Native Woody Species Research Articles

Collapse of dispersal trait diversity across a long‐term chronosequence reveals a strong negative impact of frugivore extinctions on forest resilience

Abstract Understanding how seed dispersal disruption may alter plant community diversity and dynamics over a large temporal scale remains a challenge. Here, we use a long‐term chronosequence to compare changes in the richness and composition of different dispersal trait assemblages in communities established before and after human colonization in the Mascarene archipelago. Our study was located on Réunion on the slopes of the Piton de la Fournaise which is one of the most active volcanoes worldwide. We analysed 151 vegetation surveys on lava flows dated between 1401 AD and 1956 AD and in tropical rainforests established on older substrata. We defined five classes of substratum age, according to the well‐known chronology of native frugivore defaunation: ‘old substrata’ and [1401, 1665[ when frugivores were abundant and diverse before permanent human settlement; [1665, 1800[ when large‐bodied frugivore populations were strongly reduced; [1800, 1900[ when large‐bodied frugivores went extinct and small‐bodied frugivores were still abundant; [1900, 1956] decline in the populations of small‐bodied frugivores. Based on dispersal traits, we categorized 146 native woody species as anemochorous, small fleshy‐fruited or large fleshy‐fruited, i.e. plant of which fruit could not theoretically be dispersed by extant frugivores. Changes in dispersal trait diversity strongly correlated with the chronology of defaunation. Species‐rich communities settled before human colonization was strongly dominated by fleshy‐fruited species. Large fleshy‐fruited plants in the oldest communities settled after human colonization declined markedly and almost disappeared after 1800. The richness of small fleshy‐fruited plants decreased less rapidly across the chronosequence, with medium levels on [1665, 1800[ and [1800, 1900[ lava flows and low levels on [1900, 1956] lava flows. Conversely, the richness of anemochorous plants remained unchanged. Communities settled before human colonization had a similar composition. Fleshy‐fruited assemblages showed strong species loss across the chronosequence, while anemochorous assemblages showed strong species turnover, which was probably due to lower dispersal limitation. Synthesis. Our results provide the first insights into the tremendous impact that frugivore extinction has on plant colonization dynamics over 300 years. The dramatic loss of fleshy‐fruited plant diversity on historical lava flows highlights the irreplaceable dispersal role played by frugivores, especially large‐bodied species. The conservation of plant–animal mutualistic interactions is invaluable and refaunation efforts need to be undertaken in areas where frugivores have been extirpated.

EMERGENCE AND EARLY SEEDLING GROWTH OF DILODENDRON BIPINNATUM RADLK IN DIFFERENT SUBSTRATES

Dilodendron bipinnatum Radlk is a Brazilian native woody species, widely used in landscaping and restoration of degraded lands. Due to the lack of native plant material in commercial nurseries, and very little information is available on the propagation of this study species, we investigated the effect of substrates and identified which is most suitable upon the emergence and early seedlings growth of this study species. The experiment was carried out in a greenhouse and the substrates used were: sand, Tropstrato®, chicken manure + red soil (1:1), black soil + red soil (1:1). After 30 days-period, the emergence percentage, emergence speed index, mean emergence time, root and shoot length, and root and shoot dry mass were performed. The most suitable substrates for seedling emergence percentage and emergence speed index were the sand, Tropstrato®, and black soil + red soil substrates. The substrates that added greater dry mass for root and shoot were the black soil + red soil, followed by the Tropstrato®. In conclusion, the Tropstrato® and black soil+ red soil provided the best results for early seedling growth of D. bipinnatum . In addition, black soil + red soil substrate can be produced at the nursery, as its components are easily accessible in nature, and for D. bipinnatum seedlings, it provides similar results as those obtained using the Tropstrato® substrate, with less costs.

