Seed Rain and Seed Dispersal Agents in Pure and Mixed Plantations of Native Trees and Abandoned Pastures at La Selva Biological Station, Costa Rica

Lack of seed dispersal can be an important obstacle to natural regeneration (NR) of degraded pastures in the humid tropics. Tree plantations can facilitate secondary forest succession by attracting seed dispersal agents from nearby forests. We studied seed rain and seed dispersal agents in 12–13 years old pure and mixed native tree plantations at La Selva Biological Station, Costa Rica from July to December 2004. Plantations of Balizia elegans (5,522), Dipteryx panamensis (2,263), and Jacaranda copaia (2,091) had the greatest total seed abundance; treatments with the least total seed abundance were Calophyllum brasiliense (56), nonplanted abandoned pasture control 2 (353), Mixed Species 2 (389), and control 1 (836). Plantations of J. copaia and Hyeronima alchorneoides had the greatest seed species richness density, whereas the lowest seed species richness was found in the control treatments. The NR plots had more seeds dispersed by wind, whereas in the plantations, the most important dispersal agents were birds and mammals. The most abundant seeds were those of Miconia spp. (14,492), Psychotria bracheata (2,252), and the Poaceae family (1,346), all species from early successional stages. Plantations of native species are effective in attracting seed dispersal agents and thus facilitating regeneration of degraded pasturelands in the region.     

Secondary Succession and Natural Habitat Restoration in Abandoned Rice Fields of Central Korea

Floristic composition and soil characteristics (moisture, pH, nutrient contents) in abandoned upland rice paddies of different ages were analyzed to clarify the regenerative aspects of succession as a tool for habitat restoration. The study sites represented five seral stages: newly abandoned paddy fields; successional paddy fields abandoned for 3, 7, and 10 years; and a 50‐year‐old Alnus japonica forest. A vegetation sere was apparent in changes of dominant plant species in the order Alopecurus aequalis var. amurensis (annual grass), Aneilema keisak (annual forb), Juncus effusus var. decipiens (rush), Salix koriyanagi (willow), and Alnus japonica (alder) communities. These temporal stages resemble the spatial zonation of vegetation in local riparian floodplain ecosystems, indicating a hydrosere, with soil moisture decreasing over time. Age distributions and life forms of the dominant plant species support a “tolerance” model of secondary succession, in which the established species persist into later successional stages. Persistence of earlier colonizers led to a net cumulative increase in species richness and a more even distribution of species cover with increasing field age. Between 10 and 50 years, vegetation stabilizes as an alder community. Soil moisture content decreased steadily with paddy field age after an initial rise immediately after their abandonment, whereas pools of organic matter, N, P, K, Ca, and Mg, increased with field age. The pace and direction of recovery of native vegetation and natural soil properties in these abandoned rice paddies resembled classic old field succession, a form of secondary succession that often serves as a template for guiding restoration efforts. Active intervention, in particular dismantling artificial levees, could accelerate the recovery process, but natural habitat recovery generally appears sufficiently robust to achieve “passive” restoration of this rare community without intervention.     

Temporal Dynamics of Rich Moth Ensembles in the Montane Forest Zone in Southern Ecuador1

We studied temporal dynamics of diverse moth ensembles (Arctiidae and Geometridae) in early and late succession stages of forest recovery in the montane zone of southern Ecuador. Moths were sampled using weak light sources (2 × 15 W tubes per trap) during three sampling periods (March–April 2002, wet season; October–November 2002, and August–October 2003, both “dry” seasons). Arctiid moth abundance hardly varied between sampling periods. Estimates of local diversity were lower in 2002 (wet and dry season) than in the dry season 2003, and ensemble composition was more strongly affected by sampling period rather than habitat differences. Geometridae ensembles revealed stronger temporal patterns. Geometrid abundance increased about twofold from the wet to the dry season, and temporal effects on species composition were far more pronounced that in arctiids. These differences might hint to variation in the dependence of geometrid versus arctiid larvae on ephemeral plant resources. Despite these significant temporal dynamics, in both families only a few of the more common species analyzed individually showed strong temporal changes in abundance. Almost all common species occurred as adults during all sampling periods. Therefore, even though temporal dynamics of moth ensembles are not negligible, both moth families are suitable “indicators” of community diversity and change along the succession gradient. Samples must be large enough, however, and preferably should be collated over various times of the year and in parallel, to allow for valid statements about moth diversity and species compositions in relation to habitat differences. These recommendations undermine the validity of the concept of “rapid biodiversity inventories” for speciose tropical insect communities.     

