Forests

Research

Jump to: Review

22 pages, 7910 KiB

Open AccessArticle

The Impact of Permafrost Change on Soil Organic Carbon Stocks in Northeast China

by Yang Song, Shuai Huang, Haiying Zhang, Qin Wang, Lin Ding and Yanjie Liu

Forests 2024, 15(1), 14; https://doi.org/10.3390/f15010014 - 20 Dec 2023

Viewed by 1139

Abstract

Climate warming has resulted in significant changes in permafrost in Northeast China, leading to notable alterations in soil organic carbon (SOC) stocks. These changes are crucial for both the global carbon cycle and climate change, as well as directly impacting the sustainable development [...] Read more.

Climate warming has resulted in significant changes in permafrost in Northeast China, leading to notable alterations in soil organic carbon (SOC) stocks. These changes are crucial for both the global carbon cycle and climate change, as well as directly impacting the sustainable development of ecosystems. In order to examine the SOC dynamics and the impact of permafrost changes on SOC, we investigate the changes of permafrost extent based on a regression model and TTOP (top temperature of permafrost) model and the relationship between land use and land cover (LULC), SOC stocks, and permafrost changes in Northeast China. The results showing a shrinking permafrost area from 37.43 × 10⁴ km² to 16.48 × 10⁴ km² during the period from the 1980s to the 2010s in Northeast China, and the SOC stock decreased by 24.18 Tg C from the 1980s to the 1990s and then rapidly increased by 102.84 Tg C in the 2000s. Permafrost degradation speeds up the succession of LULC, impacting about 90% of the SOC in permafrost regions. The relationship between permafrost changes and SOC in Northeast China shows that permafrost degradation significantly reduces SOC stocks in the short term but increases SOC stocks in the long term, and that LULC play a crucial role in regulating this relationship. The goals of this study are to acquire an understanding of permafrost status and deepening insights into the dynamics of SOC. Simultaneously, the study aims to furnish valuable scientific references for sha** policies on sustainable land use and management in the future, all the while advancing the cause of ecological equilibrium and sustainable development in Northeast China and other areas. Full article

(This article belongs to the Special Issue Responses of Soil Carbon and Nitrogen Dynamics and GHG Fluxes in Forest Ecosystems to Climate Change and Human Activity)

► Show Figures

Figure 1

14 pages, 2608 KiB

Open AccessArticle

The Different Factors Driving SOC Stability under Different N Addition Durations in a Phyllostachys edulis Forest

by Yue Wu, Quanxin Zeng, **anchu Su, Wei Zheng, Qiufang Zhang and Yuehmin Chen

Forests 2023, 14(9), 1890; https://doi.org/10.3390/f14091890 - 17 Sep 2023

Cited by 1 | Viewed by 1288

Abstract

As one of the most widespread driving forces in the world, atmospheric nitrogen (N) deposition can significantly alter the carbon cycling of ecosystems. In order to understand how N deposition regulates soil organic carbon (SOC) dynamics and its underlying mechanisms, a 7-year N [...] Read more.

As one of the most widespread driving forces in the world, atmospheric nitrogen (N) deposition can significantly alter the carbon cycling of ecosystems. In order to understand how N deposition regulates soil organic carbon (SOC) dynamics and its underlying mechanisms, a 7-year N addition experiment was set in a Phyllostachys edulis forest with three N addition levels (+0, +20, and +80 kg N hm⁻² year⁻¹) to evaluate the effects of N addition on the concentration and stability of SOC fractions in the third, fifth, and seventh years. The results are as follows: (1) short-term (third year) N addition markedly increased SOC stability by decreasing the concentration of particulate organic carbon (POC) and increasing the mineral-associated organic carbon (MAOC); longer duration of N addition (5 and 7 years) had an insignificant effect on SOC stability and fractions, suggesting that the effects of N deposition on the SOC stability varied under different duration regimes; (2) N addition did not significantly affect microbial community composition while increasing the ratio of fungi to bacteria (F:B) in the seventh year, and microbial biomass carbon (MBC) and carbon use efficiency (CUE) were significantly increased in the short-term (third year) high N addition regime and enzyme activity was significantly increased in the seventh years’ high N addition regime; (3) variation partitioning analysis and multiple regression analysis showed that SOC fractions are mainly regulated by CUE and MBC under short-term N addition, while enzyme activity was mainly regulated under the longer duration of N addition. Our results show that SOC stability was more sensitive in the short term, and the role of microbial characteristics varied under different N addition durations in the P. edulis forests. Overall, our findings provide a new perspective for the responses of the SOC pool to N deposition and contribute to predicting SOC dynamics in terrestrial ecosystems under future climate change. Full article

