Mixed Conifer Research Articles

Rational eucalypt logging site management patterns enhance soil phosphorus bioavailability and reshape phoD-harboring bacterial community structure

Continuous planting of eucalypt plantations negatively affects soil nutrient effectiveness, especially soil phosphorus (P) availability. Therefore, exploring the response characteristics of soil P-mineralising microbial communities and the distribution mechanism of soil P fractions under different transformation patterns on eucalypts logging sites holds great practical significance for improving soil nutrient effectiveness in plantations. This experiment investigated the effects and correlations between four different transformation patterns on soil phoD-harboring bacterial communities, alkaline phosphatase (ALP) activity, and P fractions. Management patterns mainly included non-forest area formed upon eucalypt stump germination suppression after two generations of Eucalyptus afforestation (TWE), the third generation of pure plantation planting (THE), mixing of Eucalyptus with Manglietia glauca (EM), and rotation of pure M. glauca plantation (MM), with previous mixed coniferous and broadleaf forest (CK) as the control. The results showed that, TWE and THE significantly reduced soil (0–10 cm and 10–20 cm) organic carbon (SOC), total nitrogen (TN), bioavailable P, and labile Po, and increased the occluded P and ALP activity compared to CK; however, SOC, TN, bioavailable P, and labile Po indices improved in plantations of EM or MM compared to TWE and THE. Meanwhile, the four management patterns on the logging site caused significant differences in phoD gene community structure and diversity. TWE and THE significantly increased the relative abundances (RAs) of Pseudomonadaceae and Comamonadaceae, which correlated negatively with soil bioavailable P and HCl-P and positively with ALP activity, suggesting a positive effect on Po mineralization and insoluble P mobilization. In contrast, Streptomycetaceae and Oxalobacteraceae were significantly enriched in EM or MM, implying that not all microorganisms carrying phoD genes play important roles in synthesizing ALP. The structure equation model showed that TN, resin-Pi, NaHCO3-Pi, and HCl-P had indirect effects on ALP through phoD-harbouring bacterial diversity and community composition. These findings provide a basis for understanding the soil P cycling mechanism after eucalypt plantations logging site transformation.

Correlation between Woody Species and Environmental Variables in a Tropical Forest in Central Laos

The tropical forest biome serves as a significant focal point for conservation endeavors. However, understanding the variations in woody plant composition and the underlying driving factors remains limited. The vegetation gradient within Phou Khao Khouay (PKK) National Park in central Laos presents an intriguing environmental model for investigating these patterns. This study, conducted within PKK National Park, aims to classify woody plant communities of three different forest types: mixed deciduous forest (MDF), dry evergreen forest (DEF), and mixed coniferous forest (MCF), utilizing both the phytosociology approach and multivariate analysis. Data from 32 permanent plots (each measuring 50 m × 50 m) were analyzed, revealing 5,477 tree individuals with a diameter at breast height (DBH) ≥ 5 cm, representing 194 woody species from 64 families and 133 genera. The results indicate significant diversity at the family and genus levels, identifying four distinct plant communities and 44 indicator species based on Tichy and Chytry's phi coefficient method. Stability characterizes the MCF forest type, while the stands of DEF and MDF exhibit differentiation into three communities each. Notably, high heterogeneity in species composition and environmental conditions is evident, with elevation and soil nutrient levels (specifically total phosphorus and total potassium) emerging as primary influencers on species coexistence. The study also highlights correlations between woody plant species composition and topographic and soil variables. These findings underscore the importance of identifying microhabitats conducive to growing and conserving woody plant species within PKK National Park for future research and conservation efforts.

Experimental study on fire extinguishing efficiency of polymer hydrogel fire extinguishing agent in pine-fir mixed coniferous forest fires

