Stand Stem Volume Research Articles

Accounting for forest management in the estimation of forest carbon balance using the dynamic vegetation model LPJ-GUESS (v4.0, r9710): implementation and evaluation of simulations for Europe

Abstract. Global forests are the main component of the land carbon sink, which acts as a partial buffer to CO2 emissions into the atmosphere. Dynamic vegetation models offer an approach to projecting the development of forest carbon sink capacity in a future climate. Forest management capabilities are important to include in dynamic vegetation models to account for the effects of age and species structure and wood harvest on carbon stocks and carbon storage potential. This article describes the implementation of a forest management module containing even-age and clear-cut and uneven-age and continuous-cover management alternatives in the dynamic vegetation model LPJ-GUESS. Different age and species structure initialisation strategies and harvest alternatives are introduced. The model is applied at stand and European scales. Different management alternatives are applied in simulations of European beech (Fagus sylvaticus) and Norway spruce (Picea abies) even-aged monoculture stands in central Europe and evaluated against above-ground standing stem volume and harvested volume data from long-term experimental plots. At the European scale, an automated thinning and clear-cut strategy is applied. Modelled carbon stocks and fluxes are evaluated against reported data at the continent and country levels. Including wood harvest in regrowth forests increases the simulated total European carbon sink by 32 % in 1991–2015 and improves the fit to the reported European carbon sink, growing stock, and net annual increment (NAI). Growing stock (156 m3 ha−1) and NAI (5.4 m3 ha1 yr1) densities in 2010 are close to reported values, while the carbon sink density in 2000–2007 (0.085 kg C m−2 yr1) equates to 63 % of reported values, most likely reflecting uncertainties in carbon fluxes from soil given the unaccounted for forest land-use history in the simulations. The fit of modelled and reported values for individual European countries varies, but NAI is generally closer to reported values when including wood harvest in simulations.

Stand growth and structure of mixed-species and monospecific stands of Scots pine (Pinus sylvestris L.) and oak (Q. robur L., Quercus petraea (Matt.) Liebl.) analysed along a productivity gradient through Europe

Past failures of monocultures, caused by wind-throw or insect damages, and ongoing climate change currently strongly stimulate research into mixed-species stands. So far, the focus has mainly been on combinations of species with obvious complementary functional traits. However, for any generalization, a broad overview of the mixing reactions of functionally different tree species in different mixing proportions, patterns and under different site conditions is needed, including assemblages of species with rather similar demands on resources such as light. Here, we studied the growth of Scots pine and oak in mixed versus monospecific stands on 36 triplets located along a productivity gradient across Europe, reaching from Sweden to Spain and from France to Georgia. The set-up represents a wide variation in precipitation (456–1250 mm year−1), mean annual temperature (6.7–11.5 °C) and drought index by de Martonne (21–63 mm °C−1). Stand inventories and increment cores of trees stemming from 40- to 132-year-old, fully stocked stands on 0.04–0.94-ha-sized plots provided insight into how species mixing modifies stand growth and structure compared with neighbouring monospecific stands. On average, the standing stem volume was 436 and 360 m3 ha−1 in the monocultures of Scots pine and oak, respectively, and 418 m3 ha−1 in the mixed stands. The corresponding periodical annual volume increment amounted to 10.5 and 9.1 m3 ha−1 year−1 in the monocultures and 10.5 m3 ha−1 year−1 in the mixed stands. Scots pine showed a 10% larger quadratic mean diameter (p < 0.05), a 7% larger dominant diameter (p < 0.01) and a 9% higher growth of basal area and volume in mixed stands compared with neighbouring monocultures. For Scots pine, the productivity advantages of growing in mixture increased with site index (p < 0.01) and water supply (p < 0.01), while for oak they decreased with site index (p < 0.01). In total, the superior productivity of mixed stands compared to monocultures increased with water supply (p < 0.10). Based on 7843 measured crowns, we found that in mixture both species, but especially oak, had significantly wider crowns (p < 0.001) than in monocultures. On average, we found relatively small effects of species mixing on stand growth and structure. Scots pine benefiting on rich, and oak on poor sites, allows for a mixture that is productive and most likely climate resistant all along a wide ecological gradient. We discuss the potential of this mixture in view of climate change.

Afforested farmland vs. forestland: Effects of bark stripping by Cervus elaphus and climate on production potential and structure of Picea abies forests.

