Standing Stock Research Articles

Carbon stocks in temperate forests of south-eastern Australia reflect large tree distribution and edaphic conditions

Reducing uncertainty in forest carbon estimates at local and regional scales has become increasingly important due to the centrality of the terrestrial carbon cycle in issues of climate change. Despite relatively limited geographical extent, temperate forests are among the most carbon dense forests in the world. Estimates of carbon in key understorey life forms and belowground components of these forests have often been excluded from previous studies in south-eastern Australia. We estimated above- and belowground carbon stocks (including soil to 0.3m depth) in stands of cool temperate rainforest (‘rainforest’), wet sclerophyll forest (‘eucalypt forest’), and mixed rainforest–wet sclerophyll stands (‘ecotone forest’) across a wide range of environmental conditions and forest structures. We examined relationships among component carbon stocks and a range of environmental variables (edaphic, climatic, spatial) and present the first allometric equations and carbon stock estimates for south-eastern Australian tree ferns. Component carbon stocks were within the range of published values for these stand types. Using multivariate analyses of all component stocks, we detected significantly more carbon in total above- and belowground components in ecotone (697Mgha−1, 95% confidence interval 575–819Mgha−1) and eucalypt forests (689Mgha−1, 605–773Mgha−1) than rainforest (550Mgha−1, 453–647Mgha−1). However, we found no significant differences among the stand types in the proportional distribution of carbon among components despite significant differences in structural composition as indicated by size class distributions of the main genera. Of total carbon, ∼48% was stored in trees (>2cm over-bark diameter), and ∼72% of tree carbon was stored in the largest 10% of all trees. The most important environmental variables associated with carbon stocks irrespective of stand type were edaphic variables, most commonly total and available soil nitrogen. Tree fern carbon was the only component stock more strongly associated with climatic and spatial than edaphic variables. Our findings indicate that disturbance mediated changes in stand dynamics could significantly alter total carbon stocks, particularly if more frequent fires limit tree recruitment and increase large tree mortality. Monitoring of these forests for carbon could place greater emphasis on key structural elements associated with the largest proportion of total carbon, the largest trees. By reducing uncertainties associated with estimates of carbon in key stocks, we can better understand potential future changes to the carbon cycle from altered stand dynamics under climate change.

Sistem Silvikultur Tebang Pilih Untuk Mitigasi Perubahan Iklim Melalui Kerangka Redd+

Komitmen Indonesia dalam mitigasi perubahan iklim khususnya disektor kehutanan melalui skema REDD+ (Reducing Emission from Deforestation and Degradation) dan juga melalui kegiatan konservasi, manajemen hutan lestari dan peningkatan stok karbon. Sistim silvikultur adalah proses penebangan, pemeliharaan dan penggantian suatu tegakan hutan untuk menghasilkan produksi kayu atau hasil hutan lainnya. Studi ini dilakukan dengan desk study/sistematik review. Penurunan kecepatan degradasi hutan dalam skema REDD+ berkaitan dengan kegiatan silvikultur seperti teknik pemanenan, pemeliharaan tegakan sisa dan penggantian tegakan kayu atau produk hutan lainnya. Peningkatan stok karbon terkait dengan penanaman perkayaan, pemberantasan gulma dan hama penyakit. Manajemen hutan lestari sudah diatur dalam sistim Tebang Pilih Tanam Indonesia (TPTI) dan penyempurnaannya. Kegiatan peningkatan stok dalam REDD+ terkait dengan sistim silvikukltur seperti tanaman pengayaan dan pemberantasan hama penyakit. Pengelolaan hutan lestari dalam REDD+ diakomodir dalam Tebang Pilih Tanam Indonesia dan penyempurnaannya. Pengurangan emisi melalui pencegahan atau penurunan degradasi hutan dalam skema REDD+ dapat diintervensi dengan sistim silvikultur : 1) Peningkatan stok karbon dengan menerapkan sistim TPTI secara konsisten; 2) Pelaksanaan kegiatan RIL (Reduced Impact Logging); 3) Memaksimalkan penanaman pengayaan dengan Silvikultur Intensif (SILIN); 4) Membangun kawasan konservasi dalam areal konsensi; 5) Perlindungan hutan dan 6) Merestorasi ekosistim area bekas tebangan

The dynamics of biomass production, carbon and nitrogen accumulation in grey alder (Alnus incana (L.) Moench) chronosequence stands in Estonia

