Land-use History Research Articles

Evolution of cultural landscape heritage layers and value assessment in urban countryside historic districts: the case of Jiufeng Sheshan, Shanghai, China

The heritage value of the historic urban countryside, as a remnant in the transition between the urban boundary and the natural environment, is a consequence of the spatial and temporal evolution of the city. However, through repeated social transformations, the conflicts between urban construction and cultural landscape heritage preservation have increased, resulting in the gradual disappearance of their cultural landscape heritage. This study takes the Sheshan Urban Countryside Historic District in Shanghai and interprets the layers of Sheshan's cultural landscape heritage into five periods, Emergence, Development and Exploration, Diversity and Prosperity, Turbulence and Change, and Stability and Precipitation. It analyzes the evolution of the layers of the cultural landscape heritage by applying Historic Urban Landscape Historic Land use Assessment (HUL) and interpreting the layers of the cultural heritage of Sheshan using Historical Landscape Assessment (HLA) to identify the characteristics and values of Sheshan's layers of heritage. The study indicates that the cultural landscape heritage of Jiufeng Sheshan exhibits four types of stratigraphic relationships: accretion, juxtaposition, overlay, and decline. This findings suggest a continuous evolutionary feature of superposition of multiple stratigraphic patterns. Moreover, the heritage value of the cultural landscape layers of Jiufeng Sheshan has shown a higher growth rate in the modern period. The integrity and survival status of modern religious and scientific buildings are more complete compared to the literati gardens and Buddhist relics. Based on the knowledge and value assessment of its cultural landscape heritage, it is necessary to intervene in the concept of living conservation and renewal of landscape heritage. This involves devising a conservation and renewal strategy for cultural landscape heritage that conforms to the law of historical stratification and connect the scattered historical and cultural relics. This study provides a reference for the conservation and inheritance of cultural landscape heritage in urban countryside historical areas and the organic renewal of urban and rural heritage.

Hindcasting estuary ecological states using sediment cores, modelled historic nutrient loads, and a Bayesian network

Estuaries are impacted by catchment land use changes, driving degradation associated with eutrophication and alterations in sediment dynamics. Estuarine ecological monitoring has typically covered only recent periods, so magnitudes and trajectories of degradation are often poorly described. Here, we develop a multi-method approach to hindcast historic estuary condition. We determined geochemical properties in dated sediment cores from two sites in the eutrophic New River Estuary (NRE), Aotearoa New Zealand. Mud, organic matter, carbon, and nitrogen (N) contents increased from ~1847 to 2019 (~20 to 100%, ~1 to ~7%, ~0.2 to ~3%, and ~0.03 to ~0.37% respectively). Historic land use modelling shows increasing catchment loads and water column total N rising from 165 to 663 mg m-3, with more rapid change in the late 20th and early 21st centuries. Strong correlations (R2 = 0.93-0.95) were found between sediment N content and water column N concentrations. Trophic indicators hindcasted by a Bayesian Belief Network worsened from the mid-20th to 21st centuries. This degradation is associated with increased sheep, beef and dairy farming in the catchment. Our approach identifies nutrient and sediment loadings associated with ‘tipping points’ for indicators and can inform policy by identification of hazardous levels of contaminant loading for other estuaries.

Characteristics Analysis and Prediction of Land Use Evolution in the Source Region of the Yangtze River and Yellow River Based on Improved FLUS Model

Climate change profoundly alters land use in alpine regions, and delving into the evolutionary characteristics of these changes is crucial for the sustainable development of regional land resources and the gradual enhancement of the ecological environment. Taking the source region of the Yangtze and Yellow River (SRYAYE) as a case study, we integrate permafrost and snowfall data into the Future Land Use Simulation model (FLUS). Analyzing historical land use, we predict and simulate the land use scenarios for 2030, 2035, and 2060 under SSP1-2.6, SSP2-4.5, SSP3-7.0, and SSP5-8.5 climates, and conduct a detailed analysis of the scale, composition, and pattern of land use in this area. Scale. The results showed that ① the Kappa coefficient of the improved FLUS model was higher than 0.927, and that the overall accuracy of the simulation was increased by 2.64%; ② the area of forest land and the high-coverage grassland will increase in the future and the center of gravity will migrate to the west, and that the area of moderate and low-coverage grassland will slightly decrease but tend to become green to the west; and ③ the fragmentation degree of the SRYAYE is decreasing, and the influence of human activities on the landscape pattern is weaker than in the past.

