scholarly journals Clipping defoliation eliminates the stimulating effects of nitrogen enrichment on the aboveground productivity of an alpine meadow

2020 ◽  
Vol 66 (No. 1) ◽  
pp. 47-56
Author(s):  
Ning Zong ◽  
Peili Shi
Keyword(s):  
Aboveground Biomass ◽  
Alpine Meadow ◽  
Nitrogen Addition ◽  
N Addition ◽  
Aboveground Productivity ◽  
Soil Inorganic N ◽  
Aboveground Production ◽  
Biomass Removal ◽  
Grass Growth ◽  
Degraded Grassland

To investigate how clipping (CL) regulates the effects of nutrient addition, an experiment, including CL and nitrogen (N) addition, was conducted in an alpine meadow. Nitrogen treatment increased community coverage (48–113% higher than the control) and aboveground biomass (29–117% higher than the control), which was mainly attributed to grass growth. Both N and N + CL treatments showed a tendency to reducing species richness, while significant reduction only occurred in 2016 and 2017 in CL treatment. Clipping showed a tendency to decrease community cover (3–37% lower than the control) and aboveground biomass (2–34% lower than the control), while N + CL treatment had no effect, indicating that clipping can eliminate the simulated effects of N addition. Nitrogen addition significantly increased soil inorganic N (SIN, 528–1230% higher than the control), while SIN in N + CL was 25–48% lower than N treatment. The decrease in stimulated effects in N + CL was attributed to SIN decrease, which resulted from the aboveground biomass removal by clipping. Our results show that clipping can take away aboveground biomass and cause soil nutrients to decrease, which slows down the degraded grassland recovery. This suggests that grazing exclusion may eliminate the effect of nitrogen deposition on aboveground production in alpine grasslands.

scholarly journals Effect of Short-Term Low-Nitrogen Addition on Carbon, Nitrogen and Phosphorus of Vegetation-Soil in Alpine Meadow

2021 ◽  
Vol 18 (20) ◽  
pp. 10998
Author(s):  
Zhen’an Yang ◽  
Wei Zhan ◽  
Lin Jiang ◽  
Huai Chen
Keyword(s):  
Alpine Meadow ◽  
Nitrogen Addition ◽  
Ammonium Nitrogen ◽  
N Deposition ◽  
Total Carbon ◽  
N Addition ◽  
Short Term ◽  
Nitrogen And Phosphorus ◽  
Soil Rhizosphere ◽  
And Function

As one of the nitrogen (N) limitation ecosystems, alpine meadows have significant effects on their structure and function. However, research on the response and linkage of vegetation-soil to short-term low-level N deposition with rhizosphere processes is scant. We conducted a four level N addition (0, 20, 40, and 80 kg N ha−1 y−1) field experiment in an alpine meadow on the Qinghai-Tibetan Plateau (QTP) from July 2014 to August 2016. We analyzed the community characteristics, vegetation (shoots and roots), total carbon (TC), nutrients, soil (rhizosphere and bulk) properties, and the linkage between vegetation and soil under different N addition rates. Our results showed that (i) N addition significantly increased and decreased the concentration of soil nitrate nitrogen (NO3−-N) and ammonium nitrogen, and the soil pH, respectively; (ii) there were significant correlations between soil (rhizosphere and bulk) NO3−-N and total nitrogen (TN), and root TN, and there was no strong correlation between plant and soil TC, TN and total phosphorus, and their stoichiometry under different N addition rates. The results suggest that short-term low-N addition affected the plant community, vegetation, and soil TC, TN, TP, and their stoichiometry insignificantly, and that the correlation between plant and soil TC, TN, and TP, and their stoichiometry were insignificant.

scholarly journals Effect of Nitrogen Addition on Selection of Germination Trait in an Alpine Meadow on the Tibet Plateau

2021 ◽  
Vol 12 ◽  
Author(s):  
Kun Liu ◽  
Yang Liu ◽  
Zhilong Zhang ◽  
Shiting Zhang ◽  
Carol C. Baskin ◽  
...  
Keyword(s):  
Seed Germination ◽  
Alpine Meadow ◽  
Germination Rate ◽  
Nitrogen Addition ◽  
Germination Percentage ◽  
N Addition ◽  
Percentage Germination ◽  
Alpine Meadows ◽  
Environmental Filter ◽  
Germination Traits

