Vegetation Biomass Research Articles

Different Flooding Conditions Affected Microbial Diversity in Riparian Zone of Huihe Wetland

The soil microbiome plays an important role in wetland ecosystem services and functions. However, the impact of soil hydrological conditions on wetland microorganisms is not well understood. This study investigated the effects of wetted state (WS); wetting–drying state (WDS); and dried state (DS) on the diversity of soil bacteria, fungi, and archaea. The Shannon index of bacterial diversity was not significantly different in various flooding conditions (p > 0.05), however, fungal diversity and archaeal communities were significantly different in different flooding conditions (p < 0.05). Significant differences were found in the beta diversity of bacterial, fungal, and archaeal communities (p < 0.05). Additionally, the composition of bacteria, fungi, and archaea varied. Bacteria were predominantly composed of Proteobacteria and Actinobacteria, fungi mainly consisted of Ascomycota and Mucoromycota, and archaea were primarily represented by Crenarchaeota and Euryarchaeota. Bacteria exhibited correlations with vegetation coverage, fungi with plant diversity, and archaea with aboveground vegetation biomass. The pH influenced bacterial and archaeal communities, while soil bulk density, moisture, soil carbon, soil nitrogen, and plant community diversity impacted fungal communities. This study provides a scientific basis for understanding the effects of different hydrological conditions on microbial communities in the Huihe Nature Reserve; highlighting their relationship with vegetation and soil properties, and offers insights for the ecological protection of the Huihe wetland.

How Do Vegetation Biomass, Area, and Shape Attributes Influence the Cooling Effect of Urban Green Spaces?

Despite the increasing volume of research exploring the impact of various characteristics of urban green spaces (UGS) on land surface temperature (LST), findings remain inconsistent, particularly in arid climatic zones. In this research, we examined UGS change and their temperature and analyzed the relationship between pertinent variables of vegetation biomass, area, and shape of green patches and LST in Karaj city, an Iranian semi-arid urban area in 2000 and 2020. Linear regressions were used to model the relationship between green patches’ variables and LST. The results showed that vegetation biomass of green patches was more effective in reducing temperature in comparison with area and shape complexity. Moreover, larger patches with more vegetation biomass and higher shape complexity showed lower temperatures. These results can guide urban landscape optimization by providing a clear understanding of which factors contribute most significantly to temperature mitigation in arid and semi-arid urban areas. For instance, areas identified as green but thermally not significantly cold need to be prioritized for improvements such as planting denser vegetation or introducing more heat resilient species.

Assessment of Municipal Solid Waste Compost Used In Urban Agriculture and Its’ Potential Public Health Impacts In Katsina City, Nigeria.

This research assessed the potential ecotoxicological impacts of municipal solid waste compost (MSWC) as soil fertility improvement material on soil, plants and humans in urban Katsina. MSW Compost samples were collected from different dump sites and mixed with sand and kaolin into 2:2:1 ratio respectively. Maize and beans were planted on the mixture for phytotoxicity assessment as describe by Zucconi et al., 1981. Both the mixture and plant vegetative biomass were tested in the laboratory for non-biodegradable chemicals of Zn, Pb, Mn, Fe, Cd, Cr and pH using Atomic Absorption Spectrophotometer and pH meter methods respectively. In phytotoxicity assessment, Bean show high phytotoxicity while maize considers MSWC as phytonutrients. Paired ttest reports no statistical difference of nonbiodegradable substances concentrations in soils and in plants vegetative biomass. Single factor pollution index values range from clean to slightly polluted. Ecological risk index (ERI) values indicate low risk for all the heavy metals. Estimated daily intake of contaminants in beans and maize plants are far below the maximum allowable limits of WHO/FAO while Target hazard quotients (THQ) values are likely to cause noncarcinogenic effects to the ecosystem. This finding is promising particularly to the maize farmers. Both beans and maize farmers should ensure quality standard and regulations such as source separation and matured composting to remove harmful nonbiodegradable chemical substances before application.