The aim of this study was to evaluate (1) effects of bark stripping and climatic factors on radial growth of Picea abies /L./ Karst., (2) production and structural differences between stands established on the forestland and abandoned farmland (afforested farmland–henceforth, farmland), and (3) interaction among the losses caused by ungulate damages, production, diversity, and soil types. Data acquired from four permanent research plots (PRPs) located on the forestland and eight PRPs on the farmland were used. A number of tree- and stand-level models, stand structural indices, tree-rings, and climate characteristics were analysed to evaluate the hypotheses. The results show significantly higher means of DBH, tree height and basal area on the forestland compared to those on the farmland. There was a larger mean standing stem volume on the forestland (466 m3 ha–1) compared to farmland (770 m3 ha–1). Significant difference was observed between the mean DBH and mean stem volume of healthy trees compared to those of the trees with substantial damage (girth damage >1/3 of stem circumference). A greater extent of the girth damage was found on 86% trees on the farmland, while 54% damage on the forestland. About 62% bark-strip damage was further deteriorated by rot infection on the farmland, while on the forestland such an infection was only for 39% trees. The precipitation significantly positively affected the radial growth of trees that were largely affected by ungulate damages on the farmland.

Hydrology of Drained Peatland Forest: Numerical Experiment on the Role of Tree Stand Heterogeneity and Management

A prerequisite for sustainable peatland forestry is sufficiently low water table (WT) level for profitable tree production. This requires better understanding on controls and feedbacks between tree stand and its evapotranspiration, drainage network condition, climate, and WT levels. This study explores the role of spatial tree stand distribution in the spatiotemporal distribution of WT levels and site water balance. A numerical experiment was conducted by a three-dimensional (3-D) hydrological model (FLUSH) applied to a 0.5 ha peatland forest assuming (1) spatially uniform interception and transpiration, (2) interception and transpiration scaled with spatial distributions of tree crown and root biomass, and (3) the combination of spatially scaled interception and uniform transpiration. Site water balance and WT levels were simulated for two meteorologically contrasting years. Spatial variations in transpiration were found to control WT levels even in a forest with relatively low stand stem volume (&lt;100 m3/ha). Forest management scenarios demonstrated how stand thinning and reduced drainage efficiency raised WT levels and increased the area and duration of excessively wet conditions having potentially negative economic (reduced tree growth) and environmental (e.g., methane emissions, phosphorus mobilization) consequences. In practice, silvicultural treatment manipulating spatial stand structure should be optimized to avoid emergence of wet spots.

Litterfall in relation to stand parameters and climatic factors in Pinus brutia forests in Turkey

ABSTRACTWith this study we investigated the effective factors on annual amount of total litterfall and needle litterfall in Pinus brutia forests and estimated them with a regression model based on certain stand parameters. We studied 27 permanent plots representing different stand structure and environmental conditions in South-Western Turkey. Litterfall was collected in three month intervals corresponding to each of four seasons for a three-year period. We found a significant relationship between litterfall and stand properties such as crown closure (%), basal area (m2 ha−1), stand stem volume (m3 ha−1), above-ground biomass (t ha−1), mean annual volume increment (m3 ha−1 yr−1) and site index (T = 75). Similar relationships also hold true between litterfall and each of such climatic factors as seasonal mean temperature (°C), relative humidity (%) and temperature/precipitation ratio (dimensionless). The mean annual litterfall considerably varied depending on stand characteristics and certain environmental factors. Both needle litterfall and total litterfall may be predicted for long term by regression models using certain stand parameters. Models developed for litterfall of P. brutia forests in this study may be used for national C inventory in Turkey.

Tree component biomass expansion factors and root-to-shoot ratio of Lebombo ironwood: measurement uncertainty.

