Subtropical Montane Forest Research Articles

Checklist of the genus Dendrophorbium (Senecioneae: Compositae) in Peru including a new combination and a new species

The genus Dendrophorbium occurs in South America with one species known from the Caribbean. Despite recent advances in taxonomy and phylogeny, there is a still lack of molecular studies on the delimitation and identification of the genus. Dendrophorbium is known to occupy a wide range of ecosystems mostly restricted to subtropical montane forests and montane scrub vegetation of the central Andes. In this study, a review of the species occurring in Peru is presented, in addition to material examined at different herbaria. The new combination D. ligulatum which is separated from D. yalusay, and the new species, D. arachnoideum is described from the department of Huánuco in central Peru. The species are assessed using the standards of the IUCN and additional notes are given.

Differential Responses of Bacterial and Fungal Community Structure in Soil to Nitrogen Deposition in Two Planted Forests in Southwest China in Relation to pH

Increased nitrogen deposition profoundly impacts ecosystem nutrient cycling and poses a significant ecological challenge. Soil microorganisms are vital for carbon and nutrient cycling in ecosystems; however, the response of soil microbial communities in subtropical planted coniferous forests to nitrogen deposition remains poorly understood. This study carried out a four-year nitrogen addition experiment in the subtropical montane forests of central Yunnan to explore the microbial community dynamics and the primary regulatory factors in two coniferous forests (P. yunnanensis Franch. and P. armandii Franch.) under prolonged nitrogen addition. We observed that nitrogen addition elicited different responses in soil bacterial and fungal communities between the two forest types. In P. yunnanensis Franch. plantations, nitrogen supplementation notably reduced soil bacterial α-diversity but increased fungal diversity. In contrast, P. armandii Franch. forests showed the opposite trends, indicating stand-specific differences. Nitrogen addition also led to significant changes in soil nutrient dynamics, increasing soil pH in P. yunnanensis Franch. forests and decreasing it in P. armandii Franch. forests. These changes in soil nutrients significantly affected the diversity, community structure, and network interactions of soil microbial communities, with distinct responses noted between stands. Specifically, nitrogen addition significantly influenced the β-diversity of fungal communities more than that of bacterial communities. It also reduced the complexity of bacterial interspecies interactions in P. yunnanensis Franch. forests while enhancing it in P. armandii Franch. forests. Conversely, low levels of nitrogen addition improved the stability of fungal networks in both forest types. Using random forest and structural equation modeling, soil pH, NH4+-N, and total nitrogen (TN) were identified as key factors regulating bacterial and fungal communities after nitrogen addition. The varied soil nutrient conditions led to different responses in microbial diversity to nitrogen deposition, with nitrogen treatments primarily shaping microbial communities through changes in soil pH and nitrogen availability. This study provides essential insights into the scientific and sustainable management of subtropical plantation forest ecosystems.

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.

Modeling the Role of Novel Ecosystems in Runoff and Soil Protection: Native and Non-native Subtropical Montane Forests

Modeling the Role of Novel Ecosystems in Runoff and Soil Protection: Native and Non-native Subtropical Montane Forests

Unveiling the Sources and Transfer of Mercury in Forest Bird Food Chains Using Techniques of Vivo-Nest Video Recording and Stable Isotopes.

