林窗对川西周公山柳杉人工林林下物种多样性的影响

采用典型样地法,以川西周公山柳杉人工林5种不同大小的林窗为研究对象,以林下非林窗为对照,研究了不同大小的林窗对柳杉人工林物种多样性的影响,同时分析了不同梯度林窗下林窗中心、林窗边缘、及林下群落的物种组成、物种多样性的变化情况。结果表明:(1)在所调查的18个样地231个样方中共记录到维管束植物141种,隶属于76科113属;随着林窗面积的增大,群落各层次的物种数呈现出先升高后降低的趋势,灌木层物种数在各林窗梯度上表现为林缘林下林窗中心,草本层物种数在各林窗梯度上表现为林缘林窗中心林下。(2)不同林窗优势种及其重要值不同,即在小林窗内,优势种为柳杉和野桐,其重要值之和高达0.292 3;在大林窗内,杉木及亮叶桦为群落优势物种,群落内出现大量其更新幼苗。(3)不同大小的林窗表现为灌木层物种丰富度指数(D)、Shannon-Wienner指数(H)、和Pielou均匀度指数(Jsw)值在400~450 m2面积的大林窗内达到一个均优水平,草本层物种的多样性在面积为100~150m2的小林窗内达到较高水平;不同梯度的林窗各层次群落D、H值整体表现为林缘林窗中心林下。研究认为:林窗的存在会改变群落物种组成,提高群落物种多样性水平,并且大林窗(400~450m2)更利于柳杉人工林林下树种更新及物种多样性的提高。     

Treefall gap characteristics and regeneration in the laurel forest of Tenerife

Abstract. We conducted a study in the laurel forest of Tenerife (Canary Islands, Spain) to describe the characteristics of natural gaps and to assess the role of treefall gaps in forest dynamics. Very little is left of the natural laurel forest with i.a. Laurus azorica, Ilex canariensis and Prunus lusitanica. We looked for treefall gaps in 80 randomly located 2500 m² plots. These plots represented ca. 1% of the remaining and protected laurel forest of Tenerife. We recorded the characteristics of the species causing the gaps, gap architecture and gap age in all observed gaps larger than 10 m². We inventoried the regeneration in each gap and in a neighbouring control plot with the same topography. Large gaps (>75 m²) were not common in the laurel forest. The absence of large gaps could be due to the physiognomy of the vegetation, the mild weather or the rarity of disturbances. Instead of forming gaps, many trees decompose in place and branches from neighbouring trees and suckers from the decomposed trees occupy the free space. Also, the high rate of asexual regeneration could contribute to the fast closing of the gap. The number of gaps created by Prunus lusitanica was higher than expected (based on canopy composition) while Ilex canariensis and Laurus azorica created fewer gaps. In this evergreen forest, differences between gap and non-gap conditions are not as distinct as in other forest types. Only 0.4% of the canopy is in the gap phase (0.6% including gaps smaller than 10m²). No differences were found in patterns of regeneration between gap and non-gap phases in the forest. Gaps do not explain the persistence of pioneer species in the laurel forest.     

Factors influencing sapling composition in canopy gaps of a temperate deciduous forest

To detect the factors that affect sapling species composition in gaps, we investigated 55 gaps in an old-growth temperate deciduous forest in Ogawa Forest Reserve, central Japan. Gap size, gap age, gap maker species, topographic location, adult tree composition around gaps, and saplings of tree species growing in the gaps were censused. For gaps 5 m², mean gap size was 70 m² and the maximum was 330 m². Estimated ages of gaps had a tendency to be concentrated in particular periods relating to strong wind records in the past. The sapling composition in gaps was highly and significantly correlated to that under closed canopy, indicating the importance of advance regeneration in this forest. However, some species showed significant occurrence biases in gaps or under closed canopy, suggesting differences in shade tolerance. The result of MANOVA showed that gap size and topography were important factors in determining the sapling composition in gaps. Species of gap makers affected the sapling composition indirectly by influencing gap size. The existence of parent trees around gaps had effects on sapling densities of several species. Gap age did not have clear influences on sapling composition. Variations in gap size and topography were considered as important factors that contribute to maintenance of species diversity in this forest.     