Richness of Cerrado Woody Species Engaged in Ecological Restoration in the Brazilian Federal District

Abstract This study has evaluated the richness of Cerrado woody species engaged in ecological restoration in the Brazilian Federal District (BFD). A survey gathered information on plant species traded by local nurseries, species recommended in restoration plans (PRADs), species effectively introduced in areas under restoration, and species present in preserved fragments of Cerrado. Results summed 566 Cerrado woody species from 80 botanical families of which 171 species were traded by local nurseries, 277 were recommended in PRADs, 190 were effectively used in restoration projects, and 434 species were sampled in fragments of native Cerrado. We found low similarity between species composition available in nurseries, recommended in PRADs, used in restoration projects and present in preserved fragments of native Cerrado. Such results indicate a poor connection between steps related to the selection of native woody species that make up initial plant communities on sites under ecological restoration.

Different resource-use strategies of invasive and native woody species from a seasonally dry tropical forest under drought stress and recovery

Exotic plants in semiarid region have developed strategies for efficient use or capture of resources. They have become invasive and outperform native species. To understand which factors could explain the success of invasive woody species in a semiarid region, several physiological traits were analyzed in young plants of two invasive and two native species exposed to different water availability. Invasive plants showed low leaf construction cost, high phosphorus and nitrogen contents, reduced loss of instantaneous energy use efficiency, and smaller specific leaf area when compared to native species. This strategy led to a higher biomass gain and a high root/shoot ratio in both water treatments. After rehydration, invasive plants showed faster recovery and higher rates of CO2 assimilation. This resilience is fundamental for species in semiarid regions, and also increase uptake of nutrients. Maintaining a high photosynthetic rate, whenever there is water availability is a strategy that increases the performance of the species in relation to biomass gain. The low leaf construction cost and the fast recovery of the photosynthetic metabolism of invasive plants after limiting water resources explains the success of these species, and suggests that their potential may increase under prolonged and severe drought seasons.

Comparison of water-use patterns for non-native and native woody species in a semiarid sandy region of Northeast China based on stable isotopes

In the semiarid sandy region of Northeast China, non-native woody species such as Pinus sylvestris var. mongolica L. and Populus x xiaozhuanica W.Y. Hsu & Liang frequently suffer dieback during years of extreme drought events due to water deficiency. In contrast, dieback does not usually occur in native woody species, e.g., Pinus tabuliformis Carr., Ulmus pumila L., and shrub Caragana microphylla Lam. However, the mechanism of water-use patterns between the non-native and native woody species remain unclear, which limits our understanding of the mechanisms underlying dieback of non-native woody species. During two consecutive growing seasons in 2014 and 2015, sources of water uptake by two non-native (P. mongolica and P. xiaozhuanica) and three native (P. tabuliformis, U. pumila and C. microphylla) woody species were determined using the stable isotopes of δ2H and δ18O in the twig xylem water, soil water at various depths (0–200 cm), groundwater (water from capillary fringe or beneath the water table) and precipitation, coupled with soil moisture and groundwater level measurements. Results showed that both P. mongolica and P. tabuliformis trees used the 0–100 cm soil water in the spring and the 0–40 cm and 0–100 cm soil water in summer of 2014 and autumn of 2015, respectively, when soil moisture was high. In contrast, in summer of 2015 and autumn of 2014, when soil moisture was low, P. mongolica trees used both the 0–100 cm soil water and groundwater, whereas P. tabuliformis trees used the 0–200 cm soil water and both the 40–200 cm soil water and relatively limited groundwater, respectively. The P. xiaozhuanica trees used the 40–200 cm or the 100–200 cm soil water and groundwater, whereas U. pumila trees mainly used the 0–100 cm or 0–200 cm soil water, except in autumn when soil moisture was high. P. xiaozhuanica trees used the 0–200 cm soil water, while U. pumila trees used the 0–40 cm soil water. The shrub C. microphylla mainly used the 0–200 cm soil water during the measurement period irrespective of soil moisture conditions. Compared with the native woody species, which mainly used soil water, the non-native tree species relied on groundwater besides soil water, especially under low soil moisture conditions. Therefore, a sharp decline in groundwater level during extreme drought years might have a strong negative impact on the growth and survival of non-native woody species.

Exotic eucalypts: From demonized trees to allies of tropical forest restoration?

