Positive Carbon Balance Research Articles

Soil organic carbon in an integrated crop-livestock system under different grazing intensities

An integrated crop-livestock system (ICLS) under no-till may be an effective tool to promote soil organic carbon (SOC) accumulation. However, it is not yet clear how pasture management affects SOC accumulation. In this study, we assessed the effect of grazing intensity (10, 20, 30, and 40 cm of sward height and no grazing) on SOC and coefficients of soil organic matter dynamics and used them in a simulation of SOC sequestration in a 0-20 cm soil layer. The overall study was conducted on a subtropical rhodic hapludox from southern Brazil managed as a no-till integrated soybean-beef cattle system for 13 yr. SOC sequestration rates ranged from 0.097 Mg ha?1 yr?1 with a pasture sward height of 10 cm to 0.308 Mg ha?1 yr?1 with one of 40 cm. Simulations revealed a higher potential of the soil for C sequestration with a moderate (30 cm) or low (40 cm) grazing intensity. Although the ICLS under no-till led to a positive carbon balance irrespective of grazing intensity, the simulation of temporal evolution of SOC stocks over time revealed a higher potential for SOC accumulation with the less intensive grazing treatments than with the more intensive ones.

Conservation tillage increases carbon sequestration of winter wheat-summer maize farmland on Loess Plateau in China.

The idea of mitigating anthropogenic CO2 emissions by increasing soil organic carbon (SOC) is notable. However, the estimation of the net ecosystem carbon balance after conversion from conventional tillage to conservational tillage has been poorly quantified for the Loess Plateau in China. A 2-year field experiment was conducted to estimate the agroecosystem carbon balance of a winter wheat–summer maize rotation system using a full carbon cycle analysis. The results showed that a positive net ecosystem carbon balance value in the cases of rotary tillage with straw incorporation, chisel plow tillage with straw incorporation, and no tillage with straw mulching treatments. Note that a negative value was detected for the conventional moldboard plowing tillage without crop straw treatment. The conversion from conventional tillage to conservational tillage substantially enhanced the carbon sink potential from 0.84 t C ha−1 yr−1 to 2.69 t C ha−1 yr−1 in both years. Our findings suggest that the expansion of conservational tillage could enhance the potential carbon sink of the rain-fed land in China.

Tree carbon allocation explains forest drought-kill and recovery patterns.

The mechanisms governing tree drought mortality and recovery remain a subject of inquiry and active debate given their role in the terrestrial carbon cycle and their concomitant impact on climate change. Counter-intuitively, many trees do not die during the drought itself. Indeed, observations globally have documented that trees often grow for several years after drought before mortality. A combination of meta-analysis and tree physiological models demonstrate that optimal carbon allocation after drought explains observed patterns of delayed tree mortality and provides a predictive recovery framework. Specifically, post-drought, trees attempt to repair water transport tissue and achieve positive carbon balance through regrowing drought-damaged xylem. Furthermore, the number of years of xylem regrowth required to recover function increases with tree size, explaining why drought mortality increases with size. These results indicate that tree resilience to drought-kill may increase in the future, provided that CO2 fertilisation facilitates more rapid xylem regrowth.

Biocrust contribution to ecosystem carbon fluxes varies along an elevational gradient

