scholarly journals Nitrogen input <sup>15</sup>N signatures are reflected in plant <sup>15</sup>N natural abundances in subtropical forests in China

2017 ◽  
Vol 14 (9) ◽  
pp. 2359-2370 ◽  
Author(s):  
Geshere Abdisa Gurmesa ◽  
Xiankai Lu ◽  
Per Gundersen ◽  
Yunting Fang ◽  
Qinggong Mao ◽  
...  
Keyword(s):  
Southern China ◽  
N Deposition ◽  
Pine Forest ◽  
N Cycling ◽  
N Addition ◽  
Inorganic N ◽  
Subtropical Forests ◽  
Broad Leaved Forest ◽  
Soil Δ15n ◽  
Leaved Forest

Abstract. Natural abundance of 15N (δ15N) in plants and soils can provide time-integrated information related to nitrogen (N) cycling within ecosystems, but it has not been well tested in warm and humid subtropical forests. In this study, we used ecosystem δ15N to assess effects of increased N deposition on N cycling in an old-growth broad-leaved 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 we measured N concentration (%N) and δ15N of major ecosystem compartments under ambient deposition and after decadal N addition at 50 kg N ha−1yr−1, which has a δ15N of −0.7 ‰. Our results showed that the total inorganic N in deposition was 15N-depleted (−10 ‰) mainly due to high input of strongly 15N-depleted NH4+-N. Plant leaves in both forests were also 15N-depleted (−4 to −6 ‰). The broad-leaved 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 the broad-leaved forest, indicating that the ecosystem pools are already N-rich. However, %N was marginally increased in pine leaves and significantly increased in understory vegetation in the pine forest. Soil δ15N was not changed significantly by the N addition in either forest. However, the N addition significantly increased the δ15N of plants toward the 15N signature of the added N, indicating incorporation of added N into plants. Thus, plant δ15N was more sensitive to ecosystem N input manipulation than %N in these subtropical forests. We interpret the depleted δ15N of plants as an imprint from the high and 15N-depleted N deposition that may dominate the effects of fractionation that are observed in most warm and humid forests. Fractionation during the steps of N cycling could explain the difference between negative δ15N in plants and positive δ15N in soils, and the increase in soil δ15N with depths. Nevertheless, interpretation of ecosystem δ15N from high-N-deposition regions needs to include data on the deposition 15N signal.

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.

scholarly journals Short-Term Transcriptional Response of Microbial Communities to Nitrogen Fertilization in a Pine Forest Soil

2018 ◽  
Vol 84 (15) ◽  
Author(s):  
Michaeline B. N. Albright ◽  
Renee Johansen ◽  
Deanna Lopez ◽  
La Verne Gallegos-Graves ◽  
Blaire Steven ◽  
...  
Keyword(s):  
Gene Expression ◽  
Transcriptional Response ◽  
N Fertilization ◽  
N Deposition ◽  
Plant Litter ◽  
Pine Forest ◽  
Functional Gene ◽  
N Addition ◽  
Inorganic N ◽  
Microbial Decomposition

