Tree Diversity Research Articles

Dynamic interplay between soil microbial communities, enzyme activities, and pear quality across planting years

Few studies have been reported on the effect of planting years on fruit quality and soil of pear trees. In this study, four planting years (T5, T20, T30, and T40) of Cuiguan pears were used to analyze fruit quality, rhizosphere soil enzymes, and microbial diversity of pear trees, and their correlations. The results showed that the content of sucrose, reducing sugar and ascorbic acid in Cuiguan Pear showed a tendency of increasing and then decreasing with the increase of planting years, in which the highest content was found in 20- and 30-year-old fruits, and the highest content of total acid was found in 5-year-old fruits. Rhizosphere soil enzyme activities varied with planting year, with the highest protease activity in 20-year-old soil, phosphatase and urease in 30-year-old soil, polyphenol oxidase in 5-year-old soil, and sucrase in 40-year-old soil. The microbial diversity index and the number of OTUs showed an increasing and decreasing trend with the increase of planting years. Among the top 11 bacteria in pear rhizosphere soil average relative abundance, with Bradyrhizobium decreasing in relative abundance at the peak pear fruiting stages (T20 and T30), while Acidothermus showed an increasing trend in relative abundance with increasing planting years. RDA analysis showed that there were differences in the microbial community structure of pear trees at different planting years, and that both sucrose and reducing sugar contents in pears were positively correlated with T20 and T30, ascorbic acid content was positively correlated with T40, whereas the total acid content was positively correlated with T5, and that T20 was positively correlated with soil protease and phosphate mono esterase activities, and that T30 was positively correlated with polyphenol oxidase and urease activities, whereas T40 was positively correlated with sucrase activity. In summary, with the increase of planting years, changes in soil microbial community structure and soil enzyme activity have a significant impact on pear quality formation, and the results of the study provide a theoretical basis for scientific management of pear orchards.

Assessment of Plant Diversity and Soil Quality Management in Forest Land of West Godavari District, Andhra Pradesh, India

The field experiment was set in home-garden areas under forest land of eight small towns viz. Borampalem, Venkatapuram, Gundugolanukunta, Ramannapalem, Abdullapuram, Tirumaladevpeta, Venkatakrishnapuram, Appalarajugudem in West Godavari, Andhra Pradesh during November to March in 2021–22 assess the Plant and Tree Diversity and Soil quality parameters. The plant/tree species Phoenix sylvestris, reported the highest frequency (245.00), dominance (3.27), and basal area (7542.96 cm2). Plumbago zeylanica had the highest relative density (6.96) and relative abundance (6.81) among all the shrub species. Plumbago zeylanica reported the highest Important value index (IVI) 17.10 while Herb species with highest density was found in Centella asiatica (0.95), frequency (35), and highest Important value index (IVI) 14.60. Soil quality parameters reflects that at the depth 0-15cm the average value of pH is found to be7.52, organic carbon is 0.56%, the amount of available nitrogen is 213.78 kg/ha, amount of available of phosphorus is 41.25 kg/ha and available potassium is 38.22 kg/ha. At the depth of 15-30 cm the Average value of pH is found to be 6.61, organic carbon is 0.39%, the amount of available nitrogen is 189.51 kg/ha, amount of available of phosphorus is 34.75 kg/ha and available potassium is 31.37 kg/h.

ToTE: A global database on trees of the treeline ecotone.