In the present study the chronosequence approach was applied to the analysis of the dynamics of the growth of 2–45-year-old grey alder stands (Alnus incana) growing at fertile sites as well as the dynamics of carbon (C) and nitrogen (N) accumulation in woody biomass and in the soil. A new yield table was elaborated for natural grey alder stands growing at fertile sites. The average growing stock and increment of grey alder stands were lower than those presented in earlier yield tables compiled in Estonia or in the other Baltic or Nordic states. It can be explained by an uneven spatial distribution of trees in natural grey alder stands; because of this, the production of different alder stands of the same age was highly variable. However, some stands were characterised by remarkably high production, which indicates the high growth potential of this tree species. The bulk maturity of grey alder stands is achieved at the age of 12–13years. However, the recommendable optimal harvesting age of grey alder stands could be 20–25years, as annual woody biomass increment was high even after the age of 20years. The average stemwood density found in this study was 396±3.6kgm−3 and the average density of the branches was 460±2.9kgm−3. Regarding of CN accumulation in the stands, different land use histories demonstrated different patterns. First-generation grey alder stands growing on previously non-forested lands accumulated effectively C and N in the soil. The average increase of the C pool in the 10cm topsoil layer was in the range 1.1–1.2tha−1yr−1 in young stands and 0.97–0.84tha−1yr−1 in older stands. In the case of second-generation grey alder stands the soil C pool in young and old stands was of same magnitude and these stands accumulated C mainly in woody biomass. The share of the soil C pool in middle-aged and old grey alder stands was roughly two times as large as the C storage accumulated in the above-ground woody biomass of the trees. The average N accumulation in first-generation grey alder stands of the age of 14–35years was 74kgNha−1yr−1. Also a significant acidifying effect of alders on the soil pH status was revealed. The study confirmed that grey alder has the potential to be a high yielding tree in short-rotation forestry for woody biomass production. Grey alder stands serve as efficient forest ecosystems accumulating C both in biomass and in the soil. However, previous land use history plays an essential role in this respect.

西南地区退耕还林工程主要林分50年碳汇潜力

为评估西南地区退耕还林工程主要林分未来50a碳汇潜力，调查收集该地区2011年以前退耕还林工程主要造林树种及其造林面积等相关数据资料，利用国家森林资源清查资料中人工林历史数据建立生长模型，结合文献调研获得的相关林分碳计量参数，预测出本区域退耕还林工程7种主要林分碳储量和年碳储量未来变化。结果表明：西南地区退耕还林工程主要林分总碳储量在2020、2030、2040、2050和2060年分别为52.98、73.88-80.57、73.62-102.16、88.41-115.17和77.15-123.36TgC，年总碳储量则分别为3.15、-1.11-2.45、-3.92-1.95、2.08-0.96和0.25-0.73TgC，到2060年华山松、马尾松、柳杉、杉木、柏树、杨树和桉树7种林分碳汇潜力在无采伐情景下分别达到：13.01、15.01、13.44、24.13、28.05、15.63和14.09TgC，可对本地区森林碳汇功能产生明显影响。;Vegetation growth, through photosynthesis, takes up carbon dioxide from the atmosphere and converts to organic carbon into biomass thereby forms a carbon sink. Research on carbon sequestration potential of forests has become a key content to slow down global warming by forestry. To assess carbon sequestration potential in stands under the Grain for Green Program (GGP) in Southwest China, the carbon storages and their annual changes in the GGP-stands in the region were estimated based on: (1) collected data on annual planted area of each tree species under the GGP in Southwest China from 1999 to 2010; (2) empirical growth curves developed for each species of the GGP-stands using growth data about plantation from the National Forest Inventory; (3) parameters associated with stand such as wood density, biomass expansion factor, carbon fraction, the change rate in soil organic carbon content. Two scenarios for forest management option were schemed: scenario A for no harvesting and scenario B for logging at the time of maturity followed by replanting. The results showed that there are seven tree species with over 100,000 hm²of planted area in Southwest- China throughout the recent goal period of strategic planning for the GGP, and their total acreage account for 40.7% of that of all species of the GGP-stands. The expected carbon stocks in these major stands under the Grain for Green Project in Southwest China are52.98TgC, 73.88-80.57TgC, 73.63-102.16TgC, 88.41-115.17TgC and 77.15-123.36TgC(T=10¹²) by the year of 2020, 2030, 2040, 2050 and 2060, and the estimated relevant annual carbon stock changes are 3.15TgC, -1.11-2.45TgC, -3.92-1.95TgC, 2.08-0.96TgC and 0.25-0.73TgC, respectively. In 2060, the carbon stocks in forests of <em>Pinus armandii</em>, <em>Pinus massoniara</em>,<em> Cryptomeria fortunei</em>,<em> Cunninghamia laceolata</em>,<em> Cupressus </em>spp., <em>Populus deltoides</em> and <em>Eucalyptus</em> spp.under the Grain for Green Project in Southwest China will be 13.01TgC, 15.01TgC, 13.44TgC, 24.13TgC, 28.05TgC, 15.63TgC和14.09TgC, respectively, indicating a significant contribute to forest carbon sinks in this region. The <em>Cupressus </em>spp. species play a leading role in carbon sequestration potential in stands under the Grain for Green Project due to highest area proportion in Sichuan province, Chongqing municipality and even Southwest China. The <em>Cryptomeria fortune</em> and<em> Cunninghamia laceolata</em> species play a leading role in Guizhou province; the <em>Eucalyptus</em> spp. and <em>Pinus armandii</em> species in Yunnan province; the <em>Populus deltoides</em> species in Tibet autonomous region.

