Robinia Pseudoacacia Forest Research Articles

Afforestation Reduces Deep Soil Carbon Sequestration in Semiarid Regions: Lessons From Variations of Soil Water and Carbon Along Afforestation Stages in China's Loess Plateau

AbstractAfforestation represents an effective approach for ecosystem restoration and carbon (C) sequestration. Nonetheless, it poses notable challenges concerning water depletion and soil drought in (semi)arid regions. The underlying mechanisms regulating the influence of afforestation on soil carbon‐water dynamics, particularly how deep soil C reacts to afforestation‐induced soil drying, remain largely unclear. This study examined the variations of soil water content (SWC), soil organic carbon (SOC), and soil inorganic carbon (SIC) in 500 cm depth along four afforestation stages: abandoned grasslands, shrublands, and 20‐year and 40‐year Robinia pseudoacacia forests (RP20 and RP40) in the semiarid Loess Plateau, China. The results indicated that afforestation has significantly increased SWC (+26.6%), SOC (+44.5%), and SIC (+6.5%) in the shallow layer (0–100 cm) but caused evident soil drying (−60.8%), decrease in SOC (−37.8%), and slight reduction in SIC (−0.3%) in the deep layer (300–500 cm) when compared with grasslands. The seriously decline in the coupling coordination between soil C and SWC in the middle and deep layers indicates the unsustainability of afforestation especially for RP40. Structural equation model showed that the negative impact of afforestation on deep SOC through soil water depletion (−0.38) outweighed the direct positive impact of increased aboveground biomass (AGB) (+0.33). The negative impacts of decreased SWC and increased pH on deep SIC was close to the positive impacts of AGB. Afforestation has different effects on SOC and SIC across shallow and deep layers, and its negative effects on deep soil C should be fully integrated into future forest ecosystem restoration and management efforts.

Impact of organic carbon composition on bacterial taxa assembly upon phosphorus addition in organic and mineral soil layers of a Robinia pseudoaccacia plantation

Increasing phosphorus (P) inputs significantly affect the nutrient cycle of terrestrial ecosystems. The community structure and assembly processes of soil bacteria, which are the primary participants in nutrient cycling within terrestrial ecosystems, are affected by P inputs. However, the assembly processes and driving mechanisms of soil bacterial communities in artificial forest ecosystems in response to P inputs remain unclear. Therefore, in this study, we conducted in situ experimental P additions (0, 0.5, 1, 2, and 4 g P m-2 year-1) to artificial Robinia pseudoacacia forests on the Loess Plateau. We investigated the effects of P addition on the soil organic carbon (SOC) composition, bacterial community characteristics (total, abundant, and rare taxa), and assembly processes in the organic horizon (OH) and mineral horizon (MH) layers of the soil. The results showed that P addition significantly changed soil physicochemical factors, such as available P (AP), SOC content, and SOC composition in terms of the labile (LC) and recalcitrant carbon (RC) fractions. The proportion of the LC fraction increased in OH and decreased in MH, whereas the RC fraction showed the opposite trends. P addition increased the proportion of eutrophic bacteria in OH, whereas it decreased the proportion of oligotrophic bacteria. In contrast to those in OH, the changes in eutrophic and oligotrophic bacteria in MH exhibited the opposite trend. With increasing P levels, the diversity of the bacterial communities in the OH did not change significantly. In the MH, total and rare taxa diversity increased, while the diversity of abundant taxa decreased. During P addition, the total and rare taxa bacterial communities showed stochastic assembly, whereas the assembly of abundant taxa shifted from stochastic to deterministic processes in the OH and from deterministic to stochastic processes in the MH. The structural equation model revealed that during P addition, the assembly of total and rare bacterial communities in the OH and MH was regulated by AP and the LC fraction, respectively. Meanwhile, the assembly of abundant taxa in OH and MH was influenced by the LC fraction and RC fraction, respectively. Our findings highlight the critical role of SOC composition across different bacterial taxa, with abundant bacterial taxa exhibiting heightened sensitivity to environmental filtration and the availability of SOC resources. Our study provides new insights into the community assembly and driving mechanisms of soil bacteria in artificial forest soils during P addition.