Seed germination requirements may determine the kinds of habitat in which plants can survive. We tested the hypothesis that nitrogen (N) addition can change seed germination trait-environmental filter interactions and ultimately redistribute seed germination traits in alpine meadows. We determined the role of N addition on germination trait selection in an alpine meadow after N addition by combining a 3-year N addition experiment in an alpine meadow and laboratory germination experiments. At the species level, germination percentage, germination rate (speed) and breadth of temperature niche for germination (BTN) were positively related to survival of a species in the fertilized community. In addition, community-weighted means of germination percentage, germination rate, germination response to alternating temperature and BTN increased. However, germination response to wet-cold storage (cold stratification) and functional richness of germination traits was lower in alpine meadows with high-nitrogen addition than in those with no, low and medium N addition. Thus, N addition had a significant influence on environmental filter-germination trait interactions and generated a different set of germination traits in the alpine meadow. Further, the effect of N addition on germination trait selection by environmental filters was amount-dependent. Low and medium levels of N addition had less effect on redistribution of germination traits than the high level.

scholarly journals Nitrogen addition decreases methane uptake caused by methanotroph and methanogen imbalances in a Moso bamboo forest

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Quan Li ◽  
Changhui Peng ◽  
Junbo Zhang ◽  
Yongfu Li ◽  
Xinzhang Song
Keyword(s):  
Community Structure ◽  
Forest Soils ◽  
Nitrogen Addition ◽  
N Deposition ◽  
Moso Bamboo ◽  
Bamboo Forest ◽  
N Addition ◽  
Atmospheric Methane ◽  
Key Factor ◽  
Moso Bamboo Forest

AbstractForest soils play an important role in controlling global warming by reducing atmospheric methane (CH4) concentrations. However, little attention has been paid to how nitrogen (N) deposition may alter microorganism communities that are related to the CH4 cycle or CH4 oxidation in subtropical forest soils. We investigated the effects of N addition (0, 30, 60, or 90 kg N ha−1 yr−1) on soil CH4 flux and methanotroph and methanogen abundance, diversity, and community structure in a Moso bamboo (Phyllostachys edulis) forest in subtropical China. N addition significantly increased methanogen abundance but reduced both methanotroph and methanogen diversity. Methanotroph and methanogen community structures under the N deposition treatments were significantly different from those of the control. In N deposition treatments, the relative abundance of Methanoculleus was significantly lower than that in the control. Soil pH was the key factor regulating the changes in methanotroph and methanogen diversity and community structure. The CH4 emission rate increased with N addition and was negatively correlated with both methanotroph and methanogen diversity but positively correlated with methanogen abundance. Overall, our results suggested that N deposition can suppress CH4 uptake by altering methanotroph and methanogen abundance, diversity, and community structure in subtropical Moso bamboo forest soils.

scholarly journals Nitrogen enrichment enhances the dominance of grasses over forbs in a temperate steppe ecosystem

2011 ◽  
Vol 8 (8) ◽  
pp. 2341-2350 ◽  
Author(s):  
L. Song ◽  
X. Bao ◽  
X. Liu ◽  
Y. Zhang ◽  
P. Christie ◽  
...  
Keyword(s):  
Species Richness ◽  
Aboveground Biomass ◽  
N Deposition ◽  
Soil Mineral N ◽  
N Addition ◽  
Soil Mineral ◽  
Temperate Steppe ◽  
Mineral N ◽  
N Concentration ◽  
Steppe Ecosystem

