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Aims Understanding the role of invasive species in ecological communities, and how native and invaders interact to shape the composition, biodiversity, and structure of contemporary forests, is crucial for effective management and conservation action. This is especially important in tropical regions, for which the mechanisms and consequences of invasion remain understudied compared to temperate forests despite increasing research on the effects of invasives during recent decades. Here, we evaluate the roles of invasive species composition, topography, and habitat in shaping the composition and biodiversity of native tree communities in tropical forests. Location Puerto Rico, United States. Methods We analysed data from 188 permanent plots across closed‐canopy and post‐agricultural secondary forests. Multivariate analysis of variance and variation partitioning were used to quantify the contributions of invasive species composition (NMDS axes derived from species‐level densities [stems/ha]), habitat (forest type, soil type, forest age, historical land use), and topography (elevation, slope, aspect) to variation in native tree composition and biodiversity. Analyses were conducted island‐wide and within each of three forest types (dry, moist, and wet forests). Results Invasive species composition, habitat, and topography explained ~14% of the variation in native tree composition and ~39% of the variation in biodiversity. Invasive species composition, forest type, forest age, elevation, and slope were the primary characteristics accounting for such variation at both scales (island‐wide and within each forest type). The full models for native composition and biodiversity were significant at both scales. The relative importance of invasive species composition, habitat, and topography on the composition and biodiversity of native tree communities differed among forest types, but general patterns were the same, with habitat characteristics explaining the greatest amount of variation, followed by topography and invasive species composition. Main Conclusions Invasive species modify the composition and biodiversity of native trees in Puerto Rico. Combined with land‐use changes and habitat attributes, they have the potential to significantly alter the composition of tropical forests, with long‐term consequences for biodiversity management and conservation.

AIM: To determine biotic and abiotic controls on pine invasion globally within six ecoregions that include both introduced and native ranges. LOCATIONS: Río Negro province, Argentina; Aysén and Araucanía regions, Chile; South Island (two ecoregions), New Zealand; Greater Yellowstone ecosystem, USA. METHODS: We quantified tree abundance and size across invasion fronts of the widespread invasive tree species Pinus contorta at each of the nine sites, encompassing both the native and introduced range. We also determined the relative importance of propagule pressure, abiotic characteristics and biotic factors for invasion success. Finally, key plant population metrics such as individual tree growth rates and reproductive effort were compared between native and introduced ranges. RESULTS: Pinus contorta density decreased with increasing distance from source population in all cases, but the importance and shape of this relationship differed among sites due, primarily to biotic factors. For example, areas dominated by native southern beech forest (Fuscospora cliffortioides or Nothofagus spp.) were not invaded, and this biotic resistance was not overcome by high propagule pressure. In contrast, shrublands were more highly invaded than grasslands, contradicting previous generalizations about pine invasions. Pinus contorta growth was faster, age to maturity was earlier and reproductive effort was higher in the introduced ranges compared with the native range, suggesting a demographic shift towards more rapid population growth in introduced regions. Climatic differences between the ranges may explain, at least in part, the observed pattern. MAIN CONCLUSIONS: We demonstrate that although biological invasions are driven by propagule pressure across different ecoregions, these processes interact strongly with biotic factors. Intriguingly, our results suggest that propagule pressure may become less important than biotic interactions as invasions proceed. Multi‐region studies including both the native and introduced ranges provide unparalleled opportunities for understanding how these interactions change among regions as invasions proceed.

Agroforestry has been mentioned has good potency to be selected as one of the tools to overcome the problem of degraded tropical peat swamp forest (TPSF) which was associated with social conflict. Here, we evaluated the early benefits of agroforestry for some aspects which has relationship with the attempt to overcome social conflict and peatland degradation * . We established the experimental plot of agroforestry in the conflict area at forest area with special purpose (KHDTK) in Kepau Jaya Village, Kampar District, Riau Province. We planted three native tree species of TPSF, namely were Balangeran (Shorea balangeran) , Geronggang (Cratoxylum arborescens) and Gelam (Melaleuca cajuputi subsp. cumingiana. In this plot, between rows of tree plantation the local farmer cultivated their crop. At 11 months after plantation; the ranges of survival rate, height and collar diameter increment of all tree native species were 56.2% - 72.44%, 97.4 m/year – 163.0 m/year and 2.04 cm/year – 3.2 cm/year, respectively. Furthermore, from the yields of the three types of seasonal crops (melon, chilli and luffa), the average income which was gathered by farmers was of 6,000,000 IDR. We also observed that during this agroforestry activity, the intensity of forest disturbance by the local community around KHDTK was relatively reduced. It is important to manage and increase those diverse benefits in further years.

