Nitrogen addition amplifies the nonlinear drought response of grassland productivity to extended growing‐season droughts

Abstract Extreme climate events and nitrogen (N) deposition are increasingly affecting the structure and function of terrestrial ecosystems. However, the response of plant biomass to variations to these global change drivers is still unclear in semi-arid regions, especially in degraded sandy grasslands. In this study, a manipulative field experiment run over two years (from 2017 to 2018) was conducted to examine the effect of rainfall alteration and nitrogen addition on biomass allocation of annuals and perennial plants in Horqin sandy grassland, Northern China. Our experiment simulated extreme rainfall and extreme drought (a 60% reduction or increment in the growing season rainfall with respect to a control background) and N addition (20 g/m2) during the growing seasons. We found that the sufficient rainfall during late July and August compensates for biomass losses caused by insufficient water in May and June. When rainfall distribution is relatively uniform during the growing season, extreme rainfall increased aboveground biomass (AGB) and belowground biomass (BGB) of annuals, while extreme drought reduced AGB and BGB of perennials. Rainfall alteration had no significant impacts on the root-shoot ratio (R/S) of sandy grassland plants, while N addition reduced R/S of grassland species when there was sufficient rainfall in the early growing season. The biomass of annuals was more sensitive to rainfall alteration and nitrogen addition than the biomass of perennials. Our findings emphasize the importance of monthly rainfall distribution patterns during the growing season, which not only directly affect the growth and development of grassland plants, but also affect the nitrogen availability of grassland plants.

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Linking canopy reflectance to crop structure and photosynthesis to capture and interpret spatiotemporal dimensions of per-field photosynthetic productivity

Biogeosciences ◽

10.5194/bg-14-1315-2017 ◽

2017 ◽

Vol 14 (5) ◽

pp. 1315-1332 ◽

Cited By ~ 3

Author(s):

Wei Xue ◽

Seungtaek Jeong ◽

Jonghan Ko ◽

John Tenhunen

Keyword(s):

East Asian Monsoon ◽

Canopy Structure ◽

Growing Season ◽

Nitrogen Addition ◽

Canopy Reflectance ◽

Asian Monsoon Region ◽

Regional Patterns ◽

Area Index ◽

Photosynthetic Productivity ◽

Rainfed Conditions

Abstract. Nitrogen and water availability alter canopy structure and physiology, and thus crop growth, yielding large impacts on ecosystem-regulating/production provisions. However, to date, explicitly quantifying such impacts remains challenging partially due to lack of adequate methodology to capture spatial dimensions of ecosystem changes associated with nitrogen and water effects. A data fitting, where close-range remote-sensing measurements of vegetation indices derived from a handheld instrument and an unmanned aerial vehicle (UAV) system are linked to in situ leaf and canopy photosynthetic traits, was applied to capture and interpret inter- and intra-field variations in gross primary productivity (GPP) in lowland rice grown under flooded conditions (paddy rice, PD) subject to three nitrogen application rates and under rainfed conditions (RF) in an East Asian monsoon region of South Korea. Spatial variations (SVs) in both GPP and light use efficiency (LUEcabs) early in the growing season were enlarged by nitrogen addition. The nutritional effects narrowed over time. A shift in planting culture from flooded to rainfed conditions strengthened SVs in GPP and LUEcabs. Intervention of prolonged drought late in the growing season dramatically intensified SVs that were supposed to seasonally decrease. Nevertheless, nitrogen addition effects on SV of LUEcabs at the early growth stage made PD fields exert greater SVs than RF fields. SVs of GPP across PD and RF rice fields were likely related to leaf area index (LAI) development less than to LUEcabs, while numerical analysis suggested that considering strength in LUEcabs and its spatial variation for the same crop type tends to be vital for better evaluation in landscape/regional patterns of ecosystem photosynthetic productivity at critical phenology stages.

