Soil carbon stock assessment in the tropical dry deciduous forest of the Sathanur reserve forest of Eastern Ghats,India

Climate change and carbon mitigation through forest ecosystems are some of the important topics in global perspective. Tropical dry forests are one of the most widely distributed ecosystems in tropics, which remain neglected in research. The soil organic carbon (SOC) stock was quantified on a large scale (30 1-ha plots) in the dry deciduous forest of the Sathanur reserve forest of Eastern Ghats. The SOC stock ranged from 16.92 to 44.65 Mg/ha with a mean value of 28.26 ± 1.35 Mg/ha. SOC exhibited a negative trend with an increase in soil depth. A significant positive correlation was obtained between SOC stocks and vegetation characteristics viz. tree density, shrub basal area, and herb species richness, while a significant negative correlation was observed with bulk density. The variation in SOC stock among the plots obtained in the present study could be due to differences in tree abundance, herb species richness, shrub basal area, soil pH, soil bulk density, soil texture etc. The present study generates a large-scale baseline data of dry deciduous forest SOC stock, which would facilitate SOC stock assessment at the national level as well as to understand its contribution on a global scale.     

Does tree species composition control soil organic carbon pools in Mediterranean mountain forests?

We compared soil organic carbon (SOC) stocks and stability under two widely distributed tree species in the Mediterranean region: Scots pine (Pinus sylvestris L.) and Pyrenean oak (Quercus pyrenaica Willd.) at their ecotone. We hypothesised that soils under Scots pine store more SOC and that tree species composition controls the amount and biochemical composition of organic matter inputs, but does not influence physico-chemical stabilization of SOC. At three locations in Central Spain, we assessed SOC stocks in the forest floor and down to 50 cm in the mineral in pure and mixed stands of Pyrenean oak and Scots pine, as well as litterfall inputs over approximately 3 years at two sites. The relative SOC stability in the topsoil (0-10 cm) was determined through size-fractionation (53 μm) into mineral-associated and particulate organic matter and through KMnO₄-reactive C and soil C:N ratio.Scots pine soils stored 95-140 Mg ha⁻¹ of C (forest floor plus 50 cm mineral soil), roughly the double than Pyrenean oak soils (40-80 Mg ha⁻¹ of C), with stocks closely correlated to litterfall rates. Differences were most pronounced in the forest floor and uppermost 10 cm of the mineral soil, but remained evident in the deeper layers. Biochemical indicators of soil organic matter suggested that biochemical recalcitrance of soil organic matter was higher under pine than under oak, contributing as well to a greater SOC storage under pine. Differences in SOC stocks between tree species were mainly due to the particulate organic matter (not associated to mineral particles). Forest conversion from Pyrenean oak to Scots pine may contribute to enhance soil C sequestration, but only in form of mineral-unprotected soil organic matter.     

Soil Carbon and Nitrogen Stocks Under Plantations in Gambo District,Southern Ethiopia

The effect of six plantation species in comparison to natural forest (NF) on soil organic carbon (SOC) and total nitrogen (TN) stocks, depth-wise distribution, biomass carbon (C), and N was investigated on plantations and cultivated lands on an Andic paleudalf soil in Southern Ethiopia. The SOC, N, and bulk density were determined from samples taken in 4 replicates from 10-, 20-, 40-, 60-, and 100-cm depth under each site. Similarly, the biomass C and N of the plantation species and understory vegetation were also determined. The SOC and N were concentrated in the 0- to 10-cm depth and decreased progressively to the 1-m depth. Next to the NF, Juniperous procera accrued higher SOC and N in all depths than the corresponding plantations. No evidence of significant difference on SOC and N distribution among plantations was observed below the 10-cm depth with minor exceptions. The plantations accrue from 133.62 to 213.73 Mg ha^–1 or 59.1 to 94.5% SOC, 230.4 to 497.3 Mg ha^–1 or 6.9 to 14.9% TBC and 420.37 to 672.80 Mg ha^–1 or 12.5 to 20% total C-pool of that under the NF. The N stock under Juniperous procera was the highest, while the lowest was under Eucalyptus globulus and Cupressus lusitanica. We suggest that SOC and N sequestration can be enhanced through mixed cropping and because the performance of the native species Juniperous procera is encouraging, it should be planted to restock its habitat.     

