Below- and above-ground biomass and net primary production in a paleotropical natural forest (Sulawesi,Indonesia) as compared to neotropical forests

Data on the biomass and productivity of southeast Asian tropical forests are rare, making it difficult to evaluate the role of these forest ecosystems in the global carbon cycle and the effects of increasing deforestation rates in this region. In particular, more precise information on size and dynamics of the root system is needed. In six natural forest stands at pre-montane elevation (c. 1000 m a.s.l.) on Sulawesi (Indonesia), we determined above-ground biomass and the distribution of fine (d < 2 mm) and coarse roots (d > 2 mm), estimated above- and below-ground net production, and compared the results to literature data from other pre-montane paleo- and neotropical forests. The mean total biomass of the stands was 303 Mg ha⁻¹ (or 128 Mg C ha⁻¹), with the largest biomass fraction being recorded for the above-ground components (286 Mg ha⁻¹) and 11.2 and 5.6 Mg ha⁻¹ of coarse and fine root biomass (down to 300 cm in the soil profile), resulting in a remarkably high shoot:root ratio of c. 17. Fine root density in the soil profile showed an exponential decrease with soil depth that was closely related to the concentrations of base cations, soil pH and in particular of total P and N. The above-ground biomass of these stands was found to be much higher than that of pre-montane forests in the Neotropics, on average, but lower compared to other pre-montane forests in the Paleotropics, in particular when compared with dipterocarp forests in Malesia. The total above- and below-ground net primary production was estimated at 15.2 Mg ha⁻¹ yr⁻¹ (or 6.7 Mg C ha⁻¹ yr⁻¹) with 14% of this stand total being invested below-ground and 86% representing above-ground net primary production. Leaf production was found to exceed net primary production of stem wood. The estimated above-ground production was high in relation to the mean calculated for pre-montane forests on a global scale, but it was markedly lower compared to data on dipterocarp forests in South-east Asia. We conclude that the studied forest plots on Sulawesi follow the general trend of higher biomasses and productivity found for paleotropical pre-montane forest compared to neotropical ones. However, biomass stocks and productivity appear to be lower in these Fagaceae-rich forests on Sulawesi than in dipterocarp forests of Malesia.     

Carbon accumulation in the biomass and soil of different aged secondary forests in the humid tropics of Costa Rica

Efforts are needed in order to increase confidence for carbon accounts in the land use sector, especially in tropical forest ecosystems that often need to turn to default values given the lack of precise and reliable site specific data to quantify their carbon sequestration and storage capacity. The aim of this study was then to estimate biomass and carbon accumulation in young secondary forests, from 4 and up to 20 years of age, as well as its distribution among the different pools (tree including roots, herbaceous understory, dead wood, litter and soil), in humid tropical forests of Costa Rica. Carbon fraction for the different pools and tree components (stem, branches, leaves and roots) was estimated and varies between 37.3% (±3.3) and 50.3% (±2.9). Average carbon content in the soil was 4.1% (±2.1). Average forest plant biomass was 82.2 (±47.9) Mg ha⁻¹ and the mean annual increment for carbon in the biomass was 4.2 Mg ha⁻¹ yr⁻¹. Approximately 65.2% of total biomass was found in the aboveground tree components, while 14.2% was found in structural roots and the rest in the herbaceous vegetation and necromass. Carbon in the soil increased by 1.1 Mg ha⁻¹ yr⁻¹. Total stored carbon in the forest was 180.4 Mg ha⁻¹ at the age of 20 years. In these forests, most of the carbon (51-83%) was stored in the soil. Models selected to estimate biomass and carbon in trees as predicted by basal area had R² adjustments above 95%. Results from this study were then compared with those obtained for a variety of secondary and primary forests in different Latin-American tropical ecosystems and in tree plantations in the same study area.     

Recovery process of a mountain forest after shifting cultivation in Northwestern Vietnam

The recovery process of fallow stands in the mountainous region of Northwestern Vietnam was studied, based on a chronosequence of 1–26-year-old secondary forests after intensive shifting cultivation. The number of species present in a 26-year-old secondary forest attained 49% of the 72 species present in an old-growth forest. Total stem density decreased gradually from 172,500 ha⁻¹ in a 3-year-old forest to 24,600 ha⁻¹ in the 26-year-old stand, but stem density of larger trees (diameter at breast height (D) ≥ 5 cm) increased from 60 ha⁻¹ in a 7-year-old to 960 ha⁻¹ in the 26-year-old forests, which was similar to that of an old-growth forest. Annual biomass increment of the 26-year-old stand was 4.2 Mg ha⁻¹ year⁻¹. A saturation curve was fitted to biomass accumulation in secondary forests. After an estimated time of 60 years, a secondary forest can achieve 80% of the biomass of old-growth forests (240 Mg ha⁻¹). Species diversity expressed by Shannon Index shows that it takes 60 years for a secondary forest in fallow to achieve a plant species diversity similar to that of old-growth forests.     