Abstract International forest landscape restoration commitments have promoted the restoration of millions of hectares of degraded and deforested lands globally, but few forest restoration approaches provide both ecologically‐sound and financially‐viable solutions for achieving the spatial scale proposed. One potential revenue source for restoration is selective harvesting of timber, a product for which there is a clear global market and increasing demand. The use of commercially valuable exotic trees may attract farmers to restoration, but can be a major concern for ecologists. Here, we present results collected over 7 years from experimental studies at three sites across the Brazilian Atlantic Forest to assess the impacts of incorporating exotic eucalypts as a transitional stage in tropical forest restoration on above‐ground biomass accumulation, native woody species regeneration and financial viability. Biomass accumulation was nine times greater in mixed eucalypt‐native species plantations than native only plantings due to fast eucalypt growth. Nonetheless, the growth of native non‐pioneer trees was not affected or only slightly reduced by eucalypts prior to logging. Eucalypts did not negatively affect the natural regeneration of native woody species before or after eucalypt logging. Canopy cover regrew quickly but was slightly lower a year following logging in mixed eucalypt‐native species plantations. Natural regeneration richness and planted non‐pioneer growth were similar across treatments in the post‐logging period. We found higher variation of biomass accumulation and native species regeneration among sites than between plantation types within sites. The income from eucalypt wood production offset 44%–75% of restoration implementation costs. Synthesis and applications. Many of the negative effects attributed to eucalypts on the growth and natural regeneration of native trees depend on features of the production system, landscape structure, soil, and climate in which they are grown, rather than the effects of eucalypts per se. In Brazil's Atlantic Forest region, exotic eucalypts can become important allies of tropical forest restoration, and their use and investment opportunities should be considered within the portfolio of options supported by public and private funding and policies.

Forest and woodland expansion into forestry plantations informs screening for native agroforestry species, Maputaland South Africa

ABSTRACTExpansion of natural forest or woodland in forestry plantations can potentially provide insight about the behaviour of plant communities in human-modified ecosystems. Here, we investigate the expansion of native woody vegetation into abandoned areas within timber plantations, whereby management decisions (and consequently different conditions of land abandonment) had led to variation in vegetation composition and structure. These differences were assessed to identify native species suitable for agroforestry systems within forestry plantations. Elements of sub-tropical dry forest (the reference forest) had expanded into (i) clear-felled and then abandoned plantations, and (ii) unharvested abandoned plantations. Two-way indicator species analysis, Non-metric multidimensional scaling, and Indicator species analysis were used to describe compositional intergradation between natural forest and secondary vegetation, and to assess correlation with environmental variables of fire and stand structure. Areas of vegetation expansion contained 53 native woody species from 26 families, about half the number sampled in the reference forest. The understory composition of unharvested plantation sites closely resembled regrowth forest, whereas clear-felled plantations had developed a species composition resembling woodland, comprising savanna species. Substantial intergradation among compositions of woodland, plantations and regrowth forest implied that regrowth forest was a likely propagule source for native species, but that past plantation management practices acted as an environmental filter resulting in slightly different vegetation types. Useful woody species Sclerocarya birrea, Vangueria infausta, Trichilia emetica, Strychnos spinosa, Annona senegalensis, and Hyphaene coriaceae were considered ecologically suitable for testing in silvo-pasture agroforestry systems owing to their occurrence in disturbed, open-canopy, fire-exposed environments (see also the graphical abstract in the supplemental files).

Contrasting responses of soil nematode communities to native and non-native woody plant expansion.