Tree species, mycorrhizal associations, and land-use history as drivers of cohesion in soil biota communities and microbe-fauna interactions

Community cohesion is a recent concept in ecology referring to the varying levels of connectivity and integration between populations of different taxonomic or functional groups within ecosystems. Positive cohesion denotes positive interactions such as mutualism or facilitation, while negative cohesion implies negative interactions such as competitive exclusion or a preference for different habitats. However, the effects of ecosystem characteristics such as tree species identity, mycorrhizal association and land-use history on soil biota community cohesion and microbe-fauna interactions remains poorly understood. We analyzed data on soil microbial biomass and biomass of taxonomic and functional groups of soil fauna obtained from monoculture stands of broadleaved tree species (maple and ash) associated with arbuscular mycorrhiza (AM), broadleaved tree species (beech, lime, and oak) associated with ectomycorrhizal fungi (ECM) and coniferous Norway spruce associated with ECM planted in common garden designs on former cropland and former forest land across Denmark. Our results revealed both positive and negative cohesion within soil communities, with only negative cohesion varying significantly among tree species. Soil biota communities under spruce indicated the most negative cohesion, whereas maple and ash soils showed least negative cohesion. Community cohesion varied across different sampling locations and between sites with different land-use histories. Positive cohesion was more pronounced in former cropland than in former old forest land, while negative cohesion was more pronounced in soils under tree species associated with ECM fungi than in soils beneath tree species associated with AM fungi. Both positive and negative cohesion were strongly influenced by litter chemistry and soil properties, indicating complex ecological dynamics. Soil pH, litter decomposition indices, and soil C:N ratio emerged as key drivers of microbial and faunal community structures. Additionally, the total microbial and faunal biomass, as well as the community structure of soil microbial and faunal communities, indicated strong positive interactions. Our results have the potential to support forest management by aiding in the selection of suitable tree species to support different groups of soil microbes and fauna, which play crucial role in ecosystem services such as nutrient release and transformation of soil organic matter.

Determination of soil organic carbon content of agricultural soils for proper soil management in Matazu and Musawa, Katsina State, Nigeria

Soil organic carbon is a significant parameter for estimating the global carbon cycle, which makes great sense in soil management and future climate scenario prediction. This work uses 30 heterogeneous soil samples from agricultural and non-agricultural farmlands and soil erosion areas in Matazu and Musawa LGAs to determine soil organic carbon content at the field level in Matazu and Musawa Local Government Areas, Katsina State, Nigeria. Soil samples were meticulously collected from the 0-10cm depth using a hand auger. These samples were obtained from three distinct clusters: agricultural and non-agricultural farmlands and soil erosion areas. The selection of sample locations considered the varied soil types, historical land use, and management practices. Ten soil samples were randomly gathered within each cluster, ensuring a representative and diverse set of samples for analysis. The Warlkey and Black and Hydrometer methods were used to determine the soils' organic carbon contents and particle size distribution, respectively. The data obtained were analyzed using SPSS 23 software. Two-sample t-tests and analysis of variance (ANOVA) were carried out. The soil organic carbon contents of the studied area were 0.29 ± 0.16 g/kg (0.16 – 0.34 g/kg) and 0.28 ± 0.14 g/kg (0.14 - 0.36 g/kg) for Matazu and Musawa, respectively. The study concludes that the organic carbon content helps improve sustainable agricultural productivity due to proper and efficient land use management practices.