AbstractUnderstanding how each component of an ecosystem contributes to carbon fluxes across a range of abiotic conditions enables accurate forecasts for future emission scenarios. In drylands, biological soil crust (biocrust) contribution to ecosystem carbon fluxes may vary at a regional scale but is rarely quantified due to the difficulty of parameterizing process‐based models or parsing biocrust (on the soil surface) from whole‐soil flux measurements. We measured excised biocrust carbon fluxes across current and future predicted warmer summertime temperatures from dryland sites (grassland, shrubland, savanna, and woodland) and compared those to the ecosystem and soil fluxes from eddy flux towers. Overall, biocrust fluxes showed net carbon loss during the warm growing season temperatures, suggesting that cool‐season photosynthesis is likely critical for maintaining positive biocrust carbon balance in these sites. Biocrust flux temperature responses differed by site: Grassland and shrubland biocrust gross photosynthesis was relatively invariant, while respiration increased with temperature; in the woodland and savanna, biocrust gross photosynthesis and respiration increased with temperature. Biocrust fluxes contributed <3% to the observed ecosystem gross primary productivity at 26°C and ecosystem respiration at 19°C in grassland, shrubland, and woodland, but contributed >10% of observed soil respiration in grassland and shrubland at 19°C, reinforcing the need to separate biocrust activity from root and subsurface heterotroph activity to understand drivers of fluxes at different sites. Regional resolution of biocrust type and cover will improve predictions of biocrust contribution to global carbon flux with changing temperatures.

INFLUENCE OF INTERSPECIFIC VARIATION ON TREE CARBON STOCK OF A BRAZILIAN CERRADO

ABSTRACT Cerrado is a biodiversity hotspot and possibly the most threatened tropical savanna in the world. Although Cerrado has an important role in the global carbon balance, studies about carbon stock in the biome are rare, especially with estimates per species. Thus, we estimated the carbon content and stock by species in a Cerrado area. We destructively sampled 120 trees from 18 species to determine tree aboveground biomass at a cerrado sensu stricto remnant. The carbon content in dry biomass was determined in laboratory and for the species not sampled an average value was used. The biomass of the remaining inventoried trees was estimated using an allometric equation. The carbon content in dry biomass had mean of 50.5 ± 0.20% and the carbon stock for the Cerrado remnant accounted for 22,385.46 kg ha-1. Results indicated that some species had higher carbon stock than others. The number of individuals, their size and wood density are key points that need to be considered in the evaluation of carbon stock in forests with large number of species. Maintaining species that contribute to higher carbon stock is essential to keep a positive carbon balance in Cerrado areas

Canopy nitrogen distribution is optimized to prevent photoinhibition throughout the canopy during sun flecks

As photoinhibition primarily reduces the photosynthetic light use efficiency at low light, sunfleck-induced photoinhibition might result in a fatal loss of carbon gain in the shade leaves within a canopy with barely positive carbon balance. We hypothesized that shade leaves at the lower canopy might retain a certain amount of leaf nitrogen (NL) to maintain energy consumption via electron transport, which contributes to circumventing photoinhibition during sunflecks to keep efficient utilization of low light during the rest period of daytime. We investigated excess energy production, a potential measure of susceptibility to photoinhibition, as a function of NL distribution within a Japanese oak canopy. Optimal NL distribution, which maximizes canopy carbon gain, may lead to a higher risk of photoinhibition in shade leaves during sunflecks. Conversely, uniform NL distribution would cause a higher risk of photoinhibition in sun leaves under the direct sunlight. Actual NL distribution equalized the risk of photoinhibition throughout the canopy indicated by the constant excess energy production at the highest light intensities that the leaves received. Such a homeostatic adjustment as a whole canopy concerning photoinhibition would be a key factor to explain why actual NL distribution does not maximize canopy carbon gain.

BIOMASSA, CRESCIMENTO E RESPOSTAS ECOFISIOLÓGICAS DE PLANTAS JOVENS DE <i>Bertholletia excelsa</i> BONPL. SUBMETIDAS A DIFERENTES NÍVEIS DE IRRADIÂNCIA