Woody plant expansion into grasslands is widespread, driven by both successions to dominance by native woody species or invasion by non-native woody species. These shifts from grass- to woody-dominated systems also have profound effects on both above- and belowground communities and ecosystem processes. Woody-plant expansion should also alter the functional composition of the soil biota, including that of nematodes, which are major drivers of soil food-web structure and belowground processes, but such belowground impacts are poorly understood. We determined whether succession by a widespread native (Kunzea ericoides) and invasion by a non-native woody species (Pinus nigra) into tussock grasslands affect the composition of nematode functional guilds and the structure of nematode-based food webs. Although increasing dominance by woody species in both systems altered the functional guild composition of the nematode community, we found contrasting responses of nematode functional guilds to the different dominant plant species. Specifically, nematode communities reflected conditions of resource enrichment with increasing K. ericoides tree cover, whereas communities became structurally simplified and dominated by stress-tolerant nematode families with increasing P. nigra tree cover. Because nematodes regulate both bacterial- and fungal-dominated food webs in soils, these shifts could in turn alter multiple ecosystem processes belowground such as nutrient cycling. Incorporating species' functional traits into the assessment of habitat-change impacts on communities can greatly improve our understanding of species responses to environmental changes and their consequences in ecosystems.

The Effect of Ecophysiological Traits on Live Fuel Moisture Content

Live fuel moisture content (LFMC) is an important metric for fire danger ratings. However, there is limited understanding of the physiological control of LFMC or how it varies among co-occurring species. This is a problem for biodiverse yet fire-prone regions such as southern California. We monitored LFMC and water potential for 11 native woody species, and measured ecophysiological traits related to access to water, plant water status, water use regulation, and drought adaptation to answer: (1) What are the physiological mechanisms associated with changes in LFMC? and (2) How do seasonal patterns of LFMC differ among a variety of shrub species? We found that LFMC varied widely among species during the wet winter months, but converged during the dry summer months. Traits associated with LFMC patterns were those related to access to water, such as predawn and minimum seasonal water potentials (Ψ), and water use regulation, such as transpiration. The relationship between LFMC and Ψ displayed a distinct inflection point. For most species, this inflection point was also associated with the turgor loss point, an important drought-adaptation trait. Other systems will benefit from studies that incorporate physiological mechanisms into determining critical LFMC thresholds to expand the discipline of pyro-ecophysiology.

Arbuscular mycorrhizal fungi protect native woody species from novel weapons

Arbuscular mycorrhizal fungi (AMF) play important roles in plant community structure and ecosystem functioning. The allelopathic disruption of arbuscular mycorrhizal mutualism is a potentially powerful mechanism by which non-native species can negatively impact native plant diversity. However, there is limited understanding of this mechanism on woody species in forest ecosystems. In this study, we carried out a set of experiments to explore the allelopathy of Eucalyptus urophylla on mycorrhizal mutualists. First, we examined allelopathic effects on the mycorrhizal growth responses of woody species by collecting leachates from the understory of an E. urophylla plantation. Second, we examined if AMF could counteract the allelopathy of E. urophylla by treating the target species with and without aqueous extract of E. urophylla and AMF inoculum. We conducted a third in vitro experiment to characterize the effects of identified putative allelochemicals (IPAs) of E. urophylla on AMF spore germination, namely Glomus mosseae, Claroideoglomus etunicatum and mixed spores extracted from field soil. There was a positive correlation between the stimulatory effects of natural leachates of E. urophylla and the mycorrhizal growth responses of target woody species. AMF could counteract the negative impact of E. urophylla allelopathy at a relatively low concentration. The IPAs of E. urophylla had variable effects on germination of AMF spores, from stimulatory to inhibitory, depending on chemical types and AMF species. Moreover, the AMF G. mosseae was the least sensitive to allelopathic inhibition of E. urophylla IPAs. This study does not support the hypothesis that allelopathy degrades mycorrhizal symbioses. Our study first provides preliminary evidence for a positive correlation between allelopathy and mycorrhizal growth responses and suggests that higher mycorrhizal growth responses could better protect woody species from allelopathic inhibition in E. urophylla plantations.

