scholarly journals Impacts of increasing water and nitrogen availability on ecosystem CO<sub>2</sub> fluxes in a temperate steppe of Northern China

2010 ◽  
Vol 7 (4) ◽  
pp. 5829-5858
Author(s):  
L. Yan ◽  
S. Chen ◽  
J. Huang ◽  
G. Lin
Keyword(s):  
Primary Productivity ◽  
Nitrogen Availability ◽  
Ecosystem Respiration ◽  
Precipitation Amount ◽  
Growing Season ◽  
Northern China ◽  
N Availability ◽  
Co2 Fluxes ◽  
N Addition ◽  
Temperate Steppe

Abstract. Changes in precipitation patterns and nitrogen (N) cycling across the globe are likely to affect ecosystem primary productivity and CO2 exchanges, especially in the arid and semi-arid grasslands because of their co-limitation of water and N supply. To evaluate the effects of water and N availability on ecosystem CO2 fluxes, we conducted a manipulative field experiment with water and N addition in a temperate steppe of Northern China. The growing-season CO2 fluxes, including net ecosystem exchange (NEE), gross ecosystem photosynthesis (GEP) and ecosystem respiration (ER) were examined in 2006 and 2007 with remarkably different amount of precipitation. Net carbon uptakes were found in all of treatments over the growing season in both years. However, their magnitude had inter-annual variations which coincided with the seasonal changes of precipitation amount. During these two growing seasons, water and N addition significantly increased NEE, owing to higher stimulation of GEP than ER. Our results suggest that net primary productivity, especially dominant species' biomass, correlated closely with variations in GEP and ER. Soil moisture was the driving environmental factor controlling seasonal and inter-annual variability in GEP and ER subsequently inducing changes in NEE. Moreover, the strengths of both water and N addition effects were greatly depended on the initial water condition in this temperate typical steppe.

Impacts of urea N addition on soil microbial community in a semi-arid temperate steppe in northern China

2008 ◽  
Vol 311 (1-2) ◽  
pp. 19-28 ◽  
Author(s):  
Naili Zhang ◽  
Shiqiang Wan ◽  
Linghao Li ◽  
Jie Bi ◽  
Mingming Zhao ◽  
...  
Keyword(s):  
Microbial Community ◽  
Soil Microbial Community ◽  
Northern China ◽  
N Addition ◽  
Temperate Steppe ◽  
Soil Microbial ◽  
Semi Arid

scholarly journals Environmental influences on carbon dioxide fluxes over three grassland ecosystems in China

2009 ◽  
Vol 6 (12) ◽  
pp. 2879-2893 ◽  
Author(s):  
Y. Fu ◽  
Z. Zheng ◽  
G. Yu ◽  
Z. Hu ◽  
X. Sun ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Soil Moisture ◽  
Alpine Meadow ◽  
Growing Season ◽  
Co2 Fluxes ◽  
Meadow Steppe ◽  
Temperate Steppe ◽  
Area Index ◽  
Grassland Ecosystems ◽  
Alpine Shrub

Abstract. This study compared carbon dioxide (CO2) fluxes over three grassland ecosystems in China, including a temperate semiarid steppe in Inner Mongolia (NMG), an alpine shrub-meadow in Qinghai (HB), and an alpine meadow-steppe in Tibet (DX). Measurements were made in 2004 and 2005 using the eddy covariance technique. Objectives were to document the seasonality of the net ecosystem exchange of CO2 (NEE) and its components, gross ecosystem photosynthesis (GEP), and ecosystem respiration (Reco), and to examine how environmental factors affect the CO2 exchange in these grassland ecosystems. The 2005 growing season (from May to September) was warmer than that of 2004 across the three sites, and precipitation in 2005 was less than that in 2004 at NMG and DX. The magnitude of CO2 fluxes (daily and annual sums) was largest at HB, which also showed the highest temperature sensitivity of Reco among the three sites. A stepwise multiple regression analysis showed that the seasonal variation of GEP, Reco, and NEE of the alpine shrub-meadow was mainly controlled by air temperature, whereas leaf area index can likely explain the seasonal variation in GEP, Reco, and NEE of the temperate steppe. The CO2 fluxes of the alpine meadow-steppe were jointly affected by soil moisture and air temperature. The alpine shrub-meadow acted as a net carbon sink over the two study years, whereas the temperate steppe and alpine meadow-steppe acted as net carbon sources. Both GEP and Reco were reduced by the summer and spring drought in 2005 at NMG and DX, respectively. The accumulated leaf area index during the growing season (LAIsum) played a key role in the interannual and intersite variation of annual GEP and Reco across the study sites and years, whereas soil moisture contributed most significantly to the variation in annual NEE. Because LAIsum was significantly correlated with soil moisture at a depth of 20 cm, we concluded that the available soil moisture other than annual precipitation was the most important factor controlling the variation in the CO2 budgets of different grassland ecosystems in China.

