Mixed Coniferous Broad-leaved Forest Research Articles

Litter removal exerts greater effects on soil microbial community than understory removal in a subtropical-warm temperate climate transitional forest

Litter and understory play important roles in maintaining structure and functions of belowground ecosystems in forests. However, how litter and understory affect soil microbial community is unclear. As part of a three-year (2016–2018) manipulative experiment, this study was designed to evaluate the effects of litter and/or understory removal on soil microbial community in a coniferous-broadleaved mixed forest of the subtropical-warm temperate transition zone in Central China. The results showed that soil moisture, NO3−-N, NH4+-N, and dissolved organic carbon were decreased under litter removal, but remained unchanged under understory removal. Total, bacteria, and actinomycetes PLFAs were significantly reduced by 11.2%, 16.3%, and 11.0% under litter removal, and by 10.1%, 13.3%, and 12.5% under understory removal, respectively. Both litter and understory removal suppressed network complexity of soil microbial community, but litter removal showed much stronger impacts on the biomass (−14.9 mg kg−1 vs. −10.9 mg kg−1) and composition (−7.77% vs. −2.89%) of bacteria (including gram-positive and gram-negative bacteria) as well as fungi to bacteria ratio than understory removal. Changes of soil NH4+-N and moisture might be primarily responsible for the inhibitory effects of litter removal on soil gram-positive and gram-negative bacterial biomass, respectively. Our findings highlight the contrasting responses of soil microbial community to litter and understory removal and would facilitate the mechanistic understanding of these two management practices on belowground ecology in climate transitional forests.

Shifts in ecological strategy spectra of typical forest vegetation types across four climatic zones

Ecological strategy spectrum is the relative proportion of species in different categories of ecological strategies in a biotic community. Here, we explored ecological strategy spectra in typical forest vegetation types across four climatic zones in China. We classified ecological strategy categories by using the “StrateFy” ordination method based on three leaf functional traits. Results showed that the predominant ecological strategies of species in the tropical rainforest were CS-selected, and the predominant categories in the evergreen-deciduous broadleaved mixed forest and warm-temperate coniferous-broadleaved mixed forest were CSR and S/CSR categories respectively, whereas those in the cold-temperate coniferous forest were the S-selected ones. Ecological strategy richness of forest vegetation decreased significantly with the increase of latitude. The categories of ecological strategies with more component S increased while those with more component C decreased with the change of typical forest vegetation types from tropical rainforest through evergreen-deciduous broadleaved mixed forest and warm-temperate coniferous-broadleaved mixed forest to cool-temperate coniferous forest. Our findings highlight the usefulness of Grime’s C-S-R scheme for predicting the responses of vegetation to environmental changes, and the results are helpful in further elucidating species coexistence and community assembly in varied climatic and geographic settings.

Effects of Vegetation Type on Soil Shear Strength in Fengyang Mountain Nature Reserve, China

Shear strength is an important mechanical property of soil, as its mechanical function plays critical roles in reducing land degradation and preventing soil erosion. However, shear strength may be affected by vegetation type through changes in the soil and root patterns. To understand the influences of different types of vegetation on shear strength, the soil shear indices of three typical vegetation types (broad-leaved forest, coniferous broad-leaved mixed forest, and grassland) were studied and evaluated at the Fengyang Mountain Nature Reserve, China. We employed a direct shear apparatus to measure the soil shear resistance index. We quantified the soil porosity, moisture content, and composition of particle size to determine the properties of the soil, and a root scanner was used to quantify the root index. The results revealed that there were significant differences in shear resistance indices at the stand level. Between the three vegetation types, the internal friction angle of the broad-leaved forest was the largest and the cohesion was the smallest. The soil moisture content and porosity of the coniferous broad-leaved mixed forest were higher than those of the broad-leaved forest, and the root volume density (RVD/cm3) of the broad-leaved forest was higher than that of the coniferous and broad-leaved mixed forest and grassland. Structural equation modeling results show that the soil particle size and root characteristics indirectly impacted the soil water content by affecting porosity, which finally affected shear strength. In general, there were significant differences in soil properties and plant root indices between the different stands, which had an impact on soil shear strength.

