Typical Vegetation Types Research Articles

Optimization of vegetation carbon content parameters and their application in carbon storage estimation in China

As a key parameter for C pool and flux assessments, vegetation carbon (C) content can be used in ecological models to predict climate-induced changes in the C sequestration capacity of vegetation. However, the differences in methods for upscaling C content from the organ to the community scale and their impact on regional C stock estimates have been ignored. Based on a comprehensive community structure survey of 72 typical natural ecosystems in China and 27,905 measured samples of plant organs (leaves, twigs, trunks, and roots), we first quantified the differences among scaling-up methods for vegetation C content. These methods included the community or dominant species-weighted mean, geometric mean, arithmetic mean, and traditional empirical coefficients (45 % and 50 %), and their impact on C storage estimation at the regional scale. Comparing the accuracy, variability, and response patterns of the different scaling-up methods, the dominant C species biomass-weighted mean (CDWM) method had the highest similarity to the community-weighted C mean (CCWM) method. Concerning vegetation C storage estimation in China's natural terrestrial ecosystems, the relative errors of the other methods ranged from −2.6 % to 8.22 % compared with that of the CCWM method (18.39 Pg C). The empirical coefficients had the highest uncertainty, with a 45 % empirical coefficient underestimating the vegetation C stock by 2.60 %, and a 50 % empirical coefficient overestimating it by 8.22 %. The CDWM method proposed here has high reliability for C storage estimation (overestimated by only 0.44 %), making it a preferable sampling and scaling-up method for regional C content and stock assessment. Additionally, our study provided the C content of plant organs for China's provinces and typical vegetation types based on the CCWM, which could be used for regional C stock assessment and C cycle models.

Responses of Soil Organic Carbon Fractions and Stability to Forest Conversion in the Nanling Nature Reserve, China

Studying the impact of typical vegetation types in forest conversion zones on soil organic carbon (SOC) structure and stability is crucial for developing terrestrial ecosystem carbon sequestration strategies. In this study, we selected three typical forest stands in the Nanling National Nature Reserve: a primary evergreen broad-leaved forest (BL), a secondary mixed coniferous and broad-leaved forest (ML), and a Chinese fir plantation (CL). Soil samples were collected to examine the SOC fractions and carbon pool management index (CPMI) in three forest stands. The influence of soil property factors on SOC fractions was also analyzed. The results showed that the transformation process from a BL to an ML or a CL changed the structure and stability of organic carbon by reducing the labile SOC fractions and increasing the recalcitrant carbon fraction in the soil. The higher lability index (LI) and CPMI of soils in the BL indicated better carbon accumulation and activity, making this treatment more advantageous for management strategies aimed at promoting natural forest renewal and ecological restoration. Correlation and RDA analysis revealed that the availability of soil P was a key factor limiting the variation in organic C fractions in the acidic soils of tropical forests in South China.

Unraveling local and regional determinants of high plant diversity at marine rocky outcrops in Uruguay

AbstractQuestionsMarine rocky outcrops are model systems of community assembly under harsh conditions. The prevailing environmental conditions that determine a coast–inland gradient of stress and disturbance impose a strong environmental filter on community assembly. However, the Atlantic rocky outcrops of Uruguay challenge this assumption as they exhibit high plant diversity at small spatial scales. We investigated this study system to answer: (1) which environmental factors determine diversity at the local scale; (2) and how does the regional pool influence species composition along the coast–inland gradient?MethodsWe analyzed the local and regional determinants of plant community assembly in four rocky sites along the Uruguayan coast. Through a random sampling approach stratified by distance to the coast, we recorded species occurrences and microenvironmental conditions. Observed taxa were assigned into different species assemblages according to their typical vegetation type. Generalized Linear Model (GLM)–Poisson regression, quantile regressions and hierarchical cluster analyses were used to identify the factors underlying local richness and the spatial vegetation structure.ResultsNine different vegetation types generate a mass effect that enhances local diversity. Unexpectedly, 56% of the species are from non‐marine environments — e.g. grasslands or hydrophilous herblands. Species assemblages were spatially clustered, with a turnover of these clusters along the coast–inland gradient. Elevation, distance to the coast and vegetation cover promoted richness, likely due to an attenuation of marine filters. Meanwhile, substrate availability reduced richness, likely due to competitive exclusion as a result of more resources and homogeneous microenvironmental conditions.ConclusionsThe high local diversity along the marine rocky outcrops of Uruguay is best explained by a functionally diverse regional species pool, which interacts with local heterogeneity, and by conditions that enhance or attenuate the effect of marine stress. Effective conservation and management strategies are key to minimize the detrimental effects of urbanization, fragmentation, and non‐native plant invasions on these diverse habitats.

