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In recent decades, global warming and nitrogen (N) deposition have been increasing obviously, which have led to some strong responses in terrestrial ecosystems, especially the carbon (C) cycle. The boreal forest occupies an important position in the global C cycle with its huge C storage. However, the impact of global change such as N deposition on boreal forest ecosystem C cycle has been not very clear. In order to solve this problem, the field experiment of N addition in a boreal forest has been built in the Greater Khingan Mountains of Northeast China since 2011. Four N addition gradients (0, 25, 50, 75 kg N ha−1 year−1) were set up to study the response of above- and belowground C pool to N addition. The results showed that the total forest C sequestration of low-, medium- and high-N treatments was 104.4 ± 5.9, 20.2 ± 2.7 and 5.3 ± 0.4 g C/g N, respectively. Aboveground trees were the largest C pool, followed by soil, roots and floor C pool. Low-N increased the input of C by promoting photosynthesis. Trees of Larix gmelini increased the investment in the belowground root system and increased the belowground C pool. High-N reduced the inter-annual litter biomass and decreased litter C:N that accelerated the decomposition of litter, resulting in a reduction in the floor C pool. Low-N increased total soil respiration, while medium- and high-N inhibited heterotrophic respiration and then increased soil C sequestration. The estimation of forest C pool provides valuable data for improving the C dynamic characteristics of boreal forest ecosystem and is of great significance for us to understand the impact of climate change on the global C cycle.

The adaptive capacity of boreal tree species to thrive in a warming, more variable climate has significant implications for boreal forest ecosystem structure and function. Dendrochronological and other empirical data indicate reduced growth and increased mortality of white spruce (Picea glauca [Moench] Voss) growing in warmer, drier portions of its natural range in western North America due to recent climate change. Comparatively, little is known of potential climate change effects on white spruce in the more mesic, eastern portion of its range where mean annual precipitation is relatively high. In this study, we examined the potential long-term consequences of climate warming on annual rates of mortality and height growth of mature white spruce by substituting space for time using data from 10, 31- to 40-year-old large common garden experiments (CGEs) established in Ontario, Canada. Across these CGEs, white spruce was exposed to differences of up to 5.0 °C in mean annual temperature and 405 mm in mean annual precipitation. During a 12- to 16-year measurement interval, mortality increased from the colder, more northern CGEs to the warmer CGEs near the species’ southern range margin. Along this climatic gradient, white spruce was also exposed to more frequent, severe growing season moisture deficits, with southern CGEs sometimes subject to extreme drought events with a low probability based on historical occurrence. Our results indicate that the severity of recent growing season drought events at more southern CGEs may have exceeded the drought tolerance capacity of white spruce and resulted in significantly increased mortality and reduced height growth rates. These results suggest that with projected increases in temperature and frequency/severity of growing season drought by the end of this century, white spruce is likely to experience maladaptation over a larger portion of its range in Ontario and gradually retract from its current southern range edge.

Forest management strongly influences the carbon (C) budget of boreal forests and their potential to mitigating greenhouse gas emissions. A better quantification of the net changes of carbon pools with time since harvesting is necessary to guide the development of climate-friendly forest management practices. The objective of this study was to assess the evolution of forest C pools, with a special focus on detrital biomass, in an 80-year post-harvesting chronosequence consisting of 36 very homogenous stem-only harvested plots from a humid boreal balsam fir forest of eastern Canada. Dead wood C stocks comprised of snags, stumps, downed woody debris and buried wood averaged 37 Mg C ha−1 and evolved according to an upward-facing «boomerang» shape pattern throughout the chronosequence (rapid decrease in the first years followed by a constant increase until the end of the time horizon). In contrast, soil C stocks (FH and mineral) averaged 156 Mg C ha−1 and remain constant through time. Stand C sequestration increased rapidly in the early stages up to age 50 when it reached about 250 Mg C ha−1, and then continued to accumulate at a slower rate. The temporal trends observed in C pools suggest that C originating from aboveground dead wood (snags, stumps, downed woody debris) is either leaving the system (respired or leached) or transferred into buried wood, and does not appear to influence the C stocks of the fine fraction of the organic and mineral soil horizons. However, the ultimate fate of dead wood C is still poorly understood and further research is needed in this field. We recommend fixing the length of harvest rotation at a minimum of 50 years for this ecosystem to allow the build-up of its dead wood capital, and to promote dead wood retention on site. We also recommend including buried wood in carbon inventories as this pool represents an important share of the detrital C stock in these humid boreal forests.

Fire severity affects both ecosystem N-loss and post-fire N-balance. Climate change is altering the fire regime of interior Alaska, although the effects on Siberian alder (Alnus viridis ssp. fruticosa) annual N-fixation input (kg N ha-1 yr-1) and ecosystem N-balance are largely unknown. We established 263 study plots across two burn scars within the Yukon-Tanana Uplands ecoregion of interior Alaska. Siberian alder N-input was quantified by post-fire age, fire severity, and stand type. We modeled the components of Siberian alder N-input using environmental variables and fire severity within and across burn scars and estimated post-fire N-balance using N-loss (volatilized N) and N-gain [biological N-fixation and atmospheric deposition]. Mean nodule-level N-fixation rate was 70% higher 11-years post-fire (12.88 ± 1.18 μmol N g-1 hr-1) than 40-years post-fire (7.58 ± 0.59 μmol N g-1 hr-1). Structural equation modeling indicated that fire severity had a negative effect on Siberian alder density, but a positive effect on live nodule biomass (g nodule m-2 plant-1). Post-fire Siberian alder N-input was highest in 11-year old moderately burned deciduous stands (11.53 ± 0.22 kg N ha-1 yr-1), and lowest in 11-year old stands that converted from black spruce to deciduous dominance after severe fire (0.06 ± 0.003 kg N ha-1 yr-1). Over a 138-year fire return interval, N-gains in converted black spruce stands are estimated to offset 15% of volatilized N, whereas N-gains in burned deciduous stands likely exceed volatilized N by an order of magnitude. High Siberian alder density and nodule biomass drives N-input in burned deciduous stands, while low N-fixer density (including Siberian alder) limits N-input in high severity black spruce stands not underlain by permafrost. A severe fire regime that converts black spruce stands to deciduous dominance without alder recruitment may induce progressive N-losses which alter boreal forest ecosystem patterns and processes.

Boreal forests provide important ecosystem services, most notably being the mitigation of increasing atmospheric CO2 emissions. Microbial biodiversity, particularly the local diversity of fungi, has been shown to promote multiple functions of the boreal forests of Northeastern China. However, this microbial biodiversity-multifunctionality relationship has yet to be explored in Northeastern Canada, where historical environment have shaped a different regional pool of microbial diversity. This study focuses on the relationship between the soil microbiome and ecosystem multifunctionality, as well as the influence of pH and redox potential (Eh) on the regulation of such relationship. Structural equation modelling (SEM) was used to explore the different causal relationships existing in the studied ecosystems. In a managed part of the Canadian boreal forest, 156 forest polygons were sampled to (1) estimate the &alpha, and &beta, diversity of fungal and bacterial communities and (2) measure 12 ecosystem functions mainly related to soil nutrient storage and cycling. Both bacteria and fungi influenced ecosystem multifunctionality, but on their own respective functions. Bacterial &beta, diversity was the most important factor increasing primary productivity and soil microbial biomass, while reducing soil emitted atmospheric CO2. Environmental characteristics, particularly low levels of organic matter in soil, were shown to have the strongest positive impact on boreal ecosystem multifunctionality. Overall, our results were consistent with those obtained in Northeastern China, however, some differences need to be further explored especially considering the history of forest management in Northeastern Canada.

