Resprouting Ability Research Articles

Retention of cotyledons is crucial for resprouting of clipped oak seedlings.

Although resprouting plays an important role in facilitating persistence of damaged seedlings, the functional attributes of cotyledons and taproots during resprouting of 1-year oak seedlings are not well explored. In this study, cotyledons were removed from Quercus mongolica seedlings to explore resprouting in response to simulated disturbance as a function of shoot clipping, and to examine the resprouting ability in relation to timing of clipping and cotyledon removal. Isotope labeling experiments were also performed to evaluate contribution of the cotyledons and taproots to resprouting. Regardless of timing of shoot clipping, seedlings successfully resprouted provided their cotyledons were not detached. Clipped seedlings were less likely to resprout when cotyledons were removed. Seedlings clipped at earlier development stage exhibited higher resprouting capacity than those clipped at later stage. Cotyledon removal, more than timing of clipping, decreased the dry masses of newly-resprouted shoots. However, no significant influences of cotyledon removal and timing of clipping were found on the dry masses of roots, suggesting the importance of cotyledons for resprouting. Roots became functional and accumulated more soil nitrogen after shoot clipping and cotyledon removal, representing a double security-based strategy for the clipped seedlings to resprout despite the importance of cotyledons.

Efectos de la gestión selvícola pasada y presente sobre la diversidad genética actual y futura de Quercus pyrenaica Willd. en Sierra Nevada

Valbuena-Carabana, M., Gil, L. 2014. Assessing past and present management effects on current and future levels of genetic diversity in Quercus pyrenaica Willd. in Sierra Nevada. Ecosistemas 23(2):90-98. Doi.: 10.7818/ECOS.2014.23-2.12 Quercus pyrenaica Willd. is a Mediterranean and western European oak species widely distributed in the Iberian Peninsula. Its profuse resprouting ability from the entire root system was made use of in traditional management practices, especially as coppices for firewood and charcoal production and less frequently as open woodland for cattle grazing. The abandonment of traditional management evidences the general degradation sate of these woodlands –growing stagnation, stem top drying and lack of seed production–, and causes of such degradation were theoretically attributed to the exhaustion of clonal clumps and to the lack of genetic diversity. Nevertheless, the recent survey by means of nuclear microsatellites markers of several oak woodlands, included these hereby presented, allowed to discard such hypothesis. Lack of relation between forest structure (coppice vs. open woodlands) and the asexual or sexual origin of trees, and the high heterogeneity in clonal sizes hinders to predict the current clonal structure of woodlands based on their forest structure. The present study analyses the conservation state of genetic resources in a territory intensively used by man along the history evidencing the important resilience of the species to traditional coppicing. The study shows the effect of past forest management (coppicing and maintaining open woodlands) and the most commonly applied treatment in the present (coppice thinning with standards) on the current genetic diversity and clonal structure in three plots of the same oak woodland having different forest structures at Sierra Nevada National Park. Moreover, the potential evolution of genetic diversity is evaluated through the analyses of the juvenile cohort in each plot. Although, in the adult cohort, coppices bear higher levels of genetic diversity, the asexual origin of their juvenile class may limit the genetic diversity in the future. On the contrary, in the open woodland, the sexual origin from seeds of the juvenile class will potentially increase genetic diversity in the future.

Effects of Biennial Fire and Clipping on Woody and Herbaceous Ground Layer Vegetation: Implications for Restoration and Management of Oak Barren Ecosystems

AbstractSavannas and oak barrens are threatened in North America, due, in part, to removal of natural disturbance regimes. However, the periodic prescribed fires used in savanna and oak barren management sometimes accelerate the formation of a shrub layer, which can displace herbaceous species. This may be because periodic low severity fires act much like clipping, topkilling shrubs, yet allowing them to accumulate reserves in intervals without fire for more vigorous sprouting. To test this, we compared biennial dormant season burn prescriptions to a fire surrogate (clipping) using three oak barrens sites in the Bluegrass Region of southern Ohio. Fire and clipping treatments did little to suppress the resprouting ability of shrubs (woody stems <2 cm dbh), which regrew rapidly and in equivalent densities following treatment. However, both treatments reduced shrub cover, resulting in a 35% decrease in shrub cover over the course of the study. In contrast, non‐manipulated plots experienced a 44% increase in shrub cover over the same time period. Despite this reduction in shrub cover, treatments had no effect on herbaceous plant cover, richness, diversity, or evenness. These results suggest that the use of biennial prescribed dormant season fire, as employed in this study, is equivalent to clipping, and although effective at temporarily reducing shrub cover, is not effective in reducing shrub densities or resprouting potential. Thus, burning during marginal conditions should be avoided for achieving a short‐term restoration goal of shrub removal, but can be effective for maintaining the current shrub layer.

