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Disentangling the Litter Quality and Soil Microbial Contribution to Leaf and Fine Root Litter Decomposition Responses to Reduced Rainfall
Abstract and Figures
Climate change-induced rainfall reductions in Mediterranean forests negatively affect the decomposition of plant litter through decreased soil moisture. However, the indirect effects of reduced precipitation on litter decomposition through changes in litter quality and soil microbial communities are poorly studied. This is especially the case for fine root litter, which contributes importantly to forests plant biomass. Here we analyzed the effects of long-term (11 years) rainfall exclusion (29% reduction) on leaf and fine root litter quality, soil microbial biomass, and microbial community-level physiological profiles in a Mediterranean holm oak forest. Additionally, we reciprocally transplanted soils and litter among the control and reduced rainfall treatments in the laboratory, and analyzed litter decomposition and its responses to a simulated extreme drought event. The decreased soil microbial biomass and altered physiological profiles with reduced rainfall promoted lower fine root—but not leaf—litter decomposition. Both leaf and root litter, from the reduced rainfall treatment, decomposed faster than those from the control treatment. The impact of the extreme drought event on fine root litter decomposition was higher in soils from the control treatment compared to soils subjected to long-term rainfall exclusion. Our results suggest contrasting mechanisms driving drought indirect effects on above-(for example, changes in litter quality) and belowground (for example, shifts in soil microbial community) litter decomposition, even within a single tree species. Quantifying the contribution of these mechanisms relative to the direct soil moisture-effect is critical for an accurate integration of litter decomposition into ecosystem carbon dynamics in Mediterranean forests under climate change.
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Supplementary resource (1)
Data
December 2015
... Specifically, the effect of altered precipitation regimes on litter decomposition is both direct due to the biological processes contributing to decomposition being greatly affected by moisture availability, and also indirect due to the impacts on litter quality and decomposer distribution . However, the existing studies on the effects of altered precipitation regimes mainly focus on the variations in precipitation amount, intensity and frequency with little attention given to the seasonal precipitation regime (Jackson et al., 2011;Anaya et al., 2012;García-Palacios et al., 2016). More importantly, the current meteorological data have demonstrated that under the multiple effects of altitude, ocean currents, temperature, monsoons and other factors, the seasonal precipitation regime has changed and will continue to change dramatically. ...
... In this study, litter moisture, contents of elements and refractory substances, microbial biomass and enzyme activity were all correlated with litter decomposition rate, which reflected the important influences of the decomposition environment, litter quality and decomposers (García-Palacios et al., 2016). Compared with CK, the correlations between litter moisture, contents of elements and refractory substances and litter decomposition rate were greater under both IE and IP. ...
Changes in the seasonal precipitation regime induced by global climate change may alter moisture and the dynamics of related microbes and enzymes, thereby significantly affecting forest litter decomposition; however, the specific mechanisms remain unclear. Hence, a precipitation manipulation experiment including the treatments of control (CK), decreased precipitation in the dry season with extremely increased precipitation in the wet season (IE) and decreased precipitation in the dry season with proportionally increased precipitation in the wet season (IP) was performed from October 2020 to October 2021 in a subtropical evergreen broad-leaved forest in China. The moisture, chemical properties, microbial biomass, enzyme activity, and decomposition rates of two dominant shrub species foliar litter, Phyllostachys violascens and Alangium chinense, were measured at six stages during the dry and wet seasons. The results showed that both IE and IP significantly increased the litter decomposition rates (more than 2.0% for P. violascens and more than 4.7% for A. chinense, respectively), while the effects of IE were the most significant, which was mainly related to the precipitation availability and the frequency of dry-wet cycle. Furthermore, the IE and IP increased the wet season's contribution to the annual total decomposition regardless of litter species, and more significant effects were also observed in IE. Additionally, the results of structural equation model indicated that the seasonal precipitation regime could regulate the decomposition process directly by changing moisture and the contents of elements and refractory substances, as well as indirectly by influencing the related microbial biomass and enzyme activity. These results deepen the understanding of the biogeochemical cycle in forest ecosystems under the global climate change scenarios.
