Temperate Broad-leaved Forest Research Articles

LANDSCAPES OF THE BELARUSIAN POLESIE EASTERN AREA DURING THE CLIMATIC OPTIMUM OF THE MURAVIAN INTERGLACIAL

The paleolandscapes existed in the eastern area of the Belarusian Polesie region during the climatic optimum of the Muravian Interglacial were reconstructed.
 This work was based on the paleogeomorphological chart compiled with the core data of boreholes located in the investigation area, the composition of sediments, an approximate depth to the groundwater table, as well as on the evidences of the flora and vegetation in the warmest phase of the Muravian Interglacial obtained as a result of the palynological studies of the relevant sediments.
 The data available suggest that the flat landscapes of the temperate continental broad-leaved forest type existed in the investigation area at that time. This type landscapes are divided into 6 groups including 14 kinds and 10 varieties.
 The represented chart of the paleolandscapes reflects an absolute predominance of the broad-leaved forests, but in contrast to the western part of the Belarusian Polesie with a lesser participation of the West European species peculiar to the areas with the warmer oceanic climate.
 The completed reconstructions can be used to forecast the possible future landscape changes on the Belarusian
 Polesie region under the global warming conditions, which can exceed the parameters of the Holocene climatic optimum and reach the climax of the Muravian interglacial.

Early and Middle Pleistocene vegetation and its impact on faunal succession on the Liaodong Peninsula, Northeast China

Pollen evidence from a 25.3-m-long section (~2.2–0.41 Ma) in the Jinyuan Cave, Liaodong Peninsula, indicates that from the Early–Middle Pleistocene, the climate showed a trend of gradual cooling and drying, with obvious fluctuations. The vegetation was represented by temperate broad-leaved forest from ca. 2.2 to 1.87 Ma, suggesting a relatively warm and humid climate. The period from 1.87 to 1.82 Ma witnessed an obviously cold and dry event, and coniferous and broadleaved mixed forests developed from 1.82 to 1.76 Ma. From 1.52 Ma to the Mid-Pleistocene Transition (MPT), the vegetation was dominated by forest steppe, and the climate became cold in the later stage. During the 0.59–0.41 Ma period, steppes developed, and the climate was cold and arid. At the same time, with climate variation, the faunal communities also changed obviously and co-evolved with vegetation types. In the early stage of the Early Pleistocene, the warm and humid climate was related to the presence of a wide range of thermophilous animals. From 1.7 to 1.5 Ma, the transition from forest to forest steppe might have promoted the emergence of certain grassland-adapted animals. During the MPT, grassland-adapted animals became dominant due to the flourishing forest steppe vegetation. The Middle Pleistocene witnessed the expansion of steppe and animals adapted to the arid grassland environment at that time.

Comparison of Soil Greenhouse Gas Fluxes during the Spring Freeze–Thaw Period and the Growing Season in a Temperate Broadleaved Korean Pine Forest, Changbai Mountains, China

Soils in mid-high latitudes are under the great impact of freeze–thaw cycling. However, insufficient research on soil CO2, CH4, and N2O fluxes during the spring freeze–thaw (SFT) period has led to great uncertainties in estimating soil greenhouse gas (GHG) fluxes. The present study was conducted in a temperate broad-leaved Korean pine mixed forest in Northeastern China, where soils experience an apparent freeze–thaw effect in spring. The temporal variations and impact factors of soil GHG fluxes were measured during the SFT period and growing season (GS) using the static-chamber method. The results show that the soil acted as a source of atmospheric CO2 and N2O and a sink of atmospheric CH4 during the whole observation period. Soil CO2 emission and CH4 uptake were lower during the SFT period than those during the GS, whereas N2O emissions were more than six times higher during the SFT period than that during the GS. The responses of soil GHG fluxes to soil temperature (Ts) and soil moisture during the SFT and GS periods differed. During the SFT period, soil CO2 and CH4 fluxes were mainly affected by the volumetric water content (VWC) and Ts, respectively, whereas soil N2O flux was influenced jointly by Ts and VWC. The dominant controlling factor for CO2 was Ts during the GS, whereas CH4 and N2O were mainly regulated by VWC. Soil CO2 and N2O fluxes accounted for 97.3% and 3.1% of the total 100-year global warming potential (GWP100) respectively, with CH4 flux offsetting 0.4% of the total GWP100. The results highlight the importance of environmental variations to soil N2O pulse during the SFT period and the difference of soil GHG fluxes between the SFT and GS periods, which contribute to predicting the forest soil GHG fluxes and their global warming potential under global climate change.