Abstract. Chinese grasslands are extensive natural ecosystems that comprise 40 % of the total land area of the country and are sensitive to N deposition. A field experiment with six N rates (0, 30, 60, 120, 240, and 480 kg N ha−1 yr−1) was conducted at Duolun, Inner Mongolia, during 2005 and 2010 to identify some effects of N addition on a temperate steppe ecosystem. The dominant plant species in the plots were divided into two categories, grasses and forbs, on the basis of species life forms. Enhanced N deposition, even as little as 30 kg N ha−1 yr−1 above ambient N deposition (16 kg N ha−1 yr−1), led to a decline in species richness. The cover of grasses increased with N addition rate but their species richness showed a weak change across N treatments. Both species richness and cover of forbs declined strongly with increasing N deposition as shown by linear regression analysis (p < 0.05). Increasing N deposition elevated aboveground production of grasses but lowered aboveground biomass of forbs. Plant N concentration, plant δ15N and soil mineral N increased with N addition, showing positive relationships between plant δ15N and N concentration, soil mineral N and/or applied N rate. The cessation of N application in the 480 kg N ha−1 yr−1 treatment in 2009 and 2010 led to a slight recovery of the forb species richness relative to total cover and aboveground biomass, coinciding with reduced plant N concentration and soil mineral N. The results show N deposition-induced changes in soil N transformations and plant N assimilation that are closely related to changes in species composition and biomass accumulation in this temperate steppe ecosystem.

scholarly journals Nitrogen input <sup>15</sup>N-signatures are reflected in plant <sup>15</sup>N natural abundances of sub-tropical forests in China

2016 ◽  
Author(s):  
Geshere Abdisa Gurmesa ◽  
Xiankai Lu ◽  
Per Gundersen ◽  
Yunting Fang ◽  
Qinggong Mao ◽  
...  
Keyword(s):  
Tropical Forests ◽  
Southern China ◽  
Nitrogen Addition ◽  
N Deposition ◽  
Pine Forest ◽  
N Cycling ◽  
N Addition ◽  
Higher Plant ◽  
Old Growth ◽  
Old Growth Forest

Abstract. Natural abundance of 15N (δ15N) in plants and soils can provide integrated information on ecosystem nitrogen (N) cycling, but it has not been well tested in warm and humid sub-tropical forests. In this study, we examined the measurement of δ15N for its ability to assess changes in N cycling due to increased N deposition in an old-growth broadleaved forest and a secondary pine forest in a high N deposition area in southern China. We measured δ15N of inorganic N in input and output fluxes under ambient N deposition, and N concentration (N %) and δ15N of major ecosystem compartments under ambient and after decadal N addition at 50 kg N ha−1 yr−1. Our results showed that the N deposition was δ15N-depleted (−12 ‰) mainly due to high input of depleted NH4&amp;plus;-N. Plant leafs in both forest were also δ15N-depleted (−4 to −6 ‰). The old-growth forest had higher plant and soil N %, and was more 15N-enriched in most ecosystem compartments relative to the pine forest. Nitrogen addition did not significantly affect N % in both forests, indicating that the ecosystem pools are already N-rich. Soil δ15N was not changed significantly by the N addition in both forests. However, the N addition significantly increased the δ15N of plants toward the 15N signature of the added N (~ 0 ‰), indicating incorporation of added N into plants. Thus, plant δ15N was sensitive to ecosystem N input manipulation although N % was unchanged in these N-rich sub-tropical forests. We interpret the depleted δ15N values of plants as an imprint from the high and δ15N-depleted N deposition. The signal from the input (deposition or N addition) may override the enrichment effects of fractionation during the steps of N cycling that are observed in most warm and humid forests. Thus, interpretation of ecosystem δ15N values from high N deposition regions need to include data on the deposition δ15N signal.

Effect of Nitrogen Addition on Mechanical Property of Ti-Cr-Sn Alloy

2010 ◽  
Vol 654-656 ◽  
pp. 2126-2129 ◽  
Author(s):  
Yuichi Nakahira ◽  
Tomonari Inamura ◽  
Hiroyasu Kanetaka ◽  
Shuichi Miyazaki ◽  
Hideki Hosoda
Keyword(s):  
Mechanical Properties ◽  
Room Temperature ◽  
Tensile Tests ◽  
Nitrogen Addition ◽  
N Addition ◽  
X Ray Diffraction ◽  
Solution Hardening ◽  
X Ray ◽  
Bcc Phase ◽  
Cold Workability

Effect of nitrogen (N) addition on mechanical properties of Ti-Cr-Sn alloy was investigated in this study. Ti-7mol%Cr-3mol%Sn was selected and less than 0.5wt% of N were systematically added. The alloys were characterized by optical microscopy, X-ray diffraction analysis and tensile tests at room temperature. The apparent phase was β (bcc) phase, whereas the presence of precipitates was confirmed in 0.5wt%N-added alloy only which did not exhibit sufficient cold workability. The grain size was not largely affected by N addition being less than 0.5wt%. Tensile tests revealed that less than 0.5wt%N addition improves the strength which is due to the solution hardening by interstitial N atoms.