Tree species have been planted widely beyond their native ranges to provide or enhance ecosystem services such as timber and fibre production, erosion control, and aesthetic or amenity benefits. At the same time, non-native tree species can have strongly negative impacts on ecosystem services when they naturalize and subsequently become invasive and disrupt or transform communities and ecosystems. The dichotomy between positive and negative effects on ecosystem services has led to significant conflicts over the removal of non-native invasive tree species worldwide. These conflicts are often viewed in only a local context but we suggest that a global synthesis sheds important light on the dimensions of the phenomenon. We collated examples of conflict surrounding the control or management of tree invasions where conflict has caused delay, increased cost, or cessation of projects aimed at invasive tree removal. We found that conflicts span a diverse range of taxa, systems and countries, and that most conflicts emerge around three areas: urban and near-urban trees; trees that provide direct economic benefits; and invasive trees that are used by native species for habitat or food. We suggest that such conflict should be seen as a normal occurrence in invasive tree removal. Assessing both positive and negative effects of invasive species on multiple ecosystem services may provide a useful framework for the resolution of conflicts.

Tree by Tree is a warning and a toolkit for the future of forest recovery. Scott J. Meiners investigates the critical biological threats endangering tree species native to the forests of eastern North America, providing a needed focus on this plight. Meiners suggests that if we are to save our forests, the first step is to recognize the threats in front of us. Meiners focuses on five familiar trees—the American elm, the American chestnut, the eastern hemlock, the white ash, and the sugar maple—and shares why they matter economically, ecologically, and culturally. From outbreaks of Dutch elm disease to infestations of emerald ash borers, Meiners highlights the challenges that have led or will lead to the disappearance of these trees from forests. In doing so, he shows us how diversity loss often disrupts intricately balanced ecosystems and how vital it is that we pay more attention to massive changes in forest composition. With practical steps for the conservation of native tree species, Tree by Tree offers the inspiration and insights we need to begin saving our forests.

Different vegetation restoration methods have improved soil quality to varying degrees. This study, focused on the forest–grassland–desert transition zone in the Hebei–Inner Mongolia border region, and employed a systematic grid sampling method to establish fixed monitoring plots in the Saihanba Mechanized Forest Farm and the Ulan Buh Grassland. The differences in soil quality evolution across various vegetation restoration methods under the same climatic and soil historical conditions were analyzed, elucidating the roles of these vegetation restoration methods in degraded forest ecosystems, with the aim of providing a reference for ecological restoration under similar land conditions. This study used a grid method to establish sample points in the forest–grassland–desert transitional zone and assessed five methods of vegetation restoration sites: artificial forest composed of native species of Larix principis-rupprechtii (FL), artificial forest composed of exotic Pinus sylvestris var. mongolica (FP), natural secondary broad-leaved forest (FN), open grassland (GO), and enclosed grassland (GC). The differences in soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP), total potassium (TK), alkaline hydrolysis nitrogen (AN), rapidly available phosphorus (AP) and rapidly available potassium (AK) among the different vegetation restoration sites were compared via variance analysis, and the soil quality index (SQI) was calculated to assess the soil quality at the sample points. The SOC, TN, and AN contents of forest soil were significantly greater than those of grassland, and the TN, TP, AN, AK, and SOC contents of FL, FN, and GC were significantly greater than those of FP and GO. Among them, the TN, TP, and SOC contents were the highest in the FL, reaching 2.74, 0.39, and 47.27 g kg −1 , respectively. In terms of ecological stoichiometric characteristics, the average N:P ratio in the study area was 6.68, indicating a serious lack of N in the study area. Among the different types of restoration sites, the effect was stronger in the FP than in the FL, and the TN and AN contents were only 1.48 g kg −1 and 116.69 mg kg −1 , respectively. The SQI in the FL was not significantly different from that in the FN or GC, but it was significantly greater than that in the FP and GO. These findings indicate that native tree species restoration in degraded forest ecosystems significantly improved soil quality, while the introduction of exotic tree species for afforestation had a minimal effect on improving soil quality.

Key messageConsidering their drought tolerance and growth characteristics, rare native tree species are well-suited admixed species for the development of climate-stable forests in Central Europe.In our study, we assessed the growth and drought reaction of the four rare native tree species European hornbeam (Carpinus betulus L.), European white elm (Ulmus laevis Pall.), field maple (Acer campestre L.), and wild service tree (Sorbus torminalis (L.) Crantz). Based on tree-ring data, we (I) evaluated their species-specific growth characteristics and variability and examined the influencing site and tree characteristics on annual growth. (II) We quantified their reaction to single drought events, also depending on site and tree variables. (III) We compared our results to oak (Quercus robur L., Quercus petraea (Matt.) Liebl.) and European beech (Fagus sylvatica L.). As they are well-known Central European tree species, there is a broad knowledge about their growth and drought response across wide geographical ranges available. Bringing the results of European beech and oak in relation with the rare native species, it allows to categorise their growth and drought reaction and to contextualise their performance. Our results show, that besides European white elm, the rare species showed an overall lower annual growth with a higher variability than European beech and oak. However, especially field maple and wild service tree were better adapted to drought than European beech and partially even recovered better than oak. Combining the aspects of growth stability and drought tolerance, we conclude that rare native tree species are well suited as admixed species in future forest stands. European hornbeam is a suitable match for European beech on wetter sites, while field maple and wild service tree are a sensible complement for the climate stable oak on drier sites.

