Meta-Analysis of the Effect of Saline-Alkali Land Improvement and Utilization on Soil Organic Carbon

There is a large amount of saline-alkali land in China. Through the improvement and utilization of saline-alkali land to improve the carbon content in soil, it can not only become a reserve resource of cultivated land or grazing grassland, but also become an important land “carbon sink”. In this study, we performed a comprehensive meta-analysis to identify the impact of improvement and utilization of saline-alkali soil on soil organic carbon (SOC) in China. Our results showed that the soil salt and alkali content in Heilongjiang Province and Jilin Province in China was the highest, with an SOC content between 3.05 and 17.8 g/kg and pH between 8.84 and 9.94. Among the five methods of reclamation, halophyte planting, fertilization, biochar and modifier application, only biochar and modifier application significantly increased the SOC content (p < 0.05). The content of SOC in saline-alkali soil was 2.9–6.3 g/kg before biochar application, and significantly increased to 6.2–13.05 g/kg after biochar application (p < 0.01). The SOC content was 3.05–8.12 g/kg before the application of the modifier, and significantly increased to 3.68–9 g/kg (p < 0.05) after the application of the modifier. After utilization and improvement of saline-alkali land, the total nitrogen, available phosphorus and available potassium also increased significantly (p < 0.05). This study provides a scientific basis for further understanding the improvement and utilization of saline-alkali land in China and its potential for increasing carbon sinks

Ecosystem Services and landscape change associated with plantation expansion in a tropical rainforest region of Southwest China

Rapid plantation expansion and its associated impacts on habitat fragmentation and landscape connectivity in many tropical areas has raised increasing concerns as to its impact on Ecosystem Services (ES). Using the InVEST modelling suite, we evaluated critical ES dynamics in four zones of varying plantation expansion intensity (high, medium, low and no plantation expansion) in Xishuangbanna prefecture in Southwest China from 1976 to 2012. Based on these results, we also exmained the relationship between ES and landscape pattern and connectivity derived by the “probability of connectivity” model. We found that during the study period, plantation area increased more than 20 times in Xishuangbanna prefecture as a whole, while broad-leaved forest cover decreased by nearly 30%. The impact of plantation on ES was substantial at both the regional and local scale. Carbon stocks and water yield services decreased by 15.48% and 10.85%, respectively, from 1976 to 2012 throughout the region as a whole. Within the selected study zones, carbon stock and water yeild decreased by 45% and 32%, respectively, from the no plantation to the high plantation zones in 2012 specifically. Plantation expansion has also resulted in a decrease in natural forest cover and a high level of habitat fragmentation. Landscape connectivity decreased by a range of 54.64–95.58% throughout the study area, with 134.58 km2 of forest patches of high importance reduced to medium or low importance during the study period. Correlation analysis showed that carbon storage was more closely correlated to landscape connectivity than forest habitat percentage, large patch index or cohesion index. Together, these results highlight that habitat configuration with a high connectivity level between fragmented patches is important for maintaining critical Ecosystem Services.</p

Cavity quantum-electrodynamical time-dependent density functional theory within Gaussian atomic basis. II. Analytic energy gradient

Following the formulation of cavity quantum electrodynamical time-dependent density functional theory (cQED-TDDFT) models [Flick et al., ACS Photonics 6, 2757-2778 (2019); Yang et al., J. Chem. Phys. 155, 064107 (2021)], here we report the derivation and implementation of the analytic energy gradient for the polaritonic states of a single photochrome within the cQED-TDDFT models. Such gradient evaluation is also applicable to a complex of explicitly-specified photochromes, or, with proper scaling, a set of parallel-oriented, identical-geometry, non-interacting molecules in the microcavity

Impacts of Short-Term Grazing Intensity on the Plant Diversity and Ecosystem Function of Alpine Steppe on the Qinghai&ndash;Tibetan Plateau

Livestock grazing is the primary land use of grasslands worldwide. Grazing has been asserted to alter grassland ecosystem functions, such as productivity, nutrient cycling, and biodiversity conservation. However, few studies have focused on the impact of grazing intensity on the ecosystem multifunctionality (EMF) of alpine grasslands. We conducted a field experiment of manipulating sheep grazing intensity effects on alpine steppe by surveying plant community characteristics and ecosystem functions. Our results showed that plant community composition was altered with increasing grazing intensity, and the dominant species shifted from grasses and sedges to forbs. EMF was the highest under no grazing (CK) and the lowest under heavy grazing (HG), but there was insignificant difference between CK and HG. HG significantly decreased some indicators that reflected nutrient cycling functions, such as soil available nitrogen, plant leaf nitrogen (PN) and phosphorus content (PP). Furthermore, plant diversity had strong correlations with SOC, total nitrogen (TN), and PN. The results could provide scientific bases for biodiversity conservation and sustainable grazing management of alpine steppe

Short-term grazing changed temporal productivity stability of alpine grassland on Qinghai-Tibetan Plateau via response species richness and functional groups asynchrony

The stability of grassland is pivotal in maintaining the grassland functioning and services. However, the knowledge about the consequences of grazing on stability of grassland productivity is limited. Based on a 3-year manipulated experiment with two grazing regimes (i.e., continuous grazing and rotational grazing) along four levels of grazing-intensity (0, 4, 6, and 8 sheep per hectare) on the Qinghai-Tibetan Plateau, we researched the responses of temporal stability of plant community and functional groups of alpine grasslands to different grazing management regimes. We found that grazing regimes, intensity and their interaction affected the temporal stability of aboveground net primary productivity of alpine grassland (ANPP), and intermediate rotational grazing significantly reduced the temporal stability of ANPP, whereas increased the stability of productivity of functional group of forbs. The response species to continuous grazing and rotational grazing are different, for grasses and forbs respectively. Rotational grazing and intermediate continuous grazing increased the diversity of response species. Structural equation modeling further revealed that functional groups asynchrony stabilized the productivity of the alpine grassland ecosystem under grazing in the Qinghai-Tibetan Plateau. These results showed that the rotational grazing and intermediate continuous grazing can maintain the productivity stability, and highlighted importance of regulating the relationships among functional groups for promoting the stability of alpine grassland under grazing management