Long-term decline of native tropical dry forest remnants in an invaded Hawaiian landscape

Tropical dry forests are among the most threatened vegetation types as a result of human activities, yet relatively few datasets exist that give insight into the long-term impacts of human activity in these diverse biomes, especially in insular systems. In this study we revisited remnant dry forest patches previously surveyed in 1950 and 1970 in the Mokulēʻia Forest Reserve on Oʻahu, Hawaiʻi to assess long-term native woody species’ persistence. Between June 2016 and May 2017 we resurveyed the seven original remnants and found that natives declined in basal area in every plot except one, and maintained basal area dominance over non-natives in only three of seven plots. There was a dramatic decline in the richness of native woody species in 2017 (10 species), when compared with observations in 1950 (27 species) and 1970 (32 species). Natives experienced substantial declines in densities, and the greatest reductions in basal area and species richness occurred in plots which previously had the highest native diversity. Only the most common native species were able to maintain their populations, and they are aging. At the same time, non-native woody species richness increased from 1950 (3 species) to 1970 (7 species) to 2017 (13 species). Non-native relative basal area also increased substantially from 1950 (9%) and 1970 (5%), to where it nearly equals native basal area currently (49%). These results indicate that despite there being no obvious change in disturbance levels since these areas were last surveyed, native Hawaiian dry forest remnants are being invaded by nearby non-natives, and will likely continue to decline if not supported by active management.

The effect of environment on the microbiome associated with the roots of a native woody plant under different climate types in China.

Few studies have investigated the effect of environment on the root-associated microbiome, especially for woody plants in their native environment. The roots and rhizosphere soils of a native woody species (Broussonetia papyrifera) sampled across four different climate types in China were used to elucidate the influence of environment on the root-associated microbiome. Our results showed that the B. papyrifera root-associated microbiome contained abundant Proteobacteria and Basidiomycota, especially Pseudomonas and Rhizobium. The root-associated microbiomes were found to be significantly different under different climate types except for the bacterial community in the rhizosphere, and the proportion of bacterial operational taxonomic units (OTUs) shared among different climate types was lower than that of fungi. More than 50% of the total variance between microbiomes could be explained by 15 environmental factors, six of which, especially soil concentration phosphate and nitrate, had a significant effect. This study provided a comprehensive understanding of the root-associated microbiome of B. papyrifera and further confirmed the effect of environment on the root-associated microbiome of B. papyrifera under different climate types, with some exceptions in the rhizobacterial community and fungal OTUs. Our findings advanced knowledge of the effect of environment through an exploration of environmental factors and found that the nitrogen and phosphorus content represented the key factors.

Environmental constraints to native woody species recruitment in invaded mountain woodlands of central Argentina

Nowadays forests, which were formerly considered resistant to invasion due to its shady understories, are been transformed to invaded landscapes. Thus, the aim of this study was to evaluate the regeneration of native woody species in Ligustrum lucidum invaded woodlands. In addition, we aim to identify the main environmental differences between the native and invaded woodlands and evaluate the effect of those conditions in the regeneration phase of dominant native woody species. Finally, we analyze how is the emergence and survival of the exotic species in relation to that exhibited by native species in both environmental situations. For this, we performed a seed addition experiment placing three native woody species (Celtis ehrenbergiana, Lithraea molleoides, Vachellia caven) and the dominant exotic (L. lucidum) in native and invaded woodlands of the Chaco mountains, central Argentina. Also, we performed a laboratory experiment simulating the differences in light recorded at the field (main abiotic difference between both woodland types). Our field experiment indicated that, if seeds are actively added, the percentage of seedlings emergence of native species could be similar in invaded and native woodlands. However, we observed a trend of lower seedling survival after winter within the exotic monospecific stands, which was significant only for the native species C. ehrenbergiana. We suggest that this constraint could be partly related to the shadier conditions imposed by L. lucidum, since this is the major environmental change within the invaded woodlands in comparison with native ones. Consistently, the experimental simulation showed that the increased in shade reduced the overall growth of seedlings. As was mostly observed in temperate biome, our study in a subtropical seasonally dry region indicates that invaded areas may not affect the emergence stage but limit the survival of seedlings. Among the native species, C. ehrenbergiana seems to be the most suitable species to start restoration, showing the highest performance throughout the year. Combined actions of seed addition and canopy opening might counteract the abiotic constraint and contribute to restoration success of this invaded landscape.

