Typical Subtropical Forests Research Articles

庐山亚热带典型森林植被类型下土壤肥力评价

庐山亚热带典型森林植被类型下土壤肥力评价

C:N stoichiometry of stable and labile organic compounds determine priming patterns

Priming effects (PE) can greatly influence global carbon (C) storage in soil and lead to climate feedbacks by accelerating the decomposition of organic matter (OM). Although nitrogen (N) availability can alter the magnitude and direction of priming (stoichiometric constrains), it remains unclear whether additions of NO3− (nitrate) and NH4+ (ammonium) have distinct effects on the decomposition of various OM. Thus, the aims of this study were to investigate the responses of OM decomposition along a decay continuum (i.e. decreasing decomposition degree) to labile C and N inputs and determine the PE induced by the two N forms. Four OM forms, namely leaf litter, wood litter, organic soil horizon, and mineral soil, with a broad range of C:N ratios were collected along a decay continuum in a typical subtropical forest and incubated for 38 days with labile C (13C labeled glucose) and N (NO3−) additions. Based on the very broad range of C:N ratios in OM in soil and inputs of labile C and N, we demonstrated the OM decomposition within a decay continuum as well as PE intensities and the thresholds for the switch of PE directions. In contrast to NH4+ additions, NO3− generally accelerated the decomposition of all OM. Priming of plant litter was dependent on the C:N ratios of the labile inputs. However, leaf litter decomposition was more controlled by N addition than wood litter. Glucose addition greatly increased the priming of OM decomposition in soils, demonstrating energy limitation for microorganisms. Distinct priming patterns were observed between NO3− and NH4+ additions, both for the individual OM types and for all four types of OM. On a basis of C balance between primed C and the remaining added C, PE induced by labile C and N inputs can increase or reduce C sequestration depending on C:N stoichiometric ratios of labile inputs. Our findings provide important insights into the specific role of NO3− or NH4+ together with labile C inputs (e.g. from root exudation), and thus changes in the composition of deposited N (atmospheric deposition and fertilization) may induce distinct climate feedbacks.

Divergent responses of soil organic carbon accumulation to 14 years of nitrogen addition in two typical subtropical forests

Developing an understanding of the response of soil organic carbon (SOC) to N addition is critical to quantify and predict the terrestrial carbon uptake under increasing N deposition in the future. However, results from field studies on the response of SOC content and composition to N addition are highly variable across different ecosystems. The interpretation of SOC responses to N addition are often complicated by the differences in climate, soil substrate and other factors. To address this question, we measured SOC and its components in adjacent broadleaved and coniferous subtropical forests after 14 years of N addition. SOC in the top 50 cm increased by 2.1 kg m−2, 1.8 kg m−2 and 1.2 kg m−2 for low, medium and high rates of N addition in the broadleaved forest, but did not change significantly in the coniferous forest. Increased SOC in the broadleaved forest was contributed by the significant increases in particulate organic carbon (POC), humus organic carbon (HOC) in the 0–10 cm and 30–50 cm soil layers and resistant organic carbon (ROC) in the 0–10 cm soil layer. 13C nuclear magnetic resonance (NMR) spectra of coarse SOC revealed a decrease in easily decomposed carbon (C) and a shift in recalcitrant C. The increased SOC accumulation in the broadleaved forest was largely driven by altered rates of organic matter decomposition, rather than C inputs to soil. Land-history and low nutrient availability may have contributed to the lack of significant impact of N addition on SOC in the coniferous forest. Our results suggested the different controls of SOC accumulation and less sensitivity of SOC chemical composition at the molecular level to N addition in the two subtropical forest soils.