Seasonal patterns of fine root dynamics and their contribution to net primary production in hinoki cypress (Chamaecyparis obtusa) and konara oak (Quercus serrata) forests

Key messageFine root and litterfall are major contributor of NPP and fine root production may reflect forest productivity in a warm-temperate forest in Japan.Forest ecosystems play an important role as the major carbon sink on land, with fine root dynamics and litterfall representing major carbon fluxes. The objectives of this research were to estimate NPP including annual fine root production values, to investigate fine root dynamics and the relationships between above– and belowground organs in konara oak (Quercus serrata) and hinoki cypress (Chamaecyparis obtusa) forests. Litterfall was collected seasonally for 1 year from June 2013. The ingrowth core method and the sequential soil core method were applied with a root litterbag experiment to estimate fine root (< 2 mm) production (FRP), mortality (FRM), and decomposition (FRD) for 1 year (from 2013 to 2014), using the continuous inflow estimate method and the simplified decision matrix. The total NPP ranged from 8.2 to 13.9 (t ha− 1 yr− 1), and the sum of aboveground litterfall and FRP accounted for 60% of the total NPP on average, confirming the significance of above- and belowground litter for the forest NPP as a source of detritus for the decomposer system. In hinoki cypress stand, fine root biomass peaked in the end of winter while fine root necromass showed the highest peak in late summer. In konara oak stand, only very fine root (< 0.05 mm) biomass and necromass demonstrated significant seasonal patterns. The seasonal patterns of fine root production did not differ between forest types and root diameter classes. We found a possible relationship between above- and belowground production and fine root production tended to be high in productive forests. This study improves our understanding of different patterns of carbon dynamics between temperate broadleaved and coniferous forest ecosystems.

Coarse woody debris features of a warm temperate deciduous broad-leaved forest, northern China

Stocking and structural composition of a deciduous broad-leaved forest were determined to predict coarse woody debris quantity by quantifying the empirical relationships between these two attributes. The most ecologically significant families by stem density were Salicaceae, Betulaceae, Fagaceae, and Aceraceae. Populus davidiana was the most dominant species followed by Betula dahurica, Quercus mongolica, and Acer mono. The four species accounted for 69.5% of total stems. Numerous small-diameter species characterized the coarse woody debris showing a reversed J-shaped distribution. The coarse debris of P. davidiana, B. dahurica, and Q. mongolica mainly comprised the 10–20 cm size class, whereas A. mono debris was mainly in the 5–10 cm size class. The spatial patterns of different size classes of coarse woody debris were analyzed using the g-function to determine the size of the tree at its death. The results indicate that the spatial patterns at the 0–50 m scale shifted gradually from an aggregated to a random pattern. For some species, the larger coarse debris might change from an aggregated to a random distribution more easily. Given the importance of coarse woody debris in forest ecosystems, its composition and patterns can improve understanding of community structure and dynamics. The aggregation pattern might be due to density dependence and self-thinning effects, as well as by succession and mortality. The four dominant species across the different size classes showed distinct aggregated distribution features at different spatial scales. This suggests a correlation between the dominant species population, size class, and aggregated distribution of coarse woody debris.

