Mixed Forest Research Articles

Identifying optimal cloud cover for enhanced forest carbon uptake: Periodic-case NEE-overshoot modelling

On certain kinds of cloudy days, many forested ecosystems exhibit enhanced carbon uptake and water-use efficiency-the cloudy-day forest flux anomaly. Using ensemble methods to analyze eddy-covariance fluxes, we have diagnosed net ecosystem exchange (NEE) and water-use efficiency (WUE) of a temperate broadleaf forest and a tropical evergreen forest as they responded to natural fluctuating-light regimes. Here we apply average NEE and evapotranspiration solutions of a first-order dynamic model to describe the observed whole-canopy sensitivity to periodic light. On partly-cloudy days, maximum overall NEE enhancements over conventional steady-state equilibrium estimates are ≈ 25% for a midlatitude deciduous forest and ≈ 15% for a tropical evergreen forest. This finding supports our conclusion that in many cases the cloudy-day anomaly is a consequence of a dynamic response by the trees responding to fluctuating-light regimes occasioned by passing cumulus clouds.

Modern Pollen Signatures and Vegetation Dynamics in Northwestern Himalaya, India

ABSTRACT Palynological studies have been conducted for the first time in the Renukaji Wildlife Sanctuary (RWS), a Sal-dominated region within the foothills of Northwestern (NW) Himalaya in Himachal Pradesh, India. This research enhances our understanding of the relationship between modern pollen rain and vegetation, as well as pollen representation in sediments. Furthermore, it contributes to palaeovegetation reconstruction based on paleoclimatic trends by improving our interpretation of pollen deposition patterns. The study area was delineated into three distinct zones based on biological niche characteristics: Zone 1 (Recreation Zone), Zone 2 (Buffer Zone), and Zone 3 (Core Zone). Pollen analysis conducted on 30 surface soil samples and moss cushions, collected from all three zones, reveals the dominance of dry deciduous taxa, followed by extra-terrestrial taxa and wet deciduous taxa. Land Use Land Cover (LULC) analysis performed using satellite data reveals that Shorea robusta (Sal) mixed forest covers 32% of land, followed by Pinus spp. (8%) and their associates (25%). Shorea robusta, a mixed wet deciduous taxon and high pollen producer, exhibits low pollen counts, possibly due to chemical and microbial decomposition or low pollen dispersal efficiency. This study utilises a comparative database correlating pollen data with contemporary vegetation patterns to establish a robust framework for assessing sedimentary pollen sequences. Through this approach, we aim to elucidate past vegetation dynamics and infer climate fluctuations within the NW Himalaya.

Soil Respiration in Anthropogenic Disturbed Ecosystems Compared to Deciduous Forests in the Urban Industrial Area

In urban industrial area, mining activity directly affects the dynamic of carbon, and consequently, the release of carbon dioxide (CO2) into the atmosphere. The main objective of this research is to study the impact of most important abiotic environmental factors on soil respiration in post-coalmine ecosystems. The moisture and temperature of the soil, along with CO2 outflow from the soil, were measured over three consecutive seasons, using 92 samples from coalmine heaps and 10 samples from deciduous forests in the same urban industrial region. Based on a survey of 396 species, a cluster analysis distinguished all deciduous and 22 forest plots grown on coalmine heaps from herbaceous plots from same coalmine heaps. The lowest soil respiration rate (0.62 mg CO2 per hour per square meter) was recorded in the herbaceous vegetation class on coalmine heaps, compared to (0.76 mg and 0.96 mg) from coalmine-heap forests and deciduous forests, respectively. Species richness and diversity positively affected soil respiration in heap herbaceous plots, though this effect was less pronounced in forests grown on coalmine heaps and in deciduous mixed forests. Unlike soil water content, soil temperature negatively correlated with soil respiration on coalmine heaps, diverging from the well-studied positive impact of soil temperature and respiration in deciduous mixed forests. Our spatial and temporal analyses emphasize that the water content of the substrate is the most significant abiotic element that affects the soil respiration on coalmine heaps positively during early vegetation succession.

