Interannual Dynamics Research Articles

Drivers and Environmental Impacts of Vegetation Greening in a Semi-Arid Region of Northwest China since 2000

The dynamics of terrestrial vegetation have changed a lot due to climate change and direct human interference. Monitoring these changes and understanding the mechanisms driving them are important for better understanding and projecting the Earth system. Here, we assessed the dynamics of vegetation in a semi-arid region of Northwest China for the years from 2000 to 2019 through satellite remote sensing using Vegetation Index (VI) data from the Moderate Resolution Imaging Spectroradiometer (MODIS), and analyzed the interannual covariation between vegetation and three climatic factors—air temperature, precipitation, and vapor pressure deficit (VPD)—at nine meteorological stations. The main findings of this research are: (1) herbaceous land greened up much more than forests (2.85%/year vs. 1.26%/year) in this semi-arid region; (2) the magnitudes of green-up for croplands and grasslands were very similar, suggesting that agricultural practices, such as fertilization and irrigation, might have contributed little to vegetation green-up in this semi-arid region; and (3) the interannual dynamics of vegetation at high altitudes in this region correlate little with temperature, precipitation, or VPD, suggesting that factors other than temperature and moisture control the interannual vegetation dynamics there.

Quantifying phenological asynchrony of phyto- and zooplankton in response to changing temperature and nutrient conditions in Lake Müggelsee (Germany) by means of evolutionary computation

There is a need to determine and quantify global change induced phenological asynchrony because of possible loss of biodiversity and implications for the food web. Phenological asynchrony in freshwater lakes can be studied retrospectively by analysing historical data, and prospectively by scenario analysis based on historical data. Models allowing to study phenology by scenario analysis need to be valid for multiple populations over decades limiting the suitability of process-based models that are structural rigid and calibratable only for a limited period of time.Here we applied models inferred from historical data by evolutionary computation to simulate food-web dynamics of the plankton community of Lake Müggelsee from 2002 to 2012. The models were driven by nutrient concentrations, water temperature (WT) and endogenous interrelationships within the plankton community. The validated models simulated seasonal and inter-annual dynamics of seven phyto- and zooplankton groups in response to scenarios of prospective global warming, nutrient enrichments as well as combinations of warming with nutrient enrichments and warming with nutrient reductions.Phenological WT-sensitivities resulting from the warming scenario indicated substantial shifts towards earlier timing of cyanobacteria peaks and delayed timing of cladocerans peaks in summer, suggesting significant phenological asynchrony in the plankton community of Lake Müggelsee. The phenological sensitivities of cyanobacteria and cladocerans towards phosphorus and nitrogen enrichments revealed similar trends of summer peaks as identified for warming, most likely contributing to phenological asynchrony.The combination of warming and nutrient reductions showed increased spring maxima but almost unchanged summer peaks of cyanobacteria demonstrating that gradually decreasing phosphorus and nitrogen concentrations may outweigh warming effects on phytoplankton growth.Scenarios that simulated WT- and nutrient-changes as gradual processes rather than immediately imposed events proved to be more realistic and credible. The proposed ensemble of complementary inferential models proved to be a viable tool for determining long-term dynamics and phenological asynchronies in plankton communities under the impact global changes.

Interannual dynamics of size, age composition and parameters of growth for japanese sardine <i>Sardinops melanostictus</i> in periods of its high abundance in the North-West Pacific

Interannual dynamics of size composition, age structure, and growth parameters are considered for japanese sardine Sardinops melanostictus in context of its recent and previous blooms and mass migrations to the Pacific waters at Kuril Islands and to the northern Japan Sea. Before the post-bloom catastrophic decline in the 1990s, in conditions of the highest density of the sardine population, small-sized fish with relatively slow growth rate became dominant, distinguished by lowered reproductive potential because of low population fecundity and reproduction rate. In the new, modern bloom of sardine population, two modal groups are observed in the year-classes size composition, in particular in the Japan Sea, with different exterior and biological parameters. There is assumed that they correspond with two morphological types, which alter each other at different stages of the demographic cycle, that determines total abundance of sardine population in the North-West Pacific and its long-term dynamics.