Pine and fir wood is commonly used in furniture, gardening and construction industries, and has high economic value. It is in great demand in the timber industry. Therefore, pine and fir trees are now widely planted in China. However, pine and fir trees belong to flammable species, with a high content of oil and grease, and the ignition point of pine and fir leaf litter is extremely low. Once burning occurs, it spreads rapidly and can easily turn into a major forest fire. Therefore, the use of extinguishing agents to mitigate and prevent the spread of forest fires is of great importance. In this paper, fire and extinguishing tests were investigated using mixed wood stack burning of pine and fir and mixed fuel from leaf litter. The suppression effects of three different extinguishing agents, AFFF, CAF and hydrogel, on wood fires and leaf litter combustion were compared. And the suppression supply strength of different extinguishing agents to suppress pine and fir trees was determined. The results show that both hydrogel and CAF can effectively extinguish wood stack fires, and AFFF shows re-ignition phenomenon after extinguishing wood stack fires; Comparison of extinguishing time, cooling rate and heat dissipation capacity revealed that hydrogel was superior to CAF; Hydrogel has a highly efficient fire extinguishing properties. It is calculated that the amount of hydrogel used to extinguish pine and cedar fires is only 54 % of the water required, about 87 % of the amount of Class A foam required under the same circumstances, and about 79 % of the amount of aqueous film-forming foam required; Compared with the foam extinguishing agent, the hydrogel extinguishing agent showed better cooling effect, less extinguishing agent dosage, and shorter extinguishing time of 11 s when extinguishing fires in leaf litter; For the rapid spread of leaf litter combustion and easy to re-ignite characteristics, hydrogel has a significant anti-reignition effect.

Effects of tree species composition in plantation forest on soil aggregate stability and organic carbon pools in northeastern China

Forest tree species composition influences soil aggregate stability (SAS) and labile organic carbon (LOC) components, which may affect soil organic carbon (SOC) sequestration. Despite the general belief that mixed forests enhance SOC storage, evidence suggests that certain monocultures may outperform mixed forests. Therefore, information on the specific impact of tree species mixing on SOC through SAS and LOC remains limited. This study aimed to investigate the effects of tree species composition on SAS and LOC in 49-year-old monoculture (Larix gmelinii (Lg), Pinus koraiensis (Pk)) and mixed conifer-broadleaf (Larix gmelinii - Fraxinus mandshurica (LF), and Pinus koraiensis - Populus ussuriensis (PP)) stands, and its impact on SOC sequestration. We measured SAS indices (including mean weight diameter (MWD), geometric mean diameter (GMD), and > 0.25 mm water stable aggregate proportion (WSA)), SOC storage, and LOC components (easily oxidized organic carbon (EOC), microbial biomass carbon (MBC), and dissolved organic carbon (DOC)) in 0–40 cm soil horizons during the growing season (June, August, and October). Our results showed that tree species composition significantly influenced SAS and SOC components, with the highest SAS found in the 0–20 cm soil horizon in Pk and PP forests (p < 0.05) (Jun.: MWD Pk: 0.98, GMD Pk: 1.88, WSA Pk: 1.79, MWD PP: 0.98, GMD PP: 1.90, WSA PP: 1.81; Aug.: MWD Pk: 0.99, GMD Pk: 1.85, WSA Pk: 1.77, MWD PP: 0.99, GMD PP: 1.89, WSA PP: 1.81; Oct.: MWD Pk: 0.98, GMD Pk: 1.86, WSA Pk: 1.76, MWD PP: 0.97, GMD PP: 1.83, WSA PP: 1.73) and the highest SOC components in the LF stand (p < 0.05) (soil horizon 0–20 cm: Jun.: SOC: 110.23 g/kg, EOC: 92.81 g/kg, MBC: 1418.39 mg/kg, DOC: 1090.01 mg/kg; Aug.: SOC: 108.46 g/kg, EOC: 79.57 g/kg, MBC: 1369.91 mg/kg, DOC: 1316.11 mg/kg; Oct.: SOC: 109.78 g/kg, EOC: 44.37 g/kg, MBC: 1782.6 mg/kg, DOC: 671.05 mg/kg). Correlation analysis revealed significant relationships between SOC and LOC components (p < 0.05, r EOC = 0.43, r MBC = 0.46, r DOC = 0.17) but not associated with SAS (p > 0.05, r MWD = −0.07, r GMD = −0.07). Tree species composition in plantation stands significantly affects SAS and SOC pools. In conclusion, the positive effect of mixed coniferous and broad-leaved forests on SAS and SOC pools is also contingent upon the tree species identity. The results suggest that targeted selection of tree species could better enhance SAS and SOC pools in plantation than a mere increase in species richness.

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.

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.

LightGBM hybrid model based DEM correction for forested areas.

