Functional community structure of African monodominant Gilbertiodendron dewevrei forest influenced by local environmental filtering

Monodominant patches of forest dominated by Gilbertiodendron dewevrei are commonly found in central African tropical forests, alongside forests with high species diversity. Although these forests are generally found sparsely distributed along rivers, their occurrence is not thought to be (clearly) driven by edaphic conditions but rather by trait combinations of G. dewevrei that aid in achieving monodominance. Functional community structure between these monodominant and mixed forests has, however, not yet been compared. Additionally, little is known about nondominant species in the monodominant forest community. These two topics are addressed in this study. We investigate the functional community structure of 10 one‐hectare plots of monodominant and mixed forests in a central region of the Congo basin, in DR Congo. Thirteen leaf and wood traits are measured, covering 95% (basal area weighted) of all species present in the plots, including leaf nutrient contents, leaf isotopic compositions, specific leaf area, wood density, and vessel anatomy. The trait‐based assessment of G. dewevrei shows an ensemble of traits related to water use and transport that could be favorable for its location near forest rivers. Moreover, indications have been found for N and P limitations in the monodominant forest, possibly related to ectomycorrhizal associations formed with G. dewevrei. Reduced leaf N and P contents are found at the community level for the monodominant forest and for different nondominant groups, as compared to those in the mixed forest. In summary, this work shows that environmental filtering does prevail in the monodominant G. dewevrei forest, leading to lower functional diversity in this forest type, with the dominant species showing beneficial traits related to its common riverine locations and with reduced soil N and P availability found in this environment, both coregulating the tree community assembly.     

Monodominance in an African Rain Forest: Is Reduced Herbivory Important?1

Tropical monodominant forests in which one tree species dominates the canopy occur in all three major tropical regions, but few studies have focused on the mechanisms responsible for dominance. This study tests the hypothesis that relative to other species in the community, dominant species are well defended and escape herbivore and pathogen damage. We surveyed the rate of damage on young expanding leaves of seedlings and saplings belonging to eight species within both monodominant Gilbertiodendron dewevrei forests and adjacent mixed–species forests in eastern Congo. Results showed that escape from herbivore and pathogen damage is not a mechanism by which Gilbertiodendron achieves dominance, as it suffered the highest damage level of any species surveyed. Similarly, other sub–dominant common species also suffered high rates of damage. These results are discussed in relation to the phenolic, fiber, and nitrogen content of leaves, and in the context of current theories pertaining to plant–herbivore interactions.     

Effects of Light Gaps and Litter Removal on the Seedling Performance of Six African Timber Species1

Valuable timber tree species frequently show poor regeneration after selective logging in tropical forests. Small size of logging gaps, lack of soil disturbance, and limited seed availability have each been blamed for observed regeneration failures. We investigated seed germination and seedling performance using a split‐plot factorial design involving light availability and litter removal for six Central African timber tree species, hypothesizing that canopy gaps and litter removal would improve seedling establishment, and that less shade‐tolerant species would show stronger responses to both factors. Contrary to our expectations, significantly more germinants established on intact litter than on exposed mineral soil 3 mo after seeding. After 18 mo, seedling survival, height and diameter growth, leaf area, and rooting depth were all much higher in gap plots than in the understory for all species, with the exception of Gilbertiodendron dewevrei, a highly shade‐tolerant species whose survival was higher in the understory. Leaf production was negatively influenced by litter removal in the least shade‐tolerant species, Nauclea diderrichii, with weak or positive effects in other species. G. dewevrei, while displaying a low‐light threshold for growth, exhibited a surprisingly high growth response to increasing light comparable to more shade‐intolerant species, a response that may help explain its local competitive dominance in the region. Due to the rapid closure of small gaps, we suggest that shade‐intolerant species such as N. diderrichii, Khaya anthotheca, and Entandrophragma utile might benefit from more intensive silvicultural practices that create larger canopy gaps.     

