Research

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2377 KiB

Open AccessArticle

Water, Rather than Temperature, Dominantly Impacts How Soil Fauna Affect Dissolved Carbon and Nitrogen Release from Fresh Litter during Early Litter Decomposition

by Shu Liao, Xiangyin Ni, Wanqin Yang, Han Li, Bin Wang, Changkun Fu, Zhenfeng Xu, Bo Tan and Fuzhong Wu

Forests 2016, 7(10), 249; https://doi.org/10.3390/f7100249 - 24 Oct 2016

Cited by 17 | Viewed by 4701

Abstract

Longstanding observations suggest that dissolved materials are lost from fresh litter through leaching, but the role of soil fauna in controlling this process has been poorly documented. In this study, a litterbag experiment employing litterbags with different mesh sizes (3 mm to permit [...] Read more.

Longstanding observations suggest that dissolved materials are lost from fresh litter through leaching, but the role of soil fauna in controlling this process has been poorly documented. In this study, a litterbag experiment employing litterbags with different mesh sizes (3 mm to permit soil fauna access and 0.04 mm to exclude fauna access) was conducted in three habitats (arid valley, ecotone and subalpine forest) with changes in climate and vegetation types to evaluate the effects of soil fauna on the concentrations of dissolved organic carbon (DOC) and total dissolved nitrogen (TDN) during the first year of decomposition. The results showed that the individual density and community abundance of soil fauna greatly varied among these habitats, but Prostigmata, Isotomidae and Oribatida were the dominant soil invertebrates. At the end of the experiment, the mass remaining of foliar litter ranged from 58% for shrub litter to 77% for birch litter, and the DOC and TDN concentrations decreased to 54%–85% and increased to 34%–269%, respectively, when soil fauna were not present. The effects of soil fauna on the concentrations of both DOC and TDN in foliar litter were greater in the subalpine forest (wetter but colder) during the winter and in the arid valley (warmer but drier) during the growing season, and this effect was positively correlated with water content. Moreover, the effects of fauna on DOC and TDN concentrations were greater for high-quality litter and were related to the C/N ratio. These results suggest that water, rather than temperature, dominates how fauna affect the release of dissolved substances from fresh litter. Full article

(This article belongs to the Special Issue Decomposition of Forest Litter and Its Links to Carbon Sequestration and Nutrients' Dynamics)

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881 KiB

Open AccessArticle

Early Stage Fine-Root Decomposition and Its Relationship with Root Order and Soil Depth in a Larix gmelinii Plantation

by Tao Sun, Lili Dong, Lili Zhang, Zhijie Wu, Qingkui Wang, Yuanyuan Li, Hongguang Zhang and Zhengwen Wang

Forests 2016, 7(10), 234; https://doi.org/10.3390/f7100234 - 13 Oct 2016

Cited by 29 | Viewed by 4512

Abstract

Characterization of decomposition dynamics of fine roots is essential for understanding vegetation–soil feedbacks and predicting ecosystem responses to future climate scenarios, given their more rapid turnover rates. Using a branch-order classification, we separated the fine root systems of Larix gmelinii into two classes: [...] Read more.

Characterization of decomposition dynamics of fine roots is essential for understanding vegetation–soil feedbacks and predicting ecosystem responses to future climate scenarios, given their more rapid turnover rates. Using a branch-order classification, we separated the fine root systems of Larix gmelinii into two classes: first- and second-order roots combined into one (lower-order); third- and fourth-order roots combined into another (higher-order). In a field experiment, we conducted a litterbag study to investigate fine root decomposition and its relationship with root order class and soil depth over 17 months. Despite their lower C:N ratio and smaller diameter, lower-order roots decomposed more slowly compared with higher-order roots over this period. This pattern also seems to hold true at each different depths (10, 20 and 30 cm) in the soil profile. Our data suggest that the slow decomposition rate of lower-order roots may result from their poor carbon quality. Moreover, we found that the decomposition rates of both lower-order and higher-order roots decreased linearly from 10 cm to 30 cm, which implied that a substantially larger fraction of fine root mass would be stabilized as soil organic carbon in the deeper rather than the upper soil layers. Full article

(This article belongs to the Special Issue Decomposition of Forest Litter and Its Links to Carbon Sequestration and Nutrients' Dynamics)

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1215 KiB

Open AccessArticle

Long-Term (13 Years) Decomposition Rates of Forest Floor Organic Matter on Paired Coniferous and Deciduous Watersheds with Contrasting Temperature Regimes

by Robert G. Qualls

Forests 2016, 7(10), 231; https://doi.org/10.3390/f7100231 - 12 Oct 2016

Cited by 9 | Viewed by 5945

Abstract

Two sets of paired watersheds on north and South facing slopes were utilized to simulate the effects of temperature differences that are on the scale of those expected with near-term climatic warming on decomposition. Two watersheds were pine plantations (Pinus strobus L.) [...] Read more.

