Forest crown density restoration and influencing factors in the burned area of northern Great Hing′an Mountains of China

Fire in the Great Hing′an Mountains in 1987 affected an area of more than 1.33×10⁶ hm², creating a mosaic of burn severities across the landscape, which strongly affected the postfire vegetation succession. In addition, undulate landform and anthropogenic disturbance inevitably influenced the postfire vegetation succession. In this paper, a typical area was selected for a case study, including two forest farms, covering more than 1.2×10⁵ hm². In order to reveal how the forest changed in 2000 (13 years after the fire) by comparing with 1987 (prefire) and to find out the relationship between the forest succession and the affecting factors, forest crown density was selected as the criterion, and forest type, fire severity, silviculture practice, elevation and topography gradients were designed as the affecting variables. With the support of GIS software, each variable was classified and entered into the multivariate regression model. The result showed that the forest crown density changed notably in 2000 compared with that of the prefire, and all the variables significantly affected the forest crown density. The most important affecting variable was elevation, which was positively correlated with the forest crown density. The next was fire severity, which was negatively related with the forest succession. The effects of topographic factors and silviculture practices on forest crown density were relatively small.     

Water-holding capacity of ground covers and soils in alpine and sub-alpine shrubs in western Sichuan, China

The water-holding functions of soils and ground covers in terms of moss and litters in the three major shrubs at different altitude gradients were studied using field investigation. The water-holding functions were measured and expressed with Biomass (t/hm²) of moss and litters, along with their maximal water holding capacity (MWHC, t/hm²) and maximal water holding rate (MWHR, %). The physical characteristics of the soils included bulk density, MWHC, capillary water holding capacity (CWHC), and least water holding capacity (LWHC). The result showed that Rhododendron przewalskii shrub exhibited the highest water-holding capacity among the three types. The average MWHC of the moss, litters, and at a depth of 0–40cm in R. przewalskii at different elevation gradients was 46.73,139.98 t/hm², and 2216.92 t/hm², respectively, whereas the average MWHC of the moss, litters, and soils in Quercus aquifolioides was 1.64, 72.08 t/hm² and 2114.88 t/hm², respectively. There was no moss in Quercus cocciferoides, and the average MWHC of litters and soils at a depth of 0–40 cm at different elevation gradients was 84.55 t/hm² and 2062.83 t/hm², respectively. The biomass and MWHC of the moss layer in R. przewalskii shrub significantly decreased with increasing elevation, whereas the reverse occurred in Q. aquifolioides before the maximum was reached at 3400 m, and then the SCM and MWHC decreased. MWHR of the moss layer in R. przewalskii was higher than that in Q. aquifolioides. The biomass and MWHC of the litters in R. przewalskii and Q. aquifolioides decreased with increasing elevation, whereas the reverse occurred in Q. cocciferoide. Regardless of shrub types, soil bulk density increased significantly with increasing soil depth, whereas MWHC decreased significantly with increasing soil depth. Significant decrease in CWHC and LWHC were found only in certain shrub communities. The MWHC with respect to the 0–40cm soil depth significantly decreased with increasing elevation only in R. przewalskii shrub, whereas there was no significant difference in MWHCs among the different elevation gradients for the other two types.     

Water-holding capacity of ground covers and soils in alpine and sub-alpine shrubs in western Sichuan, China

The water-holding functions of soils and ground covers in terms of moss and litters in the three major shrubs at different altitude gradients were studied using field investigation. The water-holding functions were measured and expressed with Biomass (t/hm²) of moss and litters, along with their maximal water holding capacity (MWHC, t/hm²) and maximal water holding rate (MWHR, %). The physical characteristics of the soils included bulk density, MWHC, capillary water holding capacity (CWHC), and least water holding capacity (LWHC). The result showed that Rhododendron przewalskii shrub exhibited the highest water-holding capacity among the three types. The average MWHC of the moss, litters, and at a depth of 0–40cm in R. przewalskii at different elevation gradients was 46.73,139.98 t/hm², and 2216.92 t/hm², respectively, whereas the average MWHC of the moss, litters, and soils in Quercus aquifolioides was 1.64, 72.08 t/hm² and 2114.88 t/hm², respectively. There was no moss in Quercus cocciferoides, and the average MWHC of litters and soils at a depth of 0–40 cm at different elevation gradients was 84.55 t/hm² and 2062.83 t/hm², respectively. The biomass and MWHC of the moss layer in R. przewalskii shrub significantly decreased with increasing elevation, whereas the reverse occurred in Q. aquifolioides before the maximum was reached at 3400 m, and then the SCM and MWHC decreased. MWHR of the moss layer in R. przewalskii was higher than that in Q. aquifolioides. The biomass and MWHC of the litters in R. przewalskii and Q. aquifolioides decreased with increasing elevation, whereas the reverse occurred in Q. cocciferoide. Regardless of shrub types, soil bulk density increased significantly with increasing soil depth, whereas MWHC decreased significantly with increasing soil depth. Significant decrease in CWHC and LWHC were found only in certain shrub communities. The MWHC with respect to the 0–40cm soil depth significantly decreased with increasing elevation only in R. przewalskii shrub, whereas there was no significant difference in MWHCs among the different elevation gradients for the other two types.     