scholarly journals A model for urban biogenic CO<sub>2</sub> fluxes: Solar-Induced Fluorescence for Modeling Urban biogenic Fluxes (SMUrF v1)

2021 ◽  
Vol 14 (6) ◽  
pp. 3633-3661
Author(s):  
Dien Wu ◽  
John C. Lin ◽  
Henrique F. Duarte ◽  
Vineet Yadav ◽  
Nicholas C. Parazoo ◽  
...  
Keyword(s):  
Urban Areas ◽  
Fossil Fuel ◽  
Ecosystem Respiration ◽  
Gross Primary Production ◽  
Growing Season ◽  
Carbon Fluxes ◽  
Co2 Fluxes ◽  
Biogenic Carbon ◽  
Urban Rural ◽  
Biogenic Fluxes

Abstract. When estimating fossil fuel carbon dioxide (FFCO2) emissions from observed CO2 concentrations, the accuracy can be hampered by biogenic carbon exchanges during the growing season, even for urban areas where strong fossil fuel emissions are found. While biogenic carbon fluxes have been studied extensively across natural vegetation types, biogenic carbon fluxes within an urban area have been challenging to quantify due to limited observations and differences between urban and rural regions. Here we developed a simple model representation, i.e., Solar-Induced Fluorescence (SIF) for Modeling Urban biogenic Fluxes (“SMUrF”), that estimates the gross primary production (GPP) and ecosystem respiration (Reco) over cities around the globe. Specifically, we leveraged space-based SIF, machine learning, eddy-covariance (EC) flux data, and ancillary remote-sensing-based products, and we developed algorithms to gap-fill fluxes for urban areas. Grid-level hourly mean net ecosystem exchange (NEE) fluxes are extracted from SMUrF and evaluated against (1) non-gap-filled measurements at 67 EC sites from FLUXNET during 2010–2014 (r>0.7 for most data-rich biomes), (2) independent observations at two urban vegetation and two crop EC sites over Indianapolis from August 2017 to December 2018 (r=0.75), and (3) an urban biospheric model based on fine-grained land cover classification in Los Angeles (r=0.83). Moreover, we compared SMUrF-based NEE with inventory-based FFCO2 emissions over 40 cities and addressed the urban–rural contrast in both the magnitude and timing of CO2 fluxes. To illustrate the application of SMUrF, we used it to interpret a few summertime satellite tracks over four cities and compared the urban–rural gradient in column CO2 (XCO2) anomalies due to NEE against XCO2 enhancements due to FFCO2 emissions. With rapid advances in space-based measurements and increased sampling of SIF and CO2 measurements over urban areas, SMUrF can be useful to inform the biogenic CO2 fluxes over highly vegetated regions during the growing season.

scholarly journals Nitrogen Availability in Pecan Orchard Soil: Implications for Pecan Fertilizer Management

HortScience ◽  
2011 ◽  
Vol 46 (9) ◽  
pp. 1294-1297 ◽  
Author(s):  
M. Lenny Wells
Keyword(s):  
Nitrogen Availability ◽  
Poultry Litter ◽  
Growing Season ◽  
N Fertilizer ◽  
N Availability ◽  
Soil N ◽  
N Dynamics ◽  
Available N ◽  
Crimson Clover ◽  
Soil N Dynamics

