[Show abstract][Hide abstract] ABSTRACT: Livelihood vulnerability in environmentally fragile areas is emerging as a key issue due to its positive feedback to environmental degradation. Assessment of sustainable livelihoods is a crucial prerequisite for targeting interventions. However, aggregated analysis usually obtained ambiguous conclusions because they ignored the heterogeneity of rural households. Here, we evaluated the livelihood sustainability of different rural households by constructing an improved Livelihood Sustainability Index (LSI) in hilly red soil erosion areas of southern China. Changting County was selected as the study case by virtue of its unique representativeness in soil erosion and poverty. The results showed that livelihood sustainability among rural households was far from equivalent. Different from previous studies, higher nonfarm income share was not always consistent with higher extent of livelihood sustainability. Besides nonfarm employment, agricultural specialization could be another viable pathway to attain sustainable livelihoods. We also found that intergenerational sustainability was one primary cause for long-term livelihood differentiation of rural households. The poor education in rural areas would aggravate livelihood vulnerability of the poor and threaten the sustainable livelihoods of specialized agricultural households. Policy implications include further investment in rural infrastructure, irrigation and drainage, and stimulus for land transfer and concentration to facilitate agrarian specialization; enhancing investment in rural education to improve intergenerational sustainability; as well as targeting of the most vulnerable households, for example, promoting development of social insurance, social relief, and medical services for orphans and widows.
Full-text · Article · May 2016 · Ecological Indicators
[Show abstract][Hide abstract] ABSTRACT: Litter decomposition is a key process for ecosystem fertility and carbon (C) balance, key uncertainties remain about how this fundamental process is affected by microbial community composition. Evidence is growing that plant litter generally decays fastest at the site from which it was derived, owing to the presence of specialized microbial communities that can decompose specific types of litter. The objectives were to determine the impact of sites on litter decomposition and to examine the relationships among microbial community composition, litter chemistry, and decomposition rates of coniferous Cunninghamia lanceolata litter of higher lignin content and broadleaved Mytilaria laosensis litter of lower lignin content at different stages of decomposition under plantations of the respective species. The study was conducted for 16 months using a randomized split-plot design experiment with four replications of all combinations of treatments, the treatments being litter type and site (plantation species). The results showed that decomposition rates were the same for all combinations of amendments and sites, meaning that both sites had microbial communities equally capable or adapted to decompose plant substrates it had not previously encountered, despite marked differences in soil microbial communities between sites and the chemistry of the two litter types. Initial M. laosensis litter was of lower lignin content and C:N ratio and decomposed faster in the first 8 months than C. lanceolata litter under either M. laosensis or C. lanceolata forest. Litter decomposition was significantly slower in the environment from which it was derived between month 8 and month 16. This could be attributed to the exceptionally poor decomposition of M. laosensis litter which was significantly higher lingnin content at month 8 under M. laosensis than under C. lanceolata due to the impact of site on preferential degradation of litter C. Decomposers under C. lanceolata forest were more efficient in degrading alkyl C and/or less efficient in degrading O-alkyl C than those under M. laosensis forest during the experimental period, which might be related to the microbial community composition in the decomposing litter. Our study clearly showed interactions between changing litter chemistry and litter microbial communities and their impacts on litter decomposition. Site was not important in impacting decomposition rates, but played an important role in the preferential degradation of C components. However, further studies are needed to examine the conditions in forests where more rapid litter decomposition beneath the parent species than another species is considered to be common, in order to improve our ability to model decomposition globally.
No preview · Article · May 2016 · Applied Soil Ecology
[Show abstract][Hide abstract] ABSTRACT: The replacement of native forests by tree plantations is increasingly common globally, especially in tropical and subtropical areas. Improving our understanding of the long-term effects of this replacement on soil organic carbon (SOC) remains paramount for effectively managing ecosystems to mitigate anthropogenic carbon emissions. Meta-analyses imply that native forest replacement usually reduces SOC stocks and may switch the forest from a net sink to a net source of atmospheric carbon. Using a long-term chronosequence during which areas of subtropical native forest were replaced by Chinese fir, we show by direct measurement that plantations have significantly accelerated SOC turnover compared with native forest, an effect that has persisted for almost a century. The immediate stimulation of SOC decomposition was caused by warmer soil before the closure of the plantation’s canopy. Long-term reductions in SOC mean residence times were coupled to litter inputs. Faster SOC decomposition was associated with lower soil microbial carbon use efficiency, which was due to smaller litter inputs and reduced nutrient availabilities. Our results indicate a previously unelucidated control on long-term SOC dynamics in native forests and demonstrate a potential constraint on climate mitigation when such forests are replaced by plantations.
