Aboveground Biomass Stocks Research Articles

Plant Diversity and Aboveground Carbon Stock Along Altitudinal Gradients in Quezon Mountain Range in Southern Mindanao, Philippines

Plant diversity, aboveground biomass, and carbon stock along portions of Quezon Mountain Range were assessed in three elevation gradients, e.g., low (400-799 m a.s.l.), middle (800-1,199 m a.s.l.), and high (1,200-1,600 m a.s.l.) in Southern Mindanao using quadrat sampling technique. A total of 146 plant species were identified including threatened Shorea contorta, Parashorea malaanonan, Dillenia philipinensis, Alstonia macrophylla, Cinammomum mercadoi, Palaqium luzoniense, Neolitsea vidalii, Dacrycarpus elatumi, and Dacrycarpus imbricatus. On the average, low diversity was recorded in all gradients particularly in low and middle elevation ranges where alteration of vegetation cover, and proliferation of bio-invasive Piper aduncum were observed. Biomass and carbon stock were largest in high elevation where the inaccessible old growth forest is located compared to a proposed mine site in low and middle elevation that are predominated by grassland, farmlands, disturbed secondary growth forest, and human settlements. Overall, carbon stocks ranged from 33.8 to 192.0 MgC ha-1 suggesting the good potential of the area to mitigate climate change. Sustainable management of biodiversity and carbon stock is needed by apportioning productive and protective zones in the mountain.

Sink or source—The potential of coffee agroforestry systems to sequester atmospheric CO2 into soil organic carbon

Current carbon accounting methodologies often assume interactions between above-ground and below-ground carbon, without considering effects of land management. We used data from two long-term coffee agroforestry experiments in Costa Rica and Nicaragua to assess the effect on total soil organic carbon (SOC) stocks of (i) organic versus conventional management, (ii) higher versus moderate agronomic inputs, (iii) tree shade types. During the first nine years of coffee establishment total 0–40cm depth SOC stocks decreased by 12.4% in Costa Rica and 0.13% in Nicaragua. Change in SOC differed consistently amongst soil layers: at 0–10cm SOC stocks increased by 2.14 and 1.26MgCha−1 in Costa Rica and Nicaragua respectively; however much greater reduction occurred at 20–40cm (9.65 and 2.85MgCha−1 respectively). Organic management caused a greater increase in 0–10cm SOC but did not influence its reduction at depth. Effects of shade type were smaller, though heavily pruned legume shade trees produced a greater increase in 0–10cm SOC than unpruned timber trees. No significant differences in SOC stocks were found between shaded and unshaded systems at any depth and SOC was poorly correlated with above-ground biomass stocks highlighting poor validity of “expansion factors” currently used to estimate SOC. SOC stock changes were significantly negatively correlated with initial SOC stock per plot, providing evidence that during establishment of these woody-plant-dominated agricultural systems SOC stocks tend to converge towards a new equilibrium as a function of the change in the quantity and distribution of organic inputs. Therefore it cannot be assumed that tree-based agricultural systems necessarily lead to increases in soil C stocks. While high inputs of organic fertiliser/tree pruning mulch increased surface-layer SOC stocks, this did not affect stocks in deeper soil, where decreases generally exceeded any gains in surface soil. Therefore site- and system-specific sampling is essential to draw meaningful conclusions for climate change mitigation strategies.

Effects of national forest inventory plot location error on forest carbon stock estimation using k-nearest neighbor algorithm

