Plant-soil feedback experiment is an important way for studying plant-soil biota interactions. Plant growth can change soil physical, chemical, and biotic properties in ways that then alter subsequent plant performance, population fluctuation, and community dynamics. This process, referred to as “plant-soil feedback” (PSF), might play a key role in biodiversity maintenance, sustainable agriculture development, and ecological restoration. In this review, we first provide an overview of the concept and research methods of PSF. Second, we review the research progress of the role of PSF in the maintenance of plant species diversity, plant community succession, plant invasions and range shifts, ecological response to climate change, above- and below-ground multitrophic interactions, ecosystem restoration, and crop performance in different cropping systems. We suggest three directions for future PSF studies, including: (1) the transition from single-species to community-level interactions between plants and soil biota; (2) the test of PSF experiments in field conditions; (3) the expansion of theoretical knowledge into ecological practice.

Forests are crucial terrestrial ecosystems with wide distribution and substantial biomass, playing a vital role in the global carbon cycle. The estimation of aboveground biomass (AGB) in forests serves as a significant indicator of ecosystem productivity and is pivotal for studying material cycles and global climate change. Traditional methods for AGB estimation rely on individual tree-scale or forest stand-scale tree physical structural information measurements, which are often time-consuming and labor-intensive to obtain. Remote sensing technology offers a solution for comprehensively and multi-temporally obtaining forest structural information in large scale, making it indispensable for forest AGB estimation. Therefore, it is important to review and summarize recent advancements in remote sensing techniques for estimating forest AGB to promote their application and guide the development of related industries. This paper presents a comprehensive overview of the principles and methods used for estimating forest AGB using optical data, synthetic aperture radar (SAR) data, and light detection and ranging (LiDAR) data. It also analyzes the current status of synergistic estimation of forest AGB using multiple remote sensing data sources. The study highlights three key findings: (1) The use of novel remote sensing data, such as high-resolution satellite imagery and Global Ecosystem Dynamics Investigation LiDAR data, is expanding the boundaries of spatial and temporal resolutions, providing enhanced data sources for forest AGB research. (2) Synergistic approaches that combine multiple remote sensing data sources show promise in improving the accuracy of forest AGB estimation, but further optimization of related models is needed. (3) Machine learning, artificial intelligence, and deep learning techniques have been widely applied in forest AGB estimation, but continuous research on remote sensing mechanisms remains essential for innovation. Improvements in models and methodologies should revolve around a better understanding of these mechanisms.

Aims Along with intensified climatic warming and human activities, global arid areas have expanded in an unprecedented rate during the past decades. Dryland ecosystems have witnessed increased vulnerability and sensitivity to climate change. Exploring the time lag effect of climate change on dryland vegetation growth is becoming an important research highlight in current global change related studies.

Methods In this study, we synthesized the normalized difference vegetation index (NDVI) from Moderate- resolution Imaging Spectroradiometer (MODIS), the monthly gridded CRU TS4.05 (Climatic Research Unit Time-Series version 4.05) climate and drought information developed by the University of East Anglia, solar radiation information from ERA5 (ECMWF’s Fifth Generation Atmospheric Reanalysis of the Global Climate) and soil moisture information from the European Space Agency (ESA) Climate Change Initiative program (CCI). These data were designed to investigate the effects of climatic factors and their time-lag on grassland NDVI in Asian grasslands from 2001 to 2020. This analysis was conducted based on the window cross-correlation and one-dimensional linear regression.

Important findings Our study revealed that: 1) The grassland NDVI responded strongly to average temperature and total precipitation when there was no lag, but expressed a lag response to solar radiation and soil moisture (1-month). 2) The spatial distributions of the lag response of grassland NDVI to climate change were nonuniform, with significant differences observed between the western and eastern Asian grasslands. 3) We did not detect any apparent time-lag effects on interactions between grassland NDVI and self-calibrating Palmer Drought Index. 4) We argue that altitude could partly modulate the response of grassland NDVI to climatic variables in the grassland of Asian drylands.

