Biomass estimations in forests of different disturbance history in the Atlantic Forest of Rio de Janeiro,Brazil

Tropical forests are large reservoirs of biomass and there is a need for information on existing carbon stocks in these ecosystems and especially the effects of logging on these stocks. Reliable estimates of aboveground biomass stocks within the Atlantic Forest are rarely available. Past human disturbance is an important factor affecting forest structure variation and biomass accumulation among tropical forest ecosystems. To support the efforts of improving the quality of estimations of the current and future biomass carbon storage capacity of this disturbed forest region we tested a non-experimental small scale approach to compare the aboveground tree biomass (AGB) of forest sites. Three sites with known disturbance histories have been investigated: complete cut down, selective logging and conservation since 70 years. The woody plant community (dbh ≥ 10 cm) was censused and canopy openness in conjunction with leaf area index has been obtained by hemispherical photographs at each site. Estimates of aboveground tree biomass have been carried out using an allometric equation for moist tropical forests already applied for the study area. Additionally, a FAO standard equation has been employed for crosschecking our results. We identified significant differences in recent AGB of the three compared forest sites. With 313 (±48 Mg ha⁻¹) the highest AGB-values have been found in the preserved forest area within a National Park, followed by 297 (±83) Mg ha⁻¹ at the former clear cut site. Lowest AGB has been calculated for the area with past selective logging: 204 (±38) Mg ha⁻¹. Values calculated with the FAO standard equation showed the same trend but at a lower AGB level. Our results based an a small scale approach suggest that biomass productivity can recover in a forest which was completely cleared 60 years ago to reach AGB values up to a level that almost represents the situation in a preserved forest. Selective logging may slow down AGB accumulation and the effect is measurable after several decades.     

Above- and belowground carbon stocks of two organic,agroforestry-based oil palm production systems in eastern Amazonia

Ecosystem-level assessments of carbon (C) stocks of agroforestry systems are scarce. We quantified the ecosystem-level C stocks of one agroforestry-based oil palm production system (AFS_P) and one agroforestry-based oil palm and cacao production system (AFS_P+C) in eastern Amazonia. We quantified the stocks of C in four pools: aboveground live biomass, litter, roots, and soil. We evaluated the distribution of litter, roots, and soil C stocks in the oil palm management zones and in the area planted with cacao and other agroforestry species. The ecosystem-C stock was higher in AFS_P+C (116.7 ± 1.5 Mg C ha^?1) than in AFS_P (99.1 ± 3.1 Mg C ha^?1). The total litter-C stock was higher in AFS_P+C (3.27 ± 0.01 Mg C ha^?1) than in AFS_P (2.26 ± 0.06 Mg C ha^?1). Total root and soil C stocks (0–30 cm) did not differ between agroforestry systems. Ecosystem-C stocks varied between agroforestry systems due to differences in both aboveground and belowground stocks. In general, the belowground-C stocks varied spatially in response to the management in the oil palm and non-oil palm strips; these results have important implications for the monitoring of ecosystem-level C dynamics and the refinement of soil management.     

Aboveground productivity of an unsuccessful 140-year-old <Emphasis Type="Italic">Cryptomeria japonica</Emphasis> plantation in northern Kyushu,Japan

We measured the aboveground biomass, biomass increment and litterfall production of a 140-year-old, abandoned Cryptomeria japonica plantation in order to infer the effects of topography on biomass production. The plantation was unsuccessful and the naturally regenerated broad-leaved trees contributed 93.4% (374.2 Mg ha⁻¹) of the total aboveground biomass (400.2 Mg ha⁻¹). Comparing between different slope positions, aboveground biomass decreased downslope corresponding to the decrease in broad-leaved tree biomass. The biomass of C. japonica did not vary with slope position. Biomass increment and litterfall production of the broad-leaved trees also decreased downslope. However, litterfall production per unit biomass and aboveground net primary production per unit biomass increased downslope. Results of a path analysis showed that biomass increment of C. japonica decreased with increasing topographical convexity, whereas biomass and litterfall production of broad-leaved tree increased. Litterfall production of broad-leaved tree decreased with increasing biomass of C. japonica, suggesting that, despite their small biomass, the presence of residual C. japonica may have negative effects on the distribution and productivity of the broad-leaved trees. Our results indicated that total aboveground biomass of the study site was comparable to that of old-growth C. japonica plantations. We inferred that the variation in aboveground biomass of the broad-leaved trees was largely determined by the topography, while their productivity was affected by interactions with planted C. japonica.     

