Tree regeneration after bamboo die-back in Chinese Abies-Betula forests

Abstract. Gaps created by disturbance in the forest canopy are important sites for tree regeneration from seed but plants already established in gaps may slow gap-filling. This study deals with consequences of bamboo die-back for tree regeneration and the dynamics of Abies-Betula forests in southwest China. Bamboo dominates the forest understory impeding tree regeneration when in its vegetative phase. Populations of tree seedlings were sampled in 1984–85 and 1990 in two sets of permanent plots where bamboo had died back in 1983. Both Abies and Betula density increased after bamboo die-back, Betula more so than Abies, especially in gaps. Before bamboo die-back, seedlings were established on raised surfaces such as logs but afterwards seedlings became common on the forest floor. This reduced the intensity of clumping of seedling populations between 1984 and 1990. A tree by tree replacement model predicts an increase in Abies and a decrease in Betula after bamboo die-back. Life histories of tree species, gap characteristics, and the bamboo growth cycle (mature/die-back/building) interact to promote fluctuating dominance of Abies and Betula in old-growth forests.     

Structure and dynamics of subalpine forests in the Wang Lang Natural Reserve, Sichuan, China

Population structure (size, age, spatial patterns) and radial growth patterns are used to analyze regeneration patterns of Abies faxoniana, Betula albosinensis, Betula utilis, Larix potaninii, Picea purpurea, and Sabina saltuaria and reconstruct disturbance history in 8 subalpine forest stands in Wang Lang Natural Reserve, Sichuan, China. In old-growth stands tree regeneration occurs in tree-fall gaps whereby A. faxoniana, Betula sp., P. purpurea, and S. saltuaria persist at stand scales by gap-phase regeneration. Clump sizes of young populations are similar to canopy gap sizes but clumps sizes vary among species. Young Betula patches are larger than those of A. faxoniana suggesting that gap-partitioning by size contributes to species coexistence in mixed stands. Picea purpurea and S. saltuaria are longer lived than A. faxoniana which may compensate for lower recruitment and prevent their replacement by A. faxoniana. Tree regeneration and community structure are also influenced by the understory bamboo Fargesia denudata. Seedlings, saplings, and shrub density all decline with an increase in bamboo cover. Species that regenerate in old-growth forest also regenerate after flooding as do species that establish only on bare substrates (i.e. Larix potaninii, Prunus sp.). Structural and compositional patterns in Wang Lang forests are a reflection of disturbance history, canopy species life history attributes such as dispersal ability, shade tolerance, growth rates, and longevity, and competition of trees and shrubs with understory bamboos.     

Canopy disturbance patterns and regeneration of Quercus species in two Ohio old-growth forests

This study was conducted to determine the abundance of Quercus species, the spatial pattern of Quercus regeneration, the current canopy disturbance pattern, and their interrelationship in two old-growth deciduous forests in Ohio (Goll Woods and Sears-Carmean Woods). Acer saccharum and Fagus grandifolia had the greatest density and basal area in both forests, yet the largest trees (by basal area) present at each site were Quercus spp. Quercus spp. appeared to be decreasing in abundance in both sites. Though Quercus seedlings were common, few Quercus saplings or subcanopy trees were present. The current disturbance regimes were dominated by small canopy gaps created by death of 1–2 trees; canopy gaps 100 m² in size were rare and only 2.5–2.8% of the forest area was covered by recognizable canopy gaps. No significant differences in the density of Quercus seedlings or saplings were found between gaps and non-gap areas at either site. Though no significant barrier to seedling establishment appeared to exist, the present disturbance regimes are not well suited for the growth of Quercus into the subcanopy size class or the recruitment of Quercus into the canopy. The most frequent gapmakers in Goll Woods were Tilia americana and Acer saccharum, and those in Sears-Carmean Woods were A. saccharum and F. grandifolia. The species most frequent as gap fillers were A. saccharum (in both sites) and F. grandifolia (in Goll Woods). These results suggest that A. saccharum will continue to increase in abundance, and Quercus decrease in abundance, in these two old-growth stands.     