This paper suggested simulation approaches for quantifying and reducing the effects of National Forest Inventory (NFI) plot location error on aboveground forest biomass and carbon stock estimation using the k-Nearest Neighbor (kNN) algorithm. Additionally, the effects of plot location error in pre-GPS and GPS NFI plots were compared. Two South Korean cities, Sejong and Daejeon, were chosen to represent the study area, for which four Landsat TM images were collected together with two NFI datasets established in both the pre-GPS and GPS eras. The effects of plot location error were investigated in two ways: systematic error simulation, and random error simulation. Systematic error simulation was conducted to determine the effect of plot location error due to mis-registration. All of the NFI plots were successively moved against the satellite image in 360° directions, and the systematic error patterns were analyzed on the basis of the changes of the Root Mean Square Error (RMSE) of kNN estimation. In the random error simulation, the inherent random location errors in NFI plots were quantified by Monte Carlo simulation. After removal of both the estimated systematic and random location errors from the NFI plots, the RMSE% were reduced by 11.7% and 17.7% for the two pre-GPS-era datasets, and by 5.5% and 8.0% for the two GPS-era datasets. The experimental results showed that the pre-GPS NFI plots were more subject to plot location error than were the GPS NFI plots. This study’s findings demonstrate a potential remedy for reducing NFI plot location errors which may improve the accuracy of carbon stock estimation in a practical manner, particularly in the case of pre-GPS NFI data.

Patterns of stocks of aboveground tree biomass, dynamics, and their determinants in secondary Andean forests

In this study, we aimed to identify the main factors that affect the dynamics and rates of aboveground biomass (AGB) accumulation in secondary forests located in the interandean valleys of Colombia. We used two censuses performed on trees with a diameter at breast height of⩾10cm in 10 1-ha plots to answer the following questions: (1) Does prior use of the land for raising crops (instead of pastureland for cattle ranching) promote an increase in the rate of AGB accumulation? (2) To what extent did climate, soil characteristics, the functional traits of resident species, and/or stand age affect the stocks and dynamics of the AGB in these secondary forests? We did not find any evidence that prior land use for cattle ranching had a negative effect on the tree AGB-accumulation rate, when compared with land previously used for raising crops. Greater AGB stocks at an intermediate fertility point may be associated with a higher abundance of tall, short-lived, fast-growth pioneer species. Tree mortality rates in secondary forests were primarily determined by the forest’s composition and the variation in the amount of rainfall between sites. Soil fertility, which is known to accelerate the growth rate of plant species, was significantly and positively associated with the rate of AGB recruitment. We did not find any evidence for a negative correlation between wood density and growth, as has been reported for primary tropical forests. The net AGB change (%) was primarily associated with the low soil-fertility characteristics of sandy well-drained soils that could, in the presence of steep slopes, increase forest dynamics. Land restoration that restores the natural cycle of secondary forests could assist in the mitigation of global warming by promoting key environmental functions, such as carbon sequestration.

Above-Ground Biomass and Carbon Stocks in Tropical Deciduous Forests of Nallamalais, Eastern Ghats, Andhra Pradesh, India

The present study aimed to estimate above-ground biomass and carbon stocks of different life forms in tropical dry and moist deciduous forests of Nallamalais, one of the centers of plant diversity of India, located in central part of the Eastern Ghats. The present study used a non-destructive method of biomass estimation. From the sampled inventory it is found that the dry deciduous vegetation with 114 species comprising a total of 1737 tree individuals with a mean basal area of 16.37±9.12 m2 ha-1, 61.52±41.66 Mg ha-1 (Mega gram=106 g) above-ground biomass and 26.83±15.69 Mg ha-1 carbon, the moist deciduous vegetation with 115 species, comprising 1431 tree individuals with a mean basal area of 29.78±4.83 m2 ha-1, contributing 110.37±26.12 Mg ha-1 above-ground biomass and 52.24±12.48 Mg ha-1 carbon. It is revealed that the moist deciduous forests are more efficient in terms of sequestering atmospheric carbon.

Above-ground net primary productivity in young stands of beech and spruce

AbstractOne of the expected consequences of climate change and its inherent phenomena to forest ecosystems is the gradual modification of their tree species composition (i.e. expansion of resistant species instead of less resistant ones). Climate change accompanied with increasing temperatures and a lack of precipitations may present a threat especially to spruce stands in the European part of the temperate zone. European beech is one of the possible forest tree species which might replace the potentially endangered spruce. In this paper, we observed, by using a combination of continual measurements and destructive whole-tree sampling, standing stocks of above-ground biomass (i.e. stem, branches, and foliage) and its annual net primary productivity (NPP) in naturally regenerated young stands of beech and spruce. We intentionally selected a site where the changing climate conditions are better suited to the ecological demands of beech rather than spruce (the species is dominant in the observed area). We recorded only small differences in the standing stock of stems of the beech, if based on tons per ha. However, this is in favor of spruce if based on cubic meters per ha. The largest difference between the species was found for the standing stock of foliage, spruce retained three times the biomass of beech. Also, beech allocated more carbohydrates to stem than spruce. On the other hand, we estimated nearly the same production of foliages and branches in both stands.

