Assessing Hydrological Connectivity Mitigated by Reservoirs, Vegetation Cover, and Climate in Yan River Watershed on the Loess Plateau, China: The Network Approach

A new framework combining hydrological connectivity metrics and morphological spatial pattern analysis for the hydrological connectivity evaluation of wetlands

The quantitative evaluation of wetland hydrological connectivity is essential to the hydrological connectivity restoration-oriented ecological conservation and environmental management of wetlands. We proposed a framework to evaluate wetland hydrological connectivity with a combination of hydrological connectivity metrics and morphological spatial pattern analysis and recognized potential sites and links that had been generally overlooked in previous studies. Variations in hydrological connectivity revealed a decreasing trend followed by a gradual recovery from the critical time node of 2005 in Baiyangdian Lake. The core, one of the most important landscape types, played a dominant role in maintaining wetland hydrological connectivity at both temporal and spatial scales, and its variations matched those of hydrological connectivity. More importantly, we redressed the conventional ignorance of peripheral patches and links and recognized their importance in improving the hydrological connectivity of wetlands. The proposed framework provides an effective and practical tool for the hydrological connectivity evaluation of wetlands, expanding new insights into maintaining the health and integrity of wetland ecosystems. Integr Environ Assess Manag 2022;00:1-15. © 2022 SETAC.

Land-use-mediated inconsistency of changes in the provision and delivery of soil erosion control services at the watershed scale

Soil erosion control services (SECSs) are the benefits delivered to people derived from preventing the negative impacts of soil erosion, such as avoiding the loss in soil productivity and preventing the damage to infrastructures such as dams and roads. SECS is derived from the functions of the ecosystems and is delivered to people through physical processes and social activities. The land-use change (LUC) reshapes the SECSs supply capacity, the SECS flow over the landscape, and the related benefit people received. Numerous studies have revealed how LUC shapes the SECSs supply capacity. However, the SECSs flow to local communities, and the LUC-derived SECS flow dynamics remain unclear. This study quantified the SECSs delivered to local communities following a land-use-specific cascade mechanism and using the WATEM/SEDEM framework. The effects of on-site soil erosion and sediment delivery over the watershed were combined. The cultivated lands were considered as the conveyers of SECSs. The study revealed the inconsistency of temporal change in SECS provision and the actual SECSs delivery to local communities. The results illustrated the increased capacity for soil erosion prevention and sediment flow reduction and a consequent increase in SECS supply capacity. However, the total amount of actual SECSs delivered to the local communities was declined due to the land-use change featured in reduced cropland area. The results imply that changes in SECS provision capacity cannot directly indicate the changes in SECS delivery to local communities. Though the modeled SECSs did not cover all SECSs in this region, this study highlights the effectiveness of the land-use-specific cascade framework in describing the delivery of SECSs and the importance of addressing the delivery processes of ecosystem services from ecosystem to people.

Spatiotemporal Evolution of Wetland Eco-Hydrological Connectivity in the Poyang Lake Area Based on Long Time-Series Remote Sensing Images

Hydrological connectivity is important for maintaining the stability and function of wetland ecosystems. Small-scale hydrological connectivity restricts large-scale hydrological cycle processes. However, long-term evolutionary studies and quantitative evaluation of the hydrological connectivity of wetlands in the Poyang Lake area have not been sufficiently conducted. In this study, we collected 21 Landsat remote sensing images and extracted land use data from 1989 to 2020, introducing a morphological spatial pattern analysis model to assess the wetland hydrological connectivity. A comprehensive method for evaluating the hydrological connectivity of wetlands was established and applied to the Poyang Lake area. The results showed that, over the course of 31 years, the wetland landscape in the Poyang Lake area changed dramatically, and the wetland area has generally shown a decreasing and then increasing trend, among which the core wetland plays a dominant role in the hydrological connectivity of the Poyang Lake area. In addition, the hydrological connectivity decreases as the core wetland area decreases. From 1989 to 2005, the landscape in the Poyang Lake area focused mainly on the transition from wetland to non-wetland. From 2005 to 2020, the conversion of wetland landscape types shows a clear reversal compared to the previous period, showing a predominant shift from non-wetland to wetland landscapes. The eco-hydrological connectivity of the wetlands in the Poyang Lake area from 1989 to 2020 first decreased, and then increased after 2005. In the early stage of the study (1989−2005), we found that the connectivity of 0.3444 in 2005 was the lowest value in the study period. A resolution of 30 m and an edge effect width of 60 m were optimal for studying the hydrological connectivity of wetlands in the Poyang Lake area. The main drivers of the changes in hydrological connectivity were precipitation and the construction of large-scale water conservation projects, as well as changes in land use. This study provides a good basis for assessing hydrological connectivity in a meaningful way, and is expected to provide new insights for maintaining and restoring biodiversity and related ecosystem services in the Poyang Lake area.