Fine Root Traits of Pinus koraiensis Varied with Soil Cation Exchange Capacity in Natural Forests

Adaptation of fine root plasticity to soil nutrients heterogeneity in natural forest ecosystems has not been well explored. The study aimed to determine seasonal variations of fine root traits in Pinus koraiensis natural forests and explore the relationship between fine root traits and soil properties. Root and soil samples were collected from the coniferous broad-leaved mixed forest (BP), monospecific P. koraiensis forest (MP), and coniferous mixed forest (CP). Soil available phosphorus (P) content for MP was 31.7% and 39.8% lower than for BP and CP. Soil cation exchange capacity (CEC) for MP was lower by 23.5% and 27.2% than for BP and CP, respectively. In July, specific root lengths and root surface areas for BP and CP (mixed forests) were significantly higher than for MP (monospecific forest). A structural equation model showed that CEC had a significant effect on fine root traits. Root diameter, root volume density, and root surface area density were negatively correlated with CEC. Fine root traits plasticity of P. koraiensis are closely related to soil available nutrient contents, CEC, and species composition at the ecosystem level.

Quantitatively distinguishing the impact of climate change and human activities on vegetation in mainland China with the improved residual method

ABSTRACT In recent decades, vegetation has faced the dual challenges posed by climate change and human activities. Quantitatively distinguishing the influences of climate change and human activities on vegetation changes is key to developing adaptive ecological protection policies. This study examined changes in temperature and precipitation to determine if anthropogenic land use changes have affected vegetation in mainland China. The contribution rates of temperature and precipitation changes and land use changes to vegetation dynamics are further calculated by the improved residual trend method, which considers the nonlinear relationship between vegetation and climate factors and time-lag effects from a spatiotemporal perspective and sets the base period for the equation. The results show that 68.81% of the vegetation in mainland China is in a state of sustained growth, where cultivated vegetation and grasses are the main greening vegetation types. The contribution of land use changes to vegetation changes in mainland China is higher than that of temperature and precipitation changes. Planting trees and grasses and returning farmlands to forests and grassland has increased the area covered by grasses and mixed coniferous broad-leaved forests, while cultivated vegetation coverage has decreased. Swamps are more sensitive to temperature and precipitation changes. We show that the improved residual trend method that considers temporal and spatial dimensions can reduce the uncertainty in quantifying the effects of climatic and anthropogenic factors on vegetation dynamics. This study provides a theoretical basis and a useful tool for future governmental implementation of ecological management strategies.

Forest Cover Changes in the Center of East European Plain Over the Last 150 Years

Changes in forest cover in the center of the East European Plain (Central Russian Upland) from the end of the 19th century to the end of 20th century have been assessed. Over that period, forest cover has increased in the northern part of the studied territory and declined in the southern part. After the end of the 1990s and beginning of 2000s, increases in forest cover occurred within the subzones of mixed coniferous–broad-leaved forest, while in the southern regions it has hardly manifested at all. The fallow land overgrowth rate, without any anthropogenic interference, has been determined for the Central Russian Upland (from 10 to 50% of fallow area has been covered by forest vegetation over a period of 10 years), decreasing gradually in from west-northwest to east-southeast. Special attention is paid to the forests that grew on nonforested lands over a period of 150 years. This process occurs everywhere in the northern part of the Upland and along the river valleys in the southern part. The forest structure of newly formed forests is studied as well (deciduous, mixed, pine, and spruce). In the southern parts of the Central Russian Upland, the newly grown forests are mostly pine plantations. The analysis of the field data suggests that, in the Central Russian Upland, within the broadleaved forests subzone, fallows are usually overgrown with birch (Betula pendula), or, less frequently, with aspen (Populus tremula). On the western and southwestern slopes, the overgrowth occurs with broadleaved (Querqus robur and Acer platanoides), small-leaved (Populus tremula), and steppe species (Prunus spinosa, Malus praecox, and Pyrus pyraster). In the south, overgrown fallows are dominated by steppe or adventive species (Acer negundo).

