The influence of urbanization on vegetation phenology is gaining considerable attention due to its implications for human health, cycling of carbon and other nutrients in Earth system. In this study, ...we examined the relationship between change in vegetation phenology and urban size, an indicator of urbanization, for the conterminous United States. We studied more than 4500 urban clusters of varying size to determine the impact of urbanization on plant phenology, with the aids of remotely sensed observations since 2003–2012. We found that phenology cycle (changes in vegetation greenness) in urban areas starts earlier (start of season, SOS) and ends later (end of season, EOS), resulting in a longer growing season length (GSL), when compared to the respective surrounding urban areas. The average difference of GSL between urban and rural areas over all vegetation types, considered in this study, is about 9 days.Also, the extended GSL in urban area is consistent among different climate zones in the United States, whereas their magnitudes are varying across regions. We found that a tenfold increase in urban size could result in an earlier SOS of about 1.3 days and a later EOS of around 2.4 days. As a result, the GSL could be extended by approximately 3.6 days with a range of 1.6–6.5 days for 25th ~ 75th quantiles, with a median value of about 2.1 days. For different vegetation types, the phenology response to urbanization, as defined by GSL, ranges from 1 to 4 days. In conclusion, the quantitative relationship between phenology and urbanization is of great use for developing improved models of vegetation phenology dynamics under future urbanization, and for developing change indicators to assess the impacts of urbanization on vegetation phenology.
The influence of urbanization on vegetation phenology is gaining considerable attention due to its implications for human health, cycling of carbon and other nutrients in Earth system. In this study, ...we examined the relationship between change in vegetation phenology and urban size, an indicator of urbanization, for the conterminous United States. We studied more than 4500 urban clusters of varying size to determine the impact of urbanization on plant phenology, with the aids of remotely sensed observations since 2003–2012. We found that phenology cycle (changes in vegetation greenness) in rural areas starts earlier (start of season, SOS) and ends later (end of season, EOS), resulting in a longer growing season length (GSL), when compared to the respective surrounding urban areas. The average difference of GSL between urban and rural areas over all vegetation types, considered in this study, is about 9 days. Also, the extended GSL in urban area is consistent among different climate zones in the United States, whereas their magnitudes are varying across regions. We found that a tenfold increase in urban size could result in an earlier SOS of about 1.3 days and a later EOS of around 2.4 days. As a result, the GSL could be extended by approximately 3.6 days with a range of 1.6–6.5 days for 25th ~ 75th quantiles, with a median value of about 2.1 days. For different vegetation types, the phenology response to urbanization, as defined by GSL, ranges from 1 to 4 days. The quantitative relationship between phenology and urbanization is of great use for developing improved models of vegetation phenology dynamics under future urbanization, and for developing change indicators to assess the impacts of urbanization on vegetation phenology.
Abstract
Given the increasing attention to climate change and rising CO
2
(CCRC) in the global carbon cycle, we remain unclear about how China's unprecedented land use/cover change (LUCC) in the ...carbon budget has been affected by CCRC in recent decades. Here, we combined remotely sensed land use/cover (LUC) datasets and the Biome‐BGCMuSo model to address this issue by setting different scenarios. We found that LUCC led the carbon sink to increase by approximately 104.24 ± 46.52 Tg C without considering CCRC during 1990–2020. Carbon sinks contributed by afforestation (374.97 ± 36.50 Tg C) and grassland planting (15.75 ± 9.11 Tg C) offset other LUC trajectories caused carbon loss (286.47 ± 32.18 Tg C, 87.33% owing to agricultural reclamation). LUCC contributed carbon sinks were amplified by ∼20% under CCRC at the national scale. This rate increased to 106.03% in northeast China but decreased to −26.68% in southern China. CCRC led carbon sink contributed by afforestation amplified by 85.11% in northeastern China but was only 26.35% in southern China. CCRC amplified carbon emissions due to agricultural reclamation by 103.20% in northeastern China and by 25.09% in southern China. Our results demonstrated that ecological restoration projects are efficient in enhancing carbon sinks and mitigating emissions. Divergent amplifying/reducing effect of CCRC across different geographic regions implied the sensitivity of different LUC trajectories to CCRC varied with different climate backgrounds. Land management strategies should be implemented with spatial heterogeneity to amplify afforestation and grassland planting contributed carbon sinks and decrease other LUC trajectories caused carbon loss under the global change environment.
