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Allometry reflects the quantitative relationship between the allocation of resources among different organs. Understanding patterns of forest biomass allocation is critical to comprehending global climate change and the response of terrestrial vegetation to climate change. By collecting and reorganizing the existing allometric models of tree species in China, we established a database containing over 3000 empirical allometric models. Based on this database, we analyzed the model parameters and the effect of climate on forest biomass allocation under the context of 'optimal allocation theory'. We showed that (1) the average and median exponent of power functions for above-ground biomass were 2.344 and 2.385, respectively, which significantly deviated from the theoretical prediction of 2.667 by metabolic theory (p < 0.01). (2) The parameters of the allometric model were not constant, and not significantly correlated with temperature, precipitation, latitude, and elevation (p > 0.05), but were more closely related to individual size (p < 0.01). (3) Among different types of forests, the proportion of above-ground biomass in tropical rainforests and subtropical evergreen rainforests was significantly higher than that in temperate forests and boreal forests (p < 0.05). The proportion of trunk and branch biomass allocated to tropical rainforest was significantly higher than that of boreal forest (p < 0.05), while the proportion of root and leaf biomass allocated to tropical rainforest was significantly lower than that of boreal forest (p < 0.05). (4) The abiotic environment plays a crucial role in determining the allocation of plant biomass. The ratio of below-ground/above-ground biomass is significantly and negatively correlated with both temperature and rainfall (p < 0.01), and significantly and positively correlated with altitude and latitude (p < 0.01). This means that as temperature and rainfall increase, there is a decrease in the amount of biomass allocated to below-ground structures such as roots. On the other hand, as altitude and latitude increase, there is an increase in below-ground biomass allocation. These findings highlight the importance of considering the influence of abiotic factors on plant growth and development. [ABSTRACT FROM AUTHOR]

Phylogenies are crucial for understanding historical patterns of genetic biodiversity, but very few are incorporated practically into existing conservation programs. Xishuangbanna, a tropical–subtropical forest transition, is a key biodiversity hotspot in Southwest of China; however, gaps between practical protection and national planning need to be bridged, as ongoing, rapid expansion of rubber plantations in the region increasingly threatens local diversity. Here, we used administrative regions as study units to identify spatial patterns for 158 threatened woody species and investigate the ratio of tropical floristic to temperate floristic in the transition zone. We used all-subsets regression analysis to test the impacts of environments (climatic, edaphic, topographic) on biodiversity patterns. Spatial patterns using several conservation metrics gave different results, with species richness, phylogenetic diversity, and evolutionary distinctiveness and global endangerment highly consistent spatially, while either standardized phylogenetic diversity and phylogenetic structure performed differently from others for spatial patterns. The biodiversity patterns of threatened woody species in Xishuangbanna are affected by the combined impact of rubber plantations and abiotic environments, but their evolutionary history is not, with only c. 69% of phylogenetic diversity currently protected by traditional nature reserves. Although the Menglong and Xiangming townships show high conservation values, they are not in the reserves. Eleven threatened woody species were required for ex situ conservation due to threats from clearance for rubber plantations and in all, 21 regionally and internationally important species are currently unprotected. We recommend incorporating the phylogenetic component of biodiversity in improving current and establishing new reserves. [ABSTRACT FROM AUTHOR]

Simple Summary: Species interactions are one of the main factors affecting community assembly, yet the role of such interactions remains mostly unknown. Here, we investigated roles of potential species associations in fish community assembly in the Qiupu River, China. Our results suggested that potential species associations might have been underestimated in stream fish community assembly. The contribution of potential species associations to fish community assembly can be reflected by interaction network structures. Omnivorous species play an important role in maintaining network structure as they may have more associations with other species. This study highlights the importance of capturing species associations in river ecosystems across different geographical and environmental settings. Environmental filtering, spatial factors and species interactions are fundamental ecological mechanisms for community organisation, yet the role of such interactions across different environmental and spatial settings remains mostly unknown. In this study, we investigated fish community organisation scenarios and seasonal species-to-species associations potentially reflecting biotic associations along the Qiupu River (China). Based on a latent variable approach and a tree-based method, we compared the relative contribution of the abiotic environment, spatial covariates and potential species associations for variation in the community structure, and assessed whether different assembly scenarios were modulated by concomitant changes in the interaction network structure of fish communities across seasons. We found that potential species associations might have been underestimated in community-based assessments of stream fish. Omnivore species, since they have more associations with other species, were found to be key components sustaining fish interaction networks across different stream orders. Hence, we suggest that species interactions, such as predation and competition, likely played a key role in community structure. For instance, indices accounting for network structure, such as connectance and nestedness, were strongly correlated with the unexplained residuals from our latent variable approach, thereby re-emphasising that biotic signals, potentially reflecting species interactions, may be of primary importance in determining stream fish communities across seasons. Overall, our findings indicate that interaction network structures are a powerful tool to reflect the contribution of potential species associations to community assembly. From an applied perspective, this study should encourage freshwater ecologists to empirically capture and manage biotic constraints in stream ecosystems across different geographical and environmental settings, especially in the context of the ever-increasing impacts of human-induced local extinction debts and species invasions. [ABSTRACT FROM AUTHOR]

