Allelopathy is an important mechanism in Eucalyptus plantations that causes detrimental impacts on understory diversity.Phenolic compounds are the main allelochemicals suppressing understory plants.However,the dynamic...Allelopathy is an important mechanism in Eucalyptus plantations that causes detrimental impacts on understory diversity.Phenolic compounds are the main allelochemicals suppressing understory plants.However,the dynamic changes in phenolic allelochemicals and their relationship with understory diversity with increasing age of Eucalyptus plantations remain largely unclear.In this study,the understory plant diversity was assessed and phenolic compounds identified from leaf litter,roots,and rhizosphere soil samples in a Eucalyptus grandis plantation at two-year intervals for ten years using ultra-performance liquid chromatography-tandem mass spectrometry(UPLC-MS/MS).The abundance and diversity of under story plant species were lowest in 4-year-old plantations and increased significantly with age.Seven phenolic acids and 10 flavonoids were identified from leaf litter,roots,and rhizosphere soils.Most of the potential phenolic allelochemicals,such as salicylic acid,gallic acid,4-hydroxybenzoic acid,and epicatechin,were more abundant in younger plantations,especially at4 years old.The concentrations of phenolic compounds in the rhizosphere zone were significantly lower than in litter and root samples and did not change significantly with an increase in age.Notably,phenolic compounds contributed more to the variation in the understory plants than soil factors.Hydroxyphenyllactic acid,ellagic acid,quercetin,salicylic acid,and 4-hydroxybenzoic acid were the main phenolic compounds explaining the variation in plant diversity with plantation age.These findings indicate that young E.grandis plantations,especially at four years of age,merit a greater focus because of their lower understory plant diversity and higher allelopathic potential.展开更多
A study was conducted to evaluate the status of soil nutrients under E. grandis plantation in comparison with that in its adjacent submontane rain forest. Twenty sequare plots, with an area of 20 m×20 m for each,...A study was conducted to evaluate the status of soil nutrients under E. grandis plantation in comparison with that in its adjacent submontane rain forest. Twenty sequare plots, with an area of 20 m×20 m for each, were established in both of E.grandis plantation and its adjacent sub-montane rain forest, independently. Soil samples were collected from each square plot, at five points （at the four comers and at the center） of each plot. The collected soil samples were mixed to make a composite and representative sample for each plot, independently. The analyses were done in a soil laboratory following appropriate methods. The analysis result indicated that there were no significance differences between E. grandis plantation and its adjacent sub-montane rain forest in the level of major soil nutrients （total N, available P, exchangeable K, Ca and Mg）, pH and total carbon of soils （p 〈 0.05）. There were significance differences between two sites of forest soils in percentage of clay particles, and exchangeable Na content. E. grandis plantation was found improving soil nutrients and total carbon as compared with that of its adjacent submontane rain forest.展开更多
Fire has been used to prepare land during tree plantation establishment for many years but uncertainty about how ecosystems respond to prescribed burning makes it difficult to predict the effects of fire on soil nutri...Fire has been used to prepare land during tree plantation establishment for many years but uncertainty about how ecosystems respond to prescribed burning makes it difficult to predict the effects of fire on soil nutrients.The aim of this study was to determine the effect of burning accumulated forest residues(slash)on soil chemical properties and how trees respond.We analyzed 40 burned and unburned sites and compared growth of Eucalyptus grandis W.Hill ex Maiden between sites.Soil pH increased by 39%after fire,suggesting reduced soil acidity and increased liming.Total nitrogen increased by 100%;other nutrients(Ca^2+,Mg^2+and K^+)also increased.Increase in nutrients had a significant effect on the growth of E.grandis;larger and taller trees were associated more with burned than unburned sites.This study provides evidence that burning accumulated slash during land preparation prior to plantation establishment alters soil nutrient status and enhances the growth of E.grandis.展开更多
