Principis-rupprechtii Forests Research Articles

Predicting Individual Tree Mortality of Larix gmelinii var. Principis-rupprechtii in Temperate Forests Using Machine Learning Methods

Accurate prediction of individual tree mortality is essential for informed decision making in forestry. In this study, we proposed machine learning models to forecast individual tree mortality within the temperate Larix gmelinii var. principis-rupprechtii forests in Northern China. Eight distinct machine learning techniques including random forest, logistic regression, artificial neural network, generalized additive model, support vector machine, gradient boosting machine, k-nearest neighbors, and naive Bayes models were employed, to construct an ensemble learning model based on comprehensive dataset from this specific ecosystem. The random forest model emerged as the most accurate, demonstrating 92.9% accuracy and 92.8% sensitivity, making it the best model among those tested. We identified key variables impacting tree mortality, and the results showed that a basal area larger than the target trees (BAL), a diameter at 130 cm (DBH), a basal area (BA), an elevation, a slope, NH4-N, soil moisture, crown density, and the soil’s available phosphorus are important variables in the Larix Principis-rupprechtii individual mortality model. The variable importance calculation results showed that BAL is the most important variable with an importance value of 1.0 in a random forest individual tree mortality model. By analyzing the complex relationships of individual tree factors, stand factors, environmental, and soil factors, our model aids in decision making for temperate Larix gmelinii var. principis-rupprechtii forest conservation.

Soil Microbial Community, Soil Quality, and Productivity along a Chronosequence of Larix principis-rupprechtii Forests.

Elucidating the correlation between soil microbial communities and forest productivity is the focus of research in the field of forest ecology. Nonetheless, the relationship between stand age, soil quality, soil microorganisms, and their combined influence on productivity is still unclear. In this study, five development stages (14, 25, 31, 39, and >80 years) of larch (Larix principis-rupprechtii) forests were investigated in Inner Mongolia and Shanxi provinces of China. We evaluated soil quality using the Integrated Soil Quality Index (SQI) and analyzed changes in bacterial and fungal communities using high-throughput sequencing. Regression models were also established to examine the impacts of stand age, microbial diversity, and SQI on productivity. The findings revealed an ascending trend in soil organic matter (SOM), total nitrogen (TN), total phosphorus (TP), available potassium (AK), and SQI in 14, 25, 31, and 39-year-old stands. The abundance of oligotrophic bacteria Acidobacteria exhibited a gradual decline with increasing forest age, whereas copiotroph bacteria Proteobacteria displayed a progressive increase. Stands older than 80 years exhibited a higher abundance of both the saprophytic fungus Ascomycota and mycorrhizal fungus Basidiomycota. Forest age had a significant impact on microbial diversity, particularly in terms of bacterial diversity, impacting both α and β diversity. The soil bacterial community structure was influenced by AK, SOM, TN, TP, and pH. Conversely, the fungal community structure was regulated by crucial factors including SOM, TN, TP, TK, AK, and pH. Fungal diversity demonstrated a significant and positive correlation with the basal area increment (BAI) of larch. Furthermore, microbial diversity accounted for 23.6% of the variation in BAI. In summary, the findings implied a robust association between microbial composition, diversity, and soil chemical properties throughout the chronosequence of larch forests. These factors collectively played a crucial role in influencing the productivity of larch forest.

Distribution patterns and driving mechanism of soil protozoan community at the different depths of Larix principis-chinensis forest in the Luya Mountain, China.

To reveal the assembly mechanisms of soil protozoan community in subalpine forest ecosystems, we analyzed the composition and diversity of protozoan communities and their drivers at the six strata (the litter profile, humus profile, 0-10 cm, 10-20 cm, 20-40 cm and 40-80 cm) of soil profiles in subalpine Larix principis-rupprechtii forest in Luya Mountain using Illumina Miseq high-throughput sequencing technology. The results showed that protozoa in the soil profiles belonged to 335 genera, 206 families, 114 orders, 57 classes, 21 phyla, and 8 kingdoms. There were five dominant phyla (relative abundance >1%) and 10 dominant families (relative abundance >5%). The α diversity decreased significantly with increasing soil depth. Results of PCoA analysis showed that the spatial composition and structure of protozoan community differed significantly across soil depths. The results of RDA analysis showed that soil pH and soil water content were important factors driving protozoan community structure across soil profile. Null model analysis suggested that the heterogeneous selection dominated the processes of protozoan community assemblage. Molecular ecological network analysis revealed that the complexity of soil proto-zoan communities decreased continuously with increasing depth. These results elucidate the assembly mechanism of soil microbial community in subalpine forest ecosystem.