Conserved responses of water use to evaporative demand in mixed forest across seasons in low subtropical China

The positive correlation between diversity and production has been extensively documented. Given the intrinsic relationship between production and plant water consumption, it was anticipated that mixed forests would exhibit different water use compared to pure forests. In this study, the responses of water use to vapour pressure deficit were analyzed by monitoring the sap flow of Schima superba in both pure and mixed forests, as well as Castanopsis chinensis in mixed forest. Additionally, the relationships among leaf and stem traits were examined by measuring specific leaf area (SLA), N and P concentration per unit leaf mass, leaf δ18O and δ13C and wood density of sapwood (WD) during both wet and dry seasons. The results showed that S. superba demonstrated a comparable regulation of water use during both wet and dry seasons in mixed forest, whereas it exhibited less strict water use regulation during the wet season in comparison to the dry season in pure forest. Regardless of whether the forests were pure or mixed, both leaf δ13C and WD remained consistent across seasons, while there was an increase in SLA during the wet season compared to the dry season for S. superba. There was a different seasonal change in leaf δ18O for S. superba in pure and mixed forests. Water use and leaf economic spectrum may determine the adaptive strategies of coexisting species, and the coexisting tree species in mixed forest exhibited a resource-use differentiation, as indicated by seasonal variations in leaf and stem traits, likely explaining the conserved responses of sap flow to evaporative demand. Our research might provide insights into the impact of tree interaction on water use strategies and the water use-based forest management under current climate change.

Gastrochilusbalangshanensis (Orchidaceae, Aeridinae), a new subalpine epiphytic orchid from the Mountains of Southwest China.

Gastrochilusbalangshanensis, a new orchid species from the Balang Mountain, Sichuan Province, Southwest China, is described and illustrated. It morphologically resembles G.affinis, but differs in having shorter stems, a reniform epichile and a sub-hemispherical hypochile (spur), obtuse-rounded at the apex. The results of molecular phylogenetic analyses based on nuclear ribosome internal transcribed spacer (nrITS) and four chloroplast DNA markers (matK, psbA-trnH, psbM-trnD and trnL-F) from 50 Gastrochilus species indicate that G.balangshanensis is closely related to G.heminii and G.bernhardtianus, also endemic to the Hengduan Mountains. The novelty is a branch and trunk epiphyte in mixed coniferous forest.

The influence of climatic and anthropogenic factors on the productivity of forest stands in the ecotone of the northern treeline on the Yamal peninsula

On 12 sample plots established in the ecotone of the northern forest boundary in the Khadyta-Yakha River valley on the Yamal Peninsula, time of emergence and death, as well as productivity of about 1000 Siberian larch (Larix sibirica Ledeb.) and Siberian spruce (Picea obovata Ledeb.) trees were analyzed. Over the last 140 years, there has been a sharp increase in the stocks and annual growth of stem phytomass of woody plants within the studied ecotone. Since the 1970s, the average annual growth of phytomass has been increased by 1.2–39 times, which was facilitated by a 0.9оC increase in average June–July air temperature. However, this effect is insignificant in areas of mixed open forests subjected to periodic logging.

The evolution of ectomycorrhizal symbiosis and host-plant switches are the main drivers for diversification of Amanitaceae (Agaricales, Basidiomycota)

BackgroundEvolutionary radiation is widely recognized as a mode of species diversification, but the drivers of the rapid diversification of fungi remain largely unknown. Here, we used Amanitaceae, one of the most diverse families of macro-fungi, to investigate the mechanism underlying its diversification.ResultsThe ancestral state of the nutritional modes was assessed based on phylogenies obtained from fragments of 36 single-copy genes and stable isotope analyses of carbon and nitrogen. Moreover, a number of time-, trait-, and paleotemperature-dependent models were employed to investigate if the acquisition of ectomycorrhizal (ECM) symbiosis and climate changes promoted the diversification of Amanitaceae. The results indicate that the evolution of ECM symbiosis has a single evolutionary origin in Amanitaceae. The earliest increase in diversification coincided with the acquisition of the ECM symbiosis with angiosperms in the middle Cretaceous. The recent explosive diversification was primarily triggered by the host-plant switches from angiosperms to the mixed forests dominated by Fagaceae, Salicaceae, and Pinaceae or to Pinaceae.ConclusionsOur study provides a good example of integrating phylogeny, nutritional mode evolution, and ecological analyses for deciphering the mechanisms underlying fungal evolutionary diversification. This study also provides new insights into how the transition to ECM symbiosis has driven the diversification of fungi.