Seeds Adapted to Mixed Cropping Increase Yield and Drought Resistance of Cereal–Legume Mixtures

ABSTRACTCropland diversification through mixed cropping has the potential of achieving a more sustainable agriculture while securing food production. This is of special relevance with climate change and the expected drier growing conditions in the future. Seed adaptation to this cropping method is hypothesized to be a fundamental factor to maximize these benefits, as well as the particular species combined. In this study we compared the performance of four cereal–legume mixed crops (wheat and oat mixed with lupin and lentil in pairs) with their respective monocrops. Each crop was sown using seeds adapted to monoculture and mixed cropping, respectively. Moreover, they were grown under early‐season and late‐season drought treatments and under control conditions. We measured above‐ground vegetative biomass, seed yield and harvest index to evaluate crop production, drought resistance and the effect of seed adaptation on each mixed and monocrop. Our results show that mixed cropping either had a beneficial or neutral effect on crop yield, depending on the species combination and drought conditions, but the harvest index was higher in monocrops. We also confirmed that seed adaptation to a particular type of cropping is clearly a determining factor in its performance. In accordance with the insurance hypothesis, mixed cropping has the effect of protecting crop yields in the case of a sudden bad performance of one of the species, for example, caused by adverse environmental conditions. It is necessary to focus on effective species combinations which have the best responses to mixed cropping. In our study, we show that wheat–lentil mixtures performed poorly, while wheat–lupin showed the most promising results improving yield and drought resistance. Oat mixed crops did not show differences with the respective monocrops, so they can be a viable cropping option as well and benefit from advantages of crop diversity not measured in this study.

Symbiotic Activity of Lupin when Adding Zoohumus to the Substrate

The aim of the work was to study the effect of various fertilization technologies on the processes of growth, synthesis of photosynthetic pigments, nodule formation and the dynamics of changes in their nitrogenase activity in different varieties of lupine (white and narrow-leaved). The emphasis in the work was shifted to the additional positive effect obtained from the introduction of a liquid extract of black soldier fly zoohumus (Hermetia illucens) into the lupine-rhizobial agrocenosis. According to the biomass indicators, it was found that narrow-leaved lupine was more responsive to the organo-microbial effect, the increase in which, on average, by variants amounted to 36%, compared to the control. On white lupine, it reached only 9%. It should be noted that in terms of vegetative biomass accumulation, white lupine prevailed over narrow-leaved lupine in all experimental variants by an average of 3 times. However, with a relatively small increase in weight, narrow-leaved lupine showed an increased synthesis of total chlorophyll. On average, the increase in it from the effect of the organomicrobial consortium was 19%. Regarding the values of symbiotic activity, a positive effect of zoohumus was recorded against the background of inoculation, which was reflected in an increase in the number, weight and nitrogenase activity of formed nodules in the vegetation phases. A direct correlation was found between these indicators. The highest peak in fixation for both species occurred at the budding phase, amounting to 17 059 C2H4 /g–1 h–1 nmol for white lupine and 2719 C2H4 /g–1 h–1 for narrow-leaved lupine. As both lupine species matured, the number of nodules decreased and the process of symbiotic nitrogen fixation decreased. The results obtained indicate a positive effect of H. illucens zoohumus on the studied indicators and allow us to recommend the use of its liquid extracts in lupine cultivation.

How do farming practices influence the richness and floristic composition of weeds in some Mexican maize fields?

The milpa is a historically successful Mesoamerican agroecosystem, consisting of a mixture of cultivated plants with associated vegetation that is partially managed. Conventional farming practices, like weeding and fertilization, have modified some ecological parameters of weeds, affecting their ecological, evolutionary, cultural, and productive roles. This study explores these changes from various perspectives: field experiments in fields with different management histories, contrasting treatments within these fields, farmer interviews and field walks, in San Bartolo del Llano, Ixtlahuaca, Mexico. A field experiment in milpas with different histories of farming practices (traditional vs conventional) was conducted to understand (a) the effect of the history of farming practices on richness, composition, and biomass of aboveground weed vegetation and the seed bank, (b) the effect of contrasting weeding treatments within these fields on the biomass of weeds and maize, and (c) farmers’ traditional knowledge and use of these plants. Farming practices did not affect species richness (43 species) of the aboveground weed vegetation, but a history of herbicide use increased monocot biomass and reduced useful weeds. More introduced monocots were recorded in conventionally managed fields; manual weeding led to more species, including more monocots and dicots, a higher biomass of weeds, and more native and exotic species. The composition differed between plots with different farming practices and treatments. The seed bank contained more species (54) than the aboveground vegetation. Maize ears’ and total biomass were somewhat higher in conventionally treated fields, but no differences were found between treatments. We found a considerable species turnover, with some species disappearing or becoming rare, particularly useful ones, and others being introduced‚ particularly grasses. Traditional management can help farmers keep useful weeds and higher biodiversity, thus contributing to overall productivity. Though herbicides reduce labor requirements, improved management should combine the benefits of traditional farming with some modernization.