The maximum carboxylation rate of Rubisco affects CO2 refixation in temperate broadleaved forest trees

Mesophyll resistance to CO2 diffusion (rm) and the maximum carboxylation rate of Rubisco (Vcmax) affect photosynthetic rates, and can potentially also influence the percentage of respiratory and photorespiratory CO2 being refixated (Pr) by mesophyll cells. Here we investigated how various leaf anatomical traits (e.g. leaf mass per area [LMA] and leaf dry matter content [LDMC]) influenced rm in leaves of mature forest trees. We further explored how rm and Vcmax in turn affected Pr, and if these traits varied among species and leaves along a light gradient. Photosynthetic CO2 response of leaves grown in high-, medium-, and low-light environments was measured, from Pinus sylvestris [Scots pine], Picea abies [Norway spruce], Quercus robur [English oak], and Betula pendula [Silver birch] in southern Sweden. A modified version of the Farquhar-von Caemmerer-Berry model was fitted to the leaf gas exchange data to estimate Vcmax, rm and Pr. We found that of all leaf traits measured, only LMA for Q. robur was significantly higher in leaves from high-light environments. When comparing species, both rm and LMA were significantly higher in the conifers, and rm had a negative correlation with Vcmax. We found that Pr was similar between different species and functional groups, with an average of 73.2% (and SD of ±10.4) across all species. There was a strong, positive correlation between Pr and Vcmax in broadleaves, and we hypothesise that this effect might derive from a higher CO2 drawdown near Rubisco in leaves with high Vcmax.

Influences of forest gaps on soil physico-chemical and biological properties in an oriental beech (Fagus orientalis L.) stand of Hyrcanian forest, north of Iran

Abstract: Understanding the effects of silvicultural practices including single-tree selection on soil properties is essential for forest management in temperate broadleaved beech forests. Changes in physico-chemical and biological soil properties in 15 harvest-created gaps under single-tree selection and the adjacent closed canopies, with five replications for each, were studied 6 years after gap creation in an oriental beech (Fagus orientalis L.) stand of the Hyrcanian forest. Gaps were classified into three size classes: small (85-130 m2), medium (131-175 m2) and large (176-300 m2). Soil cores were collected at the center and at the edge of gaps, and under the adjacent closed canopy. Results indicated that gap size significantly affected soil texture and bulk density, whereas soil organic carbon (SOC), total nitrogen and pH showed a significant gradient from the center to the edge of gap independently form their size. SOC and total nitrogen at the center of gaps were also significantly lower than closed-canopy, in particular for the medium-gap; contrastingly, the bulk density with the highest mean value was found at the center of the large-gap. Gap size had no significant influence on soil microbial biomass. These results highlighted that similar conditions in terms of many soil properties were still present among gaps and adjacent closed-canopy stands six years after logging, though canopy openness triggered a reduction in carbon and nitrogen availability along with the related microbial activity at the center of gaps, independently from their size. Therefore, if aimed at preserving an uneven aged structure along with soil quality in temperate broadleaved deciduous forest as the oriental beech stands in the Hyrcanian region, single-tree selection practice for harvesting trees can be recommended as sustainable forest management type.

Soil-surface pollen assemblages and quantitative relationships with vegetation and climate from the Inner Mongolian Plateau and adjacent mountain areas of northern China

We statistically analyzed 396 soil-surface pollen samples from the Inner Mongolian Plateau and its adjacent mountain areas of northern China to gain insights into pollen–vegetation–climate. The results of indicator species analysis, canonical correspondence analysis (CCA) and boosted regression tree (BRT) analysis suggest that: 1) soil-surface pollen assemblages can differentiate between desert, steppe, meadow steppe, cool broadleaved forest, cool conifer forest, and temperate forest, but fail to differentiate between steppe and forest steppe; shrub and temperate forest; and temperate broadleaved forest, temperate mixed conifer-broadleaved forest, and eurythermic conifer forest; 2) pollen taxa, with low percentages but frequent occurrences, strongly indicate presence in the vegetation; 3) mean annual precipitation (MAP) is the most dominant variable influencing soil-surface pollen assemblages and the most promising climate variable for quantitative reconstructions. Weighted averaging partial least squares regression (WA-PLS), modern analogue technique (MAT), and boosted regression trees (BRT) were used to construct a series of pollen-climate calibration sets. WA-PLS and MAT outperform BRT under leave-one-out cross-validation. WA-PLS models are less susceptible to spatial auto-correlation than MAT models, making WA-PLS models generally the best choice. Our soil-surface pollen data will contribute to modern pollen data in eastern Asia.