scholarly journals Effect of nitrogen addition on the comparative productivity of corn and velvetleaf (Abutilon theophrasti)

Weed Science ◽  
2006 ◽  
Vol 54 (02) ◽  
pp. 354-363 ◽  
Author(s):  
Darren C. Barker ◽  
Stevan Z. Knezevic ◽  
Alex R. Martin ◽  
Daniel T. Walters ◽  
John L. Lindquist
Keyword(s):  
Leaf Area ◽  
Field Experiments ◽  
Yield Loss ◽  
Biomass Accumulation ◽  
Nitrogen Addition ◽  
Corn Yield ◽  
N Addition ◽  
Area Index ◽  
Nitrogen Levels ◽  
Weed Growth

Weeds that respond more to nitrogen fertilizer than crops may be more competitive under high nitrogen (N) conditions. Therefore, understanding the effects of nitrogen on crop and weed growth and competition is critical. Field experiments were conducted at two locations in 1999 and 2000 to determine the influence of varying levels of N addition on corn and velvetleaf height, leaf area, biomass accumulation, and yield. Nitrogen addition increased corn and velvetleaf height by a maximum of 15 and 68%, respectively. N addition increased corn and velvetleaf maximum leaf area index (LAI) by up to 51 and 90%. Corn and velvetleaf maximum biomass increased by up to 68 and 89% with N addition. Competition from corn had the greatest effect on velvetleaf growth, reducing its biomass by up to 90% compared with monoculture velvetleaf. Corn response to N addition was less than that of velvetleaf, indicating that velvetleaf may be most competitive at high levels of nitrogen and least competitive when nitrogen levels are low. Corn yield declined with increasing velvetleaf interference at all levels of N addition. However, corn yield loss due to velvetleaf interference was similar across N treatments except in one site–year, where yield loss increased with increasing N addition. Corn yield loss due to velvetleaf interference may increase with increasing N supply when velvetleaf emergence and early season growth are similar to that of corn.

scholarly journals Allometric Equation Development, Biomass, and Aboveground Productivity in Ponderosa Pine Forests, Black Hills, Wyoming

2010 ◽  
Vol 25 (3) ◽  
pp. 112-119 ◽  
Author(s):  
Daniel Tinker ◽  
Gail K. Stakes ◽  
Richard M. Arcano
Keyword(s):  
Carbon Storage ◽  
Ponderosa Pine ◽  
Aboveground Biomass ◽  
Carbon Allocation ◽  
Black Hills ◽  
Allometric Equations ◽  
Pine Forests ◽  
Mature Trees ◽  
Ponderosa Pine Forests ◽  
Aboveground Productivity

Abstract Temperate forest ecosystems continue to play an important role in the global carbon cycle, and the ability to accurately quantify carbon storage and allocation remains a critical tool for managers and researchers. This study was aimed at developing new allometric equations for predicting above- and belowground biomass of both mature trees and saplings of ponderosa pine trees in the Black Hills region of the western United States and at evaluating thinning effects on biomass pools and aboveground productivity. Study sites included three stands that had been commercially thinned and one unmanaged stand. Nine allometric equations were developed for mature trees, and six equations were developed for saplings; all models exhibited strong predictive power. The unmanaged stand contained more than twice as much total aboveground biomass as any of the thinned stands. Aboveground biomass allocation among tree compartments was similar among the three older stands but quite different from the young, even-aged stand. Stand-level aboveground net primary production was higher in the unmanaged and intensively managed stands, yet tree-level annual productivity was much lower in the unmanaged stands than in any of the managed forests, suggesting that thinning of some forest stands may increase their ability to sequester and store carbon. Our data also suggest that different management approaches did not have the same effect on carbon allocation as they did on total carbon storage capacity, but rather, stand age was the most important factor in predicting carbon allocation within individual trees and stands. Identification of the relationships between stand structure and forest management practices may help identify various management strategies that maximize rates of carbon storage in ponderosa pine forests.

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