Forest In Northeastern China Research Articles

Analysing species abundance distribution patterns across sampling scales in three natural forests in Northeastern China

Understanding how and why species abundance distributions (SADs) vary with sampling scale has been a long-standing issue in ecology. By fitting various SAD models with observations collected in three large forest field plots, the objective of this study is to explore how the shape of SADs and the predictive ability of SAD models vary with sampling scales. Based on a large dataset collected in the Changbaishan, Jiaohe and Liangshui forests in northeastern China, observed SADs were compared with SADs estimated using five different models (log-normal, broken stick, Zipf, niche preemption and neutral model) at four sampling scales (10 × 10 m, 30 × 30 m, 60 × 60 m and 90 × 90 m). The results show that the studied SADs are scale dependent. Niche-based models provided a better fit at small sample sizes, the predictive ability decreasing with increasing sampling scale. The neutral model performed better at large sample sizes, the predictive ability increasing with increasing sampling scale. We identify the models that provided the best fit to observed species abundance distributions across spatial scales, and conclude that there is not one best SAD model for all spatial scales. Future studies should consider the scale effects on the species abundance distribution.

Harnessing terrestrial laser scanning to predict understory biomass in temperate mixed forests

Forest understory vegetation plays an important role in providing food, nutrition and habitat for wildlife. The impact of wildlife foraging on forest understory biomass are often subtle processes that are difficult to capture using traditional field measurements. Field measurements are labor-intensive and impractical to cover and detect understory biomass changes at an extensive range with fine spatial resolution, thereby affecting the accuracy of habitat quality and food availability assessment for wildlife. Terrestrial Laser Scanning (TLS) is considered to have potential to improve the accuracy of understory biomass prediction, allowing for detailed monitoring of biomass changes under the influence of wildlife at fine scale. In this study, we first developed an efficient method to predict forest understory biomass by using variables from TLS with regression models, and second, we compared the prediction accuracy between TLS-based variables and field-measured variables. Third, the optimal models with TLS-based variables were applied to map and quantify the effect of herbivores density on understory biomass in temperate forests in northeastern China. Our results demonstrated that TLS-derived data were more accurate than field measurements in predicting understory biomass, that TLS-derived canopy cover yielded the highest herb layer biomass estimation accuracy (R2 = 0.72, RMSE = 12.73 g/m2), and that TLS-derived vegetation volume obtained the highest accuracy assessment for the shrub layer biomass prediction (R2 = 0.69, RMSE = 43.64 g/m2). There was a significant difference in the understory herb layer biomass in different deer-density plots, but no significant difference in shrub layer biomass. To quantify biomass changes in different plots, consistent monitoring method is needed, TLS data demonstrated the potential to capture and accurately quantify the biomass variation from forest understory. As tool for monitoring understory, TLS can be used as a supplementary to traditional understory monitoring methods to guide forest management policies and wildlife conservation strategies.

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 variation of diversity and co-occurrence patterns of arbuscular mycorrhizal fungal communities in mixed broadleaf-conifer forests

Arbuscular mycorrhizal (AM) fungi are an important determinant of plant performance. The temporal distribution patterns of AM fungal communities, important groups in forest soil, are affected by various environmental factors. However, the effect of seasonal variation on AM fungal communities in forest soil is still not fully understood. To improve knowledge regarding the seasonal dynamics of AM fungal communities in forest soil, the Juglans mandshurica rhizosphere soil in a 30-year-old natural J. mandshurica and Larix gmelinii mixed forest in northeastern China was sampled and studied during different seasons. AM fungal community composition and structure in the rhizosphere soil were determined by using the Illumina MiSeq sequencing platform. The results showed that forest type significantly affected soil pH and the microbial biomass carbon (Cmic), microbial biomass nitrogen (Nmic), C, N, P, NH4+-N and NO3−-N contents. Similarly, soil moisture significantly decreased with seasonal progression in all forest types. Glomus and Diversispora were the dominant genera. The Shannon, Sobs and Chao1 indices of the mixed forest were higher in July than in May and September. The NO3−-N and water-soluble phenol (WSPh) contents were the most important factors driving the shift in the soil AM fungal community across the seasonal gradient. Network analysis revealed that AM fungal network structure was significantly different between seasons, and the number of links between species significantly increased with time. We observed a clear tendency for mixed forest management to significantly affect AM fungal community structure and composition but not diversity. Furthermore, the co-occurrence network and keystone taxa among AM fungi can change in response to environmental filtering due to mixed management in different seasons.