Globally, treelines form a transition zone between tree-dominated forest downslope and treeless alpine vegetation upslope. Treelines represent the highest boundary of "tree" life form in high-elevation mountains and at high latitudes. Recently, treelines have been shifting upslope in response to climate warming, so it has become important to understand global tree diversity and treeline distributions. However, to the best of our knowledge, no global database on tree flora of treelines exists, which limits our capacity to undertake macroecological analyses. Here, for the first time, we present a global data set on the trees of the treeline ecotone, supported by an online ToTE database. We synthesized the database from 1202 studies published over the last 60 years (1962 to 2022) following the Preferred Reporting Items in Systematic Reviews and Meta-Analysis (PRISMA) protocol. We classified the tree species in the database into three categories: treeline tree (TL) species, near to treeline (NTL) tree species, and tree species with an upper montane range limit (TUMR). The ToTE Version-1 presents a total of 208 tree taxa, including 189 species, five subspecies, and 14 varieties, belonging to 54 genera and 26 families distributed across 34 mountain regions worldwide that either grow exactly at the treeline or have a range limit below the treeline. Of the total taxa, 155, 14, and 39 belong to TL, NTL, and TUMR, respectively. Genera such as Abies, Picea, Pinus, Larix, and Juniperus are more represented in the treeline tree category. On the other hand, Acer, Prunus, Populus, and Quercus have more representatives in the near to treeline category, whereas Erica, Nothofagus, and Polylepis contribute more tree species with an upper montane range limit. Furthermore, families such as Rosaceae and Pinaceae include trees that occur both at the treeline and with an upper montane range limit, whereas Sapindaceae includes trees that occur exclusively near to treeline. Our database also includes information on the global distribution patterns of treeline tree species richness across mountains and biomes. The mountains with the highest number of tree species are the Andes (39) followed by the Himalaya (37). Close to 67% of tree species show restricted distributions in different mountains, with the highest endemism in the Andes and the Himalaya. In terms of tree species distribution, Pinus sylvestris was widespread, with a distribution across nine mountain regions, followed by Picea glauca and Fagus sylvatica, both distributed across five mountain regions. In terms of species' distribution across biomes, the temperate biome harbors the highest treeline tree species richness (152 species), which may reflect the fact that the majority of studies are available from the temperate regions of the world. The remaining 56 species are distributed within five other biomes, with the least in dry tropical and subarctic (four species each). Furthermore, currently 40 treeline tree species fall under different International Union for Conservation of Nature threat categories. We anticipate that our database will help advance research on macroecological, biogeographic, evolutionary, climate-change, and conservation aspects of the treeline on a global scale. The data are released under a Creative Commons Attribution 4.0 international license. Please cite this data paper when the data are reused.

Joint evolution of mutualistic interactions, pollination, seed dispersal mutualism, and mycorrhizal symbiosis in trees.

Mycorrhizal symbiosis, seed dispersal, and pollination are recognized as the most prominent mutualistic interactions in terrestrial ecosystems. However, it remains unclear how these symbiotic relationships have interacted to contribute to current plant diversity. We analyzed evolutionary relationships among mycorrhizal type, seed dispersal mode, and pollination mode in two global databases of 699 (database I) and 10 475 (database II) tree species. Although database II had been estimated from phylogenetic patterns and therefore had lower certainty of the mycorrhizal type than database I, whose mycorrhizal type was determined by direct observation, database II allowed analysis of many more taxa from more regions than database I. We found evidence of joint evolution of all three features in both databases. This result is robust to the effects of both sampling bias and missing taxa. Most arbuscular mycorrhizal-associated trees had endozoochorous (biotic) seed dispersal and biotic pollination, with long dispersal distances, whereas most ectomycorrhizal-associated trees had anemochorous (abiotic) seed dispersal and wind (abiotic) pollination mode, with shorter dispersal distances. These results provide a novel scenario in mutualistic interactions, seed dispersal, pollination, and mycorrhizal symbiosis types, which have jointly evolved and shaped current tree diversity and forest ecosystem world-wide.

Linking aerial hyperspectral data to canopy tree biodiversity: An examination of the spectral variation hypothesis

