Land-use History Research Articles

A Predictive Model For Quantifying The Combined Effect Of Land Use Change And Climatic Variability On Sedimentation In Malaba Sub Catchment

Over the previous years, sedimentation in Malaba sub catchment has become a major problem, this research aimed at using SWAT as a predictive model to assess the impacts of historical and future climate change and land use changes on sedimentation in Malaba sub catchment. Two variables rainfall and temperature were considered under climate change. Four scenarios were modeled in SWAT during this study, the first scenario focused on historical sedimentation in the catchment, land use data of 2000 and weather data of 1990 to 2005 was used to simulate flow and sediment yield in the catchment. The second scenario focused on the current sediment yield in the catchment where land use data of 2020 and weather data of 2003 to 2020 was used to simulate the sediment yield and flow. Calibration and validation was done using SWAT CUP software. The calibrated and validated model was then used to further simulate two future scenarios. The two future scenarios used projected land use data and projected weather data. Land use data was projected using Clerk Labs Terr set software while weather data was projected using the Statistical Downscaling Model (SDSM). The third scenario considered projected land use data of 2035 and projected weather data of 2020 to 2035 to simulate flow and sediment yield of 2023 to 2035. The forth scenario considered projected land use data of 2050 and projected weather data of 2033 to 2050 to simulate catchment flow and sediment yield of 2036 to 2050. The results obtained from climate change analysis indicated un even changes, rainfall over the catchment is expected to increase, maximum temperature is expected to increase, minimum temperature is expected to reduce. Land use change results after comparison between the historical land use and projected land use indicated that from 2020 to 2050 cropland and built up area will increase while forests and water bodies will reduce. Average annual Sediment yield of 1993 to 2020 is expected to generally increase from 4975.4 tons/km2/year to an average annual sediment yield of 5525.6 tons/km2/year from 2023 to 2050. Therefore, mitigation measures should be adopted to ensure sustainable management of the catchment. Some of the recommendations made in this research are; Government through NEMA should put restrictions on cultivation close to the river banks, encourage planting trees within the catchment, bare lands within the catchment should be converted to other sustainable land uses. The study findings of this research shall be relevant for planning, design and management of reservoirs, dams, irrigation systems and sustainability of eco systems in the catchment.

Rapid laminated clastic alluviation associated with increased Little Ice Age flooding co-driven by climate variability and historic land-use in the middle Severn catchment, UK

The analysis of exceptionally well-preserved visible clastic laminations in deep alluvial sediments at Kempsey, Worcestershire (UK), allows a new high-resolution analysis of late-Holocene flood-history in the largest UK catchment, as well as local human response. At the sample site over 4.5 m of sandy-silt overbank-alluvium accumulated on the floodplain and optically stimulated luminescence (OSL) dating of the upper 2.25 m demonstrates accretion from the late 14th century CE onwards. Sub-centimetre to centimetre resolution multi-proxy sediment analysis (loss on ignition, magnetic susceptibility, particle size, ITRAX and portable XRF) demonstrate clear variations in depositional history over the last millennium due to channel stability. Between c. 1380 and 1550 CE overbank sedimentation was driven by lower energy flood events, with negligible effect from climatic conditions during the Spörer Minimum (1460–1550 CE). After c. 1550 CE the magnitude of flooding events increased and by c. 1610 CE, the start of the visible sub-centimetre laminations, the accumulation rate regularly exceeded 3 mm year−1, which increased to 4.5 mm year−1 between c. 1690 and 1710 CE, and 3 and 3.5 mm year−1 between c. 1790 and 1840 CE before alluviation was altered by an embankment. The greatest extent of coarse overbank deposition and increased accumulation rate occur concurrently with periods of climatic instability associated with the Maunder (1645–1715 CE) and Dalton (1790–1820 CE) Minima, the periods of largest historical floods and during the intensification of arable cultivation across the middle Severn catchment. This data correlates well with other sites in the catchment suggesting that these are basin-wide forcing-responses. We also present evidence that this catchment-wide hydro-geomorphological history had local effects in shifting the geographical focus of an important settlement away from its historic floodplain edge location – which can be viewed as an adaptation to the flood risk.

