Trees on sand dunes are more sensitive to environmental changes because sandy soils have extremely low water holding capacity and nutrient availability. We investigated the dynamics of soil respiration(Rs) for seconda...Trees on sand dunes are more sensitive to environmental changes because sandy soils have extremely low water holding capacity and nutrient availability. We investigated the dynamics of soil respiration(Rs) for secondary natural Litsea forest and plantations of casuarina,pine, acacia and eucalyptus. Results show that significant diurnal variations of Rsoccurred in autumn for the eucalyptus species and in summer for the pine species, with higher mean soil respiration at night. However, significant seasonal variations of Rswere found in all five forest stands. Rschanged exponentially with soil temperatures at the 10-cm depth; the models explain 43.3–77.0% of Rs variations. Positive relationships between seasonal Rsand soil moisture varied with stands. The correlations were significant only in the secondary forest, and the eucalyptus and pine plantations. The temperature sensitivity parameter(Q10 value) of Rsranged from 1.64 in casuarina plantation to 2.32 the in secondary forest; annual Rswas highest in the secondary forest and lowest in the pine plantation. The results indicate that soil temperatures and moisture are the primary environmental controls of soil respiration and mainly act through a direct influence on roots and microbial activity. Differences in root biomass, quality of litter,and soil properties(pH, total N, available P, and exchangeable Mg) were also significant factors.展开更多
Timely monitoring and early warning of soil salinity are crucial for saline soil management. Environmental variables are commonly used to build soil salinity prediction model. However, few researches have been done to...Timely monitoring and early warning of soil salinity are crucial for saline soil management. Environmental variables are commonly used to build soil salinity prediction model. However, few researches have been done to summarize the environmental sensitive variables for soil electrical conductivity(EC) estimation systematically. Additionally, the performance of Multiple Linear Regression(MLR), Geographically Weighted Regression(GWR), and Random Forest regression(RFR) model, the representative of current main methods for soil EC prediction, has not been explored. Taking the north of Yinchuan plain irrigation oasis as the study area, the feasibility and potential of 64 environmental variables, extracted from the Landsat 8 remote sensed images in dry season and wet season, the digital elevation model, and other data, were assessed through the correlation analysis and the performance of MLR, GWR, and RFR model on soil salinity estimation was compared. The results showed that: 1) 10 of 15 imagery texture and spectral band reflectivity environmental variables extracted from Landsat 8 image in dry season were significantly correlated with soil EC, while only 3 of these indices extracted from Landsat 8 image in wet season have significant correlation with soil EC. Channel network base level, one of the terrain attributes, had the largest absolute correlation coefficient of 0.47 and all spatial location factors had significant correlation with soil EC. 2) Prediction accuracy of RFR model was slightly higher than that of the GWR model, while MLR model produced the largest error. 3) In general, the soil salinization level in the study area gradually increased from south to north. In conclusion, the remote sensed imagery scanned in dry season was more suitable for soil EC estimation, and topographic factors and spatial location also play a key role. This study can contribute to the research on model construction and variables selection for soil salinity estimation in arid and semiarid regions.展开更多
By comparison the soil physical and chemical characteristics and heavy metal content of 6 forest rehabilitation sites in Shunde District, Foshan City, Guangdong Province, were studied and analyzed. The results showed ...By comparison the soil physical and chemical characteristics and heavy metal content of 6 forest rehabilitation sites in Shunde District, Foshan City, Guangdong Province, were studied and analyzed. The results showed that the soil bulk density was heavy in all the 6 sites. The soil structure and holding water-fertility capability was the best in Jun’an followed by Longjiang and Daliang was the worst. The soil organic matter, total N, cation exchange capacity, base cation concentration and pH value showed a tendency to reduce with the different ways of silviculture from no rehabilitation to rehabilitate completely. The soil nutrient elements were losed slowly in forest rehabilitation prophase. In all sites, the soil cadmium(Cd) and plumbum(Pb) contents overstepped third scope of environmental quality standard for soils (GB 15618-1995) and nature background value respectively, reached heavier pollution and lightly pollution. The environment loading capacity of soil for heavy metals did not show the obvious correlation with the silviculture methods. In the initial stages of forest rehabilitation, the soil environment qualities were not diverged from that of before rehabilitation. Planting native broadleaf tree species had great significance to protect forest soil from heavy metal pollution and raise environment capacity.展开更多