A long-term atmospheric baseline for intercontinental exchange of airborne pathogens

The atmosphere is a potential pathway for global-scale and long-range dispersal of viable microorganisms, promoting biological interconnections among the total environment. We aimed to provide relevant baseline information for long-range long-term intercontinental exchange of potentially infectious airborne microorganisms of major interest in environmental and health-related disciplines. We used an interannual survey (7-y) with wet depositions fortnightly collected above the boundary layer (free troposphere) at a remote high-elevation LTER (Long-Term-Ecological-Research) site, analyzed by 16S and 18S rRNA genes, and compared to a database of 475 well-known pathogens. We applied a conservative approach on close relatives of pathogenic species (>98% identity) standing their theoretical upper limit for atmospheric baseline relative abundances. We identified c. 2–3% of the total airborne microbiota as potential pathogens. Their most frequent environmental origins were soil, aquatic, and anthropogenic sources. Phytopathogens (mostly fungi) were the potential infectious agents most widely present. We uncovered consistent interannual dynamics with taxa foreseeable over time (i.e., predictable seasonal behavior) and under recurrent environmental scenarios (e.g., Saharan dust intrusions), respectively, being highly valuable microbial forensic environmental indicators. Up to 8 bacterial and 21 fungal genera consistently showed temporal abundances and recurrences unevenly distributed. Incidence of allergenic fungi was lower in summer, and significantly higher in spring. Close relatives to Coccidioides posadasii consistently showed higher signals (i.e., high specificity and high fidelity) in winter, whereas Cryptococcus neoformans had a significant signal in spring. Along Saharan dust intrusions, the bacterial phytopathogens Acidovorax avenae and Agrobacterium tumefaciens and the fungal phytopathogens Pseudozyma hubeiensis and Peniophora sp. consistently showed higher signals. Potential human pathogens showed low proportion, being mostly fungal allergens. Microorganisms related to obligated human, amphibian and fish pathogens were commonly found in winter. More studies in remote field sites above the boundary layer will unveil whether or not a similar trend is found globally.

Interannual Dynamics of Ice Cliff Populations on Debris-Covered Glaciers From Remote Sensing Observations and Stochastic Modeling.

Ice cliffs are common on debris‐covered glaciers and have relatively high melt rates due to their direct exposure to incoming radiation. Previous studies have shown that their number and relative area can change considerably from year to year, but this variability has not been explored, in part because available cliff observations are irregular. Here, we systematically mapped and tracked ice cliffs across four debris‐covered glaciers in High Mountain Asia for every late ablation season from 2009 to 2019 using high‐resolution multi‐spectral satellite imagery. We then quantified the processes occurring at the feature scale to train a stochastic birth‐death model to represent the cliff population dynamics. Our results show that while the cliff relative area can change by up to 20% from year to year, the natural long‐term variability is constrained, thus defining a glacier‐specific cliff carrying capacity. In a subsequent step, the inclusion of external drivers related to climate, glacier dynamics, and hydrology highlights the influence of these variables on the cliff population dynamics, which is usually not a direct one due to the complexity and interdependence of the processes taking place at the glacier surface. In some extreme cases (here, a glacier surge), these external drivers may lead to a reorganization of the cliffs at the glacier surface and a change in the natural variability. These results have implications for the melt of debris‐covered glaciers, in addition to showing the high rate of changes at their surface and highlighting some of the links between cliff population and glacier state.

Evaluating a spatiotemporal shape-matching model for the generation of synthetic high spatiotemporal resolution time series of multiple satellite data