In the face of increasing temperature at high latitudes, ecosystem respiration (RE) is a key to determining sink and source dynamics of a boreal forest. In this paper, we analyzed four-year RE data obtained in an open black spruce forest—a typical boreal forest ecosystem with permafrost in Interior Alaska. RE measured as nighttime CO2 effluxes for both the ecosystem and the forest floor were clearly situated along the exponential temperature-dependent curve, except for the data obtained in extremely dry conditions in mid-summer. More than 93 % of RE data measured at nighttime with high vapor pressure deficit (VPD > 400 Pa) were lower than the values predicted from the temperature-dependent curve. Consequently, the year 2013 (with an unusually dry summer) had a 15 % lower amount of annual RE than that could be expected from the temperature-dependent curve without considering the effect of high VPD. The suppression of RE under dry conditions was also related to decreases in soil moisture and net ecosystem productivity. Finally, assuming daytime RE could be extrapolated from the temperature-dependent curves, annual daytime RE estimated with the effect of high VPD was decreased by up to 62% from RE estimated without the VPD effect. The down-regulation of RE presented in this study postulates a possible negative feedback for the carbon budget of boreal forests in response to climate warming.

The gross primary productivity (GPP) is the largest carbon flux in the terrestrial carbon cycle. Constraining GPP is critical for understanding the terrestrial carbon sources and sinks. In this study, we attempted to constrain the terrestrial GPP at regional to global scales through optimizing the key photosynthetic parameter (the carboxylation capacity at 25 °C, V c m a x 25 ) using solar-induced chlorophyll fluorescence (SIF) observations from the Orbiting Carbon Observatory-2 (OCO-2). The optimization was made within the Global Carbon Assimilation System (GCAS), in which the Boreal Ecosystem Productivity Simulator (BEPS) model was used to simultaneously simulate the global GPP and SIF in the process-based manner. Optimized V c m a x 25 shows a distinguishable spatial pattern, with the largest values over the crop regions. After optimization, V c m a x 25 of crop is significantly increased. Importantly, the optimized V c m a x 25 of different plant functional types (PFTs) show unambiguous seasonal variations. With these optimized V c m a x 25 , the simulated global GPP in 2015–2016 amounts to 119.1 PgC yr−1, close to the median value (121.3 PgC yr−1) of the observation-based estimates. Global GPP decreases by 8.3% relative to the value simulated using prior V c m a x 25 . In detail, GPP of crops increases by 16.4%, but it decreases over the other PFT regions, ranging from −4.4% over grasses to −34.0% over deciduous needleleaf forests. The spatiotemporal variations in the optimized PFT-dependent V c m a x 25 also reshape the seasonal cycle in GPP. We regard that it is an effective pathway to constrain GPP based on the satellite SIF and the process-based assimilation system, which can provide us an opportunity to better understand the terrestrial and global carbon cycle.

The understory plants of the boreal forests have evolved divergent strategies to succeed under low nitrogen conditions, with their ability to respond to nitrogen addition varying greatly. We examined the response of 5 key understory North American boreal forest species in the Yukon (4 shrubs and a herb) to low levels of nitrogen that could occur from natural pulses and to high levels that could occur because of anthropogenic deposition from either atmospheric deposition or as a management strategy to increase tree growth. We fertilized 240 one m2 plots for the three dwarf shrubs and one herb and 60 three m2 plots for one tall shrub at 0, 0.5, 1.0, 2.0, 4.0, and 17.5 g nitrogen/m2 in June 2004 and May 2005. We measured changes in cover, growth, leaf metrics, and berry production in three dwarf shrubs (Arctostaphylos rubra [deciduous] and A. uva-ursi and Empetrum nigrum [both evergreen]), one herb (Geocaulon lividum), and one tall shrub (Shepherdia canadensis). We predicted the first three would be strongly affected by variation in nitrogen levels but that neither Geocaulon (a hemi-parasite) nor Shepherdia (a nitrogen fixer) would be. To examine for long-term effects of nitrogen application, we also fertilized four 2.8 ha plots in 2004 and 2005 with 1.0 and 2.0 g/m2 and then measured berry production in 2006 and 2007 on the two Arctostaphylos species. Nitrogen addition at all levels had no effect on either Geocaulon or Shepherdia. There were general positive effects at low nitrogen levels and negative ones at high levels on the other 3 dwarf shrub species in a species-specific manner. There were marked year effects in some plant growth metrics and in berry production, emphasizing the role of climate, but also clear evidence that individual species tradeoff somatic growth for reproduction. There was a pronounced long-term negative effect of low nitrogen addition on the large plots, causing marked reductions in berry production in both Arctostaphylos species. We conclude that these dwarf shrubs are constrained to function optimally within a narrow range of nitrogen levels normally encountered, but are unable to cope with higher levels. Both Geocaulon and Shepherdia function independently of nitrogen limitation. Thus the life history adaptations of these understory plants to variation in nitrogen levels are species-specific and understanding their individual responses is key in predicting their fate and the biodiversity and organization of boreal forest ecosystem when challenged with higher anthropogenic levels of nitrogen.

Anthropogenic activities profoundly influence carbon sequestration in the Eurasian Steppe. In particular, grazing has been identified as having a major effect on carbon sequestration. However, the extent to which grazing affects regional patterns or carbon sequestration is unknown. In this study, we evaluated the impact of regional grazing on grassland carbon sequestration using the Boreal Ecosystem Productivity Simulator (BEPS) and the Shiyomi grazing model. Model performances were validated against the results from field measurements and eddy covariance (EC) sites. Model outputs showed that in 2008, the regional net primary productivity (NPP) was 79.5 g C m −2 , and the net ecosystem productivity (NEP) was −6.5 g C m −2 , characterizing the region as a weak carbon source. The Mongol Steppe (MS) was identified as a carbon sink, whereas the Kazakh Steppe (KS) was either carbon neutral or a weak carbon source. The spatial patterns of grazing density are divergent between the MS and the KS. In the MS, livestock was mainly distributed in China with relatively good management, while in the KS livestock was mainly concentrated in the southern countries (especially Uzbekistan and Turkmenistan) with harsh environments and poor management. The consumption percentages of NPP in Turkmenistan, Tajikistan and Uzbekistan were 5.3, 3.3 and 1.2%, respectively, whereas the percentages in other countries were lower than 1%. Correspondingly, grazing consumption contributed to the carbon sources of Turkmenistan, Tajikistan and Uzbekistan by 11.6, 6.3 and 4.3%, respectively, while it weakened the carbon sink in Inner Mongolia, China and Mongolia by 1.6 and 0.5%. This regional pattern should be affected by different sub-regional characteristics, e.g., the continuous degradation of grassland in the southern part of the KS and the restoration of grassland in Inner Mongolia, China.

In an effort to ensure the sustainability of their forests, boreal forest managers often use forest planning models to make future projections of timber supply and other key services, such as habitat for wildlife. Projecting the fate of these services has proven to be challenging, however, as major uncertainties exist regarding the principal drivers of boreal ecosystem dynamics, including the future spatial and temporal distribution of wildfire and timber harvesting. Existing forest planning models are not well suited to dealing with this uncertainty because they produce deterministic projections based on central tendencies of these drivers. Here we present a new approach for incorporating uncertainty into forest management planning, which we demonstrate using two landscapes in the Canadian boreal forest. Our approach takes the assumptions contained within the latest forest management plans for each of these landscapes, including parameterizations of their deterministic forest planning models, and converts these assumptions into equivalent parameterizations of a stochastic, spatially-explicit state-and-transition simulation model (STSM). We then use Monte Carlo simulations with the STSM to “stress-test” the forest management plan with respect to a range of possible future uncertainties, including uncertainties in future levels and patterns of wildfire and timber harvest, along with the possible changes in wildfire that might result from future climate change. Our analysis demonstrates the importance of incorporating stochastic variability into projections of future ecosystem condition. The STSM projections that acknowledged variability in wildfire and timber harvest differed from the deterministic forest planning model projections that were based solely on mean values. Our analysis also suggests that there is an increased risk of shortfalls in timber harvest, for both boreal landscapes, associated with future projections for changes in wildfire due to climate change, and that management strategies aimed at reducing the future level of timber harvest offer an opportunity to mitigate these risks. We believe our approach provides a new risk-based framework for incorporating uncertainty into forest management, including the effects of climate change.