Effects of vegetation type, season, and soil properties on soil microbial community in subtropical forests

The diversity and composition of soil microbial community in forests are affected by vegetation type, season, and soil properties, but the relative importance of these factors on the diversity and composition of microbial community is poorly understood. In this study, high-throughput sequencing was used to assess the soil prokaryote (16S rRNA) and fungal (ITS rRNA) communities of five vegetation types (evergreen broad-leaved forest [EBL], deciduous broad-leaved forest, mixed coniferous–broad-leaved forest, coniferous forest [CF], and secondary shrubland [SS]) for four seasons in a secondary subtropical forest in Eastern China. Soil physicochemical properties and plant diversity were also surveyed for each vegetation type. Vegetation type, season, and their interaction significantly affected the Shannon diversity indexes of soil prokaryotes. The Shannon index of soil fungi was affected by vegetation type. The soil prokaryote and fungal compositions of the five vegetation types were significantly different. The prokaryote compositions of EBL, CF, and SS significantly changed in four seasons, but only the fungal composition of SS changed with the seasons. Variation partition showed that vegetation type and season individually explain 25% and 29% of the variance in prokaryote composition and 19% and 1% of the variance in fungal composition, respectively. Prokaryote diversity and composition were significantly driven by soil pH and organic carbon and fungal diversity and composition were significantly driven by soil pH and electrical conductivity when controlling the effects of vegetation types and seasons.

Species composition and community structure of coniferous-broadleaved mixed forest in Xiaolong Mountain, Gansu Province, Northwest China

Xiaolong Mountain, located in warm temperate subtropical transition zone, is one of the important biodiversity conservation areas in China. We analyzed species composition, community structure, and habitat preferences of all woody plant species with DBH (diameter at breast height)≥1 cm in a 6 hm2 plot in Xiaolong Mountain, Gansu Province, Northwest China. A total of 29251 individuals (41735 stems) belonging to 33 families, 65 genera, and 124 species were recorded. The 28 species with importance value ≥1 contributed 82.9% to the total abundance. The top four species with the highest importance value were Quercus aliena var. acuteserrata, Betula platyphylla, Lindera aggregata var. playfairii and Corylus heterophylla. The structure of DBH size class of all stems showed an inverse 'J' type, indicating a successful regeneration tendency in the understory. Results from the indicator species analysis showed that 11 species had significant habitat prefe-rences, an two species (Ostrya japonica and Acer stachyophyllum subsp. betulifolium) had the most obvious preferences. Results from the redundancy analysis and partial methods showed that topographic factors played a dominant role in determining species distribution.

Renewal of Fraxinus mandshurica Rupr. in Mixed Coniferous-broad Leaved Forests of the Southern Far East

Renewal of Fraxinus mandshurica Rupr. in Mixed Coniferous-broad Leaved Forests of the Southern Far East

Understanding the effects of fire and nitrogen addition on soil respiration of a field study by combining observations with a meta-analysis

Fire disturbance and atmosphere nitrogen (N) deposition could profoundly impact terrestrial ecosystem function. A field manipulative experiment was conducted in a coniferous-broadleaved mixed forest of the subtropical-temperate transition zone in Central China to evaluate the responses of soil respiration to fire and N addition from July 2014 to December 2018. The results showed that fire significantly stimulated soil respiration by 17.5% whereas N addition had no effects across the whole experimental period. The enhancement of soil respiration intensified with year after fire, being neutral during the first two years but statistically significant in the later three years, which could be attributable to interannual variations of the changes in soil temperature and the cover of woody species. By contrast, a global meta-analysis on soil respiration responses to fire in forests revealed no overall changes in soil respiration and the negative effects were observed between one and three years after the fire and in subtropical forests (-36.6%) only. The contrast findings highlight that general patterns revealed by meta-analyses may not be able to predict ecosystem responses to environment change at a specific site.

