Net Ecosystem Production Research Articles

Urban roadside greenery as a carbon sink: Systematic assessment considering understory shrubs and soil respiration

Roadside greenery is an efficient strategy for maximizing ecosystem services, including carbon sequestration in urban settings. However, the quantification of carbon sequestration is not comprehensive because understory shrubs and soil respiration have not been thoroughly considered. We developed an integrated methodology that combined field measurements and greenhouse incubation to comprehensively assess carbon sequestration in roadside greenery systems. The system was defined as an 8 m long section comprising a single tree (Zelkova serrata), 79 shrubs (Euonymus japonicus), and soil. Annual carbon uptake by a tree was estimated using an allometric equation derived from an official government report. For shrubs, carbon uptake was measured in the field by monitoring CO2 concentration change in the chamber enclosing the leaves and stems. Annual carbon uptake by shrubs was estimated by using the regression equation among carbon uptake, air temperature, and photosynthetically active radiation. We also estimated shrub root respiration by combining net primary production (NPP) from the greenhouse incubation and measured pruning effect in the field. This enabled us to differentiate heterotrophic respiration from the total soil respiration. The overall methodology accurately assessed net ecosystem production (NEP) from the roadside greenery system, which is 0.528 kg C m−2 yr−1. If this figure is extended to all roads in the target city, it can offset daily carbon emitted from the total registered passenger vehicles in the target city. Considering that shrubs sequester an amount equivalent to 29.3 % of the carbon sequestered by tree species, the current greenhouse gas inventory should include shrubs as an important carbon sink. As we also revealed that roadside soil has high carbon vulnerability, proper soil management is needed to enhance NEP. Our systematic approach evaluating the carbon balance within the roadside greenery system can be applied to other cities, contributing to enhance global understanding of urban carbon cycle.

How urbanization shapes the ecosystem carbon sink of vegetation in China: A spatiotemporal analysis of direct and indirect effects

Rapid urbanization has led to extensive effects on the spatio-temporal patterns of the carbon sources and sinks in ecosystems. However, due to the lack of long-term continuous land use/cover change (LUCC) data, there has been limited discussion on the spatio-temporal impacts of urbanization on carbon sources/sinks and the non-linear characteristics of urban changes over time. This study focused on the impact of urbanization on vegetation net ecosystem productivity (NEP) in 31 provincial capital cities in China from 1990 to 2019, using land use change data and NEP indicators, to analyze the change patterns and response modes of urbanization intensity and NEP. The study found that: (1) During the period of 1990–1995, almost all cities in China experienced a turning point of urbanization rate from decreasing to increasing, while after 2000, the urbanization rate declined significantly; (2) Climate background affects the negative impact of urbanization on NEP, especially in warm and humid climate background, while the direct impact of urbanization on vegetation is more significant; (3) Overall, urbanization in China aggravated the negative impact of urbanization on NEP from 1990 to 2019, especially in cold and arid climate background, which would further exacerbate the negative impact of urbanization. This study helps us better understand the impact of Chinese urbanization on ecosystem carbon sinks and mitigating the carbon emissions pressure of urban environments.

Extreme low air temperature and reduced moisture jointly inhibit respiration in alpine grassland on the Qinghai-Tibetan Plateau

Alpine grassland is the main vegetation on the Qinghai-Tibetan Plateau (QTP) and exhibits high sensitivity to extreme weather events. With global warming, extreme weather events are projected to become more frequent on the QTP. However, the impact of these extreme weather events on the carbon cycle of alpine grassland remains unclear. The long-term in-situ carbon fluxes data was collected from 2013 to 2022 at an alpine grassland site to examine the impact of extreme low air temperature (ELT) and reduced moisture (including air and soil) on carbon fluxes during the growing season. Our findings indicated that a significant increase in net ecosystem production (NEP) after 2019, with the average NEP increasing from 278.91 ± 43.27 g C m−2 year−1 during 2013–2018 to 415.45 ± 45.29 g C m−2 year−1 during 2019–2022. The ecosystem carbon use efficiency (CUE) increased from 0.38 ± 0.06 during 2013–2018 to 0.62 ± 0.11 during 2019–2022. By combining concurrently measured environmental factors and remote sensing data, we identified the factors responsible for the abrupt change in the NEP after 2019. This phenomenon was caused by an abrupt decrease in ecosystem respiration (Reco) after 2019, which resulted from the inhibition imposed by ELT and reduced moisture. In contrast, gross primary production (GPP) remained stable from 2013 to 2022, which was confirmed by the remotely sensed vegetation index. This study highlights that combined extreme weather events associated with climate change can significantly impact the NEP of alpine grassland, potentially affecting different carbon fluxes at different rates. These findings provide new insights into the mechanisms governing the carbon cycle of alpine grassland.