Two sets of paired watersheds on north and South facing slopes were utilized to simulate the effects of temperature differences that are on the scale of those expected with near-term climatic warming on decomposition. Two watersheds were pine plantations (Pinus strobus L.) and two were mature deciduous forests established at similar elevation ranges and precipitation at the Coweeta Hydrologic Laboratory, but they differed in slope aspect (north vs. South facing), solar radiation, and litter temperature by about 2.0 °C. Nylon netting was placed on plots each year for 13 years and litterfall was measured. This time span in which decomposition rate was measured encompassed the time until less than 8% of the initial C remained. Decomposition rates of foliar litter were significantly faster on the slightly warmer watersheds, in both the coniferous and deciduous forests (Analysis of Variance). The turnover rate (year⁻¹) was 0.359 (±0.006) for the South facing vs. 0.295 (±0.011) for the North facing coniferous watersheds, and 0.328 (±0.011) vs. 0.297 (±0.012) for the corresponding deciduous watersheds. Turnover rates of pine vs. deciduous broadleaf litter over 13 years were not significantly different because of the high proportion of relatively refractory Quercus spp. in the deciduous litterfall and because of a trend towards convergence of the rates after two years. After a greater decomposition rate in the first year or two, years 2–13 fit a negative exponential curve well (a timespan not well represented in literature) and there was only a small accumulation of humus older than 13 years. The fate of C in litterfall in the South facing deciduous forest was as follows: 14.3% was lost as leaching of dissolved organic C, 2.2% was lost as downward fine particulate matter flux from the bottom of the forest floor, 78.2% was mineralized (by mass balance), leaving only 5.4% of foliar litter after 13 years of decomposition. In these soils with a mor type O horizon, there was evidence that translocation of DOC and in-situ root production must be more important sources of mineral soil organic matter than downward migration of particulate humus. Full article

(This article belongs to the Special Issue Decomposition of Forest Litter and Its Links to Carbon Sequestration and Nutrients' Dynamics)

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3188 KiB

Open AccessArticle

C Stocks in Forest Floor and Mineral Soil of Two Mediterranean Beech Forests

by Anna De Marco, Antonietta Fioretto, Maria Giordano, Michele Innangi, Cristina Menta, Stefania Papa and Amalia Virzo De Santo

Forests 2016, 7(8), 181; https://doi.org/10.3390/f7080181 - 22 Aug 2016

Cited by 26 | Viewed by 5396

Abstract

This study focuses on two Mediterranean beech forests located in northern and southern Italy and therefore subjected to different environmental conditions. The research goal was to understand C storage in the forest floor and mineral soil and the major determinants. Relative to the [...] Read more.

This study focuses on two Mediterranean beech forests located in northern and southern Italy and therefore subjected to different environmental conditions. The research goal was to understand C storage in the forest floor and mineral soil and the major determinants. Relative to the northern forest (NF), the southern forest (SF) was found to produce higher amounts of litterfall (4.3 vs. 2.5 Mg·ha⁻¹) and to store less C in the forest floor (~8 vs. ~12 Mg·ha⁻¹) but more C in the mineral soil (~148 vs. ~72 Mg·ha⁻¹). Newly-shed litter of NF had lower P (0.4 vs. 0.6 mg·g⁻¹) but higher N concentration (13 vs. 10 mg·g⁻¹) than SF. Despite its lower Mn concentration (0.06 vs. 0.18 mg·g⁻¹), SF litter produces a Mn-richer humus (0.32 vs. 0.16 mg·g⁻¹) that is less stable. The data suggest that decomposition in the NF forest floor is limited by the shorter growing season (178 days vs. 238 days) and the higher N concentrations in newly shed litter and forest floor. Differences in C stock in the mineral soil reflect differences in ecosystem productivity and long-term organic-matter accumulation. The vertical gradient of soluble and microbial fractions in the soil profile of SF was consistent with a faster turnover of organic matter in the forest floor and greater C accumulation in mineral soil relative to NF. With reference to regional-scale estimates from Italian National Forest Inventory data, the C stock in the mineral soil and the basal area of Italian beech forests were found to be significantly related, whereas C stock in the forest floor and C stock in the mineral soil were not. Full article