An optimal ensemble of the Noah-MP land surface model for simulating surface heat fluxes over a typical subtropical forest in South China

Accurate estimation of land surface heat fluxes is critical to climate and air quality forecasting, which needs an appropriate parameterization in land surface models. The benchmarking method was applied to search for the optimal combination of the physical parameterization based on Noah land surface model with multi-physics options (Noah-MP). The effect of integrated physical mechanisms on the simulation of land surface energy fluxes in a typical subtropical forest (Dinghushan Forest Ecosystem Research Station) over South China is further investigated. The most sensitive process is the soil moisture threshold for evaporation while there are six processes have little or no effect on heat simulation. The optimal combination options are referred as follow: prescribed table leaf area index (LAI) and vegetation fraction, Jarvis scheme for canopy stomatal resistance, Noah soil moisture scheme, SIMGM model for runoff and groundwater, original Noah consistent scheme for surface layer drag coefficient and two-stream applied to grid-cell scheme for radiation transfer.

Soil Organic Carbon Stabilization in the Three Subtropical Forests: Importance of Clay and Metal Oxides

AbstractField observations show that subtropical forests can accumulate soil organic carbon (SOC) at high rate; however, the key mechanisms of SOC accumulation in subtropical forests remain unclear. Here we selected three typical subtropical forests with soil originated from same parent material under same climate condition in Dinghushan Biosphere Reserve, southern China: coniferous forest, mixed forest, and broadleaved forest with very different rates of SOC accumulation over the last three decades. To quantify the relative importance of physical versus chemical process on SOC stabilization in these forests, we used regression analysis to evaluate the relationship between the soil physical (clay, silt, and sand) and chemical (pH, Fe, and Al oxides) properties and SOC, and explored their respective contributions to SOC stabilization. Results showed that SOC stabilization was more strongly influenced by soil clay fraction through sorptive protection or microaggregate formation with SOC in the coniferous forest (r2 = 0.89, p < 0.05), and by chemical protection through forming organo‐mineral complexes in the mixed or broadleaved forest. Increasing carbon input was likely the main cause for SOC accumulation in the coniferous forest, but was not in the broadleaved forest. The strong linear relationships between SOC and Fe/Al oxides indicate that both the mixed (r2 = 0.63 and 0.57 with Feo and Alo, p < 0.05) and broadleaved forests (r2 = 0.96 and 0.78 with Fed and Alo, p < 0.05) on acid soils in southern China still have a great potential for further carbon sequestration in the future.

Responses of water use efficiency to phenology in typical subtropical forest ecosystems—A case study in Zhejiang Province

Ecosystem-scale water-use efficiency (WUE) is an important indicator for understanding the intimately coupled relationship between carbon and water cycles in ecosystems. Previous studies have suggested that both abiotic and biotic factors have significant effects on WUE in forest ecosystems. However, responses of WUE to phenology in the context of climate change remain poorly understood. In this study, we analyzed the sensitivity and response patterns of seasonal WUE to phenology in Zhejiang Province where typical subtropical forest ecosystems are located, and discussed potential causes of the changes of the sensitivity and response patterns along different climate gradient during 2000–2014. The results of interannual partial correlation analysis showed widespread negative correlations between WUE and the start of growing season (SOS) in spring. This is because the increase in gross primary product (GPP) is larger than that of evapotranspiration (ET), resulting from an advanced SOS. The positive correlation between WUE and SOS was widely observed in summer mainly because of water stress and plant ecological strategy. The autumn WUE enhanced with the delay in the end of growing season (EOS) mainly because of the increase in GPP meanwhile the decrease or steadiness in ET, resulting from a delayed EOS. In space, the sensitivity of spring WUE to SOS significantly decreased along the radiation gradient, which might be related to strong soil evaporation in high radiation area; the sensitivity of WUE to SOS in summer showed a positive correlation with precipitation and a negative correlation with temperature, respectively, which might be attributed to the compensation of GPP to the delayed SOS and water stress caused by high temperature. The sensitivity of WUE to EOS increased significantly along the radiation and precipitation gradients in autumn, which may be because the increase of radiation and precipitation provides more water and energy for photosynthesis.

Responses of species abundance distribution patterns to spatial scaling in subtropical secondary forests.