Time series of high spatiotemporal resolution satellite data are required to monitor land surface biophysical properties and their seasonal and inter-annual dynamics at sub-field to field scales. To generate such time series, various algorithms have been developed to fuse infrequent cloud-free Landsat observations with daily Moderate Resolution Imaging Spectroradiometer (MODIS) observations. An early and widely used Spatial and Temporal Adaptive Reflectance Fusion Model (STARFM) was developed based on the assumptions that observations from the two sensors are consistent in terms of spatial aggregation and temporal variation. These assumptions are not always valid in the real world, especially in a complex heterogeneous region. In this study, we investigated a Spatiotemporal Shape-Matching Model (SSMM) to generate synthetic time series of high spatiotemporal resolution satellite data. The SSMM, which is conceptually different from the image pair-based STARFM and STARFM-like approaches, makes full use of all spatiotemporally matched fine and coarse resolution data in an entire time series to establish a temporally uniformed fusion model for a given fine resolution pixel. The SSMM assumes that the temporal shapes of both the fine and coarse resolution time series are similar, but their magnitudes and phenological phases could differ largely even for the same vegetation type. This study assessed the capability of the SSMM to generate high spatiotemporal resolution time series of two-band Enhanced Vegetation Index (EVI2). Specifically, we generated the synthetic 30 m time series using the SSMM and STARFM algorithms in the northeastern United States based on 500 m Visible Infrared Imaging Radiometer Suite (VIIRS) data and 30 m Landsat 8 and Sentinel-2 observations. We then evaluated the SSMM-derived 30 m time series across 15 land cover types and various degrees of heterogeneity. The result indicates that the SSMM is able to effectively generate synthetic time series in all different land cover types, which has advantages over the STARFM approach. Although the SSMM performance is degraded in heterogeneous regions, it can explain 82–91% of variations in 30 m EVI2 time series and produce constant root mean square error (0.053–0.056) across various levels of heterogeneity. Moreover, the SSMM can explain 87%-93% and 69%-87% of variation in 30 m EVI2 time series, respectively, with the models established using more than 10 pairs and 4–10 pairs of fine and coarse resolution observations. This suggests that the SSMM is also capable of generating high spatiotemporal resolution time series using historical Landsat time series with limited cloud-free observations, which are critical for studying vegetation dynamics and monitoring crop conditions.

Inter-Annual and Seasonal Variations of Water Quality and Trophic Status of a Reservoir with Fluctuating Monsoon Precipitation.

Long-term evaluation from 2000 to 2020 of a temperate reservoir indicated that water quality and trophic status were not critically controlled by the inter-annual dynamics of monsoon precipitation. The fluctuation of annual concentrations of TP, TSS, and EC did not always correlate with the variation of precipitation. BOD and COD demonstrated monotonically increasing trends with Sen’s slope of 0.02 and 0.01, respectively, while Chl-a manifested a decreasing trend (slope = −0.23). The increases of different magnitudes in the levels of TP, TSS, and Chl-a in the monsoon and the early post-monsoon periods were observed in the drought, flood, and normal years. The drought years showed distinct seasonal variations in many parameters, while those in the flood and the normal years were very similar. Pearson correlation and empirical regression analyses resulted in weaker correlation between water quality and hydrological parameters than other reservoirs, which, along with low impact of precipitation, was attributed to the low drainage ratio (28.8) of the study area. BOD/COD ratios were higher than 0.5 in the reservoir, indicating the presence of a significant fraction of biodegradable organic matter. The ratio increased in the longitudinal flow direction (>50% in the drought years), implying the possibility of autochthonous sources of organic matter. TSID evaluation resulted in variation of limiting factors not related to the fluctuation of annual precipitation. The loadings of the significant principal components were very similar among the different precipitation groups, supporting the other findings that annual precipitation governed by monsoon intensity would not solely control the water quality dynamics of the study area.

Remote sensing monitoring of monthly surface water changes in Bosten Lake (1990-2020)

Climate change and human activities have led to changes in the lake surface water, monitoring the long-term monthly changes of the lake surface water is of great significance to maintain the ecological balance of lakes. Based on the Landsat images and Google Earth Engine (GEE), we monitored the bi-monthly dynamics of the surface water of Bosten Lake in the past 30 years. The results show that: in the past 30 years, the maximum surface water of the lake is 1167.18 km2; the inter-annual dynamics of Bosten Lake surface water were divided into four stages: sharp decrease during 1990-1991, increase during 1992-2002, decrease again during 2003-2012, and finally recovery from 2013 to 2020; the annual changes of lake surface water have a certain pattern, decreasing from March to July, increasing from July to September, and then starting to decrease again. The inter-annual variability of the surface water of Bosten Lake was mainly affected by human activities and climate factors.