石羊河下游民勤绿洲退耕地植被自然演替特征及物种多样性分析

采用重要值、Margalef物种丰富度指数、Shannon-wiener和Simpson多样性指数、Pielou和Alatalo均匀度指数对石羊河下游民勤绿洲不同年限退耕地自然恢复的植物群落进行了研究。结果表明:(1)石羊河下游民勤绿洲退耕地在50a自然恢复过程中共出现植物34种,14科,其中灌木6种,草本28种,分别占总物种数的17.65%和82.35%;藜科(8种)、禾本科(6种)、蒺藜科(4种)植物占总物种数的52.94%。(2)研究区退耕后50a植物群落演替经历为:田旋花→藜→苦苣菜→骆驼蒿→骆驼蓬→盐生草→黑果枸杞→红砂→盐爪爪的演替过程。(3)群落物种丰富度和多样性指数均随退耕时间的延长而呈现出波动式下降的变化趋势,而均匀度指数则呈现出在退耕初期(1～5a)先下降然后呈波动式上升的变化趋势。研究表明,随着退耕年限的增加,群落物种组成逐渐减少,植物群落演替向前发展的大致经历分为4个阶段:退耕1～5a为一年生草本和宿根植物迅速恢复阶段,退耕5～15a为一年生草本植物向多年生草本演替阶段,退耕15～30a为多年生草本向多年生灌木演替阶段,退耕30～50a为多年生灌木植物稳定阶段。     

青土湖不同年限退耕地植被物种多样性及土壤酶活性研究

采用时空替代法,对甘肃省民勤县青土湖不同年限退耕地(退耕1 a、2 a、4 a、8 a、13 a、20 a、30 a、40 a)的植被演替特征、土壤酶活性进行调查,以耕地为对照(CK),分析植被群落与土壤酶活性的相关性,以揭示其变化规律及其驱动机制,为青土湖区及其相似地区退耕地生态系统修复及生态环境建设提供理论基础。结果表明：(1)青土湖在退耕40 a自然恢复过程中,9个样方中共出现16科32属42种植物,物种构成表现为：多数种归于少数科,大部分植物种为单属单科。(2)随着退耕年限的增加,群落优势种由草本植物逐渐转化成灌木植物,植物种由退耕初期(1 a或2 a)的19种降低到退耕4 a的14种、退耕20 a的13种、退耕30 a的5种;退耕30 a时耐盐碱灌木植物盐爪爪成为该地的优势种,其重要值达到52.862,但退耕40 a时优势种盐爪爪的重要值降为36.008。(3)随着退耕年限增加,植物Margalef丰富度指数呈波动式下降的趋势;Shannon多样性指数和Pielou均匀度指数总体趋势呈先增加后减小,再逐渐趋于稳定;Simpson优势度指数整体变化幅度较小,最终呈稳定的趋势。(4)在不同土层(0~20 cm和20~40 cm)中,4种土壤酶活性随退耕年限增加总体表现出先升高后下降再逐渐趋于稳定的趋势,均在退耕8 a后显著下降,且磷酸酶和脲酶活性均显著低于蔗糖酶和过氧化氢酶活性;与对照样地(CK)相比,磷酸酶活性与脲酶活性均随退耕年限增加而下降;土壤磷酸酶、蔗糖酶和脲酶活性均随土层加深而降低。(5)相关分析结果显示,0~20 cm土层中,物种数与土壤蔗糖酶活性、磷酸酶活性以及脲酶活性均呈显著正相关关系;20~40 cm土层中,物种数与土壤脲酶活性呈极显著正相关关系,与土壤过氧化氢酶活性呈显著负相关关系;Margalef丰富度指数与0~20 cm土层的磷酸酶活性和蔗糖酶活性均呈显著正相关关系,与脲酶活性呈极显著正相关关系;20~40 cm土层中,Margalef丰富度指数与脲酶活性呈极显著正相关关系;Shannon多样性指数、Pielou均匀度指数和Simpson优势度与4种土壤酶活性间相关性较低且均不显著。研究认为,在青土湖区退耕地植被自然演替过程中,植物群落变得比较单一,物种多样性逐年降低,脲酶活性对物种多样性起着关键性作用。     

