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Biomass Estimation Coefficient and Its Impacting Factors for Eucalyptus Plantation in China     Wankuan Zhu,Yuxing Xu,Zhichao Wang,Apeng Du Scientia Silvae Sinicae   2020,56(5 ):1 -11. DOI:10.11707/j.1001-7488.20200501 Abstract  （562） HTML （34） PDF（pc） （1533KB）（505） Save Objective: The relationship between the three biomass estimation coefficients and the stand structure, climatic factors, and topographic factors was analyzed, and the main influencing factors of biomass estimation coefficients were determined to provide a scientific basis for accurately estimating the biomass of Eucalyptus plantations at regional scale. Method: By collecting and collating historical data from published literature on biomass measurements of Eucalyptus plantations, we analyzed and explored the relationship between three common biomass estimation coefficients (biomass conversion and expansion factor BCEF, biomass expansion factor BEF, and root/shoot ratio R) and stand structure (stand age, mean DBH, mean tree height, stand density, and standing volume), climatic factors (annual average temperature and annual average precipitation), and topographic factor (elevation). Result: Means of BCEF, BEF, and R were 0.658 Mg·m-3 (n=119, SD=0.150), 1.251 (n=176, SD=0.167), and 0.190 (n=144, SD=0.102), respectively. The corresponding range values were 0.46-0.76 Mg·m-3, 1.05-1.35, and 0.04-0.36, respectively. BCEF value displayed a decrease followed by an increase with the increase of mean DBH. BCEF value gradually decreased with the increase of mean tree height (r2=0.366), stand density (r2=0.430), and standing volume (r2=0.405). BEF value decreased and became stable with the increase of stand age(r2=0.765), mean tree height(r2=0.734), and standing volume(r2=0.578), decreased first and then increased with the increase of mean DBH(r2=0.644). R value decreased gradually and then became stable with the increase of stand age(r2=0.665), mean tree height(r2=0.338), stand density(r2=0.275), and standing volume(r2=0.403).BCEF value showed a decrease first followed by an increase with the increases of temperature (r2=0.193) and precipitation (r2=0.200). Values of BEF and R did not show a significant functional relationship with changes in temperature and precipitation. Three biomass estimation coefficients showed a trend of increase with elevation, and the equation fitting accuracies were 0.455, 0.501, and 0.314. Conclusion: The goodness of fit between stand density and BCEF was relatively high, and so did the stand age and the BEF and R. Stand density and age were the main factors affecting the estimation coefficient of biomass. The influence of topographic factors on the three biomass estimation coefficients was next only to the stand density and the age. The climatic factor only had some effects on the BCEF. Therefore, the difference in biomass estimation coefficients caused by stand structure and topographic factors should be considered when estimating the biomass of Eucalyptus plantations at regional scale. Table and Figures丨 Reference丨 Related Articles丨 Metrics

Characteristics of Forest Ecosystem Carbon Stocks at Different Vegetation Restoration Stages in Hilly Area of Central Hunan Province, China     Zhenpeng Wang,Jinlei Chen,Shangyi Li,Shiji Zhang,Xi Fang Scientia Silvae Sinicae   2020,56(5 ):19 -28. DOI:10.11707/j.1001-7488.20200503 Abstract  （322） HTML （16） PDF（pc） （1456KB）（286） Save Objective: The aims of this study were to investigate the change trends of carbon storage and its distribution pattern(vegetation, litter and soil layer) within forest ecosystems at different restoration stages in hilly area of central Hunan Province of China, in order to provide a scientific basis for explaining the influence mechanism of vegetation restoration on carbon sink function of forest ecosystem, and implementing forest ecosystem carbon reservoir management measures in stages. Methods: By using the space-for-time substitution method, we selected four different types of ecosystems, comprising of Loropetalum chinense+Vaccinium bracteatum+Rhododendron simsii scrub-grass-land (LVR), L. chinense+Cunninghamia lanceolata+Quercus fabri shrubbery (LCQ), Pinus massoniana+Lithocarpus glaber+L.chinense coniferous-broad leaved mixed forest (PLL), and L. glaber+Cleyera japonica+Cyclobalanopsis glauca evergreen broad-leaved forest (LAG) to represent the successional sequence in the secondary forests in Changsha County, Hunan Province, China. Permanent plots were established in each ecosystems.Biomass was estimated by using the total harvesting method to establish relative growth equations of some dominant tree species and citing allometric equations of biomass of some dominant tree species. Soil samples (0-40 cm) were collected and divided into four layers (0-10, 10-20, 20-30, and 30-40 cm). Carbon contents in plant, litter, and soil samples were determinated, and carbon storage of vegetation, litter, and soil were estimated. Results: Carbon contents of different components at different vegetation layers varied with vegetation restoration. In the same restoration stage, carbon contents of different components at different vegetation layers ranked in the order of the arbor layer > the shrub layer > the herb layer. Carbon contents of litter were highest in PLL, followed by LAG and LCQ as the lowest. Soil organic carbon contents increased with the vegetation restoration.From LVR to LAG, carbon storage of vegetation, litter, 0-40 cm soil and ecosystem increased by 70.80, 1.17, 67.05 and 139.02 tC·hm-2, respectively. The growth rate of carbon reserves in vegetation layer and ecosystem between different stage showed the characteristics of first fast and