BackgroundNational and regional aboveground biomass (AGB) estimates are generally computed based on standing stem volume estimates from forest inventories and default biomass expansion factors (BEFs). AGB estimates are converted to estimates of belowground biomass (BGB) using default root-to-shoot ratios (R/S). Thus, BEFs and R/S are not estimated in ordinary forest inventories, which results in uncertainty in estimates of AGB and BGB. Here, we measured BEF and R/S values (including uncertainty) for different components of Lebombo ironwood (Androstachys johnsonii Prain) trees and assessed their dependence on tree size.ResultsThe BEF values of tree components were unrelated or weakly related to tree size, and R/S was independent of tree size. BEF values varied from 0.02 for foliage to 1.31 Mg m−3 for whole tree; measurement uncertainty (SE) varied from 2.9% for stem BEF to 10.6% for whole-tree BEF. The belowground, aboveground, and whole-tree BEF-based biomass densities were 30 ± 2.3 (SE = 3.89%), 121 ± 7.84 (SE = 3.23%), and 151 ± 9.87 Mg ha−1(SE = 3.27%), respectively. R/S was 0.24 with an uncertainty of 3.4%.ConclusionsBased on the finding of independence or weak dependence of BEF on tree size, we concluded that, for A. johnsonii, constant component BEF values can be accurately used within the interval of harvested tree sizes.

Effect of species composition on the production rate and efficiency of young Picea glauca–Populus tremuloides forests

Stand stem volume growth, aboveground tree biomass growth, and site occupancy were measured in 20-year-old mixed stands dominated by white spruce (Picea glauca [Moench] Voss) and trembling aspen (Populus tremuloides Michx.) to examine the effects of species composition on the rate and efficiency of forest production. Measures of site occupancy derived from Plant Canopy Analyzer data indicated that sample plots were fully occupied, and that leaf area index and light interception increased with increasing softwood (SW) proportion. Relationships between site occupancy and SW proportion differed among occupancy metrics, suggesting that basal area, stand density index, and crown area index do not adequately represent use of the light resource. No significant effect of species proportion on the rate of volume or biomass production was detected, contradicting the hypothesis that competitive reduction and facilitation might increase the production of mixed stands. Production efficiency based on light interception for both stand components combined varied weakly with SW proportion. Efficiency metrics based on surrogates for light interception showed differing patterns with SW proportion, underscoring the need for caution in interpreting these metrics in relation to resource use.

Estimation of above-ground biomass and sequestered carbon of Taurus Cedar (Cedrus libani L.) in Antalya, Turkey

Abstract: Based on data obtained from 36 sample trees, above-ground biomass development of Taurus Cedar was modeled according to tree components on a single-tree basis. Carbon concentrations of tree components were established with the help of samples taken from sample trees. The biomass and sequestered carbon were modeled from the standing stem volume of single trees. It was determined that a coefficient of 0.51 could be used for Taurus Cedar species as a conversion factor from fresh weight to dry weight. Carbon concentrations were found to be lowest in branch barks, with a ratio of 49.5%, and highest in needles, with a ratio of 52.8%. According to the results of a comparison between volume, biomass and stored carbon amounts, 70.27 tons of biomass and 35.56 tons of carbon are stored in each standing stem volume of 100 m3.

Modeling Survival, Yield, Volume Partitioning and Their Response to Thinning for Longleaf Pine Plantations

Longleaf pine (Pinus palustris Mill.) is an important tree species of the southeast U.S. Currently there is no comprehensive stand-level growth and yield model for the species. The model system described here estimates site index (SI) if dominant height (Hdom) and stand age are known (inversely, the model can project Hdom at any given age if SI is known). The survival (N) equation was dependent on stand age and Hdom, predicting greater mortality on stands with larger Hdom. The function that predicts stand basal area (BA) for unthinned stands was dependent on N and Hdom. For thinned stands BA was predicted with a competition index that was dependent on stand age. The function that best predicted stand stem volume (outside or inside bark) was dependent on BA and Hdom. All functions performed well for a wide range of stand ages and productivity, with coefficients of determination ranging between 0.946 (BA) and 0.998 (N). We also developed equations to estimate merchantable volume yield consisting of different combinations of threshold diameter at breast height and top diameter for longleaf pine stands. The equations presented in this study performed similarly or slightly better than other reported models to estimate future N, Hdom and BA. The system presented here provides important new tools for supporting future longleaf pine management and research.

Use of lidar data to simulate forest net primary production

A method has been recently presented to predict the net primary production (NPP) of Mediterranean forests by integrating conventional and remote-sensing data. This method was based on the use of two models, C-Fix and BIOME-BGC, whose outputs are combined with estimates of stem volume and tree age to predict the NPP of the examined ecosystems. This article investigates the possibility of deriving these two forest attributes from airborne high-resolution lidar data. The research was carried out in the San Rossore pine forest, a test site in Central Italy where several investigations have been conducted. First, estimates of stand stem volume and tree age were obtained from lidar data by application of a simplified method based on existing literature and a few ground measurements. The accuracy of these stand attributes was assessed by comparison with the independent ground data derived from a recent forest inventory. Next, the stem volume and tree age estimates were used to drive the NPP modelling strategy, whose outputs were evaluated against the inventory measurements of current annual increment (CAI). The simplified lidar data processing method produces stand stem volume and tree age estimates having moderate accuracy, which are useful to feed the modelling strategy and predict CAI at a stand level. This method's success raises the possibility of integrating ecosystem modelling techniques and lidar data for the simulation of net forest carbon fluxes.

