Mixed broadleaved-Korean Pine Research Articles

Mineral protection mediates soil carbon temperature sensitivity of nine old-growth temperate forests across the latitude transect

Temperature sensitivity (Q10) of soil microbial respiration serves as a crucial indicator for assessing the response of soil organic carbon (SOC) to global warming. However, the biogeographic variation in Q10 remains inconsistent. In this study, we examined Q10 and its potential drivers in nine old-growth mixed broad-leaved Korean pine (Pinus koraiensis Sieb. et Zucc.) forests (the climax community of Asian temperate mixed forest) under a wide range of climatic conditions. We found that stand characteristics (arbuscular mycorrhizal tree basal area to ectomycorrhizal tree basal area ratio and root to shoot ratio) contributed to soil C sequestration by facilitating the accumulation of soil recalcitrant C components. Contrary to the C quality-temperature hypothesis, Q10 was not correlated with C quality (soil C to nitrogen ratio and recalcitrant C to labile C ratio). Soil mineral protection parameters (Fe/Al oxides) had negative effect on Q10 because they inhibited microbial activities by decreasing substrate accessibility. Additionally, soils with high microbial biomass C and microbial biomass C to soil organic C ratio had high Q10. Overall, understanding the complex relationships among Q10, mineral protection, and microbial attributes on a spatial scale is essential for accurately predicting soil C cycling in forest ecosystems.

Differences and similarities in radial growth of Betula species to climate change

Betula platyphylla and Betula costata are important species in mixed broadleaved-Korean pine (Pinus koraiensis) forests. However, the specific ways in which their growth is affected by warm temperatures and drought remain unclear. To address this issue, 60 and 62 tree-ring cores of B. platyphylla and B. costata were collected in Yichun, China. Using dendrochronological methods, the response and adaptation of these species to climate change were examined. A “hysteresis effect” was found in the rings of both species, linked to May–September moisture conditions of the previous year. Radial growth of B. costata was positively correlated with the standardized precipitation-evapotranspiration index (SPEI), the precipitation from September to October of the previous year, and the relative humidity in October of the previous year. Growth of B. costata is primarily restricted by moisture conditions from September to October. In contrast, B. platyphylla growth is mainly limited by minimum temperatures in May–June of both the previous and current years. After droughts, B. platyphylla had a faster recovery rate compared to B. costata. In the context of rising temperatures since 1980, the correlation between B. platyphylla growth and monthly SPEI became positive and strengthened over time, while the growth of B. costata showed no conspicuous change. Our findings suggest that the growth of B. platyphylla is already affected by warming temperatures, whereas B. costata may become limited if warming continues or intensifies. Climate change could disrupt the succession of these species, possibly accelerating the succession of pioneer species. The results of this research are of great significance for understanding how the growth changes of birch species under warming and drying conditions, and contribute to understanding the structural adaptation of mixed broadleaved-Korean pine (Pinus koraiensis) forests under climate change.

Microbial community and enzyme activity respond differently to seasonal and edaphic factors in forest and grassland ecosystems

Although microbial community and function patterns have been extensively studied, little is known about whether the patterns are consistent in different ecosystems and how they are influenced by seasonality or other environmental factors. To test the driving factors of microbial communities and potential functions, we collected soil samples from five forests (mixed broadleaved-Korean pine forest, mixed pine and oak forest, deciduous broadleaved mixed forest, subtropical evergreen broad-leaved forest and tropical rainforest) and three grassland ecosystems (meadow steppe, semi-arid grassland and arid grassland) across China in three seasons (spring, summer and autumn). Microbial diversity based on the sequencing of 16S rRNA gene for bacteria and internal transcribed spacer (ITS) genes for fungi were measured, and potential functions represented by soil extracellular enzyme activities (EEAs) were analyzed. The results found that soil EEAs were significantly higher in summer than in spring and autumn, and both bacterial and fungal richness indices showed greater seasonal fluctuations than the diversity. Fungal richness indices were highest in summer in both forest and grassland ecosystems, while the lowest were observed in spring for forest and in autumn for grassland, respectively. In addition, fungal communities were closely related to ecosystem types, while bacterial communities were not significantly different across ecosystems and exhibited a broader habitat niche breadth, but the relative abundance of dominant bacterial phyla showed stronger correlations with environmental variables (including climate, soil properties and nutrients) in grassland than in forest ecosystems. The decoupling of microbial community and EEAs was observed in both forest and grassland ecosystems, indicating the function redundancy of soil microorganisms. The present study provided crucial information about the effects of ecosystem types, seasonality and edaphic factors on soil microbial communities and EEAs, and could advance the understanding of soil potential function responses to environmental changes.