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 characteristics and gap regeneration in a subalpine coniferous forest on Mt Ontake,central Honshu,Japan

Gap characteristics and gap regeneration were studied in three mature stands belonging to different community types in a subalpine coniferous forest on Mt Ontake, central Honshu, Japan. Gap disturbance regimes were remarkably similar among stands studied; percentage gap area to surveyed area, gap density and mean gap size were 7.3–8.5%, 17.8–20.0 ha⁻¹ and 40.8–42.5 m², respectively. The gap size class distributions were also similar and showed a strong positive skewness with a few large and many small gaps; gaps <40m² were most frequent and gaps >200m² were rare. Forty-five to 66% of gaps were due to the death of single canopy trees. Canopy trees more often died leaving standing dead wood (40–5.7%) or broken trunks (43–49%). Shade tolerantAbies mariesii andAbies veitchii, frequently, andTsuga diversifolia, less frequently, regenerated in gaps, from advance regenerations recruited before gap formation.Picea jezoensis var.hondoensis may regenerate in gaps, from new individuals recruited after gap formation. The breakage of denseSasa coverage and the mineral soils exposed by the uprooted plants that form gaps might provide regeneration opportunities for shade intolerantBetula. Of the important species limited to the ridge site,Chamaecyparis obtusa, frequently, andThuja standishii, infrequently, regenerated from plants alreadyin situ. Regeneration ofPinus parviflora was not seen. Based on the gap characteristics and gap regeneration behaviour of each species described, stand dynamics in each stand are discussed.     

马尾松人工林不同大小林窗植物多样性及其季节动态

人工林目前存在结构单一、土壤退化、生物多样性降低等人类普遍关注的生态问题。马尾松(Pinus massoniana)是长江上游低山丘陵区退耕还林的主要人工林树种。研究采伐林窗对植物物种组成和更新的影响, 对马尾松低效人工林的改造, 提升其生态服务功能具有重要的意义。该文以采伐39年生的马尾松人工林形成的7种不同大小的林窗为研究对象, 分析了不同季节林窗内的植物生活型组成及多样性变化。结果表明: 1)马尾松人工林林下植物以高位芽植物居多, 其次是地面、地下芽植物, 一年生植物较少而缺少地上芽植物。在林窗形成初期, 林窗的高位芽植物比例明显低于林下, 大林窗的高位芽植物比例稍高于小林窗, 地下芽和一年生植物的比例低于小林窗。2)林下的物种丰富度和物种多样性指数显著低于大林窗。不同林窗下植物的丰富度指数、优势度指数、多样性指数也存在显著差异。3)夏季林窗下植物多样性最高, 其次是秋季, 春季多样性最低。1225-1600 m²的大林窗能够促进马尾松人工林植物多样性恢复和植被更新。     

Gap characteristics and regeneration in Bwindi Impenetrable National Park, Uganda

Before Bwindi Impenetrable forest, Uganda, became a national park in 1991, there was a high level of human activity in much of the forest, especially cutting of large trees for timber by pitsawyers. This created extensive gaps in this tropical Afromontane rain forest. We quantified and compared tree regeneration in three sites that were logged at different intensities. Gap sizes in Bwindi, even under fairly natural conditions are very large (mean =4460.1 m²). Logging further enlarged the gap sizes and had a negative impact on tree regeneration. The study shows the strong role of logging disturbance in promoting an alternative successional pathway, where the large gaps created by logging are in a low‐canopy state dominated by a dense tangle of herbs, shrubs, and herbaceous or semi‐woody climbers. We recommend periodic monitoring of gap size and tree regeneration in the gaps to ascertain the trend of recovery from past logging disturbance.     