ABSTRACTNumerous studies have examined the long-term effect of experimental nitrogen (N) deposition in terrestrial ecosystems; however, N-specific mechanistic markers are difficult to disentangle from responses to other environmental changes. The strongest picture of N-responsive mechanistic markers is likely to arise from measurements over a short (hours to days) time scale immediately after inorganic N deposition. Therefore, we assessed the short-term (3-day) transcriptional response of microbial communities in two soil strata from a pine forest to a high dose of N fertilization (ca. 1 mg/g of soil material) in laboratory microcosms. We hypothesized that N fertilization would repress the expression of fungal and bacterial genes linked to N mining from plant litter. However, despite N suppression of microbial respiration, the most pronounced differences in functional gene expression were between strata rather than in response to the N addition. Overall, ∼4% of metabolic genes changed in expression with N addition, while three times as many (∼12%) were significantly different across the different soil strata in the microcosms. In particular, we found little evidence of N changing expression levels of metabolic genes associated with complex carbohydrate degradation (CAZymes) or inorganic N utilization. This suggests that direct N repression of microbial functional gene expression is not the principle mechanism for reduced soil respiration immediately after N deposition. Instead, changes in expression with N addition occurred primarily in general cell maintenance areas, for example, in ribosome-related transcripts. Transcriptional changes in functional gene abundance in response to N addition observed in longer-term field studies likely result from changes in microbial composition.IMPORTANCEEcosystems are receiving increased nitrogen (N) from anthropogenic sources, including fertilizers and emissions from factories and automobiles. High levels of N change ecosystem functioning. For example, high inorganic N decreases the microbial decomposition of plant litter, potentially reducing nutrient recycling for plant growth. Understanding how N regulates microbial decomposition can improve the prediction of ecosystem functioning over extended time scales. We found little support for the conventional view that high N supply represses the expression of genes involved in decomposition or alters the expression of bacterial genes for inorganic N cycling. Instead, our study of pine forest soil 3 days after N addition showed changes in microbial gene expression related to cell maintenance and stress response. This highlights the challenge of establishing predictive links between microbial gene expression levels and measures of ecosystem function.

scholarly journals Soil–atmosphere exchange flux of total gaseous mercury (TGM) at subtropical and temperate forest catchments

2020 ◽  
Vol 20 (24) ◽  
pp. 16117-16133
Author(s):  
Jun Zhou ◽  
Zhangwei Wang ◽  
Xiaoshan Zhang ◽  
Charles T. Driscoll ◽  
Che-Jen Lin
Keyword(s):  
Climate Change ◽  
Land Use ◽  
Solar Radiation ◽  
Open Field ◽  
Temperate Forest ◽  
Subtropical Forest ◽  
Pine Forest ◽  
Broad Leaved Forest ◽  
Leaved Forest ◽  
Soil Hg

Abstract. Evasion from soil is the largest source of mercury (Hg) to the atmosphere from terrestrial ecosystems. To improve our understanding of controls and in estimates of forest soil–atmosphere fluxes of total gaseous Hg (TGM), measurements were made using dynamic flux chambers (DFCs) over 130 and 96 d for each of five plots at a subtropical forest and a temperate forest, respectively. At the subtropical forest, the highest net soil Hg emissions were observed for an open field (24 ± 33 ng m−2 h−1), followed by two coniferous forest plots (2.8 ± 3.9 and 3.5 ±  4.2 ng m−2 h−1), a broad-leaved forest plot (0.18 ±  4.3 ng m−2 h−1) and the remaining wetland site showing net deposition (−0.80 ± 5.1 ng m−2 h−1). At the temperate forest, the highest fluxes and net soil Hg emissions were observed for a wetland (3.81 ± 0.52 ng m−2 h−1) and an open field (1.82 ± 0.79 ng m−2 h−1), with lesser emission rates in the deciduous broad-leaved forest (0.68 ± 1.01 ng m−2 h−1) and deciduous needle-leaved forest (0.32 ± 0.96 ng m−2 h−1) plots, and net deposition at an evergreen pine forest (−0.04 ± 0.81 ng m−2 h−1). High solar radiation and temperature during summer resulted in the high Hg emissions in the subtropical forest and the open field and evergreen pine forest at the temperate forest. At the temperate deciduous plots, the highest Hg emission occurred in spring during the leaf-off period due to direct solar radiation exposure to soils. Fluxes showed strong positive relationships with solar radiation and soil temperature and negative correlations with ambient air TGM concentration in both the subtropical and temperate forests, with area-weighted compensation points of 6.82 and 3.42 ng m−3, respectively. The values of the compensation points suggest that the atmospheric TGM concentration can play a critical role in limiting TGM emissions from the forest floor. Climate change and land use disturbance may increase the compensation points in both temperate and subtropical forests. Future research should focus on the role of legacy soil Hg in reemissions to the atmosphere as decreases in primary emissions drive decreases in TGM concentrations and disturbances of climate change and land use.

