Chi Xu

Nanjing University | NJU · School of Life Sciences

Facilitation is a major force shaping the structure and diversity of plant communities in terrestrial ecosystems. Detecting positive plant-plant interactions relies on the combination of field experimentation and the demonstration of spatial association between neighboring plants. This has often restricted the study of facilitation to particular si...

Although canopy height has long been a focus of interest in ecology, it has remained difficult to study at large spatial scales. Recently, satellite-borne LiDAR equipment produced the first systematic high resolution maps of vegetation height worldwide. Here we show that this new resource reveals three marked modes in tropical canopy height ~40, ~1...

Rainforests are among the most charismatic as well as the most endangered ecosystems of the world. However, whereas the effects of climate change on tropical forests resilience is a focus of intense research, the conditions for their equally impressive temperate counterparts remain poorly understood, and it remains unclear whether tropical and temp...

Significance Human activities have played an important role in driving biodiversity loss throughout history, but the nature of these dynamics remains unclear. Importantly, the role of cultural evolution is mostly ignored, despite strong societal changes over time worldwide. Here, we show that megafauna range contractions across China in the last 2...

Significance We show that for thousands of years, humans have concentrated in a surprisingly narrow subset of Earth’s available climates, characterized by mean annual temperatures around ∼13 °C. This distribution likely reflects a human temperature niche related to fundamental constraints. We demonstrate that depending on scenarios of population gr...

E-commerce has become a booming market for wildlife trafficking, as online platforms are increasingly more accessible and easier to navigate by sellers, while still lacking adequate supervision. Artificial intelligence models, and specifically deep learning, have been emerging as promising tools for the automated analysis and monitoring of digital...

Global eutrophication and climate warming exacerbate production of cyanotoxins such as microcystins (MCs), presenting risks to human and animal health. Africa is a continent suffering from severe environmental crises, including MC intoxication, but with very limited understanding of the occurrence and extent of MCs. By analysing 90 publications fro...

Understanding how community phylogenetic and functional structures change over succession has gained increasing attention during the last decades, but the lack of long-term time-series data has limited our understanding of the patterns and mechanisms of these changes. This is especially the case for forest communities. Here we used an exceptionally...

The increasing availability of 3-D urban data yields new insights into urban developments and their implications for population density, energy consumption, and the carbon budget. However, existing products of urban building heights at a regional or global scale are mostly subject to coarse grid size or long-time lags. Fine-resolution building heig...

Global eutrophication and climate warming exacerbate production of cyanotoxins such as microcystins (MCs), presenting risks to human and animal health. Africa is a continent suffering from severe environmental crises, but with very limited understanding on the occurrence and extent of MCs. By synthesizing 90 publications, relatively high MC concent...

Context Global biodiversity decreases rapidly, driven by various factors ranging from climate change to anthropogenic activities. Identifying driving forces of population decline is critical for biological conservation. Time-series data are especially valuable for this goal, but unfortunately, high-quality time-series data are generally lacking, ha...

The relationship between biodiversity and ecosystem functions (BEFs) has attracted great interest. Studies on BEF have so far focused on the average trend of ecosystem function as species diversity increases. A tantalizing but rarely addressed question is why large variations in ecosystem functions are often observed across systems with similar spe...

Prudent risk management requires consideration of bad-to-worst-case scenarios. Yet, for climate change, such potential futures are poorly understood. Could anthropogenic climate change result in worldwide societal collapse or even eventual human extinction? At present, this is a dangerously underexplored topic. Yet there are ample reasons to suspec...

1. Rapid technological advancements and increasing data availability have improved the capacity to monitor and evaluate Earth’s ecology via remote sensing. However, remote sensing is notoriously ‘blind’ to fine‐scale ecological processes such as interactions among plants, which encompass a central topic in ecology. 2. Here, we discuss how remote se...

Biotic interactions that hierarchically organize ecosystems by driving ecological and evolutionary processes across spatial scales are ubiquitous in our biosphere. Biotic interactions have been extensively studied at local and global scales, but how long-distance, cross-ecosystem interactions at intermediate landscape scales influence the structure...

Active restoration is frequently implemented to restore degraded drylands globally, yet predicting the overall success of these restoration projects remains challenging. Here we explore if vegetation spatial patterns can be used to monitor ecosystem recovery and anticipate the success of restoration practices. We combined field surveys and high‐res...

The costs of climate change are often estimated in monetary terms 1,2 but this raises ethical issues ³ . Here we express them in terms of numbers of people left outside the ‘human climate niche’ ⁴ – defined as the historically highly-conserved distribution of relative human population density with respect to mean annual temperature (MAT). We show t...

Since 2014, highly pathogenic avian influenza (HPAI) H5 viruses of clade 2.3.4.4 have been dominating the outbreaks across Europe, causing massive deaths among poultry and wild birds. However, the factors shaping its broad-scale outbreak patterns remain unclear. With extensive waterbird survey datasets of about 7,000 sites across Europe, we here de...

Rivers and their lakes are among the world’s most important ecosystems ‒ supporting high biodiversity and providing various services through connections with vast landscapes. Reconciling exploitation with sustainability remains one of the world’s greatest challenges to maintain and/or recover the health of river ecosystems and hence their biodivers...