Estructura, composición florística, biomasa y carbono arriba del suelo en los manglares Laguna de Gandoca y Estero Moín, Limón, Costa Rica

Se delimitó el área de dos manglares del Caribe Sur deCosta Rica, se analizó su estructura horizontal y verticaly la composición florística. Se cuantificó la biomasay el carbono arriba del suelo respecto al gradiente dedistanciamiento al borde del canal; en ambos sitios.Sobre transeptos perpendiculares al borde del canal,se establecieron parcelas circulares de siete metros deradio, dispuestas cada 25 m. Se evaluó el diámetro (d) decada individuo mayor a 5 cm (a 1,30 m del suelo o arribade la raíz más alta de los individuos con raíces aéreas).Se determinó la densidad de árboles (árboles/ha), el áreabasal (m2/ha), la distribución de los individuos por clasediamétrica, la altura total (m), la densidad de árboles porpisos de altura, el índice de valor de importancia de lasespecies, los índices de diversidad de Shannon–Wiener(H´) y Alpha de Fisher, la biomasa y la reserva de carbonoarriba del suelo. Se utilizó un diseño experimental debloques incompletos al azar (BIA). Se realizaron análisisde varianza (ANDEVA) y pruebas Duncan. El áreadelimitada del manglar de Gandoca fue de 13,34 ha y 10,73 ha en Moín. En Gandoca y Moín se encontrarondiámetros promedio de los árboles de 21,43 cm y20,01 cm, alturas totales promedio de 12,8 m y 10,5 m,densidades de 687 árboles/ha y 708 árboles/ha, áreasbasales de 26,35 m2/ha y 26,37 m2/ha respectivamente.La especie más importante en Gandoca fue Rhizophoramangle y en Moín Pterocarpus officinalis. En ambossitios también se encontraron Laguncularia racemosa yAvicennia germinans junto a otras 20 especies asociadas.El sitio más diverso fue Moín. La biomasa fue de 330, 27Mg/ha y 257,10 Mg/ha, el carbono fue de 153,25 Mg/hay 119,29 Mg/ha para Gandoca y Moín respectivamente.La composición florística y las variables estructurales seasemejaron a otras reportadas en manglares del Caribey sugieren que los manglares estudiados son madurosy se encuentran en constante renovación; sin embargo,Moín presenta un grado de disturbio mayor. Las reservasde biomasa y carbono superaron a las reportadas parabosques secundarios y primarios de Costa Rica y lasde algunos manglares del Indo - Pacífico. El manglar deGandoca presentó un aumento de área, con respecto alo reportado por Coll et al. (2001), para el manglar de Moínno se encontraron registros anteriores de este dato, porlo que este estudio no reporta aumento o disminucióndel área.

Assessing aboveground tropical forest biomass using Google Earth canopy images

Reducing Emissions from Deforestation and Forest Degradation (REDD) in efforts to combat climate change requires participating countries to periodically assess their forest resources on a national scale. Such a process is particularly challenging in the tropics because of technical difficulties related to large aboveground forest biomass stocks, restricted availability of affordable, appropriate remote-sensing images, and a lack of accurate forest inventory data. In this paper, we apply the Fourier-based FOTO method of canopy texture analysis to Google Earth's very-high-resolution images of the wet evergreen forests in the Western Ghats of India in order to (1) assess the predictive power of the method on aboveground biomass of tropical forests, (2) test the merits of free Google Earth images relative to their native commercial IKONOS counterparts and (3) highlight further research needs for affordable, accurate regional aboveground biomass estimations. We used the FOTO method to ordinate Fourier spectra of 1436 square canopy images (125 x 125 m) with respect to a canopy grain texture gradient (i.e., a combination of size distribution and spatial pattern of tree crowns), benchmarked against virtual canopy scenes simulated from a set of known forest structure parameters and a 3-D light interception model. We then used 15 1-ha ground plots to demonstrate that both texture gradients provided by Google Earth and IKONOS images strongly correlated with field-observed stand structure parameters such as the density of large trees, total basal area, and aboveground biomass estimated from a regional allometric model. Our results highlight the great potential of the FOTO method applied to Google Earth data for biomass retrieval because the texture-biomass relationship is only subject to 15% relative error, on average, and does not show obvious saturation trends at large biomass values. We also provide the first reliable map of tropical forest aboveground biomass predicted from free Google Earth images.