Assessing Energy Cane Varieties for Renewable Biomass Energy: A Comprehensive Study of Economic Opportunities in the Dominican Republic

The use of vegetable biomass as a source of renewable energy is a growing trend in line with the 2030 Sustainable Development Goals approved by the United Nations in 2015. Energy cane (Saccharum officinarum) appears to be an appealing alternative for this purpose due to its high agricultural yields (150-200 ton/ha), strong resistance to common diseases compared to sugar cane, the ability to grow on marginal or less suitable lands for other commercial crops, and the feasibility of using the same labour force and machinery used for sugar production from sugar cane. Our study’s goal was the preliminary technical-economic opportunity study for an investment in a 100-hectare energy cane farm that produces energy cane bales (with 30% relative humidity) for use as fuel in biomass boilers in the Dominican Republic. The study showed that using energy cane as biomass feedstock for electricity production would result in profits from the third year onwards, making it highly financially attractive. The specific energy consumption to produce energy cane bales was 5.33 kW/t. The calculated Net Present Value was positive at US$ 128,742.50, the estimated Internal Rate of Return was 44.20%, and the payback period was just 2 years. These figures were higher than any possible bank interest rate.

Impacts of phosphate-solubilizing bacterium strain MWP-1 on vegetation growth, soil characteristics, and microbial communities in the Muli coal mining area, China.

Due to the cold climate and low soil nutrient content, high-altitude mining areas are challenging to restore ecologically. Their poor nutrient content may be ameliorated by introducing specific microorganisms into the soil. This study aims to evaluate the effects of a highly efficient phosphate solubilizing bacterium MWP-1, Pseudomonas poae, on plant growth, soil nutrients in remedying the soil of the high-altitude Muli mining area in Qinghai Province, and analyze its impact on microbial communities through high-throughput sequencing soil microbial communities. The results showed that MWP-1 significantly increased the content of soil available phosphorus by >50%, soil organic matter and total nitrogen by >10%, and significantly increased the height, coverage, and aboveground biomass of vegetation by >40% in comparison with the control (p < 0.05). MWP-1 mainly affected the composition of the soil bacterial communities at the taxonomic level below the phylum. Its impact on soil fungal communities occurred at the phylum and below taxonomic levels. In addition, MWP-1 also significantly improved the diversity of soil bacterial and fungal communities (p < 0.05), and changed their functions. It also significantly altered the relative abundance of genes regulating phosphorus absorption and transport, inorganic phosphorus dissolution and organic phosphorus mineralization in the bacterial community (p < 0.05). It caused a significant increase in the relative abundance of the genes regulating nitrogen fixation and nitrification in nitrogen cycling (p < 0.05), but a significant decrease in the genes regulating phospholipase (p < 0.05). Although sequencing results indicated that Pseudomonas poae did not become the dominant species, its dissolved phosphorus elements can promote plant growth and development, enrich soil nutrient content, and affect the succession of microbial communities, enhance ecosystem stability, with an overall positive effect on soil remediation in the mining area.

Climate and vegetation controlling accumulation and translocation of heavy metals in water tower regions of Qinghai-Tibet Plateau

Understanding how climate and vegetation influencing accumulation and translocation of heavy metals (HMs) in soils and vegetation in the Qinghai-Tibet Plateau (QTP) is critical to assess the ecological risk induced by HMs under the global warming. To accompany this goal, we comprehensively determined the accumulation and translocation of HMs within the interface of soil-vegetation in water tower regions of the QTP. The PMF model results show that 54 %−86 % of cobalt (Co), nickel (Ni), arsenic (As), zinc (Zn) and lead (Pb) in the surface soil are mainly from rock weathering and 54 % of cadmium (Cd) comes from effect of litter return. The increase of vegetation biomass significantly promotes the accumulation of HMs in the surface soil. The increase of root biomass significantly enhances the uptake of Co, Ni, As, Cd and Pb by roots, due to the increasing availability of these HMs in surface soil, but reduces the translocation from roots to shoots. The precipitation and temperature influence HMs translocation by controlling the root biomass. Hence, we speculate that the further global warming in the QTP would enhance HMs accumulation in surface soil, but would not significantly increase HMs accumulation in ground vegetation biomass.