Carbon storage and potentials of the broad-leaved forest in alpine region of the Qinghai-Xizang Plateau,China北大核心CSCD

Aims Our objective was to explore the vegetation carbon storages and their variations in the broad-leaved forests in the alpine region of the Qinghai-Xizang Plateau that includes Qinghai Province and Xizang Autonomous Region. Methods Based on forest resource inventory data and field sampling, this paper studied the carbon storage, its sequestration rate, and the potentials in the broad-leaved forests in the alpine region of the Qinghai-Xizang Plateau. Important findings The vegetation carbon storage in the broad-leaved forest accounted for 310.70 Tg in 2011, with the highest value in the broad-leaved mixed forest and the lowest in Populus forest among the six broad-leaved forests that include Quercus, Betula, Populus, other hard broad-leaved species, other soft broad-leaved species, and the broadleaved mixed forest. The carbon density of the broad-leaved forest was 89.04 Mg•hm2, with the highest value in other hard broad-leaved species forest and the lowest in other soft broad-leaved species forest. The carbon storage and carbon density in different layers of the forests followed a sequence of overstory layer > understory layer > litter layer > grass layer > dead wood layer, which all increased with forest age. In addition, the carbon storage of broad-leaved forest increased from 304.26 Tg in 2001 to 310.70 Tg in 2011. The mean annual carbon sequestration and its rate were 0.64 Tg•a1 and 0.19 Mg•hm2•a1, respectively. The maximum and minimum of the carbon sequestration rate were respectively found in other soft broad-leaved species forest and other hard broad-leaved species forest, with the highest value in the mature forest and the lowest in the young forest. Moreover, the carbon sequestration potential in the tree layer of broad-leaved forest reached 19.09 Mg•hm2 in 2011, with the highest value found in Quercus forest and the lowest in Betula forest. The carbon storage increased gradually during three inventory periods, indicating that the broad-leaved forest was well protected to maintain a healthy growth by the forest protection project of Qinghai Province and Xizang Autonomous Region.     

Spatial pattern of soil organic carbon of the main forest soils and its influencing factors in Guangxi,China北大核心CSCD

Aims Our objectives were to study the spatial distribution of soil organic carbon (SOC) density and its influencing factors in the main forest ecosystems in Guangxi. Methods A total of 345 sample plots were established in Guangxi, and the size of each plot was 50 m × 20 m. Based on the forest resource inventory data and field investigation, the SOC storage of the main forests in Guangxi was estimated. Geostatistics was applied to analyze the spatial pattern of SOC density and the main influencing factors on SOC density were also explored by principal component analysis and stepwise regression. Important findings The total SOC storage in the main forests in Guangxi was 1 686.88 Tg, and the mean SOC density was 124.70 Mg•hm2, which is lower than that of China. The best fitted semivariogram model of SOC density was exponential model, and the spatial autocorrelation was medium. The contour map based on Kriging indicated that northeastern Guangxi had high SOC density and northwestern Guangxi had low SOC density, which corresponded to high SOC density in non-karst region and low SOC density in karst region. The SOC density followed the sequence of bamboo forest > deciduous broadleaf forest > warm coniferous forest > mixed evergreen and deciduous broadleaf forest > evergreen broadleaf forest, and yellow soil > red soil >lateritic red soil > limestone soil. The dominant environment factors affecting SOC density included soil depth, longitude, latitude, and altitude. Soil depth was the most influential factor, which was mainly attributed to the karst landscape.     

