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24. The GWR route map: a guide to the informed application of Geographically Weighted Regression

Author

Comber, Alexis, Brunsdon, Chris, Charlton, Martin, Dong, Guanpeng, Harris, Rich, Lu, Binbin, Lü, Yihe, Murakami, Daisuke, Nakaya, Tomoki, Wang, Yunqiang, and Harris, Paul

Subjects
Statistics - Methodology, 91B72 (Primary), 62M30 (Secondary), G.3
Abstract

Geographically Weighted Regression (GWR) is increasingly used in spatial analyses of social and environmental data. It allows spatial heterogeneities in processes and relationships to be investigated through a series of local regression models rather than a global one. Standard GWR assumes that the relationships between the response and predictor variables operate at the same spatial scale, which is frequently not the case. To address this, several GWR variants have been proposed. This paper describes a route map to inform the choice of whether to use a GWR model or not, and if so which of three core variants to apply: a standard GWR, a mixed GWR or a multiscale GWR (MS-GWR). The route map comprises primary steps: a basic linear regression, a MS-GWR, and investigations of the results of these. The paper provides guidance for deciding whether to use a GWR approach, and if so for determining the appropriate GWR variant. It describes the importance of investigating a number of secondary issues at global and local scales including collinearity, the influence of outliers, and dependent error terms. Code and data for the case study used to illustrate the route map are provided, and further considerations are described in an extensive Appendix., Comment: 34 pages, 8 figures

Published
2020

31. Sustainability of soil organic carbon in consolidated gully land in China's Loess Plateau.

Author

Yan, Qina, Kumar, Praveen, Wang, Yunqiang, Zhao, Yali, Lin, Henry, Ran, Qihua, An, Zhisheng, and Zhou, Weijian

Abstract

Massive gully land consolidation projects, launched in China's Loess Plateau, aim to restore 2667 [Formula: see text] agricultural lands in total by consolidating 2026 highly eroded gullies. This effort represents a social engineering project where the economic development and livelihood of the farming families are closely tied to the ability of these emergent landscapes to provide agricultural services. Whether these 'time zero' landscapes have the resilience to provide a sustainable soil condition such as soil organic carbon (SOC) content remains unknown. By studying two watersheds, one of which is a control site, we show that the consolidated gully serves as an enhanced carbon sink, where the magnitude of SOC increase rate (1.0 [Formula: see text]) is about twice that of the SOC decrease rate (- 0.5 [Formula: see text]) in the surrounding natural watershed. Over a 50-year co-evolution of landscape and SOC turnover, we find that the dominant mechanisms that determine the carbon cycling are different between the consolidated gully and natural watersheds. In natural watersheds, the flux of SOC transformation is mainly driven by the flux of SOC transport; but in the consolidated gully, the transport has little impact on the transformation. Furthermore, we find that extending the surface carbon residence time has the potential to efficiently enhance carbon sequestration from the atmosphere with a rate as high as 8 [Formula: see text] compared to the current 0.4 [Formula: see text]. The success for the completion of all gully consolidation would lead to as high as 26.67 [Formula: see text] sequestrated into soils. This work, therefore, not only provides an assessment and guidance of the long-term sustainability of the 'time zero' landscapes but also a solution for sequestration [Formula: see text] into soils.

Published
2020

39. The Characteristics and Influential Factors of Earthworm and Vermicompost under Different Land Use in a Temperate Area, China.

Author

Ma, Li, Shao, Ming'an, Wang, Yunqiang, Li, Tongchuan, Jing, Xuanxuan, Jia, Kunyu, and Zhang, Yangyang

Subjects
SOIL composition, CARBON in soils, APPLE orchards, BACTERIAL diversity, SPRING
Abstract