... After investigating 130 cases, Berg [77] found that the higher the N concentration of fresh litter (and the lower the C:N ratio), the more organic matter left the decomposing litter to become SOM. Litter with a higher N content tends to contain more labile complexes (e.g., phenolic acids and flavonoids) that are usually easily accessed by decomposers [78]. Therefore, due to their higher N content, leguminous leaf litters can boost soil N content faster than other plants [79]. ...
Plant litter decomposition figures importantly in the cycling of C and N pools in terrestrial ecosystems. We investigated how C and N fluxes changed during the decomposition of leguminous and non-leguminous leaf litters, and how these processes responded to different precipitation regimes. We used the dual-isotope tracing method to investigate differences in leaf and soil C and N, along with δ13C and δ15N, in the soil of the Loess Plateau in China. The δ15N and δ13C values were 3604‰ and 56‰ for Robinia pseudoacacia (Leguminosae) and 8115‰ and 452‰ for Populus tomentosa (Salicaceae) leaf litters. Through decomposition, δ13C decreased in all litters, and δ15N in the leguminous litter increased while it decreased in the non-leguminous litter. In the surface soil, the fraction of litter-derived N (14%) from the leguminous litter was significantly higher than that of the non-leguminous litter after 16 months. The C and N concentrations of both litters and soil always had a positive correlation during decomposition, and the responses of N to C changes in soil were reduced by the litter cover. Increased precipitation enhanced the litters’ C and N correlation. The 600 mm precipitation treatment most benefited litter C’s transformation to SOC, and drought conditions promoted the transformation of legume litter N to soil TN, but inhibited non-legume litter N. In the soil and both litters, C and N changes always had a positive correlation. After 16 months, the proportion of soil N from legumes was higher than that from non-legumes. Reduced precipitation could promote leguminous N in soil. Our results provide a scientific basis for accurately predicting the C and N cycles in terrestrial ecosystems.
... It is well acknowledged that litter can provide necessary nutrients for plant development (Loneragan, 1968). The decomposability of litter determines the quality of nutrients available for plant development (Henneron et al., 2017), and the litter layer maintains the stability of the soil environment to a large extent, which is conducive to plant physiological activities (Garcia-Palacios et al., 2016). However, different plants usually have different regeneration strategies and thus produce different degrees of feedback to environmental stress (Cruz et al., 2021;De Lombaerde et al., 2020). ...
Rapid vegetation regeneration and increased litter production have been predicted under the global greening scenario, but the overall relationship between litter production and vegetation regeneration has not been well addressed.
To bridge this knowledge gap, we quantified the responses of the seed stage, seedling stage, plant development stage and vegetation community to litter using 3193 paired observations at the global scale based on the effect size across different categories.
Overall, litter significantly decreased seedling establishment and density by 28.4% and 27.7%, increased plant height by 17.4% and decreased species richness by 15.4%. Seed germination at the seed stage was not directly controlled by litter but was positively regulated by changes in soil moisture from litter. In contrast, litter type and litter mass displayed negative effects on the seedling stage, but litter promoted seedling survival with increasing elevation. Moreover, litter composition and plant type dominated the effects of litter on the plant development stage, showing that the increase in litter production might favour the development of broadleaved trees rather than other plants.
The present results suggest that litter could restrict the stage from seed to seedling but facilitate plant development after the seedling establishment and slightly affect the vegetation community except for species richness. These results provide deep insight into the relationships between litter production and vegetation regeneration at different stages, which are important for developing models accounting for vegetation regeneration responses to ongoing global greening.
Read the free Plain Language Summary for this article on the Journal blog.
... Whereas after the fire, the lower litter layer decomposition increases significantly [18,33,58,62]. Fire changes the microenvironment and then affects the litter decomposition process [39,[63][64][65][66][67]. ...
