Top PDF Responses of soil respiration to elevated carbon dioxide and nitrogen addition in young subtropical forest ecosystems in China

Responses of soil respiration to elevated carbon dioxide and nitrogen addition in young subtropical forest ecosystems in China

Responses of soil respiration to elevated carbon dioxide and nitrogen addition in young subtropical forest ecosystems in China

2.3 Experiment design We used a completely randomized design with four treat- ments considering two levels of CO 2 and two levels of N. Since we have ten open-top chambers, the replication num- ber for the treatments was not equal. For elevated [CO 2 ] and high N deposition (CN), and elevated [CO 2 ] and ambient N deposition (CC), 3 chambers were used, respectively. For ambient CO 2 and high N deposition (NN), and no treatment as a control (CK), 2 chambers were used, respectively. The elevated CO 2 treatments were achieved by supplying addi- tional CO 2 from a tank until reaching a CO 2 concentration of ca. 700 µmol mol −1 in the chambers. The N addition treat- ments were achieved by spraying seedlings once a week for a total amount of NH 4 NO 3 at 100 kg N ha −1 yr −1 . No other fertilizer was used. Since the walls of the chambers below- ground parts blocked lateral and vertical water fluxes, the seedlings were watered with tap water. All the chambers re- ceived the same amount of water as the CK chambers. These treatments started in April 2005.
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Effect of carbon and nitrogen addition on nitrous oxide and carbon dioxide fluxes
from thawing forest soils

Effect of carbon and nitrogen addition on nitrous oxide and carbon dioxide fluxes from thawing forest soils

In Changbai Mountains area, northeastern China, continuous surface soil freezing normally lasted for two or three months each year and the following spring thaw period continued for about two weeks. The minimum air temperature during winter was low to nearly -30°C, which caused 1.0-1.5 m depth of frozen soil (Xu et al., 2016). This severe winter freezing may affect the dynamics of soil nutrients and microbial activities at initial spring thaw. In this district, broadleaf and Korean pine mixed forest (BKPF) is the major component of forest ecosystems and lies in the climax community of forest succession (Supplementary Fig. S1). Surface soils under the BKPF stand possess greater soil organic matter content and lower bulk density than an adjacent second- ary white birch forest (WBF) (Xu et al., 2016). Due to the relatively lower vegetation coverage and phototaxis property, soil available nutrients, microbial properties, and hydrothermal conditions under the white birch forest stand are different from those under the mature mixed forest. The differences in soil properties under the two forest stands may influence the responses of soil N 2 O
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Effects of nitrogen deposition on soil microbial communities in temperate and subtropical forests in China

Effects of nitrogen deposition on soil microbial communities in temperate and subtropical forests in China

Biao ; Fang, Jingyun Abstract: Increasing nitrogen (N) deposition has aroused large concerns because of its potential nega- tive effects on forest ecosystems. Although microorganisms play a vital role in ecosystem carbon (C) and nutrient cycling, the effect of N deposition on soil microbiota still remains unclear. In this study, we inves- tigated the responses of microbial biomass C (MBC) and N (MBN) and microbial community composition to 4–5 years of experimentally simulated N deposition in temperate needle-leaf forests and subtropical evergreen broadleaf forests in eastern China, using chloroform fumigation extraction and phospholipid fatty acid (PLFA) methods. We found idiosyncratic effects of N addition on microbial biomass in these two types of forest ecosystems. In the subtropical forests, N addition showed a significant negative effect on microbial biomass and community composition, while the effect of N addition was not significant in the temperate forests. The N addition decreased MBC, MBN, arbuscular mycorrhizal fungi, and the F/B ratio (ratio of fungi to bacteria biomass) in the subtropical forests, likely due to a decreased soil pH and changes in the plant community composition. These results showed that microbial biomass and community composition in subtropical forests, compared with the temperate forests, were sensitive to N deposition. Our findings suggest that N deposition may have negative influence on soil microorganisms and potentially alter carbon and nutrient cycling in subtropical forests, rather than in temperate forests.
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Estimating Soil Carbon, Nitrogen, and Phosphorus Mineralization from Short-Term Carbon Dioxide Respiration

