Castanopsis Hystrix Research Articles

Differential Responses of Soil Nitrogen Forms to Climate Warming in Castanopsis hystrix and Quercus aliena Forests of China

Climate warming impacts soil nitrogen cycling in forest ecosystems, thus influencing their productivity, but this has not yet been sufficiently studied. Experiments commenced in January 2012 in a subtropical Castanopsis hystrix Hook. f. and Thomson ex A. DC. plantation and in May 2011 in a temperate Quercus aliena Blume forest, China. Four treatments were established comprising trenching, artificial warming (up to 2 °C), artificial warming + trenching, and untreated control plots. The plots were 2 × 3 m in size. In 2021 and 2022, soil nitrogen mineralization, soil nutrient availability, fine root biomass and microbial biomass were measured at 0–20 cm soil depth in 6 replicate plots per treatment. Warming significantly increased soil temperature in both forests. In the C. hystrix plantation, warming significantly increased available phosphorus (AP) and fine root biomass (FRB), but it did not affect soil microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), microbial biomass phosphorus (MBP) and their ratios. Warming depressed the net mineralization rate (NMR) and net ammonification rate (NAR) of the C. hystrix plantation, probably because the competition for nitrogen uptake by fine roots and microorganisms increased, thus decreasing substrates for nitrogen mineralization and ammonification processes. Trenching and warming + trenching increased the net nitrification rate (NNR), which might be related to decreased NH4+-N absorption of trees in the trenched plots and the increased microbial activity involved in soil nitrification. In the Q. aliena forest, warming significantly increased NH4+-N, MBC/MBN, Root C/N, Root N/P, and decreased pH, MBN, MBN/MBP and Root P; and there was no effect of trenching. Notably, the NAR, NNR and NMR were largely unaffected by long-term warming. We attributed this to the negative effect of increasing NH4+-N and decreasing MBN/MBP offsetting the positive effect of soil warming. This study highlights the vulnerability of subtropical forest stands to long-term warming due to decreased soil N mineralization and increased NO3−-N leaching. In contrast, the soil N cycle in the temperate forest was more resilient to a decade of continuous warming.

Mixed Eucalyptus plantations enhance soil organic carbon accumulation and chemical stability through soil microbial community and multifunctionality

Forest conversion can impact soil organic carbon (SOC) fixation and ecosystem functions. The newly proposed “evenness of SOC chemical components” index can indicate the permanence of stored SOC during environmental disturbances. However, how the mixing of tree species impacts SOC accumulation and persistence and changes in soil microbial communities and multifunctionality remain unknown. Thus, we conducted a field experiment (11 years) of monospecific Eucalyptus urophylla × E. grandis plantation for evaluating the influences of the mixed planting of a non-nitrogen (N)-fixing tree, Castanopsis hystrix, and an N-fixing tree, Dalbergia odorifera, on SOC accumulation and chemical stability. Compared with pure plantations, mixed Eucalyptus plantations (particularly those mixed with D. odorifera) exhibited significantly increased SOC concentrations by 28.60–33.71 % and increased SOC chemical component evenness by 3.96–4.67 % (P < 0.05). We also found that the concentrations and chemical component evenness of SOC were strongly linked with litter quality, soil N, phosphorus and their availability, multifunctionality, microbial activity, carbon use efficiency (CUE), biomass, diversity, and network complexity. Furthermore, tree species mixing increased litter quality, soil nutrient availability, microbial biomass, activity, diversity, CUE, and network complexity. Soil microbial anabolism, community characteristics and multifunctionality influenced the SOC concentrations and SOC chemical components evenness. Specifically, microbial diversity enhanced the concentrations and chemical component evenness of SOC by increasing network complexity and soil multifunctionality. These findings revealed differential responses and mechanistic controls of SOC accumulation and chemical stability in different Eucalyptus planting patterns. Overall, mixed plantations, particularly those in which N-fixing species were introduced, effectively improved SOC accumulation and stabilization by positively altering soil quality and microbial properties, potentially representing a sustainable forestry management strategy to improve soil C benefits and multifunctionality in forest ecosystems.