Stocks of coarse woody debris in old-growth lucidophyllous forests in southwestern Japan

This study quantified the mass and inputs of coarse woody debris (CWD) in two old-growth lucidophyllous forests in southwestern Japan: in a steep slope area at Aya and in a flattish bottomland at Okuchi. CWD mass averaged 36.85 Mg ha⁻¹ with eightfold variations at Aya, and 20.77 Mg ha⁻¹ with more than 40-fold variations at Okuchi. CWD inputs estimated from long-term data on tree mortality averaged 36.76 Mg ha⁻¹ over 16 years at Aya and 44.11 Mg ha⁻¹ over 11 years at Okuchi. In both plots, fallen logs were the major form of CWD mass: 74.4% at Aya and 60.2% at Okuchi. About 19% of CWD was snapped and 7% was uprooted at Aya, and about 34% was snapped and 5.4% was uprooted at Okuchi. The CWD mass differed markedly with topographic conditions in both plots, increasing from valleys up to ridges at Aya and from forest down to a stream at Okuchi. Canopy gaps enhanced CWD mass and inputs in both plots: CWD input under gaps was two to three times that beneath closed canopy. These results imply that typhoons would increase CWD mass and inputs on upper slopes on account of the high aboveground biomass stocks and existence of large-diameter trees.     

Changes in soil carbon and nitrogen stocks after conversion of subtropical natural forest to loblolly pine plantations

Pinus plantations have increased in Brazil, and native forest areas have been converted for timber production. The clearing and the long-term loblolly pine (Pinus taeda L.) land-use effects on soil carbon and nitrogen stocks were evaluated in a natural broadleaved forest and in loblolly pine sites cultivated for 29, 35, 38 and 49 years, as well the soil contribution as ecosystem carbon pool. According to the exponential-decay model fitted to changes in carbon stock, the initial soil carbon stock of 200 Mg ha^?1 to a depth of 100 cm in the natural forest decreased by 36% over 49 years of pine cultivation (around 72.4 Mg ha^?1 of C). Around two-thirds of this decrease occurred in the top 30 cm of the soil and intensively in the first 12 years of cultivation, but slowly faded as carbon stock tended to reach a new steady state after approximately 49 years of cultivation. The soil nitrogen stock in the natural forest was 14.2 Mg ha^?1 to a depth of 100 cm and decreased by 36% over the 49 years. This decrease was linear according to the fitted model, especially in the top 30 cm where nitrogen decline was 83% and was proportionally more intense than the carbon decline. Despite the soil carbon decrease, soil remained the largest carbon reservoir in the ecosystem for the growing rotation time of loblolly pine in this region.

     

The potential of plantations of Terminalia superba Engl. & Diels for wood and biomass production (Mayombe Forest, Democratic Republic of Congo)

? In the 1940s–1950s, large limba (Terminalia superba Engl. & Diels) plantations were established in the Democratic Republic of Congo to reduce the pressure on the natural forests.

? The objective of this study was to evaluate the potential of these long-rotation plantations as production forests (timber) and carbon sinks.

? Five different plantations, between 50 and 58 years old, were sampled. Over a sample surface of more than 73 ha, the diameter above buttresses of 2 680 trees, bole height of 265 trees and tree height of 128 trees was measured.