Dynamics of soil net nitrogen mineralization and controlled effect of microbial functional genes in the restoration of cold temperate forests

Soil nitrogen mineralization (Nmin) generally controls the availability and circulation of soil nitrogen (N). To better understand the mechanisms of soil Nmin and environmental protection, this study explored the dynamics of net Nmin in soils from restored forests and the effect of soil physicochemical properties (SPPs) and soil microbial mineralization genes (SMGs) on Nmin. Field studies were conducted from July 2019 to April 2020 in five representative restored forests in the mountainous region of northwestern Hebei, China (i.e., Larix principis-rupprechtii forest (LF), Betula platyphylla forest (BF), mixed forest of Larix principis-rupprechtii and Betula platyphylla (MF), Picea asperata forest (SF) and Pinus sylvestris var. mongolica forest (MPF)), and soil net nitrogen mineralization rate (Rmin), SPPs and SMGs were determined after collecting soil samples in five plots. The influence of restored forests and seasonality on Rmin was investigated to determine the characteristics of the dynamics of soil net Nmin. Principal component analysis (PCA) and variation partitioning analysis (VPA) revealed that soil properties and functional genes could explain approximately 80 % of the variation in Nmin. SMGs significantly contributed to the variation in the soil net ammonification rate (Ramm) and nitrification rate (Rnit) compared to soil properties. SMGs were strongly correlated with Ramm\\Rnit (except in LF), implying that the shifts in functional genes may control Rmin. Given the debate on the role of soil properties and N cycling genes in driving soil N transformation, this study provides new insights into the controlled effect of microbial functional genes during the early stage of forest restoration in the cold temperate zone.

Cell characteristics of Larix principis-rupprechtii on the edge of different stand types

To analyze the effects of forest edge on radial growth and cell characteristics in different stand types of Larix principis-rupprechtii, we investigated the differences on radial growth, cell size and numbers between edge trees and inner trees of L. principis-rupprechtii in pure L. principis-rupprechtii forests and mixed forests of L. principis-rupprechtii and Betula platyphylla in Saihanba mechanical forest farm, China. The results showed that radial growth of the edge trees was significantly faster than that of the inner trees in pure forests, with the total ring width, earlywood width and latewood width of edge trees being 48.9%, 58.9% and 29.6% higher than those of inner trees, respectively. However, there was no difference in radial growth between edge trees and inner trees in mixed forest. The total number of earlywood cells, the number of large cells and small cells in earlywood of edge trees were increased by 63.3%, 55.6% and 70.0%, while the total number of latewood cells, the number of large cells and small cells in latewood of edge trees were increased by 35.4%, 37.5% and 28.5% compared with those of inner trees. There was no significant difference in the cell sizes between edge trees and inner trees. The cell numbers of earlywood and latewood of edge trees were not significantly different from those of inner trees in mixed forest, but the cell size in the earlywood of edge trees was 50.0% larger than those of inner trees in mixed forest. The sizes of the largest cells, the smallest cells, the large cells and the small cells in the earlywood of edge trees were increased by 28.6%, 33.3%, 16.6% and 25.0% compared with those of inner trees, respectively. The fast growth of edge trees and slow growth of inner trees in the pure forests could be effectively alleviated by cultivating mixed forests.

Effect of thinning intensity on the stem CO2 efflux of Larix principis-rupprechtii Mayr

BackgroundStem CO2 efflux (ES) plays a critical role in the carbon budget of forest ecosystems. Thinning is a core practice for sustainable management of plantations. It is therefore necessary and urgent to study the effect and mechanism of thinning intensity (TI) on ES.MethodsIn this study, five TIs were applied in Larix principis-rupprechtii Mayr 21-, 25-, and 41-year-old stands in North China in 2010. Portable infrared gas analyzer (Li-8100 A) was used to measure ES and its association with environmental factors at monthly intervals from May to October in 2013 to 2015. In addition, nutrients, wood structure and nonstructural carbon (NSC) data were measured in August 2016.ResultsThe results show that ES increased with increasing TI. The maximum ES values occurred at a TI of 35 % (3.29, 4.57 and 2.98 µmol∙m-2∙s-1) and were 1.54-, 1.94- and 2.89-fold greater than the minimum ES value in the CK stands (2.14, 2.35 and 1.03 µmol∙m-2∙s-1) in July for the 21-, 25- and 41-year-old forests, respectively. The ES of the trees in low-density stands was more sensitive to temperature than that of the trees in high-density stands. Soluble sugars (SS) and temperature are the main factors affecting ES. When the stand density is low enough as 41-year-old L. principis-rupprechtii forests with TI 35 %, bark thickness (BT) and humidity should be considered in addition to air temperature (Ta), wood temperature (Tw), sapwood width (SW), nitrogen concentration (N) and SS in the evaluation of ES. If a change in stand density is ignored, the CO2 released from individual 21-, 25- and 41-year-old trees could be underestimated by 168.89 %, 101.94 % and 200.49 %, respectively. CO2 release was estimated based on the stem equation in combination with the factors influencing ES for reference.ConclusionsWe suggest that it is not sufficient to conventional models which quantify ES only by temperature and that incorporating the associated drivers (e.g. density, SS, SW and N) based on stand density into conventional models can improve the accuracy of ES estimates.

