Host infestation patterns of the massive liana Hydrangea serratifolia (Hydrangeaceae) in a Chilean temperate rainforest

As competition from lianas reduces fitness of host trees, lianas could influence community composition and structure if potential host species differ in susceptibility to infestation. We quantified infestation frequencies of Chilean temperate rainforest tree species by the massive liana Hydrangea serratifolia (H. et A.) F. Phil (Hydrangeaceae), which climbs using adhesive adventitious roots, and examined relationships with host light requirements and stem diameter. We recorded presence or absence of H. serratifolia in a random sample of 515 trees ≥10 cm diameter. Fifty‐four per cent of trees were infested by at least one individual of H. serratifolia. Although there was significant interspecific variation in infestation frequency, this variation was not systematically related to light requirements of host tree species. Probability of infestation increased with diameter for most host tree species, and old trees were found to be infested by a wide range of liana size classes, including some stems <2 cm diameter. This evidence supports the proposal that lianas which attach by adhesive roots can colonize host stems of any size.     

Edge disturbance drives liana abundance increase and alteration of liana–host tree interactions in tropical forest fragments

Closed‐canopy forests are being rapidly fragmented across much of the tropical world. Determining the impacts of fragmentation on ecological processes enables better forest management and improves species‐conservation outcomes. Lianas are an integral part of tropical forests but can have detrimental and potentially complex interactions with their host trees. These effects can include reduced tree growth and fecundity, elevated tree mortality, alterations in tree‐species composition, degradation of forest succession, and a substantial decline in forest carbon storage. We examined the individual impacts of fragmentation and edge effects (0–100‐m transect from edge to forest interior) on the liana community and liana–host tree interactions in rainforests of the Atherton Tableland in north Queensland, Australia. We compared the liana and tree community, the traits of liana‐infested trees, and determinants of the rates of tree infestation within five forest fragments (23–58 ha in area) and five nearby intact‐forest sites. Fragmented forests experienced considerable disturbance‐induced degradation at their edges, resulting in a significant increase in liana abundance. This effect penetrated to significantly greater depths in forest fragments than in intact forests. The composition of the liana community in terms of climbing guilds was significantly different between fragmented and intact forests, likely because forest edges had more small‐sized trees favoring particular liana guilds which preferentially use these for climbing trellises. Sites that had higher liana abundances also exhibited higher infestation rates of trees, as did sites with the largest lianas. However, large lianas were associated with low‐disturbance forest sites. Our study shows that edge disturbance of forest fragments significantly altered the abundance and community composition of lianas and their ecological relationships with trees, with liana impacts on trees being elevated in fragments relative to intact forests. Consequently, effective control of lianas in forest fragments requires management practices which directly focus on minimizing forest edge disturbance.     

Liana cover in the canopies of rainforest trees is not predicted by local ground‐based measures

Lianas (woody climbers) are structural parasites of trees that compete with them for light and below‐ground resources. Most studies of liana–tree interactions are based on ground‐level observations of liana stem density and size, with these assessments generally assumed to reflect the amount of liana canopy cover and overall burden to the tree. We tested this assumption in a 1‐ha plot of lowland rainforest in tropical Australia. We recorded 1072 liana stems (≥1 cm diameter at breast height {dbh}) ha^?1 across all trees (≥10 cm dbh) on the plot and selected 58 trees for detailed study. We estimated liana canopy cover on selected trees that hosted 0–15 liana individuals, using a 47‐m‐tall canopy crane. Notably, we found no significant correlations between liana canopy cover and three commonly used ground‐based measurements of liana abundance as follows: liana stem counts per tree, liana above‐ground biomass per tree and liana basal area per tree. We also explored the role of tree size and liana infestation and found that larger trees (≥20 cm dbh) were more likely to support lianas and to host more liana stems than smaller trees (≤20 cm dbh). This pattern of liana stem density, however, did not correlate with greater liana coverage in the canopy. Tree family was also found to have a significant effect on likelihood of hosting lianas, with trees in some families 3–4 times more likely to host a liana than other families. We suggest that local ground‐based measures of liana–tree infestation may not accurately reflect liana canopy cover for individual trees because they were frequently observed spreading through neighbouring trees at our site. We believe that future liana research will benefit from new technologies such as high‐quality aerial photography taken from drones when the aim is to detect the relative burden of lianas on individual trees.     