Full-text · Article · Jan 2016 · Scientific Reports
[Show abstract][Hide abstract] ABSTRACT: Subsoils store over 50% of the total soil organic carbon (SOC) in terrestrial ecosystems, but the stability of this fraction of SOC and the contributions of the associated soil microbes to C dynamics remain unclear. A natural evergreen broad-leaved forest and a Chinese fir plantation converted from natural forest in Fujian Province, China, were used to test if differences in soil C decomposability and soil microbial characteristics between topsoil (0-10 cm) and subsoil (40-60 cm) were associated with the prevalence of microbes expressing a characteristic growth strategy (r- versus K-strategies). A combined approach, including modified Michaelis-Menten kinetics, substrate-induced respiration, soil C decomposition, soil basal respiration measurements, and phospholipid fatty acid (PLFA) analysis was used. Compared with topsoil, the subsoil had 3.6 and 1.6 times higher concentrations of readily decomposable C substrate (as glucose equivalents) estimated in terms of Michaelis-Menten kinetics, and 2.7 and 2.8 times faster mineralization per unit SOC, respectively, under the natural and plantation forests. Soil microbes in the subsoil tended to be r-strategist-dominated in both forests, characterized by higher maximum rate of soil respiration and half-saturation constant, higher maximal specific growth rate, higher relative abundance of Gram-negative bacteria, and higher metabolic quotient, the latter indicating smaller C use efficiency. In contrast, soil microbes in the topsoil tended to be K-strategist-dominated. Soil microbial communities shifted from K-strategy to r-strategy in the topsoil of Chinese fir plantation, reflecting lower microbial C use efficiencies, compared with natural forest. It is concluded that a substantial pool of easily decomposable C accumulated in subsoils of these two subtropical forests, a product partly of r-strategists replacing K-strategy microbes. These findings improve our understanding of the mechanisms regulating C dynamics between topsoil and subsoil and have implications for the effects of forest conversion on soil C storage.
Full-text · Article · Jan 2016 · Soil Biology and Biochemistry
[Show abstract][Hide abstract] ABSTRACT: The mechanisms about high soil organic C (SOC) loss from deep soil when natural forests are converted into forest plantations are poorly understood. In this study, we added 13C-glucose to the top soil (0–10 cm) and deep soil (60–80 cm) in order to investigate the OC mineralization and priming effect (PE) of soil under an evergreen broad-leaved forest (BF) or under Chinese fir (CF) plantation. The PE was quantified from the variation in soil C-CO2 evolution caused by adding 13C-glucose to soil. The conversion of BF into CF decreased the SOC with the soil depth significantly. The cumulative C mineralization of the top soil was significantly higher in BF than in CF (794.2 and 503.6 mg kg−1 soil, respectively), but no significant difference was found in the deep soil layer (145.2 and 150.4 mg kg−1 soil for BF and CF). Specific mineralization rate, expressed as gram C per kilogram SOC, was the highest in the deep soil of CF (36.7 g kg−1 SOC) and the lowest in top soil of BF (21.1 g kg−1 SOC), probably because the SOC was less recalcitrant to microbial decomposition in deeper than top layer of the CF due to its relatively high concentration of labile C. The PE was higher in deep layer than in top layer of BF soil (166.8 and 116.7 mg kg−1, respectively), whereas the opposite was observed in CF (100.1 and 153.9 mg kg−1, respectively). The PE was significantly correlated to the specific C mineralization (r = −0.92, P < 0.001), suggesting that PE increased significantly with SOC recalcitrance, defined as the specific mineralization rate of SOC. Moreover, Gram-negative bacteria (cy17:0), fungi (18:1ω9c), and actinomycete (10Me19:0) phospholipid fatty acids (PLFAs) were positively correlated with PE intensity, indicating that these microbial groups may promote positive SOC priming. We inferred that the priming is mainly controlled by the soil organic matter (SOM) recalcitrance and soil microbial community composition. Probably, the deep soil C losses were due to the increase in available C in the soil profile by forest conversion associated with changes in microbial diversity and increase in recalcitrant C losses in the deep soil layer.
