Native Seedlings Research Articles

Monitoring the rewilding of the Brazilian Atlantic Forest on tree and mammal diversity: From a biodiversity hotspot to a biodiversity hopespot

The implementation of rewilding initiatives is crucial for biodiversity recovery, particularly in biodiversity hotspots such as the Brazilian Atlantic Forest. Long-term monitoring of rewilding initiatives is critical for assessing progress and informing management choices. This study assesses the efficiency of different reforestation practices for biodiversity recovery, including passive restoration, active reforestation with different native seedlings, and plantations of exotic species. We applied an ecosystem approach to estimate the tree and mammal diversity, collected through forest plots and camera traps. We selected differently managed areas and included the oldest forest patches as reference points for the assessment of biodiversity; a naturally disturbed montane forest in the area was included as a control category for the disturbance analysis. Moreover, we investigated the influence of ecological variables, such as biodiversity, aboveground biomass, and altitude, on rewilding processes. Our results suggest that Eucalyptus plantations, a simplified ecosystem made up of monocultures of exotic species, support lower biodiversity. On the contrary, active reforestation with different native species resulted in an ecological status comparable to naturally regrown secondary forests. We show that active reforestation can reduce the time required for rewilding. We also found a positive correlation between tree and mammal species richness. These results underscore the importance and potential of responsible restoration efforts in recovering local biodiversity, contributing to the vision of a future where the Brazilian Atlantic Forest can be acknowledged not only as a biodiversity hotspot but also as a “hopespot.”

Assessent of tree diversity in the vegetation of ramna areas of dhaka city for better management

The present article deals with the evaluation of the existing tree species diversity in the Ramna areas of Dhaka city. Both random and stratified random quadrat sampling were used for the data collection from July 2021 to June 2022. The study identified a total of 156 tree species in 46 families. Among the sampling areas, 115 tree species were found in Ramna Park, 61 tree species in Suhrawardy Udyan, and 98 tree species in the Dhaka University area. The sampling areas overlapped significantly with many tree species. Among the species, 33% of the species were of ornamental value, followed by timber (24%), medicinal (21%), fruit (19%), and wildlife-supporting (3%). 51% of the species belonged to exotics and 49% were native. The most abundant species were Swietenia mahagoni in Ramna Park and Dhaka University and Eucalyptus camaldulensis in Suhrawardy Udyan. Based on the important value index, the most dominant species were S mahagoni in Ramna Park and Dhaka University and Ficus elastica in Suhrawardy Udyan. Among the top 15 most abundant and dominant trees, nine belonged to exotics, and the rest were native. The Shannon diversity index value ranged from 3.83 to 4.39. Ramna Park showed the highest index value (4.39), followed by Dhaka University (3.91) and Suhrawardy Udyan (3.83). Stakeholder’s consultations revealed that on average 90% of the support was found for management strategies such as native enrichment, reducing exotic dominance, planting purposeful trees, heritage plantations, and expert consultation during plantation. Identified threats included construction works, exotic presence, lack of native seedlings, and low awareness. Recommendations include promoting the dominance of native species, gradual exotic replacement, enhancing wildlife-supporting species, increasing public awareness, and integrating expert opinions into urban plantation programs. Bangladesh J. Bot. 53(3): 605-617, 2024 (September)

1116. Rhododendron boninense Nakai

SummaryRhododendron boninense Nakai, illustrated here, is a critically endangered endemic rhododendron from the Ogasawara Islands, whose population was once reduced to a single individual. Since the 1980s, Koishikawa Botanical Garden has made efforts to propagate and reintroduce this species to its original habitat, resulting in a current population of 60 mature plants and several natural seedlings. The pure white corolla, which lacks a nectar guide, is distinctive among related rhododendrons, suggesting that a pollinator shift occurred after colonisation of the Ogasawara Islands, where the ancestral pollinators are absent.

