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79
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Introduction
Professor of Biology, Senior Ecologist, Ecological modeler of forest ecosystems, interests in remote sensing, conservation ecology, global change ecology.
Xi lab webpage: https://drxilab.netlify.com/index.html
Publications
Publications (79)
Although some plant traits have been linked to invasion success, the possible effects of regional factors, such as diversity, habitat suitability, and human activity are not well understood. Each of these mechanisms predicts a different pattern of distribution at the regional scale. Thus, where climate and soils are similar, predictions based on re...
A major challenge in landscape and environmental modelling is to effectively visualize large amounts of time-series simulation output, often in various Geographic Information System (GIS) formats. We developed a software tool (LANDISVIEW), to easily visualize and animate time-series of ERDAS *.gis maps. The open source tool can also be used to gene...
Forest landscape models simulate forest change through time using spatially referenced data across a broad spatial scale (i.e. landscape scale) generally larger than a single forest stand. Spatial interactions between forest stands are a key component of such models. These models can incorporate other spatio-temporal processes such as natural distu...
We present a data set collected in 1989 of vascular plant occurrences in overlapping grids of nested plots in the Oosting Natural Area of the Duke Forest, Orange County, North Carolina, USA. The purpose of these data is to allow the study of vascular plant biodiversity at multiple spatial scales, in terms of both grain and extent. There are eight d...
Public forest management requires consideration of numerous objectives including protecting ecosystem health, sustaining habitats for native communities, providing sustainable forest products, and providing noncommodity ecosystem services. It is difficult to evaluate the long-term, cumulative effects and tradeoffs these and other associated managem...
Understanding and quantifying the resilience of forests to disturbances are increasingly important for forest management. Historical fire suppression, logging, and other land uses have increased densities of shade tolerant trees and fuel buildup in the western United States, which has reduced the resilience of these forests to natural disturbances....
In 2011, the forestlands of Texas were affected by one of the most severe droughts in the state’s history, killing an estimated 65 million trees in the East Texas region. This study uses USDA Forest Service Forest Inventory and Analysis data and a standardized precipitation-evapotranspiration index to estimate major tree species responses to the 20...
Drought-induced tree mortality has increased in many parts of the world because of climate change, and in some regions, has altered forest structure, species composition and ecosystem functions. These developments have the potential to reduce forest resilience and push forests over a tipping point to an alternate state (i.e. a different forest type...
A major challenge in landscape modeling is to effectively visualize and analyze a massive amount of simulation outputs, which usually are in various raster and vector geospatial data formats. Because the task is often time-consuming and costly, available handy data viewers are limited. Yet, it is a useful tool for land managers to prepare and deplo...
To mitigate and adapt to climate change, forest carbon sequestration and diversity of the ecosystem must be included in forest management planning, while satisfying the demand for wood products. The future provisions of ecosystem services under six realistic management scenarios were assessed to achieve that goal. These services were carbon sequest...
Changes in tree mortality due to severe drought can alter forest structure, composition, dynamics, ecosystem services, carbon fluxes, and energy interactions between the atmosphere and land surfaces. We utilized long-term (2000‒2017, 3 full inventory cycles) Forest Inventory and Analysis (FIA) data to examine tree mortality and biomass loss in drou...
With the expansion of plantations all over the world, there are increasingly more concerns about their ability to support multiple ecosystem services. We hypothesized that mixed plantations with a high number of tree species could provide a higher level of ecosystem services than monocultures. To test this hypothesis, we selected the experimental f...
Drought is one of the most complex and least understood climate-related natural hazards. Active drought mitigation and contingency plan formulation often require a reliable drought distribution map. This study analyzed different spatial interpolation techniques to produce drought distribution map in East Texas, USA. Deterministic [inverse distance...
Windthrow plays a critical role in maintaining species diversity in temperate forests. Do large-scale strong wind events (i.e., tropical cyclones, including hurricanes, typhoons and severe cyclonic storms) increase tree diversity in severely damaged forest areas? Do hurricanes (tropical cyclones that occurs in the Atlantic Ocean and northeastern Pa...
Forest ecosystems in northeast China play a vital role in the country's economic growth, sustainable development, environment protection and ecological improvement because they comprise more than 30% of the total forest area in China. These forest ecosystems are especially sensitive and vulnerable to projected climate changes because they are natur...
Understanding physiological responses and drought adaptation strategies of woody plant leaf traits in sub-humid to semi-arid regions is of vital importance to understand the interplay between ecological processes and plant resource-allocation strategies of different tree species. Seasonal variations of leaf morphological traits, stoichiometric trai...
Global climate change is expected to result in a relative high frequency of a short period of extreme high temperature (HT) on plant ecosystems and can have an adverse impact on plant growth and development, yet the response of plants to such damage is not fully understood. In this study, physiological responses of Scaevola aemula seedlings to a sh...
Zhifeng Wu E. Dai Q. Ge- [...]