Carbon sequestration potential of the stands under the Grain for Green Program in Yunnan Province,China

The carbon sequestration potential in living biomass and soil organic matter under the Grain for Green Program (GGP) in Yunnan Province, one of the most important target provinces of the GGP in China, was estimated in this paper using empirical curves and factors. The area of tree species planted during 2000–2007 was collected, and four scenarios for the annual area of GGP-stands to be planted during 2008–2010 and harvest options were schemed. Empirical growth curves for different tree species were developed based on data about the growth of existing plantation in Yunnan Province from National Forestry Inventory, and were used for the estimation of the carbon stocks in the tree biomass pools by incorporating with basic wood density, biomass expansion factors and carbon fraction. Empirical factors were introduced to estimate the stock change in soil organic carbon (SOC) under the GGP. The results show that the carbon stock in the GGP-stands in Yunnan Province will increase by 12.474–12.608 TgC, 33.016–35.161 TgC, 38.119–47.100 TgC, 43.057–53.626 TgC and 49.918–56.621 by the year 2010, 2020, 2030, 2040 and 2050, respectively. The annual carbon stock change in the GGP-stands will peak at 2.342–2.536 TgC per year in 2013, followed by a gradual decrease. The estimated potential carbon sequestration by GGP-stands amounts to 10.82–12.27% of the carbon stocks of forest ecosystems in Yunnan province in the 1990s.     

Anthropogenic disturbance of natural forest vegetation on calcareous soils alters soil organic matter composition and natural abundance of <Superscript>13</Superscript>C and <Superscript>15</Superscript>N in density fractions

In the last century, many calcareous soils in Castilla León (northwestern Spain) have been transformed from natural Quercus ilex forest to cropped land. Reforestation with Pinus halepensis has been taking place during the past 40 years. In order to obtain a better understanding of how these disturbances affect ecosystem functioning, we studied the quantity and quality of soil organic matter (SOM) in natural forest ecosystems, cropland and Pinus plantations. Density fractionation combined with ultrasonic dispersion enables separation and study of SOM fractions: free organic matter (OM), OM occluded into aggregates and OM stabilized in organo-mineral complexes, considered on the basis of the type of physical protection provided. We separated SOM density fractions and determined the concentrations of C and N, C/N ratios and the natural isotopic abundance (δ¹³C and δ¹⁵N values). Transformation of Quercus forest to cropland resulted in major losses of SOC and N, as expected. However, subsequent reforestation with Pinus resulted in good recovery of the original SOC and soil N pools. This indicates the potential for enhanced C storage in agricultural soils by their reversion to a forested state. Study of the density fractions and their ¹³C and ¹⁵N signatures enabled better understanding of the high stability of OM in calcareous soils, and analysis of δ¹³C variations throughout the profile also enabled identification of past C3/C4 vegetation change. Despite the different OC contents of soils under different land use, OM stabilization mechanisms were not significantly different. In calcareous soils, accumulation of SOC and N is mainly due to organo-mineral associations, resulting in physicochemical stabilization against further decomposition.     

