Analysis of water quality influencing factors under multi-source data fusion based on PLS-SEM model: An example of East-Liao River in China

Owing to alterations in the environment and human activities, the quality of surface water is declining. Despite a substantial number of studies on the factors that impact water quality, there is still a need for a better understanding of the major causes of water quality degradation. This study fused multi-source data using partial least squares structural equation modeling to evaluate the effects of weather, soil composition, and geographical features on the water quality of the East Liao River (ELR), Jilin Province, China. The impacts of land-use practices on water quality at different buffer scales were analyzed. The most significant correlation between land use and water quality was observed at a distance of 4 km. The severity of water pollution was significantly influenced by soil type, with a path coefficient of 0.689 (p < 0.001). Conversely, landscape factors exhibited a notable adverse effect, indicated by a path coefficient of -0.608 (p < 0.001). Additionally, meteorological factors exhibited a significant impact, with a path coefficient of 0.463 (p < 0.001). The indirect effects of landscape elements on water quality were also examined. Water quality could be indirectly influenced by landscape through soil factors, as evidenced by a path coefficient of -0.572 (p < 0.01). In this study, new ideas for studying water quality drivers using multi-source data fusion are introduced. Managers can leverage the findings of this study to improve their decision-making and effectively address water quality issues in ELR located in Jilin Province, China.

Beyond conservation: Assessing broader development outcomes of protected areas in Nepal

Protected Areas (PAs) are set aside for biodiversity conservation but at the same time they are recognized for their role in supporting development goals. However, the benefits provided by PAs also come with costs to local people. Integrated Conservation and Development Projects (ICDPs) are a PA management approach that aim to maximize local benefits through enhancing conservation and development outcomes, while also reducing costs. We implemented a household level survey in two PAs in Nepal managed using an ICDP approach to assess local people's perceived benefits and costs and determine if this approach was achieving its intended outcomes. Since both PAs are popular nature-based tourism (NBT) destinations, respondents were asked questions specific to this activity and others more general to the PA. The coded qualitative responses revealed ten categories of benefits and twelve categories of costs. Most respondents perceived extraction benefits from PAs, and when asked to reflect specifically on NBT, they mostly identified economic benefits. Crop and livestock loss was the main perceived costs from PAs, whereas sociocultural costs were the main costs from NBT. Chi square tests showed that proximity to the PA office and residency status had the most significant differences in perceptions of benefits and costs from both PAs and NBT. People perceived very few benefits related to participation, cost mitigation, and conservation, which does not match the intended outcomes of ICDPs. Although there may be practical implications for engaging distant communities in management, this may help to enhance conservation and development outcomes from PAs.

Determining the main contributing factors to nutrient concentration in rivers in arid northwest China using partial least squares structural equation modeling

Understanding the main driving factors of oasis river nutrients in arid areas is important to identify the sources of water pollution and protect water resources. Twenty-seven sub-watersheds were selected in the lower oasis irrigated agricultural reaches of the Kaidu River watershed in arid Northwest China, divided into the site, riparian, and catchment buffer zones. Data on four sets of explanatory variables (topographic, soil, meteorological elements, and land use types) were collected. The relationships between explanatory variables and response variables (total phosphorus, TP and total nitrogen, TN) were analyzed by redundancy analysis (RDA). Partial least squares structural equation modeling (PLS-SEM) was used to quantify the relationship between explanatory as well as response variables and fit the path relationship among factors. The results showed that there were significant differences in the TP and TN concentrations at each sampling point. The catchment buffer exhibited the best explanatory power of the relationship between explanatory and response variables based on PLS-SEM. The effects of various land use types, meteorological elements (ME), soil, and topography in the catchment buffer were responsible for 54.3% of TP changes and for 68.5% of TN changes. Land use types, ME and soil were the main factors driving TP and TN changes, accounting for 95.56% and 94.84% of the total effects, respectively. The study provides a reference for river nutrients management in arid oases with irrigated agriculture and a scientific and targeted basis to mitigate water pollution and eutrophication of rivers in arid lands.