Twenty-Five Years of Intensive Forest Management with Southern Pines: Important Lessons Learned

Abstract A commitment to long-term forest research provides the basis and opportunity to understand developmental processes and stand dynamics over an entire rotation. The southeastern United States has undergone a significant evolution in forest management practices over the last 60 years, especially in regard to the intensification of pine plantation silviculture. However, few studies have examined production relationships for an entire rotation. This article reviews results from a rotation-length experiment that tested factorial combinations of understory competition control and sustained fertilizer additions on the productivity and stand dynamics of loblolly (Pinus taeda L.) and slash pine (Pinus elliottii var. elliottii) in north central Florida. After 25 years, fertilizer and competition control treatments increased site index (base age, 25 years) from 64 to 87 ft in loblolly pine and from 75 to 88 ft in slash pine. In addition, these cultural treatments increased total stand stem volume accumulation by 1.8–2.2-fold compared with the control treatments for slash and loblolly pine, respectively; the proportion of volume in high-value product classes such as chip-n-saw (C/S) and sawtimber was also increased in both species (e.g., 39% in C/S and sawtimber in the loblolly pine control treatment versus 74–87% in the fertilizer and/or weed control treatments). Overall, results from this study, as well as others in the region, highlight the overriding importance of soil nutrient supply on long-term productivity of southern pine stands.

Soil–atmosphere CO 2, CH 4 and N 2O fluxes in boreal forestry-drained peatlands

Greenhouse gas emissions from managed peatlands are annually reported to the UNFCCC. For the estimation of greenhouse gas (GHG) balances on a country-wide basis, it is necessary to know how soil–atmosphere fluxes are associated with variables that are available for spatial upscaling. We measured momentary soil–atmosphere CO 2 (heterotrophic and total soil respiration), CH 4 and N 2O fluxes at 68 forestry-drained peatland sites in Finland over two growing seasons. We estimated annual CO 2 effluxes for the sites using site-specific temperature regressions and simulations in half-hourly time steps. Annual CH 4 and N 2O fluxes were interpolated from the measurements. We then tested how well climate and site variables derived from forest inventory results and weather statistics could be used to explain between-site variation in the annual fluxes. The estimated annual CO 2 effluxes ranged from 1165 to 4437 g m −2 year −1 (total soil respiration) and from 534 to 2455 g m −2 year −1 (heterotrophic soil respiration). Means of 95% confidence intervals were ±12% of total and ±22% of heterotrophic soil respiration. Estimated annual CO 2 efflux was strongly correlated with soil respiration at the reference temperature (10 °C) and with summer mean air temperature. Temperature sensitivity had little effect on the estimated annual fluxes. Models with tree stand stem volume, site type and summer mean air temperature as independent variables explained 56% of total and 57% of heterotrophic annual CO 2 effluxes. Adding summer mean water table depth to the models raised the explanatory power to 66% and 64% respectively. Most of the sites were small CH 4 sinks and N 2O sources. The interpolated annual CH 4 flux (range: −0.97 to 12.50 g m −2 year −1) was best explained by summer mean water table depth ( r 2 = 64%) and rather weakly by tree stand stem volume ( r 2 = 22%) and mire vegetation cover ( r 2 = 15%). N 2O flux (range: −0.03 to 0.92 g m −2 year −1) was best explained by peat CN ratio ( r 2 = 35%). Site type explained 13% of annual N 2O flux. We suggest that water table depth should be measured in national land-use inventories for improving the estimation of country-level GHG fluxes for peatlands.

