USING A CELLULAR-AUTOMATA MODEL TO INVESTIGATE THE EFFECTS OF GRAZING ON PLATEAU PIKA POPULATION DYNAMICS

2011 ◽  
Vol 04 (03) ◽  
pp. 275-287 ◽  
Author(s):  
HANWU LIU ◽  
LI ZHOU ◽  
WEI LIU ◽  
HUAKUN ZHOU
Keyword(s):  
Cellular Automata ◽  
Alpine Meadow ◽  
Keystone Species ◽  
Grazing Intensity ◽  
Population Based ◽  
Tibet Plateau ◽  
Average Amount ◽  
Plateau Pika ◽  
Temporal Dimension ◽  
Cellular Automata Model

The plateau pika is a keystone species of Qinghai–Tibet plateau, but its overabundance aggravates the degradation of alpine meadow. Grazing is the most convenient manner to utilize alpine meadow. Grazing would change vegetation condition, that is, change the habitat of plateau pika and so lead to variation of plateau pika population. Based on ecological characteristics of plateau pika and alpine meadow, a cellular-automata model is established to investigate the influence of grazing on dynamics of plateau pika population. Vegetation shortens with the increase of grazing intensity. When grazing intensity is light, the height of vegetation under summer grazing, continuous grazing, rotational grazing and winter grazing decrease in turn. The ACC (average carrying capacity of plateau pika) is higher on degraded meadow and is lower on undegraded meadow. On undegraded meadow grazing affects the value of ACC, whereas, on degraded meadow grazing has slight effect on it. On undegraded meadow, plateau pika occupies all cells speedly, the amount of damaged cells and the average amount of live holes in occupied cells decrease or hold the line on temporal dimension. On degraded meadow, the dispersal of plateau pika is restrained, the amount of damaged cells and the average amount of live holes in occupied cells increase on temporal dimension.

scholarly journals The burying and grazing effects of plateau pika on alpine grassland are small: a pilot study in a semiarid basin on the Qinghai-Tibet Plateau

2016 ◽  
Vol 13 (22) ◽  
pp. 6273-6284 ◽  
Author(s):  
Shuhua Yi ◽  
Jianjun Chen ◽  
Yu Qin ◽  
Gaowei Xu
Keyword(s):  
Net Primary Production ◽  
Keystone Species ◽  
Alpine Grassland ◽  
Tibet Plateau ◽  
Plateau Pika ◽  
Carbon And Nitrogen ◽  
Grazing Effects ◽  
Considerable Controversy ◽  
The One ◽  
Qinghai Tibet Plateau

Abstract. There is considerable controversy about the effects of plateau pika (Ochotona curzoniae, hereafter pika) on alpine grassland on the Qinghai-Tibet Plateau (QTP). On the one hand, pika is considered a keystone species. On the other hand, it is being poisoned. Although significant efforts have been made to study the effects of pika at a quadrat scale ( ∼  m2), our knowledge about its distribution and effects at a larger scale is very limited. In this study, we investigated the direct effects, i.e., burying and grazing, of pika by upscaling field sampling at a quadrat scale to a plot scale ( ∼  1000 m2) by aerial photographing. Altogether 168 plots were set on four different types of alpine grassland in a semiarid basin on the QTP. Results showed that (1) the effects of pika pile burying on the reduction of vegetation cover, biomass, soil carbon, and nitrogen were less than 10 %, which was much smaller than the effects of bald patches; and (2) pika consumed 8–21 % of annual net primary production of grassland. We concluded that the direct burying and grazing effects of pika on alpine grassland were minor in this region. The quadcopter is an efficient and economic tool for long-term repeated monitoring over large regions for further understanding the role of pika.

scholarly journals Improved Estimation of Aboveground Biomass of Disturbed Grassland through Including Bare Ground and Grazing Intensity

2021 ◽  
Vol 13 (11) ◽  
pp. 2105
Author(s):  
Yan Shi ◽  
Jay Gao ◽  
Xilai Li ◽  
Jiexia Li ◽  
Daniel Marc G. dela Torre ◽  
...  
Keyword(s):  
Aboveground Biomass ◽  
Vegetation Index ◽  
Grazing Intensity ◽  
Tibet Plateau ◽  
Estimation Accuracy ◽  
Bare Ground ◽  
Estimation Model ◽  
Plateau Pika ◽  
Ground Modification ◽  
Aerial Vehicle