Bamboo forests are widely distributed in the tropical and sub-tropical regions, and have a great carbon sequestration capacity. However, the carbon dynamics of bamboo forest are still poorly understood. This study developed an algorithm for assimilating LAI dynamics based on an integrated ensemble Kalman filter using MODIS LAI data, MODIS reflectance data, and canopy reflectance data modeled by PROSAIL for two typical bamboo forests. The assimilated LAI was highly consistent with the observed LAI, yielding correlation coefficient ( r ) of 0.84 and 0.94 for Moso bamboo forest and Lei bamboo forest, respectively. Then, the spatiotemporal pattern of the CO 2 fluxes within bamboo forest were modeled for Zhejiang Province during 2011–2014 using the Boreal Ecosystem Productivity Simulator model driven by assimilated LAI. The modeled CO 2 fluxes were in agreement with the CO 2 fluxes measured by eddy covariance technology at two selected sites within the study region. Average r , absolute deviation, and root mean square error values were 0.77, 0.65 g C m −2 day −1 , and 0.82 g C m −2 day −1 , respectively. Bamboo stands with high Net Ecosystem Exchange (NEE) values were found to be distributed throughout mountainous areas in the northwest, southwest, and northeast of Zhejiang, while low NEE stands were located in the mountain basin areas, high altitude areas, and the majority of coastal areas. Among the eleven cities in Zhejiang Province, Hangzhou was the highest annual total NEE city (0.34 ± 0.06 Tg C yr −1 ), and Huzhou was the highest NEE density city (7.65 ± 1.02 Mg C hm −2 yr −1 ). The carbon sequestrated by bamboo forest was 1.74 Tg C yr −1 , accounted 6.36 Tg CO 2 yr −1 , which indicated the bamboo forested area in Zhejiang Province was a carbon sink. The spatial heterogeneity of CO 2 fluxes of bamboo forest can be revealed by an exponential semivariance model. The analysis of the model structure indicated that the spatial heterogeneity of CO 2 fluxes of bamboo forest was characterized by significant autocorrelation, with an average autocorrelation range of 3.00 km, however the effect of random factors (management levels, management measures, etc .) cannot be ignored. This is the first time that the CO 2 fluxes of bamboo forest in Zhejiang Province have been mapped and this study provides a new estimate of CO 2 fluxes in this region.

In this study, high quality soil moisture data derived from the Soil Moisture Active Passive (SMAP) satellite measurements are evaluated from a perspective of improving the estimation of the global Gross Primary Production (GPP) using a process-based ecosystem model, namely the Boreal Ecosystem Productivity Simulator (BEPS). The SMAP soil moisture data are assimilated into BEPS using an Ensemble Kalman Filter. The correlation coefficient (r) between simulated GPP from the sunlit leaves and Sun-Induced chlorophyll Fluorescence (SIF) measured by Global Ozone Monitoring Experiment–2 (GOME-2) is used as an indicator to evaluate the performance of the GPP simulation. Areas with SMAP data in low quality (i. e. forests), or with SIF in low magnitude (e. g. deserts) or both are excluded from the analysis. With the assimilated SMAP data, the r value is enhanced for Africa, Asia, and North America by 0.016, 0.013, and 0.013, respectively (p

Boreal forest ecosystems are experiencing changes in plant productivity that are likely to continue with ongoing climate change. Transpiration (T) and canopy stomatal conductance (gc) are a key influence on plant productivity, and a better understanding of drivers and limitations of T and gc is necessary for constraining estimates of boreal ecosystem change. We describe patterns in T and gc of a deciduous conifer, Larix cajanderi, in an arctic boreal forest in northeastern Russia across three growing seasons from 2013 to 2015. We examine the influence of environmental drivers on gc using a phenomenological model. T was highly variable across days and varied between 0.03 and 0.75 L m−2 d−1. T and gc largely covaried with daily fluctuations in air temperature and vapor pressure deficit. gc was highly suppressed on days when the vapor pressure deficits exceeded 0.75 kPa with an average daily gc of 37.55 mmol m−2 s−1, and the average daily gc was almost double (71.25 mmol m−2 s−1) when vapor pressure deficits stayed below 0.75 kPa. Daily variation in gc was significantly related to air temperature, permafrost thaw depth, and past precipitation. The influence of past precipitation and permafrost thaw depth on gc indicates that belowground conditions relating to soil moisture status are a key limitation for T. Such limitations on gc and T suggest that soil water and plant water stress play an important role in plant productivity and water relations in far northeastern Siberia.

The forests of Newfoundland represent a unique type of boreal ecosystem with diverse environmental gradients that exercise strong control over disturbances and vegetation. We have assembled and analyzed a comprehensive database on disturbance history in Newfoundland. Defoliating insects, led by the eastern spruce budworm (Choristoneura fumiferana Clemens) and the hemlock looper (Lambdina fiscellaria Guenée), have the largest disturbance footprint on the island. Infrequent wildfires (fire cycle = 769 years) had a decisive role in driving forest succession, particularly in the Central Newfoundland Forest and Maritime Barrens ecoregions. We hypothesize that the historical disturbance regime in Newfoundland would not have enabled steady-state conditions, although the amount of old-growth forests and deadwood would likely have been greater than it is today. We argue that the implementation of the natural range of variation (NRV) concept in forest management for such non-equilibrium systems will be challenging in Newfoundland and in other regions of Canada. We propose guiding principles to adapt the NRV concept using ecological knowledge. If a sciencebased approach is desired, assumptions about NRV should be tested using a rigorous experimental design. We encourage the establishment of large-scale experiments in at least a portion of forestry operations to enable an ecosystem sciencebased approach.

Climate change and global wood products demand raise concerns about boreal forest ecosystem resilience to natural disturbances and harvesting. A chronosequence experiment located in Foret Montmorency, Quebec was used to evaluate the effects of harvesting on carbon (C) recovery trajectories at the stand level over a period of 77 years in balsam fir-white birch stands. Empirical estimates of 19 Foret Montmorency forest carbon pools were compared with those simulated by the Carbon Budget Model (CBM-CFS3) to test model assumptions for predicting carbon dynamics in this forest. The model was initialized using forest inventory data, spatially explicit environmental conditions, and disturbance matrices designed to represent historical spruce budworm epidemics in Foret Montmorency. Over the chronosequence, total ecosystem C increased significantly (p = 0.05) following harvest from 211 Mg in year-zero to 279 ± 8 Mg C ha⁻¹ in year 67 (mean ± SE), suggesting that FM carbon pools were recovering to pre-harvest levels after seven decades. The CBM-CFS3 model predicted total ecosystem C stocks within 10% of the empirical mean at stand maturity; however, several predicted C pools deviated from field observations in both C amounts and trends over time. The greatest differences were in deadwood and soil C pools, suggesting that model initialization of dead organic matter pools did not adequately simulate the 1000-yr history of C-pool transfers and stand dynamics leading up to the harvest. Modifications to CBM-CFS3 initialization assumptions and default decay parameters may more accurately simulate long-term effects of natural disturbances on C pools for this forest region.

In this follow-on study on aboveground biomass of shrubs and short-stature trees, we provide plant component aboveground biomass (herein ‘AGB’) as well as plant component AGB allometric models for five common boreal shrub and four common boreal short-stature tree genera/species. The analyzed plant components consist of stem, branch, and leaf organs. We found similar ratios of component biomass to total AGB for stems, branches, and leaves amongst shrubs and deciduous tree genera/species across the southern Northwest Territories, while the evergreen Picea genus differed in the biomass allocation to aboveground plant organs compared to the deciduous genera/species. Shrub component AGB allometric models were derived using the three-dimensional variable volume as predictor, determined as the sum of line-intercept cover, upper foliage width, and maximum height above ground. Tree component AGB was modeled using the cross-sectional area of the stem diameter as predictor variable, measured at 0.30 m along the stem length. For shrub component AGB, we achieved better model fits for stem biomass (60.33 g ≤ RMSE ≤ 163.59 g, 0.651 ≤ R2 ≤ 0.885) compared to leaf biomass (12.62 g ≤ RMSE ≤ 35.04 g, 0.380 ≤ R2 ≤ 0.735), as has been reported by others. For short-stature trees, leaf biomass predictions resulted in similar model fits (18.21 g ≤ RMSE ≤ 70.0 g, 0.702 ≤ R2 ≤ 0.882) compared to branch biomass (6.88 g ≤ RMSE ≤ 45.08 g, 0.736 ≤ R2 ≤ 0.923) and only slightly better model fits for stem biomass (30.87 g ≤ RMSE ≤ 11.72 g, 0.887 ≤ R2 ≤ 0.960), which suggests that leaf AGB of short-stature trees (&lt, 4.5 m) can be more accurately predicted using cross-sectional area as opposed to diameter at breast height for tall-stature trees. Our multi-species shrub and short-stature tree allometric models showed promising results for predicting plant component AGB, which can be utilized for remote sensing applications where plant functional types cannot always be distinguished. This study provides critical information on plant AGB allocation as well as component AGB modeling, required for understanding boreal AGB and aboveground carbon pools within the dynamic and rapidly changing Taiga Plains and Taiga Shield ecozones. In addition, the structural information and component AGB equations are important for integrating shrubs and short-stature tree AGB into carbon accounting strategies in order to improve our understanding of the rapidly changing boreal ecosystem function.

