Phenology of plants in relation to ambient environment in a subalpine forest of Uttarakhand,western Himalaya

Observations on phenology of some representative trees, shrubs, under-shrubs and herbs in a subalpine forest of Uttarakhand, western Himalaya were recorded. With the commencement of favorable growth season in April, occurrence of leaf fall was indicatory growth phenomenon in Quercus semecarpifolia, Q. floribunda and Abies spectabilis. However, active vegetative growth in herbaceous species starts onward April and fruit maturation and seed dehiscence are completed from mid of September to October. In general, vegetative growth and reproductive stages in majority of the studied species seems to be dependent on adequate moisture content and also flowering and fruiting in subalpine plants correlate ambient temperature.     

A fire history of a subalpine forest in south-eastern Wyoming, USA

Fire history was determined for part of the Routt‐Medicine Bow National Forest in south‐eastern Wyoming using fire‐scar and age‐class analysis. A composite chronology of fire events was used to determine mean fire intervals (MFI) for pre‐EuroAmerican settlement, EuroAmerican settlement (before 1868 ad ), EuroAmerican settlement and modern (after 1912) periods, for all fires and stand‐replacing fires. Point‐scale MFI was also determined using grand means from individual trees. Stand‐replacing fires were reconstructed to determine fire rotation. MFI for the entire time period is 5.5–8.4 years. MFI decreased from 9.3 to 15.7–1.9–2.9 years from the preto post‐EuroAmerican settlement periods, and increased during the modern period. Point‐scale MFIs are longer than MFI of the study area. Fire rotation is 182 years for the total period of record, but increased from 127 years during the pre‐EuroAmerican settlement period to 170 years during the EuroAmerican settlement period. Fire rotation during the modern period dramatically increased to 27,035 years. Results suggest fire suppression may have influenced the fire regime. Comparison of regional fire events with fire events from this study indicate regional weather has an important influence on Rocky Mountain fire regimes.     

卧龙自然保护区亚高山暗针叶林林隙特征研究

以卧龙亚高山暗针叶林为研究对象,分析了森林群落林隙的大小结构、形成方式及林隙形成木(GM)的结构特征．结果表明,林隙密度为18．5个·hm^-2冠林隙和扩展林隙分别占森林面积的28．4％和60．0％;冠林隙的大小变化在10～1134．7m^2之间,平均面积为153．45m^2;扩展林隙的大小变化在84．11～1646．3m^2之间,平均面积为324．34m^2;平均每个林隙的形成木为5．14株,单株形成木形成的林隙只占8．1％．不同形成木类型对林隙形成的贡献大小次序为：折干>掘根>枯立>断梢;暗针叶林林隙大多由岷江冷杉、铁杉、糙皮桦形成．径级在60～70cm,高度在30～35m之间的林冠上层的岷江冷杉,发生折倒形成林隙的可能性最大．     

The effect of environmental factors on the regeneration of Quercus semecarpifolia Sm. in Central Himalaya,Nepal

Poor regeneration of oak forest has been observed in north America and Eurasia. In the Himalaya it has mainly been explained by anthropogenic pressures. This study analyses the regeneration of two Quercus semecarpifolia Sm. forests (2–3000 m a.s.l.), where one forest has almost nil disturbance and the other has different degrees of canopy disturbance. The relationships between biotic and abiotic environmental variables and the number of Quercus semecarpifolia seedlings and saplings (i.e., recruits <10 cm Diameter at Breast Height (DBH)) were analysed by means of Generalized Additive Models (GAM). The two forests were compared with respect to size-class distributions of mature trees (i.e., >10 cm DBH), and the number of recruits.The size-class distributions indicate that regeneration is most reliable in the nearly undisturbed forest. Most recruits were found under high canopy cover and high potential radiation. Canopy disturbance has a negative effect on the number of seedlings. Seedlings seem to prefer a pH of around 6, Loss-on-Ignition between 20 and 30 %, and total nitrogen between 2 and 3 %. In general, there were very few plots with saplings, and there was not a clear relationship between the number of saplings and the soil variables. The size-class diagrams indicate a lack of young trees in the disturbed forest, and it is hypothesized that fire may inhibit recruits reaching the canopy phase.     