(This article belongs to the Special Issue Responses of Soil Carbon and Nitrogen Dynamics and GHG Fluxes in Forest Ecosystems to Climate Change and Human Activity)

► Show Figures

Figure 1

19 pages, 4286 KiB

Open AccessArticle

Effect of In Situ Large Soil Column Translocation on CO₂ and CH₄ Fluxes under Two Temperate Forests of Northeastern China

by **ngkai Xu, Tingting Xu and ** Yue

Forests 2023, 14(8), 1531; https://doi.org/10.3390/f14081531 - 27 Jul 2023

Viewed by 1050

Abstract

Global warming has a significant impact on soil carbon dioxide (CO₂) and methane (CH₄) fluxes in temperate forests. However, due to a lack of field observations, limited information is available about the responses of soil CO₂ and CH [...] Read more.

Global warming has a significant impact on soil carbon dioxide (CO₂) and methane (CH₄) fluxes in temperate forests. However, due to a lack of field observations, limited information is available about the responses of soil CO₂ and CH₄ fluxes to changes in temperature during the non-growing season and throughout the year in temperate forests. The broadleaf and Korean pine mixed mature forest (MF) and adjacent secondary white birch forest (BF) at different succession stages in the Changbai mountain region in northeastern China were selected, to study the effect of in situ soil column translocation on CO₂ and CH₄ fluxes in temperate forests. On average, the air temperature and soil temperature at 5 cm depth under BF stands from October 2018 to October 2022 increased by 0.64 and 0.42 °C during the non-growing season and by 0.49 and 0.43 °C throughout the year, respectively, compared with those under MF stands. Based on multi-year measurements in field experiments, it was shown that during the non-growing season, fluxes of CO₂ and CH₄ from soil columns under MF and BF stands ranged from 0.004 to 1.175 and from 0.015 to 1.401 (averages of 0.321 and 0.387) μmol CO₂ m⁻² s⁻¹, and from −1.003 to 0.048 and from −1.037 to −0.013 (averages of −0.179 and −0.250) nmol CH₄ m⁻² s⁻¹, respectively, accounting for approximately 20.8% and 25.3%, and 48.8% and 69.1% of the corresponding average fluxes during the growing season. When undisturbed soil columns of MF were transferred to a BF stand, to simulate warming, the cumulative soil CO₂ emissions and CH₄ uptake increased by 23.5% and 15.3% during the non-growing season, and by 9.5% and 16.3% across the year, respectively. However, when soil columns of BF were transferred to a MF stand, to simulate cooling, the cumulative soil CO₂ emissions decreased by 16.9% and 0.1% during the non-growing season and across the year, respectively. Upon cooling, the cumulative soil CH₄ uptake decreased by 21.8% during the non-growing season but increased by 15.4% across the year. The soil temperature and moisture at 5 cm depth in soil columns could explain 84–86% of the variability in CO₂ fluxes and 16–51% of the variability in CH4 fluxes under the two forest stands throughout the field measurement period. The results of the in situ soil column translocation experiments highlight that a small climate warming in nature can increase soil CO₂ emissions and CH₄ uptake in the temperate forests of northeastern China, particularly during the non-growing season, which should be considered when predicting soil C fluxes in the temperate forests of northeastern China under global warming scenarios. Full article