Knowledge gaps in mercury (Hg) biomagnification in forest birds, especially in the most species-rich tropical and subtropical forests, limit our understanding of the ecological risks of Hg deposition to forest birds. This study aimed to quantify Hg bioaccumulation and transfer in the food chains of forest birds in a subtropical montane forest using a bird diet recorded by video and stable Hg isotope signals of biological and environmental samples. Results show that inorganic mercury (IHg) does not biomagnify along food chains, whereas methylmercury (MeHg) has trophic magnification factors of 7.4-8.1 for the basal resource-invertebrate-bird food chain. The video observations and MeHg mass balance model suggest that Niltava (Niltava sundara) nestlings ingest 78% of their MeHg from forest floor invertebrates, while Flycatcher (Eumyias thalassinus) nestlings ingest 59% from emergent aquatic invertebrates (which fly onto the canopy) and 40% from canopy invertebrates. The diet of Niltava nestlings contains 40% more MeHg than that of Flycatcher nestlings, resulting in a 60% higher MeHg concentration in their feather. Hg isotopic model shows that atmospheric Hg0 is the main Hg source in the forest bird food chains and contributes >68% in most organisms. However, three categories of canopy invertebrates receive ∼50% Hg from atmospheric Hg2+. Overall, we highlight the ecological risk of MeHg exposure for understory insectivorous birds caused by atmospheric Hg0 deposition and methylation on the forest floor.

Identifying medium- and large-sized mammal species sensitive to anthropogenic impacts for monitoring in subtropical montane forests

SummaryMedium- and large-sized mammals play important roles in maintaining forest ecosystem functions, and these functions often diminish when mammal species are depleted by human activities. Understanding the sensitivity or tolerance of mammal species to human pressure and detecting species changes through monitoring programmes can inform appropriate management decisions. The objective of our study was to identify medium- and large-sized mammal species that can be included in a monitoring programme in the Southern Yungas of Argentina. We used occupancy modelling to estimate the probability of habitat use (ψ) of 13 of 25 mammal species detected by 165 camera traps placed in forests across a range of human footprint index (HFI) values. As defined by the HFI, 54% of the study area is wilderness. The probabilities of habitat use of two mammal species were significantly associated with the HFI: the lowland tapir (Tapirus terrestris; ψ = 0.33, range = 0.22–0.50) was inversely associated with HFI values, whereas the grey brocket deer (Mazama gouazoubira; ψ = 0.79, range = 0.67–0.87) was positively associated with the HFI. Monitoring the probability of habitat use of the sensitive species (lowland tapir) could help us to detect changes in areas experiencing anthropogenic impacts before they cause extirpation, whereas the high probability of the habitat use values of the tolerant species (grey brocket deer) might indicate that anthropogenic impacts are strongly influencing habitat, signalling that mitigation strategies might be warranted. The Southern Yungas retains an intact mammal fauna, and we showed that the HFI is useful for monitoring anthropogenic impacts on these mammals. There are still opportunities to develop conservation strategies to minimize threats to mammal species in the region by implementing a monitoring programme with the proposed species.

Evaluating community-wide temporal sampling in passive acoustic monitoring: A comprehensive study of avian vocal patterns in subtropical montane forests.

From passive acoustic monitoring (PAM) recordings, the vocal activity rate (VAR), vocalizations per unit of time, can be calculated and is essential for assessing bird population abundance. However, VAR is subject to influences from a range of factors, including species and environmental conditions. Identifying the optimal sampling design to obtain representative acoustic data for VAR estimation is crucial for research objectives. PAM commonly uses temporal sampling strategies to decrease the volume of recordings and the resources needed for audio data management. Yet, the comprehensive impact of this sampling approach on VAR estimation remains insufficiently explored. In this study, we used vocalizations extracted from recordings of 12 bird species, taken at 14 PAM stations situated in subtropical montane forests over a four-month period, to assess the impact of temporal sampling on VAR across three distinct scales: short-term periodic, diel, and hourly. For short-term periodic sampling analysis, we employed hierarchical clustering analysis (HCA) and the coefficient of variation (CV). Generalized additive models (GAMs) were utilized for diel sampling analysis, and we determined the average difference in VAR values per minute for the hourly sampling analysis. We identified significant day and species-specific VAR fluctuations. The survey season was divided into five segments; the earliest two showed high variability and are best avoided for surveys. Data from days with heavy rain and strong winds showed reduced VAR values and should be excluded from analysis. Continuous recordings spanning at least seven days, extending to 14 days is optimal for minimizing sampling variance. Morning chorus recordings effectively capture the majority of bird vocalizations, and hourly sampling with frequent, shorter intervals aligns closely with continuous recording outcomes. While our findings are context-specific, they highlight the significance of strategic sampling in avian monitoring, optimizing resource utilization and enhancing the breadth of monitoring efforts.

