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.     

Carbon return and dynamics of litterfall in natural forest and monoculture plantation of Castanopsis kawakamii in subtropical China

The amount of carbon returned through litterfall and its seasonal pattern were studied in a natural forest of Castanopsis kawakamii (NF) and adjacent monoculture plantations of C. kawakamii (CK) and Chinese fir (Cunninghamia lanceolata) (CF) in Sanming, Fujian Province, China. Mean annual carbon return through total litterfall over 3 years (from 1999 to 2001) was 5.097 t·hm⁻² in the NF, 4.337 t·hm⁻² in the CK and 2.502 t·hm⁻² in the CF respectively. Of the total carbon return in the three forests, leaf contribution accounted for 58.96%, 68.53% and 56.12% and twig 24.41%, 22.34% and 26.18%, respectively. The seasonal patterns of carbon return from total litterfall and leaf-litter were quite similar among the three forests. A peak of carbon input from litterfall in the NF and the CK occurred in spring except for the highest annual C return through branch litter of the NF in summer, while the CF showed the maximum C return in summer. The results of this study demonstrate that the natural forest has a greater C return through litterfall than monoculture plantations, which is beneficial to the increase of soil organic matter storage and the maintenance of soil fertility. [Supported by the Teaching and Research Award Program of MOE P.R.C. (TRAPOYT) and the Key Basic Research Project of Fujian Province (2000F004)]     

长白山高山冻原生态系统碳储量和碳动态研究

本研究分析了长白山高山冻原植被-凋落物-土壤生态系统的碳储量和碳动态.冻原植被中年净储存有机碳约17251 t;凋落物中有机碳储量为15043.1 t,凋落物中有机碳储量空间分布格局：TA＞LA＞MA＞SA＞FA;冻原土壤（0～20 cm）中年均储存有机碳为1054 t·a^-1,土壤中有机碳储量为3.16×10^5 t;每年约有1.4×104 t·a^-1土壤有机碳通过土壤呼吸释放到大气圈.植被-凋落物-土壤系统共储存碳452624 t.长白山高山冻原年均固碳为3146 t·a^-1.     

Changes in carbon stock following soil scarification of non-wooded stands in Hokkaido,northern Japan

To restore non-wooded stands dominated by dwarf bamboo species (Sasa kurilensis or S. senanensis) into forests, mechanical soil scarification has been applied in northern Japan since the 1960s. The treatment is followed both by natural regeneration and artificial planting. In this study, we quantified the total carbon stock (plants plus 0.3 m depth of soil) of these stands over 35-year age-sequences. The natural regeneration stands were gradually dominated by Betula ermanii. The carbon stock increased linearly to 215.1 ± 35.2 Mg C ha⁻¹ for a 37-year-old stand formerly dominated by S. kurilensis, and 181.1 ± 29.8 Mg C ha⁻¹ for a 34-year-old stand formerly dominated by S. senanensis. The latter was similar to that of a Picea glehnii plantation, formerly dominated by S. senanensis, with comparable stand age (160.3 ± 6.7 Mg C ha⁻¹ for 35-year-old stands). Although the carbon stock in plants quickly offset the untreated level, that in the soil remained depressed even in the older stands. This resulted in small differences in carbon stock of these stands with untreated dwarf bamboo stands. We conclude that natural regeneration following scarification could be a prime option for carbon sink management in the region. However, we should take a long rotation period (i.e., >50 years) to ensure a carbon sink state. A potential of further improvements of the practice, including that reduce intensity of soil disturbance, was presented.     

Temporal dynamics and spatial variations of forest vegetation carbon stock in Liaoning Province,China

There are many uncertainties in the estimation of forest car- bon sequestration in China, especially in Liaoning Province where vari- ous forest inventory data have not been fully utilized. By using forest inventory data, we estimated forest vegetation carbon stock of Liaoning Province between 1993 and 2005. Results showed that forest biomass carbon stock increased from 68.91 Tg C in 1993 to 97.51 Tg C in 2005, whereas mean carbon density increased from 18.48 Mg·ha -1 C to 22.33 Mg·ha -1 C. The carbon stora...     