Multi-spatial scale effects of multidimensional landscape pattern on stream water nitrogen pollution in a subtropical agricultural watershed

Multidimensional (coupled land use, soil properties, and topography) landscape effects on stream water nitrogen (N) are complex and scale-dependent. However, studies that identify critical buffer zones that explain large variations in riverine N, and estimate specific thresholds of multidimensional landscape patterns at the class level, result in a sudden changes in riverine N pollution, are still limited. Here, a new multidimensional landscape metric that combined land use, soil properties, and topography effects was applied to various riparian buffer zones and sub-watershed scales, and their relationships to riverine N levels were investigated. We used stream water ammonium-N, nitrate-N, and total-N concentrations datasets, from 2010 to 2017, in the nine subtropical sub-watersheds in China. The results of model selection and model averaging in ordinary least squares regressions, indicated that the riparian buffer zone with widths of 400 m, had more pronounced influence on water NH₄-N and TN levels than at other scales. Within the 400 m buffer zone, the key landscape metrics for NH₄-N, NO₃-N and TN concentrations in stream water were different, and explained up to 43.35%-76.55% (adjusted R²) of the total variation in river N levels. When ENN_MN_Class17 below 39-56 m, PD_Class8 above 4.63-6.55 n/km², PLAND_Class27 above 23-29%, and CONTIG_MN_Class42 below 0.35-0.37% within the 400 m buffer zone, riverine NH₄-N and TN would be abruptly increased. This study provided practical ideas for regulation regarding landscape management linked to watershed structure, and identified reference thresholds for multidimensional landscape metrics, which should help reduce riverine N pollution in subtropical China.

Effectiveness of functional zones in National Nature Reserves for the protection of forest ecosystems in China

Protected areas (PAs) have been established worldwide to conserve biodiversity. However, the conservation effectiveness of different PA functional zones remains poorly understood. Here, we investigated National Nature Reserves (NNRs) in China to explore and quantify the conservation in their core, buffer, and experimental zones. We compared the area and proportion of forest loss for these functional zones during the period from 2001 to 2018. The results showed that the forest loss in NNRs showed a decreasing trend since 2011, indicating that NNRs reduced the forest loss. There was no significant difference of forest loss proportion (p = 0.42) between the core zones (0.60 ± 1.32%) and buffer zones (0.55 ± 0.88%), implying that their performance in forest conservation was similar. There was a significant difference between experimental and core zones as well as between experimental and buffer zones both in forest loss area and proportion (p ˂ 0.05). We confirmed that the proportion of functional zones significantly affects the conservation effectiveness, i.e., an improper proportion of core zones or buffer zones may lead to forest loss. Therefore, we suggest an optimal proportion of core and buffer zones at 30%-50% and 10%-40%, respectively. Overall, the effectiveness of functional zones in forest nature reserves was assessed on a national scale. The results of this study support the recent adjustment in the PA functional zoning system in China.

Characterizing land use effect on shallow groundwater contamination by using self-organizing map and buffer zone

Nitrate-nitrogen (NO₃-N) contamination in groundwater is a major problem of drinking and domestic waters in rural areas. This study revealed the influence of land use type on shallow alluvial groundwaters in a typical rural area in South Korea by applying a self-organizing map (SOM), principal component analysis (PCA), and hierarchical cluster analysis (HCA). The uncertainty of spatial information on land use was improved by using a buffer zone of the average influence radius of 32.65 m surrounding wells. Two major land-use types, forests (44.9%) and rice fields (28.8%), occupied a total of 73.7% of the rural area. The higher concentrations of NO₃-N in public facilities and livestock areas were demonstrated to directly recharge groundwater pollutants. NO₃-N contamination in rice paddies, which also contained chlorine (Cl) and sulfate (SO₄), was assessed according to the nutrients and residual salt in the soil. In addition, different NO₃-N concentrations for the same land use indicate various biochemical reactions and NO₃-N recharge types into the groundwater system. The shallow groundwaters in the study area were classified into three clusters according to their chemical constituents and land-use properties, especially NO₃-N concentration, including pH, Cl, and SO₄, using a SOM, PCA, and HCA. Unlike existing studies, we applied a buffer zone based on the Cooper-Jacob equation to obtain an improved SOM model prediction accuracy approximately 10% greater than that using the original dataset.

Plant Species Diversity of Plant Communities and Heavy Metal Accumulation in Buffer Zone of Momianhe Stream Along a Long-Term Mine Wastes Area, China

The species composition of eight shrub communities were investigated in order to understand the species diversity of plant communities in buffer zone and wetland of Momianhe stream along a long-term mine waste area, Lanping county, Yunnan province, China. Dominant plant species and soil samples were collected to analysis heavy metal (Cu, Zn, Pb and Cd) accumulation characteristics. The results showed that 100% samples for Zn, Pb, Cd, and 87.5% samples for Cu in the investigated area exceeded the Yunnan geochemical background value of the heavy metals in the soil. There were 36 plants species in communities, among which Epilobium pyrricholophum, Elsholtzia argyi, Artemisia vestita, Tripogon chinensis were the dominant species. Plant species, the number of individuals, Ecological Dominance (Do), Shannon-Wiener index (H'), Simpson diversity index (Dsi) and Pielou evenness index (Epi) were affected by Cd and Cu contents of the soil and sediment. Therefore, the results indicate that Cu and Cd contents and ecological risk in the process of long-term vegetation restoration of small catchment in lead-zinc mine waste area should pay more attention.