RELATIONSHIP OF REGIONAL ECOSYSTEMS PRODUCTIVITY WITH THE DYNAMICS OF HYDROTHERMAL CONDITIONS ON THE TERRITORY OFTHE CRIMEAN PENINSULA

The results of assessing of the spatiotemporal relationship and interannual dynamics the of regional ecosystems productivity of the Crimean Peninsula with hydmthennal conditions аге presented. Landsat space images from 1979 to 2017 аге used as the research material. The resolution of each image is 30х30 m The NDVI index was used to account for the productivity factor of ecosystems in the study. The ArcGIS 10 image analysis module is used to determine this index On the basis of the rank correlation coefficient, several clearly defined intervals are determined, which, in tum, allow for the selected time period to identify several quite clearly defined periods in determining the influence ofhydrothennal states of regional ecosystems on the fonnation of the value of their biological productivity. For the period from 1979 to 2017, four periods characterized Ьу different degrees of spatiotemporal correlation between productivity of regional ecosystems and their heat and moisture supply are identified. The first period is characterized Ьу relatively staЫe and sufficiently high values of spatial correlation between values of regional ecosystems productivity and indicators of hydrothennal states. The second period is represented Ьу much less staЫe indicators and fluctuations of spatial relationship in dynamics from year to year. The third period is associated with stabihzation of spatial relationship indicators and their increase to the level of the fIГSt period, while the relationship of productivity with temperatures is more staЫe in time. The fourth period, is characterized Ьу violation of staЫe dynamics in considered indicators, their fluctuations towards decrease of spatial relationship degree with possiЫe sharp jumps in case of especially dry and hot seasonal states, which, in general, correlates rather tightly with the shift of seasonal states. These periods are quite clearly connected with the changes in the prevailing circulation processes. The role of different circulation groups in the interannual dynamics of the spatial-temporal relationship of the characteristics under consideration is shown. It is noted that from 1957 up to 1985, the increase in the duration of the northem circulation had aЬsolute dominance. The barrier in 1985 coincides quite clearly with the change of the lst period of the present analysis. This clearly provided stabihty of the spatial relationship indicators in the lst period and some divergence in the 2nd period after the circulation type change. The 2nd period of the meridional Southem circulation epoch coincides with the lst period of staЫe relationship between heat and moisture availabihty indicators and values of productivity of regional ecosystems. The period from 1970 to 1997 was characterized Ьу southem cyclones exiting from the sea, which led to а decrease in air temperature in the Crimea on average per year, and to unstaЫe correlations with the productivity of ecosystems. From 1998 to the present, with the dominance of the meridional Northem circulation and the minimum duration of the Zonal circulation, there is а decrease in the duration of the meridional Southem circulation, which causes а sufficiently long period of staЫe relationships between productivity and the main climatic indicators in the 3rd period of this analysis. Decrease in mean annual temperature in 1981-1997 and its sharp increase in 1998-2013 clearly enough influence on the change of hnks with these parameters in pmductivity of regional ecosystems. The increase in air temperature in the period 1998-2013 is associated with the growth of the anticyclonic regime.

Longitudinal Study on Seasonal Variation of Marine Biotoxins and Related Harmful Algae in Bivalve Mollusks Bred in Sardinia (Italy, W Mediterranean Sea) from 2015 to 2020 and Assessment of Potential Public Health Risks

Annual and interannual dynamics of shellfish toxins and associated harmful algal species (HAS) were analyzed from 2015 to 2020 in Tortolì Lagoon (Sardinia, west Mediterranean Sea). Analysis of seasonal occurrence of different harmful algae, such as Dinophysis spp., Prorocentrum spp., Pseudo-nitzschia spp. and Alexandrium minutum, was performed. The species Dinophysis acuminata and Dinophysis sacculus were responsible for the accumulation of lipophilic toxins belonging to the okadaic acid group (OAs) and pectenotoxins2 (PTX2) in bivalve mollusks. The highest HAS detection was recorded in the winter months; in particular, Dinophysis spp. was mostly present in January–February. Out of 1090 analyzed mollusk samples, 39 were non-compliant, exceeding the legal limits (160 μg OA eq/kg e.p.) reported in Regulation 853/2004 of the European Commission. A statistical analysis related to the presence of OA and PTX2 in mollusks with various environmental parameters (pH, water temperature, dissolved oxygen, algal density) was implemented, proving a clear winter seasonality. The present study highlights the necessity to better understand the different factors able to influence the production and accumulation of toxins in bivalve mollusks bred in an important Sardinian production area. The contribution of this research is important not only from an environmental and productive point of view but also from the view of implementing management in order to mitigate any harm to human health.