Exploring variability for morphological and quality traits in natural seedling origin mango germplasm of South Gujarat

Exploring variability for morphological and quality traits in natural seedling origin mango germplasm of South Gujarat

Light quality and spatial variability influences on seedling regeneration in Hawaiian lowland wet forests

Abstract Tropical forest understories tend to be light‐limited. The red‐to‐far‐red ratio (R:FR) is a useful and reliable index of light quality and its spatial variability can influence competition between native and non‐native seedlings. While per cent light transmittance has been quantified in some Hawaiian lowland wet forests (HLWF), no information exists on how the spatial distribution of understorey light varies in relation to species invasion, or if patterns of seedling regeneration and light are linked. We measured the R:FR of light in the understorey to assess light quality in three HLWF forest types: native‐dominated, partially invaded and Psidium cattleyanum‐ (strawberry guava) dominated to quantify light quality in the understorey (0–50 cm height). We also identified relationships between light quality and native and non‐native seedling presence, diversity and abundance. Together, these data can help to determine the restoration potential of HLWF. Linear mixed‐effect modelling showed that native‐dominated forests had significantly greater R:FR than P. cattleyanum‐dominated forests, demonstrating a transformation in the light environment with increased invasion. Heterogeneity in R:FR varied more across sites than among forest types. In both native‐dominated and partially invaded forests, there were more native seedlings in the low‐quality R:FR (0.0–0.40) category and fewer in the medium‐ (0.41–0.70), and high‐quality (≥0.71) light categories than would be expected by chance, and there were no native seedlings in the P. cattleyanum‐dominated forests. Native‐dominated forests had greater species richness and abundance of native seedlings than the partially invaded forests, likely due to propagule availability. However, the spatial clustering of seedlings, the mismatch of native seedlings in light environments less suitable, and a considerable proportion of open high‐quality microsites, highlights that conditions are not optimal for native species in HLWF in the long term. Synthesis and applications. The native‐dominated and partially invaded forests still hold conservation value, despite variation among sites. Seedling additions could be targeted to different R:FR environments and at different spatial scales, but the lack of a strong relationship between R:FR and seedling number suggests that other factors besides light quality should be considered in seedling enrichment or other management activities.

Changes in decomposition dynamics, soil community function and the growth of native seedlings under the leaf litter of two invasive plants

Changes in decomposition dynamics, soil community function and the growth of native seedlings under the leaf litter of two invasive plants

Shrub encroachment of coastal ecosystems depends on dune elevation

Woody plant encroachment is influenced by interactions between the physical environment and vegetation, which create heterogenous microenvironments some of which favor shrub recruitment through mitigation of the abiotic environment. Encroachment of native shrub, Morella cerifera into grasslands on Hog Island, Virginia has been attributed to warmer winter temperature; however, recruitment of seedlings in grasslands may be impacted by multiple factors at the level of the microhabitat. Our study focuses on a critical gap in understanding factors specifically influencing M. cerifera seedling recruitment and survival. By experimentally planting M. cerifera seedlings at varying dune elevations and grass densities, we tested hypotheses that dune elevation influences the microclimate, soil characteristics and vegetation cover and that grass cover/density is related to shrub establishment. We tested these hypotheses through gathering data from temperature data loggers, conducting soil water content and chloride analyses, and determining percent cover of grasses relative to dune elevation. Results indicate that dune elevation was positively related to moderated temperatures with reduced temperature extremes and vegetation cover/composition that led to favorable locations for M. cerifera establishment and growth. Where dune elevation is > 2 m, we document an upper limit of grass cover on natural seedling establishment, suggesting a switch from facilitative to competitive effects with grass density. Overall, our work demonstrates interactions between dune elevation and medium grass density has a facilitative influence on M. cerifera establishment and can be used for future predictions of shrub growth with rising sea-levels.

Impact of salvage logging on short-term natural regeneration in montane forests of the Alps after large windthrow events