鄂西南鹅掌楸天然林林分结构特征

以鄂西南鹤峰县鹅掌楸天然林为研究对象,通过对林分空间结构(角尺度、大小比、混交度)和林分非空间结构 (径级结构、树高结构、重要值)的研究与分析,直观地反映其林分结构的特征,查清该区鹅掌楸种群的发展现状,为鹅掌楸 天然林的合理保护与科学经营提供依据 。在鹅掌楸天然林集中生长的代表性地段建立 17个 20mx20m调查样地,进行 每木定位与检尺调查,应用 Excel2019、Winkelmas2.0软件对样地调查数据进行处理与分析 。结果表明:研究区鹅掌楸 天然林中共 73个树种,鹅掌楸为该群落的优势种,生长处优势地位( =0.17),种群整体呈轻微聚集分布(为 0.56),同 时该种群在林分中呈现极强度混交状态( =0.85):种群整体径级、树高分布都呈右偏正态分布,小径级林木株数很少, 种群整体呈现稳定型一衰退型 。FSI均值为 0.82,FSD 均值为 0.30,林分空间结构为接近于理想状态(41.18%)或达 到理想状态(58.82%)。鹅掌楸天然林处于演替后期,林分结构整体上较为理想,可对处于聚集分布的林木进行适当调整, 辅以 一定人为促进更新的措施,促使鹅掌楸林分结构更加合理。     

干旱和涝渍胁迫对入侵物种喜旱莲子草生长的影响

苦郎树是一种沿海防沙固堤的半红树植物，不仅在红树林群落中具有重要的生态价值，叶片提取物还有一定的医药价值。本研究通过4种光响应模型对苦郎树光响应曲线拟合，计算光合参数进行对比分析，评估最适拟合模型，并研究其光合特性。结果表明：不同模型对苦郎树光响应拟合存在差异，四种模型拟合优度均在0.996以上，苦郎树气孔导度随光合辐射增加而增加，在1800 μmol·m-2·s-1有效光合辐射下达到最大；在500 μmol·m-2·s-1有效光合辐射下水分利用效率最高，胞间二氧化碳维持在一个不变的浓度，与大部分植物的光合特性相似。非直角双曲线模型对苦郎树拟合效果最佳，如何精确拟合光饱和点还需进一步研究，应需要根据实际情况选用最适宜的光响应拟合模型，为海岸生态、防风固堤和园林绿化等工作提供理论依据。     

不同土地利用形式下表土有机碳含量和密度特征的研究

通过对西江流域肇庆市三叉顶自然保护区典型样地调查,对比分析了林地（针阔混交林、竹林、马尾松林）、农用地（果园、稻田、旱地）与邻近荒地的0～20em土壤有机碳含量和密度特征及其影响因子。结果表明：（1）有机碳含量大小顺序为林地（20．71±5．24g·kg^-1）〉农用地（13．50±6．05g·kg^-1）〉荒地（12．87±4．20g·kg^-1）。林地比农用地、荒地表土有机碳含量分别高出53．35％和60．83％。林地表土有机碳含量极显著高于农用地和荒地,而农用地和荒地间则无显著差异。表土有机碳密度差异极显著,有机碳密度大小顺序为林地（3．09±0．88kg·m^-2）〉荒地（2．99±0．93kg·m^-2）〉农用地（2．28±1．01k·m^-2）。（2）针阔混交林、竹林、马尾松叶林3种林分类型的表土有机碳含量、密度的大小顺序均为针阔混交林〉竹林〉马尾松林;在有机碳含量方面,针阔混交林与马尾松林有显著差异;针阔混交林、竹林均与荒地有显著差异,而马尾松林与荒地则无显著差异。在有机碳密度方面,针阔混交林与马尾松林有显著差异。（3）3种农用地有机碳含量大小顺序为果园〉稻田〉旱地,果园与旱地之间有显著差异,旱地有机碳含量比果园低41．91％,旱地与水稻田之间无显著差异,三者与荒地均无显著差异。有机碳密度顺序有所变化,大小顺序为果园〉旱地〉稻田,三者之间均无显著差异,但旱地、水稻田均与荒地有显著差异。（4）土壤氮水平、电导率对林地、农用地土壤碳固定有正效应,而容重则有负效应;而受施肥和耕作等因素影响,农用地的表土有机碳含量还与石砾含量显著负相关;荒地的土壤有机碳含量则仅与容重显著负相关。     

