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Leaf litter decomposition rates increase with rising mean annual temperature in Hawaiian tropical montane wet forests.

Bothwell LD, Selmants PC, Giardina CP, Litton CM - PeerJ (2014)

Bottom Line: Dominant vegetation, substrate type and age, soil moisture, and disturbance history are all nearly constant across this gradient, allowing us to isolate the effect of rising MAT on leaf litter decomposition and nutrient release.Our estimate of the Q 10 temperature coefficient for leaf litter decomposition was 2.17, within the commonly reported range for heterotrophic organic matter decomposition (1.5-2.5) across a broad range of ecosystems.The percentage of leaf litter nitrogen (N) remaining after six months declined linearly with increasing MAT from ∼88% of initial N at the coolest site to ∼74% at the warmest site.

View Article: PubMed Central - HTML - PubMed

Affiliation: Natural Sciences Division, University of Hawaii at Hilo , Hilo, HI , USA.

ABSTRACT
Decomposing litter in forest ecosystems supplies nutrients to plants, carbon to heterotrophic soil microorganisms and is a large source of CO2 to the atmosphere. Despite its essential role in carbon and nutrient cycling, the temperature sensitivity of leaf litter decay in tropical forest ecosystems remains poorly resolved, especially in tropical montane wet forests where the warming trend may be amplified compared to tropical wet forests at lower elevations. We quantified leaf litter decomposition rates along a highly constrained 5.2 °C mean annual temperature (MAT) gradient in tropical montane wet forests on the Island of Hawaii. Dominant vegetation, substrate type and age, soil moisture, and disturbance history are all nearly constant across this gradient, allowing us to isolate the effect of rising MAT on leaf litter decomposition and nutrient release. Leaf litter decomposition rates were a positive linear function of MAT, causing the residence time of leaf litter on the forest floor to decline by ∼31 days for each 1 °C increase in MAT. Our estimate of the Q 10 temperature coefficient for leaf litter decomposition was 2.17, within the commonly reported range for heterotrophic organic matter decomposition (1.5-2.5) across a broad range of ecosystems. The percentage of leaf litter nitrogen (N) remaining after six months declined linearly with increasing MAT from ∼88% of initial N at the coolest site to ∼74% at the warmest site. The lack of net N immobilization during all three litter collection periods at all MAT plots indicates that N was not limiting to leaf litter decomposition, regardless of temperature. These results suggest that leaf litter decay in tropical montane wet forests may be more sensitive to rising MAT than in tropical lowland wet forests, and that increased rates of N release from decomposing litter could delay or prevent progressive N limitation to net primary productivity with climate warming.

No MeSH data available.


Related in: MedlinePlus

Nitrogen remaining in decomposing leaf litter at three stages of decomposition across a mean annual temperature gradient on the Island of Hawaii.Nitrogen remaining in Metrosideros polymorpha leaf litter at each stage of decomposition across a 5.2 °C mean annual temperature gradient in Hawaiian tropical montane wet forests. Black circles are means with error bars representing the 95% confidence interval around the mean; n = 5 litterbags per MAT plot. Values below 100% indicate net N mineralization from decomposing leaf litter; values above 100% indicate net N immobilization in decomposing leaf litter. The header of each panel indicates the mean annual temperature (in °C) of each plot. Note that data from the two 16.1 °C plots are plotted in the same panel.
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fig-3: Nitrogen remaining in decomposing leaf litter at three stages of decomposition across a mean annual temperature gradient on the Island of Hawaii.Nitrogen remaining in Metrosideros polymorpha leaf litter at each stage of decomposition across a 5.2 °C mean annual temperature gradient in Hawaiian tropical montane wet forests. Black circles are means with error bars representing the 95% confidence interval around the mean; n = 5 litterbags per MAT plot. Values below 100% indicate net N mineralization from decomposing leaf litter; values above 100% indicate net N immobilization in decomposing leaf litter. The header of each panel indicates the mean annual temperature (in °C) of each plot. Note that data from the two 16.1 °C plots are plotted in the same panel.

Mentions: Initial N concentration of mixed M. polymorpha litter was 8.5 mg g−1. After six months of decomposition, the percentage of N remaining in decomposing M. polymorpha leaves declined significantly as a function of increasing MAT (Fig. 2), from ∼88% of initial N at the coolest site to ∼74% of initial N at the warmest site, a decline of approximately two percentage points for each 1 °C increase in MAT. Nitrogen remaining in leaf litter was never significantly larger than 100% at any stage of decomposition within any of the nine MAT plots (Fig. 3), indicating there was no net N immobilization in decaying leaf litter. Neither annual rainfall nor soil water content during the six month experiment period (Table 1) were significant predictors of leaf litter decay rates (R2 = 0.013, p = 0.34 for annual rainfall; R2 = 0.03, p = 0.67 for soil water content).