X. Wang
Global and regional environmental change such as land use and climate change have significant and interactive effects on forest. These integrated effects will undoubtedly alter the distribution, function and succession processes of forest ecosystems. In order to respond and adapt to these changes, it is necessary to understand their individual and...
Slender rush-pea (Hoffmannseggia tenella) is an endangered herbaceous legume endemic to southern Texas. Agricultural expansion and invasive nonnative grasses have caused reductions in its range, threatening existing populations. We compared three management techniques that control competition to no management (control) to determine effects on slend...
Global and regional environmental changes such as land use and climate change have significantly integrated and interactive effects on forest. These integrated effects will undoubtedly alter the distribution, function and succession processes of forest ecosystems. In order to adapt to these changes, it is necessary to understand their individual an...
Understanding the physiological response mechanisms of plant leaf traits to forest plantation types in semi-arid regions is of vital importance to better understanding the interplay between ecological process and plant resource-allocation strategies of different tree species. Experimental forest plantations were constructed on the Loess Plateau of...
Mid-subtropical forests are the main vegetation type of global terrestrial biomes, and are critical for maintaining the global carbon balance. However, estimates of forest biomass increment in mid-subtropical forests remain highly uncertain. It is critically important to determine the relative importance of different biotic and abiotic factors betw...
In the past three decades, our global climate has been experiencing unprecedented warming. This warming has and will continue to significantly influence the structure and function of forest ecosystems. While studies have been conducted to explore the possible responses of forest landscapes to future climate change, the representative concentration...
Many previous studies have shown that land use patterns are the main factors influencing soil infiltration. Thus, increasing soil infiltration and reducing runoff are crucial for soil and water conservation, especially in semi-arid environments. To explore the effects of agroforestry systems on soil infiltration and associated properties in a semi-...
Tropical cyclones are large-scale strong wind disturbance events that occur frequently in tropical and subtropical coastal regions and often bring catastrophic physical destruction to ecosystems and economic disruption to societies along their paths. Major tropical cyclones can infrequently move into the midaltitudes and inland areas. Ecologically,...
The Forest Landscape Model (FLM) is an efficiency tool of quantified expression of forest ecosystem’s structure and function. This paper, on the basis of identifying FLM, according to the stage of development, summarizes the development characteristics of the model, which includes the theoretical foundation of mathematical model, FLM of stand-scale...
Lacking of detail data, forest carbon stock estimation with forest inventory data usually excludes or underestimates understory carbon storage. To quantify the effects of understory on carbon sequestration in a natural secondary Pinus tabulaeformis forest, organ biomass models for arbor, shrub to their growth indices were regressed. Biomass of herb...
Efficient managing practices require an understanding of the root distribution of crop in walnut (Juglans regia)-crop intercropping systems, a field study was conducted in the Loess Plateau of China to examined the vertical distribution and horizontal variation of roots for soybean (Glycine max) and peanut (Arachis hypogaea) grown with walnut trees...
Background/Question/Methods
Inquiry-based learning can improve student learning and deepen their understanding of science. It may be especially beneficial in the context of ecological education given the field-observational and experimental orientations of the discipline. Field-based inquiries are often not feasible in large introductory ecology...
Six national programs—including the Natural Forest Protection Program (NFPP), Sloping Land Conversion Program (SLCP), Desertification Combating Program around Beijing and Tianjin (DCBT), Shelterbelt Network Development Program (SNDP), Wildlife Conservation and Nature Reserve Protection Program (WCNR), and Industrial Timberland Plantation Program (I...
Eastern hemlock (Tsuga canadensis Carriére) and the Carolina hemlock (Tsuga caroliniana Engelmann) are ecologically important tree species in eastern North America forests that are currently threatened by the hemlock woolly adelgid (HWA, Adelges tsugae Annand, Hemiptera: Adelgidae). HWA has spread rapidly from its original introduction site into ne...
Forest ecosystems across the Northwoods will face direct and indirect impacts from a changing climate over the 21st century. This assessment evaluates the vulnerability of forest ecosystems in the Laurentian Mixed Forest Province of northern Wisconsin and western Upper Michigan under a range of future climates. Information on current forest conditi...
Spatial simulation may be used to model the
potential effects of current biodiversity approaches on
future habitat modification under differing climate
change scenarios. To illustrate the approach, spatial
simulation models, including landscape-level forest
dynamics,were developed for a semi-natural grassland
of conservation concern in a southern I...
Background/Question/Methods
Forests in the northern Great Lakes region have been experiencing the effects of a warming climate and will be further affected by the continuous warming (and likely wetter) climate. The collective effects of changing climate are complex due to strong interactions with forest growth and succession, increasing timber ha...
Agroforestry has been widely practiced in the Loess Plateau region of China because of its prominent effects in reducing soil and water losses, improving land-use efficiency and increasing economic returns. However, the agroforestry practices may lead to competition between crops and trees for underground soil moisture and nutrients, and the trees...
Picture of apple-soybean intercropping plots in study site.
(JPG)
Picture of peanut monoculture plots in study site.