Vegetation, terrain and fire history shape the impact of extreme weather on fire severity and ecosystem response

AbstractQuestionsDo endogenous (landscape/vegetation) or exogenous (weather) factors control fire severity? During severe fire weather, is there convergence in fire severity across rain forest, forests and heathlands such that all locations burn with similarly high severity? Are there long‐term effects of fire severity in temperate crown‐fire ecosystems?LocationMontane rain forests, eucalypt forests and heaths in the temperate climate zone of eastern Australia (Washpool/Gibraltar Range National Park).MethodsThe immediate and longer‐term effects of fire weather and landscape (terrain, previous fire history and vegetation type) factors on fire severity and ecosystem response were measured using remote sensing and ground measures of microclimate, productivity and plant resprouting at 45 sites.ResultsFire weather strongly interacted with terrain, antecedent fire history and vegetation type, resulting in complex mosaics of mixed fire severity rather than convergence to uniform fire severity. Vegetation type influenced the effects of time‐since‐fire and fire frequency on fire severity, suggesting differential fire feedbacks. High fire severity left a long‐term imprint on total reflectance, ground temperatures and productivity of the vegetation, but these effects were not uniform across vegetation types. The abundance of resprouting species was not strongly affected by fire severity.ConclusionsThere was evidence for strong weather control of fire severity but fire history, terrain and vegetation shape the immediate effect due to the contrasting pyrogenic vs pyrophobic nature of the vegetation mosaic. The short‐term dominance of weather as a driver of fire severity is only weakly related to the longer‐term ecosystem response because of the strong resprouting ability of the canopy dominants, even in rain forest. The forest complexes of eastern Australia appear highly resilient to high fire severity in both structure and floristics, which may influence long‐term feedbacks.

Interspecific variation in the size‐dependent resprouting ability of temperate woody species and its adaptive significance

Summary Resprouting of woody species after above‐ground damage may help plants to persist longer at a given site and quickly reoccupy disturbed sites, thereby strongly influencing forest dynamics. Resprouting has been discussed from two adaptation perspectives: recovery from damage by catastrophic disturbance and survival in frequently disturbed shaded understorey. However, few studies have comprehensively dealt with both adaptation types to understand resprouting strategies. To understand the adaptive significance of resprouting, we assessed the size dependence of resprouting ability after stem clipping for 24 deciduous broad‐leaved species, including shrubs, sub‐canopy and canopy trees, in a cool‐temperate forest in Japan. The community assembly includes species adapted to past catastrophic disturbances (e.g. fire, logging) and to stable forest with intermittent treefall (currently the dominant disturbance). We correlated resprouting ability with life‐history strategies based on demographic parameters and plant functional traits, such as leaf mass per area (LMA), leaf toughness and wood density. All the studied species could resprout in juveniles, and resprouting ability increased as stump size increased. Most sub‐canopy and canopy trees lost their ability to resprout after attaining a particular stump size, whereas shrub species retained the ability to resprout throughout their lifetimes. The relative growth rate, LMA and foliar nitrogen did not greatly influence the resprouting ability of a species. In contrast, species with smaller maximum size, lower leaf toughness and lower wood density had better juvenile resprouting ability. This better resprouting ability may have evolved because these characteristics make them more vulnerable to shaded understorey. However, species with larger maximum size and lower leaf toughness retained their ability to resprout to a larger size. Synthesis. A better resprouting ability is related to the ability to survive frequent disturbances, in juveniles, which are characteristics of both forest understorey and frequent fire or drought. To retain resprouting ability until grown seems to be an adaptation to survive infrequent large disturbances. Light‐demanding species, which generally have better resprouting ability than shade‐tolerants both in juveniles and adults, are adapted to disturbances of various scale and frequency; however, shade‐tolerants could survive well in the understorey due to a combination of stronger physical defences and resprouting ability.