Above-ground biomass dynamics after reduced-impact logging in the Eastern Amazon

Changes in above-ground biomass (AGB) of 17 1 ha logged plots of terra firme rain forest in the eastern Amazon (Brazil, Paragominas) were monitored for four years (2004–2008) after reduced-impact logging. Over the same time period, we also monitored two 0.5 ha plots in adjacent unlogged forest. While AGB in the control plots changed little over the observation period (increased on average 1.4 Mg ha⁻¹), logging resulted in immediate reductions in ABG that averaged 94.5 Mg ha⁻¹ (±42.0), which represented 23% of the 410 Mg ha⁻¹ (±64.9) present just prior to harvesting. Felled trees (dbh > 55 cm) accounted for 73% (±15) of these immediate losses but only 18.9 Mg ha⁻¹ (±8.1) of biomass was removed in the extracted logs. During the first year after logging, the annual AGB balance (annual AGB gain by recruitment and growth − annual AGB loss by mortality) remained negative (−31.1 Mg ha⁻¹ year⁻¹; ±16.7), mainly due to continued high mortality rates of damaged trees. During the following three years (2005–2008), average net AGB accumulation in the logged plots was 2.6 Mg ha⁻¹ year⁻¹ (±4.6). Post-logging biomass recovery was mostly through growth (4.3 ± 1.5 Mg ha⁻¹ year⁻¹ for 2004–2005 and 6.8 ± 0.9 Mg ha⁻¹ year⁻¹ for 2005–2008), particularly of large trees. In contrast, tree recruitment contributed little to the observed increases in AGB (1.1 ± 0.6 Mg ha⁻¹ year⁻¹ for 2004–2005 and 3.1 ± 1.3 Mg ha⁻¹ year⁻¹ for 2005–2008). Plots with the lowest residual basal area after logging generally continued to lose more large trees (dbh ≥70 cm), and consequently showed the greatest AGB losses and the slowest overall AGB gains. If 100% AGB recovery is desired and the 30-year minimum cutting cycle defined by Brazilian law is adhered to, current logging intensities (6 trees ha⁻¹) need to be reduced by 40–50%. Such a reduction in logging intensity will reduce financial incomes to loggers, but might be compensated for by the payment of environmental services through the proposed REDD (reduced emissions from deforestation and forest degradation) mechanism of the United Nations Framework Convention on Climate Change.     

Formulating allometric equations for estimating biomass and carbon stock in small diameter trees

Biomass and carbon sequestration rate of a young (four year old) mixed plantation of Dalbergia sissoo Roxb., Acacia catechu Willd., and Albizia lebbeck Benth. growing in Terai region (a level area of superabundant water) of central Himalaya was estimated. The plantation is seed sown in the rainy season of year 2004 and spread over an area of 44 ha. Allometric equations for both above and below ground components were developed for three tree species. The density of trees in the plantation was 1322 trees ha⁻¹ The diameters of trees were below 10 cm. Five diameter classes were defined for D. sissoo and A. catechu and 3 for A. lebbeck. 5 trees were harvested in each diameter class. Individual tree allometry was exercised for developing the allometric equations relating tree component (low and above ground) biomass to d.b.h. Post analysis equations were highly significant (P > 0.001) for each component of all species. In the plantation Holoptelia integrifolia Roxb. (Family Ulmaceae) has been reduced to shrub form because of frost. Only the aboveground biomass of H. integrifolia and other shrubs were estimated by destructive harvesting method. Herbaceous forest floor biomass and leaf litter fall were also estimated. The total forest vegetation biomass was 10.86 Mg ha⁻¹ in 2008 which increased to 19.49 Mg ha⁻¹ in 2009. The forest is sequestering carbon at the rate of 4.32 Mg ha⁻¹ yr⁻¹.     

