Positive interactions between Pinus massoniana and Castanopsis hystrix species in the uneven-aged mixed plantations can produce more ecosystem carbon in subtropical China

doi:10.1016/j.foreco.2017.08.025

Forest Ecology and Management

Volume 410, 15 February 2018, Pages 193-200

https://doi.org/10.1016/j.foreco.2017.08.025 Get rights and content

Highlights

•
Strong mutual antagonism between P. massoniana and C. hystrix in even-aged mixture.
•
Positive interaction between P. massoniana and C. hystrix in uneven-aged mixed stand.
•
Uneven-aged mixture of P. massoniana and C. hystrix increase ecosystem carbon stock.
•
Uneven-aged conifer and broadleaf mixture may be a good silvicultural practice.

Abstract

Silvicultural practices are an important determinant of tree growth and stand structure. However, the potential advantages of long-term forest management, i.e., mixing valuable non-N₂-fixing broadleaf tree species, such as Castanopsis hystrix Miq., with Masson pine (Pinus massoniana Lamb.) to increase stand growth and ecosystem carbon storage, remain poorly understood. In this study, we assessed tree growth, aboveground carbon accumulation, and belowground carbon sequestration in 26-year-old monocultures of C. hystrix (¹⁰⁰C₂₆), 26-year-old monocultures of P. massoniana (¹⁰⁰P₂₆), 50-year-old monocultures of P. massoniana (¹⁰⁰P₅₀), and even- and uneven-aged (⁵⁰C₂₆ + ⁵⁰P₂₆ and ⁵⁰C₂₆ + ⁵⁰P₅₀, respectively) mixed plantations. Carbon storage within the total ecosystem and in the tree and soil layers of ⁵⁰C₂₆ + ⁵⁰P₅₀ mixed plantations was significantly greater than values predicted based on the means of the ¹⁰⁰C₂₆ and ¹⁰⁰P₅₀ monoculture plantations (p < 0.05). By contrast, differences within the shrub and litter layers were not significant, nor were the differences between observed and expected carbon storage values in the total ecosystem, except in the case of carbon stock in ⁵⁰C₂₆ + ⁵⁰P₂₆ mixed plantation soils. These results indicate that plantations of uneven-aged mixtures of P. massoniana and C. hystrix promote carbon sequestration via positive interactions.

Introduction

Conventional forest management in China over the past several decades has primarily been based on the large-scale and continuous development of monocultures of broadleaf and coniferous species. However, this approach has contributed to serious ecological problems, including soil erosion, decreases in soil nutrient content, and reduced biodiversity (He et al., 2013, Wang et al., 2013). With recent policy-guided demand for higher production levels, economic viability, and ecological services, including carbon sequestration, there has been a shift to the cultivation of mixed plantations of economically and ecologically valuable species (Piotto et al., 2010, Hvistendahl, 2012, Puettmann et al., 2015). Studies in temperate and tropical regions have shown that mixed-species plantations can improve carbon sequestration by soil or biomass (Parrotta, 1999, Resh et al., 2002, Wang et al., 2009, Forrester et al., 2013, Huang et al., 2014). Ewel et al. (2015) found that a steeply increasing growth differential between mixed stands and monocultures may account for the inferred complementarity. Other studies have shown that broadleaf tree species mixing with coniferous tree species (1) promotes the growth of the planted trees and increases overall stand productivity compared with pure stands (Binkley, 2003, Nord-Larsen and Meilby, 2016) via improving capture, supply, or resource use efficiency (i.e. light, nutrient and water) (Kelty, 2006, Pretzsch et al., 2015, Chamagne et al., 2017); (2) positively affects litter quantity and quality (Wang et al., 2013); and (3) improves the nutrient balance (Thelin et al., 2002). Although short-term studies in grasslands have clearly shown positive outcomes with mixed stands (Spehn et al., 2000, Nyfeler et al., 2009), there are large differences in the structure and physiology between trees and grasses, i.e., within a single year, short-lived grasses can rebuilding the whole canopy. In contrast, trees take much longer to develop their crowns and small differences in tree crown architectural properties could accumulate year after year to have much larger effects as the stand canopy develops, and forest ecosystems require a long time and large areas to be treatment experiment (Scherer-Lorenzen et al., 2005). To date, however, the effects on long-term forest management of introducing non-N₂-fixing broadleaf tree species into pure coniferous plantations remain largely unclear.