Estimating Soil Carbon, Nitrogen, and Phosphorus Mineralization from Short-Term Carbon Dioxide Respiration

The soil used in this study is classified as Houston Black by the Natural Resource Conservation Service and was obtained from the U.S. Department of Agriculture–Agricultural Research Service farm in Temple, Tex. Initial analysis of the soil shows that it contains 2.0% total organic C and 55% clay and has a pH of 8.1. Yearly rainfall at the research station is approximately 76 cm. For this experiment, the Houston Black soil was amended with composted dairy manure. Initial analysis of the dairy manure compost shows that it is comprises 12% total C, 1% total N, and 0.4% total P. The soil and the compost were dried at 40 uC for 24 h. The soil and the compost were ground to pass a 2-mm sieve. The composted dairy manure was added to the soil at the following rates: 0, 4.46, 8.82, 13.38, 17.84, 22.3, 26.76, 31.22, and 35.68 Mg ha 21 (0, 10, 20, 30, 40, 50, 60, 70, and 80 tons/acre). The compost and soil contained less than 3% moisture and was calculated on a dry basis.
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Laboratory analysis of the effects of elevated atmospheric carbon dioxide on respiration in biological soil crusts

Laboratory analysis of the effects of elevated atmospheric carbon dioxide on respiration in biological soil crusts

A = surface area of soil sample (6.793×10 -3 m 2 ); t = time between end of last flush and taking of gas sample (s); V s = volumetric scaling factor = 222,072; M C = molar mass of carbon (12.0107 g mol -1 ) and 3,600 is used to represent flux over one hour. Net carbon balances were based on the area under each carbon flux time series and were calculated separately for each chamber for each day using the integral function in EasyPlot™ software. In order to characterize significance of treatments (two levels of CO 2 and three levels of wetting), analysis of variance (ANOVA) was undertaken using statistical package SYSTAT 13 which determines the p-value for CO 2 , wetting and also whether or not these values are statistically significant.
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Laboratory analysis of the effects of elevated atmospheric carbon dioxide on respiration in biological soil crusts

Laboratory analysis of the effects of elevated atmospheric carbon dioxide on respiration in biological soil crusts

A = surface area of soil sample (6.793×10 -3 m 2 ); t = time between end of last flush and taking of gas sample (s); V s = volumetric scaling factor = 222,072; M C = molar mass of carbon (12.0107 g mol -1 ) and 3,600 is used to represent flux over one hour. Net carbon balances were based on the area under each carbon flux time series and were calculated separately for each chamber for each day using the integral function in EasyPlot™ software. In order to characterize significance of treatments (two levels of CO 2 and three levels of wetting), analysis of variance (ANOVA) was undertaken using statistical package SYSTAT 13 which determines the p-value for CO 2 , wetting and also whether or not these values are statistically significant.
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Growth responses of trees and understory plants to nitrogen fertilization in a subtropical forest in China

Growth responses of trees and understory plants to nitrogen fertilization in a subtropical forest in China

mented, while relatively flat stands are required to avoid N losses and minimize spatial heterogeneity among experimen- tal treatments. The actual distribution and topography of the subtropical forests limited the number of replications in the N fertilization experiment. This limitation might reduce the statistic power of N treatment on plot-averaged plant growth rate, as has been pointed out in previous studies (Wright et al., 2011; Alvarez-Clare et al., 2013). Furthermore, our ob- servation of large trees with DBH > 30 cm showed that the averaged growth rate of large C. eyrei individuals in N50 plots almost doubled the value of the corresponding large individuals in unfertilized plots. Nevertheless, the results of ANOVA showed that the effect was not significant. As the number of large trees in the experiment was relatively less than the small trees, the low replication and high spatial site heterogeneity might have reduced the statistical power of N fertilization on the large trees. Thus, fertilization experiments with more homogeneous plots and more replicates are war- ranted to further strengthen these findings. Overall, given the negative and potential positive effects of N fertilization on small and large trees, it is of urgent necessity to conduct long-term monitoring of the trees which would provide alter- natives for accurately evaluating the forest dynamics under the enhanced global N deposition.
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Divergent responses of soil carbon and nitrogen pools to short-term nitrogen addition between two plantations in Northeast China