Spatial and temporal infaunal dynamics of the Blanes submarine canyon-slope system (NW Mediterranean); changes in nematode standing stocks, feeding types and gender-life stage ratios

Despite recent advances in the knowledge of submarine canyons ecosystems, our understanding of the faunal patterns and processes in these environments is still marginal. In this study, meiobenthic nematode communities (from 300m to 1600m depth) obtained in November 2003 and May 2004 at eight stations inside and outside Blanes submarine canyon were analysed for nematode standing stocks (SSs), feeding types and gender-life stage distributions. Environmental data were obtained by sediment traps and current meters, attached to moorings (April 2003–May 2004), and sediments samples analysed for biogeochemistry and grain size (May 2004). In November 2003, nematode SSs decreased with increasing depth (367.2 individuals and 7.31μgC per 10cm2 at 388m water depth to 7.7 individuals and 0.18μgC per 10cm2 at 1677m water depth), showing a significant negative relation (abundance: R2=0.620, p=0.020; biomass: R2=0.512, p=0.046). This was not the case in May 2004 (283.5 individuals and 3.53μgC per 10cm2 at 388m water depth to 490.8 individuals and 4.93μgC per 10cm2 at 1677m water depth; abundance: R2=0.003, p=0.902; biomass: R2=0.052, p=0.587), suggesting a temporal effect that overrides the traditional decrease of SSs with increasing water depth. Both water depth and sampling time played a significant role in explaining nematode SSs, but with differences between stations. No overall differences were observed between canyon and open slope stations. Nematode standing stock (SS) patterns can be explained by taking into account the interplay of phytodetrital input and disturbance events, with station differences such as topography playing an important role. Individual nematode size decreased from November 2003 to May 2004 and was explained by a food-induced genera shift and/or a food-induced transition from a ‘latent’ to a ‘reproductive’ nematode community. Our results suggest that size patterns in nematode communities are not solely governed by trophic conditions over longer periods of time in relatively food-rich environments such as canyons. We hypothesize that food pulses in a dynamic and topographical heterogeneous environment such as canyons regulate nematode size distributions, rather than long-term food availability. Feeding type distributions in the Blanes Canyon did not clearly resemble those from other canyon systems, apart from the spring assemblage at one station in the head of the canyon.

Hemlock loss due to the hemlock woolly adelgid does not affect ecosystem C storage but alters its distribution

The 1950s introduction of the hemlock woolly adelgid (HWA,Adelges tsugae) has caused extensive hemlock (Tsuga canadensis) mortality with little understanding of the long‐term consequences for forest carbon (C) storage. In southern New England, hemlock is being replaced by the early successional species black birch (Betula lenta). The objective of this research was to measure C stocks in stand types of varying age and abundance of hemlock and/or black birch. Using information from previous studies and comparisons of data between plots with identical land‐use history, we addressed the question of whether the quantity and distribution of C pools in black birch forests are the same as those found in the hemlock stands they replace and, if so, over what time scales. If HWA did not infest hemlock stands in central MA, C stocks in these secondary stands could still increase by at least ∼30% over a period of 100 years. Girdling, intended to simulate HWA infestation, resulted in a large transfer of C from live biomass to coarse woody debris five years after treatment, but had little effect on total ecosystem C content. A former hemlock stand killed by HWA and now dominated by black birch saplings (∼23,000 stems ha−1) also had a large pool of highly decayed CWD and a rapidly aggrading C pool in live biomass. C pools in biomass in a mature, secondary growth black birch stand ∼135 years since pastureland abandonment were as large as those in a primary‐growth hemlock stand ∼235 years of age. Because of uncertainties in the intensity of former land use and time since pastureland abandonment, this analysis can only speak to the potential consequences of HWA on forest‐C balance over the long term. Based on this analysis, it appears that ecosystem C storage is resilient to the loss of hemlock because of vigorous regrowth by black birch. This empirical finding is consistent with the results of a recent modeling effort.

