that use linear regression to separate burn severity classes (RF and SVM accuracy, 83.33%, versus NBR accuracy, 73.08%). However, for the Nugget Creek burn scar, the NDVI product (accuracy: 96%) outperformed the other indices and ML classifiers. In this study, we demonstrated that when sufficient ground truth data is available, the ML classifiers can be very effective for reliable mapping of burn severity in the Alaskan boreal forest. Since the performance of ML classifiers are dependent on the quantity of ground truth data, when sufficient ground truth data is available, the ML classification methods would be better at assessing burn severity, whereas with limited ground truth data the traditional spectral indices would be better suited. We also looked at the relationship between burn severity, fuel type, and topography (aspect and slope) and found that the relationship is site-dependent.