Masson pine (Pinus massoniana Lamb.) is one of the two most important coniferous species for timber production, carbon storage, and other ecological services in subtropical China (Zeng et al., 2011). The amount of forest area planted with this species has increased greatly, reaching >17.39 million hectares and representing 8.92% of the total forest area of China (Kuang et al., 2008, SFA, 2010). The desirable features of this species include its fast growth, high yield, variable light tolerance, and drought resistance. However, pure Masson pine plantations also have lower biodiversity and soil fertility, cause extensive habitat loss and soil erosion, and thus increase the vulnerability of these forests to pests and diseases, ultimately compromising ecosystem functions. To address the sustainability requirement of forest management, even- or uneven-aged mixed broadleaf and coniferous tree species plantations are currently preferred. Castanopsis hystrix Miq. is a large evergreen member of the Fagaceae family and a valuable indigenous tree species in the evergreen broadleaf forests of subtropical China (He et al., 2013). Although combining P. massoniana and C. hystrix in mixed-species plantations could increase site productivity (He et al., 2013), the impact of this forest management strategy on carbon sequestration within the ecosystem is poorly understood.

Belowground carbon storage is the largest carbon pool in forest ecosystems, second only to aboveground biomass (Sharma et al., 2010, Chen et al., 2012). Protecting and enhancing soil carbon stock is a global challenge. Silvicultural practices can have marked effects on soil carbon stock (Wang et al., 2013) and the soil carbon cycle because tree species and forest stand structures alter light, temperature, and moisture patterns as well as the input of organic material. Forest management is a strong determinant of these processes, with large changes resulting from a shift from pure to mixed plantations. Most studies have shown that aboveground organic matter and carbon storage increase in mixed-species plantations; however, their impact on soil carbon stock is controversial. Some studies have shown that soil carbon stock is increased in mixed-species plantations because of an increase in organic matter input (aboveground and roots) (Yang et al., 2003, Zhang et al., 2012); however, others have observed few effects or even decreases (Raich et al., 2006, Wang et al., 2009). These inconsistent findings suggest that soil carbon storage reflects the inputs of plant litter and other organic detritus and that organic matter decomposition is controlled by biotic (tree traits and soil microbial communities) and abiotic (soil chemical and physical properties) factors (You et al., 2014, You et al., 2016). Thus, despite a much improved understanding of the effects of mixed-species plantations on soil carbon stock, little is known about the effects of management practices based on mixed-species plantations.

In this study, we designed a long-term coniferous plantation modification project (CPMP) in a southern subtropical region of China (Pingxiang, Guangxi Zhuang Autonomous Region) based on a multipurpose forest. The project was initiated in 1983, and the forest was a mixture of C. hystrix and P. massoniana. The main objectives of the CPMP were to examine the impacts of three management strategies (monoculture, even-aged mixture, and uneven-aged mixture) on multiple taxa, environmental variables, and layered and multipurpose forests, and therefore on ecosystem functions and processes (Cai et al., 2007). Specifically, we investigated whether the introduction of valuable broadleaf tree species (non-N₂-fixing species) into Masson pine plantations would increase stand growth and ecosystem carbon storage during long-term forest management. The results contribute to the establishment of best practices in the field of silviculture.

Section snippets

Site description and experimental design

The study site was located at the Experimental Center of Tropical Forestry (ECTF; 22 °02′–22 °04′N, 106 °51′–106 °53′E), Chinese Academy of Forestry, Pingxiang, Guangxi Zhuang Autonomous Region, China. The topography of this region largely consists of low mountains; elevations range from 430 m to 680 m. The soils are mainly lateritic, and the climate is characterized by hot, humid summers and mild winters. The mean annual temperature is 21 °C, with a daily mean of >30 °C for approximately 4 months of