Spatial patterns and associations in a Quercus‐Betula forest in northern China

Question: Are species‐specific regeneration strategies and competition the dominant processes facilitating species coexistence in a Quercus liaotungensis dominated temperate deciduous forest? Location: Dongling Mountains, North China, 1300 m a.s.l. Methods: Ripley's K‐function was used to characterize the spatial patterns and spatial associations of two dominant tree species, Quercus liaotungensis and Betula dahurica, and a common subcanopy species, Acer mono, at different growth stages (adult, sapling, seedling). Results: Seedlings, saplings and adults of all three species exhibited clumped distributions at most spatial scales. Quercus seedlings and saplings were positively associated with conspecific adult trees and spatially independent of dead trees suggesting that seed dispersal and vegetative regeneration influenced the spatial patterning of Quercus trees. Betula seedlings and saplings were positively associated with both live and dead trees of conspecific adults at small scales (<5 m) but negatively associated with live and dead trees of other species indicating sprouting as an important mechanism of reproduction. Saplings of Acer had a strong spatial dependence on the distribution of conspecific adult trees indicating its limited seed dispersal range. Negative associations between adult trees of Betula and Quercus demonstrated interspecific competition at local scales (<5 m). Conclusions: Different regeneration strategies among the three species play an important role in regulating their spatial distribution patterns, while competition between individuals of Betula and Quercus at the adult stage also contributes to spatial patterning of these communities. The recruitment limitations of Betula and Quercus may affect the persistence of these species and the long‐term dynamics of the forest.     

Photosynthetic and biomass allocation responses of Liquidambar styraciflua (Hamamelidaceae) to vine competition

This 2-year field study examined stomatal conductance, photosynthesis, and biomass allocation of Liquidambar styraciflua saplings in response to below- and aboveground competition with the vines Lonicera japonica and Parthenocissus quinquefolia. Vine competition did not affect stomatal conductance of the host trees. The leaf photosynthetic capacity and photosynthetic nitrogen-use efficiency were significantly reduced by root competition with vines, either singly or in combination with aboveground competition, early in the second growing season. However, such differences disappeared by the end of the second growing season. Trees competing below ground with vines also had lower allocation to leaves compared with steins. Aboveground competition with vines resulted in reduced photosynthetic capacity per unit leaf area, but not per unit leaf weight, in trees. No correlation was found between single leaf photosynthetic capacity and tree growth. In contrast, a high positive correlation existed between allocation to leaves and diameter growth. Results from this study suggest that allocation patterns are more affected than leaf photosynthesis in trees competing with vines.     

Above- and below-ground competition between the liana <Emphasis Type="Italic">Acacia kamerunensis</Emphasis> and tree seedlings in contrasting light environments

Proliferation of lianas in canopy gaps can restrict tree regeneration in tropical forests through competition. Liana effects may differ between tree species, depending on tree requirements for above- and below-ground resources. We conducted an experiment in a shade house over 12 months to test the effect of light (7 and 27% external irradiance) on the competitive interactions between seedlings of one liana species and three tree species and the contribution of both above- and below-ground competition. Seedlings of the liana Acacia kamerunensis were grown with tree seedlings differing in shade tolerance: Nauclea diderrichii (Pioneer), Khaya anthotheca (Non-Pioneer Light Demander) and Garcinia afzelii (Non-Pioneer Shade Bearer). Trees were grown in four competition treatments with the liana: no competition, root competition, shoot competition and root and shoot competition. Both root and root–shoot competition significantly reduced relative growth rates in all three tree species. After one year, root–shoot competition reduced growth in biomass to 58% of those (all species) grown in no competition. The root competition treatment had a more important contribution in the effect of the liana on tree growth. Tree seedlings did not respond to competition with the liana by altering their patterns of biomass allocation. Although irradiance had a great effect on tree growth and allocation of biomass, the interaction between competition treatments and irradiance was not significant. Nauclea diderrichii, the tree species which responded most to the effects of competition, showed signs of being pot-bound, the stress of which may have augmented the competition effects. The understanding of the interaction of above- and below-ground competition between lianas and trees and its moderation by the light environment is important for a proper appreciation of the influence of lianas on tropical forest regeneration.     