Soil invertebrates and microorganisms are two major drivers of litter decomposition. Even though the importance of invertebrates and microorganisms in biogeochemical soil cycles and soil food webs has been studied, the effects of invertebrates on fungi are not well understood compared to other organisms. In this work, we investigated the effects of...

Rivers and their lakes are among the world’s most important ecosystems ‒ supporting high biodiversity and providing various services through connections with vast landscapes. Reconciling exploitation with sustainability remains one of the world’s greatest challenges to maintain and/or recover the health of river ecosystems and hence their biodivers...

To identify the key soil factors influencing the vegetation differentiation in the coastal tidal flats of the Yellow−Bohai Sea in China, this study investigated the corresponding relationship between the Spartina alterniflora (SA), Suaeda salsa (SS), and Phragmites australis (PA) communities and their respective soil factors with published data, an...

Vegetation is usually sparse in the desert regions, but it plays important roles in stabilizing sand dunes and combating desertification. Establishing how desert vegetation responds to changes in both natural forcing and anthropogenic interference is essential for better understanding desertification processes and their future dynamics. In this stu...

The world has increasingly relied on protected areas (PAs) to rescue highly valued ecosystems from human activities, but whether PAs will fare well with bioinvasions remains unknown. By analyzing three decades of seven of the largest coastal PAs in China, including World Natural Heritage and/or Wetlands of International Importance sites, we show th...

Loss of submerged macrophytes resulting from high turbidity has become a global environmental problem in shallow lakes, associated with eutrophication. To help macrophyte recovery, application of artificial light-emitting diodes (LEDs) has been proposed to complement nutrient load reductions. We set up a mesocosm experiment to test if LEDs could co...

Increasing effort has been devoted to restoring coastal ecosystems to counteract their degradation globally. Restoration success of coastal ecosystems often relies on harnessing biotic interactions that shape the performance of foundation plant species. Crabs acting as essential ecosystem engineers and consumers are commonly present in coastal salt...

Climate warming in northern high latitudes has progressed twice as fast as the global average, leading to prominent but puzzling changes in vegetation structure and functioning of tundra and boreal ecosystems. While some regions are becoming greener, others have lost or shifted vegetation condition as indicated by a browning signal. The mechanisms...

The origin of the nucleus remains a great mystery in life science, although nearly two centuries have passed since the discovery of nuclei. To date, studies of eukaryogenesis have focused largely on micro-evolutionary explanations. Here, we examined macro-patterns of Cvalues (the total amount of DNA within the haploid chromosome set of an organism)...

Nebkhas, also known as nebkha dunes or coppice dunes, are a unique biogeomorphological aeolian landform that is common in arid and semi-arid regions. They are often regarded as a signal of regional desertification and could be potential dust sources due to their relatively large content of fine sediments, but they also serve as “fertile islands” th...

Ecological restoration is crucial to counteract the degradation of coastal ecosystems. Recent studies increasingly suggest that coastal restoration success can be amplified by harnessing positive interactions between individuals of foundation species, with clumped spatial designs as an easy‐to‐implement approach. However, positive interactions are...

The Asian elephant (Elephas maximus), an endangered species on the International Union for Conservation of Nature Red List, is the largest terrestrial animal living in Asia. They require a relatively large space to live in. In China, the wild Asian elephants exist only in XiShuangBanNa, Pu’Er, and LinCang of southern Yunnan Province, with 95% of th...

Significance Reliable data on economic inequality are largely limited to North America and Western Europe. As a result, we know the least about areas where inequality presents the most serious developmental policy challenge. We demonstrate that spatial variation in night-light emitted per person can reflect the distribution of income. This allows u...

The recent mass mortality event of more than 330 African elephants in Botswana has been attributed to biotoxins produced by cyanobacteria; however, scientific evidence of this is lacking. Here, by synthesizing multiple sources of data, we show that, during the past decades, the widespread hypertrophic waters in southern Africa have entailed an extr...

Despite releases of governmental guidelines for promoting physical fitness among the youth in China, the performance of college students in fitness tests has been declining over the past three decades. Obesity and physical inactivity have been proposed as two main causes. However, their relative importance for improving physical fitness remains unc...

1. Catastrophic regime shifts in various ecosystems are increasing with the intensification of anthropogenic pressures. Understanding and predicting critical transitions are thus a key challenge in ecology. Previous studies have mainly focused on single environmental drivers (e.g., eutrophication) and early warning signals (EWSs) prior to populatio...

Purpose of Review Despite the decades-long recognition of the importance of scaling in ecology, our knowledge about many ecological patterns and processes is still largely restricted to particular spatial and temporal scale domains with relatively narrow ranges. There is no exception when it comes to the study of biodiversity, one of the most impor...

Coastal wetlands provide many critical ecosystem services including carbon storage. Soil organic carbon (SOC) is the most important component of carbon stock in coastal salt marshes. However, there are large uncertainties when estimating SOC stock in coastal salt marshes at large spatial scales. So far, information on the spatial heterogeneity of S...