Cardamom (Amomum tsaoko) agroforest is important habitat for skywalker hoolock gibbon (Hoolock tianxing) in Mt. Gaoligong, Yunnan, China

Understory plantation of cardamom (genus Amomum) is an ancient and widespread agroforestry practice in the eastern Himalayas and Southeast Asia, an area that supports high regional biodiversity. Cardamom provides an important cash income to rural people, and governments encourage cardamom cultivation as a replacement for slash-and-burn agriculture to alleviate poverty, aligning with the principles of the Globally Important Agricultural Heritage Systems (GIAHS) program initiated by the FAO. This program recognizes and supports traditional agricultural practices that contributes to biodiversity conservation and sustainable development. In this context, cardamom agroforestry not only supports local economies but also provides crucial habitat for animals, including the newly described skywalker hoolock gibbon (Hoolock tianxing). Nearly half of the remnant population of the skywalker hoolock gibbon lives in cardamom agroforest. In order to evaluate if gibbons could survive in cardamom agroforest for a relatively long term, we compared foraging behavior of gibbons over a year living in cardamom agroforests (group NA) and well-preserved forests (group BB) in Mt. Gaoligong, Yunnan, China. In response to habitat degradation caused by cardamom plantation, group NA increased feeding time and spent more time feeding on leaves. Notably, they consumed nuts of Castanopsis hystrix which is an unusual food type for gibbons. On the contrary, members of group BB rarely ate nuts though Castanopsis hystrix is abundant within its home range. However, group NA did not occupy a large home range, or travel longer in time or distance than group BB. We also monitored female reproduction of five groups for 5–13 years. Two adult females living in agroforests successfully reared two or three offspring with an inter-birth interval of five years. In addition, we surveyed group size of 16 groups (9 in agroforest vs. 7 in well preserved forests) from 2017 to 2023, and we found no significant difference in group size between habitats. Our results suggested that cardamom agroforest can sustain skywalker hoolock gibbons provided it is not too fragmented and hunting is prohibited.

Genomic Selection for Growth and Wood Traits in Castanopsis hystrix

Genomic Selection for Growth and Wood Traits in Castanopsis hystrix

Conversion of pure Chinese fir plantation to multi-layered mixed plantation increases organic phosphorus accumulation and transformation within soil aggregates

Evaluation of the impacts of environmental factors and microbial communities on soil organic phosphorus (Po) availability is needed to clarify P cycling and regulate plantations productivity. However, the effects on Po accumulation and transformation of converting pure Chinese fir plantation to multi-layered mixed plantation and their regulatory mechanisms remain unclear. The aim of this study was to examine the impacts of the transformation of pure stand of Chinese fir (Cunninghamia lanceolata; PP) to mixed plantation with multiple tree species (C. lanceolata, Castanopsis hystrix, and Michelia hedyosperma; MP) on Po accumulation and transformation within topsoil (0–10 cm) aggregates in subtropical China. Our results showed that the soil organic carbon (SOC), total nitrogen (TN), ammonium nitrogen (NH4+-N), and available phosphorus (AP), as well as the carbon‑nitrogen ratio of soil (C/Nsoil) and carbon‑phosphorus ratio of soil (C/Psoil) were significantly higher (P < 0.05) of all aggregates in MP than those in PP. The quantities of soil microbial biomass C, N, P (MBC, MBN, and MBP) in all different aggregates were significantly greater (P < 0.05) in MP than in PP. The phospholipid fatty acid contents related to bacteria, fungi, arbuscular mycorrhizal fungi (AMF), and actinomycetes were significantly greater in all aggregate classes (P < 0.05) in MP relative to PP. The activities of all tested C, N, and P hydrolytic enzymes, as well as labile organic P, moderately labile organic P, moderately resistant organic P, and highly resistant organic P contents, were significantly higher of most aggregate size classes in MP. Finally, redundancy analysis (RDA) suggested that Po fractions were primarily affected by the NH4+-N, litterfall biomass (LF), carbon‑nitrogen ratio of litter (C/Nlitter), SOC and fine root biomass (FR). Our findings suggest that converting pure Chinese fir plantations into multi-layered mixed plantations may represent an effective management strategy for promoting organic P accumulation and transformation by regulating soil and microbial properties in degraded soils of Chinese fir plantations.