Estimating field-plot data of forest stands using airborne laser scanning and SPOT HRG data

Airborne laser scanner systems provide detailed forest information that can be used for important improvements in forest management decisions. Planning systems under development use plot-survey data to represent forest stands in large forest holdings which enables new flexible methods to model the forest and optimize selection of silvicultural treatments. In Sweden today, only averages of forest stand variables are used, and the survey methods used do not provide plot-survey data for all stands in large forest holdings. This is a task possibly solved using airborne laser scanner data. Various measures can be derived from laser data, each describing different forest variables, such as tree height distribution, vegetation density and vertical tree crown structure. Here, imputation of field plot (10 m radius) data using measures derived from airborne laser scanner data (TopEye) and optical image data (SPOT 5 HRG satellite sensor) were evaluated as a method to provide data for new long-term management planning systems. In addition to commonly applied measures, the semivariogram of laser measurements was evaluated as a new measure to extract spatial characteristics of the forest. The study used data from 870, 10 m radius field plots (0 to 812 m 3 ha − 1 ) surveyed for a 1200 ha large forest estate in the south of Sweden. At the best, combining measures derived from laser scanner data and SPOT 5 data, stand mean volume was estimated with a root mean square error (RMSE) of 20% of the sample mean and stem density with 22% RMSE. Bias of stem density estimates was 5%, and stand stem volume 4%. Although these accuracies are sufficient for operational application, estimates of tree species proportions and within-stand variation were clearly not.

Genotype × environment interactions in selected loblolly and slash pine plantations in the Southeastern United States

Few studies have quantified the combined effects of silvicultural treatments and genetic improvement on unit area production of full-sib family blocks of loblolly ( Pinus taeda L .) and slash pine ( P. elliottii Engelm. var. elliotttii). Efficient operational deployment of genetic materials requires an understanding of possible site and silvicultural treatment interactions to maximize yield potential. We examined genotype (family) by environmental interactions (G × E) through age 5 years using a factorial experiment consisting of silvicultural treatment intensity (operational versus intensive), planting density (1334 versus 2990 trees ha −1) and families (seven elite full-sib loblolly and six elite full-sib slash pine families). In January of 2000, randomized complete block, split-plot experiments were installed at two locations for each species in southeast Georgia and northeast Florida. Five years after planting, both loblolly and slash pine demonstrated significant interactions among several factors: genotype × location ( p < 0.028 and p < 0.016, respectively), genotype × silvicultural treatment intensity ( p < 0.055 and p < 0.059), and silvicultural treatment intensity × density ( p < 0.002 and p < 0.001) for basal area (BA) and standing stem volume (VOL). Genotype × silvicultural treatment interactions were positive, with the best overall performing families responding the greatest to intensive treatment. There were changes in slash pine family rankings between locations, which were partly explained by reductions in growth associated with a combination of fusiform rust infection [ Cronartium quercum (Berk.) Miyabe ex Shirai f. sp. fusiforme] and wind damage from the 2004 hurricane season. No three-way interactions, which included family, were evident and all genetic sources were stable across the contrasting planting densities. At age 5, loblolly pine outperformed slash pine ( p < 0.0001), especially under the intensive silvicultural intensity. While loblolly performance was similar whether deployed in mixtures or pure family blocks, slash pine tended to be more productive in intimate mixtures than when grown in pure family blocks ( p = 0.0754 for aboveground biomass).

Biomass and biomass change in lodgepole pine stands in Alberta

We describe methods and results for broad-scale estimation and mapping of forest biomass for the Canadian province of Alberta. Differences over successive decades provided an estimate of biomass change. Over 1500 permanent sample plots (PSP) were analyzed from across the range of lodgepole pine (Pinus contorta var. latifolia Engelm.), the major forest tree species of Alberta. The PSP network is densest in stands aged between 70 and 100 years and is well-represented by stands of all ages to 150 years of age. Stand biomass (Mg ha(-1)) was estimated for each PSP plot as the sum of the respective biomass components for each tree (live and standing dead). The biomass components for live trees were stem, bark, branches, foliage and roots. The components for standing dead trees excluded foliage. Equations from previous biomass studies were used for biomass component estimation. Biomass estimates of additional non-tree components were attempted, but without much success. Biomass of the soil organic layer was estimated once on 452 PSPs and a mean estimate of total dead fuels on the ground (28.4 Mg ha(-1)) was available only for the entire distribution of lodgepole pine. However, values of these two components were essentially constant over time and therefore did not alter the analysis or conclusions obtained by analyzing total tree biomass alone. We then used this spatial network of 1549 plots as the basis for mapping biomass across Alberta. Mapping methods were based on Australian National University SPLINe (ANUSPLIN) software, Hutchinson's thin-plate smoothing spline in four dimensions (latitude, longitude, elevation and biomass). Total tree biomass (mean = 172 Mg ha(-1)) was dominated by stem biomass (mean = 106 Mg ha(-1)), which was an order of magnitude greater than the mean estimates for the bark (11 Mg ha(-1)), branch (12 Mg ha(-1)) and foliage (12 Mg ha(-1)) components. A close relationship was found between total tree biomass and stand stem volume (R(2) = 0.992 with n = 3585; note that volume and biomass were calculated independently). We compared total tree biomass for two decades, the 1980s and the 1990s. After correcting for changes in harvest removals over time, the mean change in total biomass was positive (0.99 Mg ha(-1) year(-1)) and differed significantly from zero (n = 421; P < 0.001). Estimates ranged from -13.9 to 8.0 Mg ha(-1) year(-1). The heart of the lodgepole pine distribution (primarily the Foothills subregions) showed an increase in biomass, whereas isolated pockets of lodgepole pine in the boreal northern subregion indicated a decline in biomass.