Diurnal variation and light response of net ecosystem carbon exchange in a temperate broadleaved deciduous forest at Maoershan, Northeast China

Photosynthetically active radiation (PAR) is a key environmental factor affecting the change of net ecosystem exchange (NEE) during the daytime. However, the coordinate system of PAR measured by horizontal radiometers over sloping terrain does not match that of NEE after tilt-corrected of the ultrasonic anemometer. Using the temperate deciduous broad-leaved forest at the Maoershan site with an average slope of 9° and a azimuth of 296° as a case, we investigated the diurnal variations in NEE and its driving factors in the growing season (May to September) of 2016. We assessed the differences in estimating light response parameters and the explanations of NEE by other environmental factors between the PAR measured by horizontal and slope-parallel radiometers. The results showed that the diurnal change of NEE in each month of the growing season presented a morning-afternoon asymmetrically unimodal curve: the value was negative (net carbon absorption) about 2.5 h after sunrise, reached the peak around 12:00, then approached zero again at two hours before sunset. The daily net uptake maximized in July and minimized in May. During the whole growing season, the time-lag and difference in the PAR measured by the horizontal versus slope-parallel radiometers led to that the PAR values measured by the horizontal radiometer increased photosynthetic quantum yield (α) and daytime respiration rate (Rd) by 13.3% and 11.5%, respectively, and decreased the maximum photosynthetic efficiency (Amax) by 7.7%. The light response curves of NEE were asymmetrical in the morning and afternoon, with Rd and Amax in the afternoon being greater than that in the morning. Weather conditions affected light response parameters: on cloudy days, Amax was higher than that in sunny days, the α and Rd were lower versus those in sunny days for most conditions. However, the monthly Amax and Rd were generally higher for horizontally measured PAR than for slope-parallelly measured PAR, especially for Amax in the cloudy afternoon. The radiometer-orientation affected the explanation of daytime NEE by air temperature (Ta) and vapor pressure deficit (VPD). The correlation of NEE residual based on the slope-parallel radiometer with Ta and VPD (r ranged: 0.013 to 0.197, 0.098 to 0.224) was tighter than that based on the horizontal radiometer (r ranged: 0.082 to 0.219, 0.162 to 0.282) when the negative correlations with Ta for September was excluded. Our results indicated that the measurements of PAR on the inclined terrains could cause errors in the environmental interpretations of NEE. Such findings had implications for the radiometric measurement of mountain vegetation and the reasonable interpretation of carbon exchange in terrestrial ecosystems.

Effect of Soil Fauna on Home-Field Advantages of Litter Mass Loss and Nutrient Release in Different Temperate Broad-Leaved Forests

The home-field advantage (HFA) of litter decomposition dynamics has been investigated intensively in different ecosystems with a wide variety of plant types. HFA mainly occurs due to the specialization of a soil organism. However, for the HFA, the linkages between litter mass loss, nutrient release, and soil faunal community are not fully understood. Thus, in this study, we performed a reciprocal litter transplant experiment using coarse and fine mesh litterbags in a Quercus mongolica Fisch. ex Ledeb. forest dominated by Q. mongolica (QM) and Acer pseudosieboldianum (Pax) Komarov (AP) and miscellaneous wood forests dominated by Juglans mandshurica Maxim. (JM) and Ulmus laciniata (Trautv.) Mayr. (UL). Results showed that the A. pseudosieboldianum litter displayed a significantly higher total abundance of Oribatida, Tomoceridae, and Entomobryidae at home than away from home after 7 months. However, all litters showed no significant difference in the HFA between the coarse mesh and fine mesh sizes during the 12-month experiment. A. pseudosieboldianum and J. mandshurica litters showed a significantly higher positive HFA for the C release in the coarse mesh than in the fine mesh litterbags after 7 months. Q. mongolica and J. mandshurica litters showed a significantly higher positive HFA for N release in the coarse mesh than in the fine mesh litterbags after 7 months. The A. pseudosieboldianum litter showed a significantly higher positive HFA for N release in the coarse mesh than in the fine mesh litterbags after 12 months. Q. mongolica and A. pseudosieboldianum litters showed a significantly higher positive HFA for S release in the coarse mesh than in the fine mesh litterbags after 7 and 12 months, respectively. However, A. pseudosieboldianum and Q. mongolica litters showed a significantly higher negative HFA for S release in the coarse mesh than in the fine mesh litterbags after 7 and 12 months, respectively. Our results illustrated that soil faunal specialization was found in the A. pseudosieboldianum litter only at home after 7 months. Soil fauna had a weak effect on the HFA of the litter mass losses during the 12-month experiment. Soil fauna drove the positive HFA for the N release of both the high- and low-quality litters. Soil fauna have a positive and negative HFA for S release in the low-quality litter.