Improved Forest Biomass and Carbon Estimations Using Texture Measures from WorldView-2 Satellite Data

Accurate estimation of aboveground biomass and carbon stock has gained importance in the context of the United Nations Framework Convention on Climate Change (UNFCCC) and the Kyoto Protocol. In order to develop improved forest stratum–specific aboveground biomass and carbon estimation models for humid rainforest in northeast Madagascar, this study analyzed texture measures derived from WorldView-2 satellite data. A forest inventory was conducted to develop stratum-specific allometric equations for dry biomass. On this basis, carbon was calculated by applying a conversion factor. After satellite data preprocessing, vegetation indices, principal components, and texture measures were calculated. The strength of their relationships with the stratum-specific plot data was analyzed using Pearson’s correlation. Biomass and carbon estimation models were developed by performing stepwise multiple linear regression. Pearson’s correlation coefficients revealed that (a) texture measures correlated more with biomass and carbon than spectral parameters, and (b) correlations were stronger for degraded forest than for non-degraded forest. For degraded forest, the texture measures of Correlation, Angular Second Moment, and Contrast, derived from the red band, contributed to the best estimation model, which explained 84% of the variability in the field data (relative RMSE = 6.8%). For non-degraded forest, the vegetation index EVI and the texture measures of Variance, Mean, and Correlation, derived from the newly introduced coastal blue band, both NIR bands, and the red band, contributed to the best model, which explained 81% of the variability in the field data (relative RMSE = 11.8%). These results indicate that estimation of tropical rainforest biomass/carbon, based on very high resolution satellite data, can be improved by (a) developing and applying forest stratum–specific models, and (b) including textural information in addition to spectral information.

A universal approach to estimate biomass and carbon stock in tropical forests using generic allometric models

Allometric equations allow aboveground tree biomass and carbon stock to be estimated from tree size. The allometric scaling theory suggests the existence of a universal power-law relationship between tree biomass and tree diameter with a fixed scaling exponent close to 8/3. In addition, generic empirical models, like Chave's or Brown's models, have been proposed for tropical forests in America and Asia. These generic models have been used to estimate forest biomass and carbon worldwide. However, tree allometry depends on environmental and genetic factors that vary from region to region. Consequently, theoretical models that include too few ecological explicative variables or empirical generic models that have been calibrated at particular sites are unlikely to yield accurate tree biomass estimates at other sites. In this study, we based our analysis on a destructive sample of 481 trees in Madagascar spiny dry and moist forests characterized by a high rate of endemism (> 95%). We show that, among the available generic allometric models, Chave's model including diameter, height, and wood specific gravity as explicative variables for a particular forest type (dry, moist, or wet tropical forest) was the only one that gave accurate tree biomass estimates for Madagascar (R2 > 83%, bias < 6%), with estimates comparable to those obtained with regional allometric models. When biomass allometric models are not available for a given forest site, this result shows that a simple height-diameter allometry is needed to accurately estimate biomass and carbon stock from plot inventories.

