scholarly journals The role of phosphorus dynamics in tropical forests – a modeling study using CLM-CNP

2014 ◽  
Vol 11 (6) ◽  
pp. 1667-1681 ◽  
Author(s):  
X. Yang ◽  
P. E. Thornton ◽  
D. M. Ricciuto ◽  
W. M. Post
Keyword(s):  
Tropical Forest ◽  
Nutrient Limitation ◽  
Tropical Forests ◽  
Elevated Co2 ◽  
Global Climate ◽  
P Availability ◽  
Tropical Ecosystems ◽  
Model Simulations ◽  
P Limitation

Abstract. Tropical forests play a significant role in the global carbon cycle and global climate. However, tropical carbon cycling and the feedbacks from tropical ecosystems to the climate system remain critical uncertainties in the current generation of carbon–climate models. One of the major uncertainties comes from the lack of representation of phosphorus (P), currently believed to be the most limiting nutrient in tropical regions. Here we introduce P dynamics and C–N–P interactions into the CLM4-CN (Community Land Model version 4 with prognostic Carbon and Nitrogen) model and investigate the role of P cycling in controlling the productivity of tropical ecosystems. The newly developed CLM-CNP model includes all major biological and geochemical processes controlling P availability in soils and the interactions between C, N, and P cycles. Model simulations at sites along a Hawaiian soil chronosequence indicate that the introduction of P limitation greatly improved the model performance at the P-limited site. The model is also able to capture the shift in nutrient limitation along this chronosequence (from N limited to P limited), as shown in the comparison of model-simulated plant responses to fertilization with the observed data. Model simulations at Amazonian forest sites show that CLM-CNP is capable of capturing the overall trend in NPP (net primary production) along the P availability gradient. This comparison also suggests a significant interaction between nutrient limitation and land use history. Model experiments under elevated atmospheric CO2 ([CO2]) conditions suggest that tropical forest responses to increasing [CO2] will interact strongly with changes in the P cycle. We highlight the importance of two feedback pathways (biochemical mineralization and desorption of secondary mineral P) that can significantly affect P availability and determine the extent of P limitation in tropical forests under elevated [CO2]. Field experiments with elevated CO2 are therefore needed to help quantify these important feedbacks. CO2 doubling model experiments show that tropical forest response to elevated [CO2] can only be predicted if the interactions between C cycle and nutrient dynamics are well understood and represented in models. Predictive modeling of C–nutrient interactions will have important implications for the prediction of future carbon uptake and storage in tropical ecosystems and global climate change.

scholarly journals The role of phosphorus dynamics in tropical forests – a modeling study using CLM-CNP

2013 ◽  
Vol 10 (8) ◽  
pp. 14439-14473 ◽  
Author(s):  
X. Yang ◽  
P. E. Thornton ◽  
D. M. Ricciuto ◽  
W. M. Post
Keyword(s):  
Nutrient Limitation ◽  
Tropical Forests ◽  
Elevated Co2 ◽  
Field Experiments ◽  
Global Climate ◽  
P Availability ◽  
Tropical Ecosystems ◽  
Model Simulations ◽  
P Limitation

Abstract. Tropical forests play a significant role in the global carbon cycle and global climate. However, tropical carbon cycling and the feedbacks from tropical ecosystems to the climate system remain critical uncertainties in current generation carbon-climate models. One of the major uncertainties comes from the lack of representation of phosphorus (P), the most limiting nutrient in tropical regions. Here we introduce P dynamics and C–N–P interactions into the CLM4-CN model and investigate the role of P cycling in controlling the productivity of tropical ecosystems. The newly developed CLM-CNP model includes all major biological and geochemical processes controlling P availability in soils and the interactions between C, N, and P cycles. Model simulations at sites along a Hawaiian soil chronosequence indicate that the introduction of P limitation greatly improved the model performance at the P-limited site. The model is also able to capture the shift in nutrient limitation along this chronosequence (from N limited to P limited), as shown in the comparison of model simulated plant responses to fertilization with the observed data. Model simulations at Amazonian forest sites show that CLM-CNP is capable of capturing the overall trend in NPP along the P availability gradient. This comparison also suggests a significant interaction between nutrient limitation and land use history. Model experiments under elevated atmospheric CO2 ([CO2]) condition suggest that tropical forest responses to increasing [CO2] will interact strongly with changes in the P cycle. We highlight the importance of two feedback pathways (biochemical mineralization and desorption of secondary mineral P) that can significantly affect P availability and determine the extent of P limitation in tropical forests under elevated [CO2]. Field experiments with elevated CO2 are therefore needed to help quantify these important feedbacks. Predictive modeling of C–P interactions will have important implications for the prediction of future carbon uptake and storage in tropical ecosystems and global climate change.

