Search

Net ecosystem productivity (NEP) plays an important role in the quantitative evaluation of carbon source/sinks in terrestrial ecosystems. This study used Theil–Sen median trend analysis, the Mann–Kendall method, and the Geodetector model to analyze the variation patterns and its dominant factors of NEP from 2010 to 2020. The results showed the following: (1) During 2010–2020, the spatial distribution of carbon sinks in China's terrestrial ecosystems showed a pattern of high in the southeast and low in the northwest. The area with NEP < 0 accounted for 44.74% of the total area, while the area with NEP > 0 accounted for 55.26%. (2) The northwest region belonged to the significant carbon source, while the other regions belonged to significant carbon sinks. (3) The annual average NEP in different sub-regions showed an increasing trend. During 2010–2020, the overall NEP in China showed a trend in shifting from low-level to high-level, indicating that the NEP of terrestrial ecosystems in China increased during the past 11 years. (4) The NEP gravity center in Northeast China showed a trend in moving southward and then northward, while that of the NEP gravity center in East China showed a circular migration trend of 'northwest-southwest–northeast–southeast'. The gravity center of NEP in Northwest China was moving northeastward. The migration trajectory of the NEP gravity center in Southwest China presented a "Z" shape. The change in the gravity center of NEP in the central and southern regions had a strong circuitous nature, and the overall trend was to migrate southward. (5) The combined actions of climate change and human activities were the main reason for the change in NEP in China's terrestrial ecosystem from 2010 to 2020. (6) There were obvious differences in the dominant driving factors of NEP evolution in different regions and different periods in the past 40 years. [ABSTRACT FROM AUTHOR]

Global warming has largely advanced spring vegetation phenology, which has subsequently affected terrestrial carbon and water cycles. However, further shifts in vegetation phenology under future climate change remain unclear. We estimated the start of the growing season (SOS) by applying multiple extraction methods based on the NDVI3g data set, and then parameterized and evaluated 11 spring vegetation phenology models that included chilling, forcing, and the photoperiod. Based on scenario data from three Shared Socioeconomic Pathways (SSP126, SSP245, and SSP585) derived from eight climate models, future vegetation phenology was predicted using the phenology models. Results showed that all the phenology models performed better than the NULL model (mean of the SOS), with the performance of one‐phase models broadly matching that of two‐phase models, although the best models varied by vegetation type. The spatial pattern of simulated SOS was similar among the models, and it explained >75% of the variation. Based on the mean predicted SOS, we found that spring vegetation phenology will continue to advance under strong warming conditions (SSP245 and SSP585), but that the trend of advance will reverse at around 2060 under the SSP126 scenario. The continued trend in SOS advance is likely related to rapid forcing fulfillment under stronger warming conditions. However, under moderate warming, chilling might be reduced and it might require longer to compensate for higher forcing, which ultimately would result in SOS delay. Our findings highlight that trends will likely change under different warming conditions, potentially causing widespread impact on species interaction, biodiversity, and ecosystem function. Plain Language Summary: Phenological change, which is often seen as an indicator of climate change, has received widespread attention. However, despite this focus, comprehension of how vegetation phenology might alter under different climate change scenarios remains inadequate. We used 11 process‐based phenology models to forecast changes in the start of the growing season (SOS) in the Northern Hemisphere under 3 climate change scenarios (SSP126, SSP245, and SSP585). Results showed that the one‐phase models and the two‐phase models exhibited similar performance, which exceeded that of the NULL model (mean of the SOS). Under the strong warming scenarios (SSP245 and SSP585), spring phenology was projected to continue to advance, whereas under the moderate warming scenario (SSP126), the trend of advance was predicted to reverse at around 2060. Our findings suggest that climate change might alter the competition between species for spring resources, and thereby have widespread impact both on biodiversity and on the structure and function of ecosystems. Key Points: Process‐based models outperform statistical models in forecasting changes in spring vegetation phenology in the Northern HemisphereSimulated start of the growing season explained >75% of the percentage of varianceTrend of advance in the start of the growing season in the Northern Hemisphere will reverse by 2060 under moderate warming conditions [ABSTRACT FROM AUTHOR]