Wind disturbances are one of the main drivers of forest dynamics in Europe, shaping forest stands and modifying the ecosystem services provisioning. Salvage logging is often most common strategy adopted after a high-severity disturbance in managed stands. Understanding natural regeneration dynamics including their interaction with the logging operations, is crucial to understand how forests will be changing under a climate with increasing variability and to design adequate adaptive post-disturbance management strategies. In this study, we focused on 148 stands damaged by storm Vaia (2018). The aim was to analyze natural regeneration dynamics under different logging systems and to investigate influences of site characteristics and disturbance legacies on sapling growth and seedling emergence. The sampling protocol consisted of one transect per stand, perpendicular to one of the intact forest edges, and with a length of 80 m. Along the transect, we collected soil cover, natural seedling and sapling stem density, and deadwood quantity in four sample plots of 3 m radius each at distances of 0, 20, 40, and 80 meters from the edge (592 plots in total). Regeneration species composition was mainly driven by previous stand composition, with some exceptions depending on seed dispersal strategy. Distance from the edge significantly influenced seedlings and saplings occurrence in large gaps and affected the browsing damage percentage, together with deadwood presence. According to GLM’s models, distance from the edge, elevation, and logging methods influenced seedling establishment. At the same time, species characteristics, edge structure, deadwood and logging damages significantly influenced pre-storm seedlings and saplings presence and health. In conclusion site factors, disturbance legacies, and logging strategies are key points to consider in post-disturbance management for a fast forest recovery.

Influence of plant growth-promoting bacteria on leaf carbon and nitrogen metabolism of two drought-stressed neotropical tree species: a metabolomic approach.

Deforestation of Atlantic Forest has caused prolonged drought events in the last decades. The need for reforestation is growing, and the development of native seedlings that are more tolerant to drought stress is necessary. A biotechnological tool that improves plant tolerance is the use of plant growth-promoting bacteria (PGPB) as inoculants. Two species of PGPB were inoculated in drought-stressed seedlings of two neotropical tree species that have been used in environmental restoration programs: Cecropia pachystachya and Cariniana estrellensis. Biometrical, physiological, and metabolomic parameters from carbon and nitrogen pathways were evaluated. We found that the PGPB positively influenced photosynthesis and growth parameters in both trees under drought. The enzymes activities, the tricarboxylic acid cycle intermediates, the amino acids, and protein contents were also influenced by the PGPB treatments. The results allowed us to find the specific composition of secondary metabolites of each plant species. This study provides evidence that there is not a single mechanism involved in drought tolerance and that the inoculation with PGPB promotes a broad-spectrum tolerance response in Neotropical trees. The inoculation with PGPB appears as an important strategy to improve drought tolerance in Atlantic Forest native trees and enhance environmental restoration programs' success. MAIN CONCLUSION: The association with plant growth-promoting bacteria improved the tolerance to drought in Neotropical trees through biochemical, physiological, and biometrical parameters. This can enhance the success of forest restoration programs.

Disentangling the roles of bracken fronds and litter on natural seedling recruitment in fire-disturbed tropical montane habitats

Tropical montane forests are diverse ecosystems often affected by uncontrolled human-induced fires causing tree mortality and creating large deforested areas. After fires, Pteridium spp. ferns (bracken) often dominate, and forest regeneration in these areas is slow. In this study, we evaluated the effects of bracken fronds and litter, as well as the micro-environmental conditions created by the fern, on the density and species diversity of naturally recruiting seedlings. At eight sites, 120 experimental plots were established among forest and bracken-dominated areas with the following treatments: (a) fronds and litter intact (F+L+); (b) fronds intact and litter removed (F+L-); (c) fronds removed and litter intact (F-L+); and (d) fronds and litter removed (F-L-). After one year, all seedlings were registered, identified and classified according to their life-form (tree, shrub, herb, vine), dispersal vector (wind- or animal-dispersed) and successional status (early-, mid-, and late-successional). For all treatments we assessed 12 micro-environmental variables. We identified 3649 naturally-recruiting seedlings corresponding to 278 species from 70 families. We found positive effects of bracken fronds particularly on tree seedling recruitment: treatments with fronds had greater densities of both animal- and wind-dispersed tree seedlings, 1.8 and 1.4 fold higher, respectively, compared to treatments without fronds. Similarly, the density of early-, mid- and late-successional tree species was 1.3, 1.7 and 1.9 times higher in treatments with than without fronds. Furthermore, species diversity of early-, mid- and late-successional tree species was higher in the treatments with fronds. The environmental conditions generated by bracken presence, such as photosynthetically active radiation, soil temperature, live bracken biomass and litter depth, had positive effects on seedling density of all, animal-dispersed and early-successional tree species, and negative effects on seedling recruitment of other life-forms, notably from early successional stages. To promote forest regeneration in bracken-dominated areas, active restoration measures such as direct seed addition and transplants of nursery-raised seedlings of mid- and late-successional species should be considered. Since bracken can hinder the establishment of some life forms and species but favor others, it is recommended to include a trait-based approach to understand species responses to environmental factors and select species that are optimally adapted to bracken-dominated habitat conditions to promote forest regeneration.

