Root Suckers Research Articles

Genetic structuring and invasion status of the perennial Ambrosia psilostachya (Asteraceae) in Europe

The perennial western ragweed (Ambrosia psilostachya DC.) arrived from North America to Europe in the late nineteenth century and behaves invasive in its non-native range. Due to its efficient vegetative propagation via root suckers, A. psilostachya got naturalized in major parts of Europe forming extensive populations in Mediterranean coastal areas. The invasion history, the spreading process, the relationships among the populations as well as population structuring is not yet explored. This paper aims to give first insights into the population genetics of A. psilostachya in its non-native European range based on 60 sampled populations and 15 Simple Sequence Repeats (SSR). By AMOVA analysis we detected 10.4% of genetic variation occurring among (pre-defined) regions. These regions represent important harbors for trading goods from America to Europe that might have served as source for founder populations. Bayesian Clustering revealed that spatial distribution of genetic variation of populations is best explained by six groups, mainly corresponding to regions around important harbors. As northern populations show high degrees of clonality and lowest levels of within-population genetic diversity (mean Ho = 0.40 ± 0.09), they could preserve the initial genetic variation levels by long-lived clonal genets. In Mediterranean populations A. psilostachya expanded to millions of shoots. Some of those were obviously spread by sea current along the coast to new sites, where they initiated populations characterized by a lower genetic diversity. For the future, the invasion history in Europe might get clearer after consideration of North American source populations of western ragweed.

Genetic Diversity of Five Broadleaved Tree Species and Its Spatial Distribution in Self-Regenerating Stands

European forest ecosystems are currently subject to various disturbances and shifts in land-use legacies. To be able to forecast the trends and consequences of the changes in genetic diversity following these disturbances, it is of crucial importance to understand the genetic dynamics of natural tree populations. The present study aimed at determining the extent and spatial distribution of genetic diversity in five common broadleaved tree species in Lithuania in both mature (putatively maternal) stands and in natural regeneration (juveniles) of the respective species. The genetic diversity of Quercus robur, Betula pendula, Populus tremula, Alnus glutinosa, and Fraxinus excelsior was assessed using eight nuclear microsatellite loci for each species; 417 samples of regenerating juveniles and 141 samples of putatively maternal trees were analyzed in total. The investigated populations of self-regenerating Q. robur, B. pendula, A. glutinosa, and F. excelsior juveniles showed spatially random genetic structures, while P. tremula regenerated mostly via root suckers and formed clonal groups. The genetic diversity in regenerating juveniles of all species was as high as in putatively maternal stands. The detection of adequate (substantial) genetic diversity in the studied regenerating populations of these five broadleaved tree species suggests that in Lithuania these species have a good potential to adapt to changing environmental conditions.

Physiological response of adult Salix aurita in wetland vegetation affected by flooding with As-rich fine pyrite particles

An uncontrolled, natural episode of flooding with waters contaminated with As-rich pyrite (FeAsS) particles caused serious ecological damage leading to necrosis of plants growing in a fresh wet meadow located in an area characterized by unique geological structures rich in arsenopyrites. One of the few plant species capable of surviving this event was Salix aurita L., which grew in numbers in the analyzed area, but individual plants were affected differently by toxic flooding. No significant phenotypic changes (Group I), through partial leaf and/or stem necrosis (Group II) up to necrosis of the whole parental plant and root suckers (Group III), were observed for various willow clumps. These varied phenotypic responses of S. aurita to As-rich sediments were compared with the biochemical status of the foliage of willow trees, and with their rhizosphere physiological parameters.Our in situ study revealed that the biochemical status of leaves reflects the phenotypic damage incurred by adult willows growing in their natural environment and affected by the flooding. In leaves of willows with increasingly negative phenotypic changes (Groups I → II → III) as well as increasing levels of reactive oxygen species, malondialdehyde and decreased levels of glutathione and thiol groups were detected. Phytochelatins, commonly considered major As chelators, were not detected in S. aurita leaves. Despite a decrease in the size of leaves with the intensity of tree damage, all leaves expressed a normal level of leaf pigments.Phenotypic changes observed for particular willow clumps were only partly related to soil As levels. Moreover, As and S (but not Fe) foliar levels were related but did not correspond strictly with foliar biochemical features, or with soil As levels, soil pH or soil microbial activity, with the latter two drastically decreased in the rhizospheres of willows from Groups II and III.