The accuracy of digital elevation models (DEMs) in forested areas plays a crucial role in canopy height monitoring and ecological sensitivity analysis. Despite extensive research on DEMs in recent years, significant errors still exist in forested areas due to factors such as canopy occlusion, terrain complexity, and limited penetration, posing challenges for subsequent analyses based on DEMs. Therefore, a CNN-LightGBM hybrid model is proposed in this paper, with four different types of forests (tropical rainforest, coniferous forest, mixed coniferous and broad-leaved forest, and broad-leaved forest) selected as study sites to validate the performance of the hybrid model in correcting COP30DEM in different forest area DEMs. In the hybrid model of this paper, the choice was made to use the Densenet architecture of CNN models with LightGBM as the primary model. This choice is based on LightGBM's leaf-growth strategy and histogram linking methods, which are effective in reducing the data's memory footprint and utilising more of the data without sacrificing speed. The study uses elevation values from ICESat-2 as ground truth, covering several parameters including COP30DEM, canopy height, forest coverage, slope, terrain roughness and relief amplitude. To validate the superiority of the CNN-LightGBM hybrid model in DEMs correction compared to other models, a test of LightGBM model, CNN-SVR model, and SVR model is conducted within the same sample space. To prevent issues such as overfitting or underfitting during model training, although common meta-heuristic optimisation algorithms can alleviate these problems to a certain extent, they still have some shortcomings. To overcome these shortcomings, this paper cites an improved SSA search algorithm that incorporates the ingestion strategy of the FA algorithm to increase the diversity of solutions and global search capability, the Firefly Algorithm-based Sparrow Search Optimization Algorithm (FA-SSA algorithm) is introduced. By comparing multiple models and validating the data with an airborne LiDAR reference dataset, the results show that the R2 (R-Square) of the CNN-LightGBM model improves by more than 0.05 compared to the other models, and performs better in the experiments. The FA-SSA-CNN-LightGBM model has the highest accuracy, with an RMSE of 1.09 meters, and a reduction of more than 30% of the RMSE when compared to the LightGBM and other hybrid models. Compared to other forested area DEMs (such as FABDEM and GEDI), its accuracy is improved by more than 50%, and the performance is significantly better than other commonly used DEMs in forested areas, indicating the feasibility of this method in correcting elevation errors in forested area DEMs and its significant importance in advancing global topographic mapping.

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.

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.

When do contemporary wildfires restore forest structures in the Sierra Nevada?

BackgroundFollowing a century of fire suppression in western North America, managers use forest restoration treatments to reduce fuel loads and reintroduce key processes like fire. However, annual area burned by wildfire frequently outpaces the application of restoration treatments. As this trend continues under climate change, it is essential that we understand the effects of contemporary wildfires on forest ecosystems and the extent to which post-fire structures are meeting common forest restoration objectives. In this study, we used airborne lidar to evaluate fire effects across yellow pine and mixed conifer (YPMC) forests of California’s Sierra Nevada. We quantified the degree to which forest structures in first-entry burned areas (previously unburned since ~ 1900s) and unburned controls aligned with restoration targets derived from contemporary reference sites. We also identified environmental conditions that contributed to more restorative fire effects.ResultsRelative to unburned controls, structural patterns in first-entry burned areas aligned more closely with reference sites. Yet, across all burn severities, first-entry wildfires were only moderately successful at meeting targets for canopy cover (48% total area) and ladder fuels (54% total area), and achieving these targets while also producing tree clump and opening patterns aligning with reference sites was less common (16% total area). Moderate-severity patches had the highest proportion of restorative fire effects (55–64% total area), while low- and high-severity patches were either too dense or too open, respectively. Our models (and publicly-available mapped predictions) indicated a higher probability of restorative effects within 1 km of previous fires, within the mid-upper climate range of the YPMC zone, and under moderate fire intensities (~ 1–2 m flame lengths).ConclusionsFirst-entry wildfires can sometimes restore structural conditions by reducing canopy cover and ladder fuels and increasing structural heterogeneity, especially within moderate-severity patches. However, these initial fires represent just one step toward restoring dry forest ecosystems. Post-fire landscapes will require additional low- to moderate-intensity fires and/or strategic management interventions to fully restore structural conditions. In yet unburned forests, managers could prioritize mechanical treatments at lower elevations, early-season burning at mid to high elevations, and resource objective wildfires in landscapes with mosaics of past wildfires.