(This article belongs to the Special Issue Decomposition of Forest Litter and Its Links to Carbon Sequestration and Nutrients' Dynamics)

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1827 KiB

Open AccessArticle

Cellulose Dynamics during Foliar Litter Decomposition in an Alpine Forest Meta-Ecosystem

by Kai Yue, Fuzhong Wu, Wanqin Yang, Chuan Zhang, Yan Peng, Bo Tan, Zhenfeng Xu and Chunping Huang

Forests 2016, 7(8), 176; https://doi.org/10.3390/f7080176 - 19 Aug 2016

Cited by 18 | Viewed by 5428

Abstract

To investigate the dynamics and relative drivers of cellulose degradation during litter decomposition, a field experiment was conducted in three individual ecosystems (i.e., forest floor, stream, and riparian zone) of an alpine forest meta-ecosystem on the eastern Tibetan Plateau. Four litter species (i.e., [...] Read more.

To investigate the dynamics and relative drivers of cellulose degradation during litter decomposition, a field experiment was conducted in three individual ecosystems (i.e., forest floor, stream, and riparian zone) of an alpine forest meta-ecosystem on the eastern Tibetan Plateau. Four litter species (i.e., willow: Salix paraplesia, azalea: Rhododendron lapponicum, cypress: Sabina saltuaria, and larch: Larix mastersiana) that had varying initial litter chemical traits were placed separately in litterbags and then incubated on the soil surface of forest floor plots or in the water of the stream and riparian zone plots. Litterbags were retrieved five times each year during the two-year experiment, with nine replicates each time for each treatment. The results suggested that foliar litter lost 32.2%–89.2% of the initial dry mass depending on litter species and ecosystem type after two-year’s incubation. The cellulose lost 60.1%–96.8% of the initial mass with degradation rate in the order of stream > riparian zone > forest floor. Substantial cellulose degradation occurred at the very beginning (i.e., in the first pre-freezing period) of litter decomposition. Litter initial concentrations of phosphorus (P) and lignin were found to be the dominant chemical traits controlling cellulose degradation regardless of ecosystems type. The local-scale environmental factors such as temperature, pH, and nutrient availability were important moderators of cellulose degradation rate. Although the effects of common litter chemical traits (e.g., P and lignin concentrations) on cellulose degradation across different individual ecosystems were identified, local-scale environmental factors such as temperature and nutrient availability were found to be of great importance for cellulose degradation. These results indicated that local-scale environmental factors should be considered apart from litter quality for generating a reliable predictive framework for the drivers of cellulose degradation and further on litter decomposition at a global scale. Full article

(This article belongs to the Special Issue Decomposition of Forest Litter and Its Links to Carbon Sequestration and Nutrients' Dynamics)

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1649 KiB

Open AccessArticle

Physical, Chemical, and Biological Properties of Soil under Decaying Wood in a Tropical Wet Forest in Puerto Rico

by Marcela Zalamea, Grizelle González and Deborah Jean Lodge

Forests 2016, 7(8), 168; https://doi.org/10.3390/f7080168 - 04 Aug 2016

Cited by 28 | Viewed by 7765

Abstract

Decaying wood is related to nutrient cycling through its role as either a sink or source of nutrients. However, at micro scales, what is the effect of decaying logs on the physical, chemical, and biotic characteristics of the soil underneath? We took samples [...] Read more.

Decaying wood is related to nutrient cycling through its role as either a sink or source of nutrients. However, at micro scales, what is the effect of decaying logs on the physical, chemical, and biotic characteristics of the soil underneath? We took samples from a 0 to 5 cm depth under and a 50 cm distance away from decaying logs (Dacryodes excelsa and Swietenia macrophylla) at 2 stages of decay, and measured soil temperature, total and available nutrients, and root length in a tropical wet forest. We found decaying wood affected physical, chemical, and biotic properties of the underlying soil. Soil temperature was less variable under the decaying logs than away from the logs. Soil under the decaying wood had fewer roots, and lower NO₃⁻ and Mg²⁺ availability than samples collected a distance of 50 cm away from the logs. Tree species and decay stage were important factors defining the effect of decaying wood on the distribution of available nutrients. Ca²⁺, Mg²⁺, and K⁺ levels were higher in the soil associated with the youngest logs, and were higher near S. macrophylla logs. Heavy metals were also higher in the soil located near the younger logs independent of the species; other metal ions such as Al³⁺ and Fe³⁺ were higher in the soil associated with D. excelsa and the oldest logs. These results indicate decaying wood can contribute to and generate spatial heterogeneity of soil properties. Full article

