Pinus Tabulaeformis Forest Research Articles

Simulated warming reduced greenhouse gas emissions by lowering soil moisture in a Pinus tabulaeformis forest of the temperate zone

The forest soil carbon represents the largest carbon pool in the terrestrial ecosystem. To clarify the effect of climate warming on the soil carbon pool of a Pinus tabulaeformis plantation in the northern temperate zone, an Open-Top Chamber was used to study the effects of warming on soil temperature and moisture, soil enzyme activity, soil active organic carbon, and greenhouse gas emissions in different soil layers. The results showed that (1) warming increased the temperature and decreased the moisture content of the atmosphere and soil. Atmospheric temperature increased by 0.9°C on average, and atmospheric moisture decreased by 0.05%. (2) Warming had no significant effect on soil active organic carbon or enzyme activity, but had a significant effect on the active organic carbon content and enzyme activity in individual soil layers in individual months. (3) Warming reduced soil CO2 emissions from the control treatment, from 996.35 to 781.57 g·m−2. The soil of the P. tabulaeformis forest in Daqing Mountain is a sink of atmospheric CH4. Therefore, after the short-term warming treatment, the soil moisture was reduced; greenhouse gas emissions were significantly reduced, and the warming formed a negative feedback with soil greenhouse gas flux.

Microenvironment heterogeneity affected by anthropogenic wildfire-perturbed soil mediates bacterial community in Pinus tabulaeformis forests.

In recent years, the frequency and intensity of anthropogenic wildfires have drastically increased, significantly altering terrestrial ecosystems worldwide. These fires not only devastate vegetative cover but also impact soil environments and microbial communities, affecting ecosystem structure and function. The extent to which fire severity, soil depth, and their interaction influence these effects remains unclear, particularly in Pinus tabulaeformis forests. This study investigated the impact of wildfire intensity and soil stratification on soil physicochemical properties and microbial diversity within P. tabulaeformis forests in North China. Soil samples were collected from different fire severity zones (Control, Light, Moderate, High) and depths (topsoil: 0-10 cm; subsoil: 10-20 cm). Analyses included measurements of soil pH, organic carbon (SOC), total nitrogen (TN), and other nutrients. Microbial diversity was assessed using 16S rRNA gene sequencing. Our findings revealed significant variations in soil pH, SOC, TN, and other nutrients with fire severity and soil depth, profoundly affecting microbial community composition and diversity. Soil pH emerged as a critical determinant, closely linked to microbial α-diversity and community structure. We found that fire severity significantly altered soil pH (p = 0.001), pointing to noteworthy changes in acidity linked to varying severity levels. Topsoil microbial communities primarily differentiated between burned and unburned conditions, whereas subsoil layers showed more pronounced effects of fire severity on microbial structures. Analysis of bacterial phyla across different fire severity levels and soil depths revealed significant shifts in microbial communities. Proteobacteria consistently dominated across all conditions, indicating strong resilience, while Acidobacteriota and Actinobacteriota showed increased abundances in high-severity and light/moderate-severity areas, respectively. Verrucomicrobiota were more prevalent in control samples and decreased significantly in fire-impacted soils. Chloroflexi and Bacteroidota displayed increased abundance in moderate and high-severity areas, respectively. Correlation analyses illustrated significant relationships between soil environmental factors and dominant bacterial phyla. Soil organic carbon (SOC) showed positive correlations with total nitrogen (TN) and alkaline hydrolysable nitrogen (AN). Soil pH exhibited a negative correlation with multiple soil environmental factors. Soil pH and available phosphorus (AP) significantly influenced the abundance of the phylum Myxococcota. Soil water content (WC) significantly affected the abundances of Acidobacteriota and Actinobacteriota. Additionally, ammonium nitrogen (NH4 +-N) and nitrate nitrogen (NO3 --N) jointly and significantly impacted the abundance of the phylum Chloroflexi. This study highlights the significant long-term effects of anthropogenic wildfires on soil microenvironment heterogeneity and bacterial community structure in P. tabulaeformis forests in North China, 6 years post-fire. Our findings demonstrate that fire severity significantly influences soil pH, which in turn affects soil nutrient dynamics and enhances microbial diversity. We observed notable shifts in the abundance of dominant bacterial phyla, emphasizing the critical role of soil pH and nutrient availability in shaping microbial communities. The results underscore the importance of soil stratification, as different soil layers showed varying responses to fire severity, highlighting the need for tailored management strategies. Future research should focus on long-term monitoring to further elucidate the temporal dynamics of soil microbial recovery and nutrient cycling following wildfires. Studies investigating the roles of specific microbial taxa in ecosystem resilience and their functional contributions under varying fire regimes will provide deeper insights. Additionally, exploring soil amendments and management practices aimed at optimizing pH and nutrient availability could enhance post-fire recovery processes, supporting sustainable ecosystem recovery and resilience.

