2014 Vol. 0, No. 4

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Carbon Storage and Sequestration of National Key Ecological Restora-tion Programs in China: An Introduction to Special Issue
LIU Guohua, WU Xing
2014, 0(4): 393-396. doi: 10.1007/s11769-014-0695-0
Forest Carbon Storage and Tree Carbon Pool Dynamics under Natural Forest Protection Program in Northeastern China
WEI Yawei, YU Dapao, Bernard Joseph LEWIS, ZHOU Li, ZHOU Wangming, FANG Xiangmin, ZHAO Wei, WU Shengnan, DAI Limin
2014, 0(4): 397-405. doi: 10.1007/s11769-014-0703-4
The Natural Forest Protection (NFP) program is one of the Six Key Forestry Projects which were adopted by the Chinese Government since the 1980s to address important natural issues in China. It advanced to protecting and restoring the structures and functions of the natural forests through sustainable forest management. However, the role of forest carbon storage and tree carbon pool dynamics since the adoption of the NFP remains unknown. To address this knowledge gap, this study calculated forest carbon storage (tree, understory, forest floor and soil) in the forest region of northeastern (NE) China based on National Forest Inventory databases and field investigated databases. For tree biomass, this study utilized an improved method for biomass estimation that converts timber volume to total forest biomass; while for understory, forest floor and soil carbon storage, this study utilized forest type-specific mean carbon densities multiplied by their areas in the region. Results showed that the tree carbon pool under the NFP in NE China functioned as a carbon sink from 1998 to 2008, with an increase of 6.3 Tg C/yr, which was mainly sequestrated by natural forests (5.1 Tg C/yr). At the same time, plantations also acted as a carbon sink, reflecting an increase of 1.2 Tg C/yr. In 2008, total carbon storage in forests covered by the NFP in NE China was 4603.8 Tg C, of which 4393.3 Tg C was stored in natural forests and 210.5 Tg C in planted forests. Soil was the largest carbon storage component, contributing 69.5%-77.8% of total carbon storage; followed by tree and forest floor, accounting for 16.3%-23.0% and 5.0%-6.5% of total carbon storage, respectively. Understory carbon pool ranged from 1.9 to 42.7 Tg C, accounting for only 0.9% of total carbon storage.
Biomass Carbon Storage and Its Sequestration Potential of Afforestation under Natural Forest Protection Program in China
ZHOU Wangming, Bernard Joseph LEWIS, WU Shengnan, YU Dapao, ZHOU Li, WEI Yawei
2014, 0(4): 406-413. doi: 10.1007/s11769-014-0702-5
Based on the data from China's Seventh Forest Inventory for the period of 2004-2008, area and stand volume of different types and age-classes of plantation were used to establish the relationship between biomass density and age of planted forests in different regions of the country. Combined with the plantation area in the first-stage of the Natural Forest Protection (NFP) program (1998-2010), this study calculated the biomass carbon storage of the afforestation in the first-stage of the program. On this basis, the carbon sequestration potential of these forests was estimated for the second stage of the program (2011-2020). Biomass carbon storage of plantation established in the first stage of the program was 33.67 Tg C, which was majority accounted by protection forests (30.26 Tg C). There was a significant difference among carbon storage in different regions, which depended on the relationship of biomass carbon density, forest age and plantation area. Under the natural growth, the carbon storage was forecasted to increase annually from 2011 to 2020, reaching 96.03 Tg C at the end of the second-stage of the program in 2020. The annual growth of the carbon storage was forecasted to be 6.24 Tg C/yr, which suggested that NFP program has a significant potential for enhancing carbon sequestration in plantation forests under its domain.