Disentangling the response of species diversity, forest structure, and environmental drivers to aboveground biomass in the tropical forests of Western Ghats, India

Tropical forests are crucial to the global carbon cycle, but a significant knowledge gap in the precise distribution patterns of forest aboveground biomass (AGB) hinders our ability to formulate effective conservation efforts. A key unresolved issue is the lack of understanding of how forest AGB interacts with biotic and abiotic factors on large spatial scale. To address this, we used Structural Equation Modeling to disentangle the direct and indirect effects of environmental, anthropogenic, structural diversity species diversity and edaphic factors on AGB of trees, lianas and regenerating communities using the data from 96 1-ha plots in the central Western Ghats biodiversity hotspot, India. We hypothesized that the effect of structural attributes overrides AGB distribution, with relative contributions varying among plant communities. The landscape-level mean AGB was 245.12 ± 19.74 Mg ha−1, with SEM explaining 68–85 % of variations across the three vegetation communities. Structural diversity emerged as the primary mediator of the positive effects of taxonomic diversity on AGB in the regeneration community, whereas canopy cover and stem density linked diversity to AGB in adult tree and liana communities. Further, AGB showed a positive association with soil organic carbon in adult tree and regeneration communities, underscoring the significance of belowground resource availability on AGB. The results indicate that structural features were consistently the strongest AGB predictors at all levels of data aggregation, indicating the predominant role of niche complementarity and efficient space utilization in driving AGB, albeit differently across the plant communities. Our study emphasizes the importance of maintaining high structural features and managing taxonomic diversity while promoting soil fertility and minimizing disturbances to support AGB in tropical forests. We recommend testing the effects of predictor variables on biomass of vegetation communities independently to better understand the ecological principles of forest functioning.

Polyamide 6 Recycled Fishing Nets Modified with Biochar Fillers: an Effort Toward Sustainability and Circularity

In a further research effort toward sustainability and circularity, this work demonstrates the possibility of designing and producing novel blends derived from recycled polyamide 6 (PA6) fishing net, incorporating two biochars, i.e., carbonaceous materials obtained from the controlled pyrolysis of vegetable biomasses, at different loadings (namely 5, 10, and 15wt.%). The biochar derived from lignocellulosic biomass enhanced both the mechanical properties and moisture resistance of the recycled polyamide, increasing the elastic modulus from 2.6 to 4.5GPa and reducing water uptake from 3.6 to 1.8%. Interestingly, thanks to its high silica content, the biochar derived from rice husk accounted for an increase in the activation energy for combustion of the polymer matrix (from 43.6 to 70.9kJ/mol). However, it also showed a detrimental effect on the water uptake and the mechanical behaviour of the blends. Besides, the possibility of replacing up to 15wt.% of petroleum-derived carbon black pigments with the biochars decreased the overall cost of PA6 blends. Also considering the biochar densities that are lower than those of traditional carbon fillers, the proposed blends may pave the way for the design, development, and exploitation of novel sustainable materials suitable for lightweight applications.

Human settlement and destructive activities disrupt the positive contribution of dust to plant biomass growth over the past 2000 years

The dual pressures of global warming and increased anthropogenic activities pose significant threats to terrestrial vegetation ecosystems. To better understand the impacts of climate change and human activities on terrestrial vegetation ecosystems, we reconstructed the changes in vegetation and plant biomass over the past 4500 years using n-alkane records from sediments of two alpine lakes in northwestern China: Xiannv Lake and Tianchi Lake. Our results indicate that changes in the spatial variability of plant biomass are not related to temperature and precipitation. Furthermore, CO2 fertilization and nutrient inputs from dust contributed to the observed changes in plant biomass. We also compared the history of human activities in the Tianshan Mountains, the eastern Silk Road, and the Hunsandak Sandy Land, and find that the demand for plant resources—whether for human settlement, military construction, or warfare—may have caused a sudden decline in terrestrial vegetation, thereby disrupting the positive effects of dust on plant biomass growth.