Excess litter accumulates on the soil surface of fenced grasslands and alters the abiotic environment and plant population dynamics. However, little is known about the effect of litter accumulation on the interaction between environmental factors and plant population characteristics in fenced grasslands, especially over different time scales. We applied a three-year litter removal experiment to two kinds of fenced grasslands in Inner Mongolia, China. We measured soil temperature in situ and plant phenology and population characteristics of three dominant species (Stipa grandis, S. krylovii, and Leymus chinensis). During the growing season, litter accumulation (i.e., the control) significantly decreased soil temperature, with a larger effect in the daytime than at night. The diurnal negative effect gradually weakened across the growing season, whereas the negative effect in the nighttime shifted to a positive effect on soil temperature in the late growing season. The decreased soil temperature delayed plant phenology, with longer delays in S. grandis and S. krylovii than L. chinensis. Litter accumulation also significantly increased the height, cover, root biomass, and relative dominance of L. chinensis but decreased cover, density, root biomass, and relative dominance of both Stipa, driving replacement of S. grandis or S. krylovii by L. chinensis in two grasslands. Our findings emphasize the critical function of litter in grassland management and provide a new insight to elucidating the mechanism of how litter accumulation regulates the abiotic environment, community composition and structure, and successional change in fenced grasslands. [ABSTRACT FROM AUTHOR]

Top‐down and bottom‐up controls regulate the structure and stability of ecosystems, but their relative roles in terrestrial systems have been debated. Here we studied a hydro‐inundated land‐bridge system in subtropical China and tested the relative importance of these two controls in determining the rodent‐mediated regeneration of a locally dominant tree species. Our results showed that both controls operated in terrestrial habitats and that their relative importance switched as habitat size changed. Habitat loss initially removed predators of rodents that released rodent populations and triggered massive seed predation (top‐down control), leading to reduced seedling establishment. A further reduction in habitat size led to decrease in rodent population that was supposed to increase seedling survival of the tree species, but the decline in habitat size deteriorated the abiotic environments (bottom‐up control) that severely prevented seedling recruitment. As the ongoing global land use change is creating increasing number of small‐sized forest fragments, our findings provide novel insights into the restoration of seriously fragmented forests. [ABSTRACT FROM AUTHOR]

Aims Understanding how tree species regulate multiple types of secondary chemicals along elevational gradients is critical for elucidating the physiological and ecological strategies of plants in response to varying biotic and/or abiotic environments. This study aims to examine how Chinese tallow tree (Triadica sebifera) allocates resources to the production of different secondary chemicals in response to varying environments across elevational gradients. Methods We conducted field surveys of different herbivore feeding guilds and their damage rates on Chinese tallow trees along an elevational gradient in China and measured secondary chemicals (tannins and flavonoids) in damaged and undamaged leaves. Important Findings The odds of a leaf being damaged (chewing or scarring) decreased with elevation. Flavonoid concentrations increased with elevation in undamaged leaves but decreased with elevation in damaged leaves, with quercitrin contributing most strongly to this pattern, likely as results of plant responding to changing biotic or abiotic stresses along elevational gradients. Tannin concentrations did not vary with elevation, so undamaged leaves had relatively lower tannin to flavonoid ratios at high elevation than at low elevation. Our study reveals variation in herbivory and contrasting trends in plant secondary metabolism along an elevation gradient and highlights the importance of simultaneously considering multiple types of secondary chemicals in plant physiological and ecological strategies. [ABSTRACT FROM AUTHOR]