Gap regeneration of major tree species in different forest types of Japan

Gap regeneration of major tree species was examined, based on the pattern of gap phase replacement, in primary old-growth stands of warm-temperate, cool-temperate and subalpine forests, Japan. Using principal component analysis, the gap-regeneration behavior of major tree species could be divided into three guilds and that of Fagus crenata (monodominant species of cool-temperate forests). The criteria used for this division were total abundance of canopy trees and regenerations and relative abundance of regenerations to canopy trees. The gap-regeneration behavior of species in the first guild was that canopy trees regenerate in gaps from seedlings or saplings recruited before gap formation; they had higher total abundance and more abundant regenerations relative to their canopy trees. The gap-regeneration behavior of F. crenata was same as species in the first guild, but F. crenata had less abundant regenerations relative to its canopy trees. Species in the second guild had lower total abundance and less abundant regenerations to their canopy trees. The guild contained species whose canopy trees regenerate in gaps from seedlings or saplings recruited after gap formation or regenerate following largescale disturbance. The third guild consisted of species with lower total aboundance and more abundant regenerations relative to their canopy trees. The gap-regeneration behavior of some species in this guild was that trees regenerate in gaps from seedlings or saplings recruited before gap formation, and grow, mature, and die without reaching the canopy layer, while the gap-regeneration behavior of other species was same as that of species in the first guild or F. crenata. Major tree species of subalpine forests were not present in the third guild.     

The relation among soil microorganism, enzyme activity and soil nutrients under subalpine coniferous forest in Western Sichuan

Soil microorganism and enzymes are important parts of forest ecosystem and sensitive to environmental changes. They have many critical functions in energy conversion and material cycle of forest soil. However, there are few studies about soil biological properties under subalpine coniferous forest, in particular, a serial of spruce plantation chronosequences following clear-cutting of natural coniferous forest in western Sichuan. We measured the quantity of soil microorganism (including bacteria, fungi and actinomyces), enzyme activity and soil nutrients under spruce plantation chronosequences in western Sichuan to investigate soil biological properties and their relationship with soil nutrients. The results showed that soil microorganism, enzyme activity and soil nutrients of the mature spruce plantation were significantly lower than those of the young spruce plantation and secondary broad-leaved forest. Soil fertility degraded greatly with the increasing of spruce plantation age and was mainly affected by forest micro-environment. There were significant correlation between the amounts of soil microorganisms, soil enzyme activities and nutrients (e.g. soil organic matter, total N, total P, alkali-hydrolyzable N and available K). Therefore soil biological indices can be used to evaluate soil fertility. In order to accelerate the course of restoration and rehabilitation of degraded pure plantation, the strategy and measures were put forward, including application of thinning rationally for existing dense plantations and establishment of mixture forest of coniferous and broad-leaved trees for new afforestations, which would create good forest micro-environment for plant growth.     

The relation among soil microorganism, enzyme activity and soil nutrients under subalpine coniferous forest in Western Sichuan