Plain Language Summary
It is undoubted that climate change and rising CO
2
(CCRC) would alter the effect of land use/cover change (LUCC) on the carbon budget. However, to what extent CCRC will influence the effect of LUCC on the carbon budget remains unclear. In this work, we evaluated the impact of CCRC on the carbon budget change caused by LUCC. We found that CCRC would amplify or dampen the impact of LUCC on the carbon budget. Meanwhile, this amplifying or dampening rate was divergent in different geographic regions. Our work provides new insights for making climate change mitigation targeted land decisions to increase carbon sinks with ecological restoration and construction and reduce emissions through protection.
Key Points
Afforestation and grassland planting offset other land use/cover change (LUCC) caused carbon loss and continue to increase carbon sink
Climate change and rising CO
2
(CCRC) amplified China's LUCC contributed carbon sinks by approximately 20%
CCRC amplified carbon sink induced by LUCC in northeastern China, reduced it in southern China
Urban green space is an important refuge of biodiversity in urban areas. Therefore, it is crucial to understand the relationship between the landscape pattern of green spaces and biodiversity to ...mitigate the negative effects of urbanization. In this study, we collected insects from 45 green patches in Beijing during July 2012 using suction sampling. The green patches were dominated by managed lawns, mixed with scattered trees and shrubs. We examined the effects of landscape pattern on insect species density using hierarchical partitioning analysis and partial least squares regression. The results of the hierarchical partitioning analysis indicated that five explanatory variables, i.e., patch area (with 19.9% independent effects), connectivity (13.9%), distance to nearest patch (13.8%), diversity for patch types (11.0%), and patch shape (8.3%), significantly contributed to insect species density. With the partial least squares regression model, we found species density was negatively related to patch area, shape, connectivity, diversity for patch types and proportion of impervious surface at the significance level of p < 0.05 and positively related to proportion of vegetated land. Regression tree analysis further showed that the highest species density was found in green patches with an area <500 m2. Our results indicated that improvement in habitat quality, such as patch area and connectivity that are typically thought to be important for conservation, did not actually increase species density. However, increasing compactness (low-edge) of patch shape and landscape composition did have the expected effect. Therefore, it is recommended that the composition of the surrounding landscape should be considered simultaneously with planned improvements in local habitat quality.
Heat‐resistant
molding of compounds is an indispensable part in encapsulating future electronic power devices. Herein, it is used for polyfunctional epoxy resin (EP) and diamine‐phenol benzoxazine ...(BOZ) as resin matrix, 4,4'‐diaminodiphenylmethane (DDM) as curing agent, and iron acetylacetonate (Fe(acac)3) as curing accelerator, as well as inorganic fillers and other auxiliaries, to prepare heat‐resistant molding compounds. The curing behavior, processability and thermal performance of the EP/DDM/BOZ (EDB) resin blends containing different contents of DDM, BOZ, and Fe(acac)3 are first systematically investigated. The EDB molding compounds (MCEDB) with suitable BOZ content show good processability, and the molding process can be compatible with that of commercial epoxy molding compounds (EMC). With increasing the BOZ content, the glass transition temperature of cured MCEDB is greatly enhanced to a maximum of 261 °C determined by dynamic mechanical analyzer, owing to the hydrogen‐bond interaction generated after polymerization of BOZ increasing the rigidity of network chains. Moreover, the cured MCEDB also exhibits higher thermal decomposition stability, better high‐temperature (200 °C) mechanical properties, and lower water absorption compared to the cured EMC. After high‐temperature (200 °C) aging for 500 h, the cured MCEDB with suitable BOZ content still maintains outstanding performance. This study provides a promising strategy for preparing heat‐resistant electronic packaging molding compounds.