Fencing is an effective and practical method for restoring degraded grasslands in northern China. However, little is known about the role of excess litter accumulation due to long‐term fencing in regulating abiotic environment and driving changes in community structure and function. We conducted a three‐year field experiment in two fenced grasslands in Inner Mongolia, and monitored light quantity, soil temperature, and soil moisture continuously, and determined community height, community aboveground net primary productivity (ANPP), and the relative dominance of different plant functional groups. Litter accumulation reduced light quantity and soil temperature but increased soil moisture. The regulating effects of litter accumulation on soil temperature and soil moisture fluctuated temporally and gradually weakened over the growing season. Litter accumulation also altered community vertical structure and function by increasing community height and ANPP. The increase in soil moisture increased the relative dominance of rhizome grasses but suppressed bunch grasses, thereby shifting bunch grass grasslands to rhizome grass grasslands. Our findings provide a potential mechanism for community succession in the context of litter accumulation in fenced grasslands and indicate that the vegetation and ecosystem services of degraded grasslands are improved after appropriate fencing. [ABSTRACT FROM AUTHOR]

Abstract: Aim: To evaluate how a biotic filter (overstorey cover [OC]) shapes an elevational herb richness pattern and to test whether intermediate elevations represent more suitable habitats for herb species due to the minimal biotic and moderate abiotic filtering that occured there. Location: Dongling Mountain, China. Taxon: Herbs. Methods: We sampled herb richness along a 1,000‐m vertical transect (OC and elevation covary) and four horizontal transects (across the OC gradient with no change in elevation). Functional traits related to shade (leaf mass per area [LMA] and leaf stem ratio [LSR]) and freezing tolerance (leaf thickness [LT] and hair density [HD]) were collected based on vegetation sampling plots. We divided the richness data into below‐ and above‐timberline groups and then assessed the most important driver for each group. By estimating the variations in species richness and functional diversity along horizontal transects, we examined how these parameters responded to OC while controlling for associated differences in elevation. Results: Herb richness showed a unimodal relationship with elevation, with a peak around the timberline. Below the timberline, herb richness was better predicted by OC and showed a positive relationship with the functional diversity of LMA and LSR. The frost period performed better in predicting herb richness above the timberline, and herb richness was positively related to the functional diversity of HD. Main conclusions: The results support our hypothesis and highlight the importance of OC in shaping herb richness patterns. Below the timberline, OC acts as a filter, sorting species based on their ability to tolerate shade, whereas the frost period limits richness above the timberline and favours species that can tolerate low temperatures. Therefore, we suggest that biotic interactions, as well as environmental and geographical factors, should be considered the main drivers of elevational plant richness patterns. [ABSTRACT FROM AUTHOR]

Plant trait patterns contribute to understanding the process of community assembly. Using a traitbased method, recent studies have found that, both the spatial component and abiotic environment filtering drives community structuring. However, the community abiotic environment may be influenced by overstory community and species composition, and it is not enough to disentangle the environment filters only considering abiotic factors. In this paper, leaf size and SLA of 11 understory species were measured, and variation portioning was used to explore the explanation power of spatial process, three topographic variables and seven biotic factors describing the overstory community. The results indicated spatial structure, topography and overstory characters contribute to the leaf variation, and biotic environment have significant effects on leaf trait variations. We concluded that community structure and species composition play important roles in community trait patterns, and biotic filtering should be considered in future trait-based studies. [ABSTRACT FROM AUTHOR]