(This article belongs to the Special Issue Responses of Soil Carbon and Nitrogen Dynamics and GHG Fluxes in Forest Ecosystems to Climate Change and Human Activity)

► Show Figures

Figure 1

21 pages, 3473 KiB

Open AccessArticle

Effects of Snow Cover on Carbon Dioxide Emissions and Their δ¹³C Values of Temperate Forest Soils with and without Litter

by **ngkai Xu, Haohao Wu, ** Yue, Shuirong Tang and Weiguo Cheng

Forests 2023, 14(7), 1384; https://doi.org/10.3390/f14071384 - 6 Jul 2023

Cited by 1 | Viewed by 1289

Abstract

The presence of litter and winter snow cover can affect the decomposition of organic matter in forest soils and changes in δ¹³C values of soil-respired carbon dioxide (CO₂). However, limited information is available on the responses of CO₂ [...] Read more.

The presence of litter and winter snow cover can affect the decomposition of organic matter in forest soils and changes in δ¹³C values of soil-respired carbon dioxide (CO₂). However, limited information is available on the responses of CO₂ emissions from forest soils and their δ¹³C values to snow cover and litter addition over the year. We experimentally manipulated snow cover to study the impacts of light and heavy artificial snow cover on soil heterotrophic respiration and its δ¹³C values, using undisturbed large soil columns collected from two typical temperate forests in Northeastern China. Based on the average temperatures of surface forest soils in four seasons of the year in this study region, the simulations of autumn freeze–thaw, winter freeze, spring freeze–thaw, and the growing season were sequentially carried out under laboratory conditions. A set of novel analysis systems, including automated chamber equipment and laser spectroscopy analysis with high-frequency measurements for CO₂ concentrations and the ¹³C/¹²C isotopic ratios in CO₂, was used to study the effects of artificial snow cover and the presence of litter on soil heterotrophic respiration and its δ¹³C values. During the autumn freeze–thaw simulation, there were larger CO₂ emissions and less negative δ¹³C values of soil-respired CO₂ upon heavy snow cover than upon light snow cover, indicating that the presence of increased snow cover prior to winter freeze can increase the decomposition of organic C in subsurface soils under temperate forests. The δ¹³C values of soil-respired CO₂ in all treatments were, on average, less negative as the simulated spring freeze–thaw proceeded, which was contrary to the variations of the δ¹³C during the autumn freeze–thaw simulation. Soil heterotrophic respiration and its δ¹³C values during the spring freeze–thaw simulation were, on average smaller upon heavy snow cover than upon light snow cover, which differed from those during the autumn freeze–thaw and growing season simulations, respectively. Taken together, the results highlight that the effects of snow cover on soil heterotrophic respiration and its δ¹³C values under temperate forests may vary with different seasons of the year and the presence of litter. Full article

(This article belongs to the Special Issue Responses of Soil Carbon and Nitrogen Dynamics and GHG Fluxes in Forest Ecosystems to Climate Change and Human Activity)

► Show Figures

Figure 1

15 pages, 3588 KiB

Open AccessArticle

Effects of Nitrogen Deposition on Leaf Litter Decomposition and Soil Organic Carbon Density in Arid and Barren Rocky Mountainous Regions: A Case Study of Yimeng Mountain

by Baishu Kong, Jilei Zhou, Liguo Qi, Shuying Jiao, Lujie Ma, Wenwen Geng, Yuhao Zhao, Ting Gao, Jie Gong, Kun Li and Chuanrong Li

Forests 2023, 14(7), 1351; https://doi.org/10.3390/f14071351 - 30 Jun 2023

Cited by 1 | Viewed by 1039

Abstract

The ecological impact of nitrogen (N) deposition has gained significance since the advent of the industrial revolution. Although numerous studies have examined the impact of N deposition on soil organic carbon (SOC), certain arid and barren rocky mountainous regions, which experience more pronounced [...] Read more.