Driving mechanisms of productivity stability vary with selective harvesting intensities in a mixed broad-leaved Korean pine forest

Key messageWe found that the stabilizing mechanisms for forest productivity varied across harvesting intensities in a mixed broad-leaved Korean pine forest. Effects of overyielding at high species richness and species asynchrony occurred only in unharvested and lightly harvested plots, whereas asymmetries between individuals of different size contributed significantly to stabilizing productivity when harvestings became intensive.ContextUnderstanding the driving factors of forest ecosystem stability has become increasingly crucial in forest management. However, it remains unclear whether and how the stabilizing mechanisms of forest productivity might be influenced by management practices.AimsWe related the temporal stability of aboveground biomass productivity to harvesting history. We further tested how three key driving mechanisms of stability might be modulated by selective harvesting intensities.MethodsBased on a 10-year monitoring (five repeated tree inventories) of a mixed broad-leaved Korean pine forest in Northeastern China recovering from selective harvesting, we examined the relative importance of two diversity-dependent mechanisms (overyielding and species asynchrony) and one size-dependent mechanism (asymmetric growth) for productivity stability across a wide range of intensities (0–73.4% basal area removed).ResultsWe found that selective harvesting significantly lowered the productivity stability, species asynchrony, and growth dominance coefficient. Growth dominance coefficient had an overall stronger effect on stability than species richness and asynchrony. Moreover, the strengths of stabilizing mechanisms varied across harvesting intensities: effects of overyielding at high species richness and species asynchrony were detected only in unharvested and lightly harvested plots, whereas the explanatory power of growth dominance coefficient outweighed the diversity-related variables when harvesting became intensive.ConclusionsWe emphasized the importance to consider both diversity- and size-related explanatory variables as potential mechanisms for the temporal stability of forest productivity. In fact, how growth is partitioned among trees of different species as well as sizes may co-determine the response of forest stability to disturbances.

Responses of economic and anatomical leaf traits to soil fertility factors in eight coexisting broadleaf species in temperate forests

The multidimensionality of leaf traits allows plants to have diverse survival strategies to adapt to complex living environments. Whether the anatomical traits of leaves are associated with leaf economic traits and which group of traits are more strongly correlated with soil fertility factors remains unclear. We measured four leaf economic traits, four anatomical traits, and five soil fertility factors of eight coexisting broadleaf species distributed in mixed broadleaved-Korean pine (Pinus koraiensis) forests located in Northeast China. Results show a strong interdependence between economic and anatomical traits (p < 0.05). The range of variation between economic and anatomical traits were almost equal, but the causes of variation were different. Specific leaf area was positively correlated with the abaxial epidermis, negatively correlated with the ratio of spongy tissue to leaf thickness (ST/LT), and not correlated with adaxial epidermis. Leaf dry matter content was negatively correlated with the abaxial epidermis and adaxial epidermis, positively correlated with ST/LT. Specific leaf area, palisade tissue, and ST/LT showed stronger correlation with soil fertility factors than other traits. Soil fertility factors dominating trait variation were dependent upon the trait. Our results suggest anatomical traits can be considered in economic trait dimension. The coupled relationship between anatomical and economic traits is potentially a cost-effective adaptation strategy for species to improve efficiency in resource utilization. Our results provide evidence for the complex soil-trait relationship and suggest that future studies should emphasize the role of anatomic traits in predicting soil fertility changes.

