内蒙古锡林郭勒盟典型草原固碳量及固碳潜力估算

为了评价不同放牧强度对草原固碳量及固碳潜力的影响，本研究采用系统动力学建模方法耦合CASA光合利用率模型、Shiyomi放牧模型、Raich土壤呼吸模型等模型，建立了基于系统动力学库-流思路的碳循环模型，该模型包含3个子系统、4个碳库。结果表明：1998至2015年，在内蒙古锡林郭勒盟的温度降低、降水量增加的背景下，净初级生产力呈现升高的趋势，典型草原土壤固碳量呈现下降趋势；放牧强度在3羊·公顷^-1下净生态系统初级生产力最低，固碳潜力最大，分别为-16.2 gC·m^-2和24.84 TgC。因此，建议内蒙古锡林郭勒盟典型草原西部（阿巴嘎旗、那仁宝力格站）的放牧强度不宜超过1.5羊·公顷^-1；东部（多伦县、东乌珠穆沁、西乌珠穆沁、锡林浩特站）不宜超过4.5羊·公顷^-1。     

Do tillage and conversion of grassland to cropland always deplete soil organic carbon?

ABSTRACT

Conversion of grassland to cropland is widely reported to deplete soil organic carbon (SOC) largely due to tillage effects on the decomposition of SOC. However, most studies report on long-term changes in SOC following the conversion and little is known about the changes in the short term. Net ecosystem carbon budget (NECB) measures the difference between total C input (i.e., manure, above- and below-ground plant residues) and C loss through heterotrophic respiration (RH). However, most studies that report temporal SOC do not report other components of the NECB like RH, total C inputs and often do not include the cumulative annualized change of these components. This review evaluated the change in C input, RH, NECB and SOC after conversion of permanent/continuous grassland to cropland within 5 years after the conversion. We also reviewed and compared no-tillage and conventional tillage on SOC storage and accumulation. Total C input was higher in grassland than cropland largely due to high root biomass, as opposed to aboveground residue, and therefore grassland tended to have higher NECB. Despite higher NECB in grassland, the SOC stocks in cropland (cornfield) converted from grassland were greater than that in continuous grassland within first 2–3 years of conversion. The combination of manure C addition and tillage in cropland showed potential to maintain NECB and increase SOC. Within the continuous grassland C addition alone increased NECB but did not result in a corresponding increase in SOC. Residue retention and manure addition are recognized as good practices for increasing SOC, this study however, shows that combining them with occasional tillage, especially in managed grasslands, could increase the rate of SOC storage in soils.     

Ethanol extract from Cortex Albiziae attenuates mouse acute liver injury induced by carbon tetrachloride via modulation of NF-κB pathway

AIM:To investigate the protective effect of ethanol extract from Cortex Albiziae on acute liver injury, and to explore its possible mechanism. METHODS:Acute liver injury in mice was induced by single intraperitoneal injection of 25% carbon tetrachloride (olive oil solubilization). The effective parts of ethanol extract from Cortex Albizziae against acute liver injury were screened. The pathological changes of the liver tissues were examined by pathological sections with HE staining. The activity of total superoxide dismutase (T-SOD) and the content of malondialdehyde (MDA) of the liver tissues were detected, the serum levels of interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) were mea-sured by ELISA, and the protein expression levels of NF-κB p65, Bcl-2 and Bax in the liver cells of the mice in each group were determined by Western blot. RESULTS:Compared with model group, the serum levels of AST and ALT in low-dose n-butanol phase of ethanol extract from Cortex Albiziae (AB-L, 4 mg·kg^-1·d^-1) group and high-dose n-butanol phase of ethanol extract from Cortex Albiziae (AB-H, 8 mg·kg^-1·d^-1) group were significantly decreased. The necrosis extent and degree of the hepatocytes and infiltration of inflammatory cells were significantly lower than that in model group. Compared with model group, the serum levels of TNF-α and IL-6 in AB-H group and AB-L group were significantly decreased (P<0.05). The protein level of NF-κB p65 in the nuclei of mouse liver cells in AB-H group and AB-L group were also decreased significantly (P<0.05). Compared with model group, the protein expression of Bax was decreased, the protein expression of Bcl-2 was increased, and the Bcl-2/Bax ratio was increased in AB-L group and AB-H group. CONCLUSION:The n-butanol phase of ethanol extract from Cortex Albiziae may protect the liver by reducing the activation of NF-κB p65, inhibiting the excessive release of inflammatory cytokines IL-6 and TNF-α, and decreasing hepatocyte apoptosis via regulating Bcl-2 and Bax expression.     