Fire disturbance can affect the function of the boreal forest ecosystem through litter decomposition and nutrient element return. In this study, we selected the Larix gmelinii forest, a typical forest ecosystem in boreal China, to explore the effect of different years (3 years, 9 years, 28 years) after high burn severity fire disturbance on the decomposition rate (k) of leaf litter and the Carbon:Nitrogen:Phosphorus (C:N:P) stoichiometry characteristics. Our results indicated that compared with the unburned control stands, the k increased by 91–109% within 9 years after fire disturbance, but 28 years after fire disturbance the decomposition rate of the upper litter decreased by 45% compared with the unburned control stands. After fire disturbance, litter decomposition in boreal forests can be promoted in the short term (e.g., 9 years after a fire) and inhibited in the long term (e.g., 28 years after a fire). Changes in litter nutrient elements caused by the effect of fire disturbance on litter decomposition and on the C, N, and C:N of litter were the main litter stoichiometry factors for litter decomposition 28 years after fire disturbance. The findings of this research characterize the long-term dynamic change of litter decomposition in the boreal forest ecosystem, providing data and theoretical support for further exploring the relationship between fire and litter decomposition.
... In addition to the external abiotic conditions, litter quality, including Na, Fe, Mn, protein, lignin, and nitrogen (N) contents, is another important determinant of litter decomposition (Canessa et al. 2020). However, at specific regions or sites, litter decomposition rates are determined by litter quality and soil nutrient status (Aber and Melillo 1980;Melillo et al. 1982;García-Palacios et al. 2016;Pichon et al. 2020). ...
Aims
Litter decomposition is a crucial component of nutrient recycling. Short-term nitrogen (N) deposition has been shown to influence litter decomposition in temperate steppe with significant variability due to differences in atmospheric N deposition, species identity, and experimental duration. Therefore, the effect of N addition, especially long-term, on litter decomposition in alpine grassland still needs further investigation.
Methods
To address these knowledge gaps, we examined the influence of long-term N addition on litter decomposition, taking advantage of a field experiment with five N addition levels (0, 10, 30, 90, and 150 kg N ha⁻¹ yr⁻¹) with a meta-analysis, which has been running for 11 years in an alpine grassland, Northwest China.
Results
Long-term N addition consistently decreased litter decomposition rates, and N negative effect became stronger with the increasing N addition rates. Reduced litter decomposition rates were related to lower soil enzymes activities. Litter decomposition rates were strongly correlated with litter quality, but weakly correlated with soil quality, but which suggested that litter quality and soil quality played important role in regulating litter decomposition. Furthermore, a regional meta-analysis revealed that N addition accelerated litter decomposition when all data were averaged. Although N addition indirectly increased litter decomposition, it had no direct effect on decomposition. However, the direction and degree of the direct effect of N on litter decomposition were regulated by N addition rate, experimental duration and form of N fertilizer.
Conclusions
Overall, these results demonstrated that long-term N addition decreased litter decomposition and N negative effect increased over time.
Litter decomposition plays an important role in the biogeochemical cycling of elements in ecosystems. Plant trait differences especially between invasive and native species lead to changes in litter decomposition rates. The litter decomposition rate is influenced by climatic factors such as seasonal variations, humidity, temperature, and rainfall, where species litter may have different responses. This review aims to better understand how litter decomposes in ecosystems associated with plant invasion and global changes. It also reviews the effects of various factors on litter degradation as well as how quickly invasive litter decomposes and contributes to greenhouse gases (GHGs) emissions. Single species litter or only aboveground litter studies may not sufficiently represent ecosystem dynamics; therefore, the co-determination of above- and belowground litter in a mixture of species diversity is required in different biomes interaction with global change factors. As a result, comprehensive litter degradation studies must be conducted in order to understand the turnover rate of nutrients and other elements in these sensitive ecosystems.