Hydroclimatic Vulnerability of Wetlands to Upwind Land Use Changes

AbstractDespite their importance, wetland ecosystems protected by the Ramsar Convention are under pressure from climate change and human activities. These drivers are altering water availability in these wetlands, changing water levels or surface water extent, in some cases, beyond historical variability. Attribution of the effects of human and climate activities is usually focused on changes within the wetlands or their upstream surface and groundwater inputs. However, the reliance of wetland water availability on upwind atmospheric moisture supply is less understood. Here, we assess the vulnerability of 40 Ramsar wetlands to precipitation changes caused by land use and hydroclimatic change occurring in their upwind moisture‐supplying regions. We use moisture flows from a Lagrangian tracking model, atmospheric reanalysis data, and historical land use change (LUC) data to assess and quantify these changes. Our analyses show that historical LUC has decreased precipitation and terrestrial moisture recycling in most wetland hydrological basins, decreasing surface water availability (precipitation minus evaporation). The most substantial effects on wetland water availability occurred in the tropic subtropical regions of Central Europe and Asia. Overall, we found wetlands in Central Asia and South America to be the most vulnerable by a combination of LUC‐driven effects on runoff, high terrestrial precipitation recycling, and recent decreases in surface water availability. This study stresses the need to incorporate upwind effects of land use changes in the restoration, management, and conservation of the world's wetlands.

A rapid and simple method for the extraction of biogenic silica (BSi) in phytolith-poor sediments and soils

Phytoliths can be used to reconstruct human-nature dynamics over the long term (from decennial to centennial and millennial time scales) and may capture activities that cannot be reconstructed through other proxies. Phytoliths consist of fossil biogenic silica (BSi), formed in plant organs and then released into the soil with plant decay. When working in environmental contexts where the phytolith signal is highly diluted, as is the case in environments with a long history of land use, animal-plant interactions and open woody environments, the extraction of phytoliths remains a challenge. To address this issue, we developed an efficient method for the extraction of biogenic silica (BSi) from sediments and soils of contexts characterised by the long-term human and animal presence and disturbance, such as remnants of old agroforestry systems.The method we developed has a number of advantages, including:•An easy and time-efficient methodology to perform (with an overall processing time of 1.5/2 days for a batch of 16 samples)•An extraction method free from dangerous chemicals•A method amenable to non-experts without a prior background in lab extraction procedures.

Co-Creating Strategies to Optimize Traditional Silvopastoral Systems through the Management of Native Trees in Caívas in Southern Brazil

The conservation of forest remnants in southern Brazil is closely related to historical land use, for example in systems such as caívas that occur within remnants of the Araucaria Forest and include livestock production and the extraction of yerba mate. Over the last decade, technologies adapted for these systems have been developed that promote a significant increase in animal productivity, without harming forest regeneration or the maintenance of the tree layer. However, the fertilization of pastures proposed in the technology has also promoted greater growth of native trees, with a consequent increase in shade levels. This, in turn, has affected the maintenance of pasture and yerba mate in the understory. Thus, this study sought to develop a methodology to adjust shade levels based on forest management that adheres to the limits permitted by current legislation. The objective was to evaluate the effect of tree management to maintain 50% shade levels on environmental indicators in a caíva that has been implementing pasture improvement technology since 2013. Native tree management occurred in 2020 and 2022 and the results were compared with data from the floristic survey of the area carried out in 2013. The results indicate that although the adoption of forest management to adjust shade levels reduced the density of individuals, it did not affect forest diversity, nor the basal area of the caíva tree layer. As such, it is possible to maintain pasture and yerba mate production in the area. Strategies like this are fundamental so that the forest landscape can continue to offer a source of production while also supporting environmental conservation.

Spatiotemporal Characteristics of Land Cover Change in the Yellow River Basin over the Past Millennium

