Increase In Net Primary Productivity Research Articles

Spatiotemporal pattern of NPP and its response to climatic factors in the Yangtze River Economic Belt

Net primary productivity (NPP) of terrestrial ecosystems serves as a crucial carbon sink, playing a significant role in mitigating climate change. This study, focusing on the Yangtze River Economic Belt (YREB), a key area for both economic development and ecological conservation in China, evaluates the temporal and spatial changes in regional NPP and its responses to climatic factors against the backdrop of global change. Utilizing long-term NPP and meteorological grid data from 1981 to 2017, we analyzed the annual change patterns of NPP and its linear and nonlinear responses to climatic factors using copula functions. Our findings indicate that 57.00 % of the YREB has experienced a significant increase in NPP, with the most substantial decreases observed in Shanghai and its surrounding areas (P < 0.05). Temperature emerged as the primary climatic driver, positively correlating with NPP changes in over half of the study area (P < 0.05). Moreover, the nonlinear response of NPP to temperature and precipitation underscores the complex interactions between these factors, revealing a sensitivity to temperature variations that surpasses that to precipitation. The study also highlights the influence of solar radiation and topographic factors, with a significant positive correlation between NPP and solar radiation observed in 15.85 % of the area (P < 0.05). The practical significance of these findings lies in their implications for regional ecological management and climate resilience strategies. The positive correlation between temperature and NPP underscores the potential for targeted temperature management to optimize carbon sequestration across the YREB. Furthermore, the identified nonlinear responses and the role of solar radiation and topography in influencing NPP offer valuable insights for the formulation of adaptive strategies that enhance ecosystem productivity and contribute to achieving carbon neutrality goals. By elucidating the dynamics of NPP in response to a range of environmental factors, this study provides a foundation for informed decision-making in ecological conservation and climate change mitigation efforts within the YREB and similar regions globally.

Analysis of change process of NPP dominated by human activities in Northwest Hubei, China, from 2000 to 2020.

Clarifying the spatial distribution of the impact of different human disturbance activities on the net primary productivity (NPP) in regions with single climatic conditions is of considerable importance to ecological protection. Time-series NPP from 2000 to 2020 was simulated in Northwest Hubei, China, and the effects of the climate and human activities on the NPP changes were separated. Research results showed that from 2000 to 2020, the NPP change with an area of 10,166.63 km2 in Northwest Hubei is influenced by climate and human activities. Among them, human activities account for as high as 84.53%. From 2000 to 2020, the NPP in Northwest Hubei showed a slight upward trend at a rate of 1.61g C m-2year-1. The significantly increased NPP accounted for 21.4% of the total, which was mainly distributed in north of Northwest Hubei. And the farming of cultivated land led to the increase of NPP in west as well as the reduced human distribution in cultivated land, which was scattered in forests. Only 6.67% of the total area demonstrated a significantly decreased NPP, which was distributed mainly in the central affected by the expansion of rural-urban land and change of broad-leaved forests to shrubs and in southeast regions of Northwest Hubei caused by the increase in potential evapotranspiration. This study refined the driving factors of spatial heterogeneity of NPP changes in Northwest Hubei, which is conducive to rational planning of terrestrial ecosystem protection measures.

Increased leaf area index and efficiency drive enhanced production under elevated atmospheric [CO2 ] in a pine-dominated stand showing no progressive nitrogen limitation.