Changes of soil carbon along precipitation gradients in three typical vegetation types in the Alxa desert region, China

The changes and influencing factors of soil inorganic carbon (SIC) and organic carbon (SOC) on precipitation gradients are crucial for predicting and evaluating carbon storage changes at the regional scale. However, people’s understanding of the distribution characteristics of SOC and SIC reserves on regional precipitation gradients is insufficient, and the main environmental variables that affect SOC and SIC changes are also not well understood. Therefore, this study focuses on the Alxa region and selects five regions covered by three typical desert vegetation types, Zygophyllum xanthoxylon (ZX), Nitraria tangutorum (NT), and Reaumuria songarica (RS), along the climate transect where precipitation gradually increases. The study analyzes and discusses the variation characteristics of SOC and SIC under different vegetation and precipitation conditions. The results indicate that both SOC and SIC increase with the increase of precipitation, and the increase in SOC is greater with the increase of precipitation. The average SOC content in the 0–300cm profile is NT (4.13 g kg−1) > RS (3.61 g kg−1) > ZX (3.57 g kg−1); The average value of SIC content is: RS (5.78 g kg−1) > NT (5.11 g kg−1) > ZX (5.02 g kg−1). Overall, the multi-annual average precipitation (MAP) in the Alxa region is the most important environmental factor affecting SIC and SOC.

Differential response patterns of soil fungal and bacterial communities to typical vegetation types in the Yellow River floodplain ecosystem

Soil microorganisms are one of the primary driving factors of biogeochemical cycles in floodplain ecosystems. Vegetation type has an impact on the activities of soil microorganisms. However, it is currently unclear whether the composition and structure of soil bacterial and fungal communities in floodplain ecosystems have a consistent response pattern to vegetation communities. In this research, Illumina Mi-Seq sequencing technology was employed to study the soil fungal and bacterial communities covered by three typical vegetation communities in the Yellow River floodplain ecosystem. Our results showed that the underground biomass, total carbon (TC) and nitrogen (TN) were significantly different between the three vegetation communities. In the surface soil of summer, the Shannon index of fungi community was the highest in Tamarix chinensis (T. chinensis) and the lowest in Phragmites australis (P.australis). In autumn, the Shannon and Simpson indices of bacterial communities in surface soil were the highest in the P.australis and the lowest in the Sonchus arvensis (S.arvensis), but there was no significant difference in the β-diversity of bacterial community among the three vegetation communities. In autumn, the Chao1 index of fungal community in subsoil was the highest in P.australis and the lowest in S.arvensis, while there was no significant difference in the α-diversity of bacterial community among the three vegetation communities. In addition, there were considerable disparities in the fungal and bacteria community structure in various vegetation soils. Redundancy analysis (RDA analysis) showed that TN, TC, AP, pH, NO3 -, NH4 + and moisture content were key factors driving bacterial community structure, while TP, NH4 +, pH and moisture content were essential factors driving fungal community composition. These outcomes help to improve our understanding of the ecological model of soil fungal and bacterial community in floodplain ecosystems and give assistance in improving the role of an ecological barrier and floodplain service possibilities.