Variations of density-dependent seedling survival in a temperate forest

Seedling dynamics are driven by various biotic factors (for example, neighborhood interactions) and abiotic conditions (for example, light availability, topography, and soil nutrients). Therefore, quantifying the drivers of seedling survival is critical for understanding seedling dynamics within plant communities. However, how the importance of certain biotic and abiotic factors changes over growth stages is still relatively unknown. In the present study, the importance of density and distance dependence were examined, as well as the effects of abiotic factors, in regard to the survival of both newly germinated and established seedlings and saplings (<1 cm DBH; taller than 30 cm in height; and at least 2 years of age). A total of 1305 seedlings belonging to 21 species of a temperate forest in northeastern China were monitored. It was found there were significant conspecific negative density dependence (CNDD) effects impacting the survival of the established seedlings. In addition, the newly germinated seedlings were found to be less affected by the CNDD. The abiotic effects on seedling survival were not found to be significant. These results suggested that at the community level, the density dependence effects may be stronger during the seedling stage when compared with the abiotic factors. The distance dependence was observed to be mainly effective within a radius of approximately 5 m for both the newly germinated and established seedling communities. The directions and magnitudes of the aforementioned factors were affected by different life-history strategies. The seedlings which were wind-dispersed and the shade-tolerant species tended to suffer less from the CNDD. Therefore, based on an unusually large set of observations in a temperate forest, this study identified and analyzed the factors affecting seedling survival for different life-history strategies. The obtained results will potentially provide new perspectives for deepening the understanding of the dynamics of temperate forests.

Temperature signal recorded in δ2H and δ13C values of wood lignin methoxyl groups from a permafrost forest in northeastern China

Stable isotopes in wood lignin methoxyl groups (δ2HLM and δ13CLM values) have been suggested as valuable complementary paleoclimate proxies. In permafrost forests, tree growth is influenced by multiple factors, however temperature appears to have the strongest impact on tree growth and, therefore, on carbon cycling. To test whether δ2HLM and δ13CLM values of trees from permafrost regions might record climate parameters, two dominant tree species (Larix gmelinii, larch, and Pinus sylvestris var. mongolica, pine) collected from a permafrost forest in China's Greater Hinggan Mountains, were investigated. The two tree species larch and pine covered time spans of 1940 to 2013 and 1870 to 2013, respectively. Results showed significant correlations of pine and larch δ2HLM values and larch δ13CLM values with temperatures and in particular with the mean temperature of the growing season from April to August. However, only weak correlations of δ2HLM and δ13CLM values with moisture conditions, such as precipitation amount and relative humidity were observed. In addition, species specificity in the climate response was most obvious for δ13CLM values. Compared to a temperature reconstruction based on tree ring width, pine δ2HLM–based reconstruction showed strongest spatial correlations with regional temperature. Therefore, δ2HLM values might be a promising proxy to reconstruct growing-season temperatures in permafrost regions.