Comparative analysis of event runoff coefficients and curve numbers in contrasting urban environments based on observed rainfall-runoff data

Recently, there has been a growing recognition that the generic values of runoff coefficient (C) and curve number (CN) from standard lookup tables in the literature may not accurately capture the specific characteristics of a given catchment. This study aims to estimate and compare the event C and CN of two contrasting urban catchments in Ljubljana, Slovenia using observed rainfall-runoff data. Estimated parameter values were compared to the tabulated values from the literature (i.e., ASCE, 1992; USDA-NRCS, 2004). Seasonal changes of C and CN, along with diurnal streamflow patterns, were also analyzed to understand the eco-hydrological processes in the urban forest. The results demonstrated that the urban mixed forest exhibited high variability of Cs across all rainfall events with a mean and median of 0.11 and 0.062, respectively. Most of the C values observed in the urban area are clustered around the central tendency with a mean and median of 0.60. These mean C values in both catchments were lower than the tabulated values in the ASCE (1992) design manual. Mean and median CN values in the urban area were 95.45 and 96.81, respectively, lower than the urban mixed forest’s CN values of 82.69 and 83.95. An asymptotic CN∞ of 90.69 was found for the urban area and 71.71 for the urban mixed forest. Central tendency-derived CN values tend to be slightly higher than the tabulated values from USDA-NRCS (2004) and gridded values from GCN250 (Jaafar et al., 2019), while asymptotic CN∞ values were lower. Using central tendency measures as the single lumped value of C and CN may provide a reasonable representation of the runoff behavior in the studied urban area. However, this may present certain challenges in the urban forest catchment. Additionally, pre-event soil moisture conditions and specific storm characteristics contributed to the observed variations in C and CN. Bi-monthly analysis showed that C and CN were high during the autumn and winter months. Diurnal streamflow pattern is most prevalent during low-flow and precipitation-free periods while exhibiting seasonal structures in terms of the shape and timing of maxima and minima. Local estimation of C and CN allows for a more tailored representation of the catchment’s hydrological behavior.

Flammulated Owls Exhibit Diel Variation in Space Use

ABSTRACT A home range determines the resources animals can access, and the size of a home range often reflects resource availability and energetic requirements of individuals. The Flammulated Owl (Psiloscops flammeolus) is a cryptic small forest owl that breeds in mixed conifer forests in western North America. The home ranges of individuals generally comprise open forests with large trees, but we have yet to fully understand temporal variation in this species’ use of space and the habitat structures that drive space use at a fine scale. During the 2017 summer breeding season (May–July), we tracked the movement of six territorial males with GPS tags to estimate temporal variation in space use and examined resource selection for fine-scale habitat characteristics within home ranges. Results suggest that individual movement was more constrained around nests early at night, but the area of space used was consistent between the incubation and nestling stages. The owls’ activity centers near their nests had denser ground cover than available habitat, indicating that the forest understory may be valuable for this species’ breeding ecology. As forested landcover rapidly changes in western North America, understanding the spatial behavior and fine scale habitat associations of this species and others is increasingly important.

Climate change and exotic pathogens shift carbon allocation in Mediterranean mixed forests

Abstract Forecasting the effects of global change drivers on ecosystems is one of the most pressing challenges for scientists worldwide. Particularly, climate change and exotic pathogens might have a large impact on plant community dynamics and ecosystem functioning through changes in carbon uptake and sinks. Nevertheless, we still have a poor understanding of the combined effects of these two drivers on plant communities. Here, we explored the impact of rainfall reduction and exotic pathogens on the carbon balance of Mediterranean tree species. For this, we performed a 3‐year field experiment taking advantage of rainfall exclusion infrastructures (30% exclusion) installed in the southernmost European oak forests invaded by the aggressive exotic pathogen Phytophthora cinnamomi. We measured a set of 10 variables representative of tree carbon sources (photosynthetic rates) and sinks (primary production, reproduction, defence, and reserves) in adult trees of three species in two forest types: closed forests of Quercus suber and Q. canariensis, and open woodlands of Q. suber and Olea europaea. We found a large variability in the sensitivity of the different carbon sources and sinks to the effects of drought and pathogens, from variables highly sensitive to both factors (carbon fixation and reproduction, root chemistry) to variables only responsive to drought (litter production) or totally unresponsive (tree trunk, leaf chemistry). Although negative effects predominated, positive effects of rainfall exclusion were also detected in wet years, likely due to a reduction of pathogen abundance in drier soil. Trade‐offs between carbon sinks appeared in all tree species, but rainfall exclusion only modified trade‐offs in Q. suber, the species most susceptible to P. cinnamomi. Synthesis. We provide evidence on the complexity of the combined effects of abiotic (drought) and biotic (pathogens) global change drivers on carbon source and sinks of adult trees, including both negative direct effects and positive indirect effects. Our results showed that these effects varied among co‐existing species, particularly for carbon sinks directly related to tree demography (reproduction). Therefore, long‐term changes in the structure of Mediterranean mixed forests might be expected towards the dominance of species highly resistant to both drought and pathogens.