2021–2022年广东南岭站日尺度气象数据集

The mountainous forest and biodiversity ecological functional area of the Nanling Mountain forest ecosystem is one of the 25 key ecological functional areas in China, covering a variety of forest vegetation types, including tropical and subtropical moist broadleaf forests, coniferous broad-leaved evergreen mixed forest, and mountain top evergreen broad-leaved dwarf forest. The tropical and subtropical moist broadleaf forests are the most typical vegetation type in the Nanling Mountains. Monitoring the meteorological elements in the community can help understand the response mechanism of the tropical and subtropical moist broadleaf forests in the Nanling Mountains to climate change. Based on the Nanling Forest Ecosystem National Field Scientific Observation Research station ("Nanling Station" for short) in the Nanling Mountains, Guangdong, we carried out positioning research in Nanling National Nature Reserve. In this paper, we disclosed the raw data of 10 min average wind speed, precipitation, air temperature, air pressure, solar radiation (i.e. total radiation, reflected radiation, ultraviolet radiation, net radiation, photosynthetically active radiation) as well as relative humidity continuously collected in the subtropical evergreen broad-leaved forest area of the Nanling Station from 2021-2022 on a daily scale after data processing, quality control and evaluation. The dataset accessible to the public can serve as a valuable resource for further insights into the Nanling Mountain Forest Ecosystem, and provide foundation for efforts related to the restoration and protection of forest ecosystems.

Carbon Accumulation and the Possibility of Carbon Losses by Vertical Movement of Dissolved Organic Carbon in Western Siberian Peatlands

We studied the peat stratigraphy of the Mukhrino peatland, which is a typical ombrotrophic bog for the Middle Taiga zone of Western Siberia, to gain insights into its history, hydrology, and carbon fluxes. For the first time in Western Siberia, seven cores were collected from locations that were chosen to represent the typical present-day vegetation types, and this was performed for the dating of the separated dissolved (DOC) and particulate organic carbon (POC) fractions, which were determined using the Accelerator Mass Spectrometer (AMS) radiocarbon (14C) method. The oldest peat was found at the bottoms of an underlying lake (10,053 cal. year BP) and an ancient riverbed (10,989 cal. year BP). For the whole history of the peatland, the average peat accumulation rate was estimated to be 0.067 ± 0.018 cm yr−1 (ranging from 0.013 to 0.332 cm yr−1), and the carbon accumulation rate was 38.56 ± 12.21 g m−2 yr−1 (ranging from 28.46 to 57.91 g m−2 yr−1). There were clear age differences between the separated samples of the DOC and POC. The DOC was older than the POC in the uppermost 150 cm of the peat deposit and younger in the deeper layers. The difference in age increased with depth, reaching 2000–3000 years at the bottom of the peat deposit (depth of 430–530 cm). Following the consideration of a range of factors that could potentially cause the dating discrepancy, we hypothesised that the DOC continuously moves down into the mineral sediment beneath the peat, as an additional carbon flux that results in the mixing of younger and older carbon. On this basis, we estimated the apparent rate of the DOC’s downward movement and the associated rate of carbon loss. The first estimate of the average rate of the DOC’s downward movement in Western Siberia was 0.047 ± 0.019 cm yr−1, causing carbon loss in the range of 28–404 mg m−2 yr−1.

Effects of Vegetation Types and Seasonal Dynamics on the Diversity and Function of Soil Bacterial Communities in the Upper Reaches of the Heihe River