Abstract Global warming has largely advanced spring vegetation phenology, which has subsequently affected terrestrial carbon and water cycles. However, further shifts in vegetation phenology under future climate change remain unclear. We estimated the start of the growing season (SOS) by applying multiple extraction methods based on the NDVI3g data set, and then parameterized and evaluated 11 spring vegetation phenology models that included chilling, forcing, and the photoperiod. Based on scenario data from three Shared Socioeconomic Pathways (SSP126, SSP245, and SSP585) derived from eight climate models, future vegetation phenology was predicted using the phenology models. Results showed that all the phenology models performed better than the NULL model (mean of the SOS), with the performance of one‐phase models broadly matching that of two‐phase models, although the best models varied by vegetation type. The spatial pattern of simulated SOS was similar among the models, and it explained >75% of the variation. Based on the mean predicted SOS, we found that spring vegetation phenology will continue to advance under strong warming conditions (SSP245 and SSP585), but that the trend of advance will reverse at around 2060 under the SSP126 scenario. The continued trend in SOS advance is likely related to rapid forcing fulfillment under stronger warming conditions. However, under moderate warming, chilling might be reduced and it might require longer to compensate for higher forcing, which ultimately would result in SOS delay. Our findings highlight that trends will likely change under different warming conditions, potentially causing widespread impact on species interaction, biodiversity, and ecosystem function.

Based on the observations of hourly precipitation for 131 years from Hong Kong Observatory Headquarters, this study examined the long-term changes in the characteristics of hourly precipitation extremes in terms of intensity, total precipitation amount, duration, and frequency. Results show that the hourly precipitation extremes have significantly intensified by 29%–38% from 1885 to 2022. The 131-year observations evidence that the more extreme the hourly precipitation is (i.e. higher percentiles), the faster the increasing rate it has. Specifically, the magnitudes of hourly precipitation with the 95th, 97.5th, 99th, and 99.9th percentiles increased by rates of 0.03 mm, 0.05 mm, 0.07 mm, and 0.12 mm per year, respectively. Through the secular trend analysis, we found that only the maximum intensity of extreme precipitation events (i.e. events with maximum intensity exceeding the 95th percentiles) shows a significant increasing trend during 1885–2022, while the trends in the total precipitation amount, duration, and mean intensity are not significant. However, by comparing the percentile bin values between three sub-periods of the 131-year record, we found a significant rise over time in the total precipitation amount, mean intensity, and maximum intensity of extreme precipitation events with different intensities (i.e. 95th, 96th, 97th, 98th, and 99th percentiles), while the change in the duration is not significant. The analysis of the frequency of precipitation events shows significant increases in the proportion of extreme precipitation events during 1885–2022. The observations of 53 stations across Hong Kong from 1986 to 2022 show significant intensification and increasing frequency in the hourly precipitation extremes in most areas of Hong Kong. Meanwhile, the precipitation duration shows a decreasing tendency, which may explain the insignificant changes in the total precipitation amount. These findings provide important insights into the longer-term variations in the characteristics of hourly precipitation extremes.

The surface freshwater volume discharged into the Gorgan Bay is a significant part of its ecological processes. The Ghareh-Sou River is the most crucial source of surface freshwater in the Gorgan Bay watershed. It is necessary to investigate the temporal changes of surface freshwater volume series at this river's outlet to the bay. In this study, changes in surface runoff volume discharged by the Ghareh-Sou River into the Gorgan Bay (seasonal and annual time series in 1971–2018) were studied using generalized additive models for location, scale and shape (GAMLSS). Probability distribution functions, including normal, gamma, Gumbel, Weibull, and log-normal as well as six different models were applied to estimate variance and mean changes. This study indicated that the dominant probability distribution function of the studied series was gamma. All annual and seasonal series showed significant non-stationary behavior. The magnitudes of the upper quantiles' changes were more powerful than the lower ones, indicating the importance of investigating the different quantiles' changes. The differences between different quantiles of annual, spring, autumn, and winter series of surface freshwater volume series were increasing. Moreover, the GAMLSS showed the suitable ability to estimate the variation over time, contributing to a deeper understanding of changes in surface freshwater volume time series discharged into the Gorgan Bay. Moreover, changes in climatic variables and human activities were driving factors of the revealed trends in freshwater volume series. [ABSTRACT FROM AUTHOR]