The research method in this paper is based on the standard of American Society for Testing andMaterials (ASTM). Planing and sanding are selected to study the machining properties of E. urophylla × E.grandis plant...The research method in this paper is based on the standard of American Society for Testing andMaterials (ASTM). Planing and sanding are selected to study the machining properties of E. urophylla × E.grandis plantation wood. Moreover, the reasons for machining defects are analyzed. The results show E.urophylla × E. grandis planted in south China is a good species with a great potential for solid woodutilization.展开更多
The objective of this study was to understand influence of planting spacing on mechanical properties of Eucalyptus grandis × E. urophylla planted as a potential species for solid wood products in China. Four tree...The objective of this study was to understand influence of planting spacing on mechanical properties of Eucalyptus grandis × E. urophylla planted as a potential species for solid wood products in China. Four trees at age of 13 were selected from each of 6 groups of planting spacing and a total of 24 sampling trees were selected from the Dongmen Forestry Center of Guangxi Province in China. Furthermore, a one-meter-long log from each tree was cut into small blocks for wood properties testing. MOE, MOR and compression strength parallel to wood grain were determined in accordance with Chinese standards. In addition, wood density and shrinkage properties were measured. Statistical analysis by SAS software indicated significant differences among the 6 groups of planting spacings on the air-dried density, radial shrinkage and bending MOR properties at the 0.05 level, and also on the compression strength at the 0.10 level. However, it was observed that there is no significant differences among shrinkages in tangential and volume, and MOE.展开更多
The research method of this paper is based on the standards of American Society for Testing and Materials (ASTM). Four items that contain boring, mortising, shaping and turning are selected to study the machining prop...The research method of this paper is based on the standards of American Society for Testing and Materials (ASTM). Four items that contain boring, mortising, shaping and turning are selected to study the machining properties of E. urophylla × E. grandis plantation wood. The reasons for machining defects are analyzed. The resultshows thatE. urophylla × E. grandis planted in South China isa good specieswith great potential for solid wood utilization.展开更多
To use eucalyptus as solid wood products in value-added way instead of wood chips for pulp and paper, the sawing characteristics of E. grandis was studied, the strain changes in sawing process, bow deformation and end...To use eucalyptus as solid wood products in value-added way instead of wood chips for pulp and paper, the sawing characteristics of E. grandis was studied, the strain changes in sawing process, bow deformation and end-splits of lumber were analyzed. The results showed that the sawing strain changed in a random way, but the bow deformation had an evident regularity, the lumber near its bark had a big bow deformation. The end-splits had severe influence to lumber recovery, 15% of lumber recovery was influenced by end-splits. The results also indicated that planted E. grandis was a potential wood species as solid wood utilization in the fast-growing plantation.展开更多
Coastal sand dune ecosystems generally have infertile soil with low water-holding capacity and high salinity. However, many plant species have adapted to the harsh sand environment along the southeastern coast of Chin...Coastal sand dune ecosystems generally have infertile soil with low water-holding capacity and high salinity. However, many plant species have adapted to the harsh sand environment along the southeastern coast of China. Studying the microbial biomass in such an ecosystem can improve our understanding of the roles that microbes play in soil fertility and nutrient cycling. We investigated the differences in soil microbial biomass carbon(MBC) and nitrogen(MBN) contents and their seasonal dynamics in five forest types(a secondary forest and plantations of Casuarinas, Pine, Acacia, and Eucalyptus). The results indicated that the seasonal variations of soil MBC and MBN contents in all five forest stands were higher in spring and winter, but lower in summer and autumn. The MBC content was lower in the Casuarinas plantation than in the other plantations in the same soil layer. However, no significant differences were observed in MBN contents among the different forest types. The MBC and MBN concentrations were positively correlated with soil moisture, but negatively correlated with soil temperature. The MBC and MBN contents also decreased with increasing soil depth. Across all soil layers, secondary forest had the highest MBC and MBN concentrations. Our study also showed that the MBC and MBN contents were positively affected by total soil carbon(TC), pH, and litter N content, but were negatively impacted by soil bulk density and litter C content. Moreover, the MBN content was positively correlated with root N content. In summary, environmental factors and the differences in litter and fine roots, soil nutrient contents, as well as the soil physical and chemical properties caused by different tree species collectively affected the concentrations of the soil MBC and MBN.展开更多