Full-text · Article · Jun 2015 · Biology and Fertility of Soils
[Show abstract][Hide abstract] ABSTRACT: Soil erosion is by far the greatest cause of land degradation and other environmental and socio-economic problems in China. Although various conservation methods are widely utilized to reduce soil erosion and to sustain agricultural production, the cost-effectiveness and selection of these methods is less known. Using our survey and ecological data, this study evaluated four soil and water conservation methods in Changting County, Southeast China. The results show that the disparity of conservation costs is much larger than that of ecological benefits. Planting fruit trees is a kind of conservation through primarily economic development. Closing hillsides for afforestation is most cost-effective, followed by forest fertilizing, and planting trees and grass. Our findings suggest that comparatively lower cost conservation methods, for example closing hillsides for afforestation, should be considered in priority if initial ecological conditions can meet the requirements of the method. This article is protected by copyright. All rights reserved.
No preview · Article · May 2015 · Land Degradation and Development
[Show abstract][Hide abstract] ABSTRACT: Geographical detector models provide a quantitative approach for evaluating spatial correlations among ecological factors, population density and landscape connectivity. Here, we used a geographical model to assess the influence of different gradients of urbanization, human activities and various environmental factors on the connectivity of urban forest landscapes in Xiamen, China from 1996 to 2006. Our overarching hypothesis is that human activity has modified certain ecological factors in a way that has affected the connectivity of urban forest landscapes. Therefore, spatiotemporal distributions of landscape connectivity should be similar to those of ecological factors and can be represented quantitatively. Integral indices of connectivity and population density were employed to represent urban forest landscape connectivity and human activity, respectively. We then simulated the spatial relationship between forest patches and population density with Conefor 2.6 software. A geographical detector model was used to identify the dominant factors that affect urban forest landscape connectivity. The results showed that a distance of 600 m was the threshold of node importance. Mean annual temperature, mean annual precipitation, elevation, patch area, population density and dominant species had significant effects on the node importance. Mean annual temperature was more significant than population density in controlling the spatial pattern of the delta of the integral index of connectivity (dIIC). The spatial interaction between population density and various ecological factors as well as their linearly enhanced or nonlinearity enhanced urban forest landscape connectivity. In conclusion, a combination of graph theory and geographical detector models is effective for quantitatively evaluating interactive relationships among ecological factors, population density and landscape connectivity.
Full-text · Article · Dec 2014 · Landscape Ecology
[Show abstract][Hide abstract] ABSTRACT: Background and aims
Carbon (C) loss from coarse woody debris (CWD) may be important in forest ecosystem C budgets, yet few studies have assessed CWD respiration in natural evergreen broad-leaved forests in subtropical China. The objectives of this study were (1) to quantify the respiration rates of downed logs (R
log) and Q
10 of different tree species at various stages of decay, (2) to assess the effect of microclimatic (log temperature and moisture) variables on R
log and (3) to estimate annual C flux of the CWD logs in four natural evergreen broad-leaved forest types of Altingia gracilipes Hemsl. (ALG), Tsoongiodendron odorum Chun (TSO), Castanopsis carlesii (Hemsl.) Hayata (CAC) and Cinnamomum chekiangense Nakai (CIC) in southern China.