Tree–Shrub Interactions During Early Secondary Forest Succession in Uganda

Abstract One of the greatest challenges for ecologists this century will be restoring forests on degraded tropical lands. This restoration will require understanding complex processes that shape successional pathways, including interactions between trees and other plants. Shrub species often quickly invade disturbed tropical lands, yet little is known about whether they facilitate or inhibit subsequent tree recruitment and growth. We examined how shrubs and other vegetation (e.g., vines, grasses, herbs) affect tree recruitment, survival, and growth during the first 6 years of forest succession in Kibale National Park, Uganda. The study was undertaken in two recently logged exotic softwood plantations. We studied the successional trajectories in two recently logged areas that varied in their initial densities of trees and shrubs. Analyses suggested tree seedling presence and density were not strongly related to shrub density or height during succession. Tree sapling presence and density were positively significantly related to shrub density and height. We found little response in the tree community to experimental shrub removal, and although removal of all nontree vegetation temporarily enhanced tree growth, the effect disappeared after 2 years. Some early‐successional trees benefited from reduced competition, whereas some mid‐successional trees benefited from the presence of other vegetation. Some specific tree species responded strongly to vegetation removal. We interpret our findings in light of designing manipulations promoting forest restoration for biodiversity conservation and conclude with four tentative guidelines: (1) manage at the species level, not the community level; (2) increase facilitation for seedlings, reduce competition for saplings; (3) be cautious of assumptions about plant interactions; and (4) be adaptable and creative with new strategies when manipulations fail.     

黄土高原自然植被演替过程中的植物特征与土壤元素动态

在 3～ 14 9年的时间尺度上 ,对黄土高原植被次生演替过程中植物特征和土壤养分元素动态进行了研究。结果表明 :1)随着演替时间尺度的延伸 ,土壤全C、全N含量呈增加趋势 ,而土壤全K、全Na和土壤pH值呈下降趋势 ,土壤全P变化趋势不明显 ;此外 ,表层 (0～ 10cm)土壤CaO含量在演替系列上呈下降趋势 ,深层 (2 0～ 30cm ,4 0～5 0cm)则呈增加趋势。演替过程对几种土壤化学元素含量影响的程度随着土壤深度的增加而减弱。 2 )植物群落物种丰富度在演替的中间阶段最高。 3)在演替的早期阶段 ,植物群落优势种往往具有稳定的土壤种子库、CR_生活对策和S_繁殖对策 ,在贫瘠的土壤上具有较强的竞争能力 ,且具有较强的水平扩展能力和克隆繁殖能力 ,C_生活对策、在土壤全N含量较高的生境中具有较强竞争能力的多年生植物 ,在演替中后期占据群落的优势地位。此外 ,在所涉及的植物特征中 ,多年生生活史 ,C_、CR_、SC_、SR_、S_生活对策 ,以及R_、W_、Bs_、VBs_和V_繁殖对策等特征在非优势物种中出现的频率较高。 4 )C_、SC_生活对策 ,克隆能力 ,多年生生活史 ,水平扩展能力 ,种子的动物传播方式 ,秋季开花 ,荚果、坚果等特征出现的比例在一定程度上与土壤全C、全N和全K含量正相关 ;而S_、SR_、R_、CR_生活对策 ,一、二年生     