Shrub resprouting response after fuel reduction treatments: Comparison of prescribed burning, clearing and mastication

Fuel reduction treatments are commonly used to reduce the risk of severe wildfire. However, more information about the effects on plant resprouting is needed to help land managers select the most appropriate treatment. To address this question, we evaluated the resprouting ability of five shrub species after the application of different types of fuel reduction methods (prescribed burning, clearing and mastication) in two contrasting shrubland areas in northern Spain. The shrub species were Erica australis, Pterospartum tridentatum and Halimium lasianthum spp. alyssoides, Ulex gallii and Erica cinerea.For most of the species under study (E. australis, P. tridentatum, H. lasianthum spp. alyssoides and U. gallii), neither plant mortality nor the number nor length of sprouted shoots per plant differed between treatments, although in E. cinerea the number of shoots was more negatively affected by prescribed burning than by clearing or mastication.The pre-treatment plant size did not affect plant mortality or plant resprouting response, suggesting that this parameter alone is not a good indicator of plant resprouting after fuel reduction treatments. Stem minimum diameter after treatments, a proxy of treatment severity, was not related to plant mortality, number or length of resprouted shoots. The duration of temperatures higher than 300 °C during burning in plant crown had a negative effect on the length of resprouted shoots, only in E. cinerea.The results show that fuel reduction treatments did not prevent shrub response in any case. Some reflections on the applicability of treatments are discussed.

Resprouting Ability of Dry Forest Tree Species after Disturbance Does Not Relate to Propagation Possibility by Stem and Root Cuttings

AbstractTropical dry forest tree species are recognized for their high resprouting ability after disturbance. We tested whether species that commonly produce root and stem suckers can be propagated by large stem and root cuttings, a useful method for landscape restoration programs. We performed four experiments: (1) In a greenhouse, we tested the propagation of six species using large stem cuttings collected from early successional sites. We used the following treatments: (i) dry season collection and planting; (ii) dry season collection, storage in humid soil, and wet season planting; (iii) wet season collection and planting; and (iv) wet season collection and planting after treatment with commercial NAA auxin. (2) Stem cuttings of Myracrodruon urundeuva were planted in a pasture during the rainy season after either NAA, IBA, or no auxin treatment. (3) As a control experiment, we also planted cuttings of Spondias mombin, a species known for successfully regenerating from cuttings. (4) Root cuttings of six species were collected in recently plowed pastures and planted in the greenhouse with and without treatment with NAA auxin. No root cuttings rooted. Only M. urundeuva and Astronium fraxinifolium stem cuttings rooted. Maximum success was obtained for stem cuttings collected and planted in the dry season (23%). Only 13% of M. urundeuva had sprouted by the 15th month of the field experiment. As a result, large cuttings are not recommended for propagation of the studied species. Future studies should include development of suitable methods of root harvesting and prospection of traditional knowledge for species selection.

The effect of harvesting on stump mortality and re-sprouting in aged oak coppice forests

In Central Europe, traditional management of oak coppice forest was abandoned at the beginning of the last century, leaving large tracts of forest developing into aged coppice stands. Since the increasing importance and use of biomass as a renewable energy source, resumption of coppice management in these forests is being considered. However, there are uncertainties about the re-sprouting ability of large and old oak stumps. In this study we determined the re-sprouting ability of sessile oak (Quercus petraea (Mattuschka) Liebl.) stumps 80–100years after the last coppice cut. Stump mortality and re-sprouting intensity were analyzed in relation to three different harvesting methods (harvester; conventional chainsaw cut; very low chainsaw cut), browsing intensity, vitality of parent trees and stump parameters. In addition, the extent to which stump mortality may be compensated by generative regeneration was quantified.On average, 16% of all sessile oak stools died within two vegetation periods after coppicing. Stump mortality was higher in unfenced areas compared to areas protected against browsing. No clear relationships were observed between stump mortality and harvesting method or parent tree characteristics.Two vegetation periods after coppicing, numerous new stump sprouts were recorded. In unfenced areas, average maximum sprout height was reduced by nearly 80%. Maximum sprout height (used as an indicator for re-sprouting intensity) was found to be unaffected by harvesting method and not related to stump height or parent tree characteristics. When stumps were cut close to the soil surface the majority of the most vigorous oak sprouts originated below ground.Our results indicate that the re-sprouting ability of 80–100year old oak trees originating from former coppice management is still high and little influenced by harvesting methods.