The process of interaction between the plant and soil microbial communities holds the key to understanding the biogeochemical cycle and preserving the stability of vegetation ecosystems. Owing to this significance, the primary goal of this research was to give a starting point and reference methods to restore local vegetation. The vegetation distribution in the mountainous area of the upper reaches of the Heihe River Basin had notable vertical zonality, which was characterized by five typical vegetation types, including cushion vegetation(CV), herbage meadow(HM), forest steppe(FS), mountainous steppe(MS), and desert grassland(DG). The organization and diversity of soil bacterial communities in various vegetation types were examined using high-throughput sequencing techniques in both the winter and summer seasons. Sampling sites were chosen in each of the five common vegetation types in turn. Additionally, based on the FAPROTAX database, the predicted functions of microbial communities were evaluated for different vegetation types and seasons. The redundancy analysis and structural equation model were also used to investigate the primary environmental elements and uncover the mechanisms affecting the soil bacterial populations. The findings revealed that:① the physical and chemical properties of soil differed significantly among vegetation types and seasons, and the property indices varied dissimilarly with depth. In particular, the soil water content(SWC) and nutrient content of total organic carbon(TOC) and total nitrogen(TN) were significantly higher in forest grassland(FS). ② The divergences of α-diversity indices among seasons(P<0.05) were greater than that of vegetation types(P>0.05). The Chao1 index measuring the abundance of the bacterial community was higher in winter. According to the Shannon index, the species of the bacterial community were dispersed in a "W" shape in the summer and a "hump" form in the winter with altitude. ③ The predominant phyla of the bacterial community, composed of Acidobacteria, Proteobacteria, and Actinobacteria, did not significantly differ from one another. However, the organization of the bacterial community presented a significant variation seasonally at the genus level. ④ The primary functions of the soil bacterial population, which largely consisted of chemoheterotrophy, nitrification, and aerobic ammonia oxidation, were not significantly different among vegetation types and seasons. ⑤ The key factors affecting soil bacterial communities at the genus level varied significantly among seasons, with soil temperature(ST), total organic carbon(TOC), and pH in winter and soil water content(SWC), carbon-nitrogen ratio(C/N), and pH in summer. ⑥ Synergized by interrelated environmental factors, soil physical and chemical features exerted a more direct impact on the diversity and functionality of bacterial communities compared with vegetation types, including significantly changing the abundance of Acidobacteria and Bacteroidetes, as well as the role of nitrification and ammonia oxidation. Hence, improving the carbon and nitrogen contents in soil nutrients would help to enhance the diversity and function of bacterial communities. The findings of this study provided a model for determining the mechanism of regional vegetation degradation and preserving the stability of alpine ecosystems in this area by revealing the seasonal distribution pattern of bacterial communities and the key biological processes beneath the typical vertical vegetation band in the upper reaches of the Heihe River.

Investigating Soil Pore Network Connectivity in Varied Vegetation Types Using X-ray Tomography

The ecological environment in southwestern China is fragile. Due to the significant preferential flow in vertical and horizontal directions and poor water conservation ability, vegetation degradation still exists under conditions of abundant rainfall. Therefore, the pore connectivity and infiltration characteristics in shallow soil under typical local vegetation need to be studied. A calculation model for the vertical connectivity of soil macropores was independently constructed, and differences in soil macropore structures and the degree of vertical connectivity in typical vegetation types (natural secondary forest, natural grassland, Yunnan pine plantation, eucalyptus plantation, cypress plantation, mulberry bushes) were investigated by CT scanning technology of undisturbed soil columns. The results showed that the vertical connectivity of large pores in the shallow soil of the region can be quantitatively described by X-ray tomography, and the total surface area and cumulative curvature of macropores in natural grassland soil were two or three times that in artificial vegetation. The concentration area of macropores in the soil of artificial forestland was closer to the surface, and the tendency of macropore preferred path decreased by 76.18% around 30 cm depth in the soil. The vertical connection of soil macropores in artificial forests was significantly lower than that of natural secondary forestlands (33.03%) and natural grasslands (36.75%). The restoration of the plantation improved surface soil pore structure, and the vertical connectivity of soil is nearly 20% less than that of natural vegetation types (natural secondary forestland, natural grassland), which reduced water outflow rate by nearly 44% and electrolyte content by nearly 14% at a depth of 30 cm. This study provided data and research directions for the study of hydrological processes in local forest vegetation and technical support for solving the problems of soil water loss and forestland water conservation in southwestern China.