Floral composition and ecological distribution of wood-decaying fungi in Laojunshan National Park, Southwest China

Wood-decaying fungi are important components of forest ecosystem, mainly growing on the dead wood and decomposing lignin, cellulose, and hemi-cellulose. Understanding the ecological distribution of wood-decaying fungi are necessary to reveal their ecological function. In this study, we investigated wood-decaying fungi at three sites with different altitudes in Laojunshan National Park. Fruit bodies of fungi were collected and identified based on morphological and molecular analy-sis. In total 68 species were recorded, belonging to 40 genera, 21 families and 8 orders. Polyporaceae, Fomitopsidaceae, and Hymenochaetaceae were dominant families. The floral composition showed a distinct north temperate character, which was the most important element among all the bio-geographical elements with the highest percentage of 38.2%. These wood-decaying fungi can be divided into two ecological types: saprophytic (63 species) and ectomycohizal (5 species). Among these saprophytic fungi, 51 species could cause white rot and 12 species cause brown rot. The amounts of fungal species in deciduous broad-leaf forest (DBF), coniferous broad-leaved mixed forest (CBMF) and dark coniferous forest (DCF) were 34, 26 and 22, respectively. Postia fragilis and Stereum hirsutum, distributed in all the three types of forests, were dominant species of Laojunshan National Park.

Spatial structure optimization simulation of main forest types in Great Xing'an Mountains, Northeast China

Based on the data from four 1 hm2 permanent plots in main forest types [namely natural Larix gmelinii forest (LF), natural Betula platyphylla forest (BF), coniferous-broadleaved mixed forest (CBMF) and coniferous mixed forest (CMF)] in Great Xing'an Mountains, a comprehensive cutting index of individual tree (T), based on the commonly used spatial structure parameters [i.e., mingling (M), neighborhood comparison (U), uniform angle index (W), and competition index (CI)] and non-spatial structure parameters [tree vigor index (DC), tree stability index (DH)], was constructed using combined AHP and entropy evaluation method. The cutting process was simulated by Excel VBA to determine the best tending intensity on the basis of systematic comparison of comprehensive T-value under different tending intensities (10%, 20%, and 30%) of different forest types. The results showed that, in the initial state, the mean values of W were all 0.57, indicating a typical cluster distribution. The mean values of U ranged from 0.50 to 0.51 and the dominant degree of overall growth of trees was in a typical mean state. The mixed degree of four main forest types was generally low, with the mixed forest being obviously higher than the pure forest. The mean competition index within the stand was above 2.0, indicating higher competition pressure. The stability and growth vigor index of LF were significantly higher than those of other stands. Overall, the management urgency of BF was significantly higher than that of other stands. With regard to T-value growth rate between adjacent tending intensities, the optimal cutting intensity was 30% for LF forest and 10% for other types. The relative growth rates were 9.7%, 7.9%, 6.6% and 3.9% respectively. However, from the perspective of T-value and canopy density with different tending intensities, the optimal cutting intensity of BF was 20%, and the others were all 30%, in which the T-values were increased by 28.9%, 16.4%, 17.5% and 9.2% respectively. After simulated harvesting, stand structure was improved in various degrees and the mixed degree of tree species was increased. The horizontal distribution pattern of stand tended to random distribution. The dominance degree of dominant tree species was increased. The competition pressure of trees was decreased. DC of trees was slightly lower and the DH of trees was improved.

Precipitation mediates the temporal dynamics of net primary productivity and precipitation use efficiency in China’s northern and southern forests