Assemblage of forest communities in subtropical montane forests of western Mexico

Abstract Functional diversity indices have been used to differentiate the relative contribution of stochastic and deterministic processes that modulate the assemblage of communities; however, knowledge regarding the relative contribution of assemblage mechanisms in forest communities is scarce. We analysed the assembly mechanisms driving forest assemblages along a topographic gradient at two spatial scales (1000 m2 and 3000 m2) for three different forest types from subtropical mountain forests (pine-oak, mixed pine-broadleaf and broadleaf forest) in western Mexico, using null models of multi-trait indices. The forest structure differed along the topographic gradient. Upper slopes were dominated by Pinus douglasiana with an importance value index (IVI) of 0.8, while 10 and 13 tree species were required in the middle and lower slopes, respectively, to reach the same IVI. The results support the idea that the subtropical montane forest of western Mexico is a mosaic of communities, when analysed at a scale of 1000 m2 the forest assembly was mainly explained by stochastic processes, while analysis at the scale of 3000 m2 showed that functional convergence of species were the main mechanisms of the assemblage of the pine-oak forest communities due to an abiotic stressful environment.

Fine roots and extramatrical mycelia regulate the composition of soil organic carbon and nitrogen in a subtropical montane forest

Roots and extramatrical mycelia (EMM) influence carbon (C) and nitrogen (N) cycling in soil, but the effects of roots and EMM on the composition of soil organic carbon (SOC) and N are still unknown, especially in subtropical forests. A two-year field study was conducted in Cryptomeria japonica and Cyclobalanopsis multinervis forests in a subtropical montane forest. Ingrowth cores with different mesh sizes (2 mm, 48 µm, and 1 µm) were used to distinguish the effects of roots and EMM on SOC and total N concentrations, and the composition of SOC and N. Compared to the R0Emm0 (ingrowth cores with 1 µm mesh, no presence roots and EMM), presence roots and EMM (R1Emm1, ingrowth cores with 2 mm mesh) increased SOC concentration in the C. japonica forest, but had no effect on the composition of SOC. In the C. multinervis forest, R1Emm1 had no effect on SOC concentration, but increased the proportion of recalcitrant C. Presence of EMM but no roots (R0Emm1, ingrowth cores with 48 µm mesh) had no effect on SOC concentration in the C. japonica forest, but decreased the proportion of recalcitrant C in the C. multinervis forest. In the C. multinervis forest, R0Emm1 decreased SOC concentration but had no effect on the composition of SOC. Compared to the R0Emm0, R1Emm1 had higher soil total N concentration and the proportion of recalcitrant N in both forests, while R0Emm1 had no effect on total N concentration and the proportions of N fractions. The proportions of soil recalcitrant C and N were positively affected by fine root biomass, indicating that roots are important sources of recalcitrant C and N. These results highlight that in subtropical forest, roots could potentially enhance soil C and N accumulation, especially of recalcitrant C and N compounds, while EMM alone might potentially induce soil C loss, especially recalcitrant C loss. These findings enhance our understanding of the underlying mechanisms of SOC stabilization and plant-soil-fungi relationship.