Tree species mixing effects on the radial growth of Pinus massoniana and Castanopsis hystrix: A comparison between even-aged and uneven-aged stands

The establishment of mixed-species forests with complex structures and high biodiversity has emerged as a key approach for enhancing productivity and maintaining the stability of plantation forests. However, how the mixing effect changes with stand development and climate variation is still unclear. Additionally, little is known about how the mixing effects vary between even- and uneven-aged mixed planting strategies based on the same species combinations and site conditions. In this study, we used dendrochronological methods to reconstruct 37 years of annual growth series for even-aged mixed plantations (EMs) and uneven-aged mixed plantations (UEMs) of Pinus massoniana and Castanopsis hystrix, as well as their respective monocultures at the individual tree (286 trees in total) level. We found that in EMs, the growth of P. massoniana and C. hystrix was 20.8 % lower and 26.2 % higher than those of their monocultures, respectively. However, the growth of P. massoniana remained unchanged during the first 17 years of mixing, after which it was significantly suppressed by C. hystrix. The growth of P. massoniana and C. hystrix in the UEMs was 20.8 % and 26.2 % lower than that in their monocultures, respectively. Remarkably, the mixing effect on the growth of P. massoniana shifted from suppression to promotion after 30 years of mixing. Furthermore, the relative growth of P. massoniana in the UEMs increased with dry season precipitation. These results indicate that transforming pure plantations into uneven-aged mixed plantations may be a crucial forest management strategy for enhancing tree growth and to improving adaptation to future precipitation pattern changes. However, in EMs, thinning should be conducted before fast-growing, shade-intolerant species experience intense light competition.

Effects of Thinning on Carbon Storage in a Mixed Broadleaved Plantation in a Subtropical Area of China

Forest thinning is a widely used silvicultural method in forest management and has complex effects on carbon sequestration in different types of forest ecosystems. The present study examined the short-term effects of different thinning intensities on carbon storage in an 11-year-old mixed broadleaved plantation. The results partially supported that different thinning intensities have varying impacts on carbon storage in different parts of forest ecosystems. The main results were as follows: (1) The effect of thinning on promoting the growth of fast-growing tree species (Michelia macclurei Dandy and Schima superba Gardn. et Champ.) was earlier than that of slow-growing tree species (Castanopsis hystrix Miq.). (2) A greater thinning intensity conferred greater effects on promoting the tree biomass carbon growth, litter carbon storage, and understory plant diversity, in the order of 41%~50% &gt; 31%~40% &gt; 20%~30%, but these values were lower than those for the unthinned plots. (3) The soil carbon storage declined most in the 41%~50% thinned plots, due to the reduced carbon storage in the humus layer. (4) The 20%~30% thinning intensity promoted carbon sequestration in the short term in the mixed broadleaved plantation. The results suggested that a lower thinning intensity promoted carbon sequestration in the short term, a greater thinning intensity reduced carbon storage at first, but the negative effect on carbon storage exhibited trade-offs later by the growth of tree and understory plant biomass carbon and the accumulation of litter layer carbon.

Increasing stand age increases N deficiency but alleviates relative P limitations in Castanopsis hystrix plantations in Southern China

AbstractForest productivity usually declines with the increase in the age of stand, which may be associated with the disturbance in the balance of nitrogen (N) and phosphorus (P) nutrients. However, the effects of stand age on plantation nutrient balance and productivity in plantation is still unclear. Therefore, an experiment was conducted in this study to investigate the influence of the increase in the age of stand (6‐, 10‐, 15‐, 25‐, 30‐, and 34‐year‐old stands) on plant growth and the dynamics of N and P in Castanopsis hystrix plantations of Southern China. The increase in the age of stand reduced plantation productivity and leaf N:P. Moreover, productivity was found to be positively correlated with leaf N:P, reflecting that the decrease in productivity was related to changes in N and P contents in leaves. Reduction in leaf N:P was associated with declining N content and stable P content in leaves. The decrease in leaf N content may be due to the declining –N and microbial biomass N contents in soil, although activities of N‐acetylglucosaminidase, cellobiohydrolase, and polyphenol oxidase decreased with the increase in stand age. The stability of leaf P content may be associated with the increase in soil total P and microbial biomass P, boosting P supply to plants. In contrast, decreased soil phosphatase activity with the increase in the age of stand likely suggests that no additional P was needed through P mineralization. The findings indicate that increasing stand age would improve N consumption but alleviate relative P limitations. Thus, more attention needs to be paid to N fertilizer management (e.g., 10–15‐year stages) to sustain C. hystrix productivity with stand age.