Regeneration in subalpine coniferous forests

The regeneration process of a subalpine coniferous forest, a mixed forest ofTsuga diversifolia (dominant species),Abies veitchii, Abies mariessi, andPicea jezoensis var.hondoensis, was studied on the basis of annual ring data. The age class distribution was discontinuous and four age groups occurred in the study plot (30m×30m). The canopy layer was a mosaic of patches (83.8–133.7 m² patch area), which had different mean ages. The recruitment of canopy trees was carried out only by advance regeneration in the plot. The diameter growth ofAbies andPicea exceeded diameter growth ofTsuga in the gap.Abies lived for 200–300 years and their trunks were susceptible to heart rot.Picea lived for 300–400 years andTsuga for more than 400 years. The regeneration process derived from the analysis of the plot consisted of three phases leading to the development of a even-aged patch; (1) the establishment of saplings before a gap opening, (2) the opening of a gap in the canopy and repair of the canopy by advance regenerated saplings dominated by rapid growth species,Abies andPicea, and (3) the dying off of canopy trees as each species reached the end of its life-span, resulting in pure patches of long-livedTsuga.     

Structure of primary Japanese beech (Fagus japonica maxim.) forests in the Chichibu Mountains,central Japan,with special reference to regeneration processes

The floristic composition, structure and dynamics of three primaryFagus japonica stands were investigated in the Chichibu Mountains.F. japonica was dominant [RD(%): 64.9–87.0] and showed a slightly inverse J-shaped DBH class distribution in the quadrats [No. of canopy stems (H>20m): 87–138/ha]. The stems ofF. japonica for each size were distributed in the form of colonies, being scattered almost uniformly, and arranged in positive association with each other. Detailed examination of the bases of the stem groups forming colonies revealed that most of them originated from the bases of dead mother stems and that they were from common stools [No. of large stems (H>10 m) per stool: 6–11]. Among six major canopy gaps observed, only one included stems sprouting from the outer part ofF. japonica stools, while all the others were occupied by individuals of species other thanF. japonica. After tree-fall, several undercanopyF. japonica stems remained. Thus canopy gaps in these forest stands recovered through the sprouting of remainingF. japonica stools or by new sprouting ofF. japonica individuals adjacent to the gaps. However, it was considered difficult to fill canopy gaps only with sprouts when the distance between the center of a gap and that of a stool surpasses the crown vector. Such places that are not fully occupied by sprouts will be filled by individuals of other canopy and/or under-canopy species.     

玉龙雪山自然保护区丽江云杉林林窗特征研究

研究了玉龙雪山自然保护区云杉坪典型丽江云杉林林窗干扰的基本特征．结果表明,滇西北亚高山丽江云杉林林窗占林分面积比例冠层林窗和扩展林窗分别为28．8％和42．5％,干扰频率以林窗密度计算,林窗出现的平均密度为35个·hm^-2左右．林窗大小分布为面积大于100m^2的大林窗约占25％,面积为50～100m^2的中等林窗占41％,面积小于50m。的小林窗占34％．形成林窗最重要的方式是干基和干中折断,其次是枯立滇西北亚高山丽江云杉林林窗形成木80％以上是丽江云杉,通常直径为40～50cm、高度为15～25m．每个林窗形成木数量多为1～2株,约占68．8％,5株以上很少,最多为6株．随着林窗面积由大变小,林窗中更新苗木的密度逐渐变大,小林窗中更新木密度约为大林窗的5倍．     

Plant diversity in managed sal (Shorea robusta Gaertn.) forests of Gorakhpur, India: species composition, regeneration and conservation