A dataset of bird checklist and community characteristics during breeding and wintering seasons in typical forest ecosystems of Dinghushan (2015–2018)

Bird diversity and its community structure are important indicators for the long-term monitoring of biodiversity in ecosystems. Three typical forest vegetation types have been well preserved in Dinghushan National Nature Reserve, including the monsoon evergreen broad-leaved forest, the mixed Pinus massoniana/broad-leaved forest and the Pinus massoniana coniferous forest. In particularly, the monsoon evergreen broad-leaved forest has a conservation history of more than 400 years without any human disturbance. The dataset consists of organized data on the long-term monitoring of bird communities during breeding and wintering seasons from 2015 to 2018 in all three forest types. Field surveys recorded information such as bird species, number, time, distance, ground height, habitat type, activity substrate and behavior. Moreover, we carried out various data analyses of diversity index, evenness index, dominance index, similarity coefficient of bird community and occurrence frequency, individual number, as well as average density of bird species in different survey periods. The dataset includes a total of 89 species from 9 orders and 35 families. This dataset provides valuable information for future studies on bird communities, and for better understanding inter-species interaction between multiple groups of plants and animals. It is further expected to support the protection and management of forest ecosystems in this region.

Soil Quality Evaluation of Typical Vegetation and Their Response to Precipitation in Loess Hilly and Gully Areas

The selection of suitable tree species and the reasonable allocation of planting areas are important measures for improving soil quality. This study aimed to investigate the characteristics of typical vegetation type soil quality differences and their dominant factors in loess hilly–gully areas after returning farmland to the forest (grassland). The soil quality status and dominant factors of arbors, shrubs and grasslands in the study area were comprehensively analyzed using the soil quality index (SQI) and structural equation modeling (SEM). The results showed the following: (1) In the study area, the shrub forest had a high capacity for air permeability, water retention and nitrogen fixation. (2) The soil quality of the three vegetation types improved with increasing precipitation, and the soil quality indicator of shrubs was the highest, indicating a better soil quality improvement. However, the soil quality of the arbors and grasslands showed a greater percentage increase. In the precipitation range of 400–410 mm, the soil quality of shrub forests was significantly higher than that of arbors and grasslands. (3) Structural equation modeling analysis indicated that precipitation, vegetation and soil factors are closely related to soil quality. Further analysis showed that soil bulk density, porosity, capillary water-holding capacity, soil organic carbon and total phosphorus were the dominant factors affecting the soil quality in the study area. The purpose of this study was to evaluate quantitatively the soil quality after different vegetation types under different precipitation gradients, to clarify the variation trend of soil quality at different vegetation types with different precipitation gradients and to provide a scientific basis and data support for the quantitative evaluation of vegetation restoration and selection of tree species and vegetation configuration within different precipitation gradients in loess hilly and gully regions in the future.

Investigation of biogenic volatile organic compounds emissions in the Qinghai-Tibetan Plateau

Biogenic volatile organic compounds (BVOCs), which are produced and emitted by plants, have significant chemical reactivity in the atmosphere and impacting climate change. Qinghai Province, a vital component of the plateau, has abundant vegetation resources, primarily grasslands and forests, yet BVOCs emissions and their impact on air quality remain understudied. In this study, the emissions rates and compositions of BVOCs from seven dominant vegetation types in Qinghai Province were sampled and analyzed using a closed-loop stripping dynamic headspace sampling approach combined with GC–MS, and the total emissions of BVOCs in Qinghai province in 2021 were estimated by using G95 model. At the same time, the emission characteristics of various vegetation types were also analyzed. The results showed that the emissions rates and compositions of BVOCs differed significantly among vegetation types, with monoterpenes being the dominant emission composition in coniferous forests, which accounted for >70 % of the total BVOCs emissions, while isoprene being the main composition in alpine meadow, accounting for 84.96 %. The emissions of three typical vegetation types, Picea asperata, alpine meadow and alpine steppe, were monitored daily, revealing significant diurnal and clear unimodal patterns. The study also found that the annual average BVOCs emissions from vegetation sources in Qinghai Province were estimated to be 1550.63 Gg yr−1, with isoprene contributing the highest proportion of emissions, accounting for 56.94 %. Grassland was the largest BVOCs emission source in Qinghai Province, with an annual average emission of 1438.52 Gg yr−1. Additionally, BVOCs emissions in Qinghai Province showed strong seasonal and daily variation patterns, with the highest emissions occurring in summer, with the peak in July. These findings provide the characteristics of BVOCs emissions from vegetation sources in the Tibetan Plateau, which will contribute to a better understanding of their impact on atmospheric chemistry and climate change.