To quantify and assess the processes underlying community assembly and driving tree species abundance distributions(SADs) with spatial scale variation in two typical subtropical secondary forests in Dashanchong state‐owned forest farm, two 1‐ha permanent study plots (100‐m × 100‐m) were established. We selected four diversity indices including species richness, Shannon–Wiener, Simpson and Pielou, and relative importance values to quantify community assembly and biodiversity. Empirical cumulative distribution and species accumulation curves were utilized to describe the SADs of two forests communities trees. Three types of models, including statistic model (lognormal and logseries model), niche model (broken‐stick, niche preemption, and Zipf‐Mandelbrodt model), and neutral theory model, were estimated by the fitted SADs. Simulation effects were tested by Akaike's information criterion (AIC) and Kolmogorov–Smirnov test. Results found that the Fagaceae and Anacardiaceae families were their respective dominance family in the evergreen broad‐leaved and deciduous mixed communities. According to original data and random sampling predictions, the SADs were hump‐shaped for intermediate abundance classes, peaking between 8 and 32 in the evergreen broad‐leaved community, but this maximum increased with size of total sampled area size in the deciduous mixed community. All niche models could only explain SADs patterns at smaller spatial scales. However, both the neutral theory and purely statistical models were suitable for explaining the SADs for secondary forest communities when the sampling plot exceeded 40 m. The results showed the SADs indicated a clear directional trend toward convergence and similar predominating ecological processes in two typical subtropical secondary forests. The neutral process gradually replaced the niche process in importance and become the main mechanism for determining SADs of forest trees as the sampling scale expanded. Thus, we can preliminarily conclude that neutral processes had a major effect on biodiversity patterns in these two subtropical secondary forests but exclude possible contributions of other processes.

Distribution of Organic Carbon in Soil Aggregates from Four Kinds of Forest Vegetation on Jinyun Mountain

This study was intended to explore the distribution and stability of soil aggregates and the organic carbon for different forest types and to provide a scientific basis for the efficient management of soil carbon pools in subtropical forest ecosystems. Four subtropical forest types, including bamboo forest, broad-leaf forest, coniferous forest, and a mixed coniferous and broad-leaf forest on Jinyun Mountain (Chongqing Municipality), were selected as research subjects to explore the distribution of soil aggregates and organic carbon in different layers (depths of 0-20, 20-40, 40-60, and 60-100 cm). The results showed:The content of >2 mm aggregates and mean weight diameter (MWD), geometric mean diameter (GMD), and >0.25 mm aggregate content (R0.25) in broad-leaf forests decreased with soil depth, while other forests did not have a similar distribution pattern. In each soil layer, bamboo forest soils were mainly composed of >2 mm fractions of aggregates, which made up 30.73%-53.08% of the total content; The content of 2-0.25 mm particle size aggregates of broad-leaf and mixed forest soils was higher than that for other sizes, and its content ranged from 36.27% to 44.67% and 48.69% to 52.44%, respectively. The 2-0.25 mm and <0.053 mm fractions of aggregates dominated conifer soils. In general, the MWD, GMD, and R0.25 of bamboo aggregates were higher than for other stands in each soil layer, and the fractal dimension (D) was lower than for other stands. This indicated that the soil aggregates of bamboo forest have better stability. As the soil layer deepened, the organic carbon content of soil aggregates in forest types, except for coniferous forest, gradually decreased. Among them all, bamboo forest aggregates had the highest organic carbon content, and this was significantly higher than that of coniferous forest and mixed forest. In the whole soil profile, as far as different aggregate size is concerned, there was no obvious regularity about organic carbon in the four forest types soil aggregates; the organic carbon content of the 2-0.25 mm and <0.053 mm fractions of aggregates was high in every soil layer. There was a significant difference in the relative contribution of organic carbon in soil aggregates for different forest stands, among these contributions, the contribution rate of organic carbon in the <0.053 mm fraction of aggregates in the coniferous forest was the highest. The organic carbon contribution rate of the >2 mm fraction of bamboo forest aggregates was as high as 27.44%-53.47%. Broad-leaf forests and mixed forests had the highest contribution to the organic carbon of the 2-0.25 mm fractions of soil aggregates. Among the four forest types on Jinyun Mountain, the soil aggregates in bamboo forest have better stability, but the stability of aggregates in coniferous forests is poor. In each soil layer, the content of bamboo forest organic carbon in the various aggregates was the highest, and that of coniferous forest was the lowest.