Using remotely sensed indicators of primary productivity to improve prioritization of conservation areas for top predators

The need to incorporate habitat dynamics into spatial conservation prioritization is increasingly recognized but often limited by the lack of available temporal data. To overcome this limitation, model-assisted monitoring has been advocated and developed over the last decade. However, predictive modelling often relies on static habitat features or interpolated climate data, failing to consider other relevant ecological processes such as primary productivity and its dynamics. The importance of primary productivity relies on its key role in determining the availability of food resources via trophic cascades. This study aims to assess how the spatiotemporal variation in the habitat quality for top predators (using raptors as case study) can be affected by temporal fluctuations in primary productivity, and whether its incorporation into habitat modelling improves predictions in space and time. Through model predictions we then incorporate interannual habitat-quality dynamics into spatial conservation planning to identify priority areas for raptor conservation based on a new set of dynamic priority-area indices. Using raptor occurrence data from two surveys (2001 and 2014), we found high model performance and transferability for all species (AUC2001 = 0.89 ± 0.10 and Boyce’s Index2001 of 0.78 ± 0.20; AUC2014 = 0.89 ± 0.12 and Boyce’s Index2014 of 0.87 ± 0.06). Annual mean and minimum values of EVI (indicators of productivity and phenology, respectively) and elevation were the most important predictor variables for most raptor species. However, the standard deviation of EVI (an indicator of seasonality) was also found to be an important predictor for migratory species breeding in shrublands and croplands. Interannual model predictions showed a large interannual variation in habitat availability across species, partially associated with regional land-use changes. Interannual habitat-quality dynamics was translated into marked changes in the priority areas for raptor conservation —areas mostly associated with deciduous forest and water environments (rivers and dams) in our study area. Our results shed light on the role of intra- and interannual dynamics of primary productivity in driving habitat quality for top predators. They also confirm the potential of remotely sensed ecosystem functioning attributes to inform about habitat-quality dynamics in a cost-effective, standardized and repeatable way. Incorporating interannual dynamics of primary productivity in habitat modelling supports raptor conservation prioritization by informing about adequacy, stability and legacy of raptor conservation areas.

Snow cover and vegetation greenness with leaf water content control the global land surface temperature

The land surface temperature (LST) and land use land cover (LULC) are the major components of climate- and environment-related studies. The objective of this study was to assess the relationship of LST with remotely sensed LULC-derived vegetation indices during 2018 at the global, latitudinal and continental scales. Moderate resolution imaging spectroradiometer (MODIS) Aqua daytime LST and eight LULC MODIS indices (NDVI, EVI, LAI, DSI, NDWI, albedo, NDSI, NDBI) were processed using Earth Engine Code Editor. The analysis was conducted using correlation coefficient and significance of the relationship of variables based on 2050 randomly selected points at the global scale. Based on the univariate and geographically weighted regression methods, the research confirmed that vegetation greenness (NDVI), leaf water content (NDWI) and snow cover (DSI) are the codominant drivers of decreasing LST at the global scale including Europe, Asia, South America and North America at the continental scale. Snow cover during winter and vegetation greenness in summer seasons control the global LST. Although albedo shows an inverse relationship, NDBI and NDSI displayed a positive relationship to LST at the global scale. In conclusion, temporal seasonal and inter-annual dynamics of LST in response to snow cover and vegetation properties (greenness, moisture) should be focused on understanding and regulating LST at varying scales.