Age-related Changes of Carbon Accumulation and Allocation in Plants and Soil of Black Locust Forest on Loess Plateau in Ansai County, Shaanxi Province of China
LI Taijun, LIU Guobin
2014, 0(4): 414-422. doi: 10.1007/s11769-014-0704-3
The effects of reforestation on carbon (C) sequestration in China's Loess Plateau ecosystem have attracted much research attention in recent years. Black locust trees (Robinia pseudoacacia L.) are valued for their important use in reforestation and water and soil conservation efforts. This forest type is widespread across the Loess Plateau, and must be an essential component of any planning for C sequestration efforts in this fragile ecological region. The long-term effects of stand age on C accumulation and allocation after reforestation remains uncertain. We examined an age-sequence of black locust forest (5, 9, 20, 30, 38, and 56 yr since planting) on the Loess Plateau to evaluate C accumulation and allocation in plants (trees, shrubs, herbages, and leaf litter) and soil (0-100 cm). Allometric equations were developed for estimating the biomass of tree components (leaf, branch, stem without bark, bark and root) with a destructive sampling method. Our results demonstrated that black locust forest ecosystem accumulated C constantly, from 31.42 Mg C/ha (1 Mg = 106 g) at 5 yr to 79.44 Mg C/ha at 38 yr. At the ‘old forest’ stage (38 to 56 yr), the amount of C in plant biomass significantly decreased (from 45.32 to 34.52 Mg C/ha) due to the high mortality of trees. However, old forest was able to accumulate C continuously in soil (from 33.66 to 41.00 Mg C/ha). The C in shrub biomass increased with stand age, while the C stock in the herbage layer and leaf litter was age-independent. Reforestation resulted in C re-allocation in the forest soil. The topsoil (0-20 cm) C stock increased constantly with stand age. However, C storage in sub-top soil, in the 20-30, 30-50, 50-100, and 20-100 cm layers, was age-independent. These results suggest that succession, as a temporal factor, plays a key role in C accumulation and re-allocation in black locust forests and also in regional C dynamics in vegetation.
Soil Carbon Stock and Flux in Plantation Forest and Grassland Ecosystems in Loess Plateau, China
HU Chanjuan, LIU Guohua, FU Bojie, CHEN Liding, LYU Yihe, GUO Lei
2014, 0(4): 423-435. doi: 10.1007/s11769-014-0700-7
Carbon sequestration occurs when cultivated soils are re-vegetated. In the hilly area of the Loess Plateau, China, black locust(Robinia pseudoacacia) plantation forest and grassland were the two main vegetation types used to mitigate soil and water loss after cultivation abandonment. The purpose of this study was to compare the soil carbon stock and flux of these two types of vegetation which restored for 25 years. The experiment was conducted in Yangjuangou catchment in Yan'an City, Shaanxi Province, China. Two adjacent slopes were chosen for this study. Six sample sites were spaced every 35-45 m from summit to toe slope along the hill slope, and each sample site contained three sampling plots. Soil organic carbon and related physicochemical properties in the surface soil layer (0-10 cm and 10-20 cm) were measured based on soil sampling and laboratory analysis, and the soil carbon dioxide (CO2) emissions and environmental factors were measured in the same sample sites simultaneously. Results indicated that in general, a higher soil carbon stock was found in the black locust plantation forest than that in grassland throughout the hill slope. Meanwhile, significant differences in the soil carbon stock were observed between these two vegetation types in the upper slope at soil depth 0-10 cm and lower slope at soil depth 10-20 cm. The average daily values of the soil CO2 emissions were 1.27 mmol/(m2·s) and 1.39 mmol/(m2·s) for forest and grassland, respectively. The soil carbon flux in forest covered areas was higher in spring and less variation was detected between different seasons, while the highest carbon flux was found in grassland in summer, which was about three times higher than that in autumn and spring. From the carbon sequestration point of view, black locustplantation forest on hill slopes might be better than grassland because of a higher soil carbon stock and lower carbon flux.