Soil fertility quality evaluation of pure and mixed Larix principis-rupprechtii forests in Saihanba, Hebei Province of northern China

Soil fertility quality evaluation of pure and mixed Larix principis-rupprechtii forests in Saihanba, Hebei Province of northern China

Multivariate path analysis of factors influencing Larix principis-rupprechtii plantation regeneration in northern China

Forest regeneration is a critical indicator of the overall health of forest ecosystems, and is considered to be a vital process in which old and senescent trees are replaced by young ones. The seed-to-seedling transition entails seedlings’ emergence from seeds and their establishment, this phase being the most vulnerable to mortality effects from biotic and abiotic factors. Larix principis-rupprechtii is a typical tree species in northern China, where the natural regeneration of artificial forests dominated by this species is very limited. This study explored the limiting factors affecting the natural regeneration of Larix principis-rupprechtii forests via field surveys of large-scale sampling plots. Redundancy analysis and structural equation models were developed and applied to determine the relative importance of direct and indirect factors affecting the regeneration of Larix principis-rupprechtii plantations. We found a negative relationship between the regeneration index and stand structure, for which the path coefficient was –0.54, the strongest correlation. Conversely, the regeneration index was positively correlated with the herb index, soil index, and elevation, having path coefficients of 0.06, 0.07, and 0.32, respectively. The soil index was negative correlated with both elevation and herb index, with path coefficients of –0.31 and –0.53, respectively, while stand structure was negatively correlated with the herb index and positively correlated with elevation (respective path coefficients: –0.62 and 0.29). Stand density and tree height to crown base were the main factors representing stand structure and, accordingly, the most important factors influencing forest regeneration of the species. At a stand density of ca. 200 trees·hm−2, the number and quality of seedling regeneration were robust. In later stages of stand management and thinning, the proper adjustment of stand density and timely pruning interventions can promote this tree’s natural regeneration to achieve the sustainable development of forest resources.

The relationships among structure variables of larch forests in China

BackgroundLarch (Larix Mill.) forests are widely distributed in the upper parts of mountainous areas in China, playing vital roles in constructing mountain landscapes and maintaining mountain environments. Despite their importance, our knowledges on the large-scale patterns of structure characteristics and the relationships between different structure variables are unclear. In this paper, we investigated 155 plots from 11 natural larch forest types across the country to explore the biogeographic patterns of the structure characteristics and the allometric relationships between different structure variables for Chinese larch forests.ResultsThe structure characteristics were significantly different among larch forest types. For different larch forest types, the power function fits the relationships between tree height and diameter at breast height (DBH), average DBH and stem density, and taper and stem density well, but with different exponents among larch forest types. The power exponents of the allometric relationships between tree height and DBH for different larch forest types varied from 0.61 to 0.93 (mean = 0.86) by standard major axis regression (SMA), and from 0.51 to 0.78 (mean = 0.56) by ordinary least square regression (OLS). The 50%, 75% and 95% quantile regression (QR) and OLS indicated that the average DBH and taper of the L. gmelinii forests, L. gmelinii var. principis-rupprechtii forests, and L. sibirica forests were significantly correlated with stem density.ConclusionsThe relationship between tree height and DBH showed a power function relationship for all larch forest types in China, but with different exponents. Overall, stem density was negatively correlated with average DBH and taper. The Sect. Larix forests exhibited stand density effect. Our findings provide an important basis for recognizing the biogeographic patterns of structure factors and for the management of larch forests in China.

Evaluating the impact of sampling schemes on leaf area index measurements from digital hemispherical photography in Larix principis-rupprechtii forest plots