Aims This study aims to clarify the differences in ecological strategies between karst and non-karst forest tree species, in terms of leaf morphology and anatomy, hydraulics, and mechanical resistance.

Methods A total of 101 tree species were selected from typical karst and non-karst forests in tropical-subtropical regions. We measured: (1) leaf morphological and anatomical traits including leaf thickness (LT), leaf density (LD), vein density and leaf mass per area (LMA); (2) leaf mechanical traits including force to punch and force to tear (F_t); and (3) leaf hydraulic traits including maximum hydraulic conductance (K_{leaf_max}), cavitation resistance (P50_leaf), turgor loss point (Ψ_tlp), and stomatal safety margin (HSM_tlp). We compared the differences in leaf traits between karst and non-karst forest tree species, and analyzed their traits correlation networks.

Important findings (1) Compared to non-karst forest tree species, on average the karst tree species had greater F_t, higher K_{leaf_max}, lower (more negative) Ψ_tlp and HSM_tlp. (2) Leaf trait network of karst forest tree species showed shorter average path length and diameter and lower edge density than non-karst forest tree species, indicating that traits combinations were closer in karst forests. (3) Mechanical traits and LMA showed high connectedness in the trait networks of karst forest tree species, LT and LD showed high connectedness in those of non-karst tree species. In karst forest tree species, LMA was positively correlated with F_t and negatively correlated with Ψ_tlp, indicating that increasing leaf carbon investment can simultaneously enhance meachnical resistance and drought tolerance. However, no such correlations were found in non-karst forest tree species. (4) Across karst forests tree species, we found a significant tradeoff between K_{leaf_max} and P50_leaf, both of which were not related with leaf mechanical resistance, and morphological and anatomical traits. By contrast, there was no hydraulic tradeoff in non-karst forest tree species, and K_{leaf_max} was significantly correlated with LT and LD. This study further reveals that compared to non-karst forest tree species, karst forest tree species tend to exhibit isohydraulic strategy and show closer coordination among leaf traits.

Aims Trait-based methods have provided a new viewpoint for predicting community dynamics. We use these approaches to reveal how functional traits influence the key demographic rates of plant species, thereby improving our understanding of community dynamics.

Methods We monitored the growth and mortality rates of 26 common woody plant species from Dajinshan Island, Shanghai, over a five-year period (2016-2021). Nine leaf and wood traits related to competition and utilization strategies for light, water and nutrient resources were measured. Then, the relationships between the relative growth and mortality rates and each of individual trait, as well as the multi-trait synthesized plant economics spectrum, were analyzed.

Important findings Our results showed that leaf area and leaf nitrogen content were significantly and positively correlated with the relative growth rate, while leaf thickness, twig wood density and leaf dry matter content were significantly and negatively correlated with the relative growth rate. Stem wood density and twig wood density were significantly negatively correlated with the relative mortality rate. The plant economics spectrum that is formulated by nine traits, could explain 32.8% variation in relative growth rate; however, it did not correlate with the relative mortality rate. The relative growth was higher for acquisitive species than that for conservative species. Our results suggest that plant functional traits are important in affecting their growth, and that plant economics spectrum can accurately predict variations in relative growth rates among species, but its predictions for relative mortality are weaker.

Aims Haloxylon ammodendron is the major dominated species in the Gurbantünggüt Desert, which plays a key role in ecosystem services: such as biodiversity conservation and prevention of dryland degradation. Frequent droughts have a significant impact on the survival of H. ammodendron, thus understanding the drought resistant strategies of H. ammodendron is essential for the sustainability and stability of desert ecosystems. Robust hydraulic system and carbon balance are important parts of the drought resistance mechanism, but the hydraulic threshold for survival of H. ammodendron under drought stress are still unquantified.