A modelling study of a buffer zone in abating heavy metal contamination from a gold mine of Hainan Province in nearby agricultural area

The establishment of new buffer zone in the mine areas lacks the basis of theoretical model. As a case study, this study presents the partition model of new buffer zone in a small-scale mine area located in the remote mountainous region of Hainan province, China. The investigation carried out by integration of geostatistical interpolation maps using unmanned aerial vehicle has revealed that As, Cd, Pb, Zn, and Hg are mainly distributed near the tailing ponds and the dressing plant, while Cr and Cu are prominent near the agricultural area. The partition model of buffer zone was established in accordance to the transport velocity of the liquid phase heavy metal in soil. The boundary line of buffer zone is integrated by comparing the 'predicted' heavy metal concentrations with the 'measured' heavy metal concentrations. Principal component analysis (PCA) and the variations of heavy metal concentrations with elevation, slope, and distance were performed to further evaluate the reliability of the predicted buffer zone, indicating that the new buffer zone has a significant effect on minimizing transport of heavy metals from the mining area into the agricultural land. This study is suggestive to provide risk control and sustainable development strategy for the ecosystem protection in mine areas.

Crop proximity index for monitoring of peri-urban land use in agro-industrial crop regions

The agro-industrial production of genetically modified organisms uses great amounts of pesticides, close to cities, which generates growing concern due to the numerous evidence of their negative effects on health and the environment. In a context of the lack, or inaccessibility, of official data on crop dynamics and pesticide use, environmental indicators using satellite data are needed for the proper monitoring of peri-urban areas. The objective of this research is to make a crop proximity index using satellite information to assess and monitor peri-urban agro-industrial activity. Twenty cities in Argentina and ten in the United States were selected. The CPI index is designed to evaluate a city and its peri-urban areas as a whole by taking account of the land uses and factors that can potentially influence the proximity to agro-industrial activity to the population living in those cities. Agriculture factor was weighted by proximity or remoteness using perimeter rings from the urban edge. All the necessary data for the calculation of the CPI index were obtained through the classification and processing of Sentinel 2 satellite images with software and the Google Earth Engine platform. The results show a worrying situation, 90% of cities in Argentina and 80% in the United States have a negative CPI. Most of the cities examined are extremely close to extensive areas of crops, that use a high amount of pesticides and which do not have the protection of trees or buffer zones.

Towards ecologically functional riparian zones: A meta-analysis to develop guidelines for protecting ecosystem functions and biodiversity in agricultural landscapes

Riparian zones contribute with biodiversity and ecosystem functions of fundamental importance for regulating flow and nutrient transport in waterways. However, agricultural land-use and physical changes made to improve crop productivity and yield have resulted in modified hydrology and displaced natural vegetation. The modification to the hydrology and natural vegetation have affected the biodiversity and many ecosystem functions provided by riparian zones. Here we review the literature to provide state-of-the-art recommendations for riparian zones in agricultural landscapes. We analysed all available publications since 1984 that have quantified services provided by riparian zones and use this information to recommend minimum buffer widths. We also analysed publications that gave buffer width recommendations to sustain different groups of organisms. We found that drainage size matters for nutrient and sediment removal, but also that a 3 m wide buffer zone acts as a basic nutrient filter. However, to maintain a high floral diversity, a 24 m buffer zone is required, while a 144 m buffer is needed to preserve bird diversity. Based on the analysis, we developed the concept of "Ecologically Functional Riparian Zones" (ERZ) and provide a step-by-step framework that managers can use to balance agricultural needs and environmental protection of waterways from negative impacts. By applying ERZ in already existing agricultural areas, we can better meet small targets and move towards the long-term goal of achieving a more functional land management and better environmental status of waterways.