Effects of Different Altitudes on Castanopsis hystrix, the Top Community-Building Species in Southern Subtropical China: Rhizospheric Soil Chemical Properties and Soil Microbiota

Castanopsis hystrix, a dominant canopy species in the subtropical forests of south China, is renowned for its high natural regeneration ability. Therefore, this paper took C. hystrix as the subject of study. Examining the variations in microbial diversity and community composition within the soil rhizosphere of C. hystrix across different elevation gradients, we explored how this community-forming species impacts soil microbial diversity and community structure and how soil microorganisms respond to changes in soil physicochemical properties due to altitude gradients. The results show: (1) soil samples from five altitudes established 1078 fungal OTU and 5595 bacterial OTUs. (2) Basidiomycota and ascomycota are dominant fungal groups in the soil, with Acidobacteria being the predominant bacteria for C. hystrix. (3) As altitude increases, fungal communities’ richness and diversity index peaks at 849 m; for bacterial communities, the richness index peaks at 387 m and the diversity index at 670 m. (4) Total phosphorus (TP), nitrate nitrogen (NO3−-N), hydrolyzed nitrogen (HN), total nitrogen (TN), and organic matter (SOM) are significant environmental factors affecting fungal community structure. At the same time, available potassium (AK) significantly influences the composition of bacterial communities. The study underscores the intricate relationship between altitude, soil properties, and microbial diversity, offering insights into how C. hystrix contributes to ecosystem resilience. Recommendations include enhancing phosphorus supplementation and controlling nitrogen deposition to maintain forest ecological integrity, additionally, the supply of potassium in the soil should also be a key consideration. Further research is necessary to understand the broader implications for biodiversity conservation and adaptive management strategies in the face of climate change.

Effects of tree species mixing and soil depth on the soil bacterial and fungal communities in Chinese fir (Cunninghamia lanceolata) plantations

Chinese fir [Cunninghamia lanceolata (Lamb.) Hook.] is a critical timber tree species for its fast growth and high yield in southern China and is widely planted in subtropical regions of the country. However, the management of Chinese fir in the form of a monoculture plantation is not conducive to the maintenance of soil fertility and improvements in forest productivity. The establishment of mixed conifer–broad–leaved forests through near-natural transformation is developing into a promising method of forest cultivation for replacing large pure coniferous plantations. Bacteria and fungi are an important part of the soil microbiota and are involved in the soil nutrient cycle. Therefore, this study investigated the response of soil bacterial and fungal communities to the introduction of broad–leaved trees in three types of Chinese fir plantations [Cunninghamia lanceolata monoculture plantation (CMP), C. lanceolata–Castanopsis hystrix Hook. f. & Thomson ex A. DC.–Michelia hedyosperma Law. mixed plantation (CCM), and C. lanceolata–Castanopsis fissa (Champ. ex Benth.) Rehder & E.H.Wilson–Erythrophleum fordii Oliv. mixed plantation (CCE)] located in Guangxi Province, China. And the effect of soil layers (0–20, 20–40, and 40–60 cm soil depths) on the soil microbial communities was further analyzed. The results suggested that tree species mixing significantly affected bacterial and fungal communities, but soil depth only significantly affected bacterial communities (P < 0.01). The relative abundance of Basidiomycetes in CCE (53.91–78.76 %) was significantly higher than that in pure forest (P < 0.05). Bacteria exhibited more complex and multilinked networks in the mixed stands, particularly for the CCE plantation. Mixed planting patterns significantly enhanced bacterial nitrogen fixation and the presence of symbiotic fungi. Redundancy analysis (RDA) and correlation analyses indicated that the microbial community structure was strongly affected by soil environmental factors, with bacteria affected mainly by available phosphorous (AP) and fungi affected mainly by soil enzyme activity and total potassium (TK). In summary, the introduction of broad–leaved species (especially C. fissa and E. fordii) had a significant impact on the soil microbial community, increasing the relative abundance of bacterial nitrogen fixation and symbiotic fungi and generating a complex microbial network. We suggest that changes in AP, TK, and fungal communities should be considered in the near-natural transformation of Chinese fir or soil fertility maintenance and sustainable management to maintain soil fertility.