Forest Conversion Changes Soil Particulate Organic Carbon and Mineral-Associated Organic Carbon via Plant Inputs and Microbial Processes

Primary forest conversion greatly influences soil organic carbon (SOC) sequestration. However, our understanding of how primary forest conversion affects SOC fractions and chemical component evenness remains limited. We examined how primary forest conversion (from primary mixed broadleaved Korean pine forest to secondary broadleaved forest and coniferous plantation) affects free particulate OC (POC), aggregate-occluded POC, mineral-associated OC (MAOC), and their chemical component evenness via plant inputs (e.g., litter and fine roots) and microbial properties (e.g., microbial biomass and residue C) in Northeast China. Primary forest conversion led to a large increase in litter and fine root quality (lower C/N ratio), SOC, and MBC of secondary forests and a reduction in litter and fine root quantity and quality, SOC, MBC, and microbial residue C of plantations, which drove changes in POC and MAOC. As a result, after conversion to secondary forests, free POC decreased by 20.3% and aggregate-occluded POC increased by 57.2%. After conversion to plantations, free POC increased by 49.1%, while aggregate-occluded POC and MAOC decreased by 42.4% and 9.0%, respectively. Free POC was negatively correlated with fine root biomass. Aggregate-occluded POC and MAOC were positively correlated with litter and fine root quality, MBC, and microbial residue C. Meanwhile, forest conversion decreased the evenness of free and aggregate-occluded POC chemical components in secondary forests, with O-alky C being higher and aromatic C being lower, while MAOC was not affected by forest conversion. The evenness of free and aggregate-occluded POC chemical components was associated with litter and fine root quality, and that of MAOC was associated with MBC and microbial residue C. High-quality plant inputs benefit OC sequestration in soil aggregates and MAOM through microbial assimilation and residue accumulation after primary forest conversion. Future forest management should consider tree species with high-quality input as a possible compensation for climate change by sequestering more OC in soil aggregates.

Sensitivity of forest composition and productivity to climate change in mixed broadleaved-Korean pine forest of Northeastern China

Temperate forest is one of the largest forest biomes and is undergoing remarkable shifts in forest composition and ecosystem productivity under warming climates. However, there are considerable uncertainties when predicting future dynamics of temperate forest ecosystems partly because of the uncertainties in future climate predictions. Sensitivity analysis provides an effective mean to evaluate the uncertainties in the predicted forest responses to climate change. Here we evaluated the sensitivity of forest composition and productivity to climate change in the mixed broadleaved-Korean pine forest, a keystone temperate forest type in northeast China. In this study, we used a process-based forest dynamic model, FORMIND, to simulate and predict the response of the mixed broadleaved-Korean pine forest under climate change based on plant functional types (PFTs), and we performed model calibration using forest investigation. We then designed a factorial experiment to quantify the sensitivity to temperature and precipitation of forest composition and ecosystem productivity. Results showed that the uncertainty in future climate predictions could result in divergent responses of forest composition and ecosystem productivity to climate change over the 21st century. The response of PFTs to climate (temperature and precipitation) varied in terms of aboveground biomass. Both shade-tolerant and shade-intolerant PFTs exhibited higher sensitivity (>80% for most of the PFTs) to temperature than precipitation, yet they responded oppositely to climate warming with shade-tolerant PFTs generally increasing but shade-tolerant PFTs decreasing. Moderate shade-tolerant PFTs showed higher precipitation sensitiveness (>50%). Such differences in response and sensitivity of PFTs to climate change are related to PFTs’ competitiveness. Ecosystem productivity exhibited a higher sensitivity (≥50%) to temperature than to precipitation. There was more increase in ecosystem respiration than gross primary productivity (GPP) under warming climate, leading to a decrease in carbon sequestration and net ecosystem exchange (NEE). Our study addresses the importance of evaluating the sensitivity of a forest ecosystem model to climate change, which is relatively less studied. The insight from the study may help design effective forest management strategies to cope with future climate change.