The ecological impact of nitrogen (N) deposition has gained significance since the advent of the industrial revolution. Although numerous studies have examined the impact of N deposition on soil organic carbon (SOC), certain arid and barren rocky mountainous regions, which experience more pronounced N limitations, have been overlooked. This study was conducted in the Yimeng Mountains, examining eight treatments created by four N addition levels (0 kg N ha⁻¹ yr⁻¹, 50 kg N ha⁻¹ yr⁻¹, 100 kg N ha⁻¹ yr⁻¹ and 200 kg N ha⁻¹ yr⁻¹) and two tree species (Quercus acutissima Carruth. and Pinus thunbergii Parl.). The research revealed variations in the effect of N addition on leaf litter decomposition and SOC density (SOCD) between different tree species. Notably, N addition stimulated the decomposition of leaf litter from Quercus acutissima Carruth. However, the decomposition of Pinus thunbergii Parl. leaf litter was enhanced at N addition levels below 100 kg N ha⁻¹ yr⁻¹, while it was hindered at levels exceeding 100 kg N ha⁻¹ yr⁻¹. In the Quercus acutissima Carruth. forest, the N addition levels of 50 kg N ha⁻¹ yr⁻¹, 100 kg N ha⁻¹ yr⁻¹ and 200 kg N ha⁻¹ yr⁻¹ resulted in decreases in SOCD by 10.57%, 22.22% and 13.66%, respectively, compared to 0 kg N ha⁻¹ yr⁻¹. In the Pinus thunbergii Parl. forest, the N addition levels of 50 kg N ha⁻¹ yr⁻¹, 100 kg N hm⁻² ha⁻¹ and 200 kg N ha⁻¹ yr⁻¹ led to increases in SOCD by 49.53%, 43.36% and 60.87%, respectively, compared to 0 kg N ha⁻¹ yr⁻¹. Overall, N addition decreases the SOCD of Quercus acutissima Carruth., but it increases the SOCD of Pinus thunbergii Parl., attributed to the alteration in soil enzyme stoichiometry and nutrient cycling by N addition. This study fills a theoretical gap concerning leaf litter decomposition and SOC sequestration in arid and barren rocky mountainous regions under global climate change. Full article

(This article belongs to the Special Issue Responses of Soil Carbon and Nitrogen Dynamics and GHG Fluxes in Forest Ecosystems to Climate Change and Human Activity)

► Show Figures

Figure 1

10 pages, 2891 KiB

Open AccessArticle

Seasonal Dynamics of Soil Enzymatic Activity under Different Land-Use Types in Rocky Mountainous Region of North China

by Yuhua Kong, Anran Qu, Erpeng Feng, Rui Chen, **tian Yang and Yong Lai

Forests 2023, 14(3), 536; https://doi.org/10.3390/f14030536 - 9 Mar 2023

Cited by 3 | Viewed by 1534

Abstract

To reveal the effects of different land-use types on soil enzyme activities, soil samples were collected from 0–10, 10–20 and 20–30 cm soil layers to compare and analyze soil β-glucosidase (BG), urease (URE), protease (PROT) and catalase (CAT) activities in farmland (FL), abandoned [...] Read more.