Coupling of soil methane emissions at different depths under typical coastal wetland vegetation types

As an important source of atmospheric methane, methane emissions from coastal wetlands are affected by many factors. However, the methane emission process and interrelated coupling mechanisms in coastal wetland soils of a variety of environments remain unclear owing to complex interactions between intensified anthropogenic activities and climate change in recent years. In this study, we investigated methane cycling processes and the response mechanisms of environmental and microbial factors in soils at different depths under four typical coastal wetland vegetation types of the Yellow River Delta, China, using laboratory culture and molecular biology techniques. Our results show that methane generation pathways differed among the different soil layers, and that the methane emission process has a special response to soil N compounds (NO3−, NH4+). We found that nitrogen can indirectly affect methane emission by impacting key physicochemical properties (pH, oxidation reduction potential, etc.) and some functional communities (mcrA, ANME-2d, sulfate-reducing bacteria (SRB), narG, nosZII). Methane production processes in shallow soils compete closely with sulfate reduction processes, while methane emissions facilitated in deeper soils due to denitrification processes. We believe that our results provide a reference for future research and wetland management practices that seek to mitigate the global greenhouse effect and climate change.

Effects of long-term vegetation restoration on soil physicochemical properties mainly achieved by the coupling contributions of biological synusiae to the Loess Plateau

Large-scale vegetation restoration has been performed to improve the fragile ecological environment of the Loess Plateau in the last decades. At present, the effects and mechanism of long-term vegetation restoration on soil properties in ecosystems require further exploration to provide a reference for rational ecological construction. Hence, we investigated the differences in vegetation attributes and soil properties between three typical vegetation types (Pinus tabulaeformis plantation forest, PTPF; Robinia pseudoacacia plantation forest, RPPF; natural secondary forest, NSF) after long-term (30–40 years) vegetation restoration in the western Loess Region, China. Our results showed that (1) the arborous synusia biomass of the plantation forests was twice that of NSF, whereas NSF had almost 50% higher near-surface synusia biomass than the plantation forests; (2) the soil nutrient contents of the plantation forests were lower (30%) than those of NSF; (3) the soil bulk density, organic matter, total nitrogen, and phosphorus were positively related to arborous and shrub synusia biomass; (4) the coupling effects of four biological synusiae (with the contribution of 47.67%) were the dominant factors affecting soil physicochemical properties. Natural forests have the better vegetation attributes and soil properties than plantation forests, indicating that the close-to-nature restoration should be considered in ecological restoration. These findings can provide scientific support and theoretical basis for reforestation and ecological restoration in the Loess Plateau region and similar areas in the future.