Soil water content and nitrogen differentially correlate with multidimensional leaf traits of two temperate broadleaf species

The variation and correlation of leaf economics and vein traits are crucial for predicting plant ecological strategies under different environmental changes. However, correlations between these two suites of traits and abiotic factors such as soil water and nitrogen content remain ambiguous. We measured leaf economics and vein traits as well as soil water and nitrogen content for two different shade-tolerant species (Betula platyphylla and Acer mono) in four mixed broadleaved-Korean pine (Pinus koraiensis) forests along a latitudinal gradient in Northeast China. We found that leaf economics traits and vein traits were decoupled in shade-intolerant species, Betula platphylla, but significantly coupled in a shade-tolerant species, A. mono. We found stronger correlations among leaf traits in the shade tolerant species than in the shade intolerant species. Furthermore, leaf economic traits were positively correlated with the soil water gradient for both species, whereas vein traits were positively correlated with soil water gradient for the shade intolerant species but negatively correlated in the shade tolerant species. Although economic traits were positively correlated with soil nitrogen gradient in shade intolerant species but not correlated in shade tolerant species, vein traits were negatively correlated with soil nitrogen gradient in shade tolerant species but not correlated in shade intolerant species. Our study provides evidence for distinct correlations between leaf economics and vein traits and local abiotic factors of species differing in light demands. We recommend that the ecological significance of shade tolerance be considered for species when evaluating ecosystem functions and predicting plant responses to environmental changes.

Do Tree Size and Tree Shade Tolerance Affect the Photosynthetic Capacity of Broad-Leaved Tree Species?

(1) Background: leaf structure traits are closely related to leaf photosynthesis, reflecting the ability of trees to obtain external resources in the process of growth. (2) Methods: We studied the morphological, chemical, anatomical, stomatal traits and maximum net photosynthetic rate of six broad-leaf species in northern temperate mixed broad-leaved Korean pine (Pinus koraiensis) forest. (3) Aim: To investigate whether there are differences in leaf structural traits of trees with different shade tolerances and different sizes and the effects of these differences on leaf photosynthetic capacity. (4) Results: the effects of leaf structure traits on leaf photosynthesis were different among trees with different shade tolerances or different sizes. Under the condition of light saturation, the net photosynthetic rate, nitrogen use efficiency, phosphorus use efficiency and stomatal conductance of shade-intolerant trees or small trees were higher than those of shade-tolerant trees or large trees. (5) Conclusions: the shade tolerance of tree species or the size of trees affect the traits of leaf structure and indirectly affect the photosynthetic ability of plants. When constructing the leaf trait-photosynthesis model, the shade tolerance and tree size of tree species should be taken into account.

Leaf nitrogen resorption is more important than litter nitrogen mineralization in mediating the diversity–productivity relationship along a nitrogen-limited temperate forest succession chronosequence

The resorption of nutrients by plants before litter fall and the mineralization of nutrients from plant litter by soil processes are both important pathways supporting primary productivity. While the positive relationship between plant biodiversity and primary productivity is widely accepted for natural ecosystems, the roles of nutrient resorption and mineralization in mediating that relationship remains largely unknown. Here, we quantified the relative importance of nitrogen (N) resorption and N mineralization in driving plant community N investment and the correlation between species diversity and community productivity along an N-limited successional chronosequence of the mixed broadleaved–Korean pine (Pinus koraiensis) forest in northeastern China. Leaf N resorption efficiency (NRE) at the community level increased significantly along the successional chronosequence, whereas litter N mineralization rate decreased significantly. Leaf NRE was more important than litter N mineralization rate in driving the diversity–productivity relationship. However, higher leaf NRE led to less N mineralization as succession progressed along the chronosequence. Our results highlight the importance of the N resorption pathway rather than the N mineralization pathway for forest N acquisition with community succession, and they provide mechanistic insights into the positive effects of biodiversity on ecosystem functioning. In future forest management practices, we recommend appropriate application of N fertilizer to mitigate the adverse effects of N-poor soil on seedling regeneration during late succession and thus maintain the sustainable development of temperate forest ecosystems.