Exploring the distribution pattern of native and alien forests and their woody species diversity in a small Mediterranean city

Recent studies have explored the ecological relationship between native urban forests and self-sown non-native forests in large cities and metropolises but further research efforts dedicated to analyzing this relationship in small cities are still needed. To improve our understanding of the ecology of urban native and alien forests in Mediterranean small cities, we analyzed the woody species richness, the community-weight mean of moisture and nitrogen ecological indicators, and soil disturbance indicators in the main urban wood types of the city of Campobasso (Italy), as well as their spatial distribution pattern across a gradient of cover and aggregation of green areas. The study showed that both native oak forests and Robinia pseudoacacia forests contributed to the maintenance of woody species richness. If we exclude the riparian environment, R. pseudoacacia forests occupied small marginal patches, tolerating soil disturbance and a high disturbance frequency, thus occupying habitats where the native oak forests could not grow. Conversely, R. pseudoacacia forests shared the ecological niche with the native riparian forests, which calls for action to prevent the spread of this alien species along river banks. Our results highlighted that urban remnant forests should be considered important assets for the planning and upkeep of urban green areas.

Microbial mechanisms for CO2 and CH4 emissions in Robinia pseudoacacia forests along a North–South transect in the Loess Plateau

Forest soil microbes play a crucial role in regulating atmospheric-soil carbon fluxes. Environmental heterogeneity across forest types and regions may lead to differences in soil CO2 and CH4 emissions. However, the microbial mechanisms underlying these emission variations are currently unclear. In this study, we measured CO2 and CH4 emissions of Robinia pseudoacacia forests along a north–south transect in the Loess Plateau. Using metagenomic sequencing, we investigated the structural and functional profiles of soil carbon cycling microbial communities. Results indicated that the forest CO2 emissions of Robinia pseudoacacia was significantly higher in the north region than in the south region, while the CH4 emission was oppositely. This is mainly attributed to changes in gene abundance driven by soil pH and moisture in participating carbon degradation and methane oxidation processes across different forest regions. The gene differences in carbon fixation processes between regions primarily stem from the Calvin cycle, where the abundance of rbcL, rbcS, and prkB genes dominates microbial carbon fixation in forest soils. Random forest models revealed key genes involved in predicting forest soil CO2 emissions, including SGA1 and amyA for starch decomposition, TYR for lignin decomposition, chitinase for chitin decomposition, and pectinesterase for pectin decomposition. Microbial functional characterization revealed that interregional differences in CH4 emissions during methane metabolism may originate from methane oxidation processes, and the associated gene abundances (glyA, ppc, and pmoB) were key genes for predicting CH4 emissions from forest soils. Our results provide new insights into the microbial mechanisms of CO2 and CH4 emissions from forest soils, which will be crucial for accurate prediction of the forest soil carbon cycle in the future.

Infestation Rates, Seasonal Abundance of Aphids and Relationships with Some Environmental Factors in Different Forest Habitats in Southwestern Türkiye

Aim of study: It was to determine the infestation rate and seasonal abundance of aphids and their relationships with some environmental factors in forests. Area of study: The study was conducted in Pinus nigra, P. brutia, Cedrus libani, Abies cilicica, Juniperus spp., Quercus spp. and Robinia pseudoacacia forests (34 sampling areas) in Isparta. Materials and methods: Systematic sampling was carried out monthly throughout April-October in 2019-2020. As aphid density and infestation rates were determined, 30 cm shoots were taken from 10 trees. The slope, aspect, elevation, forest characteristics, daily minimum, average, and maximum temperature and total precipitation were recorded. Main results: Abundance were highest in P. nigra, Quercus and Robinia pseudoacacia forests in both years. There was a significant correlation between abundance and development stages (p

Changes in Soil Aggregate Carbon Components and Responses to Plant Input during Vegetation Restoration in the Loess Plateau, China.