A castanheira-da-amazônia (Bertholletia excelsa Bonpl.) é uma espécie exigente de luz, pois em floresta nativa, a espécie depende da formação de clareiras para alcançar o tamanho reprodutivo e em plantios florestais demonstra rápido crescimento inicial quando exposta a altos níveis de irradiância. No entanto, os aspectos ecofisiológicos dessa espécie sob condições contrastantes de irradiância não foram investigados. Nesse estudo, além das características de crescimento, objetivou-se analisar pela primeira vez o grau de plasticidade das respostas ecofisiológicas de Bertholletia excelsa quando submetida a ambientes de irradiância contrastantes. Plantas jovens de Bertholletia excelsa foram cultivadas em três condições de irradiância: baixa (20-300 µmol m-2 s-1), moderada (800-1000 µmol m-2 s-1) e alta (1900-2100 µmol m-2 s-1). Foram analisadas características de crescimento, trocas gasosas, teores de pigmentos cloroplastídicos e, no fim do experimento, o acúmulo e partição de biomassa. Plantas jovens de Bertholletia excelsa demonstraram maior acúmulo de biomassa, crescimento e fotossíntesequando expostas aos ambientes de moderada e alta irradiância. A condição de baixa irradiância estimulou maior partição de biomassa para a parte aérea em contraposição ao sistema radicular e maior concentração foliar de pigmentos cloroplastídicos. Bertholletia excelsa possui plasticidade fisiológica sob condições contrastantes de irradiância, sendo o maior crescimento e acúmulo de biomassa, em ambientes de moderada e alta irradiância, promovidos pelo melhor desempenho fotossintético, ao passo que o balanço positivo de carbono sob baixa irradiância é assegurado pelo investimento em estruturas de interceptação e captação de energia.

Quantifying the trade‐off between carbon sequestration and albedo in midlatitude and high‐latitude North American forests

AbstractAfforestation is a viable and widely practiced method of sequestering carbon dioxide from the atmosphere. However, because of a change in surface albedo, placement of less reflective forests can cause an increase in net‐absorbed radiation and localized surface warming. This effect is enhanced in northern high latitudes where the presence of snow cover exacerbates the albedo difference. Regions where afforestation could provide a climate benefit are determined by comparing net ecosystem production and net radiation differences from afforestation in midlatitude and high latitude of North America. Using the dynamic vegetation model Integrated Biosphere Simulator, agricultural version (Agro‐IBIS), we find a boundary through North America where afforestation results in a positive equivalent carbon balance (cooling) to the south, and a negative equivalent carbon balance (warming) to the north. Including the effects of stand age and fraction cover affect whether a site contributes to mitigating global warming.

Ecophysiology of bryophytes in the changing environment

Studies of the impact of climate change on plants are generally based on vascular plants. Bryophytes basically differ from tracheophytes in having a smaller size and a poikilohydric strategy for water and nutrients. Their survival and growth are highly dependent on their external environment. Bryophytes are able to lose most of their cell water without dying, and resume normal metabolism after rehydration, gaining positive carbon balance over wet-dry cycles. This sort of adaptation is called desiccation tolerance. Desiccation tolerance is a common phenomenon among bryophytes: cells of bryophytes in exposed sunny sites can switch from full turgor to air dryness quickly, while the species of moist habitats dry more slowly, and can suffer stress by even moderate drying. Bryophytes can maintain efficient photosynthesis under low light conditions, have low chl a/b ratios, and their optimum growth is possible within a limited temperature range. When certain bryophytes’ CO2 assimilation is suppressed, photorespiration activity increases and becomes the main electron sink. Bryophytes, as sensitive components of various vegetation types, are capable of effective light absorption during their desiccation, rehydration, freezing and melting, with the help of coexisting alga and vascular plant energy dissipation mechanisms. They have a relatively low optimal temperature for growth (with narrow T range for net photosynthetic gain), with only minor differences between the optimum temperatures for net photosynthesis in polar, temperate and tropical populations of the same species. Bryophytes have a low acclimatization potential for high temperatures, taking into account that they are generally drought avoiders. Temperature acclimatization potential is of high importance for the physiological basis of altitudinal distribution and the likely responses of bryophytes to climate change. Bryophytes with their small and resistant spores are able to disperse over long distances by wind, which might help their survival in a changing environment. Dominant vascular vegetation might change as temperature will increase; however, suitable microhabitats for bryophytes might still persist. The abundance and species composition of bryophytes in plant communities is predicted to be altered, just as the function of the whole ecosystem. Based on recent literature and own data, the author makes an attempt to summarize the physiological mechanisms, morphological features and alternative strategies that make bryophytes successful in a constantly changing terrestrial environment. These plants represent a sophisticated solution to the challenges of life at their scale. Further exploration of bryophyte ecophysiology in the changing and stressful environment will provide new information that will assist bryophyte conservation.