Use of direct seeding and seedling planting to restore Korean pine (Pinus koraiensis Sieb. Et Zucc.) in secondary forests of Northeast China

The poor natural regeneration of Korean pine represents a substantial hurdle limiting the restoration of secondary forests to mixed broad-leaved Korean pine forests (MBKPFs). Active restoration based on direct seeding or planting seedlings is accordingly considered to be a prerequisite for promoting Korean pine recruitment in secondary forests. To evaluate the most effective practices for restoring Korean pine in secondary forests, we studied the effects of microsites associated with gaps of different sizes and within-gap locations on direct seeding (rodent access/exclusion and soil/litter cover) and seedling planting (1-, 2-, and 3-year-old seedlings). We found that an average of 82.4% of sown seeds were eaten by rodents, with only 9.9% germinating and surviving after two growing seasons. Among the germinated seedlings, 37.6% were subsequently excised by rodents, whereas 6% died due to other natural causes. Furthermore, compared with the control sites (forest understorey), we detected no significant differences among the different microsites with respect to an effective reduction in rodent damage or promotion of seed germination, whereas rodent exclusion was more effective in protecting seeds from predation than the effect of microsite. With regards to planted seedlings, we found that the proportion of survival and relative root collar diameter growth were highest in the center (64.1%) and edge (60.0%) sites of large gaps, and that the survival of planted seedlings (43.7%) was considerably higher than that of seedlings derived from directly sown seeds (9.9%). Collectively, our findings indicate that, owing to seed predation and seedling excision by rodents, direct seeding with either mesh or soil cover would not represent an effective strategy for promoting Korean pine recruitment in secondary forests. Accordingly, for the purposes of restoring secondary forests to MBKPFs, we recommend planting 3-year-old Korean pine seedlings in large gaps within secondary forests.

Long-term (42 years) effect of thinning on soil CO2 emission in a mixed broadleaved-Korean pine (Pinus koraiensis) forest in Northeast China

Thinning is an important forest management practice that has great potential to influence regional soil carbon storage and dynamics. The present study measured soil respiration (RS, the efflux of CO2 emitted) and its two components (heterotrophic (RH) and autotrophic (RA) respiration) from soil 42 years after thinning in comparison to un-thinning (control). Autotrophic respiration was significantly greater in the thinning plot, approximately 44% higher compared to the control, while both Rs and RH were slightly, but not significantly, higher in the thinning plot. Higher fine root biomass might have contributed to the higher Ra in the thinning plot. Both Rs and RH showed clear soil temperature-dependent seasonal patterns, whereas Ra was less responsive to changes in temperature, especially within one specific season. The annual and season-specific temperature sensitivities of RS and RH were lower in the thinning plot, specifically during the mid-growing season. Furthermore, variations in the season-specific temperature sensitivity of Rs and RH were less intense in the thinning plot. We conclude that forest thinning can reduce the temperature sensitivity of RS and RH during the mid-growing season and increase soil CO2 emission in the long term.