Resprouting ability and mobile carbohydrate reserves in an oak shrubland decline with increasing elevation on the eastern edge of the Qinghai–Tibet Plateau

Resprouting is the main regeneration mechanism of most Quercus species after severe disturbance such as fire or coppicing. Yet little is known about the relationships between the amounts of resources stored in the roots and resprouting ability when the total aboveground part of plants/trees was fully removed or destroyed, and about the resprouting ability in relation to increasing elevation associated with decreasing site productivity. The present study investigated the non-structural carbohydrate (NSC) concentrations and its pool size in roots of Quercus aquifolioides clumps grown at 3000m, 3500m, and 3950m a.s.l. on Zheduo Mt., southwestern China, to test two competing hypotheses that (1) decreases in net primary productivity and growing season length with increasing elevation result in less allocation to storage of belowground NSC reserves, so that after coppicing, shrubs at higher elevations produce fewer resprouts and less total biomass than those at lower elevations, vs. (2) the shrubs growing at high-elevation sites with low-productivity produce more resprouts and biomass than those at low-elevation sites after coppicing, as it is expected that resprouting is favored in low-productivity environments. Our results indicated that early resprouting of Q. aquifolioides shrubs after coppicing is largely determined by the initial carbohydrate pool but not by the carbohydrate concentrations in roots. The large resprouting vigor of this species may be mainly ascribed to its large ratios of root to shoot biomass or root NSC pool to shoot NSC pool. The resprouting vigor of clumps decreased significantly with increasing elevation, which corresponds to significant decreases in the root biomass or root NSC pool size per clump with increasing elevation. Resprouts self-thinned more early and rapidly in clumps at lower elevations than at higher elevations, which may be mainly resulted from competition occurred more early in the more productive sites at lower elevations compared to higher elevations. Our results support the 1st but not the 2nd hypothesis. The present study has important implications for resources storage dealing with ecophysiology-based management strategy of coppicing woodland across scales.

Fires enhance flammability inUlex parviflorus

Fires enhance flammability in<i>Ulex parviflorus</i>

Fire severity and nutrient availability do not constrain resprouting in forest shrubs

Plants often survive disturbances such as fire by resprouting which involves having both protection traits and carbohydrate storage capacity. Protection traits not only act directly to insulate meristems but also prevent combustion of carbohydrate stores. Rapid stem growth also allows replenishment of carbohydrate stores ensuring persistence through another event. Resource availability may, however, constrain the ability to develop resilience to high-severity fires through either nutrient limitation or light limitation. We tested whether fire severity influenced resprouting ability of woody plants in two contrasting environments, low nutrient dry sclerophyll forest and more fertile wet sclerophyll forest. We tested which fire protection and growth traits were associated with resprouting ability (27 species) and resprouting vigour (16 species). Fire severity did not limit the ability of most species to resprout in either forest type. There was no generalized protection syndrome for surviving top kill, but combinations of bud protection and growth together with storage capacity appear to drive resprouting ability. In nutrient-limited forests, low specific leaf area (SLA) may reduce stem growth in resprouters, causing more reliance on bud protection through bark thickness. Conversely, in the more fertile forests, where light becomes limiting with time-since-fire, high SLA appears to increase the capacity for rapid stem growth with less emphasis on developing thicker bark. These different syndromes appear to be adaptive as fire severity did not influence survival in either forest type.

Bark thickness determines fire resistance of selected tree species from fire-prone tropical savanna in north Australia

We investigated the fire resistance conferred by bark of seven common tree species in north Australian tropical savannas. We estimated bark thermal conductance and examined the relative importance of bark thickness, density and moisture content for protecting the cambium from lethal fire temperatures. Eucalypt and non-eucalypt species were contrasted, including the fire-sensitive conifer Callitris intratropica. Cambial temperature responses to bark surface heating were measured using a modified wick-fire technique, which simulated a heat pulse comparable to surface fires of moderate intensity. Bark thickness was a better predictor of resistance to cambial injury from fires than either bark moisture or density, accounting for 68% of the deviance in maximum temperature of the cambium. The duration of heating required to kill the cambium of a tree (τc) was directly proportional to bark thickness squared. Although species did not differ significantly in their bark thermal conductance (k), the thinner barked eucalypts nevertheless achieved similar or only slightly lower levels of fire resistance than much thicker barked non-eucalypts. Bark thickness alone cannot account for the latter and we suggest that lower bark moisture content among the eucalypts also contributes to their apparent fire resistance. Unique eucalypt meristem anatomy and epicormic structures, combined with their bark traits, probably facilitate resprouting after fire and ensure the dominance of eucalypts in fire-prone savannas. This study emphasises the need to take into account both the thermal properties of bark and the mechanism of bud protection in characterising the resprouting ability of savanna trees.