Rice-paddy field acts as a buffer system to decrease the terrestrial characteristics of dissolved organic matter exported from a typical small agricultural watershed in the Three Gorges Reservoir Area, China

Agricultural watersheds are a crucial contributor of terrestrial dissolved organic matter (DOM) for the adjacent aquatic environment. Recently, ecological engineering of the buffer zone such as a rice-paddy field was established to reduce the export of nutrients and contaminants from a small agricultural watershed. However, the potential of the rice-paddy field to reduce the terrestrial signature of DOM is unclear. Therefore, two small agricultural sub-catchments (i.e., sub-1 and sub-2) with different land uses and hill slope angles in the Three Gorges Reservoir (TGR) area of China were studied from 2014 to 2015. The results showed that the terrestrial DOM signals are indicated by optical indices (SUVA₂₅₄, S_R, fluorescence index) in the steeper and more forest covered, but rice-paddy field buffered sub-catchment (i.e., sub-2) decreased significantly, as compared to the reference sub-catchment (i.e., sub-1). Regardless of seasonal variations, the rice-paddy field retained a buffering role to reduce the terrestrial property of DOM and the highest capacity was observed during the rice-growth period. However, during storm events, the differences of DOM properties for two sub-catchments were not significant, because the buffer system was weakened. Finally, environmental implications of the role of such a buffer zone in the TGR areas are discussed. These results demonstrate that rice-paddy fields are successful in mitigating the terrestrial property of exported DOM, but the weaker performance during storm events still needs to be considered.

Demographic pressure in Serra do Mar State Park and its buffer zone, southeastern Brazil

The Serra do Mar State Park forms a green corridor that connects significant remnants of the Atlantic Forest in Brazil, a region that presents great biodiversity. However, the mounting pressure exerted on it by disorderly urban expansion around conservation unit areas is a cause for concern. Thereby, this paper aims to analyze a geographical and demographic characterization of Serra do Mar State Park and its buffer zone in order to identify regions under the greatest pressure and provide subsidies for developing public policies. The study is based on a cartographic representation using a geographic information system associated with the 2010 Census demographic data, which has been conducted by the Brazilian Institute of Geography and Statistics (IBGE in Portuguese acronym). The study area covers the territory of 32 municipalities and it was found that almost 25,000 inhabitants live inside the park while approximately 712,000 residents live inside its buffer zone.

Effects of land use types on dissolved trace metal concentrations in the Le'an River Basin, China

Using land use types in multiple spatial scales (entire basin, buffer zones, and slopes) as well as statistical and spatial analysis, relationships between land use types and concentrations of dissolved trace metals were determined in the Le'an River Basin, China. The result showed that farmland and urban land were determined as the source of the pollutants, while forestland and grassland were identified as the sink of the pollutants. The temporal differences of relationships between land use types and concentrations of dissolved trace metals mainly due to the discrepancy of rainfall characteristics. Land use type close to river was a better indicator for the effectiveness of concentrations of trace metals, especially at scale of 0-200 m. Forestland and grassland on lower slopes greatly affected the water quality, and the former had no significant or weak influences on higher slopes. Urban land had the greater positive correlations with concentrations of dissolved trace metals on higher slopes, which are mainly due to frequent mining activity. Further analysis suggested that the buffer zones with low slope needed to be seriously taken into consideration for effective land use management in similar basin.

Pastoralism and wildlife: historical and current perspectives in the East African rangelands of Kenya and Tanzania

The relationship between pastoralists, their livestock, wildlife and the rangelands of East Africa is multi-directional, complex and long-standing. The tumultuous events of the past century, however, have rewritten the nature of this relationship, reshaping the landscapes that were created, and relied upon, by both pastoralists and wildlife. Presently, much of the interaction between wildlife and pastoralists takes place in and around protected areas, the most contentious occurring in pastoral lands surrounding national parks. In conservation terminology these areas are called buffer zones. In the past century buffer zones have been shaped by, and contributed to, restrictive conservation policies, expropriation of land, efforts to include communities in conservation, both positive and negative wildlife/livestock interactions, and political tensions. In this review paper, the authors outline the history that shaped the current relationship between pastoralists, livestock and wildlife in buffer zones in East Africa and highlight some of the broader issues that pastoralists (and pastoralism as an effective livelihood strategy) now face. Finally, they consider some of the sustainable and equitable practices that could be implemented to improve livelihoods and benefit wildlife and pastoralism alike.