阔叶红松林不同演替阶段灌木器官的N、P分配特征

氮（N）、磷（P）是植物生长发育重要的限制元素，N、P以及N、P间的关系是化学计量学研究的重要内容。植物不同器官对N、P的需求存在差异，因此N、P的分配与权衡对植物的生长发育起到重要的调节作用。为了探究阔叶红松（Pinus koraiensis）林不同演替阶段主要灌木器官的N、P化学计量特征及其分配格局，了解灌木的养分限制因子及其分配策略，在黑龙江凉水国家级自然保护区的阔叶红松林四个演替阶段——白桦（Betula platyphylla）次生林、阔叶混交林、针阔混交林和阔叶红松林内，选取主要灌木种，分析了叶片、枝条、茎干和根的N、P化学计量特征以及异速生长关系。结果发现：灌木不同器官之间的N、P含量差异显著，其中叶的N、P含量均为最高，茎干的N、P含量均为最低。所有器官中，叶的N ： P最高，为7.59；根的N ： P最低，为5.47。灌木叶、茎干、根之间的N ： P存在显著差异，而茎干、根与枝条之间的N ： P没有显著差异。阔叶红松林不同演替阶段对灌木同一器官N、P化学计量的影响不同，灌木叶片的N含量在不同演替中具有显著差异，其他器官的差异不显著；不同演替阶段灌木器官的P含量均无显著差异。在不同演替阶段中各器官的N ： P均小于14，说明N元素是阔叶红松林各演替阶段灌木生长的限制因子，而P对灌木的生长没有起到限制作用。研究表明在不同演替阶段中，N、P的异速生长关系普遍存在于灌木器官中，呈现显著的正相关关系；整体上各器官之间的斜率没有显著差异，说明灌木采取保守分配策略，以此来适应环境和满足自身生长发育的需要。;Nitrogen (N) and phosphorus (P) were important limiting elements for plant growth and development in the nature. N, P and their relationship were essential contents in stoichiometry. Different plant organs had different demands for N and P, therefore the allocation and trade-off of N and P played an important role in the growth and development of plants. In order to explore the N and P stoichiometric characteristics and allocation patterns of shrub organs in different successional stages of the mixed broadleaved-Korean pine (Pinus koraiensis) forest, and to understand the nutrient limiting factors and allocation strategies, the dominant shrub species in four successional stages (secondary birch forest, mixed broad-leaved forest, mixed broadleaved-conifer forest and the mixed broadleaved-Korean pine forest) were selected in Liangshui National Nature Reserve, Heilongjiang. In this study, to research the N and P stoichiometric characteristics and allometric relationship, leaves, twigs, stems and roots of shrubs were collected to analyzed. The results showed that the contents of N and P in different organs were significantly different. In addition, the contents of N and P in leaves were the highest, while those in stems were the lowest among all shrub organs. The N:P ratio of leaves was the highest (7.59), and that of roots was the lowest (5.47). N:P ratio in leaves, stems and roots were significantly different, but N:P ratios in stems, roots and twigs were not significantly different. The effects on N and P stoichiometry of the same organ in different successional stages of the mixed broadleaved-Korean pine forest were different. Specifically, the N content in leaves had a significant difference, though the difference in other organs was not significant. There was no significant difference in P content of shrub organs among the four successional stages. In fact, all of N:P ratios were less than 14, which showed that N was always a limiting factor for shrub growth in different successional stages of the mixed broadleaved-Korean pine forest. However, P had no limiting effect on the growth of shrubs. Our research revealed that the allometric relationship of N and P generally existed in shrub organs in different successional stages, presenting a significantly positive correlation. In general, there was no significant difference among the allometric slopes of shrub organs in the mixed broadleaved-Korean pine forest, indicating that the shrub adopted a conservative allocation strategy to adapt to the environment change and satisfy the needs of its own growth and development.

Characteristics of shrub leaf carbon, nitrogen and phosphorus stoichiometry and influencing factors in mixed broadleaved-Korean pine forests at different successional stages

Characteristics of shrub leaf carbon, nitrogen and phosphorus stoichiometry and influencing factors in mixed broadleaved-Korean pine forests at different successional stages

Effects of canopy structure on productivity in a typical mixed broadleaved-Korean pine forest

Effects of canopy structure on productivity in a typical mixed broadleaved-Korean pine forest

Effects of Korean Pine Basal Area in Mixed Broadleaved–Korean Pine Forest Stands on Its Natural Regeneration in Northeast China

Abstract Understanding the natural regeneration of Korean pine (Pinus koraiensis Sieb. et Zucc.) in mixed broadleaved–Korean pine (MBK) forests is crucial for MBK forest conservation and secondary deciduous broadleaved forest restoration. We hypothesized the ratio of Korean pine basal area (RKp) in MBK stands affected its natural regeneration. Regeneration censuses, including the height, root collar diameter, age, and growth stages (younger seedling, older seedling, smaller sapling, and taller sapling) of Korean pine, were conducted in northeast China. Results indicated the stem density and age composition of younger seedlings were positively correlated with RKp, whereas those of the saplings were negatively correlated with RKp. In the stands with lower RKp (<80% in Lesser Khingan Mountains [LKM]; <40% in Lushuihe Forestry Bureau [LFB]), individuals in all growth stages regenerated well with an age span of 65 yr. However, the regeneration of taller saplings was severely inhibited with increasing RKp (LKM: RKp ≥ 80%; LFB: RKp ≥ 40%). In summary, RKp significantly affected the natural regeneration of Korean pine in MBK forests. The basal-area thresholds limiting regeneration were found to be 80% in LKM stands and 40% in LFB stands. These basal-area thresholds provided evidence of why the zonal climax was MBK forests rather than pure Korean pine forests.