Carbon stocks in managed and unmanaged old-growth western redcedar and western hemlock stands of Canada’s inland temperate rainforests

In the inland temperate rainforests (ITRs) of east-central British Columbia (BC), there is a lack of baseline carbon (C) stocks information for managed and unmanaged stands of old-growth western redcedar and hemlock. To fill the knowledge gap, we estimated C stocks of live trees, snags, coarse woody debris and forest floor (excluding mineral soil) and evaluated impacts of harvesting on these C stocks. We also accounted for heart-rot in stem wood of live cedar and hemlock, and identified uncertainties in live-tree C stocks estimation for more accurate assessment of the C. Forests stands were selected from three previously established silvicultural systems trials that contrasted three levels of harvesting intensity (clear-cut (CC, 0% retention), group retention (GR, 30%), group selection (GS, 70%)), and uncut old-growth (100%). Despite a high incidence of heart-rot, live-tree and total forest (minus mineral soil) C stocks (348±155 and 455±156Mg C ha−1, respectively) in uncut old-growth ITR stands were within the range of regional averages for old-growth forests in the Pacific Northwest (US) and coastal cedar and hemlocks forests of BC. Intensive harvesting (CC and GR) resulted in significant reductions in total forest C stocks (78% and 64%) relative to uncut old-growth stands. By contrast, total forest C stocks in stands where high-retention harvesting (GS) occurred were reduced by only 13% (not significant) relative to uncut old-growth stands. Analysis of uncertainty identified allometric equations to be the largest contributor to total uncertainty in live-tree C stocks, indicating the need to develop more robust equations to reduce the uncertainty for more accurate evaluation of harvesting impacts in old ITRs. Although heart-rot had no significant effects on forest C stocks in this study, we need a better scientific understanding of their contribution to live-tree C in this ecosystem. Nonetheless, these results underscore the importance of conserving C-rich old ITRs where possible and the potential for high-retention harvesting to maintain C stocks in this forest type.

Fine root standing stock and production in young beech and spruce stands

AbstractFine roots (defined by a maximum diameter of 2 mm) and assimilatory organs are the compartments which rotate carbon much faster than any other tree part. We focused on quantification of fine roots in young European beech and Norway spruce trees growing under the same ecological conditions. Standing stock of fine roots was estimated by soil coring during 2009 - 2012. Fine root production was established by the in-growth bag method. Standing stock and productions of fine roots were comparable in both tree species. The quantity of fine root biomass (at a soil depth of 0 -50 cm) varied inter-annually between 6.08 and 7.41 t per ha in the beech and from 5.10 to 6.49 t per ha in the spruce stand. Annual production of fine roots (soil depth of 0 - 30 cm) was between 1.11 and 1.63 t ha-1 in beech and between 0.95 and 1.54 t.ha-1 in spruce. We found that fine root standing stock at the beginning of each growing season was related to climatic conditions in the previous year. Annual fine root production was influenced by the climatic situation of the current year. In general, a maximum standing stock of fine roots as well as a relatively slow fine root turnover is expected in young forest stands. Whereas production of fine roots prevailed over mortality in a favorable year (sufficiency of precipitations and slightly above-average temperatures in 2010), there was a reverse situation in an unfavorable year (drought episodes in 2011). We concluded that although both forest types represented contrasting turnovers of assimilatory organs (once a year and once in 5 years in beech and spruce respectively), fine root turnover rates were very similar (approx. once per four years).