? To estimate the commercial volume, a nonlinear power law regression was used (R ² = 0.95). A power law variance function was applied to counter heteroscedasticity of the residual plot. Estimates of commercial tree and stand volume at 50 to 58 y were 5.6 ± 4.1 m³ and 183.9 ± 135.0 m³ ha^?1. Stand volumes appear low but are explained by a large decrease in tree density. However, the mean volume increment of 3.2–3.7 m³ ha^?1 y^?1 corresponds well with teak plantations of a similar age. For limba, aboveground biomass and carbon estimates of this study (resp. 108.4 and 54.2 Mg ha^?1) differ significantly from those of existing aboveground biomass models (resp. 135.7–143.9 Mg ha^?1 biomass and 67.9–72.0 Mg ha^?1 C). All aboveground biomass and carbon estimates for T. superba stands were lower than for the estimates of young fast-growing plantations like Tectona grandis L. f., Eucalyptus spp. and Acacia spp. (≤ 30 y).

     

Carbon accumulation in aboveground and belowground biomass and soil of different age native forest plantations in the humid tropical lowlands of Costa Rica

Generic or default values to account for biomass and carbon accumulation in tropical forest ecosystems are generally recognized as a major source of errors, making site and species specific data the best way to achieve precise and reliable estimates. The objective of our study was to determine carbon in various components (leaves, branches, stems, structural roots and soil) of single-species plantations of Vochysia guatemalensis and Hieronyma alchorneoides from 0 to 16 years of age. Carbon fraction in the biomass, mean (±standard deviation), for the different pools varied between 38.5 and 49.7% (±3 and 3.8). Accumulated carbon in the biomass increased with the plantation age, with mean annual increments of 7.1 and 5.3 Mg ha⁻¹ year⁻¹ for forest plantations of V. guatemalensis and H. alchorneoides, respectively. At all ages, 66.3% (±10.6) of total biomass was found within the aboveground tree components, while 18.6% (±20.9) was found in structural roots. The soil (0–30 cm) contained 62.2 (±13) and 71.5% (±17.1) of the total carbon (biomass plus soil) under V. guatemalensis and H. alchorneoides, respectively. Mean annual increment for carbon in the soil was 1.7 and 1.3 Mg ha⁻¹ year⁻¹ in V. guatemalensis and H. alchorneoides. Allometric equations were constructed to estimate total biomass and carbon in the biomass which had an R ²aj (adjusted R square) greater than 94.5%. Finally, we compare our results to those that could have resulted from the use of default values, showing how site and species specific data contribute to the overall goal of improving carbon estimates and providing a more reliable account of the mitigation potential of forestry activities on climate change.     

Carbon stock potentials of woodlands in north western lowlands of Ethiopia

ABSTRACT

This paper examined the potential of dry north western woodlands of Ethiopia (Adi Goshu, Lemlem Terara, and Gemed) for carbon stocks. Allometry equations were used to determine the aboveground, belowground, and dead woods biomasses; litter and herbaceous biomasses were determined using direct harvesting method. The result showed the estimated mean carbon stocks of the aboveground, belowground, and the dead wood biomass for the Untapped Boswellia Papyrifera Woodland (UW) in Lemlem Terara site were significantly higher (P < 0.05) than that of the Adi Goshu site. In the Gemed site, the mean Herb Biomass Carbon (HBC) stock was 1.2 Mg ha^?1, which is significantly highest (P < 0.05) than the other two study sites (Lemlem Terara, 0.42 Mg ha^?1 and Adi Goshu, 0.45 Mg ha^?1) for the Tapped Boswellia Papyrifera Woodland (TW). In UW, the mean soil carbon stock of the Lemlem Terara site (58.19 Mg ha^?1) was significantly (P < 0.05) higher than that of Adi Goshu (33.61 Mg ha^?1). In the case of the total carbon stocks in UW stratum, for the Adi Goshu site, the carbon stock was estimated to be about 55.26 Mg ha^?1 while 96.74 Mg ha^?1 for Lemlem Terara. Therefore, Carbon stock in different carbon pools (aboveground and belowground biomass, dead wood, litter, herbaceous biomass, and soil) has a potential to decrease the rate of enrichment of atmospheric concentration of carbon dioxide.     