Investigating the ecological and environmental impacts stemming from historical land use and land cover change (LUCC) holds paramount importance in systematically comprehending the fundamental human-land relationship, a pivotal focus within geographical research. The Yellow River Basin (YRB), often referred to as the cradle of Chinese civilization, ranks as the fifth-largest river basin globally. Early inhabitants made significant alterations to the landscape, resulting in substantial damage to natural vegetation, giving rise to prominent regional ecological challenges. By now, the examination of historical LUCC in the YRB over the past millennium remains in the qualitative research stage, primarily due to the limited availability of high-confidence gridded historical LUCC data. This study aims to advance the current historical LUCC research in the YRB from primarily qualitative analysis to an exploration incorporating timing, positioning, and quantification. Based on reconstructed historical cropland, forest, and grassland grid data of 10 km × 10 km from 1000 AD to 2000 AD, the degree of cropland development and the depletion of forests and grasslands were calculated, respectively. Then, the kernel density method was employed for spatiotemporal analysis and interpretation of dynamic changes in land cover. Subsequently, a cartographic visualization depicting the migration trajectories of the land cover gravity centers was generated, allowing for an assessment of the distance and direction of the centroids’ movement of cropland, forest, and grassland. The results indicate that the cropland coverage in the YRB escalated from the initial 11.65% to 29.97%, while the forest and grassland coverage dropped from 63.36% to 44.49%. The distribution of cultivated land continually expanded outward from the southeast of the Loess Plateau and the southwest of the North China Plain. All three types of land cover experienced a westward shift in their gravity centers between 1000 and 2000 AD. Besides the population growth and technological advancements, the regime shifts induced by wars, along with land use policies in distinct periods, always served as the predominant factors influencing the conversion between different land covers. This research will present a paradigmatic regional case study contributing to the investigation of historical changes in land use and land cover. Additionally, it will offer historical perspectives beneficial for the advancement of China’s objectives in “Ecological Conservation and High-Quality Development of the Yellow River Basin”.

Secondary Amazon rainforest partially recovers tree cavities suitable for nesting birds in 18–34 years

Abstract Passive restoration of secondary forests can partially offset loss of biodiversity following tropical deforestation. Tree cavities, an essential resource for cavity-nesting birds, are usually associated with old forest. We investigated the restoration time for tree cavities suitable for cavity-nesting birds in secondary forest at the Biological Dynamics of Forest Fragments Project (BDFFP) in central Amazonian Brazil. We hypothesized that cavity abundance would increase with forest age, but more rapidly in areas exposed to cutting only, compared to areas where forest was cut and burned. We also hypothesized that cavities would be lower, smaller, and less variable in secondary forest than in old-growth forest, which at the BDFFP is part of a vast lowland forest with no recent history of human disturbance. We used pole-mounted cameras and tree-climbing to survey cavities in 39 plots (each 200 × 40 m) across old-growth forests and 11–34-year-old secondary forests. We used generalized linear models to examine how cavity supply was related to forest age and land-use history (cut only vs cut-and-burn), and principal components analysis to compare cavity characteristics between old-growth and secondary forest. Cavity availability increased with secondary forest age, regardless of land-use history, but the oldest secondary forest (31–34 years) still had fewer cavities (mean ± SE = 9.8 ± 2.2 cavities ha–1) than old-growth forest (20.5 ± 4.2 cavities ha–1). Moreover, secondary forests lacked cavities that were high and deep, with large entrances—characteristics likely to be important for many species of cavity-nesting birds. Several decades may be necessary to restore cavity supply in secondary Amazonian forests, especially for the largest birds (e.g., forest-falcons and parrots > 190 g). Retention of legacy trees as forest is cleared might help maintain a supply of cavities that could allow earlier recolonization by some species of cavity-nesting birds when cleared areas are abandoned. A Portuguese version of this article is available in Supplementary Material 1.

Anthropogenic climate and land-use change drive short- and long-term biodiversity shifts across taxa

Climate change and habitat loss present serious threats to nature. Yet, due to a lack of historical land-use data, the potential for land-use change and baseline land-use conditions to interact with a changing climate to affect biodiversity remains largely unknown. Here, we use historical land use, climate data and species observation data to investigate the patterns and causes of biodiversity change in Great Britain. We show that anthropogenic climate change and land conversion have broadly led to increased richness, biotic homogenization and warmer-adapted communities of British birds, butterflies and plants over the long term (50+ years) and short term (20 years). Biodiversity change was found to be largely determined by baseline environmental conditions of land use and climate, especially over shorter timescales, suggesting that biodiversity change in recent periods could reflect an inertia derived from past environmental changes. Climate–land-use interactions were mostly related to long-term change in species richness and beta diversity across taxa. Semi-natural grasslands (in a broad sense, including meadows, pastures, lowland and upland heathlands and open wetlands) were associated with lower rates of biodiversity change, while their contribution to national-level biodiversity doubled over the long term. Our findings highlight the need to protect and restore natural and semi-natural habitats, alongside a fuller consideration of individual species’ requirements beyond simple measures of species richness in biodiversity management and policy.