Soil microorganism and enzymes are important parts of forest ecosystem and sensitive to environmental changes. They have many critical functions in energy conversion and material cycle of forest soil. However, there are few studies about soil biological properties under subalpine coniferous forest, in particular, a serial of spruce plantation chronosequences following clear-cutting of natural coniferous forest in western Sichuan. We measured the quantity of soil microorganism (including bacteria, fungi and actinomyces), enzyme activity and soil nutrients under spruce plantation chronosequences in western Sichuan to investigate soil biological properties and their relationship with soil nutrients. The results showed that soil microorganism, enzyme activity and soil nutrients of the mature spruce plantation were significantly lower than those of the young spruce plantation and secondary broad-leaved forest. Soil fertility degraded greatly with the increasing of spruce plantation age and was mainly affected by forest micro-environment. There were significant correlation between the amounts of soil microorganisms, soil enzyme activities and nutrients (e.g. soil organic matter, total N, total P, alkali-hydrolyzable N and available K). Therefore soil biological indices can be used to evaluate soil fertility. In order to accelerate the course of restoration and rehabilitation of degraded pure plantation, the strategy and measures were put forward, including application of thinning rationally for existing dense plantations and establishment of mixture forest of coniferous and broad-leaved trees for new afforestations, which would create good forest micro-environment for plant growth.     

长白山次生杨桦林优势更新幼苗空间分布及环境解释

为了解长白山次生杨桦林中优势更新幼苗的空间分布及其与环境因子之间的关系,以5.2 hm²（200 m×260 m）固定样地更新幼苗的全面定位调查和环境因子调查本底数据为基础,对样地内个体数量排序前5的优势更新幼苗进行分析。结果表明：在中小距离尺度上,水曲柳（Fraxinus mandshurica）（0-90 m）、色木槭（Acer mono）（0-60 m）、紫椴（Tilia amurensis）（0-60 m、90-150 m）和假色槭（Acer pseudo-sieboldianums）（0-90 m）更新幼苗的空间分布关系为显著正自相关,呈聚集性分布;群落水平上,环境变量和空间变量对5种优势更新幼苗的空间分布变异解释能力为61%,其中,纯粹空间变量的解释度为56%,而纯粹环境变量的解释度不足1%;种群水平上,环境因子对更新幼苗的空间分布有一定影响,其中,水曲柳幼苗的空间分布与土壤有机质、土壤全钾和土壤水分显著相关,色木槭幼苗的空间分布与土壤有机质和土壤全磷显著相关,紫椴幼苗的空间分布与土壤全磷显著相关,假色槭幼苗的空间分布与土壤水分显著相关;簇毛槭（Acer barbinerve）幼苗的空间分布与环境因子未表现出显著的相关性。长白山次生杨桦林中优势更新幼苗多为聚集性分布,环境因子对其分布有一定影响。     

Structural diversity and representativeness of forest vegetation in a protected area of Kumaun Himalaya, India: implications for conservation

Forest vegetation of a Protected Area (Askot Wildlife Sanctuary) in Kumaun (west Himalaya) was analysed for structure, composition and representativeness. A high percentage of non-natives was noticed in herbaceous flora of all representative forest types. Floristic representativeness in all growth forms (tree, shrub and herbs) increased significantly (tree, p<0.05; shrub and herbs, p<0.01) with altitude. The population structures of trees suggest, (i) expansion of riverine and Pinus roxburghii forests; (ii) compositional changes in Quercus leucotrichophora and Quercus lanuginosa forests, largely owing to preferred extraction demand of inhabitants; and (iii) infrequent regeneration and declining population of Quercus semecarpifolia and Abies pindrow forests. The possible pathways of non-native introduction in the study area were examined. Considering the existing status of forest vegetation and future trends, proliferation of non-native species in most forest types was discussed. It is suggested that the compositional changes vis-a`-vis proliferation of non-native species need priority attention while initiating conservation activities in the reserve.     