Elevation-dependent pattern of net CO2 uptake across China

The elevation gradient has long been known to be vital in shaping the structure and function of terrestrial ecosystems, but little is known about the elevation-dependent pattern of net CO2 uptake, denoted by net ecosystem productivity (NEP). Here, by analyzing data from 203 eddy covariance sites across China, we report a negative linear elevation-dependent pattern of NEP, collectively shaped by varying hydrothermal factors, nutrient supply, and ecosystem types. Furthermore, the NEP shows a higher temperature sensitivity in high-elevation environments (3000–5000 m) compared with the lower-elevation environments (<3000 m). Model ensemble and satellite-based observations consistently reveal more rapid relative changes in NEP in high-elevation environments during the last four decades. Machine learning also predicts a stronger relative increase in high-elevation environments, whereas less change is expected at lower elevations. We therefore conclude a varying elevation-dependent pattern of the NEP of terrestrial ecosystems in China, although there is significant uncertainty involved.

Improving the Simulation Accuracy of the Net Ecosystem Productivity of Subtropical Forests in China: Sensitivity Analysis and Parameter Calibration Based on the BIOME-BGC Model

Subtropical forests have strong carbon sequestration potential; however, the spatiotemporal patterns of their carbon sink are unclear. The BIOME-BGC model is a powerful tool for forest carbon sink estimation while the numerous parameters, as well as the localization, limit their application. This study takes three typical subtropical forests (evergreen broadleaf forest, EBF; evergreen needleleaf forest, ENF; and bamboo forest, BF) in China as examples, assesses the sensitivity of 43 ecophysiological parameters in the BIOME-BGC model both by the Morris method and the extended Fourier amplitude sensitivity test (EFAST), and then evaluates the net ecosystem productivity (NEP) estimation accuracy based on the dataset of the fiveFi long-term carbon flux sites of those three typical forests from 2000 to 2015. The results showed that (1) both sensitivity analysis methods can effectively screen out important parameters affecting NEP simulation while the Morris method is more computationally efficient and the EFAST is better in the quantitative evaluation of sensitivity. (2) The highly sensitive parameters obtained using the two methods are basically the same; however, their importance varies across sites and vegetation types, e.g., the most sensitive parameters are k for the EBF and ENF and Ract25 for the BF, respectively. (3) The optimized parameters successfully improved the NEP simulation accuracy in subtropical forests, with average correlation coefficients increased by 25.19% and normalized root mean square error reduced by 21.74% compared with those simulated by original parameters. This study provides a theoretical basis for the optimization of process model parameters and important technical support for accurate NEP simulations of subtropical forest ecosystems.

Earlier spring greening in Northern Hemisphere terrestrial biomes enhanced net ecosystem productivity in summer

The northern terrestrial biomes are being remarkably altered by climate change. Higher springtime temperature induces the earlier greening of vegetation, which may further influence ecosystem functions during the subsequent season. However, the response of summer net ecosystem productivity to spring vegetation greenness and phenology changes has not yet been quantified. To understand the impact of such phenological changes on terrestrial carbon sink of the following season, here we integrate remotely-sensed vegetation data and model simulations of carbon flux with an explainable machine learning approach. We find that the lagged effects of widespread earlier spring greening are increasing the summer ecosystem carbon sink across the northern vegetated areas (30° to 90°N) from 1982 to 2015. In particular, response disparities exist in non-agricultural biomes, and the vegetation with moderate tree coverage is more sensitive to earlier spring greening. Furthermore, modest tree restoration can strengthen the beneficial effects of earlier spring greening. This study improves our understanding of interseasonal vegetation-climate-carbon coupling that drives the key ecological feedback within climate change projections.