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Climate change and its effects on grassland productivity and carrying capacity of livestock in the main grasslands of China

The Rangeland Journal ◽

10.1071/rj11095 ◽

2012 ◽

Vol 34 (4) ◽

pp. 341 ◽

Cited By ~ 10

Author(s):

S. Qian ◽

L. Y. Wang ◽

X. F. Gong

Keyword(s):

Climate Change ◽

Carrying Capacity ◽

Meteorological Data ◽

Growing Season ◽

Average Decrease ◽

South West ◽

Rate Of Increase ◽

Humidity Index ◽

Grassland Productivity ◽

Increase In Productivity

Climate change and its effects on grassland productivity and potential carrying capacity of livestock were systemically studied using AVIM-GRASS and other models, using daily meteorological data for the period from 1961 to 2007 for 70% (275 million ha) of grasslands across China. The results showed an overall trend for increasing temperatures per year and in the length of the grass-growing season from April to September. Sunlight hours decreased in most places. Precipitation and a humidity index had decreased in the northern grasslands of China, where the climate has become warmer and drier, and had increased in the western grasslands, where the climate has become warmer and wetter. Changes to a warmer and drier climate in the more productive northern grasslands resulted in a decrease in annual available herbage production and the carrying capacity of livestock. The greatest reductions in productivity have been in middle and east Inner Mongolia and south-east Gansu. Where there had been a trend for a warmer and wetter climate in western grassland areas, the trend in available herbage production and carrying capacity of livestock has been for a small increase or none at all. The largest rate of increase in productivity was in south-west Xinjiang and east Xizang. Annual available herbage production and carrying capacity of livestock decreased in north and east Xinjiang and south Qinghai where there was very little increase in precipitation. Overall, climate change has resulted in an average decrease in annual available herbage production and carrying capacity of livestock in most of the main grassland areas in China from 1961 to 2007.

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Nitrogen addition turns a temperate peatland from a near-zero source into a strong sink of nitrous oxide

Plant Soil and Environment ◽

10.17221/411/2021-pse ◽

2022 ◽

Vol 68 (No. 1) ◽

pp. 49-58

Author(s):

Boli Yi ◽

Fan Lu ◽

Zhao-Jun Bu

Keyword(s):

Nitrous Oxide ◽

Pearson Correlation ◽

Growing Season ◽

Nitrogen Addition ◽

Changbai Mountains ◽

High Dose ◽

N Addition ◽

Flux Dynamics ◽

Factors Affecting ◽

Hani Peatland

Peatlands, as important global nitrogen (N) pools, are potential sources of nitrous oxide (N2O) emissions. We measured N2O flux dynamics in Hani peatland in a growing season with simulating warming and N addition for 12 years in the Changbai Mountains, Northeastern China, by using static chamber-gas chromatography. We hypothesised that warming and N addition would accelerate N2O emissions from the peatland. In a growing season, the peatland under natural conditions showed near-zero N2O fluxes and warming increased N2O emissions but N addition greatly increased N2O absorption compared with control. There was no interaction between warming and N addition on N2O fluxes. Pearson correlation analysis showed that water table depth was one of the main environmental factors affecting N2O fluxes and a positive relationship between them was observed. Our study suggests that the N2O source function in natural temperate peatlands maybe not be so significant as we expected before; warming can increase N2O emissions, but a high dose of N input may turn temperate peatlands to be strong sinks of N2O, and global change including warming and nitrogen deposition can alter N2O fluxes via its indirect effect on hydrology and vegetation in peatlands.