Leaf litter decomposition rates increase with rising mean annual temperature in Hawaiian tropical montane wet forests.

Bothwell LD, Selmants PC, Giardina CP, Litton CM - PeerJ (2014)

Nitrogen remaining in decomposing leaf litter at three stages of decomposition across a mean annual temperature gradient on the Island of Hawaii.Nitrogen remaining in Metrosideros polymorpha leaf litter at each stage of decomposition across a 5.2 °C mean annual temperature gradient in Hawaiian tropical montane wet forests. Black circles are means with error bars representing the 95% confidence interval around the mean; n = 5 litterbags per MAT plot. Values below 100% indicate net N mineralization from decomposing leaf litter; values above 100% indicate net N immobilization in decomposing leaf litter. The header of each panel indicates the mean annual temperature (in °C) of each plot. Note that data from the two 16.1 °C plots are plotted in the same panel.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4260126&req=5

fig-3: Nitrogen remaining in decomposing leaf litter at three stages of decomposition across a mean annual temperature gradient on the Island of Hawaii.Nitrogen remaining in Metrosideros polymorpha leaf litter at each stage of decomposition across a 5.2 °C mean annual temperature gradient in Hawaiian tropical montane wet forests. Black circles are means with error bars representing the 95% confidence interval around the mean; n = 5 litterbags per MAT plot. Values below 100% indicate net N mineralization from decomposing leaf litter; values above 100% indicate net N immobilization in decomposing leaf litter. The header of each panel indicates the mean annual temperature (in °C) of each plot. Note that data from the two 16.1 °C plots are plotted in the same panel.
Mentions: Initial N concentration of mixed M. polymorpha litter was 8.5 mg g−1. After six months of decomposition, the percentage of N remaining in decomposing M. polymorpha leaves declined significantly as a function of increasing MAT (Fig. 2), from ∼88% of initial N at the coolest site to ∼74% of initial N at the warmest site, a decline of approximately two percentage points for each 1 °C increase in MAT. Nitrogen remaining in leaf litter was never significantly larger than 100% at any stage of decomposition within any of the nine MAT plots (Fig. 3), indicating there was no net N immobilization in decaying leaf litter. Neither annual rainfall nor soil water content during the six month experiment period (Table 1) were significant predictors of leaf litter decay rates (R2 = 0.013, p = 0.34 for annual rainfall; R2 = 0.03, p = 0.67 for soil water content).

Bottom Line: Dominant vegetation, substrate type and age, soil moisture, and disturbance history are all nearly constant across this gradient, allowing us to isolate the effect of rising MAT on leaf litter decomposition and nutrient release.Our estimate of the Q 10 temperature coefficient for leaf litter decomposition was 2.17, within the commonly reported range for heterotrophic organic matter decomposition (1.5-2.5) across a broad range of ecosystems.The percentage of leaf litter nitrogen (N) remaining after six months declined linearly with increasing MAT from ∼88% of initial N at the coolest site to ∼74% at the warmest site.

View Article: PubMed Central - HTML - PubMed

Affiliation: Natural Sciences Division, University of Hawaii at Hilo , Hilo, HI , USA.

ABSTRACT
Decomposing litter in forest ecosystems supplies nutrients to plants, carbon to heterotrophic soil microorganisms and is a large source of CO2 to the atmosphere. Despite its essential role in carbon and nutrient cycling, the temperature sensitivity of leaf litter decay in tropical forest ecosystems remains poorly resolved, especially in tropical montane wet forests where the warming trend may be amplified compared to tropical wet forests at lower elevations. We quantified leaf litter decomposition rates along a highly constrained 5.2 °C mean annual temperature (MAT) gradient in tropical montane wet forests on the Island of Hawaii. Dominant vegetation, substrate type and age, soil moisture, and disturbance history are all nearly constant across this gradient, allowing us to isolate the effect of rising MAT on leaf litter decomposition and nutrient release. Leaf litter decomposition rates were a positive linear function of MAT, causing the residence time of leaf litter on the forest floor to decline by ∼31 days for each 1 °C increase in MAT. Our estimate of the Q 10 temperature coefficient for leaf litter decomposition was 2.17, within the commonly reported range for heterotrophic organic matter decomposition (1.5-2.5) across a broad range of ecosystems. The percentage of leaf litter nitrogen (N) remaining after six months declined linearly with increasing MAT from ∼88% of initial N at the coolest site to ∼74% at the warmest site. The lack of net N immobilization during all three litter collection periods at all MAT plots indicates that N was not limiting to leaf litter decomposition, regardless of temperature. These results suggest that leaf litter decay in tropical montane wet forests may be more sensitive to rising MAT than in tropical lowland wet forests, and that increased rates of N release from decomposing litter could delay or prevent progressive N limitation to net primary productivity with climate warming.

No MeSH data available.


Related in: MedlinePlus