Relationship between Maximum Stem Volume and Density during a Course of Self-thinning in a Cryptomeria japonica Plantation

Cryptomeria japonica plantation was monitored every year during 15 years from 1983 to 1997 for stem diameter and volume. The reciprocal equation, 1/Y = A + B/N, was applied to the relationship between cumulative volume Y and cumulative number N from the largest tree in the stand each year. The parameters A and B, which means respectively the reciprocal of an asymptotic value of total stand stem volume and the reciprocal of the maximum stem volume, are related by a power function. The power functional relationship between A and B derived a linear relationship of B-points ( <TEX>$N_{B}$</TEX>, <TEX>$V_{B}$</TEX>; <TEX>$N_{B}$</TEX> = B/A, <TEX>$Y_{B}$</TEX> = 1/2A) of each Y-N curve on log-log coordinates. The gradient of B-point line was so steep that the Y-N curve moved parallel upward year by year. The time trajectory of mean stem volume (W) and density (<TEX>$\rho$</TEX>) provided evidence in favor of the 3/2 power law of self-thinning, because the gradient of W - <TEX>$\rho$</TEX> trajectory on log-log coordinates approximated to -3/2 at the final stage of stand development. On the basis of the results of Y-N curves and W - <TEX>$\rho$</TEX> trajectory, the time trajectory of maximum stem volume <TEX>$W_{max obs}$</TEX> and <TEX>$\rho$</TEX> was derived theoretically. The gradient of <TEX>$W_{max obs}$</TEX> - <TEX>$\rho$</TEX> trajectory on log-log coordinates is calculated to be -0.6105 at the final stage. The gradient of <TEX>$W_{max obs}$</TEX> - <TEX>$\rho$</TEX> trajectory was steeper than that of W - <TEX>$\rho$</TEX> trajectory at the early stage, while the former is gentler than the latter at the later stage.stage.e.age.e.

Simultaneous Estimations of Forest Parameters using Aerial Photograph Interpreted Data and the k Nearest Neighbour Method

Information about the state of the forest is of vital importance in forest management planning. To enable high-precision modelling, many forest planning systems demand input data at the single-tree level. The conventional strategy for collecting such data is a plot-wise field inventory. This is expensive and, thus, cost-efficient alternatives are of interest. During recent years, the focus has been on remote sensing techniques. The k nearest neighbour (kNN) estimation method is a way to assign plot-wise data to all stands in a forest area, using remotely sensed data in connection with a sparse sample of field reference plots. Plot-wise aerial photograph interpretations combined with information from a stand register were used in this study. Nearness to a reference plot was decided upon using a regression transform distance. Standing stem volume was estimated with a relative root mean square error (RMSE) equal to 20% at the stand level, while age could be estimated with a RMSE equal to 15%. A cost-efficient data-capturing strategy could be to assign plot data with the presented kNN method to some types of forest, while using traditional field inventories in other, more valuable, stands.

