Effects of Soil Nitrogen Addition on Crown CO2 Exchange of Fraxinus mandshurica Rupr. Saplings

The impact of atmospheric nitrogen deposition on carbon exchange between forest and atmosphere is one of the research hotspots of global change ecology, past researchers have extensively studied the impacts on leaf level, while the impacts on crown CO2 exchange are still unclear. Therefore, we explored the impacts of different nitrogen addition levels on crown CO2 exchange of Fraxinus mandshurica saplings and their responses to the changes of major meteorological factors (photosynthetically active radiation, PAR; vapor pressure deficiency, VPD; and air temperature, Tair) with a novel automated chamber system. There are four levels of nitrogen addition treatments: control (no nitrogen addition, CK), 23 (low nitrogen addition, LN), 46 (medium nitrogen addition, MN), and 69 kgN·hm−2·a−1 (high nitrogen addition, HN). Our results showed that all nitrogen addition treatments increased daily average and accumulated gross primary production (GPP), crown respiration (R), and net crown CO2 exchange (Ne), especially at medium and high nitrogen levels. Similarly, maximum net photosynthetic rate (Nemax) and apparent quantum efficiency (α) were promoted. The change of Ne with PAR, Tair, and VPD showed that nitrogen addition postponed the appearance of photosynthesis midday depression. In addition, the monthly accumulation of R with all nitrogen addition treatments showed an increasing trend (June to July), and then decreased (July to September) during the growing season, while the Ne and GPP decreased gradually with seasonal vegetation senescence. Finally, the crown shifted from carbon sink to carbon source at the end of the growing season, however, the change under high nitrogen treatment occurred 3 days later. The crown CO2 exchange measurements provide a new perspective to better understand the response of forest ecosystem CO2 exchange to elevated nitrogen deposition and provide a basis for related carbon model parameter correction under the influence of nitrogen deposition.

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Sensitivity of global gross primary production to elevated CO2

10.5194/egusphere-egu21-1744 ◽

2021 ◽

Author(s):

Wenjia Cai ◽

Iain Colin Prentice

Keyword(s):

Field Experiments ◽

Carbon Sink ◽

Gross Primary Production ◽

Light Response ◽

Terrestrial Ecosystems ◽

Percentage Increase ◽

Terrestrial Plants ◽

Fertilization Effect ◽

Vegetation Models ◽

The Impact

Terrestrial ecosystems have accounted for more than half of the global carbon sink during the past decades and offset 25%-30% of current anthropogenic CO2 emissions. The projected increase in CO2 concentration will depend on the magnitude of terrestrial plants&#8217; feedback to CO2: i.e. the sensitivity of plant carbon uptake in response to elevated CO2, and the strength of the CO2 fertilization effect (CFE) in a changing (and warming) environment. Projecting vegetation responses to future increases in CO2 concentration under climate change is a major uncertainty, as ecosystem models, field experiments and satellite-based models show large disagreements. In this study, using a recently developed, parameter-sparse model (the &#8216;P model&#8217;), we assess the sensitivity of GPP to increasing CO2 under idealized conditions, in comparison with other vegetation models and field experiments. We investigate the impact of two central parameters, the ratio of Jmax to Vcmax (at a common temperature) and the curvature of the light response curve, on the sensitivity of GPP to CO2. We also quantified the spatial-temporal trend of CFE using the &#946; factor, defined as the percentage increase in GPP in response to a 100-ppm increase in atmospheric CO2 concentration over a defined period. We show how modelled &#946; has changed over the satellite era, and infer the possible effect of climatic variables on changes of CFE from spatial patterns of the modelled trend in &#946;.

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Spatio-Temporal Variation of Drought within the Vegetation Growing Season in North Hemisphere (1982–2015)

Water ◽

10.3390/w12082146 ◽

2020 ◽

Vol 12 (8) ◽

pp. 2146 ◽

Cited By ~ 1

Author(s):

Zhaoqi Zeng ◽

Yamei Li ◽

Wenxiang Wu ◽

Yang Zhou ◽

Xiaoyue Wang ◽

...