Vegetation restoration is an effective measure to cope with global climate change and promote soil carbon sequestration. However, during vegetation restoration, the turnover and properties of carbon within various aggregates change. The effects of plant source carbon input on surface soil and subsurface soil may be different. Thus, the characteristics of carbon components in aggregates are affected. Therefore, the research object of this study is the Robinia pseudoacacia forest located in 16-47a of the Loess Plateau, and compared with farmland. The change characteristics of organic carbon functional groups in 0-20 cm, 20-40 cm, and 40-60 cm soil layers were analyzed by Fourier near infrared spectroscopy, and the relationship between the chemical structure of organic carbon and the content of organic carbon components in soil aggregates was clarified, and the mechanism affecting the distribution of organic carbon components in soil aggregates was revealed in the process of vegetation restoration. The results show the following: (1) The stability of surface aggregates is sensitive, while that of deep aggregates is weak. Vegetation restoration increased the surface soil organic carbon content by 1.97~3.78 g·kg-1. (2) After vegetation restoration, the relative contents of polysaccharide functional groups in >0.25 mm aggregates were significantly reduced, while the relative contents of aromatic and aliphatic functional groups of organic carbon were significantly increased. The opposite is true for aggregates smaller than 0.25 mm. (3) With the increase in soil depth, the effect of litter on organic carbon gradually decreased, while the effect of root input on the accumulation of inert carbon in deep soil was more lasting.

Climate drivers of litterfall biomass dynamics in three types of forest stands on the Loess Plateau

Litterfall is a link in the energy flow and material cycling of ecosystems, which maintain the primary productivity of forests. However, there is no consensus regarding the factors driving for the litterfall biomass dynamics because of the high spatial–temporal heterogeneity. Herein, we investigated and compared the stand litter biomass, litterfall biomass, including its components in the pure Robinia pseudoacacia forest (RL), pure Platycladus orientalis forest (PL), and mixed forest of Robinia pseudoacacia and Platycladus orientalis (ML) from 2020 to 2022 in the gully erosion area of the Loess Plateau. Correlation and multiple regression analyses were used to study the relationships among the amount of stand litter, litterfall biomass, and seasonal temperature and precipitation. Significant variation was found in the seasonal and annual litterfall biomass of the three types of forest stands. Annual stand litter biomass was in the order PL > RL > ML, whereas the annual litterfall biomass was in the order RL > ML > PL. The seasonal dynamics of litterfall biomass of twigs, leaf and fruits exhibited a ‘unimodal pattern’ with a peak in October. Annual leaf litterfall biomass formed, the main body of litter in all the components, accounting for 57.14–67.05 % of the total litterfall biomass. The correlation and regression analysis results showed that the stand litter biomass was primarily affected by the average temperature. Total litterfall biomass and twigs, leaf, and fruits were significantly affected by the precipitation and the maximum temperature, however, flower litterfall biomass was mainly affected by the average temperature. Overall, our results indicated that temperature plays a key role in the climatic factors affecting forest litterfall processes, while different climatic conditions and biological characteristics probably caused the differences in litterfall biomass. In the long term, temperature will potentially play a leading role in altering carbon storage and nutrient cycling as the climate warms.

In Situ Rainwater Harvesting System Slows Forest Decline through Increasing Soil Water Content, Fine-Root Traits, and Plant Hydraulic Conductivity

Large-scale vegetation restoration campaigns have been implemented on the Chinese Loess Plateau, which have resulted in higher soil moisture deficits in this region. This, in turn, has hampered the healthy growth of planted trees, leading to a decline and, in severe cases, mortality of trees. Therefore, the rational regulation and utilization of rainwater, the primary water source in this region, may alleviate drought stress, ensuring the sustainability of the ecosystem. In this study, we investigated the impact of in situ rainwater collection and infiltration systems (IRCISs) on soil water, fine-root distribution, xylem vascular, and hydraulic conductivity characteristics in declining Robinia pseudoacacia forests. The results demonstrated that the application of an IRCIS can effectively increase plant available moisture content (0–5.0 m) of declining Robinia pseudoacacia forests. In particular, IRCIS treatment significantly increased xylem conduit diameter and plant hydraulic conductivity while substantially reducing the percentage loss of hydraulic conductivity in both roots and branches. Furthermore, IRCIS treatment significantly reduced the root biomass and distribution depth of Robinia pseudoacacia during both wet and dry years. This implies that IRCISs are beneficial for plant growth and survival. The findings of this study are significant for devising strategic methodologies for the planning and management of rainwater resources.