Influence of Topography on UAV LiDAR-Based LAI Estimation in Subtropical Mountainous Secondary Broadleaf Forests

The leaf area index (LAI) serves as a crucial metric in quantifying the structure and density of vegetation canopies, playing an instrumental role in determining vegetation productivity, nutrient and water utilization, and carbon balance dynamics. In subtropical montane forests, the pronounced spatial heterogeneity combined with undulating terrain introduces significant challenges for the optical remote sensing inversion accuracy of LAI, thereby complicating the process of ground validation data collection. The emergence of UAV LiDAR offers an innovative monitoring methodology for canopy LAI inversion in these terrains. This study assesses the implications of altitudinal variations on the attributes of UAV LiDAR point clouds, such as point density, beam footprint, and off-nadir scan angle, and their subsequent ramifications for LAI estimation accuracy. Our findings underscore that with increased altitude, both the average off-nadir scan angle and point density exhibit an ascending trend, while the beam footprint showcases a distinct negative correlation, with a correlation coefficient (R) reaching 0.7. In contrast to parallel flight paths, LAI estimates derived from intersecting flight paths demonstrate superior precision, denoted by R2 = 0.70, RMSE = 0.75, and bias = 0.42. Notably, LAI estimation discrepancies intensify from upper slope positions to middle positions and further to lower ones, amplifying with the steepness of the gradient. Alterations in point cloud attributes induced by the terrain, particularly the off-nadir scan angle and beam footprint, emerge as critical influencers on the precision of LAI estimations. Strategies encompassing refined flight path intervals or multi-directional point cloud data acquisition are proposed to bolster the accuracy of canopy structural parameter estimations in montane landscapes.

Divergences in stem and leaf traits between lianas and coexisting trees in a subtropical montane forest

Abstract Patterns in functional trait variation associated with the ecological strategies of lianas and trees in subtropical montane forests remain poorly understood due to lack of trait comparisons. Here, we filled this gap by investigating trait divergence between lianas and trees with different leaf habits for 13 traits of 33 species (7 deciduous and 4 evergreen liana species, and 10 deciduous and 12 evergreen tree species) in a subtropical montane forest in southwestern China. We found that lianas had significantly larger stem xylem vessel diameter, higher theoretical hydraulic conductivity, specific leaf area, leaf nitrogen, and phosphorus concentrations, but lower leaf dry-matter content and N/P ratio than sympatric trees, indicating that lianas employ an acquisitive ecological strategy, with a more efficient stem hydraulic system and more productive leaves. In contrast to trees, lianas exhibited a larger variation in vessel diameter, with a few wide and many narrow vessels in the xylem, indicating a greater vessel dimorphism. Growth form explained 48.7% of the total trait variation, while leaf habit only explained 3.8% of trait variation, without significant interaction between growth form and leaf habit. In addition, significant stem–leaf trait relationships were only found in trees, but not in lianas, indicating decoupling of stem hydraulic function and leaf traits in subtropical lianas. These results suggest that subtropical montane lianas and trees differ strikingly in stem and leaf functional traits. Further studies are warranted to strengthen our understanding of the mechanisms underlying the strong divergence in ecological strategies between lianas and trees in subtropical forest ecosystems.

Dynamic response of root-associated fungal community structure to nitrogen and phosphorus additions in a subtropical forest

The impacts of nitrogen (N) and phosphorus (P) additions on root-associated fungi (RAF) of mixed roots in forest soils remain poorly understood. We investigated how RAF communities respond to N and P inputs in a subtropical montane forest using a time-series sampling approach. Our results showed that sampling time had a significant effect on total fungal richness, while the N addition had significant impacts on symbiotrophic rather than saprotrophic fungal richness. RAF community composition was strongly influenced by P addition treatments regardless of sampling time. Furthermore, we found that RAF community structure was mainly affected by soil NO3–-N, C/N and N/P ratios. This influence could be ascribed to the direct control of fungal activities and the indirect effects of fertilization on soil properties. Together, our findings highlight the importance of considering temporal variation in RAF responses to fertilization for a more comprehensive understanding of fungal community dynamics.