BackgroundDigital hemispherical photography (DHP) is widely used to estimate the leaf area index (LAI) of forest plots due to its advantages of high efficiency and low cost. A crucial step in the LAI estimation of forest plots via DHP is choosing a sampling scheme. However, various sampling schemes involving DHP have been used for the LAI estimation of forest plots. To date, the impact of sampling schemes on LAI estimation from DHP has not been comprehensively investigated.MethodsIn this study, 13 commonly used sampling schemes which belong to five sampling types (i.e. dispersed, square, cross, transect and circle) were adopted in the LAI estimation of five Larix principis-rupprechtii plots (25 m × 25 m). An additional sampling scheme (with a sample size of 89) was generated on the basis of all the sample points of the 13 sampling schemes. Three typical inversion models and four canopy element clumping index (Ωe) algorithms were involved in the LAI estimation. The impacts of the sampling schemes on four variables, including gap fraction, Ωe, effective plant area index (PAIe) and LAI estimation from DHP were analysed. The LAI estimates obtained with different sampling schemes were then compared with those obtained from litter collection measurements.ResultsLarge differences were observed for all four variable estimates (i.e. gap fraction, Ωe, PAIe and LAI) under different sampling schemes. The differences in impact of sampling schemes on LAI estimation were not obvious for the three inversion models, if the four Ωe algorithms, except for the traditional gap-size analysis algorithm were adopted in the estimation. The accuracy of LAI estimation was not always improved with an increase in sample size. Moreover, results indicated that with the appropriate inversion model, Ωe algorithm and sampling scheme, the maximum estimation error of DHP-estimated LAI at elementary sampling unit can be less than 20%, which is required by the global climate observing system, except in forest plots with extremely large LAI values (~ > 6.0). However, obtaining an LAI from DHP with an estimation error lower than 5% is impossible regardless of which combination of inversion model, Ωe algorithm and sampling scheme is used.ConclusionThe LAI estimation of L. principis-rupprechtii forests from DHP was largely affected by the sampling schemes adopted in the estimation. Thus, the sampling scheme should be seriously considered in the LAI estimation. One square and two transect sampling schemes (with sample sizes ranging from 3 to 9) were recommended to be used to estimate the LAI of L. principis-rupprechtii forests with the smallest mean relative error (MRE). By contrast, three cross and one dispersed sampling schemes were identified to provide LAI estimates with relatively large MREs.

Performance of Four Optical Methods in Estimating Leaf Area Index at Elementary Sampling Unit of Larix principis-rupprechtii Forests

Optical methods are frequently used as a routine method to obtain the elementary sampling unit (ESU) leaf area index (LAI) of forests. However, few studies have attempted to evaluate whether the ESU LAI obtained from optical methods matches the accuracy required by the LAI map product validation community. In this study, four commonly used optical methods, including digital hemispherical photography (DHP), digital cover photography (DCP), tracing radiation of canopy and architecture (TRAC) and multispectral canopy imager (MCI), were adopted to estimate the ESU (25 m × 25 m) LAI of five Larix principis-rupprechtii forests with contrasting structural characteristics. The impacts of three factors, namely, inversion model, canopy element or woody components clumping index ( Ω e or Ω w ) algorithm, and the woody components correction method, on the ESU LAI estimation of the four optical methods were analyzed. Then, the LAI derived from the four optical methods was evaluated using the LAI obtained from litter collection measurements. Results show that the performance of the four optical methods in estimating the ESU LAI of the five forests was largely affected by the three factors. The accuracy of the LAI obtained from the DHP and MCI strongly relied on the inversion model, the Ω e or Ω w algorithm, and the woody components correction method adopted in the estimation. Then the best Ω e or Ω w algorithm, inversion model and woody components correction method to be used to obtain the ESU LAI of L. principis-rupprechtii forests with the smallest root mean square error (RMSE) and mean absolute error (MAE) were identified. Amongst the three typical woody components correction methods evaluated in this study, the woody-to-total area ratio obtained from the destructive measurements is the most effective method for DHP to derive the ESU LAI with the smallest RMSE and MAE. In contrast, using the woody area index obtained from the leaf-off DHP or DCP images as the woody components correction method would result in a large LAI underestimation. TRAC and MCI outperformed DHP and DCP in the ESU LAI estimation of the five forests, with the smallest RMSE and MAE. All the optical methods, except DCP, are qualified to obtain the ESU LAI of L. principis-rupprechtii forests with an MAE of <20% that is required by the global climate observation system. None of the optical methods, except TRAC, show the potential to obtain the ESU LAI of L. principis-rupprechtii forests with an MAE of <5%.

Environmental Filters Drive the Assembly of the Soil Fungal Community in the Larix principis-rupprechtii Forests of the Guandi Mountains

The community assembly process, which purports that the trade-off between the stochastic process and the deterministic process, is the central issue of community ecology, and is one of the most controversial ecological issues. The current research investigated the fungal community in the Larix principis-rupprechtii forests of the Guandi Mountains and elucidated the relative role of the stochastic and deterministic processes in the assembly of soil fungal community on a local scale. The correlation analysis and redundancy analysis of the physicochemical factors in soil and dominant fungal phyla, as well as the structural equation model analysis, showed that these physicochemical factors and aboveground vegetation diversity had significant effects on fungal communities. The direct effect of vegetation diversity on fungal community structure was the most (1.1858). It is inferred that the determination process (environmental selection) has a certain influence on the assembly of fungal communities. The β-diversity of fungal community shows a distance-decay pattern; thus, it can be concluded that the stochastic process (dispersal limitation) has a certain effect on the assembly of fungal communities. Null model analysis confirmed that the deterministic process was the main driving factor for the assembly of the fungal communities in the study area, and their relative importance varied along with altitudinal gradient. The null deviations in the study area were negative, suggesting that habitat filtering was the driving factor of the assembly of fungal communities. Overall, the deterministic versus stochastic processes jointly drive the assembly of fungal communities in the study area, while the deterministic processes triumph.