Earthworm communities influence soil carbon and nitrogen circulation by altering the diversity and composition of microbial communities, which improves soil fertility. Studying the soil nutrient composition and bacterial communities change in response to earthworm community natural invasion may be key to exploring earthworm ecological functions and accurately assessing C and N mineralization in artificial forests and croplands. In this study, we examined the communities of five earthworm species in ecosystems characterized by six different land-use types, such as buttonwood forest, walnut forest, apple orchard, kiwi orchard, ryegrass land, and corn field. The Metaphire baojiensis (d) and Amynthas carnosus planus were dominant earthworm species. Among different land-use types, earthworm densities ranged from 2 to 27 ind·m−2 in summer and 15 to 40 ind·m−2 in spring. However, surface vermicompost weight in summer (296.7 to 766.0 g·m−2) was greater than in spring. There was a positive correlation between the weight of the vermicompost and earthworm numbers in the same season. Soil carbon (C) and total nitrogen (N) of vermicompost ranged from 5.12 to 20.93 g·kg−1 and from 0.52 to 1.35 g·kg−1, respectively. Compared with soil, the contents of vermicompost C and N increased 2.0 to 4.3 times and 1.6 to 7.7 times, respectively. The average C/N of vermicompost (9.5~23.5) was higher than in the soil (7.3~19.8). Due to the higher abundances of C and N in the soil of corn fields and kiwi orchards, which cultivate higher abundances of earthworms and more vermicompost, the C and N and C/N of vermicompost is higher than in the soil. C and N were accumulated by earthworms' excreting and feeding activity instead of vegetation in vermicompost. Earthworm community structure plays key roles in decreasing bacterial diversity and adding Proteobacteria, Actinobacteria, Acidobacteria, Bacteroidetes, and Chloroflex in vermicompost, resulting in enriching soil C and N content and increasing C/N in vermicompost. Therefore, the evaluation of different vegetation ecosystems in soil C and N pool accumulation and mineralization should be given more attention regarding the function of earthworm communities in the future. [ABSTRACT FROM AUTHOR]

Published
2024
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40. Soil moisture decline in China’s monsoon loess critical zone: More a result of land-use conversion than climate change

Author

Wang, Yunqiang, primary, Hu, Wei, additional, Sun, Hui, additional, Zhao, Yali, additional, Zhang, Pingping, additional, Li, Zimin, additional, Zhou, Zixuan, additional, Tong, Yongping, additional, Liu, Shaozhen, additional, Zhou, Jingxiong, additional, Huang, Mingbin, additional, Jia, Xiaoxu, additional, Clothier, Brent, additional, Shao, Ming’an, additional, Zhou, Weijian, additional, and An, Zhisheng, additional

Published
2024
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41. Arbuscular mycorrhizal fungal interactions bridge the support of root‐associated microbiota for slope multifunctionality in an erosion‐prone ecosystem

Author

Qiu, Tianyi, primary, Peñuelas, Josep, additional, Chen, Yinglong, additional, Sardans, Jordi, additional, Yu, Jialuo, additional, Xu, Zhiyuan, additional, Cui, Qingliang, additional, Liu, Ji, additional, Cui, Yongxing, additional, Zhao, Shuling, additional, Chen, Jing, additional, Wang, Yunqiang, additional, and Fang, Linchuan, additional

Published
2024
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49. Seasonal dynamics and spatial patterns of soil moisture in a loess catchment

Author

Liu, Shaozhen, van Meerveld, Ilja; https://orcid.org/0000-0002-7547-3270, Zhao, Yali, Wang, Yunqiang, Kirchner, James W; https://orcid.org/0000-0001-6577-3619, Liu, Shaozhen, van Meerveld, Ilja; https://orcid.org/0000-0002-7547-3270, Zhao, Yali, Wang, Yunqiang, and Kirchner, James W; https://orcid.org/0000-0001-6577-3619

Abstract

The spatial and seasonal patterns in soil moisture and the processes controlling them in semi-arid landscapes are not well understood. Loess landscapes minimize any confounding effects of variation in soil characteristics and are thus ideal for studying topographic influences on soil moisture in drylands. In this study, volumetric soil moisture was monitored monthly for 5.5 years at 20 cm intervals between the surface and 5 m depth at 89 sites across a small (0.43 km2) catchment on the Chinese Loess Plateau. The median soil moisture was computed for each month and depth for each monitoring site as a measure of the typical soil moisture conditions. Seasonal changes in soil moisture were mainly concentrated in the shallow (0–100 cm) soil, with a clear seasonal separation between wet conditions in October–March and dry conditions in May–July, even though precipitation is highest in July–August. Soil moisture was higher on the northwest-facing slopes due to increased drying from solar radiation on the southeast-facing slopes. This effect of slope aspect was greater between October and March, when the zenith angle of the sun was lower and the aspect-dependent difference in solar radiation reaching the surface was larger. The wetter, northwest-facing slopes were also characterized by larger annual soil moisture storage changes. Soil texture was nearly uniform across both slopes, and soil moisture was not correlated with the topographic wetness index, suggesting that variations in evapotranspiration dominated the spatial pattern of soil moisture in shallow soils under both wet and dry conditions. Water balance calculations indicate that over 90 % of the annual precipitation was seasonally cycled in the soil between 0 and 300 cm, suggesting that only a minor fraction infiltrates to groundwater and becomes streamflow. Our findings may be broadly applicable to loess regions with monsoonal climates and may have practical implications for catchment-scale hydrologic modeling and

Published
2024

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