基金supported by the National Natural Science Foundation of China(31570604,41371269)The Basal Research Fund of Fujian provincial Public Scientific Research Institution support(2014R1011-7)the Casuarina Research Center of Engineering and Technology,and the Key Laboratory of Forest Culture and Forest Product Processing Utilization of Fujian Province
文摘Trees on sand dunes are more sensitive to environmental changes because sandy soils have extremely low water holding capacity and nutrient availability. We investigated the dynamics of soil respiration(Rs) for secondary natural Litsea forest and plantations of casuarina,pine, acacia and eucalyptus. Results show that significant diurnal variations of Rsoccurred in autumn for the eucalyptus species and in summer for the pine species, with higher mean soil respiration at night. However, significant seasonal variations of Rswere found in all five forest stands. Rschanged exponentially with soil temperatures at the 10-cm depth; the models explain 43.3–77.0% of Rs variations. Positive relationships between seasonal Rsand soil moisture varied with stands. The correlations were significant only in the secondary forest, and the eucalyptus and pine plantations. The temperature sensitivity parameter(Q10 value) of Rsranged from 1.64 in casuarina plantation to 2.32 the in secondary forest; annual Rswas highest in the secondary forest and lowest in the pine plantation. The results indicate that soil temperatures and moisture are the primary environmental controls of soil respiration and mainly act through a direct influence on roots and microbial activity. Differences in root biomass, quality of litter,and soil properties(pH, total N, available P, and exchangeable Mg) were also significant factors.
基金Under the auspices of National Natural Science Foundation of China(No.41571217)National Program on Key Basic Research Project(No.2016YFD0300801)
文摘Timely monitoring and early warning of soil salinity are crucial for saline soil management. Environmental variables are commonly used to build soil salinity prediction model. However, few researches have been done to summarize the environmental sensitive variables for soil electrical conductivity(EC) estimation systematically. Additionally, the performance of Multiple Linear Regression(MLR), Geographically Weighted Regression(GWR), and Random Forest regression(RFR) model, the representative of current main methods for soil EC prediction, has not been explored. Taking the north of Yinchuan plain irrigation oasis as the study area, the feasibility and potential of 64 environmental variables, extracted from the Landsat 8 remote sensed images in dry season and wet season, the digital elevation model, and other data, were assessed through the correlation analysis and the performance of MLR, GWR, and RFR model on soil salinity estimation was compared. The results showed that: 1) 10 of 15 imagery texture and spectral band reflectivity environmental variables extracted from Landsat 8 image in dry season were significantly correlated with soil EC, while only 3 of these indices extracted from Landsat 8 image in wet season have significant correlation with soil EC. Channel network base level, one of the terrain attributes, had the largest absolute correlation coefficient of 0.47 and all spatial location factors had significant correlation with soil EC. 2) Prediction accuracy of RFR model was slightly higher than that of the GWR model, while MLR model produced the largest error. 3) In general, the soil salinization level in the study area gradually increased from south to north. In conclusion, the remote sensed imagery scanned in dry season was more suitable for soil EC estimation, and topographic factors and spatial location also play a key role. This study can contribute to the research on model construction and variables selection for soil salinity estimation in arid and semiarid regions.
文摘By comparison the soil physical and chemical characteristics and heavy metal content of 6 forest rehabilitation sites in Shunde District, Foshan City, Guangdong Province, were studied and analyzed. The results showed that the soil bulk density was heavy in all the 6 sites. The soil structure and holding water-fertility capability was the best in Jun’an followed by Longjiang and Daliang was the worst. The soil organic matter, total N, cation exchange capacity, base cation concentration and pH value showed a tendency to reduce with the different ways of silviculture from no rehabilitation to rehabilitate completely. The soil nutrient elements were losed slowly in forest rehabilitation prophase. In all sites, the soil cadmium(Cd) and plumbum(Pb) contents overstepped third scope of environmental quality standard for soils (GB 15618-1995) and nature background value respectively, reached heavier pollution and lightly pollution. The environment loading capacity of soil for heavy metals did not show the obvious correlation with the silviculture methods. In the initial stages of forest rehabilitation, the soil environment qualities were not diverged from that of before rehabilitation. Planting native broadleaf tree species had great significance to protect forest soil from heavy metal pollution and raise environment capacity.