Land-use changes affect terrestrial ecosystem carbon (C), nitrogen (N), and phosphorus (P) dynamics directly by altering above- and belowground litter inputs and decomposition, although the determining factors and their linkage to soil C, N, and P pools remain limited. Here, we investigated litter, soil, and microbial attributes during leaf and fine-root decomposition linked with soil C, N, and P pools under subtropical land-use change (that is, cropland, shrubland, and woodland). We found that leaf litter decomposed faster in shrubland than in woodland and cropland, while the fine root of cropland decomposed more than those of shrubland and woodland. Leaf and fine-root decomposition was not correlated, whereas leaf and fine-root litter quality was positively correlated. Leaf litter decomposition was considerably dependent on litter quality and soil moisture, whereas fine-root decomposition was predominantly predicted by bacterial biomass. Litter C quality in afforested lands (woodland and shrubland) substantially stimulated soil organic C accumulation primarily by the input of new fine-root-derived soil organic C. Soil total N accumulation in woodland was tightly associated with litter quality of fine root and microbial attributes, but soil total P formation in shrubland was strongly correlated with leaf litter quality and microbial attributes. These findings indicated that the variations in decomposition of leaf and fine root were mediated by different combinations of litter, soil, and microbial traits, which caused the difference in the soil C, N, and P accumulation following land-use change. Overall, our results revealed contrasting dynamics of above- and belowground litter decomposition, uncovered diverse influences on soil C, N, and P pools, and provided novel insights into accurately predicting soil C, N, and P dynamics after afforestation.
Background and aims Plant litter decomposition figures importantly in the cycling of C and N pools in terrestrial ecosystems. We investigated how C and N fluxes changed during the decomposition of leaf litters and how those processes respond to different precipitation regimes.
Methods We using dual isotope tracing and in situ decomposition methods, and investigated differences of leaf and soil C, N, δ¹³C and δ¹⁵N in northwest China.
Results δ¹⁵N and δ¹³C were 3604‰ and 56‰ for Robinia pseudoacacia (Leguminosae) and 8115‰ and 452‰ for Populus ningshanica (Salicaceae) leaf litters. Through decomposition, δ¹³C decreased in all litters, and the δ¹⁵N of leguminous increased while non-leguminous litter decreased. In surface soil, the fractions of litter-derived C (20%) and N (14%) from leguminous were higher than non-leguminous litters after 16 months. C and N concentrations of both litters and soil were always coupled during decomposition, and the responses of N to C changes in soil were reduced by litter cover. Increased precipitation enhanced the litters’ C and N coupling. The 600-mm precipitation treatment most benefited litter C transformation to SOC, and drought conditions promoted the transformation of legume litter N to soil TN, but inhibited non-legume litter N.
Conclusions C and N changes are always coupled in soil and litters. After 16 months, the proportion of C and N in soil from legumes was higher than non-legumes. Reduced precipitation can promote legumes N into soil. Our results provide a scientific basis for accurately predicting the C and N cycles in terrestrial ecosystems.
Background
Plant litter decomposition is a key process in carbon and nutrient cycling. Among the factors determining litter decomposition rates, the role of soil biota in the decomposition of different plant litter types and its modification by variations in climatic conditions is not well understood.
Methods
In this study, we used litterbags with different mesh sizes (45 µm, 1 mm and 4 mm) to investigate the effect of microorganisms and decomposer microarthropods on leaf and root litter decomposition along an altitudinal gradient of tropical montane rainforests in Ecuador. We examined decomposition rates, litter C and N concentrations, microbial biomass and activity, as well as decomposer microarthropod abundance over one year of exposure at three different altitudes (1,000, 2,000 and 3,000 m).
Results
Leaf litter mass loss did not differ between the 1,000 and 2,000 m sites, while root litter mass loss decreased with increasing altitude. Changes in microbial biomass and activity paralleled the changes in litter decomposition rates. Access of microarthropods to litterbags only increased root litter mass loss significantly at 3,000 m. The results suggest that the impacts of climatic conditions differentially affect the decomposition of leaf and root litter, and these modifications are modulated by the quality of the local litter material. The findings also highlight litter quality as the dominant force structuring detritivore communities. Overall, the results support the view that microorganisms mostly drive decomposition processes in tropical montane rainforests with soil microarthropods playing a more important role in decomposing low-quality litter material.
