•Updated forest biomass carbon sinks and density of China from 1977 to 2013.•Used carbon fraction coefficients of 46 tree species replaced 0.5.•The spatiotemporal variation of forest carbon storage ...and density is discussed;•Analysis of natural and planted forests in the past two inventories.•Compared the carbon estimation of forest by different methods.
Forests are a major contributor of terrestrial ecosystem carbon pools. Accurate estimates of forest biomass carbon sinks can improve our understanding of carbon cycles and help in developing sustainable forest management policies in the face of climate change. In this study, we update estimates of the biomass carbon stocks of China’s forests based on seven forest inventory datasets from 1977 to 2013 and carbon fraction coefficients of 46 tree species in the continuous biomass expansion factor (CBEF) model. Our findings suggest that: (1) China’s forest stands acted as an average biomass carbon sink of 99.07 Tg C year−1; and (2) biomass carbon stocks increased by 72.62% from 1977 to 2013 and recently reached 7.27 Pg C, driven by forest area expansion and forest growth. The biomass carbon density of forest stands (canopy coverage >20%) increased from 38.18 to 44.52 Mg C ha−1 during the study period, with higher carbon densities in natural compared to planted forests, and the gap increasing with forest age. The largest increases in the biomass of carbon stocks of forest stands occurred in the eastern and northern regions. Our results suggest that biomass carbon stocks of natural forests account for about 85% in the most recent inventory and that the total biomass carbon stocks of forest stands in China will keep increasing in the future because of the large area of planted forests with young and middle-aged forest growth. The results from this study can help with comprehensive investigations of forest carbon budgets and the calibration and validation of simulation model results.
Carbon pools in China’s terrestrial ecosystems Tang, Xuli; Zhao, Xia; Bai, Yongfei ...
Proceedings of the National Academy of Sciences - PNAS,
04/2018, Letnik:
115, Številka:
16
Journal Article
Recenzirano
Odprti dostop
China’s terrestrial ecosystems have functioned as important carbon sinks. However, previous estimates of carbon budgets have included large uncertainties owing to the limitations of sample size, ...multiple data sources, and inconsistent methodologies. In this study, we conducted an intensive field campaign involving 14,371 field plots to investigate all sectors of carbon stocks in China’s forests, shrublands, grasslands, and croplands to better estimate the regional and national carbon pools and to explore the biogeographical patterns and potential drivers of these pools. The total carbon pool in these four ecosystems was 79.24 ± 2.42 Pg C, of which 82.9% was stored in soil (to a depth of 1 m), 16.5% in biomass, and 0.60% in litter. Forests, shrublands, grasslands, and croplands contained 30.83 ± 1.57 Pg C, 6.69 ± 0.32 Pg C, 25.40 ± 1.49 Pg C, and 16.32 ± 0.41 Pg C, respectively. When all terrestrial ecosystems are taken into account, the country’s total carbon pool is 89.27 ± 1.05 Pg C. The carbon density of the forests, shrublands, and grasslands exhibited a strong correlation with climate: it decreased with increasing temperature but increased with increasing precipitation. Our analysis also suggests a significant sequestration potential of 1.9–3.4 Pg C in forest biomass in the next 10–20 years assuming no removals, mainly because of forest growth. Our results update the estimates of carbon pools in China’s terrestrial ecosystems based on direct field measurements, and these estimates are essential to the validation and parameterization of carbon models in China and globally.
Recent reports of local extinctions of arthropod species
, and of massive declines in arthropod biomass
, point to land-use intensification as a major driver of decreasing biodiversity. However, to ...our knowledge, there are no multisite time series of arthropod occurrences across gradients of land-use intensity with which to confirm causal relationships. Moreover, it remains unclear which land-use types and arthropod groups are affected, and whether the observed declines in biomass and diversity are linked to one another. Here we analyse data from more than 1 million individual arthropods (about 2,700 species), from standardized inventories taken between 2008 and 2017 at 150 grassland and 140 forest sites in 3 regions of Germany. Overall gamma diversity in grasslands and forests decreased over time, indicating loss of species across sites and regions. In annually sampled grasslands, biomass, abundance and number of species declined by 67%, 78% and 34%, respectively. The decline was consistent across trophic levels and mainly affected rare species; its magnitude was independent of local land-use intensity. However, sites embedded in landscapes with a higher cover of agricultural land showed a stronger temporal decline. In 30 forest sites with annual inventories, biomass and species number-but not abundance-decreased by 41% and 36%, respectively. This was supported by analyses of all forest sites sampled in three-year intervals. The decline affected rare and abundant species, and trends differed across trophic levels. Our results show that there are widespread declines in arthropod biomass, abundance and the number of species across trophic levels. Arthropod declines in forests demonstrate that loss is not restricted to open habitats. Our results suggest that major drivers of arthropod decline act at larger spatial scales, and are (at least for grasslands) associated with agriculture at the landscape level. This implies that policies need to address the landscape scale to mitigate the negative effects of land-use practices.