Soil drought during summer in Central Europe has become more frequent and severe over the last decades. European forests are suffering increasing damage, particularly Norway spruce. Douglas-fir ( (Mirbel) Franco), a non-native tree species, is considered as a promising alternative to build drought-resilient forests. The main goal of this study was to investigate the intraannual radial stem growth and sap flow performance of Douglas-fir along a precipitation gradient across Germany under severe drought. Sap flow and stem radial changes of up to ten trees each at four sites with different precipitation regimes were measured in combination with volumetric soil water content during the growing season of 2022. Measurements of stem radial changes were used to calculate the trees' stem water deficit, a proxy for tree water status and drought stress. The severe summer drought of 2022 led to an early growth cessation and a significant reduction in daily sap flow at all four sites monitored. We could identify a site-specific threshold in soil water availability ranging between 21.7 and 29.6% of relative extractable water (REW) under which stem water reserves cannot be replenished and thereby inhibiting radial growth. We could also demonstrate that at this threshold, sap flow is heavily reduced to between 43.5 and 53.3%, and for a REW below 50%, sap flow linearly decreases by 1.1-2.0% per 1% reduction in REW. This reduction tends to follow the humidity gradient, being more pronounced at the most oceanic characterized site and suggesting an adaptation to site conditions. Even though Douglas-fir is considered to be more drought stress resistant than Norway spruce, growth and sap flow are greatly reduced by severe summer drought, which became more frequent in recent years and their frequency and intensity is likely to increase. Our results suggest that timber production of Douglas-fir in Central Europe will decline considerably under projected climate change, and thus pointing to site specific growth constraints for a so far promising non-native tree species in Europe.

Douglas-fir ( (Mirb.) Franco) is considered an important non-native substitute tree species in Europe, especially for Norway spruce ( (L.) Karst.), mainly due to its higher drought tolerance. However, Douglas-fir has also shown increasing mortality in certain regions of the world. One of the main reasons is the increase in drought and heat periods due to climate change. There is still a need for research on the influence of important soil properties and rooting characteristics on the drought tolerance of Douglas-fir. Therefore, we analyzed the influence of soil texture, plant-available water capacity (PAWC), fine root density, and effective rooting depth on water status and thus drought stress in Douglas-fir during the extreme drought of 2018. We selected seven closely spaced sites along a soil texture gradient from sand to clay at an elevation of ca. 500 m a.s.l. in southern Germany and determined soil physical and rooting characteristics. Water status parameters and growth duration were derived from dendrometer data at five Douglas-firs per site. The influence of soil and rooting characteristics on these drought stress-related parameters was analyzed using mixed-effects models. The focus was on two summer drought periods in 2018. In the initial stage of the extreme summer drought of 2018 (in June), a higher PAWC and a higher fine root density reduced drought stress. However, these influences were no longer noticeable in the later stage of drought (in August), probably due to deeper soil desiccation. In August, a higher effective rooting depth reduced drought stress. Soil texture had a significant influence, particularly on growth duration. This study provides information on site selection for Douglas-fir cultivation under the predicted increase in severe drought, showing the importance of deep and intensive rooting, and points to the need for combined above- and belowground investigations for a better understanding of the drought response patterns of tree species.

Roadside trees alter biotic and abiotic factors of plants diversity in an ecosystem. Rows of plants grow along the roadside due to the interplay between the arrival of propagule and seedling establishment, which depends on the road’s specifications, land pattern, and road administration and protection practices. A field study was conducted to measure the roadside tree diversity in the city of Karachi (Pakistan). A total of 180 plots, divided into three primary road groups, were surveyed. The highest quantity of tree biomass per unit area was found on wide roads, followed by medium roads. On narrow roads, the least biomass was detected. A single species or a limited number of species dominated the tree community. Conocarpus erectus was the most dominant non-native species on all types of sidewalks or roadsides, followed by Guaiacum officinale . A total of 76 species (32 non-natives and 44 natives) that were selectively spread along the roadsides of the city were studied. There was a significant difference in phylogenetic diversity (PD), phylogenetic mean pairwise distance (MPD), and phylogenetic mean nearest taxon distance (MNTD) among wide, medium, and narrow roads. Management practices have a significant positive correlation with diversity indices. Our study identified patterns of diversity in roadside trees in Karachi. It provides the basis for future planning for plant protection, such as the protection of plant species, the maintenance of plant habitats, and the coordination of plant management in Karachi.