长苞铁杉幼苗在林窗不同位置的建立

通过2003年12月到2005年1月对福建省天宝岩国家级自然保护区长苞铁杉林内椭圆形林窗(面积118m2)中心、中部、边缘和林下样地进行种子埋藏及幼苗定位观测实验,研究了长苞铁杉幼苗在林窗不同位置中的建立。结果表明:在林窗内不同位置对长苞铁杉幼苗建立有显著影响。林窗中心样地、林窗中部样地、林窗边缘和林下样地内长苞铁杉幼苗发生率分别为10%,10.7%,6%和6%。从林冠下到林窗中心,长苞铁杉种子的幼苗发生率略有增高趋势。在林窗中心样地和林窗中部样地中雨水冲刷是幼苗死亡的最主要原因,而在林窗边缘样地和林下样地中昆虫的取食是幼苗死亡的最主要原因。林窗位置对幼苗的存活率有显著影响,林窗中部样地幼苗存活率最高(11.4%),林窗中心样地幼苗存活率次之(6.7%),而林窗边缘样地和林下样地幼苗则均全部死亡。种子营养消耗完后,在林窗中心、林窗中部、林窗边缘和林下等4个位置样地中,林窗中心样地幼苗平均高度最高。经过一个生长季后,林窗中心样地中幼苗的根生物量、茎生物量和总生物量均略高于林窗中部样地的幼苗,但差异并不显著。林窗中心样地幼苗叶生物量、叶重比、叶/地上等指标显著高于林窗中部样地的幼苗,而茎重比则低于林窗中部样地的幼苗。     

接种肉苁蓉对梭梭天然林的影响研究

在新疆准噶尔盆地东南缘广泛分布的平缓低洼地、平缓沙地和半流动沙丘等不同生境类型的梭梭天然林内,进行人工接种肉苁蓉对梭梭天然林影响的试验研究。结果表明,接种肉苁蓉对梭梭天然林林下植被的种类组成、植株数量、植被盖度、物种多样性、生物量以及天然更新的幼苗幼树等都将产生不同程度的影响。其中,在平缓低洼地的梭梭天然林内,因挖接种穴和回填,林下植被的个体数损失4.1×104株.hm-2,占接种前林下植被个体总数的18%;林下植被的生物量损失35.64kg.hm-2,占接种前林下植被生物总量的14.9%;梭梭幼苗幼树的个体数损失1320株.hm-2,占接种前梭梭幼苗幼树个体总数的24.2%。在平缓沙地的梭梭天然林内,林下植被的个体数损失2.6×104株.hm-2,占接种前林下植被个体总数的49%;林下植被的生物量损失39.87kg.hm-2,占接种前林下植被生物总量的19.0%;梭梭幼苗幼树损失345株.hm-2,占接种前梭梭幼苗幼树的18.8%。在半流动沙丘的梭梭天然林内,林下植被的个体数损失2000株.hm-2,占接种前林下植被个体总数的5%;林下植被的生物量损失9.98kg.hm-2,占接种前林下植被生物总量的6.0%;梭梭幼苗幼树损失256株.hm-2,占接种前梭梭幼苗幼树的3.8%。受挖接种穴和回填直接影响的调查样方内,植物个体数减少26%~53%,植被总盖度减少46%~52%,物种多样性下降5%~13%,生态优势度提高2%~6%,梭梭天然更新幼苗幼树减少40%~75%,林下植被地上和地下部分的生物量损失25.2%~55.7%。     