CO2 fluxes contrast between aquaculture ponds and mangrove forests and its implications for coastal wetland rehabilitation in Leizhou Peninsula, China

Coastal wetlands have great potential to mitigate climate change. However, in recent decades, the construction of aquaculture ponds has degraded coastal habitats, especially mangroves. Meanwhile, the lack of synchronized monitoring of carbon dioxide (CO2) fluxes in coastal ponds and mangroves hinders the promotion of carbon neutrality target through the implementation of coastal wetland rehabilitation. To address this issue, we deployed two eddy-covariance systems in the ponds and nearby mangroves to measure the net ecosystem CO2 exchange between atmosphere and ecosystems for two years. The results indicated that both the ponds and mangroves were CO2 sinks at the annual scale, with mean net ecosystem production (NEP) of 123 ± 39 and 1296 ± 32 g C m−2 year−1, respectively. During the 2-year period, the ponds acted as CO2 sources in certain seasons, while the mangroves displayed consistently high seasonal NEP. The construction of ponds by clearing mangroves would reduce NEP along the coasts of the Leizhou Peninsula by about 91% (96% for China), while abandoning all ponds for mangrove rehabilitation could have a significant CO2 mitigation benefit (i.e., 214.7 Gg year−1). Moreover, we compared how CO2 fluxes responded to global solar radiation and temperature by analyzing relevant parameters in the two ecosystems. Overall, the ponds showed lower light-saturated net CO2 exchange and Q10 values compared to the mangroves. Finally, we applied an advanced machine learning local interpretation algorithm to investigate the crucial drivers and their main effects on NEP. This analysis highlighted global solar radiation as the predominant driver for NEP in both ecosystems. High temperature and vapor pressure deficit inhibited mangrove NEP, particularly during summer, whereas pond NEP exhibited greater volatility in response to meteorological conditions such as temperature. Our findings provide insights for further proceeding with mangrove restoration and management to enhance the carbon sequestration capacity of coastal wetlands.

Characteristic Analysis of Carbon Sink Capacity Changes in Xinjiang’s Terrestrial Ecosystem Based on EEMD

Net Ecosystem Productivity (NEP) is an important measure to assess the carbon balance and dynamics of ecosystems, providing a direct measure of carbon source–sink dynamics in terrestrial ecosystems and finding widespread applications in carbon cycle research. However, the nonlinear characteristics of NEP in Xinjiang’s terrestrial ecosystems remain unclear. Additionally, the influence of land use patterns, temperature, and precipitation variations on carbon sink capacity remains unclear. Ensemble Empirical Mode Decomposition (EEMD) is used to investigate the nonlinear variation of NEP in Xinjiang. Landscape pattern analysis of Xinjiang’s land use patterns from 1981 to 2019 is conducted using a 30 km moving window, and the interannual relationships between NEP, land use patterns, and meteorological factors are investigated through EEMD detrending analysis and Pearson correlation. The findings indicate that: (1) NEP exhibits interannual variations, primarily concentrated in the foothills of the Tianshan Mountains, with a three-year cycle. (2) Although NEP changes in most regions are not significant, urban clusters on the northern slopes of the Tianshan Mountains show noteworthy trends, with initial decrease followed by an increase, covering around 34.87% of the total area. Areas at risk of NEP decline constitute approximately 7.32% of the total area. (3) Across Xinjiang, we observe a widespread rise in patch fragmentation and complexity, coupled with a decline in patch connectivity and the size of the dominant patch. Additionally, there is a notable increase in both the diversity and evenness of land use types. However, the correlation between land use patterns and NEP is generally found to be insignificant in the majority of areas, with a percentage exceeding 85%. (4) Approximately 62% of regions in Xinjiang have NEP that is positively correlated with temperature, with significance observed in 33% of these areas. Furthermore, almost 95% of regions demonstrate that NEP is positively correlated with precipitation, with significance noted in 83% of these regions. It appears that precipitation exerts a more pronounced influence on NEP fluctuations in Xinjiang when compared to temperature.

