My research aims to improve biological invasion management and biodiversity conservation through strengthening the theoretical underpinnings and links between theory and empirical knowledge that contribute to these subjects. I address these questions using a combination of mathematical theory, computational models, and laboratory and field experiments.
My research contributions fall into three main areas: (1) Effects of dispersal and heterogeneity on metapopulations and metacommunities. (2) What drives exotic species to outcompete natives? (3) The role of climate and other factors in driving species shifts in elevational distributions.
My research contributions fall into three main areas: (1) Effects of dispersal and heterogeneity on metapopulations and metacommunities. (2) What drives exotic species to outcompete natives? (3) The role of climate and other factors in driving species shifts in elevational distributions.
Project 1. Effects of dispersal and heterogeneity on metapopulations and metacommunities.
2018 - present
Background: The effect of environmental stressors on populations is typically studied in well-mixed conditions. However, most populations in nature are not well-mixed, and stressors tend to be heterogeneously distributed over a population’s spatial range. Little is known about how the spatial distribution of stressors interacts with dispersal to influence population dynamics.
Study Question: How do the physiological consequence and spatial distribution of a stressor interact with dispersal to determine the impact of stress on metapopulation size? |
Major Findings: We prove mathematically and observed experimentally: A uniform spatial distribution of stressor minimizes the total equilibrium size of experimental metapopulations, with the magnitude of the effect depending predictably on dispersal rate and geographic pattern of stressor heterogeneity.
Relevant publications:
- Zhang, B., D. L. DeAngelis, W. Ni, Y. Wang, L. Zhai, A. Kula, S. Xu, J. D.Van Dyken. Scaling antibiotic efficacy from cells to metapopulations. Major revision American Naturalist.
Project 2. The role of climate and other factors in driving species shifts in elevational distributions.
2015 - present
Background: Our study focus on an emerging form of land use change in mountains, cessation of human disturbances, which have widely occurred in Europe and China, due to economic transformations or ecological concerns of the disturbances.
Following the disturbance cessation, low land forest recovery may have opposite effects on plant elevational shifts to that of warming climate (i.e., upslope shifts by warming climate vs. downslope shifts by forest recovery). Therefore, under the two contrasting and simultaneous impact, it is critical to quantify their net effects on plant elevational distributions.
Following the disturbance cessation, low land forest recovery may have opposite effects on plant elevational shifts to that of warming climate (i.e., upslope shifts by warming climate vs. downslope shifts by forest recovery). Therefore, under the two contrasting and simultaneous impact, it is critical to quantify their net effects on plant elevational distributions.
Part 1 - Downslope shifts of woody species after cessation of human disturbances in spite of global warming
To quantify the net effects of the two contrasting and simultaneous impact (warming climate vs. land use change), we used extensive 20-year forest inventory data from four mountainous areas in eastern China (39,553 individuals in 481 permanent inventory plots) where intense deforestation occurred up to 1970 but was then ceased to facilitate natural forest recovery.
Our results suggest that, prior to stand succession, the disturbance cessation and consequent forest recovery at low elevations had greater effects on the species shifts than the warming climate. In systems that are being allowed to recover from past human disturbances, the forest recovery effects on species distributions should be explicitly accounted for when assessing the global warming impact. |
Relevant publications:
- Zhang, X.¶, B. Zhang¶, K. Feeley, Z. Fu**, G.G. Wang, J. Zhang and L. Zhai. Downslope shifts of woody species after cessation of human disturbances in spite of global warming. Minor revision Environmental Research Letters. ¶Co-first authorship
Relevant Presentation:
Aug 2016 - 101th Ecological Society of America Annual meeting (ESA), Fort Lauderdale, USA.
July 2016 - 4th Annual International Conference on Ecology, Ecosystems and Climate Change, Athens, Greece.
Aug 2016 - 101th Ecological Society of America Annual meeting (ESA), Fort Lauderdale, USA.
July 2016 - 4th Annual International Conference on Ecology, Ecosystems and Climate Change, Athens, Greece.
Part 2: Up- and downslope shifting woody species showed similar elevational patterns of water status but different nutrient one
Global climate change is expected to initiate species distribution shift (e.g., the warming climate causes an upslope shift of plant communities). Downscaling this general shifting pattern to species level could lead to various shifting directions, but our knowledge of the underlying mechanisms is limited. Here, we provide the first study to investigate the mechanisms of plant nutrient and water status on species shifting directions.
We found that both the up- and downslope shifting species showed higher water status at lower elevations, where soil water content was limited. In contrast, only upslope shifting species showed higher nutrient status at lower elevations, where soil fertility was limited. Non-shifting species did not show any significant response to these two status. The high nutrient-sensitivity of upslope shifting species can be explained by their faster growth rate and larger tree height. This study highlights the primary role of nutrient status on driving species elevational shifts. Notably, under the warming climate and increasing N deposition, the potentially enhanced lowland drought and improved highland fertility would exacerbate the upslope shift of nutrient-sensitive species. |
Relevant publications:
Zhang, B., L. d. S. L. Sternberg, A. Hastings, Z Fu**, Y. Yuan, J. Zhang and L. Zhai. Plant nutrient stress drives the up-slope shifts of wood species under warming climate and land use change in mountain systems. Under review. |
Part 3: Mapping nitrogen concentrations in soil - plant - leaf litter - cycles in a temperate forest along an elevational gradien
Organisms and their environments are linked together through nutrient cycling, a vital process in which nutritional building blocks of life flow through ecosystems. While a great deal of progress has been made on understanding the cycling of nutrients between plants, leaf litter, and soil, most of the research has focused only on the transitions between two parts of this cycle at one time or one. Simultaneous consideration of multiple soil - plant - leaf litter transitions and the environmental factors that influence flow through this cycle is important for developing a more complete understanding of this important ecosystem process.
Therefore, in this study, we measured carbon and nitrogen concentration in soils, plants, litter falls in a Montane ecosystem in eastern China and investigated the relationship between these nutrient pools and environmental factors. We showed that the two key soil nitrogen sources for plants, NH4+ and NO3-, both showed significant increases along elevation gradient. Elevation showed no effect on foliar nutrient concentrations but a positive effect on litter fall nitrogen content. Furthermore, it is important to note that soil depth does play an important role on nitrogen pool cycling thus ignoring the information from deeper soil might bring a bias on our understanding of nutrient cycling and forest management. Finally, the structure equation model taken together with global climatic change emphasize the importance of research that integrating environmental factors and interaction among plant – leaf litter – soil. Relevant publications:
1. Fu, Z. **, X. Zhang, L. Xu*, M. E. Afkhami, J. Zhang, B. Zhang¶. Mapping nitrogen flows in plant – leaf litter – soil cycles along an altitude gradient. Under review. ¶: Corresponding author |