The influence of competition from herbaceous vegetation and shade on simulated browsing tolerance of coniferous and deciduous saplings

The ability of saplings to tolerate browsing (i.e. the ability to persist with reduced biomass and to compensate for biomass loss) is influenced by the level of stress and their growth strategies. Ultimately, insight into species‐specific responses of saplings to browsing, shade and competition from neighbours will help explain diversity, structure and function of grazed ecosystems such as the endangered wood‐pasture systems. We measured the survival, whole‐sapling biomass and compensatory growth responses of two coniferous (Picea abies and Abies alba) and two deciduous (Acer pseudoplatanus and Fagus sylvatica) tree species to simulated summer browsing (one single clipping event), shade (installation of a shade cloth) and neighbour removal (mowing surrounding vegetation to ground level) treatments and the interactions between them after two‐growing seasons. For all species, there were interacting effects on growth of browsing and environmental condition (shade and neighbours). Simulated browsing resulted in relatively smaller growth losses when plants were growing slowly due to competitive conditions related to herbaceous neighbours. Although none of the clipped saplings could fully compensate for their biomass losses, the saplings were closer to compensation under high competitive conditions than under low competitive conditions. Survival of the clipped saplings remained relatively high and was only significantly reduced for Picea and Acer. Picea was least tolerant of competition and was the only species for which growth was not negatively affected by strong irradiance of a mountain pasture. Surprisingly, the tolerance of saplings to herbivory as browsing tolerance was enhanced under conditions that negatively affected sapling performance (i.e. survival and growth). Apparently, the relative impact of browsing at the early sapling stage is linked to tree life history characteristics such as competition and shade tolerance and will be lower in situations with intense competitive interactions and/or strong irradiance.     

Distribution and regeneration strategies of major canopy dominants in species-rich subtropical/warm temperate rainforests in south-western Japan

The distribution and regeneration strategy of the major canopy dominants in species-rich subtropical/warm temperate rainforests in south-western Japan was studied in a hilly zone below 1100 m a.s.l. Using the patch sampling method, four dominance-community types were numerically identified and they corresponded to four habitats which represented a combination of topography and altitude (i.e. ridgesvs slopes, and belowvs above 500 m a.s.l.) Seven major canopy dominants had their respective distributional core in one of these topo-altitudinal habitats. The seven canopy dominants could be classified into three species groups according to their size structure and growth habits. Group A (Tsuga sieboldii andQuercus gilva) and group B (Quercus acuta, Quercus salicina, Machilus thunbergii) were restricted to the emergent and canopy layer, respectively. These two groups had only a few subcanopy trees and saplings. Saplings of group B showed a rapid growth rate in canopy gaps. Group C (Distylium racemosum) was characterized by many subcanopy trees and saplings that grew steadily under the closed canopy.Castanopsis sieboldii showed intermediate characteristics between group B and C in the size structure and growth habit of its saplings. The density ofD. racemosum canopy trees was markedly reduced on ridges and slopes above 500 m and on slopes below 500 m. In these marginal habitats, the three species groups coexisted by sharing different strata within a community. This situation was possible due to the differences in regeneration strategies among the canopy species.     

Indirect facilitation by a liana might explain the dominance of a small tree in a temperate forest

Aims Lianas are expected to influence composition, structure and functioning of forest systems due to unequal distribution across the potential set of host plants. However, our understanding of mechanisms associated with preferences for specific hosts is still limited, and so is our ability to discern between endogenous and exogenous forces driving forest dynamics in the long run. In this paper, we evaluated whether the dominant liana Hedera helix can indirectly contribute to the eventual dominance of the small multi-stemmed tree Corylus avellana in a remnant temperate forest in central Iberian Peninsula from comparatively reduced liana infestation on C. avellana relative to co-occurring woody species.Methods Through principal component analysis and co-occurrence analysis, we studied the distribution and spatial association between woody species and the liana H. helix. We analyzed the relationship between the number of species in a plot and the number of species infested by the liana to test the hypothesis that H. helix is a generalist liana. Through generalized linear mixed models, we tested the dynamic-multi-stemmed growth form of C. avellana as a plausible life strategy to withstand, in the long run, the liana infestation. In particular, we tested (i) the relationship between stem size and the probability of H. helix infestation including all the tree species within plots and (ii) the relationship between stem size and mortality as evidence of the stem turn over in the tree C. avellana .Important findings Our results indicate that H. helix and C. avellana significantly co-occur in mature stands of this remnant temperate forest where pioneer woody species are absent. Hedera helix severely infests all the woody species whenever stem size exceed ≈25 cm perimeter and there is physical contact at the base of the stem. This implies that all the trees in the community are potential hosts for H. helix. Mixed models indicate that both, infestation by H. helix and stem mortality, are positively related to C. avellana stem perimeter. Reduced long-term infestation of the liana by means of a multi-stemmed growth form with high stem turnover in C. avellana might be an advantage with respect to unipodial tree species. Thus, the liana-tree coexistence pattern may be interpreted as an indirect positive interaction that, contrary to previous findings, results here in species dominance instead of species coexistence.     