The sal (Shorea robusta) forest vegetation of Sohagibarawa Wildlife Sanctuary, Gorakhpur, India was analysed to assess plant diversity, regeneration pattern and the status of species conservation. A total of 208 plant species representing 165 genera and 72 families were recorded. Species richness, mean density and basal area of individuals in the observed forest were compared with those of other sal-dominated forests of India. The sal forest was rich in Papilionaceae (23 species), which contributed maximally to the total number of individuals of <30 cm girth. After sal, density was maximal for a leguminous shrub, Moghania chappar. In addition to the usual recruitment by seed, a number of species also showed non-seed regeneration through storage roots, sprouts or ramet proliferation. The individuals regenerating as sprouts from underground stem or storage organs contributed significantly to the sum total of individuals/ha. As much as 45.5% of the total individuals were of ramet origin and shared 10.6% of the total species richness of the forest. In stands facing moderate to low disturbance, thickets of dense entangled mass of vegetation, predominantly composed of thorny lianas, were identified that usually contained less common and rare species like Rauwolfia serpentina, Desmodium latifolium, Crotalaria alata and Gloriosa superba in addition to the frequent ones. These thickets help to conserve the special habitat conditions and provide protection for natural regeneration of several infrequent and rare plant species and thus contribute towards the maintenance and in situ conservation of overall diversity of recurrently disturbed forest vegetation.     

Community dynamics of Ogawa Forest Reserve,a species rich deciduous forest,central Japan

Forest community dynamics were studied for 4 years in a 6 ha permanent plot of species rich, old-growth, temperate deciduous forest in Ogawa Forest Reserve, central Japan. The gap formation rate, recruitment, mortality, gain and loss rate in basal area during 4 years were 42 m2 ha^–1 yr^–1, 1.74% yr^–1, 1.19% yr^–1, 1.12% yr^–1 and 0.88% yr^–1, respectively. The turnover time calculated from them ranged from 58 to 240 years. Both the mortality and mortality factors were size dependent; trees in middle size class had smallest mortality, and the proportion of the trees killed by disturbances increased with size. Gap creations were concentrated in a particular year, suggesting a large heterogeneity in time. Spatial distribution of recruited trees were biassed to the old gaps (older than 4 years), especially that of the species with Bell-shaped dbh distribution (shade intolerant) strongly associated with the gaps. Recruitment in tree stems and the loss of basal area, thus had the larger variability than mortality of stems and this forest, and the species with L-shaped dbh distribution seemed to going to increase the importance in the future if the present trend continues to be held. The turnover time of population is positively correlated with the maximum dbh size of the species, indicating the slow change of the population of large sized species.     

Gap formation, microsite variation and the conifer seedling occurrence in a subalpine old-growth forest, central Japan

To evaluate the effects of canopy gaps and forest floor microsites (soil, fallen logs, root-mounds, buttresses and stumps) on regeneration of subalpine forests, the gap regeneration and seedling occurrence of conifers (Abies mariesii, Abies veitchii, Picea jezoensis var. hondoensis and Tsuga diversifolia) were studied in two stands of a subalpine old-growth forest, central Japan. The percentage of gap area to total surveyed area was 11.2–11.3% in the stands. Gap regeneration was not common for P. jezoensis var. hondoensis and T. diversifolia. In contrast, gap regeneration by advanced regeneration was relatively common for Abies. Seedling occurrence of P. jezoensis var. hondoensis and T. diversifolia was restricted on elevated surfaces such as stumps and root-mounds, while Abies seedlings could occur on soil as well as on elevated surfaces. Rotten stumps were the most favorable microsites for conifer seedling occurrence, which covered small area in the forest floor. Although canopy gaps were not always favorable for seedling occurrence, all conifer seedlings were larger under canopy gaps than under closed canopy. Canopy gaps and forest floor microsites clearly affected seedling occurrence and growth of conifers. This suggests that regeneration of conifers is related to the difference of growth advantage under canopy gaps and favorable microsites for seedling occurrence.     

四川卧龙亚高山林线生态交错带群落的种多度关系

以盖度作为物种多度指标,用描述物种多度分布的模型：断棍分布、几体级数分布、对数级数分布和截尾对数正态分布研究了卧龙巴郎山岷江冷棚林线交错带附近草本群落的种－－我镀分布关系。结果表明,截尾对数正态分布和对数级数分布能较好地拟合交错带附近群落的种－多度分布,截尾对数正态分布模型更适合交错带群落,对数级数分布 较好地适合亚高山草甸群落。对数级数分布的参数α和对数正态分布的参数λ是反映群落结构特征内在性质     

Effect of bryophytes on survival of conifer seedlings in subalpine forests of central Japan

