Post-fire peatland vegetation recovery: A case study in open rich fens of the Canadian boreal forest

Fire plays a major role in structuring and the functioning of boreal ecosystems. As peatlands are important components of boreal forests, the impact of fire upon these wetter ecosystems is increasingly studied, but with the main focus on treed peatlands and Sphagnum-dominated bogs so far. Important fires occurring more frequently in the past decade in southern Northwest Territories (Canada) provide the opportunity to assess early post-fire vegetation regeneration in open rich fens (1, 2 and 5-years post-fire) and to better understand early recovery succession. We aimed to 1) evaluate whether and how open rich fens are affected by fire 2) describe short-term vegetation regeneration, for both bryophytes and vascular species. A shift was observed between pioneer bryophytes and brown mosses between the second and fifth-year post-fire. Vascular plants, especially slow-growing species and the ones reproducing mainly by seeds, recovered partially. The first bryophyte species recovering were pioneer species adapted to colonize burned environment such as Marchantia polymorpha or Ceratodon purpureus. For vascular plant species, the ones previously present and capable to regrowth rapidly from unburned plant structures (base of tussocks, rhizomes, roots) were represented by species like Betula glandulosa or Carex aquatilis. The wetter conditions and lower fuel availability of fen depressional biotopes were important factors controlling the resistance and regeneration of species associated with them.

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.

Changes in global terrestrial live biomass over the 21st century

Live woody vegetation is the largest reservoir of biomass carbon, with its restoration considered one of the most effective natural climate solutions. However, terrestrial carbon fluxes remain the largest uncertainty in the global carbon cycle. Here, we develop spatially explicit estimates of carbon stock changes of live woody biomass from 2000 to 2019 using measurements from ground, air, and space. We show that live biomass has removed 4.9 to 5.5 PgC year−1 from the atmosphere, offsetting 4.6 ± 0.1 PgC year−1 of gross emissions from disturbances and adding substantially (0.23 to 0.88 PgC year−1) to the global carbon stocks. Gross emissions and removals in the tropics were four times larger than temperate and boreal ecosystems combined. Although live biomass is responsible for more than 80% of gross terrestrial fluxes, soil, dead organic matter, and lateral transport may play important roles in terrestrial carbon sink.

Assessment of spatiotemporal patterns of gross primary productivity in the arctic and boreal ecosystems using multi-source products

<p>Since an increasing number of global gross primary productivity (GPP) products have become available and been applied in climate change research, there is an urgent need to compare their performance in capturing spatial and temporal variability, especially in the regions where the number of training data is limited or model parameters are of relatively larger uncertainty. Here, we investigated the spatial patterns of interannual trends and variations, and seasonal-cycle amplitudes of GPP in the arctic and boreal zones, and explored the differences across various GPP products during the overlapping period (2000−2010). We compared three main types of state-of-the-art GPP products, including simulations derived from terrestrial biosphere models of the Multi-scale Synthesis and Terrestrial Model Intercomparison Project using drivers under different scenarios, 3 datasets up-scaled from FLUXNET eddy covariance measurements based on machine-learning algorithms, and 2 semi-empirical or empirical remotely sensed products based on different satellite data. We also examined the differences of GPP variability across the main ecosystem types, mainly including tundra and taiga, and assessed the contributions of different ecosystems to the temporal variations of total GPP in this zone. The results showed all the products could capture the interannual and seasonal variability of GPP, but the spatial patterns varied largely, which was in-deep discussed. This study will benefit the usage of the GPP products in the carbon cycle research for the arctic and boreal ecosystems.</p>

Organic nitrogen nutrition: LHT1.2 protein from hybrid aspen (Populus tremula L. x tremuloides Michx) is a functional amino acid transporter and a homolog of Arabidopsis LHT1

The contribution of amino acids (AAs) to soil nitrogen (N) fluxes is higher than previously thought. The fact that AA uptake is pivotal for N nutrition in boreal ecosystems highlights plant AA transporters as key components of the N cycle. At the same time, very little is known about AA transport and respective transporters in trees. Tree genomes may contain thirteen or more genes encoding the LYSINE HISTIDINE TRANSPORTER (LHT) family proteins, and this complicates the study of their significance for tree N use efficiency. With the strategy of obtaining a tool to study N use efficiency, our aim was to identify and characterize a relevant AA transporter in hybrid aspen (Populus tremula L. x tremuloides Michx.). We identified PtrLHT1.2, the closest homolog of Arabidopsis thaliana AtLHT1, which is expressed in leaves, stems and roots. Complementation of a yeast AA uptake mutant verified the function of PtrLHT1.2 as an AA transporter. Furthermore, PtrLHT1.2 was able to fully complement the phenotypes of the Arabidopsis AA uptake mutant lht1 aap5, including early leaf senescence-like phenotype, reduced growth, decreased plant N levels and reduced root AA uptake. AA uptake studies finally showed that PtrLHT1.2 is a high affinity transporter for neutral and acidic AAs. Thus, we identified a functional AtLHT1 homolog in hybrid aspen, which harbors the potential to enhance overall plant N levels and hence increase biomass production. This finding provides a valuable tool for N nutrition studies in trees and opens new avenues to optimizing tree N use efficiency.