Carbon allocation to wood formation in an unmanaged deciduous forest in Thuringia (Germany)-a case study of biomass production efficiency

<p>Carbon allocation to wood formation is the key process that drives biomass accumulation in forest ecosystems. Particularly important from a carbon balance perspective is the fraction of carbon taken up through photosynthesis (i.e. gross primary productivity) that is allocated to and sequestered in long-lasting wood tissues. This fraction is known as “biomass production efficiency” and a comprehensive understanding of its inter- and intra-annual variability in response to climatic fluctuations and ecosystem dynamics is still lacking. In this study, we assessed and reconstructed the above-ground biomass increment of three deciduous tree species, European beech (<em>Fagus sylvatica</em>), Sessile oak (<em>Quercus petraea</em>) and European hornbeam (<em>Carpinus betulus</em>) in Hainich National Park, Thuringia (Germany). Trees were sampled in a fixed plot design within the footprint area of a long-term eddy-covariance site (DE-Hai). We applied allometric equations to estimate tree volume and combined them with tree-ring width and wood density measurement to quantify and reconstruct the carbon stored as above-ground biomass in wood tissues. We scaled these measurements from the tree to the plot level and integrated the annual biomass increment with the carbon fluxes from the tower to quantify biomass production efficiency. Finally, we correlated species-specific growth with carbon fluxes and various climate parameters at daily, monthly, seasonal, and annual resolution to better understand, how climate variations affect carbon allocation to wood growth at this site. Our study represents a well-constrained observational framework to provide both quantitative and qualitative information on forest carbon cycling that can be used, e.g., to better parameterize tree-centered mechanistic vegetation models.</p>

Species-specific relationship between sapflux density and diameter growth rates for six years

<p>Transpiration and photosynthesis are connected each other through stomata, therefore, biomass increment of trees should have close relationships with their water use. However, the relationship is species specific and it is also dependent on various biotic and abiotic factors. The purpose of this study is to investigate the relationship of sapflux with diameter increment of individual trees among six different species using Granier type sapflow sensors and diameter growth band installed from 2012. The growth of two conifer (Pinus koraiensis, Abies holophylla), five broadleaf (Quercus aliena, Q. variabilis, Q. serrata, Carpinus laxiflora, C. cordata) were investigated at Mt. Taehwa and Gwangneung National Arboretum. Net Primary Production was calcualted based on speceis specific allometric equations. The relationship between sapflux density and diameter growth was different among species. For example, Q. aliena and A. holophylla had positive relationship between sapflux density and diameter growth (p = 0.037 and p =0.001, respectively), while P. koraiensis did not follow the trend (p = 0.5). However, when tree level transpiration was calculated by mulitiplying sapflux density with its sapwood area. In general, all species showed significant positive correlations between the transpiration and NPP (e.g., P. koraiensis(p = 0.003), Q. aliena and A. holophylla(p <0.001). In addition, comparison between conifer and broad leaves species, the conifers show the bigger changes in diameter growth and eventually NPP than that of the broad leaves tree in the same change of transpiration. Therefore, WUE for biomass increment was higher in conifer than broadleaf species.</p>

Aboveground biomass, productivity and carbon sequestration in Rhizophora stylosa mangrove forest of Southeast Sulawesi, Indonesia

Analuddin K, Kadidae LO, Haya LOMY, Septiana A, Sahidin I, Syahrir L, Rahim S, Fajar LOA, Nadaoka K. 2020. Aboveground biomass, productivity and carbon sequestration in Rhizophora stylosa mangrove forest of Southeast Sulawesi, Indonesia. Biodiversitas 21: 1316-1325. This study was aimed at analyzing the trends of aboveground biomass (AGB), productivity and carbon sequestration of Rhizophora stylosa Griff. forest in Rawa Aopa Watumohai National Park (RAWNP), Southeast Sulawesi, Indonesia. The DBH was the best predictor for partial and whole AGB of R. stylosa trees. The mean AGB was 562.76 ton ha-1. The yearly biomass increment of living trees, biomass increment of whole stands, standing dead biomass, and litterfall in R. stylosa forest were estimated as 52.87, 50.09, 2.78 and 12.00 ton ha-1, respectively, while its net primary production was about 64.88 ton ha-1 yr-1 indicating higher mangrove productivity. The total carbon stock in R. stylosa forest was 264.50 ton ha-1, while the annual net carbon budget, carbon gain and carbon input in R. stylosa forest was 23.54, 24.85 and 5.64 ton ha-1. However, the total CO2 stored in R. stylosa forest was 969.83 ton ha-1, while the annual of net CO2 uptake, CO2 gained and CO2 input was 86.33, 91.12 and 20.86 ton ha-1. The higher carbon sequestration and CO2 uptake in R. stylosa forest indicate its significant role in the global carbon accumulation and reducing atmospheric CO2.