Comparisons of rainfall partitioning and canopy interception modelling in pure and mixed forests on the Chinese Loess Plateau

AbstractRainfall partitioning is a key process in forest ecosystems that affects the forest hydrological cycle and ecological services. However, little is known about the rainfall partitioning in Pinus tabuliformis (PT), Robinia pseudoacacia (RP), and Pinus tabuliformis×Robinia pseudoacacia (PT × RP) forests, which are widely distributed on the Chinese Loess Plateau (CLP) for controlling soil and water losses. The objectives of this study were to compare the rainfall partitioning and conduct interception modelling in PT, RP, and PT × RP forests, using data from the Ansai and Changwu sites on the CLP. The sites feature similar weather conductions and both pure and mixed forests of the same age. The tree density of PT × RP was moderate at the Ansai site but higher at the Changwu site compared to PT and RP. We quantitatively measured the throughfall (Tf), stemflow (Sf), and interception loss (Ic) for the forests at the two sites during the growing season (May–October, 2022), and simulated Ic using the Revised Gash Analytical Model (RGAM) and Liu model. The results showed that measured Ic for PT × RP (26.0% of the total gross rainfall, Pg) was larger than for RP (22.0% of Pg) but smaller than for PT (27.8% of Pg) at the Ansai site, and vice versa for the Tf and Sf (RP > PT × RP > PT), while the measured Ic for PT × RP (33.7% of Pg) at the Changwu site was larger than both for PT (31.1% of Pg) and RP (19.5% of Pg). The Tf and Sf for PT × RP was smaller than for PT and RP. Given the similar weather conditions, differences in Ic for the pure and mixed forests at each site were attributed to canopy storage capacity, wet canopy evaporation rate, and tree density. Additionally, the RGAM and the Liu model effectively simulated and captured the differences in Ic for PT, RP, and PT × RP. However, the RGAM performed better with a relative error less than −7.3%, Nash‐Sutcliffe model efficiency ranging from 0.82 to 0.95, and root mean square error less than 0.5 mm. According to the RGAM, evaporation from the wet canopy during rainfall events and after rainfall cessation were the two most influential components. The results of this study suggest that mixed forest can optimize rainfall partitioning compared to pure forests, but a reasonable density should be adopted to increase rainwater replenishment to the forest floor.

Response of soil nitrogen components and its vertical distribution to rainfall redistribution during Robinia pseudoacacia forest restoration on the Loess Plateau

The effects of vegetation restoration on soil moisture dynamics and nutrient content have been widely studied; however, the knowledge on variation in rainfall redistribution and soil nitrogen component characteristics remain limited, particularly with respect to their relationship in restored ecosystems. Therefore, the characteristics of plant community structure, rainfall redistribution, and soil nitrogen components from farmland and Robinia pseudoacacia (RP) plantations of four restoration ages (12, 20, 30, and 45 a) were investigated and measured in the Wuliwan watershed in the Loess Plateau, China. The results showed that changes in plant community structure affected the rainfall redistribution processes. The throughfall and moisture entering the soil (MES) had the largest proportions (79.50 % and 60.25 %) in the initial and second distributions of atmospheric rainfall, respectively. With the increase in restoration age, the content of soil total nitrogen (STN), soil nitrate nitrogen (SNN), soil soluble total nitrogen (SSTN), soil soluble organic nitrogen (SSON), and soil soluble inorganic nitrogen (SSIN) all increased with restoration age in the upper soil (0–40 cm), fluctuated in the middle soil (40–100 cm), and increased and then decreased in the deeper soil (100–200 cm). In addition, the vegetation restoration process can indirectly affect soil nitrogen content and distribution patterns by affecting the rainfall redistribution process. In the upper soil, litter interception (LI) had a significant effect on STN by affecting SSIN and SSON. In the middle soil, both LI and MES had significant effects on STN through SSIN and SSON, respectively. In the deeper soil, LI had no significant effect on any nitrogen component, whereas MES had a significant effect on STN by affecting SSIN. Overall, this study indicates that RP plantation restoration has the potential to transform rainfall redistribution and soil nitrogen distribution, providing an important reference for the reciprocal feedback relationship between water and nitrogen.