In this work, heat‐resistant molding compounds based on epoxy resin/aromatic amine/benzoxazine are successfully developed. The cured molding compounds exhibit excellent thermal decomposition stability, high‐temperature (200 °C) mechanical properties, and lower water absorption, as well as superior high‐temperature aging resistance, compared to the typical epoxy molding compounds. This work provides a promising candidate as heat‐resistant materials for encapsulating future high‐power devices.
One‐component epoxy systems with long shelf life during storage or transportation, while high curing reactivity during molding as well as satisfactory mechanical and thermal performances after ...curing, are extremely essential for industrial application. Herein, we used salicylaldehyde and o‐phenylenediamine to synthesize 2‐(2′‐hydroxyphenyl)‐1H‐benzimidazole (HPBI), an imidazole derivative with an intramolecular hydrogen bond between the phenolic hydroxyl group and the pyridine‐type nitrogen atom of imidazole ring, and further employed HPBI as a thermal latent curing accelerator for epoxy/phenolic resins. The intramolecular hydrogen bond endowed HPBI with inert activity toward resins at room temperature, making the one‐component resin system a long‐term storage stability (21 days of shelf life at 30°C). Once rising the temperature to a high degree, a rather high activity of HPBI to accelerate the curing process of epoxy/phenolic resins. It was attributed to the effective release of high activity of the pyridine‐type nitrogen by breaking the intramolecular hydrogen bond at high temperature. In addition, the resulted thermosets from HPBI also possessed the comparable Tg (>130°C, determined by DMA) and thermostability (Td‐5% > 380°C) with that from common curing accelerators. Therefore, HPBI was proved to be a promising thermal latent curing accelerator applied in electronic packaging field.
The imidazole derivative (HPBI) with an intramolecular hydrogen bond was obtained and further developed as a thermal latent curing accelerator for epoxy/phenolic resins. Compared to the common curing accelerators, HPBI possessed the highest activity to accelerate the curing process of epoxy/phenolic resins at high temperature, whereas the one‐component resin composition has long‐term storage stability (approximately 3‐weeks' shelf life) at 30ºC. In addition, the obtained thermosets using HPBI also exhibited the comparable Tg (greater than 130ºC) and thermostability (Td‐5% > 380ºC) with that using common curing accelerators.
Lead-based halide perovskites have received great research interest in producing exceptional optoelectronic devices owing to their superior photophysical properties. However, inclusion of toxic Pb in ...these perovskites brings great risk to public health and hinders their use. Here we report the use of copper(I) to fully substitute Pb to produce Pb-free one-dimensional (1D) CsCu2I3 single crystals (SCs). High-quality, air stable, and yellow-emitting 1D CsCu2I3 SC with length as long as 13 mm is synthesized via inverse temperature crystallization method. A record photoluminescence quantum yield (PLQY) first exceeding 50% (50.4%) is obtained with oleic acid as additive during growth. White light-emitting diodes produced by using the 1D CsCu2I3 SC as yellow phosphors are strikingly capable of working continuously for more than 580 h with a half-lifetime of ~150 h in air. Photodetectors fabricated by the 1D CsCu2I3 SC show distinct UV response with fast response time as low as 50.4 ms (at 340 nm). Our findings pave a way by using the copper(I)-based 1D CsCu2I3 SCs for future high-efficiency solid-state lighting and fast UV photodetection applications.
High-quality lead-free copper(I)-based 1D CsCu2I3 halide single crystal has been synthesized via a modified inverse temperature crystallization method using oleic acid as additive during growth. A series of characterizations prove the high quality, stability, and efficiency of the 1D CsCu2I3 single crystal with a champion PLQY of 50.4%. Our findings demonstrate good optoelectronic applications for copper(I)-based CsCu2I3 single crystal. Display omitted
●Inverse temperature crystallization is newly adopted to produce CsCu2I3 single crystals.●A record PLQY of 50.4% is achieved in the CsCu2X3 halide family.●Trap intensity of the 1D CsCu2I3 SC is first measured as low as 2.95 × 1010 cm−3.●UV photodetector based on the 1D CsCu2I3 SC shows fast response time as 50.4 ms.
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