Response of Artificial Grassland Carbon Stock to Management in Mountain Region of Southern Ningxia, China
TANG Long, DANG Xiaohu, LIU Guobin, SHAO Chuanke, XUE Sha
2014, 0(4): 436-443. doi: 10.1007/s11769-014-0705-2
Grassland is a major carbon sink in the terrestrial ecosystem. The dynamics of grassland carbon stock profoundly influence the global carbon cycle. In the published literatures so far, however, there are limited studies on the long-term dynamics and influential factors of grassland carbon stock, including soil organic carbon. In this study, spatial-temporal substitution method was applied to explore the characteristics of Medicago sativa L.(alfalfa) grassland biomass carbon and soil organic carbon density (SOCD) in a loess hilly region with different growing years and management patterns. The results demonstrated that alfalfa was the mono-dominant community during the cutting period (viz. 0-10 year). Community succession began after the abandonment of alfalfa grassland and then the important value of alfalfa in the community declined. The artificial alfalfa community abandoned for 30 years was replaced by the S. bungeana community. Accordingly, the biomass carbon density of the clipped alfalfa showed a significant increase over the time during 0-10 year. During 0-30 year, the SOCD from 0-100 cm of the soil layer of all 5 management patterns increased over time with a range between 5.300 ± 0.981 kg/m2 and 12.578 ± 0.863 kg/m2. The sloping croplands had the lowest SOCD at 5.300 ± 0.981 kg/m2 which was quite different from the abandoned grasslands growing for 30 years which exhibited the highest SOCD with 12.578 ± 0.863 kg/m2. The ecosystem carbon density of the grassland clipped for 2 years increased 0.1 kg/m2 compared with the sloping cropland, while that of the grassland clipped for 10 years substantially increased to 10.30 ± 1.26 kg/m2. Moreover, the ecosystem carbon density for abandoned grassland became 12.62 ± 0.50 kg/m2 at 30 years. The carbon density of the grassland undisturbed for 10 years was similar to that of the sloping cropland and the grassland clipped for 2 years. Different management patterns imposed great different effects on the accumulation of biomass carbon on artificial grasslands, whereas the ecosystem carbon density of the grassland showed a slight increase from the clipping to abandonment of grassland in general.
Carbon Sequestration Effects of Shrublands in Three-North Shelterbelt Forest Region, China
LIU Wenhui, ZHU Jiaojun, JIA Quanquan, ZHENG Xiao, LI Junsheng, LOU Xuedong, HU Lile
2014, 0(4): 444-453. doi: 10.1007/s11769-014-0698-x
Three-North Shelterbelt Forest (TSF) program, is one of six key forestry programs and has a 73-year construction period, from 1978 to 2050. Quantitative analysis of the carbon sequestration of shrubs in this region is important for understanding the overall function of carbon sequestration of the forest and other terrestrial ecosystems in China. This study investigated the distribution area of shrubland in the TSF region based on remote sensing images in 1978 and 2008, and calculated the carbon density of shrubland in combination with the field investigation and previous data from published papers. The carbon sequestration quantity and rate from 1978 to 2008 was analyzed for four sub-regions and different types of shrubs in the TSF region. The results revealed that: 1) The area of shrubland in the study area and its four sub-regions increased during the past thirty years. The area of shrubland for the whole region in 2008 was 1.2 × 107 ha, 72.8% larger than that in 1978. The Inner Mongolia-Xinjiang Sub-region was the largest shrubland distribution area, while the highest coverage rate was found in the North China Sub-region. 2) In decreasing order of their carbon sequestration, the four types of shrubs considered in this study were Hippophae rhamnoides, Caragana spp., Haloxylon ammodendron and Vitex negundo var. heterophylla. The carbon sequestration of H.rhamnoides, with a maximum mean carbon density of 16.5 Mg C/ha, was significantly higher than that of the other three species. 3) The total carbon sequestration of shrubland in the study region was 4.5× 107 Mg C with a mean annual carbon sequestration of 1.5× 106 Mg C. The carbon density in the four sub-regions decreased in the following order: the Loess Plateau Sub-region, the North China Sub-region, the Northeast China Sub-region and the Inner Mongolia-Xinjiang Sub-region. The paucity of studies and data availability on the large-scale carbon sequestration of shrub species suggests this study provides a baseline reference for future research in this area.