Response of nitrogen transformation to glucose additions in soils at two subtropical forest types subjected to simulated nitrogen deposition

Soil nitrogen (N) transformation is an important phenomenon in forest ecosystems and it is regulated by carbon (C) input. This study aimed to evaluate the impacts of labile C levels on soil N mineralization under different simulated N deposition rates. Soils at 0–15-cm depth were collected from two contrasting subtropical forests, a coniferous fir forest (CFF) and an evergreen broadleaf forest (EBF); both soils had been subjected to 3 years of artificial NH4NO3 input or deposition (no-N control, N0; low N (30 kg N ha−1 year−1; N30), and high N (100 kg N ha−1 year−1); N100). The impacts of external glucose-C (G) on N mineralization of these N-deposited soils were investigated by the addition of six C rates (mg C kg−1 dry weight soil—0, G0; 100, G100; 300, G300; 1000, G1000; 2000, G2000; and 5000, G5000), at a temperature of 25 °C, and a 60% water-holding capacity for 21 days. The results showed that, after 21 days of incubation, concentrations of inorganic N (NH4+–N and NO3−–N) decreased significantly (P < 0.05) with increasing C rates and reached a minimum value when the added C rate was ≥ G1000. The lowest NH4+–N under G1000 was 9.2 mg kg−1 in all of these three N-deposited soils at the CFF site while 11.6 mg kg−1 in the N30 soil at the EBF site. The concentration of NO3−–N was decreased to 0 under G1000 and G2000 in the CFF and EBF soils, respectively. These results revealed that the higher the soil NO3−–N concentration was, the greater the NO3−–N reduced, with a maximum decrease of 80 mg NO3−–N kg−1 in the N100 soil from the EBF site. In addition, the soil mineralization and nitrification rates were significantly higher (P < 0.05) in soils from the EBF than from the CFF site and increased with N in soils subjected to simulated N deposition. However, the net N transformation rates also decreased with C addition and had the minimum value at G1000. Our results suggested that there could be a critical C level at which N transformation being altered in certain soils, based on their N status, and that the impacts of C on soil N mineralization were independent of soil N availability.

Evaluation of Microclimatic Detection by a Wireless Sensor Network in Forest Ecosystems

Timely and accurate detection of microclimates is extremely valuable for monitoring and stimulating exchanges of mass and energy in forest ecosystems under climate change. Recently, the rapid growth of wireless sensor networks (WSNs) has provided a new approach for detecting microclimates in a complex environment at multiple temporal and spatial scales. However, applications of wireless sensors in forest microclimate monitoring have rarely been studied, and the corresponding observation accuracy, error sources and correction methods are not well understood. In this study, through field experiments in two typical subtropical forest ecosystems in Zhejiang Province, China, the accuracy of the temperature and humidity observed by the wireless sensors was evaluated against standard meteorological data. Furthermore, the observation error sources were analyzed and corresponding correction models were established. The results showed that the wireless sensor-based temperature and humidity values performed well within the total observation accuracy. However, the observation errors varied with season, daily periodicity and weather conditions. For temperature, the wireless sensor observations were overestimated during the daytime while they were underestimated during the nighttime. For humidity, the data observed by the wireless sensors generally appeared as overestimates. Adopting humidity as the corrected factor, correction models were established and effectively improved the accuracy of the microclimatic data observed by the wireless sensors. Notably, our error analysis demonstrated that the observation errors may be associated with the shell material of the wireless sensor, suggesting that shading measures for the wireless sensors should be considered for outdoor work.