Dynamics of plant nutrient requirements and acquisition strategies after afforestation: A study on the Loess Plateau, China

Plant nutrient requirements and acquisition strategies are critical to understand the net primary productivity and community stability in terrestrial ecosystems. However, the current knowledge regarding this subject is limited, especially in the case of afforestation. Therefore, we selected four Robinia pseudoacacia (RP) forests (15-, 21-, 31-, and 46-year-old forests) in the Loess Plateau, and analyzed the nutrients in the plant organs, litter, and soil, along with the extracellular enzyme activities (EEAs), microbial biomass, and mineralization rate. In addition, the biomass of RP was determined using an allometric growth model. The results showed that during afforestation, the nitrogen and phosphorus requirement of RP increased significantly, from 3.97 to 18.14 g·m−2·year−1 and 0.17 to 0.71 g·m−2·year−1, respectively, while the nutrient resorption efficiency and the contributions of nutrient resorption to the total nutrient requirements significantly decreased. Meanwhile, the ratio of nitrogen to phosphorus resorption efficiency (NRE:PRE) significantly increased with afforestation, but were less than 1 which may indicate the phosphorus limitation of RP decreased. In addition, the vector angle significantly increased form 44.80° to 49.51° after afforestation, which may indicate the phosphorus limitation of soil microorganisms increased. Meanwhile, the vector angle was significantly positive with phosphorus mineralization rate and NRE:PRE, which may show that soil microorganisms activity alleviate the phosphorus limitation of plants. Collectively, our study contributes to a better understanding of nutrient cycling above and below the ground.

Biogeographical patterns of rhizosphere microbial communities in Robinia pseudoacacia forests along a north–south transect in the Loess Plateau

Rhizosphere microbiota play an essential role in plant productivity; however, their biogeographical patterns in restored forest ecosystems across large spatial scales remain poorly understood. We used the Ion S5TM XL sequencing platform to explore the distributions of microbial communities in the rhizosphere and bulk soil of Robinia pseudoacacia at 11 mature forest sites along a north–south precipitation gradient in the Loess Plateau, China. Microbial alpha-diversity mostly peaked in the south zone at lower latitudes, and significant distance-decay patterns were observed in both bacterial and fungal communities. Fungal communities exhibited more distinct spatial patterns in the rhizosphere than bacterial communities. The relative influence of geographic factors on bacterial/fungal community turnover in the rhizosphere (12.4/16.7%) and bulk soil (16.1/17.1%) was greater than that of local environmental factors. Microbial community assembly was mainly governed by deterministic processes (98% of nearest taxon index > 2), despite their relative importance decreasing from bulk soil to the rhizosphere in the case of bacteria. Co-occurrence patterns of sensitive taxa were more complex in the bacterial network than in the fungal network owing to a marked regional effect. Interactions of bacterial taxa differentially enriched between soil compartments were much closer than fungal interactions, indicating a stronger rhizosphere effect on bacteria. The results provide novel insights into the assembly of rhizosphere microbial communities in large-scale forest ecosystems under vegetation restoration.

Information Extraction Method of DBH of Individual Trees in Artificial Forest Based on UAV Image

<p>The information acquisition of tree height, individual tree crown and diameter at breast height is an important part of forest resources survey. In this study, the UAV images of artificial Robinia pseudoacacia forest in Zhangjiatan Town of Yan River Basin were obtained by DJI Phantom 4 UAV platform. The crown width and tree height were obtained by neural network clustering algorithm, visual interpretation and spatial measurement. The relative error between the extracted value and the measured value of individual tree crown width was 5. 98%, and the relative error of tree height was 7. 53%. We used 80% of the data to extract, crown, tree height and diameter at breast height to establish single regression models, exponential function models, logarithmic function models, power function models and binary regression models. Among those established DBH inversion models, the model with the highest fitting accuracy was y = 4.255a + 0.044b2 - 0.135a2 - 2.111, with a determination coefficient of 0.85, and the average relative error was 4.3% after being verified by using the remaining 20% of the data. The stand factors of the study area can be quickly obtained by using UAV images, and the DBH can be obtained with high precision, which can provide a reference for the realization of precision forestry.</p> <p> </p>

Differences in soil water storage, consumption, and use efficiency of typical vegetation types and their responses to precipitation in the Loess Plateau, China