Drought restricts the growth of alpine grassland vegetation. This study aimed to explore a new technical system to improve the drought resistance of forage grass. Qinghai cold-land Poa pratensis seedlings were used in the drought stress experiment. A combination of abscisic acid (ABA) and polyacrylamide (PAM) were used to affect the growth, leaf physiology, soil enzyme activity, and rhizosphere microbial diversity of P. pratensis . The fresh leaf weight and root surface area were significantly increased after ABA-PAM combined treatment, while root length was significantly reduced. Besides, the leaf catalase (CAT) and superoxide dismutase (SOD) enzyme activity, proline and chlorophyll content, increased after the treatment, while malondialdehyde (MDA) content decreased. The treatment also increased sucrase, urease, and alkaline protease activities in rhizosphere soil, while decreasing acid phosphatase and neutral phosphatase enzyme activities. ABA-PAM combined treatment enhanced the rhizosphere microbial community and forage drought resistance by altering the abundance of various dominant microorganisms in the rhizosphere soil. The relative abundances of Actinobacteria, Chloroflexi, and Acidobacteria decreased, while Proteobacteria, Firmicutes, and Ascomycota increased. Unlike the relative abundance of Gibberella that decreased significantly, Komagataeibacter, Lactobacillus, Pichia, and Dekkera were significantly increased. Single-factor collinearity network analysis revealed a close relationship between the different rhizosphere microbial communities of forage grass, after ABA-PAM treatment. This study implies that ABA-PAM combined treatment can improve the drought resistance of forages. Therefore, it provides a theoretical and practical basis for restoring drought-induced grassland degradation.
Conceptual frameworks relating plant traits to ecosystem processes such as organic matter dynamics are progressively moving from a leaf‐centred to a whole‐plant perspective. Through the use of meta‐analysis and global literature data, we quantified the relative roles of litters from above‐ and below‐ground plant organs in ecosystem labile organic matter dynamics.
We found that decomposition rates of leaves, fine roots and fine stems were coordinated across species worldwide although less strongly within ecosystems. We also show that fine roots and stems had lower decomposition rates relative to leaves, with large differences between woody and herbaceous species. Further, we estimated that on average below‐ground litter represents approximately 33 and 48% of annual litter inputs in grasslands and forests, respectively.
These results suggest a major role for below‐ground litter as a driver of ecosystem organic matter dynamics. We also suggest that, given that fine stem and fine root litters decompose approximately 1.5 and 2.8 times slower, respectively, than leaf litter derived from the same species, cycling of labile organic matter is likely to be much slower than predicted by data from leaf litter decomposition only.
Synthesis . Our results provide evidence that within ecosystems, the relative inputs of above‐ versus below‐ground litter strongly control the overall quality of the litter entering the decomposition system. This in turn determines soil labile organic matter dynamics and associated nutrient release in the ecosystem, which potentially feeds back to the mineral nutrition of plants and therefore plant trait values and plant community composition.