N and P limitation shapes plant-AMF interactions across an aridity gradient

2020 ◽  
Author(s):  
Svenja Stock ◽  
Moritz Köster ◽  
Jens Boy ◽  
Roberto Godoy ◽  
Francisco Nájera ◽  
...  
Keyword(s):  
Nutrient Limitation ◽  
Drought Resistance ◽  
Plant Nutrition ◽  
Water Shortage ◽  
Aridity Gradient ◽  
P Limitation ◽  
Mediterranean Conditions ◽  
Mediterranean Woodland ◽  
Semiarid Conditions

<p>Arbuscular mycorrhizal fungi (AMF) are important partners in plant nutrition, as they increase the range to scavenge for nutrients and can access resources otherwise occlude for plants. Under water shortage, when mobility of nutrients in soil is limited, AMF are especially important to acquire resources and can modulate plant drought resistance. Strategies of plants to cope with water and nutrient restrictions are shaped by the intensity of aridity. To investigate the effect of aridity on plant-AMF associations regarding drought resistance and plant nutrient acquisition, a <sup>13</sup>CO<sub>2</sub> pulse labeling was conducted across an aridity gradient. In a semiarid shrubland (66 mm a<sup>-1</sup>), a Mediterranean woodland (367 mm a<sup>-1</sup>), and a humid temperate forest (1500 mm a<sup>-1</sup>), root and soil samples were taken from 0-10 cm and 20-30 cm soil depth before labeling and at 1 day, 3 days, and 14 days after labeling. Carbon (C), nitrogen (N), and phosphorus (P) stocks as well as AMF root colonization, extraradical AMF biomass (phospho- and neutral lipid fatty acids (PLFA and NLFA) 16:1w5c), specific root length (SRL), and root tissue density (RTD) were measured. Plant C investment into AMF and roots was determined by the <sup>13</sup>C incorporation in 16:1w5c (PLFA and NLFA) and root tissue, respectively. Soil C:N:P stoichiometry indicated a N and P limitation under humid conditions and a P limitation in the topsoil under Mediterranean conditions. N stocks were highest in the Mediterranean woodland. A strong correlation of the AMF storage compound NLFA 16:1w5c to C:P ratio under semiarid conditions pointed to a P limitation of AMF, likely resulting from low P mobility in dry and alkaline soils. With increasing aridity, the AMF abundance in root (and soil) decreased from 45% to 20% root area. <sup>13</sup>C incorporation in PLFA 16:1w5c was similar across sites, while relative AMF abundance in topsoil (PLFA 16:1w5c:SOC) was slightly higher under semiarid and humid than under Mediterranean conditions, pointing to the importance of AMF for plant nutrition under nutrient limitation. Additionally, PLFA 16:1w5c contents in soil were higher with lower P availability in each site, underlining the role of AMF to supply P for plants under P deficiency. Under humid conditions (with strong N and P limitation) and semiarid conditions (with strong water limitation), root AMF colonization increased with lower N availability, displaying the role of AMF for plant N nutrition under nutrient and/or water shortage. Under humid and Mediterranean conditions, SRL decreased (0.5 and 0.3 times, respectively) and RTD increased (1.9 and 1.7 times, respectively) with depth, indicating a drought tolerance strategy of plants to sustain water shortage. Under semiarid conditions, SRL increased with depth (2.3 times), while RTD was consistently high, suggesting an increasing proportion of long-living fine roots with depth as scavenging agents for water. These relations point to a drought avoidance strategy of plants as adaptation to long-term water limitation. Under strong nutrient limitation, as under humid and semiarid conditions, AMF are crucial to sustain plant nutrition and to enhance plant resistance to water shortage.</p>

scholarly journals Tropical Carbon and Water Observed from Above

Eos ◽  
2021 ◽  
Vol 102 ◽  
Author(s):  
John Worden ◽  
Sassan Saatchi ◽  
Anthony Bloom
Keyword(s):  
Tropical Forests ◽  
Carbon Balance ◽  
Global Climate ◽  
Satellite Observations ◽  
Water Fluxes