Remotely sensed solar-induced chlorophyll fluorescence (SIF) has been increasingly used to probe photosynthesis and model the gross primary productivity (GPP). Although SIF at the top of canopy (TOC) can be simulated using the coupled photosynthesis-fluorescence model SCOPE (Soil Canopy Observation, Photochemistry and Energy fluxes), simulating spatially distributed TOC SIF usually requires extensive calculations, entailing some challenges when applying the model to the regional and the global scales. This study puts forward a coupling framework that combines SIF and global terrestrial biosphere models (TBMs). The theory for fluorescence emissions and the fluorescence radiative transfer algorithm described in the SCOPE model were integrated with the “two-leaf”-based BEPS (Boreal Ecosystem Productivity Simulator) model. To simplify the fluorescence radiative transfer physics, we put forward a canopy-averaged leaf-level fluorescence to represent the fluorescence emitted from sunlit and shaded leaf groups and performed a sensitivity analysis to assess the determining factors in upscaling fluorescence from leaf scale to canopy scale. We found that the relationship between the leaf and canopy fluorescence at 740 nm was mainly affected by LAI. Although brown pigments and leaf inclination angle demonstrate some impacts on the scaling process, an LAI-based coefficient can well characterize the upscaling from leaf to canopy scale. Since our BEPS-SCOPE coupling model deploys the sunlit-shaded leaf separation strategy, we expect that it can efficiently characterize the nonlinear responses of photosynthesis and the associated fluorescence to environmental factors. The performance of our model was evaluated at both site and global scales, which demonstrated a good performance for most plant functional types (PFTs) except for needleleaf types that have a more clumped nature. Apart from these limitations, the presented model can contribute to efficiently simulating SIF at regional and global scales, and has the potential to reduce uncertainties in GPP estimation.

Shifts in the climate sensitivity of trees throughout the twentieth century might indicate climate change effects in the boreal forest ecosystem. We here evaluated such potential changes by analyzing six tree-ring width (TRW) and maximum latewood density (MXD) chronologies from northern, central and southern boreal forests in Finland (60°N–69°N). Besides latitudinal effects, differing micro-sites (lakeshore and inland) were considered to evaluate the influence of ground water access on twentieth-century tree-ring formation and climate sensitivity. Overall, the boreal MXD chronologies appeared less affected by micro-site conditions compared to the TRW chronologies. Along the boreal transect, mean growth rates decrease with increasing latitude, but the ratio of earlywood-to-latewood (∼70%/∼30%) remains stable. However, latewood is slightly denser at the dry inland micro-sites. The correlations with climate data showed that TRW and MXD at all sites are positively related with summer temperature. The ...

In forested ecosystems, the aggregation of leaves into different spatial structures at the canopy, branch and shoot scales leads to a non-random spatial distribution of foliar elements. However, effect of foliar aggregation or clumping on the estimation of terrestrial evapotranspiration (ET) is not yet well understood. To evaluate the effect of foliar clumping, the process-based Boreal Ecosystem Productivity Simulator (BEPS) is used to simulate ET at eight flux tower sites in North American forests. BEPS separates a canopy into sunlit and shaded leaf groups in the calculation of canopy-level ET and clumping affects this separation. Three cases are simulated with BEPS, and the modeled ET values are compared with flux tower measurements: Case I serves as a baseline, in which LAI and clumping index at the sites are considered. In this case, BEPS can explain 43–75% the variance of measured ET at these sites. For Case II, the LAI is considered but clumping is ignored; resulting in an overestimation of annual ET at all sites by ∼5% at the most clumped sites. In Case III, when effective LAI is used (i.e. clumping is not considered), the site-averaged mean annual ET is underestimated by 11.5%, with the largest underestimation found at the site with most clumping (CA-DF49; 19.1%). In both Case II and Case III, the more clumped a canopy is, the larger bias is found in the ET estimation ( p These results demonstrate the need for considering foliage clumping in process-based ET modeling, with potential biases having large implications for carbon cycle modeling, water budget calculations and understanding and predicting ecosystem responses to future climatic scenarios.

Boreal ecosystem functioning is largely controlled by disturbance dynamics. There have been efforts at adapting forest management approaches to emulate natural disturbance effects, as this is expected to maintain ecosystem resilience. In many instances, this involves resorting to partial cutting strategies that are likely to increase windthrow losses. The objective of this study was to determine the effects of alternative silvicultural practices on windthrow damage and how these effects vary with the scale of treatment. The study was conducted in the Quebec North Shore region (Canada), an area dominated by balsam fir (Abies balsamea (L.) Mill.) and accompanied by black spruce (Picea mariana (Mill) B.S.P.). Four different silvicultural treatments (overstory removal, heavy partial cutting, and two patterns of selection cutting) and control areas were implemented in 2004 and 2005. The experiment used a nested approach where treatment at the plot level was independent and yet nested within the block-level treatment. At the block level, treatments were applied over 10–20 ha units, leaving a small portion of the block for a smaller application of each treatment (plot scale, 2500 m2). Inventory was carried out before harvesting and monitoring was done yearly after harvesting, with the aim to better understand the plot- and block-level factors that drive windthrow damage levels and the effects of alternative silvicultural treatments. Results after 6–7 years show that basal area proportion windthrown differs substantially between treatments, as well as between treated sites and control sites. Windthrow levels were higher under heavy cuts relative to selection cuts and also increased with balsam fir proportion. Windthrow proportions were better correlated to block-level treatment than plot-level treatment, showing that the environment surrounding the treated plot can have an important effect on windthrow losses. Overall, the selection cutting system, particularly SC2, retains the most green-tree basal area and thus best meets the management objective of retaining old-growth attributes. A simple empirical model was calibrated that could aid in hazard rating.

The accurate quantification of gross primary productivity (GPP) has been a major challenge in global climate change research. Satellite data-driven models have been universally used as scientific tools for investigating the carbon cycle, including vegetation index (VI)-based models, light use efficiency (LUE) models, and process-based models. However, inconsistencies and uncertainties have been found in the GPP estimations from various models. The understanding of model behaviors under different climatic conditions remains unclear. In this study, three typical satellite data-driven models, namely, Moderate Resolution Imaging Spectroradiometer (MODIS) GPP (MOD17) model, Temperature and Greenness (TG) model and Boreal Ecosystem Productivity Simulator (BEPS), respectively, were compared to better understand discrepancies and uncertainties in GPP estimations at 119 northern eddy covariance (EC) sites. Due to the variations in climatic drivers of GPP, temperature, precipitation and incoming solar radiation were selected to describe climatic conditions. The results showed that BEPS and MOD17 exhibited similar performance in simulating GPP, with root-mean-square error (RMSE) values of 2.50 g C m−2 d−1 and 2.53 g C m−2 d−1, respectively, and performed slightly better than TG (RMSE = 2.98 g C m−2 d−1). Comparison between simulated GPP and EC GPP also revealed that model performance varied substantially among different vegetation types. The three models performed better for deciduous broadleaf forest, evergreen needleleaf forest, and mixed forest, in comparison to the results from evergreen broadleaf forest and crop. Specifically, all three models showed poor performance under the conditions of high temperature and low precipitation, revealing the models’ inability to characterize the impact of water stress on photosynthesis when drought occurs. Furthermore, our results indicated that GPP estimations from satellite data-driven models were also sensitive to remotely sensed data, suggesting that the high accuracy of remotely sensed data in describing vegetation canopy is important for carbon modeling. This study highlights the importance of understanding model behaviors in different vegetation types and climatic conditions, so that the model performances may be improved in future carbon cycle studies.