Importance of organ age in driving intraspecific trait variation and coordination for three evergreen coniferous species

Plant functional traits play an important role in plant growth and community composition in forest ecosystem. However, how the intraspecific trait variations for both leaf and branch were driven by organ age is less clear. We chose three evergreen coniferous species in the mixed broadleaved-Korean pine (Pinus koraiensis) forest in Northeast China and measured the functional traits for leaf and branch across organ ages. We mainly evaluated the influences of needle or branch age on the intraspecific trait (both leaf and branch) variations and bivariate correlation of traits for three species. We found that organ age had the largest contributions to the intraspecific variations in most traits for the three species. Current organ had high specific leaf area, high leaf nitrogen content, high specific branch length and low leaf and branch dry matter content, while perennial organ showed the opposite trend, indicating the differentiation of ecological strategies at different organ ages. The organ age significantly modified most of the trait-trait relationships, indicating that the transformation of the plant ecological strategy was driven by organ age. Unexpectedly, the variation in plant hydraulic traits was not affected by branch age and decoupled with most other traits for the three species. Our results suggest that the organ age effect should be incorporated into future studies of trait-based ecology for evergreen coniferous species.

Effect of canopy gap size on soil respiration in a mixed broadleaved-Korean pine forest: Evidence from biotic and abiotic factors

Understanding the effects of forest structure, the frequency and size of canopy gaps is pivotal for precisely modelling forest soil carbon budgets. We aimed to determine the differences in soil respiration between closed canopy areas and canopy gaps with various sizes and how soil respiration is affected by biotic and abiotic factors, e.g., soil nutrients, soil microbial biomass and community composition, enzyme activities and fine root biomass. Soil respiration and these environmental factors were measured in eleven tree fall gaps (separated into small, medium and large with sizes ranging from 20 m2 to 450 m2) and three control plots in a mixed broadleaved-Korean pine forest during the growing season. Our results showed that soil respiration was similar between the control and small canopy gaps, while it was 17–49% lower in the medium and large canopy gaps compared to that of the control. There was a significant parabolic relationship between soil respiration and soil moisture, and the optimum moisture was approximately 40%. Fine root biomass and soil enzyme activities showed positive effects on soil respiration across different levels of canopy gaps. Furthermore, soil respiration was significantly declined with increasing soil microbial diversity (OTUs of bacteria). Our findings demonstrate that canopy gap has significant impact on soil CO2 emission in a temperate mixed forest, however, further studies concerning other forest ecosystem types and larger scale are warranted.

Vertical variation and economic strategy of leaf trait of major tree species in a typical mixed broadleaved-Korean pine forest

Vertical variation and economic strategy of leaf trait of major tree species in a typical mixed broadleaved-Korean pine forest

Variation and relationships between twig and leaf traits of species across successional status in temperate forests

ABSTRACTRelationships among twig size, leaf size and leafing intensity are essential for predicting structure and function of twigs and leaves and ability of plants to acquire different environmental resources. We aimed to test whether trade-offs between twig and leaf traits for species would be influenced by forest successional status and sampling orientation within canopy. We measured four twig and leaf traits for seven coexisting broadleaf species across successional statuses in mixed broadleaved-Korean pine (Pinus koraiensis) forests in Northeast China. The results showed that both twig and leaf traits varied with successional status and twig level explained the largest variations in traits. Slopes of regression of leaf traits (i.e. individual leaf area, total leaf area and volume-based leafing intensity) against twig cross-sectional area were late-successional species > middle-successional species > early-successional species. Relationships between twig cross-sectional area and total leaf area in upper south and lower north canopy orientations did not vary with successional status of species. However, slopes of regression of twig cross-sectional area against total leaf area varied with successional status in other four sampling orientations. Our results highlight the importance of successional status and sampling orientation within canopy in controlling variations and trade-offs between twig and leaf traits.