Alternative pathways of liana communities in the forests of northwestern Argentina

Liana dynamics in secondary and mature forests are well known in tropical areas dominated by native tree species. Outside the tropics and in secondary forests invaded by exotic species, knowledge is scarce. In this study, we compare liana communities between secondary and mature forests dominated by native species in a subtropical montane area of Sierra de San Javier, Tucuman, Argentina. Additionally, we evaluate changes of liana communities in secondary forests with increasing densities of Ligustrum lucidum and Morus alba, two of the most invasive exotic trees of the area. We surveyed liana species richness and density in three 30-year secondary patches, four 60-year secondary patches, and four mature patches dominated by native tree species, to analyze changes in liana communities with forest age. Within each patch, we sampled 10–25 20 × 20 m quadrats. Additionally, we surveyed liana density and species richness in secondary forest patches with different densities of L. lucidum and M. alba. In native-dominated forests, liana species richness increased and showed a tendency of increasing basal area from 30-year secondary forests to mature forests. Liana density was highly variable, and most of the species were shared between native-dominated secondary and mature forests. Liana density and species richness decreased with L. lucidum density, whereas in secondary forests highly dominated by M. alba, lianas increased in density. Overall, lianas followed different pathways influenced by native forest succession and exotic tree invasions.     

No evidence that elevated CO2 gives tropical lianas an advantage over tropical trees

Recent studies indicate that lianas are increasing in size and abundance relative to trees in neotropical forests. As a result, forest dynamics and carbon balance may be altered through liana‐induced suppression of tree growth and increases in tree mortality. Increasing atmospheric CO₂ is hypothesized to be responsible for the increase in neotropical lianas, yet no study has directly compared the relative response of tropical lianas and trees to elevated CO₂. We explicitly tested whether tropical lianas had a larger response to elevated CO₂ than co‐occurring tropical trees and whether seasonal drought alters the response of either growth form. In two experiments conducted in central Panama, one spanning both wet and dry seasons and one restricted to the dry season, we grew liana (n = 12) and tree (n = 10) species in open‐top growth chambers maintained at ambient or twice‐ambient CO₂ levels. Seedlings of eight individuals (four lianas, four trees) were grown in the ground in each chamber for at least 3 months during each season. We found that both liana and tree seedlings had a significant and positive response to elevated CO₂ (in biomass, leaf area, leaf mass per area, and photosynthesis), but that the relative response to elevated CO₂ for all variables was not significantly greater for lianas than trees regardless of the season. The lack of differences in the relative response between growth forms does not support the hypothesis that elevated CO₂ is responsible for increasing liana size and abundance across the neotropics.     

Host preference and growth patterns of ivy (Hedera helix L.) in a temperate alluvial forest

Recent studies have highlighted the role of lianas in shaping stand dynamics both in tropical and temperate forests. However, English ivy (Hedera helix L.), one of the most widespread lianas in Europe, has received little attention. We conducted a study in the Siro Negri alluvial forest (NW Italy) to determine what factors most affected ivy distribution and investigate its interactions with the trees in the stand. We evaluated the influence of tree size, age, species, and neighborhood crowding on ivy occurrence. In addition, growth ring widths were used to explore the development pattern of climbing stems. Fifty-two percent of trees in our study plots carried ivy, a value comparable to liana incidence found in mature tropical forests. Tree characteristics and their spatial pattern significantly influenced ivy distribution. Preferred hosts were large, isolated trees, while the effect of tree age and species on ivy occurrence was marginal. Growth pattern analysis revealed that radial growth was positively related to the available space on the tree trunk for each ivy stem. We conclude that neighborhood crowding around trees and competition among climbing stems relying on the same trunk may reduce the colonization rate of ivy.     