Changes in taxonomic and phylogenetic dissimilarity among four subtropical forest communities during 30 years of restoration

Enhancement and conservation of biodiversity in recovering communities is one of the primary goals of forest ecology and restoration. To achieve a better understanding of the mechanisms underlying community assembly during restoration, we examined changes in taxonomic and phylogenetic dissimilarity in four types of subtropical forests, consisting of a Eucalyptus plantation (EE), an Acacia mangium plantation (AM), a mixed native species plantation (NS), and a mixed coniferous plantation (MC), over 30 years of restoration (1985–2015). Temporal variation in taxonomic and phylogenetic dissimilarity patterns were found to differ among the four plantation types, although their taxonomic diversity (species richness) and phylogenetic diversity (PD) increased monotonically as succession proceeded. Community dissimilarity decreased nonlinearly over the 30 years, and species composition within each plantation tended to stabilize at around 20 years. Overall, the phylogenetic structure of each plantation was random during the succession period. Taxonomic and phylogenetic rates did not vary markedly along the 30 years of restoration, but the taxonomic turnover rate of MC increased significantly while the phylogenetic turnover rate of NC augmented remarkably. These results indicated that deterministic processes played a more important role in determining the temporal dynamics of community composition while stochastic processes were more important for phylogenetic structure. Our findings further inform the development and design of appropriate restoration strategies, and provide insights into understanding the mechanisms regulating community assembly during the process of forest restoration.

Spatial variation of organic carbon density in topsoils of a typical subtropical forest, southeastern China

Spatial variation of regional soil organic carbon (SOC) stocks and the effects of environmental factors on SOC in forest soils play an essential part in modeling the global carbon cycle and climatic change. In this study, we analyzed topsoil samples (0–30 cm) from 838 plots in a typical subtropical forest of Zhejiang Province, southeastern China, using Moran's I, geostatistics and geographical information system (GIS) techniques. The results showed that the mean SOC density in the topsoils was 71.15 Mg ha−1 and the total storage in topsoils of Zhejiang Province was 0.47 Pg (Pg = 1015 g). The spatial distribution of SOC density based on kriging interpolation and local Moran's I hotspot analysis showed a decreasing trend from the southwest to northeast area, roughly in line with Zhejiang Province's topographic feature, as well as differences in land use, economic and social development. The results herein revealed that both dominant tree species and altitude (P < 0.01) have markedly affected SOC balance and accumulation in a typical subtropical forest of Zhejiang Province. Therefore, management of SOC should focus on the selection of dominant tree species (broad-leaved species), management of forest stand-age structures and implementation of sustainable practices so that the potential for carbon sequestration in forest soils can be maximized in the future.

Gaseous elemental mercury (GEM) fluxes over canopy of two typical subtropical forests in south China

Abstract. Mercury (Hg) exchange between forests and the atmosphere plays an important role in global Hg cycling. The present estimate of global emission of Hg from natural source has large uncertainty, partly due to the lack of chronical and valid field data, particularly for terrestrial surfaces in China, the most important contributor to global atmospheric Hg. In this study, the micrometeorological method (MM) was used to continuously observe gaseous elemental mercury (GEM) fluxes over forest canopy at a mildly polluted site (Qianyanzhou, QYZ) and a moderately polluted site (Huitong, HT, near a large Hg mine) in subtropical south China for a full year from January to December in 2014. The GEM flux measurements over forest canopy in QYZ and HT showed net emission with annual average values of 6.67 and 0.30 ngm-2h-1, respectively. Daily variations of GEM fluxes showed an increasing emission with the increasing air temperature and solar radiation in the daytime to a peak at 13:00, and decreasing emission thereafter, even as a GEM sink or balance at night. High temperature and low air Hg concentration resulted in the high Hg emission in summer. Low temperature in winter and Hg absorption by plant in spring resulted in low Hg emission, or even adsorption in the two seasons. GEM fluxes were positively correlated with air temperature, soil temperature, wind speed, and solar radiation, while it is negatively correlated with air humidity and atmospheric GEM concentration. The lower emission fluxes of GEM at the moderately polluted site (HT) when compared with that in the mildly polluted site (QYZ) may result from a much higher adsorption fluxes at night in spite of a similar or higher emission fluxes during daytime. This shows that the higher atmospheric GEM concentration at HT restricted the forest GEM emission. Great attention should be paid to forests as a crucial increasing Hg emission source with the decreasing atmospheric GEM concentration in polluted areas because of Hg emission abatement in the future.