P-limitation regulates the accumulation of soil aggregates organic carbon during the restoration of Pinus tabuliformis forest

Artificial forest restoration is widely recognized as a crucial approach to enhance the potential of soil carbon sequestration. Nevertheless, there is still limited understanding regarding the dynamics of aggregate organic carbon (OC) and the underlying mechanisms driving these dynamics after artificial forest restoration. To address this gap, we studied Pinus tabuliformis forests and adjacent farmland in three recovery periods (13, 24 and 33 years) in the Loess Plateau region. Samples of undisturbed soil from the surface layer were collected and divided into three aggregate sizes: >2 mm (large aggregate), 0.25–2 mm (medium aggregate), and <0.25 mm (small aggregate). The aim was to examine the distribution of OC and changes in enzyme activity within each aggregate size. The findings revealed a significant increase in OC content for all aggregate sizes following the restoration of Pinus tabuliformis forests. After 33 years of recovery, the OC of large aggregates, medium aggregates and micro-aggregates increased by (30.23 ± 9.85)%, (36.71 ± 21.60)% and (37.88 ± 16.07)% respectively compared with that of farmland. Moreover, the restoration of Pinus tabuliformis forests lead to increased activity of hydrolytic enzymes and decreased activity of oxidative enzymes. It is noteworthy that the regulation of carbon in all aggregates is influenced by soil P-limitation. In large aggregates, P-limitation promotes the enhancement of hydrolytic enzyme activity, thereby facilitate OC accumulation. Conversely, in medium and small aggregates, P-limitation inhibits the increase in oxidative enzyme activity, resulting in OC accumulation. The results emphasize the importance of P-limitation in regulating OC accumulation during the restoration of Pinus tabulaeformis forest, in which large aggregates play a leading role.

Effects of Forest Gaps on Forest Floor Microbial Community Composition in Pinus tabulaeformis Forests in a Rocky Mountain Area, Beijing, China

Forest gaps induce environmental heterogeneity, but their effects on the local forest floor microbial communities are not fully understood. This research investigated the impact of forest gap positions on the forest floor microbial community composition to provide baseline information for projects to accelerate nutrient cycling and forest regeneration and enhance ecosystem services. A one-year-old forest gap and an area of 40–50 m2 in Pinus tabulaeformis plantations were selected in the Beijing mountainous area. Forest floor samples were collected from the following positions: gap center, gap border, and adjacent closed canopy. Our study demonstrated that gap positions significantly influenced the forest floor microbial community composition. The Gram-positive bacteria, Gram-negative bacteria, and total bacteria, as well as the fungi, were significantly greater in the forest gap center and gap border compared to those in the closed canopy, and the dissolved organic carbon, readily oxidized organic carbon, ammonia nitrogen, and nitrate nitrogen followed the same trend. Compared with those of the closed canopy, the Gram-positive bacteria, Gram-negative bacteria, total bacteria, and fungi in the gap center were markedly greater by 23%, 25%, 22%, and 24% and by 14%, 14%, 11%, and 16% in the gap border, respectively (p &lt; 0.05). Redundancy analysis demonstrated that shifts in the litter microbial community composition were predominantly predicted by litter moisture and β-1,4-glucosidase. In addition, we discovered that the microbial community composition was greater in the undecomposed forest layer than that in the semi-decomposed layer. In summary, gap positions and forest floor layers have a significant impact on microbial community composition. Nevertheless, additional long-term investigations are needed. Our study provides a reference for the promotion of nutrient cycling to guide future ecological management.

Soil mineralized carbon drives more carbon stock in coniferous-broadleaf mixed plantations compared to pure plantations.

Forest soil carbon (C) sequestration has an important effect on global C dynamics and is regulated by various environmental factors. Mixed and pure plantations are common afforestation choices in north China, but how forest type and environmental factors interact to affect soil C stock remains unclear. We hypothesize that forest type changes soil physicochemical properties and surface biological factors, and further contributes to soil active C components, which together affect soil C sequestration capacity and C dynamic processes. Three 46-year-old 25 m × 25 m pure Pinus tabulaeformis forests (PF) and three 47-year-old 25 m × 25 m mixed coniferous-broadleaf (Pinus tabulaeformis-Quercus liaotungensis) forests (MF) were selected as the two treatments and sampled in August 2016. In 2017, soil temperature (ST) at 10 cm were measured every 30 min for the entire vegetation season. Across 0–50 cm (five soil layers, 10 cm per layer), we also measured C components and environmental factors which may affect soil C sequestration, including soil organic carbon (SOC), soil total nitrogen (STN), dissolved organic carbon (DOC), microbial biomass carbon (MBC), soil moisture (SM) and soil pH. We then incubated samples for 56 days at 25 °C to monitor the C loss through CO2 release, characterized as cumulative mineralization carbon (CMC) and mineralized carbon (MC). Our results indicate that ST, pH, SM and litter thickness were affected by forest type. Average SOC stock in MF was 20% higher than in PF (MF: 11.29 kg m−2; PF: 13.52 kg m−2). Higher CMC under PF caused more soil C lost, and CMC increased 14.5% in PF (4.67 g kg−1 soil) compared to MF (4.04 g kg−1 soil) plots over the two-month incubation period. SOC stock was significantly positively correlated with SM (p < 0.001, R2 = 0.43), DOC (p < 0.001, R2 = 0.47) and CMC (p < 0.001, R2 = 0.33), and significantly negatively correlated with pH (p < 0.001, R2 = −0.37) and MC (p < 0.001, R2 = −0.32). SOC stock and litter thickness may have contributed to more DOC leaching in MF, which may also provide more C source for microbial decomposition. Conversely, lower SM and pH in MF may inhibit microbial activity, which ultimately makes higher MC and lower CMC under MF and promotes C accumulation. Soil mineralized C drives more C stock in coniferous-broadleaf mixed plantations compared to pure plantations, and CMC and MC should be considered when soil C balance is assessed.

