Pinus massoniana(P)forest and explore the dynamic changes for dissolved organic carbon(DOC)during the mixed decomposition process of P. massoniana and native broad-leaved tree species. Our research focuses on the leaf litter of P. massoniana, Cinnamomum camphora(C)and Toona sinensis(T), and combine them into the 15 treatments(3 single tree treatments + 12 mixed treatments)according to different tree species combinations and mass proportions, and then conducted field decomposition experiments to further explore the optimal tree species combination and the proportion of mixed planting for DOC release. The results were as follows:(1)DOC content of Pinus massoniana and most of mixed treatments(except for PT64)significantly increased during the early stages of decomposition(0-6 months), leading to carbon enrichment. The DOC content of leaf litter decreased with the extension of decomposition time, and also exhibited carbon enrichment in small degree during the middle to late stages of decomposition(12-18 months)or the late stages of decomposition(18-24 months). Mixed leaf litter showed that the higher the proportion of broad-leaved, the lower the DOC content in the later stage.(2)The antagonistic effect of DOC release rate in the early stage of decomposition(0-6 months)was strong(58.33%), and only 8.33%(1/12)of mixed treatments showed the synergistic effect. Its synergistic effect gradually strengthened(91.67%)after 6-18 months, but the synergistic effect of leaf litter(66.67%)during the late stage of decomposition weakened(18-24 months). Among all mixed treatments, PT64 exhibited synergistic effects throughout the entire decomposition stage, followed by PT73, PCT622 and PCT613(3/4).(3)Partial least-squares(PLS)regression showed that N content, P content, lignin content, condensed tannin content, C/N, C/P, lignin/N, and lignin/P were important quality factors affecting the release of DOC from litter in this study area. Overall, the DOC release from mixed Pinus massoniana and broad-leaved leaf litter is affected by tree species, mixed proportion and decomposition time. Compared to other mixed treatments, the proportion of broad-leaved greater is than or equal to 30.00% and the mixed leaf litter treatments including Toona sinensis(PT64, PT73, PCT622 and PCT613)show strong synergistic effects for DOC release.]]> 2024/8/5 10:00:45 1, ZHANG Yan¹, SONG Simeng¹, ZHOU Yang¹, ZHANG Jian^2*]]> LI Xun¹, ZHANG Yan¹, SONG Simeng¹, ZHOU Yang¹, ZHANG Jian^2* 5true Pinus massoniana plantations after close-to-nature transformation, the pure P. massoniana plantations(PP)and P. massoniana-broad-leaved mixed plantations(CP)after close-to-nature transformation were investigated in southern subtropical China. Soil samples collected from 1-10 cm were screened into >2 mm, 0.25-2 mm and <0.25 mm three-part aggregates using the dry-sieving method. The Po fraction, microbial biomass phosphorus(MBP)content and acid phosphatase(ACP)activity in the bulk soil and aggregates were measured to understand the distribution of the Po fraction and its drivers. The results were as follows:(1)Soil Po fractions changed in CP compared to PP, with highly recalcitrant organic phosphorus(HRO-P)and moderately labile organic phosphorus(MLO-P)significantly greater in the bulk soil and soil aggregates than in PP(P<0.05), while labile organic phosphorus(LO-P)and moderately recalcitrant organic phosphorus(MRO-P)were not significantly different in CP and PP. In addition, there was no consistent pattern of change in Po fractions in the bulk soil and soil aggregates between PP and CP.(2)The size of the proportion of each form of Po in PP was HRO-P>MRO-P>MLO-P>LO-P, while CP was HRO-P>MLO-P>MRO-P>LO-P.(3)The MBP content and ACP activity in CP were significantly greater than that of PP in the bulk soil and soil aggregates, and there was a tendency for the ACP activity to increase with the decrease in the size of aggregates.