Tree characteristics in even- and uneven-aged mixed plantations

Tree characteristics are presented in Table 1. In the ⁵⁰C₂₆ + ⁵⁰P₂₆ mixed plantations, the mean DBH and tree height of C. hystrix (C₂₆) were significantly higher (67.66% and 35.56%, respectively; p < 0.05) and those of P. massoniana (P₂₆) significantly lower (21.50% and 16.90%, respectively; p < 0.05) than in the respective monoculture plantations. The total stem density was also lower in the ⁵⁰C₂₆ + ⁵⁰P₂₆ mixed plantations than in either the ¹⁰⁰C₂₆ or ¹⁰⁰P₂₆ plantations. However, the DBH of C₂₆ in the

Stand characteristics and competition between species: Monocultures versus even- and uneven-aged mixed plantations

Interspecific interactions between mixtures of species depend on the associations between those species, the climate of the site, abiotic stress factors, soil fertility, and stand ages (Forrester et al., 2006, Laclau et al., 2008, Viera and Schumacher, 2011). For example, planting N₂-fixing with non-N₂-fixing tree species may reduce competition, enhance N soil availability, and improve growth in the latter trees (Kaye et al., 2000, Binkley et al., 2003, Richards et al., 2010). Inappropriate

Conclusion

This study examined the benefits of introducing valuable broadleaf tree species (non-N₂-fixing species) into coniferous plantations for increased ecosystem carbon storage. We found a strong mutual antagonism between P. massoniana and C. hystrix in an even-aged mixed plantation after 26 years of growth, with the broadleaf species C. hystrix outcompeting the coniferous P. massoniana. The major underlying mechanism for this could be attributed to canopy stratification (P. massoniana in the lower

Acknowledgments

We gratefully acknowledge the support of the Guangxi Youyiguan Forest Ecosystem National Research Station for access to the site and logistical support. This study was jointly funded by grants from the National Natural Science Foundation of China (Nos. 31460121 and 31560201), the China Postdoctoral Science Foundation (No. 2017M612861) and the National Key Technology and Development Program of China (No. 2012BAD22B01).

References (68)

D. Binkley et al.
Light absorption and use efficiency in forests: why patterns differ for trees and stands
For. Ecol. Manage.
(2013)
D. Binkley et al.
Twenty years of stand development in pure and mixed stands of Eucalyptus saligna and nitrogen-fixing Facaltaria moluccana
For. Ecol. Manage.
(2003)
O. Campoe et al.
Fertilization and irrigation effects on tree level aboveground net primary production, light interception and light use efficiency in a loblolly pine plantation
For. Ecol. Manage.
(2013)
L. Chen et al.
Comparing carbon sequestration and stand structure of monoculture and mixed mangrove plantations of Sonneratia caseolaris and S. apetala in Southern China
For. Ecol. Manage.
(2012)
M. del Río et al.
Analyzing size-symmetric vs. size-asymmetric and intra-vs. inter-specific competition in beech (Fagus sylvatica L.) mixed stands
For. Ecol. Manage.
(2014)
K. Eerikäinen et al.
Models for the regeneration establishment and the development of established seedlings in uneven-aged, Norway spruce dominated forest stands of southern Finland
For. Ecol. Manage.
(2007)
P.D. Erskine et al.
Tree species diversity and ecosystem function: can tropical multi-species plantations generate greater productivity?
For. Ecol. Manage.
(2006)
D.I. Forrester et al.
Mixed-species plantations of Eucalyptus with nitrogen-fixing trees: a review
For. Ecol. Manage.
(2006)
D.I. Forrester et al.
Growth dynamics in a mixed-species plantation of Eucalyptus globulus and Acacia mearnsii
For. Ecol. Manage.
(2004)
Y. He et al.
Carbon storage capacity of monoculture and mixed-species plantations in subtropical China
For. Ecol. Manage.
(2013)

X. Huang et al.

Changes of soil microbial biomass carbon and community composition through mixing nitrogen-fixing species with Eucalyptus urophylla in subtropical China

Soil Biol. Biochem.

(2014)

D.M. Iponga et al.

Superiority in competition for light: a crucial attribute defining the impact of the invasive alien tree Schinus molle (Anacardiaceae) in South African savanna

J. Arid Environ.

(2008)

J. Kanowski et al.

Consequences of broadscale timber plantations for biodiversity in cleared rainforest landscapes of tropical and subtropical Australia

For. Ecol. Manage.

