Effect of thinning intensity on the carbon sequestration of natural mixed coniferous and broadleaf forests in Xiaoxing'an Mountains, China

To study the effect of thinning intensity on the carbon sequestration by natural mixed coniferous and broad-leaf forests in Xiaoxing’an Mountains,China,we established six 100 m×100 m experimental plots in Dongfanghong For-est that varied in thinning intensity:plot A(10%),B(15%),C(20%),D(25%),E(30%),F(35%),and the control sample area(0%).A principal component analysis was performed using 50 different variables,including species diversity,soil fertility,litter characteristics,canopy structure param-eters,and seedling regeneration parameters.The effects of thinning intensity on carbon sequestration were strongest in plot E(0.75),followed by D(0.63),F(0.50),C(0.48),B(0.22),A(0.11),and the control(0.06).The composite score of plot E was the highest,indicating that the carbon sequestration effect was strongest at a thinning intensity of 30%.These findings provide useful insights that could aid the management of natural mixed coniferous and broadleaf forests in Xiaoxing’an Mountains,China.This information has implications for future studies of these forests,and the methods used could aid future ecological assessments of the natural forests in Xiaoxing’an Mountains,China.

Remote Sensing Monitoring of the Subalpine Coniferous Forests and Quantitative Analysis of the Characteristics of Succession in East Mountain Area of Tibetan Plateau——A Case Study With Zamtang County

The study area lies in the Dadu River drainage area in upstream Yangtze River.The spatial distribution of subalpine coniferous forests in 1989 and 2009 was extracted by means of a combined method of object orientation and visual interpretation,and then the overlaying analysis of these data was conducted.The type and spatial location of succession were discovered and served as the sample of dependant variable.Meanwhile,supported by GIS technology and based on DEM and thematic data,the eight variables including altitude,slope,sin and cosin of aspect,curvity of land surface,and distance to residential area,cultivated land and road were extracted served as the sample of spatial succession of subalpine coniferous forests to fit Logistic Regression,and then the contribution of each independent variable as well as the spatial property of the occurrence probability of succession was calculated.The results suggested that,during the succession of subalpine coniferous forests to meadow,the closer to the residential area and cultivated land,the greater the contribution to succession is.In particular,when the distance to the residential area decreases by one unit,the probability for its conversion to meadow will be increased by 1.15 times.During the succession of subalpine coniferous forests to deciduous-broadleaved shrubs,the sin of aspect and distance to residential area contribute more,and the probability of succession increases with increasing degree of northwardness,i.e.when the degree of northwardness increases by one unit,the probability will be increased by 1.2 times.The quantitative analysis of spatial succession property of subalpine coniferous forests will supply scientific basis to the protection and restoration of subalpine coniferous forests.

Vegetation-environment relationship in conifer dominating forests of the mountainous range of Indus Kohistan in northern Pakistan

Environmental variables play a crucial role in shaping vegetation structure,mainly in mountainous ecosystems.Different studies have attempted to identify the environment-vegetation relationship of Conifer Dominating Forests(CDF)worldwide.However,due to differences in local climate and soil composition,different environmental drivers can be found.By applying multivariate analysis techniques,this study investigated the vegetation-environment relationship of CDF of Indus Kohistan in northern Pakistan.Our results showed that CDF of Indus Kohistan are distributed in five distinct ecological groups,which are dominated by different trees and understory species.A total of 7 trees and 71 understory species were recorded from the sampling sites.Cedrus deodara was the leading species among four groups,having the highest importance value(IV),density and basal area.Group I was dominated by Pinus wallichiana with the second highest importance value,density and basal area.In addition,elevation,slope,maximum water holding capacity(MWHC),soil moisture(SM),total organic matter(TOM),sodium,phosphorus and nickel showed highly significant influence on composition and distribution pattern of Indus Kohistan vegetation.Therefore,this study shows a new evidence of vegetation-environment relationship,pointing out specific drivers of vegetation structure in CDF of Indus Kohistan region in northern Pakistan.