AbstractImaging spectroscopy is emerging as a leading remote sensing method for quantifying plant biodiversity. The spectral variation hypothesis predicts that variation in plant hyperspectral reflectance is related to variation in taxonomic and functional identity. While most studies report some correlation between spectral and field‐based (i.e., taxonomic and functional) expressions of biodiversity, the observed strength of association is highly variable, and the utility in applying spectral community properties to examine environmental drivers of communities remains unknown. We linked hyperspectral data acquired by airborne imaging spectrometers with precisely geolocated field plots to examine the spectral variation hypothesis along a temperate‐to‐boreal forest gradient in southern Québec, Canada. First, we examine the degree of association between spectral and field‐based dimensions of canopy tree composition and diversity. Second, we ask whether the relationships between field‐based community properties and the environment are reproduced when using spectral community properties. We found support for the spectral variation hypothesis with the strength of association generally greater for the functional than taxonomic dimension, but the strength of relationships was highly variable and dependent on the choice of method or metric used to quantify spectral and field‐based community properties. Using a multivariate approach (comparisons of separate ordinations), spectral composition was moderately well correlated with field‐based composition; however, the degree of association increased when univariately relating the main axes of compositional variation. Spectral diversity was most tightly associated with functional diversity metrics that quantify functional richness and divergence. For predicting canopy tree composition and diversity using environmental variables, the same qualitative conclusions emerge when hyperspectral or field‐based data are used. Spatial patterns of canopy tree community properties were strongly related to the turnover from temperate‐to‐boreal communities, with most variation explained by elevation. Spectral composition and diversity provide a straightforward way to quantify plant biodiversity across large spatial extents without the need for a priori field observations. While commonly framed as a potential tool for biodiversity monitoring, we show that spectral community properties can be applied more widely to assess the environmental drivers of biodiversity, thereby helping to advance our understanding of the drivers of biogeographical patterns of plant communities.

Second-growth forests of the Mexican tropics are reservoirs of timber species similar to old-growth forest: Perspectives for sustainable forest management

Second-growth forests represent the largest area of forest in southern Mexico and can provide relevant information on how their structural attributes in are linked to anthropogenic factors and for their forest management. However, a knowledge gap remains at national level with little scientific literature available. Therefore, this research aimed to investigate the structure and tree richness of second-growth forests in the south of Quintana Roo State, México. With stratified sampling through participatory mapping of local collaborators, secondary tropical forests of 7, 15, 27, 37, and ≥ 48 to 80 years (y) old-growth were identified. We categorized forests into three successional stage classes: 5-20 y (Class I; forests of 7 and 15 y); 25-40 y (Class II; forests of 27 and 37 y), and old-growth forest (Class III; forests 48-80 y). In each forest (7, 15, 27, 37, 48, and 80 y of time since abandonment [tSA]) three plots were randomly chosen and established within the forest. Each age class was composed of two forests and six sample plots. In total there were 18 plots of 500 m2 each. Subsequently, we: i) calculated the land use intensity (LUI) to which the sites were subjected, ii) described the following structural attributes: floristic similarity, true diversity (effective number of species), stem density, and basal area (AB), and iii) evaluated if tSA and LUI influence the aforementioned structural attributes. Tree diversity was characterized with Hill numbers associated with observed species richness (0D), richness of equally abundant species (1D), and dominant species (2D). Forest structure was analyzed by density (number of trees ha−1) and distribution of stems by diameter class ha−1 and basal area (BA, m2 ha−1). The second-growth forest was derived from the milpa agricultural system under moderate land use intensity (LUI index = 0.02 - 0.1). Floristic structure was at least similar between Class I and Class III. Forest age and LUI do not affect tree composition of the forests (p ≥ 0.1667). However, these two factors affected stem density and BA. Only the species richness (0D) of second-growth forest and old-growth forest was influenced by tSA (p = 0.0002). In second-growth forests, Classes I and II, 78 species (0D) were recorded, 8 and 8 exclusive species, 28 and 36 equally abundant species (1D), and 15 to 24 dominant species (2D). In the old-growth forest, Class III, 70 species were recorded, and 38 and 26 equally abundant (1D) and dominant species (2D), as well as 5 exclusive species. The density of stems decreased with increasing forest age and increasing BA. Second-growth forest and old-growth forest all showed a high density of small diameter stems. These results indicate that second-growth forests are important tree species reservoirs (including those for timber purposes), comparable to old-growth or mature forests, and therefore they are relevant not only as biodiversity conservation areas or carbon sinks, but also for planned sustainable forest management.