Biomass of a man-made forest of timber tree species in the humid tropics of West Java, Indonesia

Biomass of a mature man-made forest in West Java, Indonesia, was estimated to evaluate the carbon sequestration potential of plantation forest in the humid tropics. Twenty plots, each 0.25 ha in area and containing one to six planted species over 40 years of age and with closed canopies, were selected. Trunk dry mass was estimated from trunk diameter, tree height, and bulk density. Maximum trunk diameter (122 cm) was observed in a 46-year-old Khaya grandifoliola C. DC. tree, and the tallest tree (51 m) was a 46-year-old Shorea selanica (DC.) Blume. The largest trunk biomass (911 Mg ha⁻¹) was achieved in the plot composed of two Khaya spp. Among the plots composed of indigeneous Dipterocarpaceae species, the largest trunk biomass was 635 Mg ha⁻¹. These trunk biomasses were larger than those reported from primary rainforests in Southeast Asia (e.g., 403 Mg ha⁻¹ in East Kalimantan, 522 and 368 Mg ha⁻¹ in Peninsular Malaysia). The large biomass in this forest suggests that, given favorable conditions, man-made forests can accumulate the quantities of atmospheric carbon that were lost by the logging of primary forests in the humid tropics.     

Temporal changes in soil carbon and nitrogen in west African multistrata agroforestry systems: a chronosequence of pools and fluxes

The conversion of forests to agroecosystems or agroforests comes with many changes in biological and chemical processes. Agroforestry, a tree based agroecosystem, has shown promise with respect to enhanced system nutrient accumulation after land conversion as compared to sole cropping systems. Previous research on tropical agroforestry systems has revealed increases in soil organic matter and total organic nitrogen in the short term. However, research is lacking on long-term system level sustainability of nutrient cycles and storage, specifically in traditional multi-strata agroforestry systems, as data on both the scope and duration of nutrient instability are inconclusive and often conflicting. This study, conducted in Ghana, West Africa, focused on carbon and nitrogen dynamics in a twenty-five year chronosequence of cacao (Theobroma cacao Linn.) plantations. Three treatments were selected as on-farm research sites: 2, 15 and 25-year-old plantations. Soil carbon (C, to a depth of 15 cm) varied between treatments (2 years: 22.6 Mg C ha⁻¹; 15 years: 17.6 Mg C ha⁻¹; 25 years: 18.2 Mg C ha⁻¹) with a significant difference between the 2- and 15- and the 2- and 25-year-old treatments (p < 0.05). Total soil nitrogen in the top 15 cm varied between 1.09 and 1.25 Mg N ha⁻¹ but no significant differences were noted between treatments. Soil nitrification rates and litter fall increased significantly with treatment age. However, photosynthetically active radiation (PAR) and soil temperature showed a significant decrease with age. No difference was found between decay rates of litter at each treatment age. By 25 years, system carbon sequestration rates were 3 Mg C ha⁻¹ y⁻¹, although results suggest that even by 15 years, system-level attributes were progressing towards those of a natural system.     

Biomass production and C-sequestration of Gmelina arborea in plantation and agroforestry system in India

Tree based land use systems make a valuable contribution to sequester carbon and improve productivity and nutrient cycling within the systems. This study was conducted to determine biomass production, C-sequestration and nitrogen allocation in Gmelina arborea planted as sole and agrisilviculture system on abandoned agricultural land. At 5 years, total stand biomass in agrisilviculture system was 14.1 Mg ha⁻¹. Plantations had 35% higher biomass than agrisilviculture system. At 5 years, leaves, stem, branches and roots contributed 4.1, 65.2, 10.0 and 20.7%, respectively to total standing biomass (17.9 Mg ha⁻¹). Over the 5 years of study, trees had 3.5 Mg ha⁻¹ more C and 36 kg ha⁻¹ more N in plantation than agrisilviculture system. Biomass and C storage followed differential allocation. Relatively more C was allocated in above ground components in plantations compared to agrisilviculture system. C:N ratios for tree components were higher in stem wood (135–142) followed by roots (134–139), branches (123–128) and leaves (20–21). In agrisilviculture system crops recommended are: soybean and cowpea in rainy season; wheat and mustard in winter season. After 5 years, soil organic C increased by 51.2 and 15.1% and N by 38.4 and 9.3% in plantation and agrisilviculture system, respectively. Total C storage in abandoned agricultural land before planting was 26.3 Mg ha⁻¹, which increased to 33.7 and 45.8 Mg ha⁻¹ after 5 years in plantation and agrisilviculture system, respectively. Net C storage (soil + tree) was 7.4 Mg ha⁻¹ in agrisilviculture system compared to 19.5 Mg ha⁻¹ in G. arborea monoculture stands. The studies suggest that competitive interactions played a significant role in agrisilviculture system. Plantations were more efficient in accreting C than agrisilviculture system on abandoned agricultural land.     

