Linking plant functional traits with post‐fire sprouting vigour in woody species in central Argentina

Sprouting vigour is determined by the plant amount of reserves and intrinsic growth rate of plants. While the first factor has been well studied, the second is far less understood. Although a higher growth rate would imply a higher sprouting vigour, fast‐growing species may have less below‐ground reserves, and thus, a lower sprouting potential. The relative importance of both opposite effects was little explored in the literature. To analyse the influence of growth rate on sprouting vigour, one growth season after a fire we measured plant height of the old (pre‐fire) and new (post‐fire) tissue in 194 individuals of 14 woody species from a woodland in central Argentina. We calculated a mean value of pre‐ and post‐fire height for each species, and obtained from a database potential height at maturity, wood density (WD) and specific leaf area (SLA), as surrogates of intrinsic growth rate. We performed a forward stepwise multiple regression using WD and SLA, together with mean pre‐fire height or potential height as independent variables, and mean post‐fire height (as an indicator of resprout vigour) as the dependent variable. Interactions were also tested. Pre‐fire height, WD and their interaction term were the variables that best explained post‐fire height. We also analysed the relationship between pre‐ and post‐fire size for each species independently by fitting hyperbolic functions. Then we correlated both parameters of the functions to species characteristics (WD, SLA, potential height and mean pre‐fire height). Both parameters of the hyperbolic functions were significantly correlated only with WD, but not with the other species characteristics. All results together indicate that species with low WD (i.e. high potential growth rate) regrow more vigorously than species with high WD when pre‐fire individuals were tall. In contrast, when pre‐fire individuals were small, WD had no influence on sprout vigour. A trade‐off between allocation of biomass to underground reserves and shoot growth seems to be responsible for the patterns obtained. For small individuals, below‐ground reserves seem to play a more important role than inherent growth rate (here measured through WD) in determining the sprouting vigour, while for large individuals, growth rate seems more important than reserves.

QuestionsTo comprehensively understand ecological dynamics within a forest ecosystem, it is vital to explore how surrounding trees influence the growth of individual trees in a community. This study investigates the importance of biotic interactions on tree growth by examining several metrics of competitive interactions and community structure and considering three classes of intrinsic growth rates among the focal individuals: slower, intermediate, and faster‐growing trees. We also separated the focal trees based on their canopy position.LocationBrazilian subtropical forests.MethodsWe assessed various factors related to the focal trees and their neighbors, including differences in traits, neighborhood crowding, phylogenetic distance, and overall trait composition within the community. We then ran linear mixed‐effects models to test how these different metrics influenced the growth rates of the focal trees.ResultsOur results indicate that phylogenetic distance is linked to higher growth. Specific leaf area (SLA), leaf area (LA), and wood density (WD) are significantly related to tree growth. Trees surrounded by neighbors with higher SLA than themselves grow better, particularly smaller trees. Similarly, taller trees with smaller LA than their neighbors grow better. Trees in the intermediary growth class grow better when they have higher WD than their neighbors. Conversely, smaller trees benefit from greater WD difference between the focal trees and their neighbors, while height difference negatively impacts faster‐growing trees. Moreover, communities with higher SLA and WD positively impact the growth of faster‐growing trees.ConclusionsWe conclude that the interactions between trees are mediated by their ecological differences, but the performance and responses to surrounding competitors vary along with their grow class and position within a community. This study has revealed that the tree's intrinsic growth rate mediates the effect of traits and phylogeny of surrounding trees on individual tree growth.