Emerging reservoir delta‐backwaters: biophysical dynamics and riparian biodiversity

AbstractDeltas and backwater‐affected bottomlands are forming along tributary and mainstem confluences in reservoirs worldwide. Emergence of prograding deltas, along with related upstream hydrogeomorphic changes to river bottomlands in the backwater fluctuation zones of reservoirs, signals the development of new and dynamic riparian and wetland habitats. This study was conducted along the regulated Missouri River, USA, to examine delta‐backwater formation and describe vegetation response to its development and dynamics. Our research focused specifically on the delta‐backwater forming at the confluence of the White River tributary and Lake Francis Case reservoir. Objectives of the research were to: (1) describe and analyze the process of delta‐backwater formation over space and time; (2) determine by field sampling and GIS mapping how vegetation has responded to development of the delta‐backwater; and (3) compare the woody plant communities of the delta‐backwater to those along free‐flowing and regulated remnant river reaches. In response to base level changes caused by reservoir filling, the thalweg of the lower 31 km of the original White River channel and adjacent floodplain aggraded by up to 12 m between 1954 and 2011. The overall channel slope flattened from 0.70 to 0.29 m/km. Riparian Populus–Salix forests increased in area by nearly 50% during the post‐dam period by colonizing new deltaic and floodplain deposits. Many of the native woody species found along natural and regulated river reaches were also found on the delta‐backwater. Woody species sorted along a fluvial to delta gradient; wetland affiliated species (Salix spp., Typha spp.) dominated the delta‐backwater near the reservoir while riparian species (Populus, Fraxinus) dominated in upstream portions of the delta‐backwater. This habitat complex supports young stands of native riparian vegetation now in decline in remnant reaches protected from flooding.

White-tailed deer browse preference for an invasive shrub, Amur honeysuckle (Lonicera maackii), depends on woody species composition

AbstractSelective browsing by abundant, generalist herbivores on preferred species could allow less-preferred invasive species to flourish. We tested such an effect by examining rates at which white-tailed deer (Odocoileus virginianus Zimmermann) consume Amur honeysuckle [Lonicera maackii (Rupr.) Herder], an invasive shrub, relative to native woody species across eight forested sites in southwestern Ohio. We tested three hypotheses: (1) deer prefer to browse on L. maackii versus other woody plants; (2) L. maackii is not a preferred source of browse, but is consumed where preferred foods are scarce; and (3) L. maackii provides an important food resource for deer in early spring when other foods are scarce. We used counts of browsed and unbrowsed twigs of each species to calculate, for each site, both the proportion of each species’ twigs browsed and the degree to which deer selectively favor each species (“electivity”) during early to mid-growing season. Across the eight sites, electivity of L. maackii correlated with the proportion of its twigs browsed, and both measures were negatively associated with the density of L. maackii twigs. Lonicera maackii electivity was negative at most sites, indicating it is generally not preferred, undermining hypothesis 1. The hypothesis that deer consume L. maackii when more-preferred foods are depleted was not supported, as there was no negative relationship between L. maackii browse and the density of twigs of more-preferred species. We found a negative relationship between the proportion of L. maackii twigs browsed and the density of L. maackii among sites, which supports the third hypothesis. This finding, combined with seasonal patterns of deer browse on L. maackii, indicates that this invasive shrub is an important source of browse for deer during early spring, regardless of its abundance.

Biological invasion threatens the sandy-savanna Mussununga ecosystem in the Brazilian Atlantic Forest

The sandy-savanna Mussununga is a little-known ecosystem that is already presenting signs of degradation due to effects of invasive species, anthropogenic disturbances, and land-use change. We investigated the effect of biological invasion by Acacia mangium and A. auriculiformis, disturbance promoted by fire and Eucalyptus management, as well as land-use change around Mussununga patches in this neglected ecosystem. Acacia occurrence is negatively related to abundance, basal area, and height of native woody species, and positively correlated with the proportion of dead woody plants. There is a trend of change in vegetation type from open savanna to woodland Mussununga promoted by Acacia. Mussununga patches disturbed by the planting of Eucalyptus species in the past have greater richness in the woody layer (large shrubs and trees), but lower abundance of species in the ground layer (small shrubs and herbs). The land-use change from forest to Eucalyptus plantation was associated with an increase of richness and abundance in the ground layer. Acacia tends to dominate the woody community in Mussununga by invading treeless patches, presenting a correlation with death of woody plants. Subsequently, Acacia promotes several changes that culminate in a height increment and change of the vegetation type. Different from Acacia, disturbance and land-use change associated with Eucalyptus, the main economic activity in the study area, affected both woody and ground layers. The conservation of Mussununga should include actions to preclude disturbance and land-use change, as well as monitoring and control of biological invasion.