Fire history in northern Sierra Nevada mixed conifer forests across a distinct gradient in productivity

BackgroundUnderstanding the role of fire in forested landscapes is fundamental to fire reintroduction efforts, yet few studies have examined how fire dynamics vary in response to interactions between local conditions, such as soil productivity, and more broadscale changes in climate. In this study, we examined historical fire frequency, seasonality, and spatial patterning in mixed conifer forests across a distinct gradient of soil productivity in the northern Sierra Nevada. We cross-dated 46 different wood samples containing 377 fire scars from 6 paired sites, located on and off of ultramafic serpentine soils. Forests on serpentine-derived soils have slower growth rates, lower biomass accumulation, and patchier vegetation than adjacent, non-serpentine sites. Due to these differences, we hypothesized that historical fire frequency and spatial extent would be reduced in mixed conifer forests growing on serpentine soils.ResultsFire scars revealed a history of frequent fire at all of our sites (median composite interval: 6–22.5 years) despite clear differences in soil productivity. Fire frequency was slightly shorter in more productive non-serpentine sites, but this difference was not consistently significant within our sample pairs. While fires were frequent, both on and off of serpentine, they were also highly asynchronous, and this was largely driven by differing climate–fire relationships. Fires in more productive sites were strongly associated with drought conditions in the year of the fire, while fires in less productive serpentine sites appeared to be more dependent on a cycle of wet and dry conditions in the years preceding the fire. Widespread fires that crossed the boundary between serpentine and non-serpentine were associated with drier than normal years.ConclusionsIn our study, fine-scale variation in historical fire regime attributes was linked to both bottom-up and top-down controls. Understanding how these factors interact to create variation in fire frequency, timing, and spatial extent can help managers more effectively define desired conditions, develop management objectives, and identify management strategies for fire reintroduction and forest restoration projects.

Mixed Coniferous Broad-Leaved Forests as Road Shelter Forests: Increased Urban Traffic Noise Reduction Effects and Economic Benefits

Mixed Coniferous Broad-Leaved Forests as Road Shelter Forests: Increased Urban Traffic Noise Reduction Effects and Economic Benefits

Effectiveness of pre-fire forest management on post-fire forest conditions in southeastern Arizona

BackgroundWestern forests in the United States are facing multiple threats that have the potential to permanently alter forest composition and structure. In particular, wildfire can either have beneficial or adverse effects on overall forest health and resilience. Monitoring and assessing the effectiveness of existing forest treatment plans for meeting forest management goals is becoming more critical to increase the capacity for managers to prepare for and accommodate uncertainty associated with changing disturbance regimes. We used a combination of fine-scale vegetation and microclimate surveys on 57 plots, active remotely sensed data (light detection and ranging: LiDAR), and high-resolution satellite imagery to evaluate the effectiveness of an existing management strategy to increase disturbance resistance and resilience of an isolated mixed-conifer forest following a recent large-scale wildfire in southeastern Arizona, USA. We specifically assessed the effectiveness of forest overstory live tree thinning treatments (silviculture) as well as understory fuel reduction treatments (fuel) for influencing post-fire abiotic and biotic conditions, reducing direct post-fire tree mortality, and increasing resilience as compared to untreated forest stands.ResultsWe found that forest silviculture and fuel reduction treatments implemented prior to a large wildfire had mixed results on post-fire fine-scale vegetation composition and structure, microclimate conditions, tree mortality, and tree resilience. Fine-scale vegetation characteristics within silviculture- and fuel-treated forest units displayed higher herbaceous diversity and decreased density of new tree snags as compared to untreated units post-fire. Relevant to seedling emergence, we found that variance in spring soil moisture content was lower overall in treated units; however, units that received overstory thinning (silviculture) treatments were also associated with higher average summer high soil temperatures as compared to untreated units. Additionally, direct tree mortality and rate of recovery of trees post-fire differed between two treatment types (silviculture and fuel reduction) when compared to untreated units and among contrasting levels of burn severity. Post-fire tree mortality and tree resilience did not differ between control and silviculture units; however, these characteristics did differ between control and fuel units. Unlike control units, probability of tree mortality changed little between burn severity categories in fuel treatments (53.4% of mortality occurring in unburned/low vs. 46.7% in moderate/high severity) and resilience increased an average of 2.04% for trees from unburned/low to moderate/high-severity burn categories.ConclusionsOur methodology could be applied to any forested system experiencing increasing intensity and frequency of wildfire. Our results indicate that post-fire forest conditions and resilience are influenced by forest management strategies, particularly fuel reduction treatments. To accommodate uncertainty associated with changing disturbance regimes and climate change, implementing post-fire and post-treatment assessments and monitoring as presented in this study will be essential for developing attainable goals and for maintaining desired forest conditions.