A dynamic chamber method was used to measure R
log in four decay classes (DCs) (ranging from freshly felled logs in DC 1 to highly decomposed logs in DC 4). The effects of changes in log temperature (T
log) and log moisture content (M
log) on R
log were determined and annual R
log exhibited a distinct seasonal pattern, and it was predominantly controlled by the log temperature. The temperature sensitivity of R
log to log temperature as indicated by Q
10 ranged from 1.82 to 2.86 and was variable among decay classes and forests. Significant relationships between moisture content of logs and R
log were only observed for logs in the ALG (P = 0.001), TSO (P = 0.002) and CIC (P
[Show abstract][Hide abstract] ABSTRACT: Aims
This study aimed to determine the influence of tree species on soil microbial community structure.
We conducted a litter and root manipulation and a short-term nitrogen (N) addition experiment in 19-year-old broadleaf Mytilaria laosensis (Hamamelidaceae) and coniferous Chinese fir (Cunninghamia lanceolata) plantations in subtropical China. Phospholipid fatty acid (PLFA) analysis was used to examine treatment effects on soil microbial community structure. Redundancy analysis (RDA) was performed to determine the relationships between individual PLFAs and soil properties (soil pH, carbon (C) and N concentration and C:N ratio).
Soil C:N ratio was significantly greater in M. laosensis (17.9) than in C. lanceolata (16.2). Soil C:N ratio was the key factor affecting the soil microbial community regardless of tree species and the litter, root and N treatments at our study site. The fungal biomarkers, 18:1ω9 and 18:2ω6,9 were significantly and positively related to soil C:N ratio and the abundance of bacterial lipid biomarkers was negatively related to soil C:N ratio. N addition for 8 months did not change the biomass and structure of the microbial community in M. laosensis and C. lanceolata soils. Soil nutrient availability before N addition was an important factor in determining the effect of N fertilization on soil microbial biomass and activity. PLFA analysis showed that root exclusion significantly decreased the abundance of the fungal biomarkers and increased the abundance of the Gram-positive bacteria. Rootless plots had a relatively lower Gram-positive to Gram-negative bacteria ratio and a higher fungi to bacteria ratio compared to the plots with roots under both M. laosensis and C. lanceolata. The response of arbuscular mycorrhizal fungi (16:1ω5) to root exclusion was species-specific.
These observations suggest that soil C:N ratio was an important factor in influencing soil microbial community structure. Further studies are required to confirm the long-term effect of tree species on soil microbial community structure.
[Show abstract][Hide abstract] ABSTRACT: • Context
Coarse woody debris (CWD, ≥10 cm in diameter) is an important structural and functional component of forests. There are few studies that have estimated the mass and carbon (C) and nitrogen (N) stocks of CWD in subtropical forests. Evergreen broad-leaved forests are distributed widely in subtropical zones in China.
This study aimed to evaluate the pools of mass, C and N in CWD in five natural forests of Altingia gracilipes Hemsl., Tsoongiodendron odorum Chun, Castanopsis carlesii (Hemsl.) Hayata, Cinnamomum chekiangense Nakai and Castanopsis fabri Hance in southern China.
The mass of CWD was determined using the fixed-area plot method. All types of CWD (logs, snags, stumps and large branches) within the plot were measured. The species, length, diameter and decay class of each piece of CWD were recorded. The C and N pools of CWD were calculated by multiplying the concentrations of C and N by the estimated mass in each forest and decay category.
Total mass of CWD varied from 16.75 Mg ha−1 in the C. fabri forest to 40.60 Mg ha−1 in the A. gracilipes forest; of this CWD, the log contribution ranged from 54.75 to 94.86 %. The largest CWD (≥60 cm diameter) was found only in the A. gracilipes forest. CWD in the 40–60 cm size class represented above 65 % of total mass, while most of CWD accumulations in the C. carlesii, C. chekiangense and C. fabri forests were composed of pieces with diameter less than 40 cm. The A. gracilipes, T. odorum, C. carlesii and C. chekiangense forests contained the full decay classes (from 1 to 5 classes) of CWD. In the C. fabri forest, the CWD in decay classes 2–3 accounted for about 90 % of the total CWD mass. Increasing N concentrations and decreasing densities, C concentrations, and C:N ratios were found with stage of decay. Linear regression showed a strong correlation between the density and C:N ratio (R
2 = 0.821). CWD C-stock ranged from 7.62 to 17.74 Mg ha−1, while the N stock varied from 85.05 to 204.49 kg ha−1. The highest overall pools of C and N in CWD were noted in the A. gracilipes forest.