Tree species regeneration in a mid-elevation,temperate rain forest in Isla de Chiloé, Chile

The regeneration of canopy and subeanopy species in a mid-elevation, primary rain forest in the Coastal Range of Isla de Chiloé (42°30S), in the cold-temperate region of Chile, was studied by comparing seedling and sapling abundances under the forest canopy, and within 36 tree-fall gaps. The forest was dominated byAmomyrtus luma andLaurelia philippiana (33 and 32% of the main canopy individuals), and two subcanopy species (Myrceugenia ovata, andMyrceugenia planipes) were also important. Uncommon species in the canopy wereDrimys winteri, Amomyrtus meli, andRaphithamnus spinosus. Tree-fall gaps were created generally by the fall of several trees, and the main canopy species were the principal gap-makers. Gap sizes varied between 28 and 972 m², with a mean of 197 m². Seedling and sapling abundances indicate that the dominant species are capable of regenerating below the canopy, but they also germinate and show enhanced growth within small light gaps. For one of the common subcanopy species (M. planipes) and the two infrequent canopy species (D. winteri, andA. meli) regeneration seems to depend entirely on tree-fall gaps. Thus, in this forest, light gaps allow the persistence of infrequent canopy species, but seem less important for the regeneration and maintenance of dominant canopy species.     

Burrowing seabirds affect forest regeneration, Rangatira Island, Chatham Islands, New Zealand

The forests of Rangatira Island (218 ha) in the Chatham Islands are a critical breeding site for a number of rare and threatened forest bird species, but are also home to more than three million seabirds, which could significantly affect forest regeneration processes. We surveyed the forests of Rangatira Island by establishing 40 permanent forest plots, estimated seabird density through burrow counts, and analysed soil properties. To determine if seabirds were impacting on forest regeneration, we established exclosures (0.25 m²) in 30 of the forest plots, and examined the role of canopy gaps in forest regeneration. The tallest current forest (c. 15 m), dominated by Plagianthus chathamicus, has mostly regenerated since stock were removed in 1959. Mean burrow density was estimated to be 1.19 per square metre, all soils were highly acidic (pH 3.36–5.18), and burrow density was positively correlated with soil phosphorus. Seedling density of woody species in seabird exclosures measured after 9, 24 and 33 months was significantly higher than in the adjacent non-gap plots, and seedling density was positively associated with reduced canopy cover. Seedling densities were also significantly higher in canopy gaps than in adjacent non-gap plots, but seabird burrow density was significantly lower in gaps. These results suggest that canopy gaps allow forest regeneration despite the negative impacts of seabird burrowing. However, the gap makers, largely senescing Olearia traversii, are slowly disappearing from the forests. The cohort of Plagianthus that has regenerated following farm abandonment may progressively collapse, allowing regeneration to continue in small openings, but there is also the potential for a catastrophic blowdown. This might have serious implications for forest-dwelling birds, invertebrates, and plants.     

林窗尺度对马尾松人工林林下灌草层优势种生态位的早期影响北大核心CSCD

马尾松作为中国广泛栽植的乡土树种,其人工林群落结构简单和生物多样性低下是普遍存在的生态学问题。探究不同林窗尺度对马尾松人工林林下植被群落的影响,可为马尾松人工林近自然经营提供理论依据。该研究在45 a生马尾松人工林中分别设置A(50 m^(2))、B(100 m^(2))、C(200 m^(2))和D(667 m^(2))4种不同尺度的林窗,以不做任何处理的马尾松人工林作为对照(CK),探究采伐开窗后林窗内自然更新1 a后的灌草层植物组成、优势种生态位宽度和生态位重叠度分布特征。结果显示:(1)除100 m^(2)林窗下灌木层物种数与对照无显著差异外,其余林窗灌草层物种数均显著高于对照(P<0.05),且200 m^(2)林窗下灌草层物种数均最多,分别为35种和20种;4种林窗下灌草层物种丰富度指数较对照均显著增加(P<0.05),最大值均出现在200 m^(2)林窗下,其值分别为对照的1.5倍和2.6倍。(2)林窗增加了灌草层喜光植物种类,且在200 m^(2)林窗下种类最多,灌木层喜光植物有13种,草本层喜光植物有5种。(3)4种林窗下灌草层优势种中,喜光植物生态位宽度均较大,200 m^(2)林窗下灌草层生态位宽度平均值最小,其对资源利用程度低,重要值与生态位宽度之间无显著相关性(P>0.05)。(4)4种林窗下灌草层优势种间生态位重叠度指数均较小。667 m^(2)林窗下,灌草层优势种平均生态位重叠度指数最小,分别为0.029和0.024,200 m^(2)林窗下灌草层优势种高生态位重叠度占总数比例最大,分别为20%和23.8%。研究表明,采伐开窗促进了马尾松人工林林下植被发育,丰富了林下植物多样性,有利于马尾松林稳定持续发展,对精准提升马尾松人工林质量具有重要意义。     