Nitrogen retranslocation, allocation, and utilization in bare root Larix olgensis seedlings

We quantified biomass accumulation and nitrogen (N) retranslocation, allocation, and utilization of Changbai larch (Larix olgensis) seedlings subjected to four fertilization treatments (24, 59, 81, 117 kg·ha-1 N) with an unfertilized control during summer and autumn 2009. Ammonium phosphate (18-46-0) was the fertilizer used in all treatments. On both sampling dates, the needles had greater biomass and N content than new (2009) stems and old (2008) stems, and coarse, medium and fine roots (diameters of >5, 2-5 mm, and 0-2 mm, respectively). Higher N concentration was observed in old stems and coarse roots than that in new stems and medium roots. In mid-summer, fine roots had higher N concentration than coarse roots. The treatment with 24 kg·ha-1 N had the greatest biomass and N content in needles and old stems, and highest net N retranslocation (NRA) and amount of N derived from soil. On September 21, no N translocation was observed, while the treatment with 24 kg·ha-1 N had the highest N utilization efficiency and fertilizer efficiency. Vector analysis revealed that all four fertilization treatments induced N excess relative to the control. The treatments with 59, 81, 117 kg·ha-1 N induce N excess compared with treatments at 24 kg·ha-1 N. We conclude that the traditional local fertilizer application rates exceeded N requirements and N uptake ability for Changbai larch seedlings. The application rate of 24 kg·ha-1 N is recommended.     

孟加拉吉大港地区丘陵森林有机物积累

在孟加拉吉大港丘陵地区,调查了热带季风气候条件下的3种人工林(7年生大叶相思(Acacia auriculiformis)林、15年生大叶相思林和18年生混交林)和1种天然林的森林凋落物及其对土壤性质的作用.结果表明,总的有机质积累随人工林树龄增加而增加,但是年积累量随之降低.在同一植被类型内,不同坡位新鲜或部分分解的凋落物有机质累计量变化较大,坡底部有机质积累量最高,沿着山坡向上逐渐减少.在15年生大叶相思人工林内,土壤整合有机物积累量变化趋势与新鲜或部分分解有机质积累量变化趋势相反.在7年生和15年生的大叶相思林以及18年龄的阔叶混交人工林内,新鲜、部分分解和完全分解(含土壤整合有机质)有机质总生产速率分别是2554.31、705.79和1028.01kg.ha-1·a-1,新鲜凋落物有机质在3种林分中的生产速率分别是38.23,19.40和30.48 kg·ha-1·a-1.3种人工林和自然林内,平均新鲜凋落物的有机质积累占有机质产出总量的32.45%,部分分解凋落物占13.50%,而全分解整合土壤有机质占54.56%.森林土壤酸度随凋落物分解阶段的深入而增加.     

Effects of different treatments on seed germination and breaking seed dormancy of <Emphasis Type="Italic">Prosopis koelziana</Emphasis> and <Emphasis Type="Italic">Prosopis Juliflora</Emphasis>

For improving seed germination of Prosopis koelziana and Prosopis juliflora, different treatments of seeds were conducted, including scarification with sulfuric acid 98% for 10 and 15 min, sandy paper, hot water for 5 and 10 min, potasium nitrate 0.1%, gibberellic acid at 250 mg·L⁻¹ and 500 mg·L⁻¹ and combinational treatment of scarification with gibberellic acid of 250 mg·L⁻¹ and 500 mg·L⁻¹. The results show that scarifications with sandy paper and sulfuric acids 98% were the most effective treatments on breaking seed dormancy and seed germination induction. Scarification with sulfuric acid 98% for 15 min was the best treatment. According to the positive effect of scarification and lack of reaction of seeds against KNO₃ and gibberellic acid, the kind of seed dormancy was determined as exogenous.     

Above- and belowground biomass,nutrient and carbon stocks contrasting an open-grown and a shaded coffee plantation