Plant functional traits are the features (morphological, physiological, phenological) that represent ecological strategies and determine how plants respond to environmental factors, affect other trophic levels and influence ecosystem properties. Variation in plant functional traits, and trait syndromes, has proven useful for tackling many important ecological questions at a range of scales, giving rise to a demand for standardised ways to measure ecologically meaningful plant traits. This line of research has been among the most fruitful avenues for understanding ecological and evolutionary patterns and processes. It also has the potential both to build a predictive set of local, regional and global relationships between plants and environment and to quantify a wide range of natural and human-driven processes, including changes in biodiversity, the impacts of species invasions, alterations in biogeochemical processes and vegetation–atmosphere interactions. The importance of these topics dictates the urgent need for more and better data, and increases the value of standardised protocols for quantifying trait variation of different species, in particular for traits with power to predict plant- and ecosystem-level processes, and for traits that can be measured relatively easily. Updated and expanded from the widely used previous version, this handbook retains the focus on clearly presented, widely applicable, step-by-step recipes, with a minimum of text on theory, and not only includes updated methods for the traits previously covered, but also introduces many new protocols for further traits. This new handbook has a better balance between whole-plant traits, leaf traits, root and stem traits and regenerative traits, and puts particular emphasis on traits important for predicting species’ effects on key ecosystem properties. We hope this new handbook becomes a standard companion in local and global efforts to learn about the responses and impacts of different plant species with respect to environmental changes in the present, past and future.
Standing crop, rates of production, mortality, decomposition, and nitrogen dynamics of two size classes of fine roots (0-05 mm and 0.5-3.0 mm diameter) were estimated for 1 yr in a 53-yr-old red pine (Pinus resinosa Ait.) plantation and in an adjacent 80-yr-old mixed hardwood stand in north-central Massachusetts. Dry matter of live fine roots was higher in the hardwoods (mean = 6.1 Mg/ha; annual range 3.6-8.6 Mg/ha) than in the plantation (mean = 5.1 Mg/ha; annual range 2.5-7.8 Mg/ha.) Dead root mass was similar in the hardwoods (mean = 4.4 Mg/ha) and the plantation (mean = 4.0 Mg/ha). Nitrogen standing crop of live roots in the hardwoods was higher than in the plantation (mean = 65 kg/ha and 42 kg/ha, respectively). Net fine root production was estimated from changes in standing crop. Production estimates ranged from 4.1 to 11.4 Mg@?ha^-^1@?yr^-^1 in the hardwoods and from 3.2 to 10.9 Mg@?ha^-^1@?yr^-^1 in the plantation, depending on the assumptions made in the calculations. Concurrent estimates of total nitrogen requirement for this production ranged from 73 to 184 kg@?ha^-^1@?yr^-^1 in the hardwoods and from 44 to 122 kg@?ha^-^1@?yr^-^1 in the plantation. Decomposition, measured as mass loss from buried cloth bags, was @?20% in 0.4-mm mesh bags and as high as 47% in 3-mm mesh bags after 1 yr. Integrating production and nitrogen requirements with estimates of decomposition rates and nitrogen mineralization for these ecosystems suggested that the lower estimates of production are more accurate.
Why should we study the Mediterranean evergreen forests of holm oak (Quercus ilex L.)? Besides the pursuit of knowledge, two major reasons can be put forward. First, holm oak forests are a dominant type of vegetation in a transition zone between temperate forests, mostly dominated by deciduous trees and the scrublands (maquis, chaparral, phrygana, etc.) that herald the tropical regions. In this transition zone, plants have had to cope with a selective pressure resulting from a double stress - winter cold and summer drought - that has determined their morphological and ecophysiological evolutive responses. One of our aims is to provide an insight into the features of holm oak as related to environmental factors and in comparison with other tree types (broadleaved deciduous hardwoods, needle-leafed conifers).
The timing and magnitude of rainfall events are expected to change in future decades, resulting in longer drought periods and larger rainfall events. Although microbial community composition and function are both sensitive to changes in rainfall, it is unclear whether this is because taxa adopt strategies that maximise fitness under new regimes. We assessed whether bacteria exhibited phylogenetically conserved ecological strategies in response to drying-rewetting, and whether these strategies were altered by historical exposure to experimentally intensified rainfall patterns. By clustering relative abundance patterns, we identified three discrete ecological strategies and found that tolerance to drying-rewetting increased with exposure to intensified rainfall patterns. Changes in strategy were primarily due to changes in community composition, but also to strategy shifts within taxa. These moisture regime-selected ecological strategies may be predictable from disturbance history, and are likely to be linked to traits that influence the functional potential of microbial communities.