Understanding the relative contribution of abiotic and biotic factors to the formation of ecosystem functioning across scales is vital to evaluate ecosystem services. Here, we elucidate the effects of abiotic site conditions (i.e., soil and topographic properties) and plant functional traits on variations of stand aboveground carbon (AGC) stock in an old-growth tropical montane rain forest. The response-effect framework in functional ecology is adopted in examining how plant functional traits respond to environmental changes and affect ecosystem functioning. We measured specific leaf area and wood density of 270 woody plant species and estimated stand AGC stocks in a 30-ha forest plot. The relationships among environmental factors (ENVIRONMENT), community-weighted means of functional traits (TRAITS) and stand AGC stocks across nested spatial scales were disentangled by structural equation modeling. The results showed that the stands composed of ‘acquisitive’ species (high specific leaf area and low wood density) had low AGC, whereas stands composed of ‘conservative’ species (low specific leaf area and high wood density) had high AGC. TRAITS responded to ENVIRONMENT and affected AGC directly. ENVIRONMENT had an indirect effect on AGC through its direct effect on TRAITS. TRAITS were more important than ENVIRONMENT in driving variations of AGC. The effects of TRAITS on AGC increased, while the effects of ENVIRONMENT on AGC decreased with the increase of spatial scales in the tropical montane rain forest. Our study suggests that plant functional traits are the mediators in regulating effects of abiotic site conditions on ecosystem functions.

A 4-year fertilization experiment with nitrogen (N) and phosphorus (P) was carried out in natural gaps of a subtropical forest in northeastern Argentina. Saplings of six dominant canopy species differing in shade tolerance were grown in five control and five N + P fertilized gaps. Hydraulic architectural traits such as wood density, the leaf area to sapwood area ratio (LA : SA), vulnerability to cavitation (P50) and specific and leaf-specific hydraulic conductivity were measured, as well as the relative growth rate, specific leaf area (SLA) and percentage of leaf damage by insect herbivores. Plant growth rates and resistance to drought-induced embolisms increased when nutrient limitations were removed. On average, the P50 of control plants was -1.1 MPa, while the P50 of fertilized plants was -1.6 MPa. Wood density and LA : SA decreased with N + P additions. A trade-off between vulnerability to cavitation and efficiency of water transport was not observed. The relative growth rate was positively related to the total leaf surface area per plant and negatively related to LA : SA, while P50 was positively related to SLA across species and treatments. Plants with higher growth rates and higher total leaf area in fertilized plots were able to avoid hydraulic dysfunction by becoming less vulnerable to cavitation (more negative P50). Two high-light-requiring species exhibited relatively low growth rates due to heavy herbivore damage. Contrary to expectations, shade-tolerant plants with relatively high resistance to hydraulic dysfunction and reduced herbivory damage were able to grow faster. These results suggest that during the initial phase of sapling establishment in gaps, species that were less vulnerable to cavitation and exhibited reduced herbivory damage had faster realized growth rates than less shade-tolerant species with higher potential growth rates. Finally, functional relationships between hydraulic traits and growth rate across species and treatments were maintained regardless of soil nutrient status.

1. Species differences in growth and shade tolerance might contribute to coexistence of tree species. To explore how such differences depend on underlying plant traits, 14 tree species were investigated in temperate forests on sand and loess soils in the Netherlands. Plant traits were measured for 0.5?1 m tall saplings: 10 saplings growing at low light conditions and 10 at high light conditions. Growth was determined from annual lengths of leader shoots, and shade tolerance from an independently tested scale. 2. Shade tolerance and extension growth of the leader shoot were negatively correlated. Plant traits that related positively with shade tolerance were negatively related to extension growth, and vice versa. Photosynthetic capacity, leaf dark respiration and total leaf mass related weakly to shade tolerance and extension growth. Specific leaf area (SLA, leaf area/leaf mass) and wood density were the traits most strongly correlated to shade tolerance and extension growth. 3. Shade-tolerant species had denser wood and slower extension growth. They also had larger crowns, suggesting that dense stems provide strength for supporting larger crowns. 4. More shade-tolerant species had a higher SLA, which is opposite to tree communities with larger leaf life span variation. In winter deciduous tree communities, more shadetolerant species benefit from investing leaf area at low costs (high SLA) rather than from investing in durable leaves (low SLA). 5. Species on sand had higher growth rates and higher light requirements than species on loess. In line with the resource-ratio hypothesis, the dominance of the more shadetolerant species on nutrient rich loess soils may be attributed to the denser vegetation supported and the resultant lower light availability for saplings compared with saplings on infertile and drought-prone sand soils. 6. Synthesis: These results provide plant trait-based predictions for the regeneration success and composition of species of temperate forests with management based on natural regeneration. These forests are expected to become dominated by shade-tolerant species with high wood density and high SLA on the more productive soils, and by light demanding species with low wood density and low SLA on poorer soils. Key-words: carbon balance, extension growth, natural forest development, photosynthetic capacity, shade tolerance, soil, specific leaf area, temperate forests, total leaf mass, wood density

