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Background and aims While the coupled effects of root exudates and microbial feedbacks on soil processes are well-recognized, we still lack an understanding of differences in root exudate fluxes and the associated ecological consequences among tree growth forms. Methods Two deciduous tree species (i.e., Cercidiphyllum japonicum and Larix kaempferi ) and two evergreen tree species (i.e., Pinus armandi and Pinus tabulaeformis ) were selected to perform an in-situ collection of root exudates during the growing season in 2016. The net N mineralization rates and associated microbial enzyme activities were measured in rhizosphere and bulk soils to evaluate rhizosphere effects. Moreover, we compiled the dataset related to root exudation and their associated biological traits and the soil chemical properties for 21 tree species from temperate forests. Results The root exudation rates and the annual root exudate carbon (C) fluxes of two deciduous tree species were significantly higher than those of the two evergreen tree species. Correspondingly, the rhizosphere effects of deciduous tree species on the microbial biomass, enzyme activity and net N mineralization rate were approximately 1.9, 1.6 and 2.4 times greater than those of the evergreen tree species, respectively. Rhizosphere effects were positively correlated with the root exudation rate. The compiled dataset also suggest that deciduous tree species tend to have higher exudation rates than evergreen tree species in temperate forests. Conclusions Collectively, these results suggest that the two tree growth forms exhibit different patterns in root exudate inputs and associated rhizosphere microbial processes. Generally, deciduous tree species tend to exude more C into the soil and consequently induce greater microbial feedback on soil N transformations during the growing season in temperate regions, implying that deciduous tree species induced a greater effect on the C and nutrient cycling in rhizosphere soil than evergreen tree species.

Context Trees play a vital role in reducing street-level particulate matter (PM) pollution in metropolitan areas. However, the optimal tree growth type for maximizing the retention of various sizes of PM remains uncertain. Objectives This study assessed the PM reduction capabilities of evergreen and deciduous broadleaf street trees, focusing on how leaf phenology influences the dispersion of pollutants across particle sizes. Methods We collected data on six PM size fractions from 72 sites along streets lined with either evergreen or deciduous broadleaf trees in Wuhan, China, during the summer and winter of 2017–2018. Results Evergreen trees demonstrated superior PM reduction capabilities compared to deciduous trees, with evergreen street canyons showing 27.2% and 12.6% lower PM 2.5 and PM 10 concentrations in summer, and 13% and 5.5% lower concentrations in winter. During summer, evergreen streets predominantly contained fine particles (PM 1 , PM 2.5 ), posing potential health risk due to their ability to infiltrate the human respiratory system. In contrast, deciduous streets primarily harbored coarser particles (PM 4 , PM 7 , PM 10 , and total suspended particulate [TSP]). During winter, larger particles were dominant, regardless of the tree growth form. Conclusions Evergreen trees showed superior PM reduction capabilities compared to deciduous trees due to their year-round leaf retention, enhanced surface properties, and denser canopies that maximize PM capture. We recommend prioritizing evergreen broadleaf trees as the primary street trees while interspersing deciduous trees at appropriate intervals. This approach will ensure that urban greenery provides maximum ecological benefits while reducing the PM concentration.

Trees positively improve the annual thermal comfort of the built environment in tropical areas, where climate change is slight throughout the year. However, for areas with high changes in climate all year, the current studies have only explored the summer cooling performance of trees without the impact of different types of trees on annual thermal comfort, especially in cold seasons. Therefore, to quantify the impacts and scientifically guide the optimization of green space layout in hot summer and cold winter areas, this study selected Changsha City as the study area and analyzed how the annual thermal comfort is affected by evergreen trees and deciduous trees, which are two common types of trees in hot summer and cold winter areas. The analytical results indicated that the difference in the effect of deciduous and evergreen trees on outdoor thermal comfort was insignificant in summer, where the difference in the monthly mean PET for the three summer months was slight, being 0.28 °C, 0.14 °C, and 0.29 °C, respectively. However, evergreen trees greatly exacerbated winter cold compared to deciduous trees, with a monthly mean PET decrease by nearly 1.0 °C and an hourly PET reduced by up to 3.57 °C. The difference is mainly attributed to the absorption and reflection of solar radiation by the tree canopy, as well as the cooling and humidifying effect of the tree leaf. In hot summer and cold winter areas, outdoor thermal comfort is still in the “comfortable” and “slightly warm” acceptable stage despite the warming effect of deciduous trees in the spring and autumn seasons. Planting evergreen trees is an inevitable thermal mitigation choice for tropical areas. However, for the areas with high annual climate change, such as hot summer and cold winter areas in China, a change in empirical tree planting patterns and selecting deciduous trees where appropriate will improve year-round outdoor thermal comfort.