AbstractKey messagePrecipitation mediates the dynamic of net primary productivity and precipitation use efficiency across the North-South Transect forests of China, which may result from an increase of productivity in warm temperate deciduous broad-leaved forests or a decrease of precipitation use efficiency in temperate coniferous broad-leaved mixed forests.ContextPrecipitation use efficiency (PUE), the ratio of net primary productivity (NPP) to annual precipitation, is one of the key factors that can clarify the response of forest ecosystem carbon and water cycles to ongoing climate change.AimsTo investigate large-scale patterns of NPP and PUE, and to determine how NPP and PUE would respond to climate and soil variables across the North-South Transect forests (TNSTF) of China.MethodsWe revealed the spatial pattern dynamics of NPP and PUE in the TNSTF from 2000 to 2010 employing MOD17 NPP data and further explored the responses of NPP and PUE to environment factors across the TNSTF. Additionally, the temporal dynamics of NPP and PUE in different forest types and their dependencies on climate variation were investigated.ResultsThe results indicated that NPP increased from 2000 to 2010 in most regions across the TNSTF. The spatial distribution pattern of NPP was mainly correlated with climate factors in the TNSTF rather than soil properties. Spatially, an increased trend of PUE (2000–2010) was found in the south and decreased PUE was revealed in the north of the TNSTF. In addition, the spatial distribution of PUE in the TNSTF was associated with both climate and soil factors. For different forests, only the NPP in warm temperate deciduous broad-leaved forests significantly increased (2000–2010, R2 = 0.33, P < 0.05) due to the increase in precipitation (R2 = 0.82, P < 0.0005). Moreover, only the PUE in temperate coniferous broad-leaved mixed forests presented a significantly decreasing trend (2000–2010, R2 = 0.38, P < 0.05), which was significantly negatively correlated with precipitation (R2 = 0.80, P < 0.0005).ConclusionOur findings demonstrated that climate governed the spatial distribution of NPP; in addition to the climate, soil properties also played an important role in shaping the spatial distribution of PUE. Our findings highlight that the dynamics of precipitation rather than those of temperature mediated the variations in NPP and PUE in forests across the TNSTF.

Responses of soil Collembolans to vegetation restoration in temperate coniferous and broad-leaved mixed forests

A total of 900 soil samples were collected from five habitats, including primary coniferous broad-leaved mixed forests, secondary coniferous broad-leaved mixed forests, secondary broad-leaved forests, secondary shrub forests, and cutover lands in spring, summer, and autumn to quantify responses of soil Collembolans (springtails) to the restoration of vegetation of temperate coniferous and broad-leaved mixed forests. The results reveal that the taxonomic composition of Collembolans varied in the different stages of vegetation restoration. Seasonal variations were in regard to their abundance and richness. High similarities existed in Collembola communities at different stages of vegetation restoration, and distribution patterns of Collembola taxa displayed an evenness throughout all habitats. Soil Collembolans tended to gather on litter layers and soil surface; the highest abundance was found in the upper 5 cm soil layer during the initial stages of vegetation recovery. Tomocerus, Proisotoma, and Folsomia genera responded positively to the restoration of vegetation. However, responses of Ceratophysella and Parisotoma genera were negative. In addition, the Onychiuridae family did not respond to the vegetation restoration process. It was concluded that restoration of vegetative cover can increase the abundance of soil Collembolans, but different genera respond differently.

Effects of simulated acid rain on soil respiration and its component in a mixed coniferous-broadleaved forest of the three gorges reservoir area in Southwest China

BackgroundSoil respiration in forest ecosystems is an important part of the forest carbon (C) cycle. Studying the variation patterns of soil respiration under acid rain conditions is critically important for understanding forest C balance and performing rational forest management and operations.MethodsA split-plot design field experiment was performed in a mixed coniferous-broadleaved forest in the Three Gorges Reservoir Area of Jinyun Mountain, Chongqing from January 2016–January 2018. There were 4 main blocks; each was split into untrenched (UT) and trenched (T) treatments. Treatments with four gradient pH levels of 4.5 (control), 4.0, 3.25 and 2.5 were randomly assigned to the untrenched and trenched treatments. The soil CO2 fluxes, soil temperature, and soil moisture content were evaluated under simulated acid rain. Additionally, the effects of soil properties (soil pH, organic C, C:N ratio, microbial biomass, and enzyme activity) on soil respiration were analysed.ResultsThe soil CO2 fluxes exhibited seasonal variation trends. The annual mean soil respiration rates of the UTCK (control), UT4.0, UT3.25, and UT2.5 treatments in untrenched plots were 1.91, 1.91, 1.77, and 1.74 μmol∙m− 2∙s− 1 in 2016 and 1.91, 1.81, 1.55 and 1.37 μmol∙m− 2∙s− 1 in 2017, respectively. The annual mean heterotrophic respiration rates of the TCK (control), T4.0, T3.25, and T2.5 treatments in the trenched plots were 1.39, 1.32, 1.19 and 1.14 μmol∙m− 2∙s− 1 in 2016 and 1.28, 1.18, 1.02 and 0.83 μmol∙m− 2∙s− 1 in 2017, respectively. Acid rain had a significant cumulative effect on soil respiration and heterotrophic respiration (P < 0.01). In 2016, soil respiration was similar in the UTCK versus the UT4.0 treatment but significantly inhibited under higher acidity. In 2017, soil respiration and heterotrophic respiration were significantly decreased by simulated acid rain. The treatments increased the temperature sensitivity of soil respiration but did not significantly affect the soil temperature or moisture content (P > 0.05); moreover, they significantly increased the soil organic C content and C:N ratio, lowered the hydrolysable N and total P concentrations, and lowered the soil pH and fine root biomass at a later experimental stage. Urease and sucrase activities were significantly reduced in the higher-acidity treatments. Soil respiration rate was significantly positively correlated with the soil pH, fine root biomass, and urease and sucrase activity and significantly negatively correlated with the soil organic C and C:N ratio.ConclusionsAcid rain had a significant cumulative and inhibitory effect on soil respiration and heterotrophic respiration, while soil temperature and moisture had a limited effect on soil respiration under simulated acid rain. The variation in soil properties (e.g., soil organic C, C:N ratio, and fine root biomass) caused by acid rain inhibited the microbial utilization of substrates, which was the main cause of the respiration differences.