Differences among five forests can be attributed mainly to characteristics of the tree species. It is very important to preserve the current natural evergreen broad-leaved forest and maintain the structural and functional integrity of CWD.
[Show abstract][Hide abstract] ABSTRACT: To fully understand how soil respiration is partitioned among its component fluxes and responds to climate, it is essential to relate it to belowground carbon allocation, the ultimate carbon source for soil respiration. This remains one of the largest gaps in knowledge of terrestrial carbon cycling. Here, we synthesize data on gross and net primary production and their components, and soil respiration and its components, from a global forest database, to determine mechanisms governing belowground carbon allocation and their relationship with soil respiration partitioning and soil respiration responses to climatic factors across global forest ecosystems. Our results revealed that there are three independent mechanisms controlling belowground carbon allocation and which influence soil respiration and its partitioning: an allometric constraint; a fine-root production vs. root respiration trade-off; and an above- vs. belowground trade-off in plant carbon. Global patterns in soil respiration and its partitioning are constrained primarily by the allometric allocation, which explains some of the previously ambiguous results reported in the literature. Responses of soil respiration and its components to mean annual temperature, precipitation, and nitrogen deposition can be mediated by changes in belowground carbon allocation. Soil respiration responds to mean annual temperature overwhelmingly through an increasing belowground carbon input as a result of extending total day length of growing season, but not by temperature-driven acceleration of soil carbon decomposition, which argues against the possibility of a strong positive feedback between global warming and soil carbon loss. Different nitrogen loads can trigger distinct belowground carbon allocation mechanisms, which are responsible for different responses of soil respiration to nitrogen addition that have been observed. These results provide new insights into belowground carbon allocation, partitioning of soil respiration, and its responses to climate in forest ecosystems and are, therefore, valuable for terrestrial carbon simulations and projections.
Full-text · Article · Apr 2014 · Global Change Biology
[Show abstract][Hide abstract] ABSTRACT: Burned and unburned mineral soils (0–10 cm) from a 40-year-old Chinese fir (Cunninghamia lanceolata) forest in Nanping, Fujian, China were incubated for 90 days at different temperatures (25 °C and 35 °C) and humidity [25%, 50%, and 75% of water holding capacity (WHC)] conditions. Carbon (C) mineralization of all soils was determined using CO2 respiration method. The results showed that CO2 evolution rates of the burned and control soils exhibited similar temporal patterns, and similar responses to temperature and moisture. CO2 evolution rates for all soil samples decreased with incubation time. At different humidity conditions, average rate of C mineralization and cumulative mineralized C from burned and control soils were significantly higher at 35 °C than at 25 °C. This implied that C mineralization was less sensitive to soil moisture than to temperature. In both soils at 25 °C or 35 °C, the amount of soil evolved CO2 over the 90 days incubation increased with increasing moisture content from 25% to 75% WHC. A temperature coefficient (Q10) varied with soil moisture contents. The maximum values recorded for Q10 were 1.7 in control soil and 1.6 in burned soil both at 25% WHC. However, there were no significant differences in Q10 values between the control and burned soils over all moisture ranges (P > 0.05). The data of cumulative C–CO2 released from control and burned soils were fitted to two different kinetic models. The two simultaneous reactions model described mineralization better than the first-order exponential model, which reflected the heterogeneity of substrate quality. Based on these results, it is possible to conclude that temperature and moisture are important in the controls of C mineralization, and the combined effects of these variables need to be considered to understand and predict the response of CO2 release in subtropical ecosystems to climate change.