A central goal of comparative plant ecology is to understand how functional traits vary among species and to what extent this variation has adaptive value. Here we evaluate relationships between four functional traits (seed volume, specific leaf area, wood density, and adult stature) and two demographic attributes (diameter growth and tree mortality) for large trees of 240 tree species from five Neotropical forests. We evaluate how these key functional traits are related to survival and growth and whether similar relationships between traits and demography hold across different tropical forests. There was a tendency for a trade-off between growth and survival across rain forest tree species. Wood density, seed volume, and adult stature were significant predictors of growth and/or mortality. Both growth and mortality rates declined with an increase in wood density. This is consistent with greater construction costs and greater resistance to stem damage for denser wood. Growth and mortality rates also declined as seed volume increased. This is consistent with an adaptive syndrome in which species tolerant of low resource availability (in this case shade-tolerant species) have large seeds to establish successfully and low inherent growth and mortality rates. Growth increased and mortality decreased with an increase in adult stature, because taller species have a greater access to light and longer life spans. Specific leaf area was, surprisingly, only modestly informative for the performance of large trees and had ambiguous relationships with growth and survival. Single traits accounted for 9-55% of the interspecific variation in growth and mortality rates at individual sites. Significant correlations with demographic rates tended to be similar across forests and for phylogenetically independent contrasts as well as for cross-species analyses that treated each species as an independent observation. In combination, the morphological traits explained 41% of the variation in growth rate and 54% of the variation in mortality rate, with wood density being the best predictor of growth and mortality. Relationships between functional traits and demographic rates were statistically similar across a wide range of Neotropical forests. The consistency of these results strongly suggests that tropical rain forest species face similar trade-offs in different sites and converge on similar sets of solutions.

Seedling planting plays a key role in active forest restoration and regeneration of managed stands. Plant attributes at outplanting can determine tree seedling survival and consequently early success of forest plantations. Although many studies show that large seedlings of the same age within a species have higher survival than small ones, others report the opposite. This may be due to differences in environmental conditions at the planting site and in the inherent functional characteristics of species. Here, we conducted a global-scale meta-analysis to evaluate the effect of seedling size on early outplanting survival. Our meta-analysis covered 86 tree species and 142 planting locations distributed worldwide. We also assessed whether planting site aridity and key plant functional traits related to abiotic and biotic stress resistance and growth capacity, namely specific leaf area and wood density, modulate this effect. Planting large seedlings within a species consistently increases survival in forest plantations worldwide. Species' functional traits modulate the magnitude of the positive seedling size-outplanting survival relationship, showing contrasting effects due to aridity and between angiosperms and gymnosperms. For angiosperms planted in arid/semiarid sites and gymnosperms in subhumid/humid sites the magnitude of the positive effect of seedling size on survival was maximized in species with low specific leaf area and high wood density, characteristics linked to high stress resistance and slow growth. By contrast, high specific leaf area and low wood density maximized the positive effect of seedling size on survival for angiosperms planted in subhumid/humid sites. Results have key implications for implementing forest plantations globally, especially for adjusting nursery cultivation to species' functional characteristics and planting site aridity. Nursery cultivation should promote large seedlings, especially for stress sensitive angiosperms planted in humid sites and for stress-resistant species planted in dry sites.