Disturbance intensity and seasonality affect the resprouting ability of the neotropical dry-forest tree Acacia pennatula: do resources stored below-ground matter?

Abstract:Many plant species in tropical dry forests partly base their ability to persist after disturbance on resprouting. Yet little is known if this ability can be affected by the intensity and seasonality of disturbance and whether the amount of resources (starch, N, P) stored in the taproot may constrain this response. We investigated resprouting after experimental clipping or burning, applied before or after the dry season and repeatedly in Acacia pennatula individuals in wooded rangelands of North-West Nicaragua. Each treatment was applied to 12 trees and replicated in six plots. One year after the onset of the experiment, survival and biomass recovery were significantly lower in burned than in clipped individuals (78% ± 4% and 75.3 ± 8.0 g vs. 94% ± 2% and 79.1 ± 6.8 g; mean ± SE). Whatever the disturbance applied, trees disturbed after the dry season significantly showed the lowest survival, growth and concentration of N and P. These results suggest that resprouting in dry tropical species may be constrained by intense disturbances (e.g. burning) but especially if they occur towards the end of the dry season. This phenological constraint could be due to the reduced availability of N and P as this dry season progresses.

Regional and local effects on reproductive allocation in epicormic and lignotuberous populations of Banksia menziesii

Reproductive allocation (RA) is a measure of how resources (biomass, nutrients) are partitioned between reproductive structures and the rest of the plant. For plants that resprout after fire, the percentage of resources allocated to reproduction may vary depending on their resprouting ability. Our study examines the percentage RA (biomass, N, P, K) and nutrient content of current season’s growth in southern (Swan Coastal Plain) epicormic and northern (Eneabba Plain) lignotuberous resprouter populations of Banksia menziesii (Proteaceae), a species endemic to nutrient-impoverished sandplains of southwestern Australia. Within each population, plants along road edges were compared with plants not associated with road edges. There was no difference in total nutrient content of current year’s growth between both resprouting types, except that total K in the shoots of lignotuberous populations was >2 times that in the epicormic populations. Non-road lignotuberous plants allocated twice the biomass, N and P, and 13.5 times the K, to reproduction as non-road epicormic plants. Lignotuberous populations had the highest RA (17–34% of biomass, N, P, K), with non-road epicormic populations the lowest RA (3–15%). This can be viewed as an adaptive (ultimate) response to the poorer postfire survival and recruitment conditions where the lignotuberous populations occur. Total biomass and nutrient content of road-edge plants was 2–3 times that of non-edge plants. Lignotuberous populations in both road positions allocated the same fraction of biomass, N and P to reproduction, whereas road-edge populations allocated 10% less K than non-road. Road-edge epicormic populations allocated 5–10% more biomass, N, P and K to reproduction than non-road populations. This can be viewed as an ecophysiological (proximate) response to the better growing conditions created by the roadways that may also ultimately have an adaptive explanation.

Strong regeneration ability from rhizome fragments in two invasive clonal plants (Solidago canadensis and S. gigantea)

The two rhizomatous perennials Solidago canadensis and S. gigantea belong to the most widespread alien plants in Europe. Anecdotal observations suggest that they disperse also by rhizome fragments. For testing their resprouting ability, rhizome fragments of different sizes from both species were buried at four different soil depths (0, 5, 10 and 20 cm, respectively) in a common garden. Rhizome fragments of S. canadensis ranged 3–6 cm in length, those of S. gigantea 5–20 cm in length. Resprouting plants were harvested after 3 months and growth related traits measured to assess their vitality. Resprouting rate in S. gigantea was far higher than in S. canadensis (85 and 19%, respectively). In S. gigantea, fragments of all sizes resprouted from all soil depths whereas none rhizome of S. canadensis emerged from 20 cm burial depth. In S. gigantea, size related traits showed significant interactions between fragment size and burial depth, but not relative shoot growth rate. At all burial depths, vitality of plants emerging from small rhizomes was lower than plants emerging from large rhizomes. Effects of rhizome size became stronger with increasing burial depth. The results show that both species are able to resprout from buried rhizome fragments, and that succesful regeneration is more likely to occur in S. gigantea. Managing these species should avoid any activities promoting rhizome fragmentation and dispersal of fragments.