Population dynamics and types of habitats at breeding sites of raptors (Falconiformes) of the Donetsk Ridge along a gradient of anthropogenic disturbance

Studies of diurnal birds of prey may be quite indicative of the state of natural ecosystems and of the level of impact of human-induced factors on their functions. The aim of this work was to analyse the long-term dynamics of the raptor populations within the Donetsk Ridge, to identify which habitat or habitat mosaics are preferred in nesting territories and home ranges depending on the level of anthropogenic transformation of the environment. The studies were conducted in 1999–2019. The total length of the walking routes was 2,864 km while a distance of 1,548 km was covered by car routes. 306 nests of the birds of prey or those potentially belonging to the members of this group were found and re-examined. The long-term dynamics of the population of Falconiformes was characterized by a general decline in the numbers of most species. There was a loss of representatives of the boreal and desert-steppe faunistic complexes and simultaneous increase in the participation of representatives of the nemoral and forest steppe faunistic complexes associated with the floodplain forests of the Siversky Donets River valley and the bayrak oak forests of the central part of the Donetsk Ridge. The impact of the anthropogenic factor on the dynamics of the population of the birds of prey is ambiguous. For the species which are sensitive to changes in the environment, such as the European Honey Buzzard, the Northern Goshawk, the Merlin and the Red-footed Falcon, a general negative dynamics of the populations is observed. The positive trend in the numbers of the Long-legged Buzzard and the Saker Falcon is linked to the expansion of the both species into the territory of the Donetsk Ridge. The habitat structure of the nesting territories is quite diverse in different species of diurnal birds of prey. This is especially noticeable in the ratio of forest and grassland habitats. Based on the selectivity index, we found that the vast majority of the raptors of the Donetsk Ridge prefer temperate broad-leaved forests when choosing nesting territories. The structure of the home ranges of all forest species of diurnal birds of prey not only depends on the optimal ratio of open and forested areas but on the presence of ecotones of considerable length which originated in the complex mosaics of habitat complexes. The stable number of dendrophiles and the disappearance (decrease in number) of sclerophiles and campophiles indicates the least anthropogenic transformation of forest habitats and a radical transformation of open spaces – meadows and steppes. The most successful were eurytopic birds of prey and species with pronounced anthropotolerance.

From tree to stand-level structural complexity — Which properties make a forest stand complex?

Management for complexity has become an important paradigm for European and North American forestry. Recent advancements in data processing allow for a detailed, three-dimensional and objective quantification of structural complexity in forests based on terrestrial laser scanning data. In our study, we used such 3D data from an exemplary temperate broad-leaved forest in Thuringia, Germany, to gain insights to the relationship between tree-level structural complexity and stand-level structural complexity. From our study site, which was 80 by 80 m in extent with a total of 215 trees growing in it, we created a dataset that contained each tree as an independent point cloud. Random sample plots of varying size (10 × 10 m; 15 × 15 m; 20 × 20 m) where used to create sub-plots (sampling with replacement) and to enable for the investigation of effects of scale. Our study revealed that plot-level complexity of plots up to 20 × 20 m is largely determined by the complexity of the most complex-structured tree individual. Furthermore, a high tree complexity and variability thereof in the stand was generally beneficial to stand structural complexity. Other individual tree characteristics, such as a large crowns, were also identified to have positive effects on plot-level complexity. We conclude that management for complexity should focus on large-crowned, highly-complex tree individuals as key elements of stand structural complexity. This indicates that large and old trees may not only be of great importance as habitat trees potentially increasing biodiversity, but also due to their contribution to the overall stand-level complexity.