Effect of Two Exogenous Organic Acids on the Excitation Effect of Soil Organic Carbon in Beijing, China

Significance: The study of the effects and pathways of catechol and pyrogallic acid on soil organic carbon mineralization has a positive effect on mastering soil carbon transformation. Methods and objectives: In this study, we took 0–20 cm soil from Pinus tabulaeformis forest as an object to investigate the effects of catechol and pyrogallic acid with different concentrations on soil organic carbon mineralization through a 60-day mineralization incubation test. The soil active carbon content and changes in soil microbial diversity and community composition were analyzed by using single exponential fitting, quantitative PCR, and high-throughput sequencing to explore the influencing mechanisms of catechol and pyrogallic acid on soil organic carbon excitation. Results: Catechol and pyrogallic acid had the effect of enhancing the soil organic carbon mineralization and soil active carbon content, and the higher the concentration, the stronger the enhancement effect. Catechol reduced the Ace index, Chao1 index, and Shannon index of bacteria and fungi, and further changed the relative abundance of two dominant groups (Proteobacteria and Acidobacteriota) in bacteria and Basidiomycota in fungi at high concentrations. There was no obvious regularity in the effects of pyrogallic acid on bacteria and fungi, but the Ace index and Chao1 index of bacteria underwent drastic and disordered changes. Conclusions: Catechol and pyrogallic acid can trigger positive excitation of the soil organic carbon through two pathways: increasing the soil active carbon content and modulating soil microorganisms, but the way they modulate soil microorganisms are different. Catechol regulates soil microorganisms by reducing the number, richness, and evenness of the bacteria and fungi species, as well as the community composition, while the way pyrogallic acid regulates only closely relates to the changes in the number, richness, and evenness of bacteria species.

贺兰山东坡不同海拔典型植被带土壤微生物磷酸脂肪酸分析

PDF HTML阅读 XML下载 导出引用 引用提醒 贺兰山东坡不同海拔典型植被带土壤微生物磷酸脂肪酸分析 DOI: 10.5846/stxb202104130959 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 宁夏自然科学基金项目（2020AAC03102）；宁夏重点研发计划项目（2018BFG02015，2021BGF02005）；国家自然科学基金项目（31960359） Phospholipid fatty acid analysis of soil microbes in typical vegetation types at different elevation on the east slope of Helan Mountain Author: Affiliation: 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:土壤微生物在维持干旱区森林生态系统功能稳定方面具有重要作用，但有关干旱区微生物群落结构及多样性沿海拔分布规律研究较少，采用磷酸脂肪酸（PLFA）法定量分析贺兰山自然保护区东坡不同海拔典型植被带（荒漠草原HM、蒙古扁桃MG、油松林YS、混交林HJ、青海云杉林QH）土壤微生物群落结构特征及多样性。结果表明，不同海拔植被带土壤中共检测出59种PLFA生物标记，YS土壤中生物标记的含量明显高于其他植被类型，5个植被带共有且含量较高的PLFA生物标记为16：0、18：1ω9c、18：1ω7c、10Me 16：0和18：2ω6c，特征微生物的含量在不同植被带土壤中分布不同，细菌分布数量最大，其次是真菌、放线菌，原生动物分布数量最小。聚类分析发现，不同植被带土壤PLFA生物标记可分成不同的类群，16：0、18：1ω9c和18：1ω7c基本在每个植被带都会单独聚为一类。对不同植被带所共有的PLFA生物标记绘制热图，发现不同的PLFA生物标记在不同植被带分布不同，YS植被带PLFA生物标记分布最高。不同植被带土壤微生物群落多样性显示，HJ土壤中微生物多样性指数大于其他植被类型，HM土壤中微生物多样性指数最小，说明土壤微生物多样性与植被多样性密切相关。主成分分析表明，与土壤微生物群落相关的2个主成分解释量为78.01%和8.80%，对第1主成分起主要作用的微生物类群有非特异性细菌、革兰氏阳性细菌、革兰氏阴性细菌、真菌、放线菌和原生动物等，对第2主成分起主要作用的微生物类群为厌氧细菌。土壤微生物与土壤因子相关性分析表明，土壤有机碳（SOC）、全氮（TN）与微生物类群及多样性指数正相关，pH、容重（BD）与微生物类群及多样性指数负相关，海拔引起土壤因子的改变是影响土壤微生物群落结构及多样性的重要因素。研究表明YS土壤中微生物含量最大，HJ土壤中微生物多样性最高，与山地生态系统中中部区域生物多样性高的其他研究结果相吻合，可为贺兰山自然保护区土壤微生物的研究及保护区的管理提供科学依据。 Abstract:Soil microorganisms play an important role for maintaining the functional stability of forest ecosystem in arid areas. However, distribution of soil microbial community structure and diversity along an elevation gradient remains poorly understood, especially in the arid areas. In this study, the phospholipid fatty acid analysis (PLFA) was used to examine variations in soil microbial community diversity along an elevational eastern slope in the Helan Mountain (Desert Steppe (HM), Amygdalus mongolica (Maxim) Ricker (MG), Pinus tabulaeformis forest (YS), Mixed forest (HJ), Picea crassifolia Kom forest(QH)). The results showed that, there existed 59 PLFAs which were significantly different in the soil samples from different vegetation types. The YS soil exhibited richer PLFAs distribution amount than the other vegetation types. The PLFAs biomarkers of five vegetation types with the highest contents were 16:0, 18:1ω9c, 18:1ω7c, 10Me 16:0 and 18:2ω6c, respectively. The amount of characteristic microorganisms was different in soil of different vegetation types, the bacteria had the richest distribution, followed by fungi, actinomycetes and protozoa. Cluster analysis showed that soil PLFAs could be divided into different groups in different vegetation types, 16:0, 18:1ω9c and 18:1ω7c could be divided into one group in different vegetation types. The heat map of the common PLFAs in different vegetation types was drawn. It was found that the distribution of different PLFAs was different in different vegetation types, and the distribution of PLFAs in YS vegetation was the highest. The diversity of soil microbial communities in different vegetation types showed that the microbial diversity index in HJ was higher than the other vegetation types, and the HM was the lowest, indicating that soil microbial diversity was closely related to vegetation diversity. Component analysis (PCA) identified 2 principal component factors in relation to microbial community diversity, explaining 78.01% and 8.80% of the variation, respectively. The microorganisms, which play a major role on first principal component, are nonspecific bacteria; Gram-positive bacteria and Gram-negative bacteria, fungi, actinomycetes and protozoa, which play a major role on second principal component, are anaerobic bacteria. Correlation analysis between soil microorganisms and soil factors showed that soil organic carbon (SOC) and total nitrogen (TN) were positively correlated with soil microbial groups and diversity index, while pH and bulk density (BD) were negatively correlated with microbial groups and diversity index. The change of soil factors caused by altitude was an important factor affecting soil microbial community structure and diversity. The results show that YS soil has the highest microbial content, and HJ soil has the highest microbial diversity, which accords with the theory of high biodiversity in the central region of mountain ecosystem, and can provide scientific basis for the study of soil microorganisms and the management of Helan Mountain Nature Reserve. 参考文献 相似文献 引证文献

