scholarly journals Effect of Long-Term Nitrogen and Phosphorus Additions on Understory Plant Nutrients in a Primary Tropical Forest

Forests ◽  
2021 ◽  
Vol 12 (6) ◽  
pp. 803
Author(s):  
Qinggong Mao ◽  
Hao Chen ◽  
Cong Wang ◽  
Zongqing Pang ◽  
Jiangming Mo ◽  
...  
Keyword(s):  
Tropical Forests ◽  
N Deposition ◽  
Primary Forest ◽  
N Saturation ◽  
P Deficiency ◽  
N:P Ratios ◽  
P Concentration ◽  
N Concentration ◽  
P Addition

Humid tropical forests are commonly characterized as N-rich but P-deficient. Increased N deposition may drive N saturation and aggravate P limitation in tropical forests. Thus, P addition is proposed to mitigate the negative effects of N deposition by stimulating N cycling. However, little is known regarding the effect of altered N and P supply on the nutrient status of understory plants in tropical forests, which is critical for predicting the consequences of disturbed nutrient cycles. We assessed the responses of N concentration, P concentration, and N:P ratios of seven understory species to N and P addition in an 8-year fertilization experiment in a primary forest in south China. The results showed that N addition had no effect on plant N concentration, P concentration, and N:P ratios for most species. In contrast, P addition significantly increased P concentration, and decreased N:P ratios but had no effect on plant N concentration. The magnitude of P concentration responses to P addition largely depended on the types of organs and species. The increased P was more concentrated in the fine roots and branches than in the leaves. The gymnospermous liana Gnetum montanum Markgr. had particularly lower foliar N: P (~9.8) and was much more responsive to P addition than the other species studied. These results indicate that most plants are saturated in N but have great potential to restore P in primary tropical forests. N deposition does not necessarily aggravate plant P deficiency, and P addition does not increase the retention of deposited N by increasing the N concentration. In the long term, P inputs may alter the community composition in tropical forests owing to species-specific responses.

scholarly journals Long-Term Nitrogen Addition Decreases Soil Carbon Mineralization in an N-Rich Primary Tropical Forest

Forests ◽  
2021 ◽  
Vol 12 (6) ◽  
pp. 734
Author(s):  
Xiankai Lu ◽  
Qinggong Mao ◽  
Zhuohang Wang ◽  
Taiki Mori ◽  
Jiangming Mo ◽  
...  
Keyword(s):  
Microbial Biomass ◽  
Organic Carbon ◽  
Tropical Forest ◽  
Soil Carbon ◽  
Tropical Forests ◽  
Carbon Mineralization ◽  
N Deposition ◽  
Soil Carbon Mineralization ◽  
N Additions

Anthropogenic elevated nitrogen (N) deposition has an accelerated terrestrial N cycle, shaping soil carbon dynamics and storage through altering soil organic carbon mineralization processes. However, it remains unclear how long-term high N deposition affects soil carbon mineralization in tropical forests. To address this question, we established a long-term N deposition experiment in an N-rich lowland tropical forest of Southern China with N additions such as NH4NO3 of 0 (Control), 50 (Low-N), 100 (Medium-N) and 150 (High-N) kg N ha−1 yr−1, and laboratory incubation experiment, used to explore the response of soil carbon mineralization to the N additions therein. The results showed that 15 years of N additions significantly decreased soil carbon mineralization rates. During the incubation period from the 14th day to 56th day, the average decreases in soil CO2 emission rates were 18%, 33% and 47% in the low-N, medium-N and high-N treatments, respectively, compared with the Control. These negative effects were primarily aroused by the reduced soil microbial biomass and modified microbial functions (e.g., a decrease in bacteria relative abundance), which could be attributed to N-addition-induced soil acidification and potential phosphorus limitation in this forest. We further found that N additions greatly increased soil-dissolved organic carbon (DOC), and there were significantly negative relationships between microbial biomass and soil DOC, indicating that microbial consumption on soil-soluble carbon pool may decrease. These results suggests that long-term N deposition can increase soil carbon stability and benefit carbon sequestration through decreased carbon mineralization in N-rich tropical forests. This study can help us understand how microbes control soil carbon cycling and carbon sink in the tropics under both elevated N deposition and carbon dioxide in the future.

scholarly journals Effects of nitrogen and phosphorus additions on nitrous oxide emission in a nitrogen-rich and two nitrogen-limited tropical forests