Love your wet grass! Dry season grazing reserves show highest grass regrowth in communal semi-arid rangelands of Tanzania.

Land management by seasonal migratory herding, traditionally implemented by pastoralists, has allowed semi-arid rangeland ecosystems to remain productive and resilient to highly erratic, seasonal rainfall patterns. Changing pastoralist practices and rainfall patterns due to climate change have the potential to negatively influence the resilience of rangelands. To test the impact of different communal rangeland practices and increasing frequency of disturbance on the rangelands' vegetation, we established a clipping experiment in three rangeland management types: rainy season rangeland, dry season rangeland and seasonal exclosures, in the Maasai Steppe, northern Tanzania. Across these rangeland management types, we tested two clipping frequencies monthly vs. once per growing period and either fenced or open to grazing (herbivory) over two consecutive growing periods. We found that rainy season rangeland exhibited lowest regrowth rates and highest proportion of bare ground across herbivory, clipping frequency and growing period. When rainfall was low, seasonal exclosures showed lowest proportion of bare ground across herbivory and clipping frequency and plots that were seasonally clipped and excluded herbivores generated significantly more grass biomass, higher grass regrowth rates and lowest proportion of bare ground compared to all other treatments. Excluding herbivores had little impact on the vegetation biomass and cover but had a positive impact on grass regrowth rates when rainfall was high. Seasonal clipping allowed for lower proportion of bare ground, and in most cases higher regrowth rates and higher biomass compared to monthly clipping. We conclude that traditional seasonal migratory herding is a relevant concept to sustain rangeland productivity and resilience under increasing intensity of disturbance if grazing pressure on rainy season rangelands is adapted to rainfall conditions and sufficient resting time after heavy defoliation is granted. Dry season grazing (including rainy season resting) proved to be the most sustainable concept to maintain regrowth and control erosion.

Pilot Evaluation of Field Pea Accessions Under Water Deficit Conditions

Field pea, a key pulse crop for sustainable agriculture, faces significant production challenges due to drought, exacerbated by extreme climatic changes. This study evaluated 17 field pea plant introductions (PIs) and two commercial varieties under greenhouse conditions to assess their performance, determine the relationships between agronomic traits and grain yield (GY), and identify genotypes with stable yields under drought stress. Two water treatments were applied: 100% field capacity for well-watered (WW) and 60% field capacity for water deficit (WD) conditions, with drought stress imposed 21 days after planting. Significant genotypic variation was observed under both conditions. Water deficit significantly reduced GY, the number of pods per plant (NPP), plant height (PH), aboveground dry vegetative biomass (ADVB), and days to maturity (DTM) while increasing stomatal density on both adaxial (SD.ADX) and abaxial leaf surfaces (SD.ABX). Traits associated with GY in WW, such as NPP, PH, ADVB, and SD.ADX, showed stronger correlations under WD, with DTM being significantly associated with GY only in WD. Top-performing genotypes in both conditions exhibited higher pod numbers, increased aboveground dry vegetative biomass, late maturity, and lower adaxial stomatal density. Notably, PI 272215 was identified as a top performer under both conditions, with an 88% yield stability index. PI 180702 demonstrated comparable performance to PI 272215 but with no yield loss under the same conditions. These findings can be used for future field pea breeding programs aimed at developing drought-tolerant field pea varieties.