Present status and rate of carbon sequestration of forest vegetation in Jilin Province,Northeast China北大核心CSCD

Aims Forests represent the most important component of the terrestrial biological carbon pool and play an important role in the global carbon cycle. The regional scale estimation of carbon budgets of forest ecosystems, however, have high uncertainties because of the different data sources, estimation methods and so on. Our objective was to accurately estimate the carbon storage, density and sequestration rate in forest vegetation in Jilin Province of China, in order to understand the role of the carbon sink and to better manage forest ecosystems. Methods Vegetation survey data were used to determine forest distribution, size of area and vegetation types regionally. In our study, 561 plots were investigated to build volume-biomass models; 288 plots of shrubs and herbs were harvested to calculate the biomass of understory vegetation, and samples of trees, shrubs and herbs were collected to analyze carbon content. Carbon storage, density and sequestration rate were estimated by two forest inventory data (2009 and 2014), combined with volume-biomass models, the average biomass of understory vegetation and carbon content of vegetation. Finally, the distribution patterns of carbon pools were presented using ArcGIS soft ware. Important findings Understory vegetation biomass overall was less than 3% of the tree layer biomass, varying greatly among different forest types and even among the similar types. The carbon content of trees was between 45.80% 52.97%, and that of the coniferous forests was higher than that of the broadleaf forests. The carbon content of shrub and herb layers was about 39.79% 47.25% and 40%, respectively. Therefore, the vegetation carbon conversion coefficient was 0.47 or 0.48 in Jilin Province, and the conventional use of 0.50 or 0.45 would cause deviation of ±5.26%. The vegetation carbon pool of Jilin Province was at the upper range of regional carbon pool and had higher capacity of carbon sequestration. The value in 2009 and 2014 was 471.29 Tg C and 505.76 Tg C, respectively, and the total increase was 34.47 Tg C with average annual growth of 6.89 Tg C•a1. The corresponding carbon sequestration rate was 0.92 t•hm 2•a1. The carbon density rose from 64.58 t•hm 2 in 2009 to 66.68 t•hm2 in 2014, with an average increase of 2.10 t•hm2. In addition, the carbon storage of the Quercus mongolica forests and broadleaved mixed forests, accounted for 90.34% of that of all forests. The carbon increment followed the order of young > over-mature > near mature > middle-aged > mature forests. The carbon sequestration rate of followed the order of over-mature > young > near mature > middle-aged > mature forests. Both the carbon increment and the carbon sequestration rate of mature forests were negative. Furthermore, spatially the carbon storage and density were higher in the east than in the west of Jilin province, while the carbon increment was higher in northeast and middle east than in the west. The carbon sequestration rate was higher in Tonghua and Baishan in the south, followed by Jinlin in the middle and Yanbian in the east, while Baicheng and Songyuan, etc. in west showed negative values.     

Impact of whitefish on an enclosure ecosystem in a shallow eutrophic lake: changes in nutrient concentrations,phytoplankton and zoobenthos

Large bag-type (75 m³) and tube-type (105 m³) enclosures were set up in the shallow eutrophic Lake Suwa and were each stocked with exotic planktivorous whitefish (Coregonus lavaretus maraena). The release of whitefish caused the increase in nutrient concentration in the tube-type enclosure whereas no such increase was observed in the bag-type enclosure. Bottom sediment seemed to be an important source of chironomid food for whitefish. The proportion of phytoplankton measuring<10μm and 20–40μm, which respectively corresponded toOchromonas spp. andCryptomonas sp., were lower in the fish enclosures than in the control, which might have been caused by high grazing pressure by rotifers. The predation by whitefish might have affected the species composition of phytoplankton through reducing copepod predation on rotifers, not through reducing the densities of cladocerans which directly feed on phytoplankton as many investigators have reported. The phytoplankton biomass was not affected much by the release of fish. Possible reasons are that the increase in density of rotifers reduced the biomass of available phytoplankton and also that inedible Cyanophyceae were in the decreasing phase of their seasonal succession and could not increase successfully in spite of elevated nutrient levels.     