Vertical gradients and seasonal variations in the stem CO2 efflux of Larix principis-rupprechtii Mayr

Stem CO2 efflux (ES) plays an essential role in the carbon balance of forest ecosystems. Therefore, it is necessary to study the vertical and seasonal variations in ES in forests with different ages, especially in response to factors associated with temperature, nutrients and wood structure. In this study, we investigated ES and its association with temperature factors using a carbon flux system (Li-8100A) at monthly intervals during the growing season (May to September) and the non-growing season (October) from 2013 to 2015. In addition, we collected data on nutrients and wood structure in August 2016 from 16- (young), 25- (immature), and 41-year-old (mature) Larix principis-rupprechtii Mayr stands in North China. Our analysis showed that the ES values at stem positions near the crown and the root system were generally higher than those in the middle and that the minimum ES values in July occurred at 2.0 m (3.61 μmol m−2 s−1), 3.0 m (2.42 μmol m−2 s−1), and 5.0 m (4.03 μmol m−2 s−1) in the young, immature, and mature forests, respectively. Air temperature and wood temperature influenced the vertical variation in ES, as did stem nitrogen concentration and sapwood width. Compared to the method that uses the vertical ES gradient to determine tree-scale CO2 effluxes for 16-, 25- and 41-year-old L. principis-rupprechtii forests, the method that uses the ES value at the 1.3-m stem position underestimated the CO2 effluxes by 5%, 6%, and 24%, respectively. The ES and Q10 models for each stem position for the three forest ages in this study can be used to accurately estimate tree-scale CO2 effluxes. These results not only clarified the relationships between the vertical variation in ES and temperature, nutrient content and wood structure, but also revealed the likely response mechanisms of ES to these factors. Methodologically, incorporating the vertical variation in ES and the associated drivers into conventional models would improve the accuracy of annual ES estimates.

Carbon stocks of three secondary coniferous forests along an altitudinal gradient on Loess Plateau in inland China.

Natural forests in inland China are generally distributed in montane area and secondary due to a semi-arid climate and past anthropogenic disturbances. However, quantification of carbon (C) stock in these forests and the role of altitude in determining C storage and its partition among ecosystem components are unclear. We sampled 54 stands of three secondary coniferous forests (Larix principis-rupprechtii (LP) forest, Picea meyerii (PM) forest and Pinus tabulaeformis (PT) forest) on Loess Plateau in an altitudinal range of 1200-2700m a.s.l. C stocks of tree layer, shrub layer, herb layer, coarse wood debris, forest floor and soil were estimated. We found these forests had relatively high total C stocks. Driven by both higher vegetation and soil C stocks, total C stocks of LP and PM forests in the high altitudinal range were 375.0 and 368.4 t C ha-1 respectively, significantly higher than that of PT forest in the low altitudinal range (230.2 t C ha-1). In addition, understory shrubs accounted for about 20% of total biomass in PT forest. The proportions of vegetation to total C stock were similar among in the three forests (below 45%), so were the proportions of soil C stock (over 54%). Necromass C stocks were also similar among these forests, but their proportions to total C stock were significantly lower in LP and PM forests (1.4% and 1.6%) than in PT forest (3.0%). Across forest types, vegetation biomass and soil C stock simultaneously increased with increasing altitude, causing fairly unchanged C partitioning among ecosystem components along the altitudinal gradient. Soil C stock also increased with altitude in LP and PT forests. Forest floor necromass decreased with increasing altitude across the three forests. Our results suggest the important role of the altitudinal gradient in C sequestration and floor necromass of these three forests in terms of alleviated water conditions and in soil C storage of LP and PM forests in terms of temperature change.