then slow. However the growth rate of carbon reserves in soil showed fast-slow-fast. Carbon stock within ecosystem showed a consistant spatial distribution pattern:0-40 cm soil layer > vegetation layer > litter layer in different restoration stages. With vegetation restoration, the contribution rate of carbon stock in vegetation layer to the ecosystem carbon stock increased, while that of soil carbon stock was in the decline, and that of litter carbon stock did not change. Carbon storages of ecosystem, vegetation, and soil were significantly positively correlated with species diversity index (except for vegetation), biomass in vegetaion, and soil organic carbon content. Conclusion: With vegetation restoration, plant diversity, vegetation biomass, soil organic carbon content, carbon storages of ecosystem and its each components (vegetation, litter and soil) increased. However the growth rates of carbon reserves in vegetation, soil and ecosystem showed different among different restoration stages. Therefore, it is an important way to improve the carbon reserve of subtropical forest ecosystem to promote forest vegetation restoration and improve tree species diversity, vegetation biomass, and soil organic carbon content in order to improve carbon reserves of the vegetation and soil by reasonable management measures in the early and middle of restoration stages, and to protect the above-ground vegetation and ensure the continuous increase of soil organic carbon content in the late stage of vegetation restoration. Table and Figures丨 Reference丨 Related Articles丨 Metrics

Effects of Structure-Based Forest Management on Stand Space Structure and Its Stability of Mixed Oak-Pine Forest     Pan Wan,Wenzhen Liu,Ruihong Liu,Peng Wang,Hongxiang Wang,Gangying Hui Scientia Silvae Sinicae   2020,56(4 ):35 -45. DOI:10.11707/j.1001-7488.20200404 Abstract  （277） HTML （15） PDF（pc） （3798KB）（405） Save Objective: The univariate and bivariate distribution characteristics of stand space structure were studied, and the stand stability in the mixed oak-pine forest under structure-based forest management was also analyzed, in order to provide the scientific basis for the implementation and evaluation of structure-based forest management in Quercus aliena var. acuteserrata mixed forest. Methods: The natural mixed oak-pine forest in Daganzigou, Baihua forest Farm, Xiaolongshan nature reserve, Gansu Province, as object was studied. In 2012, one 50 m×50 m, two 30 m×30 m and three 20 m×20 m fixed plots were established, the total station (TOPCON-GIS-602AF) was used to locate each tree with a diameter of more than 5 cm in all plots and investigate its species, diameter, height and crown. After those, one 50 m×50 m and two 30 m×30 m plots were used for structure-based forest management, and others plots were used for without any management as control. In 2017, the characteristics of stand spatial structure in managed and unmanaged plots were compared by the stand spatial structure parameters, such as uniform angle, dominance and mingling. The nine indicators of mixed oak-pine forest were selected as the parameters to construct the stability evaluation system, and stand stability was evaluated by the new rule of π value method of optimal stand state. Results: 1) The stand trees of managed plots before operation were close to aggregated distribution, and the stand trees of managed plots after five years of operation were randomly distributed, however, the stand trees of unmanaged plots were always presented an aggregated distribution. Simultaneously, the proportion of highly mixed by species in managed forest after five years of operation was increased by 10.4% compared with the managed forest before operation, the proportion of highly mixed by species in unmanaged forest grown for five years was increased by 5.5% compared with the unmanaged forest before five years. 2) Bivariate distribution of spatial structural parameters showed that the proportion of micro-structure that was the four or three neighbours were of different species to the reference tree and had a random distribution pattern in managed stand was higher than unmanaged stand, and the proportion of micro-structure that was the reference tree was dominant and surrounded by different species in managed stand was higher than unmanaged stand, on the whole, the proportion of micro-structure that was dominant and four neighbours had a random distribution pattern was not obviously different between unmanaged and managed stand. 3) Unit circle analysis of stand status showed that the ω value of managed forest after five years of operation was increased 27.09% compared with the managed forest before operating, the stand status was from poor to good, while theωvalue of unmanaged forest grown for five years was increased 13.24%, but the stand status was always poor. Conclusion: The trees of structure-based managed stand has a reasonable distribution and highly mingling, and dominant wood in highly mixed. Meanwhile, stand status of structure-based forest managed presented at a good level, which shows higher stand stability. Table and Figures丨 Reference丨 Related Articles丨 Metrics