广东黑石顶南亚热带森林幼苗的区系和生态研究（英文）

 本文研究了自然林下和深入林内2km新开公路的斜坡(当作特殊的林窗)的幼苗的种类组成、多样性、分布格局和生长。林下幼苗种丰富度(99种)和Shannon-Wiener多样性指数(5.43)与所在林分立木种的丰富度(117种)和多样性指数(5.42)相当,而比公路斜坡相近面积上幼苗的相应值(59种,多样性指数4.21)高。林下幼苗的乔木种类占的比例(46％)较公路斜坡幼苗的乔木种类的比例(34％)高,而草本种类占的比例(23%)较后者(32％)低。林下幼苗的木本种类和林分立木的S ф rensen相似系数(0.500)较公路斜坡幼苗木本种类和林分的相似系数(0.171)高得多,林下幼苗的种类组成和公路斜坡幼苗的种类组成的相似性很低(S ф rensen 系数(0.247)。两个生境中大多数优势种群都表现为集群分布。公路斜坡上的幼苗种群似乎集群程度更高。先锋树种的幼苗在公路斜坡较瘦瘠的土壤条件下1～5年生幼苗的平均相对生长率为：0.944～1.555g·g-1·a-1,比在林下耐阴树种幼苗的相对生长率(0.765～1.402)高或相当,但生物量积累较后者慢。在森林中,耐阴树种的幼苗未显出休眠的特性。先锋树种的幼苗有较高比例的叶生物量,而演替后期树种的幼苗则有较高比例的生物量分配给根。     

光强对马尾松幼苗出土和早期生长的影响

先锋树种马尾松(Pinus massoniana)在南方红壤丘陵区退化生态系统恢复和水土流失治理中发挥重要作用。但绝大多数马尾松人工林质量不高,存在大量的"稀疏小老头林",林下幼苗更新困难。本研究设置5个光强处理(透光率分别为自然光的5%、15%、40%、60%、100%),探讨马尾松幼苗出土、存活、生长、形态可塑性对不同光强的响应策略,揭示光是否是限制马尾松幼苗出土和生长的限制因子。结果表明,马尾松出苗率、出苗指数、活力指数在不同光强处理间差异显著(P0.05),最大值均出现在40%光强处理。随光强增大,苗高逐渐降低,地径逐渐增粗,根长逐渐增长。幼苗总生物量,根、茎、叶生物量,粗壮度均在全光照下达到最大值。随光强增大,根冠比、根生物量比呈递增趋势,茎生物量比、叶生物量比呈降低趋势。研究证明,光照过强和过弱均不利于马尾松幼苗出土,弱光环境不利于幼苗生长,验证了林下弱光环境可能是马尾松人工林林下更新能力差的一个主要因素。     

辽东山区林权制度改革中林下种植模式对林下植物物种多样性的影响

以样方调查数据为基础,采用物种丰富度指数、均匀度指数和多样性指数,对辽宁省东部山区森林生态系统中种植林下参和大叶芹这两种作物对林下植物物种多样性的影响进行了研究,并分析了不同作物种植样地和未种植样地以及不同种植作物样地之间的各种指数的差异程度。结果表明:(1)种植两种作物均对灌木层物种产生了显著的影响,降低了物种多样性。(2)种植林下参使得草本层的物种丰富度显著降低,均匀度显著增加,而多样性指数差异不显著。(3)种植大叶芹使得草本层的物种丰富度、均匀度和多样性指数均显著降低。(4)林下参种植样地和大叶芹种植样地之间草本层的物种丰富度指数、均匀度指数和多样性指数之间存在显著差异。     