Bryophytes form the major seedbed for coniferous trees in the subalpine forests of central Japan. Field experiments were conducted on the floor of a closed stand dominated byTsuga on Mt Fuji to examine the seedling survival ofAbies veitchii andTsuga diversifolia in seven substrate types in relation to the morphological characteristics of the seeds and seedlings. NeitherAbies norTsuga seedlings could survive on dwarf-bamboo litter beyond 2 years after the seed rain.Abies seedlings survived not only in all types of bryophyte communities but also in larch litter. In contrast, the survival ofTsuga seedlings was restricted to communities of smaller-statured bryophytes found on logs. The seeds and 1st year seedlings ofA. veitchii were larger than those ofT. diversifolia. Abies seedlings produced hypocotyls taller than any bryophyte community and radicles which were long enough to penetrate into the moist humus layer, whereasTsuga seedling radicles presumably penetrate into humus only in bryophyte communities forming a thin mat on logs. The effect of bryophytes on survival of tree seedlings therefore depends on the relationships between the morphology of seeds and seedlings and the structure of bryophyte communities.     

Size distribution and expansion of canopy gaps in a northern Appalachian spruce-fir forest

Canopy gap area/age distributions and growth mechanisms were examined in a virgin subalpine forest in the White Mountains, New Hampshire, USA. The gap area distribution was negative exponential in form. Whithin gap tree ages varied widely in response to stepwise gap expansion caused by windthrow of peripheral trees or death of standing mature Picea rubens at gap edges. As a consequence, the density of small gaps may have been underestimated and the density of large gaps overestimated. The estimates of canopy turnover time, 303 yr, and of patch birth rate on an area basis, 3.3×10^-3 ha new patches/ha land area/yr, were not affected by the gap expansion phenomenon. However, any estimate of patch birth rate as numbers of new patches formed per year would have been too low. Because of increasingly widespread Picea death, the patch area/age distribution of this forest may not currently be in steady-state.     

Roles of riparian and secondary forests in maintaining the near-threatened butterfly, Sasakia charonda (Lepidoptera, Nymphalidae), populations in Japan

To clarify the habitat requirements of the near-threatened butterfly, Sasakia charonda (Lepidoptera, Nymphalidae), we studied the distribution pattern of its host trees, Celtis sinensis and Celtis jessoensis, and the utilization patterns of various vegetation types by this butterfly in the Oofukasawa River basin in Hokuto City, Yamanashi Prefecture, central Japan. Two species of host trees, C. sinensis and C. jessoensis (height = 2 m or more) were found in riparian forests on sandbanks (hereinafter, riparian forest), in forest regenerated after landslides on valley walls (landslide tracks), in secondary deciduous forests consisting mainly of Quercus acutissima or Quercus serrata and in forests established at abandoned paddy fields and their periphery, where weeds and shrubs used to be mown frequently to avoid shade on the paddies before their abandonment. This suggests that they are pioneer species, and their distribution and regeneration depend on natural and/or human disturbances. Host trees above 2 m were preferred by larvae, and there were very few such trees in secondary forests. More overwintering larvae occurred in riparian forests than at other sites. The number of S. charonda adults was highest at the edge of riparian forests, and we observed a variety of behaviors such as puddling, chasing and mating there. Although the number of adult butterflies was smaller inside and at the edge of secondary forests than in riparian forests, puddling by males and roosting on the trunk of Q. acutissima or Q. serrata by females were observed more frequently there than in riparian forests. Thus, we conclude that landscapes including both riparian forests with natural disturbance and secondary forests with Quercus trees are necessary to maintain host Celtis trees and S. charonda populations.     