Nitrogen fertilization overweighs intercropping in promotion of dissolved organic carbon concentration and complexity in potato-cropped soil

Intercropping promoted land productivity and be performed worldwide. This study aimed to assess the effect of intercropping on soil dissolved organic carbon (DOC) and its nitrogen (N) regulation. The potato was monocropped and intercropped with maize under four N levels (0, 62.5, 125 and 187.5 kg ha−1 for N0, N1, N2 and N3, respectively) in a fixed plot experiment from 2014 in subtropical China. Soil DOC concentration was determined and seasonal and interannual dynamics were analyzed from 2016 to 2018; Absorption values of specified wavelength were selected to characterize the annul DOC composition. Finally, the driving factors of DOC variation were explored using structural equation modeling (SEM). Soil DOC concentration and accumulation under N-applied treatments were higher than N0 and the increase peaked at N1. Compared with monocropping, intercropping significantly increased DOC accumulation by 20.29% only at N0. N application significantly improved the contents of amines and aromatic compounds and the average molecular weight of DOC, thus improving the degree of humification and aromatization of soil DOC. The SEM showed that the chemical composition of DOC was complicated with increasing soil temperature, aboveground and root biomass, while DOC concentration and chemical composition significantly affected the accumulation of DOC. Agricultural diversified cropping affects the dynamics and composition of soil DOC, which is intensively regulated by N fertilization. This study expands the insight into the variable DOC concentration and composition and its role in soil organic carbon turnover under the varying fertilization and cropping patterns.

Towards a better understanding of grass bed dynamics using remote sensing at high spatial and temporal resolutions

Wetlands conservation and resilience capacities are key issues in many places over the globe. Understanding these issues will benefit from a precise knowledge of seagrass species occupancy and coverage over time and over space. Such information can be obtained from remote sensing images and their classification thanks to a vegetation index, to be used in a complementary manner to field work inventories. Sentinel-2 data, which are available with a frequent revisit time (<5 days) and a high spatial resolution (10m pixel size) can be used to map grassbeds at the surface or slightly below the surface of permanent lagoons, hence enabling the characterization of its seasonal dynamics, which was not possible with previous remote-sensing tools. We have proved the feasibility of such a method in the natural reserve of the Bagnas (Herault, France) where Stuckenia pectinata coverage can be tracked over a full year thanks to Sentinel-2 images and field work. Inter-annual dynamics (seasonal growth and senescence) can be mapped over time with 10m resolution and will be extended to pluriannual studies thanks to the long-term objective of the Sentinel-2 mission. This opens the way to a concerted management of natural reserves based on data analysis and field knowledge, a better understanding of seagrass coverage with fluctuating environmental conditions, and predictive mechanistic and/or stochastic models of future qualitative trends.

Interannual dynamics, diversity and evolution of the virome in Sclerotinia sclerotiorum from a single crop field.

Mycovirus diversity is generally analyzed from isolates of fungal culture isolates at a single point in time as a snapshot. The stability of mycovirus composition within the same geographical location over time remains unclear. Not knowing how the population fluctuates in the field can be a source of unpredictability in the successful application of virocontrol. To better understand the changes over time, we monitored the interannual dynamics and abundance of mycoviruses infecting Sclerotinia sclerotiorum at a rapeseed-growing field for three years. We found that the virome in S. sclerotiorum harbors unique mycovirus compositions each year. In total, sixty-eight mycoviruses were identified, among which twenty-four were detected in all three successive years. These twenty-four mycoviruses can be classified as the members of the core virome in this S. sclerotiorum population, which show persistence and relatively high transmissibility under field conditions. Nearly two-thirds of the mycoviruses have positive-sense, single-stranded RNA genomes and were found consistently across all three years. Moreover, twenty-eight mycoviruses are newly described, including four novel, multi-segmented narnaviruses, and four unique bunyaviruses. Overall, the newly discovered mycoviruses in this study belong to as many as twenty families, into which eight were first identified in S. sclerotiorum, demonstrating evolutionarily diverse viromes. Our findings not only shed light on the annual variation of mycovirus diversity but also provide important virus evolutionary clues.