半干旱黄土区植被恢复对土壤团聚体稳定性及抗侵蚀能力的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 半干旱黄土区植被恢复对土壤团聚体稳定性及抗侵蚀能力的影响 DOI: 10.5846/stxb202202090324 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 山西省回国留学人员科研资助项目（2021-097）；山西省基础研究计划（20210302123333）；国家自然科学基金项目（41971129） Effect of vegetation restoration on stability and erosion resistance of soil aggregates in semi-arid loess region Author: Affiliation: 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:土壤水稳性团聚体强烈影响土壤过程和功能，是反映土壤质量和土壤抗侵蚀能力的重要指标。为探究半干旱黄土区植被恢复对土壤抗侵蚀能力的影响，以甘肃省定西市龙滩流域为研究区，选取3种恢复方式（天然荒草、自然恢复、人工恢复）7种植被类型（大针茅草地、长芒草草地、赖草草地、苜蓿草地、柠条灌丛、山杏林以及油松林）为研究对象，通过测定0-20 cm、20-40 cm和40-60 cm土壤水稳性团聚体，分析土壤团聚体组成、稳定性及抗侵蚀能力特征。结果表明：1）不同恢复方式不同植被类型间土壤水稳性团聚体稳定性差异显著（P<0.05），自然恢复方式的土壤水稳性团聚体平均重量直径显著高于天然荒草和人工恢复方式，且7种植被类型土壤大团聚体质量百分比均在67.97%-90.12%之间；人工恢复方式土壤水稳性团聚体稳定性较差，其中油松林稳定性最差。2）土壤团聚体破坏率和土壤抗侵蚀能力均表现出自然恢复方式更有利于土壤结构稳定性的提高。3）土壤水稳性大团聚体含量越高，土壤团聚体越稳定，土壤结构稳定性就越好；平均重量直径与土壤可蚀性因子K值呈极显著性负相关（P<0.01）。本研究结果表明自然恢复方式能够显著提高土壤团聚体的稳定性，从而提升土壤的抗侵蚀能力，建议当地在未来植被恢复规划中采取自然恢复方式更有利于生态恢复的有效进行。 Abstract:Soil water-stable aggregates strongly affect soil process and function, which is an important index to reflect soil quality and soil erosion resistance. In order to explore the effect of vegetation restoration on soil erosion resistance in semi-arid loess region, in this study, through three restoration methods (natural grassland, natural restoration, artificial restoration) and seven vegetation types (Stipa grandis grassland, Stipa bungeana grassland, Leymus secalinus grassland, Medicago sativa grassland, Caragana korsinskii shrub, Armeniaca sibirica forest and Pinus tabulaeformis forest) were selected in the Longtan catchment of Dingxi in Gansu Province. The composition, stability and erosion resistance characteristics of soil aggregates were analyzed by measuring 0-20 cm, 20-40 cm and 40-60 cm soil water-stable aggregates. The results showed that:1) there are significant differences in the stability of soil water-stable aggregates among different vegetation types and different restoration methods (P<0.05). The average weight diameter of soil aggregates in natural restoration grassland was significantly higher than that in natural restoration and artificial restoration vegetation, and the mass percentage of soil macroaggregates of the seven vegetation types was 67.97%-90.12%. The stability of soil water-stable aggregates under artificial restoration was poor, among which the stability of Pinus tabulaeformis forest was the worst. 2) The destruction rate of soil aggregates and the ability of soil erosion resistance showed that the natural restoration method was more beneficial to the improvement of soil structure stability. 3) The higher the content of water-stable macroaggregates in soil, the more stable the soil aggregate, the better the soil structural stability; there was a very significantly negative correlation between soil average weight diameter and soil erodibility factor K (P<0.01). The results of this study show that the natural restoration method can significantly improve the stability of soil aggregates, thus improving the soil anti-erosion ability, so as to improve the soil erosion resistance, suggested the plant in the future. 参考文献 相似文献 引证文献

