Qiongzhuea tumidinoda stands out as an endemic bamboo species of significant conservation importance in Southwest China, particularly in the upper reaches of the Yangtze River. It holds a pivotal role in poverty alleviation through the commercialization of its wood and bamboo shoots. However, the suitable area of this species is undergoing rapid changes due to climate change, resulting in species redistribution and potential losses for bamboo farmers. We utilized 209 presence records and 25 environmental variables from 1987 to 2012 to predict the potentially suitable habitats for Q. tumidinoda using MaxEnt (version 3.4.1), ArcGIS (version 10.8.2), and R (4.3.3). We rigorously screened the recorded data for reliability and accuracy through expert consultations and observer interviews. We performed pre-processing to select the variables with high contributions for modeling, and 11 variables were selected for the final modeling. Our findings reveal that the top three most influential variables associated with Q. tumidinoda’s distribution were the mean monthly potential evapotranspiration (Pet), annual range of air temperatures (Bio7), and mean diurnal air temperature range (Bio2), and the rates of contributions from 1987 to 2012 were 4.8333, 3.5833, and 1.7000. There was a southeastward shift and an elevation increase in the potentially suitable habitats for Q. tumidinoda. The area of potentially suitable habitats in the study region exhibited fluctuating growth, expanding from 3063.42 km² to 7054.38 km². The mean monthly potential evapotranspiration (Pet) emerged as a critical determinant shaping the distribution of potentially suitable habitats for Q. tumidinoda. Our study sheds light on the response of Q. tumidinoda to climate change, offering valuable insights for the development and management of plantation industries associated with this species. In the future, to enhance prediction accuracy, researchers could equally consider both organic and inorganic environmental variables. For better preservation of environment and development, Q. tumidinoda could be introduced into nature restoration projects in areas with a suitable habitat or as a commodity that participates in forest carbon sink trading.

Objectives: Bamboo is a globally significant plant with ecological, environmental, and economic bene-fits. Choosing suitable native tree species for mixed planting in bamboo forests is an effective measure for achieving both ecological and economic benefits of bamboo forests. However, little is currently known about the impact of bamboo forests on nitrogen cycling and utilization efficiency after mixing with other tree species. Therefore, our study aims to compare the nitrogen cycling in pure bamboo forests with that in mixed forests.Methods: Through field experiments, we investigated pure Qiongzhuea tumidinoda forests and Q. tumidinoda-Phellodendron chinense mixed forests, and utilized ¹⁵N tracing technology to explore the fertilization effects and fate of urea-¹⁵N in different forest stands.Results: The results demonstrated the following: 1) in both forest stands, bamboo culms account for the highest biomass percentage (42.99%-51.86%), while the leaves exhibited the highest nitrogen concentration and total nitrogen uptake (39.25%-44.52%/29.51%-33.21%, respectively) Additionally, the average nitrogen uptake rate of one-year-old bamboo is higher (0.25 mg kg^-1 a^-1) compared to other age groups. 2) the urea-¹⁵N absorption in mixed forests (1066.51–1141.61 g ha^-1, including 949.65–1000.07 g ha^-1 for bamboo and 116.86–141.54 g ha^-1 for trees) was significantly higher than that in pure forests (663.93–727.62 g ha^-1, P<0.05). Additionally, the ¹⁵N recovery efficiency of culms, branches, leaves, stumps, and stump roots in mixed forests was significantly higher than that in pure forests, with increases of 43.14%, 69.09%, 36.84%, 51.63%, 69.18%, 34.60%, and 26.89%, respectively. 3) the recovery efficiency of urea-¹⁵N in mixed forests (45.81%, comprising 40.43% for bamboo and 5.38% for trees) and the residual urea-¹⁵N recovery rate in the 0–60 cm soil layer (23.46%) are significantly higher compared to those in pure forests (28.61%/18.89%). This could be attributed to the nitrogen losses in mixed forests (30.73%, including losses from ammonia volatilization, runoff, leaching, and nitrification-denitrification) being significantly lower than those in pure forests (52.50%).Conclusion: These findings suggest that compared to pure bamboo forests, bamboo in mixed forests exhibits higher nitrogen recovery efficiency, particularly with one-year-old bamboo playing a crucial role.

Introduction: The effects of potassium fertilization on the quality of Qiongzhuea tumidinoda shoots and soil nutrients were investigated by using a completely randomized block design with no fertilization as the blank control group (CK). In order to provide aiming to establish a theoretical foundation for optimizing cultivation practices and fertilization strategies in Q. tumidinoda forests. Methods: The effects of four different levels of potassium fertilizer application [K1 (75 kg/ha), K2 (150 kg/ha), K3 (225 kg/ha), K4 (300 kg/ha)] on different nutrients (ash, crude fiber, protein, crude fat, soluble sugar, starch) and amino acid content of Q. tumidinoda shoots and soil nutrient content were studied. Results: The application of potassium fertilizer significantly reduced the ash content of Q. tumidinoda shoots but had no significant effect on crude fiber content. However, it significantly influenced soluble sugar, starch, and protein levels, which exhibited an initial increase followed by a decrease. K3 treatment had the highest soluble sugar content, K2 treatment had the highest starch content, and K3 treatment had the lowest crude fat content. There was no significant difference in the content of essential amino acids between different treatments, but the application of potassium fertilizer significantly affected other amino acid components, especially significantly promoted the accumulation of umami amino acids and sweet amino acids, indicating that the application of potassium fertilizer improved the umami and sweet taste of Q. tumidinoda shoots. With the increase of potassium application rate, the contents of soil organic matter, total nitrogen and total potassium increased first and then decreased, while the content of total phosphorus increased continuously. In the 0~20 cm soil layer, the highest contents of soil organic matter, total nitrogen, total phosphorus, total potassium, hydrolyzed nitrogen, available phosphorus and available potassium were K2, K1, K4, K1, K2, K2 and K1 treatments, respectively. In the 20~40 cm soil layer, the highest contents of soil organic matter, total nitrogen, total phosphorus, total potassium, hydrolyzable nitrogen, available phosphorus and available potassium were K2, K1, K4, K2, K4, K3 and K1 treatments, respectively. Discussion: Appropriate application of potassium fertilizer can not only improve the nutritional quality of bamboo shoots, but also significantly improve the content of soil organic matter and nitrogen, phosphorus and potassium nutrients. The optimal application amount of potassium fertilizer in this study was K2 treatment, that is, 150 kg/ha.