Effects of nitrogen addition on the morphological and chemical traits of fine roots with different orders of &lt;i&gt;Castanopsis hystrix&lt;/i&gt;

Effects of nitrogen addition on the morphological and chemical traits of fine roots with different orders of &lt;i&gt;Castanopsis hystrix&lt;/i&gt;

Seasonal stem radial growth of &lt;i&gt;Castanopsis hystrix&lt;/i&gt; plantation and its response to climatic factors in Guangxi, China

Seasonal stem radial growth of &lt;i&gt;Castanopsis hystrix&lt;/i&gt; plantation and its response to climatic factors in Guangxi, China

Effects of mixed broadleaved tree species with pure Pinus massoniana plantation on soil microbial necromass carbon and organic carbon fractions

Mixing native broadleaved tree species is a widely used method for renovating Pinus massoniana plantations. Soil microbial necromass carbon and organic carbon fractions are important parameters for evaluating the impacts of tree species mixing and soil organic carbon (SOC) stability. However, their responses to the mixing and renovation of P. massoniana plantation has not been understood yet. Here, we selected a pure P. massoniana plantation (PP) and a mixed P. massoniana and Castanopsis hystrix plantation, with ages of 16 (MP16) and 38 years (MP38), respectively, as the research objects. We quantified soil physical and chemical properties, microbial necromass carbon content, and organic carbon components at different soil layers to reveal whether and how the introduction of C. hystrix into P. massoniana plantation affected soil microbial necromass carbon and organic carbon components. The results showed that the mixed P. massoniana and C. hystrix plantation significantly reduced fungal necromass carbon content and the ratio of fungal/bacterial necromass carbon in the 0-20 cm and 20-40 cm soil layers. There were no significant differences in microbial necromass carbon contents, bacterial necromass carbon contents, and their contributions to SOC among the different plantations. The contribution of fungal necromass carbon to SOC was higher than that of bacterial necromass carbon in all plantation types. The contribution of soil mineral-associated organic carbon (MAOC) to SOC was higher than that of occluded particulate organic carbon (oPOC) and light-free particulate organic carbon (fPOC) for all plantation types. Mixing the precious broadleaved tree species (i.e., C. hystrix) with coniferous species (P. massoniana) significantly increased MAOC content and the contribution of MAOC, oPOC, and fPOC to SOC in the 0-20 cm and 20-40 cm soil layers. The MAOC of MP38 was significantly higher than that of PP in all soil layers and the MAOC of MP38 stands were significantly higher than MP16 stands in the 20-40 cm, 40-60 cm, and 60-100 cm soil layers, indicating that hybridization enhanced SOC stability and that the SOC of MP38 stands were more stable than MP16 stands. SOC and total nitrogen contents were the main environmental factors driving the changes in soil microbial necromass carbon, while soil total nitrogen and organically complexed Fe-Al oxides were the primary factors affecting organic carbon fraction. Therefore, SOC stability can be enhanced by introducing native broadleaved species, such as C. hystrix, during the management of the P. massoniana plantation.

Radial cracks in Castanopsis hystrix wood and its dimensional stability improvement by resin-impregnated modification

Abstract This study investigated the characteristics of radial cracks in Castanopsis hystrix wood and evaluated its dimensional stability after impregnation with low-molecular-weight polyacrylate (PA), melamine-urea-glyoxal (MUG), and melamine-urea-formaldehyde (MUF) resins. The physical properties were examined by dimensional stability measurements, dynamic vapor sorption (DVS) analysis, and scanning electron microscopy (SEM). The results showed that radial cracks were easily produced in the transverse section of untreated wood during drying. The surfaces of the radial cracks exhibited an even and clean structure without fluffs on the pair of surfaces, and cracks spanned 4–5 annual rings. The resin-impregnated wood showed no radial cracks on its transverse surface. C. hystrix wood modified with MUG and MUF exhibited a higher weight percentage gain (WPG) than wood modified with the same concentration of PA resin. The resin-impregnated C. hystrix wood also showed reduced anisotropy and improved dimensional stability. The SEM images of the modified wood showed that the wood pits and cells were filled with resin, while the cell wall surfaces were covered with a layer of resin.