Tree diversity and ethnomedicinal plants for the benefit of the inhabitants of Remuna Block Balasore District, Odisha

Tree diversity and ethnomedicinal plants for the benefit of the inhabitants of Remuna Block Balasore District, Odisha

The low diversity of vegetation seedling and sapling threatening the tree existence at the university green space of Universitas Sumatera Utara, Indonesia

University of Sumatera Utara (USU) located in the densely populated urban area and committed to maintain the vegetations of green space which are fundamental to the key indicator in green campus ranking. Green open spaces are a vital element in urban areas providing the comfortable-healthy spaces for urban communities and numerous of environmental services. Specifically, the quality of environmental services depends on the extensive of green spaces, climate characteristic, and existing vegetation as the natural element at the area. Vegetation analysis is the method to study the composition, structure, and form of plant communities that is a prerequisite for describing diverse ecological processes and dynamics of species community in a forest. This study aims to analyze the important value, diversity, evenness, and richness index of USU green space vegetation based on the growth levels from seedlings to trees. The sampling plot was quantified using 2% sampling intensity and positioned with a simple random method. Species name, individual and species number, diameter at breast height (DBH), and stand height were recorded in the designated plots and subplots for each life stage. This research documented 21 species belonging to 12 families at USU green space. Swietenia mahagoni was the dominant species at all growth level with the IVI of 141.07 % (trees), 144.21 % (poles), 133.33 % (saplings), and 135.37 % (seedlings). The species diversity of trees and poles was moderate (H’= 1.6 – 1.7), whereas of saplings and seedlings was low (H’= 0.6 – 0.7). Vegetation evenness at all growth levels was high (E= 0.6 – 1.0). The species richness of trees was identified as moderate (R= 3.5) and of seedlings, saplings, and poles was low (R= 0.2 – 2.5). The seedlings and saplings were inadequate indicating the poor regeneration threatening the tree existence at USU green space.

Combining chronosequences and multi‐census approaches to understand patterns of succession in subtropical montane forests of NW Argentina

AbstractQuestionHow does the diversity of successional forests evolve with stand age, and to what extent do permanent plots validate the previously studied successional patterns of tree diversity and composition observed through chronosequences? To evaluate the role of successional forests as reservoirs for many species, it is essential to examine how biodiversity recovers with the age of the stand. We studied patterns of taxonomic and functional diversity, as well as species composition during forest succession, by combining chronosequences and permanent plot monitoring.LocationSubtropical montane forests in NW Argentina.MethodsWe used data from two chronosequences of plots monitored for 30 years in lower and upper montane forests dominated by native trees (LMF‐Native and UMF‐Native), and one chronosequence of plots dominated by the exotic tree Ligustrum lucidum, monitored for 10 years in low montane forests (LMF‐Invaded). We analyzed changes in taxonomic (species richness, Shannon diversity, Simpson diversity) and functional diversity, as well as composition with forest age.ResultsTaxonomic and functional diversity increased between 30 and 70 years of succession in LMF‐Native and UMF‐Native. Successional LMF‐Native forests reached the diversity of mature forests earlier than UMF‐Native. In LMF‐Invaded, taxonomic and functional diversity decreased in the same period because of the increasing dominance of the exotic species Ligustrum lucidum. In non‐invaded chronosequences (LMF‐Native and UMF‐Native) we observed a convergence towards the composition of mature forests; however, each successional forest kept its identity for 30 years.ConclusionsDiversity and composition followed different successional trajectories depending on the type of forest. We found that successional patterns, such as changes in taxonomic and functional diversity, predicted with the chronosequence approach, were confirmed with data from plot monitoring. The effects of pre‐abandonment conditions persist in the diversity and composition of successional forests monitored between 10 and 30 years.