Divergent responses of soil carbon and nitrogen pools to short-term nitrogen addition between two plantations in Northeast China

(1. College of Resources and Environment, Jilin Agricultural University, Changchun 130118, China; 2. Jingyue High-Tech Industrial Development Zone Division, Changchun Ecology and Environment Bureau, Changchun 130117, China; 3. IER Environmental Protection Engineering Technology Co., Ltd., Shenzhen 518071, China; 4. School of Urban Planning and Design, Shenzhen Graduate School, Peking University, Shenzhen 518055, China) Abstract: Nitrogen (N) deposition has a profound influence on forest soil carbon (C) and N pools, but there was no consensus on the responses of different C and N components in different forest types. In this study, a two-year simulated N deposition experiment with four levels of N (NH 4 NO 3 )-addition treatments (0, 50, 100, and 150 kg N/hm 2 ·a) were conducted in Larix gmelinii (LG) and Quercus mongolica (QM) plantation in Northeast China, in order to investigate the C and N pool dynamics under continuously enhanced N deposition. Soil organic carbon (SOC), soil total N (STN) and their active components (readily oxidizable C, ROC; dissolved organic C, DOC; microbial biomass C, MBC, dissolved organic N, DON; microbial biomass N, MBN) of the forest soil were measured monthly from May to October 2017. C and N contents in LG were observed higher than in QM. N addition had no effect on SOC and STN of LG, but significantly increased SOC and STN of QM at low N addition level. Low N addition generally raised active C components (ROC, DOC, and MBC) in both plantations, whereas high N addition did not significantly affect these components, or even decreased ROC in LG soil. Low N addition also increased STN and MBN of QM, while no significant change in STN and MBN of LG was observed. DON was directly affected by N addition and increased significantly with elevated N addition levels. The results indicated that N addition, especially of low rate, might enhance the C sequestration capacity of the forest soils and mitigate climate change.
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Responses of soil respiration and its temperature/moisture sensitivity to precipitation in three subtropical forests in southern China

Responses of soil respiration and its temperature/moisture sensitivity to precipitation in three subtropical forests in southern China

Received: 26 October 2012 – Published in Biogeosciences Discuss.: 8 November 2012 Revised: 5 May 2013 – Accepted: 9 May 2013 – Published: 18 June 2013 Abstract. Both long-term observation data and model sim- ulations suggest an increasing chance of serious drought in the dry season and extreme flood in the wet season in south- ern China, yet little is known about how changes in precip- itation pattern will affect soil respiration in the region. We conducted a field experiment to study the responses of soil respiration to precipitation manipulations – precipitation ex- clusion to mimic drought, double precipitation to simulate flood, and ambient precipitation as control (abbr. EP, DP and AP, respectively) – in three subtropical forests in southern China. The three forest sites include Masson pine forest (PF), coniferous and broad-leaved mixed forest (MF) and mon- soon evergreen broad-leaved forest (BF). Our observations showed that altered precipitation strongly influenced soil res- piration, not only through the well-known direct effects of soil moisture on plant and microbial activities, but also by modification of both moisture and temperature sensitivity of soil respiration. In the dry season, soil respiration and its tem- perature sensitivity, as well as fine root and soil microbial biomass, showed rising trends with precipitation increases in the three forest sites. Contrarily, the moisture sensitivity of soil respiration decreased with precipitation increases. In the wet season, different treatments showed different effects in three forest sites. The EP treatment decreased fine root biomass, soil microbial biomass, soil respiration and its tem- perature sensitivity, but enhanced soil moisture sensitivity
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Response of soil mineral weathering to elevated carbon dioxide

