Wetland plants are important components in constructed wetlands (CWs), and one of their most important functions in CWs is to purify the water. However, wetland plant litter can also increase eutrophication of water via decomposition and nutrient release, and few studies have focused on the interspecific variation in the decomposition rate and nutrient release of multiple plant species in CWs. Here a greenhouse litter-bag experiment was conducted to quantify the decomposition rates and nutrient release of 7 dominant macrophytes (2 floating plants and 5 emergent plants) in three types of water substrate. The results showed that plant litter species and growth forms significantly affected the litter mass losses. The nutrient release was significantly different among plant litter species, but not between floating and emergent plants. Litter traits, such as litter lignin, total nitrogen (TN) and total phosphorus (TP) can well predict the decomposition rates of submerged litter. These results indicated that submerging litter in water did not change the relationships between litter traits and litter decomposition rates, and leaching might play a more important role in the decomposition of submerged litter in CWs than that in other terrestrial ecosystems. These findings can provide suggestions for managers about the maintenance of constructed wetlands.

Global climate change and intensifying anthropogenic pressures pose unprecedented challenges to global biodiversity, with endangered species often experiencing particularly severe reductions in suitable habitats. In this study, we used the MaxEnt model to predict and evaluate the potential suitable habitats of Machilus nanmu in China under current and future climate scenarios. After parameter optimization (RM = 0.5, FC = LQH), the model showed excellent predictive performance, with a mean AUC of 0.946 and a CBI value of 0.988. The analysis of key environmental variables indicated that Mean UV-B of the High-est Month (Uvb3, 24.5% contribution), Temperature Seasonality (bio4, 19.6%), and Population Distribution (human_pd, 19.5%) were the dominant factors shaping habitat suitability, while Temperature Seasonality had the highest permutation importance (34.1%). Under current conditions, the highly suitable habitat area was estimated to be approximately 21,109.94 km², accounting for 0.22% of the total study area, and was mainly concentrated in the Sichuan Basin and the Yunnan-Guizhou Plateau. Under future climate scenarios, the highly suitable area of M. nanmu under the low-emission scenario (SSP1–2.6) showed an overall fluctuating trend, with an initial decline followed by a later expansion, resulting in an approximately 6.3% increase by the 2090s relative to the current period. In contrast, under the medium-emission scenario (SSP2–4.5), the highly suitable area also exhibited fluctuations but ultimately increased by approximately 3.9% by the 2090s. Centroid shift analysis further revealed an oscillatory east–west migration pattern of distribution centroids under SSP1–2.6, with a brief southwestward shift between the 2050s and 2070s, whereas under SSP2–4.5 the centroid trajectory was more complex: it first shifted westward and northward, then moved significantly southwestward, and finally turned eastward. These findings highlight the significant impacts of climate change on the suitable habitats of M. nanmu and provide a scientific basis for its conservation and sustainable management.