The boreal forest ecosystem is one of the largest frontier forests of the world, providing many ecological services to society. Boreal forests are also economically important, but forest harvesting and management become increasingly difficult when one moves from south to north in boreal environments. An approach was thus developed to assess the suitability of land units for timber production in a sustainable forest management (SFM) context in the northern boreal forest of Quebec (Canada). This area includes all of Quebec’s spruce – feather moss bioclimatic domain (closed forest), as well as the southern portion of the spruce–lichen bioclimatic domain (open woodland). Four criteria specific to the biophysical aspects of SFM were evaluated in 1114 land districts: physical environment, timber production capacity, forest vulnerability to fire (e.g., probability that it reaches maturity), and conservation of biodiversity. Indicators and acceptability cutoff values were determined for each selected criterion, and a sequential analysis was developed to evaluate if a land district has the potential to be sustainably managed. This analytical process led to the classification of land districts into three categories: slightly sensitive (SFM possible); moderately sensitive (SFM possible under certain conditions); and highly sensitive (SFM not possible). The results show that 354 land districts were highly sensitive, 62 due to physical constraints (7.5% of the area), 130 due to insufficient potential productivity (15.4% of the area), 92 due to insufficient potential productivity to account for the fire risk (13.8% of the area), and 70 due to an insufficient proportion of tall and dense forest habitats (7.7% of the area — biodiversity criterion). This work provides scientific background to proposing a northern limit for forest management activities in Quebec. The developed approach could be useful in other jurisdictions to address similar issues.

In this study, we applied a process-based model, boreal ecosystem productivity simulator (BEPS) to simulate net primary productivity (NPP) over Fujian Province in 2015, and the responses of NPP to various environmental factors (e.g. temperature, elevation, slope, aspect) was analyzed. The results showed that: (1) the total NPP and mean NPP of Fujian province in 2015 are 43.13 × 106 tC and 540.75gC m−2yr−1, and the rank of annual mean NPP of different forest types was as follows: Evergreen Broadleaf Forest(EBF)>Evergreen Needleleaf Forest (ENF)>Needle-Broadleaf Mixed Forest(NBMF)>Deciduous Needleleaf Forest (DNF)>Deciduous Broadleaf Forest(DBF), with the values of: 625.6gC m−2yr−1, 525.3gC m−2yr−1, 436.6gC m−2yr−1, 412.4gC m−2yr−1, 399.9gC m−2yr−1, respectively; (2) monthly mean NPP show “M” distribution temporally due to the high temperature in summer;(3)a significant correlation existed between NPP and terrain factors.

Wildfires release the greatest amount of carbon into the atmosphere compared to other forest disturbances. To understand how current and potential future fire regimes may affect the role of the Eurasian boreal forest in the global carbon cycle, we employed a new, spatially-explicit fire module DISTURB-F (DISTURBance-Fire) in tandem with a spatially-explicit, individually-based gap dynamics model SIBBORK (SIBerian BOReal forest simulator calibrated to Krasnoyarsk Region). DISTURB-F simulates the effect of forest fire on the boreal ecosystem, namely the mortality of all or only the susceptible trees (loss of biomass, i.e., carbon) within the forested landscape. The fire module captures some important feedbacks between climate, fire and vegetation structure. We investigated the potential climate-driven changes in the fire regime and vegetation in middle and south taiga in central Siberia, a region with extensive boreal forest and rapidly changing climate. The output from this coupled simulation can be used to estimate carbon losses from the ecosystem as a result of fires of different sizes and intensities over the course of secondary succession (decades to centuries). Furthermore, it may be used to assess the post-fire carbon storage capacity of potential future forests, the structure and composition of which may differ significantly from current Eurasian boreal forests due to regeneration under a different climate.

The boreal forest (taiga or snow forests) is the world’s largest terrestrial biome characterized by a subarctic climate and coniferous tree species (spruce, pine and larch) (Hamet-Ahti 1981). A long and cold winter is the dominant feature there, and snow processes are principal hydrological phenomena. In Finland, boreal forests cover 74% of the land area; therefore, forestry practices can affect nature capital of headwater catchments. These benefits can address all four groups of ecosystem services (MEA 2005): provisioning (timber yield, water resources recharge, fisheries), regulating (control of floods, carbon and bio-geo-chemical cycles), supporting (biodiversity) and cultural (recreation or aesthetic values).

Many methods for the study of timber-yielding plants exist. These methods encompass a variety of issues. They are based on traditional approaches and approaches of nonlinear dynamics. The greatest attention is paid to the study of forest stand biomass. Regression method is considered the most accurate and versatile. The set of functions is available to approximate tree biomass depending on its diameter. Allometric function is the most biologically driven. However, all these biomass functions belong to the regression method. They cannot claim to be a universal dependency, which can be used in a wide age range and geographic range. Therefore, prediction on this basis is not accurate. Logistics systems of equations are more versatile. Our research has shown that the use of systems of differential equations gives good results for the study of the joint growth of two wood species. This approach allows one to predict the role of valuable wood species in the forest stand structure in the process of reforestation. It is useful for the planning of forest management and environmental measures. However, the gap between the mathematical and experimental ecology continues to exist. The development of new universal methods of forecasting the state of timber-yielding plants and their ecosystems is still relevant.

In this paper, a global carbon assimilation system (GCAS) is developed for optimizing the global land surface carbon flux at 1° resolution using multiple ecosystem models. In GCAS, three ecosystem models, Boreal Ecosystem Productivity Simulator, Carnegie-Ames-Stanford Approach, and Community Atmosphere Biosphere Land Exchange, produce the prior fluxes, and an atmospheric transport model, Model for OZone And Related chemical Tracers, is used to calculate atmospheric CO2 concentrations resulting from these prior fluxes. A local ensemble Kalman filter is developed to assimilate atmospheric CO2 data observed at 92 stations to optimize the carbon flux for six land regions, and the Bayesian model averaging method is implemented in GCAS to calculate the weighted average of the optimized fluxes based on individual ecosystem models. The weights for the models are found according to the closeness of their forecasted CO2 concentration to observation. Results of this study show that the model weights vary in time and space, allowing for an optimum utilization of different strengths of different ecosystem models. It is also demonstrated that spatial localization is an effective technique to avoid spurious optimization results for regions that are not well constrained by the atmospheric data. Based on the multimodel optimized flux from GCAS, we found that the average global terrestrial carbon sink over the 2002–2008 period is 2.97 ± 1.1 PgC yr−1, and the sinks are 0.88 ± 0.52, 0.27 ± 0.33, 0.67 ± 0.39, 0.90 ± 0.68, 0.21 ± 0.31, and 0.04 ± 0.08 PgC yr−1 for the North America, South America, Africa, Eurasia, Tropical Asia, and Australia, respectively. This multimodel GCAS can be used to improve global carbon cycle estimation.

There are mainly three types of gross primary production (GPP), including light use efficiency (LUE) model, rectangular hyperbolic model (RHM), and process-based model (PBM). RHM is not widely used because its parameters, namely, quantum yield (α) and maximum photosynthetic rate (Pm), vary temporally with temperature and spatially with vegetation type under natural conditions. In the study, we present a temperature- and vegetation-type-adapted RHM by linking it to the Baldocchi's model to obtain the relationship between α-Pm and Vcmax,25-temperature to overcome the shortcomings of traditional RHM. The modified RHM (MRHM) coupled with a two-leaf upscaling strategy makes it possible to accurate and fast estimation of GPP at large scale. Twenty-two CO2 eddy-covariance sites with different vegetation types, including evergreen needleleaf forest, deciduous broadleaf forest, grassland, and evergreen broadleaf forest, are used to evaluate the performance of MRHM for GPP estimation. The comparisons of the simulated GPP using MRHM with measured and Boreal Ecosystem Productivity Simulator-simulated GPP demonstrate that the MRHM can simulate GPP as accurately as PBM and in the meantime with the advantage of simplicity as LUE model. These results show the promising potential of MRHM for accurately simulating GPP with relative high computational efficiency, providing an ideal alternative tool for large-scale and long time series GPP simulations.

