Spatial analysis of Deschampsia antarctica and environmental factors in King George Island, Antarctica

Abstract

ABSTRACT

The extremely cold and infertile Antarctica is one of the harshest ecosystems for the growth of terrestrial vegetation, but the simple terrestrial ecosystem provides a suitable opportunity for studying species distribution pattern and dynamics in relation to environmental gradient. Deschampsia antarctica Desv. (Poaceae) is one of the two species of vascular plants native to Antarctica. Despite of harsh condition of maritime Antarctica in the forms of cold temperature, high UV radiation, strong wind and seawater spray, several studies have documented that the distribution of D. antarctica expanded with increases in temperature and lengthening of the growing season. This grass is attracting researchers attention as a useful bio-indicator of climate change in sub-Antarctica and its survival ability under diverse extreme environmental stress. I applied several geostatistic methods and regression model including spatial effect to analyze the spatial patterns and relations between the abundance of D. antarctica and environmental variables. Most variables showed a severe anisotropic characteristic. Soil texture and moss cover were spatially correlated with elevation and electric conductivity was influenced by the distance from the shoreline. Geostatistic results showed that topographic characteristics might more directly influence the soil chemical and physical attributes in maritime Antarctica than in the temperate zone because the Antarctic area has fewer interference factors such as dense vegetation and thick topsoil. The results of spatial regression models presented that moss cover has positive association with the distribution of D. antarctica significantly. Moss could positive effect on growing the grass by maintaining optimal soil water content and nutrient. Soil water content was another important environmental variable that affects the abundance of D. antarctica. Even if the supplement of stable water is essential for survival of D. antarctica, the frequent soil saturation with melting snow was not suitable for growing this grass by blocking root respiration. In addition, I could speculate that early snow melting is a critical factor governing organic matter accumulation and nutrition availability in King George Island. I examined the effect of diverse environmental factors on the survival of D. antarctica on King George Island by using Bayesian statistical methods. When comparing the density of the grass between 2 sites for three years, one of sites (site 2) severely decreased its density. Although site 2 showed the adequate soil nutrition condition for growth of plant, its poor drainage and low soil pH may affected the survival of D. antarctica by altering nutrition availability and inhibiting root respiration. Bayesian regression models suggested that seabirds and mammals might have greatly influenced the distribution of the grass in King George Island by transferring nutrients from the sea into land. Lastly, I investigated the oxidative damage and changes in antioxidant substances in response to cold and flooding stress. This indoor experiment indicated that root flooding may lead to the overproduction of reactive oxygen species in D. antarctica, causing damage to the growth and metabolism. Especially, when plant experience whole plant anoxia, total soluble sugars and chlorophyll were rapidly decreased on account of a blockage of photosynthesis and cellular respiration, which could negatively influence the survival of D. antarctica under the harsh polar environmental conditions.

Keywords: Deschampsia antarctica, maritime Antarctica, Bayesian statistics, geostatistics, spatial analysis, flooding stress,

Student number: 2008-30105