Estimations of total ecosystem carbon pools distribution and carbon biomass current annual increment of a moist tropical forest

With increasing CO₂ in the atmosphere, there is an urgent need of reliable estimates of biomass and carbon pools in tropical forests, most especially in Africa where there is a serious lack of data. Information on current annual increment (CAI) of carbon biomass resulting from direct field measurements is crucial in this context, to know how forest ecosystems will affect the carbon cycle and also to validate eddy covariance flux measurements. Biomass data were collected from 25 plots of 13 ha spread over the different vegetation types and land uses of a moist evergreen forest of 772,066 ha in Cameroon. With site-specific allometric equations, we estimated biomass and aboveground and belowground carbon pools. We used GIS technology to develop a carbon biomass map of our study area. The CAI was estimated using the growth rates obtained from tree rings analysis. The carbon biomass was on average 264 ± 48 Mg ha⁻¹. This estimate includes aboveground carbon, root carbon and soil organic carbon down to 30 cm depth. This value varied from 231 ± 45 Mg ha⁻¹ of carbon in Agro-Forests to 283 ± 51 Mg ha⁻¹ of carbon in Managed Forests and to 278 ± 56 Mg ha⁻¹ of carbon in National Park. The carbon CAI varied from 2.54 ± 0.65 Mg ha⁻¹ year⁻¹ in Agro-Forests to 2.79 ± 0.72 Mg ha⁻¹ year⁻¹ in Managed Forests and to 2.85 ± 0.72 Mg ha⁻¹ year⁻¹ in National Park. This study provides estimates of biomass, carbon pools and CAI of carbon biomass from a forest landscape in Cameroon as well as an appropriate methodology to estimate these components and the related uncertainty.     

The Brazil Eucalyptus Potential Productivity Project: Influence of water,nutrients and stand uniformity on wood production

We examined the potential growth of clonal Eucalyptus plantations at eight locations across a 1000+ km gradient in Brazil by manipulating the supplies of nutrients and water, and altering the uniformity of tree sizes within plots. With no fertilization or irrigation, mean annual increments of stem wood were about 28% lower (16.2 Mg ha⁻¹ yr⁻¹, about 33 m³ ha⁻¹ yr⁻¹) than yields achieved with current operational rates of fertilization (22.6 Mg ha⁻¹ yr⁻¹, about 46 m³ ha⁻¹ yr⁻¹). Fertilization beyond current operational rates did not increase growth, whereas irrigation raised growth by about 30% (to 30.6 Mg ha⁻¹ yr⁻¹, about 62 m³ ha⁻¹ yr⁻¹). The potential biological productivity (current annual increment) of the plantations was about one-third greater than these values, if based only on the period after achieving full canopies. The biological potential productivity was even greater if based only on the full-canopy period during the wet season, indicating that the maximum biological productivity across the sites (with irrigation, during the wet season) would be about 42 Mg ha⁻¹ yr⁻¹ (83 m³ ha⁻¹ yr⁻¹). Stands with uniform structure (trees in plots planted in a single day) showed 13% greater growth than stands with higher heterogeneity of tree sizes (owing to a staggered planting time of up to 80 days). Higher water supply increased growth and also delayed by about 1 year the point where current annual increment and mean annual increment intersected, indicating opportunities for lengthening rotations for more productive treatments as well as the influence of year-to-year climate variations on optimal rotations periods. The growth response to treatments after canopy closure (mid-rotation) related well with full-rotation responses, offering an early opportunity for estimating whole-rotation yields. These results underscore the importance of resource supply, the efficiency of resource use, and stand uniformity in setting the bounds for productivity, and provide a baseline for evaluating the productivity achieved in operational plantations. The BEPP Project showed that water supply is the key resource determining levels of plantation productivity in Brazil. Future collaboration between scientists working on silviculture and genetics should lead to new insights on the mechanisms connecting water and growth, leading to improved matching of sites, clones, and silviculture.     

Tree height in Brazil's ‘arc of deforestation’: Shorter trees in south and southwest Amazonia imply lower biomass

This paper estimates the difference in stand biomass due to shorter and lighter trees in southwest (SW) and southern Amazonia (SA) compared to trees in dense forests in central Amazonia (CA). Forest biomass values used to estimate carbon emissions from deforestation throughout, Brazilian Amazonia will be affected by any differences between CA forests and those in the “arc of deforestation” where clearing activity is concentrated along the southern edge of the Amazon forest. At 12 sites (in the Brazilian states of Amazonas, Acre, Mato Grosso and Pará) 763 trees were felled and measurements were made of total height and of stem diameter. In CA dense forest, trees are taller at any given diameter than those in SW bamboo-dominated open, SW bamboo-free dense forest and SA open forests. Compared to CA, the three forest types in the arc of deforestation occur on more fertile soils, experience a longer dry season and/or are disturbed by climbing bamboos that cause frequent crown damage. Observed relationships between diameter and height were consistent with the argument that allometric scaling exponents vary in forests on different substrates or with different levels of natural disturbance. Using biomass equations based only on diameter, the reductions in stand biomass due to shorter tree height alone were 11.0, 6.2 and 3.6%, respectively, in the three forest types in the arc of deforestation. A prior study had shown these forest types to have less dense wood than CA dense forest. When tree height and wood density effects were considered jointly, total downward corrections to estimates of stand biomass were 39, 22 and 16%, respectively. Downward corrections to biomass in these forests were 76 Mg ha⁻¹ (∼21.5 Mg ha⁻¹ from the height effect alone), 65 Mg ha⁻¹ (18.5 Mg ha⁻¹ from height), and 45 Mg. ha⁻¹ (10.3 Mg ha⁻¹ from height). Hence, biomass stock and carbon emissions are overestimated when allometric relationships from dense forest are applied to SW or SA forest types. Biomass and emissions estimates in Brazil's National Communication under the United Nations Framework Convention on Climate Change require downward corrections for both wood density and tree height.     