Keyword(s):

Northern Hemisphere ◽

Gross Primary Production ◽

Coniferous Forest ◽

Critical Time ◽

Growing Season ◽

Well Being ◽

Estimation Methods ◽

Drought Risk ◽

Drought Characteristics ◽

The Impact

Drought disasters jeopardize the production of vegetation and are expected to exert impacts on human well-being in the context of global climate change. However, spatiotemporal variations in drought characteristics (including the drought duration, intensity, and frequency), specifically for vegetation areas within a growing season, remain largely unknown. Here, we first constructed a normalized difference vegetation index to estimate the length of the growing season for each pixel (8 km) by four widely used phenology estimation methods; second, we analyzed the temporal and spatial patterns of climate factors and drought characteristics (in terms of the Standardized Precipitation Evapotranspiration Index (SPEI)), within a growing season over vegetation areas of the northern hemisphere before and after the critical time point of 1998, which was marked by the onset of a global warming hiatus. Finally, we extracted the highly drought-vulnerable areas of vegetation by examining the sensitivity of the gross primary production to the SPEI to explore the underlying effects of drought variation on vegetation. The results revealed, first, that significant (p < 0.05) increases in precipitation, temperature, and the SPEI (a wetting trend) occurred from 1982 to 2015. The growing season temperature increased even more statistically significant after 1998 than before. Second, the duration and frequency of droughts changed abruptly and decreased considerably from 1998 to 2015; and this wetting trend was located mainly in high-latitude areas. Third, at the biome level, the wetting areas occurred mainly in the tundra, boreal forest or taiga, and temperate coniferous forest biomes, whereas the highly drought-vulnerable areas were mainly located in the desert and xeric shrubland (43.5%) biomes. Our results highlight the fact that although the drought events within a growing season decreased significantly in the northern hemisphere from 1998 to 2015, the very existence of a mismatch between a reduction in drought areas and an increase in highly drought-vulnerable areas makes the impact of drought on vegetation nonnegligible. This work provides valuable information for designing coping measures to reduce the vegetative drought risk in the Northern Hemisphere.

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Relationships between GPP, Satellite Measures of Greenness and Canopy Water Content with Soil Moisture in Mediterranean-Climate Grassland and Oak Savanna

Applied and Environmental Soil Science ◽

10.1155/2011/839028 ◽

2011 ◽

Vol 2011 ◽

pp. 1-14 ◽

Cited By ~ 9

Author(s):

Shishi Liu ◽

Oliver A. Chadwick ◽

Dar A. Roberts ◽

Chris J. Still

Keyword(s):

Soil Moisture ◽

Water Content ◽

Gross Primary Production ◽

Resistance Index ◽

Growing Season ◽

Middle Part ◽

Oak Savanna ◽

Similar Response ◽

The Impact ◽

Canopy Water

We investigated the impact of soil moisture on gross primary production (GPP), chlorophyll content, and canopy water content represented by remotely sensed vegetation indices (VIs) in an open grassland and an oak savanna in California. We found for the annual grassland that GPP late in the growing season was controlled by the declining soil moisture, but there was a 10–20-day lag in the response of GPP to soil moisture. However, during the early and middle part of the growing season, solar radiation accounted for most of the variation in GPP. In the oak savanna, the grass understory exhibited a similar response, but oak trees were not sensitive to soil moisture in the upper 50 cm of the soil profile. Furthermore, while we found most VIs to be more or less related to soil moisture, the Visible Atmospherically Resistance Index (VARI) was the most sensitive to the change of soil moisture.

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Modelling Nitrogen Deposition on a Local Scale—A Review of the Current State of the Art

Environmental Chemistry ◽

10.1071/en06038 ◽

2006 ◽

Vol 3 (5) ◽

pp. 317 ◽

Cited By ~ 60

Author(s):

Ole Hertel ◽

Carsten Ambelas Skjøth ◽

Per Løfstrøm ◽

Camilla Geels ◽

Lise Marie Frohn ◽

...