To reveal the effects of different land-use types on soil enzyme activities, soil samples were collected from 0–10, 10–20 and 20–30 cm soil layers to compare and analyze soil β-glucosidase (BG), urease (URE), protease (PROT) and catalase (CAT) activities in farmland (FL), abandoned land (AL) and three plantation forests: Platycladus orientalis (L.) Franco (PO), Robinia pseudoacacia L. (RP) and Quercus variabilis Bl. (QV) in the rocky mountainous region of North China. The results showed that the soil enzyme activities varied significantly under different land-use types, and the interannual mean values of FL and PO were remarkably higher than those of other land uses in the 0–30 cm soil layer, in which the soil BG and URE activities of FL were 22% and 12% higher than those of AL, and 428% and 179% higher than those of QV, respectively; the soil PROT and CAT activities of PO were 66% and 23% higher than those of AL, and 479% and 113% higher than those of QV, respectively. Soil BG, URE and PROT activities were all higher in June and lower in December, while soil CAT activity was slightly lower in June. The soil enzymatic activities all showed a notable decrease with the depth of the soil layer. Soil BG, URE, PROT and CAT activities were remarkably (p < 0.01) or significantly (p < 0.05) positively correlated with available nitrogen, available phosphorus, available potassium, dissolved organic carbon (DOC), NO₃⁻-N, soil organic carbon, water content, clay and silt volume fraction, and significantly negatively correlated with sand volume fraction. Soil DOC and pH were important factors influencing soil enzymatic activity, implying that changes in soil enzymatic activity under different land-use types may be the result of a combination of temperature, moisture and plant type. In conclusion, PO plantations are conducive to improving the physicochemical and biological properties of soil and enhance soil fertility, which is a reasonable land-use method to achieve sustainable development in the rocky mountainous region of North China. Full article

(This article belongs to the Special Issue Responses of Soil Carbon and Nitrogen Dynamics and GHG Fluxes in Forest Ecosystems to Climate Change and Human Activity)

► Show Figures

Figure 1

15 pages, 6089 KiB

Open AccessArticle

Distribution Characteristics of Active Soil Substances along Elevation Gradients in the Southern of Taihang Mountain, China

by Erpeng Feng, Liwei Zhang, Yuhua Kong, **ngkai Xu, Ting Wang and Caifeng Wang

Forests 2023, 14(2), 370; https://doi.org/10.3390/f14020370 - 12 Feb 2023

Cited by 2 | Viewed by 1316

Abstract

Active soil substances, which can indicate environmental changes sensitively, have the fastest turnover rate. Vegetation diversity and soil bio-physicochemical properties according to five elevations classes (800 m, 1000 m, 1100 m, 1200 m, and 1500 m a.s.l.) in the Southern Taihang Mountain were [...] Read more.

Active soil substances, which can indicate environmental changes sensitively, have the fastest turnover rate. Vegetation diversity and soil bio-physicochemical properties according to five elevations classes (800 m, 1000 m, 1100 m, 1200 m, and 1500 m a.s.l.) in the Southern Taihang Mountain were investigated. Soil ammonium-N (NH₄⁺—N), nitrate-N (NO₃⁻—N), microbial biomass carbon (MBC), and nitrogen (MBN), as well as soil urease (URE) and sucrose (SUC) activities were determined. The results showed that elevation gradients, soil layers, and their interaction had significant effects on most of the active soil substances. With the rise of elevation, soil NO₃⁻—N, inorganic N, MBC, and MBN contents, as well as SUC activity and SUC/MBC ratio basically showed an inverted V-shaped distribution trend and reached the peak value at 1100 m (p < 0.05). Soil URE showed a fluctuating upward trend and reached the peak value at 1500 m (p < 0.05), and the URE/MBC ratio showed a straight upward trend. With the depth of soil layer, the contents of active soil substances tended to decrease, showing a phenomenon of surface aggregation. Active soil substances were correlated with plant community diversity indexes, soil water content, pH, available N, and available phosphorus contents, and available N was the main factor affecting active soil substances, which could explain 34.4% of the variation. In summary, at the intermediate slope of 1100 m, soil moisture and tightness were suitable for soil microbial activity and plant growth, the highest contents of active soil substances, indicating a fast turnover of soil carbon and nitrogen. The present study enriched our understanding of soil carbon and nitrogen turnover mechanisms in the mountain ecosystem. Full article

(This article belongs to the Special Issue Responses of Soil Carbon and Nitrogen Dynamics and GHG Fluxes in Forest Ecosystems to Climate Change and Human Activity)

► Show Figures

Figure 1

19 pages, 4436 KiB

Open AccessArticle

Biochar-Based Fertilizer Decreased Soil N₂O Emission and Increased Soil CH₄ Uptake in a Subtropical Typical Bamboo Plantation

by Enhui Wang, Ning Yuan, Shaofeng Lv, ** Tang, Gang Wang, Linlin Wu, Yufeng Zhou, Guomo Zhou, Yongjun Shi and Lin Xu

Forests 2022, 13(12), 2181; https://doi.org/10.3390/f13122181 - 19 Dec 2022

Cited by 2 | Viewed by 1592

Abstract

Soil is a crucial contributor to greenhouse gas (GHG) emissions from terrestrial ecosystems to the atmosphere. The reduction of GHG emissions in plantation management is crucial to combating and mitigating global climate change. A 12-month field trial was conducted to explore the effects [...] Read more.

