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Different soil respiration responses to litter manipulation in three subtropical successional forests.

ABSTRACT: Aboveground litter inputs have been greatly altered by human disturbances and climate change, which have important effects on soil respiration. However, the knowledge of how soil respiration responds to altered litter inputs is limited in tropical and subtropical forests. We conducted an aboveground litterfall manipulation experiment in three successional forests in the subtropics to examine the soil respiration responses to different litter inputs from January 2010 to July 2012. The soil respiration decreased by 35% in the litter exclusion treatments and increased by 77% in the doubled litter additions across all three forests. The reduction in soil respiration induced by the litter exclusion was greatest in the early successional forest, which may be related to a decrease in the soil moisture and shifts in the microbial community. The increase in soil respiration produced by the doubled litter addition was largest in the mature forest, which was most probably due to its relatively high quantity and quality of litterfall. Our results suggest that the effect of reduced litter inputs on the soil respiration lessened with forest succession but that the doubled litter inputs resulted in a stronger priming effect in the mature forest than in the other two forests.

SUBMITTER: Han T

PROVIDER: S-EPMC4676067 | biostudies-other | 2015

REPOSITORIES: biostudies-other

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Project description:Global change is affecting primary productivity in forests worldwide, and this, in turn, will alter long-term carbon (C) sequestration in wooded ecosystems. On one hand, increased primary productivity, for example, in response to elevated atmospheric carbon dioxide (CO 2), can result in greater inputs of organic matter to the soil, which could increase C sequestration belowground. On other hand, many of the interactions between plants and microorganisms that determine soil C dynamics are poorly characterized, and additional inputs of plant material, such as leaf litter, can result in the mineralization of soil organic matter, and the release of soil C as CO 2 during so-called "priming effects". Until now, very few studies made direct comparison of changes in soil C dynamics in response to altered plant inputs in different wooded ecosystems. We addressed this with a cross-continental study with litter removal and addition treatments in a temperate woodland (Wytham Woods) and lowland tropical forest (Gigante forest) to compare the consequences of increased litterfall on soil respiration in two distinct wooded ecosystems. Mean soil respiration was almost twice as high at Gigante (5.0 μmol CO 2 m-2 s-1) than at Wytham (2.7 μmol CO 2 m-2 s-1) but surprisingly, litter manipulation treatments had a greater and more immediate effect on soil respiration at Wytham. We measured a 30% increase in soil respiration in response to litter addition treatments at Wytham, compared to a 10% increase at Gigante. Importantly, despite higher soil respiration rates at Gigante, priming effects were stronger and more consistent at Wytham. Our results suggest that in situ priming effects in wooded ecosystems track seasonality in litterfall and soil respiration but the amount of soil C released by priming is not proportional to rates of soil respiration. Instead, priming effects may be promoted by larger inputs of organic matter combined with slower turnover rates.

Project description:Background and aimsSoil respiration is the second-largest terrestrial carbon (C) flux, and soil temperature and soil moisture are the main drivers of temporal variation in soil respiration and its components. Here, we quantified the contribution of soil temperature, soil moisture, and their intersection on the variation in soil respiration and its components of the evergreen broad-leaved forests (EBF), mixed evergreen and deciduous broad-leaved forests (MF), deciduous broad-leaved forests (DBF), and subalpine coniferous forests (CF) along an elevation gradient.MethodsWe measured soil respiration of four types of forests along the elevation gradient in Shennongjia, Hubei China based on the trenching experiments. We parameterized the relationships between soil respiration and soil temperature, soil moisture, and quantified the intersection of temperature and moisture on soil respiration and its components.ResultsTotal soil respiration (R S), heterotrophic respiration (R H), and autotrophic respiration (R A) were significantly correlated with soil temperature in all four forests. The Q 10 value of soil respiration significantly differed among the four types of forest, and the Q 10 was 3.06 for EBF, 3.75 for MF, 4.05 for DBF, and 4.49 for CF, respectively. The soil temperature explained 62%-81% of the variation in respiration, while soil temperature and soil moisture together explained 91%-97% of soil respiration variation for the four types of forests. The variation from the intersection of soil temperature and moisture were 12.1%-25.0% in RS, 1.0%-7.0% in R H, and 17.1%-19.6% in R A, respectively.ConclusionsOur results show that the temperature sensitivity (Q 10) of soil respiration increased with elevation. The intersection between soil temperature and soil moisture had strong effects on soil respiration, especially in R H. We demonstrated that the intersection effects between soil temperature and soil moisture on soil respiration were essential to understand the response of soil respiration and its components to climate change.

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Different soil respiration responses to litter manipulation in three subtropical successional forests.

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