黄土高原自然植被演替过程中的植物特征与土壤元素动态

在3～149年的时间尺度上,对黄土高原植被次生演替过程中植物特征和土壤养分元素动态进行了研究.结果表明:1) 随着演替时间尺度的延伸,土壤全C、全N含量呈增加趋势,而土壤全K、全Na和土壤pH值呈下降趋势,土壤全P变化趋势不明显;此外,表层(0～10 cm)土壤CaO 含量在演替系列上呈下降趋势,深层(20～30 cm,40～50 cm)则呈增加趋势.演替过程对几种土壤化学元素含量影响的程度随着土壤深度的增加而减弱.2)植物群落物种丰富度在演替的中间阶段最高.3) 在演替的早期阶段,植物群落优势种往往具有稳定的土壤种子库、CR-生活对策和S-繁殖对策,在贫瘠的土壤上具有较强的竞争能力,且具有较强的水平扩展能力和克隆繁殖能力,C-生活对策、在土壤全N含量较高的生境中具有较强竞争能力的多年生植物,在演替中后期占据群落的优势地位.此外,在所涉及的植物特征中,多年生生活史,C-、CR-、SC-、SR-、S-生活对策,以及R-、W-、Bs-、VBs- 和V-繁殖对策等特征在非优势物种中出现的频率较高.4) C-、 SC-生活对策, 克隆能力, 多年生生活史, 水平扩展能力, 种子的动物传播方式,秋季开花,荚果、坚果等特征出现的比例在一定程度上与土壤全C、全N 和全K含量正相关; 而 S-、SR-、R-、CR-生活对策,一、二年生生活史, 种子繁殖, S-繁殖对策,以及胞果、蒴果等特征的比例与土壤全Na、CaO含量和土壤pH正相关.5)在演替过程中出现的植物均属草本植物生活型,因此,草原可能是黄土高原上受制于大尺度环境条件(显域生境)下的优势植被类型(特别是降雨量不超过550 mm的地区).     

Early Successional Patterns and Potential Facilitation of Woody Plant Colonization by Rotting Logs in Premontane Costa Rican Pastures

We examined the size, species, location (x and y coordinates), and microsite inhabited by colonizing trees and shrubs in five abandoned pastures in southern Costa Rica. All woody stems greater than 1 m tall in the pastures were measured and mapped, from the overhanging forest edge to 50 m into the abandoned pasture. Species composition of colonists differed substantially among pastures: Croton draco (Euphorbiaceae) dominated one site, two species of Miconia (Melastomataceae) another site, and Verbesina tapentiensis (Asteraceae) a third site. Site 4 had the highest cover of rotting logs (11%), and a four‐fold greater density of colonizing woody plants than the site with the next highest colonist density. For all species pooled, and for several individual taxa, density was positively correlated across sites with abundance of log microsites. Four of the six most common woody species in site 4 occurred on logs significantly more often than expected had they been randomly distributed relative to logs. Site 5 had less abundance of logs, but the common Miconia species was again significantly more likely to be found on log microsites. These results strongly suggest that rotting wood microsites facilitate establishment of bird‐dispersed pioneer trees, which in turn could foster regrowth of other forest species.     

黄土丘陵区退耕地先锋群落演替过程中细根特征的变化

采用空间序列取代时间序列的方法,对退耕时间分别为2、4、6和8年的退耕地群落细根特征进行了分析,以探讨退耕地植被演替过程中细根特征在土壤剖面上的变化及其在演替过程中的作用.结果表明:(1)群落细根根长密度和根面积密度随植被演替显著增加;比根长、比根面积和地下/地上生物量也有增加趋势;细根平均直径随植被演替波动,但有减少趋势;(2)在土壤剖面上根长密度、根面积密度和根系生物量均随土壤深度的增加而降低.其中超过63%的根长、61%的根面积和72%的生物量分布在0～20 cm的表层土壤中;(3)根径级统计表明,多数细根直径在0～0.5和0.5～1.0 mm之间,这两级细根长度占细根总长度的80%以上;(4)逐步回归分析表明,植被演替过程中细根特征的变化主要与土壤有效氮(第2年)、有效磷(第2～8年)和土壤水分(第8年)的含量有关,且随着植被演替,2～6年退耕地中细根特征与土壤资源正相关,而第8年中二者呈负相关.这可能与植物生长对资源的需求与土壤提供资源的能力之间的平衡有关.研究表明,退耕地植被演替过程对土壤资源有一定影响,尤其是土壤水分含量显著减少;而土壤水分等土壤资源的变化又对群落产生影响,导致茵陈蒿先锋群落向地带性长芒草群落演替.     