Enhancement of net primary production (NPP) in forests as atmospheric [CO2 ] increases is likely limited by the availability of other growth resources. The Duke Free Air CO2 Enrichment (FACE) experiment was located on a moderate-fertility site in the southeastern US, in a loblolly pine (Pinus taeda L.) plantation with broadleaved species growing mostly in mid-canopy and understory. Duke FACE ran from 1994 to 2010 and combined elevated [CO2 ] (eCO2 ) with nitrogen (N) additions. We assessed the spatial and temporal variation of NPP response using a dataset that includes previously unpublished data from 6 years of the replicated CO2 × N experiment and extends to 2 years beyond the termination of enrichment. Averaged over time (1997-2010), NPP of pine and broadleaved species were 38% and 52% higher under eCO2 compared to ambient conditions. Furthermore, there was no evidence of a decline in enhancement over time in any plot regardless of its native site quality. The relation between spatial variation in the response and native site quality was suggested but inconclusive. Nitrogen amendments under eCO2 , in turn, resulted in an additional 11% increase in pine NPP. For pine, the eCO2 -induced increase in NPP was similar above- and belowground and was driven by both increased leaf area index (L) and production efficiency (PE = NPP/L). For broadleaved species, coarse-root biomass production was more than200% higher under eCO2 and accounted for the entire production response, driven by increased PE. Notably, the fraction of annual NPP retained in total living biomass was higher under eCO2 , reflecting a slight shift in allocation fraction to woody mass and a lower mortality rate. Our findings also imply that tree growth may not have been only N-limited, but perhaps constrained by the availability of other nutrients. The observed sustained NPP enhancement, even without N-additions, demonstrates no progressive N limitation.

Projected decline in the strength of vegetation carbon sequestration under climate change in India

Tropical vegetation plays a critical role in terrestrial carbon budget and supply many ecological functions such as carbon sequestration. In recent decades, India has witnessed an increase in net primary productivity (NPP), an important measure of carbon sequestration. However, uncertainties persist regarding the sustainability of these land carbon sinks in the face of climate change. The enhanced NPP is driven by the strong CO2 fertilization effect (CFE), but the temporal patterns of this feedback remain unclear. Using the carbon flux data from the Earth System Models (ESMs), an increasing trend in NPP was observed, with projections of NPP to 2.00 ± 0.12 PgCyr-1 (25 % increase) during 2021-2049, 2.36 ± 0.12 PgCyr-1 (18 % increase) during 2050-2079, and 2.67 ± 0.07 PgCyr-1 (13 % increase) during 2080-2099 in Indian vegetation under SSP585 scenario. This suggests a significant decline in the NPP growth rate. To understand the feedback mechanisms driving NPP, the relative effects of CFE and warming were analyzed. Comparing simulations from the biogeochemically coupled model (BGC) with the fully coupled model, the BGC model projected a 74.7 % increase in NPP, significantly higher than the 55.9 % increase projected by the fully coupled model by the end of the century. This indicates that the consistent increase in NPP was associated with CO2 fertilization. More importantly, results reveal that the decrease in the NPP growth rate was due to the declining contribution of CFE at a rate of -0.62 % per 100 ppm CO2 increase. This decline could be attributed to factors such as nutrient limitations and high temperatures. Additionally, significant shifts in the strength of carbon sinks in offsetting the CO2 emissions were identified, decreasing at a rate of -1.15 % per decade. This decline in the strength of vegetation carbon sequestration may increase the societal dependence on mitigation measures to address climate change.

Trade-off of ecosystem productivity and water use related to afforestation in southcentral USA under climate change

The increase of tree canopy cover due to woody plant encroachment and tree plantations modifies both carbon and water dynamics. The tradeoffs between ecosystem net primary productivity (NPP) and water use with increasing tree cover in different climate conditions, particularly under future climate scenarios, are not well understood. Within the climate transition zone of the southern Great Plains, USA, we used the Soil and Water Assessment Tool+ (SWAT+) to investigate the combined impacts of increasing tree cover and climate change on carbon and water dynamics in three watersheds representing semiarid, subhumid, and humid climates. Model simulations incorporated two land use modifications (Baseline: existing tree cover; Forest +: increasing evergreen tree cover), in conjunction with two climate change projections (the RCP45 and the RCP85), spanning two time periods (historic: 1991–2020; future: 2070–2099). With climate change, the subhumid and humid watersheds exhibited a greater increase in evapotranspiration (ET) and a corresponding reduction in runoff compared to the semi-arid watershed, while the semi-arid and subhumid watersheds encountered pronounced losses in water availability for streams (>200 mm/year) due to increasing tree cover and climate change. With every 1 % increase in tree cover, both NPP and water use efficiency were projected to increase in all three watersheds under both climate change scenarios, with the subhumid watershed demonstrating the largest increases (>0.16 Mg/ha/year and 170 %, respectively). Increasing tree cover within grasslands, either through woody plant expansion or afforestation, boosts ecosystem NPP, particularly in subhumid regions. Nevertheless, this comes with a notable decrease in water resources, a concern made worse by future climate change. While afforestation offers the potential for greater NPP, it also brings heightened water scarcity concerns, highlighting the importance of tailoring carbon sequestration strategies within specific regions to mitigate unintended repercussions on water availability.