(2005)

M.J. Kelty

The role of species mixtures in plantation forestry

For. Ecol. Manage.

(2006)

Y.W. Kuang et al.

Tree-ring growth patterns of Masson pine (Pinus massoniana L.) during the recent decades in the acidification Pearl River Delta of China

For. Ecol. Manage.

(2008)

J.P. Laclau et al.

Mixed-species plantations of Acacia mangium and Eucalyptus grandis in Brazil: 1. Growth dynamics and aboveground net primary production

For. Ecol. Manage.

(2008)

J.E. Mitchell et al.

Comparison of linear and nonlinear overstory-understory models for ponderosa pine

For. Ecol. Manage.

(1991)

R. Parajuli et al.

Carbon sequestration and uneven-aged management of loblolly pine stands in the Southern USA: A joint optimization approach

Forest Policy Econ.

(2012)

J.A. Parrotta

Productivity, nutrient cycling, and succession in single-and mixed-species plantations of Casuarina equisetifolia, Eucalyptus robusta, and Leucaena leucocephala in Puerto Rico

For. Ecol. Manage.

(1999)

J.M. Peek et al.

Overstory-understory biomass changes over a 35-year period in south central Oregon

For. Ecol. Manage.

(2001)

B. Petit et al.

Growth in pure and mixed plantations of tree species used in reforesting rural areas of the humid region of Costa Rica

Central America. For. Ecol. Manage.

(2006)

D. Piotto

A meta-analysis comparing tree growth in monocultures and mixed plantations

For. Ecol. Manage.

(2008)

E. Rouhi-Moghaddam et al.

Comparison of growth, nutrition and soil properties of pure stands of Quercus castaneifolia and mixed with Zelkova carpinifolia in the Hyrcanian forests of Iran

For. Ecol. Manage.

(2008)

C.M. Sharma et al.

Tree diversity and carbon stocks of some major forest types of Garhwal Himalaya

India. For. Ecol. Manage.

(2010)

G. Thelin et al.

The nutrient status of Norway spruce in pure and in mixed-species stands

For. Ecol. Manage.

(2002)

Q. Wang et al.

Assessing the effects of vegetation types on carbon storage fifteen years after reforestation on a Chinese fir site

For. Ecol. Manage.

(2009)

H. Zhang et al.

Biomass and carbon storage of Eucalyptus and Acacia plantations in the Pearl River Delta, South China

For. Ecol. Manage.

(2012)

M.M. Amoroso et al.

Comparing productivity of pure and mixed Douglas-fir and western hemlock plantations in the Pacific Northwest

Can. J. Forest Res.

(2006)

M. Barrufol et al.

Biodiversity promotes tree growth during succession in subtropical forest

PLoS One.

(2013)

D. Binkley

Seven decades of stand development in mixed and pure stands of conifers and nitrogen-fixing red alder

Can. J. Forest Res.

(2003)

D. Cai et al.

On large-size timber plantation forestry of valuable hardwood species in warm subtropical areas of China

For. Res.

(2007)

B. Castagneyrol et al.

Effects of plant phylogenetic diversity on herbivory depend on herbivore specialization

J. Appl. Ecol.

(2014)

J. Chamagne et al.

Forest diversity promotes individual tree growth in central European forest stands

J. Appl. Ecol.

(2017)

D.S. Debell et al.

Growth, development, and yield in pure and mixed stands of Eucalyptus and Albizia

Forest Sci.

(1997)

Cited by (35)