(4)Redundancy analysis revealed that soil available phosphorus(AP), soil aggregate mean weight diameter(MWD), MBP and total nitrogen(TN)were the main drivers of soil Po fractions. In conclusion, the close-to-nature transformation is beneficial to the accumulation and transformation of soil phosphorus in P. massoniana plantation. This study provides a theoretical reference for the improvement of soil quality and productivity in P. massoniana plantations.]]> 2024/8/5 10:00:45 1, YAN Jinliu¹, HUANG Haimei¹, LI Jiajun¹, XIANG Mingzhu¹, LI Changhang¹, HUANG Xueman^1,2, ZHAO Lijun¹, YOU Yeming^1,2*]]> QIN Huiting¹, YAN Jinliu¹, HUANG Haimei¹, LI Jiajun¹, XIANG Mingzhu¹, LI Changhang¹, HUANG Xueman^1,2, ZHAO Lijun¹, YOU Yeming^1,2* 4true Eucalyptus plantations is a common model of forest management in south subtropical China. To explore the response characteristics and mechanisms of soil fungal community diversity and function to native tree species and Eucalyptus plantations. four native tree species plantations(Pinus massoniana, Michelia macclurei, Mytilaria laosensis, Castanopsis hystrix)and exotic tree species Eucalyptus urophylla × E. grandis(EUG) plantations in south subtropical China were studied. Based on 18S rRNA high-throughput sequencing data of fungi in soil(0-20 cm)of each stand and FUNGuild database, the differences of diversity and functional group of soil fungal communities between native tree species and EUG plantations were compared and analyzed, as well as the dominant soil environmental factors affecting them. The results were as follows:(1)The dominant phyla of soil fungi in five stands were both Ascomycota and Basidiomycota, but there were differences in the dominant orders of soil fungi between different native tree species and EUG plantations.(2)The α diversity of soil fungal community in EUG plantation was higher than that in native tree plantations, and the community composition structure was significantly different from the native tree plantations(P<0.05).(3)The relative abundance of saprotroph in the native tree plantations was higher than that of EUG plantation, and the relative abundance of soil arbuscular mycorrhizal fungi in Michelia macclurei and Mytilaria laosensis plantations was significantly higher than that of EUG plantation. The relative abundance of soil symbiotroph, ectomycorrhizal fungi and wood saprotroph in EUG plantation was significantly higher than that in the native tree plantations.(4)pH was the crucial soil environmental factor that led to the difference of soil fungal community diversity and functional group between EUG and native tree plantations. In general, there were significant differences in the structure and function of soil fungal community between native tree species and EUG plantations, which indicated that different stand types had great effects on soil fungal community and function. In conclusion, the soil nutrient level can be improved by converting the EUG plantation into native tree species plantations in south subtropical China, and the soil ecological function can be improved by choosing Michelia macclurei plantation or Mytilaria laosensis plantation as native tree species plantation.]]> 2024/8/5 10:00:45 1, MING An'gang^2,3, TAN Ling¹, HE Jiang¹, QIN Lin^1*]]> XI Shouhong¹, MING An'gang^2,3, TAN Ling¹, HE Jiang¹, QIN Lin^1* 3true Acacia mangium on particle size distribution and stability of soil aggregates of Eucalyptus grandis X urophylla plantations, we measured the distribution and stability of aggregates indicators such as mean weight diameter(MWD), geometric mean diameter(GMD), mass fractal dimension(Dm), water stable aggregates(WSA), percentage of aggregates destruction(PAD)and aggregates stability index(ASI)in the 0-10 cm and 10-20 cm soil layers by the dry sieving method and the wet sieving method, and a pure plantation of E. grandis X urophylla(PP)and a mixed plantation containing E. grandis X urophylla and Acacia mangium(nitrogen-fixing tree species)(MP)were selected as the research objects. The results were as follows:(1)Compared with PP, the soil physicochemical properties of MP were improved in varying degrees, especially soil pH, organic carbon(SOC)and total nitrogen(TN).