The relationships between cover and AGB for the dominant and widely distributed alpine grasslands on the northern Tibetan Plateau is still not fully examined. The objectives of this study are to answer the following question: (1) How does aboveground biomass (AGB) of alpine grassland relate to plant cover at different spatial scales? (2) What are the major biotic and abiotic factors influencing on AGB-cover relationship? A community survey (species, cover, height, and abundance) was conducted within 1 m × 1 m plots in 70 sites along a precipitation gradient of 50-600 m. Ordinary linear regression was employed to examine AGB-cover relationships of both community and species levels at regional scale of entire grassland and landscape scale of alpine meadow, alpine steppe, and desert steppe. Hierarchical partitioning was employed to estimate independent contributions of biotic and abiotic factors to AGB and cover at both scales. Partial correlation analyses were used to discriminate the effects of biotic and abiotic factors on AGB-cover relationships at two spatial scales. AGB and community cover both exponentially increased along the precipitation gradient. At community level, AGB was positively and linearly correlated with cover for all grasslands except for alpine meadow. AGB was also linearly correlated with cover of species level at both regional and landscape scales. Contributions of biotic and abiotic factors to the relationship between AGB and cover significantly depended on spatial scales. Cover of cushions, forbs, legumes and sedges, species richness, MAP, and soil bulk density were important factors that influenced the AGB-cover relationship at either regional or landscape scale. This study indicated generally positive and linear relationships between AGB and cover are at both regional and landscape scales. Spatial scale may affect ranges of cover and modify the contribution of cover to AGB. AGB-cover relationships were influenced mainly by species composition of different functional groups. Therefore, in deriving AGB patterns at different spatial scales, community composition should be considered to obtain acceptable accuracy. [ABSTRACT FROM AUTHOR]

Cyanobacterial blooms frequently occur in Lake Taihu (China), but the intertwined relationships between biotic and abiotic factors modulating the frequency and duration of the blooms remain enigmatic. To better understand the relationships between the key abiotic and biotic factors and cyanobacterial blooms, we measured the abundance and diversity of prokaryotic organisms by high-throughput sequencing, the abundance of key genes involved in microcystin production and nitrogen fixation or loss as well as several physicochemical parameters at several stations in Lake Taihu during a cyanobacterial bloom of Microcystis sp.. Measurements of the copy number of denitrification-related genes and 16S rRNA analyses show that denitrification potential and denitrifying bacteria abundance increased in concert with non-diazotrophic cyanobacteria ( Microcystis sp.), suggesting limited competition between cyanobacteria and heterotrophic denitrifiers for nutrients, although potential bacteria-mediated N loss may hamper Microcystis growth. The present study provides insight into the importance of different abiotic and biotic factors in controlling cyanobacteria and heterotrophic bacteria spatial variability in Lake Taihu. [ABSTRACT FROM AUTHOR]

Seedlings are vulnerable to many biotic and abiotic agents, and studying seedling dynamics helps understand mechanisms of species coexistence. In this study, the relative importance of biotic neighbors and habitat heterogeneity to seedling survival was examined by generalized linear mixed models for 33 species in a spruce-fir valley forest in northeastern China. The results showed that the relative importance of these factors varied with species and functional groups. Conspecific negative density dependence ( CNDD) was important to the survival of Abies nephrolepis and Picea koraiensis seedling, whereas phylogenetic negative density dependence ( PNDD) was critical to Pinus koraiensis and Betula platyphylla, as well as functional groups of tree, deciduous, and shade-intolerant seedlings. For shrubs and Acer ukurunduense, habitat heterogeneity was significant. Despite of the significance of CNDD, PNDD, and habitat heterogeneity on seedling survival, large proportions of the total variance were not accounted for by the studied variables, suggesting the needs to examine the influences of other factors such as pests, diseases, herbivores, forest structure, species functional traits, and microclimatic conditions on seedling survival in the future. [ABSTRACT FROM AUTHOR]