Spatial pattern of Quercus regeneration limitation and Acer rubrum invasion in a Piedmont forest

Abstract. Across eastern North America, there is a temporal trend from open Quercus forests to closed forests with increased Acer rubrum in the understory. We used a series of Ripley's K(d) analyses to examine changes in the spatial pattern of Quercus and Acer rubrum stems greater than 2.5 cm DBH over 45 yr in a 2‐ha mapped stand. Specifically, we asked whether changes over time were consistent with the hypothesis that Quercus is being competitively replaced by Acer rubrum. Both Acer rubrum and Quercus stems are spatially clumped, but have become less clumped over time. Stem mortality from Hurricane Fran (1996) was more clumped in all strata of the forest, at all spatial scales, than expected if damage had occurred to stems at random. Acer rubrum ingrowth occurred more often near established trees (all species) in the midstory, whereas Quercus ingrowth occurred less often near established trees in the midstory. The specific hypothesis that stems of Acer rubrum in the midstory of the forest are associated with a lack of Quercus regeneration was strongly supported. This effect occurred at all spatial scales tested, including scales larger than that at which direct competition for light can occur. Edaphic gradients in the plot are correlated with many of the observed trends at large spatial scales, and our results suggest that the presence of such gradients can generate complex spatial patterns over time.     

Relationship between field-layer vegetation and canopy openings in a Carpathian subalpine spruce forest

The field-layer structure relative to the distribution of canopy gaps was analysed in a subalpine spruce forest in the Babia Góra massif – one of the highest in the Polish West Carpathians. Nineteen synusiae (floristically, physiognomically and ecologically homogenous one-layered vegetation units) in the field-layer were distinguished on the basis of the dominance of 8 vascular plants and 1 moss species. The presence of synusiae was noted in a grid of points spaced at 10 × 10 m which was established in a 14.4 ha area. This grid was then laid over a map of gap distribution. The main results are: 1. Nearly 2/3 of the area was covered with two mono-dominant synusiae: Athyrium distentifolium and Vaccinium myrtillus. 2. The spatial structure of the field layer was related to the distribution of gaps. A significant departure from a random distribution was noted for eight synusiae, which together covered 88% of the area under the spruce canopy and 92% in gaps. 3. The percentage of area covered by Athyrium distentifolium in gaps was nearly twice as great as outside them. A positive relationship to gaps also showed patches dominated by Calamagrostis villosa and Dryopteris dilatata + Rubus idaeus, while a negative relationship occurred for synusiae dominated by: Dryopteris dilatata, Vaccinium myrtillus, V. myrtillus + D. dilatata, and V. myrtillus + Polytrichum formosum. 4. There were significant differences in the structure of the field layer between the understory of closed stands and in gaps larger than 50 m². This means that even a small-scale disturbance touching a few trees and causing only a small modification in light and soil conditions can result in considerable changes in the field-layer vegetation in subalpine spruce forests.     

Niches of plant populations in mangrove reserve of Qi’ao Island, Pearl River Estuary

Thirty-two 10 × 10 m² quadrats were set up in four mangrove communities for the study of the niches of nine plants with horizontal and vertical resource sequences in Dawei Bay, Qi’ao Island, Zhuhai City. Generally, species diversities of natural mangroves were higher than those of plantations. The diversities decreased along sequence of substrate layer, shrub layer and tree layer in natural mangroves; and were highest on the shrub layer in plantations. At the horizontal resource sequence, the niche breadth varied 0.132–0.896 (B_(sw)) and 0.120–0.693 (B_(L)). The niche breadth of Acanthus ilicifolius and Aegiceras corniculatum were the highest and that of Spartina alterniflora was the lowest. At the vertical resource sequence, the niche breadth varied 0–0.400 (B_(sw)) and 0.333–0.747 (B_(L)). All the niche breadth values were the lowest except those of A. ilicifolius and A. corniculatum. The niche similarity of the populations varied 0–0.746 and 0–1.000 at the horizontal and vertical resource sequences, respectively. A. ilicifolius and A. corniculatum had niche overlap with all plants at the horizontal resource sequence, while the introduced Sonneratia caseolaris and Sonneratiaapetala had no such overlapping between six and five plants in the community, respectively. At the vertical resource sequence, A. ilicifolius and A. corniculatum had niche overlapping with all the populations. The more niche overlapping existed among the other populations. The results indicated that, currently, the mangrove plantation in Qi’ao Island had a simplex structure and composition of species. The status of plant populations’ niche was determined by the species selected and structure of afforestation. It is suggested to create forest gaps artificially and introduce Kandelia obovata saplings to reverse its current status of lower niche breadth, facilitate natural regeneration and spreading of A. corniculatum and A. ilicifolius, and accelerate the restoration process of natural mangrove. Simultaneously, the species matching and planting methods of mix stands should be emphasized in the future.     