How <i>Betula ermanii</i> Maintains a Positive Carbon Balance at the Individual Leaf Level at High Elevations

Generally, plant species with shorter leaf longevity maintain a positive carbon balance by decreasing leaf mass per area (LMA) and increasing photosynthesis. However, plants at high elevations need to increase LMA against environmental stresses. Therefore, plants need to increase both LMA and photosynthesis at high elevations. To examine how deciduous plants maintain a positive carbon balance at high elevations, photosynthesis and related leaf traits for deciduous broad-leaved tree Betula ermanii were measured at three elevations. LMA was greater at middle and high elevations than at low elevation. Leaf δ13C was greater at higher elevations, and positively correlated with LMA, indicating greater long-term deficiency of CO2 in leaves at higher elevations. However, the Ci/Ca ratio at photosynthetic measurement was not low at high elevations. Nitrogen content per leaf mass and stomatal conductance were greater at higher elevations. Photosynthetic rates and photosynthetic nitrogen use efficiency (PNUE) did not differ among the three elevations. Photosynthetic rate showed a strong positive correlation with stomatal conductance on a leaf area basis (R2 = 0.83, P B. ermanii compensates the deficiency of CO2 in leaves at high elevation by increasing stomatal conductance, and maintains photosynthesis and PNUE at high elevation as much as at low elevation.

Ecophysiology of Adonis distorta, a high-mountain species endemic of the Central Apennines

Morphological, anatomical and physiological plant and leaf traits of A. distorta , an endemic species of the Central Apennines on the Majella Massif, growing at 2,675 m a.s.l, were analyzed. The length of the phenological cycle starts immediately after the snowmelt at the end of May, lasting 128 ± 10 days. The low A. distorta height (H max = 64 ± 4 mm) and total leaf area (TLA= 38 ± 9 cm 2 ) associated to a high leaf mass area (LMA =11.8±0.6 mg cm −2 ) and a relatively high leaf tissue density (LTD = 124.6±14.3 mg cm −3 ) seem to be adaptive traits to the stress factors of the environment where it grows. From a physiological point of view, the high A. distorta photosynthetic rates ( P N =19.6 ± 2.3 µmol m −2 s −1 ) and total chlorophyll content (Chl a + b = 0.88 ± 0.13 mg g −1 ) in July are justified by the favorable temperature. P N decreases by 87% in September at the beginning of plant senescence. Photosynthesis and leaf respiration ( R D ) variations allow A. distorta to maintain a positive carbon balance during the growing season becoming indicative of the efficiency of plant carbon use. The results could be an important tool for conservation programmes of the A. distorta wild populations.

Morphological variations of the Solidago virgaurea L. complex along an elevational gradient on Mt Norikura, central Japan

Morphological variations in vegetative and reproductive organs in the Solidago virgaurea complex were examined for eight elevations between 1600 and 2400 m a.s.l. in Japan. The rosette diameter and stem height were lower at higher elevations. The stem diameter at any stem height was greater at higher elevations, suggesting that the S. virgaurea complex increases mechanical stiffness against strong wind at high elevations. The number of flower heads at any stem height was less at high elevations (2000–2400 m a.s.l.) than at low elevations (1600–1900 m a.s.l.). Leaf nitrogen concentration did not change along the elevational gradient. Leaf mass per area (LMA) tended to decrease with increasing elevation, except for 2400 m a.s.l. The decrease of LMA would contribute to maintaining a positive carbon balance at high elevations. The number of involucral rays of flower heads was mostly four at low elevations (1600–1900 m a.s.l.) and three at high elevations (2000–2400 m a.s.l.). The number of involucral scales and diameter of flower heads were greater at high elevations (2000–2400 m a.s.l.) than at low elevations (1600–1900 m a.s.l.). Therefore, the S . virgaurea complex is suggested to adapt to high elevations that have cool temperature, a short growing season and strong wind conditions by changing its vegetative and reproductive traits.