Coffee (Coffea canephora var robusta) is grown in Southwestern Togo under shade of native Albizia adianthifolia as a low input cropping system. However, there is no information on carbon and nutrient cycling in these shaded coffee systems. Hence, a study was conducted in a mature coffee plantation in Southwestern Togo to determine carbon and nutrient stocks in shaded versus open-grown coffee systems. Biomass of Albizia trees was predicted by allometry, whereas biomass of coffee bushes was estimated through destructive sampling. Above- and belowground biomass estimates were respectively, 140 Mg ha⁻¹ and 32 Mg ha⁻¹ in the coffee–Albizia association, and 29.7 Mg ha⁻¹ and 18.7 Mg ha⁻¹ in the open-grown system. Albizia trees contributed 87% of total aboveground biomass and 55% of total root biomass in the shaded coffee system. Individual coffee bushes consistently had higher biomass in the open-grown than in the shaded coffee system. Total C stock was 81 Mg ha⁻¹ in the shaded coffee system and only 22.9 Mg ha⁻¹ for coffee grown in the open. Apart from P and Mg, considerable amounts of major nutrients were stored in the shade tree biomass in non-easily recyclable fractions. Plant tissues in the shaded coffee system had higher N concentration, suggesting possible N fixation. Given the potential for competition between the shade trees and coffee for nutrients, particularly in low soil fertility conditions, it is suggested that the shade trees be periodically pruned in order to increase organic matter addition and nutrient return to the soil. An erratum to this article can be found at     

Carbon stock measurements of a degraded tropical logged-over secondary forest in Manokwari Regency, West Papua, Indonesia

Several studies have been conducted in the past on carbon stock measurements in the tropical forests of Indonesia.This study is the first related research conducted in the New Guinea Island.In a degraded logged-over secondary forest in Manokwari Regency (West Papua,Indonesia),carbon stocks were measured for seven parts,i.e.,above-ground biomass (AGB),below-ground biomass (BGB),under-storey biomass (B u),necromass of dead leaves (N l),necromass of dead trees (N t),litter (L) and soil (S) using appropriate equations and laboratory analysis.Total carbon stocks were measured at 642.8 tC·ha-1 in the low disturbance area,536.9 tC·ha-1 in the moderate disturbance area and 490.4 tC·ha-1 in the high disturbance area.B u,N l and N t were not significant in the carbon stock and were collectively categorized as a total biomass complex.The carbon stock of litter was nearly equal to that of the total biomass complex,while the total carbon stock in the soil was eight times larger than the total biomass complex or the carbon stock of the litter.We confirmed that the average ratio of AGB and BGB to the total biomass (TB) was about 84.7% and 15.3%,respectively.Improvements were made to the equations in the low disturbance logged-over secondary forest area,applying corrections to the amounts of biomass of sample trees,based on representative commercial trees of category one.TB stocks before and after correction were estimated to be 84.4 and 106.7 tC·ha-1,indicating that these corrections added significant amounts of tree biomass (26.4%) during the sampling procedure.In conclusion,the equations for tree biomass developed in this study,will be useful for evaluating total carbon stocks,especially TB stocks in logged-over secondary forests throughout the Papua region.     

Carbon and nitrogen storage in agroforests, tree plantations, and pastures in western Oregon, USA

Pastures store over 90% of their carbon and nitrogen below-ground as soil organic matter. In contrast, temperate conifer forests often store large amounts of organic matter above-ground in woody plant tissue and fibrous litter. Silvopastures, which combine managed pastures with forest trees, should accrete more carbon and nitrogen than pastures or timber plantations because they may produce more total annual biomass and have both forest and grassland nutrient cycling patterns active. This hypothesis was investigated by conducting carbon and nitrogen inventories on three replications of 11 year-old Douglas-fir (Pseudotsuga menziesii)/perennial ryegrass (Lolium perenne)/subclover (Trifolium subterraneum) agroforests, ryegrasss/subclover pastures, and Douglas-fir timber plantations near Corvallis, Oregon in August 2000. Over the 11 years since planting, agroforests accumulated approximately 740 kg ha^–1 year ^–1 more C than forests and 520 kg ha^–1 year^–1 more C than pastures. Agroforests stored approximately 12% of C and 2% of N aboveground compared to 9% of C and 1% of N above ground in plantations and less than 1% of N and C aboveground in pastures. Total N content of agroforests and pastures, both of which included a nitrogen-fixing legume, were approximately 530 and 1200 kg ha^–1 greater than plantations, respectively. These results support the proposition that agroforests, such as silvopastures, may be more efficient at accreting C than plantations or pasture monocultures. However, pastures may accrete more N than agroforests or plantations. This apparent separation of response in obviously interrelated agroecosystem processes, points out the difficulty in using forest plantation or pasture research results to predict outcomes for mixed systems such as agroforests. This revised version was published online in June 2006 with corrections to the Cover Date.     