Protected areas and agricultural expansion: Biodiversity conservation versus economic growth in the Southeast of Brazil

The conversion of natural ecosystems to agricultural land and urban areas plays a threat to the protected areas and the natural ecosystems conservation. The aim of this paper is to provide an analysis of the agricultural expansion and its impact on the landscape spatial and temporal patterns in a buffer zone of a protected area located in the transition zone between the Atlantic Forest and Cerrado, in the State of São Paulo, Brazil. The land use and land cover were mapped between 1971 and 2008 and landscape metrics were calculated to provide a spatiotemporal analysis of the forest structure and the expansion of the croplands. The results showed that the landscape patterns were affected by the economic cycles. The predominant crop surrounding the protected area is sugar cane, which increased by 39% during this period, followed by citrus. This landscape change is connected to the Brazilian oil crisis in 1973. The rapid expansion of sugar cane was largely driven by Brazil's biofuel program, the "Proálcool" (pro-alcohol), a project in 1975 that mixed ethanol with gas for automotive fuel. The forest loss occurred mainly between 1971 and 1988, decreasing the forest cover from 17% in 1971 to 12.7% in 2008. Most of the forest patches are smaller than 50 ha and has low connectivity. Throughout the years, the fragments in the buffer zone have become smaller and with an elongated shape, and the park has become isolated. This forest fragmentation process and the predominance of monoculture lands in the buffer zone threaten the protected areas, and can represent a barrier for these areas to provide the effective biodiversity conservation. The measures proposed are necessary to ensure the capability of this ecosystem to sustain its original biodiversity.

Modelling the spread and control of Xylella fastidiosa in the early stages of invasion in Apulia, Italy

Xylella fastidiosa is an important plant pathogen that attacks several plants of economic importance. Once restricted to the Americas, the bacterium, which causes olive quick decline syndrome, was discovered near Lecce, Italy in 2013. Since the initial outbreak, it has invaded 23,000 ha of olives in the Apulian Region, southern Italy, and is of great concern throughout Mediterranean basin. Therefore, predicting its spread and estimating the efficacy of control are of utmost importance. As data on this invasive infectious disease are poor, we have developed a spatially-explicit simulation model for X. fastidiosa to provide guidance for predicting spread in the early stages of invasion and inform management strategies. The model qualitatively and quantitatively predicts the patterns of spread. We model control zones currently employed in Apulia, showing that increasing buffer widths decrease infection risk beyond the control zone, but this may not halt the spread completely due to stochastic long-distance jumps caused by vector dispersal. Therefore, management practices should aim to reduce vector long-distance dispersal. We find optimal control scenarios that minimise control effort while reducing X. fastidiosa spread maximally-suggesting that increasing buffer zone widths should be favoured over surveillance efforts as control budgets increase. Our model highlights the importance of non-olive hosts which increase the spread rate of the disease and may lead to an order of magnitude increase in risk. Many aspects of X. fastidiosa disease invasion remain uncertain and hinder forecasting; we recommend future studies investigating quantification of the infection growth rate, and short and long distance dispersal.

Spatial and temporal use of floodplain habitats by lentic and lotic species of aquatic turtles

We investigated the use of aquatic and terrestrial floodplain habitats by lentic and lotic turtles inhabiting the Missouri River, a contemporary, regulated large river. Specifically, we tested whether habitats were used differentially by turtle species, sexes, and life stages over biologically determined spatial and temporal scales. We monitored female and male false map turtles (Graptemys pseudogeographica) and slider turtles (Trachemys scripta) for 14 months, using radiotelemetry. In addition, over a 3-year period we trapped G. pseudogeographica (n=591) and T. scripta (n=129) to supplement data on habitat use. Movements based on radiotelemetry and recaptures were summarized for each individual. Both species of turtles displayed dynamic annual activity patterns and used diverse habitats including those typically considered terrestrial. Although G. pseudogeographica and T. scripta spent a substantial portion of the year in the Missouri River (primarily in the cool months), newly created scour habitats also appeared to attract turtles during the cool season. However, in the warm months, habitat use became much more diverse, with turtles occupying all identified habitats including flooded agriculture and forest. Relative to their proportions, slough and scour habitats appeared to be highly favored while forests older than 4 years and agricultural habitats were proportionally less favored. We found few differences between species. However, males of both species were consistently more sedentary, used half as many habitats, and moved half as far from the river as did females, especially during May through July. Juveniles of both species were captured on average farther from the river than were adults, perhaps reflecting the close proximity of both nesting areas and shallow, productive habitats free of aquatic predators. We estimate a riparian zone of 449 m that encompasses 95% of the population movements away from the river and discuss the quality of habitats important to reproduction and survival of lentic and lotic floodplain turtles. These spatial and temporal movement patterns, in light of their potential adaptive costs and benefits to G. pseudogeographica and T. scripta, are critical to understanding the ecology of long-lived vertebrates that depend on contemporary large rivers.