After massive afforestation, the Loess Plateau is facing the severe challenge of water shortages. Water use efficiency (WUE) is an important indicator of plant drought resistance, and high WUE is an important way to reconcile the contradiction between vegetation growth and soil water consumption (SWC). Different vegetation types significantly influence hydrological cycle process and WUE. In this study, the Biome-BGC model was used to simulate and analyze the soil water storage (SWS), SWC, and WUE of 3 typical vegetation types in the Loess Plateau from 2005 to 2020. The results showed that the order of SWS of different vegetation types from largest to smallest was grassland (GL, 81.82 mm/day), abandoned farmland (AF, 66.92 mm/day), and Robinia pseudoacacia forest (RP, 55.64 mm/day); SWC was RP (480.09 mm/year), GL (464.68 mm/year), and AF (421.79 mm/year); WUE was RP (2.37 gC/kgH2O), GL (1.10 gC/kgH2O), and AF (0.60 gC/kgH2O). GL showed a better water retention capacity. Precipitation recharge did not meet the full SWC of vegetation. In years of high vegetation growth, as well as in the dry season when water was scarce, both RP and GL showed varying degrees of water deficit. Correlation analysis revealed that a positive effect of precipitation on WUE has a threshold effect, and the thresholds range from approximately 15–50 mm/day for RP, 15–25 mm/day for GL, and no clear pattern for AF. Overall, in water-stressed areas, a large expansion of forest land should be reduced and GL should be increased. In seasons and areas where vegetation is growing vigorously or extremely arid, irrigation regarding precipitation thresholds should be carried out to improve the WUE of vegetation and promote the sustainable development of regional ecology.

Mineralization Characteristics of Soil Organic Carbon and Its Relationship with Organic Carbon Components in Artificial Robinia pseudoacacia Forest in Loess Hilly Region

In order to explore the characteristics of organic carbon mineralization and the variation law of organic carbon components of an artificial forest in a loess hilly area, an artificial Robinia pseudoacacia forest restored for 13 years and the adjacent slope farmland were selected as the research objects, and indoor culture experiments under three different temperature treatments (15, 25, and 35℃) were carried out. The results indicated that the mineralization rate of soil organic carbon decreased sharply at first and then stabilized. The cumulative release of organic carbon increased rapidly in the initial stage of culture and gradually slowed in the later stage. Soil organic carbon mineralization in sloping farmland was more sensitive to temperature change, and its temperature sensitivity coefficient Q10 was 1.52, whereas that in R. pseudoacacia forest land was only 1.38. According to the fitting of the single reservoir first-order dynamic equation, the soil mineralization potential Cp of R. pseudoacacia forest land and slope farmland was between 2.02-4.32 g·kg-1 and 1.25-3.17 g·kg-1, respectively, that is, the mineralization potential of the R. pseudoacacia forest was higher. During the cultivation period, the content of various active organic carbon components decreased with time, and that in the R. pseudoacacia forest land was greater than that in the slope land. The cumulative carbon release of soil was significantly positively correlated with the contents of MBC and DOC (P<0.05), and Q10 (15-25℃) was negatively correlated with the contents of SOC, EOC, and SWC (P<0.05). These results could provide some reference for the study of soil carbon sequestration in loess hilly regions under climate change.