Gap characteristics and gap regeneration in subalpine old-growth coniferous forests,central Japan

Gap characteristics and gap regeneration were studied in three old-growth stands of subalpine coniferous forests in the northern Yatsugatake and the northern Akaishi mountains, central Japan. With the results of the present study and those of a previous study conducted in another locality, general features of gap characteristics and gap regeneration behavior of major tree species in subalpine coniferous forests of central Japan were summarized and discussed. Of the total 237 gaps investigated in the 14.48 ha of forested area, the percentage gap area to surveyed area, gap density and mean gap size were 7.3%, 17.2 ha⁻¹, and 43.3 m², respectively. The gap size distributions were similar among stands and showed a strong positive skewness with a few large and many small gaps; gaps <40m² were most frequent and those >200 m² were rare. Gaps due to the death of multiple canopy trees comprised 44.7% of the total ones. Canopy trees died in various states; standing dead (42.6%) or trunk broken (43.7%) were common and uprooted (12.2%) was an uncommon type of death of canopy trees. These figures indicate that general features of gap characteristics in this forest type are the low proportion of gap area and the high proportions of small gap size and multiple-tree gap formation. In general, shade-tolerantAbies frequently, andTsuga, infrequently, regenerate in gaps from advance regenerations recruited before gap formation, whilePicea and shade-intolerantBetula possibly regenerate in gaps from new individuals recruited after gap formation. Gap successors of conifers occurred in a wide range of gap size and did not show the clear preference to species specific gap size. In old-growth stands without large-scale disturbance (≥0.1 ha in area) of subalpine coniferous forests of central Japan, major tree species may coexist with their different gap-regeneration behaviors and, probably, different life history traits.     

Gap dynamics in climaxFagus crenata forests

Gap characteristics and gap regeneration were studied in several climaxFagus crenata forests in Japan. 278 gaps were observed. Gaps covered 12% of the total land area of 20.05 ha. Gap density was 13.9 gaps per ha and, mean gap size was 92.0 m². Smaller gaps were much more frequent than larger ones. Gaps larger than 400 m² were rare. Most gaps were created by the death of single trees. Canopy trees died more often standing or with broken trunks than by uprooting, although uprooted trees were relatively abundant in the site with poor soil drainage and in the site on upper slope. Differences of gap regeneration behaviour were recognized among tree species.F. crenata regenerates in gaps from saplings recruited before gap creation and can replace not only its own gaps but also gaps of other species. Most species other thanF. crenata andMagnolia obovata could not regenerate in their own gaps. More successful regeneration ofF. crenata may occur in gaps smaller than 200 m², althought it regenerated in a wide range of gap size. However, increased relative density ofF. crenata in the canopy layer seems to prevent its successful regeneration. Gap regeneration of other species did not clearly depend on a species-specific gap size.     

云南亚高山云冷杉林林窗的研究

研究了云南碧塔海两块亚高山云冷杉（Ｐｉｃｅａ－Ａｂｉｅｓ）林内中小尺度林窗的干扰体系,结果表明：林窗和扩展林窗分别占林地面积的１９％和４１％,平均面积为４４ｍ２和１３９ｍ２,林窗的形成频率为０．００５～０．００７／ｙ。估计平均林窗周期为１６７年。大多数林窗（占８７％）的制造林窗树木（ｇａｐ－ｍａｋｅｒ,简记为ＧＭ）为１个以上,平均每个林窗的ＧＭ为２．９个,同一林窗内的ＧＭ常常死于不同的时间。在所有调查的ＧＭ中,折断占６０％,而根拔和直立死亡分别为２８％和１２％     

Nitrogen mineralization in high elevation forests of the Appalachians. I. Regional patterns in southern spruce-fir forests

Annual and seasonal rates of net nitrogen mineralization were determined for 19 sites in the spruce-fir forests of the Southern Appalachian Mountains. These sites included high and low elevation stands of red spruce (Picea rubens Sarg.) and Fraser fir (Abies fraseri (Pursh.) Poir.) on east and west exposures on Whitetop Mountain, Virginia; Mt. Mitchell, North Carolina; and Clingman's Dome in the Great Smoky Mountains National Park. Mineralization rates were determined using in situ soil incubations in PVC tubes with ion exchange resin bags placed in the bottom of the tubes to collect leachate. Throughfall was collected in resin bags placed in the top of the tubes. Average initial NH₄-N + NO₃-N ranged from 0.6 to 4.8 kg N/ha across all plots, and average mineralization rates ranged from 26 to 180 kg-N ha⁻¹ yr⁻¹. Throughfall ranged from 18 to 32 kg-N ha⁻¹ yr⁻¹ with NH₄-N accounting for about two-thirds of the throughfall N across all sites. Throughfall and mineralization rates were not related to elevation or exposure. The high rates of N mineralization and relatively high nitrate concentrations indicate that leaching losses of nitrogen and associated cations could be substantial. Requests for offprints     