Reef state and performance as indicators of cumulative impacts on coral reefs

Coral bleaching, cyclones, outbreaks of crown-of-thorns seastar, and reduced water quality (WQ) threaten the health and resilience of coral reefs. The cumulative impacts from multiple acute and chronic stressors on “reef State” (i.e., total coral cover) and “reef Performance” (i.e., the deviation from expected rate of total coral cover increase) have rarely been assessed simultaneously, despite their management relevance. We evaluated the dynamics of coral cover (total and per morphological groups) in the Central and Southern Great Barrier Reef over 25 years, and identified and compared the main environmental drivers of State and Performance at the reef level (i.e. based on total coral cover) and per coral group. Using a combination of 25 environmental metrics that consider both the frequency and magnitude of impacts and their lagged effects, we find that the stressors that correlate with State differed from those correlating with Performance. Importantly, we demonstrate that WQ metrics better predict Performance than State. Further, inter-annual dynamics in WQ (here available for a subset of the data) improved the explanatory power of WQ metrics on Performance over long-term WQ averages. The lagged effects of cumulative acute stressors, and to a lesser extent poor water quality, correlated negatively with the Performance of some but not all coral groups. Tabular Acropora and branching non-Acropora were the most affected by water quality demonstrating that group-specific approaches aid in the interpretation of monitoring data and can be crucial for the detection of the impact of chronic pressures. We highlight the complexity of coral reef dynamics and the need of evaluating Performance metrics in order to prioritise local management interventions.

2000—2015年青海高原植被碳源/汇时空格局及变化

陆地生态系统碳循环能够综合反映全球气候变化及区域响应，是全球及区域气候变化及人类活动影响研究的重要内容。青海高原作为青藏高原的重要组成部分，在全球及区域气候与环境变化中具有极其重要的作用。因此，研究青海高原植被碳源/汇时空变化及气候因子的影响具有重要意义。采用土壤呼吸模型和改进的CASA模型，结合MODIS、气象数据估算了青海高原2000-2015年植被净生态系统生产力（NEP），分析了植被NEP、碳汇的年际时空分布、年际动态变化、多年累积空间分布与植被NEP变异系数，定量分析了降水量、气温对植被NEP的影响。结果表明：1）2000-2015年，青海高原植被年NEP空间分布特点呈东高西低、南高北低，由西北向东南逐步增加趋势，年NEP多年平均值为128.40 gC m^-2a^-1；2）青海高原不同生态区植被NEP与碳汇量空间分异显著，碳汇区约占植被分布区面积的73.11%，其中，祁连山生态区和三江源生态区为主要的碳汇区；3）2000-2015年，青海高原植被碳汇功能逐步增强，年固碳量为-3.2-64.42 TgC，年际变化呈平稳上升；4）受自然与人为因素的协同影响，青海高原年NEP呈现逐步好转的趋势，平均趋势系数为1.52，NEP增加的区域占植被总面积的25.72%；5）青海高原植被NEP变异系数空间分布以较低、中等波动为主，稳定性颇高；6）降水量对植被NEP以促进作用为主，气温以抑制作用为主，气温对青海高原植被NEP的影响占主导地位。;The carbon cycle of terrestrial ecosystem relates to global climate change and its regional response comprehensively. Therefore, it is an important part of climate changes research and the impact of human activities. As an important part of the Qinghai-Tibet Plateau, the Qinghai Plateau plays an important role in the global and regional climate and environmental changes. Therefore, it is of great significance to study the temporal and spatial variation of carbon source/sink of vegetation and the influence of climate factors in Qinghai Plateau. By using the soil respiration model and the improved Carnegie Ames Stanford Approach (CASA) model, combined with MODIS and meteorological data, we estimated the net ecosystem productivity (NEP) of the Qinghai Plateau from 2000 to 2015, analyzed the inter-annual spatial and temporal distribution, the inter-annual dynamics and the multi-year accumulation spatial distribution of vegetation NEP and carbon sink, calculated the coefficient variation of vegetation NEP. We quantitatively discussed the impact of precipitation and temperature on vegetation NEP. The results indicate that 1) during 2000 and 2015, the spatial distribution characteristics of the annual vegetation NEP are high in the east and the south, low in the west and the north, and gradually increase from the northwest to the southeast. The annual average of NEP is 128.40 gC m^-2a^-1. 2) There is a significant spatial distribution of vegetation NEP and the amount of carbon sinks between different ecological regions, the total carbon sink area accounts for about 73.11% of the total vegetation area in Qinghai Plateau, of which the Qilian Mountain Ecological Area and the Sanjiangyuan Ecological Area are the main carbon sink areas.3) From 2000 to 2015, the carbon sink function of vegetation in Qinghai Plateau is gradually enhanced, and the annual carbon sequestration is -3.2—64.42 TgC. And the inter-annual variation of the carbon sequestration increases stably. 4) Influenced by the combination of natural and human factors, the annual NEP of Qinghai Plateau shows a gradually improvement trend, with an average trend coefficient of 1.52, and the area where NEP increases accounted for 25.72% of the total vegetation area. 5) The spatial distribution of NEP variation coefficient in Qinghai Plateau is mainly low and medium fluctuation, and the stability is quite high. 6) The precipitation mainly promotes vegetation NEP accumulation, the temperature inhibits the accumulation of NEP. And the influence of temperature on NEP accumulation is dominant.