Background: The use of tree species’ functional traits is a promising approach in forest restoration. However, some traits may change during ontogeny. Questions: Does intraspecific variation in functional traits occur between sapling and adult stages? Do groups of species can be delimited based on functional traits regardless of their ontogenetic stage? Study sites and dates: Cloud forest restoration, Veracruz, Mexico, 2016. Methods: Saplings and adults of eight native tree species in different age plantations were measured for leaf area (LA), specific leaf area (SLA), stomatal density (SD), foliar nutrient content (C, N, P) and relative growth rate (RGR). Wood density (WD) was measured for adults. Data were analyzed using linear mixed models and principal component analysis (PCA). Results: Overall, SLA was higher in saplings than in adults. A few species showed intraspecific variation for LA (three species), SD (three) and foliar N content (one). Species with high WD ( Quercus spp . ) and intermediate WD ( e.g . Liquidambar styraciflua ) tended to have lower LA and SLA, and higher SD. Species with low WD ( e.g . Heliocarpus donnellsmithii) had high SLA, RGR, and N content. PCA highlighted that saplings and adults of a same species were close to each other within the ordination space. Conclusions: Intraspecific variation between saplings and adults was small for most traits (except SLA) in comparison to differences across species. Therefore species trait values (measured in individuals of any age) could be a useful tool to characterize groups of species during the forest restoration trajectory.

Understanding how trees mediate the effects of chronic anthropogenic disturbance is fundamental to developing forest sustainable management strategies. The role that intraspecific functional diversity plays in such process is poorly understood. Several tree species are repeatedly defoliated at large scale by cattle breeders in Africa to feed livestock. In addition, these tree species are also debarked for medicinal purposes. These human-induced disturbances lead to biomass loss and subsequent decline in the tree growth. The main objective of this work is to investigate how functional traits mediate tree response to chronic anthropogenic disturbance. We used a unique data set of functional traits and growth rate of 503 individual tree of Afzelia africana. We collected data on leaf mass per area (LMA), wood density (WD) and growth rate, and recorded history of human disturbances (debarking, pruning) on individual tree from 12 populations of A. africana distributed in two ecological zones in Benin (West Africa). We tested the effect of disturbances on absolute growth rate across ontogenetic stages, assessed the role of intraspecific trait variability on growth and tested the role of tree functional strategy on the tree growth response to debarking and pruning. We found that debarking did not affect stem growth, suggesting a fast compensatory regrowth of bark wounded. Moreover, tree response to debarking was independent of the functional strategy. By contrast, we found that pruning reduced tree absolute growth; however, trees with low WD were more strongly affected by pruning than trees with high WD. Our results emphasize the importance for plant functioning of the interplay between the availability of leaves for resource acquisition and a resilience strategy by mobilizing stored resources in stem wood to be reinvested for growth under severe disturbances.

Wood volume and quality are the most important aspects of commercial forestry production, and studies of wood formation are important in order to increase the value and efficiency of forestry production. The phenylpropanoid pathway produces various compounds with diverse functions both for plant defence against biotic and abiotic stress as well as structural development. One of the main roles is monolignol production for lignin biosynthesis, which is a crucial aspect of wood formation. For this study three candidate genes involved in lignin biosynthesis were selected: phenylalanine ammonialyase (PAL1), cinnamyl alcohol dehydrogenase (CAD) and cinnamoyl-CoA reductase (CCR). Candidate gene expression was analysed in selected individuals with high and low wood density from open-pollinated Scots pine families during early wood (EW) and late wood (LW) formation and correlation between expression of these genes, total lignin content, and wood density was determined. Wood density values for analysed trees were similar within tree families but differed significantly between families with high and low wood density (p=1,06E-20). Wood density was slightly negatively correlated with lignin content (r=-0.36, p=0.038), but only in individuals in the high density wood group. In trees with low wood density, expression of the CAD gene was significantly lower in late wood formation compared to early wood (p=0.00179). In trees with high wood density, expression of the PAL1 gene was five times higher during early wood formation compared to late wood formation. A positive correlation was detected between PAL1 and CCR gene expression during early wood formation (r=0.804) and late wood formation (r=0.466).