In-situ verification of a deep-learning-based larval identification system for the Pacific oyster Magallana gigas

Natural seedlings are collected for use at Pacific oyster (Magallana gigas) aquaculture sites in Japan. For seedling collection to be successful, aquaculture farmers identify target larvae through microscopic observation, using morphological features such as the shell height/shell length ratio, lateral asymmetry of the shell, and umbo development. To reduce the time and labor associated with larval identification, we developed a deep-learning-based Pacific oyster larvae identification system, which consisted of a tablet connecting a new photographic device to capture images for identification. The final accuracies of the trained identification system for the learning datasets for measuring accuracy were 82.5% and 80.5% for precision (P) and recall (R), respectively, for all sizes of larvae (shell height ≥100 µm). We verified our identification system at an oyster aquaculture site. The obtained accuracy in the verification was low for some samples (63.6%–100.0% and 41.9%–100.0% for P and R, respectively, for pre-attachment stage larvae), indicating a decrease in identification accuracy for the in-situ samples. The decrease likely occurred owing to the natural variability of larvae. We modified the learning dataset with high variation in oyster larval images and retrained the identification system. The accuracy of the retrained identification system was increased to 83.9%–100.0% for P and R and thus satisfied the requirements for practical application for pre-attachment stage larvae. For small-sized larvae, P was improved but R was relatively low, indicating that although the detection level of our identification model for oyster larvae is low, the accuracy of the detected oyster larvae is high.

Early development of Acacia longifolia is more severely impacted by water and nutrient stress in invasive than native seedlings

Acacia longifolia (Andrews) Willd. is a legume native to southeast mainland Australia and Tasmania and has two described subspecies: A. l. subsp. longifolia and A. l. subsp. sophorae. The species has been introduced around the world and is considered invasive in several Mediterranean-type climate regions, including in South America, South Africa, and southern Europe. Previous studies comparing native and invasive populations of A. longifolia have focused on its reproductive ecology and population genetics, and little information exists on the species’ early life development and how abiotic factors influence it. Here, we performed a glasshouse experiment to compare the phenotypic responses of native and invasive (in Portugal) A. longifolia seedlings to different levels of water and nutrient availability. We found that seedlings of both subspecies responded similarly to different water and nutrient availability conditions in terms of biomass accumulation, root length, the number of phyllodes produced, phyllode water content, and root-to-shoot ratio. However, compared to native seedlings, invasive seedlings had limited capacity for stress responses. We found that invasive seedlings had lower drought tolerance than native seedlings, and thus the speed of invasion by A. longifolia into drier parts of Portugal may be hindered. Our results also hint of a possible role of seed “imprinting” in this species’ early growth responses, resulting in different resource allocation strategies such as favouring early growth and development over drought resistance in the invaded range. Further studies are required to better understand the species’ abiotic stress responses at the intraspecific level and their relation to its invasiveness.

Post-fire reference densities for giant sequoia seedlings in a new era of high-severity wildfires