Ecological implications of different water use strategies in three coexisting mediterranean tree species

The ability of trees to grow and survive during periods of water scarcity is determined by the water use strategy of each individual. In this study we evaluated how water use strategies can influence the establishment phase of three coexisting species in forests where harvesting intensity and silvicultural interventions have been reduced over recent decades. We conducted a greenhouse experiment between February and July, applying two watering regimes (moist and dry) to current year seedlings in 1.5m high pots to avoid root growth constraint. At the same time, the physiological performance of seedlings of the same species was monitored under natural conditions in the field over a period of decreasing soil moisture. Our results indicated that resprouter species allocated more than 40% of total biomass to roots whereas the non-resprouter P. pinea allocated only 26%. The plasticity index for the root traits was highest in Q. ilex, in which the highest stomatal conductance was measured in early summer. The slowest growth and lowest root plasticity, root hydraulic conductance and leaf water potential were measured in J. oxycedrus. The three species exhibited a positive carbon balance under low water availability. Coexisting species displayed a continuum in the water use strategies adopted. P. pinea would be the least competitive species under the forecasted increasing drought conditions in contrast to J. oxycedrus, which presents traits more suited to coping with droughts.

Sustainability assessment of Ricinus communis biodiesel using LCA Approach

Biofuels are considered as eco-friendly fuels and can readily replace fossil fuels while helping to reduce greenhouse gas emissions and promoting sustainable rural development. Although Algeria is an oil producer and exporter, the development of renewable energies is a strategic goal for public authorities, which are giving new impetus to this sector to replace the fossil energy resources of which are becoming increasingly scarce. In this context, the life-cycle assessment (LCA) of a second-generation biodiesel derived from Ricinus communis feedstock is undertaken. LCA is a tool that can be used effectively in evaluating various renewable energy sources for their sustainability and can help policy makers to choose the optimal energy source for specific purpose. The life cycle of Castor bean-based biodiesel production includes the stages of cultivation, oil extraction, and biodiesel production. The impact categories studied were global warming, Energy return-on-energy investment (EROEI), human health, and ecosystem. We have used the impact 2002 + evaluation method which is implemented in the SimaPro© software package. Moreover, it is the most useful method for identifying and measuring the impact of industrial products on the environment. Results show that among all the production stages, the cultivation process of Ricinus communis and the conversion of oil to biodiesel are the largest contributors to most of environmental impact categories. Life-cycle analysis revealed that the use of castor for biodiesel production could have many advantages like an energy return-on-energy investment (EROEI) of 2.60 and a positive contribution to climate-change reduction as revealed by a positive carbon balance.

Combining no-tillage, rice straw mulch and nitrogen fertilizer application to increase the soil carbon balance of upland rice field in northern Benin