Soil is a crucial contributor to greenhouse gas (GHG) emissions from terrestrial ecosystems to the atmosphere. The reduction of GHG emissions in plantation management is crucial to combating and mitigating global climate change. A 12-month field trial was conducted to explore the effects of different fertilization treatments (control, without fertilizer (CK); biochar-based fertilizer treatment (BFT); chemical fertilizer treatment (CFT); and mixture of 50% BFT and 50% CFT (MFT)) on the soil GHG emissions of a typical bamboo (Pleioblastus amarus (Keng) Keng f.) plantation. The results demonstrated that compared with the CK, BFT reduced the annual cumulative soil N₂O emission by 16.3% (p < 0.01), while CFT and MFT significantly increased it by 31.0% and 23.3% (p < 0.01), respectively. Meanwhile, BFT and MFT increased the annual cumulative soil CH₄ uptake by 5.8% (p < 0.01) and 7.5% (p < 0.01), respectively, while there was no statistically significant difference between CFT and the control. In addition, BFT, CFT, and MFT significantly increased the annual cumulative soil CO₂ emission by 9.4% (p < 0.05), 13.0% (p < 0.01), and 26.5% (p < 0.01). The global warming potential (GWP) of BFT did not change significantly, while CFT and MFT increased the GWP by 13.7% (p < 0.05) and 28.6% (p < 0.05), respectively, compared with the control. Structural equation modeling revealed different treatments affected soil N₂O and CH₄ emission by changing soil labile carbon and labile nitrogen pools. This study suggests utilizing BFT new ideas and strategies for mitigating GHG emissions from soils in subtropical Pleioblastus amarus plantations. Full article

(This article belongs to the Special Issue Responses of Soil Carbon and Nitrogen Dynamics and GHG Fluxes in Forest Ecosystems to Climate Change and Human Activity)

► Show Figures

Figure 1

16 pages, 3259 KiB

Open AccessArticle

Effects of Nitrogen and Phosphorus Additions on Soil N₂O Emissions and CH₄ Uptake in a Phosphorus-Limited Subtropical Chinese Fir Plantation

by Binjie Li, Guangsheng Chen, **aochen Lu and Hongbo Jiao

Forests 2022, 13(5), 772; https://doi.org/10.3390/f13050772 - 17 May 2022

Cited by 4 | Viewed by 2486

Abstract

Increased nitrogen (N) inputs in subtropical forest ecosystems were widely reported. Extra N additions were reported to cause nutrient imbalance and phosphorus (P) limitation in many tropical and subtropical forests, and further result in changes in soil nitrous oxide (N₂O) and [...] Read more.