Many forests globally are experiencing increases in large, high-severity wildfires, often with increasingly inadequate post-fire tree regeneration. To identify areas that might need post-fire planting, forest managers have a growing need for seedling reference densities – the natural seedling densities expected to be adequate to regenerate a forest – to compare with observed post-fire seedling densities. The most useful reference densities will meet five criteria: they will (1) be specific to natural post-fire reproduction rather than planted seedlings (because planted seedlings can have substantially greater survival than natural seedlings, thus underestimating adequate natural reproduction), (2) apply to the first few years following fire (when management decisions and actions are most likely), (3) be specific to each of those post-fire years (because post-fire seedling densities can change rapidly with time since fire), (4) be associated with estimates of uncertainty, and (5) include consideration of novel environmental conditions during management applications (because most reference densities will be based on data collected under more environmentally benign conditions). The world’s most massive tree species, the giant sequoia (Sequoiadendron giganteum) of California’s Sierra Nevada, recently experienced historically unprecedented wildfires that killed an estimated 13–19% of mature sequoias across their native range. Seedlings germinating after these fires then experienced exceptional summer heat and the two most severe summer droughts of the 121-year historical record. To help inform management responses to these events, we used seedling censuses from past fires (mostly prescribed fires) to calculate sequoia seedling reference densities meeting the five criteria. The reference densities had three striking features, which are partly attributable to giant sequoia’s status as a pioneer species. First, despite being inherently conservative, the reference densities were quite high. For example, mean first-year reference density was 172,599 seedlings ha−1. Second, reference densities declined precipitously with time since fire: the mean fifth-year reference density was only 5% of the mean first-year density. Third, the reference densities were associated with relatively substantial uncertainty, a consequence of density variations among seedling plots; for example, the 95% credible interval for first-year reference density was 64,377 to 313,438 seedlings ha−1. Despite this uncertainty, a case-study sequoia grove that recently burned in a high-severity wildfire had second-year post-fire seedling densities that were significantly (and dramatically) lower than the corresponding second-year reference density, suggesting inadequate post-fire reproduction. Our results highlight the value of the five criteria for reference densities – criteria that, in current practice, are rarely all met.

Impact of Invasive Ageratina adenophora on Soil Fungi in Native Plant-Grown Soils in Nepal

Invasion of alien plants impacts both the above- and below-ground communities. The specific response of soil microbes to alien plants may depend upon the presence of native inhabitants and the origin of the byproducts released from different parts of invasive plants. This study evaluated the response of common soil fungi against Ageratina adenophora byproducts (extracts) in the presence of two native shrubs, Elsholtzia blanda and Osbeckia stellata, in Nepal. A total of eight fungal species were isolated from soils where these two native species were grown separately, and the occurrence of the fungi was evaluated. The occurrence and frequency of fungus species varied with extracts of A. adenophora leaves, litter and roots as well as with the presence of specific native plants. Particularly, A. adenophora further inhibits the fungi that are naturally less frequent in soil, like Hormodendrum sp. and fresh leaves and litter of A. adenophora were responsible for inhibiting antagonistic fungi like Trichoderma harzianum. Influence in below-ground fungal communities by A. adenophora is one of the reasons for poor growth and development of native seedlings and the mechanism could be a strategy of invasion of A. adenohora in novel areas.

Exploring the potential of topsoil pellets to improve native seedling establishment on degraded agricultural land

Background and aimsAgricultural activities can degrade soils and promote weeds, posing challenges to native species restoration. In agricultural restoration, removing contaminated topsoil is a method designed to reduce elevated soil nutrients caused by fertilisation. This strategy targets weed control by eliminating both aboveground weeds and their soil seed bank before direct seeding. However, it also diminishes native soil seed banks and beneficial soil microbes. We investigated the potential of fresh topsoil pellets containing seeds to improve seedling performance in a degraded grassy woodland where topsoil had been removed.MethodsWe tested various pellet recipes, including one using commercial ingredients and three with different topsoil proportions (30%, 50%, and 70%). The study was conducted in a degraded grassy woodland in southeastern Australia, where topsoil was removed for restoration. We explored the effect of these pellet varieties on seedling emergence and growth of six native species common in this community, as well as microbial activity in the soil surrounding the seedlings.ResultsPellets significantly improved the emergence of Chrysocephalum apiculatum, providing evidence of their effectiveness. However, pellets significantly reduced Arthropodium milleflorum and Glycine tabacina emergence. Linum marginale and Rytidosperma caespitosum emergence remained unaffected by pellets. One species, Bothriochloa macra, had insufficient emergence for analysis. The microbial activity of the soil surrounding Rytidosperma caespitosum seedlings was significantly improved by pellets, with no significant effects observed for other species.ConclusionOur results demonstrate that topsoil pellets improved the emergence of one native species, but reduced emergence for two others, indicating species-specific responses to pelleting.