Biometric and Eddy Covariance Methods for Examining the Carbon Balance of a Larix principis-rupprechtii Forest in the Qinling Mountains, China

The carbon balance of forests is controlled by many component processes of carbon acquisition and carbon loss and depends on the age of vegetation, soils, species composition, and the local climate. Thus, examining the carbon balance of different forests around the world is necessary to understand the global carbon balance. Nevertheless, the available information on the carbon balance of Larix principis-rupprechtii forests in the Qinling Mountains remains considerably limited. We provide the first set of results (2010–2013) from a long-term project measuring forest-atmosphere exchanges of CO2 at the Qinling National Forest Ecosystem Research Station (QNFERS), and compare the net ecosystem exchange (NEE) based on biometric measurements with those observed via the eddy covariance method. We also compare the total ecosystem respiration via scaled-up chamber and eddy covariance measurements. The net primary productivity (NPP) was 817.16 ± 81.48 g·C·m−2·y−1, of which ΔBliving and Dtotal accounted for 77.7%, and 22.3%, respectively. Total ecosystem respiration was 814.47 ± 64.22 g·C·m−2·y−1, and cumulative annual soil respiration, coarse woody debris respiration, stem respiration, and leaf respiration were 715.47 ± 28.48, 15.41 ± 1.72, 35.28 ± 4.78, and 48.31 ± 5.24 g·C·m−2·y−1, respectively, accounting for 87.85%, 1.89%, 4.33%, and 5.93% of the total ecosystem respiration. A comparison between ecosystem respiration from chamber measurements and that from eddy covariance measurements showed a strong linear correlation between the two methods (R2 = 0.93). The NEE of CO2 between forests and the atmosphere measured by eddy covariance was −288.33 ± 25.26 g·C·m−2·y−1, which revealed a carbon sink in the L. principis-rupprechtii forest. This number was 14% higher than the result from the biometric measurements (−336.71 ± 25.15 g·C·m−2·y−1). The study findings provided a cross-validation of the CO2 exchange measured via biometric and eddy covariance, which are beneficial for obtaining the true ecosystem fluxes, and more accurately evaluating carbon budgets.

Characteristics of Fungi Community Structure and Genetic Diversity of Forests in Guandi Mountains

Soil microorganisms drive the biogeochemical process of carbon, nitrogen, phosphorus and sulfur, and play a key role in maintaining soil carbon sink and ecosystem function. The study on effects of environmental and spatial factors on the structure of microbial community in boreal coniferous forest soil will provide theoretical basis for making management measures in local forest ecosystem. Our research analyzed five soil fungi communities (LpMC1, LpMC2, PwMC, PtMC, and BMC) in four forest types, including Larix principis-rupprechtii forest, Picea wilsonii forest, Pinus tabulaeformis forest and Betula spp. forest, respectively, in Pangquangou Nature Reserve in Guandi Mountains with Illumina high-throughput sequencing technology. Meanwhile, soil environmental factors and diversity of undergrowth plants were determined to analyze the relationship between fungi community structure and vegetation as well as soil environmental factors. The results showed that:①There were seven eumycota and thirty-three advantageous fungal genera in the five sample sites; ②Redundancy analysis results showed that soil pH, temperature, moisture, total nitrogen, the content of NH4+, total carbon, invertase activity, urease activity, undergrowth dominance and evenness were significantly associated with soil fungi community structure; ③Cluster analysis and principal component analysis showed that forest vegetation type, soil environmental factors and undergrowth had significant effects on soil fungi community structure; ④The results of PCNM analysis showed that at a local scale, dispersal limitation had no significant influence on fungi community structure in the study area. The forest soil fungi community structure in the study area was significantly affected by environmental selection (soil pH, temperature, moisture, total nitrogen, the content of NH4+, total carbon, invertase activity, urease activity, undergrowth dominance and evenness, forest type).