Exotic mangrove Laguncularia racemosa litter input accelerates nutrient cycling in mangrove ecosystems.

Exotic plant litter presents different chemical and physical properties relative to native plant litter and alters ecosystem processes and functions that may facilitate exotic plant dispersal. However, these effects are largely unknown, especially within wetland ecosystems. This study examines whether introducing litter from theexotic mangrove Laguncularia racemosa could result in (1) accelerated community litter decomposition rates and increased nutrient cycling rates and (2)microbial community structure changes in the invaded areas. A single decomposition experiment using litterbags was conducted to examine the short-term effects of L. racemosa litter in the native mangrove forest ecosystem. The soil nutrients and microbial communities of Rhizophora stylosa, L. racemosa, and mixed forests were also compared to explore the long-term cumulative effects of L. racemosa litter in native ecosystems. The results indicated that L. racemosa has lower-quality leaf litter than R. stylosa and a significantly faster decomposition rate. This may result from changes in the soil microbial community structure caused by L. racemosa leaf litter input, which favors the decomposition of its own litter. Both the short-term and cumulative effect experiments demonstrated that L. racemosa leaf litter significantly increased the relative abundance of microbes related to litter decomposition, such as Proteobacteria and Bdellovibrionota, and enhanced the alpha diversity of soil fungi, thus creating a microbial environment conducive to L. racemosa leaf litter decomposition. Moreover, the accumulation of soil nutrients was lower under L. racemosa than under R. stylosa over several years. This may be related to the more rapid growth of L. racemosa, which causes soil nutrient absorption and storage within the plant tissues, thereby reducing the soil nutrient content. Inputting exotic mangrove L. racemosa leaf litter reduced the soil blue carbon content, potentially adversely affecting global climate change. L. racemosa may employ a unique strategy to lower soil nutrient levels in native mangroves based on its low-quality leaf litter, thereby weakening the competitive ability of native plants that are intolerant to low-nutrient conditions and enhancing its own competitive advantage to further spread into these areas. In summary, the input of exotic L. racemosa leaf litter accelerates nutrient cycling in local mangroves.

The Responses of Soil Extracellular Enzyme Activities and Microbial Nutrients to the Interaction between Nitrogen and Phosphorus Additions and Apoplastic Litter in Broad-Leaved Korean Pine Forests in Northeast China