Estimating state-wide biomass carbon stocks for a REDD plan in Acre, Brazil

As in many other developing countries, the state government of Acre, Brazil, is developing a program for compensating forest holders (such as communities of rubber tappers and indigenous peoples as well as small, medium and large private land holders) reducing their emission of atmospheric heat-trapping gases by not deforesting. We describe and then apply to Acre a method for estimating carbon stocks by land cover type. We then compare the results of our simple method, which is based on vegetation mapping and ground-based samples, with other more technically demanding methods based on remote sensing. We estimated total biomass carbon stocks by multiplying the measured above-ground biomass of trees >10 cm DBH in each of 18 forest types and published estimates for non-forest areas, as determined by measurement of 44 plots throughout the state (ranging from 1 to 10 ha each), by land-cover area estimated using a geographical information system. State-wide, we estimated average above-ground biomass in forested areas to be 246 ± 90 Mg ha⁻¹; dense forest showed highest (322 ± 20 Mg ha⁻¹) and oligotrophic dwarf forest (campinarana) the lowest biomass (20 ± 30 Mg ha⁻¹). The two most widespread forest types in Acre, open canopy forests dominated by either palms and bamboo (for which ground-based data are scant), support an estimated 246 ± 44 and 224 ± 50 Mg ha⁻¹ of above-ground biomass, respectively. We calculate the total above-ground biomass of the 163,000 km² State of Acre to be 3.6 ± 0.8 Pg (non-forest biomass included). This estimate is very similar to two others generated using much more technologically demanding methods, but all three methods, regardless of sophistication, suffer from lack of field data.     

Uncertainty of 21st century growing stocks and GHG balance of forests in British Columbia, Canada resulting from potential climate change impacts on ecosystem processes

Over the coming decades, climate change will increasingly affect forest ecosystem processes, but the future magnitude and direction of these responses is uncertain. We designed 12 scenarios combining possible changes in tree growth rates, decay rates, and area burned by wildfire with forecasts of future harvest to quantify the uncertainty of future (2010-2080), timber growing stock, ecosystem C stock, and greenhouse gas (GHG) balance for 67 million ha of forest in British Columbia, Canada. Each scenario was simulated 100 times with the Carbon Budget Model of the Canadian Forest Sector (CBM-CFS3). Depending on the scenario, timber growing stock over the entire land-base may increase by 14% or decrease by 9% by 2080 (a range of 2.8 billion m³), relative to 2010. However, timber growing stock available for harvest was forecast to decline in all scenarios by 26-62% relative to 2010 (a range of 1.2 billion m³). Forests were an annual GHG source in 2010 due to an ongoing insect outbreak. If half of the C in harvested wood was assumed to be immediately emitted, then 0-95% of simulations returned to annual net sinks by 2040, depending on scenario, and the cumulative (2010-2080) GHG balance ranged from a sink of −4.5 Pg CO₂e (−67 Mg CO₂e ha⁻¹) for the most optimistic scenario, to a source of 4.5 Pg CO₂e (67 Mg CO₂e ha⁻¹) for the most pessimistic. The difference in total ecosystem carbon stocks between the most optimistic and pessimistic scenarios in 2080 was 2.4 Pg C (36 Mg C ha⁻¹), an average difference of 126 Tg CO₂e yr⁻¹ (2 Mg CO₂e yr⁻¹ ha⁻¹) over the 70-year simulation period, approximately double the total reported anthropogenic GHG emissions in British Columbia in 2008. Forests risk having reduced growing stock and being GHG sources under many foreseeable scenarios, thus providing further feedback to climate change. These results indicate the need for continued monitoring of forest responses to climatic and global change, the development of mitigation and adaptation strategies by forest managers, and global efforts to minimize climate change impacts on forests.     