文峪河上游华北落叶松林的种子雨、种子库与幼苗更新

PDF HTML阅读 XML下载 导出引用 引用提醒 文峪河上游华北落叶松林的种子雨、种子库与幼苗更新 DOI: 10.5846/stxb201406181268 作者: 作者单位: 山西农业大学林学院,山西农业大学林学院,山西农业大学林学院,山西省林业科学研究院 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目(31400536);山西省自然科学基金项目(2012011033-6);山西农业大学作物学博士后流动站基金项目(125376);山西农业大学2010年引进人才科研启动项目(2010008)资助 Seed rain, soil seed bank and regeneration of Larix principis-rupprechtii stands in the Upper Reaches of Wenyuhe Author: Affiliation: Forestry College of Shanxi Agricultural University,Forestry College of Shanxi Agricultural University,Forestry College of Shanxi Agricultural University, Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:华北落叶松林下更新不良,为探究其制约因素,开展了山西省文峪河上游5个华北落叶松林分的种子雨、土壤种子库和幼苗更新的研究。结果表明:(1) 华北落叶松种子主要集中于9-10月散落。2011年为华北落叶松种子丰年:种子产量高,种子雨密度达(961.93±377.40)粒/m2;种子质量高,完整种子占(89.31±16.13)%。2012年为种子平年,种子产量低,种子雨密度为(252.73±115.12)粒/m2。华北落叶松种子雨主要源于毗邻树木,华北落叶松纯林和落叶松云杉林的种子雨密度显著高于其他3个针阔混交林。(2) 土壤种子库主要由上年种子雨组成,2012年4月的土壤种子库密度为(695.18±297.23)粒/m2,完整种子占(59.73±9.56)%。种子自然萌发前,约(78.98±24.76)粒/m2具发芽力,基本可满足更新需要。但种子活力保持期少于2 a,只能形成短期持久土壤种子库。(3) 华北落叶松更新不良,种子年后仍难以实现幼苗建成,当年生幼苗的出现频度平均为1.6%,且林下难以存活。幼苗发生与种子储量关联性不强,种源条件不是制约华北落叶松更新的主要因素。 Abstract:Larix principis-rupprechtii is one of dominant deciduous coniferous tree species in subalpine temperate forests of North China. It plays significant roles in water conservation, ecotourism and biodiversity maintenance in its distributional areas. It is also one of major economic tree species in this region due to its fast growth and good-quality timber. Previous studies suggest that L. principis-rupprechtii experiences natural regeneration failure, as indicated by low proportion of saplings and seedlings in natural conditions. The failure of regeneration is a threat to persistence of L. principis-rupprechtii forests in its distributional areas. However, the causes of natural regeneration failure are still poorly understood. This study was to examine whether the natural regeneration failure of this species was driven by seed limitation. We investigated seed rain, soil seed bank and seedling regeneration in five typical larch stand types, i.e., pure L. principis-rupprechtii stand, L. rincipis-rupprechtii + Betula platyphylla stand, L. principis-rupprechtii + Populus davidiana stand, L. principis-rupprechtii + P. davidiana + B. platyphylla stand, L. principis-rupprechtii + Picea wilsonii stand. Fifteen 50 cm × 50 cm seed traps were deployed in each plot for seed rain collecting. For each plot, 15 quadrats of 20 cm×20 cm with 10cm depth and 50 quadrats of 1 m × 1 m were examined nearby seed traps for soil seed bank and recruitment survey, respectively. We found that most of seeds were dispersed from September to October. In 2011, which was a seed year of L. principis-rupprechtii, seed production was amounted to (961.93±377.40) seeds/m2, (89.31±16.13)% of which was full seeds. In 2012, a common seed year, both seed production and full seeds proportion were lower than those in previous year, with (252.73±115.12) seeds/m2 and (36.04±4.26)%, respectively. Furthermore, seed rain of L. principis-rupprechtii was mainly from the surrounding mother trees. Seed rain densities of pure L. principis-rupprechtii stand and L. principis-rupprechtii + P. wilsonii stand were higher than those of the other three stand types, which were mixed with broad-leave trees. Thirdly, soil seed bank of L. principis-rupprechtii was mainly from the seed rain that produced in previous year. Seed bank in April of 2012 was (695.18±297.23) seeds/m2, accounting for (76.05±13.79)% of seed rain in autumn of 2011. More than 85% of seeds were found in the litter layer. About (59.73±9.56)% of the seed bank was full seeds. There were (78.98±24.76) seeds/m2 remained viable to germinate before natural regeneration, accounting for (19.02±5.00)% of full seeds in soil seed bank. The germination capacity decreased with time being in forest floor, hence, forming a short-term persistent soil seed bank for L. principis-rupprechtii. Lastly, the emergence of seedlings uncoupled with the seed storage. The frequency of seedling emergence was 1.6%. Seedlings could hardly survive understory. Collectively, this study demonstrates that seed source, especially in seed year, is not the limiting factor for the poor natural regeneration of L. principis-rupprechtii. Our study suggests that further studies should be carried out to examine the detrimental or limiting factors, such as effects of soil moisture and litter, for the natural regeneration failure of the species. 参考文献 相似文献 引证文献