The interplay between historical land‐use and the distribution of Helichrysum shrubs in an African‐protected grassland

AbstractHuman land use can have lasting impacts on landscape characteristic, yet there remains a lack of information on how former land use affects plant communities in protected African grasslands. In this study, we investigated how land uses prior to the creation of Kitulo National Park, Tanzania, shaped the presence and abundance of the native shrub, Helichrysum species. We evaluated both plant species composition and soil properties across the park by dividing our sample into three different zones of historical land use based on participatory mapping. We divided the park into three former land uses: (1) livestock grazed and cultivated; (2) grazed only and (3) wild grazing with limited human impact. We observed that former grazed cultivated land use had five times higher Helichrysum abundance than former ‘wild’ land use. Soil pH, magnesium and phosphorus levels varied significantly across zones of historical land use but not between sites with and without Helichrysum species. Helichrysum splendidum was more abundant in soils with low soil phosphorus and magnesium concentrations. Our study demonstrates that historic grazing and cropping land uses through changes in soil nutrient properties can explain current Helichrysum species spread in protected areas. As such, conservation management plans would benefit from integrating mapping of former land uses to target interventions for problematic encroaching shrubs.

Climate-limited vegetation change in the conterminous United States of America.

The effects of climate change on vegetation composition and distribution are evident in different ecosystems around the world. Although some climate-derived alterations on vegetation are expected to result in changes in lifeform fractional cover, disentangling the direct effects of climate change from different non-climate factors, such as land-use change, is challenging. By applying "Liebig's law of the minimum" in a geospatial context, we determined the climate-limited potential for tree, shrub, herbaceous, and non-vegetation fractional cover change for the conterminous United States and compared these potential rates to observed change rates for the period 1986 to 2018. We found that 10% of the land area of the conterminous United States appears to have climate limitations on the change in fractional cover, with a high proportion of these sites located in arid and semiarid ecosystems in the Southwest part of the country. The rates of change in lifeform fractional cover for the remaining area of the country are likely limited by non-climate factors such as the disturbance regime, land management, land-use history, soil conditions, and species interactions and adaptations.

Grounded desires: Grazing regime, desires, and development in a Diné community

This article highlights the demands for development within the Diné community of Shonto in 2017. Using interviews with Shonto community members, I center the voices and desires of those most affected by development. Shonto is the site of conjuncture of a grazing regime that limits land use and a history of development that produces conflicting community desires for infrastructure, employment, and traditional livestock practices. Despite the plural views of development, community members express a collective desire for Diné continuity and self- determination. My research demonstrates that Diné desires for development are not monolithic but are grounded in land histories, a sense of shared collective continuity, and Diné self- determination. I draw upon Eve Tuck’s generative work on Native desire to demonstrate that land histories, in the form of a grazing regime and histories of development, inform Native desires for development. I argue that Native desires are grounded in historical and everyday land use and relations. These grounded desires center the lived-experiences of Natives in relation to development, colonial land regimes, and traditional practices. Moreover, these grounded desires draw from the daily lives and experiences of Native people to provide open narratives that do not impose expectations on Native peoples or their desires.

Analyzing urban influence on extreme winter precipitation through observations and numerical simulation of two South China case studies