Cyanoboletus abieticola (Boletaceae, Basidiomycota), a new species from Mexico

Cyanoboletus abieticola is described as a new species to science. This species is characterized by the viscid pileus,cylindric to bacilliform basidiospores ([14.1] 16.2 ± 1.1 [17.5] × [5] 5.5 ± 0.3 [5.9] μm, Q [2.8] 3.0 ± 0.1 [3.2]), and its gregarious habit in mixed coniferous forests dominated by Abies religiosa or A. guatemalensis. Photographs, drawings, and the phylogenetic analysis of 3 genetic data sets (ITS, nucLSU, and RPB2) of the new species are presented.

Population dynamics and its relationship with functional traits in different succession stages of temperate mixed coniferous broad-leaved forest in Northeast China.

Functional traits regulate plant response to environmental changes, with consequences on population dynamics. However, how plant functional traits impact population dynamics, including growth, mortality, and recruitment, remains elusive in temperate forests across different successional stages. In this study, we compiled data on population dynamics and eight functional traits, encompassing hydraulic, wood, and leaf traits, from 35 species commonly found in a secondary poplar-birch forest and a broad-leaved Korean pine forest in Northeast China. We quantified the intrinsic relationships between plant population dynamics and assessed how plant functional traits influenced these dynamics. The results demonstrated a gradual increase in the correlation among population dynamics as forest succession progressed. In the secondary forest, tree growth rate and mortality rate were negatively correlated, while growth-death rate and growth-recruitment rate were not related. Conversely, in the broad-leaved Korean pine forest, there was a significant negative correlation between tree growth rate and mortality rate, as well as between growth rate and recruitment rate, while tree mortality rate positively correlated with recruitment rate. Additionally, functional traits effectively predicted population dynamics, but the predictive ability varied across successional stages. Functional traits, particularly xylem hydraulic traits (e.g., Huber value) and anatomical traits (e.g., mean xylem conduit diameter), were stronger predictors of tree growth, mortality, and recruitment rates at the late successional stage compared with the early stage. These findings indicated that population dynamics and functional traits exhibited strong regularity in the late successional stage of broad-leaved Korean pine forests.

Natural Conditions for Heliophilous Tree-Species Following Forest Dieback in Temperate Zone After Periglacial Habitats

Abstract Widespread forest dieback following a series of exceptionally dry seasons has made restoration by relic heliophilous tree-species uncertain. Using logistic regression, we identified conditions suitable for relic Norway spruce (Picea abies /L./Karst.), Scots pine (Pinus sylvestris L.), European larch (Larix decidua Mill.), birches (Betula sp.), poplars (Populus sp.) and willows (Salix sp.) by comparing the relief and bedrock under stands that died abruptly between 2018 and 2020 at temperate zone after periglacial habitats of the Czech Republic. Extent of forest dieback was determined through automated object analysis on the basis of vectorised Planet Scope and Sentinel-2 satellite images. The object analysis consisted of mainly spruce stands and dieback indicated by a deep inter-year decrease in the vegetation indices. The overall occurrence of tree-species in pure or mixed stands was determined from a polygon geodatabase of forest management plans, while growth condition types were determined by overlaying biogeographically subdivided polygons. Dead forests provided suitable conditions for mixed conifer, birch, and poplar stands on 64.4 % of the greywackes, acid metamorphites, and waterlogged sediments on broken plateaus, depressions, and slopes. In comparison, pure stands of relic tree-species can cover 35.6 % of dead forest area. Restoration of mixed forests differenting over a range of growth conditions seems to be suitable for adaptation to climate change impacts.

Enhanced Carbon Storage in Mixed Coniferous and Broadleaf Forest Compared to Pure Forest in the North Subtropical–Warm Temperate Transition Zone of China