Homogenization and species compositional shifts in subalpine vegetation during the 60-year period

Subalpine and alpine plant communities are considered highly sensitive and hence endangered by global changes. In central Europe, the highly sensitive habitats are also influenced by human activities: land use, industrial pollution, and tourism. That is especially true for subalpine plant communities formed on mid-latitude mountains during specific postglacial development. Our study aimed to (1) document changes in cover and plant species diversity between the past (1950s and 1970s) and present (2019) and (2) reveal differences in the functional composition of the species among the studied periods. In 2019, quasi-permanent marked plots originally surveyed in the 1950s and 1970s were resurveyed at Králický Sněžník (Śnieżnik Kłodski) Mountains, the High Sudetes Mts.. We assessed temporal changes in plant species composition, species cover, functional groups, growth forms, and degree of specialization. We found homogenization of the vegetation over time and changes in the cover of specific functional groups that were attributed to environmental factors connected with the cessation of historical land use, atmospheric deposition, and climate change. Implementing a suitable combination of mowing and grazing to support diversity, and to prevent homogenization of vegetation is highly recommended.

Multi-Scale Drivers of Land-Use Changes at Farm Level II: Application of Conceptual Framework in the Salinity Intrusion Zone of the Vietnamese Mekong Delta and Cross-Case Comparison with the Highly Flooded Zone

Frequent drought and worsening salinity intrusion challenge future land uses and livelihoods in the Vietnamese Mekong Delta. The central government is, therefore, formulating a new strategy premised on adaption to natural environmental dynamics. For an achievable strategy that bridges the gap between plans and practice, it is important to understand what drives land-use changes at the farm level. Previous research developed and applied a multi-scale drivers framework in the highly flooded zone of the delta. The current study uses that same framework to investigate the land-use history and drivers of change in the salinity intrusion zone of this delta from 1975 to 2016. We interviewed 32 farmers in Tra Vinh Province and used transcript analysis to quantify the influence of the drivers that the farmers mentioned. We then compared the drivers of land-use change with those found earlier in the highly flooded zone. Results show more diversification of land uses and land-use changes in the salinity intrusion zone. Farmers here followed three main pathways: rice intensification, integrated farming of rice and vegetables/aquaculture, or intensive shrimp farming. Land-use changes were conditional on the regional infrastructure construction to preserve freshwater conditions. However, household-scale drivers, especially natural and financial assets, were most frequently mentioned. Socio-economic context also emerged as an important driver, particularly trends and pressures from the community and markets.

Carbon dioxide fluxes and soil carbon storage in relation to long‐term grazing and no grazing in Icelandic semi‐natural grasslands

AbstractQuestionWhat is the effect of long‐term grazing and no grazing (NG) on carbon dioxide flux and soil carbon storage in Icelandic semi‐natural grasslands.LocationThree farms, with known history of land use, in W Iceland.MethodsOn each farm, we located an intensively and an extensively grazed site, which both had been constantly grazed for centuries, and a parallel site with no grazing for over 50 years. We measured net ecosystem exchange (NEE), ecosystem respiration and normalized difference vegetation index on a regular basis over the growing season. Samples were taken from 60 cm deep soil profiles for analysis of soil organic carbon (SOC).ResultsThe grazed sites showed significantly more negative NEE than the NG sites, indicating more carbon dioxide uptake on the grazed sites compared to the NG sites. The normalized difference vegetation index was also significantly higher on the grazed sites. On all farms, the total SOC content was higher in the grazed sites than in the parallel NG sites.ConclusionsThe study indicates that cessation of grazing decreases productivity and carbon dioxide uptake in a semi‐natural grassland in Iceland, as well as SOC content in the soil. Historically, all the NG sites in the study had the same grazing history as the continuously grazed sites until grazing exclusion. The measured lower SOC on the NG sites seems to indicate that, without grazing, SOC is lost with time and/or grazing is needed to maintain SOC in these grasslands.