木兰围场典型落叶松-杨桦混交林生物量及固碳能力研究

A mixed Dahurian larch and polar birch forest,artificial Larix principis-rupprechtii forest,natural Betula platyphylla secondary forest,and natural Populus davidiana secondary forest,which are all part of the Bei-gou Forest Farm in Mulan Forestry Bureau were studied here. The layered cut method was used to measure aboveground biomass in all four forests. The layered mining method was used to measure underground biomass. The trunks were divided into segments 0. 5m in diameter and 5 cm thick. The north-south diameter of each disk was recorded. Tree roots were divided into 0. 5 cm layers,and the crown projection area was dug up. Fresh weights of the trunks( with bark),branches,leaves,and roots of model trees were recorded in the open air. Samples of each organ were dried to( 105℃) constant weight and weighed. To determine biomass,leaf and branch samples were collected from different parts of the crown cover. They were weighed and dried,and their moisture content was calculated. For trunks,disk sections were obtained and weighed before and after drying. Moisture content was calculated. The leaf,branch,and root biomass of each model tree was calculated. Incrementswere measured in analytic trees. Then models of biomass and increments were established. Carbon reserve and carbon sequestration were estimated. Significant power functions and logistic equations were chosen as biomass prediction models.DBH( diameter at breast height) served as an independent variable and the napierian logarithm of biomass and total biomass of organs as the dependent variable. Optimization was performed according to regression curve and residual sum of squares( SSE),discriminant coefficient( R2),total relative error( RS),average relative error( E1),absolute value of average relative error( E2),AIC( Akaike Information Criterion),and BIC( Bayesian Information Criterion). DBH increments were measured with analytic trees,wooden cores,and DBH increments of the past five years as a baseline. A power function regression model was established. Then the DBH increments of trees over the past five years were estimated.Then the fixed carbon content of each forest was calculated for that period using the carbon content of different tree species and organs. Results showed the Dahurian larch and polar birch mixed forest stored more carbon than other forests. The Dahurian larch,Betula platyphylla,and Populus davidiana in the mixed forest were all superior to their respective artificial and natural forests. The mean DBH( diameter at breast height) was higher by about 6. 7%,12. 8%,and 4. 1%. The mean was higher by about 12. 1%,1. 4%,and 11. 1%. The fixed carbon content growth rates of Dahurian larch,Betula platyphylla,and Populus davidiana in the mixed forest were 29. 74%,28. 36%,and 34. 52%,respectively. The rate of carbon fixation was 27. 09% in the artificial Larix principis-rupprechtii forest; 26. 34% in the natural Betula platyphylla secondary forest; and 26. 24% in the natural Populus davidiana secondary forest. The rates of carbon fixation of Dahurian larch,Betula platyphylla,and Populus davidiana in the Dahurian larch and polar-birch mixed forest were 2. 65%,2.02%,and 8. 28% higher,respectively,than in the corresponding monoculture forests.

Density structure and growth dynamics of a Larix principis-rupprechtii stand for water conservation in the Wutai Mountain Region of Shanxi Province, North China

To discover the site adaptability and density suitability of Larix principis-rupprechtii as a water conservation forest in Wutai Mountain, Shanxi Province, the growth process and diameter distribution characteristics of 10-year-old artificial L. principis-rupprechtii forests with density structures of 2600 trees/hm2 and 3500 trees/hm2 were studied using trunk analysis of a sample tree. The results showed that: 1) The tree height increment of the two kinds of forests were the same, and it was almost not affected by density. However, the growth process of the diameter and timber volume showed a great distinction. The growth status and density structure of the low density forest were superior to the high density forest. 2) The skewness (S k) of diameter distribution had great distinction. The S k (0.01) of the low density forest approached a normal distribution, which showed that the density structure was reasonable, while the S k (0.45) of the high density forest was partial to a normal distribution, which showed that the density structure was on the high side. The kurtosis (K) of the two forests (one was −0.64, the other was −0.74) had little distinction and the density factor had limited function to forest polarization. 3) The increment of diameter at breast height, timber volume and trunk stock of the low density forest increased yearly without the effect of density. However, the increment of high density forests had declined from the sixth year, which was restricted by high density. 4) The reasonable density of the 10-year-old L. principis-rupprechtii artificial forest was about 2600 trees/hm2, which is also the reasonable planting density if the utilization of double cutting is not considered.

Point pattern analysis of different age-classes of Larix principis-rupprechtii in Luya Mountain Reserve, Shanxi Province, China

Larix principis-rupprechtii forest is an important vegetation formation and has a large distribution area in Luya Mountain Reserve, China. Spatial pattern analysis on individual trees in different age-classes of Larix principis-rupprechtii was made in this paper. Here, we employed the technique of point pattern analysis, which could analyze patterns under all scales along a gradient. It was based on spatial mapped points of individual distribution. The results of this study showed that the densities of the five age-classes varied in the order: age-class 3 > age-class 4 > age-class 5 > age-class 2 > age-class 1. Although age-classes 1 and 2 have much fewer individuals than other three age-classes do, the population was stable at present. However, it would be necessary to take some measures for improving population regeneration for a long-time view. The individuals of all age-classes focused on clumping distribution in space; however, their distribution pattern varied with the change of scale. This mainly depended on biological features of Larix principis-rupprechtii and forest environments, but it also meant that the scale was an important factor in controlling spatial distribution pattern of tree individuals. The feature of clumping distribution became more significant with the increase of age. The relationships between individuals in different age-classes were almost all significantly correlated with each other. These associations became more significant within the older age-classes. This suggested that the individuals of different age-classes were interdistributed, by which the population could get benefits in resource utilization. The technique of point pattern analysis is effective and easy to be used in species pattern study. Its results are more closer to the reality, especially for community structure.