Evolutionary characteristics of carbon sources/sinks in Chinese terrestrial ecosystems regarding to temporal effects and geographical partitioning

Whereas the current complex diversity in Chinese terrestrial ecosystems and the significant differences in net ecosystem productivity (NEP) among various regions, as well as the temporal effect between vegetation and climate factors, the NEP in Chinese terrestrial ecosystems was estimated between 2001 and 2020, and characterized the spatiotemporal dynamics of NEP and its driving mechanisms, taking into account geographic subdivisions. The results demonstrated that the multiannual mean of NEP in Chinese terrestrial ecosystems ranged from 42.79 to 61.91 g C/m2a over the past two decades, indicating a volatile upward trend. Spatially, the NEP of Chinese terrestrial ecosystems indicated significant spatial differentiation, with carbon sinks encompassing 68.83 %, primarily focused in Northeast Region (DB), East China (HD), South China (HN), and Central China (HZ). Moving forward, Chinese terrestrial ecosystems will be predominantly restored, with 40.88 % of the area going from degradation to improvement, and 14.17 % of the area undergoing sustained improvement. There were geographic differences in the temporal effects between NEP and climate elements (precipitation and temperature). Precipitation was identified as the dominant factor affecting the variation of NEP in DB, HB, HZ, XB, and XN. While solar radiation was the major factor influencing the variation of NEP in HD (51.72 %) and HN (76.07 %). Compared with human activities, climate change emerged as the primary driver impacting the spatiotemporal evolution of NEP in Chinese terrestrial ecosystems, with 61.40 % of the area of NEP increasing due to climate change, while 58.42 % increased due to human activities. Additionally, changes in land use/land cover played a crucial role in altering NEP of terrestrial ecosystems in China.

Albedo‐Induced Global Warming Potential Following Disturbances in Global Temperate and Boreal Forests

AbstractForest disturbances can result in very different canopies that carry elevated albedo, thus causing substantial cooling effects on the climate. Unfortunately, the resulting dynamic global warming potential from altered albedo (GWPΔα) is poorly understood. We examined and modeled the changes in albedo over time after disturbances (i.e., forest age) by forest type, disturbance type and geographic location using direct measurements from 107 sites in temperate and boreal regions. Albedo in undisturbed forests was used as the reference to calculate albedo changes (Δα) and GWPΔα after a disturbance. We found that age is a significant factor for predicting albedo amid the obvious regulations from forest type and geographic locations. We found the strongest cooling GWPΔα in the first 10 years after a disturbance, but it decreased rapidly with time. The changes in GWPΔα were very different from the chronosequence of net ecosystem production (NEP). In the first decade after disturbances, GWPΔα was negative (i.e., cooling) and surprisingly larger in magnitude, with an average of −0.609 kg CO2 m−2 yr−1, compared to NEP of −0.166 kg CO2 m−2 yr−1. Albedo continued to decrease and approached pre‐disturbance levels until around 50 years, resulting in a nearly zero GWPΔα. This research illustrates that many forests in temperate and boreal regions can be considered significant cooling agents by taking into account the high albedo of young forests following disturbances.

Deconstructing the mangrove carbon cycle: Gains, transformation, and losses

AbstractMangroves are one of the most carbon‐dense forests on the Earth and have been highlighted as key ecosystems for climate change mitigation and adaptation. Hundreds of studies have investigated how mangroves fix, transform, store, and export carbon. Here, we review and synthesize the previously known and emerging carbon pathways in mangroves, including gains (woody biomass accumulation, deadwood accumulation, soil carbon sequestration, root and litterfall production), transformations (food web transfer through herbivory, decomposition), and losses (respiration as CO2 and CH4, litterfall export, particulate and dissolved carbon export). We then review the technologies available to measure carbon fluxes in mangroves, their potential, and their limitations. We also synthesize and compare mangrove net ecosystem productivity (NEP) with terrestrial forests. Finally, we update global estimates of carbon fluxes with the most current values of fluxes and global mangrove area. We found that the contributions of recently investigated fluxes, such as soil respiration as CH4, are minor (&lt;1 Tg C year−1), while the contributions of deadwood accumulation, herbivory, and lateral export are significant (&gt;35 Tg C year−1). Dissolved inorganic carbon exports are an order of magnitude higher than the other processes investigated and were highly variable, highlighting the need for further studies. Gross primary productivity (GPP) and ecosystem respiration (ER) per area of mangroves were within the same order of magnitude as terrestrial forests. However, ER/GPP was lower in mangroves, explaining their higher carbon sequestration. We estimate the global mean mangrove NEP of 109.1 Tg C year−1 (7.4 Mg C ha−1 year−1) or through a budget balance, accounting for lateral losses, a global mean of 66.6 Tg C year−1 (4.5 Mg C ha−1 year−1). Overall, mangroves are highly productive, and despite losses due to respiration and tidal exchange, they are significant carbon sinks.