How does understory vegetation diversity and composition differ between monocultures and mixed plantations of hybrid poplar and spruce?

Although monocultures are important for timber production, they are often associated with lower biological diversity than mixtures. Thus, mixed plantations have been suggested as a way to enhance biodiversity because of their inherent compositional diversity. However, the effects of monocultures versus mixtures on understory diversity and composition can vary in different ecosystems. The objective of this study was to assess how monocultures and mixed plantations influence understory vegetation diversity and composition in the boreal forest region of southern Quebec. We sampled plantations established with deciduous Populus trichocarpa Torrey & A. Gray × balsamifera L. and P. maximowiczii Henry × balsamifera L. and coniferous Picea abies (L.) Karst. and Picea glauca (Moench) species planted in monocultures and in mixed plantations on abandoned farmlands and a forest site. We assessed understory vegetation diversity and composition in each canopy type (coniferous, deciduous, mixed) and in each plantation type. We evaluated bryophyte and lichen diversity and composition specifically in tree microhabitats: soil, tree bases, and tree trunks. We found that vascular plant and lichen species richness was similar in all plantation types, while bryophyte species richness was higher in spruce monocultures and in mixed plantations compared to poplar monocultures. Our results also highlight how land-use history influenced vascular plant composition as abandoned farmland sites were composed of more ruderal vascular plants, while the previously forested site was composed of species found in natural forests. In the context of reforestation and plantations, our study suggests mixing spruce with poplars to maximize understory vegetation diversity as the addition of spruce in mixed plantations promoted the establishment of terrestrial bryophytes, while poplars favored the establishment of epiphytic lichens.

Park conservation or degradation? iCLUE modelling of land use change projections in the upper Manafwa watershed on Mount Elgon, Uganda

Land use changes result from interactions between different factors over time. Land use models support natural resource conservation by helping stakeholders to understand and predict these changes. Through such model-based projections, governments and conservationists can identify hotspots of encroachment and formulate informed decisions for sustainable conservation. Land use on Mount Elgon has undergone rapid changes in the conservation area and community land since the 1970s. Park encroachment has threatened natural cover due to population pressure and increasing demand for agricultural land. To support conservation efforts, this study conducted near-future potential land use change projections using historical land use change and iCLUE model simulations. This study established hotspots of land use conversion, locations of park encroachment and the extent of land use intensification in the upper Manafwa watershed of Mount Elgon. The study applied remote sensing, a geographic information system, and a land use change model (iCLUE), while considering nine land use classes to project land use change for 2030, 2040 and 2050 using a “business-as-usual” scenario. Stakeholder verification of the model output was conducted in a dedicated workshop. The results showed that in 2050, agriculture (44.24%) and low-stocked tropical high forest (22.56%) will be the largest land cover classes with bushland and shrubs as the smallest land cover classes (∼0.5%). Most of the land use conversion in the park is projected to occur along the boundary of the conservation area by agriculture and built-up areas. This study will guide stakeholders and decision makers in planning future sustainable management strategies to conserve and enhance remaining forest tracts in Mount Elgon.