scholarly journals H+ budget in a Subtropical Evergreen Broad-Leaved Forest in Southern China

Tropics ◽  
2002 ◽  
Vol 11 (2) ◽  
pp. 101-108 ◽  
Author(s):  
Yasunori NAKAGAWA ◽  
Changhua LI ◽  
Goro IWATSUBO
Keyword(s):  
Southern China ◽  
Broad Leaved Forest ◽  
Leaved Forest

scholarly journals Species Differences in Nitrogen Acquisition in Humid Subtropical Forest Inferred From 15N Natural Abundance and Its Response to Tracer Addition

Forests ◽  
2019 ◽  
Vol 10 (11) ◽  
pp. 991 ◽  
Author(s):  
Geshere Abdisa Gurmesa ◽  
Xiankai Lu ◽  
Per Gundersen ◽  
Qinggong Mao ◽  
Yunting Fang ◽  
...  
Keyword(s):  
Plant Species ◽  
N Uptake ◽  
N Deposition ◽  
Subtropical Forest ◽  
Species Variation ◽  
N Addition ◽  
Subtropical Forests ◽  
The Impact ◽  
N Acquisition ◽  
Leaf N

Differences in nitrogen (N) acquisition patterns between plant species are often reflected in the natural 15N isotope ratios (δ15N) of the plant tissues, however, such differences are poorly understood for co-occurring plants in tropical and subtropical forests. To evaluate species variation in N acquisition traits, we measured leaf N concentration (%N) and δ15N in tree and understory plant species under ambient N deposition (control) and after a decade of N addition at 50 kg N ha−1 yr−1 (N-plots) in an old-growth subtropical forest in southern China. We also measured changes in leaf δ15N after one-year of 15N addition in both the control and N-plots. The results show consistent significant species variation in leaf %N in both control and N-plots, but decadal N addition did not significantly affect leaf %N. Leaf δ15N values were also significantly different among the plant species both in tree and understory layers, and both in control and N-plots, suggesting differences in N acquisition strategies such as variation in N sources and dominant forms of N uptake and dependence on mycorrhizal associations among the co-occurring plant species. Significant differences between the plant species (in both control and N-plots) in changes in leaf δ15N after 15N addition were observed only in the understory plants, indicating difference in access (or use) of deposited N among the plants. Decadal N addition had species-dependent effects on leaf δ15N, suggesting the N acquisition patterns of these plant species are differently affected by N deposition. These results suggest that co-occurring plants in N-rich and subtropical forests vary in their N acquisition traits; these differences need to be accounted for when evaluating the impact of N deposition on N cycling in these ecosystems.

scholarly journals Responses of Soil C-, N-, and P-Hydrolyzing Enzyme Activities to N and P Addition in an Evergreen Broad-Leaved Forest in Southwest China

2021 ◽  
Author(s):  
Xing Liu ◽  
Shixing Zhou ◽  
Liehua Tie ◽  
Shengzhao Wei ◽  
Junxi Hu ◽  
...  
Keyword(s):  
Acid Phosphatase ◽  
Enzyme Activities ◽  
Urease Activity ◽  
P Availability ◽  
N Addition ◽  
Soil C ◽  
Broad Leaved Forest ◽  
N Treatment ◽  
P Addition ◽  
Leaved Forest