2016 ◽  
Vol 13 (11) ◽  
pp. 3503-3517 ◽  
Author(s):  
Mianhai Zheng ◽  
Tao Zhang ◽  
Lei Liu ◽  
Weixing Zhu ◽  
Wei Zhang ◽  
...  
Keyword(s):  
Nitrous Oxide ◽  
Tropical Forests ◽  
N2o Emission ◽  
N Deposition ◽  
Soil N ◽  
N Addition ◽  
Old Growth ◽  
Old Growth Forest ◽  
P Addition ◽  
Stimulation Of

Abstract. Nitrogen (N) deposition is generally considered to increase soil nitrous oxide (N2O) emission in N-rich forests. In many tropical forests, however, elevated N deposition has caused soil N enrichment and further phosphorus (P) deficiency, and the interaction of N and P to control soil N2O emission remains poorly understood, particularly in forests with different soil N status. In this study, we examined the effects of N and P additions on soil N2O emission in an N-rich old-growth forest and two N-limited younger forests (a mixed and a pine forest) in southern China to test the following hypotheses: (1) soil N2O emission is the highest in old-growth forest due to the N-rich soil; (2) N addition increases N2O emission more in the old-growth forest than in the two younger forests; (3) P addition decreases N2O emission more in the old-growth forest than in the two younger forests; and (4) P addition alleviates the stimulation of N2O emission by N addition. The following four treatments were established in each forest: 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). From February 2007 to October 2009, monthly quantification of soil N2O emission was performed using static chamber and gas chromatography techniques. Mean N2O emission was shown to be significantly higher in the old-growth forest (13.9 ± 0.7 µg N2O-N m−2 h−1) than in the mixed (9.9 ± 0.4 µg N2O-N m−2 h−1) or pine (10.8 ± 0.5 µg N2O-N m−2 h−1) forests, with no significant difference between the latter two. N addition significantly increased N2O emission in the old-growth forest but not in the two younger forests. However, both P and NP addition had no significant effect on N2O emission in all three forests, suggesting that P addition alleviated the stimulation of N2O emission by N addition in the old-growth forest. Although P fertilization may alleviate the stimulated effects of atmospheric N deposition on N2O emission in N-rich forests, this effect may only occur under high N deposition and/or long-term P addition, and we suggest future investigations to definitively assess this management strategy and the importance of P in regulating N cycles from regional to global scales.

scholarly journals Soil Nitrogen and Sulfur Leaching in a Subtropical Forest at a Transition State under Decreasing Atmospheric Deposition

Forests ◽  
2021 ◽  
Vol 12 (12) ◽  
pp. 1798
Author(s):  
Piaopiao Ke ◽  
Gaoyue Si ◽  
Yao Luo ◽  
Zhenglin Cheng ◽  
Qian Yu ◽  
...  
Keyword(s):  
Transition State ◽  
Soil Layer ◽  
N Deposition ◽  
Subtropical Forest ◽  
N Leaching ◽  
N Saturation ◽  
Subtropical Forests ◽  
Net Flux ◽  
Throughfall Deposition

Anthropogenic emissions of nitrogen- (N) and sulfur (S)-containing pollutants have declined across China in recent years. However, the responses of N and S depositions and dynamics in soil remain unclear in subtropical forests. In this study, the wet and throughfall depositions of dissolved inorganic N (DIN) and SO42− were continuously monitored in a mildly polluted subtropical forest in Southeast China in 2017 and 2018. Moreover, these solutes in soil water along the soil profile were monitored in 2018. Throughfall deposition of DIN and S decreased by 59% and 53% in recent 3 years, respectively, which can be majorly attributed to the decreases in wet depositions of NO3− and SO42−. Meanwhile, NH4+ deposition remained relatively stable at this site. Even though N deposition in 2018 was below the N saturation threshold for subtropical forests, significant N leaching still occurred. Excess export of N occurred in the upper soil layer (0–15 cm), reaching 6.86 ± 1.54 kg N/ha/yr, while the deeper soil (15–30 cm) was net sink of N as 8.29 ± 1.71 kg N/ha/yr. Similarly, S was excessively exported from the upper soil with net flux of 14.7 ± 3.15 kg S/ha/yr, while up to 6.37 ± 3.18 kg S/ha/yr of S was retained in the deeper soil. The significant N and S leaching under declined depositions suggested that this site possibly underwent a transition state, recovering from historically high acid deposition. Furthermore, the rainfall intensity remarkably regulated leaching and retention of SO42− and DIN at this site. The impacts of climate changes on N and S dynamics require further long-term monitoring in subtropical forests.