Mapping aboveground forest biomass is central for assessing the global carbon balance. However, current large-scale maps show strong disparities, despite good validation statistics of their ...underlying models. Here, we attribute this contradiction to a flaw in the validation methods, which ignore spatial autocorrelation (SAC) in data, leading to overoptimistic assessment of model predictive power. To illustrate this issue, we reproduce the approach of large-scale mapping studies using a massive forest inventory dataset of 11.8 million trees in central Africa to train and validate a random forest model based on multispectral and environmental variables. A standard nonspatial validation method suggests that the model predicts more than half of the forest biomass variation, while spatial validation methods accounting for SAC reveal quasi-null predictive power. This study underscores how a common practice in big data mapping studies shows an apparent high predictive power, even when predictors have poor relationships with the ecological variable of interest, thus possibly leading to erroneous maps and interpretations.
Global importance of large-diameter trees Lutz, James A.; Furniss, Tucker J.; Johnson, Daniel J. ...
Global ecology and biogeography,
July 2018, Letnik:
27, Številka:
7/8
Journal Article
Recenzirano
Odprti dostop
Aim: To examine the contribution of large-diameter trees to biomass, stand structure, and species richness across forest biomes. Location: Global. Time period: Early 21st century. Major taxa studied: ...Woody plants. Methods: We examined the contribution of large trees to forest density, richness and biomass using a global network of 48 large (from 2 to 60 ha) forest plots representing 5,601,473 stems across 9,298 species and 210 plant families. This contribution was assessed using three metrics: the largest 1% of trees ≥ 1 cm diameter at breast height (DBH), all trees ≥ 60 cm DBH, and those rank-ordered largest trees that cumulatively comprise 50% of forest biomass. Results: Averaged across these 48 forest plots, the largest 1% of trees ≥ 1 cm DBH comprised 50% of aboveground live biomass, with hectare-scale standard deviation of 26%. Trees ≥ 60 cm DBH comprised 41% of aboveground live tree biomass. The size of the largest trees correlated with total forest biomass (r2 = .62, p < .001). Large-diameter trees in high biomass forests represented far fewer species relative to overall forest richness (r2 = .45, p < .001). Forests with more diverse large-diameter tree communities were comprised of smaller trees (r2 = .33, p < .001). Lower large-diameter richness was associated with large-diameter trees being individuals of more common species (r2 = .17, p = .002). The concentration of biomass in the largest 1% of trees declined with increasing absolute latitude (r2 = .46, p < .001), as did forest density (r2 = .31, p < .001). Forest structural complexity increased with increasing absolute latitude (r2 = .26, p < .001). Main conclusions: Because large-diameter trees constitute roughly half of the mature forest biomass worldwide, their dynamics and sensitivities to environmental change represent potentially large controls on global forest carbon cycling. We recommend managing forests for conservation of existing large-diameter trees or those that can soon reach large diameters as a simple way to conserve and potentially enhance ecosystem services.
After being launched in September 2018, measurements from the ICESat-2 (Ice, Cloud, and land Elevation Satellite-2) will be available to the science community starting in the Spring of 2019. These ...data offer new possibilities for the mapping of global terrain and vegetation as well as monitoring of the Earth's carbon stocks. The Advanced Topographic Laser Altimeter System (ATLAS) instrument on-board ICESat-2 will utilize photon counting technology for the altimetry observations. Photon counting technology is relatively new to the vegetation mapping community thus requires development of new algorithm approaches for terrain surface and canopy height retrievals. Photon counting systems provide range measurements for individual photons given the instrument's detection sensitivity. The sensitivity enables higher laser repetition rates for improved spatial coverage but is susceptible to solar background noise making the separation of signal and noise challenging and the data volume large. The algorithm developed specifically for the extraction of terrain and canopy heights from the ATLAS point clouds produces the ATL08 geophysical data product. This paper provides a detailed description of the ATL08 methodology, presents the data format, discusses many of the critical parameters likely to be of interest to future ICESat-2 data users, and describes the predicated uncertainties for terrain and canopy heights using two simulated ATLAS data sets. The first critical function in the ATL08 algorithm needs to accurately retrieve the surface is to identify the signal photons apart from the noise photons. Using a series of iterative filters, the ground and top of canopy surfaces are then identified in the signal. Next, individual photons are classified as either noise, canopy, or ground photons based on their distance above (or below) the estimated ground and top of canopy surfaces. The ATL08 algorithm has been tested on several simulated ATLAS data sets, and the results from two different ecosystems are described. The terrain extraction results saw sub-meter RMSE for the Alaska Tundra/Taiga ecotone and <2 m RMSE in Sonoma County, California which is characterized by complex topography and dense vegetation. Although canopy heights on the ATL08 data product will underestimate the true canopy height within a segment, the ICESat-2 derived canopy height is found to be correlated with relative height metrics produced from airborne lidar (i.e. truth). For the sparse boreal forests of Alaska, the ATL08 canopy height was most correlated with the 95th percentile relative height (RH95). However, for the dense coniferous forests of Sonoma County, CA, ATL08 canopy height is correlated with 75th percentile relative height (RH75). Data from ICESat-2 will provide a new and exciting data set to the scientific community by providing global terrain and canopy height estimates as well as showing potential for estimation of forest biomass.