Understanding the relationships between species' demography and functional traits is crucial for gaining a mechanistic understanding of community dynamics. While leaf morphology represents a key functional dimension for plants worldwide (i.e., the leaf economics spectrum), its ability to explain variation in trees' life history strategies remains limited. Plant growth is influenced by both leaf morphology and allocation; hence, incorporating both dimensions is essential but rarely done. Additionally, trait–performance relationships have mainly been studied in tropical communities, leaving gaps in our understanding of temperate forests where different seasonality patterns may alter these relationships. We examined whether species' leaf area index (leaf area per crown size, LAI), a measure of leaf allocation, explains the variation of juvenile tree species' potential growth rates in a winter‐deciduous broadleaf forest. LAI has not been characterized as a species‐level trait, but its ability to predict plant productivity at the ecosystem scale highlights its potential for explaining plant growth. We evaluated species' maximum LAI both individually and in conjunction with wood density (WD) and leaf mass per area (LMA). We expected that models would improve when both leaf morphology (LMA) and leaf allocation (LAI) were included and that species with denser crowns would have higher potential growth rates. LAI and LMA were significant predictors of growth but only when both were incorporated, and together explained a high proportion of species' growth variations (R2adj = 0.59). We found evidence of a trade‐off between LAI and LMA, with a negative relationship between them and each having a positive influence on species' growth, suggesting that there are multiple allocation strategies to achieve fast growth. A surprisingly positive LMA–growth relationship contrasts with observations from tropical forests. We did not find significant relationships with WD in this forest. Our results highlight that incorporating leaf allocation improves models of trait–performance relationships. They also suggest, in agreement with the limited literature, that temperate forests may exhibit different trait–performance relationships from those of tropical forests, where LMA is negatively related to growth and WD is often important. Clarifying the details and contexts of trait–performance relationships is crucial for applying the functional trait framework to understanding community structure and dynamics of forests globally.

The identification of AFLP markers and their subsequent conversion to SCAR-markers linked to wood density of Norway Spruce (Picea abies L [Karst.]) is described for the first time. In AFLP-analyses, 102 different primer enzyme combinations were screened in a bulked segregant approach comparing individuals with high and low wood density. A total of 107 polymorphic AFLP fragments were obtained between the DNA-pools. Twenty-three markers were selected for further analyses to verify their linkage to wood density based on individuals used for pool constitution and additional unrelated clonal material. For 15 markers, a significant linkage to wood density was confirmed by a two-sided Fisher’s-exact test. Four markers were converted into SCAR markers and validated for plant material assayed for wood density by X-ray microdensitometry. For each marker a monomorphic band was obtained using sets of nested primers or restriction site-specific primers (RSS), which include the AFLP-restriction recognition sites. For two markers that are linked to high wood density, a separation from unlinked size homologous marker-alleles was realized by a PCR-restriction approach. Validation of these markers in different full-sib families confirmed their usability to separate the classes for low and high wood density of Picea abies.

Plant growth rates strongly determine ecosystem productivity and are a central element of plant ecological strategies. For laboratory and glasshouse‐grown seedlings, specific leaf area (SLA; ratio of leaf area to mass) is a key driver of interspecific variation in growth rate (GR). Consequently, SLA is often assumed to drive GR variation in field‐grown adult plants. However, there is an increasing evidence that this is not the general case. This suggests that GR – SLA relationships (and perhaps those for other traits) may vary depending on the age or size of the plants being studied. Here we investigated GR – trait relationships and their size dependence among 17 woody species from an open‐canopy, fire‐prone savanna in northern Australia. We tested the predictions that SLA and stem diameter growth rate would be positively correlated in saplings but unrelated in adults while, in both age classes, faster‐GR species would have higher light‐saturated photosynthetic rate (Asat), higher leaf nutrient concentrations, higher branch‐scale biomass allocation to leaf versus stem tissues and lower wood density (WD). SLA showed no relationship to stem diameter GR, even in saplings, and the same was true of leaf N and P concentrations, and WD. However, branch‐scale leaf:stem allocation was strongly related to GR in both age groups, as was Asat. Together, these two traits accounted for up to 80% of interspecific variation in adult GR, and 41% of sapling GR. Asat is rarely measured in field‐based GR studies, and this is the first report of branch‐scale leaf:stem allocation (analogous to a benefit:cost ratio) in relation to plant growth rate. Our results suggest that we may yet find general trait‐drivers of field growth rates, but SLA will not be one.