Infiltration rate under the most dominant tree stands at the University Green Space: Swietenia macrophylla, Mimusops elengi, and Polyalthia longifolia

Infiltration is crucial for determining how much rainfall enters the soil and how much becomes runoff. The Universitas Sumatera Utara (USU) Campus Medan is one of the green campuses with diverse tree species. The ability of tree stands on the USU Campus Medan to absorb water needs to be studied for flood mitigation. This study aims to analyze the infiltration rate under the most dominant tree stands at the University Green Space: Swietenia macrophylla (mahagony), Mimusops elengi (tanjung), and Polyalthia longifolia (glodokan tiang) using the Horton method. The infiltration measurement uses double ring infiltrometer. The infiltration data will process using Horton Method. The results show that the infiltration rate under mahogany and tanjung stands are included to medium infiltration. While the infiltration rate under glodokan tiang stand is included to fast infiltration. The correlation test on mahogany, tanjung, and glodokan tiang stands indicate a strong correlation between the actual infiltration rate with Horton’s infiltration rate and have a positive trend, so it can be concluded that Horton method can be used to estimate the infiltration rate in each stand.

Biodiversity of Banana Trees (Musa sp.) in Purwodadi Botanical Gardens

Banana is a fruit that is often found in everyday life. This fruit is a daily consumption to meet daily nutritional needs. Indonesia has approximately 200 types of bananas scattered throughout the island. Diversity of banana trees (Musa sp.) in an effort to conserve Indonesian plants that live in lowland forests by carrying out plant exploration and collection activities. This research was conducted at the Purwodadi Botanical Gardens (KRP) with the aim of knowing the collection of banana trees (Musa sp.) in KRP. The method used is the roaming method with observation data collection. The results showed that there were 44 species of banana trees (Musa sp.) found alive, including the wild species with seeds Musa acuminate Colla and Musa balbisiana Colla. The species found consisted of 6 kinds of cultivar genome groups that had different characteristics. Banana tree cultivation was developed because it has many benefits and nutritional content for health.

Modelling and Mapping of Forest Biodiversity Indicators Using Sentinel-2 and PlanetScope Remotely Sensed Data

Tropical montane forests harbour exceptionally high biodiversity yet face severe threats from human activities. Assessing forest biodiversity over large areas is crucial yet extremely challenging. Remote sensing provides an efficient monitoring solution, but few studies have focused on Tanzania's diverse, montane forests. We collected field data on tree species composition within 159 plots across montane forests in Tanzania's West Usambara region. We calculated species richness, evenness, and Shannon diversity index as indicators of tree diversity. Using Sentinel-2 and PlanetScope satellite imagery, we derived spectral, textural, and vegetation index predictors to model these indices via generalized additive models and extreme gradient boosting. PlanetScope-based XGBoost models performed best, explaining 19.7% of variation in Shannon diversity. Incorporating textural predictors further improved model accuracy. Despite inherent challenges in modelling complex tropical forests, our findings demonstrate promising potential of Sentinel-2 and PlanetScope for regional biodiversity monitoring where field surveys are limited. Further research could enhance these initial results by leveraging higher resolution data and increasing field sampling for effective monitoring of tropical biodiversity.

Monumental trees of Ukraine and public awareness of them

Studying the species diversity and condition of monumental trees contributes to their preservation and is important for public awareness of their role in ecosystems and the country’s ecological heritage. The purpose of the study was to reveal the significance of such trees for society. The task of the work was to research the characteristics of monumental trees in Ukraine. The history of environmental protection is analysed and the features of monumental tree preservation in Ukraine are presented. The beginning of environmental protection activity related to the preservation of trees in Ukraine and the most active periods have been revealed of it. The national features of the popularization of monumental trees are given. Based on the analysis of botanical natural monuments cadastres of Ukraine and Kyiv, quantitative and species composition of monumental trees were established. The most common (Quercus robur), common, less common and rare (Buxus sempervirens, Catalpa bignonioides, Metasequoia glyptostroboides, Pseudotsuga menziesii, Rhododendron myrtifolium, Sequoiadendron giganteum and others) species of monumental trees have been established, and important issues regarding their conservation are indicated. According to the types of street plantings, the majority (68%) are single trees. To assess the awareness of the population about ancient trees, the method of sociological survey of respondents was used. The most significant values of monumental trees for the population were studied. The importance of the populations’ awareness of old trees through the development of an emotional connection with them, which contributes to their protection, has been established. The obtained results can be used in future environmental protection activity, exchanging of scientists’ experience from different countries regarding the preservation of such trees, enrichment of information about growth characteristics, historical facts or other issues related to these trees