Dune systems can have alternative stable states that coexist under certain environmental conditions: a vegetated, stabilized state and a bare active state. This behavior implies the possibility of abrupt transitions from one state to another in response to gradual environmental change. Here, we synthesize stratigraphic records covering 12,000 years...

Inter‐specific root separation is an important example of spatial niche differentiation that drives species coexistence in many ecosystems. Particularly under water‐stressed conditions, it is believed to be an inevitable outcome of species interactions. However, evidence for and against this idea has been found. So far, studies aiming at reconcilin...

Urban natural surfaces and non-surface human activities are key factors determining the urban heat island (UHI), but their relative importance remains highly controversial and may vary at different spatial scale and focal urban systems. However, systematic studies on the scale-dependency system-specificity remain largely lacking. Here we selected 3...

Worldwide, various tree species have been worshiped and praised because they are culturally significant in many nations. To address the questions of whether and how the preference for cultural trees influences the plant diversity in urban ecosystems characterized by human-created vegetation, we surveyed the plant composition in 239 designed landsca...

Livestock grazing is the most extensive human land use and one of the key drivers of the conversion of tropical forests into grasslands. Livestock effects on vegetation structure are complex, as they can prevent tree recruitment and growth through browsing and trampling, but they can also affect vegetation indirectly through fire interactions. Howe...

The biodiversity of food webs is composed of horizontal (i.e. within trophic levels) and vertical diversity (i.e. the number of trophic levels). Understanding their joint effect on stability is a key challenge. Theory mostly considers their individual effects and focuses on small perturbations near equilibrium in hypothetical food webs. Here, we st...

To understand the effects of urban artificial nighttime light on the growth of evergreen trees, we conducted a field investigation in a typical urban street planted with Cinnamomum camphora (a common evergreen street tree species in eastern China) in the Nanjing City, China. Along the street, trees from two types of growing locations with contrasti...

Studies on the highly pathogenic avian influenza (HPAI) H5N1 suggest that wild bird migration may facilitate its long‐distance spread, yet the role of wild bird community composition in its transmission risk remains poorly understood. Furthermore, most studies on the diversity–disease relationship focused on host species diversity without consideri...

Self-organized spatial patterns are increasingly recognized for their contribution to ecosystem functioning, in terms of enhanced productivity, ecosystem stability, and species diversity in terrestrial as well as marine ecosystems. Most studies on the impact of spatial self-organization have focused on systems that exhibit regular patterns. However...

Aim The aim was to assess whether and to what extent the role of local landscape attributes in shaping macroscopic biodiversity patterns is sensitive to spatial and thematic resolutions of land cover data. Location Sub‐Saharan Africa and continental China. Time period Early 21st century. Taxa studied Terrestrial mammals. Methods We conducted sp...

Presently, China has the largest high-speed rail (HSR) system in the world. However, our understanding of the network structure of the world's largest HSR system remains largely incomplete due to the limited data available. In this study, a publicly available data source, namely, information from a ticketing website, was used to collect an exhausti...

Due to excess nutrient loading, loss of submersed macrophytes is a worldwide phenomenon in shallow lakes. Phosphorus is known to contribute significantly to macrophyte recession, but the role of nitrogen has received increasing attention. Our understanding of how high nitrogen concentrations affect the growth of submersed macrophytes, particularly...

The composition and structure of urban landscape and human activity intensity are key factors shaping urban thermal fields, whereas the relative importance of influencing factors for urban thermal distribution remains unclear. We carried out a case study in Yixing City. Land surface temperature (LST), ecological infrastructure (including vegetation...

China now has the largest high-speed rail system in the world. However, due to data limitations, understanding of this system remains incomplete. Here we combined open big data, complex network indicators and spatial analyses to reveal the hierarchical and modular structure of the system. Many spatial features well coincide with the planning, while...

Context Emissions of greenhouse gases in urban areas play an important role in climate change. Increasing attention has been given to urban landscape structure–emission relationships (SERs). However, it remains unknown if and to what extent SERs are dependent on observational scale. Objective To assess how changing observational scales (in terms o...

Fires and herbivores shape tropical vegetation structure, but their effects on the stability of tree cover in different climates remains elusive. Here we integrate empirical and theoretical approaches to determine the effects of climate on fire‐ and herbivore‐driven forest‐savanna shifts. We analyzed time series of remotely sensed tree cover and fi...

Recent studies have interpreted patterns of remotely sensed tree cover as evidence that forest with intermediate tree cover might be unstable in the tropics, as it will tip into either a closed forest or a more open savanna state. Here we show that across all continents the frequency of wildfires rises sharply as tree cover falls below ~40%. Using...

The ranges of tree cover above which the fire frequency drops (see also Fig 3). The range of the steepest drop is defined as the area where the fire frequency is between 25% and 75% of the maximum. (PDF)

Multimodality in tree cover and the shape of the fire function match within different classes of mean annual precipitation (MAP in mm yr-1) for all tropics. The grayed areas approximate the range of logistic growth functions where alternative stable states are possible. a: MAP<500 mm yr-1; b: MAP between 500 and 1000 mm yr-1; c: MAP between 1000 an...