Abstract Marine ecosystems worldwide are affected by both natural variation and human activities; to disentangle and understand their individual role in influencing the macrobenthic community composition is challenging. The relationship between interannual variability in atmospheric circulation, dictated by the climatic oscillation indices, and the benthic macrofauna composition was assessed at four sampling sites located in the Bay of Banyuls‐sur‐Mer (NW Mediterranean Sea). Between 2004 and 2013, these sites were sampled annually during autumn/winter and analyzed for sediment grain‐size and benthic macrofauna composition (species richness, abundance, and biomass). Temporal changes in these descriptors were correlated with two climatic indices (NAO and WeMO indices) and a set of environmental parameters integrated over three different time periods (i.e., whole year, springtime, and wintertime). Our results confirm the occurrence of major temporal changes in the composition of macrobenthic communities within the Gulf of Lions. More specifically, the results indicate that (a) the WeMO appears to be more closely related to benthic macrofauna composition in the Bay of Banyuls‐sur‐Mer than the NAO, (b) winter is a better integration period than spring or the whole year as a proxy for community composition changes, and (c) Rhône River water flow is likely involved in the control of benthic macrofauna composition in the whole Gulf of Lions. The present study highlights the importance of WeMO as a regional proxy, which can be used to evaluate changes in benthic macrofauna linked to climatic variability.

Temporal changes in body size have been documented in a number of vertebrate species, with different contested drivers being suggested to explain these changes. Among these are climate warming, resource availability, competition, predation risk, human population density, island effects and others. Both life history traits (intrinsic factors such as lifespan and reproductive rate) and habitat (extrinsic factors such as vegetation type, latitude and elevation) are expected to mediate the existence of a significant temporal response of body size to climate warming but neither have been widely investigated. Using examples of rodents, we predicted that both life history traits and habitat might explain the probability of temporal response using two tests of this hypothesis. Firstly, taking advantage of new data from museum collections spanning the last 106 years, we investigated geographical and temporal variation in cranial size (a proxy for body size) in six African rodent species of two murid subfamilies (Murinae and Gerbillinae) of varying life history, degree of commensality, range size, and habitat. Two species, the commensal Mastomys natalensis, and the non-commensal Otomys unisulcatus showed significant temporal changes in body size, with the former increasing and the latter decreasing, in relation with climate warming. Commensalism could explain the increase in size with time due to steadily increasing food availability through increased agricultural production. Apart from this, we found no general life history or habitat predictors of a temporal response in African rodents. Secondly, in order to further test this hypothesis, we incorporated our data into a meta-analysis based on published literature on temporal responses in rodents, resulting in a combined dataset for 50 species from seven families worldwide; among these, 29 species showed no significant change, eight showed a significant increase in size, and 13 showed a decline in size. Using a binomial logistic regression model for these metadata, we found that none of our chosen life history or habitat predictors could significantly explain the probability of a temporal response to climate warming, reinforcing our conclusion based on the more detailed data from the six African species. [ABSTRACT FROM AUTHOR]

According to the intergovernmental panel on climate change, Northern Chile will be one of the most affected territories by changes in the atmospheric dynamics in next years. These climate change effects will be noticed in several ways, and temperatures will be one of the most sensitive variables to these changes, and with high importance because of their relationship with the hydrological cycle in one of the most arid regions in the world. Extreme temperatures of 77 observatories have been analysed by the calculation of 14 indices and their temporal trends. Also, the relationship of these indices between them, between observatories, with elevation and latitude has been taken into consideration, while they imply significant differences of the behaviour of the analysed indices. The results showed general warming trends but with particular differences depending on the behaviour of minimum temperatures. Examining the relationship between the indices and elevation, it appears that this variable has more implications in minimum temperatures. The analysis showed significant correlations also between the indices and latitude, agreeing with not evident general warming trends in the intertropical area of Northern Chile. Considering the different behaviours of the trends and their relationships with latitude and elevations, it has to be analysed in the future the possible existing relations with the spatial and temporal changes in the hydrological cycle such as precipitations. [ABSTRACT FROM AUTHOR]