Distance and T-square sampling for spatial measures of tree diversity

Distance sampling and its statistically improved variant, T-square sampling, are important sampling methods in plant ecology. They have often been applied in the context of plant density estimations and are comparatively easy to implement, since they intuitively follow the nearest-neighbour principle and thus do not require the layout of sample plots. Previous research studying distance sampling suggested that T-square sampling may also lead to an improved estimation of spatial tree diversity indices. We simulated distance and T-square sampling in six large fully mapped forest areas for seven tree diversity indices of which some competed for the same diversity aspect, i.e. tree location (dispersion), tree species and tree size diversity. Our results demonstrated that both distance and T-square sampling are indeed robust methods for sampling spatial measures of tree diversity. The sample size required for a sampling error of 10% does not exceed 20% of the total number of trees in a sampling area. T-square sampling has the ability to adapt to different spatial patterns of tree locations and this ability is key to the way the method controls estimation bias. The sample size required for species mingling and size differentiation clearly depends on the underlying spatial tree pattern in the sampling area. With most diversity indices, sample size reductions between 0.06% and 40% could be achieved by the application of T-square sampling compared to traditional distance sampling. All other conditions being equal, we could identify the uniform angle index, the species mingling index and the size differentiation index as those diversity indices achieving lower sampling error values than their competitors. For tree density estimations the Diggle and Byth estimators performed best. Based on our results, T-square sampling can be considered a robust sampling method for spatial tree diversity indices that is easy to apply in the field.

Influence of tree mycorrhizal type, tree species identity, and diversity on forest root-associated mycobiomes.

Understanding the complex interactions between trees and fungi is crucial for forest ecosystem management, yet the influence of tree mycorrhizal types, species identity, and diversity on tree-tree interactions and their root-associated fungal communities remains poorly understood. Our study addresses this gap by investigating root-associated fungal communities of different arbuscular mycorrhizal (AM) and ectomycorrhizal (EcM) tree species pairs (TSPs) in a subtropical tree diversity experiment, spanning monospecific, two-species, and multi-species mixtures, utilizing Illumina sequencing of the ITS2 region. The study reveals that tree mycorrhizal type significantly impacts the alpha diversity of root-associated fungi in monospecific stands. Meanwhile, tree species identity's influence is modulated by overall tree diversity. Tree-related variables and spatial distance emerged as major drivers of variations in fungal community composition. Notably, in multi-species mixtures, compositional differences between root fungal communities of AM and EcM trees diminish, indicating a convergence of fungal communities irrespective of mycorrhizal type. Interestingly, dual mycorrhizal fungal communities were observed in these multi-species mixtures. This research underscores the pivotal role of mycorrhizal partnerships and the interplay of biotic and abiotic factors in shaping root fungal communities, particularly in varied tree diversity settings, and its implications for effective forest management and biodiversity conservation.

Status of Tree Diversity in Digha, West Bengal, India with Special Reference to their Phytochemical Constituents

Status of Tree Diversity in Digha, West Bengal, India with Special Reference to their Phytochemical Constituents

Uncovering drivers of global tree diversity.

Uncovering drivers of global tree diversity.

Spatial phylogenetics of Fagales: Investigating drivers of temperate forest distributions

AbstractAimQuantifying the phylogenetic diversity of temperate trees is essential for understanding the processes that have shaped the modern distribution of temperate broadleaf forest and other major forest biomes. Here, we focus on Fagales, an iconic member of forests worldwide, to uncover global diversity and endemism patterns and investigate the distribution of root nodule symbiosis (RNS), an important morphological specialisation in this clade, as a key factor behind these patterns.LocationGlobal.TaxonFagales.MethodsWe combined phylogenetic data covering 60.2% of living species, fine‐scale distribution models covering 90% of species, and nodulation data covering all species to investigate the distribution of species richness and phylogenetic diversity at fine spatial scales compared to the distribution of RNS. We identify abiotic environmental factors associated with RNS and with Fagales diversity in general.ResultsWe find the highest species richness in temperate east Asia, eastern North America, and equatorial montane regions of Asia and Central America. By contrast, relative phylogenetic diversity (RPD) is highest at higher latitudes, where RNS also predominates. We found a strong spatial structuring of regionalisations of Fagales floras, reflecting distinct Northern and Southern Hemisphere floras (except a unique Afro‐Boreal region), each with distinct RNS‐environment relationships.Main ConclusionsAlthough species richness and phylogenetic regionalisation for Fagales accord well with traditional biogeographic concepts for temperate forests, this is not the case for RPD. RNS is almost universal in the highest RPD regions, which may reflect ecological filtering promoting RNS in these regions. Our results highlight the utility of global‐scale, clade‐specific spatial phylogenetics and its utility for understanding drivers of diversity in species‐rich clades.