Early evaluation of salt-stress tolerance of new released olive cultivars based on physiological and biomass allocation indicators

The evaluation of salt-tolerant olive tree genotypes released from breeding program has become intrinsic in order to develop sustainable agriculture in these regions. The current study aims to i) evaluate the tolerance of two new released olive cultivars (Zeitoun Ennour and Zeitoun Ennwader), issued from a Tunisian breeding program in comparison with the main olive cultivar ‘Chemlali Sfax’, and ii) identify suitable salt-tolerance indicators for this evaluation. The trial was conducted under controlled conditions in a greenhouse, for six months, and plants were irrigated with half-strength Hoagland nutrient solution containing NaCl at various levels (0, 75, 150 and 225 mM). Vegetative growth, biomass allocation and biochemical parameters were considered for the assessment of salt-tolerant capacity. Results revealed that growth and biomass should be considered as useful indicators for early evaluation method of salt-stress tolerance. ‘Chemlali Sfax’ displayed a gradual significant decrease of vegetative growth with increasing salinity. The reduction of shoot elongation and trunk diameter was most evidently at 150 mM with 43.2 % and 80.8 %, respectively. However, the new released cultivars showed unaffected vegetative growth, despite a slight decrease at the salt level of 225 mM. Moreover, results demonstrated the importance of certain physiological and biochemical indicators such as ions contents. The new released cultivars maintained a high K+/Na+ ratio at moderate salinity then a significant decrease occurred at 150 mM. In conclusion, vegetative growth, biomass allocation and K+/Na+ ratio seemed to be the suitable salt-tolerance indicators for early evaluation. Based on these indicators, ‘Zeitoun Ennour’ seems to be the most salt tolerant genotype and ‘Zeitoun Ennwader’ proves to have a similar salt tolerant capacity as ‘Chemlali Sfax’, which is a valuable information for olive growers in arid region.

Effects of grazing on the relationship between dominant shrubs and understory vegetation along sand dune stability gradient.

During the process of dune vegetation restoration, understanding how grazing disturbance affects the relationship between plant species is a critical issue in ecological studies. However, there is insufficient evidence on the changes in the interaction between dominant shrubs and understory vegetation under grazing behavior. We aimed to study how grazing and dune stabilization affects the relationship between Caragana microphylla and understory vegetation. We established fencing at various stages of dune stabilization and proceeded to compared the performance indicators (e.g., richness and biomass) and the relative interaction index of understory vegetation and different functional groups along the dune stability under grazing and fencing conditions. Results showed that C. microphylla had facilitation on understory plants, and increased with dune stability, while the facilitation of Caragana microphylla on understory vegetation was stronger under grazing conditions. As sand dune stabilization increases, the facilitation of C. microphylla on understory vegetation diversity decreases significantly. However, there was no significant difference in the facilitation of C. microphylla on understory vegetation biomass at different stages of sand dune stabilization. This is related to the survival strategy of perennials being less tolerant to environmental stress than annuals, because grazing increased the richness of both annuals and perennials while reducing the overall biomass, and in the later stages of sand dune stabilization, and the facilitation of C. microphylla on perennials was higher than on annuals. Our study highlights the importance of the responses of different life-form groups to environmental factors and grazing disturbance during the process of sand dune vegetation restoration, as they play a crucial role in shaping the development of the relationship between understory vegetation and dominant shrubs.

Comprehensive genome-wide characterization of the MIKC-type MADS-box family members and the dynamic expression profiling throughout the development of floral buds in Populus tomentosa

Poplar is a major silvicultural tree species for industrial production, with versatile applications in construction, furniture, pulp and biofuel. The phenotypic appearance of male or female floral buds in poplar trees, exhibits a strikingly similar morphology at corresponding developmental stages. However, there are significant differences in internal anatomical structures. The MIKC-type MADS-box transcription factor family plays an indispensable role in regulating the development of floral organs and increasing vegetative biomass, and it is also of great significance in elucidation of the aforementioned morphological differences. This study systematically analyzed the MIKC-type MADS-box transcription factor family in Populus tomentosa. A total of 100 MIKC-type MADS-box genes were identified, which were divided into 14 subfamilies. We examined the physicochemical properties, gene structure, conserved motifs, chromosome distribution, collinearity, promoter cis-acting elements, gene expression profiles, and protein-protein interaction network of these 100 MIKC-type MADS-box members. Excitingly, four clusters of PtMADS members exhibited a high level of abundant expression in the initial and mature floral buds of both male and female, suggesting critical significance in tuning the morphogenesis and development of floral organs, as well as in the modulation of reproductive fitness. The protein-protein interaction network diagram corroborated these findings, substantiating the speculated roles of these genes. Our findings lay a foundational framework for future functional explorations and potential applications of MIKC-type MADS-box genes in this industry tree species.