Effect of dry-wet cycles on carbon dioxide release from two different volcanic ash soils in a Japanese temperate forest

ABSTRACT In the present study, two volcanic ash soils (soil A and B) from a temperate broad-leaved forest in eastern Japan were aerobically incubated under repeated dry-wet cycles and continuously constant moisture conditions. The primary aims were to quantify the potential for enhancement of carbon dioxide (CO2) release owing to increased water fluctuation and to examine differences in the responses of volcanic ash soils with different physicochemical properties. Soil B, rather than soil A, was a typical Andosol. During incubation at 20°C for 120 days with five dry-wet cycles, the CO2 release rate was measured periodically. Abundance of the stable carbon isotope in CO2 (δ13C-CO2) was measured to capture changes in the origin of decomposed soil organic matter (SOM) owing to the dry-wet cycles. The CO2 release rate under the dry-wet cycles was up to 49% higher than the values predicted from a parabolic relationship between CO2 release and water content during incubation under the continuously constant moisture condition. The magnitude of CO2 release enhancement was 2.7-fold higher in soil B relative to that in soil A. The δ13C-CO2 value in the dry-wet cycles was enriched by 0.3–2.3‰ compared to that during incubation under the continuously constant moisture conditions, suggesting that the decomposition of well-metabolized and/or old SOM was enhanced by the dry-wet cycles. Thus, the present study suggests that Andosols, which have been believed to have a strong SOM stabilization ability, are vulnerable to dry-wet cycles. Then, increased water fluctuation in a future warmer world would have significant potential to stimulate CO2 release from soils.

Significant shift in the terrestrial ecosystem at the Paleogene/Neogene boundary in the Tibetan Plateau

<p indent=0mm>The shift from the Paleogene to the Neogene represents an important timeline in the history of life on Earth: A point when the biotic realm approached that of nature today. The uplift of the Tibetan Plateau in the Cenozoic Era has imposed profound influence on the evolution of the terrestrial ecosystem by creating a sustainable life system in a freezing climate. A reconstruction of this epic scene on the plateau relies on fossil discoveries. Based on a recent study of numerous well-preserved fossils from the Paleogene and Neogene deposits of the Lunpola and Nima basins in the central Tibetan Plateau, we recognized therein, for the first time, the turnover of the Late Oligocene tropical or subtropical ecosystem, and the subsequent transition toward a plateau-type biotic assemblage during the Early Miocene epoch. The fossil biota consisting of fishes, insects and plants from the Upper Oligocene suggests that in 26−24 Ma, the hinterland of the Tibetan Plateau was a warm and humid lowland nourished by tropical moisture from the Indian Ocean, which would have been able to reach northern Tibet then. This biota, represented by climbing perches and palms, shows typical tropical or subtropical climatic patterns and maintained a paleoelevation no higher than <sc>2300 m</sc> in the depositional areas. In the Early Miocene, the Tibetan ecosystem underwent comprehensive transformation into the one we recognize today. Primitive snow carps, which are endemic to the plateau today, emerged and, in an “Ascending with the Modifications” mode, evolved into more and more specialized species all the way up until the Pliocene epoch. The vegetation of the Early Miocene was dominated by temperate broad-leaved forests mixed with abundant coniferous trees and booming herbs, hence showing a cool climatic setting. Some mammals adapted to the temperate forest, e.g., <italic>Plesiaceratherium</italic> (a kind of extinct rhinos), appeared at the center of the plateau during the Early Miocene, and gave way to the ancestors of the Ice Age mammals, e.g., the woolly rhino of the Pliocene epoch. Such a dramatic transformation of the Tibetan ecosystem around the Paleogene and Neogene boundary was due to the cooling-down effect accompanying the rise of the main body of the plateau to ca. <sc>3000 m</sc> and the global climate evolution toward icehouse conditions during the Cenozoic.