Long-term field translocation differentially affects arbuscular mycorrhizal and ectomycorrhizal trees in a sub-tropical forest

Arbuscular mycorrhizal (AM) and ectomycorrhizal (EcM) trees are commonly represented in tropical forests, but their response to warming is generally not known. We conducted a long-term (9-year) field experiment in subtropical China by translocating AM tree species (Machilus breviflora and Schima superba) and EcM tree species (Syzygium rehderianum and Castanopsis hystrix) from a cooler high-elevation site (300 m) to a 1 °C warmer low-elevation site (30 m). Here, we report leaf chemical and physiological data from the last three years (Years 7–9) of the translocation experiment. Translocation to warmer site induced higher air (Tair) and soil (Tsoil) temperatures, but lower soil volumetric water content (SVWC). Translocation treatment significantly increased the light-saturated photosynthetic rate (Asat) for AM trees due to higher stomatal conductance (gs) and Rubisco carboxylation capacity (Vcmax), generating increased growth in AM trees. Translocation treatment reduced the maximum efficiency of photosynthetic quantum yield (Fv/Fm) and growth in EcM trees. Translocation treatment increased leaf turgor loss point (TLP) in AM trees, but reduced TLP in EcM trees. Translocation treatment increased foliar nitrogen (N) concentrations and phosphorus (P) concentrations for AM trees. In EcM trees, stable foliar N and P concentrations were related to higher N and P resorption efficiencies. Translocation treatment was more beneficial for the growth of AM trees than EcM trees, while EcM trees were more tolerant of soil water deficit. Differential responses to these co-occurring climate drivers may alter the composition of tree functional groups and ecosystem function in tropical forests in response to future warmer and drier climate conditions.

Effects of Shading on the Growth and Photosynthetic Fluorescence Characteristics of Castanopsis hystrix Seedlings of Top Community-Building Species in Southern Subtropical China

Castanopsis hystrix is a major community-building species in the top communities of southern subtropical China, with a high natural regeneration capacity. However, excessive logging and the introduction of exotic tree species have substantially reduced the area of natural forest patches of Castanopsis hystrix, and seedling regeneration is essential for the long-term continuation of Castanopsis hystrix populations. To explore the effects of light intensity on the seedling emergence and early growth of Castanopsis hystrix, shading experiments were conducted under four shading treatments (0%, 40%, 60%, and 80%). The growth, biomass accumulation, and distribution, the quality index of seedlings, the morphology and structure of the root systems of seedlings, and the leaf chlorophyll content and chlorophyll fluorescence properties of seedlings under different shading treatments were analyzed. The results displayed the following: (1) Shade intensity impacts growth of Castanopsis hystrix seedlings and biomass allocation, with optimal results observed at 60% shade, leading to the promotion of organic matter production in leaves and the limitation of stem growth. (2) Using a multi-indicator composite index, it was determined that seedling quality for Castanopsis hystrix peaks at 60% shade intensity. (3) Shade significantly impacts the morphology and structure of Castanopsis hystrix’s root system, with most root characteristics peaking at 60% shade, indicating a substantial increase in root development compared to no-shade conditions. (4) The D-values indicated the most suitable shade intensity for seedling growth to be 60%, suggesting that Castanopsis hystrix seedlings are sensitive to light and excessive light can be detrimental to their growth. (5) The 60% shade treatment showed the maximum values of chlorophyll fluorescence characteristics and photochemical activity, with variations in energy conversion efficiency and dissipation reflected in parameters like photochemical burst coefficient (qP), photochemical burst coefficient (qN), the actual photometric yield of PSII under light acclimation (YII), and the maximum photosynthetic electron transport rate in photoinhibition (ETR), thereby supporting seedling growth and maintaining the normal function of photosynthetic organs. In conclusion, 60% shade treatment can effectively improve the growth and photosynthetic characteristics of Castanopsis hystrix seedlings and promote the accumulation of nutrient elements, ultimately promoting their growth.