Effects of vegetation structure and environmental characteristics on pollinator diversity in urban green spaces

With accelerating urbanization, insect pollinators in urban ecosystems face challenges such as reduced pollen sources, habitat fragmentation, and damage to the nesting environment. Urban green spaces (UGS) are essential for the stability of pollinator communities. However, little is known about the relationship between vertical layer heterogeneity and horizontal layer complexity of vegetation structure in UGS and pollinator communities. The present study aimed to assess how vegetation structure and environmental characteristics shape the insect pollinator community in UGS. To this end, this study was conducted with seven typical vegetation types which were selected according to the biotope mapping classification system (BMCS) in the ring parks around Hefei City, in Anhui province, China. A total of 11,401 pollinators belonging to 6 orders and 34 families were identified during the eight-month survey. Among the seven habitats under the BMCS, mainly successional short-cut shrub and partly open green space, trees two- or multi-layered broad-leaved mixed forest and partly closed green space, and mainly successional tall grass and partly open green space were identified as high-quality insect pollinator habitats. According to the results of the generalized linear regression, the explanatory power of the four best-fitting generalised linear models is relatively high (over 77%). In four optimal models, the effect of vegetation structure on pollinator community was greater than that of environmental characteristics. The redundancy discriminant analysis showed that the flowering abundance of nectar plants, herb richness, and shrub coverage rate were the three most important factors influencing insect pollinator communities, with a cumulative explanatory power of up to 78.8%. Pollinator abundance was positively influenced by spontaneous herbs and low-intensity management. However, high-intensity management, low diversity of plants, low nectar plant richness, ignoring seasonal nectar plant configuration, and dense tree distribution could limit pollinator reproduction and population growth. These results reflect the status of insect pollinator community in UGS in Hefei city and present a possible direction for improving urban green habitats and plant configurations.

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.

Spatiotemporal dynamic of subtropical forest carbon storage and its resistance and resilience to drought in China.

Subtropical forests are rich in vegetation and have high photosynthetic capacity. China is an important area for the distribution of subtropical forests, evergreen broadleaf forests (EBFs) and evergreen needleleaf forests (ENFs) are two typical vegetation types in subtropical China. Forest carbon storage is an important indicator for measuring the basic characteristics of forest ecosystems and is of great significance for maintaining the global carbon balance. Drought can affect forest activity and may even lead to forest death and the stability characteristics of different forest ecosystems varied after drought events. Therefore, this study used meteorological data to simulate the standardized precipitation evapotranspiration index (SPEI) and the Biome-BGC model to simulate two types of forest carbon storage to quantify the resistance and resilience of EBF and ENF to drought in the subtropical region of China. The results show that: 1) from 1952 to 2019, the interannual drought in subtropical China showed an increasing trend, with five extreme droughts recorded, of which 2011 was the most severe one; 2) the simulated average carbon storage of the EBF and ENF during 1985-2019 were 130.58 t·hm-2 and 78.49 t·hm-2, respectively. The regions with higher carbon storage of EBF were mainly concentrated in central and southeastern subtropics, where those of ENF mainly distributed in the western subtropic; 3) The median of resistance of EBF was three times higher than that of ENF, indicating the EBF have stronger resistance to extreme drought than ENF. Moreover, the resilience of two typical forest to 2011 extreme drought and the continuous drought events during 2009 - 2011 were similar. The results provided a scientific basis for the response of subtropical forests to drought, and indicating that improve stand quality or expand the plantation of EBF may enhance the resistance to drought in subtropical China, which provided certain reference for forest protection and management under the increasing frequency of drought events in the future.

A dataset of woody plant biomass models for subtropical mixed evergreen and deciduous broad-leaved forests

Tree biomass equations are the most commonly used method to estimate tree and forest biomass on various spatial and temporal scales because of their minor damage, ease of use, and high relative accuracy. The systematic compilation of models for the biomass of mixed evergreen and deciduous broad-leaved forest (a unique and essential class of typical vegetation types in the subtropical zone of China) has not been reported so far. In this paper, we compiled a species list through an inventory of 28.9 hm2 of mixed evergreen deciduous broad-leaved forests in southwestern Hubei Province with fixed detection sample plots, produced a species list, and used it to retrieve, collect and establish a model dataset of woody plant biomass in subtropical mixed evergreen and deciduous broad-leaved forests. The species list contains a total of 665 biomass models in 167 groups as well as the information corresponding to each mode, such as the plant species name, Latin name, plant life type, plant components calculated by the model, model independent variables, measurement units and ranges of independent variables, model correlation coefficient or coefficient of determination, model sample size, climate zone, and soil type. is also recorded. By establishing this dataset, this paper not only provides essential information for in-depth research on the productivity and carbon sink of this specific vegetation but also serve as a scientific basis for the management of this type of forest, the conservation of biodiversity, and the evaluation of forest ecological benefits.