Chrysanthemum: A Comprehensive Review on Recent Developments on In Vitro Regeneration.

Chrysanthemum is a flowering plant grown worldwide and is one of the most popular ornamental plants. Chrysanthemums are usually cultivated using root suckers and shoot cuttings. This conventional technique is relatively slow. In addition, as cuttings are gained regularly from mother plants, there is a chance of viral infection and degeneration, which raises the production cost. The hurdles mentioned above have been managed by applying in vitro propagation techniques, which can enhance reproduction rates through in vitro culture and use very small explants, which are impossible with the conventional approach. Usually, it is difficult to get true-to-type plants as the parents with good quality, but clonal propagation of a designated elite species makes it possible. Hence, this review highlights recent studies of the in vitro propagation of Chrysanthemum included; the appropriate explant sources, medium compositions, alternative disinfection of culture media, plant growth regulators (PGRs), different mutagenesis applications, acclimatization efficiency, and alternative light sources to overcome the shortcomings of conventional propagation techniques.

Cut–dip–budding delivery system enables genetic modifications in plants without tissue culture

Of the more than 370 000 species of higher plants in nature, fewer than 0.1% can be genetically modified due to limitations of the current gene delivery systems. Even for those that can be genetically modified, the modification involves a tedious and costly tissue culture process. Here, we describe an extremely simple cut-dip-budding (CDB) delivery system, which uses Agrobacterium rhizogene to inoculate explants, generating transformed roots that produce transformed buds due to root suckering. We have successfully used CDB to achieve the heritable transformation of plant species in multiple plant families, including two herbaceous plants (Taraxacum kok-saghyz and Coronilla varia), a tuberous root plant (sweet potato), and three woody plant species (Ailanthus altissima, Aralia elata, and Clerodendrum chinense). These plants have previously been difficult or impossible to transform, but the CDB method enabled efficient transformation or gene editing in them using a very simple explant dipping protocol, under non-sterile conditions and without the need for tissue culture. Our work suggests that large numbers of plants could be amenable to genetic modifications using the CDB method.

Differences in colonization strategies of three common pioneer woody species in post mining heaps.

Willow (Salix caprea), birch (Betula pendula) and aspen (Populus tremula) are common pioneer woody species, however little is known about colonization strategies in large-scale disturbances. Here we have compared the strategies of establishment of these pioneer woody species in unreclaimed sites on a large (1957ha) spoil heap in Czechia. For all species, seedlings numbers peaked in the 17 year old (successional age - time since overburden heaping) plot, suggesting that initial soil development promotes seedling establishment while covering of the surface by litter and organic layers reduces the establishment of pioneer species. The proportion of willow decreased from the edge of the heap and analysis of the age structure suggests that willow establishment was correlated with the presence of older willows in the vicinity of willows of certain ages (13 and 23 years being particularly important). The proportion of birch increased with its distance from the heap edge, and it is correlated with suitable weather conditions in the year of establishment, mainly July rainfall. Aspen proportion does not change significantly with its distance from the heap edge and year of establishment. It correlates with the number of trees in both surrounding and climatic conditions. Detailed analysis of young trees shows that vegetative propagation by root suckers (offspring) is rare in birch. In willow they represent about half of the trees while in aspen all of the young trees were root suckers derived from older aspen trees. This indicates a different colonization strategy of individual species. Birch is capable of long-distance seed transfer, which establishes most of the population, and its establishment is highly influenced by climatic conditions. Willow spreads massively over a short distance, and its establishment is highly influenced by the presence of 21-23 year old willow individuals in the vicinity. Only few scattered trees are able to establish at longer distances, where they can later spread locally by seeds. Aspen spreads over a long distance in low numbers but when some trees are established it spreads massively locally by clones.