Simulation of carbon pool changes in woodlots in eastern Zambia using the CO2FIX model

Agroforestry systems have the potential to contribute significantly to climate change mitigation and adaptation. However, data on tree and soil organic carbon (SOC) pools for most agroforestry systems are lacking because reliable methods for estimating ecosystem carbon (C) pools are scarce. This study quantified the effects of five Leucaena species (L. leucocephala, L. macrophylla, L. diversifolia, L. collinsii and L. pulverulenta) on vegetal and soil C stocks and on mean annual increment (MAI) in aboveground tree C stocks. Specifically, it tested the validity of the CO2FIX model using empirical data from 7?year-old woodlots at Msekera, Zambia, and assessed the impact of converting a degraded agricultural ecosystem to woodlots on C stocks. Measured above- and below-ground tree C stocks and MAI of aboveground biomass differed significantly among the Leucaena species. Measured stem and total aboveground tree C stocks in seven-year old woodlots ranged from 17.1 to 29.2 and from 24.5 to 55.9?Mg?ha^?1, respectively. Measured SOC stocks at 0?C200?cm depth in Leucaena stands ranged from 106.9 (L. diversifolia) to 186.0?Mg?ha^?1 (L. leucocephala). Modeled stem and branch C stocks closely matched measured stocks, but the soil module of CO2FIX did not predict the soil C. The soil C data are inconclusive at this stage. We recommend that a fractionation and a soil aggregate hierarchy study backed by C dating is carried out to explain soil C dynamics in these soils. However, the model can be used only for estimating changes in aboveground tree C stocks in woodlots until soil C module is proven to predict SOC stocks.     

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.     

Biomass,and carbon and nitrogen pools in a subtropical evergreen broad-leaved forest in eastern China

Subtropical evergreen broad-leaved forest is the most widely distributed land-cover type in eastern China. As the rate of land-use change accelerates worldwide, it is becoming increasingly important to quantify ecosystem biomass and carbon (C) and nitrogen (N) pools. Above and below-ground biomass and ecosystem pools of N and C in a subtropical secondary forest were investigated at Laoshan Mountain Natural Reserve, eastern China. Total biomass was 142.9 Mg ha⁻¹ for a young stand (18 years) and 421.9 Mg ha⁻¹ for a premature stand (ca. 60 years); of this, root biomass was from 26.9 (18.8% of the total) to 100.3 Mg ha⁻¹ (23.8%). Total biomass C and N pools were, respectively, 71.4 Mg ha⁻¹ and 641.6 kg ha⁻¹ in the young stand, and 217.0 Mg ha⁻¹ and 1387.4 kg ha⁻¹ in the premature stand. The tree layer comprised 91.8 and 89.4% of the total biomass C and N pools in the young stand, and 98.0 and 95.6% in the premature stand. Total ecosystem C and N pools were, respectively, 101.4 and 4.6 Mg ha⁻¹ for the young stand, and 260.2 and 6.6 Mg ha⁻¹ for the premature stand. Soil C comprised 23.8–29.6% of total ecosystem C whereas soil N comprised 76.9–84.4% of the total. Our results suggest that a very high percentage of N in this subtropical forest ecosystem is stored in the mineral soil, whereas the proportion of organic C in the soil pool is more variable. The subtropical forest in eastern China seems to rapidly accumulate biomass during secondary succession, which makes it a potentially rapid accumulator of, and large sink for, atmospheric C.     

Fine root dynamics in three central Himalayan high elevation forests ranging from closed canopied to open-canopied treeline vegetation