Relationships between carbon and nitrogen contents and enzyme activities in soil of three typical subtropical forests in China

Relationships between carbon and nitrogen contents and enzyme activities in soil of three typical subtropical forests in China

Spatial pattern of carbon stocks in forest ecosystems of a typical subtropical region of southeastern China

Abstract Spatial pattern information of carbon (C) density and storage in forest ecosystems plays an important role in the evaluation of C sequestration potential and forest management practices. However, such information related to subtropical forests still remain poorly understood. In this study, we collected forest samples from 838 plots in a typical subtropical forest of Zhejiang Province, southeastern China. The Moran’s I, geostatistics and geographical information system (GIS) techniques were applied to reveal the spatial pattern of C stocks in forest ecosystems. The results showed that the mean C density of forest ecosystems in Zhejiang Province was 145.22 Mg ha−1, and the forest vegetation, soil, litter, and dead wood layer C densities were 27.34, 108.89, 1.79, and 1.38 Mg ha−1, respectively. The spatial distribution of forest ecosystems C density showed a decreasing trend from the southwest to northeast area, roughly in line with Zhejiang Province’s topographic feature, as well as differences in land use, forest management, economic and social development. In addition, the C storage of forest ecosystems in Zhejiang Province was approx. 877.19 Tg (1 Tg = 1012 g), with 203.88 Tg in the vegetation layer, 656.20 Tg in the soil layer, 10.84 Tg in the litter layer, and 6.27 Tg in the dead wood layer, accounting for 23.24%, 74.81%, 1.24%, and 0.71% of the total C storage, respectively. These results indicated that the soil layer is the most important contributor to C storage in subtropical forest ecosystems. The young and middle-aged forests with low C densities dominated in the study area. Therefore, in order to enhance the C sequestration potentials, forest management should focus on the selection of tree species, management of stand-age structures and implementation of sustainable afforestation and reforestation practices in the future.

The fate of mercury and its relationship with carbon, nitrogen and bacterial communities during litter decomposing in two subtropical forests

Forests play a significant role in the biogeochemical cycling of mercury (Hg). Litterfall represent a dominant pathway for Hg to reach the ground surface under a forest canopy. In order to understand Hg accumulation in the litterfall, the dynamics of Hg, carbon (C), nitrogen (N), microbial C and N, as well as bacterial community in the decaying litterfall of two typical subtropical forest stands in southwest China were investigated for one year. THg levels in the litterfall after one-year increased to 124.64% and 135.90%, and MeHg levels in the litterfall increased up to 295.65% and 209.38% of the initial values in the mixed broadleaf-conifer forest and evergreen broadleaf forest respectively. Differently, the concentrations of THg and MeHg in the organic layer of the underlying soil were quite stable. The concentrations of THg in the decaying litterfall corresponded negatively with C/N ratios. Bacterial community analysis found that the bacteria previously being confirmed as Hg methylators did not occur in the genera of the decomposing litterfall in the two forest stands, which might imply that the increase of MeHg during decomposing did not mainly due to the contribution of confirmed Hg methylators, and other sources of MeHg might exert certain roles.