Resprouting Response of Aquatic Clonal Plants to Cutting May Explain Their Resistance to Spate Flooding

Resprouting ability may increase a plant’s resistance to recurrent disturbances in aquatic ecosystems. We investigated the effect of mechanical disturbances on survival and regrowth patterns in three clonal aquatic species of similar growth form but with different ecological ranges in terms of flooding (Myriophyllum verticillatum, Myriophyllum spicatum and Potamogeton coloratus). P. coloratus prefers to colonize stable habitats, whereas M. verticillatum occurs in intermediately flooded habitats and M. spicatum is tolerant to a high flooding frequency. Two cutting treatments (single cuts or repeated cuts) were applied under controlled conditions. We hypothesized that M. verticillatum and M. spicatum would be resistant to cutting displaying either a tolerant or an escape strategy whereas P. coloratus would be sensitive to cutting. Our hypothesis was validated, as the three species displayed contrasting responses to disturbance. M. verticillatum displayed efficient clonal propagation following breakage (escape strategy), but its growth rate decreased after recurrent disturbances. P. coloratus displayed a close response but was unable to compensate biomass loss even after one cut. M. spicatum maintained a similar growth rate by developing a densely branched form despite recurrent disturbances but with a low investment in clonal growth (tolerance strategy). Both biomass compensation and clonal propagation influence plant fitness, but their relative advantage differs depending on the flooding frequency experienced by plants in their natural habitats. Clonal propagation may promote recolonization after disturbances in infrequently flooded sites, but seems less efficient than a tolerance strategy for survival in frequently flooded sites.

Defoliation depletes the carbohydrate reserves of resprouting Acacia saplings in an African savanna

Over the past century there has been a global trend towards tree expansion and densification in rangelands and savannas. This phenomenon is commonly referred to as bush encroachment. In South Africa Acacia karroo is one of the key species responsible for bush encroachment. It has been suggested that the combination of fire and browsing might limit bush encroachment by A. karroo more effectively than either browsing or fire alone. We hypothesized that these repeated disturbances progressively deplete root carbohydrates and compromise resprouting ability. This was tested by burning and then manually defoliating A. karroo once a month for 1 year. Manual defoliation did not inhibit the rapid shoot elongation after topkill of A. karroo saplings. During this initial phase, the growth of the new shoots of A. karroo was dependent more on mobilised root reserves than on photoassimilates from the new shoots. Frequent manual defoliation of resprouting A. karroo saplings prevented the replenishment of starch reserves. We suggest a mechanism for how the interaction of browsing and fire can suppress and perhaps reverse bush encroachment in African savannas. Saplings that have reduced starch reserves at the end of dry season due to browsing will struggle to resprout if they are burnt. Even if they do not die, they will be less able to escape fire damage in the next fire than if they had been able to resprout unimpeded.

Resprouting as a persistence strategy of tropical forest trees: relations with carbohydrate storage and shade tolerance