Shrub cover declined as Indigenous populations expanded across southeast Australia.

Wildfires in forests globally have become more frequent and intense because of changes in climate and human management. Shrub layer fuels allow fire to spread vertically to forest canopy, creating high-intensity fires. Our research provides a deep-time perspective on shrub fuel loads in fire-prone southeastern Australia. Comparing 2833 records for vegetation cover, past climate, biomass burning, and human population size across different phases of human occupation, we demonstrated that Indigenous population expansion and cultural fire use resulted in a 50% reduction in shrub cover, from approximately 30% from the early to mid-Holocene (12 to 6 thousand years ago) to 15% during the late to mid-Holocene (6 to 1 thousand years ago). Since the start of British colonization to the present, shrub cover has increased to the highest ever recorded (mean of 35% land cover), increasing the risk of high-intensity fires.

Grazing exclusion promotes soil organic carbon accumulation in Tibetan grasslands with lower temperatures

BackgroundGrazing exclusion is a practical approach to restore vegetation in degraded grasslands and enhance soil organic carbon (SOC) sequestration. However, the dynamics and drivers of SOC in grasslands after grazing exclusion have not been well documented, especially in ecosystems with cold climates.MethodsHere, we established 14 paired treatments (grazing exclusion vs. free-grazing) along a 600-km transect in the northeastern zone of the Qinghai-Tibet Plateau. After six years, we analyzed vegetation biomass dynamics and measured the soil physicochemical properties and organic C concentration across three depths (0–10, 10–20, and 20–30 cm).ResultsGrazing exclusion significantly increased above- and belowground biomass (139.85% and 43.30%, respectively), pH (1.38%), total phosphorus (3.29%), nitrate nitrogen (18.03%), and ammonium nitrogen (17.81%), but significantly decreased soil bulk density (2.43%) and clay content (10.49%), particularly in 0–30 cm. Specifically, SOC concentrations positively responded to grazing exclusion (0–10 cm) in 9 of the 14 sites evaluated. The effects of grazing exclusion on SOC concentrations were significantly higher in areas with a mean annual temperature (MAT) below 0 °C compared to those in sites with a high MAT (> 0 °C). The SOC concentrations significantly correlated with the mean annual precipitation (MAP) in both treatments, but these correlations diminished with increasing soil depth. Ridge regression analysis showed that soil chemical properties (e.g., total nitrogen and phosphorus) positively influenced SOC accumulation, while MAT negatively influenced it after grazing exclusion. Path analysis further revealed that MAT indirectly regulated SOC dynamics via soil chemical properties.ConclusionsOur study highlights that grazing exclusion results in an asynchronous SOC and plant biomass accumulation and may be more beneficial for SOC sequestration in Qinghai-Tibet Plateau grasslands with lower temperatures. Also, humid climates promote SOC concentration in alpine grasslands. These results could help develop management practices and policies that promote sustainable grassland management.

Evaluation of the spatial responses in vegetation phenology to drought and the analysis of their driving factors in China

The warming and drying trend accompanying climate change challenges global ecosystem stability. Vegetation phenology, which can serve as a sensitive indicator of climate change, is crucial in understanding ecosystem carbon cycling and climate-carbon cycle feedback. Therefore, assessing the phenological responses to drought is essential for addressing climate change. In this study, vegetation phenology data [including the start and end of season (SOS, EOS) and length of growing season (LOS)] and the Palmer drought severity index (PDSI) were employed to analyze the impacts of drought on plant phenology in China by maximum Pearson correlation coefficients and partial least squares regression. The findings showed that drought significantly affected the timing of phenology, delaying senescence in approximately 62% of China and extending the growing season in about 53% of the country, indicating the critical role of water availability in vegetation biomass. Preseason nocturnal warming was found to advance SOS, delay EOS, and extend LOS across China, with significant effects observed in approximately 60% of the country. Meanwhile, daytime warming delayed SOS, delayed EOS and extended LOS in 50∼60% of the regions. Moreover, preseason precipitation is conducive to advanced SOS, delayed EOS and extended LOS in northern China and areas susceptible to drought. It is suggested that vegetation management should be strengthened to mitigate the impact of climate change in temperate and drought-prone regions in China since climate warming will lead to frequent droughts.