The southern portions of the boreal region across Canada are dominated by boreal mixedwoods forests, which are character ized by varying canopy dominance of boreal broadleaf and conifer trees. This forest region encompasses a large east-to-west gradient of climate and disturbance regimes. Although the same major boreal tree species occur in all parts of the boreal mixedwood region, they vary greatly in relative abundance. This is a reflection of the interactions among the different abiotic and biotic components. As a result, there is considerable variation in post-disturbance stand development, producing a wide variety of mixedwood forest conditions existing as a mosaic in time and space. Post-disturbance dominance by broadleaf species followed by a transition to conifers is the “classic” pathway in all regions. However, there is wide variation in the transition rate and the species sequence across the gradient depending on factors such as moisture, abundance of each species, fire cycle, climate and secondary disturbances (mainly insect outbreaks). Future changes in climate and disturbance regime could influ ence the nature of stand dynamics of boreal mixedwoods and the prominence of different pathways among regions. Focussing on the commonality of processes in mixedwood stand development across the boreal is a promising way to address the management of this important forest ecosystem.

[1] We assess Canada's gross primary productivity (GPP) and net primary productivity (NPP) using boreal ecosystem productivity simulator (BEPS) at 250 m spatial resolution with improved input parameter and driver fields and phenology and nutrient release parameterization schemes. BEPS is a process-based two-leaf enzyme kinetic terrestrial ecosystem model designed to simulate energy, water, and carbon (C) fluxes using spatial data sets of meteorology, remotely sensed land surface variables, soil properties, and photosynthesis and respiration rate parameters. Two improved key land surface variables, leaf area index (LAI) and land cover type, are derived at 250 m from Moderate Resolution Imaging Spectroradiometer sensor. For diagnostic error assessment, we use nine forest flux tower sites where all measured C flux, meteorology, and ancillary data sets are available. The errors due to input drivers and parameters are then independently corrected for Canada-wide GPP and NPP simulations. The optimized LAI use, for example, reduced the absolute bias in GPP from 20.7% to 1.1% for hourly BEPS simulations. Following the error diagnostics and corrections, daily GPP and NPP are simulated over Canada at 250 m spatial resolution, the highest resolution simulation yet for the country or any other comparable region. Total NPP (GPP) for Canada's land area was 1.27 (2.68) Pg C for 2008, with forests contributing 1.02 (2.2) Pg C. The annual comparisons between measured and simulated GPP show that the mean differences are not statistically significant (p > 0.05, paired t test). The main BEPS simulation error sources are from the driver fields.

Alaskan spruce forests are exposed to both fire and spruce beetles [Dendroctonus rufipennis (Kirby)]. To understand the influence of spruce beetles on the process through which fire affects ecosystem function, we developed a reconstruction technique to measure prefire damage to trees caused by the spruce beetle. We validated our evaluation of prefire tree conditions using a high-resolution multispectral satellite image by comparing our results with a postfire ground survey. The prefire tree conditions determined by the two methods coincided well with each other. This result suggests that combining high-resolution multispectral imaging and postfire ground surveys of spruce beetles on snags is a powerful tool to determine the prefire condition of a forest in a changing boreal forest ecosystem.

Aboveground deadwood, consisting of downed woody debris (DWD), snags, and stumps, is an important component of boreal forest ecosystem structure. Accurate deadwood density estimates are essential for evaluating ecosystem biomass and carbon stocks. The objective of this study was to examine the relationships between deadwood density, tree species, and decay status, identified in the field by morphological character- istics. We sampled DWD, snags, and stumps of trembling aspen (Populus tremuloides Michx.), paper birch (Betula papyrifera Marsh.), jack pine (Pinus banksiana Lamb.), black spruce (Picea mariana (Mill.) B.S.P.), and balsam fir (Abies balsamea (L.) Mill.) in the boreal forest of central Canada. A total of 240 samples (99 DWD, 94 snags, and 47 stumps) were collected. Decay class and tree species explained 80% of the variation in wood density of all deadwood types. Wood density decreased consistently from the lowest to the highest decay class. Tree species identity was also important in determining the relationships between wood density and field- assigned decay class for snags and stumps, but not for DWD, probably because of the five-class system used for DWD, rather than the three-class system used for snags and stumps. These results indicate that decay class and tree species are adequate predictors of deadwood density. FOR .S CI. 59(3):261-266.

Background. One of the pressing aims of today's natural resource management is its re-orientation to preserving and restoring ecological functions of ecosystems, among which the function of biodiversity maintenance plays an indicator role. The majority of today's forests have not retained their natural appearance as the result of long-standing human impact. In this connection, refugia studies are becoming particularly interesting, as they give us an insight into the natural appearance of forests. Materials and methods. Studies were performed in dark conifer forests of the Pechora-Ilych reserve, in the lower reaches of the Bol'shaya Porozhnyaya River in 2013 yr. Vegetation data sampling was done at 50 temporary square plots of a fixed size (100 m2) randomly placed within a forest type. A list of plant species with species abundance was made for each forest layer. The overstorey (or tree canopy layer) was denoted by the Latin letter A. The understorey layer (indicated by the letter B) included tree undergrowth and tall shrubs. Ground vegetation was subdivided into the layers C and D. Layer C (field layer) comprised the herbaceous species (herbs, grasses, sedges) and dwarf shrubs together with low shrubs, tree and shrub seedlings. The height of the field layer was defined by the maximal height of the herbaceous species, ferns, and dwarf shrubs; the height varied from several cm to more than 200 cm in the ‘tall-herb' forest types. Layer D (bottom layer) included cryptogamic species (bryophytes and lichens). Species abundance in the each layer was usually assessed using the Braun-Blanquet cover scale (Braun-Blanquet 1928). The nomenclature used follows Cherepanov's (1995) for vascular plants, and Ignatov & Afonina's (1992). Results. The present article contains descriptions of unique tall-herb boreal forests of European Russia preserved in certain refugia which did not experience prolonged anthropogenic impact or any other catastrophes. Comparative research into species and ecological diversity of typical (anthropogenically transformed) and unique (tall-herb) boreal forests has been conducted. On the basis of the collected field data, a map of the diffuse area for tall-herb boreal forests has been compiled and a set of species characteristic for these forests has been determined. The obtained data fundamentally change our notions of potential vegetation in boreal forests. Conclusions. Considerable speciesand ecological diversity of tall-herb forest flora fundamentally changes our notion of the appearance of European boreal forests and determines their unique role in maintaining the highest possible level of biodiversity. The presence of tall-herb forests in various parts of eastern European taiga together with Eurasian habitats of most tall-herb species lead us to a suggestion that it is exactly this type of forests that represented the prehistoric boreal forests. In this connection, further research into still preserved fragments of tall-herb forests within the boundaries of northern Eurasia acquires huge significance. This research will help put forward systems of forest management aimed at restoring potential biodiversity of boreal forests in general.

We conducted a simulated nitrogen (N) and sulfur (S) deposition experiment in the Athabasca oil sands region (AOSR) where NOx and SO2 have been emitted from oil sands mining/extracting and upgrading activities and then deposited to the surrounding ecosystems for decades. To evaluate changes in tree growth rates, N pool sizes, and nutrient losses by S and N deposition, the following four treatments were applied: control (CK), N addition (+N, 30 kg N ha−1 yr−1), S addition (+S, 30 kg S ha−1 yr−1), and +NS additions (+NS, 30 kg N and 30 kg S ha−1), from 2006 through 2009. Nitrogen addition increased (p NO 3 - were leached below 45 cm (considered to be below the main rooting zone) of the soil profile in any of the treatments. Decreases in exchangeable Ca2+ and Mg2+ by N and S additions were likely due to increased tree uptake following increased tree growth in the former and increased leaching with sulfate in the latter. Although the lack of significant N leaching indicates that the risk of N saturation was low after 4 yr of elevated N deposition, reduction of exchangeable base cations implies that nutrient imbalance remains a concern in AOSR in the long term.