(JPG)
To evaluate if hedgerows could improve the soil physicochemical properties and enhance the soil anti-scouring and anti-shearing capabilities, the effects of Herba Andrographitis hedgerows on soil erodibility and fractal features on sloping cropland in the Three Gorges Reservoir Area were investigated. Results showed that: (1) the clay particle accu...
Chronic wind is an important ecological factor, but its direct roles in shaping plant communities remain poorly understood. We hypothesized that chronic wind can modulate community productivity, inter-specific competition, and species abundance in inland dunes. We conducted an experiment with three shrubs (Artemisia ordosica, Caragana intermedia, a...
Root-carving artwork is among the most highly appreciated traditional forms of art in China because of its ornamental and collection value. However, this ancient and highly appreciated art form is in fact currently a major cause of environmental damage. We argue that the state and local forestry administrations and related industry associations sho...
H. Xu Huaxing Bi L. Gao- [...]
B. Bao
In order to provide scientific and technological guide for efficient and sustainable agroforestry management, spatial distribution and morphological variation of fine root in a walnut-soybean intercropping system were examined using stratified excavation method in the Loess Plateau of western Shanxi Province, China. Fine root dry weight (FRDW) of w...
The southern pine beetle (Dendroctonus frontalis Zimmermann) is the most destructive insect pest of pine (Pinus spp.) forests in the southern United States. Restoring and managing pine stands infested by southern pine beetle are critically important for forest health and sustainability in the region. The successful restoration of damaged pine fores...
During the past 20 years, China has increasingly invested in ecological restoration programs that addressed protection of its existing natural forests and restoration of its degraded lands. Since the late 1990s, China has launched several nationwide programs that aimed both at solving regional environmental problems and improving domestic ecologica...
Background/Question/Methods
Northern Wisconsin forests have been experiencing the effects of climate changing, but the collective effects are complex due to strong interactions with continuous forest growth and succession, increasing land development, harvesting, and frequent natural disturbance (e.g., fire and windthrow). We conducted a spatial...
Small Footprint LiDAR (Light Detection And Ranging) has been proposed as an effective tool for measuring detailed biophysical characteristics of forests over broad spatial scales. However, by itself LiDAR yields only a sample of the true 3D structure of a forest. In order to extract useful forestry relevant information, this data must be interprete...
Y. Wu Jianping Tao Weimin Xi- [...]
J. Hao
Lianas are an important component in tropical rain forests and are often cited as the most obvious physiognomic difference between temperate and tropical forests. Lianas can have profound impacts on the diversity, structure, dynamics and functions of tropical rain forests. However, due to their relative smaller stem size, defining liana individuals...
Stochastic weather generators are useful tools for exploring the relationship between organisms and their environment. This paper describes a simple weather generator that can be used in ecological modeling projects. We provide a detailed description of methodology, and links to full C++ source code (http://weathergen.sourceforge.net) required to i...
Background/Question/Methods
Spatial forest landscape simulation with LANDIS-II were conducted as preliminary work to answer questions of forest type and species change under future climate scenarios, and including natural and management disturbance on the Chequamegon-Nicolet National Forest in northern Wisconsin.
Results/Conclusions
Spatial si...
The southern pine beetle, Dendroctonus frontalis (Zimmerman) (Coleoptera: Curculionidae: Scolytinae) (SPB) is an indigenous invasive species that infests and causes mortality to pines (Pinus spp.) throughout the southern US. The hemlock woolly Adelgid, Adelges tsugae (Annand) (Homoptera: Adelgidae) (HWA), is a non- indigenous invasive species that...
Matrix models have been used to model population growth of organisms for many decades. They are popular because of both their conceptual simplicity and their computational efficiency. For some types of organisms they are relatively accurate in predicting population growth; however, for others the matrix approach does not adequately model growth rat...
Restoration planning, evaluation, and implementation are important in areas where abiotic disturbances (e.g., wildfires, hurricanes, and ice storms), biotic disturbances (e.g., outbreaks of native and exotic invasive pests and diseases), and anthropogenic disturbances (e.g., harvesting, planting, and fire exclusion) have altered forest landscapes....
The forests of southeastern North America are influenced by a variety of disturbances including fire and insect outbreaks. In this paper, we discuss the role of disturbances in structuring forest landscapes with particular emphasis placed on the reciprocal interaction between forest structure and outbreaks of the southern pine beetle (Dendroctonus...
Aims
Large hurricanes have profound impacts on temperate forests, but owing to their infrequent nature these effects have rarely been examined in detail. In 1996, Hurricane Fran significantly damaged many long-term tree census plots in the Duke Forest on the North Carolina Piedmont, thereby providing an exceptional opportunity to examine pre- and p...
The reciprocal interaction of landscape structure and ecological processes is a cornerstone of modern landscape ecology. We use a simulation model to show how landscape structure and herbivory interact to influence outbreaks of southern pine beetle (Dendroctonus frontalis Zimmermann) in a landscape representative of the southern Appalachian Mountai...