Full-text · Article · Feb 2014 · Acta Ecologica Sinica
[Show abstract][Hide abstract] ABSTRACT: Understanding the allocation of gross primary production (GPP) and its response to climate is essential for improving terrestrial carbon (C) modelling. Here, we synthesize data on component GPP fluxes from a worldwide forest database to determine the allocation patterns of GPP across global gradients in climate and nitrogen deposition (Ndep ). Our results reveal that allocation of GPP is governed in an integrated way by allometric constraints and by three trade-offs among GPP components: wood production (NPPwood ) vs fine-root production (NPPfroot ), NPPwood vs foliage production (NPPfoliage ), and autotrophic respiration (Ra ) vs all biomass production components. Component fluxes were explained more by allometry, while partitioning to components was related more closely to the trade-offs. Elevated temperature and Ndep benefit long-term woody biomass C sequestration by stimulating allometric partitioning to wood. Ndep can also enhance forest C use efficiency by its effects on the Ra vs biomass production trade-off. Greater precipitation affects C allocation by driving the NPPwood vs NPPfoliage trade-off toward the latter component. These results advance our understanding about the global constraints on GPP allocation in forest ecosystems and its climatic responses, and are therefore valuable for simulations and projections of ecosystem C sequestration.
[Show abstract][Hide abstract] ABSTRACT: We investigated microbial biomass and composition (lipid profile), mineral N pools and soil physicochemical parameters in the top 5-cm soils 19 years after reforestation of Chinese fir (Cunninghamia lanceolata (Lamb.) Hook) woodland with itself or a native broadleaf species, Mytilaria laosensis. The results suggested that tree species transition had a large impact on microbial biomass and a small impact on the composition of the microbial community as indicated by the relative abundance of individual lipid biomarkers. Between November 2011 and October 2012, there was on average 50% greater microbial biomass carbon (C) measured by the fumigation extraction procedure under M. laosensis than under C. lanceolata. A one-time measurement of phospholipid fatty acids in soil samples collected in May 2012 suggested M. laosensis plots had greater content of individual lipid biomarkers than C. lanceolata plots. Using a litter manipulation experiment, we found that the increases in content of lipid biomarkers under M. laosensis can be attributed to changed litter chemistry. Analysis of soil mineral N pools indicated that there were significantly lower +4NHNH4+ and −3NONO3− pools as well as potential net N mineralization rates in M. laosensis soil than in C. lanceolata soil. The relationships among N dynamics, soil chemistry and microbial properties were analysed. The results suggested tree species induced differences in soil N mineralization rates and mineral N pools were related to labile C availability, soil C:N ratio and the composition of the microbial community. Our data of mineral N pools and soil δ15N implied that the transition of land use from C. lanceolata to M. laosensis leads to an enhanced N retention in the plantation.
[Show abstract][Hide abstract] ABSTRACT: Recovery of carbon stocks after afforestation in degraded lands provides a management practice to mitigate rising atmospheric carbon dioxide concentrations, however carbon accumulation after afforestation of severely eroded lands is poorly understood. Large areas of the red soils in subtropical China suffer from severe erosion and have very low carbon density. We investigated above- and below-ground carbon pools in bare land on a severely eroded red soil (BL), a Pinus massoniana plantation that had been established on bare land in 1981(PM) and a nearby secondary forest (SF) in southeastern China. The ecosystem carbon pool in PM (130.1 ± 7.2 Mg C ha−1) was 10 times higher than in BL (13.0 ± 1.3 Mg C ha−1), and 22% lower than that in SF (166.7 ± 7.0 Mg C ha−1) (p < 0.05). The above ground biomass carbon pool was 91.9 ± 4.8 Mg C ha−1 in PM, similar to 98.2 ± 5.5 Mg C ha−1 in SF. The soil organic carbon (SOC) pool (to 1 m depth) in PM (38.2 ± 3.4 Mg C ha−1) was 2.9 times higher than that in BL (13.0 ± 1.3 Mg C ha–1), but was significantly lower than that in SF (68.5 ± 2.5 Mg C ha–1). About 70% of the organic C to 1 m depth was stored in the top 40 cm in the two forests. The storage of light fraction organic carbon (LFOC) at the 0–60 cm depth in PM was significantly higher than that in BL, but not significantly different from that in SF. PM had significantly higher proportions of LFOC to SOC for all soil depths in comparison with BL and SF (p < 0.05). The mean accumulation rates of ecosystem carbon pools, aboveground biomass carbon pools, and SOC pools in PM were 4.88 ± 0.25, 3.83 ± 0.16, and 1.05 ± 0.09 Mg C ha−1 yr−1, respectively. Our results indicate that afforestation of severely eroded red soils with P. massoniana may be a successful forest management practice to achieve rapid carbon accumulation.