Predicting plant–soil N cycling and soil N2O emissions in a Chinese old-growth temperate forest under global changes: uncertainty and implications

Soil-emitted N2O contributes to two-thirds of global N2O emissions, and is sensitive to global change. We used DayCent model to simulate major plant–soil N cycling processes under different global change scenarios in a typical temperate mixed forest in north-eastern China. Simulated scenarios included warming (T), elevated atmospheric CO2 concentration ([CO2]) (C), increased N deposition (N) and precipitation (P), and their full factorial combinations. The responses of plant–soil nitrogen cycling processes including net N mineralization, plant N uptake, gross nitrification, denitrification and soil N2O emission were examined. Concurrent increase of elevated [CO2] and N deposition displayed most strong interactive effects on most fluxes. Using the results from experimental studies for evaluation, simulation uncertainty was highest under elevated [CO2] and increased precipitation among the four global change factors. N deposition had a fundamental impact on soil N cycle and N2O emission in our studied forest. Despite forest soil acting as a N sink for added N, scenarios which included increased N deposition showed higher cumulative soil N2O emissions (summed up from 2001 to 2100). In particular, the scenario which included T, P, and N had the largest cumulative soil N2O emission, which was a 24.4% increase over that under ambient conditions. Our study points to the importance of the interactive effects of global change factors on plant–soil N cycling and the necessity of multi-factor manipulation experiments.

Individual Identification of Male Ural Owls Based on Territorial Calls

Effective individual identification is important in many aspects of animal studies. Leg bands and wing tags are commonly used to mark individual birds in the field; however, for nocturnal or cryptic birds it is difficult to directly observe individual tags due to darkness or dense vegetation. Alternatively, some studies suggest that many birds have individually distinctive vocalizations, and these differences could be used to identify individuals. Here we assessed the possibility of identifying individual Ural Owls (Strix uralensis) based on their defensive territorial hooting calls. During breeding season, we recorded hooting calls of 15 males in 2018 and of 16 males in 2019 respectively at the Dagangzi national forest in northeastern China. We measured 19 variables for each call. Using forward stepwise discriminant function analysis, we correctly classified 92.8% of the calls of individuals in 2018 and 93.9% in 2019, based on leave-one-out cross validation. The most important discriminating variables included duration of the interval between the first and second notes, duration of the interval between the second and third notes, the third note duration, and the number of “humps” (upward projections in a note in the sound spectrogram) in the first note. The calls of individuals remained stable both within a breeding season and between years. Our results suggest that territorial calls are effective for identifying male Ural Owl individuals, and this technique could contribute to population surveys and long-term monitoring.

Abiotic niche partitioning and negative density dependence across multiple life stages in a temperate forest in northeastern China

Abstract Negative density dependence (NDD) and niche partitioning have been proposed to explain the species coexistence in plant communities. However, the majority of previous studies have examined either only resource partitioning or NDD, or have focused only on a single life‐history stage. We thus lack knowledge regarding the relative importance of biotic neighbourhood interactions and abiotic conditions on survival at the various life stages of a tree. Using tree and seedling demographics data, and combined with spatially explicit abiotic and biotic data, we assessed the relative importance of abiotic and biotic variables for survival from the seedling to tree stage in a temperate forest in northeastern China. We provide strong evidence that both biotic and abiotic neighbourhood variables affect individual survival. We also observed that their relative importance varied with the life‐history stages of a tree. The strength of the effect of conspecific tree neighbours decreases along ontogeny, while the roles of the topographic and edaphic variables increase at later life stages. Heterospecific tree neighbours show consistent negative effects on individual survival at all life stages, yet had the strongest influence on survival at the seedling stage. We demonstrated that species vary widely in their probability of survival under different environmental conditions, as well as in response to differences in neighbour identity and density. Overall, the effects of conspecific neighbours varied more among species than the effects of heterospecific neighbour density. Wide variation among species in response to abiotic variables is a necessary requirement for niche differentiation and coexistence via resource partitioning processes. Our findings indicate that conspecific NDD and abiotic niche partitioning are major structuring mechanisms in our temperate forest in northeastern China. Synthesis. Both biotic and abiotic neighbourhood variables affected individual survival, but the relative importance varied with the life‐history stages and among species. Our results indicated that niche partitioning may contribute to the coexistence through differential responses to abiotic factors, as well as to conspecific negative density dependence (NDD). Finally, our results demonstrated the necessity to incorporate multiple life stages and multiple influence factors when elucidating the maintenance of species diversity in temperate forests.