The impact of nitrogen and phosphorus deposition alternations, as well as apoplastic litter quality and quantity, on soil nutrient cycling and soil carbon pool processes in forest ecosystems is of considerable importance. Soil ecological enzyme chemistry is a powerful tool for elucidating the nutrient limitations of microbial growth and metabolic processes. In order to explore the responding mechanisms of soil ecological enzyme chemistry to the simultaneous changes in apoplast input and nitrogen and phosphorus deposition in temperate coniferous and broad-leaved mixed forests, an outdoor simulating experiment was conducted. The results demonstrate that the treatments involving apoplastic material and nitrogen and phosphorus additions had significantly impacted soil nutrient levels across different forest types. Apoplastic treatments and N-P additions had a significant effect on the soil total organic carbon (TOC), dissolved organic carbon (DOC), soil total soluble nitrogen (TSN), soil available phosphorus (SAP), soil total nitrogen (TN), soil total phosphorus (TP), and microbial biomass carbon (MBC). However, the effects on soil microbial biomass (MBN) and microbial biomass phosphorus (MBP) were insignificant. The apomictic treatments with N and P addition did not result in a statistically significant change in soil C-hydrolase activities (β-1,4-glucosidase BG, β-1,4-xylosidase BX, cellobiohydrolase CBH, phenol oxidase POX, and peroxidase PER), N-hydrolase activities (β-1,4-N-acetylglucosaminidase NAG and L-leucine aminopeptidase LAP), or P-hydrolase activities (Acid phosphatase AP). Although the apomictic treatments did not yield a significant overall impact on carbon hydrolase activity, they influenced the activity of specific enzymes, such as CBH, LAP, and PER, to varying degrees. The effects on BG, BX, CBH, AP, and C-hydrolase activities were significant for different stand types. The impact of apomictic treatments and N-P additions on soil nitrogen hydrolase activities was inconsequential with a minimal interactive effect. The highest correlation between PER, LAP, and N-hydrolase activities was observed in conjunction with elevated levels of nitrogen and phosphorus addition (N3L0, original litter treatment, and high amounts of N and P addition). These findings may provide a theoretical foundation for the management of ecosystem function in broad-leaved Korean pine forests.

Nitrogen and phosphorus additions affect fruiting of ectomycorrhizal fungi in a temperate hardwood forest

The functioning of mycorrhizal symbioses is tied to soil nutrient status, suggesting that nutrient availability should influence the reproduction of mycorrhizal fungi. To quantify the effects of nitrogen (N) and phosphorus (P) availability on ectomycorrhizal fungal fruiting, we collected >4000 epigeous sporocarps representing 19 families during the course of a season in a full factorial NxP addition experiment in six replicate forest stands. Nutrient effects on fruiting shifted as the season progressed, with early fruiting species responding more to P and late-fruiting species responding more to N. The composition of species fruiting in young successional forests differed more with nutrient addition than in mature forests. Sporocarp abundance and species richness were suppressed by N addition. This work shows that N and P availability affect ectomycorrhizal fungal fruiting, with these effects taking place within a context defined by stand age and the progression of fruiting across the season.

Temperature‐driven convergence and divergence of ecohydrological dynamics in the ecosystems of a sky island mountain range

AbstractForest and woodland decline is predicted to be increasingly influenced by meteorological variation and climate change in the future. By determining how meteorological variation leads to similar versus differing ecohydrological dynamics of forest and woodland ecosystems, we can gain insight on how future climate‐driven declines may be realized. We characterized 23 mixed conifer forest (MC), ponderosa pine forest (PP) and piñon pine–juniper woodland (PJ) sites with different canopy covers in southern Nevada, USA. We compared meteorological variation between these sites and employed water balance modelling and information theory to estimate similarity in the density distributions of soil temperature (Ts), soil water potential (SWP) and transpiration partitioning into total evapotranspiration (T/ET) within and across ecosystems in wetter and drier seasons and in cooler and warmer decades. From 1941 to 2020, this location experienced declines in meteorological water deficit due to higher precipitation, although temperatures increased over more recent time periods (1981–2020). From 1981 to 2020, we generally found greater similarity in SWP and T/ET distributions within MC sites and PP sites in the cool season and in the warm season generally found greater similarity in Ts and T/ET distributions within and between PP and PJ sites (excepting T/ET between PJ sites and higher canopy cover PP sites). Recent warm decades promoted convergence in warm and cool season Ts dynamics, such that Ts dynamics generally became more similar between higher elevation MC sites and lower elevation PP–PJ sites. At the same time, warmer decades initiated divergence of SWP and T/ET dynamics within groups of MC–PP and PP–PJ sites that were formerly more similar to each other (excepting SWP in wet seasons). Although their dynamics will remain strongly coupled to precipitation, warming temperatures have the potential to promote divergence in the ecohydrological dynamics of ecosystems at lower and higher elevations in this sky island system and may also promote novel within‐ecosystem divergence associated with variation in vegetation structural attributes.