Seasonal variations in leaf litter substrate-induced respiration and metabolic quotient in a warm temperate broad-leaved forest

ABSTRACTSeasonal variations in microbial biomass and metabolic quotient within the litter layer and the microorganism-mediated mechanisms causing seasonal variation in litter heterotrophic respiration in warm temperate forests have yet to be determined. We aimed to elucidate seasonal variations in substrate-induced respiration (SIR) as an index of microbial biomass and the ratio of basal respiration to SIR (BR/SIR) as a relative measure of the metabolic status of a microbial community in the litter layer and to investigate the microorganism-mediated mechanisms causing seasonal variation in litter heterotrophic respiration. We collected samples of unfragmented leaf litter (LL) and <1-cm litter fragments (FL) within the litter layer on a monthly basis over a 1-year period. SIR varied in accordance with seasonal temperature changes. Additionally, SIR showed a negative relationship with the C/N ratio in the early decomposition phase and a positive relationship when the C/N ratio was less than 30. BR/SIR in both LL and FL decreased as decomposition proceeded – possibly resulting from succession in the microbial community. Moreover, seasonal hysteresis in litter heterotrophic respiration at the site was similar for SIR; it was higher in spring than in autumn at the similar temperature, which may have been affected by the depletion of available carbon for microorganisms as decomposition proceeded in the mobilization phase. Our findings suggest that studies such as these should integrate assessments of the microbial community to better understand the microorganism-mediated heterotrophic respiration process.

Post-agricultural restoration: Implications for dynamics of soil organic matter pools

In order to bridge the gap of knowledge in respect of soil organic matter (SOM) dynamics of post-agricultural Luvisols during restoration, the study focused on alteration processes of functionally different SOM pools, 14C ages, and C turnover rates in a chronosequential approach. The study comprises three Luvisol chronosequences of 37 years (North), 120 years (Middle), and 42 years (South) across a climate gradient of the temperate broad-leaved forests of European Russia. Restoration led to SOM accumulation within both active (free particulate organic matter (POM) and occluded POM and passive (clay fraction) pools, and as a result, in gains of total organic carbon (C). Accumulation of new C was confirmed by increasing ∆14C signatures of occluded POM and clay fractions. After 22 years of restoration, ∆14C signatures progressed from negative to positive values for the occluded POM fraction, whereas they showed a similar development but remained negative for the clay faction. This highlights the fact that the incorporation of new C into the passive pool takes place, but that it occurs at a slower rate compared to that of the active pool. The 14C age of occluded POM fraction declined from 600 to 1200 years before present (BP) in arable sites to about 200 years BP after 22 years of restoration and thereafter. The 14C age of the clay fraction decreased from 1670 to 2660 years BP in arable soils to 750 years BP in 22 year abandoned site, 450–310 years BP in 32–66 year abandoned sites, and 200–370 years BP in near-natural forests. This decline of the 14C age reveals a change of the proportions between old and young C within the passive pool caused by management and the development of an ecosystem towards a steady state. Recovery of C was accompanied by initially increasing and then decreasing turnover rates of SOM, both again, much more pronounced in the active pool. These dynamics trace an initial ecosystem disturbance after abandonment, which slows down with time. Although C recovery and adjusted turnover rates of SOM progressed towards a new steady state of ecosystem; full restoration was not achieved within the chronosequential time scale of 120 years.

Palynological record of Holocene climate change from a Sphagnum peat mire on Qizimei Mountain, Central China

The palynological sequence in core QZMS from Qizimei Mountain, central China, reflects the vegetation and climate dynamics since 12,900 calibrated years before present (cal yr BP). A palynological analysis demonstrated that the temperate deciduous broadleaved and coniferous mixed forest that was present from 12,900 to 10,600 cal yr BP changed to a deciduous broadleaved and coniferous mixed forest from 10,600 to 10,300 cal yr BP due to climate warming. From 10,300 to 7000 cal yr BP, a subtropical and temperate broadleaved and coniferous mixed forest was present. Then, the climate cooled from 7000 to 3000 cal yr BP. The variations in freshwater algae and Sphagnum (AS) and aquatic herbs (AH) indicate that rainfall increased from the early Holocene to 6890 cal yr BP and then gradually decreased. This change in rainfall coincided with changes in the Asian Summer Monsoon (ASM) and rainfall patterns in southern and northern China during different periods. The rainfall pattern was dominated by a shift in the summer rainbelt in the Chinese ASM region, which was mainly driven by orbitally forced changes in insolation and shifts in the El Nino/Southern Oscillation during the Holocene.