Fine root biomass, rates of dry matter production and nutrients dynamics were estimated for 1 year in three high elevation forests of the Indian central Himalaya. Fine root biomass and productivity were higher in closed canopied cappadocian maple forest (9.92 Mg ha⁻¹ and 6.34 Mg ha⁻¹ year⁻¹, respectively), followed by Himalayan birch forest (6.35 Mg ha⁻¹ and 4.44 Mg ha⁻¹ year⁻¹) and Bell rhododendron forest (6.23 Mg ha⁻¹ and 2.94 Mg ha⁻¹ year⁻¹). Both fine root biomass and productivity declined with an increase in elevation. Across the sites, fine root biomass was maximal in fall and minimal in summer. In all sites, maximum nutrient concentration in fine roots was in the rainy season and minimum in winter. Fine root biomass per unit basal area was positively related with elevation, Bell rhododendron forest having the largest fine root biomass per unit of basal area (0.53 Mg m⁻²) and cappadocian maple the least (0.18 Mg m⁻²). The production efficiency of fine roots per unit of leaf biomass also increased with elevation and ranged from 1.13 g g⁻¹ leaf mass year⁻¹ in cappadocian maple forest to 1.28 g g⁻¹ leaf mass year⁻¹ in Bell rhododendron forest. Present fine root turnover estimates showed a decline towards higher elevations (0.72 year⁻¹ in cappadocian maple and 0.58 year⁻¹ in Bell rhododendron forest) and are higher than global estimates (0.52).     

Profiles of carbon stocks in forest, reforestation and agricultural land, Northern Thailand

A study was conducted to assess carbon stocks in various forms and land-use types and reliably estimate the impact of land use on C stocks in the Nam Yao sub-watershed (19°05'10"N, 100°37'02"E), Thailand. The carbon stocks of aboveground, soil organic and fine root within primary forest, reforestation and agricultural land were estimated through field data collection. Results revealed that the amount of total carbon stock of forests (357.62 ± 28.51 Mg·ha-1, simplified expression of Mg (carbon)·ha-1) was significantly greater (P＜ 0.05) than the reforestation (195.25 ±14.38 Mg·ha-1) and the agricultural land (103.10±18.24 Mg·ha-1). Soil organic carbon in the forests (196.24 ±22.81 Mg·ha-1) was also significantly greater (P＜ 0.05) than the reforestation (146.83± 7.22 Mg·ha-1) and the agricultural land (95.09 ± 14.18 Mg·ha-1). The differences in carbon stocks across land-use types are the primary consequence of variations in the vegetation biomass and the soil organic matter. Fine root carbon was a small fraction of carbon stocks in all land-use types. Most of the soil organic carbon and fine root carbon content was found in the upper 40-cm layer and decreased with soil depth. The aboveground carbon(soil organic carbon: fine root carbon ratios (ABGC: SOC: FRC), was 5:8:1, 2:8:1, and 3:50:1 for the forest, reforestation and agricultural land, respectively. These results indicate that a relatively large proportion of the C loss is due to forest conversion to agricultural land. However, the C can be effectively recaptured through reforestation where high levels of C are stored in biomass as carbon sinks, facilitating carbon dioxide mitigation.     

Biomass production potential of three short rotation woody crop species under varying nitrogen and water availability

A study was conducted in an agricultural field to examine the biomass production of three fast-growing short rotation woody crop (SRWC) species, Populus deltoides, Quercus pagoda, and Platanus occidentalis using fertilization and irrigation (fertigation). The study included a randomized complete block (RCB) with five treatments; control, irrigated, and irrigated with 56, 112, and 224 kg nitrogen (N) ha⁻¹ year⁻¹. We quantified survival, basal area, standing biomass, aboveground net primary productivity (ANPP), leaf area index (LAI), and growth efficiency (GE) for each species along the soil nitrogen and water gradient. P. deltoides had low rates of survival (83, 82, and 77% years six, seven, and eight, respectively), but had production values greater than Q. pagoda and P. occidentalis. Standing biomass reached its peak for P. deltoides and P. occidentalis (17.56 and 10.36 Mg ha¹, respectively) in the irrigation treatment, and in the 112 kg N treatment for Q. pagoda (5.42 Mg ha⁻¹). P. deltoides and P. occidentalis ANPP peaked in the irrigation treatment (6.66 and 6.31 Mg ha⁻¹ year⁻¹, respectively) and in the 112 kg N (4.43 Mg ha⁻¹ year⁻¹) for Q. pagoda. ANPP was correlated with LAI; however, the relationship was species specific. Maximum ANPP was reached below the maximum LAI for Q. pagoda and P. occidentalis. P. deltoides ANPP was highest at the maximum LAI, which was achieved with IRR. These results suggest that species-specific cultural practices producing optimum LAI and maximum ANPP should be identified before fertigation techniques are adopted widely for SRWC production on agricultural fields.     