A comparative phytosociological study of the subalpine coniferous forests in northeastern Asia

Previous classification systems of the subalpine coniferous forests, belonging to the class Vaccinio-Piceetea Br.-Bl. 1939, in northeastern Asia were reviewed based on phytosociological data of Korea and Japan. A new order, the Abieti nephrolepidis-Piceetalia jezoensis was proposed for the subalpine coniferous forests in the continental part of northeastern Asia. Its distribution range and subordinate vegetation units are as follows:Order Abieti nephrolepidis-Piceetalia jezoensis ordo nov.In Korea:Alliance Abieti nephrolepidis-Piceion jezoensis Song 1991Association Taxo-Pinetum pumilae Song et Nakanishi 1985Association Thujo-Abietetum nephrolepidis Song 1991Association Abieti koreanae-Piceetum jezoensis Song 1991Alliance Abietion koreanae Song 1991Association Saso-Abietetum koreanae Song et Nakanishi 1985Association Betulo saitoanae-Abietetum koreanae (Song et Nakanishi 1985) em. Song 1991In northeast China and Maritime Province of Siberia, U.S.S.R.: (one separate alliance level or the same alliance as Abieti nephrolepidis-Piceion jezoensis)Formation Abies nephrolepis form. (Wu 1980)Formation Picea jezoensis-Abies nephrolepis form. (Wu 1980)Generally the Abieti nephrolepidis-Piceetalia jezoensis develops under the dry and cool continental climate and on the monophylogenic Dark Brown Conifer Soil Group derived mostly from granite and granitic gneiss. The subalpine or subarctic coniferous forests in Hokkaido, Sakhalin and Southern Kuriles may also belong to the Abieti nephrolepidis-Piceetalia jezoensis because of their floristic composition and the historical relevance of plant geography. The subordinate vegetation units are as follows:Alliance Piceion jezoensis Suz.-Tok. ex Jinno et Suzuki 1973Association Piceo-Abietetum sachalinensis Ohba 1967Association Piceetum glehnii Suz.-Tok. ex Miyawaki 1988The Abieti veitchii-Piceetalia jezoensis hondoensis Miyawaki et al. 1968 seems to fit only to the subalpine coniferous forests of Honshu and Shikoku of the Japanese Archipelago.     

卧龙自然保护区亚高山暗针叶林树种更新研究

在卧龙亚高山暗针叶林中选取有代表性的18个林窗斑块以及对照的林下样方进行群落学调查,记录乔木树种和灌木树种的相关数量特征。按照树种在林窗内外的重要值差异结合树种本身生态学特性将群落中出现的乔木层树种划分为先锋组和耐荫组两类生态种组。林窗内外乔木树种的组成明显不同,两类生态种组树种幼苗在林窗与林下环境中的更新表现出差别,这与树种本身的生态学特性以及所处林窗的环境有关,同时亚高山暗针叶林中灌木层优势种小径竹的生长对树种更新方式也产生一定的影响。     

Community dynamics of evergreen broadleaf forests in southwestern Japan. I. Wind damaged trees and canopy gaps in an evergreen oak forest

The rates of treefall and canopy opening in the evergreen oak forest in southwestern Japan were determined by studying the number and size distribution of overstory trees, wind damaged trees, and canopy gaps in a belt transect in the Kasugayama Forest Reserve in Nara City. Thirty three percent of the overstory trees wereCastanopsis cuspidata. The total area of canopy gaps was about 20% of the total land area in the study area. The ages of the gaps were determined by counting the annual rings of various kinds of trees growing in gaps. By comparing gap ages with meteorological data, it became evident that gap formation was mainly caused by strong typhoons. The mean time interval between strong typhoons visiting the forest reserve, 6.57 years, was determined by applying the MNY method to the meteorological data. The treefall rate and the mean area of canopy openings per year were 0.84 overstory trees/ha·year and 55.6 m²/ha·year, respectively. The mean residence time of the forest canopy was about 180 years.