Mycorrhizal type and tree diversity affect foliar elemental pools and stoichiometry.

Species-specific differences in nutrient acquisition strategies allow for complementary use of resources among plants in mixtures, which may be further shaped by mycorrhizal associations. However, empirical evidence of this potential role of mycorrhizae is scarce, particularly for tree communities. We investigated the impact of tree species richness and mycorrhizal types, arbuscular mycorrhizal fungi (AM) and ectomycorrhizal fungi (EM), on above- and belowground carbon (C), nitrogen (N), and phosphorus (P) dynamics. Soil and soil microbial biomass elemental dynamics showed weak responses to tree species richness and none to mycorrhizal type. However, foliar elemental concentrations, stoichiometry, and pools were significantly affected by both treatments. Tree species richness increased foliar C and P pools but not N pools. Additive partitioning analyses showed that net biodiversity effects of foliar C, N, P pools in EM tree communities were driven by selection effects, but in mixtures of both mycorrhizal types by complementarity effects. Furthermore, increased tree species richness reduced soil nitrate availability, over 2 yr. Our results indicate that positive effects of tree diversity on aboveground nutrient storage are mediated by complementary mycorrhizal strategies and highlight the importance of using mixtures composed of tree species with different types of mycorrhizae to achieve more multifunctional afforestation.

Shade tree trait diversity and functions in agroforestry systems: A review of which traits matter

Abstract Shade trees in agroforestry systems confer ecosystem services, such as enhanced soil fertility from diverse litter inputs, microclimate regulation via shade, and disease mitigation through trophic and abiotic interactions. With this thriving role of agroforestry in sustainable agriculture, particularly for tree crops, systematic and reliable methods to select shade trees for specific agroecosystem outcomes are crucial. Plant functional traits offer a framework to describe, select and manage shade trees. Over the last decade, shade tree leaf functional traits and whole plant traits have been assessed in agroforestry systems. Yet, we lack amalgamated information on (i) what we know about shade tree trait relationships with functions to achieve desired agroecosystem outcomes, (ii) how decades of shade tree selection by farmers impacts agroforests inter‐ and intraspecific trait diversity, and (iii) which shade tree traits should be considered for achieving farmer priorities. We consolidate literature on Coffea arabica (coffee) and Theobroma cacao (cocoa) agroforestry systems to summarize the role of shade tree functional traits in three key ecosystem functions: soil fertility, microclimate modification and crop productivity. We compile global and regional datasets on tree functional trait diversity to show the functional space of agroforestry tree species compared with the overall functional space observed in plants. Despite, or maybe because of, high shade tree diversity, shade tree trait characterization remains coarse and commonly measured at the community scale in the literature. Based on published trait data, we show that farmers adjust the functional composition of shade trees to increase the recycling of soil nutrients (high leaf nitrogen), the production of wood (skewing towards lower wood densities) and the production of fruits (tendency towards high seed size). Common shade trees in coffee and cocoa systems fall in the mid‐range of leaf acquisitive to conservative strategies, providing evidence that expanding shade tree portfolios can improve, or even accelerate, functions. Synthesis and applications: Based on the agroforestry literature and on trait‐environment relationships, we propose a matrix of shade tree traits that influence desirable agroecosystem outcomes for farmers, which can guide fine‐scale coordination of trait expression and agroforestry functions.