Relationship between P and N concentrations in timothy

1999 ◽  
Vol 79 (1) ◽  
pp. 65-70 ◽  
Author(s):  
G. Bélanger ◽  
J. E. Richards
Keyword(s):  
N Fertilization ◽  
Phleum Pratense ◽  
Growth And Yield ◽  
Shoot Biomass ◽  
P Deficiency ◽  
P Concentration ◽  
N Concentration ◽  
Critical P Concentration ◽  
The Relationship ◽  
Phleum Pratense L

Tools quantifying the status of N and P in plants may help to achieve efficient management of these nutrients and to optimize crop growth and yield. The objective of this study was to establish the relationship between P and N concentrations during the regrowth of timothy (Phleum pratense L.) and, in particular, to estimate the critical P concentration required to diagnose P deficiency. The relationship between P and N concentrations was determined for timothy grown in two experiments conducted with early- and late-maturing cultivars under non-limiting N conditions in spring of 1991 and 1992, and in two experiments with four rates of N fertilization conducted in the spring of 1993 and the summer of 1994. Shoot biomass and P and N concentrations were determined weekly during each regrowth cycle. The P and N concentrations decreased with time in all four experiments. The decrease in P concentration with increasing shoot biomass was generally similar to the decrease in N concentration. The relationship between P concentration and shoot biomass was not different for early- and late-maturing timothy cultivars. This relationship, however, was affected by N fertilization. For a given shoot biomass, increasing N fertilization rates increased P concentration. The relationship between P and N concentrations under non-limiting N conditions is described by a linear relationship (P = 1.46 + 0.069N, R2 = 0.79, P < 0.001, n = 48) in which P concentration (P) and N concentration (N) are expressed in g kg−1 DM. The relationship between P and N concentrations was different under N limiting conditions. For a given N concentration, the P concentration was greater under limiting N conditions than under non-limiting N conditions. Our results show that the critical P concentration for shoot growth is a function of the N concentration in the shoot biomass and the level of N deficiency. The present study provides the relationship required to estimate the critical P concentration which is essential for quantifying levels of P deficiency in timothy, and in developing models to predict the quantity of fertilizer P needed to correct that deficiency. Key words: Phleum pratense L., timothy, nitrogen, phosphorus, grasses

scholarly journals Variations in nitrogen, phosphorus, and δ15N in Sphagnum mosses along a climatic and atmospheric deposition gradient in eastern Canada

Botany ◽  
2017 ◽  
Vol 95 (8) ◽  
pp. 829-839 ◽  
Author(s):  
Tatjana Živković ◽  
Kristina Disney ◽  
Tim R. Moore
Keyword(s):  
N:P Ratio ◽  
N Deposition ◽  
Atmospheric N Deposition ◽  
Eastern Canada ◽  
N Value ◽  
The North ◽  
P Concentration ◽  
N Concentration ◽  
N Acquisition ◽  
Deposition Gradient

We examined concentrations of nitrogen (N) and phosphorus (P) and δ15N value in Sphagnum sections Acutifolia and Cuspidata inhabiting hummocks and hollows from eight bogs along a transect from ∼45 to ∼55°N in Ontario and Quebec. The N concentration in Sphagnum declined from south to north, correlating with a decrease in atmospheric N deposition. Although the overall N concentration was larger in hollows than hummocks, the pattern was inconsistent across the sites. There was a proportionally larger decline in P concentration from south to north and an overall larger P concentration in hollows than hummocks, but there were inconsistent differences across the sites. The N:P ratio ranged from 12:1 to 29:1, driven primarily by the variation in P concentration. Ratios of N and P concentration in Sphagnum capitulum:stem averaged 1.2:1, suggesting nutrient resorption from stem to capitulum during growth; the ratio rose with increasing N and P concentration in the capitulum. The δ15N value of Sphagnum rose from ∼−6‰ in the south to ∼−1‰ in the north, correlated with the decrease in Sphagnum N concentration and with a rise in the water table. We interpret this to indicate a greater dependence on N2-fixation for N acquisition in the northern and wetter sites.