Are lianas more drought-tolerant than trees? A test for the role of hydraulic architecture and other stem and leaf traits

Lianas are an important component of Neotropical forests, where evidence suggests that they are increasing in abundance and biomass. Lianas are especially abundant in seasonally dry tropical forests, and as such it has been hypothesized that they are better adapted to drought, or that they are at an advantage under the higher light conditions in these forests. However, the physiological and morphological characteristics that allow lianas to capitalize more on seasonal forest conditions compared to trees are poorly understood. Here, we evaluate how saplings of 21 tree and liana species from a seasonal tropical forest in Panama differ in cavitation resistance (P ₅₀) and maximum hydraulic conductivity (K _h), and how saplings of 24 tree and liana species differ in four photosynthetic leaf traits (e.g., maximum assimilation and stomatal conductance) and six morphological leaf and stem traits (e.g., wood density, maximum vessel length, and specific leaf area). At the sapling stage, lianas had a lower cavitation resistance than trees, implying lower drought tolerance, and they tended to have a higher potential hydraulic conductivity. In contrast to studies focusing on adult trees and lianas, we found no clear differences in morphological and photosynthetic traits between the life forms. Possibly, lianas and trees are functionally different at later ontogenetic stages, with lianas having deeper root systems than trees, or experience their main growth advantage during wet periods, when they are less vulnerable to cavitation and can achieve high conductivity. This study shows, however, that the hydraulic characteristics and functional traits that we examined do not explain differences in liana and tree distributions in seasonal forests.     

Changes in spatial distribution during the life history of a tropical tree,Scaphium macropodum (Sterculiaceae) in borneo

We studied the spatial distribution of fruits and plants, mortality and growth rates ofScaphium macropodum (Sterculiaceae) in four 1-ha plots in a tropical rain forest in West Kalimantan, Indonesia. The species is a large deciduous tree and produces wind-dispersed fruits on defoliated twigs. The density of dispersed fruits on the ground decreased with increasing distance from a parent tree. The area under the parent's crown had the highest density of the fruits and the highest mortality of the seedlings immediately after germination. Consequently, the density of the established seedlings peaked 14 m from the tree which is outside its crown. Thick litter mainly from the parent tree seemed to physically prevent the seedlings' root from reaching the soil surface and caused the high mortality. Juvenile and mature trees distributed exclusively, suggesting that regeneration is the most successful outside of the crown of mature trees. Saplings under canopy shade did not grow well.Scaphium macropodum is hypothesized to require a gap for seedling growth and successful regeneration, whereas it can germinate and last under closed canopies as suppressed seedlings or saplings.     

How liana loads alter tree allometry in tropical forests

Intense competition with lianas (wood climbers) can limit tree growth, reproduction, and survival. However, the negative effects of liana loads on tree allometry have not yet been addressed. We investigated the hypothesis that liana loading on tree crown alters tree’s allometry, expressed through slenderness (height–diameter ratio). The relationship between trunk slenderness and percentage of tree crown covered by lianas was investigated for 12 tree species from 10 fragments of the Semideciduous Seasonal Forest in Southeastern Brazil. We also tested whether the relationship between slenderness and wood density differ between trees without lianas and trees heavily infested. Liana loads significantly altered tree allometry by decreasing slenderness, even when lianas covered less than 25% of tree crown. Heavy-wood species decreased their trunk slenderness in a greater ratio than light-wood species. Our findings indicate that liana infestation shifts tree allometry, and these effects are stronger on heavy-wood tree species.     

The relative importance of above- versus belowground competition for tree growth during early succession of a tropical moist forest

Competition between neighboring plants plays a major role in the population dynamics of tree species in the early phases of humid tropical forest succession. We evaluated the relative importance of above- versus below-ground competition during the first years of old-field succession on soil with low fertility in Southern Mexico, using the premise that competition for light is size-asymmetric, unlike competition for nutrients. Plant growth is thus expected to be disproportionally impeded by larger neighbors. We studied how growth and survival of 3.5–5.5 m tall saplings of Cecropia peltata and Trichospermum mexicanum, two pioneer species that dominate the secondary forests in the study region, varied with the abundance and size of neighboring trees in 1–2 year old secondary vegetation. We found that local neighborhood basal area varied 10-fold (3 to 30 cm² m^-2) and explained most of the variation in diameter and height growth of the target saplings. Most growth variables were strongly affected by the neighbors bigger than the focal trees with no significant additive effect of the smaller neighbors, indicating asymmetric competition. Smaller neighbors did have a small but significant additive effect on the diameter growth of Cecropia saplings and stem slenderness of Trichospermum saplings. We conclude that competition for light was more important than belowground competition in this initial phase of moist tropical forest successional, despite the low soil fertility.     