Carbon Storage Capacity of Different Plantation Types Under Sands­torm Source Control Program in Hebei Province, China
SHEN Huitao, ZHANG Wanjun, YANG Xue, LIU Xiuping, CAO Jiansheng, ZENG Xinhua, ZHAO Xin, CHEN Xuexun, ZHANG Wenxi
2014, 0(4): 454-460. doi: 10.1007/s11769-014-0699-9
Afforestation and reforestation are effective and ecological ways of mitigating elevated atmospheric carbon dioxide (CO2) concentration and increasing carbon (C) storage in terrestrial ecosystems. In this study, we measured the above-ground (tree, herbaceous plants and litter) and below-ground (root and soil) C storage in an aspen plantation(Populus davidiana)monoculture (PD), a larch plantation (Larix pincipis-rupprechtii) monoculture (LP), a pine plantation (Pinus tabulaeformis) monoculture (PT), a larch and birch mixed plantation (L. pincipis-rupprechtii and Betula platyphlla mixed) (MLB), and an apricot plantation (Armeniaca sibirica) monoculture (AS) under the Desertification Combating Program in Hebei Province, the northern China. The objective was to assess the effect of afforestation species on ecosystem C pools of different plantation types. Results showed that C storage of LP stand (258.0 Mg/ha) and MLB (163.4 Mg/ha) were significantly higher than the C storage in PD (45.5 Mg/ha), PT (58.9 Mg/ha) and AS (49.4 Mg/ha), respectively. Soil C was the main carbon pool of the ecosystem C storage in the five plantation stands, ranging from 31.4 Mg/ha to 232.5 Mg/ha, which accounted for 69.0%-90.1% of the total ecosystem C storage. The C storage in tree layer was about 5.2%-23.2% of ecosystem C storage. The herbaceous plants and litter layers contained 1.0%-6.0% and 1.5%-3.3% of ecosystem C storage, respectively. Our results suggest that tree species should be incorporated to accurately develop regional C budget of afforestation program, and also imply that substantial differences in ecosystem C stocks among plantation types can facilitate decision making on C management.
Change of Soil Organic Carbon after Cropland Afforestation in ‘Beijing- Tianjin Sandstorm Source Control’ Program Area in China
ZENG Xinhua, ZHANG Wanjun, LIU Xiuping, CAO Jiansheng, SHEN Huitao, ZHAO Xin, ZHANG Nannan, BAI Yuru, Yi Mei
2014, 0(4): 461-470. doi: 10.1007/s11769-014-0701-6
Land use change is one of the major factors that affect soil organic carbon (SOC) variation and global carbon balance. However, the effects of land use change on SOC are always variable. In this study, using a series of paired-field experiments, we estimated the effects of revegetation types and environmental conditions on SOC stock and vertical distribution after replacement of cropland with poplar (Populus tomentosa) and korshinsk peashrub (Caragana korshinskii) in three climate regions (Chifeng City, Fengning City and Datong City of the ‘Beijing-Tianjin Sandstorm Source Control’ (BTSSC) program area. The results show that SOC sequestration rate ranges from 0.15 Mg/(ha·yr) to 3.76 Mg/(ha·yr) in the soil layer of 0-100 cm in early stage after cropland afforestation in the BTSSC program area. The SOC accumulation rates are the highest in Fengning for both the two vegetation types. Compared to C. korshinskii, P. tomentosa has greater effects on SOC accumulation in the three climate regions, but significantly greater effect only appears in Datong. The SOC density increases by 20%-111% and 15%-59% for P. tomentosa and 9%-63% and 0-73% for C. korshinskii in the 0-20 cm and 20-100 cm soil layers, respectively. Our results indicate that cropland afforestation not only affects SOC stock in the topsoil, but also has some effects on subsoil carbon. However, the effect of cropland afforestation on SOC accumulation varied with climate regions and revegetation types. Considering the large area of revegetation and relatively high SOC accumulation rate, SOC sequestration in the BTSSC program should contribute significantly to decrease the CO2 concentration in the atmosphere.
Vegetation Traits and Soil Properties in Response to Utilization Patterns of Grassland in Hulun Buir City, Inner Mongolia, China
LIU Miao, LIU Guohua, WU Xing, WANG Hao, CHEN Li
2014, 0(4): 471-478. doi: 10.1007/s11769-014-0706-1
Numerous studies have focused on vegetation traits and soil properties in grassland, few of which concerned about effects of human utilization patterns on grassland yet. Thus, this study hypothesized that human disturbance (e.g., grazing, mowing and fencing) triggered significant variation of biomass partitioning and carbon reallocation. Besides, there existed some differences of species diversity and soil fertility. To address these hypotheses of grassland with diverse utilization patterns in Hulun Buir City, Inner Mongolia, China, we sampled in situ about aboveground biomass (AGB) and belowground biomass (BGB) to evaluate their biomass allocation. Species diversity and soil properties were also investigated. Subsequently, we discussed the relationship of species diversity with environmental conditions, using data collected from 23 sites during the ecological project period of Returning Grazing Lands to Grasslands (RGLG) program. The results were as follows: 1) both AGB and BGB were lower on grazing regime than those on fencing and mowing, but the ratio of root-to-shoot (R/S) was higher on grazing regime than the other two utilization patterns; 2) neither of evenness and Simpson Index was different significantly among all grassland utilization patterns in desert, typical, and meadow grassland at 0.05. In meadow grassland, species richness of fencing pattern was significantly higher than that of grazing pattern (p< 0.05); 3) both of soil organic carbon content and soil available phosphorous content were increased significantly on fencing pattern than grazing pattern (p< 0.05) in desert grassland, and mowing patterns increased the soil nutrients (soil organic carbon, soil total phosphorous, soil available phosphorous, and soil total nitrogen) significantly compared with grazing patterns (p< 0.05) in typical grassland. However, there were no significant differences among utilization patterns in meadow grassland. In conclusion, both of AGB and BGB were increased significantly by fencing. Moreover, species diversity and soil nutrients can be promoted via mowing and fencing. This study suggested that implementation of Ecological Project played a positive role in sustainable grassland utilization of Hulun Buir City and a strong positive influence on the entire temperate grassland.