Purpose Although plant functional type can modulate soils and their processes in natural, nitrogen (N)-limited ecosystems, little is known about their ability to influence soil N dynamics in urban ecosystems that have high excess N input. We investigated whether i) plant functional type effects on soil N dynamics in urban parks follow the same pattern as those in undisturbed natural/semi-natural forests, and ii) park age influences plant functional type effects on soil N dynamics under boreal climate. Methods We selected 13 urban parks of varying ages (young: 10 to 15, old: > 70 years), and 5 undisturbed natural/semi-natural forests (> 80 years) in southern Finland. In these parks and forests, we measured soil total N concentration, availability of inorganic N, nitrous oxide (N 2 O) flux and earthworm biomass under three plant functional types (evergreen tree, deciduous tree, lawn). Results Our results showed that plant functional type influenced N dynamics also in urban greenspace soils, which may relate to the clear effect of plant functional type on earthworm biomass. Evergreen trees tended to have the highest ability to foster N accumulation and reduce N 2 O emissions in urban parks. Moreover, with increasing park age, N accumulation increased under trees but decreased under lawns, further emphasising the role of vegetation in affecting soil N dynamics in urban greenspaces. Conclusions Our results show that, similar to natural/semi-natural forests, plant functional type, irrespective of park age, can influence soil N dynamics in urban parks.

Questions: Mosaics of evergreen and deciduous trees that are characteristic of evergreen broad-leaved forests (EBLF) are thought to arise from habitat heterogeneity, but empirical evidence for this is limited. We test this assertion asking: (1) whether environmental heterogeneity explains the distribution of deciduous and evergreen trees; (2) which are the most important environmental variables; and (3) does their importance change with scale? Location: Tiantong National Forest Park, Ningbo, Zhejiang, China. Methods: We used data from a 20-ha individual-mapped EBLF in spatial point-pattern analyses testing the scale of aggregation within, and segregation between, the two life forms. We used a heterogeneous Poisson process model to remove the effects of environmental heterogeneity, predicting segregation would disappear if the mosaic was due to habitat heterogeneity alone. Finally, we tested the relative importance of theoretically important environmental variables using multivariate regression trees at three spatial scales (10, 20 and 50 m grid cells). Results: We found evergreen and deciduous trees were aggregated at scales below 125 m and 60 m, respectively, and mutually exclusive at scales <120 m. Evidence of any spatial segregation between the life forms was removed at all scales after controlling for environmental heterogeneity. Only soil phosphorus concentrations contributed to spatial patterns at all scales, with values >0.27-0.30 g·kg⁻¹ favouring deciduous species. Conclusions: Our study is consistent with habitat heterogeneity creating the observed mosaics of evergreen and deciduous tree species, but micro-habitat heterogeneity contributed even at scales <20 m. Soil phosphorus availability appears to be the major environmental variable maintaining these mosaic patterns at hillslope scales in EBLF.

Although perennial fruit crops represent 1% of global agricultural land, they are of a great economic importance in world trade and in the economy of many regions. The perennial woody nature of fruit trees, their physiological stages of growth, the root distribution pattern, and the presence of herbaceous vegetation in alleys make orchard systems efficient in the use and recycling of nitrogen (N). The present paper intends to review the existing literature on N nutrition of young and mature deciduous and evergreen fruit trees with special emphasis to temperate and Mediterranean climates. There are two major sources of N contributing to vegetative tree growth and reproduction: root N uptake and internal N cycling. Optimisation of the use of external and internal N sources is important for a sustainable fruit production, as N use efficiency by young and mature fruit trees is generally lower than 55% and losses of fertilizer N may occur with the consequent economic and environmental concern. Organic alternatives to mineral N fertilizer like the application of manure, compost, mulching, and cover crops are scarcely used in perennial fruit trees, in spite of the fact that society’s expectations call for more sustainable production techniques and the demand for organic fruits is increasing.

Compared with other seasons, winter usually has low mental restorative quality due to the lack of greenness. Reasonably adding evergreen trees to winter landscapes can improve the quality. However, what proportion, species and planting site of evergreen trees are better for mental restoration? To address this question, two original pictures (describing two landscape types) and 24 manipulated pictures (including three categories and four grades of proportion of evergreen trees) were collected, and 381 respondents were employed to score the mental restorative quality of each picture. The results revealed that planting evergreen trees in the landscape with water was more efficient in promoting mental restoration than planting them in the landscape without water. Adding broad-leaved evergreen trees was much better than adding coniferous trees and the mixture of the two. And, for the landscape with water, moderate proportion of evergreen trees possessed significantly higher mental restoration than low or high proportion.