Integrated carbon-nitrogen-phosphorus cycling for sustainable agriculture – a knowledge gap and investigation of the role of phosphatase enzymes

2021 ◽  
Author(s):  
Victoria Janes-Bassett ◽  
Phil Haygarth ◽  
Martin Blackwell ◽  
Malika Mezeli ◽  
Gavin Stewart ◽  
...  
Keyword(s):  
Enzyme Activity ◽  
Crop Yields ◽  
Organic P ◽  
Experimental Conditions ◽  
P Deficiency ◽  
Soil C ◽  
P Addition ◽  
Phosphatase Enzyme

&lt;p&gt;Phosphorus is closely linked to other nutrient cycles, notably carbon and nitrogen, therefore, to understand potential risks to food production models are required that simulate integrated nutrient cycling over long timescales. The soil-plant system model N14CP meets these requirements and simulates both semi-natural and agricultural environments. N14CP has been validated both spatially and temporally across a range of long-term agricultural experimental sites comparing soil C, N and P, and crop yields, and in most instances performs well. However, under experimental conditions where N is applied in the absence of P, the model indicates exhaustion of P reserves and a decline in yields that is not observed at these sites, highlighting a gap in the model process representation. Potential sources of this &amp;#8216;missing P&amp;#8217; such as enhanced atmospheric deposition, weathering and flexible plant stoichiometries were explored yet cannot account for this deficit. We hypothesise that access of organic P through other mechanisms not fully represented within the model, such as phosphatase enzymes, could be part of this explanation.&lt;/p&gt;&lt;p&gt;In order to test this, we conducted a meta-analysis of phosphatase enzyme activity in agricultural settings, comparing response to P sufficient and deficient conditions. Results suggest phosphatase enzyme activity is higher in P deficient conditions compared to inorganic P addition, yet lower compared to organic P addition. Meta-regression analysis indicates magnitude of P addition and pH of substrate are significant factors influencing enzyme response. However, due to numerous additional processes and adaption strategies in response to P deficiency and the difficulty isolating the role of phosphatase enzymes it is not possible to determine the degree to which this mechanism alone accounts for the missing P. We discuss the continuing need for additional empirical evidence to understand the cycling of organic P, and the development of models to include these processes to inform sustainable land management and ensure long-term food security.&lt;/p&gt;

Divergent Responses of Soil Buffering Capacity to Long-Term N Deposition in Three Typical Tropical Forests with Different Land-Use History

2015 ◽  
Vol 49 (7) ◽  
pp. 4072-4080 ◽  
Author(s):  
Xiankai Lu ◽  
Qinggong Mao ◽  
Jiangming Mo ◽  
Frank S. Gilliam ◽  
Guoyi Zhou ◽  
...  
Keyword(s):  
Land Use ◽  
Tropical Forests ◽  
N Deposition ◽  
Buffering Capacity ◽  
Land Use History ◽  
Soil Buffering

scholarly journals Trends in nitrogen deposition and leaching in acid-sensitive streams in Europe

2001 ◽  
Vol 5 (3) ◽  
pp. 299-310 ◽  
Author(s):  
R. F. Wright ◽  
C. Alewell ◽  
J. M. Cullen ◽  
C. D. Evans ◽  
A. Marchetto ◽  
...  
Keyword(s):  
Surface Waters ◽  
Nitrogen Saturation ◽  
Inorganic Nitrogen ◽  
N Deposition ◽  
N Saturation ◽  
The Past ◽  
Run Off ◽  
Nitrate Concentrations ◽  
Long Term Trends

Abstract. Long-term records of nitrogen in deposition and streamwater were analysed at 30 sites covering major acid sensitive regions in Europe. Large regions of Europe have received high inputs of inorganic nitrogen for the past 20 - 30 years, with an approximate 20% decline in central and northern Europe during the late 1990s. Nitrate concentrations in streamwaters are related to the amount of N deposition. All sites with less than 10 kgN ha-1 yr-1 deposition have low concentrations of nitrate in streamwater, whereas all sites receiving > 25 kgN ha-1 yr-1 have elevated concentrations. Very few of the sites exhibit significant trends in nitrate concentrations; similar analyses on other datasets also show few significant trends. Nitrogen saturation is thus a process requiring many decades, at least at levels of N deposition typical for Europe. Declines in nitrate concentrations at a few sites may reflect recent declines in N deposition. The overall lack of significant trends in nitrate concentrations in streams in Europe may be the result of two opposing factors. Continued high deposition of nitrogen (above the 10 kgN ha-1 yr-1 threshold) should tend to increase N saturation and give increased nitrate concentrations in run-off, whereas the decline in N deposition over the past 5 – 10 years in large parts of Europe should give decreased nitrate concentrations in run-off. Short and long-term variations in climate affect nitrate concentrations in streamwater and, thus, contribute "noise" which masks long-term trends. Empirical data for geographic pattern and long-term trends in response of surface waters to changes in N deposition set the premises for predicting future contributions of nitrate to acidification of soils and surface waters. Quantification of processes governing nitrogen retention and loss in semi-natural terrestrial ecosystems is a scientific challenge of increasing importance. Keywords: Europe, acid deposition, nitrogen, saturation, recovery, water

scholarly journals Long-term modelling of nitrogen turnover and critical loads in a forested catchment using the INCA model