Thinning, Age, and Site Quality Influence Live Tree Carbon Stocks in Upland Hardwood Forests of the Southern Appalachians

This study examines the effects of thinning, age, and site quality on aboveground live tree carbon (ATC) (Mg/ha) stocks in upland hardwood forests of mixed-species composition in the southern Appalachian Mountains. In 1974, 80 plots ranging in size from 0.06 to 0.1 ha were established in even-aged, mixed-hardwood forests throughout the southern Appalachians. All trees 2.54 cm dbh within each plot were tagged and measured. Sixty-two plots received a low thinning to a broad range of residual basal areas (BAs) (m 2 /ha) whereas 18 of the 80 plots remained unthinned and served as controls. Remeasurement of plots occurred every 5 years through 2005. Individual tree volumes were converted to stand-level estimates of ATC stocks for each inventory cycle. The average net annual rate of carbon (C) storage in aboveground live tree biomass was significantly greater in thinned versus unthinned stands. We found that light low thinnings had a neutral to slightly positive effect on net ATC stocks over the long-term relative to unthinned stands of similar age and initial BA. Relative differences, however, varied with age when ingrowth data were excluded from the analysis and with age and BA when ingrowth data were included in the analysis. In general, the gains in net ATC stocks in thinned verses unthinned stands were minor. The increased rate at which thinned stands stored C coupled with substantial mortality in unthinned stands was probably responsible for this crossover effect of thinning on ATC stocks. FOR .S CI. 58(5):407-418.

Predicting soil and forest floor carbon stocks in Western Anatolian Scots pine stands, Turkey

The objective of this study was to determine the models which estimate the soil plus forest floor carbon stocks (TC) using some stand, climate, and topographic parameters in Scots pine (Pinus sylvestris L.) stands. 40 sample plots were taken from sites differing in aspects, elevation, slope degree, slope position, and stand growth condition. TC of the stands, as dependent variables, and stand, climate, and topographic properties, as independent variables, were determined and evaluated with multiple regression analysis (MRA) and classification and regression tree technique (CART). In conclusion, TC were related with elevation, slope degree, slope position, aspect, actual evapotranspiration, mean annual precipitation, length of vegetation period, rainfall in the driest month, rainfall from June to September, stand volume, and site index. 91% of the variance in TC was explained with CART while 60% with MRA in a local scale. The results showed that soil and forest floor might become a carbon source where the rainfall decreased, but a sink, especially in productive sites where rainfall of the driest month increased. Key words: Carbon stocks, forest floor, regression tree, Scots pine, soil.

Capability of ETM+ in estimates standing stock in beech stands of mountain forest

Stand volume is an important criterion in forest sciences for monitoring status and function of forests, estimation of productivity, prediction and modeling of forest disturbance, economic and environmental issues, and forest planning. The aim of this research is to evaluate the ETM+ sensor of Landsat 7 satellite data ability for forest timber volume estimation. For this purpose, 40 selective sample plots with 60 × 60 m dimension were selected, and in each sample plot, standing volume was calculated. Correspondent digital data to plots were extracted from spectral and considered as independent variables. Original stand volume data, square root, and logarithm of them were considered as dependent potential for stand volume estimation. Variables using stepwise regression, the best model with coefficient of determination, and adjusted coefficient of determination with regard to determining the appropriate model were modified Log V= 07.546 + 0.85Greenness − 10.564NDWI − 28 0.063Band1. In this model, the coefficient of determination and adjusted coefficient of determination were obtained 0.778 and 0.770, respectively. Result showed that spectral data of the mentioned sensor have a moderate.

Soil carbon stocks and soil solution chemistry in Quercus ilex stands in Mainland Spain