深圳市森林植被碳储量特征及其空间分布

基于2005年深圳市森林资源二类调查资料数据,采用材积源生物量法,计测深圳市森林植被碳储量和碳密度,分析了深圳市森林植被碳储量空间分布格局.结果表明,2005年深圳市森林植被总碳储量为225.04×10⁴Mg,平均碳密度为25.63MgC·hm^-2.深圳市各区的森林植被碳储量空间分布上有显著差异.表现为龙岗区(123.13×10⁴Mg)>宝安区(46.70×10⁴Mg)>盐田区(20.49×10⁴Mg)>罗湖区(14.75×10⁴Mg)>南山区(12.79×10⁴Mg)>福田区(5.63×10⁴Mg)>保护区(1.57×10⁴Mg).各区碳密度分布为盐田区(46.18MgC·hm^-2)>福田区(37.63 MgC·hm^-2)>罗湖区(36.78MgC·hm^-2)>龙岗区(26.60MgC·hm^-2)>保护区>(24.19 MgC·hm^-2)>宝安区(19.53MgC·hm^-2),与碳储量大小分布无明显相关.深圳市乔木林碳储量为146.11×10⁴Mg,以中幼龄林为主,占73.2%,平均碳密度为30.76MgC·hm^-2.根据森林植被碳储量与碳密度的空间差异性对深圳市森林进行了区划,并分区提出了提高深圳市森林碳吸存能力的有效措施.     

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.     

亚高山针叶林人工恢复过程中物种多样性变化

通过样方调查,以空间代替时间的方法,对亚高山人工针叶林恢复过程中,乔木、灌木和草本层物种多样性的变化进行了研究,探讨了不同恢复阶段各层物种的相关系数．结果表明,亚高山人工针叶林恢复过程中物种的丰富度、多样性和均匀性都在波动中逐渐增加,云杉人工林恢复过程中总体上是朝着有利于物种多样性恢复的方向发展．在人工林恢复序列中群落乔木物种的平均相关系数为41．88％。灌木为50．61％,草本为37．22％,说明在70年的人工林恢复过程中,灌木种类具有较高的连续性和稳定性;草本植物则随着人工林环境条件的改变而出现较大的消亡和更新,显示出较大的波动性．乔木层物种的稳定性和连续性介于灌木和草本植物之间．     

Tree structure,regeneration and survival of seedlings and sprouts in highmontane forests of the Garhwal Himalayas,India

The tree structure of some timberline and sub-alpine forests of the Garhwal Himalayas was studied with reference to the regeneration status and survival of tree seedlings and sprouts. Nine tree and shrub species were chosen. The dominating tree species wereAbies pindrow andQuercus semicarpifolia. Sprouts were found to have a higher survival rate than seedlings, but both suffered from winter conditions. Girth class measurements showed that trees between 1.6 and 2.5 m were best represented.     