基金funded by the National Nature Science Foundation of China (No.32171775,31770671)。
文摘Allelopathy is an important mechanism in Eucalyptus plantations that causes detrimental impacts on understory diversity.Phenolic compounds are the main allelochemicals suppressing understory plants.However,the dynamic changes in phenolic allelochemicals and their relationship with understory diversity with increasing age of Eucalyptus plantations remain largely unclear.In this study,the understory plant diversity was assessed and phenolic compounds identified from leaf litter,roots,and rhizosphere soil samples in a Eucalyptus grandis plantation at two-year intervals for ten years using ultra-performance liquid chromatography-tandem mass spectrometry(UPLC-MS/MS).The abundance and diversity of under story plant species were lowest in 4-year-old plantations and increased significantly with age.Seven phenolic acids and 10 flavonoids were identified from leaf litter,roots,and rhizosphere soils.Most of the potential phenolic allelochemicals,such as salicylic acid,gallic acid,4-hydroxybenzoic acid,and epicatechin,were more abundant in younger plantations,especially at4 years old.The concentrations of phenolic compounds in the rhizosphere zone were significantly lower than in litter and root samples and did not change significantly with an increase in age.Notably,phenolic compounds contributed more to the variation in the understory plants than soil factors.Hydroxyphenyllactic acid,ellagic acid,quercetin,salicylic acid,and 4-hydroxybenzoic acid were the main phenolic compounds explaining the variation in plant diversity with plantation age.These findings indicate that young E.grandis plantations,especially at four years of age,merit a greater focus because of their lower understory plant diversity and higher allelopathic potential.
基金supported by the Canadian International Development Agency (CIDA)
文摘A study was conducted to evaluate the status of soil nutrients under E. grandis plantation in comparison with that in its adjacent submontane rain forest. Twenty sequare plots, with an area of 20 m×20 m for each, were established in both of E.grandis plantation and its adjacent sub-montane rain forest, independently. Soil samples were collected from each square plot, at five points （at the four comers and at the center） of each plot. The collected soil samples were mixed to make a composite and representative sample for each plot, independently. The analyses were done in a soil laboratory following appropriate methods. The analysis result indicated that there were no significance differences between E. grandis plantation and its adjacent sub-montane rain forest in the level of major soil nutrients （total N, available P, exchangeable K, Ca and Mg）, pH and total carbon of soils （p 〈 0.05）. There were significance differences between two sites of forest soils in percentage of clay particles, and exchangeable Na content. E. grandis plantation was found improving soil nutrients and total carbon as compared with that of its adjacent submontane rain forest.
文摘Fire has been used to prepare land during tree plantation establishment for many years but uncertainty about how ecosystems respond to prescribed burning makes it difficult to predict the effects of fire on soil nutrients.The aim of this study was to determine the effect of burning accumulated forest residues(slash)on soil chemical properties and how trees respond.We analyzed 40 burned and unburned sites and compared growth of Eucalyptus grandis W.Hill ex Maiden between sites.Soil pH increased by 39%after fire,suggesting reduced soil acidity and increased liming.Total nitrogen increased by 100%;other nutrients(Ca^2+,Mg^2+and K^+)also increased.Increase in nutrients had a significant effect on the growth of E.grandis;larger and taller trees were associated more with burned than unburned sites.This study provides evidence that burning accumulated slash during land preparation prior to plantation establishment alters soil nutrient status and enhances the growth of E.grandis.
文摘The research method in this paper is based on the standard of American Society for Testing andMaterials (ASTM). Planing and sanding are selected to study the machining properties of E. urophylla × E.grandis plantation wood. Moreover, the reasons for machining defects are analyzed. The results show E.urophylla × E. grandis planted in south China is a good species with a great potential for solid woodutilization.