Spatio-temporal dynamics of ecosystem service values in China’s Northeast Tiger-Leopard National Park from 2005 to 2020: Evidence from environmental factors and land use/land cover changes

The Northeast Tiger-Leopard National Park (NTLNP) in China is an area of great ecological significance, known for its abundant wilderness resources and biodiversity. However, the habitats in NTLNP have been threatened by historical land use and land cover (LULC) changes caused by urban expansion and economic development. In response to this challenge, this study based on remote sensing-derived LULC products from 2005 to 2020, utilized the equivalent factors refined ecosystem service values (ESV) assessment model, and in conjunction with Moran’s I and Getis-Ord Gi* spatial analysis methods to evaluate the macro-scale and pixel-scale spatio-temporal dynamics of ESV in the NTLNP. We also employed the cold and hot spot analysis (CHSA) method to identify zones of ESV improvement and degradation within the NTLNP. Our findings indicate that over the past 15 years: (1) Forestland in the NTLNP possesses the most substantial ESV proportion (97.48%), and the regulating service value is the major contributor among the four types of services (71.31%). (2) Despite a fluctuating trend of increasing, decreasing, and then growing overall ESV growth within the NTLNP, the ecological benefits have been difficult to return to their peak values of 42.184 billion CNY in 2015. (3) The waters of NTLNP exhibit a high LULC dynamic of 27.91%, with an ESV underestimation of 28.4 million CNY. (4) The pixel-scale analysis unveils a dispersed distribution of ESV degradation pixels, with their cumulative area significantly larger than the share of ESV improvement pixels. (5) The CHSA results showed that areas with intensive human activity, such as towns and their surrounding areas, tend to experience ESV degradation, while regions with effective river management, such as the river basin of Hunchun county-level city, experience ESV improvement. Therefore, this study delineates the regulatory zones of the NTLNP by the result of the CHSA-based decision tree, pinpoints ecologically threatened core areas and further categorizes these based on risk levels and types, helping maintain a dynamic balance between the allocation of human and physical resources for park management and the primary conservation needs within the national park. Moreover, the study recommends that policymakers take measures to strengthen risk mitigation, enhance their focus on areas where ESV is fragile, and optimize the allocation of internal resources in national parks.

White-tailed deer responses to acoustic predator cues are contingent upon past land use and contemporary fire regime

Abstract Prey can assess the immediate risk of predation by detecting cues of predator presence, and it is expected that prey should invest in costly antipredator behaviors when a cue of predator presence is detected. Features of the habitat in which the cue is detected, such as vegetative concealment, serve as indirect cues of risk and can mediate how prey respond to direct cues of predator presence. Past agricultural land use and contemporary fire regimes are common disturbances that may modify prey perceptions of risk and could, therefore, alter prey responses to direct cues of predator presence. We examined whether the overlap of these two disturbances affected white-tailed deer (Odocoileus virginianus) responses to cues of predator presence by measuring deer vigilance and foraging bout duration in response to coyote (Canis latrans) vocalizations across 20 woodlands that varied in past land use and contemporary fire regime. Frequent fire regimes consistently increased deer visibility to predators across both land-use history contexts. Deer exhibited no behavioral response to the predator cue in habitats containing infrequent fire regimes or agricultural legacies. Deer responded to the cue in frequently burned woodlands without agricultural legacies through increased vigilance and time spent at a foraging location. These findings reveal that land-use legacies and contemporary fire regimes can mediate how prey respond to direct cues of risk. They also suggest that prey may balance the uncertainty associated with cues of predation risk with the urgency of responding to a potential attack by being vigilant and remaining in place.

Fleeting fields of Zadar (Croatia): characterizing millennial-scale urban landcover change, green space, and resilience into the twenty first century