Intensive silviculture enhances biomass accumulation and tree diversity recovery in tropical forest restoration.

Maximizing initial aboveground woody biomass (AGB) accumulation in order to obtain early payments for carbon stocking is essential for the financial viability of reforestation programs fostered by climate mitigation efforts. Intensive silviculture, i.e., silviculture traditionally used in commercial forestry to maximize productivity and gains, has recently been advocated as a promising approach to enhance AGB accumulation in restoration plantations. However, this approach may hamper natural forest regeneration and ecological succession due to high competition between colonizing plants and planted trees. We investigated the impacts of different silvicultural treatments applied to restoration plantations with 20 native tree species on AGB accumulation and spontaneous regeneration of native woody species in an experiment set up in the Atlantic Forest of Brazil. Intensive silviculture demonstrated a remarkable potential to enhance AGB accumulation in restoration plantations by increasing up to three times the AGB of tree stands (from ~25 to 75Mg/ha in the 12th year). Intensive fertilization/weed control enhanced AGB accumulation, while higher tree density and the proportion of pioneers did not have a significant effect on AGB over the time. In spite of higher costs (cost increase of 13-19%), the cost-effectiveness for AGB accumulation of intensive silviculture was comparable to that of traditional silviculture applied to restoration (US$50-100/Mg AGB for 3×2m spacing). Contrary to our expectations, we did not find a trade-off between AGB accumulation by planted trees and the spontaneous regeneration of tree species, since intensive silviculture enhanced the regeneration of both planted (total of 12 species) and colonizing woody species (total of 30 species) in the plantation understory. Specifically, a strong association was found between AGB stocks and the abundance and richness of colonizing species, a vast majority of which (90% of species and 95% of individuals) were dispersed by animals. We report a case of positive correlation between AGB stocking and woody species regeneration in the restoration of the Atlantic Forest. Fostering the establishment and maintenance of restoration tree plantations can, in some cases, be a win-win strategy for climate mitigation and biodiversity conservation in human-modified tropical landscapes.

Regeneración de Sebastiania commersoniana (Euphorbiaceae) en relación al ganado y la distancia al bosque en las sierras del centro de Argentina

Entender los requerimientos de regeneración de especies leñosas es importante para guiar prácticas de conservación y restauración de los bosques. Evaluamos el nicho de regeneración de Sebastiania commersoniana en relación a la vegetación, suelo y luminosidad comparando micrositios con y sin renoval en dos potreros con densidad de ganado alta y baja y a tres distancias del borde de los parches de bosque dominados por la especie: -2 m (dentro del bosque), 1 m y 3 m (fuera del bosque). También evaluamos la densidad de renovales y la proporción de tallos ramoneados. Los renovales se encontraron en micrositios con abundante vegetación herbácea y suelo poco compactado. La densidad de renovales fue un 134 % mayor con baja densidad de ganado que con alta fuera del bosque, sin diferencias dentro, y disminuyó marcadamente al aumentar la distancia al borde. La proporción de tallos ramoneados fue 13 veces mayor ante alta densidad de ganado que ante baja. Concluimos que el establecimiento puede verse favorecido en micrositios con vegetación y suelo conservados; que el reclutamiento de renovales puede encontrarse limitado a las cercanías de los parches de bosque, y que la reducción en densidad de ganado puede favorecer la regeneración de la especie.