Effects of Grazing Exclusion on Soil Carbon and Nitrogen Storage in Semi-arid Grassland in Inner Mongolia, China
WU Xing, LI Zongshan, FU Bojie, LU Fei, WANG Dongbo, LIU Huifeng, LIU Guohua
2014, 0(4): 479-487. doi: 10.1007/s11769-014-0694-1
The semi-arid grasslands in Inner Mongolia, China have been degraded by long-term grazing. A series of ecological restoration strategies have been implemented to improve grassland service. However, little is known about the effect of these ecological restoration practices on soil carbon and nitrogen storage. In this study, characteristics of vegetation and soil properties under continued grazing and exclusion of livestock for six years due to a nationwide conservation program—‘Returning Grazing Lands to Grasslands (RGLG)’ were examined in semi-arid Hulun Buir grassland in Inner Mongolia, China. The results show that removal of grazing for six years resulted in a significant recovery in vegetation with higher above and below-ground biomass, but a lower soil bulk density and pH value. After six years of grazing exclusion, soil organic C and total N storage increased by 13.9% and 17.1%, respectively, which could be partly explained by decreased loss and increased input of C and N to soil. The effects of grazing exclusion on soil C and N concentration and storage primarily occurred in the upper soil depths. The results indicate that removal of grazing pressure within the RGLG program was an effective restoration approach to control grassland degradation in this region. However, more comprehensive studies are needed to evaluate the effectiveness of the RGLG program and to improve the management strategies for grassland restoration in this area.
Effects of Grazing Exclusion on Plant Productivity and Soil Carbon, Nitrogen Storage in Alpine Meadows in Northern Tibet, China
XIONG Dingpeng, SHI Peili, SUN Yinliang, WU Jianshuang, ZHANG Xianzhou
2014, 0(4): 488-498. doi: 10.1007/s11769-014-0697-y
Grazing exclusion is widely adopted in restoring degraded alpine grasslands on the Qinghai-Tibetan Plateau. However, its effectiveness remains poorly understood.In this study, we investigated the effects of grazing exclusion on plant productivity, species diversity and soil organic carbon (SOC) and soil total nitrogen (STN) storage along a transect spanning from east to west of alpine meadows in northern Tibet, China. After six years of grazing exclusion, plant cover, aboveground biomass (AGB), belowground biomass (BGB), SOC and STN were increased, but species diversity indices declined. The enhancement of AGB and SOC caused by grazing exclusion was correlated positively with mean annual precipitation (MAP). Grazing exclusion led to remarkable biomass increase of sedge species, especially Kobresia pygmaea, whereas decrease of biomass in forbs and no obvious change in grass, leguminous and noxious species. Root biomass was concentrated in the near surface layer (10 cm) after grazing exclusion. The effects of grazing exclusion on SOC storage were confined to shallow soil layer in sites with lower MAP. It is indicated that grazing exclusion is an effective measure to increase forage production and enhance soil carbon sequestration in the studied region. The effect is more efficient in sites with higher precipitation. However, the results revealed a tradeoff between vegetation restoration and ecological biodiversity. Therefore, carbon pools recover more quickly than plant biodiversity in the alpine meadows. We suggest that grazing exclusion should be combined with other measures to reconcile grassland restoration and biodiversity conservation.