万木林中亚热带常绿阔叶林物种多样性林隙梯度变化

根据万木林中亚热带常绿阔叶林林隙内外物种的调查数据,研究了林隙各区物种多样性的梯度变化及物种多样性随林隙级的梯度变化.结果表明,从林隙中心区到非林隙区,物种丰富度指数和物种多样性指数逐渐降低;生态优势度呈中间高、两端低的变化趋势;均匀度呈中间低、两端高的变化趋势.林隙各区的物种多样性在林隙面积为200～300 m²时均达到最大.     

闽北闽粤栲天然林林隙物种数量特征及更新规律分析

以福建省顺昌县的闽粤栲〔Castanopsis fissa(Champ.ex Benth.)Rehd.et Wils.〕天然林为研究对象,根据林隙面积(A)划定4个等级(A<50 m2、50 m2≤A<100 m2、100 m2≤A<150 m2和150 m2≤A<200 m2)的样地,并以非林隙样地为对照,对林隙和非林隙的乔木层、灌木层和灌草层中的物种分布、组成及生长状况进行调查和统计;在此基础上,对林隙和非林隙中主要物种的数量特征和更新响应规律进行比较分析.结果表明:闽粤栲天然林林隙和非林隙的乔木层分别有54和35种植物,共有种28种;灌木层分别有61和37种植物,共有种29种;灌草层分别有72和49种植物,共有种37种.从乔木层和灌木层各种类的重要值及灌草层各种类的密度看,林隙和非林隙中的优势种类均为闽粤栲和木荷(Schima superba Gardn.et Champ.)等,且林隙和非林隙间各优势种类的重要值差异不明显,其中,闽粤栲的重要值和密度均位居第一.从林隙和非林隙间各优势种类的重要值差值看,林隙的主要优势种类(如闽粤栲和木荷等)对林隙更新响应不明显,而其他种类对林隙则有强烈或中等的正、负更新响应,且在不同林层间有差异.从平均更新密度看,林隙面积对各优势树种的更新有一定影响,其中,林隙面积在150~200 m2时闽粤栲和丝栗栲(Castanopsis fargesii Franch.)的平均更新密度最大,林隙面积在100~150 m2时米槠〔Castanopsis carlesii(Hemsl.)Hay.〕、木荷、青冈〔Cyclobalanopsis glauca(Thunb.)Oerst.〕和黄毛润楠(Machilus chrysotricha H.W.Li)的平均更新密度最大,但在不同面积林隙间各树种的平均更新密度无显著差异(P=0.867).研究结果说明:在闽粤栲天然林中,对林隙更新响应不明显的种类较易成为林分的优势种或建群种,但林隙面积对树种的更新密度没有明显影响;从林隙到林冠的发育过程中,闽粤栲始终处于该林分的优势地位.     

Treefall Gaps and Regeneration Composition in the Laurel Forest of Anaga (Tenerife): a Matter of Size?