Germination and establishment of forest sedges (Carex, Cyperaceae): tests for home-site advantage and effects of leaf litter

We investigated aspects of germination and seedling establishment that might influence the distribution and diversity of Carex species growing in the forest understory. We tested the ability of Carex communis and C. platyphylla to germinate and establish at plots where adult individuals of one of these two species, or one of two other Carex species (C. backii and C. plantaginea), occurred in an old-growth forest in southern Québec, Canada. We also tested for effects of leaf litter on germination and establishment of these sedges. From a series of experiments in the field and in a lath house, we found no evidence of home-site advantage with respect to germination or seedling establishment. Leaf litter had a negative effect on germination and establishment. The results emphasize the importance of dispersal and colonization events in determining local diversity and distribution of Carex species in upland forests. High frequency of occurrence of C. communis at our study site may result from relatively wide dispersal provided by ants, and a suite of traits associated with ant dispersal in some understory Carex species.     

Mixed-Forest Species Establishment in a Monodominant Forest in Central Africa: Implications for Tropical Forest Invasibility

Background

Traits of non-dominant mixed-forest tree species and their synergies for successful co-occurrence in monodominant Gilbertiodendron dewevrei forest have not yet been investigated. Here we compared the tree species diversity of the monodominant forest with its adjacent mixed forest and then determined which fitness proxies and life history traits of the mixed-forest tree species were most associated with successful co-existence in the monodominant forest.

Methodology/Principal Findings

We sampled all trees (diameter in breast height [dbh]≥10 cm) within 6×1 ha topographically homogenous areas of intact central African forest in SE Cameroon, three independent patches of G. dewevrei-dominated forest and three adjacent areas (450–800 m apart). Monodominant G. dewevrei forest had lower sample-controlled species richness, species density and population density than its adjacent mixed forest in terms of stems with dbh≥10 cm. Analysis of a suite of population-level characteristics, such as relative abundance and geographical distribution, and traits such as wood density, height, diameter at breast height, fruit/seed dispersal mechanism and light requirement–revealed after controlling for phylogeny, species that co-occur with G. dewevrei tend to have higher abundance in adjacent mixed forest, higher wood density and a lower light requirement.

Conclusions/Significance

Our results suggest that certain traits (wood density and light requirement) and population-level characteristics (relative abundance) may increase the invasibility of a tree species into a tropical closed-canopy system. Such knowledge may assist in the pre-emptive identification of invasive tree species.     

Leaf herbivory and monodominance in a Cerrado–Amazonia transitional forest,Mato Grosso,Brazil

Monodominant tropical forests occur on several continents, including the Brazilian Amazon. In this study, we tested the hypothesis that seedling escape from leaf herbivory contributes to the maintenance of the monodominant Brosimum rubescens forest. The study was undertaken both in a monodominant forest of B. rubescens and in an adjacent seasonal forest in the transitional zone between the Cerrado and the Amazonian forest biomes. Percentage of leaf area damaged and herbivory rates were evaluated on young and mature leaves of seedlings of Brosimum rubescens, Protium pilosissimum and Tetragastris altissima in the understory and in the gap between the monodominant and seasonal forests. Little evidence of any significant relationship between leaf herbivory and seedling density indicates that the monodominant species does not follow the hypothesized pattern of an intensive herbivore attack in areas of higher seedling density. The escape of Brosimum rubescens from herbivore pressure under conditions of high seedling density may be part of a set of conditions that determine the maintenance of this monodominant forest.     

Slowed decomposition is biotically mediated in an ectomycorrhizal, tropical rain forest

Bacteria and fungi drive the cycling of plant litter in forests, but little is known about their role in tropical rain forest nutrient cycling, despite the high rates of litter decay observed in these ecosystems. However, litter decay rates are not uniform across tropical rain forests. For example, decomposition can differ dramatically over small spatial scales between low-diversity, monodominant rain forests, and species-rich, mixed forests. Because the climatic patterns and soil parent material are identical in co-occurring mixed and monodominant forests, differences in forest floor accumulation, litter production, and decomposition between these forests may be biotically mediated. To test this hypothesis, we conducted field and laboratory studies in a monodominant rain forest in which the ectomycorrhizal tree Dicymbe corymbosa forms >80% of the canopy, and a diverse, mixed forest dominated by arbuscular mycorrhizal trees. After 2 years, decomposition was significantly slower in the monodominant forest (P < 0.001), but litter production was significantly greater in the mixed forest (P < 0.001). In the laboratory, we found microbial community biomass was greater in the mixed forest (P = 0.02), and the composition of fungal communities was distinct between the two rain forest types (P = 0.001). Sequencing of fungal rDNA revealed a significantly lower richness of saprotrophic fungi in the monodominant forest (19 species) relative to the species-rich forest (84 species); moreover, only 4% percent of fungal sequences occurred in both forests. These results show that nutrient cycling patterns in tropical forests can vary dramatically over small spatial scales, and that changes in microbial community structure likely drive the observed differences in decomposition.     