Water holding effect of subalpine dark coniferous forest soil in Gongga Mountain, China

Because of the distinction of soil property and humus content, soil water content is not ideal to indicate whether it is suitable to the growth of plant. Mainly based on the PF-a numerical value denoting the water regime of soil and connected with the growth of plant, the study combined the moisture percentage of soil with PF to research in quantity the interrelation between the moisture percentage and PF in different succession phases of subalpine dark coniferous forest in Gongga Mountain. The results showed that: (1) In the same PF value, the moisture percentage in humus horizon increased gradually with the devel-opment of the succession of the dark coniferous forest; The moisture percentage of over-mature forest was the highest and>mature forest>half-mature forest>young growth forest; (2) With the increase of soil depth, the soil bulk density increased and the moisture percentage decreased, but the difference in the percentage of moisture was not notable in different succession phases. (3) In different succession series, the vegetation affected the soil water characteristics by increasing the soil organic matter, improving the soil construction, receding the soil bulk density and enhancing the soil porosity; (4) The humus horizon of the dark coniferous forest soil has the highest water holding capability in this region.

Contribution of Root Respiration to Total Soil Respiration in a Betula ermanii-Dark Coniferous Forest Ecotone of the Changbai Mountains, China

Total and root-severed soil respiration rates for five plots set up 50 m apart in a Betula ermanii Cham.-dark coniferous forest ecotone on a north-facing slope of the Changbai Mountains, China, were measured to evaluate the seasonal variations of soil respiration, to assess the effect of soil temperature and water content on soil respiration, and to estimate the relative contributions of root respiration to the total soil respiration. PVC cylinders in each of 5 forest types of a B. ermanii-dark coniferous forest ecotone were used to measure soil respirations both inside and outside of the cylinders. The contribution of roots to the total soil respiration rates ranged from 12.5% to 54.6%. The mean contribution of roots for the different plots varied with the season, increasing from 32.5% on June 26 to 36.6% on August 3 and to 41.8% on October 14. In addition, there existed a significant (P < 0.01) logarithmic relationship between total soil respiration rate and soil temperature at 5 cm soil depth. Also, a similar trend was observed for the soil respiration and soil water content at the surface (0-5 cm) during the same period of time.

Nutrient and Litter Patterns in Three Subalpine Coniferous Forests of Western Sichuan, China

Investigations were conducted to quantify litterfall, and litter and nutrient accumulation in forest floor, and to acquire information on litter decomposition and nitrogen and phosphorus release patterns in three different subalpine coniferous forests, a plantation （P1）, a secondary forest （SF）, and a primitive forest （PF）, in western Sichuan, China. The litter trap method was used to evaluate litterfall with the litterbag method being utilized for litter decomposition. Seasonal patterns of litterfall were similar in the three forests, with two peaks occurring in September-November and March-May. The plantation revealed an annual litterfall of 4.38 x 103 kg ha-1, which was similar to those of SF and PF, but P1 had a lower mass loss rate and a higher C/N ratio. The C/N ratio may be a sound predictor for the decomposition differences. N concentrations of leaf litter in both the secondary forest and primitive forest increased first and then decreased, and the percentages of their final/initial values were 108.9% and 99.9%, respectively. P concentration in the three forests increased by the end of the study. The results of litterfall and decomposition indicated that in the plantation the potential to provide nutrients for soil organic matter was similar to those of SF and PF; however, its slower decomposition rate could result in a somewhat transient accumulation of litter in the forest floor.