Cities are a growing factor in global change today, but urbanization as a process has played a significant role in shaping our planet’s environments for millennia. Exploring the longevity or persistence of cityscapes can therefore reveal qualities that may have strengthened urban sustainability or resilience over long periods. In the Mediterranean, many ancient cities lie in ruin and are fully formed archaeological sites, while others reflect continuous growth and expansion into the modern era, often replacing what has traditionally been a rural mosaic of green space with a more homogenized urban landcover. Green spaces like cultivated lands, urban forests, recreational parks, and green belts are essential components of urban resilience, as they build adaptive capacity by improving human health and livelihoods, reducing surface runoff and erosion, and mitigating urban heat island effects, among others. Protection of green space in urban and peri-urban contexts also offers greater capacity to transform in the face of uncertain change. This paper centers on the ancient city of Zadar along Croatia’s Adriatic coast to characterize broad millennial-scale changes in urban landcover and green space. The results suggest that the distribution of urban landcover and green space appears to have been fairly stable for much of Zadar’s 3,000-year history, which arguably played a significant role in its persistence into the present era. However, the pace and scale of urban development, as well as the corresponding losses of green space, have accelerated from the mid-twentieth century onward, depleting a major source of socioecological resilience that has benefitted the city since the Iron Age. Archaeological and historical fields of study provide a deep temporal context to these contemporary challenges and are well-suited to identify and promote the locally and historically distinctive character of surviving green spaces. Land use legacies stemming from Roman surveying and historic field clearance practices around Zadar have resulted in one of the most distinctive and well-preserved physical manifestations of ancient and historic land use in the Mediterranean. Recognition of their cultural significance, even in their diminished state, would add further value for their protection and continued capacity toward urban resilience in the next century.

S10-2 U.S. CDC’s Active People Health Nation: Michigan’s Story for Promoting Physical Activity in Local Communities

Abstract Purpose Being physically active is one of the most important ways people of all ages and abilities can improve their health. Survey data show that 76 percent of Asian Americans in Michigan USA do not meet the federal physical activity minimum guidelines. Guided by Active People, Healthy Nation (APHN), a national initiative to help 27 million Americans become more physically active, the Eastern Michigan University (EMU) Racial and Ethnic Approaches to Community Health (REACH) initiative promotes physical activity through local partnerships in geographic areas where the priority population (Asian Americans) lives. Methods Working with the state department of transportation, local municipalities, public schools, faith-based organizations, local businesses, and community health partners, EMU REACH used the following strategies to increase physical activity: 1) implement policies and activities to connect pedestrian, bicycle, or transit transportation networks (i.e., activity-friendly routes) to everyday destinations. 2) launch safe routes to school programs to increase walking and bicycling to and from school and 3) promote equitable park programs and policies that make it safe and easy for residents to be physically active. The team adopted the action planning guide and assessment modules in the Active Communities Tool (ACT) to facilitate cross-sector collaborations in developing an action plan to improve the community built environments that promote physical activity. Results The EMU CHDIS has successfully reached 24,510 people impacted by new/improved policies and plans in 2018-22. In the process, our environment scan showed that people living in underserved areas and from racial and ethnic minority groups are less likely to have access to these places due to historical land use, housing, and transportation policies. Based on the results from project implementation, it is recommended that creating or modifying streets, parks, and trails to connect activity-friendly routes to everyday destinations and offer access to safe places for physical activity for people of all ages and abilities can promote active lifestyles and provide physical-active environment. Conclusion While celebrating wins through the APHN initiative in Michigan, we advocate for new supportive policies and engage with more community members to raise awareness about the new resources to maintain the active momentum.

Land use change analysis and modeling of its future trajectories in Morogoro Region, Tanzania: Implication for conservation

In Sub-Saharan Africa, where people's livelihoods depend largely on natural resources, understanding land use change dynamics and its implications for the sustainability of social-ecological systems is critical. This study analyzed both historic land use and land cover (LULC) change and trajectories for future change in the Morogoro Region, Tanzania. We mapped LULC in the study area for 1994, 2007 and 2020 using Random Forest in Google Earth Engine and projected future LULC in 2033 using Land Change Modeler. Results revealed that conversion of natural vegetation and wetlands has occurred at a high rate due to cropland expansion and will likely continue over the next decade. Conversion to cropland occurred on the edges of protected areas, in remnant forests and near existing cropland, and was associated with slope, elevation, proximity to settlements and variation in annual precipitation. In landscapes where wildlife shares areas with humans, converting natural vegetation into crop production increases tension and human-wildlife conflicts. Given compounding impacts of a growing human population in Tanzania, and reduced crop yields due to unpredictable rains and prolonged droughts, both human wellbeing and biodiversity conservation require understanding the resulting pressure on land and ecosystems.