Methods We set up a control group and a drought treatment group for adult H. ammodendron, and determined the water status of assimilation twigs, the loss rate of xylem hydraulic conductivity in branches, gas exchange characteristics, nonstructural carbohydrate (NSC) contents and morphological characteristics at upper, lower and middle branches of H. ammodendron. We used one-way ANOVA for each trait among different treatments and heights, linear regression for stomatal sensitivity and principal component analysis for drought resistance of H. ammodendron, respectively.

Important findings (1) The predawn and midday water potential of assimilation twig, assimilation twig water content and branch water content of H. ammodendron decreased under drought stress, but did not affected by the increase of height; P50 and P88 (xylem tension causing 50% and 88% loss of maximum hydraulic conductivity) did not change significantly under drought and with increasing height, and the mean value of P50 was -4.12 MPa and P88 was -7.10 MPa for each height and treatment groups, while the hydraulic safety margin was significantly reduced under drought. (2) The stomatal opening of H. ammodendron was not sensitive to drought stress, and thus drought stress and branch height increase did not significantly affect net photosynthetic rate and stomatal conductance in general. (3) The NSC contents of assimilation twigs and branches did not decrease under drought stress or with increasing branch height; the value of NSC contents in the assimilation twigs and branches were 22.11% and 13.10% higher, compared to the control group. (4) The Huber value of H. ammodendron increased by 73.78% in the drought treatment group compared to the control group; the specific leaf area decreased by 14.60% compared to the control group, but there were no significant difference between the two treatment groups. In conclusion, the hydraulic traits of H. ammodendron were significantly affected by drought stress, but not by the increase of branch height, and there was no hydraulic limitation with increasing branch height. Under drought stress, the risk of simultaneous hydraulic failure of the peripheral branches at the crown edge was high, the hydraulic safety margin (difference between midday assimilation twig water potential and P88) was only 40.85% of that of the control group. Due to the low sensitivity of stomata to water stress, the shrub can maintain the capacity of photosynthetic carbon fixation under drought stress, and even slightly increased NSC contents of the assimilation twigs and branches.

Aims Water is the main limiting factor for revegetation and ecorestrotion in arid sandy areas. Soil available water content directly affects the xylem water transport capacity of plant. However, the differences in xylem hydraulic traits and leaf gas exchange of different shrub species with different ages under varied soil water content are still unclear.

Methods The 10-year-old and 30-year-old Caragana korshinskii and C. liouana in the sand-binding area were employed to explore the differences and relationships between their hydraulic traits and photosynthetic traits during the dry and rainy season.

Important findings The results showed that the shrub age has no significant effect on xylem hydraulic conductivity, degree of natural embolism, leaf water potential and relative water content of C. korshinskii and C. liouana, while soil water content significantly effects on these functional traits. Both shrub age and soil water content have significant effects on leaf photosynthesis of two shrub species, but the effect of shrub age on them is little significant during the rainy season. In addition, there was a significant positive linear relationship between soil water content with leaf water content and xylem-stem specific hydraulic conductivity. Xylem hydraulic conductivity also had a significant positive correlation with leaf water content and stomatal conductance, whereas net photosynthetic rate was also positive related to xylem hydraulic conductivity and leaf water content. Results indicated that soil water content directly affected leaf water status and the capacity of photosynthetic carbon assimilation by affecting xylem hydraulic conductivity and embolization degree. In conclusion, the change of soil water content significantly affected the xylem hydraulic conductivity and leaf photosynthetic carbon assimilation capacity of C. caraganaand C. Liouana.

Aims The growth and survival of plants are being threatened by more frequent extreme high temperature events under global climate change. Therefore, for species conservation and adaptability prediction, it is essential to accurately evaluate the physiological heat tolerance across plant species. Magnoliaceae, as a typical basal angiosperm lineage, is one of the representative lineages in subtropical evergreen forests in China, with high ecological and evolutionary significance. However, the photosynthetic heat tolerance of Magnoliaceae plants is still unclear.

Methods In this study, we used chlorophyll fluorescence method to exam the photosynthetic heat tolerance of 23 species of Magnolicaeae plants in a common garden. In order to analyze the relationships of photosynthetic heat tolerance with leaf morphology and temperature niche, for each species, we measured leaf morphological traits and calculated the temperature niche across their geographic distribution areas.