Aquatic community dynamics are closely dominated by flow regime and water quality conditions, which are increasingly threatened by dam regulation, water diversion, and nutrition pollution. However, further understanding of the ecological impacts of flow regime and water quality conditions on aquatic multi-population dynamics has rarely been integrated into existing ecological models. To address this issue, a new niche-based metacommunity dynamics model (MDM) is proposed. The MDM aims to simulate the coevolution processes of multiple populations under changing abiotic environments, pioneeringly applied to the mid-lower Han River, China. The quantile regression method was used for the first time to derive ecological niches and competition coefficients of the MDM, which are demonstrated to be reasonable by comparing them with the empirical evidence. Simulation results show that the Nash efficiency coefficients for fish, zooplankton, zoobenthos, and macrophytes are more than 0.64, while the Pearson correlation coefficients for them are no less than 0.71. Overall, the MDM performs effectively in simulating metacommunity dynamics. For all river stations, the average contributions of biological interaction, flow regime effects, and water quality effects to multi-population dynamics are 64%, 21%, and 15%, respectively, suggesting that the population dynamics are dominated by biological interaction. For upstream stations, the fish population is 8%–22% more responsive to flow regime alteration than other populations, while other populations are 9%–26% more responsive to changes in water quality conditions than fish. For downstream stations, flow regime effects on each population account for less than 1% due to more stable hydrological conditions. The innovative contribution of this study lies in proposing a multi-population model to quantify the effects of flow regime and water quality on aquatic community dynamics by incorporating multiple indicators of water quantity, water quality, and biomass. This work has potential for the ecological restoration of rivers at the ecosystem level. This study also highlights the importance of considering threshold and tipping point issues when analyzing the "water quantity-water quality-aquatic ecology" nexus in future works. [Display omitted] • A new niche-based metacommunity dynamics model (MDM) is established. • Identification of flow regime and water quality effects on metacommunity. • Quantile regression is used to derive ecological niche and competition coefficient. • Dynamics of multiple populations are effectively simulated using the MDM. [ABSTRACT FROM AUTHOR]

In this study, the microbial community and the physico-chemical properties of soil samples from seven oil-fields in the north of China were analyzed using multiple methods. The study's purpose was to analyze the influence of abiotic factors on the microbial activity and the biotic community. By using the Ultrasonic- Soxhle extraction method of hydrocarbon in oil composition were analyzed, and column chromatography combined with GC-MS was used to analyze the contaminant composition. The results showed that the highest oil concentrations in the soil reached 97.3 g/kg dry soil, which amounts to about 500-1,000 times higher than the background in uncontaminated soil. Moreover, the average nutrient content of contaminated soils was lower than the unpolluted controls. The total bacterial load in the soil was measured using the most probable number (MPN) method and the microbial activity was determined by fluorescein diacetate (FDA) activity. The results showed that soil contaminated with oil seriously affects and limits the microbial populations and their activities. The water content of the soil was the key limiting factor of the microbial populations and the FDA activity. With a water content of 6%, oil content below 15%, and a pH of 7.5-8.0, the conditions supported the highest levels of microbial growth and activity. Microbial populations were 10-100 times and the FDA activity was 2-5 times lower in samples originating from the arid Northwest of China compared to samples from Northwest China. In the northwestern region the microbial diversity was 3 times higher. The microbial communities were limited and suppressed whereby the local environment, the temperature, the water content and the oil content were the key factors that induced the biodiversity of the soil contaminated with oil in different analyses of the geography and the climate environment. [ABSTRACT FROM AUTHOR]

Wildfire is reported to exert strong influences on N cycling, particularly during the early succession period immediately after burning (i.e., < 1 year). Previous studies have mainly focused on wildfires influences on inorganic N concentrations and N mineralization rates; but plant and soil 15N natural abundance (expressed by Î'15N), as a spatial-temporal integrator of ecosystem N cycling, could provide a more comprehensive understanding of wildfire on various N cycling processes at a relatively broader time scale. In this study, we attempted to evaluate legacy effects of wildfire on nitrogen cycling using Î'15N in a boreal forest of northeastern China, which is an important yet understudied ecosystem. We measured inorganic N concentrations (NH4+ and NO3-) and net N transformation rates (net ammonification, net nitrification, and net mineralization) of organic and mineral soil 4 years after a wildfire and compared with unburned area. We also measured Î'15N of plant and soil samples in 4 and 5 years after the fire. We found that even 4 years after burning, wildfire still increased net mineralization and net ammonification in the organic soil and increased NH4+ and total inorganic N (TIN) concentrations in the mineral soil. Organic soil and foliar Î'15N were significantly higher (by 2.2 ‰ and 7.4 ‰, respectively) in the burned area than the unburned area. Five years after fire, plant tissues such as foliar, branch, fine roots and moss in the burned area were increased significantly (by 1.7 ‰ to 6.4 ‰) greater than that in unburned area. The wildfire also significantly increased the Î'15N of Oi, Oa+e and 0-10 cm mineral soil, but had no significant effects on deeper layer of mineral soil. These results indicate the wildfire had a strong legacy effect on N cycling. We suggest that the change of abiotic environment was the primary mechanism determining inorganic nitrogen transformation rates, and the NH3 volatilization might play a key role in severe N losses and thereby affect soil and plant 15N in this ecosystem. [ABSTRACT FROM AUTHOR]