Impacts of Extreme Precipitation and Diurnal Temperature Events on Grassland Productivity at Different Elevations on the Plateau

The impact of extreme climate events on vegetation growth and ecosystem function has garnered widespread attention, particularly in plateau regions, which are facing increasingly severe environmental pressures. This study employs the Events Coincidence Analysis (ECA) method to examine the impacts of extreme climate events on the Net Primary Productivity (NPP) of vegetation in plateau regions. Specifically, we focus on the unique phenomenon of asymmetric daytime and nighttime warming and evaluate the compounding effect of extreme precipitation with extreme temperature events. The results indicate that grassland NPP has higher overall sensitivity and Coincidence Rates (CR) to extreme precipitation events compared to extreme temperature events. Specifically, extreme drought events significantly negatively impact grassland NPP, and the sensitivity of NPP increases with the severity of extreme drought events. In lower elevations (&lt;3200 m), grassland NPP shows a strong response to extreme precipitation events, with sensitivity decreasing with increasing elevation, especially for alpine meadows. Extreme high-temperature events contributed significantly to NPP in mid to high elevations (3000–5000 m). Compound extreme climate events amplify the average coincidence degree with NPP anomalies, with extreme precipitation events playing a major role in compound effects. The CR of compound climate events can reach above 0.6, reflected in the anomaly increase of NPP in temperate grasslands at higher elevations caused by compound events of extremely wet and extremely high temperatures.

Quantifying the contributions of climatic and human factors to vegetation net primary productivity dynamics in East Africa

As an important part of the terrestrial ecosystem, vegetation dynamics are subject to impacts from both climate change and human activities. Clarifying the driving mechanisms of vegetation variation is of great significance for regional ecological protection and achieving sustainable development goals. Here, net primary productivity (NPP) was used to investigate the spatiotemporal variability of vegetation dynamics from 2000 to 2020 in East Africa, and its correlations with climate factors. Furthermore, we utilized partial derivatives analysis and set up different scenarios to distinguish the relative contributions of climatic and human factors to NPP changes. The results revealed that NPP exhibited a significant increase with 4.16 g C/m2/a from 2000 to 2020 in East Africa, and an upward trend was detected across 71.06% of the study area. The average contributions of precipitation, temperature, and solar radiation to the NPP inter-annual variations in East Africa were 2.02, −1.09, and 0.31 gC⋅m–2⋅a–1, respectively. Precipitation made the greatest positive contribution among all of the climatic factors, while temperature made strong negative contributions. The contributions of climate change and human activities to NPP changes were 1.24 and 2.34 gC⋅m–2⋅a–1, respectively. Moreover, the contribution rate of human activities to NPP increase was larger than that of climate change, while the role of climate change in NPP decrease was larger than that of human activities. The findings of the study can provide new evidence for a deeper understanding of ecosystem stability and carbon cycling in East Africa, as well as a reference for decision-making and scientific support for ecological environmental protection.

Unexpected contribution of cloud seeding to NPP increase during drought

Abstract Cloud seeding is generally used to secure additional water resources, which is not an easy goal to achieve, as the spatial variability of rainfall is high. Instead, the increased rain may moisten the neighboring forest. This study focuses on this situation and estimates the possible increase in the net primary production (NPP) due to cloud seeding. This study considers the Boryeong Dam basin in Korea as a study area and uses the Carnegie–Ames–Stanford Approach (CASA) model to estimate the NPP at 8-day intervals. As a result, first, the increase of the current 8-day NPP is greater when the rainfall amount during the last 16-day period is 50 mm or more. The mean increase of the 8-day NPP is estimated at about 1.873 g/m2 of carbon. Second, the increase of the NPP with the target 16-day rainfall of 50 mm is estimated at about 3%, which is about 4% with the target 16-day rainfall of 100 mm. Simply extrapolating the derived result to the entire forest in Korea, the increased carbon accumulation can be extended to about 0.6 and 0.8% of the total carbon emission in 2018, respectively. These amounts correspond to about 1.2 and 1.5% of the target amount of carbon reduction by 2030 in Korea.

