The soils of southern Guam are formed from very deep;well-drained Saprolite derived from volcanic based tuff and tuff breccias.These soils suffer severe erosion as the result of rapid overland flow,wind and intensive ...The soils of southern Guam are formed from very deep;well-drained Saprolite derived from volcanic based tuff and tuff breccias.These soils suffer severe erosion as the result of rapid overland flow,wind and intensive rain events typical of southern Guam.An integrated approach to control the accelerated soil erosion was designed to include conservation tillage,crop rotation with leguminous plant,and residue management for soil surface cover.The objectives of this study are;1)to evaluate the use of crop rotation and tillage management for increasing organic-matter content to improve the overall quality of these severely eroded soils,2)to evaluate the effect of conservation practices on harvested yield and crop productivity of these eroded soils and,3)to assess the effects of conservation techniques including no-tillage systems on water runoff and infiltration.This paper discusses the effect of conservation strategies and techniques on these severely eroded soils of southern Guam.展开更多
Soil acidification via acid precipitation is recognized to have detrimental impacts on forest ecosystems, which is in part associated with the function of ethylene released from the soil. However, the impacts of acidi...Soil acidification via acid precipitation is recognized to have detrimental impacts on forest ecosystems, which is in part associated with the function of ethylene released from the soil. However, the impacts of acidification on the cycling of ethylene in forest soils have not been fully taken into consideration in global change studies. Forest topsoils （0-5 cm） under four temperate forest stands were sampled to study the effects of a pH change on the emissions of ethylene and carbon dioxide from the soils and concentrations of dissolved organic carbon （DOC） released into the soils. Increasing acidification or alkalinization of forest soils could increase concentrations of DOC released into the soils under anoxic and oxic conditions. The ethylene emission from these forest topsoils could significantly increase with a decreasing pH, when the soils were acidified experimentally to a pH〈4.0, and it increased with an increasing concentration of DOC released into the soils, which was different from the carbon dioxide emission from the soils. Hence, the short-term stimulating responses of ethylene emission to a decreasing pH in such forest soils resulted from the increase in the DOC concentration due to acidification rather than carbon mineralization. The results would promote one to study the effects of soil acidification on the cycling of ethylene under different forest stands, particularly under degraded forest stands with heavy acid depositions.展开更多
Soil is a large terrestrial carbon pool so that the evaluation and prediction of soil respiration is important for understanding and managing carbon cycling between the pedosphere and the atmosphere. For better unders...Soil is a large terrestrial carbon pool so that the evaluation and prediction of soil respiration is important for understanding and managing carbon cycling between the pedosphere and the atmosphere. For better understanding about characteristics and mechanisms of soil respiration, this study monitored seasonal behaviors of soil gaseous CO<sub>2</sub> concentration profile with relevant soil physical conditions in a meadow field, and numerically analyzed the monitored data sets to inversely determine time-series of depth distributions of CO<sub>2</sub> production rate in the field by assuming optimum ranges of depth and moisture condition for aerobic respiration of soil fauna and flora. The results of the inverse analyses showed that the depth range of intense CO<sub>2</sub> production resided in top soil layers during summer and moved down into subsoil layers in winter, implying that the depth range of main CO<sub>2</sub> sources can change dynamically with seasons. The surface CO<sub>2</sub> emission rates derived from the inverse analyses fell in the range typically found in the same kind of land use. The evaluated mean residence time of gaseous CO<sub>2</sub> in the study field was around half a day. These findings suggested that the modelling assumptions about soil respiration in this study are effective to probe spatial and temporal behavior of respiratory activity in a soil layer, and it is still important to integrate facts about in-situ CO<sub>2</sub> concentration profiles with soil physical parameters for quantitatively predicting possible behaviors of soil respiration in response to hypothetical changes in atmospheric and soil climates.展开更多
文摘The soils of southern Guam are formed from very deep;well-drained Saprolite derived from volcanic based tuff and tuff breccias.These soils suffer severe erosion as the result of rapid overland flow,wind and intensive rain events typical of southern Guam.An integrated approach to control the accelerated soil erosion was designed to include conservation tillage,crop rotation with leguminous plant,and residue management for soil surface cover.The objectives of this study are;1)to evaluate the use of crop rotation and tillage management for increasing organic-matter content to improve the overall quality of these severely eroded soils,2)to evaluate the effect of conservation practices on harvested yield and crop productivity of these eroded soils and,3)to assess the effects of conservation techniques including no-tillage systems on water runoff and infiltration.This paper discusses the effect of conservation strategies and techniques on these severely eroded soils of southern Guam.
基金funded jointlyby the National Natural Science Foundation of China(Grant Nos.40875085,20777071,and 20477044)the Hundred Talents Project from the Chinese Academy of Sciencesthe Japan Society for the Promotion of Sciences
文摘Soil acidification via acid precipitation is recognized to have detrimental impacts on forest ecosystems, which is in part associated with the function of ethylene released from the soil. However, the impacts of acidification on the cycling of ethylene in forest soils have not been fully taken into consideration in global change studies. Forest topsoils （0-5 cm） under four temperate forest stands were sampled to study the effects of a pH change on the emissions of ethylene and carbon dioxide from the soils and concentrations of dissolved organic carbon （DOC） released into the soils. Increasing acidification or alkalinization of forest soils could increase concentrations of DOC released into the soils under anoxic and oxic conditions. The ethylene emission from these forest topsoils could significantly increase with a decreasing pH, when the soils were acidified experimentally to a pH〈4.0, and it increased with an increasing concentration of DOC released into the soils, which was different from the carbon dioxide emission from the soils. Hence, the short-term stimulating responses of ethylene emission to a decreasing pH in such forest soils resulted from the increase in the DOC concentration due to acidification rather than carbon mineralization. The results would promote one to study the effects of soil acidification on the cycling of ethylene under different forest stands, particularly under degraded forest stands with heavy acid depositions.
文摘Soil is a large terrestrial carbon pool so that the evaluation and prediction of soil respiration is important for understanding and managing carbon cycling between the pedosphere and the atmosphere. For better understanding about characteristics and mechanisms of soil respiration, this study monitored seasonal behaviors of soil gaseous CO<sub>2</sub> concentration profile with relevant soil physical conditions in a meadow field, and numerically analyzed the monitored data sets to inversely determine time-series of depth distributions of CO<sub>2</sub> production rate in the field by assuming optimum ranges of depth and moisture condition for aerobic respiration of soil fauna and flora. The results of the inverse analyses showed that the depth range of intense CO<sub>2</sub> production resided in top soil layers during summer and moved down into subsoil layers in winter, implying that the depth range of main CO<sub>2</sub> sources can change dynamically with seasons. The surface CO<sub>2</sub> emission rates derived from the inverse analyses fell in the range typically found in the same kind of land use. The evaluated mean residence time of gaseous CO<sub>2</sub> in the study field was around half a day. These findings suggested that the modelling assumptions about soil respiration in this study are effective to probe spatial and temporal behavior of respiratory activity in a soil layer, and it is still important to integrate facts about in-situ CO<sub>2</sub> concentration profiles with soil physical parameters for quantitatively predicting possible behaviors of soil respiration in response to hypothetical changes in atmospheric and soil climates.