Effects of Non-Native Annual Plant Removal on Native Species in Mediterranean-Climate Shrub Communities

Removal of non-native plants is known to increase overall native cover within degraded communities that contain at least a small percentage of native plant cover. We investigated the mechanisms behind this pattern, asking whether removal of non-native annual species increases the density and species richness of the native community through increased seedling recruitment or through the growth of established native shrubs. We also investigated whether the effectiveness of non-native removal was influenced by region (coastal versus inland) and whether there was a threshold of native cover required for invasive removal to be effective. We established 13 study sites (7 coastal and 6 inland) located throughout the Nature Reserve of Orange County, CA, USA. Each degraded site contained four paired plots corresponding to a range of existing native plant cover: low 20–29%, medium-low 30–39%, medium-high 40–49%, and high cover 50–59% with one plot per pair subjected to non-native removal. We collected plant density, species richness, and established native shrub volume measurements to clarify the effectiveness of non-native removal. Non-native plant removal reduced non-native annual recruitment, increased that of native shrub seedlings, but had no impact on native forb recruitment. Non-native removal increased the number and reduced mortality of established native shrubs but did not influence shrub size. Native seedling density, species richness, and established native shrub number were highest inland, but coastal sites had larger adult shrubs. We found that non-native removal was most effective for increasing native density and species richness for degraded inland sites with less than 40% of existing native cover. The initial native cover did not affect established shrub volume or number. Our results confirm the importance of non-native plant removal in areas with medium-low or low native cover to increase native recruitment, species richness, adult shrub number, and to reduce established shrub mortality, especially during extreme drought.

Hydrosedimentological monitoring in runoff plots of a degraded tropical area under restoration of the Brazilian Atlantic Forest

Rainfall erosion is a concerning process for landowners, government agencies and civil society as it involves soil loss, an indispensable natural resource for the production of food, fibers, and biofuels, as well as a means to support enterprises or even preservation of large conservation areas for sustainability and potential carbon sink. Specific Projects using runoff and soil loss plots have been adopted in different parts of the world, contributing to the understanding of erosion dynamics. This research is the result of extensive fieldwork carried out on a rural property undergoing forest restoration through a Payment for Environmental Service initiative. Four runoff plots with dimensions of 22m x 4m x 0.5m (length x width x depth) connected to sediment catchment tanks were implemented on a convex slope to analyze erosion in four different treatments: planting native seedlings, seedlings with green manure, natural regeneration with selective pruning, and exposed soil. The results of monitoring over approximately one year showed that 80.15% of all accumulated surface runoff occurred in the plot with exposed soil, as well as 99.15% of all soil loss. The treatment that presented the best conservation rates was natural regeneration, since there was no need to dig holes to introduce seedlings, causing less soil disturbance. Thus, it was concluded that land use and changes in land use are one of the main factors controlling erosion and surface runoff in the study area, however, in the long term, variations in soil properties due to vegetation may reflect more strongly this dynamic.

Factores que influyen en la regeneración de plántulas de Argania spinosa y Tetraclinis articulata en el valle inferior del Wadi Tamri (Marruecos)

The forest landscape of the lower valley of Wadi Tamri is a geographical space composed of interaction and perpetual dynamics elements. The degradation observed in the past results from often inadequate silvopastoral practices. Nevertheless, a light of hope for the future of this forest currently lies in the existence of the natural regeneration of the Argan and Thuya trees, the effect of the agricultural abandonment on the slopes following the rural exodus, the development of the forestry capital by the State and the impact of good management practices of natural resources adopted by the local population itself. To examine the dynamics of the forester landscape, we have prospected dozens of plots in the Argan and Thuya zones. In this sample, we counted the natural seedlings, conducted floristic surveys, and briefly described various ecological and geomorphological variables. Then, we developed a statistical database to spatialize and quantify this phenomenon with cartographic tools (GIS). The analysis of these dynamics highlighted the factors of installing young seedlings with all the necessary explanations. The results have clearly shown that the most significant families in this landscape include the Asteraceae and Fabaceae (13%), with the Lamiaceae (10%) following closely. Additionally, the Euphorbiaceae, Solanaceae, Cistaceae, and Anacardiaceae contribute the same percentage (5%). The remaining 18 families each constitute only 3%. Regeneration of young Argan and Thuya trees from seedlings displays varied morphologies, influenced by age and grazing effects, often accompanied by nursery plants. Rocks and blocks serve as significant shelters for seedling germination. Meanwhile, topographic analysis highlights the impact of differing slope gradients for this seedlings. Argan and Thuya seedlings both presents the highest percentage (40% and 50%) observed on mid-slopes and upper slopes. Notable presence of seedlings observed on various slope exposures, especially those facing West, North, North-West, and South-West. Field sampling reveals a correlation between natural regeneration and tree cover density, emphasizing the significance of medium-dense tree cover, even in humanized landscapes, with notable regeneration observed in abandoned terraces and formerly cultivated land in Thuya unit, showcasing ecosystem resilience in this region. Overall, this study offers a preliminary scientific foundation for further investigation into the natural regeneration of Argan and Thuya amidst ongoing climate change, while also serving as a cornerstone for decision-making in conserving these forest heritages.