(2)The particle size distribution of soil aggregates in MP was better than that of PP, and the differences mainly in the particle sizes of >2.00 mm and <0.25 mm, but both were dominated by large aggregates(>0.25 mm). Compared with PP, the mechanical stability of aggregates in MP only increased significantly at 0-10 cm soil layer, but the water stability of aggregates in MP increased significantly at 0-10 cm and 10-20 cm soil layer. The mechanical stability and water stability of soil aggregates tended to decrease with the deepening of soil layer.(3)Mantel analysis showed that the stability of aggregates was significantly correlated with pH, SOC, TN, TP, BD and SP, and the stability of aggregates had the strongest correlation with TN. RDA analysis indicated that TN was the most critical factor driving the variation of stability aggregates. Our findings suggest that nitrogen-fixing tree species A. mangium can significantly improve proportion of macroaggregates(>0.25 mm)and the stability of soil aggregates in Eucalyptus plantations. This study can provide a theoretical reference for soil and water conservation, soil nutrient management and sustainable management of Eucalyptus plantations in the South Asian tropics.]]> 2024/8/5 0:00:00 1, LI Jiajun¹, XIANG Mingzhu¹, HUANG Haimei¹, LI Changhang¹, YAN Jinliu¹, GAO Guannü¹, SU Xiaoyan¹, YOU Yeming^1,2, HUANG Xueman^1,2*]]> ZHANG Wen¹, LI Jiajun¹, XIANG Mingzhu¹, HUANG Haimei¹, LI Changhang¹, YAN Jinliu¹, GAO Guannü¹, SU Xiaoyan¹, YOU Yeming^1,2, HUANG Xueman^1,2* 2true Eucalyptus plantations in subtropical China, we used biochar(BC)as a soil amendment to investigate the soil of Eucalyptus plantations(15 years old). Meanwhile, we added the different amounts [0(CK), 2%, 5%, 10% and 20%] of BC through the laboratory culture experiment to evaluate the effects of different amounts of BC on P components and transformation in soil and its relationship with soil physicochemical properties. The results were as follows:(1)Compared to CK, the nitrate nitrogen(NO₃^--N), total phosphorus(TP), microbial biomass phosphorus(MBP)and pH values were significantly increased at 20% BC addition, respectively(P<0.05), the MBP and pH values were significantly increased at 2%, 5%, and 10% BC addition, respectively(P<0.05), while no marked difference was found in other soil physicochemical properties.(2)Compared to CK, the labile P(LP)was significantly increased at 2% of BC addition(P<0.05), the available P(AP)and LP were significantly increased at 5% and 10% of BC additions, respectively(P<0.05). Moreover, the AP, LP and occluded P(OP)were significantly increased at 20% BC addition(P<0.05), whereas the moderately available P(MP)had no significant change under the four BC additions.(3)The total activities of β-glucosidase(BG), β-N-acetylglucosaminidase(NAG), L-leucine aminopeptidase(LAP), and acid phosphatase(ACP)involved in C, N and P transformations increased significantly at 10% and 20% BC additions than those in CK(P<0.05).(4)Correlation analysis showed that ln(BG)and ln(NAG+LAP)were positively correlated with ln(ACP), respectively(P<0.05). In addition, redundancy analysis(RDA)indicated that pH, TN and TP appeared to be the primary drivers of variations in soil P components of Eucalyptus plantations. Furthermore, structural equation model(SEM)revealed that the pH, C:P and N:P of soil were the most critical factors driving P transformation. In conclusion, our findings suggest that different amounts of BC improve the enzyme activities related to C, N cyclings by affecting soil physicochemical properties and improving the P supply potential of soil in Eucalyptus plantations. Notably, 20% BC addition had the optimum effect. This study provides critical theoretical guidance for gaining knowledge on soil nutrient management in Eucalyptus plantations and facilitating the sustainable development of forests in subtropical China.]]> 2024/8/5 10:00:45 1, GAO Guannü¹, ZHANG Wen¹, YOU Yeming^1,2, HUANG Xueman^1,2*]]> YE Xiaomin¹, GAO Guannü¹, ZHANG Wen¹, YOU Yeming^1,2, HUANG Xueman^1,2* 1true