Identification and scoring of conservation gaps in wetlands of China's coastal provinces: Implications for extending protected areas.

Wetlands in China's coastal provinces are strategically positioned along migratory flyways for waterbirds, serving as essential habitats and stopover sites due to the expansive land area and abundant wetland resources they offer. This study aimed to introduce a simplified index system to enable rapid assessment and prioritization of unprotected areas for wetlands in China's coastal provinces. A spatial analysis was conducted, combining wetland distribution and existing protected areas data and spatial extent of wetlands extracted by remote sensing data. Results indicate substantial gaps in coverage, covering an area of 108.33 × 104 ha, with 76% being natural wetlands. Over half of these gaps are identified as high-value wetlands with significant ecological functions. The uneven distribution of unprotected wetlands reflects a tension between economic development and wetland conservation. Our findings support the expansion of the existing coastal wetland protected areas' coverage, as well as protecting critical habitats in conservation gaps, and establishing of a network-based waterbird protection system. This research contributes to informed decision-making and policy in wetlands' conservation planning.

Water use conflict between wetland and agriculture.

To analyze the water use conflict and its driving factors between wetland and agriculture at both regional and local scales, agricultural water consumption and wetland water storage changes in the Sanjiang Plain, the main grain-producing area in Heilongjiang Province of Amur River Basin, were investigated based on statistical data, field survey and GIS calculation. A specific case study in the Qixing River National Nature Reserve (QNNR) wetland-farmland system was completed using a water balance approach. Results showed that the proportion of agricultural water increased from 71.8% to 88.0% while that of ecological water only hovered around approximately 1% in Heilongjiang Province during 2004-2015. Due to wetland loss and degradation, the total surface water storage in the Sanjiang Plain wetlands decreased from 14.46 × 109 t in the 1980s to 4.70 × 109 t in 2010. Agricultural development in successive years, and the dramatic increased requirement for water in paddy fields, intensified the water use conflict between wetlands in the QNNR and surrounding farmlands. Groundwater extraction for irrigation was approximately twice as high as the total infiltration recharge from wetlands and farmlands. It is concluded that the degraded natural water resource endowments are struggle to sustainably support stable grain production as a mainstay of national food safety, which determined the competitive relationship between wetland and agriculture. To mitigate this conflict, adaptive wetland (e.g. water transfer at stagger time, precise water recharge, resourced meltwater) and agricultural techniques (e.g. water-saving irrigation and planting, soil water capacity increment, rainfed agriculture) and five key management solutions were recommended.

Spatiotemporal variation in vegetation spring phenology and its response to climate change in freshwater marshes of Northeast China.

Understanding wetland vegetation phenology and its response to climate change is important to predict the changes of wetland vegetation in wetland regions. Using the NDVI and climate data, this work studied the spatiotemporal change of start date of vegetation growing season (SOS) and explored the possible effects of climate change on the SOS over freshwater marshes of Northeast China. The results showed that the SOS significantly advanced by 0.52 day per year throughout the freshwater marshes of Northeast China during 2001 to 2016. The significant advancing of SOS was mainly concentrated in freshwater marshes of the Khingan Mountains (the Greater Khingan Mountains and the Lesser Khingan Mountains) and central arid or semi-arid regions (Songnen plain and Liaohe plain) in Northeast China. By contrast, there were weak delay trends of SOS in freshwater marshes of Eastern Inner Mongolia region, and Sanjiang plain. We found that precipitation was a dominant factor determining the SOS in arid or semi-arid regions (Songnen plain and Liaohe plain), while temperature played a bigger role in determining the SOS in Sanjiang plain and three cold mountains of the Northeast China. During the study period, increasing precipitation in the winter and spring contributed to advancing SOS in Songnen plain and Liaohe plain; the decrease of temperature from December to April explain the delaying SOS in freshwater marshes of Sanjiang Plain; the weak warming of temperature between November and May account for the advancing SOS of freshwater marshes in three cold mountains. In freshwater marshes of cold and the most arid region of Northeast China (Eastern Inner Mongolia), the SOS was influenced by both precipitation and temperature. Decreasing precipitation between January and April, as well as temperature decreases in March and April explain the delay of SOS in freshwater marshes of Eastern Inner Mongolia region.

Niche modelling of marsh plants based on occurrence and abundance data.

The information of species' response (optimum or critical limits along environmental gradients) is a key to understanding ecological questions and to design management plans. A large number of plots (762) from 70 transects of 13 wetland sites in Northeast China were sampled along flooding gradient from marsh to wet meadow. Species response (abundance and occurrence) to flooding were modelled with Generalized Additive Models for 21 dominant plant species. We found that 20 of 21 species showed a significant response to flooding for the occurrence and abundance models, and four types of response were found: monotonically increasing, monotonically decreasing, skewed unimodal and symmetric unimodal. The species with monotonically increasing response have the deepest flooding optimum and widest niche width, followed by those with unimodal curve, and the monotonically decreasing ones have the smallest values. The optima and niche width (whether based on occurrence or abundance models) both significantly correlated with the frequency, but not with mean abundance. Abundance models outperformed occurrence models based on goodness of fit. The abundance models predicted a rather sharp shift from dominance of helophytes (Carex pseudo-curaica and C. lasiocarpa) to wet meadow species (Calamagrostis angustifolia and Carex appendiculata) if water levels drop from about 10cm above soil surface to below the surface. The defined optima and niche width based on the abundance models can be applied to better instruct restoration management. Given the time required to collect abundance data, an efficient strategy could be to monitor occurrence in many plots and abundance in a subset of these.

[Influence of land use change on dissolved organic carbon export in Naoli River watershed. Northeast China].

The present study was conducted to evaluate the influence of land use change on dissolved organic carbon (DOC) export in Naoli River watershed, Northeast China. Seasonal variation of DOC concentrations of the river water and its relationship with land use in the whole watershed and 100 m riparian zone at the annual average scale were analyzed using the method of field sampling, laboratory analysis, GIS and statistics analysis. The results showed that the concentrations of DOC under base flow conditions in spring and summer were significantly higher than that in fall in the study watershed. The seasonal trend of DOC concentrations in wetland-watersheds was similar to that in all the sub-watersheds, while significantly different from that in non-wetland watersheds. On the annual average scale, percentage of wetland in the whole watershed and paddy field in the 100 m riparian zone had positive relationship with the DOC concentration in the river water, while percentage of forest in the whole watershed had negative relationship with it (P < 0.05). It indicated that wetland in the sub-watershed played a significant role in the seasonal variation of DOC in river water of Naoli River watershed. Wetland in the watershed and paddy field in the 100 m riparian zone significantly promoted DOC export, while forest alleviated it. Land use change in the watershed in the past few decades dramatically changed the DOC balance of river water.