Multilayer perceptron and Markov Chain analysis based hybrid-approach for predicting land use land cover change dynamics with Sentinel-2 imagery

As urbanization accelerates, the degree of human impact on land use is increasing. land use land cover change (LULC) is acknowledged as crucial factor in environmental change. The best way to understand historical land use patterns, changes, drivers, and developments is through a rigorous assessment of LULC changes. In this study, we aim to identify LULC changes from 2015 to 2022, and predict changes for 2030. Sentinel-2 images were employed to analyze LULC change patterns and predict future trends. The Random Forest algorithm was used to classify the various LULC classes with high accuracy and reliability. Multilayer Perceptron and Markov Chain Analysis (MLP-MCA) based Hybrid-Approach was employed to predict the future dynamics of LULC change for 2030. The study revealed that built-up area expanded 90.64 km2 from 2015 to 2022 due to natural resource substitution. Predictions indicate that 58.84% of the study area will be transform into built-up by 2030.

The role of land use and land cover changes in triggering soil losses in the SE Alentejo, Portugal

AbstractThis study analyses and interprets the effects of historical and contemporary land use and cover changes (LULC) on soil erosion in the Serra de Mértola region, Portugal, by using the 58 years of measurements in 8 × 22 m erosion plots at the Vale Formoso Erosion Centre and employing methodologies including field observations, aerial image analysis and Landsat NDVI trend assessment. Land cover and management changes, influenced by agricultural policies since the early 20th century, notably during the wheat campaigns of the fascist regime, have exacerbated soil erosion, with the highest rates observed in vertical fallow (964 g m−2 yr−1), wheat (90 g m−2 yr−1) and horizontal fallow (66 g m−2 yr−1). These practices continue to be somewhat relevant today, as cereal production is still being subsidized. However, Quercus, Pines—introduced since agrarian reforms and Portugal's entry into the common agricultural policy (CAP)—and spontaneous vegetation from CAP's set‐aside policies and recent land abandonment trends show lower erosion rates, underlining vegetation's role in erosion protection. Using NDVI trend analysis, we distinguish between natural fluctuations and land cover changes impacts. Understanding these changes and how they relate to slope and valley floor dynamics, such as incision, aggradation or stabilization, is crucial for recognizing human influences on the earth's surface. Our research highlights sustainable land management's role in reducing soil erosion in desertification‐prone areas.

Ecohydrological response to multi-model land use change at watershed scale

Study regionThe Min River basin, China. Study focusIn order to investigate the ecohydrological response under historical and future land use changes, we simulated daily runoff sequences under different land use scenarios by coupling the PLUS model with the Physical Hydrological Model and quantitatively assessed the ecohydrological impacts of different land use changes in the watershed by combining the IHA method. New hydrological insights for the regionThe Min River Basin is dominated by grassland, woodland and, cultivated land which account for 94 % of the total. During the period 2000–2020, the area of cultivated land decreased by 4.47 % overall, and construction land increased by 78.68 % overall. Compared to the base year of 2010, the multi-year average monthly runoff increased under different land use scenarios. The high flow indicators (1 daymax, 7 daymax, and 30 daymax) had the largest increasing trend under the natural development scenario in 2030, 54 m3/s, 33 m3/s, and 24 m3/s, respectively, whereas their increase decreased under the ecological protection scenario in 2030; the low flow indicators (1 daymin, 7 daymin, and 30 daymin) decreased less in the 2030 eco-protection scenario than in the natural development scenario, where they decreased by − 5 m3/s, − 9 m3/s, and − 11 m3/s, respectively. The results of the study contribute to a deeper understanding of the response of watershed hydrological processes to land-use change.