The quantification of terrestrial carbon pools is important for the modeling of carbon fluxes in forest ecosystems. As a contribution to the understanding of the factors that influence the carbon sequestration capacity of Mediterranean forest soils, the present study focuses on the quantification of the superficial soil carbon stocks in evergreen oak stands (Quercus ilex L.) representative of its distribution area in Mainland Spain and to analyze the influence of site factors (climate and topography) and the soil chemical properties in the topsoil carbon storage capacity. For that purpose, 103 Quercus ilex stands were studied grouped in four main formations: 40 wooded grassland ecosystems with scattered oak trees (dehesas), 14 open Holm oak stands, 28 mixed Holm oak forests and 21 dense Holm oak forests. The soil organic carbon stocks (SOCS) in the upper organo-mineral soil layer ranged between 1.4–15.6 kg m−2 and total soil carbon stocks (TSCS) between 1.4–17.9 kg m−2. Tree density was a significant factor for SOC storage in the soil. The wooded grassland dehesas presented the minimum superficial SOC stocks (3.6 kg m−2), while dense Holm oak forests reached the maximum average values (7.6 kg m−2). Maximum SOCS (>10 kg m−2) were measured in the mixed and dense Holm oak forests over soils with calcareous substrates. Summer mean temperature (R = −0.46; P < 0.001) was the climatic variable that most influenced the SOCS. Soil properties had stronger positive correlations with SOCS than site factors: nitrogen concentrations (R = 0.70; P < 0.001), clay content (R = 0.62; P < 0.001), soluble calcium (R = 0.60; P < 0.001) and magnesium (R = 0.42; P < 0.001). Climatic and topographic variables together explained 30 % of the SOCS variability. An increase up to 63 % was obtained by including soil variables. Under Mediterranean climate conditions, the soil properties that enhance the organic matter protection achieve a notable relevance. The soil carbon storage is favored by large organic matter inputs, high soil clay contents, a calcium-saturated soil matrix and reduced summer aridity.

Management Impacts on Forest Floor and Soil Organic Carbon in Northern Temperate Forests of the US

BackgroundThe role of forests in the global carbon cycle has been the subject of a great deal of research recently, but the impact of management practices on forest soil dynamics at the stand level has received less attention. This study used six forest management experimental sites in five northern states of the US to investigate the effects of silvicultural treatments (light thinning, heavy thinning, and clearcutting) on forest floor and soil carbon pools.ResultsNo overall trend was found between forest floor carbon stocks in stands subjected to partial or complete harvest treatments. A few sites had larger stocks in control plots, although estimates were often highly variable. Forest floor carbon pools did show a trend of increasing values from southern to northern sites. Surface soil (0-5 cm) organic carbon content and concentration were similar between treated and untreated plots. Overall soil carbon (0-20 cm) pool size was not significantly different from control values in sites treated with partial or complete harvests. No geographic trends were evident for any of the soil properties examined.ConclusionsResults indicate that it is unlikely that mineral soil carbon stocks are adversely affected by typical management practices as applied in northern hardwood forests in the US; however, the findings suggest that the forest floor carbon pool may be susceptible to loss.

The carbon neutrality assumption for forest bioenergy: A case study for northwestern Ontario

Minimum break-even and carbon-neutral periods resulting from displacing coal with wood pellets for energy generation at the Atikokan Generating Station (GS) were estimated using forest resource inventory for four forest management units (FMU) in northwestern Ontario. The break-even period was defined as the time since harvest at which the combined greenhouse gas (GHG) benefit of displacing coal with wood pellets and the amount of carbon in the regenerating forest equalled the amount of carbon in the forest had it not been harvested for wood pellets. The carbon-neutral period was defined as the time since harvest at which the amount of carbon in the regenerating forest equalled the amount of carbon in the forest had it not been harvested for wood pellets. Theoretically achievable minimum break-even and carbon-neutral periods were estimated as equal to 18 and 28 years after harvest, respectively. However, for the current forest age structure in the selected FMUs, production of wood pellets required for operation of the Atikokan GS would result in a minimum break-even period of 32 years after harvest. These results must be treated as optimistic since we assumed that all forest was available for harvest for wood pellet production, applied the “best” post-harvest silvicultural regime, and may have underestimated merchantable volume and total carbon stocks in older stands.

Heavy metals in Phalaris arundinacea growing in a constructed wetland treating municipal sewage

Constructed wetlands with horizontal subsurface horizontal flow are commonly used for treatment of municipal sewage and are well monitored for removal of organics, suspended solids, nutrients and bacteria. However, the information on removal of heavy metals and their sequestration in plants growing there is very limited. The present study deals with sequestration of six heavy metals in Phalaris arundinacea growing in a constructed wetland treating municipal sewage in the Czech Republic during the period 2004–2008. The aboveground biomass of Phalaris arundinacea is higher that the average Phalaris biomass in other Czech constructed wetlands and also as compared to natural stands. Contrary to natural stands, the root to shoot (R/S) ratio is lower than 1.0 and varied between 0.34 and 0.68 with a mean value of 0.49. For all studied heavy metals the concentrations are the highest in the roots while in other parts, i.e. leaves, stems, rhizomes and flowers, the concentrations usually do not differ significantly. Because of low belowground biomass, the standings stocks are higher aboveground for Zn, Cd, Pb and Cu with copper standing stock being significantly higher than belowground. On the other hand, for Cr and Ni the belowground standing stocks were significantly higher than aboveground because of very high Cr and Ni concentrations in the roots. In most cases the concentrations found in our study are within the order of magnitude as compared to results from other constructed wetlands and natural stands. Heavy metal aboveground standing stocks represented between 1.6% (Cr) and 15.1% (Cd) of the annual metals inflow with an average value of 6.5%. The amount of heavy metals sequestered in the aboveground biomass accounted for between 3.7% (Zn) and 38.4% (Cd) of the heavy metal removal in the filtration beds with an average value of 13.2%.