Gene Flow and Recruitment Patterns among Disjunct Populations of Allocasuarina verticillata (Lam.) L.A.S. Johnson

Allocasuarina verticillata (Lam.) L.A.S. Johnson is a widespread species in south-eastern Australia providing vegetation cover, protecting fragile soils and providing food for birds. Understanding the effects of gene flow on the recruitment patterns, genetic differentiation and structure of fragmented populations provides fundamental guidelines to underpin plant conservation strategies and activities. In this study, four spatially disjunct populations of A. verticillata were sampled to explore the effects of population size, reproductive patterns and pollen and seed dispersal on among-population genetic diversity, genetic differentiation and structure, using field survey and microsatellite marker techniques. It was found that stands of A. verticillata were predominantly sexually reproductive, but asexual reproduction through root suckering was an additional mode of reproduction. The reproductive success of A. verticillata is positively correlated with the effective population size rather than actual population size. The reduction in effective population size and increment of spatial isolation resulted in lower genetic diversity and higher inbreeding coefficient of progenies. Moderate pairwise genetic differentiation and weak genetic structure were identified. The results suggest that exogenous, wind-mediated pollen flow provides some maintenance of genetic diversity in the isolated stands. Seed dispersal appears mainly to be over short distances (i.e., within populations), but the infrequent transport of seeds between disjunct locations cannot be ruled out as another factor that may help maintain genetic diversity.

Induction of somatic embryogenesis in Tecomella undulata (Sm.) Seem using a pistillate explant

Desert teak (Tecomella undulata (Sm.) Seem) a multipurpose ornamental tree native to the arid and semi-arid tropics has entered the endangered plant category mainly as a result of the species' ineffective seed reproduction system. The tree usually reproduces through a few root suckers in old stands. Conventional methods of plants multiplication could not offer a viable practice for its mass multiplication. Low adventitious rooting of the cuttings has been the principal cause of failure in its vegetative propagation. Hence, the present research was planned and conducted to evaluate the feasibility of somatic embryogenesis in this species, the pathway that bypasses the need for rooting stage by developing bipolar embryos. Ovary explant was cultured in modified Murashigue & Skoog (MS) medium supplemented with different auxins and cytokinins. The results showed α-naphthalene acetic acid (NAA) was superior in inducing embryogenic callus. NAA ranging 5.4-21.5 μM could induce the highest embryogenic calli which exhibited developing pro-embryogenic masses (PEM) and globular somatic embryos. The calli which were induced by the use of 2,4-dichlorophenoxyacetic acid (2,4-D) were poor in quality and showed no morphogenesis potency. Individual application of Thidiazuron (TDZ) and N6-benzyladenine (BA) induced good callogenesis at low concentrations but the calli were non-embryogenic with both. The proliferation of embryogenic calli was the best in a hormone-free medium. However, the media containing 40.5 and 54 μM NAA alone could induce somatic embryos along with callus proliferation. Low BA-contained medium (0.9-4.44 μM) led to recurrent somatic embryogenesis. Neither BA and GA3, nor the elevating sucrose concentration could cause further development and maturation of the somatic embryos induced during previous stages (callogenesis and callus proliferation). More research is required to optimize the maturation stage. The findings of the present study can be useful for future studies in the micropropagation of this recalcitrant specieslationships in Indian mustard under heat stress and the differential remobilization efficiencies in the advanced breeding lines.

Effect of soilless growing media compositions on quality flower production of potted Chrysanthemum (Chrysanthemum morifolium)

The suitability of soilless growing media compositions was evaluated for quality flower production of potted Chrysanthemum morifolium Ramat cultivar Anmol at Punjab Agricultural University, Ludhiana during 2014-16. The rotted cuttings were grown in six different potted media compositions – control: garden soil + (farmyard manure (FYM) 2: 1), cocopeat + FYM (1: 1), cocopeat + FYM (2: 1), vermiculite + FYM (1: 1), vermiculite + FYM (2: 1) and cocopeat + vermiculite + FYM (1: 1: 1). The results revealed that the cocopeat + FYM (2:1) exhibited maximum plant height, number of leaves and root suckers per plant whereas; vermiculite + FYM (2:1) gave highest flower diameter and duration of flowering. The days to bud appearance, colour break stage and full bloom were delayed in cocopeat based media. However, significant vegetative growth with better flowering time and quality was obtained in cocopeat + vermiculite t + FYM (1:1:1). Thus for sustained quality flower production of potted Chrysanthemum cv. Anmol, cocopeat + vermiculite + FYM (1:1:1) media was ideal with better plant morphological development.