Evaluating community-wide temporal sampling in passive acoustic monitoring: A comprehensive study of avian vocal patterns in subtropical montane forests

Background: Passive acoustic monitoring (PAM) has become a popular tool for bird monitoring, with vocal activity rate (VAR) being a key metric to gauge bird populations. However, the effective temporal sampling design at the community level for representative VAR data remains underexplored. Methods: In this study, we used vocalizations extracted from recordings of 12 bird species, taken at 14 PAM stations situated in subtropical montane forests over a four-month period, to assess the impact of temporal sampling on VAR across three distinct scales: seasonal, diel, and hourly. For seasonal sampling analysis, we employed hierarchical clustering analysis (HCA) and the coefficient of variation (CV). Generalized additive models (GAMs) were utilized for diel sampling analysis, and we determined the average difference in VAR values per minute for the hourly sampling analysis. Results: We identified significant day and species-specific VAR fluctuations. The survey season was divided into five segments; the earliest two showed high variability and are best avoided for surveys. Data from days with heavy rain and strong winds showed reduced VAR values and should be excluded from analysis. Continuous recordings spanning at least seven days, extending to 14 days is optimal for minimizing sampling variance. Morning chorus recordings effectively capture the majority of bird vocalizations, and hourly sampling with frequent, shorter intervals aligns closely with continuous recording outcomes. Conclusions: While our findings are context-specific, they highlight the significance of strategic sampling in avian monitoring, optimizing resource utilization and enhancing the breadth of monitoring efforts.

Soil Phosphorus Availability Controls Deterministic and Stochastic Processes of Soil Microbial Community along an Elevational Gradient in Subtropical Forests

Revealing the assembly mechanisms of the soil microbial community, which is crucial to comprehend microbial biodiversity, is a central focus in ecology. The distribution patterns of microbial elevational diversity have been extensively studied, but their assembly processes and drivers remain unclear. Therefore, it is essential to unravel the relationship between the deterministic and stochastic processes of the microbial community assembly and elevational gradients. Here, our study built upon previous physicochemical analyses of soil samples collected along an elevational gradient (900–1500 m) in Daiyun mountain, a subtropical forest located in southeastern China. Using the phylogenetic-bin-based null model analysis (icamp) and multiple regression on matrices approach, we explored the major drivers that influence the assembly processes of soil bacterial and fungal community across elevations. The results showed that: (1) bacterial rare taxa exhibited a broad habitat niche breadth along the elevational gradient; (2) homogeneous selection and homogenizing dispersal proved to be the most important assembly processes for the bacterial and fungal community; (3) soil phosphorus availability mediated the relative importance of deterministic and stochastic processes in the soil microbial community. Notably, the relative abundance of dominant microbial taxa controlled by homogeneous selection and homogenizing dispersal increased with increasing soil phosphorus availability. Collectively, the assembly processes of microbial elevational communities of the subtropical mountains in China can be explained to some extent by variations in the soil phosphorus availability. This conclusion provides valuable insights into the prediction of soil microbial diversity and phosphorus nutrient cycling in subtropical montane forests.

Seeing Trees from Drones: The Role of Leaf Phenology Transition in Mapping Species Distribution in Species-Rich Montane Forests

The complex topography of subtropical montane forests favors the coexistence of diverse plant species, making these species-rich forests a high priority for biodiversity monitoring, prediction, and conservation. Mapping tree species distribution accurately in these areas is an essential basis for biodiversity research and is often challenging due to their complex structure. Remote sensing has widely been used for mapping tree species, but relatively little attention has been paid to species-rich montane forests. In this study, the capability of high-resolution UAV remote sensing imagery for mapping six tree species, standing dead trees, and canopy gaps was tested in a subtropical montane forest at an elevation of 816~1165 m in eastern China. Spectral, spatial geometrical, and textural features in a specific phenological period when obvious color differences among the leaves of different species were extracted, and four object-based classification algorithms (K-nearest neighbor (KNN), classification and regression tree (CART), support vector machine (SVM), and random forest (RF)) were used for tree species classification. We found that: (1) mapping tree species distribution using low-cost UAV RGB imagery in a specific leaf phenological period has great application potential in subtropical montane forests with complex terrain. (2) Plant spectral features in the leaf senescence period contributed significantly to species classification, while the contribution of textural features was limited. The highest classification accuracy was 83% using KNN with the combination of spectral and spatial geometrical features. (3) Topographical complexity had a significant impact on mapping species distribution. The classification accuracy was generally higher in steep areas, especially in the low slope area.