Carbon storage of the forests and its spatial pattern in Nei Mongol,China北大核心CSCD

Aims Forest carbon storage in Nei Mongol plays a significant role in national terrestrial carbon budget due to its large area in China. Our objectives were to estimate the carbon storage in the forest ecosystems in Nei Mongol and to quantify its spatial pattern. Methods Field survey and sampling were conducted at 137 sites that distributed evenly across the forest types in the study region. At each site, the ecosystem carbon density was estimated thorough sampling and measuring different pools of soil (0 100 cm) and vegetation, including biomass of tree, grass, shrub, and litter. Regional carbon storage was calculated with the estimated carbon density for each forest type. Important findings Carbon storage of vegetation layer in forests in Nei Mongol was 787.8 Tg C, with the biomass of tree, litter, herbaceous and shrub accounting for 93.5%, 3.0%, 2.7% and 0.8%, respectively. Carbon density of vegetation layer was 40.4 t•hm2, with 35.6 t•hm2 in trees, 2.9 t•hm2 in litter, 1.2 t•hm2 in herbaceous and 0.6 t•hm2 in shrubs. In comparison, carbon storage of soil layer in forests in Nei Mongol was 2 449.6 Tg C, with 79.8% distributed in the first 30 cm. Carbon density of soil layer was 144.4 t•hm2. Carbon storage of forest ecosystem in Nei Mongol was 3 237.4 Tg C, with vegetation and soil accounting for 24.3% and 75.7%, respectively. Carbon density of forest ecosystems in Nei Mongol was 184.5 t•hm2. Carbon density of soil layer was positively correlated with that of vegetation layer. Spatially, both carbon storage and carbon density were higher in the eastern area, where the climate is more humid. Forest reserves and artificial afforestations can significantly improve the capacity of regional carbon sink.     

Carbon stock and allocation of five restoration ecosystems in subalpine coniferous forest zone in Western Sichuan Province, Southwest China

As the largest carbon pool of the terrestrial ecosystem, forest plays a key role in sequestrating and reserving greenhouse gases. With the method of replacing space with time, the typical restoration ecosystems of herb (dominated by Deyeuxia scabrescens, P1), shrub (dominated by Salix paraqplesia, P2), broadleaf (dominated by Betula platyphylla, P3), mixed forest (dominated by Betula spp. and Abies faxoniana, P4), and climax (dominated by Abies faxoniana, P5) were selected to quantify the carbon stock and allocation in the subalpine coniferous forest in Western Sichuan (SCFS). The results indicated that the soil organism carbon (SOC) stock decreased with the depth of soil layer, and the SOC per layer and the total SOC increased largely with the vegetation restoration. The contribution of SOC to the carbon stock of ecosystems decreased with the vegetation restoration from 89.45% to 27.06%, while the quantity was from 94.00 to 223.00 t C hm^?2. The carbon stock in ground cover increased with the vegetation restoration, and its contribution to the carbon stock of ecosystems was similar (3–4% of the total). Following the vegetation restoration, the plant carbon stock multiplied and reached to 430.86 ± 49.49 t C hm^?2 at the climax phase. During the restoration, the carbon stock of different layers increased, and the contribution of belowground to the carbon stock of ecosystems decreased sharply. The carbon stock on ecosystem scale of the climax phase was 5.89 times that of the herb phase. Our results highlighted that the vegetation restoration in SCFS was a large carbon sink.     

The changes in water-use efficiency and stoma density of Leymus chinensis along Northeast China Transect

Leymus chinensis is a keystone species in the temperate zone grassland of China. Along the NECT (Northeast China Transect) in 2001, water-use efficiency of L. chinensis was analyzed with δ¹³C, and changes in the stoma density of its leaves were observed and computed under a microscope. Results showed that the ecological plasticity modulation of the stoma density of L. chinensis and its water-use efficiency were two important mechanisms for its broad ecological adaptability. From east to west along the NECT, the δ¹³C of the species varied from -27.49‰ to -23.57‰, consisting with the reduction of annual precipitation, soil water and annual average temperature, but increased with the increase of the elevation of sampling sites. The stoma density increased from 96.9/mm² to 169.5/mm², indicating that the water-use efficiency for the species was improved along the gradient. The linear coefficient between the two parameters was significant (R² = 0.7338). The results of a stepwise regression analysis showed that the soil water was the first marked factor for determining the stoma density, and the next was the annual precipitation, which suggested that the water factors were the primary ecological factors influencing the stoma density of L. chinensis. The findings in this study showed that the responses of the stoma density and the water-use efficiency for L. chinensis to environmental changes were very complicated. They may be the outcome operated synthetically by all environmental factors in the long-term adaptation to different ecological environments, including human activity, for L. chinensis.     