Influence of weather conditions and weediness on barley (Hordeum vulgare) yield

Barley belongs to the leading grain crops. This is due to its good adaptive abilities to various climatic conditions, as well as its high nutritional and feed value. However, this crop, when developed in the field, is forced to compete with weeds, which inevitably leads to a decrease in yield. The relationship between clogging, weather and climatic conditions and crop yields has been observed. However, for the geographical region of Siberia, there are few similar works exploring this relationship. Therefore, study on the influence of weather conditions and weeds on the formation of the yield of spring barley in the southeast of Western Siberia is a prerequisite for the development of the protection of this crop from weeds. This research included the study of the species composition of weeds and hydrothermal characteristics and their influence on the formation of the yield of spring barley. The studies were carried out in the steppe zone of the Kuznetsk Basin and the Mariinsky forest-steppe of the West Siberian Plain of the Kemerovo Region (Russia) from 2014 to 2018. To characterize the dynamics of yield, sown areas and gross harvests of spring barley, data from statistical bulletins of the territorial body of the Federal State Statistics Service for the Kemerovo region were used. An increase in the yield of barley was observed. In 2018, compared to 2014, the difference was 0.19 t/ha and revealed a significant reduction in acreage and, due to this, a decrease in the gross yield of barley was noted. Thirtyfour species of weeds belonging to 16 families were recorded on the plot. The biological groups of weeds are represented by six types: ephemera, early spring, late spring, annual wintering, rhizome perennials, and root suckers. The yield of spring barley is greatly reduced by dicotyledonous biennial species of weeds from the Cabbage and Bluegrass families.

Gap dynamics and disease-causing invasive species drive the development of an old-growth forest over 250 years

Investigating the disturbance regimes of unharvested forests helps us understand their past, present, and future trajectory and gives us a model for forest management. It can also clarify the relative importance of small-scale gap dynamics versus more severe disturbances. Here we used tree rings to examine the recruitment patterns, growth dynamics, and disturbance chronologies of American beech (Fagus grandifolia), sugar maple (Acer saccharum), and eastern hemlock (Tsuga canadensis) in A.B. Williams Woods, an old-growth forest in Ohio, USA, over the past 250 years. We found that beech and sugar maple recruitment peaked around 1900 and continued through the 1900s, while hemlock recruitment peaked during 1825–1875, then declined and effectively ended in the early 1900s. Hemlock grew fastest during the 1800s according to ring width and basal area increment, while sugar maple ring width surpassed beech and hemlock in the 1900s. All three species showed a dramatic increase in growth from 1980 to 2010. Beech and sugar maple established regardless of canopy gaps, but 73% of hemlocks originated in gaps. In most decades, <10% of trees experienced gap recruitment or growth release, suggesting that ongoing, endogenous canopy mortality was the primary disturbance shaping this forest. However, a more severe forest-wide disturbance occurred during the 1980s–1990s when the scale insect causing beech bark disease was introduced, with greater than 30% of living trees showing growth releases in those decades. Another synchronous release occurred in the 1930s when blight-killed chestnuts were removed; 16% of trees showed releases. Both of these intermediate-severity disturbances involved human introduction of invasive species. Thus, we documented a natural disturbance regime of small-scale gap dynamics, punctuated by more severe anthropogenic disturbances in the twentieth century. These relatively frequent, intermediate-severity events probably mean that the forest’s current composition is non-equilibrial. Hemlock may continue to decline while beech maintains its dominance by constant regeneration in both gaps and shade, and by responding to disturbance with root suckering and growth pulses. The codominance of sugar maple may be relatively recent, and perhaps temporary, as we found little sugar maple recruitment before 1875 or after 1950, and three times fewer sugar maple saplings now than in the early 1900s. Despite being protected as a park, the development of this old-growth forest has been shaped more by disease-causing invasive species than natural disturbances over the past century. This result emphasizes the pervasiveness of human impacts even in communities we look to as examples of natural pattern and process.