Impact of wild boars on the feeding behavior of smaller frugivorous mammals

We examined the interspecific relationships among wild boars, raccoon dogs, and badgers with regard to the consumption of fallen fruits to assess how the presence of the largest mammal, the boar, affects the frugivory behavior of the two smaller species. In our 2-year survey, automatic cameras were set under the crown of wild cherry trees to observe frugivory; all mammals had access to the trees in the first year, but only wild boars were blocked access with a fence in the second year. The survey was conducted in a temperate broad-leaved forest in central Japan. All three species frequently visited those trees with abundant fruit production, and the presence of wild boars affected the feeding behavior of smaller badgers and raccoon dogs. When wild boars were present, the raccoon dogs partly shifted the time of day when they fed and tended to shift to places that the wild boars visited infrequently. In contrast, the badgers partly shifted the time of day when they fed and reduced their feeding time per visit. When wild boars were excluded from the area, raccoon dogs and badgers, which are generally nocturnal, consumed fruit under the crown not only at night but also during the day. The reason for this may be that the smaller species may not have yet responded to the sudden exclusion of the boar as a competitor. Our findings indicate that these three frugivorous mammals exhibit resource partitioning of fallen fruits on the forest floor.

Modelling Soil Greenhouse Gas Fluxes from a Broad-Leaved Korean Pine Forest in Changbai Mountain: Forest-DNDC Model Validation

Fluctuations in soil greenhouse gas (GHG) are an important part of the terrestrial ecosystem carbon-nitrogen cycle, but uncertainties remain about the dynamic change and budget assessment of soil GHG flux. Using high frequency and consecutive soil GHG fluxes measured with an automatic dynamic chamber system, we tested the applicability of the current Forest-DNDC model in simulating soil CH4, CO2 and N2O fluxes in a temperate broad-leaved Korean pine forest at Changbai Mountain. The results showed that the Forest-DNDC model reproduced general patterns of environmental variables, however, simulated seasonal variation in soil temperature, snow melt processes and soil moisture partly deviated from measured variables, especially during the non-growing season. The modeled CH4 flux was close to the field measurement and co-varied mainly with soil temperature and snowpack. The modeled soil CO2 flux had the same seasonal trend to that of the observation along with variation in temperature, however, simulated CO2 flux in the growing season was underestimated. The modeled N2O flux attained a peak in summer due to the influence of temperature, which was apparently different from the observed peak of N2O flux in the freeze-thaw period. Meanwhile, both modeled CO2 flux and N2O flux were dampened by rainfall events. Apart from consistent estimation of annual soil CH4 flux, the annual accumulation of CO2 and N2O was underestimated. It is still necessary to further optimize model parameters and processes using long-term high-frequency observation data, especially transference of heat and water in soil and GHG producing mechanism. Continues work will improve modeling, ecosystem carbon-nitrogen budget assessment and estimation of soil GHGs flux from the site to the region.

Tree species persistence under warming conditions: A key driver of forest response to climate change

From a forest management stand point, it is crucial to know which ecological processes are most likely to drive changes in tree species distributions and abundance under warming climate conditions. In this study, we simulated forest dynamics in a 703,580 km2 territory that straddles the boreal and temperate broadleaved forest biomes in the province of Québec (Canada), under a RCP 8.5 climate change scenario. The objective was to evaluate how future forest composition is sensitive to variation in four potential drivers: fire regimes, harvesting regimes, the capacity of tree species to persist under warmer climate conditions, and species capabilities for long-distance colonization. The results indicate that forest composition in 2100 is most sensitive to variation in the parameters controlling species persistence when conditions become warmer or dryer than the conditions found in their current range. Concretely, this points to avenues of research to improve the accuracy of our predictions regarding the impacts of climate change on forest composition. For instance, we should further investigate the underlying ecological (competition) or physiological (drought stresses) processes that influence tree species persistence at the receding edge of their current distributions.