Succession of a broad-leaved Korean pine mixed forest: Functional plant trait composition

Abstracts A longstanding goal of ecology and conservation biology is to understand the climatic and biological controls of forest succession. However, the patterns and mechanisms that guide forest succession, especially within broad-leaved forests, remain unclear. We collected leaf traits and abiotic data across a 200-year chronosequence within a broad-leaved Korean pine forest in northeastern China. We focused on five key leaf traits related to resource acquisition and competition by quantifying the community-weighted trait distributions for specific leaf area (SLA), leaf dry matter concentration (LDMC), leaf nitrogen content (Nmass (g/kg)), leaf phosphorus content (Pmass (g/kg)) and the ratio of nitrogen content to phosphorus content (Nmass/Pmass). We also studied how these traits respond to changing environmental variables (climatic, soil and topographical) during succession. Redundancy analysis was used to examine the importance of the environmental variables in shaping the successional variation in plant traits. Our results revealed the following. Older forests differed significantly from younger forests in species composition and trait distribution. For example, SLA, leaf N and P content and the N/P ratio tended to increase and then decrease throughout the community during forest succession (p

The Economic Achievements of Polish Diaspora in Manchuria an Inner Mongolia, 1898-1936

&lt;p&gt;Daleki Wschód, w tym Mongolia Wewnętrzna i Mandżuria, przez ponad półtora wieku był miejscem niekończącej się tułaczki i długoletniej zsyłki Polaków, których rosyjska tyrania wygnała na nieznane odludzia. Jednocześnie wielu z nich przyczyniło się do rozwoju gospodarczego tej części Azji. W miarę upływu czasu znacząca ilość Polaków – częściowo zesłańców politycznych, a częściowo dobrowolnych emigrantów obdarzonych duchem przedsiębiorczości – dorobiła się fortuny i zarazem przyczyniła się do budowy dużych manufaktur, zarówno na terenie słabo zaludnionych stepów Mongolii Wewnętrznej, jak i rozległych lasów północno-wschodnich Chin. Przykładem tego mogą być losy przedsiębiorcy Władysława Kowalskiego (1870-1940) i inżyniera Kazimierza Grochowskiego (1873-1937), którzy byli wybitnymi przedstawicielami polskiej diaspory w Mandżurii i Mongolii Wewnętrznej.&lt;/p&gt;

Soil nutrients, forest structure and species traits drive aboveground carbon dynamics in an old-growth temperate forest

Forests store a substantial amount of terrestrial carbon (C), but the drivers of forest C dynamics remain poorly understood, especially in old-growth forests. Here, we evaluate how aboveground C dynamics (i.e., net C change and its demographic processes: C gain from the growth of surviving trees (∆C-surv), C gain from the growth of recruited trees (∆C-recr) and C loss by tree mortality (∆C-mort)) are driven by vegetation attributes (diversity, trait composition and forest structure) and habitat conditions (soil properties and light environment), as well as how ∆C-surv, ∆C-recr and ∆C-mort contribute to net C change. Using 10-year interval demographic data from a 9-ha permanent plot in an old-growth temperate forest in northeastern China, we performed structural equation model to relate the C dynamics to the vegetation attributes and habitat conditions. The net C change is most strongly determined by ∆C-mort. High soil phosphorus concentrations increased ∆C-surv, soil moisture increased ∆C-recr, and leaf area index increased both ∆C-surv and ∆C-recr. Diversity (i.e., structural diversity) had a positive relationship with ∆C-surv but was not related to ∆C-recr or ∆C-mort. Trait composition was significantly related to all three demographic processes. Forest structure was the best predictor of ∆C-surv and ∆C-recr. The net C change increased with higher soil phosphorus concentrations and basal area and in communities dominated by conservative traits (i.e., high wood density). This study highlights that soil nutrients, forest structure and trait composition are important drivers of net C change in old-growth temperate forests. Better insights into C storage and productivity can be gained by simultaneously evaluating the vegetation attributes and habitat conditions of C dynamics in natural ecosystems.