Effects of Soil Fauna on Cellulose and Lignin Decomposition of Plant Litter in the Changbai Mountain, China.

Cellulose and lignin decomposition is crucial for efficient nutrient cycling, yet few studies have been performed regarding the effects of soil fauna on cellulose and lignin decomposition. This study was conducted to better understand the effects of soil fauna on lignin and cellulose decomposition in the Changbai Mountain. Litterbags of two different mesh sizes were used to examine cellulose and lignin decomposition of 11 species of plant litter in the four vegetation zones of the Changbai Mountain North Slope over a 24-mo period. Cellulose and lignin clearly declined over time for all 11 species of plant litter. Cellulose decomposition rate faster than the rate of lignin decomposition in the majority of plant species. Soil fauna could promote the decomposition of cellulose and lignin. The abundance and richness of soil fauna in coniferous broad-leaved mixed forests were greater than in coniferous forest, Betula ermanii Cham. (Fagales: Betulaceae) forest, and alpine tundra. Soil fauna had a greater effect on Abies nephrolepis Maxim. (Pinales: Pinaceae) cellulose and lignin, whereas contribution rates were relatively lower in the Fraxinus mandshurica Rupr. (Contortae: Oleaceae) and Acer mono Maxim. (Sapindales: Aceraceae) litterbags at the end of the experiment. Litter quality was negatively correlated with the soil faunal contribution to litter decomposition directly. Overall, the findings of this study have implications for the effects of soil fauna on cellulose and lignin decomposition in the alpine ecosystem, and also can provide experimental evidence that soil faunal contribution is affected by soil faunal communities and litter quality.

Responses of soil invertebrates to different forest types in the Changbai Mountains of China

ABSTRACTSoil invertebrates can potentially respond to variation of soil and vegetation in a timely manner, yet the relationships between soil invertebrates to the forest ecosystem remain a matter of debate. In order to better understand the responses of soil invertebrates to different forest types in the temperate forest ecosystem, a total of 450 soil invertebrates’ samples were collected from 5 forest types, namely primeval coniferous broad-leaved mixed forests, secondary coniferous broad-leaved mixed forests, secondary broad-leaved forests, secondary Quercus mongolica forests, and secondary shrub forests in spring, summer, and autumn. The results revealed that the distribution patterns of soil invertebrates differed among the forests, and the taxonomic compositions of soil invertebrates slightly varied among the different forest types in the Changbai Mountains, yet high similarities exist in the soil invertebrates’ communities. Seasonal variation in the abundance and richness of soil invertebrates was observed, though no significant differences were detected among the seasons. Hypogastruridae were more suitable for the forest types with relatively higher levels of canopy cover. Furthermore, soil invertebrates responded mostly to soil temperature and moisture (RV = 0.44, p = 0.02), available nutrients (RV = 0.42, p = 0.04), and minerals (RV = 0.39, p = 0.04). Overall, the findings of this study provide evidence that different forest types affect the distribution patterns of soil invertebrates, but the responses of soil invertebrates to forest types differed between their taxa.