Agricultural management practices are frequently non conservative and can lead to substantial loss of soil organic carbon and soil fertility, but for many regions in Africa the knowledge is very limited. To study the effect of local agricultural practices on soil organic carbon content and to explore effective ways to increase soil carbon storage, field experiments were conducted on an upland rice soil (Lixisol) in northern Benin in West Africa. The treatments comprised two tillage systems (no-tillage, and manual tillage), two rice straw managements (no rice straw, and rice straw mulch at 3 Mgha⿿1) and three nitrogen fertilizer levels (no nitrogen, 60kgha⿿1, 120kgha⿿1). Phosphorus and potassium fertilizers were applied to be non-limiting at 40kg P2O5ha⿿1 and 40kgK2Oha⿿1 per cropping season. Heterotrophic respiration was higher in manual tillage than no-tillage, and higher in mulched than in non-mulched treatments. Under the current management practices (manual tillage, with no residue and no nitrogen fertilization) in upland rice fields in northern Benin, the carbon added as aboveground biomass and root biomass was not enough to compensate for the loss of carbon from organic matter decomposition, rendering the upland rice fields as net sources of atmospheric CO2. With no-tillage, 3Mgha⿿1 of rice straw mulch and 60kgNha⿿1, the soil carbon balance was approximately zero. With no other changes in management practices, an increase in nitrogen level from 60kgNha⿿1 to 120kgNha⿿1 resulted in a positive soil carbon balance. Considering the high cost of inorganic nitrogen fertilizer and the potential risk of soil and air pollution often associated with intensive fertilizer use, implementation of no-tillage combined with application of 3 Mg ha⿿1 of rice straw mulch and 60kgNha⿿1 could be recommended to the smallholder farmers to compensate for the loss of carbon from organic matter decomposition in upland rice fields in northern Benin.

Changes in leaf area, nitrogen content and canopy photosynthesis in soybean exposed to an ozone concentration gradient

Influences of ozone (O3) on light-saturated rates of photosynthesis in crop leaves have been well documented. To increase our understanding of O3 effects on individual- or stand level productivity, a mechanistic understanding of factors determining canopy photosynthesis is necessary. We used a canopy model to scale photosynthesis from leaf to canopy, and analyzed the importance of canopy structural and leaf ecophysiological characteristics in determining canopy photosynthesis in soybean stands exposed to 9 concentrations of [O3] (37–116 ppb; 9-h mean). Light intensity and N content peaked in upper canopy layers, and sharply decreased through the lower canopy. Plant leaf area decreased with increasing [O3] allowing for greater light intensity to reach lower canopy levels. At the leaf level, light-saturated photosynthesis decreased and dark respiration increased with increasing [O3]. These data were used to calculate daily net canopy photosynthesis (Pc). Pc decreased with increasing [O3] with an average decrease of 10% for an increase in [O3] of 10 ppb, and which was similar to changes in above-ground dry mass production of the stands. Absolute daily net photosynthesis of lower layers was very low and thus the decrease in photosynthesis in the lower canopy caused by elevated [O3] had only minor significance for total canopy photosynthesis. Sensitivity analyses revealed that the decrease in Pc was associated with changes in leaf ecophysiology but not with decrease in leaf area. The soybean stands were very crowded, the leaves were highly mutually shaded, and sufficient light for positive carbon balance did not penetrate to lower canopy leaves, even under elevated [O3].

Gas exchange, carbon balance and stomatal traits in wild and cultivated rice (Oryza sativa L.) genotypes

Carbon balancing within the plant species is an important feature for climatic adaptability. Photosynthesis and respiration traits are directly linked with carbon balance. These features were studied in 20 wild rice accessions Oryza spp., and cultivars. Wide variation was observed within the wild rice accessions for photosynthetic oxygen evolution or photosynthetic rate (A), dark (Rd), and light induced respiration (LIR) rates, as well as stomatal density and number. The mean rate of A varied from 10.49 μmol O2 m−2 s−1 in cultivated species and 13.09 μmol O2 m−2 s−1 in wild spp., The mean Rd is 2.09 μmol O2 m−2 s−1 and 2.31 μmol O2 m−2 s−1 in cultivated and wild spp., respectively. Light induced Respiration (LIR) was found to be almost twice in wild rice spp., (16.75 μmol O2 m−2 s−1) compared to cultivated Oryza spp., Among the various parameters, this study reveals LIR and A as the key factors for positive carbon balance. Stomatal contribution towards carbon balance appears to be more dependent on abaxial surface where several number of stomata are situated. Correlation analysis indicates that Rd and LIR increase with the increase in A. In this study, O. nivara (CR 100100, CR 100097), O. rufipogon (IR 103404) and O. glumaepatula (IR104387) were identified as potential donors which could be used in rice breeding program. Co-ordination between gas exchange and patchiness in stomatal behaviour appears to be important for carbon balance and environmental adaptation of wild rice accessions, therefore, survival under harsh environment.