Nitrogen (N) fertilizer application to plants at rates not adjusted for the N contribution from soil N availability may result in overapplication of fertilizer. Further understanding of proper timing of N applications based on soil N dynamics and plant demand can be valuable information for the efficient use of fertilizer N. The present study measures soil N dynamics in a pecan orchard under various N fertilizer regimes on a southeastern U.S. Coastal Plain soil. The following treatments were evaluated: 1) crimson clover (Trifolium incarnatum L.); 2) poultry litter; 3) crimson clover + poultry litter; 4) ammonium nitrate (NH4NO3); and 5) untreated control. Crimson clover provided from 20 to 75 kg·ha−1 N over the course of the two growing seasons; however, most of the available N from crimson clover became available late in the growing season. As a result, supplemental N may be required in spring where crimson clover is used as an orchard cover crop. Poultry litter, with and without clover, provided available N consistently throughout the growing season with more N becoming available later in the season than earlier. This suggests that poultry litter applications for pecan should be timed before budbreak. Under optimum environmental conditions, N from NH4NO3 is most available within the first 30 days of application. Thus, it appears that synthetic fertilizer applications using NH4NO3 as the N source should be targeted at or 2 to 3 weeks after pecan budbreak.

scholarly journals Differential Responses of Plant Primary Productivity to Nutrient Addition in Natural and Restored Alpine Grasslands in the Qinghai Lake Basin

2021 ◽  
Vol 12 ◽  
Author(s):  
Chunli Li ◽  
Yonghui Li ◽  
Xinwei Li ◽  
Li Ma ◽  
Yuanming Xiao ◽  
...  
Keyword(s):  
Plant Community ◽  
Primary Productivity ◽  
Plant Biomass ◽  
Growing Season ◽  
N Deposition ◽  
Qinghai Lake ◽  
Lake Basin ◽  
N Addition ◽  
Alpine Grasslands ◽  
Qinghai Lake Basin

Climate, land-use changes, and nitrogen (N) deposition strongly impact plant primary productivity, particularly in alpine grassland ecosystems. In this study, the differential responses of plant community primary productivity to N and phosphorus (P) nutrient application were investigated in the natural (NG) and “Grain for Green” restored (RG) alpine grasslands by a continuous 3-year experiment in the Qinghai Lake Basin. N addition only significantly promoted plant aboveground biomass (AGB) by 42% and had no significant effect on belowground biomass (BGB) and total biomass (TB) in NG. In comparison with NG, N addition elevated AGB and BGB concurrently in RG by 138% and 24%, respectively, which further significantly increased TB by 41% in RG. Meanwhile, N addition significantly decreased BGB and the AGB ratio (R/S) both in NG and RG. Compared with N addition, P addition did not perform an evident effect on plant biomass parameters. Additionally, AGB was merely negatively influenced by growing season temperatures (GST) under the N addition treatment in NG. AGB was negatively associated with GST but positively related to growing season precipitation (GSP) in RG. By contrast, changes in the R/S ratio in RG were positively correlated with GST and negatively related to GSP. In sum, the results revealed that plant community biomass exhibited convergent (AGB and R/S) and divergent (BGB and TB) responses to N addition between NG and RG. In addition, the outcomes suggested that climate warming would enhance plant biomass allocation to belowground under ongoing N deposition, and indicated the significance of precipitation for plant growth and AGB accumulation in this restored alpine grassland ecosystem.

Relationship between soil apparent electrical conductivity and forage yield in temperate pastures according to nitrogen availability and growing season

2019 ◽  
Vol 70 (10) ◽  
pp. 908 ◽  
Author(s):  
P. L. Cicore ◽  
M. Castro Franco ◽  
N. R. Peralta ◽  
J. R. Marques da Silva ◽  
J. L. Costa
Keyword(s):  
Electrical Conductivity ◽  
Tall Fescue ◽  
Nitrogen Availability ◽  
Grid Cell ◽  
Growing Season ◽  
Forage Yield ◽  
N Availability ◽  
Forage Production ◽  
Seasonal Interactions ◽  
Management Zones