• We analysed data from grazing pastures sites of a long-term monitoring study. • We studied the potential of remote sensing to indicate temporal changes in soil carbon. • Remotely sensed green vegetation cover indicated future changes in topsoil carbon. • Below 10 cm soil depth, the changes in soil carbon were not predicted by cover. Temporal variation of soil organic carbon (SOC) is driven by land use/management practice, ecosystem conditions and climatic variation. Robust quantification of changes in SOC that is cost-effective and provides a statistical assessment of uncertainty is challenging, particularly in the face of large spatial variability and slow soil SOC changes. Remote-sensing indicators of above-ground vegetation provide some indication of the amount of fresh organic material being supplied to the soil. Although, because of the time taken for this organic material to decay and become incorporated into the soil, there will be a lag between the changes in the indicator of vegetation growth and the resulting changes in SOC. In this work, we investigate how a remotely sensed indicator of vegetation cover can be used with a lag period to predict or indicate changes in SOC for grazed pasture sites at a long-term monitoring study, which has been monitoring soil under different land uses for over forty years. We assessed how well this worked for indicating the SOC changes for different depths in the soil profile. Results suggested that a lagged remotely sensed vegetation cover—the average cover of the two preceding years—provides some indication of SOC changes for the 0–10 cm soil depth, but changes for deeper soil depths were not well predicted. Further, we investigated the potential of using soil data from a point-in-time spatial dataset (e.g. data from a baseline sampling round) to calibrate a relationship between the remotely sensed cover and SOC, which can then be applied to predict or indicate the temporal variation of SOC. Results showed this approach gave large prediction errors, likely because the temporal variation (at a fixed point in space) and spatial variation (for a fixed point in time) of SOC that is predictable by cover differences are not interchangeable. [ABSTRACT FROM AUTHOR]

Tropical forests are dynamic communities where stochastic and unpredictable events such as climate change affect key ecological processes. The objective of this study was to describe the dynamic behaviour of a semideciduous seasonal forest during 15 years of monitoring, with four sampling intervals, in order to verify if fluctuations in forest dynamics are related to precipitation variations. The work was carried out based on diameter at breast height measured in 25 plots of 400 m² each in four forest inventories (2000, 2005, 2009, 2015). To evaluate the direction of forest dynamic changes over time, we performed analyses of mortality rates, recruitment and net changes in number of individuals and rates of loss and gain in basal area. The results suggested that the forest was undergoing a rhythmic cycle characterised by the imbalance in forest dynamics, with rates of mortality and gain in basal area greater than those of recruitment and loss in basal area respectively. However, this natural cycle may be influenced by variation in precipitation, since in the periods characterised as dry, mortality rates increased and there was less increment in basal area. [ABSTRACT FROM AUTHOR]

The thermal regime of rivers in the Baltic States (Estonia, Latvia and Lithuania) is not sufficiently studied. The presented research describes the spatial distribution and temporal variation of river water temperature (WT) in the Baltic States using a unified methodology. The object of the research is the WT of rivers during the warm season (May-October) and the warmest month of the year (July). The contour maps of WT were compiled for the rivers of the Baltic States using data series for the period 1961-1990 from 17 water measuring stations in Estonia (EST), 36 stations in Latvia (LV) and 40 stations in Lithuania (LT). These maps allow the evaluation of WT for the unmonitored rivers. Analysis of long-term (1951-2010) changes of river WT showed that during the first half of this period (1951-1980), river WT decreased significantly (0.003 °C/warm season). Meanwhile, only positive trends prevailed over the last three decades (1981-2010) in the river WT of the Baltic States. During the latest period, rivers which show significant positive trends in WT warm up significantly - by 0.04 °C/warm season. [ABSTRACT FROM AUTHOR]

Abstract: Aim: In response to climate change, species distribution shifts resulting from local extinctions, colonizations and variations in population abundances potentially lead to community‐level reorganizations. Here, we assess changes over time in stream fish communities, quantify the extent to which these changes are attributable to population declines or increases and identify their main drivers. Location: France. Time period: 1980–2012. Major taxa studied: Stream fish species. Methods: We used abundance‐monitoring data to quantify changes in composition and uniqueness for 332 stream fish communities between a cold historical period (1980–1993) and a warm contemporary period (2004–2012). Then, we used a model‐averaging procedure to test the impacts of factors related to climate, land use and non‐native species density and their interacting effects in shaping community reorganization. Results: We observed biotic homogenization over time in stream fish communities, although some communities experienced differentiation. Changes in composition mainly resulted from population declines and were favoured by an increase in temperature seasonality and in non‐native species density. Population declines decreased with fragmentation and changes in non‐native species density, whereas population increases were negatively driven by changes in precipitation and positively by fragmentation. Our results provide evidence that environmental changes can interact with other factors (e.g., upstream–downstream, fragmentation intensity) to determine community reorganization. Main conclusions: In the context of global change, fish assemblage reorganizations mainly result from population declines of species. These reorganizations are spatially structured and driven by both climatic and human‐related stressors. Here, we emphasize the need to take into account several components of global change, because the interplay between stressors might play a key role in the ongoing biodiversity changes. [ABSTRACT FROM AUTHOR]