Assessment of phytoplankton photosynthetic activity in the Upper Volga reservoirs via fluorescence diagnosis

Based on the materials of field observations in 2015–2018, the first data on the photosynthetic activity of phytoplankton in the Upper Volga reservoirs are estimated using fluorescence diagnostics. During the summer maximum of phytoplankton, the coefficient of photosynthetic activity (CPhA) varied from 0,18 to 0,84 (standard error &lt;0,005), averaging 0,49±0,003, 0,52±0,002, and 0,51±0,004 in Ivankovo, Uglich, and Rybinsk reservoirs. Spatial and interannual changes of CPhA are considered. In interannual dynamics, higher CPhA values were noted in 2015 and 2018 (average 0,53), lower values in 2016 and 2017 (0,47–0,50). A decrease in CPhA with an increase in the concentration of chlorophyll (r = -0.30 – -0.56) was revealed.

СТРУКТУРА И МЕЖГОДОВАЯ ДИНАМИКА РАДИАЦИОННОГО БАЛАНСА РЕГИОНАЛЬНЫХ ЭКОСИСТЕМ РАВНИННОГО КРЫМА

The research team calculated the values of the radiation balance elements of the plain Crimea ecosystems on the bases of open databases of climate data and GIS-modeling and, moreover, analyzed their spatial and temporal differentiation. It is revealed that the spatial distribution of the radiation balance is characterized by an increase in values from the center to the coast of the peninsular. It correlates with the spatial differentiation of both total solar radiation and all other elements of the short-wave part of the radiation balance. There is a significant excess of radiation balance values of the plateau landscape level ecosystems over values of the hydromorphic landscape level ecosystems. This difference is determined by the location of selected key areas on the western coast of the Crimean Peninsula, which is characterized by the maximum values of total solar radiation supply. The elements of the long-wave part of the radiation balance change in the opposite direction, compared with the short-wave part of the radiation balance, which is associated with an increase of air temperature and climate continentality in the direction from the coast to the center of the peninsula. Two periods were identified in the interannual dynamics corresponding to the change of the circulatory periods of the Northern Hemisphere. In general, the considered ecosystems are characterized by trends of increasing radiation balance values in conditions of growth of all its elements. Such growth is provided by significant increase of values during the second period compared with the negative trends of radiation balance values for a number of ecosystems in the first one.

Comparison of Soil Moisture Dynamics in Fixed Dune and Sandy Grassland on Korqin Sandy Land

Based on the fixed-point observation data of soil moisture in different soil layers (0~150 cm) of fixed dunes and sandy grassland in the semi-arid region of Horqin Sandy Land, in the growing season (May to September) from 2005 to 2014, we conducted a comparative study on the seasonal, inter-annual, and spatial dynamics of soil moisture in the two types of sandy land. The results revealed that: (1) in the growing season, the soil moisture in sandy grassland was significantly higher than that in fixed dunes, and the multi-year average soil moisture in both types of sandy land was higher in July than in other months; (2) from 2005 to 2014, the average soil moisture in both types of sandy land was relatively high in 2010, and the average soil moisture in sandy grassland increased gradually with each year; specifically, there was a significant increase in soil moisture in June, while the average soil moisture in fixed dunes did not show an obvious increase; (3) the soil moisture in fixed dunes and sandy grassland generally showed a trend of “first increase, then decrease, and finally increase again”, with the increase in soil depth, and this change was more obvious for sandy grassland.