Sapling root ecological stoichiometric characteristics of dominant species in three forests in Yunnan, China, and their relationship with soil physicochemical factors

Abstract Question This study aimed to explore the nutrient‐cycling patterns, supply mechanisms and limiting characteristics of elements in saplings of tropical and subtropical forest ecosystems. Location Tropical seasonal rainforests, tropical montane rainforests and mid‐montane moist evergreen broad‐leaved forests in Yunnan, China. Methods We sampled sapling roots from 21 vascular plant species that are dominant in the upper and lower canopies of three forest types. We assessed stoichiometric contents of carbon (C), nitrogen (N) and phosphorus (P), and investigated their relationships with soil nutrients. Results The C content ranged from 449.67 to 483.00 mg/g in the roots of the dominant species, the N content ranged from 1.98 to 9.67 mg/g and the P content ranged from 0.32 to 0.53 mg/g. The C:N ratio was highest in the tropical seasonal rainforest, whereas the C:P and N:P ratios were highest in the tropical montane rainforest. The root average C:N and C:P ratios were higher than Chinese plant averages, which indicated that the forest ecosystems in southern Yunnan had higher absorption and utilization efficiency of C. The average N:P ratio was >12 and <14, which indicated that plant root growth was restricted by N and P availability. In the saplings of upper canopy species, the C:N ratio was higher, the C:P ratio was similar and N:P ratio was lower compared with those of lower canopy species. The N:P ratio in the upper canopy was <12, whereas that in the lower canopy was >14, which indicated that growth in the upper canopy was mainly N‐limited and growth in the lower canopy was mainly P‐limited. Nutrient absorption and utilization efficiency in the upper canopy was slightly higher than in the lower canopy. Conclusions The sapling roots of the dominant species in Yunnan had the characteristics of high C:N, high C:P and low N:P, and the growth and development of plants is mainly restricted by N and P availability. The C, N and P contents and their stoichiometric characteristics in roots were affected mainly by the soil P content. This study provides a scientific basis for further revealing the ecological strategies of plants in response to changes in the external environment.