Increased nitrogen (N) inputs in subtropical forest ecosystems were widely reported. Extra N additions were reported to cause nutrient imbalance and phosphorus (P) limitation in many tropical and subtropical forests, and further result in changes in soil nitrous oxide (N₂O) and methane (CH₄) fluxes. Here, we conducted experiments with N (high N addition: 15 g N/m², HN), P (low: 5 g P/m², LP; high: 15 g P/m², HP) and their interactive (HNLP and HNHP) treatments to investigate how N and P additions affected CH₄ and N₂O exchanges in an N-rich Chinese fir plantation (Cunninghamia lanceolata), and further explored the underlying mechanisms through the structural equation model (SEM) analysis. The results indicated that N addition alone (HN) significantly (p < 0.05) increased the soil N₂O emissions by 30.15% and 80.47% over annual and 4-month periods, mainly owing to the elevated NH₄⁺-N content. P addition alone (LP and HP) did not significantly affect the soil N₂O emissions as compared with the control. The SEM analysis indicated that increased N₂O emissions under N addition were primarily explained by the increase in available N and contributed more to the stimulated NH₄⁺-N contents. N and P interactive additions slightly (not significant) stimulated the N₂O emissions as compared with that under the N addition alone treatment. High-dose P addition significantly increased the soil CH₄ uptake by 15.80% and 16.23% under the HP and HNHP treatments, respectively, while N addition alone and low P addition (LP and HNLP) did not significantly affect CH₄ uptake as compared with the control. The increased water-soluble organic carbon and microbial biomass carbon explained the increased CH₄ uptake under high P addition. The fertilization effects on N₂O emissions and CH₄ uptake mainly occurred in the first 4 months and diminished after that. Our results suggested that the direction, magnitude and timing of the N and P addition effects on N₂O emissions and CH₄ uptake would depend on the soil nutrient status and plant–microbial competition for N and P in subtropical forests. Full article

(This article belongs to the Special Issue Responses of Soil Carbon and Nitrogen Dynamics and GHG Fluxes in Forest Ecosystems to Climate Change and Human Activity)

► Show Figures

Figure 1

Review

Jump to: Research

20 pages, 3257 KiB

Open AccessReview

Effect of Changes in Throughfall on Soil Respiration in Global Forest Ecosystems: A Meta-Analysis

by **ngkai Xu

Forests 2023, 14(5), 1037; https://doi.org/10.3390/f14051037 - 17 May 2023

Cited by 2 | Viewed by 1555

Abstract

To date, there has been limited knowledge about how soil carbon dioxide (CO₂) emissions from forest ecosystems at a global scale respond to the altered precipitation, and the key influencing mechanisms involved. Thirty-seven studies conducted under throughfall manipulation conditions in forest [...] Read more.

To date, there has been limited knowledge about how soil carbon dioxide (CO₂) emissions from forest ecosystems at a global scale respond to the altered precipitation, and the key influencing mechanisms involved. Thirty-seven studies conducted under throughfall manipulation conditions in forest ecosystems around the globe were selected in this meta-analysis, with a total of 103 paired observations. Experimental categories such as climate types, forest types, soil texture, and the area size of changes in throughfall manipulation were included to qualify the responses of annual soil CO₂ emissions to the altered throughfall. The responses of the annual soil CO₂ emissions to the altered throughfall would be more sensitive in temperate forests than those in tropical and subtropical forests, probably due to the relatively long residence time of soil carbon (C) and the seasonal freeze–thaw events in temperate forests, as well as the relatively high concentration of non-structural carbohydrates in the belowground part of temperate terrestrial plants. A relatively large positive response of the soil CO₂ emissions to the increased throughfall was observed in Mediterranean forests due to small precipitation during the growing season and mostly coarse-textured soils. Besides climate types, the sizes of the effect of the altered throughfall on the soil CO₂ emissions (lnR_CO2) varied with forest types and soil texture categories. Based on the regression analysis of the lnR_CO2 values against the changes in throughfall, the annual soil CO₂ emissions in forest ecosystems at a global scale would be increased by 6.9%, provided that the change in annual precipitation was increased by 10%. The results of structural equation modeling analysis indicate that fine root biomass and soil microbial biomass, along with the changes in annual precipitation, would substantially affect the altered throughfall-induced annual soil CO₂ emissions in global forest ecosystems. The findings of this meta-analysis highlight that the measurement of soil respiration components, the priming effects of soil organic C decomposition, and C allocation between the aboveground and belowground parts of different tree species under the altered precipitation conditions, deserve more attention in the future. Full article

(This article belongs to the Special Issue Responses of Soil Carbon and Nitrogen Dynamics and GHG Fluxes in Forest Ecosystems to Climate Change and Human Activity)

► Show Figures