Effects of forest management on soil C and N storage: meta analysis

The effects of forest management on soil carbon (C) and nitrogen (N) are important to understand not only because these are often master variables determining soil fertility but also because of the role of soils as a source or sink for C on a global scale. This paper reviews the literature on forest management effects on soil C and N and reports the results of a meta analysis of these data. The meta analysis showed that forest harvesting, on average, had little or no effect on soil C and N. Significant effects of harvest type and species were noted, with sawlog harvesting causing increases (+18%) in soil C and N and whole-tree harvesting causing decreases (−6%). The positive effect of sawlog harvesting appeared to be restricted to coniferous species. Fire resulted in no significant overall effects of fire on either C or N (when categories were combined); but there was a significant effect of time since fire, with an increase in both soil C and N after 10 years (compared to controls). Significant differences among fire treatments were found, with the counterintuitive result of lower soil C following prescribed fire and higher soil C following wildfire. The latter is attributed to the sequestration of charcoal and recalcitrant, hydrophobic organic matter and to the effects of naturally invading, post-fire, N-fixing vegetation. Both fertilization and N-fixing vegetation caused marked overall increases in soil C and N.     

树种选择与配置对森林生态系统服务的影响

我国森林面积和蓄积量连续增长,但造林树种单一、林分幼龄化、径级持续偏小、单位面积蓄积量低。在气候变化挑战及全球经济一体化大背景下,如何发挥森林在木材生产、生物多样性保护、固碳、涵养水源及社会文化等方面的多重服务功能以满足经济社会发展对森林的多元化需求,是我国现代林业建设的当务之急。文中通过梳理国内外相关文献,分析不同树种与配置模式和不同森林经营选择对森林生态系统服务的影响,以及对森林生态系统服务影响的模拟预测方法与工具,进而总结当前研究与实践的总体趋势,以期为我国树种选择及其优化配置、增强森林生态系统服务功能提供决策参考。     

Soil Carbon and Nitrogen Dynamics Followed by a Forest-to-pasture Conversion in Western Mexico

Gains and losses of soil carbon (C), have been reported when tropical forests are converted to pastures. Regional studies are crucial for setting regional baselines and explaining each particular trend, in order to solve this controversy. Tropical deciduous forest (TDF) is under high deforestation pressure, mainly for conversion to pastures. The present study compared soil organic C (SOC) and nitrogen (SON) in the surface layer (0–5 cm) of forest and pasture soils in a TDF of western Mexico. SOC and SON concentrations were 18 and 60% lower in pasture soils than in forest soils, and C:N ratio increased in pasture soils. Furthermore, pasture soils had lower labile C and available inorganic nitrogen (N) than forest soils. These results can be explained as a reduction in C inputs to pasture soils and management-induced disruption of soil aggregates. In forest soils, macroaggregates (> 250 μm) were predominant (85%), whereas in pasture soils they were reduced to 35% of dry sand-free soil mass. The estimated SOC and SON losses from the top 5 cm of soil were 3 Mg C ha⁻¹ and 0.9 Mg N ha⁻¹, respectively.     

Loss of carbon sequestration potential after several decades of shifting cultivation in the Southern Yucatán

Cumulative losses from shifting cultivation in the tropics can affect the local to regional to global balance of carbon and nutrient cycles. We determined whether shifting cultivation in the Southern Yucatán causes feedbacks that limit future forest productivity and carbon sequestration potential. Specifically, we tested how the recovery of carbon stocks changes with each additional cultivation-fallow cycle. Live aboveground biomass, coarse woody debris, fine woody debris, forest floor litter and soil were sampled in 53 sites (39 secondary forests 2–25 years old, with one to four cultivation-fallow cycles, and 14 mature forests) along a precipitation gradient in Campeche and Quintana Roo, Mexico. From the first to the third or fourth cultivation-fallow cycle, mean carbon stocks in live aboveground biomass debris declined 64%. From the first to the third cycle, coarse woody debris declined by 85%. Despite declining inputs to soil with each cultivation-fallow cycle, soil carbon stocks did not further decline after the initial conversion from mature to secondary forest. The combined aboveground and soil carbon stock declined almost 36% after conversion from mature forest, however two additional cultivation cycles did not promote further significant decline, largely because of the stability of the soil carbon pool. Although age was the dominant factor in predicting total carbon stocks of secondary forests under shifting cultivation, the number of cultivation-fallow cycles should not be neglected. Understanding change beyond the first cycle of deforestation will enhance forest management at a local scale by improving predictions of secondary forest productivity and related agricultural productivity. A multi-cycle approach to deforestation is critical for regional and national evaluation of forest-based carbon sequestration. Finally, models of the global carbon cycle can be better constrained with more accurate quantification of carbon fluxes from land-use change.     