Quantitative Assessment of Factors Influencing the Spatiotemporal Variation in Carbon Dioxide Fluxes Simulated by Multi-Source Remote Sensing Data in Tropical Vegetation

Vegetation plays a vital role in the global carbon cycle, a function of particular significance in regulating carbon dioxide fluxes within tropical ecosystems. Therefore, it is crucial to enhance the precision of carbon dioxide flux estimates for tropical vegetation and to explore the determinants influencing carbon sequestration. In this study, Landsat series images and Sentinel-2 Multispectral Instrument satellite data were used to invert vegetation biophysical parameters, thereby improving the timeliness and resolution of state variables from the boreal ecosystem productivity simulator (BEPS). The BEPS model at a 30 m resolution was developed to accurately capture tropical vegetation carbon dioxide fluxes across Hainan Island (HN) over the preceding two decades. The impacts of climate variations and anthropogenic activities on the carbon dioxide fluxes of tropical vegetation were further quantified using quantile regression models and a land-use transfer matrix. Results indicate significant increases in both net primary productivity (NPP) and net ecosystem productivity (NEP) in HN during the period 2000–2020, by 5.81 and 4.29 g C/m2 year, respectively. Spatial trends in vegetation carbon dioxide fluxes exhibited a consistent decline from inland regions to coastal zones. Anthropogenic activities were the dominant factor in the reduced stability of coastal NPP, while the post-2005 vegetation restoration promoted the southward expansion of high NPP (&gt;1200 g C/m2) in the central part of HN. NPP in this tropical island was more sensitive to temperature than to precipitation, with a 1 °C temperature increase resulting in 4.1 g C/m2 reduction in dry-season NPP compared to wet-season NPP. Upgrades of cropland quality and grassland restoration have improved NPP yields, and land use transfers have resulted in a 0.301 Tg C net increase in NPP. This study provides new insight into the improvement of the carbon dioxide flux model at a finer scale for tropical vegetation and highlights ecological construction as an adaptation strategy to enhance the carbon sinks of tropical vegetation under negative climate change conditions.

Investigating the long-term response of plateau vegetation productivity to extreme climate: insights from a case study in Qinghai Province, China.

Over the past three decades, there has been a significant global climate change characterized by an increase in the intensity and frequency of extreme climate events. The vegetation status in Qinghai Province has undergone substantial changes, which are more pronounced than other regions in the Qinghai-Tibet Plateau. However, a clear understanding of the response characteristics of plateau vegetation to extreme climate events is currently lacking. In this study, we investigated the response of net primary productivity (NPP) to different forms of extreme climate events across regions characterized by varying levels of aridity and elevation gradients. Specifically, we observed a significant increase in NPP in relatively arid regions. Our findings indicate that, in relatively arid regions, single episodes of high-intensity precipitation have a pronounced positive effect (higher correlation) on NPP. Furthermore, in high-elevation regions (4000-6000m), both the intensity and frequency of precipitation events are crucial factors for the increase in regional NPP. However, continuous precipitation can have significant negative impacts on certain areas within relatively wet regions. Regarding temperature, a reduction in the number of frost days within a year has been shown to lead to a significant increase in NPP in arid regions. This reduction allows vegetation growth rate to increase in regions where it was limited by low temperatures. Vegetation conditions in drought-poor regions are expected to continue to improve as extreme precipitation intensifies and extreme low-temperature events decrease.