Enhanced spring phenological temperature sensitivity explains the extension of carbon uptake period in temperate forest protected areas

Land surface phenology (LSP) and its trend are important for understanding the vegetation–climate relationship. However, whether LSP and LSP trends for different forest communities vary with the intensity of forest disturbance and the main cause of the change is still unclear. In this study, LSP indicators and their temperature sensitivity (Ts) were obtained for coniferous (Larch Coniferous forests (LC) and Spruce Fir Korean Pine forests (SFKP)), mixed (Broadleaf Korean Pine forests (BKP) and Spruce Fir Broadleaf forests (SFB)), and broadleaf (Aspen White Birch forests (AWB) and White Birch forests (WB)) communities in protected (Fenglin National Natural Reserve, FNNR) and unprotected (Lilin Experimental Forest Farm, LEFF) areas in Northeastern China from remote sensing and climate data. Statistical comparisons of the LSP, LSP trends, and Ts were conducted for various forest communities in both FNNR and LEFF. The results show that the values of mean start of the season (SOS) and mean end of the season (EOS) in FNNR were significantly different from those in LEFF, and the SOS, EOS, and the length of season (LOS) trends for various forest communities in FNNR were significantly different from those in LEFF, except for the SFB. In broadleaf forests, both the mean LOS and LOS trends for various forest communities were significantly higher in FNNR. However, significantly higher LOS but lower LOS trends in FNNR were identified for coniferous and mixed forests. In addition, the SOS Ts for various forest communities in FNNR were significantly higher than those in LEFF, and the Ts for broadleaf forests in FNNR were significantly lower than that in other forest communities. The results of this study suggest that the carbon uptake periods of most temperate forest communities are apparently enhanced by the high spring phenological Ts in protected areas, which provides important insights into future carbon sequestration potential and forest management strategies for temperate forests in Northeastern China.

Organic N deposition favours soil C sequestration by decreasing priming effect

Atmospheric nitrogen (N) deposition alters the priming effect (PE), which is defined as the change in native soil organic carbon (SOC) decomposition by exogenous C inputs. However, how the priming intensity varies under chemically heterogeneous N deposition, particularly with increasing labile C input, remains unclear. We collected soils from a temperate forest in northeastern China that had received simulated organic and/or inorganic N deposition for 6 years. The soils were incubated with or without three levels of 13C-labelled glucose solution for 152 days. CO2 emission and its 13C value were continuously measured to calculate the PE. Enhanced SOC decomposition (i.e., a positive PE) was observed after glucose addition, regardless of the N deposition form. The PE intensity increased with the increase in the glucose addition level. However, organic N decreased the PE by 12.3-23.2%. The SOC-derived microbial biomass was 16.2-34.3% lower in organic N-treated soil, indicating that preferential utilization of exogenous labile C by microorganisms was responsible for the decrease in PE. The PE inhibition by organic N increased nonlinearly as a function of glucose level. Furthermore, the net annual change in SOC as a balance between the replenishment of added glucose-C and primed C was larger in organic N-treated soil due to a decrease in soil microbial metabolic quotient. In this study, we found that organic N deposition inhibited the PE, and the inhibition effect was intensified with increasing C inputs, favouring SOC sequestration.