[Show abstract][Hide abstract] ABSTRACT: The relationship between landscape patterns and functions is the central research theme of landscape ecology and forest management. This study assesses the interactive relationship of landscape heterogeneity with the carbon stock of urban forests in the city of Xiamen, Fujian Province, China, using spatial and statistical analyses. The objectives of this study are to explore the most appropriate scale for studying urban landscape patterns in Xiamen, analyze the dynamics of forested landscape heterogeneity at different scales, and identify suitable landscape metrics that are closely related to and can be used to describe vegetation carbon density. This study is based on data from 31,933 plots measured during the years 1972, 1996, and 2006 and collected as part of the Chinese National Forest Resource Planning and Inventory Program. A total of 12 landscape metrics were used to quantify spatial patterns and were subsequently related to vegetation carbon density. The results show that the most appropriate scale for landscape pattern analysis is 80 km2. With urbanization advancing between 1972 and 1996, landscape heterogeneity at both class and landscape levels showed a significant increase and then remained stable from 1996 to 2006. Shannon’s diversity index was the most sensitive landscape metric among all selected landscape heterogeneity metrics, and its ability to explain the variation of carbon density was better than that of forest types. This study clearly shows that information on spatial patterns of landscape heterogeneity is important for urban forest landscape planning to achieve forest carbon objective.
[Show abstract][Hide abstract] ABSTRACT: Research on the effects of urban sprawl on carbon stocks within urban forests can help support policy for sustainable urban design. This is particularly important given climate change and environmental deterioration as a result of rapid urbanization. The purpose of this study was to quantify the effects of urban sprawl on dynamics of forest carbon stock and density in Xiamen, a typical city experiencing rapid urbanization in China. Forest resource inventory data collected from 32,898 patches in 4 years (1972, 1988, 1996 and 2006), together with remotely sensed data (from 1988, 1996 and 2006), were used to investigate vegetation carbon densities and stocks in Xiamen, China. We classified the forests into four groups: (1) forest patches connected to construction land; (2) forest patches connected to farmland; (3) forest patches connected to both construction land and farmland and (4) close forest patches. Carbon stocks and densities of four different types of forest patches during different urbanization periods in three zones (urban core, suburb and exurb) were compared to assess the impact of human disturbance on forest carbon. In the urban core, the carbon stock and carbon density in all four forest patch types declined over the study period. In the suburbs, different urbanization processes influenced forest carbon density and carbon stock in all four forest patch types. Urban sprawl negatively affected the surrounding forests. In the exurbs, the carbon stock and carbon density in all four forest patch types tended to increase over the study period. The results revealed that human disturbance played the dominant role in influencing the carbon stock and density of forest patches close to the locations of human activities. In forest patches far away from the locations of human activities, natural forest regrowth was the dominant factor affecting carbon stock and density.
Full-text · Article · Nov 2012 · Journal of Environmental Management
[Show abstract][Hide abstract] ABSTRACT: This paper systematically analyzes the driving forces and mechanism of fuelwood substitution and related ecological consequences in an under-developed county in rural Southeast China. Based on 358 respondents from rural households in Changting County, as well as additional statistical data, we present strong evidence in support of the argument that changes in the livelihoods of rural households lead to fuelwood substitution and finally, hilly ecosystem restoration. Important factors influencing fuelwood substitution are closely linked with changes in rural livelihoods: off-farm employment and agricultural specialization. Therefore, these changes are argued to be the primary driving force of fuelwood substitution. Reasons include the increasing opportunity costs of fuelwood collection, increases in household income, and decreases in household energy consumption for cooking, feeding and heating. Such changes have unexpectedly caused significant progress in hilly ecosystem restoration, particularly in mitigation of soil erosion and forest degradation. Thus, it is suggested that the progressive change and improvement in the livelihoods of rural households should be included in the mix of policies intended to restore hilly ecosystems.
Full-text · Article · Jun 2012 · Renewable and Sustainable Energy Reviews