Microbial-explicit processes and refined perennial plant traits improve modeled ecosystem carbon dynamics

Globally, soils hold approximately half of ecosystem carbon and can serve as a source or sink depending on climate, vegetation, management, and disturbance regimes. Understanding how soil carbon dynamics are influenced by these factors is essential to evaluate proposed natural climate solutions and policy regarding net ecosystem carbon balance. Soil microbes play a key role in both carbon fluxes and stabilization. However, biogeochemical models often do not specifically address microbial-explicit processes. Here, we incorporated microbial-explicit processes into the DayCent biogeochemical model to better represent large perennial grasses and mechanisms of soil carbon formation and stabilization. We also take advantage of recent model improvements to better represent perennial grass structural complexity and life-history traits. Specifically, this study focuses on: 1) a plant sub-model that represents perennial phenology and more refined plant chemistry with downstream implications for soil organic matter (SOM) cycling though litter inputs, 2) live and dead soil microbe pools that influence routing of carbon to physically protected and unprotected pools, 3) Michaelis-Menten kinetics rather than first-order kinetics in the soil decomposition calculations, and 4) feedbacks between decomposition and live microbial pools. We evaluated the performance of the plant sub-model and two SOM cycling sub-models, Michaelis-Menten (MM) and first-order (FO), using observations of net ecosystem production, ecosystem respiration, soil respiration, microbial biomass, and soil carbon from long-term bioenergy research plots in the mid-western United States. The MM sub-model represented seasonal dynamics of soil carbon fluxes better than the FO sub-model which consistently overestimated winter soil respiration. While both SOM sub-models were similarly calibrated to total, physically protected, and physically unprotected soil carbon measurements, the models differed in future soil carbon response to disturbance and climate, most notably in the protected pools. Adding microbial-explicit mechanisms of soil processes to ecosystem models will improve model predictions of ecosystem carbon balances but more data and research are necessary to validate disturbance and climate change responses and soil pool allocation.

Carbon sinks/sources' spatiotemporal heterogeneity and their spatial response to economic-social factors in relatively developed regions: A case of China's coastal area

With the global climate change, carbon reduction in economically active regions has gradually become a focus of attention and its underlying drivers were essential for understanding alterations in ecosystems in response to human behavior. However, the exploration of Carbon Sinks/Sources Patterns (CSSP) in an Economic-Social context was lacking. Distinguished from traditional Net Ecosystem Productivity (NEP) estimation methods, we optimized model parameters, adjusted estimation logic, and revealed CSSP more reasonably. Moreover, spatial econometric model was used to reveal the spatial effects mechanism of Economic-Social Development on CSSP. Over the past 20 years, we revealed that: (a) The pattern of NEP exhibited distinct spatial heterogeneity, with higher sinks observed in the north and offshore regions. It demonstrated regular cyclic fluctuations, averaging a 3-4-year cycle, featuring a gradual ascent followed by a rapid descent; (b) The Carbon Sequestration Capacity (CSC) of vegetation significantly increased. Based on the carbon sink properties, the study area was distinctly divided into three clusters; (c) CSSP have been profoundly affected by economic-social factors. Economic growth and industrial structure optimization contributed to the enhancement of CSC, but population aggregation and urban expansion had negative impacts. The direct effect of innovation capacity and the spatial spillover effect of industrial structure optimization were negative. Overall, exploring CSSP against the backdrop of economic-social factors not only provides a new perspective for understanding the regularities of change and the underlying mechanisms driven by human factors but also offers valuable insights for achieving sustainable development and green growth in other coastal regions globally.

Spatiotemporal patterns of net regional productivity and its causes throughout Ordos, China.