Human activities significantly impact China’s net primary production variation from 2001 to 2020

Formulating ecological restoration strategies requires accurately quantifying how climate and anthropogenic factors influence net primary production (NPP). A Carnegie-Ames-Stanford approach (CASA) model was applied to estimate China’s terrestrial NPP from 2001 to 2020. We adopted a random forest (RF) method to identify the main driving forces for NPP change in China. Total NPP in China increased noticeably with a 24.91 Tg C/yr rate, as shown in our results. The significantly increased NPP was mainly attributed to human activities (64.29 ± 0.17%), chiefly due to human management and ecological projects (afforestation or other) fostered vegetation growth. The primary drivers of NPP variation varied in different geographic regions. Climate dominated the NPP dynamic in north China (52.38 ± 0.91%), where the main factor that restricted the increase of NPP was precipitation. Human activities strongly impacted the NPP variation in the remaining regions. Human management measures increased NPP in northwest and southwest China. In the northeast, east, and south-central China, the NPP change resulted from land use change, primarily grassland, cropland, and forest change. Collectively, our study expands the understanding of the driving forces of NPP change, informing different strategies for achieving ecological restoration and carbon neutrality.

Spatiotemporal Characteristic Prediction and Driving Factor Analysis of Vegetation Net Primary Productivity in Central China Covering the Period of 2001–2019

Unveiling the variation mechanism of vegetation net primary productivity (NPP) and elucidating the underlying drivers of these changes is highly necessitated for terrestrial carbon cycle research and global carbon emission control. Taking Henan Province, renowned as the anciently central China and current China’s foremost grain producer, as an example, this study employed the Theil–Sen Median Trend Analysis to evaluate the spatiotemporal characteristics and trends of NPP. Correlation Analysis and Residual Analysis were used to explain the drivers of NPP dynamics. To deepen the inquiry, the Geodetector method was employed to scrutinize the multifaceted effects and interplay among diverse variables influencing NPP. The result showed demonstrated that approximately 85.72% of the area showed an increase in NPP, covering a broad geographical distribution. Notably, 89.31% of the province has witnessed a positive human-driven NPP change. It means human activities emerged as a driving force with a positive effect on vegetation NPP, consequently fostering an increasing trend of NPP. Among climatic factors, the correlation between NPP and precipitation was stronger than that between the temperature and NPP, the determined power of factors in Henan Province was population density, (0.341) &gt; GDP (0.326) &gt; precipitation (0.255) &gt; elevation (0.167) &gt; slope (0.136) &gt; temperature (0.109), and a single factor had a lesser interaction effect than two factors. The implications of these findings extend beyond the realms of research, potentially offering valuable insights into the formulation of targeted ecosystem restoration measures tailored to the distinct context of Henan Province, and also expect to provide crucial references for carbon emission control in China and across the world.

Spatial–Temporal Variation Characteristics and Driving Factors of Net Primary Production in the Yellow River Basin over Multiple Time Scales

Vegetation net primary productivity (NPP) serves as a crucial and intuitive indicator for assessing ecosystem health. However, the nonlinear dynamics and influencing factors operating at various time scales are not yet fully understood. Here, the ensemble empirical mode decomposition (EEMD) method was used to analyze the spatiotemporal patterns of NPP and its association with hydrothermal factors and anthropogenic activities across different temporal scales for the Yellow River Basin (YRB) from 2000 to 2020. The results indicate that: (1) the annual average NPP was 236.37 g C/m2 in the YRB and increased at rates of 4.64 g C/m2/a1 (R2 = 0.86, p &lt; 0.01) during 2000 to 2020. Spatially, nonlinear analysis indicates that 72.77% of the study area exhibits a predominantly increasing trend in NPP, while 25.17% exhibits a reversing trend. (2) On a 3-year time scale, warming has resulted in an increase in NPP in the majority of areas of the study area (69.49%). As the time scale widens, the response of vegetation to climate change becomes more prominent; especially under the long-term trend, the percentage areas of the correlation between vegetation and precipitation and temperature increased with significance, reaching 48.21% and 11.57%, respectively. (3) Through comprehensive time analysis and multivariate regression analysis, it was confirmed that both human activities and climate factors had comparable impacts on vegetation growth. Among different vegetation types, climate was still the main factor affecting grassland NPP, and only 15.74% of grassland was affected by human activities. For shrubland, forest, and farmland, human activity was a dominating factor for vegetation NPP change. There are still few studies on vegetation change using nonlinear methods in the Yellow River Basin, and most studies have not considered the effect of time scale on vegetation evolution. The findings highlight the significance of multi-time scale analysis in understanding the vegetation dynamics and providing scientific guidance for future vegetation restoration and conservation efforts.