The effect of mixed forest identity on soil carbon stocks in Pinus massoniana mixed forests
2024, Science of the Total Environment
Increased productivity generally promotes the accumulation of soil organic carbon (SOC) stocks. The productivity of mixed forests is mainly influenced by plant species richness (PSR), mixed forest age (MFA), and mixed species proportion (MSP). However, the influence of PSR, MFA, and MSP on SOC stocks along the soil profiles in Pinus massoniana mixed forests remains to be determined. We conducted a meta-analysis employing paired observations of SOC stocks from 1010 paired mixed and pure stands of P. massoniana from 110 publications. The findings revealed that SOC stocks were highly dependent on MFA and increased with increasing MFA in various soil layers, rather than the expected influence of PSR. MFA contributed 48.97 %, 83.20 %, and 38.41 % to the increased SOC stocks in the topsoil, midsoil, and subsoil, respectively. Furthermore, MSP also significantly affected the increase in SOC stock in the topsoil and midsoil when 40 % < MSP ≤ 60 %. Over the next 60 years, subsoil SOC accumulation will be limited by increased PSR and MSP in mixed forests. Mixing between P. massoniana and broadleaf tree species (especially Schima superba and Lespedeza bicolor) significantly enhanced SOC stocks along the soil profiles. SOC stocks along the soil profiles decreased with increasing dominant mixed tree species richness (e.g., broadleaf, deciduous broadleaf, arbuscular mycorrhizal, and the sum of conifer and broadleaf trees). Incorporating lower PSR (e.g., 2 ≤ N ≤ 10) and dominant mixed tree species richness (e.g., N = 2) practices may be optimization options for increasing SOC stocks. Overall, based on the expected goals, including optimizing productivity, enhancing carbon storage, mitigating climate change, and promoting biodiversity conservation, we emphasize the importance of incorporating MFA, MSP, tree species identity, and subsoil into forest management.
Decomposition of harvest residues and soil chemical properties in a Eucalyptus urophylla × grandis plantation under different residue management practices in southern China
2023, Forest Ecology and Management
Retained residues can return large amounts of nutrients to soil in high-intensity management eucalypt plantations, in which recycling of nutrients is critical for soil quality and forest sustainability. However, the effects of different residue treatments on eucalypt residue decomposition remain unclear. The aim in this study was to determine residue decomposition and nutrient release and soil chemical properties under different treatments of residues in a Eucalyptus urophylla × grandis plantation in southern China. Harvest residues were removed (RR), retained and spread evenly on the soil surface (ER), or retained but stacked into strips on the soil surface (SR). Decomposition of leaves was significantly faster than that of twigs and thick branches and was negatively correlated with initial carbon:nitrogen ratio. The loss of potassium was rapid, whereas losses of carbon, nitrogen, and phosphorus were generally slow. Compared with SR, mass loss and nutrient release accelerated significantly in ER, with shorter half-lives of leaves, twigs, and thick branches. The lowest levels of soil nutrients were in RR, but there were no significant differences between ER and SR. Thus, in this study, residue decomposition was affected by residue type and residue treatment. Decomposition of residues affected soil nutrients by affecting nutrient outflow. In the ER treatment, residues accelerated nutrient cycling and facilitated the accumulation of soil organic carbon, but appropriate fertilization is still needed in E. urophylla × grandis plantations. However, future studies are required to determine whether changes in decomposition rate under different residue management practices lead to long-term changes in soil organic carbon content.
Root-soil facilitation in mixed Eucalyptus grandis plantations including nitrogen-fixing species
2022, Forest Ecology and Management
Citation Excerpt :
Belowground interactions in mixed forest ecosystems are a function of tree rooting patterns (Jose et al., 2006; Bardgett et al., 2014). Differences in root distribution, root system plasticity, root growth, and the resulting belowground niche separation reduce interspecific competition belowground and improve resource use efficiency, thus facilitating species coexistence, biodiversity, and community stability (Forrester et al., 2006; Jose et al., 2006; You et al., 2018). Spruce trees exhibit shallower rooting distribution and beech trees show deeper rooting in mixture cultivation, compared to corresponding pure stands (Mackenthum, 1990).