Satellite observations of carbon balance and water fluxes are changing the role of tropical forests in local and global climate.

scholarly journals The role of earthworms in nitrogen and solute retention in a tropical forest in Sabah, Malaysia: a pilot study

2012 ◽  
Vol 28 (6) ◽  
pp. 611-614 ◽  
Author(s):  
Sarah Johnson ◽  
Arshiya Bose ◽  
Jake L. Snaddon ◽  
Brian Moss
Keyword(s):  
Pilot Study ◽  
Tropical Forest ◽  
Tropical Forests ◽  
Direct Evidence ◽  
Terrestrial Ecosystems ◽  
Retention Mechanisms ◽  
Solute Retention ◽  
Living Organisms ◽  
Very High

Compounds of the 20 elements needed by living organisms are relatively soluble in water and therefore vulnerable to being leached and lost from terrestrial ecosystems during mineralization. Intact systems have thus acquired retention mechanisms that sequester nutrients and minimize losses. Such mechanisms should be particularly important where rainfall is very high but direct evidence of retention mechanisms in tropical forests is scarce (Snaddon et al. 2012, Turner et al. 2007).

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.

Introducing Tropical Forests in Prehistory, History, and Modernity

2019 ◽  
Author(s):  
Patrick Roberts
Keyword(s):  
Tropical Forest ◽  
Tropical Forests ◽  
Video Game ◽  
Western World ◽  
Human Relationships ◽  
Urban Settlements ◽  
Sir Walter Raleigh ◽  
Human Foraging

Friedrich Wöhler was referring to the field of organic chemistry during the early 1800s when he wrote the above but his comments would not be out of place in the context of embarking upon a global study of past and present human relationships with tropical forests. Dense vegetation, difficulty of navigation, issues of preservation, political and health concerns, poisonous plants, animals, and insects, and the prospect of carrying out sampling or excavation in high humidity have all meant that our knowledge of human history and prehistory in these environments is under-developed relative to temperate, arid, or even polar habitats. There have been theoretical questions as to what kind of human activity one would even expect to find in tropical forest environments, which seem hostile to human foraging (Hart and Hart, 1986; Bailey et al., 1989) let alone thriving agricultural or urban settlements (Meggers, 1971, 1977, 1987). This has, until relatively recently, left the state of archaeological tropical forest research in a similar position to popular conceptions of these environments—untouched, primeval wilderness. Public ideas of an archaeologist investigating a tropical forest are probably synonymous with someone in a shabby-looking leather hat being chased, if not by a large stone boulder then by a group of Indigenous people with blowpipes, as they wade through dense undergrowth and vines while clutching a golden discovery that has been lost to the western world for thousands of years (Spielberg, 1981). The more recent development of the best-selling Uncharted video game series has done little to change these ideas amongst the next generation of media consumers, with players taking on the role of Francis Drake’s mythical ancestor in search of long lost treasure, frequently hidden within caves and ruins surrounded by vines and dense canopies (Naughty Dog et al., 2016). The idea of treasure hidden within tropical forest is also not a modern conception. The long-term myth of El Dorado, a city covered in gold, fuelled exploration of the tropical forests of South America by renowned individuals, including Sir Walter Raleigh, from the sixteenth to the nineteenth centuries (Nicholl, 1995).

scholarly journals An observationally constrained estimate of global dust aerosol optical depth

2016 ◽  
Vol 16 (23) ◽  
pp. 15097-15117 ◽  
Author(s):  
David A. Ridley ◽  
Colette L. Heald ◽  
Jasper F. Kok ◽  
Chun Zhao
Keyword(s):  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Global Climate ◽  
Middle Eastern ◽  
Dust Emission ◽  
Dust Aerosol ◽  
Model Simulations ◽  
State Of The Science