Abstract Background and Aims Human activities-mediated input of nitrogen (N) and phosphorus (P) to ecosystem may significantly affect soil hydrolyzing enzyme activities (Hy-EAs). However, the mechanisms underlying the responses of soil Hy-EAs to change in N and P availability remains unclear. Methods Here, a two-year field N and P addition experiment was conducted in a subtropical evergreen broad-leaved forest to elucidate the effects of N addition, P addition, and NP co-additions on soil Hy-EAs and biochemistry properties. Results The invertase, cellulase, and acid phosphatase activities were increased in N treatment but reduced in P treatment. The urease activity was reduced in N treatment but did not alter in P treatment. NP treatment significantly increased the invertase and cellulase activities. Furthermore, the cellulase activity was positively correlated with soil organic carbon concentration. The acid phosphatase activity was negatively correlated with microbial biomass carbon (MBC), total P, and available P concentrations. Whereas the urease activity was not strongly dependent on total N concentrations, but positively correlated with soil pH and MBC. These Hy-EAs were significantly correlated with C-to-P and N-to-P ratios, while no significantly correlation with C-to-N ratio. Conclusions Overall, our results indicated that N and P addition significantly affected the soil C-, N-, and P-hydrolyzing enzyme activities. With ongoing imbalanced N and P input in our studied subtropical evergreen broad-leaved forest, N addition may exacerbate the limitation of soil C and P availability, while the exogenous P addition may improve the soil C and P availability.

scholarly journals Increased phosphorus availability mitigates the inhibition of nitrogen deposition on CH<sub>4</sub> uptake in an old-growth tropical forest, southern China

2011 ◽  
Vol 8 (9) ◽  
pp. 2805-2813 ◽  
Author(s):  
T. Zhang ◽  
W. Zhu ◽  
J. Mo ◽  
L. Liu ◽  
S. Dong
Keyword(s):  
Tropical Forest ◽  
Uptake Rate ◽  
Southern China ◽  
N Deposition ◽  
P Availability ◽  
N Addition ◽  
Old Growth ◽  
P Limitation ◽  
Ch4 Uptake ◽  
P Addition

Abstract. It is well established that tropical forest ecosystems are often limited by phosphorus (P) availability, and elevated atmospheric nitrogen (N) deposition may further enhance such P limitation. However, it is uncertain whether P availability would affect soil fluxes of greenhouse gases, such as methane (CH4) uptake, and how P interacts with N deposition. We examine the effects of N and P additions on soil CH4 uptake in an N saturated old-growth tropical forest in southern China to test the following hypotheses: (1) P addition would increase CH4 uptake; (2) N addition would decrease CH4 uptake; and (3) P addition would mitigate the inhibitive effect of N addition on soil CH4 uptake. Four treatments were conducted at the following levels from February 2007 to October 2009: control, N-addition (150 kg N ha−1 yr−1), P-addition (150 kg P ha−1 yr−1), and NP-addition (150 kg N ha−1 yr−1 plus 150 kg P ha−1 yr−1). Static chamber and gas chromatography techniques were used to quantify soil CH4 uptake every month throughout the study period. Average CH4 uptake rate was 31.2 ± 1.1 μg CH4-C m−2 h−1 in the control plots. The mean CH4 uptake rate in the N-addition plots was 23.6 ± 0.9 μg CH4-C m−2 h−1, significantly lower than that in the controls. P-addition however, significantly increased CH4 uptake by 24% (38.8 ± 1.3 μg CH4-C m−2 h−1), whereas NP-addition (33.6 ± 1.0 μg CH4-C m−2 h−1) was not statistically different from the control. Our results suggest that increased P availability may enhance soil mathanotrophic activity and root growth, resulting in potentially mitigating the inhibitive effect of N deposition on CH4 uptake in tropical forests.

Sprouting traits and population structure of co-occurring Castanopsis species in an evergreen broad-leaved forest in southern China

2004 ◽  
Vol 19 (3) ◽  
pp. 341-348 ◽  
Author(s):  
Satoshi NANAMI ◽  
Hideyuki KAWAGUCHI ◽  
Ryunosuke TATENO ◽  
Changhua LI ◽  
Shigeo KATAGIRI
Keyword(s):  
Population Structure ◽  
Southern China ◽  
Broad Leaved Forest ◽  
Leaved Forest
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