氮添加对天然油松林油松不同器官N-P分配策略的影响

作为植物重要器官, 叶、茎、根对环境变化的响应策略一直是生态学研究的重要课题。然而, 植物不同器官的氮-磷(Nitrogen-Phosphorus)分配策略对氮沉降的响应规律仍不清楚。为了揭示不同器官的养分对氮添加的响应规律, 本研究以山西太岳山天然油松林为研究对象, 设置4个人工氮添加水平, 分别为对照(CK, 0 kg hm^-2 a^-1)、低氮(LN, 50 kg hm^-2 a^-1)、中氮(MN, 100 kg hm^-2 a^-1)和高氮(HN, 150 kg hm^-2 a^-1), 模拟氮沉降对油松不同器官N-P分配策略的影响。实验结果表明：1)随着氮添加浓度的增加, 茎N含量显著降低(P < 0.05), 根N含量显著增加(P < 0.05)；茎P含量在低氮条件下与其他氮添加水平相比显著降低(P < 0.05)；叶N∶P在低氮条件下与其他氮添加水平相比显著增加(P < 0.05), 茎N∶P在高氮条件下与其他氮添加水平相比显著降低(P < 0.05)。2)叶片的N含量和P含量在不同氮添加浓度下表现出显著的异速生长关系, 高氮条件下会导致植物分配给叶和茎基于单位磷含量分配的氮含量显著降低, 根在N、P养分关系中的变化速率具有一致性。3)氮添加处理下, 根比茎和叶在分配单位含量的P素时会分配更多的N素。低氮条件下是油松生长的最佳环境, 根、茎、叶三个器官氮磷分配的异速生长关系存在显著差异, 其生长表现为对P的快速分配。以上结果表明, 油松不同器官对氮沉降的响应存在差异, 并且持续的氮添加会导致油松适应性的改变。;As important plants' organs, the response strategy of leaves, stems and roots to environmental changes plays an important role in ecological research. However, the response of nitrogen-phosphorus allocation strategies to nitrogen deposition in different plant organs is still unclear. In order to reveal the response of nutrients in different organs under nitrogen addition, we selected Pinus tabulaeformis forest in Taiyue Mountain of Shanxi Province as the research materials. Four artificial nitrogen levels were set as control (CK, 0 kg hm^-2 a^-1), low nitrogen (LN, 50 kg hm^-2 a^-1), medium nitrogen (MN, 100 kg hm^-2 a^-1) and high nitrogen (HN, 150 kg hm^-2 a^-1). The results showed that: 1) With the increase of nitrogen addition level, the N content in stem decreased significantly (P < 0.05), the N content in root increased significantly (P < 0.05); The P content in stem decreased significantly under low nitrogen condition (P < 0.05); The N∶P of leaf increased significantly under low nitrogen condition (P < 0.05) and the N∶P of stem decreased significantly under high nitrogen condition (P < 0.05). 2) The N and P contents of leaves showed a significant allometric relationship under different N addition levels. Under high N condition, the N content allocated to leaves and stems based on P content per unit was significantly reduced, and the rate of change in the N and P nutrient relationship between roots was consistent. 3) Under nitrogen addition, the root allocated more N than the stem and leaf by using per unit P content. Low nitrogen was the best environmental condition for the growth of Pinus tabulaeformis. There were significant differences in the allometric growth relationship of nitrogen and phosphorus distribution in root, stem and leaf, and the growth showed rapid distribution of P. The results showed that the responses of different organs of Pinus tabulaeformis to nitrogen deposition were different, and nitrogen addition would lead the changes of adaptability of Pinus tabulaeformis.

High-throughput Sequencing Analysis of Soil Bacterial Community in the Grain for Green Project Areas of the Loess Plateau

This study analyzed the characteristics of the soil bacterial community under different types of vegetation restoration, and explored the role of microorganisms in the vegetation restoration process, within the soil ecosystem of Grain for Green areas of the Loess Plateau. Typical artificial forest (artificial Robinia pseudoacacia forest, Pinus tabulaeformis forest), natural secondary forest, and grassland were selected as the research objects. High-throughput sequencing technology was used to analyze the α diversity and community structure of soil bacteria, and the correlation between soil environmental factors and bacterial communities. The Chinese National Ecosystem Research Network in Jixian County Station was chosen as the research area. The results showed that the bacterial communities of the five types of forest restoration comprised 25 phyla, 66 classes, 129 orders, 240 families, 392 genera, 760 species, and 2213 OTUs. There were significant differences in the abundance of bacterial communities, which could be ranked as follows: CD > CSL > CH2 > CH1 > YS. The dominant bacteria phyla in the different vegetation restoration types were Actinobacteria, Proteobacteria, Acidobacteria, and Chloroflexi. The relative abundances of natural secondary forest, grassland, and plantation were different, but not significantly. The relative abundances of α-Proteobacteria, β-Proteobacteria, and δ-Proteobacteria were higher in natural secondary forest soilthan in the soil of the other four restoration models, and the relative abundance was the lowest in grassland soil. The dominant bacteria were significantly correlated with soil pH and TN. Among them, TN was significantly positively correlated with Actinobacteria, pH was significantly positively correlated with Proteobacteria and negatively correlated with Actinobacteria, while Acidobacteria was significantly negatively correlated with soil pH and TN. PICRUSt analysis showed that the functional gene families were mainly related to 24 sub-functions, including cell motility, signal transduction mechanisms, amino acid transport and metabolism, as well as coenzyme transport and metabolism. These results can provide a good foundation for the evaluation of vegetation restoration in the Loess Plateau, as well as a scientific basis for the rational management of plantations.

Effects of terracing measures on water retention of pinus Tabulaeformis forest in the dryland loess hilly region of China

Terraces, which are distributed worldwide, play a key role in water conservation, vegetation restoration and agricultural production particularly in dryland mountainous environments. Due to the uncertainties caused by water balance dynamics and diverse terrace structures, different findings on the soil-water retention effects of terracing were identified across the globe. To further understand the effect of terraces on soil water retention, a field experiment was conducted between 2015 and 2019 in the dryland loess hilly region of China. The experiment compared the combination of Pinus tabulaeformis with natural slope (PS), zig terrace (PT), and fish-scale pit (PF). We found that terrace measures can greatly manipulate the hydrological dynamics and compounds. Compared with the non-terraced treatments, terrace fields reduced runoff (26.9 mm/a for PF and 34.6 mm/a for PT), increased interception (13.6 mm/a for PF and 12.1 mm/a for PT) and transpiration (14.8 mm/a for PF and 2.4 mm/a for PT) during five years of the experiment. The advantage of terracing in soil water retention was temporal, mainly during heavy rainfall periods (e.g., June to August). Zig terrace promoted soil infiltration and transpiration while fish scale pit suppressed evaporation but increased transpiration. The results indicated that temporal factor and terrace structure were essential in understanding its soil-water retention services.