The changes in water-use efficiency and stoma density of Leymus chinensis along Northeast China Transect

Leymus chinensis is a keystone species in the temperate zone grassland of China. Along the NECT (Northeast China Transect) in 2001, water-use efficiency of L. chinensis was analyzed with δ¹³C, and changes in the stoma density of its leaves were observed and computed under a microscope. Results showed that the ecological plasticity modulation of the stoma density of L. chinensis and its water-use efficiency were two important mechanisms for its broad ecological adaptability. From east to west along the NECT, the δ¹³C of the species varied from -27.49‰ to -23.57‰, consisting with the reduction of annual precipitation, soil water and annual average temperature, but increased with the increase of the elevation of sampling sites. The stoma density increased from 96.9/mm² to 169.5/mm², indicating that the water-use efficiency for the species was improved along the gradient. The linear coefficient between the two parameters was significant (R² = 0.7338). The results of a stepwise regression analysis showed that the soil water was the first marked factor for determining the stoma density, and the next was the annual precipitation, which suggested that the water factors were the primary ecological factors influencing the stoma density of L. chinensis. The findings in this study showed that the responses of the stoma density and the water-use efficiency for L. chinensis to environmental changes were very complicated. They may be the outcome operated synthetically by all environmental factors in the long-term adaptation to different ecological environments, including human activity, for L. chinensis.     

How does tree age influence damage and recovery in forests impacted by freezing rain and snow?

The response and recovery mechanisms of forests to damage from freezing rain and snow events are a key topic in forest research and management. However, the relationship between the degree of damage and tree age, i.e., whether seedlings, young trees, or adult trees are most vulnerable, remains unclear and is rarely reported. We investigated the effect of tree age on the degrees of vegetation damage and subsequent recovery in three subtropical forest types-coniferous, mixed, and broad-leaved —in the Tianjing Mountains, South China, after a series of rare icy rain and freezing snow events in 2008. The results showed that damage and recovery rates were both dependent on tree age, with the proportion of damaged vegetation increasing with age(estimated by diameter at breast height, DBH) in all three forest types and gradually plateauing. Significant variation occurred among forest types. Young trees in the coniferous forest were more vulnerable than those in the broad-leaved forest. The type of damage also varied with tree age in different ways in the three forest types. The proportion of young seedlings that were uprooted(the most severe type of damage) was highest in the coniferous forest. In the mixed forest, young trees were significantly more likely to be uprooted than seedlings and adult trees, while in the broad-leaved forest, the proportion of uprooted adult trees was significantly higher than that of seedlings and young trees. There were also differences among forest types in how tree age affected damage recovery. In the coniferous forest, the recovery rate of trees with broken trunks or crowns(DBH 2.5 cm) increased with tree age. However, in the mixed and broad-leaved forests, no obvious correlation between the recovery rate of trees with broken trunks or crowns and tree age was observed. Trees with severe root damage did not recover; they were uprooted and died. In these forests, vegetation damage and recovery showed tree age dependencies, which varied with tree shape, forest type, and damage type. Understanding this dependency will guide restoration after freezing rain and snow disturbances.     

Coupling effects of altitude and human disturbance on landscape and plant diversity in the vicinity of mountain villages of Beijing, China

Cone-cores discarded by Eurasian red squirrels were used to study the habitat selection of Korean pine-seeds hoarding, in forest patch Nos. 16 and 19 in Liangshui Nature Reserve, China. Ten transects with a total length of 15 km were uniformly set, and data from 343 valid samples were collected in a 369 hm² area. One hundred and eighty four were hoarding samples which were determined according to the cluster analysis based on the number of the cone-cores, while the other 159 were control samples. The principal component analysis, using 11 habitat factors, suggested that the distance from Korean pine forest, forest type, number of Korean pine seedlings, density and type of bush significantly influenced the habitat selection of hoarding by Eurasian red squirrels. The results of Bailey’s method indicated that the squirrels showed (1) preference for natural coniferous forest, natural fir and spruce forest and planted spruce forest; (2) avoidance of planted Korean pine forest and planted larch forest; and (3) random use of natural Korean pine forest. Moreover the distance from the Korean pines in the range of 150–600 m showed no effect on the habitat selection of hoarding by the Eurasian red squirrels. More than 50% of the cone-cores were discarded in either fringe or gap of the Korean pine forest with more cone-cores found at <300 m than at 300 m away (One-Way ANOVA; df = 3, 183, F = 5.76, p = 0.0009). This demonstrated that the Eurasian red squirrels could take the cone-cores out of the Korean pine forest. The density of bushes in samples of hoarding area was significantly lower than that in control samples (Kruskal–Wallis test; df = 1, χ² = 83.99, p < 0.0001). The number of the Korean pine seedlings in samples of hoarding area was significantly higher than that in the control samples (Kruskal–Wallis test; df = 1, χ² = 104.13, p < 0.0001). This illustrated that the hoarding habitat favoured the germination of the Korean pine seedlings. In conclusion the behavior of hoarding Korean pine seeds by the Eurasian red squirrels can promote the regeneration and dispersal of the Korean pines.     