Abiotic and biotic drivers of species diversity in understory layers of cold temperate coniferous forests in North China

Understory plants are important components of forest ecosystems and play a crucial role in regulating community structures,function realization,and community succession.However,little is known about how abiotic and biotic drivers affect the diversity of understory species in cold temperate coniferous forests in the semiarid climate region of North China.We hypothesized that(1)topographic factors are important environmental factors affecting the distribution and variation of understory strata,and(2)different understory strata respond differently to environmental factors;shrubs may be significantly affected by the overstory stratum,and herbs may be more affected by surface soil conditions.To test these hypotheses,we used the boosted regression tree method to analyze abiotic and biotic environmental factors that influence understory species diversity,using data from 280 subplots across 56 sites in cold temperate coniferous forests of North China.Elevation and slope aspect were the dominant and indirect abiotic drivers affecting understory species diversity,and individual tree size inequality(DBH variation)was the dominant biotic driver of understory species diversity;soil water content was the main edaphic factors affecting herb layers.Elevation,slope aspect,and DBH variation accounted for 36.4,14.5,and 12.1%,respectively,of shrub stratum diversity.Shrub diversity decreased with elevation within the range of altitude of this study,but increased with DBH variation;shrub diversity was highest on north-oriented slopes.The strongest factor affecting herb stratum species diversity was slope aspect,accounting for 25.9%of the diversity,followed by elevation(15.7%),slope(12.2%),and soil water content(10.3%).The highest herb diversity was found on southeast-oriented slopes and the lowest on northeast-oriented slopes;herb diversity decreased with elevation and soil water content,but increased with slope.The results of the study provide a reference for scientific management and biodiversity protection in cold temperate coniferous forests of North China.

Soil Properties in Coniferous Forest Stands Along a Fly Ash Deposition Gradient in Eastern Germany

Physical, chemical, and microbial properties of forest soils subjected to long-term fly ash depositions were analyzed in spruce (Picea abies (L.) Karst.) stands of eastern Germany on three forest sites along an emission gradient of 3 (high input), 6, and 15 km (low input) downwind of a coal-fired power plant. Past emissions resulted in an atypical high mass of mineral fly ash constituents in the organic horizons at the high input site of 128 t ha-1 compared to 58 t ha-1 at the low input site. Magnetic susceptibility measurements proved that the high mineral content of the forest floor was a result of fly ash accumulation in these forest stands. Fly ash deposition in the organic horizons at Site I versus III significantly increased the pH values, effective cation exchange capacity, base saturation and, with exception of the L horizon, concentrations of mobile heavy metals Cd, Cr, and Ni, while stocks of organic C generally decreased. A principal component analysis showed that organic C content and base status mainly controlled soil microbial biomass and microbial respiration rates at these sites, while pH and mobile fractions of Cd, Cr, and Ni governed enzyme activities. Additionally, it was hypothesized that long-term fly ash emissions would eventually destabilize forest ecosystems. Therefore, the results of this study could become a useful tool for risk assessment in forest ecosystems that were subjected to past emissions from coal-fired power plants.

Carbon and Nitrogen Transformations in Surface Soils Under Ermans Birch and Dark Coniferous Forests

Soil samples were taken from an Ermans birch （Betula ermanii）-dark coniferous forest （Picea jezoensis and Abies nephrolepis） ecotone growing on volcanic ejecta in the northern slope of Changbai Mountains of Northeast China, to compare soil carbon （C） and nitrogen （N） transformations in the two forests. The soil type is Umbri-Gelic Cambosols in Chinese Soil Taxonomy. Soil samples were incubated aerobically at 20℃ and field capacity of 700 g kg^-1 over a period of 27 weeks. The amount of soil microbial biomass and net N mineralization were higher in the Ermans birch than the dark coniferous forest （P 〈 0.05）, whereas the cumulative C mineralization （as CO2 emission） in the dark coniferous forest exceeded that in the Ermans birch （P 〈 0.05）. Release of the cumulative dissolved organic C and dissolved organic N were greater in the Ermans birch than the dark coniferous forest （P 〈 0.05）. The results suggested that differences of forest types could result in considerable change in soil C and N transformations.