Why are woody plants fleshy‐fruited at low elevations? Evidence from a high‐elevation oceanic island

AbstractQuestionThe composition of fruit types, fleshy vs dry fruits, greatly influences the functioning of plant communities. Literature documenting spatial patterns of fruit types at fine scale is abundant. However, studies at larger geographical scale remain scarce, especially on high‐elevation oceanic islands that provide a great environmental heterogeneity. Here, we investigated how abiotic factors explained the proportion of fleshy‐fruited species (pFF) on Réunion. We asked (a) which abiotic factors were most related to pFF, (b) if fleshy‐fruited canopy species were more sensitive than fleshy‐fruited shrubs to harsh climatic conditions and (c) what are the relationships between pFF, endemism and phylogenetic relatedness.LocationRéunion (3,070 m a.s.l), Mascarene archipelago, South‐West Indian Ocean.MethodsWe used a dataset of 429 vegetation plots and assigned fruit types, growth forms and geographical distribution to 213 native woody species. Phylogenetic trees were constructed for each plot. We used GLMs to measure the relationship between pFF and abiotic factors, controlling for spatial autocorrelation. We then assessed the relationship between pFF, the standardized net relatedness index and the proportion of endemic species.ResultsThe top model explained 78% of the variation in pFF. Elevation was by far the best predictor, with pFF decreasing from 81% at 50 m a.s.l to 0% at 3,000 m a.s.l. At low elevations, pFF was higher on the wet windward (81%) than on the leeward (70%) where phylogenetic clustering was evident. Almost half (48%) of woody plants was fleshy‐fruited trees at low elevations. The proportion of fleshy‐fruited trees declined sharply with elevation and was significantly related to precipitation of the driest month contrary to the proportion of fleshy‐fruited shrubs that showed a hump shaped pattern along elevational gradient and no correlation with precipitation of the driest month. At high elevations, most plant assemblages were phylogenetically clustered and strongly dominated by single‐island endemic dry‐fruited plants.ConclusionsThe striking relationship between pFF and elevation, the shift among fleshy‐fruited growth forms along climatic gradients and the phylogenetic clustering of assemblages subjected to harsh climatic conditions, suggested that climatic factors were the main drivers of the distribution of fruit types on Réunion. To explain the absence of fleshy‐fruited species at high elevations, we hypothesized that native fleshy‐fruited lineages lacked the evolutionary potential to adapt and fleshy‐fruited cold‐adapted lineages had major difficulties reaching Réunion.

Effects of different herbivores on an actinorhizal species in Northwest Patagonia

Above-ground herbivory has a direct impact on plant life cycles, particularly at more sensitive stages, due to reduction of vegetative biomass. However, this effect may not be negative if it results in net biomass compensation. As sapling stage could be the best stage for native species to be outplanted, understanding the impact of aboveground herbivory on tree saplings is necessary for restoration purposes. We studied the effect of herbivory on saplings of Ochetophila trinervis (Rhamnaceae), a native woody species from North-west Patagonia, which forms an actinorhizal symbiosis with the N2-fixing actinobacteria Frankia. This tree species has the potential to be used for recovering degraded lands. Nevertheless, there is a perplexing contradiction between the high seed output of O. trinervis and the scarcity of saplings in the field. For 4 months, 1-year-old O. trinervis saplings were exposed to aboveground herbivory by generating different protection degrees (unprotected, protected against some kind of walking herbivores—protected saplings; and protected against all kind of walking herbivores—excluded saplings). The impact of herbivores over sapling survival was minimal (92 ± 3%, mean ± SE) and it was similar among saplings exposed to different protection degrees. The highest frequency of foliar damage in excluded saplings suggests the attack of flying herbivores. The increased emergence of new sprouts and root length growth in saplings highly damaged by herbivores (about three fold and two fold higher than in excluded saplings, respectively), evidenced the capacity of O. trinervis to develop a compensatory growth. The results contradict the assumption that herbivory explains the low density of saplings despite high seed production. Given the high-sapling survival and biomass compensation of O. trinervis after herbivory, we suggest that this species might be appropriate for restoration of degraded areas in the region.