Grassland Carbon Change in Northern China under Historical and Future Land Use and Land Cover Change

Land use and land cover (LULC) change has greatly altered ecosystem carbon storage and exerted an enormous impact on terrestrial carbon cycling. Characterizing its impact on ecosystem carbon storage is critical to balance regional carbon budgets and make land use decisions. However, due to the availability of LULC data and the strong variability in LULC change, uncertainty remains high in quantifying the effect of LULC change on the historical and future carbon stock. Based on four historical LULC maps and one future LULC projection, this study combined the Land Use and Carbon Scenario Simulator (LUCAS) with a process-based CENTURY model to evaluate the historical and future LULC change and its impact on grassland carbon storage from 1991 to 2050 in northern China. Results showed that grassland experienced a drastic decrease of 16.10 × 103 km2 before 2005, while agriculture and barren land increased by 16.91 × 103 km2 and 3.73 × 103 km2, respectively. After that, grassland was projected to increase, agriculture kept steady, and barren land decreased. LULC change has resulted in enormous total ecosystem carbon loss, mainly in agro-pasture areas; the maximum 8.54% of carbon loss happened in 2000, which was primarily attributed to agriculture to grassland, forest to grassland, grassland to agriculture, and grassland to barren. Before 2000, the grassland net biome productivity was projected to be −15.54 Tg C/yr and −2.69 Tg C/yr with and without LULC change. After 2001, the LULC change showed a positive impact on the grassland carbon balance, and the region was projected to be a carbon sink. Ecological projects have made a significant contribution to grassland carbon storage. The paper provides a framework to account for the effects of LULC change on ecosystem carbon and highlights the importance of improving grassland management in balancing the grassland carbon budget, which is helpful to understand the regional carbon budget and better inform local land use strategies.

Response of soil microbial community structure, carbon and nitrogen cycling to drying and rewetting

Global change scenarios predict that precipitation regimes will become more variable in many parts of the world, extending drought periods and increasing rainfall intensity. Under these conditions, soil microbial community composition will likely change in ways that have implications for microbially-mediated nutrient cycling. Understanding these responses is key to predicting consequential changes in ecosystem functions. A 30 day incubation experiment was used to investigate the response of microbial community structure to three different soil moisture treatments, namely, constantly moist (CM), constantly dry (CD), and drying-rewetting (DRW), in soils of three different land condition types (Remnant, Restored, and Old-field) from Para Woodlands Nature Reserve, South Australia. Soil respiration and inorganic N transformations were approximately the same across soils, despite fundamental differences in physicochemical properties, vegetation communities, and land-use history. Soil microbial community structure changed in response to the different soil moisture treatments; responses of taxa was divergent among soils. These results demonstrate that changes to soil moisture regimes under climate projections will almost certainly have consequences for soil microbial communities and C and N dynamics. The results highlight the need for further research to understand the mechanisms driving divergent responses to soil moisture, particularly in areas of different land-use types.

Effects of historical land use and recovery pathways on composition, structure, ecological function, and ecosystem services in a Caribbean secondary forest