Active organic carbon pool of coniferous and broad-leaved forest soils in the mountainous areas of Beijing

In order to explore the effects of different forest types on active soil carbon pool, the amounts and density of soil organic carbon （SOC） were studied at different soil horizons under typical coniferous and broad-leaved forests in the mountainous area of Beijing. The results showed that the amount of total SOC, readily oxidizable carbon and particulate organic carbon decreased with increasing depths of soil horizons and the amounts at depths of 0-10 cm and 10-20 cm in broad-leaved forest was clearly higher than that in coniferous forests. The trend of a decrease in SOC density with increasing depth of the soil horizon was similar to that of the amount of SOC. However, no regular trend was found for SOC density at different depths between coniferous forest and broad-leaved forests. The ratio of readily oxidizable carbon to total amount of SOC ranged from 0.36-0.45 and the ratio of particulate organic carbon to total amount of SOC from 0.28-0.73; the ratios decreased with increasing depths of soil horizons. Active SOC was significantly correlated with total SOC; the relationship between readily oxidizable carbon and particulate organic carbon was significant. A broad-leaved forest may produce more SOC than a coniferous forest.

Effect of thinning intensity on understory herbaceous diversity and biomass in mixed coniferous and broad-leaved forests of Changbai Mountain

Background:Herbs are an important part of the forest ecosystem,and their diversity and biomass can reflect the restoration of vegetation after forest thinning disturbances.Based on the near-mature secondary coniferous and broad-leaved mixed forest in Jilin Province Forestry Experimental Zone,this study analyzed seasonal changes of species diversity and biomass of the understory herb layer after different intensities of thinning.Results:The results showed that although the composition of herbaceous species and the ranking of importance values were affected by thinning intensity,they were mainly determined by seasonal changes.Across the entire growing season,the species with the highest importance values in thinning treatments included Carex pilosa,Aegopodium alpestre,Meehania urticifolia,and Filipendula palmata,which dominated the herb layer of the coniferous and broad-leaved mixed forest.The number of species,Margalef index,Shannon-Wiener index and Simpson index all had their highest values in May,and gradually decreased with months.Pielou index was roughly inverted“N”throughout the growing season.Thinning did not increase the species diversity.Thinning can promote the total biomass,above-and below-ground biomass.The number of plants per unit area and coverage were related to the total biomass,above-and below-ground biomass.The average height had a significantly positive correlation with herb biomass in May but not in July.However,it exerted a significantly negative correlation with herb biomass in September.The biomass in the same month increased with increasing thinning intensity.Total herb biomass,above-and below-ground biomass showed positive correlations with Shannon-Winner index,Simpson index and Pielou evenness index in May.Conclusions:Thinning mainly changed the light environment in the forest,which would improve the plant diversity and biomass of herb layer in a short time.And different thinning intensity had different effects on the diversity of understory herb layer.The findings provide theoretical basis and reference for reasonable thinning and tending in coniferous and broad-leaved mixed forests.

Species Diversity Based on Vertical Structure as Indicators of Artificial Restoration for Coniferous Forests in Southwest China

Five indices of species richness, species diversity and species evenness were used to assess a diversity of four types of coniferous forests undergone different artificial regeneration time. The study was based on the vertical structure of forests, involving growth-forms of total plants as well as vertical layers of woody plants. The results showed that, except for the fourth layer of woody plants, the vertical structure of the four forests exhibited significant difference in terms of their species richness, species diversity and species evenness, suggesting that a species diversity index provided more detailed information and was a better index reflecting the regeneration processes in this region. It was recommended that silvicultural management of artificially regenerated forests should be strengthened to conserve the biodiversity of the forests, optimize forest structure and, in the long run, promote sustainable development of forest ecosystems.