Leaf litter decomposition characteristics and controlling factors across two contrasting forest types

两种不同森林类型叶凋落物分解特征及影响因子研究 叶凋落物分解为森林生态系统提供了重要的能量和养分来源。除传统的环境因素外,叶凋落物的降解过程也受到绿叶功能性状和叶凋落物基质质量的影响。然而,在群落水平上,绿叶功能性状和叶凋落物基质质量对不同森林群落叶凋落物分解的相对重要性仍不清楚。因此,本研究以北京东灵山地区7种典型森林群落类型的混合叶凋落物为研究对象,利用分解袋法通过360天的野外相似环境分解实验对叶凋落物的分解过程进行了研究。这些森林群落包括6种分别以胡桃楸(Juglans mandshurica)、青杨(Populus cathayana)、棘皮桦(Betula dahurica)、白桦(Betula platyphylla)、油松(Pinus tabuliformis) 和华北落叶松(Larix gmelinii var. principis-rupprechtii) 为优势种的单优种群落,以及一种以大叶白蜡(Fraxinus rhynchophylla)、蒙古栎(Quercus mongolica)和蒙椴(Tilia mongolica)为优势种的共优种群落。研究结果表明,不同森林群落之间叶凋落物分解速率存在显著差异。群落聚合的植物功能性状和叶凋落物基质质量分别解释了群落叶凋落物分解速率变异的35.60%和9.05%,两者交互作用解释率为23.37%,表明群落聚合的植物功能性状及其与叶凋落物基质质量的共同作用是影响群落叶凋落物分解速率变异的主要因素。通过冗余分析发现,叶片氮含量、叶干物质含量、叶片单宁含量和比叶面积能显著影响群落叶凋落物分解速率的变异。因此,在对群落水平上叶凋落物分解的研究应该关注群落聚合的绿叶功能性状对分解的影响。     

Removal of invasive shrubs alters light but not leaf litter inputs in a deciduous forest understory

The establishment and spread of non‐native, invasive shrubs in forests poses an important obstacle to natural resource conservation and management. This study assesses the impacts of the physical removal of a complex of woody invasive shrub species on deciduous forest understory resources. We compared leaf litter quantity and quality and understory light transmittance in five pairs of invaded and removal plots in an oak‐dominated suburban mature forest. Removal plots were cleared of all non‐native invasive shrubs. The invasive shrubs were abundant (143,456 stems/ha) and diverse, dominated by species in the genera Ligustrum, Viburnum, Lonicera, and Euonymus. Annual leaf litter biomass and carbon inputs of invaded plots were not different from removal plots due to low leaf litter biomass of invasive shrubs. Invasive shrub litter had higher nitrogen (N) concentrations than native species; however, low biomass of invasive litter led to low N inputs by litter of invasive species compared to native. Light transmittance at the forest floor and at 2 m was lower in invaded plots than in removal plots. We conclude that the removal of the abundant invasive shrubs from a native deciduous forest understory did not alter litter quantity or N inputs, one measure of litter quality, and increased forest understory light availability. More light in the forest understory could facilitate the restoration of forest understory dynamics.     

Litter mixture effects on tropical tree seedling growth--a greenhouse experiment

Decomposing litter provides critical nutrients for plants, particularly in nutrient-poor ecosystems such as tropical forests. We hypothesised that decomposing litter improves the performance of a variety of tropical tree seedlings, and that this litter effect varies depending on the species of litter present in litter mixtures. We addressed these hypotheses with a large pot experiment manipulating a range of different litter mixtures of contrasting quality and using seedlings of four tree species from the Amazonian forest of French Guiana. In contrast to our initial hypothesis, decomposing litter had either neutral or negative impacts on seedling growth, despite strongly different growth rates, biomass allocation patterns and leaf and root traits among tree species. Tree species varied in their responses to litter additions, which were further modified by species identity of the added litter. Our data show litter species-specific effects on growth, biomass allocation and leaf and root traits of tropical tree seedlings. These results suggest that a net nutrient release from decomposing litter does not necessarily improve tree seedling growth, even under nutrient-limiting conditions. In conclusion, litter layer composition may affect seedling establishment and recruitment success beyond litter-derived plant nutrient availability, which may contribute to tree species composition and dynamics in the studied tropical forest.     