Tree stand development and carbon sequestration in drained peatland stands in Finland – a simulation study

Drained peatland forests form an important timber resource in Finland. They also form a sink for atmospheric carbon (C) because of the increased growth and C sequestration rates following drainage. These rates have, however, been poorly quantified. We simulated the tree stand dynamics for drained peatland stands with and without cuttings over two stand rotations. Simulations were done on four peatland site types and two regions in Finland with different climatic conditions, using recently published peatland tree growth models applied in a stand simulator. We then calculated the amount of C stored in the stands on the basis of previously published tree-level biomass and C content models. Finally, we developed regression models to estimate C stores in the tree stands using stand stem volume as the predictor variable. In the managed stands, the mean growth (annual volume increment) ranged from 2 to 9 m3 ha–1 a–1, depending on the rotation (first/second), site type and region. Total yield during one rotation varied from 250 to 920 m3 ha–1. The maximum stand volumes varied from 220 to 520 m3 ha–1 in the managed stands and from 360 to 770 m3 ha–1 in the unmanaged. By the end of the first post-drainage rotation the total C store in the managed stands had increased by 6–12 kg C m–2 (i.e. 45–140 g C m–2 a–1) compared to that in the undrained situation. Averaged over two rotations, the increase in the total C store was 3–6 kg C m–2. In the corresponding unmanaged stands the C stores increased by 8–15 kg m–2 over the same periods. At stand level, the C stores were almost linearly related to the stem volume and the developed regression equations could explain the variation in the simulated C stores almost entirely.

Leaf area and tree increment dynamics of even-aged and multiaged lodgepole pine stands in Montana

Age structure and distribution of leaf area index (LAI) of even and multiaged lodgepole pine (Pinus contorta var. latifolia Engelm.) stands were examined on three study areas in western and central Montana. Projected leaf area was determined based on a relationship with sapwood cross-sectional area at breast height. Stand structure and LAI varied considerably between individual plots. LAI and stand stem volume increment were significantly higher in multiaged than even-aged stands with the exception of one study area, which had higher volume increment in even-aged stands. Older cohorts and higher canopy strata generally had greater LAI than younger cohorts and lower strata. Ratios of stem volume increment to leaf area were used to assess stand, cohort, and individual tree vigor or growing space efficiency (GSE). Even-aged stands had significantly higher GSEs in individual study areas and overall than multiaged stands. Cohort GSE generally increased with increasing age of the cohort. Stand increment was weakly associated with stand LAI. Individual tree volume increment was strongly related to projected leaf area when stands were divided by age-classes or canopy strata. These results suggest separating these stands into components, such as age classes or canopy strata, and summing predicted increment for each component may provide more accurate prediction of stand increment than using whole-stand LAI.

Net ecosystem productivity, net primary productivity and ecosystem carbon sequestration in a Pinus radiata plantation subject to soil water deficit.

Tree carbon (C) uptake (net primary productivity excluding fine root turnover, NPP') in a New Zealand Pinus radiata D. Don plantation (42 degrees 52' S, 172 degrees 45' E) growing in a region subject to summer soil water deficit was investigated jointly with canopy assimilation (A(c)) and ecosystem-atmosphere C exchange rate (net ecosystem productivity, NEP). Net primary productivity was derived from biweekly stem diameter growth measurements using allometric relations, established after selective tree harvesting, and a litterfall model. Estimates of A(c) and NEP were used to drive a biochemically based and environmentally constrained model validated by seasonal eddy covariance measurements. Over three years with variable rainfall, NPP' varied between 8.8 and 10.6 Mg C ha(-1) year(-1), whereas A(c) and NEP were 16.9 to 18.4 Mg C ha(-1) year(-1) and 5.0-7.2 Mg C ha(-1) year(-1), respectively. At the end of the growing season, C was mostly allocated to wood, with nearly half (47%) to stems and 27% to coarse roots. On an annual basis, the ratio of NEP to stand stem volume growth rate was 0.24 +/- 0.02 Mg C m(-3). The conservative nature of this ratio suggests that annual NEP can be estimated from forest yield tables. On a biweekly basis, NPP' repeatedly lagged A(c), suggesting the occurrence of intermediate C storage. Seasonal NPP'/A(c) thus varied between nearly zero and one. On an annual basis, however, NPP'/A(c) was 0.54 +/- 0.03, indicating a conservative allocation of C to autotrophic respiration. In the water-limited environment, variation in C sequestration rate was largely accounted for by a parameter integrative for changes in soil water content. The combination of mensurational data with canopy and ecosystem C fluxes yielded an estimate of heterotrophic respiration (NPP' - NEP) approximately 30% of NPP' and approximately 50% of NEP. The estimation of fine-root turnover rate is discussed.