Biomass production and carbon sequestration of dense downy birch stands on cutaway peatlands

The establishment of biomass plantations with short-rotation forestry principles is one of the after-use options for cutaway peatlands. We studied biomass production and carbon sequestration in the above- and below-ground biomass of 25 naturally afforested, 10–30 years old downy birch (Betula pubescens Ehrh.) stands located in peat cutaway areas in Finland. Self-thinning reduced the stand density from 122,000 trees ha^?1 (stand age of 10 years) to 10,000 trees ha^?1 (25–30 years), while the leafless above-ground biomass increased from 17?Mg ha^?1 up to 79–116?Mg ha^?1. The total leafless biomass (including stumps and roots) varied from 46 to 151?Mg ha^?1. The mean annual increment (MAI) of the above-ground biomass increased up to the stand age of 15 years, after which the MAI was on the average 3.2?Mg ha^?1a^?1. With below-ground biomass, the MAI of the stands older than 15 years was 4.7?Mg ha^?1. The organic matter accumulated in the O-layer on the top of the residual peat increased linearly with the stand age, reaching 29.3?Mg ha^?1 in the oldest stand. The O-layer contributed significantly to the C sink, and the afforestation with downy birch converted most of sites into C sinks.     

Carbon stocks in coffee agroforests and mixed dry tropical forests in the western highlands of Guatemala

Tree removal in Latin American coffee agroforestry systems has been widespread due to complex and interacting factors that include fluctuating international markets, government-supported agricultural policies, and climate change. Despite shade tree removal and land conversion risks, there is currently no widespread policy incentive encouraging the maintenance of shade trees for the benefit of carbon sequestration. In facilitation of such incentives, an understanding of the capacity of coffee agroforests to store carbon relative to tropical forests must be developed. Drawing on ecological inventories conducted in 2007 and 2010 in the Lake Atitlán region of Guatemala, this research examines the carbon pools of smallholder coffee agroforests (CAFs) as they compare to a mixed dry forest (MDF) system. Data from 61 plots, covering a total area of 2.24 ha, was used to assess the aboveground, coarse root, and soil carbon reservoirs of the two land-use systems. Results of this research demonstrate the total carbon stocks of CAFs to range from 74.0 to 259.0 Megagrams (Mg)?C ha^?1 with a mean of 127.6?±?6.6 (SE)?Mg?C ha^?1. The average carbon stocks of CAFs was significantly lower than estimated for the MDF (198.7?±?32.1?Mg?C?ha^?1); however, individual tree and soil pools were not significantly different suggesting that agroforest shade trees play an important role in facilitating carbon sequestration and soil conservation. This research demonstrates the need for conservation-based initiatives which recognize the carbon sequestration benefits of coffee agroforests alongside natural forest systems.     

Carbon stocks and productivity of mangrove forests in Tanzania

Mangroves offer a number of ecosystem goods and services, including carbon (C) storage. As a carbon pool, mangroves could be a source of CO₂ emissions as a result of human activities such as deforestation and forest degradation. Conversely, mangroves may act as a CO₂ sink through biomass accumulation. This study aimed to determine carbon stocks, harvest removals and productivity of mangrove forests of mainland Tanzania. Nine species were recorded in mainland Tanzania, among them Avicennia marina (Forssk.) Vierh., Rhizophora mucronata Lam. (31%) and Ceriops tagal (Perr.) C.B.Rob. (20%) were dominant. The aboveground, dead wood, belowground and total carbon were 33.5 ± 5.8 Mg C ha^?1, 1.2 ± 1.1 (2% of total carbon), 30.0 ± 4.5 Mg C ha^?1 (46% of total carbon) and 64.7 ± 8.4 Mg C ha^?1 at 95% confidence level, respectively. Carbon harvest removals accounted for loss of about 4% of standing total carbon stocks annually. Results on the productivity of mangrove forests (using data from permanent sample plots monitored for four years [1995-1998]) showed an overall carbon increment of 5.6 Mg C ha^?1 y^?1 (aboveground carbon), 4.1 C ha^?1 y^?1 (belowground carbon) and 9.7 C ha^?1 y^?1 (total carbon) at 23%, 32% and 27% levels of uncertainty, respectively. Both natural death and tree cutting/harvest removals resulted in significant decline of annual carbon productivity. Findings from this study demonstrate that mangroves store large quantities of carbon and are more productive than other dominant forest formations in southern Africa. Both their deforestation and forest degradation, therefore, is likely to contribute to large quantities of emission and loss of carbon sink functionality. Therefore, mangroves need to be managed sustainably.     