Abstract. The role of mineral dust in climate and ecosystems has been largely quantified using global climate and chemistry model simulations of dust emission, transport, and deposition. However, differences between these model simulations are substantial, with estimates of global dust aerosol optical depth (AOD) that vary by over a factor of 5. Here we develop an observationally based estimate of the global dust AOD, using multiple satellite platforms, in situ AOD observations and four state-of-the-science global models over 2004–2008. We estimate that the global dust AOD at 550 nm is 0.030 ± 0.005 (1σ), higher than the AeroCom model median (0.023) and substantially narrowing the uncertainty. The methodology used provides regional, seasonal dust AOD and the associated statistical uncertainty for key dust regions around the globe with which model dust schemes can be evaluated. Exploring the regional and seasonal differences in dust AOD between our observationally based estimate and the four models in this study, we find that emissions in Africa are often overrepresented at the expense of Asian and Middle Eastern emissions and that dust removal appears to be too rapid in most models.

Long-term potential for tropical-forest degradation due to deforestation and fires in the Brazilian Amazon

Biologia ◽  
2009 ◽  
Vol 64 (3) ◽  
Author(s):  
Manoel Cardoso ◽  
Carlos Nobre ◽  
Gilvan Sampaio ◽  
Marina Hirota ◽  
Dalton Valeriano ◽  
...  
Keyword(s):  
Tropical Forest ◽  
Tropical Forests ◽  
Large Scale ◽  
Global Climate ◽  
Brazilian Amazon ◽  
Forest Degradation ◽  
Large Scale Data ◽  
Fire Activity ◽  
Arc Of Deforestation

AbstractBiome models of the global climate-vegetation relationships indicate that most of the Brazilian Amazon has potential for being covered by tropical forests. From current land-use processes observed in the region, however, substantial deforestation and fire activity have been verified in large portions of the region, particularly along the Arc of Deforestation. In a first attempt to evaluate the long-term potential for tropical-forest degradation due to deforestation and fires in the Brazilian Amazon, we analysed large-scale data on fire activity and climate factors that drive the distribution of tropical forests in the region. The initial analyses and results from this study lead to important details on the relations between these quantities and have important implications for building future parameterizations of the vulnerability of tropical forests in the region.

scholarly journals Variability in solar radiation and temperature explains observed patterns and trends in tree growth rates across four tropical forests

2012 ◽  
Vol 279 (1744) ◽  
pp. 3923-3931 ◽  
Author(s):  
Shirley Xiaobi Dong ◽  
Stuart J. Davies ◽  
Peter S. Ashton ◽  
Sarayudh Bunyavejchewin ◽  
M. N. Nur Supardi ◽  
...  
Keyword(s):  
Solar Radiation ◽  
Tropical Forest ◽  
Temporal Variation ◽  
Tropical Forests ◽  
Tree Growth ◽  
Growth Rates ◽  
Global Climate ◽  
Night Time ◽  
Temperature And Precipitation

The response of tropical forests to global climate variability and change remains poorly understood. Results from long-term studies of permanent forest plots have reported different, and in some cases opposing trends in tropical forest dynamics. In this study, we examined changes in tree growth rates at four long-term permanent tropical forest research plots in relation to variation in solar radiation, temperature and precipitation. Temporal variation in the stand-level growth rates measured at five-year intervals was found to be positively correlated with variation in incoming solar radiation and negatively related to temporal variation in night-time temperatures. Taken alone, neither solar radiation variability nor the effects of night-time temperatures can account for the observed temporal variation in tree growth rates across sites, but when considered together, these two climate variables account for most of the observed temporal variability in tree growth rates. Further analysis indicates that the stand-level response is primarily driven by the responses of smaller-sized trees (less than 20 cm in diameter). The combined temperature and radiation responses identified in this study provide a potential explanation for the conflicting patterns in tree growth rates found in previous studies.

The Role of Tropical Forests in Supporting Biodiversity and Hydrological Integrity

2005 ◽  
Author(s):  
Ellen M. Douglas ◽  
Kate Sebastian ◽  
Charles J. Vorosmarty ◽  
Stanley Wood ◽  
Kenneth M. Chomitz
Keyword(s):  
Tropical Forests
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