木麻黄浸提液对榄仁树幼苗生长及生理生化的影响

该研究试图将榄仁树引入木麻黄海防林以期形成混交林型的海防林。以15 d榄仁树种子苗为材料,分别采用浓度为125 g·L~-1的木麻黄根、木麻黄凋落物和林下表层土壤的水浸提液胁迫处理榄仁树幼苗60 d,研究木麻黄化感作用对榄仁树幼苗生长、光合作用、膜系统伤害、抗氧化系统酶活性及游离Pro含量的影响。结果表明:木麻黄根、木麻黄凋落物及林下表层土壤的水浸提液都能降低榄仁树幼苗的存活率,影响幼苗株高、叶和根生物量,可以推断不同浸提液中对影响植物生长成分的浓度有所不同。3种浸提液均显著降低处理15~45 d期间幼苗的净光合速率(Pn)、气孔导度(Ccond)、胞间CO_2浓度(Ci)、蒸腾速率(Tr),且显著增加幼苗水分利用率(WUE)。第60天时3种木麻黄浸提液能显著增加幼苗叶片、根的Pro含量,使得幼苗根系组织细胞膜通透性增加,而木麻黄根浸提液能显著增加幼苗Ccond、Ci、叶SOD、根CAT含量,木麻黄凋落物浸提液能显著增加幼苗Ccond和Tr,同时凋落物浸提液会显著降低幼苗根POD含量。榄仁树幼苗通过调整自身的生理生化能适应木麻黄化感胁迫的影响,为此可考虑榄仁树作为沿海防护林建设的树种之一。     

外来树种日本落叶松和日本花柏对鄂西北森林群落的影响

【目的】研究大面积栽植外来树种日本落叶松和日本花柏对鄂西北森林群落物种多样性的影响,为评价外来树种的入侵风险提供依据。【方法】采用样地调查法对比研究外来树种日本落叶松和日本花柏人工林与当地森林群落特征差异。【结果】日本落叶松人工林样地林下植物种类丰富,样地平均物种数与当地天然林样地物种数相比无显著差异;林下灌木层和草本层多样性指数较高,草本层多样性指数与当地天然林相比无显著差异;林下未发现日本落叶松的更新苗。日本花柏人工林样地平均物种数显著少于当地其他人工林样地;乔木层、灌木层和草本层的4个多样性指数值均小于当地其他人工林样地;在3个样地中出现日本花柏更新苗,更新苗数量达479株·hm~(-2)。【结论】引种栽培日本落叶松不会导致当地森林群落的物种多样性降低,不会引起生物入侵风险;但引种栽培日本花柏会明显降低当地森林群落的物种多样性,对当地森林生态系统的稳定构成一定威胁。     

水淹对枫杨幼苗光合生理特征的影响

通过设置对照(CK)、连续性水淹(CF)和间歇性水淹(PF)3个水分处理,模拟三峡库区库岸带土壤水分变化,研究乡土树种枫杨当年实生幼苗的生理生态适应机制.结果表明:不同水分处理均显著影响枫杨幼苗的光合作用、生物量积累和生长.与CK相比,CF和PF组枫杨幼苗除胞间CO2浓度升高,净光合速率(Pn)、气孔导度(gs)均显著降低.其变化趋势是枫杨幼苗的Pn、gs在试验初期下降,然后逐渐恢复或趋于稳定.随着处理时间的延长,CF和PF组枫杨幼苗的总生物量、根生物量、茎生物量、叶生物量、株高和地径均呈现上升趋势.CF和PF组的总生物量、根生物量、叶生物量和株高,以及PF组的茎生物量均显著低于CK,而CF组的茎生物量与CK无显著差异,其地径还高于CK.枫杨幼苗具有耐受水湿而不耐水淹-干旱交替的生理生态特征.     

