Environmental assessment of water, sediment and plants in the Mankyeong River, ROK

Assessing the interlinkage of green and blue water in an arid catchment in Northwest China

Water resource assessment is crucial for human well-being and ecosystem health. Assessments considering both blue and green water are of great significance, as green water plays a critical but often ignored role in the terrestrial ecosystem, especially in arid and semi-arid regions. Many approaches have been developed for green and blue water valuation; however, few approaches consider the interrelationship between green and blue water. This study proposed a new framework for green and blue water assessment by considering the interactions between green and blue water and the connections between human and natural ecosystems in an arid endorheic river basin where hydrological cycling is dramatically altered by human activities. The results show that even though green water is the dominant water resource, blue water is also critical. Most of the blue water is redirected back into the soil through physical and human-induced processes to meet the water demand of the ecosystem. The blue and green water regimes are found to be totally different in different ecosystems due to the temporal and spatial variability in water supply and consumption. We also found that humans are using an increasing proportion of water, resulting in decreasing water availability. Extensive water use by humans reduces the water availability for the natural ecosystem. Approximately 38.6% of the vegetation-covered area, which is dominated by farmland and forest, may face a moderate or high risk of increased conflict and tension over freshwater. This study provides crucial information to better understand the interactions between green and blue water and the relations between humans and nature by explicitly assessing water resources. It also provides crucial information for water management strategies that aim to balance humankind and nature.

Historical changes in the major and trace elements in the sedimentary records of Lake Qinghai, Qinghai-Tibet Plateau: implications for anthropogenic activities

Sediment sequences in Lake Qinghai spanning the past 100 years were explored to assess the effects of changes in local land desertification, dust input and agriculture on sediment deposition in different parts of Lake Qinghai. Three short sediment cores (QH01, QH02, QH07) were collected from the main lake and one sediment core (Z04) from a sublake (Lake Gahai) of Lake Qinghai, China, during 2012 and 2013. The concentrations of Fe, Mn, Al, Rb, Ti, Ca, and Sr were analysed to determine the effects of historical and regional anthropogenic activities in the Lake Qinghai catchment from 1910 to 2010. The elemental concentrations in the sediment cores ranged from 1.85 to 2.79% for Fe, 397 to 608 μg/g for Mn, 3.04 to 5.64% for Al, 13.5 to 19.7 μg/g for Rb, 0.171 to 0.268% for Ti, 9.43 to 13.9% for Ca, 652 to 1020 μg/g for Sr, and 0.049 to 0.075% for P. Good correlations were found between the concentrations of Fe, Mn, Al, and Rb, and the Ti/Al ratios in the sediments suggest that these elements share a similar source. The enrichment factors (EFs) of Ti [EF(Ti)] and P [EF(P)] in each core were utilized to reflect variations in anthropogenic activities from 1950 to 2010. EF(Ti) ranged from 1 to 1.17 in QH01 and QH02, reflecting the variation of land desertification areas in the Buha River catchment from 1950 to 2010. The EF(Ti) showed positive linear correlations with the variation in cropland area in Gangcha County, suggesting that agricultural activity in the Quanji River and Shaliu River catchments was enhanced from 1950 to 2010. The sediment records showed similar biogeochemical changes in most lakes and bays in China, indicating that the intensity of changes in anthropogenic activities was caused by national policy enforcement from the 1950s to 2010. EF(Ti) can serve as a tracer for anthropogenic activities in Lake Qinghai, with the anthropogenic activities in different parts of the Lake Qinghai catchment represented in the homologous sediments from parts of Lake Qinghai over the past 100 years. The variation of EF(P) increased from 1 to 1.55 from deep layer to upper layer in all sediment cores, reflecting the increased fertilizer input and tourism activity from 1980 to 2010, a period during which the lake was evolved into a eutrophic lake.

Association Between the Success of an Invasive Macrophyte, Environmental Variables and Abundance of a Competing Native Macrophyte

The success of invasive species depends on the overcoming of abiotic and biotic filters. Abiotic variables likely have greater relative importance over invasion at broad spatial scales, while biotic interactions are more important at fine spatial scales. In this study, we tested the hypotheses that (i) the abundance of the invasive Hydrilla verticillata is more correlated with abiotic factors than with competing native species at broad spatial grain; and that (ii) H. verticillata abundance is more correlated with competing native species than with abiotic factors at fine spatial grain. Here, we considered spatial scale as the grain size (i.e., the extent of sampling unit) assuming broad spatial scales as a large area encompassing the entire patches of macrophytes, and fine spatial scales as a small area inside one macrophyte patch. We collected the abundance of hydrilla and the competing native species along with environmental variables in a large subtropical reservoir. To evaluate how the relative importance of the abiotic factors and the competing native species vary between spatial grains we used Bayesian Generalized Linear Models. At broad grain, the abundance of the competing native species, maximum fetch (positive correlation), turbidity and conductivity (negative correlation) were the most important factors to explain the hydrilla abundance. At fine grain, alkalinity, total organic matter of the sediment and the abundance of a competitive native species (all negative correlations) were the most important variables. Our results indicate a greater importance of abiotic factors at broader grains while competitive interactions seem to be important only in the finer spatial grains. Environmental heterogeneity may explain the positive correlation between native and invasive abundances at broad grain, while the negative correlation at fine grain suggests the effect of competition. In synthesis, we show that the abiotic factors that explain the invasion success of a submerged invasive macrophyte are the same in two spatial grains, but the importance of biotic interactions changed with grain. Thus, our data suggest that models that attempt to explain the success of invasive plants, should consider spatial scales.