Correlation between Landscape Pattern and Net Primary Productivity of Vegetation: A Case Study in the Arid and Semi-Arid Regions of Northwest China

Human activities and environmental changes have influenced the changes in landscape patterns, which in turn profoundly impact the variation in net primary productivity (NPP) of vegetation. Understanding the relationship between landscape patterns and NPP is of significant importance for maintaining ecosystem stability and improving the ecological environment. In this study, six land use types in the arid and semi-arid regions of Northwest China were selected, and five landscape pattern indices at the landscape level and four landscape pattern indices at the class level were used. Pearson correlation and multiple linear regression models were employed to analyze the relationship between landscape indices and NPP at a 100 km × 100 km grid scale. The results indicate that there are varying degrees of correlation between landscape pattern indices and NPP from 2001 to 2020, with different levels of variation over the 20-year period. The correlation between indices and NPP is higher at the class level than at the landscape level, and the increase in landscape abundance and fragmentation promotes an increase in NPP. At the landscape level, three landscape indices, namely NP (Number of Patches), PR (Patch Richness), and SHDI (Shannon’s Diversity Index), explain 45.4% of the variation in NPP. At the class level, NP, TE (Total Edge Length), and IJI (Dispersion and Juxtaposition Index) are the main influencing factors for NPP in cropland, forestland, and grassland. Therefore, in ecological governance, it is necessary to consider landscape pattern changes appropriately to maintain ecosystem stability.

Spatial–Temporal Dynamics of Grassland Net Primary Productivity and Its Driving Mechanisms in Northern Shaanxi, China

Grasslands, a vital ecosystem and component of the global carbon cycle, play a significant role in evaluating ecosystem health and monitoring the global carbon balance. In this study, based on the Carnegie–Ames–Stanford Approach (CASA) model, we estimated the Net Primary Productivity (NPP) of grasslands in northern Shaanxi from 2000 to 2020. Employing trend analysis, stability analysis, multiple regression analysis, and residual analysis, the research examined the dynamic changes of grassland NPP and its response to climatic and human factors. Key findings include: (1) Grassland NPP showed a significant increasing trend during 2000–2020, with high-coverage grasslands showing a higher rate of increase than medium and low-coverage grasslands. (2) Most grasslands (&gt;90%) exhibited unstable growth and high NPP fluctuation. (3) While temperature, precipitation, and radiation undulate, the trends were not significant. Rainfall and radiation emerged as dominant factors affecting NPP, with temperature suppressing NPP increase to some extent. (4) Policies like returning farmland to grassland had a positive impact on grassland recovery, vegetation productivity, and regional ecosystem health.

Quantitative assessment of spatiotemporal dynamics in vegetation NPP, NEP and carbon sink capacity in the Weihe River Basin from 2001 to 2020

Vegetation carbon storage is crucial role in terrestrial ecosystems, impacting material and energy conversion processes. The combined influence of climate change and anthropogenic activities underscores their significance in achieving carbon neutrality. Understanding regional climate change necessitates the examination of spatiotemporal variations in net primary productivity (NPP) and net ecosystem productivity (NEP) of vegetation, as well as quantifying the relative contributions of climate change and anthropogenic activities to vegetation dynamics. This study conducts a comprehensive analysis of NPP and NEP changes and influencing factors in the Weihe River Basin (WHRB) employing various analytical techniques, including the Mann-Kendall (M-K) test, partial correlation analysis, and a land use and cover change (LUCC) matrix. The relative contributions of anthropogenic activities and climate change to NPP are investigated through a two-step linear regression approach. Results indicate a significant increase in NPP and NEP within the WHRB from 2001 to 2020, with both climate change and anthropogenic activities exerting positive impacts on vegetation growth. Conversion from grassland to forest results in the greatest net increase in NEP, while conversion to cropland leads to the largest net decrease. Climate change and anthropogenic activities contribute 4.6 gC·m−2·a−1 (64.16%) and 2.57 gC·m−2·a−1 (35.84%) to NPP, respectively. The capacity for vegetation carbon sink demonstrates an overall increase from 2001 to 2020, with higher values observed in the southern region and lower values in the northern region. The western region and areas along the river have transitioned from carbon sinks to carbon sources, while the potential for source-to-sink transformation has gradually intensified from the central to eastern, northern, and southeast regions. This study enhances the understanding of drivers and patterns of vegetation dynamics in response to climate change and anthropogenic activities in the WHRB. The findings provide valuable scientific insights for improving NPP and carbon sink capacities and advancing sustainable development objectives.