Changes in the understory diversity of secondary Pinus tabulaeformis forests are the result of stand density and soil properties

Although the responses of forests to the regulation of stand density are better understood, a further elucidation is required as to how it impacts understory vegetation and soil properties. The relationships between understory soil properties and vegetation also warrants attention; thus, for this study we endeavored to develop new strategies to explore changes in understory vegetation. To investigate the effects of stand density on the diversity of understory vegetation and soil properties of a secondary Pinus tabulaeformis forest, fifteen sample plots with different stand densities were established. Furthermore, the soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP), nitrate nitrogen (NN), ammonium nitrogen (AN), microbial biomass carbon (MBC), and microbial biomass nitrogen (MBN) contents were determined. The Simpson, Shannon Weiner, and Pielou indices, C:N, C:P, and N:P ratios, microbial entropy carbon (qMBC), and microbial entropy nitrogen (qMBN) were calculated. It was observed that stand density substantially influenced soil attributes and the variety of understory vegetation, whereas the soil nutrient content and the diversity index of different stand density levels had significant differences. Moderate stand density promoted the retention of soil nutrients and the organic decomposition rate of the soil in a secondary Pinus tabulaeformis forest. Excessive forest stand density limited the availability of soil P; thus, microorganisms and plants transitioned to a P-restricted state, and the diversity index was reduced with higher stand densities. There was a strong correlation between soil properties and the diversity index of understory vegetation. Soil properties were one of the primary drivers toward the formation of understory vegetation diversity, whereas those of herbs were more affected by soil properties. Stand density influenced the diversity of understory vegetation by altering the nature of the soil, which was also a critical factor for how stand density influenced understory vegetation.

Effects of nitrogen addition on root respiration of trees and understory herbs at different temperatures in Pinus tabulaeformis forest

Nitrogen (N) addition had differential effects on root respiration. However, the reasons and mechanism have not yet been analyzed. We speculated that the differential effects of N addition are related to the N addition rate, root diameter, and temperature. Meanwhile, tree and understory herb in forest ecosystems maybe another reason that root respiration has different responses. N addition was performed in a Pinus tabulaeformis forest for six years. P. tabulaeformis and Carex lanceolata fine roots with three size classes (< 0.5 mm; 0.5–1.0 mm; 1.0–2.0 mm) were sampled for respiration and temperature sensitivity measurement at three temperatures and chemical analysis. (1) N addition increased the root respiration of P. tabulaeformis and had the maximum values in 3, 6, and 9 g N m−2 y−1 at 1 °C, 14 °C, and 18 °C, respectively. (2) The root respiration of C. lanceolata significantly decreased under N addition only at 18 °C. (3) The effect of N addition on temperature sensitivity of root respiration was also varied due to N addition rate. (4) N and carbon/nitrogen ratio were the main driving factors of root respiration of P. tabulaeformis, while chemical properties had a slight driving effect on root respiration of C. lanceolata. N addition rate and temperature were the reasons for the differential effect of N addition on root respiration, but not root diameter. Furthermore, root respirations of tree and understory herb have varied changing mechanism, which demonstrated an apparent species specificity.

The production and nutrients in the fine roots of fertilized Pinus tabulaeformis plantation forests in the Loess Plateau in China

ABSTRACT Fine roots (FRs; <2 mm in diameter) might act as substantial pools of underground carbon and nutrients in the forest ecosystem. Since nutrient availability directly impacts plant growth, any changes in soil fertilization and subsequent changes in nutrients would alter the production of FRs. Here, we investigated the impact of fertilization with nitrogen (N) and phosphorus (P) [control, N (200 kg/ha/y), P (100 kg/ha/y), and N + P (200 kg N/ha/y + 100 kg P/ha/y)] on the FR production, biomass, turnover rate, N:P ratio in young (10-year) and nearly mature (40-year) Pinus tabulaeformis forest stands in the Loess Plateau in China. The production and biomass of FRs were evaluated using the ingrowth core and the soil core methods, respectively. The results showed that during the first growing season after N or P fertilization, neither the production, biomass nor the turnover rate of FRs responded significantly to the treatments. A substantial increase in the TN content was observed after fertilization with N, P, and N + P in the FR of the young forest stand, but not in the mature forest stand. The ratio of N:P in FRs increased after N addition but did not respond to P addition significantly in either the young or mature forest stands, indicating that FR N:P ratio was affected more by N availability than by P availability in P. tabulaeformis forests on the Loess Plateau.

The effects of nitrogen addition on soil organic carbon decomposition and microbial C-degradation functional genes abundance in a Pinus tabulaeformis forest

Nitrogen (N) deposition affects soil organic carbon (SOC) decomposition, therefore altering the global terrestrial carbon (C) cycle. However, it remains unclear how N deposition affects SOC decomposition by regulating microbial community composition and function, especially C-cycling functional gene composition. We investigated the effects of N addition (0, 3, 6, and 9 g N m−2y–1) on the composition of soil microbial C-cycling functional gene, SOC-degrading enzyme activities, and CO2 emissions in a Pinus tabulaeformis forest. Under low N addition (3 or 6 g N m−2y–1), labile C-degradation gene abundances were significantly increased. Under high N addition (9 g N m−2y–1), C-cycling functional gene abundance and diversity were significantly decreased. These effects were related to the changes in soil NO3–-N, dissolved organic C, total N, and microbial biomass C contents. Furthermore, low N addition stimulated the activities of SOC-degrading enzyme and CO2 emissions, whereas high N addition had the inhibitory effect. C-degradation gene abundances were significantly correlated with the SOC-degrading enzyme activities and CO2 emissions. Increase in CO2 emission rates were related to the high microbial functional potentials for labile C degradation under low N addition, whereas the lower CO2 emission rates were related to the low microbial functional potentials for labile as well as recalcitrant C degradation under high N addition. Our study indicated that N deposition may change SOC decomposition by altering the abundance of labile C and recalcitrant C degradation genes.