Seed rain and seed bank of Chinese yew (Taxus chinensis var. mairei) population in Tianmu Mountain☆

Seed rain and seed bank of a Chinese yew (Taxus chinensis var. mairei) population in Tianmu Mountain were researched in 2008 and 2009. The seed rain lasted from 16th–23th of October to 5th–14th of December, and the heaviest seed falling period was from 2nd to18th of November. The intensity of seed rain showed a great inter-annual variation, with a good harvest in 2008. The fallen seeds were composed of 49.9% proportion of immature seed, 33.8% proportion of chewed seed and 16.3% proportion of mature seed. The analysis on the soil seed bank under mother forest showed that the number of intact seeds was 122.75 ± 108.08 grain/m² in October, 279.25 ± 210.73 grain/m² in December 2008, and 166.5 ± 165.34 grain/m² in October, 322.5 ± 275.73 grain/m² in December 2009. The increased number of seed was 156.5 ± 222.723 grain/m² in 2008 and 156 ± 275grain/m² in 2009, which showed a significant variation. Large number of intact seeds added into soil seed bank after seed rain each year. The number of intact seeds in soil seed bank decreased 112.75 ± 47.74 grain/m² from December 2008 to October 2009. Large number of intact seeds lost from seed rot and seed predation by animals. The number of seeds in soil bank under bamboo forest was much lower than that of mother tree forest, and the increased number of seeds was 0.63 ± 1.60 grain/m² in 2008 and 2.88 ± 1.86 grain/m² in 2009. The number of seedling was 0.73 ± 1.10 trees/m² in mother tree forest and 0.09 ± 0.35 trees/m² in bamboo forest. Seedling survival ratio was 0.37% in mother tree forest and 10.23% in bamboo forest. The micro-habitat in bamboo forest was fit for seed germination. Birds transported seeds to bamboo forest, and had an important effect on the regeneration of Chinese yew.     

The effects of hoarding habitat selection of Eurasian red squirrels (Sciurus vulgaris) on natural regeneration of the Korean pines

Cone-cores discarded by Eurasian red squirrels were used to study the habitat selection of Korean pine-seeds hoarding, in forest patch Nos. 16 and 19 in Liangshui Nature Reserve, China. Ten transects with a total length of 15 km were uniformly set, and data from 343 valid samples were collected in a 369 hm² area. One hundred and eighty four were hoarding samples which were determined according to the cluster analysis based on the number of the cone-cores, while the other 159 were control samples. The principal component analysis, using 11 habitat factors, suggested that the distance from Korean pine forest, forest type, number of Korean pine seedlings, density and type of bush significantly influenced the habitat selection of hoarding by Eurasian red squirrels. The results of Bailey’s method indicated that the squirrels showed (1) preference for natural coniferous forest, natural fir and spruce forest and planted spruce forest; (2) avoidance of planted Korean pine forest and planted larch forest; and (3) random use of natural Korean pine forest. Moreover the distance from the Korean pines in the range of 150–600 m showed no effect on the habitat selection of hoarding by the Eurasian red squirrels. More than 50% of the cone-cores were discarded in either fringe or gap of the Korean pine forest with more cone-cores found at <300 m than at 300 m away (One-Way ANOVA; df = 3, 183, F = 5.76, p = 0.0009). This demonstrated that the Eurasian red squirrels could take the cone-cores out of the Korean pine forest. The density of bushes in samples of hoarding area was significantly lower than that in control samples (Kruskal–Wallis test; df = 1, χ² = 83.99, p < 0.0001). The number of the Korean pine seedlings in samples of hoarding area was significantly higher than that in the control samples (Kruskal–Wallis test; df = 1, χ² = 104.13, p < 0.0001). This illustrated that the hoarding habitat favoured the germination of the Korean pine seedlings. In conclusion the behavior of hoarding Korean pine seeds by the Eurasian red squirrels can promote the regeneration and dispersal of the Korean pines.     