Emissions of isoprenoids from dominant tree species in subtropical China

Emission factors (Es) are among the major sources of uncertainty in regional or global emission estimates of biogenic volatile organic compounds (BVOCs). Tropical vegetation contributes approximately 70% of global BVOC emissions, yet in situ measurements of BVOC emissions from tropical tree species, especially naturally grown mature trees, are quite limited. In this study, BVOC emissions from twenty mature trees (15 evergreen broad-leaved and 5 evergreen needle-leaved) were measured using dynamic chambers, and the emitted BVOCs were collected using sorbent tubes and speciated with a thermal desorption-gas chromatography/mass spectrometry system (TD-GC/MS). Twenty BVOC compounds including, isoprene, 14 monoterpene (MT) species and 9 sesquiterpene (SQT) species were quantified to calculate their Es. The results showed that Eucalyptus urophylla had the largest Es of isoprene (26.47 ± 3.70 μg g–1 h–1) among all the measured trees, followed by Ficus hispida (20.74 ± 1.78 μg g–1 h–1), Syzygium hainanense (20.49 ± 1.36 μg g–1 h–1), Casuarina equisetifolia (18.70 ± 2.91 μg g–1 h–1), and Mangifera indica (11.71 ± 7.04 μg g–1 h–1). α-Pinene, β-pinene, and limonene were the most abundant MTs, of which the largest Es were observed for Magnolia denudata (8.33 ± 2.05 μg g–1 h–1), Castanopsis hystrix (5.29 ± 3.24 μg g–1 h–1), and Magnolia denudata (3.11 ± 1.07 μg g–1 h–1), respectively. The Es of SQTs for the measured trees were lower than 0.50 μg g–1 h–1 except for Magnolia denudata (1.10 ± 0.41 μg g–1 h–1). β-Caryophyllene was the most common SQT, with Magnolia denudata having the highest Es of 0.09 ± 0.03 μg g–1h–1. The localized Es for dominant tree species could be used to update BVOC emission factors for typical vegetation types and help improve BVOC emission estimates in typical subtropical regions and narrow their uncertainties.

Characterizing Aqueous Cd2+ Removal by Plant Biochars from Qinghai–Tibet Plateau

Increased anthropogenic activities have caused cadmium pollution in Qinghai–Tibet Plateau, which is harmful to human health. This paper investigated aqueous Cd2+ adsorption using biochar of three typical vegetation types in cold and arid areas of the Qinghai–Tibet Plateau: (i) Chinese wolfberry (GBB), (ii) highland barley (QBB), and (iii) seabuckthorn (SBB). In order to investigate the effect of pyrolysis temperature on the performance of biochar for cadmium adsorption, three types of biochar were prepared at 350 °C, 500 °C, and 650 °C. The as-prepared biochar was characterized by scanning electron microscopy (SEM), Thermogravimetric (TG), Fourier transform infrared spectroscopy (FT-IR), and Brauer–Emmett–Teller (BET) analysis. The results showed that the biochar prepared at 650 °C had the best adsorption capacity. Compared with QBB and SBB, the GBB had a higher Cd2+ adsorption capacity of 19.48 mg/g. Moreover, the effects of biochar dosage, experimental temperature, and biochar preparation temperature on the adsorption of Cd2+ by biochar and the interaction between the factors were investigated using Box–Behnken Design (BBD). As a result, the amount of biochar dosage showed the most obvious influence on Cd2+ adsorption capacity, followed by sample preparation temperature and experimental adsorption temperature. This study paves the way for the design of biochar for Cd2+ adsorption in wastewater.