Soil nitrogen transformations varied with plant community under Nanchang urban forests in mid-subtropical zone of China

Soil N transformations using the polyvinyl chloride (PVC) closed-top tube in situ incubation method were studied in Nanchang urban forests of the mid-subtropical region of China in different months of 2007. Four plots of 20 m × 20 m were established in four different plant communities that represented typical successional stages of forest development including shrubs, coniferous forest, mixed forest and broad- leaved forest. Average concentrations of soil NH 4 + -N from January to December were not different among the four plant communities. The concentrations of soil NO 3 - -N and mineral N, and the annual rates of ammonification, nitrification and net N-mineralization under the early successional shrub community and coniferous forest were generally lower than that of the late successional mixed and broad-leaved forests (p<0.05). Similar differences among the plant communities were also shown in the relative nitrification index (NH 4 + -N/NO 3 - -N) and relative nitrification intensity (nitrification rate/net N-mineralization rate). The annual net N-mineralization rate was increased from younger to older plant communities, from 15.1 and 41.4 kg·ha -1 ·a -1 under the shrubs and coniferous forest communities to 98.0 and 112.9 kg·ha -1 ·a -1 under the mixed and broad-leaved forests, respectively. Moreover, the high annual nitrification rates (50-70 kg·ha -1 ·a -1 ) and its end product, NO 3 - -N (2.4-3.8 mg·kg -1 ), under older plant communities could increase the potential risk of N loss. Additionally, the temporal patterns of the different soil N variables mentioned above varied with different plant community due to the combined affects of natural biological processes associated withforest maturation and urbanization. Our results indicated that urban for- ests are moving towards a state of "N saturation" (extremely nitrification rate and NO 3 - -N content) as they mature.     

Carbon Stock in Community Managed Hill Sal (Shorea robusta) Forests of Central Nepal

Community forests of developing countries are eligible to participate in the Reducing Emissions from Deforestation and Forest Degradation (REDD+) scheme. For this, estimation of carbon stock and the sequestration is essential. The carbon stock in the living biomass of nine community managed Shorea robusta forests of the mid hill regions of central Nepal (managed for 4–29 yr) were estimated. The carbon stock of trees and shrubs was estimated using an allometric equation while the biomass of herbaceous vegetation was estimated by the harvest method. The carbon stock in the living biomass of the studied forests ranged from 70–183 Mg ha^?1(mean: 120 Mg ha^?1) and it increased with increasing soil organic carbon. However, the carbon stock did not vary significantly with species richness and litter cover. The biomass and carbon stock in the forests managed for >20 yr were significantly higher than in the forests managed for < 20 yr. The carbon stock increased with the management duration (p < .05) with sequestration rate of 2.6 Mg C ha^?1 yr^?1. The local management has had positive effects on the carbon stock of the forests and thus the community forests have been acting as a sink of the atmospheric CO₂. Therefore, the community managed forests of Nepal are eligible to participate in the REDD+ scheme.     

Soil organic carbon and aggregation under poplar based agroforestry system in relation to tree age and soil type

The poplar based agroforestry system improves aggregation of soil through huge amounts of organic matter in the form of leaf biomass. The extent of improvement may be affected by the age of the poplar trees and the soil type. The surface and subsurface soil samples from agroforestry and adjoining non-agroforestry sites with different years of poplar plantation (1, 3 and 6 years) and varying soil textures (loamy sand and sandy clay) were analyzed for soil organic carbon, its sequestration and aggregate size distribution. The average soil organic carbon increased from 0.36 in sole crop to 0.66% in agroforestry soils. The increase was higher in loamy sand than sandy clay. The soil organic carbon increased with increase in tree age. The soils under agroforestry had 2.9–4.8 Mg ha⁻¹ higher soil organic carbon than in sole crop. The poplar trees could sequester higher soil organic carbon in 0–30 cm profile during the first year of their plantation (6.07 Mg ha⁻¹ year⁻¹) than the subsequent years (1.95–2.63 Mg ha⁻¹ year⁻¹). The sandy clay could sequester higher carbon (2.85 Mg ha⁻¹ year⁻¹) than in loamy sand (2.32 Mg ha⁻¹ year⁻¹). The mean weight diameter (MWD) of soil aggregates increased by 3.2, 7.3 and 13.3 times in soils with 1, 3 and 6 years plantation, respectively from that in sole crop. The increase in MWD with agroforestry was higher in loamy sand than sandy clay soil. The water stable aggregates (WSA >0.25 mm) increased by 14.4, 32.6 and 56.9 times in soils with 1, 3 and 6 years plantation, respectively, from that in sole crop. The WSA >0.25 mm were 6.02 times higher in loamy sand and 2.2 times in sandy clay than in sole crop soils.     