Morphological characterization of certain Jasminum sambac genotypes using principal component analysis

Jasminum sambac is one of the most important traditional flower crops of India especially Tamil Nadu. Understanding the genetic variability among the different genotypes of Jasminum sambac helps in its exploitation in breeding programmes. A total of 34 genotypes comprising of traditional landraces collected from all over Tamil Nadu were evaluated for 40 qualitative traits according to the DUS descriptors specified for Jasminum sambac (Kannan M. et al., Plant Variety Journal, 2016). In order to reduce the dimensionality of the data, examine the variation and the relative contribution of the traits for the total variability, Principal Component Analysis (PCA) method was adopted. PCA test in 34 genotypes for all the 40 characters resulted in fifteen Principal Components (PCs) with an eigenvalue more than one accounted for 97.21 per cent of the total variability and revealed that the traits leaf margin undulation, flower bud shape, flower shape, shape of corolla lobe, flower petal tip, leaf blade undulations, flower bud length and root suckers exhibited maximum variation. Agglomerative Hierarchical Clustering and PCA results showed that the genotypes Acc. Js- 11, Acc. Js- 12, Acc. Js- 13, Acc. Js- 14, Acc. Js- 20, Acc. Js- 25, Acc. Js- 27 and Acc. Js- 32 were found to be the most diverse genotypes.

Root sucker technique for successful clonal multiplication of Melia dubia Cav. without sacrifice of mother tree

Root sucker technique for successful clonal multiplication of Melia dubia Cav. without sacrifice of mother tree

Disturbance impacts on the persistence niche of key species in the Baikiaea–Guibourtia–Pterocarpus woodlands of north-western Zimbabwe

The persistence niche (studied through different modes of regeneration) of three key species (Baikiaea plurijuga (Harms), Guibourtia coleosperma (Benth.) J. Leonard, and Pterocarpus angolensis) (DC) under five different disturbance regimes (eight years after cessation of disturbance) was studied in the Baikiaea–Guibourtia–Pterocarpus woodlands of north-western Zimbabwe. The disturbance regimes were: protected area (no disturbance); timber concession area (timber harvesting); pole and firewood harvesting sites; abandoned crop fields (after clearing for agriculture); and burnt sites (fire disturbance). Influence of stump diameter and height on regeneration factors was investigated. For each disturbance regime, six main plots (100 m × 100 m) each were systematically laid out (20 m apart) to assess regeneration. In each main plot, 10 m wide transects (5 m apart) were surveyed for seedlings and saplings of the target species (at least 100 plants of each species), resulting in 7 transects per main plot, 42 transects in each study site and 210 transects in total. Number of seedlings with or without a rootstock (i.e., just grown from seed) was recorded. Diameter of stumps was measured at the cut surface. Shoot height was measured from their origin. Each target species was associated with mode of regeneration (χ² = 27 642, p < 0.001). Most plants regenerated from root suckers. Regeneration mode is dependent on disturbance regime (B. plurijuga χ² = 225.66, p < 0.001; G. coleosperma χ² = 158.62, p < 0.001; and P. angolensis χ² = 144.01, p < 0.001). Stump diameter negatively influenced number of sprouts for B. plurijuga and P. angolensis, but positively influenced sprout height for all species. Stump height positively influenced sprout height for G. coleosperma and P. angolensis. The study therefore concludes that disturbances are necessary in facilitating sprouting and growth of suppressed shoots. Stump height and diameter influence the ability of stumps to regrow vegetatively through sprouting. Weak relationships between stump diameter/height and coppice density and shoot height suggest that there are other factors that affect vegetative regrowth through coppicing.