基于DEB理论的皱纹盘鲍个体生长模型参数的测定

为获取皱纹盘鲍(Haliotis discus hannai)个体生长模型所需的6个关键参数，设计了饥饿耗能、温度对耗氧的影响等相关生理实验，计算得到各项参数值。单位体积维持耗能率的值 、形成单位体积结构物质所需的能量值 、单位体积最大储存能量 和储备能量值 4个参数，通过连续测定皱纹盘鲍饥饿过程中呼吸耗氧率和软组织干重不断下降直至保持稳定时的能量值计算；温度函数中Arrhenius温度 的数值根据皱纹盘鲍在不同温度梯度下的单位干重耗氧率测定、计算；形状系数δm值通过统计测量的壳长、软组织湿重等生物学参数拟合回归得到。结果显示，皱纹盘鲍在饥饿后，呼吸耗氧率和软组织干重分别降低了26.3%和70.0%，呼吸耗氧率由2.69 mg/(ind.?h)逐渐降低并稳定在0.8 mg/(ind.?h)，软组织干重由(5.21±0.89) g降低至(3.84±0.22) g；根据公式计算得 和 的值分别为20.18 J/(cm3?d)和8120 J/cm；皱纹盘鲍饥饿前后有机物含量分别为80%和58%，经过换算， 和 的值分别为2726 J/cm3和32583 J/g。不同规格的皱纹盘鲍在水温为5℃~20℃范围内，温度与单位干重耗氧率呈正比；当水温超过20℃之后，温度与单位干重耗氧率呈反比。在转折点20℃之前，单位干重耗氧率的ln值与温度(热力学温度，K)的倒数呈线性关系，线性回归方程斜率的绝对值为Arrhenius温度 值( =7196 K)。生物学统计分析鲍壳长(L)与体积(V)呈三次函数关系：V=0.0639 L3.1621(R²=0.9852)，根据公式对软组织湿重的立方根与壳长进行线性回归，所得的斜率即为形状系数δm值(δm=0.43)。本研究对建立以DEB理论为指导的皱纹盘鲍个体生长模型提供了数据支撑。     

Soil organic carbon fractions and humic substances are affected by land uses of Caatinga forest in Brazil

Caatinga is a Brazilian dry ecosystem that occupies around 1 million km² and is one of the largest tropical dry forests of the world. About 46% of the area that was originally covered has been deforested. Land use can cause pronounced reduction in soil carbon stocks that play a major role in the global carbon cycle. The objective of this study was to improve our understanding of the effect of land use on oxidizable carbon fractions, total carbon stocks and humic substances in different layers of soil in a Brazilian semi-arid region. We analyzed soils from tropical dry forest (TDF), forest succession with Anadenanthera falcata (ANA), with Tabebuia alba (TAB), secondary scrubby regeneration (SCR), and non-irrigated maize (MS). Forests showed larger fractions of more labile carbon, except for TDF. The most recalcitrant fraction of carbon stock, humin fraction stock, with the different land use decreased by 38–53% compared to TDF. Oxidizable carbon fractions, carbon stocks, and humic fraction stocks were able to differentiate the successional land uses and agricultural cover from TDF, mainly in the 0–5?cm layer. Our results show that changes in land use, especially with ANA forest succession, showed a larger labile carbon fraction, indicating easy decomposition and loss. Our results provide an alternative tool for the management of deforested areas in tropical dry caatinga ecosystems. This would contribute to the conservation of dry forest systems and could serve as guideline for sustainable management of agriculturally impacted caatinga areas.     