Effect of tree species on carbon stocks in forest floor and mineral soil and implications for soil carbon inventories

Forest soil organic carbon (SOC) and forest floor carbon (FFC) stocks are highly variable. The sampling effort required to assess SOC and FFC stocks is therefore large, resulting in limited sampling and poor estimates of the size, spatial distribution, and changes in SOC and FFC stocks in many countries. Forest SOC and FFC stocks are influenced by tree species. Therefore, quantification of the effect of tree species on carbon stocks combined with spatial information on tree species distribution could improve insight into the spatial distribution of forest carbon stocks.We present a study on the effect of tree species on FFC and SOC stock for a forest in the Netherlands and evaluate how this information could be used for inventory improvement. We assessed FFC and SOC stocks in stands of beech (Fagus sylvatica), Douglas fir (Pseudotsuga menziesii), Scots pine (Pinus sylvestris), oak (Quercus robur) and larch (Larix kaempferi).FFC and SOC stocks differed between a number of species. FFC stocks varied between 11.1 Mg C ha⁻¹ (beech) and 29.6 Mg C ha⁻¹ (larch). SOC stocks varied between 53.3 Mg C ha⁻¹ (beech) and 97.1 Mg C ha⁻¹ (larch). At managed locations, carbon stocks were lower than at unmanaged locations. The Dutch carbon inventory currently overestimates FFC stocks. Differences in carbon stocks between conifer and broadleaf forests were significant enough to consider them relevant for the Dutch system for carbon inventory.     

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.     

Five-year vegetation control effects on aboveground biomass and nitrogen content and allocation in Douglas-fir plantations on three contrasting sites

Despite widespread use of intensive vegetation control (VC) in forest management, the effects of VC on allocation of biomass and nutrients between young trees and competing vegetation are not well understood. On three Pacific Northwest sites differing in productivity, soil parent material, and understory vegetation community, we evaluated year-5 effects of presence/absence of 5 years of VC on allocation of aboveground biomass and nitrogen (N) between planted Douglas-fir (Pseudotsuga menziesii var. menziesii) and competing vegetation. Equations for predicting bole, branch, foliar, and total dry weights based on stem diameter at a height of 15 cm and total tree height did not differ significantly among sites or by presence or absence of VC. This contrasts with previous research, using diameter at breast height rather than at 15 cm, which found that separate equations were warranted for trees with and without competing vegetation. Estimated whole-tree biomass among the six site/VC combinations ranged from 0.8 to 7.5 Mg ha⁻¹, and increases in tree biomass associated with VC ranged from 62% to 173% among sites. Among the three sites, there were positive, linear relationships between soil total N content to a depth of 60 cm and both N content of aboveground vegetation (trees plus competing vegetation) and Douglas-fir foliar N concentration. Tree N content increased by 8.4, 8.2, and 40.0 kg N ha⁻¹ with VC at the three sites, whereas competing vegetation N content decreased with VC by 0.9, 18.8, and 32.0 kg N ha⁻¹, respectively, at the same sites. Thus, VC did not lead to a direct compensatory tradeoff between aboveground N content of trees and other vegetation. However, soil N content was linearly related to N accumulation and plant growth across the three sites. In addition to differences in N availability among sites, the effect of VC on the redistribution of resources among trees and competing vegetation also was influenced by vegetation community composition and efficacy of VC treatments.