Homalotheciella subcapillata (Hedw.) Broth., a new moss species to Canada from old broadleaved forests of Nova Scotia

We report Homalotheciella subcapillata (Hedw.) Broth. for the first time in Nova Scotia, found in the western-most part of the province. Upon examination of a previously reported collection of this species from Saskatchewan, we determined that the previous collection was misidentified and conclude that our collections represent the first records of this species for Canada. The moss was found to grow only on old beech (Fagus grandifolia Ehrh.) trees in mature to old growth mixed broadleaved forests. The species has likely been present in Nova Scotia for many decades but was not previously detected due to low search effort. Given the apparent rarity and substrate specificity, the decline of its host tree, and the fact that it is threatened or vulnerable in the USA, we recommend that steps be taken to conserve this species and its habitats in Nova Scotia. Keywords: arboreal, Brachytheciaceae, bryophyte, epiphyte, moss

Eurasian Sparrowhawk (Accipiter nisus) Population Trend and Productivity in Central Israel

ABSTRACT Israel’s nationwide multiyear campaigns, particularly in the late 18th and early 19th centuries, involved deforestation and the development of natural areas for agriculture and human settlement, and resulted in the local extirpation of several animal species. However, reforestation began in the 1940s and promoted the resurgence of extirpated populations. One species that has benefited from these landscape changes is the Eurasian Sparrowhawk (Accipiter nisus). Based on the analysis of population trends in the Judea region (central Israel), we found that this species’ abundance increased by 8.9% over a 5-yr study period (2006–2010). We also found that hatching day was the only reproductive parameter in our study area that varied significantly among years. This breeding parameter depended on three habitat characteristics: (1) the height of the nest; (2) the amount of mixed forest with sparse cover in the area around the nest; and (3) the amount of herbaceous vegetation around the nest. Hatching began earlier in higher nests, and hatching began later in nests surrounded by a high percentage of mixed forest and herbaceous vegetation. However, productivity was independent of the habitat type surrounding the nest site. Our descriptive analysis of prey types suggested that most species in the prey remains and pellets likely came from outside the forest, typically from open areas such as agricultural fields, water reservoirs, or aquaculture ponds. Further, only three species dominated the prey remains and pellets below the nests. We documented reproductive parameters and changes in population size during the early years of this population increase. We predict that the population will continue to thrive and spread into the surrounding areas, as there have been no significant changes in land management in the study area over the past 13 yr.

Patterns of Soil Stoichiometry Driven by Mixed Tree Species Proportions in Boreal Forest

Soil stoichiometry is essential for determining the ecological functioning of terrestrial ecosystems. Understanding the stoichiometric relationships in mixed forests could enhance our knowledge of nutrient cycling. In a mixed forest zone of Larix principis-rupprechtii (LP) and Betula Platyphylla (BP) in Hebei China, we conducted a study at six different sites with varying levels of tree species mixing. The proportion of L. principis-rupprechtii ranged from 0% to 100%, with intermediate values of 8.58%, 10.44%, 18.62%, and 38.32%. We compared soil stoichiometry, including carbon (C), nitrogen (N), and phosphorus (P), as well as chemical and physical properties across these sites. Piecewise structural equation modeling (piecewiseSEM) was used to assess the direct and indirect links between key ecosystem factors and their effects on soil stoichiometry. In mixed forests, the soil exhibited higher contents of soil organic matter (SOM), total nitrogen (TN), and total phosphorus (TP) compared to those in pure LP forests. Additionally, the soil C: N ratio in the 8.58% and 18.62% mixed forests as well as pure BP forests was significantly higher than that in LP forests. Structural equation modeling (SEM) revealed that the contents and ratios of soil C, N, and P exhibited different responses to mixed species proportions. The effect of mixed species proportions on soil nutrients was predominantly indirect, mediated primarily by variations in soil-available nutrients and, to a lesser extent, by physical properties and pH. Specifically, an increase in the proportion of LP in mixed forests had a direct negative effect on soil-available nutrients, which in turn had a positive effect on the content of SOM, TN, and TP and their respective ratios. Based on these findings, we can predict that soil nutrient limitation becomes more pronounced with increasing proportions of Larix principis-rupprechtii in the mixed forest. Our results emphasized the significance of changes in mixed species proportions on soil stoichiometry, providing valuable references for the sustainable development of forests.