A simplified method for application of natural regeneration in black locust (Robinia pseudoacacia L.) stands in Hungary

Black locust (Robinia pseudoacacia L.) is one of the most important forest tree species in Hungary, covering approximately 24% of the forest land and providing 25% of the annual timber supply. One third of these black locust stands are high forests (planted with seedlings) and the remaining stands are coppices. An auxiliary table was developed for planning the black locust natural regeneration in order to determine the sprouting criteria based on stand volume at the final cutting age. Twenty forest subcompartments were selected for investigating the possibility of black locust regeneration by root suckers. The basic yield and stand structure factors were determined using the numerical yield table for black locust stands. The results show that the regeneration of black locust stands from root suckers can be recommended on good and medium quality sites without a decrease in yield or stem quality. Black locust stands of good and medium quality (yield classes I, II, III and IV) may be regenerated from suckers in general until their growing stock attains and if their health is adequate. The simplicity of the practice-oriented auxiliary table based on the black locust yield table may further the development of management and wood utilization of the species.

76-year decline and recovery of aspen mediated by contrasting fire regimes: Long-unburned, infrequent and frequent mixed-severity wildfire.

Quaking aspen (Populus tremuloides) is a valued, minor component on northeastern California landscapes. It provides a wide range of ecosystem services and has been in decline throughout the region for the last century. This decline may be explained partially by the lack of fire on the landscape due to heavier fire suppression, as aspen benefit from fire that eliminates conifer competition and stimulates reproduction through root suckering. However, there is little known about how aspen stand area changes in response to overlapping fire. Our study area in northeastern California on the Lassen, Modoc and Plumas National Forests has experienced recent large mixed-severity wildfires where aspen was present, providing an opportunity to study the re-introduction of fire. We observed two time periods; a 52-year absence of fire from 1941 to 1993 preceding a 24-year period of wildfire activity from 1993 to 2017. We utilized aerial photos and satellite imagery to delineate aspen stands and assess conifer cover percent. We chose aspen stands in areas where wildfires overlapped (twice-burned), where only a single wildfire burned, and areas that did not burn within the recent 24-year period. We observed these same stands within the first period of fire exclusion for comparison (i.e., 1941–1993). In the absence of fire, all aspen stand areas declined and all stands experienced increases in conifer composition. After wildfire, stands that burned experienced a release from conifer competition and increased in stand area. Stands that burned twice or at high severity experienced a larger removal of conifer competition than stands that burned once at low severity, promoting expansion of aspen stand area. Stands with less edge:area ratio also expanded in area more with fire present. Across both time periods, stand movement, where aspen stand footprints were mostly in new areas compared to footprints of previous years, was highest in smaller stands. In the fire exclusion period, smaller stands exhibited greater loss of area and changes in location (movement) than in the return of fire period, highlighting their vulnerability to loss via succession to conifers in the absence of disturbances that provide adequate growing space for aspen over time.

Population structure of Rosa spinosissima L. on the Frisian Islands and introgression from cultivated material

Rosa spinosissima L. is part of the highly dynamic coastal habitat of the Wadden Sea, between the coast of northwestern continental Europe and the Frisian Islands. Plants of this species grow clonally via root suckers to form large patches, which stabilize dunes and help to protect the islands and used for this purpose locally on the island Sylt. Rosa spinosissima plants are affected by both water and wind in their harsh environment, and are threatened by human impact via habitat destruction and introduction of foreign species. In these northern parts of its range R. spinosissima is categorized as endangered.The population structure of R. spinosissima was investigated using ten microsatellite loci and 195 individuals of Frisian Island populations and European coastal continental samples. DAPC, Kmeans and Structure analyses were conducted to study the genetic composition and integrity of these natural populations relative to cultivated and nursery material mostly consisting of central continental genotypes.The DAPC and Structure analyses differentiated populations of the Frisian Islands between each other and separated them from nursery samples, but some natural populations showing an impact of nursery and cultivated genotypes. In addition, some clonal patches of R. spinosissima were detected. Our results show that the natural Frisian Island populations of R. spinosissima are threatened by the introduction of nonadaptive genotypes into the gene pool.