Response of soil respiration to nitrogen addition in two subtropical forest types

Anthropogenic activities have increased nitrogen (N) deposition in terrestrial ecosystems, which directly and indirectly affects soil biogeochemical processes, including soil respiration. However, the effects of the increases in N availability on soil respiration are not fully understood. In this study, soil respiration was measured using an infrared gas analyzer system with soil chambers under four N treatments (0, 5, 15, and 30 g N m–2 year–1 as control, low N (LN), moderate N (MN), and high N (HN), respectively) in camphor tree and slash pine forests in subtropical China. Results showed that soil respiration rates decreased by 37% in the camphor tree forest and 27% in the slash pine forest on average on an annual base, respectively, in the N-fertilized treatments when compared with the control. No significant differences were found in the soil respiration rate among the LN, MN, and HN treatments in both forest types as these fertilized plots reached an adequate N content zone. In addition, soil microbial biomass carbon (C) content and fine root biomass declined in N-treated plots compared to the control. Our results indicated that elevated N deposition might alter the tree growth pattern, C partitioning, and microbial activity, which further affect soil C sequestration by reducing soil respiration in subtropical forests of China.

Damage assessment to subtropical forests following the 2008 Chinese ice storm

Abstract: Ice storm is a major form of extreme climatic event and may occur more frequently in the future under a changing climate. The 2008 Chinese ice storm provided a natural laboratory to study ecosystem responses and feedbacks to climate variability and extreme events. Four typical subtropical forests (Chinese fir plantation, pine plantation, moso bamboo plantation, and secondary mixed broadleaved forest) were selected to assess the damage caused by the ice storm. The ice damage rate of typical subtropical forests varied between 25% and 81%. The secondary broadleaved forest had most extensive damage while the Chinese fir plantation experienced the most severe damage. Exotic pine species (Pinus elliottii Engelm. and Pinus taeda Linn.) were more severely damaged than the native species, Pinus massoniana Lamb. Ice damage was also affected by tree/culm size, age, stand density, site altitude, and management practices. Large-sized trees/culms were more vulnerable to stem breakage, decapitation, and uprooting, while small-sized trees/culms were more vulnerable to bending and leaning. Younger trees/culms had the highest damage rate, and were more susceptible to bending damage. Ice damage rate increased linearly with the stand density, and higher altitude led to a significant increase of stem breakage. Oleoresin tapping aggravated the damage to pine trees. Resistance of trees to ice damage is an emergent consequence of tree attributes, species origin, site conditions, and human disturbance. Forest silviculture and management practices can play significant roles in controlling forest susceptibility to extreme events. Inappropriate utilization of non-timber forest products can reduce trees’ resistance to extreme events. For sustainable forest development, balance needs to be achieved between the high productivity of introduced exotic tree species and the resistance of native species to extreme climatic events.

Conversion Parameters for Stand Biomass Estimation of Four Subtropical Forests in Southern China

Even though the National Forest Resource Inventory (NFRI) does not provide detailed forest biomass information directly, the NFRI data are useful for estimating forest biomass and carbon stocks by using conversion parameters. However, the accuracy and errors of this approach for estimating the stand biomass of subtropical forests remain unclear. In this study, we selected four typical subtropical forests (Cunninghamia lanceolata plantation, Pinus massoniana evergreen coniferous forest, Choerospondias axillaris deciduous broadleaved forest, and Lithocarpus glaber–Cyclobalanopsis glauca evergreen broadleaved forest) in Dashanchong Forest Park to calculate the biomass expansion factor (BEF) and the root:shoot ratio (R). Our results showed that the average BEF values for the four forests were 1.144, 1.301, 1.592 and 1.396, respectively, while the average R values were 0.197, 0.192, 0.226 and 0.221, respectively. These results may be important for estimating forest biomass in the subtropical zone of southern China.