Mapping tropical forest biomass with radar and spaceborne LiDAR in Lopé National Park, Gabon: overcoming problems of high biomass and persistent cloud

Abstract. Spatially-explicit maps of aboveground biomass are essential for calculating the losses and gains in forest carbon at a regional to national level. The production of such maps across wide areas will become increasingly necessary as international efforts to protect primary forests, such as the REDD+ (Reducing Emissions from Deforestation and forest Degradation) mechanism, come into effect, alongside their use for management and research more generally. However, mapping biomass over high-biomass tropical forest is challenging as (1) direct regressions with optical and radar data saturate, (2) much of the tropics is persistently cloud-covered, reducing the availability of optical data, (3) many regions include steep topography, making the use of radar data complex, (5) while LiDAR data does not suffer from saturation, expensive aircraft-derived data are necessary for complete coverage. We present a solution to the problems, using a combination of terrain-corrected L-band radar data (ALOS PALSAR), spaceborne LiDAR data (ICESat GLAS) and ground-based data. We map Gabon's Lopé National Park (5000 km2) because it includes a range of vegetation types from savanna to closed-canopy tropical forest, is topographically complex, has no recent contiguous cloud-free high-resolution optical data, and the dense forest is above the saturation point for radar. Our 100 m resolution biomass map is derived from fusing spaceborne LiDAR (7142 ICESat GLAS footprints), 96 ground-based plots (average size 0.8 ha) and an unsupervised classification of terrain-corrected ALOS PALSAR radar data, from which we derive the aboveground biomass stocks of the park to be 78 Tg C (173 Mg C ha−1). This value is consistent with our field data average of 181 Mg C ha−1, from the field plots measured in 2009 covering a total of 78 ha, and which are independent as they were not used for the GLAS-biomass estimation. We estimate an uncertainty of &amp;amp;pm;25% on our carbon stock value for the park. This error term includes uncertainties resulting from the use of a generic tropical allometric equation, the use of GLAS data to estimate Lorey's height, and the necessity of separating the landscape into distinct classes. As there is currently no spaceborne LiDAR satellite in operation (GLAS data is available for 2003–2009 only), this methodology is not suitable for change-detection. This research underlines the need for new satellite LiDAR data to provide the potential for biomass-change estimates, although this need will not be met before 2015.

Methods to Estimate Above-Ground Biomass and Carbon Stock in Natural Forests - A Review

Carbon exists as carbon dioxide in the atmosphere and constitutes about 0.04% of the atmosphere. In the recent past, it has gained a lot of attention as a greenhouse gas, as it has potential to influence the climate pattern of the world. Anthropogenic activities like industrialisation, deforestation, forest degradation and burning of fossil fuel, has caused an increase in the level of carbon in the atmosphere and disrupted the global carbon cycle. However, nature has its own mechanism of sequestering and storing the carbon in its “reservoirs” or “sinks’’. Forest plays an important role in the global carbon cycle as carbon sinks of the terrestrial ecosystem. The carbon sequestered or stored on the forest trees are mostly referred to as the biomass of the tree or forest. The Intergovernmental Panel on Climate Change identified five carbon pools of the terrestrial ecosystem involving biomass, namely the aboveground biomass, below-ground biomass, litter, woody debris and soil organic matter. Among all the carbon pools, the above-ground biomass constitutes the major portion of the carbon pool. Estimating the amount of forest biomass is very crucial for monitoring and estimating the amount of carbon that is lost or emitted during deforestation, and it will also give us an idea of the forest’s potential to sequester and store carbon in the forest ecosystem. Estimations of forest carbon stocks are based upon the estimation of forest biomass. Forest’s carbon stocks are generally not measured directly; however, many authors assume the carbon concentration of tree parts to be 50% or 45% of the dry biomass. This paper, aims to review and summarise the various methods and studies that were carried out to estimate the above-ground biomass of the forest.

