Seasonal variations in water uptake and transpiration for plants in a karst critical zone in China.

Despite substantial drought conditions in the karst critical zone (KCZ), the KCZ landscapes are often covered with forest woody plants. However, it is not well understood how these plants balance water supply and demand to survive in such a water-limited environment. This study investigated the water uptake and transpiration relationships of four coexisting woody species in a subtropical karst forest ecosystem using measurements of microclimate, soil moisture, stable isotopes (δ18O, δ2H, and δ13C), intrinsic water-use efficiency (WUEi), sap flow, and rooting depth. The focus was on identifying differences within- and between-species across soil- and rock-dominated habitats (SDH and RDH) during the rainy growing season (September 2017) and dry season (February 2018). Species across both habitats tended to have higher transpiration with lower WUEi during the rainy season and lower transpiration with higher WUEi during the dry season. Compared to those in the SDH, species in the RDH showed lower transpiration with higher WUEi in both seasons. The dominant water sources were soil water and rainwater for supporting rainy-season transpiration in the SDH and RDH, respectively, and groundwater was the main water source for supporting dry-season transpiration in both habitats. A clear ecohydrological niche differentiation was also revealed among species. Across both habitats, shallower-rooted species with higher soil-water uptake, compared to deeper-rooted species with higher groundwater uptake, showed higher transpiration and lower WUEi during the rainy season and vice versa during the dry season. This study provides integrated insights into how forest woody plants in the KCZ regulate transpiration and WUEi in response to drought stress through interactions with seasonal water sources in the environment.

The impact of ecotourism on ecosystem functioning along main rivers and tributaries: Implications for management and policy changes.

Tourism along river basins benefits both tourists and the economy, but its management necessitates trade-offs between nature-based recreation and ecological functioning. Despite ecosystem services being helpful in managing environmental challenges, there are limited data on the impact of tourism activities on ecosystem functioning across different river types globally. This study investigates how people's recreational activities and values affect ecosystem functioning in high-order rivers. The original field data were collected from 308 transects along the main river and tributaries of the Three Gorges Dam Reservoir in China during 2019. Kruskal-Wallis tests (p < 0.01) revealed that the ecosystem functioning indices were significantly higher than the recreational activity and value indices around the rivers and that ecosystem functioning was highest around tributaries. The critical variables of ecotourism activities and ecosystem functioning identified by principal component analysis accounted for 66.49% of the total variance. The Pearson correlation coefficient strengths among tourism and ecosystem functioning parameters were correlated mildly to moderately, but they exhibited positive and negative connections with a range of r = -0.27 to 0.37 (p < 0.05). Furthermore, the distribution patterns of these parameters that were determined by hierarchical cluster analysis were diverse for both the main river and its tributaries. The findings suggest that the development and enforcement of zoning may be necessary for the long-term use of natural resources by all sectors of society. Therefore, it is imperative to raise public awareness and urge governments to adopt more progressive ecotourism policies.

Nature-based tourism influences ecosystem functioning along waterways: Implications for conservation and management.

Nature-based tourism has an influence on ecosystem functioning around watercourses, but this influence lacks scientific evidence. Additionally, strategic and operational management of streams necessitates trade-offs between the recreational activities and values of tourists and riparian zone hospitality services. This paper aims to assist environmentalists and planners by exploring the effects of tourism-based recreational activities on ecosystem functioning along the drawdown zone. The study uses multivariate statistical techniques to delineate the relevant global tourism issues for planners. Kruskal-Wallis tests (p < 0.01) were conducted using quantitative data from 284 transects within the Three Gorges Dam Reservoir in China. The results revealed higher ecosystem function indices than tourism indices. Indicators of tourism contributed both positively and negatively to ecological indicators, with the Pearson correlation coefficients ranging from minor to moderate (r = ̶ 0.24 to 0.38, p < 0.05). Principal component analysis revealed that the critical variables of ecosystem functioning and tourism activities explained 72.26 % of the overall variance. Nevertheless, hierarchical cluster analysis revealed that these indicators responded differently in the upstream, midstream, and downstream sections. Our findings suggest that policymakers should consider the different characteristics of riparian zones in future planning, as doing so will improve both national and global strategic and operational management.

Environmental literacy affects riparian clean production near major waterways and tributaries.

Although environmental illiteracy threatens the functioning of landscapes throughout the world, it is frequently ignored. The traditional wisdom assumes that suspicions will evaporate when the public and government authorities are provided with new information. Despite significant efforts to enhance riparian corridor output, limited data are available on the effect of environmental literacy metrics (ELMs) on clean production elements (CPEs) across various streams (e.g., main rivers and tributaries) within impoundments. This study examined such effects within the China Three Gorges Dam Reservoir area (TGDRA) by collecting 336 transects that assessed the breadth of effects on 58,000 km2 in 2019. The network visualization revealed 7234 papers published over the last 121 years, each of which focused on themes such as plant cover, regeneration, exotics, erosion, habitat, and stressors. The bar graph showed that the general public lacked understanding of environmental literacy (e.g., knowledge, attitudes, and behavior), which influenced plant cover elements most in tributary zones but had little direct effect on regeneration. Locals' environmental literacy had the greatest impact on CPEs, with Pearson correlation coefficients ranging from -0.69

Tunneling-induced groundwater depletion limits long-term growth dynamics of forest trees.

Human interventions such as tunnel construction have caused groundwater depletion, which substantially affected the functions of forest tree species and their communities. However, the extent to which tunneling-induced groundwater depletion (TIGD) degrades their function levels at various spatial-temporal scales under varying climate conditions remains still unclear. Researchers used stand-scale dendrological records to track and extract the effects of TIGD associated with a single or series of tunneling events (three tunneling events during 1999-2001, 2006-2008, and 2010-2013) on short- and long-term growth levels of two dominant drought-tolerant tree species across (karst and non-karst) landscapes affected by tunnel construction and landscapes not subjected to tunnel construction in a mountainous forest ecosystem located in the southwest of China. The results showed that growth responses of both trees stand to TIGD, and the TIGD-linked water losses of other available water sources were negative and widespread across tunnel-affected landscapes, particularly in the karst landscapes known as delicate landscapes. Tree stands with faster (more vigorous) growth rates showed more significant adverse growth levels in response to either tunneling-induced or drought-induced water stresses. Also, they showed the highest recovered growth levels in response to favorable climatic conditions. Moreover, the growth level in the tunnel-affected forest never fully recovered during six years of very wet weather (2012-2018) after the construction of the final (third) tunnel in 2010-2013. Current research shows that tunnel construction has a cumulatively detrimental impact on the long-term survival of the forest. Even with the mediation of long-term very wet circumstances, it can substantially restrict the development dynamics of the forest compared to drought.