川西亚高山不同森林生态系统碳氮储量及其分配格局

森林采伐和恢复是影响森林碳氮储量的重要因素。以川西亚高山岷江冷杉原始林、粗枝云杉阔叶林、天然次生林和粗枝云杉人工林为研究对象,采用样地调查和生物量实测的方法,研究了不同森林生态系统各组分碳、氮储量及其分配特征。结果表明岷江冷杉原始林、粗枝云杉阔叶林、天然次生林和粗枝云杉人工林生态系统碳储量分别为611.18、252.31、363.07 tC/hm~2和239.06 tC/hm~2;氮储量分别为16.44、12.11、15.48 tN/hm~2和8.92 tN/hm~2。恢复林分与原始林碳储量在土壤—植被的分配格局发生了变化,而氮储量未发生变化。岷江冷杉原始林以植被碳储量为主,恢复林分以土壤为主,氮储量均以土壤为主。乔木层碳储量分别占生态系统总储量的56.65%、17.63%、13.57%和22.05%,土壤层(0—80 cm)分别占32.03%、69.87%、76.20%和72.12%;土壤层氮储量占生态系统总储量的76.80%—92.58%。植物残体碳氮储量分别占生态系统总储量的4.40%—9.83%和2.94%—7.08%,林下植被所占比例最小。空间格局上,岷江冷杉原始林植被部分具有较高的碳储量,应进行保护。3种恢复林分具有较高的碳汇潜力,且地上/地下碳储量较低,表明其碳汇潜力尤其表现在地上部分。天然次生林利于土壤有机碳的积累,而人工林乔木层碳储量较高。     

Effects of Environmental Factors on Germination and Seedling Growth in Quercus floribunda and Cupressus torulosa, Tree Species of Central Himalaya

Quercus floribunda Lindl. (tilonj oak), a late successionalspecies, and Cupressus torulosa D. Don. (surai), an early successionalspecies, were compared in terms of seed germination and seedlinggrowth. In Petri dish germination tests in which light quality,temperature and osmotic water stress were varied, the germinationof both species was reduced by continuous dark or far-red lightand by osmotic water stress. These effects were greater on thegermination of surai than on that of tilonj oak. The growthof seedlings in soil was measured over a twelve-month periodduring which different levels of shading and different wateringregimes were applied. Surai was less affected than tilonj oakby reduced soil moisture, but the effect of deep shade treatmentswas greater on surai than with tilonj oak. At higher soil moisturestress seedlings of surai attained greater height then tilonjoak, but the latter achieved higher dry weight and a higherroot: shoot and lower leaf-weight ratio. Quercus floribunda Lindl. (tilonj oak), Cupressus torulosa D. Don. (surai), seed germination, seedling growth, environmental factors, regeneration     

川西亚高山带森林生态系统外生菌根的形成

利用样方法于2003年8月对四川西部亚高山带分布的川滇高山栎(Quercus aquifolioides)、云杉(Picea asperata)、红桦(Betulaalbo-sinensis)、山杨(Populus davidiana)、铁杉(Tsuga chinensis)、华山松(Pinus armandi)、落叶松(Larix japonica)和冷杉(Abiesfaxoniana)8个主要森林类型的外生菌根进行了调查。结果表明,所有调查的森林类型均被外生菌根真菌所侵染,不同森林类型的宿主植物外生菌根的侵染强度不同,同种森林类型由于受海拔高度、坡度、林龄等条件的影响,植物的菌根侵染率、侵染强度指数以及细根生物量都发生相应的改变。高山栎林型随着海拔高度的增加,土壤上层(0~20cm)菌根侵染率增高、下层(20~40cm)菌根侵染强度指数增大,土壤上下层有效磷浓度都明显减少;坡度小的云杉林型内上下两层细根生物量、菌根侵染率都高于坡度大的云杉林,但是菌根侵染强度指数却较低;相同立地条件下,云杉林型在种群建立(幼林龄)和衰退(成过熟林)时菌根侵染率和侵染强度指数都显著高于种群相对稳定(中林龄)时期,在养分较为肥沃的土壤环境中,菌根侵染率、侵染强度指数与营养因子不存在明显的相关性;山杨、落叶松、冷杉和红桦林型土壤上层菌根侵染率都超过了65%;华山松林型由于坡度最大(50°),其土壤上层菌根侵染强度指数也最大(55.78%);铁杉林型菌根形成状况最差,但细根生物量最大。亚高山带森林类型中的上层植物细根生物量都显著高于下层,表明植物的营养主要由上层根系所输送。