How do nitrogen-limited alpine coniferous forests acquire nitrogen?A rhizosphere perspective

Background:Alpine coniferous forest ecosystems dominated by ectomycorrhizal(ECM)tree species are generally characterized by low soil nitrogen(N)availability but stabilized plant productivity.Thus,elucidating potential mechanisms by which plants maintain efficient N acquisition is crucial for formulating optimized management practices in these ecosystems.Methods:We summarize empirical studies conducted at a long-term field monitoring station in the alpine coniferous forests on the eastern Tibetan Plateau,China.We propose a root-soil interaction-based framework encompassing key components including soil N supply,microbial N transformation,and root N uptake in the rhizosphere.Results:We highlight that,(i)a considerable size of soil dissolved organic N pool mitigates plant dependence on inorganic N supply;(ii)ectomycorrhizal roots regulate soil N transformations through both rhizosphere and hyphosphere effects,providing a driving force for scavenging soil N;(iii)a complementary pattern of plant uptake of different soil N forms via root-and mycorrhizal mycelium-pathways enables efficient N acquisitions in response to changing soil N availability.Conclusions:Multiple rhizosphere processes abovementioned collaboratively contribute to efficient plant N acquisition in alpine coniferous forests.Finally,we identify several research outlooks and directions to improve the understanding and prediction of ecosystem functions in alpine coniferous forests under on-going global changes.

Responses of soil Collembolans to vegetation restoration in temperate coniferous and broad-leaved mixed forests

A total of 900 soil samples were collected from five habitats,including primary coniferous broad-leaved mixed forests,secondary coniferous broad-leaved mixed forests,secondary broad-leaved forests,secondary shrub forests,and cutover lands in spring,summer,and autumn to quantify responses of soil Collembolans(springtails)to the restoration of vegetation of temperate coniferous and broad-leaved mixed forests.The results reveal that the taxonomic composition of Collembolans varied in the different stages of vegetation restoration.Seasonal variations were in regard to their abundance and richness.High similarities existed in Collembola communities at different stages of vegetation restoration,and distribution patterns of Collembola taxa displayed an evenness throughout all habitats.Soil Collembolans tended to gather on litter layers and soil surface;the highest abundance was found in the upper 5 cm soil layer during the initial stages of vegetation recovery.Tomocerus,Proisotoma,and Folsomia genera responded positively to the restoration of vegetation.However,responses of Ceratophysella and Parisotoma genera were negative.In addition,the Onychiuridae family did not respond to the vegetation restoration process.It was concluded that restoration of vegetative cover can increase the abundance of soil Collembolans,but different genera respond differently.

Analysis of solute preferential transport in a dark coniferous forest ecosystem of Gongga Mountain,Sichuan Province,southwestern China

We selected a dark coniferous forest ecosystem of Gongga Mountain in the upper reaches of the Yangtze River as our research area to study the preferential flow and solute preferential transport by adding the tracers KNO3 and KBr to the self-made soil column equipment in different ways to examine density and volume changes of inflows and outflows of a mass input （impulse input） and a stable, well-distributed input （step input））. The results showed that this dark coniferous forest ecosystem of Gongga Mountain is a typical area of preferential flow and solute preferential transport, a process that can be classified into five parts. A great amount of solute was transported at high speed as the result of preferential flow in the soil and caused the density of the solute in both deep water and in groundwater to rise rapidly, which definitely increased pollution in the deep soil layer.

ORDINATION AND GRADIENT ANALYSIS OF CONIFEROUS FOREST IN DAXINGANLING

In this paper,the quantitative approach is applied on the study of coniferous forestbased on the data which were collected by the field investigation in Daxinganling region.The mainpurpose is objectively to show the position of communities in the space and the relationship be-tween the community and environment.By means of ordination,it is found that dahurian larch for-est,mongolian scots pine forest and korean fir forest lie in different positions. Gradient analysis ofthree dominant types of conigerous forest has revealed the difference of ecological amplitude,thedifference is one of the important reasons that determine the different communities in the differentenvironment.