High-marsh invertebrates are susceptible to eutrophication

In salt marshes, high-marsh habitats are infrequently flooded (typically only during spring tides). Organisms in these habitats, however, may still be susceptible to the effects of increased nutrients delivered by tidal water (i.e. eutrophication). In a Massachusetts salt marsh, I examined the responses of the epibenthic invertebrates in the Spartina patens-dominated high marsh to long-term (7 yr) and landscape-level (4−5 ha) nutrient enrichment. In this ecosystemlevel experiment, nutrients (N and P; ~15× reference conditions) were added to the flooding waters of tidal creeks — which flooded the high marsh during spring tides — to mimic cultural eutrophication. Three detritivores: Melampus bidentatus (gastropod), Philoscia vittata (isopod), and Orchestia grillus (amphipod) numerically dominated the benthic invertebrate community (97% by abundance). These species had higher densities (47 to 199% increase) in enriched versus reference creeks. Melampus size structure shifted to larger individuals with enrichment. End-of-season aboveground biomass and detritus stocks of S. patens did not differ between treatments; thus, increased litter quality and/or alternative food-source increases (e.g. microbes) led to increased detritivore density/biomass. Predator densities (spiders and Tabanus larvae) increased 125 to 160% with enrichment, likely due to increased prey densities (including Orchestia and Philoscia). Analysis of similarities (ANOSIM) revealed that communities were dissimilar between treatments; differences were driven primarily by changes in detritivore abundance. These results suggest that despite being infrequently flooded and thus infrequently exposed to elevated nutrients, high-marsh invertebrates are susceptible to eutrophication. Hence, the high marsh should be integrated into our understanding of how eutrophication impacts saltmarsh functioning.

Deforestation and forest degradation monitoring and assessment of biomass and carbon stock of lowland rainforest in the Analanjirofo region, Madagascar

Madagascar is currently developing a policy and strategies to enhance the sustainable management of its natural resources, encouraged by United Nations Framework Convention on Climate Change (UNFCCC) and REDD. To set up a sustainable financing scheme methodologies have to be provided that estimate, prevent and mitigate leakage, develop national and regional baselines, and estimate carbon benefits. With this research study this challenge was tried to be addressed by analysing a lowland rainforest in the Analanjirofo region in the district of Soanierana Ivongo, North East of Madagascar. For two distinguished forest degradation stages: “low degraded forest” and “degraded forest” aboveground biomass and carbon stock was assessed. The corresponding rates of carbon within those two classes were calculated and linked to a multi-temporal set of SPOT satellite data acquired in 1991, 2004 and 2009. Deforestation and particularly degradation and the related carbon stock developments were analysed. With the assessed data for the 3 years 1991, 2004 and 2009 it was possible to model a baseline and to develop a forest prediction for 2020 for Analanjirofo region in the district of Soanierana Ivongo. These results, developed applying robust methods, may provide important spatial information regarding the priorities in planning and implementation of future REDD+ activities in the area.

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.

Necromasa de los bosques de Madre de Dios, Perú; una comparación entre bosques de tierra firme y de bajíos

Stocks of dead wood or necromass represent an important portion of biomass and nutrients in tropical forests. The objectives of this study were: 1) to evaluate and compare the necromass of “terra firme” and lowlands forests, (2) to study the relationship between necromass, above-ground biomass and wood density, and (3) to estimate the necromass of the department of Madre de Dios, Peru. Stocks of necromass and above-ground biomass were estimated at three different locations using permanent plots and line intercept transects. The average volume of necromass for the three sites was 72.9 m3 ha-1 with an average weight varying between 24.8 and 30.7 Mg ha-1, depending on the estimations of dead wood density used for the calculations. Terra firme forests had significantly higher stocks of necromass than lowland forests. The amount of necromass was 11% of the total above-ground biomass in Madre de Dios forests. The total stock of carbon stored in dead wood for the entire department of Madre de Dios was estimated to be approximately 100 mega tonnes of carbon. This is ten times more than the annual fossil fuel emissions of Peru between 2000 and 2008. The substantial stocks of necromass emphasize the importance of these types of field studies, considering that this component of tropical forest carbon cannot be detected using other methods such as satellite remote sensing.