Changes in defense traits of young leaves in subtropical forests succession

Plants develop diverse adaptive traits in changeable environments, yet whether plant defense traits change during succession remains unclear. In this study, we investigated the young leaf physical traits (i.e., upright orientation of leaves, trichomes, an enhanced cuticle, and a multilayered epidermis) and leaf color trait (i.e., red pigmentation) of dominant plants in three subtropical forests. These forests included a pioneer forest, a mixed coniferous-broadleaved forest, and a monsoon-evergreen broadleaved forest representing early, middle, and later successional stages, respectively. Our results show that the red color trait in young leaves is related to anti-herbivory defense, and the percentage of species with red young leaves is higher in later than in early succession. Physical defense tends to be weaker for red young leaves than for green young leaves in early and middle successions. In addition, the number of defense traits of young leaves increases with succession. We speculate that young leaves in subtropical forests depend increasingly on multiple defense traits during succession because of the increased biotic stresses and environmental complexity in later succession.

Vegetation and climate changes since the middle MIS 3 inferred from a Wulagai Lake pollen record, Inner Mongolia, Northeastern China

The climate conditions during Marine Isotope Stage (MIS) 3 were similar to present-day conditions, but whether humidity then exceeded present levels is debated, and the driving mechanisms of palaeoclimate evolution since MIS 3 remain unclear. Here, we use pollen data from Wulagai Lake, Inner Mongolia, to reconstruct vegetation and climate changes since the middle MIS 3. The steppe biome is reconstructed as the first dominant biome and the desert biome as the second, and the results show that the vegetation was steppe over the last 43,800 years. Poaceae, Artemisia, Caryophyllaceae and Humulus were abundant from middle to late MIS 3, indicating humid climate conditions. As drought-tolerant species such as Hippophae, Nitraria and Chenopodiaceae spread during MIS 2, the climate became arid. The Holocene is characterized by the dominance of steppe with mixed coniferous-broadleaved forests in the Greater Hinggan Range, and the desert biome retains high affinity scores, indicating that the climate was semi-arid. The climate from middle to late MIS 3 was wetter than in the Holocene; this shift was related to changes in the Northern Hemisphere's solar insolation and ice volume. The humid conditions during MIS 3 were attributed to strong ice–albedo feedback, which led to evaporation that was less than the precipitation. The enhanced evaporation caused by increased solar insolation and decreased ice volume might have exceeded the precipitation during the Holocene and resulted in low effective humidity in the Wulagai Lake basin.

Spatial distribution characteristics of soil organic carbon in subtropical forests of mountain Lushan, China.

The study on the spatial distribution of forest soil organic carbon (SOC) is of great significance for accurate assessment of carbon storage in forest ecosystems. In the present study, by taking eight kinds of forest soils of Mountain Lushan in the subtropical area as the research object, we studied the spatial distribution characteristics of SOC in this mountainous area. The results showed that the SOC content and SOC density (SOCD) of main forest types in the Mountain Lushan were lower than the national and the world average. The soil layer of Lushan forest was thinner, and the SOC and active SOC (ASOC) contents of different forest types and SOCDs are the highest in the surface soil. SOCD of the topsoil accounts for 32.64-54.03% of the total SOCD in the whole soil profile. Surface litter is an important source of SOC, and the different vegetation types are the important reason for the different spatial distribution of SOC in this area. Soil SOC contents in the high-altitude forest (bamboo forest, deciduous broadleaf forest, Pinus taiwanensis forest, evergreen-deciduous forest, and coniferous-broadleaved mixed forest) were higher than those in the low-altitude forest (evergreen broadleaf forest, shrub, and Pinus massoniana forest). However, the difference in SOC content exhibited at the altitude gradient is significantly lower than that in SOC in the soil profile. This indicates that both soil depth and elevation are the important factors that affected SOC distribution. However, the influence of soil depth on spatial distribution of SOC may be more complex than that of altitude. Vegetation types and soil properties are the main reasons for the large differences of reduction rate in the contents of SOC and ASOC.