Keyword(s):

Nitrogen Deposition ◽

Environmental Assessment ◽

State Of The Art ◽

N Deposition ◽

Model Systems ◽

Special Focus ◽

Ammonia Emissions ◽

High Nitrogen ◽

Current State ◽

The Impact

Abstract. Local ammonia emissions from agricultural activities are often associated with high nitrogen deposition in the close vicinity of the sources. High nitrogen (N) inputs may significantly affect the local ecosystems. Over a longer term, high loads may change the composition of the ecosystems, leading to a general decrease in local biodiversity. In Europe there is currently a significant focus on the impact of atmospheric N load on local ecosystems among environmental managers and policy makers. Model tools designed for application in N deposition assessment and aimed for use in the regulation of anthropogenic nitrogen emissions are, therefore, under development in many European countries. The aim of this paper is to present a review of the current understanding and modelling parameterizations of atmospheric N deposition. A special focus is on the development of operational tools for use in environmental assessment and regulation related to agricultural ammonia emissions. For the often large number of environmental impact assessments needed to be carried out by local environmental managers there is, furthermore, a need for simple and fast model systems. These systems must capture the most important aspects of dispersion and deposition of N in the nearby environment of farms with animal production. The paper includes a discussion on the demands on the models applied in environmental assessment and regulation and how these demands are fulfilled in current state-of-the-art models.

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Influence of the Asian Monsoon on net ecosystem carbon exchange in two major plant functional types in Korea

Biogeosciences Discussions ◽

10.5194/bgd-6-10279-2009 ◽

2009 ◽

Vol 6 (6) ◽

pp. 10279-10309 ◽

Cited By ~ 4

Author(s):

H. Kwon ◽

J. Kim ◽

J. Hong

Keyword(s):

Summer Monsoon ◽

Carbon Sink ◽

Ecosystem Respiration ◽

Gross Primary Production ◽

Co2 Exchange ◽

Plant Functional Types ◽

Net Ecosystem Co2 Exchange ◽

Area Index ◽

Functional Types ◽

Net Ecosystem Carbon Exchange

Abstract. Considering the feedback loops in radiation, temperature, and soil moisture with alterations in rainfall patterns, the influence of the changing monsoon on net ecosystem CO2 exchange can be critical to the estimation of carbon balance in Asia. In this paper, we examined the eddy covariance CO2 fluxes observed from 2004 to 2008 in two major plant functional types in KoFlux, i.e., the Gwangneung deciduous forest (GDK) site and the Haenam farmland (HFK) site. The objectives of the study were to (1) quantify the net ecosystem CO2 exchange (NEE), ecosystem respiration (RE), and gross primary production (GPP), (2) examine their interannual patterns, and (3) assess the mechanism for the coupling of carbon and water exchange associated with the summer monsoon. The GDK site, which had a maximum leaf area index (LAI) of ~5, was on average a relatively weak carbon sink with NEE of −84 gC m−2 y−1, RE of 1028 gC m−2 y−1, and GPP of 1113 gC m−2 y−1. Despite about 20% larger GPP (of 1321 gC m−2 y−1) in comparison with the GDK site, the HFK site (with the maximum LAI of 3 to 4) was a weaker carbon sink with NEE of −58 gC m−2 y−1 because of greater RE of 1263 gC m−2 y−1. In both sites, the annual patterns of NEE and GPP had a striking "mid-season depression" each year with two distinctive peaks of different timing and magnitude, whereas RE did not. The mid-season depression at the GDK site occurred typically from early June to late August, coinciding with the season of summer monsoon when the solar radiation decreased substantially due to frequent rainfalls and cloudiness. At the HFK site, the mid-season depression began earlier in May and continued until the end of July due to land use management (e.g., crop rotation) in addition to such disturbances as summer monsoon and typhoons. Other flux observation sites in East Asia also show a decline in radiation but with a lesser degree during the monsoon season, resulting in less pronounced depression in NEE. In our study, however, the observed depression in NEE changed the forest and farmland from a carbon sink to a source in the middle of the growing season. Consequently, the annually integrated values of NEE lies on the low end of the range reported in the literature. Such a delicate coupling between carbon and water cycles may turn these ecosystems into a stronger carbon sink with the projected trends of less frequent but more intensive rainfalls in this region.