Contrasting nutrient stocks and litter decomposition in stands of native and invasive species in a sub-tropical estuarine marsh

We compared the influence of invasion by an alien invasive species ( Spartina alterniflora, smooth cordgrass) and a native aggressive species ( Phragmites australis, common reed) as they have expanded into the native Cyperus malaccensis (shichito matgrass)-dominated wetland ecosystem in the Min River estuary of southeast China. S. alterniflora is a perennial grass native to North America, which has spread rapidly along the southeast coast of China since its introduction in 1979. Our study compared the above and belowground biomass, net primary production, litter decomposition, plant nutrient stocks and soil organic carbon storage of the grasses in three ecosystems: (1) the native ecosystem dominated by C. malaccensis; (2) ecosystems previously dominated by C. malaccensis but presently replaced by P. australis; and (3) ecosystems previously dominated by C. malaccensis but presently replaced by S. alterniflora. Our results demonstrate that the recent invasion (3 years) of the exotic invasive species S. alterniflora has already significantly increased live aboveground biomass and aboveground plant nutrient stocks. However, there was no significant difference in these variables between native aggressive species P. australis and native C. malaccensis. The majority of belowground root Carbon (C), Nitrogen (N) and phosphorus (P) stocks of the three plant species were all distributed in the upper surface layer and there was a decrease with soil depth. There was little difference in litter decomposition rates among the three grass species; they were ranked in the following order: C. malaccensis>S. alterniflora> P. australis. Litter element concentration showed similar patterns for the three species. However, important differences were found between N and P; the litter N concentrations in each of the three species were greater at the end of the 280 days decomposition than at the start, but P concentrations followed a fluctuating pattern during the decomposition period. Soil organic carbon stocks (0–50 cm) under S. alterniflora, P. australis and C. malaccensis stands were statistically indistinguishable, which may be due to the invasion of S. alterniflora having been a relatively recent phenomenon. Thus, recent invasion of the exotic species S. alterniflora has already altered the nutrient cycle of C. malaccensis in the ecosystem in the Min River estuary.

Allometric equations for young northern hardwoods: the importance of age-specific equations for estimating aboveground biomass

Estimates of aboveground biomass and nutrient stocks are commonly derived using equations that describe tree dimensional relationships. Despite the widespread use of this approach, there is little information about whether equations specific to stand age are necessary for accurate biomass predictions. We developed equations for small trees (2–12 cm diameter) of six species in four young northern hardwood stands. We then compared our equations with equations used frequently in the literature that were developed in mature stands (Whittaker et al. 1974. Ecol. Monogr. 44: 233–252). Our equations for yellow birch ( Betula alleghaniensis Britt.) predicted 11%–120% greater stem wood for individual trees compared with the equations from Whittaker et al. and, on average, 50% greater aboveground yellow birch biomass in the four stands that we studied. Differences were less pronounced for sugar maple ( Acer saccharum Marsh.) and American beech ( Fagus grandifolia Ehrh.); our equations predicted, on average, 9% greater aboveground stand biomass for sugar maple and 3% lower biomass for American beech compared with Whittaker et al. Our results suggest that stand age may be an important factor influencing the aboveground allometry and biomass of small yellow birch trees in these developing northern hardwood stands.

Impact of logging on aboveground biomass stocks in lowland rain forest, Papua New Guinea

Greenhouse-gas emissions resulting from logging are poorly quantified across the tropics. There is a need for robust measurement of rain forest biomass and the impacts of logging from which carbon losses can be reliably estimated at regional and global scales. We used a modified Bitterlich plotless technique to measure aboveground live biomass at six unlogged and six logged rain forest areas (coupes) across two approximately 3000-ha regions at the Makapa concession in lowland Papua New Guinea. "Reduced-impact logging" is practiced at Makapa. We found the mean unlogged aboveground biomass in the two regions to be 192.96 +/- 4.44 Mg/ha and 252.92 +/- 7.00 Mg/ha (mean +/- SE), which was reduced by logging to 146.92 +/- 4.58 Mg/ha and 158.84 +/- 4.16, respectively. Killed biomass was not a fixed proportion, but varied with unlogged biomass, with 24% killed in the lower-biomass region, and 37% in the higher-biomass region. Across the two regions logging resulted in a mean aboveground carbon loss of 35 +/- 2.8 Mg/ha. The plotless technique proved efficient at estimating mean aboveground biomass and logging damage. We conclude that substantial bias is likely to occur within biomass estimates derived from single unreplicated plots.

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.