Researchers at the Cold and Arid Regions Environmental and Engineering Research Institute of the Chinese Academy of Sciences found that the growth of Populus euphratica forest in the desert oasis of the Ejina Banner in the lower reaches of the Heihe River is restricted by elements such as nitrogen and phosphorus. Related results were recently published in the "China Desert" magazine.
Feng Qi, a researcher at the institute, said that the Ejina Banner Desert Oasis is one of the main distribution areas of natural Populus euphratica forests in China. In Ejina, the existing Populus euphratica forest is gradually declining: there are many old trees, few young trees, more disease, more health, less sparse forests and less jungles.
Through the study of the changes of chemical constituents such as carbon, nitrogen, phosphorus and potassium in the leaves of Populus euphratica in different months and different microhabitats of the growing season and the correlation between them, it is found that carbon is the most abundant dry matter in Populus euphratica. The main elements; nitrogen and phosphorus are the main limiting factors for the growth of Populus euphratica, which are related to important physiological activities such as photosynthesis and cell growth and division of Populus euphratica.
Feng Qi said that in the whole growth period of Populus euphratica, the carbon, nitrogen, phosphorus and potassium contents of the leaves showed a downward trend. The highest value appeared in May of each year, and the lowest value appeared in September of each year. "This is mainly because the middle of May coincides with the return to green, the temperature rises, the soil moisture condition is also good, and the plant accumulates nutrients at a faster rate. After entering the autumn, the Populus euphratica slowly enters the senescence and the yellowing stage, and the Populus euphratica leaves The level of nutrients is very low."
The researchers found that the growth rate of organic matter in Populus euphratica was faster in the early growing season, and then with the extension of the growing season, the leaves gradually matured, the rate of synthetic compounds slowed down, the decomposition rate increased, and the accumulation of organic matter gradually decreased. When the ratio of nitrogen to phosphorus in the leaves is less than 14, it indicates that plant growth is more restricted by nitrogen; when the ratio of nitrogen to phosphorus is greater than 16, it indicates that plant productivity is more strongly restricted by phosphorus; The relationship between the nitrogen and phosphorus elements is shown to be limited.
The study also confirmed that in the senescence process of Populus euphratica leaves, nutrient transfer reduced the nutrient loss caused by litter, and the low nutrient loss rate could make the Populus euphratica plant grow healthily and reduce the dependence of plants on soil nutrient absorption. This is especially important for Populus euphratica growing on the banks of poor deserts.
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