Global patterns of leaf mechanical properties

Leaf mechanical properties strongly influence leaf lifespan, plant-herbivore interactions, litter decomposition and nutrient cycling, but global patterns in their interspecific variation and underlying mechanisms remain poorly understood. We synthesize data across the three major measurement methods, permitting the first global analyses of leaf mechanics and associated traits, for 2819 species from 90 sites worldwide. Key measures of leaf mechanical resistance varied c. 500-800-fold among species. Contrary to a long-standing hypothesis, tropical leaves were not mechanically more resistant than temperate leaves. Leaf mechanical resistance was modestly related to rainfall and local light environment. By partitioning leaf mechanical resistance into three different components we discovered that toughness per density contributed a surprisingly large fraction to variation in mechanical resistance, larger than the fractions contributed by lamina thickness and tissue density. Higher toughness per density was associated with long leaf lifespan especially in forest understory. Seldom appreciated in the past, toughness per density is a key factor in leaf mechanical resistance, which itself influences plant-animal interactions and ecosystem functions across the globe.     

Large‐sized rare tree species contribute disproportionately to functional diversity in resource acquisition in African tropical forest

Increasing evidence is available for a positive effect of biodiversity on ecosystem productivity and standing biomass, also in highly diverse systems as tropical forests. Biodiversity conservation could therefore be a critical aspect of climate mitigation policies. There is, however, limited understanding of the role of individual species for this relationship, which could aid in focusing conservation efforts and forest management planning. This study characterizes the functional specialization and redundancy for 95% of all tree species (basal area weighted percentage) in a diverse tropical forest in the central Congo Basin and relates this to species' abundance, contribution to aboveground carbon, and maximum size. Functional characterization is based on a set of traits related to resource acquisition (wood density, specific leaf area, leaf carbon, nitrogen and phosphorus content, and leaf stable carbon isotope composition). We show that within both mixed and monodominant tropical forest ecosystems, the highest functional specialization and lowest functional redundancy are solely found in rare tree species and significantly more in rare species holding large‐sized individuals. Rare species cover the entire range of low and high functional redundancy, contributing both unique and redundant functions. Loss of species supporting functional redundancy could be buffered by other species in the community, including more abundant species. This is not the case for species supporting high functional specialization and low functional redundancy, which would need specific conservation attention. In terms of tropical forest management planning, we argue that specific conservation of large‐sized trees is imperative for long‐term maintenance of ecosystem functioning.     

Can Growth Form Classification Predict Litter Nutrient Dynamics and Decomposition Rates in Lowland Wet Forest?

This study investigates whether it is possible to simplify the complex influence of numerous species on leaf litter decomposition in a diverse tropical forest using functional classifications to predict litter quality, decomposition rate, and nutrient dynamics during decomposition, over a 2-yr period. Thirty-three lowland tropical forest plant species from contrasting growth forms (canopy trees, pioneer trees, lianas, palms, herbs) were studied. Twelve of 18 indices of litter quality varied significantly among growth forms, with canopy trees and palms showing lower litter quality than pioneer trees and herbs. Canopy leaves decomposed more slowly than understory leaves. Decomposition rate and mass loss trended greater ( P <0.1) in herbs and pioneer trees compared with other growth forms. There were no significant differences between monocots and dicots, and no phylogenetic signal for decomposition was observed. Significant correlations between continuous litter quality variables and decomposition rate were observed with correlation coefficients up to 0.72. Litter lignin:Mg, P concentration, and lignin:K, were the litter quality variables most related to decomposition rate. All elements showed significant negative correlations between initial litter concentration and percent remaining, but many elements showed significant correlation between percent element remaining and initial concentrations of other elements, indicating a stoichiometric balance between these elements during decomposition. The results show that although classification by growth form and canopy position are helpful for considering the ecosystem implications of changing community composition, litter quality traits provide additional predictive power for estimating the effects of species change on decomposition.
Abstract in Spanish is available at http://www.blackwell-synergy.com/loi/btp     

