Effects of different warming patterns on nutrients and stoichiometric characteristics of spruce trees in alpine coniferous
The asymmetrical warming rate between day and night results in differences between the responses of plants to daytime and nighttime temperature changes.To deepen the understanding of the influential mechanisms of climate warming on plants at high altitudes,we investigated the differential responses of nutrients,including carbon(C),nitrogen(N),phosphorus(P),potassium(K),calcium(Ca),and magnesium(Mg),and their stoichiometric characteristics in roots and leaves of Picea asperata to daytime and nighttime warming in a southwestern subalpine region of China.Infrared radiation heating was used to increase the day and night temperatures.Additionally,a control group was used.Three main results were obtained.First,the morphological structure of roots and the nutrient content in P.asperata appeared to have modular characteristics.Specific root length and surface area,and contents of N,K,Ca,and Mg in lower-level roots(levels 1 and 2)were significantly higher than those in higher-level roots(levels 3-5).The contents of C,N,P,and K in leaves were significantly higher than those in roots.Moreover,the contents of N,P,K,and Mg in leaves were significantly increased by both daytime warming(respective increases of 17.58％,66.12％,11.00％,and 18.31％)and nighttime warming(respective increases of 37.12％,6.63％,29.50％,and 4.97％).However,the nutrient uptake and distribution responses in the roots were different.The contents of C,N,and P in all-level roots and K in higher-level roots were significantly increased by daytime warming(respective increases of 2.09％-2.69％,15.28％-69.87％,26.39％-86.26％,and 19.73％-32.28％),whereas the contents of Mg in all-level roots and K in lower-level roots were significantly decreased(respective decreases of 8.09％-19.68％and 14.98％-27.73％).In roots,nighttime warming significantly increased N content(9.70％-50.14％)and decreased C,P,K,and Mg contents(respective decreases of 4.85％-17.88％,5.27％-29.92％,16.52％-25.56％,and 4.99％-16.92％).Furthermore,the C:N and C:P ratios in the lower-level roots and leaves were higher than those in the higher-level roots,and their values were significantly reduced by daytime warming.Nighttime warming significantly decreased the C:N ratios in roots and leaves and the C:P ratios in lower-level roots but increased the C:P ratios in higher-level roots.Daytime and nighttime warming alleviated the limitations of N and P on plant growth to some extent.The effects of both daytime and nighttime warming should be considered in the study of forest ecosystems under global warming to accurately predict the impact of global warming on plant growth in high-altitude areas,considering the differing changes in the accumulation and distribution of different nutrients P.asperata by daytime and nighttime warming,and the differing influence of warming on the effect of nutrients on the mechanisms of plant growth.
daytime warmingnighttime warmingroot system classificationnutrientstoichiometric characteristics
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