Cyclones cause profound immediate impacts on tropical rainforest trees, including defoliation, limb loss, snapping of stems and uprooting. Some studies have shown that plant functional traits such as tree size, buttress roots and wood density are correlated with these forms of cyclone damage. On 20 March 2006, Severe Tropical Cyclone Larry crossed the north Queensland coast and proceeded inland across the Atherton Tablelands, impacting the critically endangered Mabi Type 5b rainforest. We investigated the effects of Cyclone Larry on common tree species by categorizing damage to trees as uprooted, snapped, limbs damaged (light, moderate, severe) or upright and estimating levels of defoliation. Damage was then related to functional traits including tree size, presence of buttress roots, wood density, and leaf size and strength. Levels of damage differed between species. Tree size (diameter at breast height) and the presence of buttress roots were not related to damage levels. Wood density was significantly negatively correlated to proportion of trees with snapped stems and significantly positively correlated with the proportion of trees upright with no or light limb damage. Levels of defoliation were significantly related to leaf strength (specific leaf area – SLA) and to leaf width, but not other components of leaf size (area or length) or petiole length. Species with high wood density and low SLA (e.g. Argyrodendron spp.) were found to have high cyclone resistance, the ability to resist damage, while species with low wood density and high SLA (e.g. Dendrocnide photinophylla) exhibited low resistance. However, traits related to low resistance are also those linked to rapid growth and high cyclone resilience, the ability to recover from damage, so it is unlikely that the Mabi forest will experience long‐term changes in floristic composition following Cyclone Larry.

Growth rate is a central element of a plant's ecological strategy in its competition with other plants. It is well known that traits give rise to differences in growth between species, but there is limited understanding of how trait–growth relationships change with age and whether these relationships vary depending on how growth is measured. Field growth rates were measured at different plant ages for 14 shrub species in an eastern Australian heathland. Ages were identifiable from local fire history because all species regenerate from seed, post‐fire. One year of growth was tracked on plants at six ages: 1.4, 2.4, 5, 7, 9 and 32 years old. A novel sampling protocol allowed us to express annual growth rate increments of (i) stem diameter, (ii) total leaf area, (iii) height, (iv) above‐ground standing biomass, and (v) total above‐ground biomass including losses to tissue turnover. Overall, wood density (WD) and leaf mass fraction (LMF, ratio of total leaf to above‐ground plant dry mass) emerged as the two traits most clearly influencing growth rates, higher WD corresponding to slower growth and higher LMF to faster growth. Higher leaf mass per area (LMA) also corresponded to faster growth rates; however, this was seemingly a secondary correlation originating via a negative relationship between WD and LMA. More weakly and less consistently, higher leaf N and (less so) higher leaf P per unit leaf area corresponded to faster growth. In general, trait–growth relationships were weaker in the younger age classes (1.4 and 2.4 years) and strongest at ages 5, 7 and 9 years. WD and LMA effects on growth were markedly heterogeneous among ages; effects of LMF and leaf nutrients were more consistent. Although our five growth metrics each measure distinct aspects of changes in plant size, their correlations with traits showed considerable similarity. Synthesis. We demonstrate that key functional traits undergo shifts in their relationship with growth as plants mature. Therefore, it will be valuable to shift our understanding of plant strategies away from the notion that traits influence growth rates in a fixed manner across plant sizes and ages.