(This article belongs to the Special Issue Decomposition of Forest Litter and Its Links to Carbon Sequestration and Nutrients' Dynamics)

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1301 KiB

Open AccessArticle

Towards Harmonizing Leaf Litter Decomposition Studies Using Standard Tea Bags—A Field Study and Model Application

by Markus Didion, Anna Repo, Jari Liski, Martin Forsius, Michael Bierbaumer and Ika Djukic

Forests 2016, 7(8), 167; https://doi.org/10.3390/f7080167 - 01 Aug 2016

Cited by 53 | Viewed by 9099

Abstract

Decomposition of plant litter is a key process for the transfer of carbon and nutrients in ecosystems. Carbon contained in the decaying biomass is released to the atmosphere as respired CO₂, and may contribute to global warming. Litterbag studies have been [...] Read more.

Decomposition of plant litter is a key process for the transfer of carbon and nutrients in ecosystems. Carbon contained in the decaying biomass is released to the atmosphere as respired CO₂, and may contribute to global warming. Litterbag studies have been used to improve our knowledge of the drivers of litter decomposition, but they lack comparability because litter quality is plant species-specific. The use of commercial tea bags as a standard substrate was suggested in order to harmonize studies, where green tea and rooibos represent more labile and more recalcitrant C compounds as surrogates of local litter. Here we examine the potential of the use of standardized material for improving our understanding of litter decomposition across climate regions, and to further develop pertinent models. We measured the decomposition of incubated local and standard litters over two years along an elevation gradient in the Austrian Limestone Alps. The similar response to changes in temperature and precipitation of the pairs of local and standard litter—i.e., Fagus sylvatica and green tea, and Pinus nigra and rooibos tea, respectively—suggests the suitability of the standard litters for further examining the role of environmental drivers of decomposition. Harmonized data obtained from standardized litter experiments would provide a key prerequisite for further developing simulation models for the estimation of the C balance of ecosystem litter pools. Full article

(This article belongs to the Special Issue Decomposition of Forest Litter and Its Links to Carbon Sequestration and Nutrients' Dynamics)

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Review

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6522 KiB

Open AccessReview

From Litter to Humus in a Norwegian Spruce Forest: Long-Term Studies on the Decomposition of Needles and Cones

by Sigmund Hågvar

Forests 2016, 7(9), 186; https://doi.org/10.3390/f7090186 - 25 Aug 2016

Cited by 9 | Viewed by 5734

Abstract

The aim of this review and synthesis is to illustrate the gradual transformation of needles and cones from litter to humus. Individual needles may follow quite different decomposition pathways, which contributes to a diverse humus structure. In the litter layer (Oi), about 40% [...] Read more.

The aim of this review and synthesis is to illustrate the gradual transformation of needles and cones from litter to humus. Individual needles may follow quite different decomposition pathways, which contributes to a diverse humus structure. In the litter layer (Oi), about 40% of the needles were excavated by special mites that produced slowly decomposable excrements. In the fermentation layer (Oe), needles which happened to be in close contact with fine roots decomposed more rapidly. Cones decomposed slower than needles during the first 3–5 years, so the role of cones in carbon (C) storage may be greater than indicated by their fraction of fresh litter. Over a 13 years period, potassium (K), magnesium (Mg) and phosphorus (P) in cones was released, while the total amount of calcium (Ca), manganese (Mn), iron (Fe) and aluminium (Al) increased strongly. Nitrogen concentration increased but the total nitrogen content remained rather constant. After 13 years, the cones had sunk about 6 cm into the soil and lost 60% of their dry weight but were morphologically intact. A cone monitored for 28 years was fully recognizable and had not yet reached the stable Oa layer. The most inert decomposition products in the Oa layer were fragments of needles and cone scales, microarthropod excrements and chitinous insect remains. Full article

(This article belongs to the Special Issue Decomposition of Forest Litter and Its Links to Carbon Sequestration and Nutrients' Dynamics)

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