Background: With the increasing fragmentation of landscape induced by rapid urbanization, the construction of ecological networks is of great significance to alleviate the degradation of urban habitats and protect natural environments. However, there is considerable uncertainty when constructing ecological networks, especially the different approaches to selecting ecological sources. We used the southern Chinese city of Shenzhen as a study area to construct and optimize ecological networks using a coupling approach. Ecological source areas were extracted using morphological spatial pattern analysis (MSPA) and the landscape index method. Ecological networks were constructed using the minimal cumulative resistance (MCR) model and the gravity model. Stepping stones and ecological fault points were added in corridors to optimize the ecological network. Results: Ten core areas with maximum importance patch values were extracted by the landscape index method as ecological source areas according to MSPA, after which corridors between ecological sources were constructed based on the MCR model. The constructed ecological networks were optimized using 35 stepping stones and 17 ecological fault points. The optimized ecological networks included 11 important corridors, 34 general corridors, and seven potential corridors. The results of corridor landscape-type analysis showed that a suitable ecological corridor is 60 to 200 m wide. Conclusions: Overall, our results imply that ecological source areas can be identified virtually, and that ecological networks can be significantly optimized by combining MSPA and MCR models. These results provide a methodological reference for constructing ecological networks, and they will be useful for urban planning and biodiversity protection in Shenzhen and other similar regions around the world.

The rapid development of urbanization has caused many ecological issues and greatly threatened the sustainable development of human society. The construction of ecological security patterns (ESPs) offers an effective way to balance ecological conservation and urbanization. This study aimed to take the highly urbanized city of Shenzhen, China, as a study area to construct an urban ESP and put forward suggestions for the urban development of ecological security. Ecological sources were identified through the Habitat Quality module in the InVEST model, and ecological corridors, strategic ecological nodes, and stepping-stone patches were extracted based on the minimum cumulative resistance (MCR) model. These elements together constituted the ESP. In particular, with the results of the continuous decline in the overall habitat quality, this study identified ten ecological sources with superior habitat quality, mainly distributed in rural woodlands, in urban green land, and in forest park patches. An optimized pattern for Shenzhen City with one axis, three belts, and four zones is proposed, with the study area divided into an ecological preservation zone, a limited development zone, an optimized development zone, and a key development zone. Moreover, forty-five ecological corridors were extracted and graded into three levels, presenting a spatial pattern of one axis and three belts. The appropriate widths of these ecological corridors were suggested to be between 30 and 60 m in Shenzhen City. In addition, we identified twenty-five ecological nodes, sixteen ecological fracture points, and sixteen stepping stones to improve the maintenance and construction of the ecological corridor network. More generally, this study demonstrates a scientific approach to identifying ESPs based on habitat quality, and can serve as a reference for the planning of urban ecological function regionalization.

Predicted intensified climate warming will likely alter the ecosystem net carbon (C) uptake of the Qinghai–Tibetan Plateau (QTP). Variations in C sink–source responses to climate warming have been linked to water availability; however, the mechanisms by which net C uptake responds to soil water content in saturated swamp meadow ecosystems remain unclear. To explore how soil moisture and other environmental drivers modulate net C uptake in the QTP, field measurements were conducted using the eddy covariance technique in 2014, 2015, 2017, and 2018. The alpine swamp meadow presented in this study was a persistent and strong C sink of CO₂ (−168.0 ± 62.5 g C m⁻² yr⁻¹, average ± standard deviation) across the entire 4-year study period. A random forest machine-learning analysis suggested that the diurnal and seasonal variations of net ecosystem exchange (NEE) and gross primary productivity (GPP) were regulated by temperature and net radiation. Ecosystem respiration (Re), however, was found mainly regulated by the variability of soil water content (SWC) at different temporal aggregations, followed by temperature, the second contributing driver. We further explored how Re is controlled by nearly saturated soil moisture and temperature comparing two different periods featuring almost identical temperatures and significant differences on SWC and vice versa. Our data suggest that, despite the relatively abundant water supply, periods with a substantial decrease in SWC or increase in temperature produced higher Re and therefore weakened the C sink strength. Our results reveal that nearly saturated soil conditions during the growing seasons can help maintain lower ecosystem respiration rates and thus enhance the overall C sequestration capacity in this alpine swamp meadow. We argue that soil respiration and subsequent ecosystem C sink magnitude in alpine swamp meadows could likely be affected by future changes in soil hydrological conditions caused by permafrost degradation or accelerated thawing–freezing cycling due to climate warming.

Southwest China is an ecologically fragile area with a high proportion of karstland and large variations in terrain, and it can be greatly affected by land use change. From 2000 to 2020, with the acceleration of urbanization in the whole country, the macro-scale Grain-for-Green Program (GFGP) has been developed in the karstland of southwest China. This has resulted in the expansion of forest and construction land with a reduction in cultivated land. The response of ecosystem services (ESs) to these changes needs to be investigated. However, there is a lack of in-depth analysis of the karstland of southwest China, and current studies mostly focus on the spatio-temporal variation in individual ESs or how the whole land use change affects ESs. Thus, our study uses an InVEST model and geographically and temporally weighted regression (GTWR) to examine the spatio-temporal variation in land use associated with four ESs, namely water conservancy (WC), soil conservancy (SC), carbon sequestration (CS), and habitat quality (HQ). We found that the GFGP area first increased and then decreased, aggregating to 4.48 × 10⁴ km² from 2000 to 2020. We also observed that from 2000 to 2020, ESs remained stable or gradually increased (despite fluctuations), SC was the most stable, whereas WC, CS, and HQ first decreased and then fluctuated more. This may be related to the destruction of topsoil in the early stages of the GFGP and the relatively weak ES supply capacity of the young trees. Moreover, the response of ecosystem services to the GFGP was spatially heterogeneous, suggesting a strong driving influence of the local environment, mainly caused by the distribution of karstland and terrain, differentiated urbanization levels, and the intensity of the GFGP. Specifically, the relatively significantly positive effects of WC, SC, and CS were found in western and northern cities, and so was the HQ in southeastern cities. On the contrary, the negative impacts of urbanization were found to weaken over time, suggesting the trade-off effect of the GFGP. Our findings would contribute to the development of effective forest management strategies and provide valuable insights for policymakers and stakeholders involved in ecosystem restoration and conservation efforts by exploring the impacts of the GFGP and urbanization on ESs.