Summertime extreme heat events, defined by the Universal Thermal Climate Index (UTCI), have shown increasing trends in Shanghai from 1973 to 2015. There is a clear shift to higher temperatures for the daily maximum UTCI values, and the number of days with daily maximum UTCI exceeding 38 °C significantly increased by 4.34 days/10a. An upward trend of 3.67 days/10a was detected for the number of hot days which also displays an abrupt increase around 1998. Both the frequency and total duration of heat waves have significantly increased by 0.77 times/10a and 3.51 days/10a respectively. Their inter-decadal variations indicate a three-part division of the study period showing more and more heat waves and longer total duration, which are 1.0 times/a and 4.13 days/a for 1973-1987, 1.71 times/a and 7.64 days/a for 1988-2001, and 3.57 times/a and 16.0 days/a for 2002-2015. In addition to that are more occurrences of long-lasting heat waves. Compared with the UTCI, air temperature-based definitions have indicated substantially higher increases in extreme heat events, especially for hot nights. The relatively low humidity and strong wind speeds in the twenty-first century are considered to be responsible for this difference. Our study provides a more in-depth case to monitor extreme heat events under the combining effects of air temperature, humidity, wind speeds, total cloud cover, etc. and can support studies over other regions. [ABSTRACT FROM AUTHOR]

ABSTRACT Aim To assess the potential impacts of future climate change on spatio-temporal patterns of freshwater fish beta diversity. Location Adour-Garonne River Basin (France). Methods We first applied an ensemble modelling approach to project annually the future distribution of 18 fish species for the 2010-2100 period on 50 sites. We then explored the spatial and temporal patterns of beta diversity by distinguishing between its two additive components, namely species turnover and nestedness. Results Taxonomic homogenization of fish assemblages was projected to increase linearly over the 21st century, especially in the downstream parts of the river gradient. This homogenization process was almost entirely caused by a decrease in spatial species turnover. When considering the temporal dimension of beta diversity, our results reveal an overall pattern of decreasing beta diversity along the upstream-downstream river gradient. In contrast, when considering the turnover and nestedness components of temporal beta diversity we found significant U-shaped and hump-shaped relationships, respectively. Main conclusions Future climate change is projected to modify the taxonomic composition of freshwater fish assemblages by increasing their overall similarity over the Adour-Garonne River Basin. Our findings suggest that the distinction between the nestedness and turnover components of beta diversity is not only crucial for understanding the processes shaping spatial beta-diversity patterns but also for identifying localities where the rates of species replacement are projected to be greatest. Specifically we recommend that future conservation studies should not only consider the spatial component of beta diversity but also its dynamic caused by climate warming. [ABSTRACT FROM AUTHOR]

The Pacific red alga Heterosiphonia japonica has dispersed rapidly along European shores. Due to the species' high abundance in many habitats, an impact on species richness and composition of local macroalgal communities might be expected. Higher sea temperatures may also influence local macroalgal composition, by providing more favourable conditions for species requiring higher temperatures. Macroalgal composition at 22 sublittoral sites along the south-western coast of Norway investigated prior to the establishment of H. japonica (1994-1995) were reinvestigated in 2003-2004, using similar methods. The total number of species collected in the area was approximately the same in the present investigation as in the previous study. With regard to number and composition of species at each site, there were no significant differences between sites with high abundance of H. japonica and sites with low or no abundance. Similarity percentage analysis (SIMPER) showed that there were temporal changes in composition of the macroalgal communities, mainly caused by higher frequency of 'southern species' (species with a northern limit on our coast). There was a significant increase in the percentage share of such species in the reinvestigations. The temporal differences observed are most likely caused by several warm summers/autumns and mild winters since the first investigation, which may favour a higher abundance of 'southern species'. Heterosiphonia japonica was the most important species contributing to temporal dissimilarity in the area. This paper concludes that H. japonica has caused no negative impact on regional algal species richness in the relatively short time span since its introduction. [ABSTRACT FROM AUTHOR]