Natural disturbance emulation (NDE) has been proposed as a general approach to ecologically sustainable forest management. We reviewed the concepts, theories, and strategies related to NDE in boreal forest management. We also reviewed publications that discussed NDE in the boreal forest in general and those that specifically compared NDE-based management with conventional even-aged management. The papers generally focused on northern North America and landscape-scale wildfire as the main disturbance factor, whereas information from Eurasia was exclusively theoretical. Within this limited scope, NDE was generally found to have a positive effect on biodiversity in terms of forest structure and species diversity when compared with conventional even-aged management. Studies on timber supply and social implications of NDE were so few that they preclude generalizations. We conclude that the ecological and economic performance of NDE as a management approach still remains poorly examined. To advance the development of NDE, particular attention should be given to (1) augmenting the knowledge base on natural range of variability of unmanaged forest ecosystems and evaluating the validity of this information in a changing climate, (2) fostering multidisciplinary research with better integration of ecological theory to both integrative and analytical research on NDE, and (3) better integration of socioeconomic concerns, adaptive management schemes, and international collaboration into NDE initiatives.

Boreal forests play an important role in global environment systems. Understanding boreal forest ecosystem structure and function requires accurate monitoring and estimating of forest canopy and biomass. We used partial least square regression (PLSR) models to relate forest parameters, i.e. canopy closure density and above ground tree biomass, to Landsat ETM+ data. The established models were optimized according to the variable importance for projection (VIP) criterion and the bootstrap method, and their performance was compared using several statistical indices. All variables selected by the VIP criterion passed the bootstrap test (p

Widespread climate change is expected to lead to altered patterns of disturbance, thereby driving future ecosystem change. This interaction, which is often poorly recognized or understood, may be particularly important in the sub-arctic due to rapid climate change and frequent fire. Our objective was to investigate how an altered fire return interval can interrupt successional pathways in a serotinous boreal ecosystem. We conducted this research in black spruce ( Picea mariana [Mill.] BSP.) forests on the northern margin of the species’ distribution in Yukon Territory, Canada. We compared seed availability and seedling establishment of black spruce in stands of varying fire return interval using experimental manipulations within areas varying in their natural fire histories. Recruitment was drastically reduced following two closely timed fires, compared to stands burned under a typical fire return interval. However, recruitment was also limited in mature forest stands. On-site germination experiments demonstrated that black spruce recruitment was limited by seed availability after a short fire return interval, and by substrate quality in unburned stands. The vegetation of the boreal forest is thought to be highly resilient to climatic change, due in part to the adaptations that conifers have for post-fire regeneration. We show that shortened fire return intervals, through effects on seed availability, disrupt the normal sequence of post-fire recovery on seedbeds released by fire for colonisation. The results of this study provide strong empirical evidence that disturbance, although essential for stand renewal, may limit forest recovery or expansion when misaligned with reproductive cycles.

An ecosystem model (Sima) was utilised to investigate the impact of forest management (by changing both the initial stand density and basal area thinning thresholds from current recommendations) on energy wood production (at energy wood thinning and final felling) and management-related carbon dioxide (CO2) emissions for the energy wood production in Finnish boreal conditions (62°39′ N, 29°37′ E). The simultaneous effects of energy wood, timber and C stocks in the forest ecosystem (live and dead biomass) were also assessed. The analyses were carried out at stand level during a rotation period of 80 years for Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies L. Karst.) growing in different fertility sites. Generally, the results showed that decreased basal area thinning thresholds, compared with current thinning, reduced energy wood (logging residues) and timber production, as well as carbon stocks in the forest ecosystem. Conversely, increased thinning thresholds increased energy wood production (ca. 1–27%) at both energy wood thinning and final felling and reduced CO2 emissions (ca. 2–6%) related to the production chain (e.g. management operations), depending on the thinning threshold levels, initial stand density, species and site. Increased thinning thresholds also enhanced timber production and carbon stocks in the forest ecosystem. Additionally, increased initial stand density enhanced energy wood production for energy wood thinning for both species, but this reduced energy wood production at final felling for Scots pine and Norway spruce. This study concluded that increases in both initial stand density and thinning thresholds, compared with the current level, could be useful in energy wood, timber and carbon stocks enhancement, as well as reducing management-related CO2 emissions for energy wood production. Only 2.4–3.3% of input of the produced energy (energy wood) was required during the whole production chain, depending on the management regime, species and sites. However, a comprehensive substitution analysis of wood-based energy, in respect to environmental benefits, would also require the inclusion of CO2 emissions related to ecosystem processes (e.g. decomposition).

In order to assess the capacity of the boreal forest ecosystem to intercept atmospheric carbon over a period of years, a climate-driven growth model (FinnFor, process-based) was applied to calculate the seasonal and inter-annual variability of net ecosystem CO 2 exchange (NEE) and component carbon fluxes (gross primary production – GPP and total ecosystem respiration – TER) against a 10-year (1999–2008) period of eddy covariance (EC) measurements in a Scots pine ( Pinus sylvestris L.) stand in Eastern Finland. Furthermore, the role of climatic factors, leaf area index ( LAI ) and physiological responses of trees regarding the ecosystem carbon fixation processes were evaluated. An hourly time-step was used to simulate the carbon exchange based on measured tree/stand characteristics and meteorological input for the experimental site, and the dynamic LAI was used throughout the 10-year simulations. The model predicted well the annual course of NEE compared to the measured values for most of the years, with the development of LAI (2.4–3.3 m 2 m −2 , as simulated). The simulated NEE over the study period shows that, on average, 62% of the variation refers to daily and 88% to monthly measured NEE. Both modeled and measured daily NEE showed similar responses to the temperature, photosynthetically active radiation and vapor pressure deficit during the growing seasons. In the simulation, the annual amount of GPP varied from 720.8 to 910.4 g C m −2 with a mean value of 825.3 g C m −2 , and the annual mean TER/GPP ratio was 0.79, close to the measured value. Carbon efflux from the forest floor was the dominant contributor to the forest ecosystem respiration. The inter-annual variation of GPP mostly corresponded to the development of LAI , temperature sum and total incoming radiation over the 10-year simulation period. It was suggested that the process-based model could be applied to study the carbon processes for natural and management-induced dynamics of Scots pine forest ecosystem over longer periods across a wider climate gradient in the boreal zone.

Terrestrial carbon cycle and the global atmospheric CO2 budget are important foci in global climate change research. Simulating net primary productivity (NPP) of terrestrial ecosystems is important for carbon cycle research. In this study, a plant-atmosphere-soil continuum nitrogen (N) cycling model was developed and incorporated into the Boreal Ecosystem Productivity Simulator (BEPS) model. With the established database (leaf area index, land cover, daily meteorology data, vegetation and soil) at a 1 km resolution, daily maps of NPP for Lantsang valley in 2007 were produced, and the spatial-temporal patterns of NPP and mechanisms of its responses to soil N level were further explored. The total NPP and mean NPP of Lantsang valley in 2007 were 66.5 Tg C and 416 g·m−2·a−1 C, respectively. In addition, statistical analysis of NPP of different land cover types was conducted and investigated. Compared with BEPS model (without considering nitrogen effect), it was inferred that the plant carbon fixing for the upstream of Lantsang valley was also limited by soil available nitrogen besides temperature and precipitation. However, nitrogen has no evident limitation to NPP accumulation of broadleaf forest, which mainly distributed in the downstream of Lantsang valley.