Effects of bamboo invasion on forest structures and diameter–height allometries

Forest structure is fundamental in determining ecosystem function, yet the impact of bamboo invasion on these structural characteristics remains unclear. We investigated 219 invasion transects at 41 sites across the distribution areas of Moso bamboo (Phyllostachys edulis) in China to explore the effects of bamboo invasion on forest structural attributes and diameter–height allometries by comparing paired plots of bamboo, mixed bamboo-tree, and non-bamboo forests along the transects. We found that bamboo invasion decreased the mean and maximum diameter at breast height, maximum height, and total basal area, but increased the mean height, stem density, and scaling exponent for stands. Bamboo also had a higher scaling exponent than tree, particularly in mixed forests, suggesting a greater allocation of biomass to height growth. As invasion intensity increased, bamboo allometry became more plastic and decreased significantly, whereas tree allometry was indirectly promoted by increasing stem density. Additionally, a humid climate may favour the scaling exponents for both bamboo and tree, with only minor contributions from topsoil moisture and nitrogen content. The inherent superiority of diameter–height allometry allows bamboo to outcompete tree and contributes to its invasive success. Our findings provide a theoretical basis for understanding the causes and consequences of bamboo invasion.

Quercus acutissima exhibits more adaptable water uptake patterns in response to seasonal changes compared to Pinus massoniana

BackgroundSeasonal precipitation variability significantly affects water use in forests; however, whether water uptake is adapted to changes in precipitation, particularly whether it could affect the coexistence of tree species, has rarely been quantified in forest systems. MethodIn this study, dual stable isotopes and the Li-6400 portable photosynthesis system were used to determine the water sources of a mixed conifer (Pinus massoniana) and broadleaf (Quercus acutissima) forest and changes in hydraulic characteristics during the dry and wet seasons in a southern hilly region of China. ResultsAlthough the hydraulic characteristics of P. massoniana were lower than those of Q. acutissima, it maintained a stable water source from the deep soil layer and a higher stomatal conductance (Gs), leading to a higher transpiration rate (Tr) during the growing seasons. Q. acutissima mainly absorbed water from deeper soil layers in the dry season and took up from shallow soil layers in the wet season. Its Gs values exhibited sensitivity to precipitation, while it maintained a lower Tr value during the growing seasons. The excessive water-use strategy observed in P. massoniana may confer weak drought-tolerance during higher frequency and more intense extreme precipitation events, whereas Q. acutissima may exhibit better ecological adaption to precipitation changes. ConclusionsThe overlap of water niches in mixed forests did not appear to affect the coexistence of tree species. The present study provides insights into reforestation and water management in the southern hilly regions of China.

Dominant Tree Species and Litter Quality Govern Fungal Community Dynamics during Litter Decomposition.

Litter decomposition is a crucial biochemical process regulated by microbial activities in the forest ecosystem. However, the dynamic response of the fungal community during litter decomposition to vegetation changes is not well understood. Here, we investigated the litter decomposition rate, extracellular enzyme activities, fungal community, and nutrient cycling-related genes in leaf and twig litters over a three-year decomposition period in a pure Liquidamabar formosana forest and a mixed L. formosana/Pinus thunbergii forest. The result showed that during the three-year decomposition, twig litter in the mixed forest decomposed faster than that in the pure forest. In both leaf litter and twig litter, β-cellobiosidase and N-acetyl-glucosamidase exhibited higher activities in the mixed forest, whereas phosphatase, β-glucosidase, and β-xylosidase were higher in the pure forest. The fungal α-diversity were higher in both litters in the pure forest compared to the mixed forest, with leaf litter showing higher α-diversity than twig litter. Fungal species richness and α-diversity within leaf litter increased as decomposition progressed. Within leaf litter, Basidiomycota dominated in the mixed forest, while Ascomycota dominated in the pure forest. Funguild analysis revealed that Symbiotroph and ectomycorrhizal fungi were more abundant in the mixed forest compared to the pure forest. In the third-year decomposition, genes related to phosphorus cycling were most abundant in both forests, with the pure forest having a higher abundance of cex and gcd genes. Fungal community structure, predicted functional structure, and gene composition differed between the two forest types and between the two litter types. Notably, the fungal functional community structure during the first-year decomposition was distinct from that in the subsequent two years. These findings suggest that dominant tree species, litter quality, and decomposition time all significantly influence litter decomposition by attracting different fungal communities, thereby affecting the entire decomposition process.