广州市森林生态系统碳储量格局分析

相对准确地计量地带性森林碳库大小是估算区域森林碳汇潜力的前提。根据全市不同森林类型设置样地900个,运用样地清查法估算广州市森林生态系统碳储量和碳密度。结果表明:广州市森林生态系统碳储量为52.16 Tg C。其中,植被层和土壤层碳储量分别为21.97 Tg C和27.16 Tg C。碳储量空间分布主要集中在从化区和增城区;总碳储量的组成中,土壤层碳库比例最大(58%),其次为乔木层碳库比例(40%),而灌木层、草本层、凋落物层和细根(≤ 2.0 mm)的生物量比例大多在1%~2%;天然林碳储量与人工林接近,但是碳密度显著大于人工林(p < 0.05);不同林龄从小到大排序为:幼龄林、中龄林、近熟林、过熟林、成熟林;天然林以阔叶混和它软阔的碳储量最高,阔叶混和黎蒴的碳密度最高。人工林不同林型从大到小排序为:南洋楹 > 黎蒴 > 木荷 > 木麻黄 > 它软阔 > 阔叶混 > 湿地松。森林生态系统碳密度为178.03 t C hm-2,其中,植被层和土壤层碳密度分别为79.61 t C hm-2和98.42 t C hm-2。本研究全面计量了广州市森林生态系统碳库现状,这对评估该地区森林固碳潜力和指导碳汇林经营管理具有重要参考价值。     

Effect of land-use conversion from forest to cocoa agroforest on soil characteristics and quality of a Ferric Lixisol in lowland humid Ghana

Soil fertility decline caused by deforestation, soil degradation and low input use has become a primary factor limiting sustainable utilization of soil resources in cocoa agroforestry systems on acid soils in lowland humid Ghana. Changes in and responses of soil physico-chemical properties and soil quality to land-use change was investigated along a chronosequence of farm fields on a Ferric Lixisol in the Ashanti region of Ghana. Soil bulk density increased significantly only in the top 0–10 cm soil layer. Concentrations and stocks of soil organic carbon (SOC) and total N decreased significantly in the top 0–10 and 10–20 cm soil depths. By 30 years after forest conversion, cocoa system had re-accumulated up to 38.8 Mg C ha^?1 or 85 % of initial forest carbon stock values. Total porosity (%) decreased significantly in shaded-cocoa fields in comparison with the natural semi-deciduous forest. An assessment of soil deterioration using degradation indices (DIs) revealed that total soil quality (0–20 cm) deteriorated significantly (DI = –60.6) in 3-year-old of cocoa system but improved in 15 and 30-year-old systems. Available P stocks declined consistently while soil exchangeable Ca, K and Mg stocks as well as cation exchange capacity (CEC) and base saturation remained more or less stable with a tendency to improve. The inclusion of leguminous shade trees during early plantation development, development of mechanisms for the integration of cover crops and enhancement of farmer capability in improved farm management are required to maintain high C and nutrient base, minimize soil quality degradation during plantation development phase and sustain long-term productivity.     