The effects of hoarding habitat selection of Eurasian red squirrels (Sciurus vulgaris) on natural regeneration of the Korean pines

Cone-cores discarded by Eurasian red squirrels were used to study the habitat selection of Korean pine-seeds hoarding, in forest patch Nos. 16 and 19 in Liangshui Nature Reserve, China. Ten transects with a total length of 15 km were uniformly set, and data from 343 valid samples were collected in a 369 hm² area. One hundred and eighty four were hoarding samples which were determined according to the cluster analysis based on the number of the cone-cores, while the other 159 were control samples. The principal component analysis, using 11 habitat factors, suggested that the distance from Korean pine forest, forest type, number of Korean pine seedlings, density and type of bush significantly influenced the habitat selection of hoarding by Eurasian red squirrels. The results of Bailey’s method indicated that the squirrels showed (1) preference for natural coniferous forest, natural fir and spruce forest and planted spruce forest; (2) avoidance of planted Korean pine forest and planted larch forest; and (3) random use of natural Korean pine forest. Moreover the distance from the Korean pines in the range of 150–600 m showed no effect on the habitat selection of hoarding by the Eurasian red squirrels. More than 50% of the cone-cores were discarded in either fringe or gap of the Korean pine forest with more cone-cores found at <300 m than at 300 m away (One-Way ANOVA; df = 3, 183, F = 5.76, p = 0.0009). This demonstrated that the Eurasian red squirrels could take the cone-cores out of the Korean pine forest. The density of bushes in samples of hoarding area was significantly lower than that in control samples (Kruskal–Wallis test; df = 1, χ² = 83.99, p < 0.0001). The number of the Korean pine seedlings in samples of hoarding area was significantly higher than that in the control samples (Kruskal–Wallis test; df = 1, χ² = 104.13, p < 0.0001). This illustrated that the hoarding habitat favoured the germination of the Korean pine seedlings. In conclusion the behavior of hoarding Korean pine seeds by the Eurasian red squirrels can promote the regeneration and dispersal of the Korean pines.     

Current stocks and potential of carbon sequestration of the forest tree layer in Qinghai Province,China北大核心CSCD

Aims Our objective was to estimate the carbon storage in the forest tree layer in Qinghai Province, China. Methods Based on forest resource inventory data and field investigation data, we estimated the carbon storage, sequestration rate and potentials in the forest tree layer in the Qinghai Province. Important findings The carbon density and total carbon storage of forest tree layer in Qinghai Province was 76.54 Mg·hm-2 and 27.38 Tg, respectively, of which four forest types (Picea spp. forest, Cupressus funebris forest, Betula spp. forest and Populus spp. forest) accounted for 86.67% while their areas were 96.23% of total forest areas in Qinghai. The carbon density and carbon storage of Picea spp. forest was 106.93 Mg·hm-2 and 14.78 Tg, respectively, which was the largest among all forest types. The carbon storage of the forest tree layer at different stand ages followed the sequence of over-mature forest > middle-aged forest > mature forest > near-mature forest > young forest. In addition, the carbon storage of forest tree layer in the province increased from 23.30 Tg in 2003 to 27.38 Tg in 2011. The average annual growth of carbon and carbon sequestration rate were 0.51 Tg and 1.06 Mg·hm-2·a-1, respectively. The maximum and minimum of carbon sequestration rate were respectively found in Cupressus funebris forest (0.44 Mg·hm-2·a-1) and Betula spp. forest (-1.06 Mg·hm-2·a-1). The mean carbon sequestration potential reached 8.50 Tg in 2011, with the highest value found in Picea spp. forest (3.40 Tg). These findings suggested high carbon sequestration potential of forest tree layer in Qinghai Province. Therefore, the carbon storage in Qinghai Province could be increased through better forest management and utilization. © 2018 Editorial Office of Chinese Journal of Plant Ecology. All rights reserved.     