This study investigates the impact of urbanization on extreme winter rainfall in the South China Greater Bay Area (GBA) through the analysis of hourly station observations and simulations using the Weather Research and Forecasting Model with the Single Layer Urban Canopy Model (WRF-SLUCM). Data from 2008 to 2017 reveal that urban areas in the GBA experience lower 99th percentile hourly winter rainfall intensity compared to surrounding rural regions. However, urban locations exhibit higher annual maximum hourly rainfall (Rmax) and very extreme rainfall events (99.99th percentile) in winter, suggesting a positive influence of urbanization on extreme winter precipitation. A case study further underscores the role of the Urban Heat Island (UHI) effect in enhancing extreme rainfall intensity and probability in the GBA urban areas. Additionally, two extreme cases were dynamically downscaled using WRF-SLUCM, involving four parallel experiments: replacing urban land use with cropland (Nourban), using historical urban land use data from 1999 (99LS), projecting near-future urban land use for 2030 (30LS), and considering 2030 urban land use without anthropogenic heat (AH) (30LS-AH0). Synoptic analysis demonstrates that cold air intrusion suppresses the GBA UHI in Case 2013 but not in Case 2015. Reduced evaporation and humidity induced by urban surfaces significantly decrease urban precipitation in Case 2013. In contrast, the persistent UHI in Case 2015 enhances local convection and land–ocean circulation, leading to increased moisture flux convergence and amplified urban precipitation intensity and probability in 30LS compared to Nourban. This amplification is primarily attributed to AH, while the change in 99LS remains insignificant. These findings suggest that urban influences on extreme precipitation in the GBA persist during winter, particularly when the UHI effect is maintained.

A Comprehensive Review of Remediation Strategies for Soil and Groundwater Contaminated with Explosives

This study offers an updated overview of the soil and water remediation strategies employed to address the widespread environmental and public health risks associated with explosive compounds, particularly TNT and RDX. Recognizing soil contamination originating from military activities, industrial accidents, and historical land use, this review delves into physical, chemical, and biological approaches to mitigating ecological and human health concerns. While physical methods like excavation and disposal are effective, their applicability is constrained by cost and logistical challenges for large contaminated areas. Chemical methods, such as oxidation and reduction, focus on transforming explosives into less toxic byproducts. Biological remediation utilizing plants and microorganisms emerges as a cost-effective and sustainable alternative. This review highlights challenges, including the persistence of explosive compounds, potential groundwater leaching, and the necessity for long-term monitoring. Emphasizing the need for site-specific strategies, considering the contaminant type, concentration, soil properties, and regulatory requirements, this study advocates for integrated and sustainable remediation approaches in pilot-scale applications. It concludes by evaluating the appropriate solution based on the advantages and disadvantages of the categories of soil and groundwater remediation methods. The duration, the effectiveness, and the cost of available technologies were estimated.

Deciphering the biotic and abiotic drivers of coalescence asymmetry between soil and manure microbiomes

Manure application improves soil fertility, yet its implications on the success of invasion of manure-borne microorganisms in the soil are poorly understood. Here, we assessed the importance of abiotic and biotic factors in modulating the extent to which manure-borne fungal and bacterial communities can invade resident soil microbial communities. For this purpose, we applied varying frequencies of two different amounts of manure to nine soils differing in physico-chemical properties, as well as in land-use history, over 180 days and monitored changes in bacterial and fungal communities. Variance partitioning revealed differential contributions of abiotic and biotic factors to invasion success, which together accounted for up to 82 % of the variance explained. We showed that the effects of interactions between biotic and abiotic factors increased with coalescence frequency and manure amount for the bacterial and fungal communities, respectively. Both abiotic and biotic factors were important for modulating coalescence asymmetry for the bacterial community, whereas abiotic factors had a greater effect on the fungal community. These results provide new insights into the drivers of coalescence events between manure and resident soil microbial communities. Moreover, our findings highlight the roles of the mixing ratio and frequency of coalescence events in modulating the survival of manure-borne microorganisms.