Contrasting effects of nitrogen addition on rhizosphere soil CO2, N2O, and CH4 emissions of fine roots with different diameters from Pinus tabulaeformis forest using laboratory incubation.

Nitrogen (N) addition has variable effects on chemical composition, function, and turnover of roots with different diameters. However, it is unclear whether N addition has variable effects on greenhouse gas (GHG) emission in rhizosphere soil. We performed N addition (0-9gNm-2 y-1) experiment in a Pinus tabulaeformis forest and a lab-incubation experiment to determine the effects of N addition on carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4) emissions in rhizosphere soils of roots with different diameters (very fine roots: <0.5mm, intermediate fine roots: 0.5-1.0mm, largest fine roots: 1.0-2.0mm). Nitrogen addition significantly promoted CO2 emission and CH4 uptake, with maximum values (CO2, 623.15mg C kg soil-1; CH4, 1794.49μg C kg soil-1) in the 6 or 9gNm-2 y-1 treatments (P<0.05). Nitrous oxide emissions were inhibited, with the greatest inhibitory effect in the 9gNm-2 y-1 treatment (48.63μgNkg soil-1). Total phosphorus (TP) content significantly decreased and increased in rhizosphere soil and non-rhizosphere soil after N addition, respectively, while organic carbon (OC), total N (TN), ammonium (NH4+), and nitrate (NO3-) contents in rhizosphere soil increased. A greater change in chemical properties occurred in rhizosphere soil of largest fine roots than very fine roots. Carbon dioxide and nitrous oxide emissions in rhizosphere soil among root sizes exhibited similar responses to N addition. While CH4 uptake was more responsive to N addition in rhizosphere soil with very fine roots than with largest fine roots. Basically, OC, TN, NO3-, and NH4+ were key soil components driving GHG emissions; NO3- promoted CH4 uptake and N2O emissions, NH4+ inhibited CO2 emissions. GHG response to N addition varied greatly, particularly in rhizosphere soil with different root sizes mainly related to its chemical properties.

Application of High‐Resolution Remote Sensing Image for Individual Tree Identification of Pinus sylvestris and Pinus tabulaeformis

Aiming at applying unmanned aerial vehicle (UAV) remote sensing technology in extracting individual standing tree information, a new automatic single‐tree information extraction method is proposed in this paper. The spectral information enhancement processing was performed on the original UAV image to highlight detailed local features; by importing DBI index, the optimal cluster number of the K‐means clustering was automatically determined, and image pixels were then marked; Gauss Markov random field (GMRF) model was employed to segment the image further; by mathematical morphology, operators to postprocess the segmentation results to obtain the individual standing tree crown information, and individual standing tree position was calculated through image geometric moment as the basis for its identification. The results show that with the proposed extraction method, the overall accuracy of standing tree identification for the Pinus sylvestris and Pinus tabulaeformis forest areas are 95.65% and 89.52%; the single‐tree crown extraction accuracy is 95.65% and 81.90%, respectively. This method exhibits good applicability while it does not require a large amount of manual intervention and prior knowledge, which significantly improves the automation of information extraction.