Mapping of the apparent soil electrical conductivity (ECa) can be used to estimate the variability of forage yield within a plot. However, forage production can vary according to the growing season and to soil properties that do not affect the ECa (e.g. nitrogen (N) content). The aim of this study was to assess the relationship between ECa and forage yield of tall fescue (Lolium arundinaceum (Schreb.) Darbysh.) during different regrowth periods and contrasting levels of N availability and then use this information to determine potential management zones. The ECa was measured and geo-referenced in a 5.75-ha paddock that sustained a permanent pasture dominated by tall fescue. In addition, a 30 m by 30 m grid cell size was chosen and 43 sampling areas, each 4 m2 in size, were geo-referenced and divided into two experimental units of 1 m by 2 m, one of which was fertilised with 250 kg N ha–1 (N250) at the beginning of four regrowth periods (spring 2015, spring 2016, autumn 2016 and autumn 2017) and the other was not fertilised with N (N0). At the end of each regrowth period, we estimated the accumulated biomass. During the spring growing season, accumulated biomass was positively associated with ECa in both N0 and N250 treatments (R2 = 47% and 54%, respectively). By contrast, in autumn, accumulated biomass and ECa were poorly associated (R2 = 10% and 27% for N0 and N250). This may be due to seasonal interactions that alter soil–yield relationships. To assess whether ECa can be used to determine management zones, the differences in accumulated biomass were compared through analysis of variance. Results showed that ECa is associated with the spatial distribution of tall fescue forage yield variability in spring at different N availabilities. Thus, ECa can be reliably used for defining management zones in marginal soils under permanent pastures.

scholarly journals Contrasting Responses of Soil Respiration Components in Response to Five-Year Nitrogen Addition in a Pinus tabulaeformis Forest in Northern China

Forests ◽  
2018 ◽  
Vol 9 (9) ◽  
pp. 544 ◽  
Author(s):  
Bo Zhao ◽  
Yan Geng ◽  
Jing Cao ◽  
Lu Yang ◽  
Xiuhai Zhao
Keyword(s):  
Soil Respiration ◽  
Microbial Biomass Carbon ◽  
Northern China ◽  
Nitrogen Addition ◽  
N Deposition ◽  
Fine Root Biomass ◽  
Pinus Tabulaeformis ◽  
N Availability ◽  
N Addition ◽  
N Enrichment

Increasing atmospheric nitrogen (N) deposition has profound effects on carbon (C) cycling in forest ecosystems. As an important part of belowground C dynamics, soil respiration is potentially affected by changing N availability. However, the responses of total soil respiration (RST) and its three components, soil respiration derived from plant roots (RSR), root-free soil (RSS) and the litter layer (RSL), to such N enrichment remains poorly understood. To assess the effects of N enrichment on soil respiration components, three levels of N addition, namely low (LN, 50 kg N ha−1 year−1), medium (MN, 100 kg N ha−1 year−1) and high (HN, 150 kg N ha−1 year−1), were conducted over five growing seasons from 2011 to 2015 in a temperate Chinese pine (Pinus tabulaeformis) forest in northern China. A control plot without N addition (CK) was also established. The five-year mean annual rate of RST was 2.18 ± 0.43 μmol m−2 s−1, and the contributions of RSR, RSS and RSL were 8.8 ± 3.1%, 82.2 ± 4.5% and 9.0 ± 5.5%, respectively. Compared with CK, RST was significantly increased by 16.5% in the HN plots, but not in the LN or MN treatments. RSS was significantly decreased by 18.1%, 26.6% and 18.4% in the LN, MN and HN plots, respectively, due to the reduction of both microbial biomass carbon (MBC) and enzyme activity. In contrast, RSR was increased by more than twice under the MN treatment, which promoted root growth and activity (higher fine root biomass and N concentration). A significant elevation in RSL was only detected in the HN plots, where the increased litter input enhanced litter decomposition and hence RSL. Our findings clearly demonstrated that N addition of different intensities had different effects on soil components. In particular, the above- and belowground components of heterotrophic respiration, RSL and RSR, showed contrasting responses to high level addition of N. Thus, we highlight that the response of soil respiration components to N addition should be examined individually. Our results may contribute to a better understanding of soil respiration dynamics under future N scenarios, and have important implications in forest management.

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