Forest regeneration in artificial gaps twelve years after canopy opening in Acre State Western Amazon

The main objectives were to study the effect of gap size and canopy openness on the natural regeneration dynamics considering the parameters of sapling growth, recruitment, mortality, density, species composition and above-ground biomass accumulation. The study was carried out in 32 artificial gaps with sizes varying from 100 to 1200 m² and canopy openness from 10 to 45%, from the second to the twelfth year after gap creation. The gap size was measured using the vertical projection of the tree crowns on the ground (Brokaw's definition), and the canopy openness measurement by hemispherical photography. In the first five years, mean sapling growth (0.54 cm year⁻¹), mortality (3.9% year⁻¹) and AGB (26.2 Mg ha⁻¹ or 8.7 Mg ha⁻¹ year⁻¹) were significantly higher in the gaps than in the forest understorey (0.17 cm year⁻¹, 1.5% year⁻¹ and −0.59 Mg ha⁻¹ year⁻¹ respectively) and positively correlated with gap size and canopy openness. In the same period, recruitment was also significantly higher in the gaps (5.8% year⁻¹) than in the forest understorey (0.4% year⁻¹) but decreased with gap size and negatively correlated with canopy openness. In the first five years, the relative density of pioneer species was higher in the gaps but not significantly correlated with gap size or canopy openness. AGB increased linearly since canopy opening, and twelve years after gap creation it was still higher in larger (121.2 Mg ha⁻¹ or 10.1 Mg ha⁻¹ year⁻¹) rather than smaller (62.5 ha⁻¹ or 5.2 ha⁻¹ year⁻¹) gaps. Twelve years after gap creation there were no significant differences in the parameters of sapling growth, recruitment, and mortality which could be attributed to the original gap size and canopy openness.     

Tree diversity and carbon stocks of some major forest types of Garhwal Himalaya,India

Four forest stands each of twenty major forest types in sub-tropical to temperate zones (350 m asl–3100 m asl) of Garhwal Himalaya were studied. The aim of the study was to assess the stem density, tree diversity, biomass and carbon stocks in these forests and make recommendations for forest management based on priorities for biodiversity protection and carbon sequestration. Stem density ranged between 295 and 850 N ha⁻¹, while total biomass ranged from 129 to 533 Mg ha⁻¹. Total carbon storage ranged between 59 and 245 Mg ha⁻¹. The range of Shannon–Wiener diversity index was between 0.28 and 1.75. Most of the conifer-dominated forest types had higher carbon storage than broadleaf-dominated forest types. Protecting conifer-dominated stands, especially those dominated by Abies pindrow and Cedrus deodara, would have the largest impact, per unit area, on reducing carbon emissions from deforestation.     

Nitrogen leaching in response to increased nitrogen inputs in subtropical monsoon forests in southern China

Dissolved inorganic nitrogen (DIN) (as ammonium nitrate) was applied monthly onto the forest floor of one old-growth forest (>400 years old, at levels of 50, 100 and 150 kg N ha⁻¹ yr⁻¹) and two young forests (both about 70 years old, at levels of 50 and 100 kg N ha⁻¹ yr⁻¹) over 3 years (2004–2006), to investigate how nitrogen (N) input influenced N leaching output, and if there were differences in N retention between the old-growth and the young forests in the subtropical monsoon region of southern China. The ambient throughfall inputs were 23–27 kg N ha⁻¹ yr⁻¹ in the young forests and 29–35 kg N ha⁻¹ yr⁻¹ in the old-growth forest. In the control plots without experimental N addition, a net N retention was observed in the young forests (on average 6–11 kg N ha⁻¹ yr⁻¹), but a net N loss occurred in the old-growth forest (−13 kg N ha⁻¹ yr⁻¹). Experimental N addition immediately increased DIN leaching in all three forests, with 25–66% of added N leached over the 3-year experiment. At the lowest level of N addition (50 kg N ha⁻¹ yr⁻¹), the percentage N loss was higher in the old-growth forest (66% of added N) than in the two young forests (38% and 26%). However, at higher levels of N addition (100 and 150 kg N ha⁻¹ yr⁻¹), the old-growth forest exhibited similar N losses (25–43%) to those in the young forests (28–43%). These results indicate that N retention is largely determined by the forest successional stages and the levels of N addition. Compared to most temperate forests studied in Europe and North America, N leaching loss in these seasonal monsoon subtropical forests occurred mainly in the rainy growing season, with measured N loss in leaching substantially higher under both ambient deposition and experimental N additions.     