林冠环境对润楠幼苗构型和生物量分配的影响

植物幼苗早期适应对策对种群的更新具有决定性的作用。润楠(Machilus nanmu)是国家Ⅱ级保护植物,是重庆缙云山常绿阔叶林优势乔木树种之一。研究润楠幼苗的适应对策对于维持种群更新和保护常绿阔叶林生物多样性具有重要意义。本研究采集了重庆缙云山常绿阔叶林中不同林冠环境(林窗/林下)下不同年龄阶段(阶段1: 1～3年;阶段2: 4～6年;阶段3: 7～9年)的润楠幼苗,从构型和生物量分配角度研究其早期适应对策的时间动态及其对异质生境的响应。结果表明: 林窗中润楠幼苗的茎构型各指标(除枝倾角)和叶倾角在阶段2和阶段3显著大于林下,根构型各指标(除根直径)和叶面积在阶段1和阶段2显著大于林下;而林窗中润楠幼苗的比叶面积在3个阶段均显著小于林下。不同林冠环境和年龄阶段的生物量分配均以叶为主,但林窗中润楠幼苗从阶段2开始增加了茎的生物量分配,减少了根的生物量分配,林下润楠幼苗根的生物量分配则无显著变化。润楠幼苗各器官的协调性随生境条件不同产生适应性进化,即林窗中润楠幼苗的根与叶之间显著相关,且此相关关系随年龄增大由正到负;林下润楠幼苗的根和茎呈显著正相关,根和叶之间无显著相关。不同林冠环境下润楠幼苗枝干重与枝长的标准化主轴回归(SMA)方程斜率仅在阶段3差异显著,而叶、根生物量与构型间的SMA方程斜率的差异均不显著;大部分生物量与构型间的SMA方程截距在阶段2差异显著。     

水淹对枫杨幼苗光合生理特征的影响

通过设置对照(CK)、连续性水淹(CF)和间歇性水淹(PF)3个水分处理,模拟三峡库区库岸带土壤水分变化,研究乡土树种枫杨当年实生幼苗的生理生态适应机制.结果表明: 不同水分处理均显著影响枫杨幼苗的光合作用、生物量积累和生长.与CK相比,CF和PF组枫杨幼苗除胞间CO₂浓度升高,净光合速率(P_n)、气孔导度(g_s)均显著降低.其变化趋势是枫杨幼苗的P_n、g_s在试验初期下降,然后逐渐恢复或趋于稳定.随着处理时间的延长,CF和PF组枫杨幼苗的总生物量、根生物量、茎生物量、叶生物量、株高和地径均呈现上升趋势.CF和PF组的总生物量、根生物量、叶生物量和株高,以及PF组的茎生物量均显著低于CK,而CF组的茎生物量与CK无显著差异,其地径还高于CK.枫杨幼苗具有耐受水湿而不耐水淹-干旱交替的生理生态特征.     

Impact of the invasive plant Syzigium jambos (Myrtaceae) on patterns of understory seedling abundance in a Tropical Premontane Forest, Costa Rica

Habitat fragmentation, along with other human-induced disturbances, increase the vulnerability of native habitats to be invaded by aggressive, ecologically released, exotic species. Syzigium jambos (L.) Alston (Myrtaceae, Rose Apple) is an important invader still spreading throughout Hawaii, the Antilles, Central and South America. This study examines the effects of S. jambos on plant understory diversity in a 25 ha Tropical Premontane Moist Forest in Atenas, Alajuela, Costa Rica, a protected watershed that supplies drinking water for several human communities. Our final objective is to develop a management strategy combining water protection with the preservation of a representative sample of the original plant diversity in the area. Thirty 2 x 2 m plots were distributed throughout the Municipal Forest maintaining a minimum of 10 m between plots, and 2 m from trails, to sample all understory seedlings and saplings of S. jambos, Coffea arabica (coffee) and tree seedlings. We found a clear dominance of S. jambos over all other understory plants. Of the total 1,285 sampled plants, S. jambos comprised 51%, coffee seedlings represented 14.78%, being the rest tree seedlings. Syzigium jambos had the highest density (5.46 plants/m2, S.D. = 6.44) compared to tree (3.67 plants/m2, S.D. = 3.44) and coffee seedlings (1.58 plants/m2, S.D. = 2.13). There was a highly significant negative relationship between the relative abundance of S. jambos and tree (r2 = 0.52, p < 0.00001) and coffee seedlings (r2 = 0.28, p < 0.002). The abundance of coffee seedlings did not affect the abundance of tree seedlings (r2 = 0.01, p < 0.58). Since the canopy of the Municipal Forest is relatively closed and composed of a monolayer of trees with almost no overlapping crowns, we found no relationship between canopy cover and the abundance of S. jambos. The height distribution indicated that the majority of S. jambos individuals were seedlings and saplings (height < or = 1.5 m), with only 4.6% classified as adults, (height > or = 2 m). The results show a clear role of S. jambos as an aggressive, invasive species within the Municipal Forest. This invasion is enhanced by both the ecological characteristics of the species and the fragmentation of the forest by coffee farming around the site. Among a variety of management possibilities, an ecosystem-level approach of manually removing S. jambos over time while replanting native species appears to be the preferred strategy, given the intended continued use of the Municipal Forest as a source of drinking water and as a representative sample of the original vegetation of the area.     