Do changes in spatial distribution, structure and abundance of silver fir ( Abies alba Mill.) indicate its decline?

Silver fir decline was investigated based on changes in spatial distribution of fir, fir abundance in forest stands, dbh (age) structure of fir, and abundance of fir regeneration. The authors used a large-scale approach to study the dynamics of silver fir over nearly 40 years. Based on Silva-SI, a spatial information system, the majority of total forest area in Slovenia was analysed for changes in the distribution of silver fir in the period 1970–2008 using artificial neural networks (ANNs), with respect to site, stand, and forest management variables. Additionally, changes in abundance of silver fir (hereafter fir) in the same period were analysed with a general linear model, while changes in the dbh structure of fir and fir regeneration were analysed with non-parametric tests. Most selected indicators confirmed the hypothesis of fir decline in the period 1970–2008, as evidenced by a reduction in the area of forests with a share of fir in the total growing stock >25% (from 18.9% to 9.5% of total area), a reduction in the share of fir in the growing stock of forest stands (from 17.5% to 7.5%), ageing of the fir population, and a disproportionate share of fir saplings in the total saplings relative to fir's share in the growing stock of forest stands. A 1.5% increase in fir distribution area in the observed period contradicts the decline hypothesis. ANNs showed that the spatiotemporal dynamics of fir was most affected by four variables: forest type, share of fir in the potential natural vegetation, mean annual precipitation, and mean annual temperature. The latter two, together with the growing stock at the start of study period, the degree of connectivity between fir stands, and bedrock type, were significant predictors of decline of fir abundance in forest stands. Significant differences in spatiotemporal dynamics and changes in fir abundance were found between forest types representing a complex of site conditions and past forest management. A further decline of abundance of fir on a large spatial scale in the next decades is expected. Conservation of fir in forest stands will depend mainly on the successful regeneration of fir and sufficient recruitment.

Variability patterns differ between standing stock and process rates

Standing stocks are typically easier to measure than process rates such as production. Hence, stocks are often used as indicators of ecosystem functions although the latter are generally more strongly related to rates than to stocks. The regulation of stocks and rates and thus their variability over time may differ, as stocks constitute the net result of production and losses. Based on long-term high frequency measurements in a large, deep lake we explore the variability patterns in primary and bacterial production and relate them to those of the corresponding standing stocks, i.e. chlorophyll concentration, phytoplankton and bacterial biomass. We employ different methods (coefficient of variation, spline fitting and spectral analysis) which complement each other for assessing the variability present in the plankton data, at different temporal scales. In phytoplankton, we found that the overall variability of primary production is dominated by fluctuations at low frequencies, such as the annual, whereas in stocks and chlorophyll in particular, higher frequencies contribute substantially to the overall variance. This suggests that using standing stocks instead of rate measures leads to an under- or overestimation of food shortage for consumers during distinct periods of the year. The range of annual variation in bacterial production is 8 times greater than biomass, showing that the variability of bacterial activity (e.g. oxygen consumption, remineralisation) would be underestimated if biomass is used. The P/B ratios were variable and although clear trends are present in both bacteria and phytoplankton, no systematic relationship between stock and rate measures were found for the two groups. Hence, standing stock and process rate measures exhibit different variability patterns and care is needed when interpreting the mechanisms and implications of the variability encountered.