Response of soil mineral weathering to elevated carbon dioxide

implications of the observed oxalate-enhanced dissolution are not as clear. Low-molecular-weight (LMW) organic acids in soils are excreted from plant roots, leached from litter and other organic material, and produced by bacteria and fungi, which are often associated with the rhizosphere, the root zone. Due to the death of the vegetation within the high-CO 2 areas and the consequent decrease in exudate production by living roots, lower concentrations of organic acids might be expected. However, the increased amount of decomposing organic material and the associated microbial activity in the high-CO 2 soils may provide additional sources of organic acids. It is not obvious, therefore, whether the soils within the anomalous area at Mammoth Mountain are exposed to higher or lower concentrations of LMW organic acids. The results of a comparative analysis of LMW organic acid composition, discussed in Chapter 3, did not show distinct differences in LMW organic acids compositions in the high-CO 2 and control site. However, since this analysis of LMW organic acids was performed on soil samples collected in June just after the snow-melt, the organic acid concentrations and their relative abundance in the high-CO 2 and control soils may not be entirely
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Effects of Nitrogen and Phosphorus Addition  on Soil Respiration in Northern Hardwood Forests

Effects of Nitrogen and Phosphorus Addition on Soil Respiration in Northern Hardwood Forests

I hypothesized that the response of TSR to nutrient additions would differ between young and older northern hardwood stands. In young, N-limited stands N addition should result in decreased TSR because of N suppression of microbial activity and possibly also decreased plant C allocation to roots. In contrast, in older, P-limited stands I expected the greatest decline in TSR in N+P treated plots, again reflecting N suppression of microbial heterotrophs and reduced C allocation to roots when P limitation is relieved. I hoped that this study of NP co-limitation of TSR would contribute to a better understanding of the intricate mechanisms whereby
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Impact of cloudiness on net ecosystem exchange of carbon dioxide in different types of forest ecosystems in China

Impact of cloudiness on net ecosystem exchange of carbon dioxide in different types of forest ecosystems in China

In contrast, temperature and moisture of the subtropical for- est ecosystem reached their maximum in summer, but solar radiation received by ecosystem was insufficient because of heavy precipitation and increased cloudiness. Thus, we as- sume that the high temperature and moisture could increase ecosystem respiration under cloudy sky conditions, but insuf- ficient solar radiation received by ecosystem could restrain photosynthesis. Therefore, net carbon uptake of the subtrop- ical forest would decrease. However, clear skies might bene- fit to net carbon uptake of the subtropical forest ecosystem in summer, because solar radiation received by ecosystem in- creased under clear sky conditions. Based on these assump- tions, when the environmental factors changed with the pat- tern of precipitation and cloudiness in China, changes in net carbon uptake of the two forest ecosystems would be differ- ent.
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Soil Carbon Dioxide Emission: Soil Respiration Measurement in Temperate Grassland, Nepal

Soil Carbon Dioxide Emission: Soil Respiration Measurement in Temperate Grassland, Nepal

DOI: 10.4236/jep.2019.102017 303 Journal of Environmental Protection perature, and then starts emitting high CO 2 after the pores are reopened when the soil water evaporates. Apart from this, in April, some of the chambers also showed higher soil respiration throughout the measurements period that may cause the overlapping of the actual temperature effect on soil respiration, which was not clearly visible from the measurements. This could be solved with conti- nuous digitalized measurements of soil respiration, soil temperature and preci- pitation for longer period of time to effectively determine the temperature and soil moisture effects on soil respiration. Our measurements provided an appro- priate result to understand the temperature effect of soil respiration and seasonal water availability. Liebig et al. [67] observed that it could not established the correlation between soil respiration and soil temperature in summer due to the effect of stable soil temperature, and variations were found only in spring and autumn caused by rapid growth and senescence in semiarid grazing grassland, United States. This proved that this study was better enough to understand the overall soil respiration trend to the variations of its influencing factors in the temperate grassland.
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Increased mercury in forest soils under elevated carbon dioxide