The success of mixed plantation systems is ultimately the net result of positive and negative interactions, including belowground interactions, among the respective species. Despite increasing knowledge on positive interactions on biomass and productivity in mixed-species plantations, relatively little is known about the mechanisms underlying belowground interactions. Based on biodiversity data from four mixed Eucalyptus grandis plantations, we determined the optimal ecological facilitative interactions of mixed plantation, i.e., E. grandis and Alnus formosana. We then investigated in situ root exudation of E. grandis using a cuvette-based method and analysed root patterns, defence chemicals, bacterial communities, and biochemical properties of rhizosphere soils in mixed E. grandis with alder. Compared with pure Eucalyptus plantations, the fine root production by E. grandis was higher in subsoil layers (40–80 cm) in mixed plantations with alder. Autotrophic root respiration and associated enzymes were also increased in mixed plantations. Root exudates and defence allelochemicals of E. grandis changed in the presence of alder. Compared with the pure Eucalyptus plantations, E. grandis roots in mixed plantations reduced the release of potential allelochemicals, such as phenolic acids, flavonoids, unsaturated lactone, and glycosides. Methyl jasmonate, a common signal chemical, was significantly decreased in mixed-species plantations. The bacterial community of E. grandis rhizosphere soil was improved in mixed stands and recruited more nitrifying, N-fixing, and cellulose-decomposing bacteria, such as family Nitrosomonadaceae, genera MND1, Marmoricola, and Rikenellaceae RC9 gut groups. Thus, belowground ecological facilitative interactions occurred in mixed plantations with alder, which were due to E. grandis altering its rooting pattern, reducing the levels of released allelochemicals, recruiting more beneficial bacteria, and improving the biochemical properties of rhizosphere soil. This mechanism may be useful in reforestation programs for Eucalyptus monocultures that are suffering from problems associated with low biodiversity and reduced soil fertility.
Network analysis reveals the regulatory effect of mixed stands on ecosystem structure and functions in the Loess Plateau, China
2022, Science of the Total Environment
Citation Excerpt :
The relationship between the structure and functions of an ecosystem has long been of great interest in ecology (Gonzalez et al., 2020; Parker, 1982; Saint-Béat et al., 2015; Turner et al., 2003). There have been numerous studies on the structure of plantations, from traditional studies on stand structure (Xiang et al., 2021), vertical stratification (Wu et al., 2021a; You et al., 2018), species composition and diversity (Chen et al., 2019; Santos et al., 2021). The overstory controls the input of organic matter such as fallen leaves, bark, roots and sawdust (Wei et al., 2021; Xu et al., 2021).
Afforestation, an important measure for ecological restoration, has been implemented all over the world, but fragile ecosystem structures and climate change endanger its ecological functions. One major obstacle to optimizing ecological function has been quantifying and characterizing a complex ecosystem structure. Here, the structure and functions of six types of land-use restoration were investigated in the hilly-gully region of the Loess Plateau, China. In total, 44 ecological factors from canopy, understory and soil were determined. We constructed the related network of reforestation ecosystems, quantified the structure of ecosystem through network topology, and explored the relationships between structure and functions. The results showed that changes in plantation type altered the network hubs, but some nodes, such as species height, breast-height diameter and understory biomass, were often keystone hubs. Mixed plantations enhanced the connectivity among different modules. In addition, we found that closeness of network connectivity was an important factor influencing ecological functions, while soil erodibility was the main limiting factor for reforestation ecosystem structure in this region. Moreover, mixed plantations tended to have more balanced topological metrics and ecological functions. Overall, this study suggests that mixed plantations or monoculture plantations should be designed according to the characteristics and ecological demands of the regional ecological environment. Although monoculture plantations may support local ecosystems, mixed plantations offer more resilience to a landscape because they were help to achieve a balance among the ecological functions.
Abundant fungal and rare bacterial taxa jointly reveal soil nutrient cycling and multifunctionality in uneven-aged mixed plantations
2021, Ecological Indicators
Citation Excerpt :
In contrast, an uneven-aged silviculture regime can regenerate the stand in a more continuous and heterogeneous manner (Falkowski et al., 2008; Nyland, 2003; Pukkala et al., 2012). Similarly, several studies have reported that uneven-aged mixed plantations (especially mixed broadleaf-conifer plantations) showed higher biodiversity and carbon sequestration levels than those of even-aged mixed plantations (Joelsson et al., 2017; You et al., 2018). Accordingly, the uneven-aged mixed plantations (created by introducing broadleaf tree species into C. lanceolata plantation in our study) may be an effective model for sustainable development of C. lanceolata plantations.