Background and aims: Variations in community-level plant functional traits might indicate the adaptation strategies of vegetations under changing environment. Here, we assess the key factors in controlling functional community compositions across different forest types. Methods: We established 12 1-ha permanent forest dynamics sites, two in each of the six old-growth forests. Each site was divided into 25 plots (20 m × 20 m). We measured five plant traits and eight abiotic factors in each plot. Correlations between environmental factors and plant traits were assessed by step-wise multiple regression. Results: The key abiotic factors controlling community-level plant functional traits in TDMRF were CO, SWC and AN. Those in TCF were CO and AN, in TLRF was AP, in TMRF were CO and TP, in TMEF were pH, SOM and TP, and in TMDF were SWC, pH, TN and TP, respectively. The controlling factors for each of the trait across the vegetations were: SWC, pH,TN,TP and AN for CWM_SLA; CO and AN for CWM_CC;CO, pH, SOM,TN and AN for CWM_LNC;CO,pH,TN and TP for CWM_LPC;and CO,SWC,TN, AN and AP for CWM_WD. Conclusions: Key soil and microclimatic factors controlling plant functional traits change with vegetation types. Each community-level plant functional trait is associated with 3-5 abiotic factors across the vegetations. [ABSTRACT FROM AUTHOR]

In this study, the spatial distribution and seasonal variation of large tintinnids (>76 μm) were investigated in Shenhu Bay during three seasons of 2012. Of the 36 species identified, 9 were dominant (i.e. Tintinnopsis radix, Leprotintinnus simplex, Tintinnopsis japonica, Tintinnopsis tubulosoides, Leprotintinnus nordqvisti, Tintinnopsis beroidea, Stenosemella parvicollis, Tintinnidium primitivum, Tintinnopsis nana). A clear seasonal shift of the taxonomic composition as well as the lorica size of the dominant species was observed. The highest numbers of tintinnid species occurred in spring, while the highest abundance and biomass occurred in summer. Clustering indicated that the seasonal variations of the community structure were more obvious than spatial variations. Spearman correlation analysis revealed that density of phytoplankton prey had a significant impact on the tintinnid abundance. Redundancy analysis (RDA) illustrated that temperature, salinity and the nutrient level were the most important abiotic factors affecting the spatial and seasonal pattern of tintinnid communities in Shenhu Bay. [ABSTRACT FROM AUTHOR]

Highlights: [•] We compiled data of soybean traits and their abiotic variables from 18,686 samples across China. [•] Statistical models were used to remove collinearity and autocorrelation among variables. [•] Climatic effects were significant but varied with individual phenotypic traits. [•] There would be no places to produce a variety with all ideal germplasm traits simultaneously. [Copyright &y& Elsevier]

• Soil respiration (Rs) was continuously measured in a subtropical forest for 3 years. • Significant diurnal, seasonal and annual variations of Rs were observed. • Significant temperature effects on Rs were found in the active phenological seasons. • The highest value of Q 10 occurred at the end-season. • Despite higher daytime Rs, no significant diurnal variations in Q 10 were detectable. Soil respiration (Rs) is a major flux of the carbon cycle in forest ecosystems, and time-scale-dependent variations in Rs are critical for evaluating carbon sequestration capacity, which is not fully understood. In this study, we investigated diurnal, phenological seasonal and annual variations in Rs over three years (2015–2017) in a Pinus massoniana forest in subtropical China based on automated Rs chamber measurements at hourly intervals. Soil temperature and moisture at the 5 cm soil depth were simultaneously measured, and precipitation data were collected to examine their influences on Rs. Our results showed that the daytime mean and total Rs were significantly higher than their respective nighttime counterparts over the course of a year. Daily Rs ranged from 0.42 to 4.63 µmol CO 2 m−2s−1, with the maximum value in August and the minimum value in February. The temperature sensitivity of Rs (Q 10) did not significantly differ between daytime and nighttime, but it was significantly higher at the end-season (autumn) than during the nongrowing season. The effects of soil temperature but not soil moisture on Rs varied with phenological season, showing significant soil temperature effects in the active phenological seasons (spring and autumn) but not in the steady-state phenological seasons (growing season and nongrowing season). This seasonal-dependent temperature effect on Rs may be a result of the effect of rapidly changing temperature in spring and autumn on leaf phenology, plant growth and physiological activity, soil microbial and enzyme activity, and litter decomposition rate. Our results suggest that long-term data covering monthly, seasonal, and annual variations in Rs and its biotic and abiotic environments are needed for more precisely calculating and predicting the carbon balance of forest ecosystems on various time scales. [ABSTRACT FROM AUTHOR]