Increased mercury in forest soils under elevated carbon dioxide

Our litter, throughfall and stemXow deposition data allow us to reject the hypothesis that higher soil Hg concen- trations in elevated-CO 2 soils were driven by increased deposition. These data support the hypothesis that CO 2 - mediated changes in soil properties are increasing the Hg storage capacity of forest soils. Future research e Vorts should focus on soil processes (i.e., root dynamics, SOM and Hg) under elevated CO 2 to gain a better understanding of potential changes in soil Hg cycling with increasing CO 2 . One challenge of conducting research at large-scale multi-user facilities such as the FACE sites is the restric- tions on sample size. The fact that a CO 2 eVect on soil Hg was detected, in spite of this limitation, suggests that the observed response is robust, but future studies at other FACE sites would strengthen these conclusions.
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Impact of elevated precipitation, nitrogen deposition and warming on soil respiration in a temperate desert

Impact of elevated precipitation, nitrogen deposition and warming on soil respiration in a temperate desert

Climate change and elevated N deposition play important roles in controlling R s in temperate deserts. We found that increasing precipitation and N deposition significantly in- creased R s in the Gurbantunggut Desert, but warming re- duced R s , mostly because of the variation of soil moisture. In addition, we found that the interactive responses of R s were much lower for the combination of precipitation, N deposi- tion and warming than for any single factor. Additionally, R s is mainly mediated by soil moisture, soil temperature and soil NH + 4 -N content, but soil temperature is the most impor- tant, with between-year variation in R s mainly controlled by ephemeral plants. These results showed that R s is very sen- sitive to increasing precipitation, N deposition and warming, and their interactive effects could reduce soil carbon emis- sions and thus the impacts of climate change.
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Soil nitrogen transformation responses to seasonal precipitation changes are regulated by changes in functional microbial abundance in a subtropical forest

Soil nitrogen transformation responses to seasonal precipitation changes are regulated by changes in functional microbial abundance in a subtropical forest

42 % of the total variation in N 2 O emission was attributed to the combined effects of SWC, nitrification rate, MBC and nosZ gene abundance. The accumulation of NH + 4 due to dry- season precipitation reduction may stimulate nitrification in the wet season, and consequently accelerate N loss by NO − 3 leaching. Therefore, the predicted long-term seasonal pre- cipitation changes in subtropical forests may result in pro- found changes to different N pools and fluxes, including re- duced N 2 O emission and enhanced NO − 3 leaching. These, in turn, could exert a feedback to climate and environmental changes. Meanwhile, changes in functional microbial abun- dance induced by soil EOC and NH + 4 substrate availabilities will determine the extent and direction of soil N transforma- tion changes.
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The Carbon-Nitrogen Balance of the Nodule and Its Regulation
under Elevated Carbon Dioxide Concentration

The Carbon-Nitrogen Balance of the Nodule and Its Regulation under Elevated Carbon Dioxide Concentration

Copyright © 2014 Marc Libault. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Legumes have developed a unique way to interact with bacteria: in addition to preventing infection from pathogenic bacteria like any other plant, legumes also developed a mutualistic symbiotic relationship with one gender of soil bacteria: rhizobium. This interaction leads to the development of a new root organ, the nodule, where the differentiated bacteria fix for the plant the atmospheric dinitrogen (atmN 2 ). In exchange, the symbiont will benefit from a permanent source of carbon compounds, products of the photosynthesis. The substantial amounts of fixed carbon dioxide dedicated to the symbiont imposed to the plant a tight regulation of the nodulation process to balance carbon and nitrogen incomes and outcomes. Climate change including the increase of the concentration of the atmospheric carbon dioxide is going to modify the rates of plant photosynthesis, the balance between nitrogen and carbon, and, as a consequence, the regulatory mechanisms of the nodulation process. This review focuses on the regulatory mechanisms controlling carbon/nitrogen balances in the context of legume nodulation and discusses how the change in atmospheric carbon dioxide concentration could affect nodulation efficiency.
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Relationships between soil microbial physiology, community structure and carbon and nitrogen cycling in temperate forest ecosystems