Tree height is more important than bark thickness, leaf habit or habitat preference to survive fire in the cerrado of south-east Brazil

Although cerrado trees have evolved with fire for millions of years, it is not well-understood which tree attributes are more important to survive fire in the Brazilian savanna. To address this issue, we used pre- and post-fire data on 367 cerrado trees (113 native species) planted in an arboretum in south-east Brazil and then left unburnt until 2019, when a prescribed burn was applied. Tree size (height and diameter) had been measured in 2017. Four months after the fire, we assessed tree size, relative bark thickness (bark-to-diameter ratio), leaf habit (evergreen or deciduous) and habitat preference (savanna specialist or generalist). These were the predictor variables used in generalised linear models exploring tree survival and resprouting type. Most trees survived fire: 59% resprouted epicormically, 25% resprouted basally, 6% had root suckers, and only four trees died. Basal and epicormic resprouting were related to tree size: small trees (diameter ≤ 5 cm) resprouted basally more frequently, whereas tall trees (height ≥ 3.7 m) resprouted epicormically more frequently. Our results suggest that rapid growth is more important than bark thickness, leaf habit or habitat preference to escape the fire trap, because it allows cerrado trees to reach a fire-resistant height more quickly.

Extensive clonal propagation and resprouting drive the regeneration of a Brazilian dry forest

AbstractWoody plant resprouting has received considerable attention in the last two decades as human disturbances continue to encroach on terrestrial ecosystems globally. We examined the regeneration mechanisms of a Caatinga dry forest in the context of slash-and-burn agriculture and resprouting ability of the local flora. We excavated two old fields (from 32) experiencing early forest regeneration dominated by the tree Pityrocarpa moniliformis (Fabaceae) to map clonal propagation and, in parallel, submitted 260 seedlings from 13 woody plant species to experimental clipping. What seemed to be ‘seedlings’ popping up around P. moniliformis stumps and remaining adults actually were condensed sets of root suckers connected via complex networks of long, ramified shallow horizontal roots without taproots. We mapped respectively 39 and 783 connected root suckers, which summed 96 m and 910 m in root length. Regarding the seedlings, 33% resprouted across nine species with resprouting rates varying between 5–100%. Seedling height before clipping positively influenced resprouting vigour. Our preliminary results suggest that the Caatinga dry forest supports a relatively high proportion of resprouting species, some of them able to clonally propagate and playing an ecosystem-level role by responding to early forest regeneration and high abundance/biomass across both regenerating and old-growth forests.

Resprouting drives successional pathways and the resilience of Caatinga dry forest in human-modified landscapes

Tropical forest regeneration has gained renewed interest in recent years as secondary forests have being considered biodiversity repositories and a key source for globally relevant ecosystem services as climate regulation and carbon sequestration and storage. Here, we address the regeneration of a Caatinga dry forest in the context of slash-and-burn agriculture and chronic anthropogenic disturbance by examining forest regeneration mechanisms and a comprehensive set of community-level plant diversity measures (i.e., taxonomic, functional, and phylogenetic) in regenerating (4 to 70-yr old) and old-growth forest stands. Resprouting from root suckers was the predominant regeneration mechanism across recently abandoned crop fields. Overall, regenerating forests were similar to old-growth forests in terms of taxonomic and functional composition, and functional and phylogenetic diversity. Moreover, except for the taxonomic diversity, community-level plant diversity measures were not related to forest age or soil properties. Our results suggest that Caatinga dry forest covering sandy soils is particularly resilient due to regeneration driven by resprouting. The same set of plant species dominates the entire regeneration process, including old-growth forest stands. Accordingly, Caatinga dry forest regeneration may follow an initial composition model, rather than following a directional and deterministic trajectory associated with species replacements. This initial composition model probably results from a combination of three factors: (1) early regeneration driven by resprouting rather than seed arrival and seedling recruitment; (2) biomass accumulation mostly due to growth by early colonizers and by those species able to resprout after chronic anthropogenic disturbance and during forest regeneration; and (3) the co-occurrence of functionally distinct plant species. Accordingly, resprouting can guarantee some level of resilience, and hence, the services provided by secondary forests. Nevertheless, forest dynamics in landscapes inhabited by forest-dependent people are affected to a great extent by the nature of the imposed pressures and the ecological profile of the remaining flora.