贺兰山不同林分凋落物微生物群落特征与影响因素

贺兰山是我国重要生态屏障，贺兰山生态森林生态系统保护受到极大关注，森林凋落物及土壤微生物对全球气候变化研究具有重要意义。目前，贺兰山不同林分的凋落物分解过程中微生物群落结构特征差异、不同凋落物化学组成对微生物群落结构的影响尚不清楚。以贺兰山具有代表性的3种林分（油松林、青海云杉林以及油松-山杨混交林）凋落物为研究对象，开展凋落物化学组成、微生物群落组成及多样性特征研究，揭示不同林分凋落物的优势微生物群落特征和影响因子。结果表明，3种林分凋落物的细菌和真菌在多个多样性指数之间差异性均不显著，但是在多样性指数中真菌PD whole tree指数显著大于细菌，真菌Shannon指数与Ghao1指数却显著小于细菌。在门水平上不同林分凋落物的微生物优势菌类无显著差异，但在属水平上差异显著，而且细菌差异小于真菌，在各个分类水平上，凋落物细菌和真菌群落组成均表现为油松-山杨混交林＜青海云杉林＜青海云杉林，凋落物微生物多样性在青海云杉林中最为丰富。细菌不同节点间连接线负相关数量略大于正相关，真菌则相反。油松林凋落物与其它林分凋落物相比，微生物群落之间联系更加紧密。油松林凋落物OC含量最大、青海云杉林凋落物的TK含量最大、油松-山杨混交林的TN含量最大，且在3种林分中显著差异。相关性分析表明OC、TN、TP、TK是影响凋落物细菌和真菌群落组成及多样性的主要因素，冗余分析表明不同林分凋落物的微生物多样性指数受养分影响，凋落物OC、TN、TP、TK是影响微生物群落组成和多样性的重要因素，其中OC与微生物群落多样性相关性最显著，是影响凋落物细菌和真菌群落组成和多样性最主要的因子。;Helan Mountains is an important ecological barrier in China, Enhancing the protection of ecological forest ecosystem in Helan Mountains has received great attention. Litter is the main source of soil nutrients, and forest litter and soil microorganisms are of great significance to the study of global climate change, while Difference of microbial community structure in litter decomposition of different forest types in Helan Mountains and the influence of different litter physical and chemical groups on microbial community structure are not fully revealed. In this study, composition and diversity characteristics of microbial communities in litter of Qinghai spruce forest, and Pinus tabulaeformis, and mixed forest of Pinus tabulaeformis and Populus davidiana were studied, sampling routine methods and high throughput sequencing methods were used to reveal difference in chemical composition, microbial community composition and diversity characteristics, and explore impact factors of advantage. Results showed that organic carbon content was the largest in the three kinds of forest litters, total phosphorus, the contents of organic carbon, total nitrogen and total potassium in the litter of Pinus tabulaeformis forest, coniferous and broad-leaved mixed forest and Picea crassifolia forest were the largest, and the differences were significant. The C/N and C/P ratios of the litter of Pinus tabulaeformis forest were significantly higher than those of the other two stands, and the value of N/P ratio of the litter of Picea crassifolia forest was significantly lower than that of the other two stands. There was no significant difference in dominant fungi at phylum level among different stands, but there was significant difference at genus level, and the difference of fungi was greater than that of bacteria. At each classification level, the composition of bacteria and fungi community was as follows:coniferous and broadleaved mixed forest<Pinus tabulaeformis<Picea crassifolia forest, and the diversity of microorganism in the litter of Picea crassifolia forest was the most abundant. Correlation analysis shows that organic carbon, total nitrogen, total phosphorus and total potassium are the main factors affecting the composition and diversity of bacterial and fungal communities. Redundancy analysis showed that the microbial diversity index of litter in different stands was affected by nutrients. Litter OC, TN, TP and TK were important factors affecting the composition and diversity of microbial community. It indicates that OC had the most significant correlation with microbial community diversity and was the main factor affecting the composition and diversity of bacterial and fungal communities in litter.

Changes in microbial communities at different soil depths through the first rainy season following severe wildfire in North China artificial Pinus tabulaeformis forest

Wildfire could result in dramatic changes to soil temperatures and environments, with immediate, short- or long-lasting impacts on soil microbes. However, relatively little research has documented how fire disturbance, soil depth, time variation and their interactions affect soil microbial communities in wet conditions. This study investigated a severe wildfire influenced on bacterial and fungal communities at four soil depths (0–5, 5–10, 10–15 and 15–20 cm) after two quarters (with similar precipitation and exactly during the rainy season). Soil sampling was conducted in a burned site relative to an undisturbed contiguous site in the North China artificial Pinus tabulaeformis forest. Results indicated that fire had significant effects on bacterial and fungal richness, diversity, composition and structure, including most impacts on the surface mineral soil (0–5 cm) within the first period post-fire and minor impacts on the subsoils (5–20 cm) up to the second period. The microbial richness and some dominant taxa in the undisturbed soils changed with time and depth, suggesting spatiotemporal variation in soil microbial communities although the effects of rainfall were weakened. These differences in microbes between burned and undisturbed soils were mainly driven by soil pH, whereas organic matter and available potassium mediated the distribution of microbial communities along depth and time, respectively. In addition, fungal community was more sensitive to fire and time than bacterial community but an opposite result was found in depth. Nevertheless, soil microbes showed some signs of adaptation to fire. This work advocate that non-intervention should be considered in the short term after a fire or low-intensity water replenishment in the case of aridity.

Spatial patterns of Pinus tabulaeformis and Pinus massoniana forests in Qinling-Daba Mountains and the boundary of subtropical and warm temperate zones

The Qinling Mountains is not only the geographical boundary between North and South China, but also the boundary between subtropical and warm temperate zones. It plays an important role in the geo-ecological pattern of China. However, there is controversy about the specific location of this geographical boundary in academic community due to the complexity, transition and heterogeneity of the transitional zone, as well as the differences in the delimitation indicators and research purposes. To further reveal the characteristics of the North-South transitional zone and clarify the specific location of the geo-ecological boundary between North and South China, combined with SRTM topographic data, temperature and precipitation data, Pinus massoniana forest and Pinus tabulaeformis forest, which represent subtropical coniferous forest in South China and temperate coniferous forest in North China respectively, were chosen to analyze their spatial distributions in the Qinling-Daba Mountains and the climatic conditions at their boundary with the climatic indexes of annual precipitation, the coldest month (January) average temperature, the warmest month (July) average temperature and the annual average temperature. The results show that: (1) Pinus massoniana and Pinus tabulaeformis forests and the climate indicators of their boundary can be used as one of the vegetation-climate indexes for the delimitation of subtropical and warm temperate zones. The boundary between the subtropical coniferous forest (Pinus massoniana forest) and temperate coniferous forest (Pinus tabulaeformis forest) is located along the south slope of Funiu Mountain to the north edge of Hanzhong Basin (the south slope of Qinling Mountains) at an altitude of 1000–1200 m, where the climatic indictors are stable: the annual precipitation is about 750–1000 mm, the annual average temperature is about 12–14°C, the coldest monthly average temperature is 0–4°C, and the warmest monthly average temperature is about 22–26°C. (2) It can be more scientifically to delimitate the boundary of subtropical and warm temperate zones in China by comprehensively considering the vegetation-climate indicators. Additionally, the boundary between subtropical and warm temperate zones in Qinling-Daba Mountains should be a transitional zone consisting of the boundaries of coniferous forests, broad-leaved forests and shrubs between subtropical and warm temperate zones. The results provide a scientific basis for the selection of delimitation index of subtropical and warm temperate zones.