Relationships between soil microbial physiology, community structure and carbon and nitrogen cycling in temperate forest ecosystems

I am especially thankful for the many ways in which he encouraged me to reach for opportunities I would have otherwise shied away from, and for providing me with confidence in learning a variety of new methods. I have been extremely fortunate to have the advice of a talented committee. Jennifer Bhatnagar, my second reader, essentially provided me a second home in her lab, where I was able to learn new molecular techniques. I will be forever thankful for the times when I left Jenny’s office with newfound enthusiasm and motivation for my dissertation. Pamela Templer, my committee chair, has been incredibly supportive throughout my graduate experience. Many of the ideas for my work on N cycling were developed while in her Forest Ecology class. Working with Michael Dietze has transformed the way I understand models and data, while making a number of once-intimidating tools more accessible to me.
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enrichment increases nutrient leaching from model forest ecosystems in subtropical China

enrichment increases nutrient leaching from model forest ecosystems in subtropical China

The aboveground section was wrapped with impermeable and transparent plastic sheets, leaving the top totally open. Sunlight intensity in the chamber was 97% of that in open space with no spectral change detected. Rainfall intensity and air temperature were also identical inside and outside chambers. The belowground section was delimited by a brick wall preventing any lateral or vertical water movement and/or element flux to or from the outside surrounding soil. Three holes at the bottom of the cylinder were connected to stain- less steel water collection boxes. Holes were capped by a 2-mm net to prevent losses other than those of leachates. In treatments with elevated CO 2 , CO 2 was distributed in each chamber by a transparent pipe with pinholes. A big fan was connected to the pipe to ensure equal distribution of CO 2 in the entire chamber. Air was introduced into the chambers via the fan at an exchange rate of about 1.5 chamber volumes per minute. The CO 2 flux from the tank was controlled by a flow meter and the CO 2 concentrations in the chambers were pe- riodically controlled using a Licor-6400 (LI-COR Inc., Lin- coln, NE, USA). Air temperatures were recorded by the ther- mometers inside and outside the chambers. No significant difference of air temperatures were found inside and outside all the cambers during the experiment. Soil moisture in each chamber was recorded every week at several random points using time-domain reflectometry (TDR).
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Responses of soil microbial communities and enzyme activities to nitrogen and phosphorus additions in Chinese fir plantations of subtropical China

Responses of soil microbial communities and enzyme activities to nitrogen and phosphorus additions in Chinese fir plantations of subtropical China

contrasting results may be attributed to the factor that, un- like agricultural systems, nutrient additions to forest ecosys- tems often lead to changes in the composition and diversity of plant species, which in turn have an influence on the for- est litter. Consistent with our research, Wei et al. (2012) re- ported that nutrient additions led to a significant enhance- ment of soil C sequestration and nutrient status in Chinese fir forest soils. Huang et al. (2011) also considered that soil nutrient enrichment, especially N, could reduce SOC decom- position. Moreover, nutrient-induced increases in forest litter and subsequent inputs of organic matter to the forest floor, and ultimately to the mineral soil, could lead to increases in soil nutrient concentrations (Moorhead and Sinsabaugh, 2006). The litter on the forest floor acts as input–output sys- tem of nutrient and the rates at which forest litter falls and subsequently decomposes contribute to the maintenance of soil fertility in forest ecosystems (Wang et al., 2011). Zeng et al. (2015) found that while exogenous N and P additions could promote forest ecosystem biomass and could also lead to increases in the litter on the forest floor in the form of root exudates and above-ground residues, P addition had no in- fluence on forest biomass. Therefore, total P did not change when only P was added; there were however significant in- creases in total P in response to combined applications of N and P. Besides, other related unpublished studies at our study site have demonstrated that, after P additions, P concentra- tions in leaves and twigs increased significantly. Soil P was largely absorbed by plants, and soil P remained unchanged.
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