秦岭山地典型次生林木本植物幼苗更新特征

采用样方法调查了秦岭山地5种典型次生林--油松林、锐齿栎林、红桦林、云杉林和华山松林幼苗的更新特征.结果表明: 不同次生林木本植物幼苗物种分化明显,除锐齿栎林和华山松林外,其余次生林幼苗物种相似性系数均较低;油松林和锐齿栎林木本植物幼苗数量、物种丰富度指数、Simpson优势度指数及均匀度指数均较高,红桦林均最低;云杉林和华山松林幼苗数量及物种多样性指数基本一致.不同次生林幼苗和幼树所占比例存在明显差异,除红桦林幼树数量的比例较大外,其余林分幼苗的比例较大,为云杉林＞油松林＞锐齿栎林＞华山松林.不同林分幼苗萌生比例差异明显,为华山松林＞云杉林＞红桦林＞锐齿栎林＞油松林.锐齿栎林和油松林乔木幼苗比例最高,分别占木本幼苗总种数的68%和51.4%,群落处于演替中期,持续更新能力较强;云杉林、华山松林乔木幼苗比例分别为40%和15%,处于演替后期,更新能力较差;而红桦林中幼苗很难发育成幼树,持续更新能力欠缺.     

Effects of Selective Vegetation Thinning on Seed Removal in Secondary Forest Succession1

Seed removal was assessed for two tree species in three forest types: (1) secondary forest with and (2) without selective vegetation thinning, and (3) mature forest. Selective vegetation thinning meant the removal of all stems ≤3 cm in diameter of secondary‐forest species and was intended as a management technique to accelerate succession toward mature forest. Thinning did not have an effect on seed removal. One of the species showed lower seed removal in mature forest compared to secondary forest.     

Recovery of amphibian,reptile, bird and mammal diversity during secondary forest succession in the tropics

In tropical regions, many studies have focused on how vegetation and ecosystem processes recover following the abandonment of anthropogenic activities, but less attention has been given to the recovery patterns of vertebrates. Here we conduct a meta‐analysis (n = 147 studies) of amphibian, reptile, bird and mammal recovery during tropical secondary forest succession (i.e. natural regeneration). For each taxonomic group, we compared changes in species richness and compositional similarity during natural secondary succession to reference forests (mature or old growth forest). In addition, we evaluated the response of forest specialists and the change in bird and mammal functional groups during natural secondary succession in the tropical moist forest biome. Overall, species richness of all groups reached levels of the reference forests during natural secondary succession, but this was not the case for species compositional similarity. The delay in recovery of forest specialists may be the reason for the delay in recovery of species compositional similarity. Overall, vertebrate recovery increased with successional stage, but other potential predictors of diversity recovery, such as, the geographical setting (amphibian and reptile species compositional similarity recovered more rapidly on islands), rainfall (mammal species richness and compositional similarity recovered faster in regions of low rainfall), and the landscape context (amphibian, reptile and mammal species compositional similarity recovered faster in regions with more forest patches) influenced vertebrate recovery. These results demonstrate the important role of secondary forests in providing habitat for many vertebrates, but the slow recovery of species compositional similarity, forest specialists and some functional groups (e.g. insectivorous birds) highlighted the challenge of secondary forest persistence, and strongly argues for the continued protection of old growth/mature forest as habitat for forest specialists and as sources for secondary forest sites.     

Species Richness,Forest Structure,and Functional Diversity During Succession in the New Guinea Lowlands

Much of the world's tropical forests have been affected by anthropogenic disturbance. These forests are important biodiversity reservoirs whose diversity, structure and function must be characterized across the successional sequence. We examined changes in structure and diversity along a successional gradient in the lowlands of New Guinea. To do this, we measured and identified all stems ≥5 cm diameter in 19 0.25 ha plots ranging in age from 3 to >50 yr since disturbance. We also measured plant functional traits related to establishment, performance, and competitive ability. In addition, we examined change in forest structure, composition, species diversity, and functional diversity through succession. By using rarefaction to estimate functional diversity, we compared changes in functional diversity while controlling for associated differences in stem and species density. Basal area and species density increased with stand age while stem density was highest in intermediate secondary forests. Species composition differed strongly between mature and secondary forests. As forests increased in basal area, community‐weighted mean wood density and foliar carbon increased, whereas specific leaf area and proportion of stems with exudate decreased. Foliar nitrogen peaked in medium‐aged forests. Functional diversity was highest in mature forests, even after accounting for differences in stem and species diversity. Our study represents one of the first attempts to document successional changes in New Guinea's lowland forest. We found robust evidence that as succession proceeds, communities occupy a greater range of functional trait space even after controlling for stem and species density. High functional diversity is important for ecological resiliency in the face of global change.     