The rapid growth of cities—along with the increasing connectedness of the world's social, economic, and political systems—has been hypothesized to generate a homogenization of urban form and associated environmental impacts. These hypotheses, however, have rarely been tested. Employing satellite imagery of 150 of the most populous cities in China, India, and the United States, we examine how the area and configuration of built-up land within cities has changed between 1995 and 2015 and assess impacts on the urban heat island effect. We find similar urban form trends across the three countries. The strongest evidence of homogenization is in the connectivity of urban form, while the shape of cities is linked to higher daytime surface urban heat island (SUHI) intensity. In the context of this and other research, we postulate that the identified urban form trends may lead to the homogenization of the biotic and abiotic environment of cities. Homogenization presents an opportunity for cities to learn from each other as they encounter similar ecological outcomes driven, in part, by their increasingly similar urban form. • Populous cities in China, India, and the U.S. have similar trends in urban form. • Urban form exhibits a homogenizing trend for connectivity. • Increasing shape compactness and complexity are linked with increasing SUHI intensity. • If urban form homogenizes, cities can expect similar SUHI consequences. [ABSTRACT FROM AUTHOR]

Reservoirs are hotspots of greenhouse gas (GHG) emission, and the global warming potential of nitrous oxide (N 2 O) is higher than that of CO 2 and CH 4. To promote our understanding of the relationship of biotic and abiotic environments with the mechanism of N 2 O production in a quintessential karst reservoir, water samples were collected in a weak thermal stratification period (WTSP) and a strong thermal stratification period (STSP) in 2019 in the Longtan (LT) Reservoir. In the LT Reservoir, higher N 2 O concentrations and functional gene abundances (nitrification and denitrification genes) were found in the STSP than in the WTSP. In detail, the N 2 O concentrations were 10.45 ± 6.99 nmol L−1 and 23.77 ± 7.06 nmol L−1 in the WTSP and STSP, respectively; the functional gene abundances were higher in the STSP than in the WTSP in each water layer. During the STSP, the nitrification gene abundances were higher at a 30 m depth than at a 100 m depth, while denitrification gene abundances were higher at 100 m than at 30 m. Along the river, N 2 O flux was significantly higher in the LT Reservoir's released water than in upstream water in the STSP, while it exhibited no significant difference in whole river-reservoir system in the WTSP. In conclusion, stratification and nitrogen (N) loading facilitated higher N 2 O production in STSP than in WTSP; different N transformation processes and sources of N 2 O were present between the water layers above and below the thermocline (in deep water); finally, the river-reservoir system here acted as a source of N 2 O release to the atmosphere in the STSP, while it exhibited different emission patterns in the WTSP. This work highlights the mechanism of N 2 O production and functional gene abundances in water layers during different thermal stratification periods, which will help to elucidate the biotic and abiotic environment in a karst deep-water reservoir and will help to inform N 2 O production mechanisms in other reservoirs worldwide. More sampling campaigns and the denitrification potential of sediment were worthy of conducting to comprehend the mechanisms of N 2 O production from stratification to turnover period in the reservoir. AMO is the enzyme encoding genes of amoA and amoB, HAO is the enzyme encoding gene of hao, NXR is the enzyme encoding gene of nxrA, NAS is the enzyme encoding genes of nas, narG and napA, NIR is the enzyme encoding genes of nirS and nirK, NOS is the enzyme encoding gene of nosZ. [Display omitted] • The reservoir was a source of N 2 O totally in summer while not in spring. • Thermal stratification and functional gene abundances stratified in summer. • N 2 O production at 30 m water was mainly contributed by nitrification in summer. • Denitrification mainly contributed to N 2 O production at 100 m water in summer. [ABSTRACT FROM AUTHOR]