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Carbon balance of a Finnish bog: temporal variability and limiting factors

10.5194/bg-2020-488 ◽

2021 ◽

Author(s):

Pavel Alekseychik ◽

Aino Korrensalo ◽

Ivan Mammarella ◽

Samuli Launiainen ◽

Eeva-Stiina Tuittila ◽

...

Keyword(s):

Eddy Covariance ◽

Wind Direction ◽

Gross Primary Production ◽

Net Ecosystem Exchange ◽

Source Area ◽

Growing Season ◽

Co2 Exchange ◽

Southern Taiga ◽

Limiting Factors ◽

Ch4 Emission

Abstract. Pristine boreal mires are known as substantial sinks of carbon dioxide (CO2) and net emitters of methane (CH4). Natural bogs constitute a major fraction of boreal mires. However, the bog CO2 and CH4 balances are poorly known, having been largely estimated based on discrete and short term measurements by manual chambers, and seldom using the eddy-covariance (EC) technique. Eddy-covariance (EC) measurements of CO2 and CH4 exchange were conducted in the Siikaneva mire complex in southern Finland in 2011–2016. The site is a patterned bog having a moss/sedge/shrub vegetation typical of Eurasian southern Taiga, with several ponds near the EC tower. The study presents a complete series of CO2 and CH4 EC flux measurements and identifies the environmental factors controlling the ecosystem-atmosphere CO2 and CH4 exchange. A 6-year average growing season (May–September) cumulative CO2 exchange of −60 g C m−2 was observed, which partitions into mean total respiration (Re) of 167 (146–197 annually) g C m−2 and mean gross primary production (GPP) of 228 (193–257 annually) g C m−2, while the corresponding CH4 emission amounts to 7.1 (6.4...8.4) g C m−2. The contribution of October–December CO2 and CH4 fluxes to the cumulative sums was not negligible based on the measurements during one winter. GPP, Re and CH4 fluxes increased with temperature, and did not show a strong decline even after a substantial water table drawdown in 2011. Instead, GPP, Re and FCH4 became suppressed in cool, cloudy and wet conditions of 2012. May–September cumulative net ecosystem exchange (NEE) of 2013–2016 remained at about −73 g C m−2, in contrast to the hot and dry year 2011 and the wet and cool year 2012, when suboptimal weather likely degraded the net sink by 20 and 40 g C m−2, correspondingly. The cumulative growing season sums of GPP and CH4 emission showed a strong positive relationship. The EC source area was found to be comprised of 8 distinct surface types. However, footprint analyses revealed that contributions of different surface types varied only within 10–20 % with respect to wind direction and stability conditions. Consequently, no clear link between CO2 and CH4 fluxes and footprint composition was found, despite the apparent variation of fluxes with wind direction.

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Moisture and heat advection as drivers of global ecosystem productivity

10.5194/egusphere-egu2020-11870 ◽

2020 ◽

Author(s):

Dominik L. Schumacher ◽

Jessica Keune ◽

Diego G. Miralles

Keyword(s):