Carbon budget response to climate change varies with grassland type in Qilian Mountains, China

Carbon budget estimation is crucial for scientifically assessing the ecosystem’s carbon sequestration capacity. Grasslands in the Qilian Mountains are widely recognized as vulnerable and sensitive to ongoing climate change. However, it is still unclear how the carbon budget of different grassland types responds to climate change in this area. Here, we evaluated the net primary productivity (NPP), soil heterotrophic respiration (RH), and net ecosystem productivity (NEP) of grassland ecosystems in the Qilian Mountains. Correlation analysis, linear regression, and standardized coefficient methodologies were employed to explore the response of NPP, RH, and NEP in various grassland types to changes in temperature, precipitation, and solar radiation over the past two decades. The results showed that the alpine meadow has the highest NPP and NEP while the temperate typical steppe has the highest RH. Grassland NPP, RH, and NEP increased significantly from 2001 to 2020, with a distinct spatial pattern of being low in the northwest and high in the southeast of the Qilian Mountains. NPP and NEP correlated with precipitation and solar radiation more closely than with temperature. Precipitation and solar radiation, respectively, explained 43.7% and 52.9% of grassland NEP alterations, and there was a threshold effect on the response of NEP and NPP to climate factors. Specifically, the NPP and NEP increased at first and then decreased as the precipitation, temperature, and solar radiation increased. The highest NEP and NPP occurred when precipitation ranged from 415 to 455 mm, along with temperatures between − 0.1–1.5 ℃ and solar radiation reaching 7685–7905MJ/m2. The warming and humidification of climate is conducive to the increase of NPP and NEP in alpine meadows and alpine steppes, but when the precipitation exceeds 415 mm and the temperature is greater than 1.5 ℃, the NPP and NEP begin to decrease. Solar radiation dominated changes in NPP and NEP of alpine meadows, alpine steppes, and temperate desert steppes. With the increase of solar radiation, NPP and NEP of these three grasslands first increased and then decreased. However, the changes in NPP and NEP of the temperate typical steppe were most affected by precipitation, and NPP and NEP first increase and then decrease with the increase of precipitation The higher the temperature, the higher the NPP, RH, and NEP of the temperate typical steppe. This study helps better understand how climate change impacts the carbon budget components of different grassland types in the Qilian Mountains and provides more theoretical thoughts on managing local grasslands sustainably.

Increasing sensitivity of dryland water use efficiency to soil water content due to rising atmospheric CO2

Examining the intricate interplay between ecosystem carbon-water coupling and soil moisture sensitivity serves as a crucial approach to effectively assess the dilemma arising from escalating global carbon emissions and concomitant water scarcity. Using the Lund–Potsdam–Jena Dynamic Global Vegetation Model (LPJ), this study investigated the potential effects of climate change and soil water content (SWC) on terrestrial ecosystem water use efficiency (WUE) across China from 1982 to 2060. The results revealed that: (1) WUE was higher in South China and Northeast China, but lower in Northwest China and it had shown a significant upward trend in the past 40 years, especially in Northwest China where grasslands were widely distributed. The increase in WUE was mainly closely related to the greening of vegetation. In the past 40 years, the area of net primary productivity (NPP), evapotranspiration (ET), and WUE showing an upward trend accounted for 85.85 %, 63.66 %, and 83.88 % of the total area of the country, respectively. Although ET also showed an increasing trend nationwide, the increase of NPP was more obvious; (2) The control experiment showed that WUE showed a significant increase trend in arid and semi-arid areas of Northwest China with the increase of CO2 concentration, while SWC showed a significant drying trend, but both WUE and SWC showed an increasing trend in humid areas. The sensitivity of WUE to SWC was enhanced in arid and semi-arid areas, and the effect of soil drought was partially offset by the increase of WUE; (3) Future climate projections also indicated that the CO2 fertilization effect will contribute to an increase in WUE while causing drier soil moisture conditions in the arid and semi-arid regions. Especially under the SSP5-8.5 scenario, CO2 fertilization in Northwest China contributed more than 14 % to WUE from 2015 to 2060, while the impact on SWC depletion exceeded 3 %. This highlights the potential implications of rising atmospheric CO2 concentration, as it may promote a significant rise in WUE and exacerbate the drying of soil moisture in these areas. These findings emphasize the need for careful attention and consideration in managing water resources in arid and semi-arid regions in the face of future climate change.