基于模型数据融合的中国温带和亚热带典型森林生态系统碳通量模拟

PDF HTML阅读 XML下载 导出引用 引用提醒 基于模型数据融合的中国温带和亚热带典型森林生态系统碳通量模拟 DOI: 10.5846/stxb201510132066 作者: 作者单位: 中国科学院地理科学与资源研究所,中国科学院地理科学与资源研究所 作者简介: 通讯作者: 中图分类号: 基金项目: 中国科学院战略性先导科技专项（XDA05050600）；国家科技支撑计划（2013BAC03B00）；中国科学院科研信息化“科技领域云”项目（XXH12503-05-03） Carbon flux simulation of typical temperate and subtropical forest ecosystems in China based on model-data fusion approach Author: Affiliation: Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Science,Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Science Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:生态系统碳循环过程对水分响应的研究已成为全球变化关注的焦点问题之一。基于长白山温带针阔混交林与千烟洲亚热带人工针叶林观测站2003-2009年生长季的碳通量（NEE）和气象观测数据，综合考虑水分对光合、呼吸作用的影响，构建不同的NEE模型，并应用模型数据融合方法优化模型参数、遴选最适模型，系统分析了水分因子对不同森林生态系统碳循环的影响。结果表明：（1）优化后的模型参数均能被NEE实测数据较好约束。长白山生长季的光合、呼吸参数值均高于千烟洲，未考虑空气饱和水汽压差（VPD）的模型高估了千烟洲温度敏感性参数（Q10）值、低估了千烟洲基础呼吸速率参数（BR）值；（2）仅考虑VPD对光合作用影响的模型是长白山生长季碳通量模拟的最优模型，但模拟精度提高不显著。不同模型间碳通量组分模拟结果差异较小；（3）考虑VPD和土壤含水量对光合、呼吸作用共同影响的模型是千烟洲生长季碳通量模拟的最优模型，并且显著提高了模拟精度。未考虑水分的模型在生长季高估了总生态系统生产力（GEP）总量2.0%（21.85 g C/m2），同时更大幅度地高估了生态系统呼吸（RE）总量4.4%（38.02 g C/m2），从而导致NEE总量低估于实测值7.8%（18.55 g C/m2）。 Abstract:Moisture effect on the carbon balance of terrestrial ecosystems is a key issue in global change research. It is crucial to accurately analyze the response of terrestrial ecosystem carbon cycle to moisture. However, the carbon flux models responding to environmental factors rarely consider the moisture effects on photosynthesis and respiration simultaneously; meanwhile there are still large uncertainties in model structures and parameters. Thus, this study was designed to (1) choose the optimal carbon flux model with accurate parameters for different ecosystems through model-data fusion approach, reducing the uncertainties of modeled results; (2) systematically analyze the influence of water factors on carbon flux simulation, including gross ecosystem productivity (GEP), ecosystem respiration (RE) and net ecosystem exchange (NEE). To consider the effects of moisture on both GEP and RE, we developed four different NEE models. Then, based on carbon flux and meteorological data during growing season from 2003 to 2009 in Changbaishan temperate mixed forest (CBS) and Qianyanzhou subtropical coniferous plantation (QYZ), Markov Chain Monte Carlo was employed to estimate model parameters, and Bayesian Information Criterion was applied to choose the optimal model for two forest ecosystems. The results showed that (1) the posterior values of model parameters were normally distributed, indicating that the parameters were well constrained by NEE. Photosynthetic and respiratory parameter values of CBS were higher than those of QYZ during the growing season. The model without vapor pressure deficit (VPD) overestimated the value of temperature sensitivity (Q10) and underestimated the value of basal respiration rate (BR) in QYZ; (2) the model considering VPD only was the optimal model for CBS,but its performance was not improved much. The modeled flux components were similar among the four models; (3) the model considering both VPD and soil water content (Sw) was the optimal model for QYZ, and its performance was improved significantly. The model ignored water factors overestimated 2% (21.85 g C/m2) of the total GEP, and 4.4% (38.02 g C/m2) of the total RE, and therefore, underestimated 7.8% (18.55 g C/m2) of the total measured NEE during the growing season. 参考文献 相似文献 引证文献