孟加拉哈提亚地区海岸造林对土壤性质的影响

在孟加拉诺阿卡利地区及相临裸地,对海岸植被(12年和17年生无瓣海桑Sonneratia apetala)进行探索性研究,以便了解海岸造林对土壤特性的影响.在三种不同地带(内陆、中部、海边),在12年生和17年生无瓣海桑林下,土壤深度分别为0-10,10-30和30-40cm,土壤湿度、土壤粒度、有机质、C含量、总N、pH、有效P、K、Na、Ca和Mg含量明显高(p≤0.05,p≤0.01,p≤0.001)于其相临裸地的数据,土壤含盐量明显(p≤0.01)低于其相临裸地的数据.在内陆CharAlim植被,土壤表面的土壤湿度,土壤粒度,有机质,C含量、总N、pH、土壤含盐量、有效P、K、Na、Ca和Mg含量分别为:31.09%、2.24 g·cm-3、2.41%、4.14%、0.58%、7.07、O.09 dS·cm-1、28.06 mg·L-1、O.50 mg·L-1、11.5 mg·L-1、3.30 mg·L-1和2.7 mmol·kg-1;而在相邻的Char Rehania贫瘠地区的相同土壤深度,其相关值分别为:16.69%、1.25g·cm-3、O.43%、0.74%、O.25%、6.57、0.13 dS·cm-1、13.07mg·L-1、O.30mg·L-1、1.4 mg·L-1、O.30 mmol·kG-1和0.50 nag·L-1.然而,在小内陆到海边的植被中,土壤湿度、土壤密度、有机质、C含量、总N、pH、有效P、K、Na和Ca含量逐渐降低,而土壤含盐量、Na和Mg含量却逐渐增加.虽然,在植被与相临裸地的不同土壤深度中土壤质地不同,植被地中砂土份额明显(p≤0.01)低于相临裸地,而粉砂土份额则明显(p≤0.001)高于裸地.在本研究中,所有参数的评价也在为其他地区相关研究得到应用.     

Nitrogen budget of a rehabilitated forest on a degraded granitic hill

Rehabilitated forests established about 100 years ago on denuded lands in a hilly granitic area are widespread in the Kyoto–Osaka area, the second largest megalopolis in Japan. From 2001 to 2003, we monitored the annual nitrogen (N) budget of a rehabilitated forest watershed dominated by Quercus serrata and Ilex pedunculosa. The ion concentrations of bulk rain in the watershed were similar to those of other watersheds in Japan. The annual bulk rain input of N ranged from 5.1 to 6.3 kg N ha⁻¹ year⁻¹, and the N deposition from throughfall and stem-flow ranged from 7.5 to 8.2 kg N ha⁻¹ year⁻¹. Estimated annual outputs of N from the stream ranged from 3.3 to 10.6 kg N ha⁻¹ year⁻¹. These results indicate that the amount of N deposition in this area is less than that in urban Tokyo (>10 kg N ha⁻¹ year⁻¹), but the N output of the watershed is comparable with that of the Tokyo area. We discuss the characteristics of N dynamics in rehabilitated forests, focusing on the biogeochemical processes of this watershed.     

Estimation and economic evaluation of aboveground carbon storage of <Emphasis Type="Italic">Tectona grandis</Emphasis> plantations in Western Panama

Tropical tree plantations may play an important role in mitigating CO₂ emissions through their potential to capture and sequester carbon from the atmosphere. The Clean Development Mechanism (CDM) as well as voluntary initiatives provide economic incentives for afforestation and reforestation efforts through the generation and sale of carbon credits. The objectives of our study were to measure the carbon (C) storage potential of 1, 2 and 10-years old Tectona grandis plantations in the province of Chiriquí, Western Panama and to calculate the monetary value of aboveground C storage if sold as Certified Emission Reduction (CER) carbon credits. The average aboveground C storage ranged from 2.9 Mg C ha⁻¹ in the 1-year-old plantations to 40.7 Mg C ha⁻¹ in the 10-year-old plantations. Using regression analysis we estimated the potential aboveground C storage of the teak plantation over a 20 year rotation period. The CO₂-storage over this period amounted to 191.1 Mg CO₂ ha⁻¹. The discounted revenues that could be obtained by issuance of carbon credits during a 20 year rotation period were about US$460 for temporary CER and US$560 for long-term CER, and thus, contribute to a minor extent (1%) to overall revenues, only.