Resprouting is an important persistence strategy for woody species and represents a dominant pathway of regeneration in many plant communities, with potentially large consequences for vegetation dynamics, community composition, and species coexistence. Most of our knowledge of resprouting strategies comes from fire-prone systems, but this cannot be readily applied to other systems where disturbances are less intense. In this study we evaluated sapling responses to stem snapping for 49 moist-forest species and 36 dry-forest species from two Bolivian tropical forests. To this end we compared in a field experiment the survival and height growth of clipped and control saplings for a two-year period, and related this to the shade tolerance, carbohydrate reserves, and the morphological traits (wood density, leaf size) of the species. Nearly all saplings resprouted readily after stem damage, although dry-forest species realized, on average, a better survival and growth after stem damage compared to moist-forest species. Shade-tolerant species were better at resprouting than light-demanding species in moist forest. This resprouting ability is an important prerequisite for successful regeneration in the shaded understory, where saplings frequently suffer damage from falling debris. Survival after stem damage was, surprisingly, only modestly related to stem reserves, and much more strongly related to wood density, possibly because a high wood density enables plants to resist fungi and pathogens and to reduce stem decay. Correlations between sampling performance and functional traits were similar for the two forest types, and for phylogenetically independent contrasts and for cross-species analyses. The consistency of these results suggests that tropical forest species face similar trade-offs in different sites and converge on similar sets of solutions. A high resprouting ability, as well as investments in stem defense and storage reserves, form part of a suite of co-evolved traits that underlies the growth-survival trade-off, and contributes to light gradient partitioning and species coexistence. These links with shade tolerance are important in the moist evergreen forest, which casts a deep, more persistent shade, but tend to diminish in dry deciduous forest where light is a less limiting resource.

Long-term control of the invasive tree Ailanthus altissima: Insights from Mediterranean protected forests

Ailanthus altissima is an invasive tree species which has colonized numerous ecosystems and affected ecosystem processes worldwide. Despite its importance as an invasive species and the high economic costs incurred from its spread, there is a lack of long-term management planning for its control. Although mechanical disturbance is commonly applied, the effect that this treatment may have exhausting its resprouting ability and also its joint effect with phytochemical treatments are poorly understood, especially in Mediterranean environments. We tested three treatments (plus a control) aimed to reduce A. altissima growth in Mediterranean forests throughout 5 years of study. The treatments (one cut stump, double cut stump and cut stump with glyphosate application) were repeated annually. General plant performance (biomass, height and resprout-type density) was measured yearly during the study. Water potential and stomatal conductance were also measured at the end of the study to evaluate particular ecophysiological factors which might affect the response of A. altissima to assayed treatments, together with leaf area index. Our results show that only the cut stump with glyphosate application treatment was able to reduce the long-term growth and spread of A. altissima. The treatments applied favoured collar sprout growth in response to disturbance events (treatments) opposite to the control, where new sprouts grew mainly from the root. Treated resprouts displayed ecophysiological changes depending on the assayed treatment. To our knowledge, this is the only study testing the long-term effect of both physical disturbance and phytochemical application on A. altissima growth. Our study further refines our knowledge on the effects of repeating both commonly and newly used treatments, improving our management techniques to reduce the presence and growth of this invasive tree.

Resprouting as a persistence strategy in dry and moist tropical forest trees: its relation with carbohydrate storage and shade tolerance

Resprouting is an important persistence strategy for woody species and represents a dominant pathway of regeneration in many plant communities, with potentially large consequences for vegetation dynamics, community composition, and species coexistence. Most of our knowledge of resprouting strategies comes from fire-prone systems, but this cannot be readily applied to other systems where disturbances are less intense. In this study we evaluated sapling responses to stem snapping for 49 moist-forest species and 36 dry-forest species from two Bolivian tropical forests. To this end we compared in a field experiment the survival and height growth of clipped and control saplings for a two-year period, and related this to the shade tolerance, carbohydrate reserves, and the morphological traits (wood density, leaf size) of the species. Nearly all saplings resprouted readily after stem damage, although dry-forest species realized, on average, a better survival and growth after stem damage compared to moist-forest species. Shade-tolerant species were better at resprouting than light-demanding species in moist forest. This resprouting ability is an important prerequisite for successful regeneration in the shaded understory, where saplings frequently suffer damage from falling debris. Survival after stem damage was, surprisingly, only modestly related to stem reserves, and much more strongly related to wood density, possibly because a high wood density enables plants to resist fungi and pathogens and to reduce stem decay. Correlations between sapling performance and functional traits were similar for the two forest types, and for phylogenetically independent contrasts and for cross-species analyses. The consistency of these results suggests that tropical forest species face similar trade-offs in different sites and converge on similar sets of solutions. A high resprouting ability, as well as investments in stem defense and storage reserves, form part of a suite of co-evolved traits that underlies the growth–survival trade-off, and contributes to light gradient partitioning and species coexistence. These links with shade tolerance are important in the moist evergreen forest, which casts a deep, more persistent shade, but tend to diminish in dry deciduous forest where light is a less limiting resource.