Long-term development of soil organic carbon and nitrogen stocks after shelterwood- and clear-cutting in a mountain forest in the Bavarian Limestone Alps

Forest soils store large stocks of soil organic matter (SOM) and are of vital importance for the ecosystem supply with nutrients and water. According to the available literature, depending on management regime and site properties, different negative and positive effects of forest management (particularly of forest thinnings and shelterwood cuttings) on soil organic carbon (SOC) and nitrogen (N) stocks are observed. To elucidate the long-term impact of different shelterwood systems and small clear-cuttings on the OC and N stocks of shallow calcareous soils in the Bavarian Alps, we conducted soil humus inventories on different plots of a mixed mountain forest management experiment started in 1976. The silvicultural multi-treatment experiment consists of a NW-exposed Main Experiment (ME) site with eight plots of different cutting intensity (two unthinned controls, two light shelterwood cuttings = 30 % of basal tree area removed, two heavy shelterwood cuttings = 50 % removed, and two clear-cuttings = 100 % removed) on Triassic dolostone. Additionally, plots were installed at a N-exposed dolostone (ND) site and two sites (FL, FH) on Flysch sandstone (each with one unthinned control and one heavy shelterwood cutting). The shelterwood cuttings from 1976 were repeated in 2003 to re-establish the overstorey basal area as produced by the first cutting in the different plots. Thirty-five years after the first treatments, forest floor SOC and N stocks were significantly decreased (up to ?70 %) at the different shelterwood and clear-cut treatments compared to the unthinned control at the ME site despite vigorous development of natural rejuvenation. Also significantly smaller topsoil (forest floor plus mineral soil 0–10 cm depth) OC stocks (between ?16 and ?20 %) were detected at the thinned compared to the control plots. Differences in topsoil N stocks were also considerable (between ?3 and ?14 %), but substantially smaller than OC stock changes. For the total soil down to 30 cm depth, OC stocks in the differently thinned plots were consistently smaller compared to the unthinned control plots. Comparable to our findings at the ME site, heavy shelterwood plots at the three other sites (ND, FL, and FH) showed significant losses of OC in the forest floor (up to 43 %), mineral soil (up to 38 %), topsoil (up to 38 %), and total soil (up to 34 %). Significant large absolute and relative SOC decreases coincided with sites characterized by large initial humus stocks. Moreover, significant effects of heavy shelterwood cuttings on SOC and N stocks (on average 23 % SOC loss and 13 % soil N loss for the forest floor plus the uppermost 10 cm mineral soil) were detected on a regional level. Our results show that different shelterwood systems are accompanied with a considerable long-term decrease in OC and N stocks in shallow calcareous forest soils of the Bavarian Alps. However, a comparison with a windthrown forest stand at a nearby similar site indicates that SOM losses after thinning operations are small compared to decreases following windthrow or other calamities with subsequent large soil erosion and increased mineralization processes.     

Carbon and nitrogen in forest floor and mineral soil under six common European tree species

The knowledge of tree species effects on soil C and N pools is scarce, particularly for European deciduous tree species. We studied forest floor and mineral soil carbon and nitrogen under six common European tree species in a common garden design replicated at six sites in Denmark. Three decades after planting the six tree species had different profiles in terms of litterfall, forest floor and mineral soil C and N attributes. Three groups were identified: (1) ash, maple and lime, (2) beech and oak, and (3) spruce. There were significant differences in forest floor and soil C and N contents and C/N ratios, also among the five deciduous tree species. The influence of tree species was most pronounced in the forest floor, where C and N contents increased in the order ash = lime = maple < oak = beech ? spruce. Tree species influenced mineral soil only in some of the sampled soil layers within 30 cm depth. Species with low forest floor C and N content had more C and N in the mineral soil. This opposite trend probably offset the differences in forest floor C and N with no significant difference between tree species in C and N contents of the whole soil profile. The effect of tree species on forest floor C and N content was primarily attributed to large differences in turnover rates as indicated by fractional annual loss of forest floor C and N. The C/N ratio of foliar litterfall was a good indicator of forest floor C and N contents, fractional annual loss of forest floor C and N, and mineral soil N status. Forest floor and litterfall C/N ratios were not related, whereas the C/N ratio of mineral soil (0–30 cm) better indicated N status under deciduous species on rich soil. The results suggest that European deciduous tree species differ in C and N sequestration rates within forest floor and mineral soil, respectively, but there is little evidence of major differences in the combined forest floor and mineral soil after three decades.     