2002 ◽  
Vol 6 (3) ◽  
pp. 395-402 ◽  
Author(s):  
J.-J. Langusch ◽  
E. Matzner
Keyword(s):  
Steady State ◽  
Critical Load ◽  
Mass Balance ◽  
Critical Loads ◽  
Forest Ecosystems ◽  
N Deposition ◽  
N Saturation ◽  
Negative Consequences ◽  
Hydrological Conditions

Abstract. Many forest ecosystems in Central Europe have reached the status of N saturation due to chronically high N deposition. In consequence, the NO3 leaching into ground- and surface waters is often substantial. Critical loads have been defined to abate the negative consequences of the NO3 leaching such as soil acidification and nutrient losses. The steady state mass balance method is normally used to calculate critical loads for N deposition in forest ecosystems. However, the steady state mass balance approach is limited because it does not take into account hydrology and the time until the steady state is reached. The aim of this study was to test the suitability of another approach: the dynamic model INCA (Integrated Nitrogen Model for European Catchments). Long-term effects of changing N deposition and critical loads for N were simulated using INCA for the Lehstenbach spruce catchment (Fichtelgebirge, NE Bavaria, Germany) under different hydrological conditions. Long-term scenarios of either increasing or decreasing N deposition indicated that, in this catchment, the response of nitrate concentrations in runoff to changing N deposition is buffered by a large groundwater reservoir. The critical load simulated by the INCA model with respect to a nitrate concentration of 0.4 mg N l–1 as threshold value in runoff was 9.7 kg N ha–1yr–1 compared to 10 kg ha–1yr–1 for the steady state model. Under conditions of lower precipitation (520 mm) the resulting critical load was 7.7 kg N ha–1yr–1 , suggesting the necessity to account for different hydrological conditions when calculating critical loads. The INCA model seems to be suitable to calculate critical loads for N in forested catchments under varying hydrological conditions e.g. as a consequence of climate change. Keywords: forest ecosystem, N saturation, critical load, modelling, long-term scenario, nitrate leaching, critical loads reduction, INCA

scholarly journals Long-term nitrogen addition decreases carbon leaching in nitrogen-rich forest ecosystems

2013 ◽  
Vol 10 (1) ◽  
pp. 1451-1481 ◽  
Author(s):  
X. Lu ◽  
F. S. Gilliam ◽  
G. Yu ◽  
L. Li ◽  
Q. Mao ◽  
...  
Keyword(s):  
Tropical Forests ◽  
Critical Role ◽  
C Sequestration ◽  
Nitrogen Addition ◽  
N Deposition ◽  
N Addition ◽  
Soil C ◽  
Rooting Zone ◽  
C Cycle

Abstract. Dissolved organic carbon (DOC) plays a critical role in the carbon (C) cycle of forest soils, and has been recently connected with global increases in nitrogen (N) deposition. Most studies on effects of elevated N deposition on DOC have been carried out in N-limited temperate regions, with far fewer data available from N-rich ecosystems, especially in the context of chronically elevated N deposition. Furthermore, mechanisms for excess N-induced changes of DOC dynamics have been suggested to be different between the two kinds of ecosystems, because of the different ecosystem N status. The purpose of this study was to experimentally examine how long-term N addition affects DOC dynamics below the primary rooting zones (the upper 20 cm soils) in typically N-rich lowland tropical forests. We have a primary assumption that long-term continuous N addition minimally affects DOC concentrations and effluxes in N-rich tropical forests. Experimental N addition was administered at the following levels: 0, 50, 100 and 150 kg N ha−1 yr−1, respectively. Results showed that seven years of N addition significantly decreased DOC concentrations in soil solution, and chemo-physical controls (solution acidity change and soil sorption) rather than biological controls may mainly account for the decreases, in contrast to other forests. We further found that N addition greatly decreased annual DOC effluxes from the primary rooting zone and increased water-extractable DOC in soils. Our results suggest that long-term N deposition could increase soil C sequestration in the upper soils by decreasing DOC efflux from that layer in N-rich ecosystems, a novel mechanism for continued accumulation of soil C in old-growth forests.

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