Enunciating the carbon storage across various types of forests is a precondition for comprehending forest ecosystem carbon cycling. However, previous studies regarding forest carbon storage were primarily conducted in the general temperature zones, with a limited understanding of carbon storage in different forest types within climate transition zones. In this study, we employed biomass models to explore the carbon storage in three types of natural secondary forests (Pinus armandii forest, Quercus aliena forest, and Q. aliena–P. armandii mixed forest) in the transition zone between the northern subtropical and warm temperate regions of China. Furthermore, we used the variance decomposition analysis and random forest model to determine the key factors influencing carbon storage in three types of natural secondary forests. Our results indicated that the carbon storage of wood and soil layers in the Q. aliena–P. armandii mixed forest was significantly higher than that in the P. armandii and Q. aliena forests. Total carbon storage was ranked as follows: Q. aliena–P. armandii mixed forest (266.09 t/ha) &gt; P. armandii forest (222.89 t/ha) &gt; Q. aliena forest (212.46 t/ha). Our results also revealed that carbon storage of the wood layer was jointly regulated by environmental factors, plant physiological characteristics, and soil properties, while soil carbon storage was mainly affected by soil properties. These results highlight the significant advantages of mixed conifer–broadleaf forests in carbon storage, emphasizing the importance of mixed natural secondary forests in carbon cycling and ecosystem services. This study provides scientific evidence for enhancing forest carbon sink functions and developing forest conservation and management policies to combat climate change.

Responses of Soil Organic Carbon Fractions and Stability to Forest Conversion in the Nanling Nature Reserve, China

Studying the impact of typical vegetation types in forest conversion zones on soil organic carbon (SOC) structure and stability is crucial for developing terrestrial ecosystem carbon sequestration strategies. In this study, we selected three typical forest stands in the Nanling National Nature Reserve: a primary evergreen broad-leaved forest (BL), a secondary mixed coniferous and broad-leaved forest (ML), and a Chinese fir plantation (CL). Soil samples were collected to examine the SOC fractions and carbon pool management index (CPMI) in three forest stands. The influence of soil property factors on SOC fractions was also analyzed. The results showed that the transformation process from a BL to an ML or a CL changed the structure and stability of organic carbon by reducing the labile SOC fractions and increasing the recalcitrant carbon fraction in the soil. The higher lability index (LI) and CPMI of soils in the BL indicated better carbon accumulation and activity, making this treatment more advantageous for management strategies aimed at promoting natural forest renewal and ecological restoration. Correlation and RDA analysis revealed that the availability of soil P was a key factor limiting the variation in organic C fractions in the acidic soils of tropical forests in South China.

Anatomy of a fossil liana from the Upper Cretaceous of British Columbia, Canada

Summary Fossil woods are preserved as calcareous permineralizations in the Upper Cretaceous Northumberland Formation on Collishaw Point, Hornby Island, British Columbia, Canada. They are well preserved, often including peripheral tissues, and reveal the diversity and structure of vegetation in the region ca. 72 million years ago. We describe a new genus and species based on two specimens. Two specimens were cut using a rock saw to expose the fossil wood in transverse and longitudinal sections. Thin sections were prepared using the cellulose acetate peel technique. Peels were mounted on slides with Eukitt mounting medium. Anatomical description follows the IAWA guidelines. We compared the anatomy of the fossils with that of other plants using data available in the published literature and the InsideWood database. The combination of wide vessels and high vessel frequency given the narrow diameter of the stem, combined with the abrupt increase in vessel diameter near the pith indicates this plant had hydraulic properties typical of a climbing plant (liana). The anatomy of the rays, the arrangement of the vessels and their pitting, and the thickness of the bark are also consistent with the climbing habit, but not diagnostic of any extant family. This is the second species of liana to be described from the Hornby Island assemblage, providing new information about the composition of structurally complex mixed conifer–angiosperm forests in the Late Cretaceous of western North America.

Effect of thinning intensity on the carbon sequestration of natural mixed coniferous and broadleaf forests in Xiaoxing’an Mountains, China

To study the effect of thinning intensity on the carbon sequestration by natural mixed coniferous and broadleaf forests in Xiaoxing’an Mountains, China, we established six 100 m × 100 m experimental plots in Dongfanghong Forest that varied in thinning intensity: plot A (10%), B (15%), C (20%), D (25%), E (30%), F (35%), and the control sample area (0%). A principal component analysis was performed using 50 different variables, including species diversity, soil fertility, litter characteristics, canopy structure parameters, and seedling regeneration parameters. The effects of thinning intensity on carbon sequestration were strongest in plot E (0.75), followed by D (0.63), F (0.50), C (0.48), B (0.22), A (0.11), and the control (0.06). The composite score of plot E was the highest, indicating that the carbon sequestration effect was strongest at a thinning intensity of 30%. These findings provide useful insights that could aid the management of natural mixed coniferous and broadleaf forests in Xiaoxing’an Mountains, China. This information has implications for future studies of these forests, and the methods used could aid future ecological assessments of the natural forests in Xiaoxing’an Mountains, China.