Composition and Dynamics of Functional Groups of Trees During Tropical Forest Succession in Northeastern Costa Rica

We compared the functional type composition of trees ≥10 cm dbh in eight secondary forest monitoring plots with logged and unlogged mature forest plots in lowland wet forests of Northeastern Costa Rica. Five plant functional types were delimited based on diameter growth rates and canopy height of 293 tree species. Mature forests had significantly higher relative abundance of understory trees and slow-growing canopy/emergent trees, but lower relative abundance of fast-growing canopy/emergent trees than secondary forests. Fast-growing subcanopy and canopy trees reached peak densities early in succession. Density of fast-growing canopy/emergent trees increased during the first 20 yr of succession, whereas basal area continued to increase beyond 40 yr. We also assigned canopy tree species to one of three colonization groups, based on the presence of seedlings, saplings, and trees in four secondary forest plots. Among 93 species evaluated, 68 percent were classified as regenerating pioneers (both trees and regeneration present), whereas only 6 percent were classified as nonregenerating pioneers (trees only) and 26 percent as forest colonizers (regeneration only). Slow-growing trees composed 72 percent of the seedling and sapling regeneration for forest colonizers, whereas fast-growing trees composed 63 percent of the seedlings and saplings of regenerating pioneers. Tree stature and growth rates capture much of the functional variation that appears to drive successional dynamics. Results further suggest strong linkages between functional types defined based on adult height and growth rates of large trees and abundance of seedling and sapling regeneration during secondary succession.
Abstract in Spanish is available at http://www.blackwell-synergy.com/loi/btp     

小径竹对亚高山暗针叶林优势 树种林窗更新的影响

在亚高山岷江冷杉林中选取面积≤50m2,50~150m2,>150m2的林窗,每种类型内均包含3种小径竹盖度(≤20%、20%~50%、>50%),共调查林窗9个,并调查包含这3种小径竹盖度的三块林下对照样地,研究了该类森林林窗更新与小径竹生长的关系。结果表明:(1)无论林窗大小,林窗内的更新幼苗数量都比林下的多,林窗更新是岷江冷杉群落更新的主要途径;(2)所选林窗均为发育早期,林窗对更新树种的种类组成和数量的影响主要表现在幼苗上。糙皮桦幼树及幼苗数量随林窗面积的增加而急速增加,它的更新更需要较大的林窗;(3)不同小径竹盖度下幼苗的密度呈现显著性变化,小径竹的生长明显抑制了森林幼苗的更新及填充的进程;(4)华西箭竹的分散程度随林窗面积的增大而降低,而平均高度和基径则有增加的趋势。     

Dendroecological study of a subalpine fir (<Emphasis Type="Italic">Abies fargesii</Emphasis>) forest in the Qinling Mountains,China

Dendroecological techniques were used to investigate the stand dynamics and the disturbance history of the subalpine fir forest in the Qinling Mountains of Shaanxi Province, China. The results indicated that 68% of the fir trees experienced 1–2 release events for a total of 10–29 (an average of 15.8) years, and 1–2 suppression events for a total of 10–27 (an average of 13.4) years before they reached canopy. Large number of Abies fargesii and Betula albo-sinensis recruitment coincided temporally with larger increases in the ring-width index from the 1830s to 1880s, suggesting occurrence of a major stand-wide disturbance during this time period. Few seedlings and saplings were found in the forest, and there was a dramatic decline in recruitment after 1890, probably because of the intensive cover of understory umbrella bamboo (Fargesia spathacea). Radial growth analyses indicated frequent canopy opening resulting from small-scale disturbances in the forest. Thus, the subalpine fir forest experienced frequent small-scale disturbances and infrequent large-scale disturbances in its developmental history, and these disturbances coupled with the understory umbrella bamboo might have influenced tree growth and species recruitment.     