Estimating the productive potential of five natural forest types in northeastern China

BackgroundThere is a serious lack of experience regarding the productive potential of the natural forests in northeastern China, which severely limits the development of sustainable forest management strategies for this most important forest region in China. Accordingly, the objective of this study is to develop a first comprehensive system for estimating the wood production for the five dominant forest types.MethodsBased on a network of 384 field plots and using the state-space approach, we develop a system of dynamic stand models, for each of the five main forest types. Four models were developed and evaluated, including a base model and three extended models which include the effects of dominant height and climate variables. The four models were fitted, and their predictive strengths were tested, using the “seemingly unrelated regression” (SUR) technique.ResultsAll three of the extended models increased the accuracy of the predictions at varying degrees for the five major natural forest types of northeastern China. The inclusion of dominant height and two climate factors (precipitation and temperature) in the base model resulted in the best performance for all the forest types. On average, the root mean square values were reduced by 13.0% when compared with the base model.ConclusionBoth dominant height and climate factors were important variables in estimating forest production. This study not only presents a new method for estimating forest production for a large region, but also explains regional differences in the effect of site productivity and climate.

Understanding and protecting forest biodiversity in relation to species and local contributions to beta diversity

Beta diversity is an essential topic for understanding the spatial organization of species composition. By partitioning beta diversity into local contributions to beta diversity (LCBDs) and species contributions to beta diversity (SCBDs), this study can help to arrive at a more general and specific understanding of how beta diversity responds to environmental conditions and is affected by ecological and biological traits of species, which will provide useful advice for the conservation of forest biodiversity. In this study, we used data from a temperate near-mature forest in northeastern China. We used the method of beta regression to point out important factors affecting LCBD and SCBD. The results showed that LCBD was strongly related to species richness, abundance and abiotic environmental conditions, while SCBD was significantly affected by abundance and species niche characteristics. We conclude that our results are of considerable importance for the conservation of forest biodiversity and are of the opinion that these can provide detailed plans in conservation decision making.

Evaluation of the Water Conservation Function of Different Forest Types in Northeastern China

Water conservation is an important function of forest ecosystems, but it is still unclear which forest types function best in this regard. We investigated the water conservation function indicators including the water-holding rate of branches and leaves (BLwr), water-holding capacity of litter (Lwc), water absorption rate of litter (Lwr), soil infiltration rate (Ir), soil and water content (SWC), soil water storage (SWS), and soil organic matter (SOM) accumulation of five forest types (Larix gmelinii forests, Pinus koraiensis forests, Robinia pseudoacacia forests, Pinus tabulaeformis forests, and mixed forests) and evaluated them using the gray correlation method (GCM). The results indicate that the BLwr of five stands in the study area varied from 18.3% to 33.5%. The SWC and SWS of the R. pseudoacacia stand were 13.76% and 178.9 mm, respectively, which was significantly higher than that of the other stands (p &lt; 0.05). The SOM was similar for the R. pseudoacacia (0.23%), mixed forest (0.22%), and L. gmelinii (0.22%) sites. The BLwr, Lwc, Lwr, SWC, and SWS values of broad-leaved tree species were higher than those of the mixed species, followed by those for coniferous tree species. Soil infiltration rate followed the order L. gmelinii &gt; P. koraiensis &gt; mixed forest &gt; P. tabulaeformis &gt; R. pseudoacacia. Based on our results, the R. pseudoacacia stand had the highest water conservation ability, while the lowest performance was found for the P. tabuliformis site. This suggests that, in order to enhance the water conservation function of forests in northeastern China, the focus should be on the establishment of R. pseudoacacia forests.

The effects of masting on rodent-mediated seed dispersal interaction of sympatric tree species