Considering Historical Land Use When Estimating Soil Carbon Stock Changes of Transitional Croplands

Understanding changes to soil organic carbon storage (SOC) requires knowledge of detailed land use history. Many satellite-based analyses of land use change have been conducted over short periods (typically 5 to 10 years) to investigate causality to a demand increase in an agricultural commodity. However, statistically significant changes in SOC are not readily observable during this time and typically require decades for meaningful differences to accrue. This study aimed to determine land use and soil organic carbon stocks on land parcels over 36 years (1985–2021) located in areas where historical land use transitions between cropland and non-cropland are prevalent. Aerial and satellite imagery were analyzed across 25,992 hectares in ten counties across the Corn Belt. Grower interviews were conducted to solicit feedback on the drivers of land use change. Finally, SOC analyses associated with land use changes were determined using two process-based models. Analysis showed that 371 of the parcels had remained in cropland, 611 parcels transitioned into non-cropland, and 18 parcels were identified as non-cropland. The grower surveys indicated that the most common reasons for returning land to crop was the difficulty getting land re-enrolled in the CRP and reduced cattle prices. Both the SALUS and GREET-CCLUB models were parameterized to assess soil carbon changes for the respective land use history, and both models returned consistent SOC increases at the county level over time.

Observations of Decadal-Scale Brine Geochemical Change at the Bonneville Salt Flats

Over the past century, the Bonneville Salt Flats, which lies on the western edge of the Great Salt Lake watershed, has experienced changing environmental conditions and a unique history of land use, including resource extraction and recreation. The perennial halite salt crust has decreased in thickness since at least 1960. An experimental restoration project to return mined solutes began in 1997, but it has not resulted in anticipated salt crust growth. Here, primary observations of the Bonneville Salt Flats surface and subsurface brine chemistry and water levels collected from 2013 to 2023 are reported. Spatial and temporal patterns in chemistry, focused on density and water stable isotopes, are evaluated and compared with observations across seven periods of research spanning from 1925 to 2023. Declining salinity in the areas to the east of extraction ditches and south of Interstate 80 were observed. Brine extracted for potash production decreased in salinity as extraction rates increased. Between the years 1964 and 1997, the salinity of the shallow aquifer brine located beneath and to the east of the crust experienced a decrease. However, following this period, the salinity stabilized and subsequently increased. Salinity recovery was concurrent with declines in brine extraction and the salt restoration project, with the largest decrease in brine extraction being concurrent with the largest recovery in salinity. The specific impact of the restoration project on the brine salinity increase remains unclear. To the west, the shallow aquifer in the area between the Silver Island Mountains and the salt crust has increased in salinity. This increase is accompanied by a decline in groundwater levels, which enables the underground movement of solutes from east to west, following a salinity gradient away from the saline pan. Over the past 25 years, the alluvial-fan aquifer along the Silver Island Mountains has markedly declined, leading to increasingly more saline and isotopically heavier basinal waters to be extracted for industrial use. This change is concurrent with the onset of the salt restoration project, which relies on alluvial-fan aquifer waters. This compilation of changes in groundwater chemistry provides an important resource for stakeholders working to understand and manage this dynamic and ephemeral evaporite system. It also offers an example of decadal-scale change in a highly managed Great Salt Lake watershed saline system.

Plant roots are more strongly linked to microorganisms in leaf litter rather than in soil across tropical land-use systems

Tropical soil microorganisms are major recyclers of the biosphere organic carbon. However, the link of tropical microorganisms to the two main pathways of how carbon enters the belowground system, i.e., plant roots and leaf litter, is poorly understood. To investigate the relative importance of these pathways, we studied the response of microorganisms in leaf litter and underlying topsoil to root trenching (exclusion of living roots) and litter removal in tropical rainforests, and how this is altered by rainforest conversion to rubber and oil palm plantations. Unexpectedly, the linkage between living roots and microbial biomass was stronger in litter than in soil across land-use types, indicating that tropical trees prioritize mining for nutrients in leaf litter rather than in soil. After trenching, microbial biomass and basal respiration in leaf litter decreased by 32% and 38%, respectively, whereas microbial biomass and basal respiration remained unchanged in soil. However, fatty acid profiles indicated that root trenching decreased the proportion of total and mycorrhizal fungi in soil, with the effect on mycorrhizal fungi being especially strong when litter was present. Litter removal neither significantly affected microbial biomass nor community structure in soil, suggesting compartmentalization of carbon processing between litter and soil. Overall, the results suggest that across tropical land-use types root-derived resources shape microorganisms in soil and litter via different pathways, with litter microbial communities relying heavily on root-derived carbon, whereas microbial communities in soil being structured predominantly by long-term factors related to land-use history.