Successful management of forest fire risk in the Northeastern China boreal forest ecosystem often involves trade-offs between fire dynamics, fire hazard reduction, and fiscal input. We used the LANDIS model to study the effects of alternative fuel reduction strategies on fire dynamics and analyzed cost effectiveness for each fuel reduction strategy based on cost–benefit theory. Five levels of fuel treatment area (2, 4, 6, 8, and 10% for each decade) and two fuel treatment types (prescribed burning [PB] and mechanical treatments in combination with prescribed fire [PR]) under current fire suppression simulated by LANDIS were compared in a 5 × 2 factorial design over a 300-year period. The results showed that PR scenarios are more effective at reducing the occurrence and burn area of catastrophic fires than PB scenarios. In addition, area burned by high intensity fire can be tremendously reduced by increasing low intensity fires with a higher level of treatment area under the various PR scenarios. The cost effectiveness of alternative fuel reduction strategies is strongly dependent on treatment area. In general, PB scenarios will be more cost effective in larger treatment areas and PR scenarios in smaller. We recommend mechanical treatments in combination with prescribed fire, with 4% of landscape treated in each decade (PR04) to be the optimal fuel reduction strategy in the study area based on risk control and cost efficiency analysis. However, the most challenging work in China is to make local forest policy makers and land managers accept the ecological function of fire on forest ecosystems.

Containing approximately one-third of all remaining global forests, the boreal ecosystem is a crucial store of carbon and a haven for diverse biological communities. Historically, fire and insects primarily drove the natural dynamics of this biome. However, human-mediated disturbances have increased in these forests during recent years, resulting in extensive forest loss for some regions, whereas others face heavy forest fragmentation or threat of exploitation. Current management practices are not likely to maintain the attendant boreal forest communities, nor are they adequate to mitigate climate change effects. There is an urgent need to preserve existing boreal forests and restore degraded areas if we are to avoid losing this relatively intact biodiversity haven and major global carbon sink.

The clear cuts and seedling stands can speed up winds and may trigger blowdown at the edges of neighbour stands. Therefore, the height contrast of the neighbour stands and fragmentation at landscape level could be used to indicate the susceptibility of windthrow. In this study, we studied how forest fragmentation affects the susceptibility of a boreal forest ecosystem to wind damage, both at patch and landscape level based on theoretical computations. For this purpose we generated, based on real stand inventory data of a Finnish forest ecosystem, different landscape configurations of Scots pine and Norway spruce forests using Monte Carlo simulation. Thereafter, we applied a mechanistic wind damage model to predict the wind speeds needed for wind damage at forest edges. The fragmentation metrics of Contrast-Weighted Edge Density with three different height dissimilarity calculation methods were used to analyze the fragmentation at the landscape level. At the patch (stand) level, susceptibility of downwind stand to wind damage could be expressed in terms of a quadratic function, based on the tree height of upwind neighbouring stand or the height ratio between the neighbouring stands. At the landscape level, the relative risk of wind damage correlated linearly with the fragmentation despite of fragmentation metrics used. Both in single species and mixed forests, the metrics using empirical regression function based on patch level results (DS3) seemed more applicable in general than those using the ratio of tree heights between neighbouring stands (DS1) or constrained height contrast (DS2).

Habitat alteration caused by forest harvesting seems to contribute to the decline of forest-dwelling caribou, an ecotype of woodland caribou (Rangifer tarandus caribou) inhabiting the boreal ecosystem. To serve as basework to the establishment of conservation measures for the species, we have studied the hierarchical habitat selection of forest-dwelling caribou in a boreal landscape of Quebec strongly impacted by logging. Fifteen females were surveyed by GPS telemetry between April 2004 and March 2006. Home ranges showed a high proportion of 90–120 year-old forests, a low proportion of regenerating forests (20–40 years old) and a tendency to include a greater proportion of 6–20 year-old clearcuts in relation to their availability in the study area. At the home range scale, selection patterns differed between periods, possibly reflecting specific requirements linked to caribou life cycle. Caribou selected open lichen woodlands throughout the year while mature closed forests (≥50 years) were selected uniquely during summer. The 6–20 year-old clearcuts were avoided during calving, in summer and during the rutting period but were selected during spring. Our results indicate that mature forest and open lichen woodlands are highly selected forest cover types by caribou at both spatial scales. Although clearcuts were generally avoided at the home range scale, such avoidance was not observed at the larger scale, the search for 90–120 year-old forests being hampered by a uniform distribution of clearcuts. An a posteriori landscape analysis highlighted the spatial association between 6–20 year-old clearcuts and 90–120 year-old forests, an association that can be explained by the current regulations used in Quebec. Our results underline the importance of pursuing research concerning the impact of such an exploitation regime on the long-term maintenance of the forest caribou in the boreal landscape.

Black spruce (Picea mariana (Mill.) B.S.P.) is the dominant tree species in the Canadian province of Quebec’s boreal ecosystem, particularly in the black spruce-feathermoss (BSFM) domain (between the 49th and the 52nd parallels). While black spruce is generally well adapted to regenerate after wildfires, regeneration failure can sometimes occur, resulting in the irreversible conversion of closed-crown BSFM to open black spruce-lichen woodlands (OW). With OWs representing approximately 7% (1.6 M ha) of Quebec’s BSFM domain, the afforestation of OWs carries significant theoretical potential for carbon (C) sequestration, which has not yet been evaluated. The main objectives of the study were then: (i) to estimate the theoretical C balance of OW afforestation within the closed-crown BSFM domain in Quebec’s boreal forest; (ii) to calculate, using the life cycle analysis (LCA) method, all the GHG emissions related to black spruce OW afforestation in the closed-crown BSFM domain of Quebec. The CO2FIX v. 3.1 model was used to calculate the biological C balance between the baseline (natural OW of site index 9 at age 50) and afforestation (black spruce plantation of site index 6 at age 25) scenarios, using the best estimates available for all five recommended C compartments (aboveground biomass, belowground biomass, litter, deadwood, and soil). The simulation revealed a biological C balance of 77.0 t C ha−1, 70 years following afforestation, for an average net sequestration rate of 1.1 t C ha−1 year−1. Biological C balance only turns positive after 27 years. When integrating the uncertainties related to both the plantation growth yield and the wildfire disturbance, the average sequestration rate varies between 0.2 and 1.9 t C ha−1 year−1. GHG emissions are 1.3 t CO2 equiv. ha−1 for all afforestation-related operations, which is less than 0.5% of the biological C balance after 70 years. Thus, GHG emissions do not significantly affect the net C balance of the afforestation project simulated. Several recommendations are made, mostly centered on the factors influencing the growth rate of carbon stocks and the impact of natural disturbances, to minimize the range of uncertainties associated to the sequestration potential and maximize the mitigation benefits of an OW afforestation project.

A gap-type ecosystem model was used to assess how climate change may affect the growth (stemwood production), timber production (sawlogs and pulpwood) and carbon stocks in the forest ecosystem (trees and soil) under varying thinning regimes in Finland. Simulations were carried out over a 100-year period under current and changing climate for seven thinning regimes by changing both the basal area threshold when the thinning is performed and the remaining basal area after the thinning. The management recommendations, currently applied in Finnish forestry, were used to define the “business-as-usual” treatment. The results indicated that climate change may substantially increase the growth, timber production and carbon stocks in the forest ecosystem. The largest relative changes were found in northern (above 64° N) Finland (south: growth 37–45%, timber production 23–40%, carbon stocks 8–10%; north: 75–78%, 59–70%, 21–23%, respectively, depending on the thinning regimes applied), although the absolute...

Interactions of fire cycle and plant species’ reproductive characteristics could determine vegetation distribution pattern of a landscape. In Canada’s boreal region, fire cycles before the Little Ice Age (c. 1850s) ranged from 30–130 years and 25–234 years afterwards until the settlement period (c. 1930s) when longer fire cycles occurred in response to climatic change and human interference. Analysis indicated that fire cycles were correlated with growing season (April–October) temperature and precipitation departure from the 1961–1990 normal, varying by regions. Assuming that wildfires will respond to future warming similar to the manner during the past century, an assessment using climatic change scenarios CGCM1, CGCM2 and HadCM2 indicates fire cycles would divert to a range of 80–140 years in the west taiga shield, more than 700 years for the east boreal shield and east taiga shield, and 300–400 years for the boreal plains in 2050.