A comprehensive understanding of the terrestrial carbon sink is essential for proficient regional carbon management. However, previous studies predominantly relied on net ecosystem productivity (NEP) as an indicator of regional carbon sink, overlooking the impacts of carbon emissions from physical processes and carbon leakage associated with anthropogenic activities. In this study, net region productivity (NRP), a vital metric representing carbon sink dynamics in regional multi-landscape ecosystems, was employed to systematically analyze the patterns, trends, and causes of carbon sink in Ordos. The results revealed that spatially averaged NRP in Ordos was 70.334 g·m-2·a-1, indicating a carbon sink effect. The coefficient of variation of NRP was 68.035%, with a higher NRP in the southern region. Normalized difference vegetation index (NDVI) predominantly controlled the spatial heterogeneity of NRP in Ordos, while precipitation emerged as the primary climatic factor influencing spatial differences in NRP. Regional variations in the impact of environmental factors on NRP were evident. In most areas, NRP showed a notable increasing trend influenced by various factors. Specifically, the simultaneous rise in NDVI and improvements in hydrothermal conditions contributed to the gradual elevation of NRP, each with varying degrees of influence across Ordos and its sub-regions.

Characterization of carbon fluxes, stock and nutrients in the sacred forest groves and invasive vegetation stands within the human dominated landscapes of a tropical semi-arid region

In the semi-arid plains of Southern India, outside the protected area network, sacred groves forests and the barren lands invaded by Prosopis juliflora are reckoned to be the major greenery, but have homogenous and heterogeneous vegetation respectively. This study attempted to compare 50 Sacred Groves Stands (SGS) and 50 monodominant Prosopis juliflora Stands (PJS) for the functional diversity, evenness, floral diversity, carbon stock and dynamics, carbon-fixing traits, dendrochronology of trees, soil nutrient profiles, and soil erosion. Quadrat sample survey was adopted to record stand density, species richness, abundance, basal area and leaf area index; composite soil samples were collected at depths 0–30 cm for nutrient profiling (N, P, K, and OC). Photosynthesis rate (µmole co2 m2/sec), air temperature (°c), leaf intracellular co2 concentration (ppm), ambient photosynthetic active radiation (µmole m2/sec), transpiration rate (m. mole H2O m2/sec) were determined for the 51 tree species existed in SGS and PJS using Plant Photosynthesis system. Structural Equation Model (SEM) was applied to derive the carbon sequestering potential and photosynthetic efficiency of eight dominant tree species using vital input parameters, including eco-physiological, morphological, and biochemical characterization. The Revised Universal Soil Loss Equation (RUSLE) model, in conjunction with ArcGIS Pro and ArcGIS 10.3, was adopted to map soil loss. Carbon source/sink determinations inferred through Net Ecosystem Productivity (NEP) assessments showed that mature SGS potentially acted as a carbon sink (0.06 ± 0.01 g C/m2/day), while matured PJS acted as a carbon source (−0.34 ± 0.12 g C/m2/day). Soil erosion rates were significantly greater (29.5 ± 13.4 ton/ha/year) in SGS compared to PJS (7.52 ± 2.55 ton/ha/year). Of the eight selected tree species, SEM revealed that trees belonging to the family Fabaceae [Wrightia tinctoria (estimated coefficient: 1.28, p = 0.02) > Prosopis juliflora (1.22, p = 0.01) > Acacia nilotica (1.21, p = 0.03) > Albizia lebbeck (0.97, p = 0.01)] showed comparatively high carbon sequestering ability.

Temporal and Spatial Assessment of Carbon Flux Dynamics: Evaluating Emissions and Sequestration in the Three Northern Protection Forest Project Areas Supported by Google Earth Engine

Contemporary research on terrestrial carbon exchange processes is paramount for a nuanced comprehension of global and local climatic fluctuations and their interaction with anthropogenic activities. This study delves into the spatiotemporal dynamics of vegetation carbon exchanges within the Three Northern Protection Forest Project Area, leveraging two decades of MODIS NPP data and an innovative NEP estimation model. Our analysis highlights a generally increasing trend in Net Ecosystem Productivity (NEP) from 2000 to 2020, with significant growth in approximately 32.97% of the study area and slight increases in 24.18%. Notably, lower NEP values were found in desert and arid zones, whereas higher values were observed in more vegetated regions like Ningxia, Hebei, Inner Mongolia, and the northeast. The study also assesses the impact of climate variables and land-use changes on NEP, identifying both negative and positive correlations in specific regions. Despite the overall positive trend towards ecological restoration and enhancement, significant uncertainties remain, emphasizing the urgent need for further research to support ecosystem resilience and sustainable management practices.