Assessment of satellite-based Net Primary Productivity models in different biogeochemical provinces over the northern Indian Ocean

ABSTRACT The biological productivity in the oceanic ecosystem plays a vital role in the global carbon cycle and energy flow in the oceanic food chain. Therefore, proper monitoring of phytoplankton primary production in the ocean is essential to understand the role and responses of aquatic ecosystems to global climate change. Its quantification is also important for higher trophic-level studies and sustainable ecosystem management. The advent of satellite technology has provided an opportunity to retrieve Net Primary Productivity (NPP) at high spatial and temporal resolution. However, for efficient utilization of satellite NPP it is imperative to assess the models for their accuracy and variability. The present study described NPP estimated from MODIS-Aqua satellite data (2003–2021) using five models (VGPM, Eppley-VGPM, CbPM, CAFE, and SABPM) and their variability in the four biogeochemical provinces (ARAB, MONS, INDW and INDE) in the northern Indian Ocean. The temporal variability indicated all models exhibit seasonal variability in ARAB and INDW with two prominent peaks during peak southwest monsoon (June-August) and winter monsoon (December-January). However, there was significant difference in the magnitude. The seasonal peak was primarily due to increase in NPP due to summer upwelling and winter mixing. The spatially averaged diversity index indicated maximum variability in INDW (74.6–77.1%), followed by INDE (77.2–78.0%), ARAB (77.2–78.4%), and MONS (78.6–78.9%). The satellite retrieved NPP by various models showed maximum diversity in the region above 15°N and west of 60°E in AS and 20°N and east 90°E in the BoB indicating a significant influence of discharge from perennial rivers resulting in poor performance of the models in these regions. The variability of other models was then assessed with respect CbPM as the model was known to perform better. The Eppley-VGPM showed a maximum (55%) and SABPM showed a minimum (11%) Mean Absolute Percentage Difference with respect to CbPM. The long-term spatio-temporal and quantifiable variability between the NPP models, and biogeochemical provinces, indicated that the study provided useful information on the selection and utilization of an appropriate model for future sustainability and climate change studies.

Trophic amplification: A model intercomparison of climate driven changes in marine food webs.

Marine animal biomass is expected to decrease in the 21st century due to climate driven changes in ocean environmental conditions. Previous studies suggest that the magnitude of the decline in primary production on apex predators could be amplified through the trophodynamics of marine food webs, leading to larger decreases in the biomass of predators relative to the decrease in primary production, a mechanism called trophic amplification. We compared relative changes in producer and consumer biomass or production in the global ocean to assess the extent of trophic amplification. We used simulations from nine marine ecosystem models (MEMs) from the Fisheries and Marine Ecosystem Models Intercomparison Project forced by two Earth System Models under the high greenhouse gas emissions Shared Socioeconomic Pathways (SSP5-8.5) and a scenario of no fishing. Globally, total consumer biomass is projected to decrease by 16.7 ± 9.5% more than net primary production (NPP) by 2090-2099 relative to 1995-2014, with substantial variations among MEMs and regions. Total consumer biomass is projected to decrease almost everywhere in the ocean (80% of the world's oceans) in the model ensemble. In 40% of the world's oceans, consumer biomass was projected to decrease more than NPP. Additionally, in another 36% of the world's oceans consumer biomass is expected to decrease even as projected NPP increases. By analysing the biomass response within food webs in available MEMs, we found that model parameters and structures contributed to more complex responses than a consistent amplification of climate impacts of higher trophic levels. Our study provides additional insights into the ecological mechanisms that will impact marine ecosystems, thereby informing model and scenario development.