The predator satiation hypothesis (PSH) and the seed dispersal hypothesis (SDH) are widely adopted to predict the effects of masting on seed dispersal. However, the effects of masting composition on rodent-mediated seed dispersal interaction of sympatric tree species are largely overlooked in testing the two hypotheses. Here, masting in Quercus mongolica and Corylus mandshurica with contrasting seed traits was studied over two masting years and three non-masting years in a temperate deciduous forest in northeastern China, to investigate how masting composition regulates the indirect seed-seed interactions of sympatric tree species mediated by granivorous rodents. Our results showed that more seeds of Q. mongolica survived in seed stations and were less likely to be dispersed in masting years, well supporting the idea of PSH. However, seed dispersal of C. mandshurica was in congruence with the prediction of the SDH because of increased seed dispersal probability and dispersal distances in masting years. Rodents scatterhoarded more seeds of C. mandshurica not only in its own masting years but also in the masting years of another sympatric plant species, Q. mongolica, resulting in a positive relationship between seed caching and the sum of per capita seed availability. Moreover, masting of Q. mongolica or C. mandshurica decreased the proportion of seeds eaten by predators, benefiting each other’s seed survival. In addition, seeds of Q. mongolica were dispersed farther in the masting years of C. mandshurica despite rare seedling establishment. Our study using two sympatric masting tree species provided evidence that the effects of masting can be potentially influences by seed-seed interactions between sympatric tree species. We recommend that future work tests the PSH and SDH using long term data of several sympatric tree species, emphasizing the role of seed traits and seed-seed interactions in determining the effects of seed masting on tree regeneration.

Species-Area Relationship and Its Scale-Dependent Effects in Natural Forests of North Eastern China

The Species-area relationship is one of the core issues in community ecology and an important basis for scale transformation of biodiversity. However, the effect of scale on this relationship, together with the selection of an optimal species-area model for different sampling methods, is still controversial. This study is based on the data from two sampling areas of 40 km2 in size, one in a Korean pine (Pinus koraiensis Sieb. et Zucc) broad-leaved mixed forest in Mt. Changbai and the other in Jiaohe, Jilin Province. The logarithmic, power, and logistic model were established on a scale of 10 km2, 20 km2, and 30 km2, respectively, using a nested sampling plot and random sampling plot. The goodness of the species-area model was tested by the Akaike information criterion (AIC). The results show that the sampling method affected the relationship between species and area, and the data were fitted better under random sampling compared with nested sampling. The construction of the relationship between species and area was closely related to the upper limit of the sampling area size. On a small scale (10 km2), the data were fitted best with the logarithmic and logistic model, whereas the logistic model was the best fit on a medium (20 km2) and large scale (30 km2). We evaluated the scale dependence of species-area relationship in two forests with nested and random sampling methods. We further showed that the logistic model based on the random sampling plot can explain most soundly the species-area relationship in Jiaohe and Mt. Changbai. More studies are needed in other regions to develop models to optimize sampling designs for different forest types under different density constraints at different spatial scales, and for a more accurate estimation of forest dynamics under long-term observations.

Long-term effects of post-fire restoration types on nitrogen mineralisation in a Dahurian larch (Larix gmelinii) forest in boreal China

Fire is an important disturbance agent in Chinese boreal forests but the long-term effects of wildfires on soil nitrogen (N) net mineralisation rates (Rmin) in natural versus human-assisted restorations are not well understood. In this study, we analysed upper (0–10cm) and lower layer (10–20cm) soil samples from natural restoration and afforestation plots in a Dahurian larch (Larix gmelinii) forest in north-eastern China 29years after a mega fire disturbance. Our results showed that the soil inorganic N (NH4+-N and NO3−-N) pool of the upper and lower layers of the regenerated plots remained significantly lower than in unburned control plots. This suggests that the effects of a high burn severity fire on soil N availability were still significant almost 30years after the event. Restoration type (natural restoration versus afforestation) also had significant effects on upper layer soil N availability; compared with afforestation, natural restoration was more beneficial for the accumulation of soil inorganic N and the recovery of Rmin after fire disturbance. Specifically, the concentration of inorganic N and the mean Rmin in upper layer soils in the natural restoration plots were approximately 41% greater and 3.6 times greater, respectively, than in the afforestation plots. The differences in soil N availability between the two restoration types were attributed to differences in soil water content (SWC), soil microbial biomass nitrogen (MBN), and the recovery of vegetation after the fire disturbance. Our study demonstrates that natural restoration has proved more successful than afforestation in countering soil N losses in boreal forests in China resulting from a high burn severity fire disturbance.