Nitrogen and phosphorus budget of a Haliotis discus hannai and Apostichopus japonicus polyculture system

The system nitrogen (N), phosphorous (P) budget, N/P utilization rate and the physiological response mechanism of the abalone Haliotis discus hannai (body weight: 12.87 ± 0.82 g) and the sea cucumber Apostichopus japonicus (body weight: 10.85 ± 1.16 g) to different co‐culture environment conditions were examined. Animals were kept in a multilayer, cubic recirculating aquaculture system at different polyculture densities (abalones at 400 ind/m²in monoculture [Group C] and abalones at 400 ind/m²with sea cucumbers at 10 ind/m² [AS1] or 20 ind/m² [AS2]). Each treatment was replicated four times, and the experimental cycle was 90 days. No significant difference in survival rate of abalones was detected when the stocking density of sea cucumbers increased from 10 to 20 ind/m², but the concentrations of total ammonia nitrogen and nitrite nitrogen in the water were significantly higher in AS2 than in AS1. Survival rate, specific growth rate (SGR) of body weight of sea cucumbers and SGR of body weight of abalones were significantly lower in AS2 than in AS1. No significant difference in protease (PES), lipase, amylase and cellulase activities of abalones was identified between Group C and AS1, but the PES and amylase activities of abalones and sea cucumbers in AS1 were significantly higher than those in AS2. In AS1, the N/P output from harvesting of abalones and sea cucumbers and the N/P utilization rates were significantly higher than those in AS2. Although the N/P output from faeces was significantly lower in AS2 than in Group C and AS1, the N/P output from the water layer was significantly higher than that in AS1. The expression levels of Cu/Zn superoxide dismutase (Cu/Zn‐SOD) and heat shock protein 70 (HSP70) of both abalones and sea cucumbers in AS2 were significantly higher than those in AS1. No significant difference in expression of catalase (CAT) and HSP90of abalones was identified among these groups, but the expression levels of CAT and HSP90of sea cucumbers in AS2 were significantly higher than those in AS1. These results indicate that stocking sea cucumbers at 10 ind/m² in the polyculture system will relieve the organic load on the system and improve the N/P utilization rate. It will also increase aquaculture production and improve the ecological and economic benefits of the system.     

江苏徐州市果树经济林的碳储量估算

采用生物量法和重铬酸钾-硫酸氧化法测定全碳含量,对徐州市果树经济林的碳贮量、分布格局进行初步研究。徐州市果树经济林碳储量为39.21×104 t,其中,银杏18.45×104 t、梨3.82×104 t、苹果16.63×104 t、桃2.67×104 t。碳密度为8.7 t/hm2,并分析其空间分布特点。     

The role of lignin and cellulose in the carbon-cycling of degraded soils under semiarid climate and their relation to microbial biomass

A high level of biological degradation is usually observed in soils under semiarid climate where the low inputs of vegetal debris constraint the development of microbiota. Among vegetal inputs, cellulose and lignin are dominant substrates but their assimilation by the microbial community of semiarid soils is yet not understood. In the present study, ¹³C-labeled cellulose and ¹³C-labeled lignin (75 μg ¹³C g⁻¹ soil) were added to two semiarid soils with different properties and degradation level. Abanilla soil is a bare, highly degraded soil without plant cover growing on it and a total organic C content of 5.0 g kg⁻¹; Santomera soil is covered by plants (20% coverage) based on xerophytic shrubs and has a total organic C content of 12.0 g kg⁻¹. The fate of added carbon was evaluated by analysis of the carbon isotope signature of bulk soil-derived carbon and extractable carbon fractions (water and sodium-pyrophosphate extracts). At long-term (120 days), we observed that the stability of cellulose- and lignin-derived carbon was dependent on their chemical nature. The contribution of lignin-derived carbon to the pool of humic substances was higher than that of cellulose. However, at short-term (30 days), the mineralization of the added substrates was more related to the degradation level of soils (i.e. microbial biomass). Stable isotope probing (SIP) of phospholipid fatty acids (PLFA-SIP) analysis revealed that just a minor part of the microbial community assimilated the carbon derived from cellulose and lignin. Moreover, the relative contribution of each microbial group to the assimilation of lignin-derived carbon was different in each soil.     

复合农林业系统碳贮量研究进展

CO2作为一种主要温室气体,其固存与排放对全球气候变化有重要影响。本文以复合农林业系统为研究对象,介绍了农林复合类型中林木、农作物、凋落物、土壤碳贮量的估算方法,并指出目前碳贮量研究方面的问题和发展方向,为碳循环研究提供部分基础研究数据和理论支持。