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.     

Seedling Establishment of a Canopy Tree Species in Malaysian Tropical Rain Forests

Abstract Unlike many other canopy tree species in tropical rain forests, Dryobalanops aromatica (Dipterocar-paceae, local name: Kapur) establishes monospecific dominant (monodominant) forests in Peninsular Malaysia. In natural conditions, monodominance of Kapur does not necessarily mean low species diversity of the Kapur forests. While the emergent canopy layer is occupied by Kapur, many other plant species, which are common to lowland dipterocarp primary forests in the same region, are found in lower canopy layer and understory.
To understand the ecological implications of the monodominance of Kapur, we monitored post dispersal survival and seedling establishment in a pure stand of Kapur in a plantation in Kepong, near Kuala Lumpur. Immediately after seed fall, seeds and cotyledon-stage seedlings suffered high predation by vertebrates such as rodents. The predation pressure was higher in a more general fruiting year (1991) than in a sporadic fruiting year (1992). In contrast to the high mortality of seeds and newly emerged seedlings, seedlings surviving to the six-leaf stage showed low mortality, which allowed the establishment of a sapling bank.
The occurrence of saplings of Kapur with a wide range of size classes in natural forests indicates that this species is more shade tolerant than other dipterocarp species such as the Shorea group and that it could well respond to enhanced light conditions caused by canopy opening. These characteristics may partly contribute to maintaining monodominance of Kapur.     

Multivariate path analysis of the relationships between seedling regeneration and environmental factors beneath a dwarf bamboo understory

Seedling emergence and establishment are fragile processes that determine the direction and structure of forest succession and regeneration. However, seedling emergence and establishment are easily affected by biotic and abiotic (environmental) factors. A dense and expanding understory of dwarf bamboo is one such important factor that can seriously hinder the seedling regeneration. We conducted a field experiment to investigate the emergence and establishment of canopy tree seedlings under artificially controlled densities of dwarf bamboo. We found that understory dwarf bamboo obstructed seedling emergence but reduced the death of seedlings. Although understory dwarf bamboo reduced the median retention time of seedlings, dense bamboo increased the mean survival time of seedlings. Our results suggest that understory dwarf bamboo has multiple selectivities for tree seedling emergence and establishment: high‐density dwarf bamboo was beneficial to evergreen species but lower‐density of bamboo was conducive to the survival of deciduous species, it means the dwarf bamboo potentially alters successional trajectories of forest communities. Path analysis revealed that the most important factors affecting tree seedling emergence and death were the abundance of seeds in the seed bank and the density of emerged seedlings, and that the soil temperature promoted seedling emergence but increased seedling death, the thickness of litter limited seedling emergence, and the leaf area index of the bamboo canopy limited seedling death. The present study suggests that dwarf bamboo can directly alter the microenvironment, significantly reducing light levels and soil temperature but increasing the thickness of litter and soil humus, thereby indirectly impacting the regeneration of tree seedlings. Our results indicate that various factors affected seedling emergence, and there were complex indirect relationships among these factors. In general, biological factors had a stronger influence on tree seedling regeneration than environmental factors.     