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

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

Soil carbon and physical property changes in Brazilian Coastal Tableland soils with land use following deforestation

The Atlantic Forest has been deforested to the point that only about 7% of the original forest remains. Soil degradation, including loss of soil organic carbon (SOC), has often been associated with deforestation. In extensive areas previously occupied by Atlantic Forest the soil has a naturally compact subsoil horizon called the coeso. This layer challenges root development and plant productivity. The purpose of this study was to investigate soil carbon and selected physical characteristics under the influence of the native forest and post-deforestation agricultural practices. The management regimes were a native forest, a rubber tree plantation, a pasture and annual cropping. Two soil depths were investigated: 0 to 15 cm, corresponding to the A horizon; and 35 to 50 cm, corresponding to the coeso. Management influenced both SOC concentration and soil bulk density; however, SOC content was not significantly changed by any of the post-deforestation land uses. This result supports the annual cropping system that has been adapted by small landholders. Most interesting was the quantity of SOC found in the coeso, which was as much as 50% of the surface horizon.     

Selective harvesting at rational intervals promotes carbon sequestration in temperate coniferous and broad-leaved mixed forests in China

Evidence-based selective cutting at prescribed intervals as part of good forest management can enhance the carbon sequestration capacity of the forest. The effect of forest management on carbon sequestration has, however,not been quantified. Thus, carbon content of various organs was measured for 323 tree species, 247 shrub species, and233 herb species in seven temperate coniferous and broadleaved mixed forests that were subjected to selective cutting with restoration durations of 100, 55, 45, 36, 25, 14, and6 years to explore dynamic changes in carbon storage. The results showed that biomass carbon allocation in different organs followed a pattern: trunk root branch leaf for all forests. With longer restoration durations, more carbon accumulated in different organs and in soils. Interestingly,when the restoration duration exceeded 50 years, carbon storage in ecosystem was larger than that in primary forests with 100-year cutting intervals, suggesting that a reasonable selective cutting interval can increase forest carbon sequestration. Mean diameter at breast height(DBH) and forest carbon storage were significantly positively correlated, and carbon storage of selectively cut forests exceeded that of primary forests when the stand mean DBH exceeded 15.66 cm. Therefore, mean DBH of forests can be an indicator for combining sustainable forest management and forest carbon sequestration. Additionally, the classic coefficients of 0.45 and 0.50 used to estimate carbon sequestration underestimated values by 2.65% and overestimated by 8.16%, respectively, in comparison with the measured carbon content from different plant organs.     

Nitrogen availability regulates deep soil priming effect by changing microbial metabolic efficiency in a subtropical forest

In terrestrial ecosystems,deep soils(below30 cm) are major organic carbon(C) pools.The labile carbon input could alter soil organic carbon(SOC) mineralization,resulting in priming effect(PE),which could be modified by nitrogen(N) availability,however,the underlying mechanism is unclear for deep soils,which complicates the prediction of deep soil C cycling in response to N deposition.A series of N applications with 13 C labeled glucose was set to investigate the effect of labile C and N on deep SOC mineralization.Microbial biomass,functional community,metabolic efficiency and enzyme activities were examined for their effects on SOC mineralization and PE.During incubation,glucose addition promoted SOC mineralization,resulting in positive PE.The magnitude of PE decreased significantly with increasing N.The N-regulated PE was not dependent on extracellular enzyme activities but was positively correlated with carbon use efficiency and negatively with metabolic quotient.Higher N levels resulted in higher microbial biomass and SOC-derived microbial biomass than lower N levels.These results suggest that the decline in the PE under high N availability was mainly controlled by higher microbial metabolic efficiency which allocated more C for growth.Structural equation modelling also revealed that microbial metabolic efficiency rather than enzyme activities was the main factor regulating the PE.The negative effect of additional N suggests that future N deposition could promote soil C sequestration.