The size of treefall gaps is an important determinant of regeneration composition in tropical and temperate forests. Preliminary studies in the laurel forest of Tenerife have shown that small gaps (<100 m²) were the most numerous. However, due to this small size, no significant differences were found between regeneration in gaps and regeneration below the canopy. Because infrequent large gaps (>100 m²) are present in the laurel forest, we analyzed the regeneration in these large uncommon gaps, considering their potentially important role in the dynamics of the system. Our main hypothesis is that large gaps are important disturbance to ensure the regeneration and stablishment of shade intolerant species. Only five gaps larger than 100 m² (ranging from 125–268 m²) were found in the study area. Data from a further 20 small gaps (<100 m²), analysed in a previous study, was also included. Control plots were examined close to the gaps in order to determine regeneration below the closed canopy. We did not find a significant difference between regeneration density in the gaps (<100 m²) and regeneration below the canopy in the control plots. Contrary to our expectations, regeneration was lower in the large gaps than under the canopy. The open canopy in the large gaps increases light intensity, and has a negative effect on the germination and growth of shade-tolerant tree species like Viburnum tinus (although non-statistically significant); however, the increase in light intensity is not sufficient to stimulate the germination of shade-intolerant tree species. The effects of treefall gaps in the dynamics of the laurel forest of Anaga should be not considered as significant in comparison to other factors such as human disturbances or infrequent disturbances (land slides or hurricanes).     

Chance versus determinism in canopy gap regeneration in coastal scarp forest in South Africa

Question: Is tree regeneration in canopy gaps characterized by chance or predictable establishment. Location: Coastal scarp forests, Umzimvubu district, Eastern Cape Province, South Africa. Methods: Estimation of richness of gap‐filling species across canopy gaps of different size. Data are compared with regeneration under the canopy. Probability of self‐replacement of gap forming species is calculated. Results: Forest area under natural gap phase was 7.8%, caused mostly by windthrow (54%). The abundance and average size of gaps (87.8 m²) suggests that species diversity may be maintained by gap dynamics. However, only four of 53 gap‐filler species displayed gap size specialization and these were pioneer species. An additional 13 species were more common in larger gaps but there was no gradient in composition of gap‐filler species across gap size (p= 0.61). Probabilities of self‐replacement in a gap were low (< 0.3) and common canopy species were equally abundant in gaps and the understorey. Species composition in gaps showed no pattern of variation, i.e. was unpredictable, which suggests absence of a successional sequence within tree‐fall gaps. There was also only a slight increase in species richness in gaps at intermediate levels of disturbance. Conclusions: Coastal scarp forest appears not to comprise tightly co‐evolved, niche‐differentiated tree species. Unpredictable species composition in gaps may be a chance effect of recruitment limitation of species from the species pool. Chance establishment slows competitive exclusion and may maintain tree diversity in these forests. These data suggest that current levels (≤ 3 gaps per ha) of selective tree harvesting may not cause a reduction in species richness in this forest.     

阔叶红松林林隙结构与树种多样性关系研究

对阔叶红松林林隙与林下不同层次树种多样性进行比较,探讨林隙大小及发育阶段与树种多样性间的关系.结果表明,林隙与林下树种多样性存在显著差异（P<0.01）.与林下相比,林隙更新层树种多样性、丰富度和均匀度增大,生态优势度减小（P<0.01）;演替层树种多样性、丰富度和均匀度减小,生态优势度增大（P<0.0001）.林隙中不同层次树种多样性随着林隙大小呈现出相反的变化趋势.长白山阔叶红松林林隙演替层树种多样性和丰富度总体上呈单峰形变化,中等大小林隙（100～250 m²）中树种多样性和丰富度较高,生态优势度较小.而更新层树种多样性和均匀度在≥250 m²和<100 m²的林隙中最大,在200～250 m²的林隙中最小;生态优势度在200～250 m²的林隙中达到最大.更新层和演替层树种对林隙面积大小反应不同,有利于更新层幼苗建立的林隙面积并不是演替层幼树发育和成活的最适面积;随林隙年龄的增加,更新层和演替层树种多样性在不同层次上呈互补关系.     

The role of canopy gaps in the regeneration of coastal dune forest

In regenerating coastal dune forest, the canopy consists almost exclusively of a single species, Acacia karroo. When these trees die, they create large canopy gaps. If this promotes the persistence of pioneer species to the detriment of other forest species, then the end goal of a restored coastal dune forest may be unobtainable. We wished to ascertain whether tree species composition and richness differed significantly between canopy gaps and intact canopy, and across a gradient of gap sizes. In three known‐age regenerating coastal dune forest sites, we measured 146 gaps, the species responsible for gap creation, the species most likely to reach the canopy and the composition of adults, seedlings and saplings. We paired each gap with an adjacent plot of the same area that was entirely under intact canopy and sampled in the same way. Most species (15 of 23) had higher abundance in canopy gaps. The probability of self‐replacement was low for A. karroo even in the largest gaps. Despite this predominance of shade‐intolerant species, regenerating dune forest appears to be in the first phase of succession with ‘forest pioneers’ replacing the dominant canopy species. The nature of these species should lead to successful regeneration of dune forest.     