Derivation of a spatially explicit 86-year retrospective carbon budget for a landscape undergoing conversion from old-growth to managed forests on Vancouver Island,BC

To understand the influence of disturbance, age–class structure, and land use on landscape-level carbon (C) budgets during conversion of old-growth forests to managed forests, a spatially explicit, retrospective C budget from 1920 through 2005 was developed for the 2500 ha Oyster River area of Fluxnet-Canada's coastal BC Station. We used the Carbon Budget Model of the Canadian Forest Sector (CBM-CFS3), an inventory-based model, to simulate forest C dynamics. A current (circa 1999) forest inventory for the area was compiled, then overlaid with digitized historic disturbance maps, a 1919 timber cruise map, and a series of historic orthophotographs to generate a GIS coverage of forest cover polygons with unique disturbance histories dating back to 1920. We used the combined data from the historic and current inventory and forest change data to first estimate initial ecosystem C stocks and then to simulate forest dynamics and C budgets for the 86-year period. In 1920, old-growth forest dominated the area and the long-term landscape-level net ecosystem C balance (net biome productivity, NBP) was a small sink (NBP 0.2 Mg C ha⁻¹ year⁻¹). From 1930 to 1945 fires, logging, and slash burning resulted in large losses of biomass C, emissions of C to the atmosphere, and transfers of C from biomass to detritus and wood products (NBP ranged from −3 to −56 Mg C ha⁻¹ year⁻¹). Live biomass C stocks slowly recovered following this period of high disturbance but the area remained a C source until the mid 1950s. From 1960 to 1987 disturbance was minimal and the area was a C sink (NBP ranged from 3 to 6 Mg C ha⁻¹ year⁻¹). As harvest of second-growth forest began in late 1980s, disturbances again dominated the area's C budget, partially offset by ongoing C uptake by biomass in recovering young forests such that the C balance varied from positive to negative depending upon the area disturbed that year (NBP from 6 to −15 Mg C ha⁻¹ year⁻¹). Despite their high productivity, the area's forests are not likely to attain C densities of the landscape prior to industrial logging because the stands will not reach pre-logging ages. Additional work is underway to examine the relative role historic climate variability has had on the landscape-level C budget.     

Thinning method and intensity influence long-term mortality trends in a red pine forest

Tree mortality shapes forest development, but rising mortality can represent lost production or an adverse response to changing environmental conditions. Thinning represents a strategy for reducing mortality rates, but different thinning techniques and intensities could have varying impacts depending on how they alter stand structure. We analyzed trends in stand structure, relative density, stand-scale mortality, climate, and correlations between mortality and climate over 46 years of thinning treatments in a red pine forest in Northern Minnesota, USA to examine how thinning techniques that remove trees of different crown classes interact with growing stock manipulation to impact patterns of tree mortality. Relative density in unharvested plots increased during the first 25 years of the study to around 80%, then began to plateau, but was lower (12–62%) in thinned stands. Mortality in unharvested plots claimed 2.5 times more stems yr⁻¹ and 8.6 times as large a proportion of annual biomass increment during the last 21 years of the study compared to the first 25 years, but showed few temporal trends in thinned stands. Mortality in thinning treatments was generally lower than in controls, particularly during the last 21 years of the study when mortality averaged about 0.1% of stems yr⁻¹ and 4% of biomass increment across thinning treatments, but 0.8% of stems yr⁻¹ and 49% of biomass increment in unharvested plots. Treatments that combined thinning from above with low growing stock levels represented an exception, where mortality exceeded biomass production after initial thinning. Mortality averaged less than 0.1% of stems yr⁻¹ and less than 1% of annual biomass production in stands thinned from below. These trends suggest thinning from below minimizes mortality across a wide range of growing stock levels while thinning from above to low growing stock levels can result in dramatic short-term increases in mortality. Moderate to high growing stock levels (21–34 m² ha⁻¹) may offer greater flexibility for limiting mortality across a range of thinning methods. Mean and maximum annual and growing season temperatures rose by 0.6–1.8 °C during the study, and temperature variables were positively correlated with mortality in unharvested plots. Mortality increases in unharvested plots, however, were consistent with self-thinning principles and probably not driven by rising temperatures. These results suggest interactions between thinning method and intensity influence mortality reductions associated with thinning, and demonstrate the need for broader consideration of developmental processes as potential explanations for increased tree mortality rates in recent decades.     