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     

The Demography of Miconia prasina (Melastomataceae) During Secondary Succession in Puerto Rico1

Miconia prasina (Melastomataceae) is an important colonizing species during early stages of secondary succession in Puerto Rico but its abundance declines with increasing stand age. We studied its demography for 2 yr (1995–1997) in three populations across a pasture to forest chronosequence (1‐, 12‐, and 25‐yr old) and in one population in a hurricane‐disturbed older forest (>60‐yr old). Vegetative growth was positive in the two young sites, but negative in the two older sites. The highest percentage of plants that flowered occurred in the two younger sites but highest seed production occurred in the 25‐yr‐old site. Although seed germination occurred in the two older sites, no seedlings established. Vegetative reproduction (root sprouts) was found in all sites, with most sprouts occurring in young sites. The 2 yr of census data were used to construct stage‐based transition matrices. In the two young sites, the average population growth rate was positive (λ > 1), while average population growth was negative in the two older sites (λ < 1). Elasticity, a measure of the effects of proportional changes in life‐history transitions to the long‐term population growth rate, varied across both stages and sites. Elasticity shifted from large plants in young sites to small plants in older sites. Across all sites, elasticities related to survival were more important than those of growth or vegetative reproduction. The demographic analysis supported the previous observations of changes in the density of M. prasina based on the chronosequence and also suggests that establishment via seeds must occur prior to abandonment in active pastures.     

Community Characteristics of Early Recovery Vegetation on Abandoned Lands of Shifting Cultivation in Bawangling of Hainan Island, South China

Shifting cultivation is a major form of agricultural practice in most parts of tropical regions worldwide. In places where the bush fallow period is excessively shortened or the period of cultivation is extended for too long, the rate of vegetation recovery and biodiversity on abandoned lands of shifting cultivation would decline. The recovery of the secondary plant communities could even be inhibited for a prolonged period because of grass occupancy. Because of the vital significance of the early recovery communities to secondary succession, we studied the community characteristics of early recovery vegetation on abandoned lands of shifting cultivation in Bawangling of Hainan Island. Measurements were made of the community composition and structure of early recovery vegetation. The sprouting abilities of different functional groups and different species in the same functional group, and the effect of the grass functional group on the composition and quantitative characteristics of tree and shrub functional groups were analyzed. Results indicated that only a few families, genera, or species apparently dominated in the early recovery vegetation on the abandoned lands of shifting cultivation and that deciduous species occurred with a rather high percentage in this early recovery community compared with the natural secondary or old growth forests. Smallsized individuals dominated the woody community. The abundance and basal area of sprouting stems for species in the tree functional group were greater than those of seeder stems, whereas the abundance and basal area of resprouters and seeders for species in the shrub functional group did not differ. The total abundance of stems for the community, stem abundances for species in tree or shrub functional groups, and for seeder or resprouter stems were all negatively correlated with coverage of the grass functional group. The mean sprouting ability in the tree functional group was greater than in the shrub functional group. The sprouting ability for different species in the same functional group was also significantly different.     

Secondary Succession and Indigenous Management in Semideciduous Forest Fallows of the Amazon Basin1

To the discussion on secondary succession in tropical forests, we bring data on three under‐addressed issues: understory as well as overstory changes, continuous as opposed to phase changes, and integration of forest succession with indigenous fallow management and plant uses. Changes in vegetation structure and species composition were analyzed in secondary forests following swidden agriculture in a semideciduous forest of Bolivian lowlands. Twenty‐eight fallows, stratified by four successional stages (early = 1–5 yr, intermediate = 6–10 yr, advanced = 12–20 yr, and older = 22–36 yr), and ten stands of mature forests were sampled. The overstory (plants ≥5 cm diameter at breast height [DBH]) was sampled using a 20 × 50 m plot and the understory (plants <5 cm DBH) in three nested 2 × 5 m subplots. Semistructured interviews provided information on fallow management. Canopy height, basal area, and liana density of the overstory increased with secondary forest age. The early stage had the lowest species density and diversity in the overstory, but the highest diversity in the understory. Species composition and abundance differentiated mature forests and early successional stage from other successional stages; however, species showed individualistic responses across the temporal gradient. A total of 123 of 280 species were useful with edible, medicinal, and construction plants being the most abundant for both over‐ and understories. Most of Los Gwarayo preferred mature forests for making new swidden, while fallows were valuable for crops, useful species, and regenerating timber species.