Spatiotemporal distribution of essential elements through Populus leaf ontogeny.

We examined the spatiotemporal distribution and accumulation of calcium (Ca), potassium (K), and zinc (Zn) during the growth and maturation of grey poplar (Populus tremula × alba) leaves covering plastochrons 01 through 10. This period spans the sugar sink-to-source transition and requires coordinated changes of multiple core metabolic processes that likely involve alterations in essential and non-essential element distributions as tissues mature and effect a reversal in phloem flow direction. Whole-leaf elemental maps were obtained from dried specimens using micro X-ray fluorescence spectroscopy. Additional cross-sections of fresh leaves were scanned to check for tissue specificity in element accumulation. The anatomical distribution of Zn and K remains relatively consistent throughout leaf development; Ca accumulation varied across leaf developmental stages. The basipetal allocation of Ca to the leaf mesophyll matched spatially and temporally the sequence of phloem maturation, positive carbon balance, and sugar export from leaves. The accumulation of Ca likely reflects the maturation of xylem in minor veins and the enhancement of the transpiration stream. Our results independently confirm that xylem and phloem maturation are spatially and temporally coordinated with the onset of sugar export in leaves.

Life Cycle Analysis of Carbon Flow and Carbon Footprint of Harvested Wood Products of Larix principis-rupprechtii in China

Larix principis-rupprechtii is a native tree species in North China with a large distribution; and its harvested timbers can be used for producing wood products. This study focused on estimating and comparing carbon flows and carbon footprints of different harvested wood products (HWPs) from Larix principis-ruppechtii based on the life cycle analysis (from seedling cultivation to HWP final disposal). Based on our interviews and surveys, the system boundary in this study was divided into three processes: the forestry process, the manufacturing process, and the use and disposal process. By tracking carbon flows of HWPs along the entire life cycle, we found that, for one forest rotation period, a total of 26.81 tC/ha sequestered carbon was transferred into these HWPs, 66.2% of which were still stored in the HWP when the rotation period had ended; however, the HWP carbon storage decreased to 0.25 tC/ha (only 0.9% left) in the 100th year after forest plantation. The manufacturing process contributed more than 90% of the total HWP carbon footprint, but it was still smaller than the HWP carbon storage. In terms of the carbon storage and the carbon footprint, construction products had the largest net positive carbon balance compared to furniture and panel products. In addition, HWP are known to have a positive impact on global carbon mitigation because they can store parts of the sequestered carbon for a certain period of time and they have a substitution effect on carbon mitigation. Furthermore, there still exist great opportunities for carbon mitigation from HWPs through the use of cleaner energy and increasing the utilization efficiency of wood fuel.

CO2 soil emission under different methods of oil palm replanting

Colombian oil palm plantations have started a large-scale replanting phase. The replanting process has an effect on the disposal of biomass, plant health management, and agro-ecological conditions due to the disturbance that is generated. This document addresses soil respiration (CO2 flux) as a response variable of crop replanting. Seven renovation methods used in Colombia were tested. The measurements were taken over time after the disturbance and planting of the new crop. This study was carried out in the municipality of Tumaco between August of 2009 and June of 2011 using 7 methods of renovation and 4 stages of crop development. The CO2 flow was measured at 12 points in each plot. There were no significant differences for the CO2 emission among the replanting methods. The average value for respiration was 929 mg CO2 m-2 h-1 (± 270.3); however, significant differences were found over time. This response was not related to fluctuations of soil temperature and moisture; therefore, there should be an associated response to biotic factors (microbial organisms) not established in this study. The values suggested that the soil of the plots under a replanting process emitted considerable quantities of carbon into the atmosphere, but the emissions declined over time and, in turn, were offset by the photosynthesis of the new crop (14 μ CO2 m-2s-1 ± 1.4, data not shown), creating an overall positive carbon balance.