Effects of lightning on trees: A predictive model based on in situ electrical resistivity

The effects of lightning on trees range from catastrophic death to the absence of observable damage. Such differences may be predictable among tree species, and more generally among plant life history strategies and growth forms. We used field‐collected electrical resistivity data in temperate and tropical forests to model how the distribution of power from a lightning discharge varies with tree size and identity, and with the presence of lianas. Estimated heating density (heat generated per volume of tree tissue) and maximum power (maximum rate of heating) from a standardized lightning discharge differed 300% among tree species. Tree size and morphology also were important; the heating density of a hypothetical 10 m tall Alseis blackiana was 49 times greater than for a 30 m tall conspecific, and 127 times greater than for a 30 m tall Dipteryx panamensis. Lianas may protect trees from lightning by conducting electric current; estimated heating and maximum power were reduced by 60% (±7.1%) for trees with one liana and by 87% (±4.0%) for trees with three lianas. This study provides the first quantitative mechanism describing how differences among trees can influence lightning–tree interactions, and how lianas can serve as natural lightning rods for trees.     

两种光强下木质藤本与树木幼苗的竞争关系

 为了探讨木质藤本和树木幼苗的相互作用关系,对两种光强(4%和35%的光强)、4种竞争处理下(全竞争、地上竞争、地下竞争和无竞争),一种 需光木质藤本(刺果藤(Byttneria grandifolia))和3个树种(耐荫种：五桠果木姜子(Litsea dilleniifolia)和绒毛番龙眼(Pometia tomentosa);需光种：羊蹄甲(Bauhinia variegata))幼苗的地上部分和地下部分的竞争关系进行了研究。结果表明：木质藤本的竞争显著影响 着3种树木幼苗的光合能力、形态特征和生长,但生长环境的不同光强影响地上部分竞争和地下部分竞争的相对强度。在低光下,地上部分竞争 比地下部分竞争对3种树木幼苗的相对生长速率(Relative growth rate,RGR)和光合能力造成更大的影响;而高光下,地下竞争对树木幼苗的 生长有更强的抑制作用。不同的竞争处理和光强对树木幼苗的生物量积累造成显著的影响。光强对3种树种的比叶面积(Specific leaf area, SLA)和叶面积比(Leaf area ratio,LAR)有显著的抑制作用,但竞争只对需光的羊蹄甲的SLA和LAR有显著影响。不同的光照和竞争处理之间, 同种植物表现出不同的表型特征。由于竞争的影响,苗木在形态上较为矮小、叶片数目较少、叶面积减小,但是长细比改变较少 。     

元江干热河谷木质藤本的多样性及其与宿主树木的关系

木质藤本是森林生态系统的重要组分。本研究在元江干热河谷地区随机设置了30个20 m×20 m的样方,调查样方中胸径≥0.5 cm的木质藤本多样性及其与宿主树木之间的关系。结果显示:30个样方中记录到胸径≥0.5 cm的木质藤本植物共945株(隶属于22种20属11科),其中,豆科木质藤本的丰富度和多度最高;胸径≤2 cm的木质藤本占个体总数的63.7%;茎缠绕类木质藤本的个体数最多。样方中胸径≥5 cm的树木共有1060株(隶属于38种31属16科),36.0%的树木上至少附藤1株。不同径级和不同树皮粗糙度的树木被木质藤本侵扰的百分比之间存在极显著差异(P0.001)。随着宿主树木平均枝下高的增加,附藤率呈下降趋势。76.5%的木质藤本选择离其根生长点最近的树木进行攀援。表明元江干热河谷中的木质藤本以小径级占优势,树木胸径、枝下高、树皮粗糙度和木质藤本根生长点到树木的距离是影响木质藤本侵扰树木的重要因素,支持木质藤本对宿主树木的侵扰具有选择性的假说。研究结果对中国西南干热河谷退化植被的恢复与物种多样性保护具有重要意义。     

The negative effect of lianas on tree growth varies with tree species and season

Lianas reduce tree growth, reproduction, and survival in tropical forests. Liana competition can be particularly intense in isolated forest fragments, where liana densities are high, and thus, host tree infestation is common. Furthermore, lianas appear to grow particularly well during seasonal drought, when they may compete particularly intensely with trees. Few studies, however, have experimentally quantified the seasonal effects of liana competition on multiple tree species in tropical forests. We used a liana removal experiment in a forest fragment in southeastern Brazil to test whether the effects of lianas on tree growth vary with season and tree species identity. We conducted monthly diameter measurements using dendrometer bands on 88 individuals of five tree species for 24 months. We found that lianas had a stronger negative effect on some tree species during the wet season compared to the dry season. Furthermore, lianas significantly reduced the diameter growth of two tree species but had no effect on the other three tree species. The strong negative effect of lianas on some trees, particularly during the wet season, indicates that the effect of lianas on trees varies both seasonally and with tree species identity. Abstract in Portuguese is available with online material.