Accurate approaches to aboveground biomass (AGB) estimation are required to support appraisal of the effectiveness of land use measures, which seek to protect grazing-adapted grasslands atop the Qinghai-Tibet Plateau (QTP). This methodological study assesses the effectiveness of one commonly used visible band vegetation index, Red Green Blue Vegetation Index (RGBVI), obtained from unmanned aerial vehicle (UAV), in estimating AGB timely and accurately at the local scale, seeking to improve the estimation accuracy by taking into account in situ collected information on disturbed grassland. Particular emphasis is placed upon the mapping and quantification of areas disturbed by grazing (simulated via mowing) and plateau pika (Ochotona curzoniae) that have led to the emergence of bare ground. The initial model involving only RGBVI performed poorly in AGB estimation by underestimating high AGB by around 10% and overestimating low AGB by about 10%. The estimation model was modified by the mowing intensity ratio and bare ground metrics. The former almost doubled the estimation accuracy from R2 = 0.44 to 0.81. However, this modification caused the bare ground AGB to be overestimated by about 38 and 19 g m−2 for 2018 and 2019, respectively. Although further modification of the model by bare ground metrics improved the accuracy slightly to 0.88, it markedly reduced the overestimation of low AGB values. It is recommended that grazing intensity be incorporated into the micro-scale estimation of AGB, together with the bare ground modification metrics, especially for severely disturbed meadows with a sizable portion of bare ground.

scholarly journals Modelling the shrub encroachment in a grassland with a Cellular Automata Model

2014 ◽  
Vol 364 ◽  
pp. 20-25 ◽  
Author(s):  
D. Caracciolo ◽  
L. V. Noto ◽  
E. Istanbulluoglu
Keyword(s):  
Cellular Automata ◽  
Chihuahuan Desert ◽  
Plant Competition ◽  
Grazing Intensity ◽  
Moisture Stress ◽  
Shrub Encroachment ◽  
Influential Factors ◽  
Distributed Model ◽  
Creosote Bush ◽  
Cellular Automata Model

Abstract. Arid and semi-arid grasslands of southwestern North America have changed dramatically over the last 150 years as a result of shrub encroachment, i.e. the increase in density, cover and biomass of indigenous shrubby plants in grasslands. Numerous studies have documented the expansion of shrublands in the southwestern American grasslands; in particular shrub encroachment has occurred strongly in part of the northern Chihuahuan desert since 1860. This encroachment has been simulated using an ecohydrological Cellular Automata model, CATGraSS. It is a spatially distributed model driven by spatially explicit irradiance and runs on a fine-resolution gridded domain. Plant competition is modelled by keeping track of mortality and establishment of plants; both are calculated probabilistically based on soil moisture stress. For this study CATGraSS has been improved with a stochastic fire module and a grazing function. The model has been implemented in a small area in Sevilleta National Wildlife Refuge (SNWR), characterized by two vegetation types (grass savanna and creosote bush shrub), considering as encroachment causes the fire return period increase, the grazing increase, the seed dispersal caused by animals, the role of wind direction and plant type competition. The model is able to reproduce the encroachment that has occurred in SNWR, simulating an increase of the shrub from 2% in 1860 to the current shrub percentage, 42%, and highlighting among the most influential factors the reduced fire frequency and the increased grazing intensity.

A GIS-Based Irregular Cellular Automata Model of Land-Use Change

2007 ◽  
Vol 34 (4) ◽  
pp. 708-724 ◽  
Author(s):  
Daniel Stevens ◽  
Suzana Dragićević
Keyword(s):  
Land Use ◽  
Cellular Automata ◽  
Land Use Change ◽  
Spatial Data ◽  
Cellular Automata Model ◽  
Population Growth Rates ◽  
Asynchronous Development ◽  
Canadian City ◽  
Ca Model ◽  
Developing Area

This study proposes an alternative cellular automata (CA) model, which relaxes the traditional CA regular square grid and synchronous growth, and is designed for representations of land-use change in rural-urban fringe settings. The model uses high-resolution spatial data in the form of irregularly sized and shaped land parcels, and incorporates synchronous and asynchronous development in order to model more realistically land-use change at the land parcel scale. The model allows urban planners and other stakeholders to evaluate how different subdivision designs will influence development under varying population growth rates and buyer preferences. A model prototype has been developed in a common desktop GIS and applied to a rapidly developing area of a midsized Canadian city.

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