Nitrogen addition increased CO2 uptake more than non-CO2 greenhouse gases emissions in a Moso bamboo forest

Atmospheric nitrogen (N) deposition affects the greenhouse gas (GHG) balance of ecosystems through the net atmospheric CO2 exchange and the emission of non-CO2 GHGs (CH4 and N2O). We quantified the effects of N deposition on biomass increment, soil organic carbon (SOC), and N2O and CH4 fluxes and, ultimately, the net GHG budget at ecosystem level of a Moso bamboo forest in China. Nitrogen addition significantly increased woody biomass increment and SOC decomposition, increased N2O emission, and reduced soil CH4 uptake. Despite higher N2O and CH4 fluxes, the ecosystem remained a net GHG sink of 26.8 to 29.4 megagrams of CO2 equivalent hectare−1 year−1 after 4 years of N addition against 22.7 hectare−1 year−1 without N addition. The total net carbon benefits induced by atmospheric N deposition at current rates of 30 kilograms of N hectare−1 year−1 over Moso bamboo forests across China were estimated to be of 23.8 teragrams of CO2 equivalent year−1.

How can forest management increase biomass accumulation and CO2 sequestration? A case study on beech forests in Hesse, Germany

Background While the capability of forests to sequester carbon dioxide (CO2) is acknowledged as an important component in fighting climate change, a closer look reveals the difficulties in determining the actual contribution by forest management when indirect and natural impacts are to be factored out. The goal of this study is to determine the direct human-induced impacts on forest growth by cumulative biomass growth and resulting structural changes, exemplified for a dominating forest species Fagus sylvatica L. in central Europe. In 1988, forest reserves with directly adjacent forest management areas (under business as usual management) were established in the federal state of Hesse, Germany. Thereof, 212 ha of forest reserve and 224 ha of management area were selected for this study. Biomass changes were recorded for a time span of 19 to 24 years by methods used in the National Inventory Report (NIR) and structural changes by standard approaches, as well as by a growth-dominance model. Results The results indicate a higher rate of cumulative biomass production in the investigated management areas and age classes. The cumulative biomass growth reveals a superior periodic biomass accumulation of about 16%. For beech alone, it is noted to be about 19% higher in management areas than in forest reserves. When harvests are not included, forest reserves provide about 40% more biomass than management areas. The analysis of growth-dominance structures indicates that forest management led to a situation where trees of all sizes contributed to biomass increment more proportionally; a related increase in productivity may be explained by potentially improved resource-use efficiency. Conclusions The results allow a conclusion on management-induced structural changes and their impact on carbon sequestration for Fagus sylvatica L., the dominating forest species in central Germany. This affirms a potential superiority of managed forests to forests where the management was abandoned in terms of biomass accumulation and reveal the impact and effect of the respective interventions. Especially the analysis of growth-dominance structures indicates that forest management resulted in more balanced dominance structures, and these in higher individual biomass increment. Forest management obviously led to a situation where trees of all sizes contributed to biomass increment more proportionally.

Assessing site productivity based on national forest inventory data and its dependence on site conditions for spruce dominated forests in Germany

Aim of study: (i) To estimate site productivity based on German national forest inventory (NFI) data using above-ground wood biomass increment (ΔB) of the stand and (ii) to develop a model that explains site productivity quantified by ΔB in dependence on climate and soil conditions as well as stand characteristics for Norway spruce (Picea abies (L.) Karst.).Area of study: Germany, which ranges from the North Sea to the Bavarian Alps in the south encompassing lowlands in the north, uplands in central Germany and low mountain ranges mainly in southern Germany.Material and methods: Biomass increment of the stand between the 2nd and 3rd NFI was calculated as measure for site productivity. Generalized additive models were fitted to explain biomass increment in dependence on stand age, stand density and environmental variables.Main results: Great part of the variation in biomass increment was due to differences in stand age and stand density. Mean annual temperature and summer precipitation, temperature seasonality, base saturation, C/N ratio and soil texture explained further variation. External validation of the model using data from experimental plots showed good model performance.Research highlights: The study outlines both the potential as well as the restrictions in using biomass increment as a measure for site productivity and as response variable in statistical site-productivity models: biomass increment of the stand is a comprehensive measure of site potential as it incorporates both height and basal area increment as well as stem number. However, it entails the difficulty of how to deal with the influence of management on stand density.Keywords: Site index; site potential; biomass increment; statistical model; climate.

Aboveground Net Primary Production at Acacia mangium Plantation in Northern Vietnam

Net primary production (NPP) is an important index for understanding carbon cycling in forest ecosystems. In this study, aboveground NPP at Acacia mangium plantation was estimated basing on allometry for aboveground biomass increment (ΔM) and litter trap technique for litterfall (Lf). The experiment was conducted in two plots of 300 m2 each (15 × 20 m), established at a 21-month old plantation. Data were collected five times of 3-month intervals in a total duration of 357 days. The results indicated that Lf and ΔM were seasonal-dependent. Litterfall was highest (4.06 g m-1 day-1) during Sep-Jan (late rainy season, early winter) and lowest (1.10 g m-1 day-1) during Mar-Jun (early rainy season, early summer). While, ΔM was highest (13.51 g m-1 day-1) during Jun-Sep (rainy season, summer) and lowest (3.10 g m-1 day-1) during Jan-Mar (dry season, winter). Total Lf in a duration of 357 days was 9.69 tons ha-1 and ΔM was 27.71 tons ha-1, leading to total aboveground NPP of the present study plantation of 37.40 tons ha-1. It is concluded that aboveground NPP of acacia plantation was much higher than other forests of different types and ages around the world. Such difference indicates the importance of acacia plantation in soil nutrient cycling through litterfall decomposition and carbon sequestration through aboveground biomass increment.