Primary Production ◽

Interannual Variability ◽

Carbon Sink ◽

Gross Primary Production ◽

Terrestrial Ecosystems ◽

Ecosystem Productivity ◽

Climate Conditions ◽

Source Regions ◽

Heat And Moisture ◽

The Impact

Terrestrial ecosystems play a key role in climate by dampening the increasing atmospheric CO2 concentrations primarily caused by anthropogenic fossil fuel emissions. The capability of the land biosphere to act as a carbon sink largely depends on climate conditions, which determine the energy and water availability required by plants to grow. Even though only a small part of the global land area is covered by vegetation, the impact of extreme dry and wet seasons has been shown to largely drive the global interannual variability of gross primary production. The climate in a certain area can be seen as the balance of different heat and moisture fluxes: local surface&#8211;atmosphere fluxes from below, entrainment of heat and moisture from aloft, and &#8216;horizontal&#8217; advection of heat and moisture from upwind regions. The latter provides a mechanism for remote regions to impact gross primary production downwind, and has received less scientific attention. Here, advection is inferred from a bird&#8217;s eye perspective, focussing on the five ecoregions with the largest interannual variability in peak productivity around the globe. Employing the atmospheric Lagrangian trajectory model FLEXPART, driven by ERA-Interim reanalysis data, we track the air residing over ecoregions back in time to deduce the origins of heat and moisture that affect ecosystem gross primary production. Utilizing the evaporative source regions supplying water for precipitation to these ecosystems, as well as the analogous source regions of advected heat, we estimate the contribution of advection to gross primary production. Our findings show that source regions of heat and moisture are not congruent: upwind land surfaces typically supply most of the advected heat, whereas upwind oceans tend to provide more moisture. Moreover, low gross primary production in heat-stressed and water-limited ecosystems is often accompanied by enhanced heat and reduced moisture advection from land regions, exacerbated by upwind land&#8211;atmosphere feedbacks. These results demonstrate that anomalies in atmospheric advection can cause ecosystem productivity extremes. Particularly in light of ongoing climate change, we emphasize the potentially detrimental effects of upwind areas that may cause long-lasting impacts on the terrestrial carbon budget, thereby further affecting the climate.

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The morphological and chemical properties of fine roots respond to nitrogen addition in a temperate Schrenk’s spruce (Picea schrenkiana) forest

Scientific Reports ◽

10.1038/s41598-021-83151-x ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Haiqiang Zhu ◽

Jingjing Zhao ◽

Lu Gong

Keyword(s):

Nitrogen Deposition ◽

Root Length ◽

Fine Roots ◽

Fine Root ◽

Specific Root Length ◽

Nitrogen Addition ◽

Nonstructural Carbohydrates ◽

High Nitrogen ◽

Picea Schrenkiana ◽

Nitrogen Treatment

AbstractFine roots (< 2 mm in diameter) play an important role in belowground ecosystem processes, and their physiological ecology is easily altered by nitrogen deposition. To better understand the response of physiological and ecological processes of fine roots to nitrogen deposition, a manipulation experiment was conducted to investigate the effects of exogenous nitrogen addition (control (0 kg ha−1 a−1), low (5 kg ha−1 a−1), moderate (10 kg ha−1 a−1), and high nitrogen (20 kg ha−1 a−1)) on the biomass, morphological characteristics, chemical elements and nonstructural carbohydrates of fine roots in a Picea schrenkiana forest. We found that most fine roots were located in the 0–20 cm of soil layer across all nitrogen treatment groups (42.81–52.09% of the total biomass). Compared with the control, the biomass, specific root length and specific root area of the fine roots increased in the medium nitrogen treatment, whereas the fine roots biomass was lower in the high nitrogen treatment than in the other treatments. In fine roots, nitrogen addition promotes the absorption of nitrogen and phosphorus and their stoichiometric ratio, while reducing the content of nonstructural carbohydrates. The content of nonstructural carbohydrates in the small-diameter roots (< 1 mm in diamter) in each nitrogen treatment group was lower than that in the large-diameter roots. Correlation analysis showed that soil carbon and nitrogen were positively correlated with fine root biomass and specific root length and negatively correlated with the nonstructural carbohydrates. Our findings demonstrate that medium nitrogen addition is conducive to the development of fine root morphology, while excessive nitrogen can suppress the growth of root systems.

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Carbon balance of a Finnish bog: temporal variability and limiting factors based on 6 years of eddy-covariance data

Biogeosciences ◽

10.5194/bg-18-4681-2021 ◽

2021 ◽

Vol 18 (16) ◽

pp. 4681-4704

Author(s):

Pavel Alekseychik ◽

Aino Korrensalo ◽

Ivan Mammarella ◽

Samuli Launiainen ◽

Eeva-Stiina Tuittila ◽

...