Background Lauraceae is well known for its significant phylogenetic position as well as important economic and ornamental value; however, most evergreen species in Lauraceae are restricted to tropical regions. In contrast, camphor tree ( Cinnamomum camphora ) is the most dominant evergreen broadleaved tree in subtropical urban landscapes. Results Here, we present a high-quality reference genome of C. camphora and conduct comparative genomics between C. camphora and C. kanehirae . Our findings demonstrated the significance of key genes in circadian rhythms and phenylpropanoid metabolism in enhancing cold response, and terpene synthases ( TPSs ) improved defence response with tandem duplication and gene cluster formation in C. camphora . Additionally, the first comprehensive catalogue of C. camphora based on whole-genome resequencing of 75 accessions was constructed, which confirmed the crucial roles of the above pathways and revealed candidate genes under selection in more popular C. camphora , and indicated that enhancing environmental adaptation is the primary force driving C. camphora breeding and dominance. Conclusions These results decipher the dominance of C. camphora in subtropical urban landscapes and provide abundant genomic resources for enlarging the application scopes of evergreen broadleaved trees.

Variation in shade tolerance is a primary mechanism driving succession in subtropical forests. However, little attention has been given to ontogenetic variation in light tolerance of late succession tree species such as Phoebe bournei. To investigate the differences in adaptive strategies between seedlings and saplings in response to sun and shade, we systematically studied the physiological and morphological leaf plasticity of P. bournei and how these variables are influenced by ontogeny. This study provided experimental evidence that leaf plasticity increases with the ontogeny of juvenile P. bournei adapting to the changing light resources. Investment in leaf construction increased with age and light resources in the evergreen P. bournei, as shown by leaf mass per unit area (LMA). Six-month-old seedlings lacked the adjustment of stomatal conductance (gs) and stomatal density responding to sun and shade. For seedlings, maintaining high gs under sun conditions increased stress risk instead of carbon gain. However, the leaves of 2-year-old saplings accumulated more soluble sugars and showed lower stomatal conductance and higher stomatal density under the sun than under shade conditions. The nonphotochemical quenching of sun leaves increased with plant age, indicating that the photoprotective capacity was enhanced with ontogeny. The leaf plasticity increasing along the ontogeny of juvenile P. bournei may contribute to the adaptation from shade to sun. Our study provides new insights into understanding the influence of ontogeny on shade responses of late succession trees in subtropical forests.

Research Highlights: To demonstrate the effectiveness of configuration modes and tree types in regulating local microclimate. Background and Objectives: Urban trees play an essential role in reducing the city’s heat load. However, the influence of urban trees with different configurations on the urban thermal environment has not received enough attention. Herein we show how spatial arrangement and foliage longevity, deciduous versus evergreen, affect transpiration and the urban microclimate. Materials and Methods: We analyzed the differences between physiological parameters (transpiration rate, stomatal conductance) and meteorological parameters (air temperature, relative humidity, vapor pressure deficit) of 10 different species of urban trees (five evergreen and five deciduous tree species), each of which had been planted in three configuration modes in a park and the campus green space in Xi’an. By manipulating physiological parameters, crown morphology, and plant configurations, we explored how local urban microclimate could be altered. Results: (1) Microclimate regulation capacity: group planting (GP) > linear planting (LP) > individual planting (IP). (2) Deciduous trees (DT) regulated microclimate better than evergreen trees (ET). Significant differences between all planting configurations during 8 to 16 h were noted for evergreen trees whereas for deciduous trees, all measurement times were significantly different. (3) Transpiration characteristics: GP > LP > IP. The transpiration rate (E) and stomatal conductance (Gs) of GP were the highest. Total daily transpiration was ranked as group planting of deciduous (DGP) > linear planting of deciduous (DLP) > group planting of evergreen (EGP) > linear planting of evergreen (ELP) > isolated planting of deciduous (DIP) > isolated planting of evergreen (EIP). (4) The microclimate effects of different tree species and configuration modes were positively correlated with E, Gs, and three dimensional green quantity (3DGQ), but weakly correlated with vapor pressure deficit (VpdL). (5) A microclimate regulation capability model of urban trees was developed. E, Gs, and 3DGQ could explain 93% variation of cooling effect, while E, Gs, VpdL, and 3DGQ could explain 85% variation of humidifying effect. Conclusions: This study demonstrated that the urban heat island could be mitigated by selecting deciduous broadleaf tree species and planting them in groups.