气候变化驱动下黄土高原刺槐林气候适宜性和脆弱性

PDF HTML阅读 XML下载 导出引用 引用提醒 气候变化驱动下黄土高原刺槐林气候适宜性和脆弱性 DOI: 10.5846/stxb202003140544 作者: 作者单位: 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(42141007, 41877539);中国气象科学研究院基本科研业务费专项(2020Z004) Climate suitability and vulnerability of Robinia pseudoacacia forest driven by climate change on the Loess Plateau 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:刺槐是黄土高原乡土树种,具有优良的水土保持和固碳功能。黄土高原生态恢复实践中实施了大规模的植树造林,刺槐林面积占沟壑丘陵区人工植树造林面积90%以上。由于种植时没有考虑刺槐的气候适宜性,一些地区的刺槐林出现了退化现象。采用最大熵模型,在0.5km×0.5km空间精度上分别模拟了1961-1990、1966-1995、1971-2000、1976-2005、1981-2010,以及2100年(典型浓度路径RCP4.5和RCP8.5气候情景下)黄土高原刺槐的气候适宜性和敏感性。模拟结果显示:黄土高原刺槐分布及其动态变化主要受到最冷月温度、极端低温、降水量、年辐射量等气候因子影响,低温(最冷月温度、极端低温)是影响刺槐的最关键因子。黄土高原西北和北部广大地区,自然环境条件不适合刺槐林生长;黄土高原东南部(关中平原和山西南部)比较适合刺槐生长。相对1961-1990年,1961-2010年期间刺槐林适宜区分布格局基本没有改变,RCP4.5和RCP8.5气候情景下刺槐林适宜区分布格局也没有显著改变。图层叠加分析发现,刺槐的气候适宜度(即存在概率)发生了明显改变。黄土高原西部和北部属于不适宜刺槐生长的非敏感区,东部和东南部是适宜刺槐生长的区域,尤其是山西中南部和陕西关中平原对气候变化非常敏感,展示了刺槐气候脆弱性的一面。研究结果对植树造林,优化人工林空间分布格局,应对气候变化风险和维持黄土高原森林生态系统可持续健康发展具有重要参考价值。 Abstract:Robinia pseudoacacia is a native tree species on the Loess Plateau, which has excellent functions of soil and water conservation, and carbon sequestration. Large scale afforestation was carried out in the practice of ecological restoration in the Loess Plateau, and the area of Robinia pseudoacacia forest accounted for more than 90% of artificial afforestation in the gully and hilly areas. However, Robinia pseudoacacia forest degenerated in some areas because climate suitability of Robinia pseudoacacia was not considered during afforestation. In this study, MaxEnt (maximum entropy model) was used to simulate the climate suitability and sensitivity of Robinia pseudoacacia on the Loess Plateau in 1961-1990, 1966-1995, 1971-2000, 1976-2005, 1981-2010, and 2100 (under the climate scenarios of Representative concentration pathway RCP4.5 and RCP8.5, respectively) at the spatial resolution of 0.5 km × 0.5 km. The simulation results showed that the distribution and dynamic changes of Robinia pseudoacacia on the Loess Plateau were mainly affected by the coldest month temperature, extreme low temperature, annual precipitation, annual radiation and other climate factors. Low temperature (the coldest month temperature, extreme low temperature) was the most important factor affecting Robinia pseudoacacia. The natural environment was not suitable for Robinia pseudoacacia forest in the northwest and the north of the Loess Plateau, but it was suitable in the southeast (the Guanzhong Plain and the south of Shanxi Province) of the Loess Plateau. Compared with the period of 1961-1990, the geographical distribution pattern of Robinia pseudoacacia forest was basically unchanged during 1961-2010, and its geographical distribution pattern was not significantly changed under the climate scenarios of RCP4.5 and RCP8.5. Overlay analysis showed that climate suitability (namely exist probability) of Robinia pseudoacacia changed significantly. The regions in the west and north of the Loess Plateau were not suitable for Robinia pseudoacacia, where belonged to non-sensitive areas. The regions in the east and southeast were suitable for Robinia pseudoacacia, where was very sensitive to climate change, especially in the south central of Shanxi Province and the Guanzhong Plain in Shaanxi Province, showing significant climate vulnerability. This study has important reference value for choosing suitable area for afforestation, optimizing the spatial distribution of plantation, coping with climate change risk, maintaining the sustainable and healthy development of forest ecosystem on the Loess Plateau. 参考文献 相似文献 引证文献

In Situ Rainwater Collection and Infiltration System Alleviates the Negative Effects of Drought on Plant-Available Water, Fine Root Distribution and Plant Hydraulic Conductivity

Soil water status and fine-root characteristics are the foundation for implementing forest water-management strategies in semiarid forest plantations, where rainwater is always the sole source of water for plant growth. Rainwater management and utilization are effective strategies to alleviate water scarcity in semiarid areas as ground water is always inaccessible there. Through the implementation of an in situ rainwater collection and infiltration system (IRCIS), we investigated the effects of IRCIS on soil water and fine-root distributions in the 0–5 m soil profile in a wet (2015, 815 mm) and a dry year (2016, 468 mm) in rainfed Robinia pseudoacacia forests in the Loess Plateau region of China. The results showed drought significantly decreased plant water availability and hydraulic conductivity of roots and branches, but strongly increased soil moisture deficits and fine-root (&lt;2 mm diameter) biomass. With the implementation of IRCIS, soil profile available water and plant hydraulic conductivity can be significantly increased, but soil moisture deficits and fine-root (&lt;2 mm diameter) biomass can be significantly decreased. Drought also significantly influenced the root distribution of Robinia pseudoacacia. The maximum depth of Robinia pseudoacacia roots in the dry year was significantly greater than in the wet year. Therefore, Robinia pseudoacacia can absorb shallow (0–1.5 m) soil water in wet years, while utilizing deep (&gt;1.5 m) soil water in dry years to maintain normal growth and resist drought stress. The results of this study will contribute to the formulation of appropriate strategies for planning and managing rainwater resources in forest plantations.