雪被厚度对土壤温湿度的影响

以牡丹江森林生态系统国家定位观测研究站为平台,针对雪被覆盖期(积雪形成期、积雪稳定期、积雪融化期)雪被厚度、土壤温度、土壤含水量三者间的相关关系开展研究。结果表明,土壤含水量在积雪期呈现先降低再升高趋势,同一时期的不同雪被厚度土壤含水量无显著差异;积雪形成期及稳定期,雪被厚度与土壤温度呈显著正相关,随着雪被厚度增加,土壤温度升高。该研究对加深非生长季土壤生态认知、解释温度升高、林窗或林冠下生境变化等规律具有重要意义。

山西太岳山不同针叶纯林及混交林土壤有机碳库的变异性

为研究不同针叶林型土壤有机碳及其碳库管理指数变化特征,以山西太岳山林区油松(Pinus tabuliformis)林、华北落叶松(Larix gmelinii var.principis-rupprechtii)林、油松和华北落叶松混交林3种人工林为研究对象,测定了各森林群落的根系生物量、土壤理化性质,分析不同林型土壤理化性质及碳库管理指数的变化特征。结果表明:土壤有机碳质量分数、全氮质量分数、土壤含水率、β-葡萄糖苷酶活性、酸性磷酸酶活性等均在油松落叶松混交林中出现最大值。3种林型的土壤有机碳库中,稳定有机碳的质量分数最高,约占总有机碳的80%以上。在0<h≤10 cm土层中,油松林土壤碳库管理指数显著低于落叶松林和油松落叶松混交林(P<0.05),前者分别比后两者低22.32%、21.69%。相关性分析及结构方程模型(SEM)表明,林分类型的转变对土壤含水率、土壤酶活性有显著正向影响(P<0.05),根系生物量显著促进了土壤养分及土壤酶活性的增加,土壤养分及根系生物量对土壤碳库管理指数产生显著正向影响(P<0.05)。油松和华北落叶松混交可以提高土壤养分质量分数,增强土壤微生物活性,有利于土壤碳库管理指数和碳库质量的提高。

黔中地区马尾松-甜槠针阔混交林群落结构特征与林木空间分布格局及其关联性

为探究黔中地区天然次生马尾松针阔混交林群落结构及其空间分布格局特征,选取典型的马尾松-甜槠针阔混交林和马尾松纯林为调查对象,采用成对相关函数分析环境异质性对主要树种空间分布的影响、主要树种及径级空间格局和空间关联性研究。调查共记录91种植物,其中马尾松-甜槠针阔混交林和马尾松纯林分别为42种和68种。2个森林群落中乔木总径级整体均呈倒“J”形结构,结构稳定,自然更新良好。结果表明,生境异质性对2种群落类型在小距离上空间分布格局的影响作用明显。2块样地幼树、中树及总体分布格局相似,均为点距离在0~10 m内呈聚集分布、在10~25 m内呈随机分布,而大树在整个观察尺度内均为随机分布。马尾松纯林中马尾松-甜槠、甜槠-槲栎的空间关联性均以不相关为主,马尾松-槲栎以负相关为主;而马尾松-甜槠针阔混交林中马尾松与甜槠在10~20 m以负相关为主。2种群落类型不同径级的空间关联性总体为不相关。黔中山地天然次生马尾松-甜槠针阔混交林、马尾松纯林群落结构存在差异,环境异质性、径级结构和空间尺度对两者空间分布格局及其关联性影响明显。

中国鹿蹄草属的地理分布及其区系意义

本研究通过查阅植物志和标本,获取了中国鹿蹄草属(Pyrola)的地理分布信息。结果显示:(1)我国所有省份皆有鹿蹄草属分布,其中吉林省和四川省分布最多,达到了10种;(2)鹿蹄草属为北温带分布型,但种一级以中国特有分布型最多;(3)从海平面以上至海拔4100 m皆有鹿蹄草属分布,主要集中分布于海拔1500~2500 m;(4)我国鹿蹄草属分布区与针叶林高度重叠,最多见于寒温性针叶林,具有植被恢复的指示意义。