Biomass functions and expansion factors in young Norway spruce (Picea abies [L.] Karst) trees

Roots, stems, branches and needles of 160 Norway spruce trees younger than 10 years were sampled in seven forest stands in central Slovakia in order to establish their biomass functions (BFs) and biomass expansion factors (BEFs). We tested three models for each biomass pool based on the stem base diameter, tree height and the two parameters combined. BEF values decreased for all spruce components with increasing height and diameter, which was most evident in very young trees under 1 m in height. In older trees, the values of BEFs did tend to stabilise at the height of 3–4 m. We subsequently used the BEFs to calculate dry biomass of the stands based on average stem base diameter and tree height. Total stand biomass grew with increasing age of the stands from about 1.0 Mg ha⁻¹ at 1.5 years to 44.3 Mg ha⁻¹ at 9.5 years. The proportion of stem and branch biomass was found to increase with age, while that of needles was fairly constant and the proportion of root biomass did decrease as the stands grew older.     

Implications of fires on carbon budgets in Andean cloud montane forest: The importance of peat soils and tree resprouting

Fire in tropical montane cloud forests (TMCFs) is not as rare as once believed. Andean TMCFs sit immediately below highly flammable, high-altitude grasslands (Puna/Páramo) that suffer from recurrent anthropogenic fire. This treeline is a zone of climatic tension where substantial future warming is likely to force upward tree migrations, while increased fire presence and fire impacts are likely to force it downwards. TMCFs contain large carbon stocks in their peat soils and their loss through fire is a currently unaccounted for regional source of CO₂. This study, conducted in the southern Peruvian Andes (>2800 m), documents differences in live tree biomass, fine root biomass, fallen and standing dead wood, and soil organic carbon in 4 paired-sample plots (burned versus control) following the severe ground fires that occurred during the 2005 Andean drought. Peat soils contributed the most to biomass burning emissions, with lower values corresponding to an 89% mean stock difference compared to the controls (mean ± SE) (54.1 ± 22.3 vs. 5.8 ± 5.3 MgC ha⁻¹). Contrastingly, carbon stocks from live standing trees differed by a non-significant 37% lower value in the burned plots compared to the controls, largely compensated by vigorous resprouting (45.5 ± 17.4 vs. 69.2 ± 13.4 MgC ha⁻¹). Both standing dead trees and fallen dead wood were significantly higher in the burned plots with a three-fold difference from the controls: dead Trees 45.2 ± 9.4 vs. 16.4 ± 4.4 MgC ha⁻¹, and ca. a 2 fold difference for the fallen dead wood: 11.2 ± 5 vs. 6.7 ± 3.2 MgC ha⁻¹ for the burned plots versus their controls. A preliminary estimate of the regional contribution of biomass burning emissions from Andean TMCFs for the period 2000-2008, resulted in mean carbon emission rates of 1.3 TgC yr⁻¹ (max-min: 1.8-0.8 TgC yr⁻¹). This value is in the same order of magnitude than South American annual fire emissions (300 TgC yr⁻¹) suggesting the need for further research on Andean forest fires. On-going projects on the region are working on the promotion of landowner participation in TMCFs conservation through REDD+ mechanism. The heart of the proposed initiative is reforestation of degraded lands with green fire breaks enriched with economically valuable Andean plant species. The cultivation of these species may contribute to reduce deforestation pressure on the Amazonian cloud forest by providing an alternative income to local communities, at the same time that they prevent the spread of fire into Manu National Park and adjacent community-held forests, protecting forest and reducing CO₂ emissions.     

Estimation of biomass and carbon stocks in plants,soil and forest floor in different tropical forests

An accurate characterization of tree carbon (TC), forest floor carbon (FFC) and soil organic carbon (SOC) in tropical forest plantations is important to estimate their contribution to global carbon stocks. This information, however, is poor and fragmented. Carbon contents were assessed in patula pine (Pinus patula) and teak (Tectona grandis) stands in tropical forest plantations of different development stages in combination with inventory assessments and soil survey information. Growth models were used to associate TOC to tree normal diameter (D) with average basal area and total tree height (H_T), with D and H_T parameters that can be used in 6–26 years old patula pine and teak in commercial tropical forests as indicators of carbon stocks. The information was obtained from individual trees in different development stages in 54 patula pine plots and 42 teak plots. The obtained TC was 99.6 Mg ha⁻¹ in patula pine and 85.7 Mg ha⁻¹ in teak forests. FFC was 2.3 and 1.2 Mg ha⁻¹, SOC in the surface layer (0–25 cm) was 92.6 and 35.8 Mg ha⁻¹, 76.1 and 19 Mg ha⁻¹ in deep layers (25–50 cm) in patula pine and teak, respectively. Carbon storage in trees was similar between patula pine and teak plantations, but patula pine had higher levels of forest floor carbon and soil organic carbon. Carbon storage in trees represents 37 and 60% of the total carbon content in patula pine and teak plantations, respectively. Even so, the remaining percentage corresponds to SOC, whereas FFC content is less than 1%. In summary, differences in carbon stocks between patula pine and teak trees were not significant, but the distribution of carbon differed between the plantation types. The low FFC does not explain the SOC stocks; however, current variability of SOC stocks could be related to variation in land use history.     