Variations of soil organic carbon fractions in response to conservative vegetation successions on the Loess Plateau of China

Land use changes profoundly affect the equilibrium of soil organic carbon (SOC) sequestration and greenhouse gas emissions. With the current global climatic changes, it is vital to understand the influence of ecological restoration and conservation management on the dynamics of SOC under different land uses, especially in erosion-endangered Loess soils. Therefore, we investigated changes in SOC through a suit of labile fractions, namely: light fraction organic C (LFOC), heavy fraction organic C (HFOC), coarse particulate organic C (CPOC), fine particulate organic C (FPOC), and dissolved organic C (DOC), from two forests i.e., Robinia pseudoacacia (RP) and Platycladus orientalis (PO), with different ages, in comparison with farmland (FL). The SOC and STN contents significantly increased over 42 years in the RP forest where the contents of CPOC and FPOC were significantly higher than in the FL. Moreover, total SOC and its labile fractions, in the studied land use types, significantly correlated with soil CaCO3, pH, and STN contents, indicating their key roles in SOC sequestration. The results reported here from different vegetation with different ages provide a better understanding of SOC and STN alterations at different stages of vegetation restoration. Our findings suggest that long-term natural vegetation restoration could be an effective approach for SOC sequestration and soil conservation on the Loess soil.

Spatial Patterns and Composition Traits of Soil Microbial Nitrogen-Metabolism Genes in the Robinia pseudoacacia Forests at a Regional Scale.

Microbial-driven processes related to the nitrogen-metabolism (N-metabolism) in soil are critical for ecosystem functioning and stability. There are spatial patterns of microbial-mediated nitrogen processes, but we still lack an overview of the soil N-metabolism genes of single nitrogen-fixing tree species pure forests at a regional scale. Here, we investigated the spatial variation and drivers of microbial N-metabolism genes in the rhizosphere soil of Robinia pseudoacacia on the Loess Plateau by metagenomic technology. We found that the distance-decay of soil N functional gene similarities in Robinia pseudoacacia forests on the Loess Plateau spanning a geographic distance of 230 km was significant (p < 0.001). The gene composition and co-occurrence patterns in the process of soil microbial N-metabolism were very different, and they were mainly driven by soil pH and MAP (mean annual precipitation). The proportion of positive links and edges co-occurrence networks between N functional genes increased with increasing pH, suggesting that increasing pH promoted connections between functional genes. The relative frequencies of N-metabolism pathways were consistent on the Loess Plateau, the abundance of ammonia assimilation pathway was highest, and the abundance of the nitrogen fixation pathway was the lowest; only the abundance of the nitrogen fixation pathway was not significantly different. The bacterial and archaeal communities involved in soil nitrogen metabolism were significantly different. Structural equation modeling showed that decreases in soil pH and MAP mainly affected the increase in nitrogen functional gene abundance through an increase in the diversity of N-metabolism microorganisms. In conclusion, this study provides a baseline for biogeographic studies of soil microbe functional genes.

Health assessment of plantations based on LiDAR canopy spatial structure parameters

ABSTRACT The Yellow River Delta (YRD) has China's largest artificial Robinia pseudoacacia forest, which was planted in the late 1970s and suffered extensive dieback in the 1990s. The health grade of the R.pseudoacacia forest (named canopy vigor grade, CVG) could be achieved by using high-resolution images and canopy vigor indicators (CVIs). However, a previous study showed that there was no significant correlation between CVG and the field-estimated aboveground biomass (AGB) of R.pseudoacacia forest. Therefore, this study aims to construct forest health indicators (FHIs) based on canopy spatial structure parameters extracted from LiDAR. The FHIs included Weibull_α (the scale parameter of the Weibull density function that reflects the shape of the tree canopy), VCI (vertical complexity index), sdCC (the standard deviation of canopy cover), H99 (the 99th percentile height) and cvLAD (the coefficient of variation of leaf area density), and could significantly distinguish three forest health grades (FHG) (p < 0.05). The FHG was positively correlated with forest AGB (rs = 0.51, p = 0.004), and the similarity value with CVG was 63.33%. The results of this study confirmed that the FHIs can reflect both canopy vigor and tree productivity, and distinguish forest health status without prior classification information.