Important findings The temperature that causes 50% decrease of the maximum photochemical quantum efficiency of photosystem II (T50) ranged from 46.1 to 56.7 °C, with significantly higher T50 of evergreen species than that of deciduous species. For leaf morphology, T50 was positively correlated with the leaf area but was not significantly correlated with the leaf thickness. For temperature niches, T50 was positively correlated with mean annual air temperature and minimum air temperature of the coldest month but was not significantly correlated with maximum air temperature of the warmest month. A weak phylogenetic signal was found in T50, indicating that T50 was influenced by leaf morphology and environment conditions, rather than phylogeny. Our results suggested that photosynthetic heat tolerance of Magnoliaceae species were generally strong, but its adaptation may not be driven by high temperature environment. Future extreme high temperature events may severely threaten deciduous Magnoliaceae plants living in the warmer areas.

Aims Kobresia pygmaea is a typical low temperature-tolerant arid mesophyte, and mainly distributes at low slope and high mountains ranging from 3 000 to 5 960 m on the Qingzang Plateau. Low temperature is a frequently occurring abiotic stress factor during the plants growing season on the Qingzang Plateau. The objectives of this study were to analyze the photochemical and non-photochemical energy distribution characteristics of the photosystem II (PSII) reaction center of K. pygmaea leaves, and explore their quenching protection mechanism in response to low temperature stress.

Methods Turf blocks (30 cm × 30 cm) of K. pygmaea meadow were collected from the Alpine Grassland Ecosystem Research Station of the Resource of Three Rivers, moved and kept in a culture room with air temperature of 24 °C/18 °C (day/night) at a diurnal photoperiod of 12 h and relative humidity of 45%; being irradiated with artificial LED light source of 500 µmol·m⁻²·s⁻¹ light intensity. When the turf black had been kept in culture room for one day, the measurements of chlorophyll fluorescence were performed immediately using chlorophyll fluorescence imager with built-in protocol. The trial of light response curves at different leaf temperatures, temperature response at a steady-state light intensity and light-temperature interaction effects were performed at controlled temperature using thermostatic control instruments. Based on the “Lake Model”, the relative variation of the PSII actual photochemical efficiency (Φ_PSII), the quantum yield of regulated energy dissipation (Φ_NPQ) and non-regulated energy dissipation (Φ_NO) were investigated. Furthermore, the interaction effects of low temperature and high light intensity was analyzed by two-way ANOVA of the general linear model (GLM).

Important findings The maximum quantum efficiency of PSII photochemistry (F_v/F_m and 1/F_o - 1/F_m) were higher at 10 °C and their coefficient of variation (CV) was smaller relative to other temperatures. The rapid light-response curves of the PSII relative electron transfer rate (rETR) showed a downward as a whole with the decreasing of temperature, and their initial slope (α) also decreased accordingly. Low temperature caused a decrease in Φ_PSII and Φ_NO, and an increase in Φ_NPQ, accompanied with enhancement of CV values. Under 1 000 µmol·m⁻²·s⁻¹ steady-state light intensity, the relative ratios of Φ_PSII:Φ_NPQ:Φ_NO at the temperature of 20, 10, 5, 0, and -5 °C were in turn 23:57:20, 18:63:19, 15:68:17, 11:75:14, and 8:80:12, showing remarkable decrease in Φ_PSII and increase in Φ_NPQ. The relative limitation of PSII photochemical efficiency (L_PPFD) increased gradually with the increase of light intensity, and also with the decrease of temperature. The two-way ANOVA of GLM showed that there were no interaction effects of low temperature and high light intensity in both PSII photochemical and non-photochemical energy dissipation processes. Therefore, the excited energy absorbed by PSII antenna pigments can be transferred and dissipated effectively by the photochemical energy conversion of Φ_PSII and protective regulatory mechanisms of Φ_NPQ avoiding the exacerbation of Φ_NO, which exhibited a strong tolerance and adaptation to alpine habitats. However, the increased instability of photosynthetic activities at low temperatures indicated that the photosynthetic apparatus of K. pygmaea still suffer the stress while maintaining normal operation. It can be inferred that the low temperature is an important factor affecting the photosynthetic physiological process and limiting growth and development and its distribution.