Keyword(s):

Eddy Covariance ◽

Wind Direction ◽

Gross Primary Production ◽

Net Ecosystem Exchange ◽

Source Area ◽

Growing Season ◽

Co2 Exchange ◽

Limiting Factors ◽

Strong Positive Relationship ◽

Carbon Dioxide Co2

Abstract. Pristine boreal mires are known as substantial sinks of carbon dioxide (CO2) and net emitters of methane (CH4). Bogs constitute a major fraction of pristine boreal mires. However, the bog CO2 and CH4 balances are poorly known, having been largely estimated based on discrete and short-term measurements by manual chambers and seldom using the eddy-covariance (EC) technique. Eddy-covariance (EC) measurements of CO2 and CH4 exchange were conducted in the Siikaneva mire complex in southern Finland in 2011–2016. The site is a patterned bog having a moss–sedge–shrub vegetation typical of southern Eurasian taiga, with several ponds near the EC tower. The study presents a complete series of CO2 and CH4 EC flux (FCH4) measurements and identifies the environmental factors controlling the ecosystem–atmosphere CO2 and CH4 exchange. A 6-year average growing season (May–September) cumulative CO2 exchange of −61 ± 24 g C m−2 was observed, which partitions into mean total respiration (Re) of 167 ± 33 (interannual range 146–197) g C m−2 and mean gross primary production (GPP) of 228 ± 46 (interannual range 193–257) g C m−2, while the corresponding FCH4 amounts to 7.1 ± 0.7 (interannual range 6.4–8.4) g C m−2. The contribution of October–December CO2 and CH4 fluxes to the cumulative sums was not negligible based on the measurements during one winter. GPP, Re and FCH4 increased with temperature. GPP and FCH4 did not show any significant decline even after a substantial water table drawdown in 2011. Instead, GPP, Re and FCH4 were limited in the cool, cloudy and wet growing season of 2012. May–September cumulative net ecosystem exchange (NEE) of 2013–2016 averaged at about −73 g C m−2, in contrast with the hot and dry year 2011 and the wet and cool year 2012. Suboptimal weather likely reduced the net sink by about 25 g C m−2 in 2011 due to elevated Re, and by about 40 g C m−2 in 2012 due to limited GPP. The cumulative growing season sums of GPP and CH4 emission showed a strong positive relationship. The EC source area was found to be comprised of eight distinct surface types. However, footprint analyses revealed that contributions of different surface types varied only within 10 %–20 % with respect to wind direction and stability conditions. Consequently, no clear link between CO2 and CH4 fluxes and the EC footprint composition was found despite the apparent variation in fluxes with wind direction.

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Responses of Forest Carbon Cycle to Drought and Elevated CO2

Atmosphere ◽

10.3390/atmos12020212 ◽

2021 ◽

Vol 12 (2) ◽

pp. 212

Author(s):

Jun-Lan Xiao ◽

Feng Zeng ◽

Qiu-Lan He ◽

Yu-Xia Yao ◽

Xiao Han ◽

...

Keyword(s):

Water Stress ◽

Elevated Co2 ◽

Carbon Sink ◽

Ecosystem Respiration ◽

Co2 Exchange ◽

Positive Influence ◽

Research Field ◽

Co2 Fertilization ◽

Global Trends ◽

Elevated Atmospheric Co2

Forests play a pivotal role in mitigating global warming as an important carbon sink. Recent global greening trends reflect a positive influence of elevated atmospheric CO2 on terrestrial carbon uptake. However, increasingly frequent and intense drought events endanger the carbon sequestration function of forests. This review integrates previous studies across scales to identify potential global trends in forest responses to drought and elevated CO2 as well as to identify data needs in this important research field. The inconsistent responses of ecosystem respiration to drought contributes to the change of forest net CO2 exchange, which depends on the balance of opposite effects of warming and water stress on respiration. Whether CO2 fertilization can offset the effects of drought remains controversial, however, we found a potential overestimation of global CO2 fertilization effects because of increasing water stress and other limitations such as light and nutrients (N, P) as well as the possibility of photosynthetic acclimation.

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