Relationship among vegetation structure and mixed-species flocks composition along the latitudinal gradient of the subtropical montane forest of the Yungas, Argentina.

The structural and physiognomic characteristics of forests and mountain forest are fundamental aspects that influence the richness, abundance and composition in the bird community. The objective of the present work was to analyse how the vegetation structure could influence the species composition of mixed-species flocks (MSF), along the latitudinal gradient of the subtropical montane forest of the Yungas of Argentina. Eight sites were studied along the 700 km of distribution of the Argentine Yungas. Richness and abundance of MSF were determined. In addition, different variables of composition and structure of the vegetation were analysed. Multivariate analysis indicated that vertical strata coverage and litter depth were the main variables associated with changes in the species composition of MSF along the gradient. Variation in MSF composition within the Yungas was associated with the physiognomy of the subtropical montane forest, which could indicate that it is strongly linked to the condition of the local vegetation. Substantial changes in vegetation could drastically change the composition of the resident flocks. This article is part of the theme issue 'Mixed-species groups and aggregations: shaping ecological and behavioural patterns and processes'.

Leaf phenotypic plasticity coupled with integration facilitates the adaptation of plants to enhanced N deposition

The response of leaf functional traits can provide vital insight into the adaptive strategies of plants under global change. However, empirical knowledge on the acclimation of functional coordination between phenotypic plasticity and integration to increased nitrogen (N) deposition is still scarce. The variation of leaf functional traits of two dominant seedling species, Machilus gamblei and Neolitsea polycarpa, across four N deposition rates (0, 3, 6, and 12 kg N ha−1yr−1), along with the relationship between leaf phenotypic plasticity and integration were investigated in a subtropical montane forest. We found that enhanced N deposition promoted the development of seedling traits toward the direction of resource acquisition, including improved leaf N content, specific leaf area and photosynthetic performance. Appropriate N deposition (≤6 kg N ha−1 yr−1) might induce the optimization of leaf functional traits to promote the capability and efficiency of nutrient use and photosynthesis in seedlings. However, excessive N deposition (12 kg N ha−1 yr−1) would result in detrimental effects on leaf morphological and physiological traits, thus inhibiting the efficiency in resource acquisition. A positive relationship occurred between leaf phenotypic plasticity and integration in both seedling species, implied that higher plasticity of leaf functional traits likely led to better integration with other traits under N deposition. Overall, our study emphasized that leaf functional traits could rapidly respond to changes in N resource, while the coordination between leaf phenotypic plasticity and integration can facilitate the adaptation of tree seedlings in coping with enhanced N deposition. Further studies are still needed on the role of leaf phenotypic plasticity and integration in plant fitness for predicting ecosystem functioning and forest dynamics, especially in the context of future high N deposition.

Birds Visiting Flowers of Erythrina suberosa: Their Abundance, Frequency of Visits and Role as Pollinators in a Sub-Tropical Montane Forest of Garhwal Himalaya