Leaf functional traits and monodominance in Southern Amazonia tropical forests

Tropical monodominant forests are rare communities with low tree species diversity. Species monodominance is not the product of a single mechanism, but the result of a set of not yet fully understood integrated ecological factors acting together. We compared populations of Brosimum rubescens in monodominant and mixed forests in Southern Amazonia to test whether leaf functional traits are ecological factors related to monodominance. Individuals of B. rubescens in the mixed forest invest in conservative strategies, while those in the monodominant forest invest in acquisitive strategies. Leaf functional traits, such as petiole length and adaxial cuticle thickness, could be associated with the monodominance of B. rubescens. Our study highlights for the first time the power of integrating leaf functional traits as a component of the set of ecological conditions to explain species monodominance. B. rubescens showed different functional strategies to establish and maintain its population in different forests, which makes it a strong competitor for resources, such as water and light, through variation in its leaf functional traits. We also suggest that such high plasticity can be an important condition for the persistence of the species over time.

     

Ecology and diversity of leaf litter fungi during early-stage decomposition in a seasonally dry tropical forest

Leaf litter samples of 12 dicotyledonous tree species (belonging to eight families) growing in a dry tropical forest and in early stages of decomposition were studied for the presence of litter fungi. Equal-sized segments of the leaves incubated in moist chambers were observed every day for 30 d for the presence of fungi. Invariably, the fungal assemblage on the litter of each tree species was dominated by a given fungal species. The diversity of fungi present in the litter varied with the tree species although many species of fungi occurred in the litter of all 12 species. A Pestalotiopsis species dominated the litter fungal assemblage of five trees and was common in the litter of all tree species. The present study and earlier studies from our lab indicate that fungi have evolved traits such as thermotolerant spores, ability to utilize toxic furaldehydes, ability to produce cell wall destructuring enzymes and an endophyte-litter fungus life style to survive and establish themselves in fire-prone forests such as the one studied here. This study shows that in the dry tropical forest, the leaf litter fungal assemblage is governed more by the environment than by the plant species.     

Monospecific dominance in tropical rain forests

Old-growth rain forests that are dominated by a single canopy species occur throughout the tropics, though they account for a limited proportion of the total rain forest area. These forests have been considered anomalies in which development of a more diverse community is deflected by harsh conditions. Very poor soils or an otherwise extreme environment may promote monodominance by excluding potentially competing species, but it is now apparent that monodominant tropical forests also develop under more benign conditions. Field studies have shown that a single species may dominate on undisturbed sites where the soils are similar to those of adjacent old-growth, mixed forests. In these situations the dominant is a superior competitor and/or is particularly tolerant to stresses such as shade. Assertion of dominance by a single species in an old-growth forest appears most likely in areas where the species pool contains few late-succession species with similar life history traits.     

Forest structure predicts species richness and functional diversity in Amazonian mixed-species bird flocks

Secondary forest has the potential to act as an important habitat for biodiversity and restoring ecological benefits. Functional diversity, which includes morphological and behavioral traits that mediate species interactions with the surrounding environment, relates to the resilience of ecosystems. To assess the relationship between habitat structural differences in primary and secondary forest and the resultant differences in functional diversity of avian species, we followed 11 mixed-species flocks at the Biological Dynamics of Forest Fragments Project, near Manaus, Brazil. We used remote sensing LiDAR to assess which three-dimensional forest structural features are most closely associated with variation in species richness and functional diversity in secondary and primary tropical forest flocks. The species richness of flocks in primary forest increased in areas with higher elevation and higher leaf area density in the understory and subcanopy but was not correlated with habitat structure in secondary forest. Functional diversity increased at lower elevations and with a denser subcanopy in both primary forest and secondary forest but only increased with greater understory leaf area density in primary forest. Together, these results indicate that a dense subcanopy and understory can be important for mixed-species flocks and that flock richness and functional diversity can be predicted by vegetation structure.     

Monopolization of litter processing by a dominant land crab on a tropical oceanic island