Fossil pollen and spore records provide highly creditable proxy data to investigate the past environmental changes such as palaeovegetation and palaeoclimate. Pollen database promotes past environmental studies from local to regional and global scales and from qualitative to quantitative reconstructions. This is of great significance on exploring the interactions among past vegetation, climates and anthropogenic disturbances at large spatial scale and long temporal scale, to better understand the evolution of the earth system. In this paper, a fossil pollen dataset of China is compiled, by synthesizing 372 original or digitized fossil pollen records including 790 pollen taxa in China’s land and ocean during the late-Quaternary (since 50 ka BP). The dataset includes site names, latitude, longitude and altitude, pollen data source, sample type, sediment length or span, sample number of each site, dating method and dating number, age span and reference, as well as the fossil pollen percentage of each sampling site. The pollen data, mostly published from late 1980s to present, are concentrated in vegetation regions of temperate and subtropical forests, temperate grasslands, temperate deserts and alpine vegetation on the Qingzang Plateau. Sample sites are distributed at different altitudes from deep sea to high Qingzang Plateau, but the majority of the sites are located between 0-2 000 m. The dataset comprises of 178 raw pollen records (47.8%) and 194 digitized pollen records (52.2%). Pollen samples are mainly from lake sediment (151 sites), alluvial/fluvial sediment (99 sites), and peat (67 sites), accounting for 85.2% of the total sampling sites. Radiocarbon is the main dating method that accounts for 93.8% of total samples, and most of the sites have 2-10 radiocarbon dating data. Each site has an average number of pollen taxa of 19, with the most sites having 4-30 pollen taxa. The temporal and spatial distribution of representative pollen taxa (Pinus, Quercus, Artemisia and Poaceae) reveals increasing trends both in their distributional range and pollen concentration from the last glacial maximum to Holocene, but such trends have various regional patterns in different parts of China. This fossil pollen dataset is a fruitful work of collection of pollen records in most territory of China that conducted by palynologists from China and overseas during the last half century. It consolidates the valuable and fundamental data that can be potentially utilized to explore the evolution of past environments and their driving mechanism of climate change and human disturbance.

For the universal grassland degradation and associated human utilization in the world, authors expound ecosystem restoration, climate climax in ecological succession, environment change and grassland state transition, grazing and disturbance climax, restoration by human intervention, thereby put forward the restoration path and state model of the degraded grassland ecosystem. This paper emphasizes that the restoration of degraded grassland should be carried out from the perspective of ecosystem, rather than only vegetation or soil processes, because there will be multiple alternative restoration states for grasslands in the context of environmental change or human disturbance. Three basic restoration modes of degraded grassland and possible restoration states are described as the followings: (1) Gradual restoration according to natural succession: based on the theory of ecological succession, grasslands from light to moderate degradation under favorable environments might reach the climax or near climax state for a long time by the systematical self-organization. (2) Intervention restoration by human activity: for those severely or extremely degraded grasslands, it needs to break through a series of abiotic (soil structure, nutrients, etc.) and biotic (plant colonization, species interaction, etc.) restrictions, and restore to a certain equilibrium or stable state, even climax state by using engineering, physical, chemical or biological-ecological methods or practices. It will take a long-time. (3) Restoration by grazing disturbance: grassland ecosystem structure (species composition and diversity), productivity and nutrient processes could be regulated through light to moderate livestock grazing, thereby maintaining and promoting grassland ecosystem multifunctionality and stability. This restoration method can be selected for medium-mild degraded grasslands. In conclusion, the holistic goal of grassland restoration is to achieve its long-term stable ecosystem multifunctionality.