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Effects of nitrogen fertilization on the understorey carbon balance over the growing season in a boreal Pine forest

Biogeosciences Discussions ◽

10.5194/bgd-10-14093-2013 ◽

2013 ◽

Vol 10 (8) ◽

pp. 14093-14113

Author(s):

D. B. Metcalfe ◽

B. Eisele ◽

N. J. Hasselquist

Keyword(s):

Boreal Forests ◽

Nitrogen Availability ◽

Growing Season ◽

Carbon Fluxes ◽

Nitrogen Addition ◽

Carbon Uptake ◽

Sink Strength ◽

Understorey Vegetation ◽

Ecosystem Carbon ◽

Photosynthetic Carbon

Abstract. Boreal forests play a key role in the global carbon cycle and are facing rapid shifts in nitrogen availability with poorly understood consequences for ecosystem function and global climate. We quantified the effects of nitrogen availability on carbon fluxes from a relatively understudied component of these forests – understorey vegetation – at three intervals over the summer growing period in a northern Swedish Scots Pine stand. Nitrogen addition altered both photosynthetic carbon uptake and respiratory release, but the magnitude and direction of this effect depended on the time during the growing season and the amount of nitrogen added. Specifically, nitrogen addition stimulated net ecosystem carbon uptake only in the late growing season. We find evidence for species-specific control of understorey carbon sink strength, as photosynthesis per unit ground area was positively correlated only with the abundance of the vascular plant Vaccinium myrtillus and no others. Comparison of photosynthetic carbon uptake with data on plant carbon dioxide release from the study site, indicate that understorey vegetation photosynthate was mainly supplying respiratory demands for much of the year. Only in the late season with nitrogen addition did understorey vegetation appear to experience a large surplus of carbon in excess of respiratory requirements. Further work, simultaneously comparing all major biomass and respiratory carbon fluxes in understorey and tree vegetation, is required to resolve the likely impacts of environmental changes on whole-ecosystem carbon sequestration in boreal forests.

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Short Legacy Effects of Growing Season Nitrogen Addition and Reduced Precipitation alter Soil Respiration during Nongrowing Season

Forests ◽

10.3390/f11030358 ◽

2020 ◽

Vol 11 (3) ◽

pp. 358

Author(s):

Guoyong Yan ◽

Yajuan Xing ◽

Qinggui Wang ◽

Changcheng Mu

Keyword(s):

Soil Respiration ◽

Temperate Forest ◽

Growing Season ◽

Nitrogen Addition ◽

Late Winter ◽

N Addition ◽

Legacy Effects ◽

Manipulative Experiment ◽

Soil C ◽

C Cycle

The short legacy effects of growing season nitrogen (N) addition and reduced precipitation on nongrowing season soil respiration (Rs), autotrophic respiration (Ra), and heterotrophic respiration (Rh) are still unclear. Therefore, a field manipulative experiment to determine the responses of nongrowing season Rs and its components to growing season N addition and reduced precipitation was conducted in a temperate forest. The results show that growing season N addition and reduced precipitation significantly increased nongrowing season Rs by regulating the response of Ra and Rh. The combination of N addition and reduced precipitation also showed a much stronger effect on Rs and its components, but the magnitude and direction largely depended on the snowpack thickness. The effects of growing season N addition and reduced precipitation on nongrowing season Rs and its components were mediated by different sampling periods. N addition significantly decreased Rs by decreasing Rh in early winter and significantly increased Rs by increasing Ra in deep winter and late winter. All treatments decreased temperature sensitivity (Q10) of Rs and Rh. Our findings contribute to a better understanding of how nongrowing season Rs and its components will change under growing season N addition and reduced precipitation and could improve predictions of the future states of the soil C cycle in response to climate change.

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

Forests ◽

10.3390/f12091170 ◽

2021 ◽

Vol 12 (9) ◽

pp. 1170

Author(s):

Chunjuan Gong ◽

Anzhi Wang ◽

Fenghui Yuan ◽

Yage Liu ◽

Chen Cui ◽

...