Forest Height Estimation Method Using TanDEM-X Interferometric Coherence Data     Yaxiong Fan,Erxue Chen,Zengyuan Li,Lei Zhao,Wangfei Zhang,Yudong Jin,Lijie Cai Scientia Silvae Sinicae   2020,56(6 ):35 -46. DOI:10.11707/j.1001-7488.20200604 Abstract  （258） HTML （8） PDF（pc） （11104KB）（118） Save Objective: Using single polarization TanDEM-X InSAR data, we studied the forest height estimation method with InSAR coherence amplitude, and analyzed the effects of different DEMs spatial resolutions (one is LiDAR DEM of 5 m resolution and the other is SRTM DEM of 30 m resolution) on forest height estimation accuracy. Method: First, non-volumetric decorrelation was corrected from the observed coherence in order to obtain the volumetric decorrelation (γVol), and then based on the SINC model, the amplitude of γVol was used to estimate forest height. Then forest height inversion results were validated against LiDAR CHM data and compared with the method based on phase difference. Plot sizes of 15 m×15 m, 30 m×30 m, 50 m×50 m and 100 m×100 m were selected to analyze the effects of spatial interpolation. Result: The effects of DEMs in two kinds of resolutions (5 m×5 m, 30 m×30 m) on inversion accuracy are small, when plot size is 100 m×100 m, the R2 are 0.54 and 0.51, the RMSEs are 2.38 m and 2.51 m, and the overall accuracies are 77.19% and 75.99%, respectively. Although the method based on phase difference has a better performance than the SINC model over different plot sizes, its results are obviously underestimated and should be calibrated with some known forest height samples. If the plot size is set as 100 m×100 m, the R2 is 0.79, the RMSEs before and after calibration are 2.57 m and 1.63 m, the overall accuracies are 75.44% and 84.41%, respectively. Conclusion: The forest height estimation method using SINC model with the TanDEM-X InSAR coherence amplitude can obtain a good performance even if using a low spatial resolution DEM, such as SRTM DEM of 30 m resolution for terrain compensation and geo-coding. Although the accuracy of SINC model is less accurate than that of phase difference method, it requires neither plot measurements for model calibration nor high-resolution DEM for terrain compensation and geo-coding, so it has the potential for large-scale forest height mapping and higher value for practical applications. Table and Figures丨 Reference丨 Related Articles丨 Metrics

Spatial Pattern of Points Distribution of Sandpiles of Nitraria tangutorum Nebkhas at Different Developmental Stages in Desert-Oasis Ecotone of Minqin     Tao Sun,Zhiqing Jia,Hujun Liu,Wen Shang,Jiang Liu,Liheng Zhang Scientia Silvae Sinicae   2020,56(7 ):12 -21. DOI:10.11707/j.1001-7488.20200702 Abstract  （245） HTML （11） PDF（pc） （3633KB）（307） Save Objective: The vegetation and shape characteristics and spatial distribution of Nitraria tangutorum Nebkhas in different developmental stages were studied to characterize the spatial point distribution and patterns of variation of N. tangutorum Nebkhas with the increase of size of the sandpiles in order to reveal the characteristics of community formation and the mechanism of maintaining ecological patterns of N. tangutorum Nebkhas during the development process. Methods: Based on field investigation,four typical sample plots of N. tangutorum Nebkhas in 4 different developmental stages,i.e,prototype,developing,stabilizing,and activating,in Minqin desert-oasis ecotone were selected. In light of the two-dimensional coordinates,the N. tangutorum Nebkhas were graded into 3 classes,i.e. small,medium and large,respectively,according to the volumes of sandpiles. Their spatial distribution were analyzed with the univariate O-ring function while the correlation among different grades of the sandpiles at different scales was determined by the bivariate O-ring function under the quantitative statistical methods. Results: With the development of the sandpiles,the overall growth changed from good to poor,and the vegetation coverage tended to increase at the beginning and followed by a decrease,which was 51.4% at the prototype stage,reached to the highest 68.8% at the stabilizing stage,then decreased to 60% at the activating stage,whereas the bush deadwood rate showed an opposite trend,which increased from 15% at the prototype stage to 27% at the activating stage. Different distribution patterns appeared for different grades of sandpiles at different scales. At the prototype stage,they tended to be evenly distributed under the scale of 0-5 m,and randomly distributed on the scale of 2-25 cm,whereas distributed in aggregate under the scale of >25 m; at the developing stage,they tended to be uniformly distributed under the scale of 0-5 m,but were randomly distributed under the scale of 5-30 m; at the stabilizing stage and activating stage,they showed a uniform distribution under small scales(< 5 m),a random distribution under the scales >5 m,respectively. The sandpiles of different sizes at different developmental stages showed different association with changing scales. For the small grade sandpiles(grade 1 and 2),except that there was no correlation between the small sandpiles(grade 1 and 2) at the developing stage,it was positively correlated with each other in small sandpiles(grade 1 and 2) along with the increasing spatial scale in other different stages. For the grades 2 and 3,their spatial correlations with other sandpiles showed as a negative correlation under the scale of < 10 m,whereas there were gradually strengthen negative correlation or even disappearing with increasing scales under the scale of >10 m. Conclusion: The sandpiles of N. tangutorum Nebkhas showed no significant aggregation although the different grades of sandpiles at different development stages have different proportions in each sample plot. With the gradual progress of the sandpile development,large sandpiles tended to be randomly distributed,but,the correlations between the small sandpiles grades showed positive on the small scale,while,the negative correlations appeared strengthen or uncorrelated on the medium and large scales,indicating the composition and structure of the sandpiles of N. tangutorum Nebkhas community become less stabilized as the development progresses. Table and Figures丨 Reference丨 Related Articles丨 Metrics