Carbon storage and its distribution of forest ecosystems in Zhejiang Province,China北大核心CSCD

Aims The concentration of CO2 and other greenhouse gases in the atmosphere has considerably increased over last century and is set to rise further. Forest ecosystems play a key role in reducing CO2 concentration in the atmosphere and mitigating global climate change. Our objective is to understand carbon storage and its distribution in forest ecosystems in Zhejiang Province, China. Methods By using the 8th forest resource inventory data and 2011 2012 field investigation data, we estimated carbon storage, density and its distribution in forest ecosystems of Zhejiang Province. Important findings The carbon storage of forest ecosystems in Zhejiang Province was 602.73 Tg, of which 122.88 Tg in tree layer, 16.73 Tg in shrub-herb layer, 11.36 Tg in litter layer and 451.76 Tg in soil layer accounting for 20.39%, 2.78%, 1.88% and 74.95% of the total carbon storage, respectively. The carbon storage of mixed broadleaved forests was 138.03 Tg which ranked the largest (22.90%) among all forest types. The young and middle aged forests which accounted for 70.66% of the total carbon storage were the main body of carbon storage in Zhejiang Province. The carbon density of forest ecosystems in Zhejiang Province was 120.80 t•hm2 and that in tree layer, shrub-herb layer, litter layer and soil layer were 24.65 t•hm2, 3.36 t•hm2, 2.28 t•hm2 and 90.51 t•hm2, respectively. The significant relationship between soil organic carbon storage and forest ecosystem carbon storage indicated that soil carbon played an important role in shaping forest ecosystem carbon density. Carbon density of tree layer increased with age in natural forests, but decreased in the order over-mature > near-mature > mature > middle-aged > young forest in plantations. The proportions of young and middle aged forests were larger than any other age classes. Thereby, the carbon storage of forest ecosystems in Zhejiang Province could be increased through a proper forest management.     

川西米亚罗地区暗针叶林采伐迹地早期植被演替过程的研究

 A secondary succession of vegetation on clearcut sites was studied in Western Sichuan. The coverage and biomass of trees, shrubs and herbs at different stages of succession have been surveyed. The result showed that the coverage and biomass of trees and shrubs have changed greatly in the succession. After the forest was cut, raspberry’s (Rubus daeus) coverage was the greatest during the first 0–15 years, Red birch’s coverage was the greatest during 16–29 years, while the total coverage of other shrubs was greater than those of raspberry and red birch during 10–20 years.The following empirical formulas with good fitness have been used:Ctree=0.803+2.347t1/2 (r=0.88 p<0.01) Cshrub=l0.481 l0.392T+0.373T2 (r=0.87 p<0.01)Cherb=0.489+87.001/T (r=0.93 p<0.01) C: biomass, kilogram/ha T: time period, year According to the curves, the succession of vegetation can be divided into four stages: herb stage. 0—3 years; raspberry stage: 4—10 year; shrub and small broad-leaved forest stage: 11—20 years, and small broad–leaved forest stage: 21—29 years.     

圣海伦斯火山和高山植被

 Mt. St. Helens is an active volcano on the western flank of the Cascade: range in the southwestern Washington State, USA. It is located at lat. 46˚00′—46˚30′N, long 121˚52′—122˚40′W.We had investigated the alpine vegetation at Pine Creek, Butte Camp on Mt. St. Helens for three times, totaling ten days during August and eptember of 1983.The volcano had erupted sending out much pyroclastic, pumice and lava, which devdstated the vegetation around the crater. They not only mechanically destroyed plants tissue, but also buried entirely or partly of the plants.The radiant heat from the volcanic eruption caused the melting of ice and snow, creating huge mudflows, which estroyed and buried vegetation. The high temperture from direct radiant heat incinerated and scorched all the plants. On the other hand, the higher the elevation is, the stronger the wind and the lower the temperture; also snow was present on the alpine range, and this provided a lee for plants, and consequently some plants survived, and new ones row out of the ground. The alpine vegetation on Mt. St. Helens bears both the characteristic of alpine plants and the brand of volcanic activities: vegetation is sparse, species composition of plants limited, structure of community simple, production low and vegetation propagation being the main type of vegetative reproduction.The different types of lpine vegetation grow in different habitats: The community of Luekea pectinata grow in places covered by ice and snow; the community of Polygonum newberryi, Eriogonum pyroleafolium in localities covered by mudflow; the community of Phyllodace empetriformis on slopes of steep rocks and the community of grasses and sedges on low hills and plains. Hese are the four main communities on Mt. St. Helens. The recovery and succession of the alpine vegetation has been discussed. There are two types of succession, the primary and the secodary, with the secondary being the main one.Finally, the paper has analysed the reason why no forest occurs, on Mt. St. Helens. We think that it is a result of the ctive period of the volcano and that the climate conditions are favouable for forest. Also, we have suggested that some herbaceous plants be sown as soon as possible for they can accelerate the recovery of vegetation, and prevent the runoff of soil and water.