Environmental drivers of Euphorbia resinifera seed germination and seedling establishment for conservation purpose.

Euphorbia resinifera O. Berg is a prickly, leafless and succulent, Moroccan endemic shrub. Field data indicate that the plant faces many challenges related to its natural regeneration and its gradual decline that can lead to a probability of extinction, at least in some areas. Successful seed germination and survival of E. resinifera seedlings during the dry period is one of the main obstacles encountered in establishing natural seedlings. With this in mind, 3080 seeds of two morphotypes of E. resinifera (M1 and M2) were harvested in the Atlas of Beni Mellal to study their germinative potential and determine suitable conditions for growth and development of the seedlings. In the laboratory, five temperatures (10 °, 15 °C, 18 °C, 25 °C, and 35 °C) and two photoperiods (12 h light/12 h dark and 24 h dark) were tested. Whereas in field research, two factors were considered: the availability of water and the type of substrate (clay, peat, and limestone). Results show a maximum germination rate of around 52% for M2 at 15 °C and 48% for M1 at 18 °C. The Monitoring of plant seedling establishment and growth revealed a high vulnerability to prolonged periods of drought. However, consolidated soil is more conducive to seedling establishment. For this species, it is therefore essential to conserve the habitat within the karst geosystem. Furthermore, the variability of this species' morphotypes and their growth form architecture shows a tendency to favor the dwarf, cushion-shaped morphotype, which is the most widespread in the study area.

Status of forest remnants invaded by tradescantia (Tradescantia fluminensis Vell.) following introduction of biocontrol beetles and manual clearance after three years

ABSTRACT We compared biocontrol beetles and manual clearing of tradescantia in forest remnants invaded by tradescantia (Tradescantia fluminensis Vell.) on the agriculturally modified Hikurangi floodplain, northern New Zealand, to inform best practice in enhancing native biodiversity. Four forest remnant study sites were used: two on dairy farms and two protected in a reserve. We assessed tradescantia biomass and cover as indicators of biocontrol effectiveness in the short term, and composition and seedling establishment for effectiveness in the longer term. We found the biocontrol treatment (a combination of tradescantia beetles Neolema ogloblini, Neolema abbreviata, and Lema basicostata) was slow in reducing tradescantia biomass and had little effect in promoting regeneration of native forest species after 3 years. Beetle feeding damage was significantly higher at the biocontrol sites; however, tradescantia biomass or cover was not significantly lower. Although tradescantia biomass in the biocontrol treatment was decreasing, several more years would probably be required for beetle populations to increase and reduce biomass sufficiently to facilitate survival of native seedlings. Results between sites were variable, although dairy farm sites had overall higher nutrient status with higher total potassium levels, and lower nitrogen/phosphorus ratios, and generally higher tradescantia biomass. Manual clearing (‘handclear’) of tradescantia increased vascular species richness but was much more labour intensive and required ongoing management of resprouts. Handclear plots also had lower soil water content than control (means = 36% dry weight, 49% dry weight, respectively), a wider range of daily temperatures, and high species losses (as well as gains). Species losses were probably exacerbated by the greater environmental extremes caused by removal of the tradescantia living mulch, and the incomplete recovery of ground cover vegetation and microclimate suitable for seedling regeneration. Biodiversity benefits are likely to accrue slowly following the introduction of biocontrol agents; longer-term, these should prove more cost-effective than handclear.