Carbon pools and productivity in a 1-km heterogeneous forest and peatland mosaic in Minnesota,USA

Determining the magnitude of carbon (C) storage in forests and peatlands is an important step towards predicting how regional carbon balance will respond to climate change. However, spatial heterogeneity of dominant forest and peatland cover types can inhibit accurate C storage estimates. We evaluated ecosystem C pools and productivity in the Marcell Experimental Forest (MEF), in northern Minnesota, USA, using a network of plots that were evenly spaced across a heterogeneous 1-km² mosaic composed of a mix of upland forests and peatlands. Using a nested plot design, we estimated the standing C stock of vegetation, coarse detrital wood and soil pools. We also estimated aboveground net primary production (ANPP) as well as coarse root production. Additionally we evaluated how vegetation cover types within the study area differed in C storage. The total ecosystem C pool did not vary significantly among upland areas dominated by aspen (160 ± 13 Mg C ha⁻¹), mixed hardwoods (153 ± 19 Mg C ha⁻¹), and conifers (197 ± 23 Mg C ha⁻¹). Live vegetation accounted for approximately 50% of the total ecosystem C pool in these upland areas, and soil (including forest floor) accounted for another 35–40%, with remaining C stored as detrital wood. Compared to upland areas, total C stored in peatlands was much greater, 1286 ± 125 Mg C ha⁻¹, with 90–99% of that C found in peat soils that ranged from 1 to 5 m in depth. Forested areas ranged from 2.6 to 2.9 Mg C ha⁻¹ in ANPP, which was highest in conifer-dominated upland areas. In alder-dominated and black spruce-dominated peatland areas, ANPP averaged 2.8 Mg C ha⁻¹, and in open peatlands, ANPP averaged 1.5 Mg C ha⁻¹. In treed areas of forest and peatlands, our estimates of coarse root production ranged from 0.1 to 0.2 Mg C ha⁻¹. Despite the lower production in open peatlands, all peatlands have acted as long-term C sinks over hundreds to thousands of years and store significantly more C per unit area than is stored in uplands. Despite occupying only 13% of our study area, peatlands store almost 50% of the C contained within it. Because C storage in peatlands depends largely on climatic drivers, the impact of climate changes on peatlands may have important ramifications for C budgets of the western Great Lakes region.     

Carbon density and accumulation in woody species of tropical dry forest in India

We studied the carbon density and accumulation in trees at five sites in a tropical dry forest (TDF) to address the questions: how is the TDF structured in terms of tree and carbon density in different DBH (diameter at breast height) classes? What are the levels of carbon density and accumulation in the woody species of TDF? Is the vegetation carbon density evenly distributed across the forest? Does carbon stored in the soil reflect the pattern of aboveground vegetation carbon density? Which species in the forest have a high potential for carbon accumulation? The WSG among species ranged from 0.39 to 0.78 g cm⁻³. Our study indicated that most of the carbon resides in the old-growth (high DBH) trees; 88-97% carbon occurred in individuals ?19.1 cm DBH, and therefore extra care is required to protect such trees in the dry forest. Acacia catechu, Buchanania lanzan, Hardwickia binata, Shorea robusta and Terminalia tomentosa accounted for more than 10 t ha⁻¹ carbon density, warranting extra efforts for their protection. Species also differed in their capacity to accumulate carbon indicating variable suitability for afforestation. Annually, the forest accumulated 5.3 t-C ha⁻¹ yr⁻¹ on the most productive, wettest Hathinala site to 0.05 t-C ha⁻¹ yr⁻¹ on the least productive, driest Kotwa site. This study indicated a marked patchy distribution of carbon density (151 t-C ha⁻¹ on the Hathinala site to 15.6 t-C ha⁻¹ on the Kotwa site); the maximum value was more than nine times the minimum value. These findings suggest that there is a substantial scope to increase the carbon density and accumulation in this forest through management strategies focused on the protection, from deforestation and fire, of the high carbon density sites and the old-growth trees, and increasing the stocking density of the forest by planting species with high potential for carbon accumulation.