Bird pollination is specific among flowering plants which support mostly cross pollination and has been regarded as an important pollination syndrome. Frequency of bird pollinators visiting flowers of the corky coral tree Erythrina suberosa Roxb., was studied in a subtropical montane forest located in Garhwal Himalaya, India. Forty trees were selected randomly in the population and the observations on birds visitors were recorded for 10 days during peak flowering. In total 18 bird species were found visiting flowers of E. suberosa. The bird species belonging to Passeriformes, Piciformes, Psittaciformes, and Cuculiformes were observed most frequently. The highest bird frequency and abundance among flower-visiting birds were recorded for the red-billed blue magpie Urocissa erythrorhyncha (26 ± 3.2 individuals per hour per branch and 60 birds per tree, respectively), whereas the lowest – for the verditer flycatcher Eumyias thalassinus (2 ± 0.02 individuals per hour per branch and 6 individuals per tree, respectively). Majority of the bird species followed bimodal pattern of foraging on nectar in a day (mostly morning and evenings), which is consistent with other studies carried out for other ornithophilous tree species in the Himalayan region. The birds observed in this study are presumed to be pollinators, as the majority of birds foraged on nectar of properly opened flowers oriented upwards; however, possibility of nectar robbing cannot be excluded and requires further investigation in future studies.

Tree species composition along environmental and disturbance gradients in tropical sub-montane forests, Tanzania.

Understanding the environmental and disturbance determinants of tree species dominance and community composition in an ecosystem, is important for informing management and conservation decisions, through maintaining or improving the existing forest composition and structure. This study was carried out to quantify the relationship between forest tree composition structure and environmental and disturbance gradients, in a tropical sub-montane forest of Eastern Usambara. Vegetation, environmental, and anthropogenic disturbance data for 58 plots across Amani and Nilo nature forest reserves were obtained. Agglomerative hierarchical cluster analysis and canonical correspondence analysis (CCA) were used to identify plant communities and analyze the influence of environmental variables and anthropogenic disturbances on tree species and community composition respectively. Four communities were identified and CCA results showed that the variation was significantly related to elevation, pH, Annual mean temperature, temperature seasonality, phosphorus nutrients and pressures from adjacent villages and roads. Likewise, environmental factors (climate, soil and topography) explained the most variation (14.5%) of tree and community composition in relation to disturbance pressure (2.5%). The large and significant variation in tree species and community patterns explained by environmental factors suggests a need for site-specific assessment of environmental properties for biodiversity conservation plans. Similarly, the intensification of human activities and associated impacts on natural environment should be minimized to maintain forest species composition patterns and communities. The findings are useful in guiding in policy interventions that focus on minimizing human disturbances in the forests and could aid in preserving and restoring the functional organization and tree species composition of the sub-tropical montane forests.

A new Rattus species and its associated micromammals from the Pliocene Yangyi Formation in Baoshan, western Yunnan, China

ABSTRACT Rattus (sensu stricto) is one of the groups of rodents and is most closely related to human activities. The diversity of extant Rattus species is the highest among rodents, but fossil species are rare, mainly found in Asia during the Late Pliocene to Early Pleistocene. Here, we described a Late Pliocene new species of Rattus based on material from the upper Yangyi Formation in Baoshan county, Yunnan Province, China. The primitive morphological characteristics of fewer molar roots, t12 preserved on M1–2, t9 preserved on M3, and buccal stylids well developed on lower molars indicate that the new Rattus is by far the most primitive form in the Rattus genus. In dental morphology of Rattus, the molars have an evolutionary trend of gradually increasing the number of roots and fusing cusps into an arched ridge, reduction to disappearance of the t7 and t12 on upper molars, and reduction to disappearance of the mesiocentral cusp on m1, the anterior buccal stylid on m1–3 and hypoconid on m3. Discovery of the new Rattus from Baoshan confirms that Rattus probably originated in southern Asia before the Late Pliocene, and also provides new fossil evidence to calibrate the molecular clock of the divergence of Rattus from other murines. In addition, we also reported five associated small mammals: Neotetracus sp. nov., Anourosorex qianensis, Soricidae gen. et sp. indet., Ia io, and Kowalskia sp. Most of them inhabit warm and humid tropical or subtropical montane forests or shrubland environments. The composition of this mammalian assemblage indicates that the paleoelevation and paleoclimate of Baoshan area in the Pliocene are very similar to those of the present.