Cultivation of Non‐timber Forest Products Alters Understory Light Availability in a Humid Tropical Forest in Mexico1

The planting of non‐timber forest products (NTFPs) in the understory of tropical forests is promoted in many regions as a strategy to conserve forested lands and meet the economic needs of rural communities. While the forest canopy is left intact in most understory plantations, much of the midstory and understory vegetation is removed in order to increase light availability for cultivated species. We assessed the extent to which the removal of vegetation in understory plantations of Chamaedorea hooperiana Hodel (Arecaceae) alters understory light conditions. We also examined how any changes in light availability may be reflected by changes in the composition of canopy tree seedlings regenerating in understory plantations. We employed a blocked design consisting of four C. hooperiana plantation sites; each site was paired with an adjacent, unmanaged forest site. Hemispherical canopy photographs were taken and canopy tree seedlings were identified and measured within 12 3 × 2 m randomly placed plots in each site for a total of 96 plots (4 blocks × 2 sites × 12 plots). Plantation management did not affect canopy openness or direct light availability but understory plantations had a higher frequency of plots with greater total and diffuse light availability than unmanaged forest. Comparisons of canopy tree seedling composition between understory plantations and unmanaged forest sites were less conclusive but suggest that management practices have the potential to increase the proportion of shade‐intolerant species of tree seedlings establishing in plantations. Given the importance of advanced regeneration in gap‐phase forest dynamics, these changes may have implications for future patterns of succession in the areas of forest where NTFPs are cultivated.     

Weak Competition Among Tropical Tree Seedlings: Implications for Species Coexistence

The intensity of competition among forest tree seedlings is poorly understood, but has important ramifications for their recruitment and for the maintenance of species diversity. Intense competition among seedlings could allow competitively dominant species to exclude subordinate species. Alternatively, the low density and small stature of forest tree seedlings could preclude intense interseedling competition. In this case, other processes, such as size-asymmetric competition with adults, interactions with consumers, or neutral dynamics would prevail as those structuring the forest understory. We tested the intensity of, and potential for, intraspecific competition among tree seedlings of three species ( Brosimum alicastrum , Matisia cordata , and Pouteria reticulata ) in two Neotropical rain forests. We reduced stem densities by up to 90 percent and monitored individual growth and survival rates for up to 24 mo. Individual growth and survival rates were generally unrelated to stem density. Contrary to the predicted behavior of intensely competing plant populations, the distribution of individual heights did not become more left-skewed with time for any species, regardless of plot density; i.e. , excesses of short, suppressed individuals did not accumulate in high-density plots. We further measured the overlap of zones of influence (ZOIs) to assess the potential for resource competition. Seedling ZOIs overlapped only slightly in extremely dense monodominant plots, and even less in ambient-density plots of mixed composition. Our results thus suggest that interseedling competition was weak. Given the low density of tree seedlings in Neotropical forests, we infer that resource competition among seedlings may be irrelevant to their recruitment.     

Does forest restoration using taungya foster tree species diversity? The case of Afram Headwaters Forest Reserve in Ghana

The taungya agro‐forestry system is an under‐researched means of forest restoration that may result in high tree diversity. Within a forest reserve in Ghana, the forest core and its surrounding Teak‐ and Cedrela‐taungya on logged, cropped and burned land were mapped with ALOS satellite imagery. Native trees, seedlings and saplings were enumerated in 70 random, nested plots, equally divided between forest and taungya. The native tree regeneration was assessed by species richness (SR), Shannon‐Wiener Index (SWI), Shannon Evenness Index (SEI) and species density (SeD) for seedlings, saplings and trees separately and combined and subsequently correlated with canopy covers (CC) in taungya. As anticipated, the taungya diversity was lower than the forest diversity but higher than reported from nontaungya exotic plantations. In the forest, the diversity of native trees increased from seedlings through saplings to trees. The reverse was found in the taungya. Taungya seedling diversity was not significantly different from the forest, while the sapling and tree diversity were significantly lower. Weak correlations of CC with SR, SWI, SEI and SeD were found. Our results suggest the need for treatment to maintain the tree diversity beyond the seedling stage in the taungya.