Keyword(s):

Nitrogen Deposition ◽

Carbon Sink ◽

Gross Primary Production ◽

Growing Season ◽

Nitrogen Addition ◽

Co2 Exchange ◽

Fraxinus Mandshurica ◽

High Nitrogen ◽

Four Levels ◽

The Impact

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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Linking canopy reflectance to crop structure and photosynthesis to capture and interpret spatiotemporal dimensions of per-field photosynthetic productivity

10.5194/bg-2016-492 ◽

2016 ◽

Author(s):

Wei Xue ◽

Seungtaek Jeong ◽

Jonghan Ko ◽

John Tenhunen

Keyword(s):

East Asian Monsoon ◽

Canopy Structure ◽

Growing Season ◽

Nitrogen Addition ◽

Time Shift ◽

Drought Event ◽

Canopy Reflectance ◽

Asian Monsoon Region ◽

Regional Patterns ◽

Photosynthetic Productivity

Abstract. Nitrogen and water availability are two of staple environmental elements in agroecosystems that can substantially alter canopy structure and physiology then crop growth, yielding large impacts on ecosystem regulating/production provisions. However, to date, explicitly quantifying such impacts remains challenging partially due to lack of adequate methodology to capture spatial dimensions of ecosystem changes associated with nitrogen and water effects. A data assimilation, where close-range remote sensing measurements of vegetation indices derived from a hand-held instrument and an unmanned aerial vehicle (UAV) system are linked to leaf and canopy photosynthetic traits quantified at plot level by portable chamber systems, was applied to capture and interpret inter- and intra-field variations in gross primary productivity (GPP) in lowland rice grown under flooded condition (paddy rice, PD) subject to three available nutrient availability and under rainfed condition (RF) in East-Asian monsoon region, South Korea. Spatial variations (SVs) in both GPP and light use efficiency (LUEcabs) early in growing season were amplified by nitrogen addition, and such nutritional effects narrowed over time. Shift planting culture from flooded to rainfed conditions strengthened SVs in GPP and LUEcabs. Intervention of prolonged drought event at late growing season dramatically intensified their SVs that are supposed to seasonally decrease. Nevertheless, nitrogen addition effects on SV of LUEcabs at early growth stage made PD field exert greater SVs than RF field. SV of GPP across PD and RF rice were likely related to LAI development less to LUEcabs while, numerical analysis suggested that consider spatial variation and strength in LUEcabs for the same crop type tends to be vital for better evaluation in landscape/regional patterns of ecosystem photosynthetic productivity at critical phenology stages.

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Effects of nitrogen fertilization on the forest floor carbon balance over the growing season in a boreal pine forest

Biogeosciences ◽

10.5194/bg-10-8223-2013 ◽

2013 ◽

Vol 10 (12) ◽

pp. 8223-8231 ◽

Cited By ~ 7

Author(s):

D. B. Metcalfe ◽

B. Eisele ◽

N. J. Hasselquist

Keyword(s):

Boreal Forests ◽

Forest Floor ◽

Nitrogen Availability ◽

Environmental Changes ◽

Vascular Plant ◽

Growing Season ◽

Carbon Fluxes ◽

Nitrogen Addition ◽

Sink Strength ◽

Understorey Vegetation

Abstract. Boreal forests play a key role in the global carbon cycle and are facing rapid shifts in nitrogen availability with poorly understood consequences for ecosystem function and global climate change. We quantified the effects of increasing nitrogen availability on carbon fluxes from a relatively understudied component of these forests – the forest floor – at three intervals over the summer growing period in a northern Swedish Scots pine stand. Nitrogen addition altered both the uptake and release of carbon dioxide from the forest floor, but the magnitude and direction of this effect depended on the time during the growing season and the amount of nitrogen added. Specifically, nitrogen addition stimulated net forest floor carbon uptake only in the late growing season. We find evidence for species-specific control of forest floor carbon sink strength, as photosynthesis per unit ground area was positively correlated only with the abundance of the vascular plant Vaccinium myrtillus and no others. Comparison of understorey vegetation photosynthesis and respiration from the study site indicates that understorey vegetation photosynthate was mainly supplying respiratory demands for much of the year. Only in the late season with nitrogen addition did understorey vegetation appear to experience a large surplus of carbon in excess of respiratory requirements. Further work, simultaneously comparing all major biomass and respiratory carbon fluxes in forest floor and tree vegetation, is required to resolve the likely impacts of environmental changes on whole-ecosystem carbon sequestration in boreal forests.

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