Regenerated secondary forests in the tropics are resilient ecosystems. Differences in land-use history and disturbance, abiotic and biotic site conditions, and successional pathways can influence secondary forest biodiversity, structure, ecological functions, and ecosystem services. However, studies assessing the supply of ecosystem services of secondary forests are limited. We examined trees in plots located across late successional stage secondary forest in the Luquillo Experimental Forest, Puerto Rico with three combinations of historical canopy cover (circa 1936) and post-agricultural recovery pathways: (1) > 50% canopy cover and passive regeneration (>50 P), (2) < 50% canopy cover and passive regeneration (<50 P), and (3) < 50% canopy cover and assisted + passive regeneration (<50 A+P). Using i-Tree Eco methodology, we investigated if differences in historical cover and passive vs assisted natural regeneration resulted in differences in composition and structure, hydrological functions, and estimated regulating ecosystem services, and compared the results between native and non-native species. The <50 P plots had greater species richness than the >50 P and <50 A+P plots, while the <50 A+P plots had significantly greater DBH, height, basal area, aboveground biomass, and estimated quantities of evaporation and transpiration, carbon storage, and removal of airborne contaminants compared to the other recovery pathways. Differences among plot groups can be attributed to historical management actions in concert with successional trajectories characteristic of novel secondary forests. Native species dominated throughout these secondary forests and cumulatively exhibited services that were 1.3 to 3.5 times greater than those of non-native species. However, non-native trees contributed disproportionally to basal area and aboveground biomass, and thus to some ecosystem services. Both natives and non-natives exhibited service provision that varied significantly with diameter size class and service type, and large trees were observed to be dominant service providers irrespective of species origin. Our study marks the first landscape-scale quantitative assessment of forest composition, structure and ecological functioning that is explicitly linked to exploring regulating ecosystem services within the montane secondary forest in Puerto Rico and expands representation of this research from the Caribbean. The findings underscore the role of historical land use and recovery pathways in driving services of tropical forests and show how ecosystem functions can vary in accordance with dynamic structural attributes of individual trees. This research can provide a useful point of comparison for analysis of biomass accumulation, ecosystem service provision, and evaluating service tradeoffs associated with forest structure in other recovering and old-growth tropical landscapes.

Land-Use-Change-Induced Cooling and Precipitation Reduction in China: Insights from CMIP6 Models

In the 21st century, the effect of land use/land cover change (LULCC) on climate has become an area of active research. To explore the effects of LULCC on temperature and precipitation in China, we used outputs from the BCC-CSM2-MR, CESM2, IPSL-CM6A-LR, and UKESM1 models, which participated in the Land Use Model Intercomparison Project (LUMIP) of the Coupled Model Intercomparison Project Phase 6 (CMIP6). Based on these models, we identified temporal variations in precipitation and near-surface air temperature (hereinafter temperature) with and without historical land use changes and their relation with LULCC in China during 1850–2014. We then determined the significant changing period (1972–2012) and revealed the relation between the spatial distribution of historical change in vegetation cover types, precipitation, and temperature. The results showed that annual historical precipitation decreased faster (132.23 mm/(1000 a) faster), while annual historical temperature increased slower (2.70 °C/(1000 a) slower) than that without LULCC during 1850–2014. LULCC not only influenced surface properties to change local precipitation and temperature distributions and mean values, but also affected other components through atmospheric circulations due to typical monsoon characteristics in China. The relative contribution of grassland change to precipitation variation was the largest, while relatively, cropland change contributed the most to temperature variation. Our study innovatively used new model outputs from LUMIP to analyze the impacts of LULCC on precipitation and temperature, which can help to guide and improve future land use management and predictions of precipitation and temperature.

Vegetation, topography, and soil depth drive microbial community structure in two Swedish grasslands.

Soil microbial diversity and community composition are shaped by various factors linked to land management, topographic position, and vegetation. To study the effects of these drivers, we characterized fungal and bacterial communities from bulk soil at four soil depths ranging from the surface to below the rooting zone of two Swedish grasslands with differing land-use histories, each including both an upper and a lower catenary position. We hypothesized that differences in plant species richness and plant functional group composition between the four study sites would drive the variation in soil microbial community composition and correlate with microbial diversity, and that microbial biomass and diversity would decrease with soil depth following a decline in resource availability. While vegetation was identified as the main driver of microbial community composition, the explained variation was significantly higher for bacteria than for fungi, and the communities differed more between grasslands than between catenary positions. Microbial biomass derived from DNA abundance decreased with depth, but diversity remained relatively stable, indicating diverse microbial communities even below the rooting zone. Finally, plant-microbial diversity correlations were significant only for specific plant and fungal functional groups, emphasizing the importance of functional interactions over general species richness.