Litter processing by macroinvertebrates typically involves suites of species that act together to determine rates of breakdown and decomposition. However, tropical oceanic islands and coastal fringes on continents are often dominated by one or a few species of omnivorous land crabs that consume leaf litter. We used an exclusion experiment, together with other leaf removal and litter decomposition studies, to assess the role of a single dominant species, the red crab (Gecarcoidea natalis), in litter dynamics in rain forest on Christmas Island, Indian Ocean. In the presence of red crabs, litter cover and biomass varied seasonally, from almost complete cover and high biomass at the end of the dry season to almost total absence of litter at the end of each wet season. When crabs were excluded from both the shaded understory and light gaps in rain forest, litter increased rapidly to almost complete cover, which was then maintained year round. Leaf tether experiments, and measures of litter input and standing crops, indicated that red crabs monopolize litter processing, removing between 39 and 87% of the annual leaf fall from the forest floor. Rates of litter turnover were over twice as high in the presence of land crabs: the decomposition constant, k, was 2.6 in the understory exclusion plots, but rose to 6.0 in the presence of crabs. Red crabs occur at biomass densities (114 g m⁻²) far greater than those reported elsewhere for entire litter faunas. They significantly reduced the abundance of other litter invertebrates, but we did not detect any change in the relative frequencies of the major invertebrate groups (mites, collembolans, pulmonate snails, ants, psocopterans, and spiders). Wherever omnivorous land crabs are abundant, their activities may be paramount in litter decomposition and in regulating the rate of nutrient cycling. In monopolizing litter processing, they may also be important physical “ecosystem engineers”, translocating organic matter and nutrients into the soil and reducing available habitat for other animals. Received: 19 August 1998 / Accepted: 11 January 1999     

Distinct Bacterial Communities Dominate Tropical and Temperate Zone Leaf Litter

Little is known of the bacterial community of tropical rainforest leaf litter and how it might differ from temperate forest leaf litter and from the soils underneath. We sampled leaf litter in a similarly advanced stage of decay, and for comparison, we also sampled the surface layer of soil, at three tropical forest sites in Malaysia and four temperate forest sites in South Korea. Illumina sequencing targeting partial bacterial 16S ribosomal ribonucleic acid (rRNA) gene revealed that the bacterial community composition of both temperate and tropical litter is quite distinct from the soils underneath. Litter in both temperate and tropical forest was dominated by Proteobacteria and Actinobacteria, while soil is dominated by Acidobacteria and, to a lesser extent, Proteobacteria. However, bacterial communities of temperate and tropical litter clustered separately from one another on an ordination. The soil bacterial community structures were also distinctive to each climatic zone, suggesting that there must be a climate-specific biogeographical pattern in bacterial community composition. The differences were also found in the level of diversity. The temperate litter has a higher operational taxonomic unit (OTU) diversity than the tropical litter, paralleling the trend in soil diversity. Overall, it is striking that the difference in community composition between the leaf litter and the soil a few centimeters underneath is about the same as that between leaf litter in tropical and temperate climates, thousands of kilometers apart. However, one substantial difference was that the leaf litter of two tropical forest sites, Meranti and Forest Research Institute Malaysia (FRIM), was overwhelmingly dominated by the single genus Burkholderia, at 37 and 23 % of reads, respectively. The 454 sequencing result showed that most Burkholderia species in tropical leaf litter belong to nonpathogenic “plant beneficial” lineages. The differences from the temperate zone in the bacterial community of tropical forest litter may be partly a product of its differing chemistry, although the unvarying climate might also play a role, as might interactions with other organisms such as fungi. The single genus Burkholderia may be seen as potentially playing a major role in decomposition and nutrient cycling in tropical forests, but apparently not in temperate forests.     

Diversification and phylogenetic correlation of functional traits for co-occurring understory species in the Chinese boreal forest

Functional traits impact species interactions, community composition, and ecosystem functioning. However, few studies have focused on the diversification and phylogenetic correlation of multiple functional traits over geological time. We conducted phylogenetic comparative analysis for boreal forest understory species in northeast China to examine the diversification and phylogenetic correlation in several functional traits: leaf area (LA), leaf carbon content (LCC), leaf dry matter content (LDMC), leaf nitrogen content (LNC), plant height (PH), and specific leaf area (SLA). Phylogenetic signals showed that there were very low levels of phylogenetic niche conservatism (PNC) in understory leaf-related traits and plant height, suggesting divergence of functional traits for the co-occurring understory species. The disparity through time analyses (DTT) indicated that trait disparities mainly originated during recent divergence events and there were no differences in the observed trait disparities compared with that expected under Brownian motion. Furthermore, we found both positive and negative phylogenetic correlations among the measured functional traits. The very low levels of PNC suggest that these functional traits diverged among co-occurring understory species, and that those species are distantly phylogenetically related. The phylogenetic correlations among traits may be caused by both positively and negatively correlated adaptions that correspond to resource acquisition strategies. This study provides evidence that divergence in functional traits may reflect understory adaptions to boreal conditions.