Maximum density-size relationships for Sitka spruce and coastal Douglas-fir in Britain and Canada

In this study, we examined density–size relationships for Sitka spruce (Picea sitchensis (Bong.) Carr.) and Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) using data collected in stands in Great Britain (GB) and Western Canada. These two conifers are native to Western North America and have been widely planted in GB. Results indicate differences between stands in Canada and GB in both the intercept and slope of the log maximum density–log size boundary lines. In GB, the slope (b) of the relationship between log of stand density (number of trees per hectare) and log of quadratic mean diameter (Dq) is steeper than the theoretical value of −1.605 (−2.063 for Sitka spruce and −1.864 for Douglas-fir). Values of b are lower in Canada (−1.437 for Sitka spruce and −1.241 for Douglas-fir) than in GB. Within each region, b is similar for the two species. However, the intercept term differs for Sitka spruce and Douglas-fir in GB. These differences provide additional evidence that density–size boundary line relationships are influenced by environmental and other factors and indicate the need for development of density–size relationships for each species and for each region where the species is grown. Maximum stand density index (SDI) values calculated using these relationships are 1868 and 2073 for Sitka spruce and 1491 and 1815 for Douglas-fir in GB and Canada, respectively. Differences in maximum SDI between these two regions may be related to differences in climate, provenance, stand history and other factors. Maximum density–size relationships presented in this paper can be used as a starting point for managing stand density for both even-aged and continuous cover stands and for identifying potential maximum stocking in stands of these species in GB and Canada.

Estimation of root biomass based on excavation of individual root systems in a primary dipterocarp forest in Pasoh Forest Reserve, Peninsular Malaysia

Abstract:Precise estimation of root biomass is important for understanding carbon stocks and dynamics in tropical rain forests. However, limited information is available on individual root masses, especially large trees. We excavated 121 root systems of various species (78) and sizes (up to 116 cm in dbh), and estimated both above- and below-ground biomass in a lowland primary dipterocarp forest in the Pasoh Forest Reserve, Peninsular Malaysia. A tree census was conducted in four research plots (each 0.2 ha) and stand-level biomass was estimated. We examined relationships between tree size parameters and masses of coarse roots (roots ≥5 mm in diameter) and derived a dbh-based allometric equation. The amounts of coarse roots that were lost during excavation were corrected. Coarse-root biomass before and after correction for lost roots was estimated to be 63.8 and 82.7 Mg ha−1, indicating that significant amounts of roots (23%) were lost during the sampling. We also estimated the biomass of small root (&lt;5 mm) by applying pipe-model theory. The estimate, 13.3 Mg ha−1, was similar to another estimate of small roots, 16.4 Mg ha−1, which was obtained directly by the soil-pit sampling method. Total below-ground (BGB) and above-ground biomass (AGB) was estimated to be 95.9 and 536 Mg ha−1, respectively. The biomass-partitioning ratio (BGB/AGB) was about 0.18. In conclusion, the dbh-based allometric equation for coarse roots developed in this study, which kept good linearity even including the data of larger trees, might be useful for evaluating below-ground carbon stocks in other stands of similar forest (old-growth dipterocarp) in South-East Asia.

Predicting mature cork biomass with t years of growth from one measurement taken at any other age

Cork is a natural product that is extracted from the outer bark of the cork oak tree. According to Portuguese legislation, the interval between two consecutive cork extractions on the same tree must be equal or greater than 9 years. Although the majority of the cork oak stands are debarked at the end of this period, this rotation may not be the optimum in many cases. The existing models for cork weight prediction can only be used for trees debarked at a 9 years or, in one model, at a 10-years rotation period, since the data used for its development was limited to these growth periods. The development of a method that allows for the prediction of the mature cork biomass with t years of growth, based in one measurement taken at any other age, was the main objective of this work. The method is based on the knowledge that the density of the cork tissue is constant between the inner and outer cork rings, being significantly different from density of the cork back. It can be implemented using two different equations that were developed during this work: a model to estimate cork biomass with 9 years of age and a model to estimate the cork back weight proportion at 9 years of age. For the first model, four different alternative models were developed, considering different levels of information collected during forest inventory. The model to estimate the cork back weight proportion leads to the biomass of cork tissue. Cork biomass at t years is obtained by decreasing or increasing the biomass of cork tissue according to the difference in cork thickness between t and 9 years of growth. The proposed method was evaluated by comparing the observed and estimated values of cork biomass from an independent data set with corks with 9, 10 and 11 years of age. The results showed similar precision for corks with 9, 10 or 11 years of age. As expected the precision of the predictions increases when the model to estimate cork biomass with 9 years of age uses more information. The presented method should be an important tool for cork oak stand management, for the prediction of the evolution of carbon stocks in cork oak stands, and will allow analyzing the impact in cork biomass production of decreasing or extending the interval between two consecutive cork extractions.