基金China-ACIRA (Australian Centre for International Agricultural Research) cooperation project (FST/1999/095) Chinese"948" Project (No. 2005-4-73).
文摘The objective of this study was to understand influence of planting spacing on mechanical properties of Eucalyptus grandis × E. urophylla planted as a potential species for solid wood products in China. Four trees at age of 13 were selected from each of 6 groups of planting spacing and a total of 24 sampling trees were selected from the Dongmen Forestry Center of Guangxi Province in China. Furthermore, a one-meter-long log from each tree was cut into small blocks for wood properties testing. MOE, MOR and compression strength parallel to wood grain were determined in accordance with Chinese standards. In addition, wood density and shrinkage properties were measured. Statistical analysis by SAS software indicated significant differences among the 6 groups of planting spacings on the air-dried density, radial shrinkage and bending MOR properties at the 0.05 level, and also on the compression strength at the 0.10 level. However, it was observed that there is no significant differences among shrinkages in tangential and volume, and MOE.
文摘The research method of this paper is based on the standards of American Society for Testing and Materials (ASTM). Four items that contain boring, mortising, shaping and turning are selected to study the machining properties of E. urophylla × E. grandis plantation wood. The reasons for machining defects are analyzed. The resultshows thatE. urophylla × E. grandis planted in South China isa good specieswith great potential for solid wood utilization.
基金This research is supported by ITTO Project PD 69/01 Rev.2 (I) "Improved and diversified use of tropical plantation timbers in China tosupplement diminishing supplies from natural forests".
文摘To use eucalyptus as solid wood products in value-added way instead of wood chips for pulp and paper, the sawing characteristics of E. grandis was studied, the strain changes in sawing process, bow deformation and end-splits of lumber were analyzed. The results showed that the sawing strain changed in a random way, but the bow deformation had an evident regularity, the lumber near its bark had a big bow deformation. The end-splits had severe influence to lumber recovery, 15% of lumber recovery was influenced by end-splits. The results also indicated that planted E. grandis was a potential wood species as solid wood utilization in the fast-growing plantation.
基金The Science and Technology Major Project of Fujian Province (2018NZ0001-1)The Basal Research Fund of Fujian Province Public Scientific Research Institution (2019R1009-6)+1 种基金The Casuarina Research Center of Engineering and TechnologyThe Key Laboratory of Forest Culture and Forest Product Processing Utilization of Fujian Province。
文摘Coastal sand dune ecosystems generally have infertile soil with low water-holding capacity and high salinity. However, many plant species have adapted to the harsh sand environment along the southeastern coast of China. Studying the microbial biomass in such an ecosystem can improve our understanding of the roles that microbes play in soil fertility and nutrient cycling. We investigated the differences in soil microbial biomass carbon(MBC) and nitrogen(MBN) contents and their seasonal dynamics in five forest types(a secondary forest and plantations of Casuarinas, Pine, Acacia, and Eucalyptus). The results indicated that the seasonal variations of soil MBC and MBN contents in all five forest stands were higher in spring and winter, but lower in summer and autumn. The MBC content was lower in the Casuarinas plantation than in the other plantations in the same soil layer. However, no significant differences were observed in MBN contents among the different forest types. The MBC and MBN concentrations were positively correlated with soil moisture, but negatively correlated with soil temperature. The MBC and MBN contents also decreased with increasing soil depth. Across all soil layers, secondary forest had the highest MBC and MBN concentrations. Our study also showed that the MBC and MBN contents were positively affected by total soil carbon(TC), pH, and litter N content, but were negatively impacted by soil bulk density and litter C content. Moreover, the MBN content was positively correlated with root N content. In summary, environmental factors and the differences in litter and fine roots, soil nutrient contents, as well as the soil physical and chemical properties caused by different tree species collectively affected the concentrations of the soil MBC and MBN.