Genetic Parameter Estimates for the Growth and Morphological Traits of Castanopsis hystrix Families and the Genotype × Environment Interaction Effects

Castanopsis hystrix, a timber resource from Southeast Asia, is characterized by rapid growth and high yield, but plantation quality and efficiency improvements are required. Twenty-year-old C. hystrix experimental forests in Yulin, Liuzhou, and Pingxiang in Guangxi Province, China, comprising 21 open-pollinated half-sib families, were used in this study. Genetic variations in the growth (tree height, diameter at breast height (DBH), and volume (V)) and morphological (height to live crown base (HCB), crown width (CW), and branch angle) traits were assessed, and the genetic parameters were estimated to clarify the genotype × environment interaction effects. The average values for the tree height, DBH, V, HCB, CW, and branch angle were 16.33 m, 17.25 cm, 0.21 m3, 6.68 m, 2.15 m, and 45.45°, respectively. The most important sources of variance for the tree height, DBH, V, and HCB were the block and family, whereas the location, family, and family × location had significant impacts on the tree height, DBH, V, and HCB (p &lt; 0.01). The family heritability for each trait was 0.35, 0.38, 0.62, and 0.19, respectively. Excellent families with strong adaptability and genetic stability were identified using BLUP–GGE biplots for single and multiple traits. The results provide a theoretical basis for the efficient cultivation of C. hystrix in South China.

Tree species mixing begets admixture of soil microbial communities: Variations along bulk soil, rhizosphere soil and root tissue

Tree species can substantially impact the structure and functioning of soil microbial communities. However, how tree species mixing affects soil microbial communities along different soil compartment niches remains unknown, despite the theoretical (e.g., plant-soil feedback) and practical (e.g., rhizosphere engineering) importance of such knowledge in understanding and managing forest ecosystems. In this study, we analyzed soil samples taken from three microhabitats (bulk soil, rhizosphere soil, and root tissue) of pure conifer species (Pinus massoniana) plantations (PP), pure broadleaf species (Castanopsis hystrix) plantations (PC), and mixed plantation forest of the two species (MF) to understand the effects of tree species mixing on core soil microbial communities. We found that the diversity of soil bacterial and fungal communities was not affected by tree species mixing in most cases, but community composition (relative abundance and functional composition) was largely shaped by tree species mixing. Non-metric multidimensional scaling (NMDS) analysis revealed that the core bacterial and fungal communities of MF were between those of PP and PC. This suggests that tree species mixing can lead to a combination of soil microbial communities associated with each of the two tree species, potentially resulting in higher nutrient contents in the bulk soil of MF and lower phosphorus and carbon limitations in both the bulk and rhizosphere soils of MF compared to those of PP and PC. The Mantel test and redundancy analysis (RDA) showed that pH and NO3–-N content were the main environmental variables influencing soil microbial communities. Overall, the effects of tree species mixing varied markedly with microhabitat and season, with rhizosphere soil having the highest microbial diversity and network complexity and root tissue having the lowest. These results suggest that the mixing effects of tree species are more pronounced in the rhizosphere and dry season, on which silvicultural practices should focus.

Adding Castanopsis hystrix to a Pinus massoniana plantation changed leaf phosphorus and nitrogen investment and soil nitrogen concentrations

Adding Castanopsis hystrix to a Pinus massoniana plantation changed leaf phosphorus and nitrogen investment and soil nitrogen concentrations

Changes in Soil Properties, Microbial Quantity and Enzyme Activities in Four Castanopsis hystrix Forest Types in Subtropical China.

It is well established that forest type can have a profound impact on soil physicochemical properties but the associated changes in soil microbial communities and the mechanisms by which soil quality is improved by various plantations are not fully understood. In this study, soil physicochemical properties and microbial and enzyme activities were investigated in four forest types-Castanopsis hystrix pure forests (CHPF), C. hystrix-Pinus elliottii mixed forests (CHPEF), C. hystrix-Michelia macclurei mixed forests (CHMMF), and C. hystrix-Mytilaria laosensis mixed forests (CHMLF) in the subtropical region of China. The purpose of this study was to assess the effects of afforestation types on characteristics of soil-its physical, chemical, and biological properties. The results showed that the contents of soil total organic carbon (TOC), soil total nitrogen (TN), microbial biomass carbon (MBC), and microbial biomass nitrogen (MBN) were significantly improved in both CHMMF and CHMLF mixed forest stands when compared to the CHPF pure stand. Soil enzyme activities were enhanced in the mixed forests. In particular, high phosphatase activity was observed in CHMLF stands, leading to the transformation of soil phosphorus to available phosphorus in this forest type. Our study demonstrated that the broad-leaved mixed forests, but not coniferous mixed forests, could significantly improve soil quality in the study region. Our research provides a scientific insight into the promotion of vegetation restoration and plantation forest management in plantation regions of subtropical areas.