Uneven-aged silvicultural practices can maintain habitat continuity and enhance biodiversity. Soil microorganisms play critical roles in multiple ecosystem functions (i.e., multifunctionality). However, little is currently known regarding the role of the microbial community in driving soil nutrient cycling and multifunctionality (SMF) in uneven-aged mixed plantations. In this study, we investigated soil bacterial and fungal community compositions and diversities, single-function related carbon (C), nitrogen (N), and phosphorus (P) cycling, and SMF indices in monoculture plantation (as a control) and three uneven-aged mixed plantation stands (4, 7, and 11 years old). Our results demonstrated that the soil C, N, P cycling, and SMF indices in uneven-aged mixed plantations increased by 17.9–55.2%, 20.0–54.0%, 0.7–21.6%, and 16.3–30.1% compared to monoculture plantation. The soil fungal alpha diversity (richness and Shannon diversity), nutrient cycling, and SMF significantly improved with stand age, but bacterial alpha diversity showed less variation. The beta diversities of bacteria and fungi showed notable variation with stand age and were predominantly affected by stand age and soil properties (soil organic C, total P, and C/N ratio), respectively. Additionally, the temporal turnover within the fungal community was higher than the turnover rates of the bacterial community. Soil fungal diversity and biomass were more sensitive to the stand structure change over a short period (11 years) than bacterial diversity and biomass. Furthermore, the fungal beta diversity and fungi/bacteria (F/B) ratio were strongly and positively correlated with nutrient cycling and SMF. Most importantly, the abundant fungal taxa (e.g., Mucoromycota and Mortierellomycota) were the major drivers of SMF, followed by rare bacterial taxa (e.g., Nitrospirae and Elusimicrobia). These findings indicate soil fungal and bacterial communities have different responses and undertake important roles in maintaining nutrient cycling and SMF when a monoculture plantation is converted into an uneven-aged mixed plantation.
Native broadleaf tree species stimulate topsoil nutrient transformation by changing microbial community composition and physiological function, but not biomass in subtropical plantations with low P status
2020, Forest Ecology and Management
Citation Excerpt :
This study was conducted at the Guangxi Youyiguang Forest Ecosystem Research Station of the Experimental Center of Tropical Forestry, Chinese Academy of Forestry (22°10′N, 106°50′E), in Pingxiang City, Guangxi Zhuang Autonomous Region, China. The study area is located in a subtropical region and has a typical subtropical monsoon climate; annual precipitation is approximately 1400 mm, and mean annual temperature is 21 °C (You et al., 2018). Soils are derived from granite and are sandy in texture.
Microbial communities and their associated enzyme activities affect carbon (C), nitrogen (N), and phosphorus (P) metabolism in soils. We used phospholipid fatty acids (PLFAs) analysis and extracellular enzyme activity assays to evaluate the effects on topsoil microbial community and nutrient transformation of converting Chinese fir (CF) plantations to native broadleaf (Castanopsis hystrix [CH] and Mytilaria laosensis [ML]) plantations in this study. We found that CH and ML plantations had significantly higher soil organic C (SOC), total N (TN), NH₄⁺-N, soil C/N ratios (C/N_soil), soil C/P ratios (C/P_soil) and soil N/P ratios (N/P_soil) but significantly lower total P (TP) compared to CF plantations. A distinct shift in soil microbial community composition, but not microbial biomass was evident 23 years after stand conversion. Redundancy analysis (RDA) showed that soil microbial community composition was substantially influenced by litterfall mass (LF), TP, N/P_soil, SOC, fine root biomass (FR), C/N_soil, TN, litter C/N ratios (C/N_litter), and C/P_soil; of these, LF appeared to be the primary driver of differences in soil microbial community composition (p < 0.05). In addition, the total activity of hydrolytic enzymes involved in C metabolism (β-glucosidase and cellobiohydrolase), N metabolism (N-acetyl-glucosaminidase), and P metabolism (acid phosphatase) increased significantly in the two native broadleaf plantations, whereas the total activity of oxidase (phenol oxidase) decreased significantly. Furthermore, the change trends of specific enzyme activity (i.e., enzymes per unit microbe) were similar to total enzyme activity. The dynamics of soil microbial enzymatic activity after stand conversion provide a functional link between changes in microbial community composition and soil nutrient transformation. Our findings suggest a mechanism in native, non-N₂-fixing broadleaf tree species that stimulates soil nutrient transformation in subtropical planted forests with low P via increases in the quantity and quality of litter and the physiological function per unit of microbial biomass.

View all citing articles on Scopus

¹: These authors contributed equally to this work.

View full text