Effect of Tree‐Fall Gaps on Fruit‐Feeding Nymphalid Butterfly Assemblages in a Peruvian Rain Forest

One of the main natural disturbances that affects the structure of rain forests is treefalls, frequently resulting in gaps. Tree‐fall gaps can bring drastic changes in environmental conditions compared with the undisturbed understory. We investigated the effect of tree‐fall gaps on fruit‐feeding butterfly (Nymphalidae) species assemblages in an undisturbed lowland rain forest in southeastern Peru. We used fruit‐baited traps suspended 2 m above ground in 15 tree‐fall gaps ranging in area from 100 to 1000 m² and in adjacent undisturbed understory. Our data support the hypothesis that tree‐fall gap and understory habitats are utilized by different butterfly species assemblages. There were morphological differences between gap and understory species, where the understory species had a larger wing area to thoracic volume. Vegetation structure and composition were important factors affecting the butterfly assemblages. Most of the butterfly species showed an avoidance of vines and a strong association with the presence of trees and shrubs in gaps. There were also differences among gap assemblages that increased with gap size. Some of the species that were associated with gaps have been considered as canopy species. Other gap species in the present study, however, are known to feed on fruits and/or use host plants mainly, or only, occurring in gaps, implicating that the gap assemblage is a mix of canopy species and those unique to gaps. This indicates that, in an undisturbed Amazon forest, tree‐fall gaps may contribute to maintain species diversity by creating a mosaic of specific habitats and resources that favors different butterfly assemblages.     

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.     

Forest development in canopy gaps in old-growth beech (Nothofagus) forests,New Zealand

Abstract. Tree size and age structures, treefall and canopy gap characteristics, and regeneration responses to treefalls were compared for three stands of old-growth beech (Nothofagus) forest dominated by N. fusca and N. menziesii on the South Island, New Zealand. Treefall gaps (up to 1000 m²) were most often caused by standing trees killed by drought and/or insect attack, or by trees snapped by wind. The causes of gap formation and the size and age distributions of treefall gaps varied between localities because of spatial and temporal differences in the histories of disturbance. At Fergies Bush where drought-related dieback had produced many large gaps with standing dead trees, gaps were generally young. Conversely, at Station Creek, small, old gaps formed by bolesnap dominated the disturbance regime. At Rough Creek, gaps of all ages and sizes were found along with an almost complete fern cover, and abundant shrubs and occasional subcanopy hardwood trees. Although overall patterns of regeneration were unrelated to differences in gap size, the relative abundance of N. fusca and N. menziesii varied between localities according to the seemingly minor differences in forest structure and disturbance history described above. Interpretations of regeneration response to gap parameters, therefore, need to account for differences in disturbance history between sites. Differences in the disturbance history between localities will also influence rates of gap closure, and because closure rates are used to estimate forest turnover times, meaningful comparisons of disturbance regimes for different forest types can only be made if this intersite variability is addressed.     

草地生态学领域空斑研究进展

空斑(gap)是近几十年来草地生态学领域的重点研究对象之一,在草地植被更新、群落结构和草地生态系统物种多样性维持方面起着重要作用。本文在介绍空斑的概念、功能分类和形成的基础上,总结分析了国内外对空斑的研究现状,发现目前对草地空斑的研究主要集中在空斑大小、空斑类型对物种更新以及空斑对群落结构和物种多样性影响等方面,而对空斑小环境和土壤的研究较少,对空斑内生理生态学、机理和机制性的问题尚缺乏深入探讨;建议在今后加强对空斑内环境变化、空斑内物种的生理生态学特性和物种对空斑更新的响应机制等方面的研究。