•NASA's ICESat-2 Mission is launching in September 2018.•The methodology for the ATL08 Land/Vegetation data product is described.•ICESat-2 terrain estimates are sub-meter for some ecosystems.•ICESat-2 canopy heights are correlated to ideal relative canopy height metrics.
Forest disturbance regimes are expected to intensify as Earth's climate changes. Quantifying forest vulnerability to disturbances and understanding the underlying mechanisms is crucial to develop ...mitigation and adaptation strategies. However, observational evidence is largely missing at regional to continental scales. Here, we quantify the vulnerability of European forests to fires, windthrows and insect outbreaks during the period 1979-2018 by integrating machine learning with disturbance data and satellite products. We show that about 33.4 billion tonnes of forest biomass could be seriously affected by these disturbances, with higher relative losses when exposed to windthrows (40%) and fires (34%) compared to insect outbreaks (26%). The spatial pattern in vulnerability is strongly controlled by the interplay between forest characteristics and background climate. Hotspot regions for vulnerability are located at the borders of the climate envelope, in both southern and northern Europe. There is a clear trend in overall forest vulnerability that is driven by a warming-induced reduction in plant defence mechanisms to insect outbreaks, especially at high latitudes.
•Boreal forests show biomass gains linked to temperature.•Warmer areas benefit from lower tree mortality.•Younger forests might benefit more from climate warming.•Key temperature threshold identified ...for biomass increase.•Northeast regions may suffer from higher CO2 levels.
Boreal forests, vital carbon sinks storing about 32% of the world's forest carbon, face significant threats from climate change. In west-central Canada, studies have primarily focused on the impacts of forest fires and water availability on forest biomass. However, the effects of rising atmospheric CO2 and climate warming, particularly in relation to spatial variations in mean annual temperature (MAT), remain less understood. Our comprehensive study utilizes data from 871 permanent sample plots, encompassing 208,961 trees across western boreal forests of Canada over 50 years. Our findings reveal a net biomass increase of 0.052 Mg ha-1 yr-1 per degree increase in plot MAT. Two-thirds of this increase can be attributed to reduced mortality rates at higher MATs. Notably, warmer regions showed a more pronounced decrease in growth with stand age, suggesting that younger forests might benefit more from climate warming compared to mature ones. We identified a MAT threshold of 3 °C, beyond which forests show net biomass increase with rising CO2, while colder forests exhibit a decline. Future projections indicate that net biomass change in northeastern regions in our study area, particularly above 56° N, may experience adverse effects from increasing CO2 levels, while southwestern regions could benefit. Besides, in some regions south of 52°N under the 2041–2070 SSP5–8.5 scenario, where predicted temperatures exceed historical maximums, the potential instability and unpredictability of biomass-climate-CO2 relationships under such extreme conditions should be noted. Our study underscores the complex interplay between climate change factors and boreal forest biomass, highlighting the need for tailored forestry management strategies that consider these spatial and dynamic patterns.
This paper focuses on the classification of forest biomass into two categories: premature and mature forest biomass. The third variable considered is industrialization. The growth of the wood-based ...industry is believed to be closely tied to the population of mature forest biomass. Any scarcity of the mature population could have a negative impact on industrialization. So, pre-mature forest biomass is provided as an alternative for industrial growth. The industrialization growth is assumed to be based on a modified Leslie-Gower equation. The positivity and boundedness of the system are calculated using the comparison theorem. Stability analysis is done about nonzero equilibrium points with the help of the Routh-Hurwitz theorem. When there is no delay in the system, the system is stable. At τ< 1.8, the system shows asymptotic stability, but at τ ≥ 1.8, system shows Hopf-bifurcation and periods oscillations occur. Furthermore, sensitivity analysis is examined about different parameters of the systems. MATLAB is used to draw the numerical simulation.
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