Resilience changes of carbon stocks to quantify the long‐term effects of ecological engineering projects in subtropical forests of China based on satellite‐derived net ecosystem production time series and inventory data

AbstractUnderstanding how resilient forests are to ecological engineering projects (EEPs) is essential to forest management and ecosystem health. Despite growing evidence that EEPs achieve increasing carbon stocks, whether such benefits can be sustainable and what are the consequences of EEPs on forest health remain unclear. This study aimed to investigate the long‐term effects of EEPs using forest resilience from aspects of resistance and recovery, by applying a change detection algorithm (breaks for additive seasonal and trend; BFAST) spatially on net ecosystem production (NEP) (proxy for carbon stocks) time series (1981–2019) in red soil hilly region (RSHR) of subtropical China. The spatial parameters (e.g., the number, magnitude, and time of changes) used to construct resilience metrics were generated based on BFAST‐derived breakpoints. These metrics were then utilized to analyze the dynamics of forest resilience in relation to EEPs factors in terms of plantation area, forest type, and stand age. Our results observed 92.77% of breakpoints in NEP after 2000, which corresponds well with the periods that multiple EEPs were conducted. NEP resilience showed great variability during 2001–2019, with a positive increasing trend in resistance (R2 = 0.72) and a continuous decline (R2 = 0.37) in recovery, indicating an unhealthy ecosystem in RSHR. Our findings revealed that forest resistance was strongly associated with plantation area (R = 0.71), and the presence of monoculture and young coniferous forest may be the potential factors for the decline in recovery. This suggested that forest resilience in RSHR is mainly modulated by large‐scale EEPs.

Metabolism Regimes in Regulated Rivers of the Illinois River Basin, USA

Metabolism estimates organic carbon accumulation by primary productivity and removal by respiration. In rivers it is relevant to assessing trophic status and threats to river health such as hypoxia as well as greenhouse gas fluxes. We estimated metabolism in 17 rivers of the Illinois River basin (IRB) for a total of 15,176 days, or an average of 2.5 years per site. Daily estimates of gross primary productivity (GPP), ecosystem respiration (ER), net ecosystem productivity (NEP), and the air-water gas exchange rate constant (K600) are reported, along with ancillary data such as river temperature and saturated dissolved oxygen concentration, barometric pressure, and river depth and discharge. Workflows for metabolism estimation and quality assurance are described including a new method for estimating river depth. IRB rivers are dominantly heterotrophic; however, autotrophy was common in river locations coinciding with reported harmful algal blooms (HABs) events. Metabolism of these regulated Midwestern U.S. rivers can help assess the causes and consequences of excessive algal blooms in rivers and their role in river ecological health.

Drought response of the boreal forest carbon sink is driven by understorey–tree composition

The boreal forest is an important global carbon sink, but its response to drought remains uncertain. Here, we compiled biometric- and chamber-based flux data from 50 boreal forest stands to assess the impact of the 2018 European summer drought on net ecosystem production (NEP) across a 68 km2 managed landscape in northern Sweden. Our results reveal a non-uniform reduction in NEP (on average by 80 ± 16 g C m−2 yr−1 or 57 ± 13%) across the landscape, which was greatest in young stands of 20–50 years (95 ± 39 g C m−2 yr−1), but gradually decreased towards older stands (54 ± 57 g C m−2 yr−1). This pattern was attributed to the higher sensitivity of forest-floor understorey to drought and its decreasing contribution to production relative to trees during stand development. This suggests that an age-dependent shift in understorey–tree composition with increasing stand age drives the drought response of the boreal forest NEP. Thus, our study advocates the need for partitioning ecosystem responses to improve empirical and modelling assessments of carbon cycle–climate feedbacks in boreal forests. It further implies that the forest age structure may strongly determine the carbon sink response to the projected increase in drought events across the managed boreal landscape.

Widespread temporal and spatial variability in net ecosystem productivity under climate change

Widespread temporal and spatial variability in net ecosystem productivity under climate change