橡胶人工林地土壤酶活性与有效态微量元素关系研究

文章以海南省儋州市南部植胶区各农场橡胶人工林地为研究对象,运用典型相关分析研究了橡胶人工林地土壤酶活性和土壤微量元素含量关系。结果表明,土壤有效锰与土壤过氧化氢酶活性的关系最大;土壤有效锌、有效铜与土壤脲酶、多酚氧化酶活性关系密切。各橡胶人工林样点,在典型变量排序图上以不同成土母岩聚集。     

比例溢流阀在拉力轴承试验液压加载系统中的应用

比较了3种液压加载系统调节方式的原理和特点,介绍了该拉力轴承寿命试验装置中采用电比例溢流阀调节方式的组成及工作原理,重点分析了其在恒力加载状态经过闭环控制的工作特性.试验表明,此加载方式调节方便,加载载荷准确,系统性能稳定可靠,应用效果良好.     

Exotic Pinus carbaea causes soil quality to deteriorate on former abandoned land compared to an indigenous Podocarpus plantation in the tropical forest area of southern China

Soil properties under an exotic plantation (Pinus caribaea) and an indigenous plantation (Podocarpus imbricatus) were compared with adjacent secondary forests and abandoned land in the tropical forest areas of Jianfengling National Nature Reserve in Hainan province, southern China. The surface soil (0–0.2 m) under Pi. caribaea has higher bulk density, lower soil organic carbon, total N, total K, available N, microbial biomass carbon, and smaller soil microbial communities (as indicated by soil Biolog profiles) than under Po. imbricatus. Both land use types showed negative cumulative soil deterioration index (DI) compared to secondary forests. However, compared to abandoned land (DI = –262), the soil quality of Po. imbricatus showed improvement (DI = –194) while that of Pi. caribaea showed deterioration (DI = –358). These results demonstrated that these exotic pine plantations can significantly and negatively influence soil properties. By contrast, our results showed that adoption of indigenous species in plantations, or natural regeneration, can improve soil quality.     

Water relations of Eucalyptus nitens × Eucalyptus grandis: is there interclonal variation in response to experimentally imposed water stress?

This study tested the hypothesis that water stress increases the hydraulic efficiency of Eucalyptus nitens × E. grandis saplings as a result of osmotic and elastic adjustments. Eucalyptus nitens × E. grandis clones (NH00, NH58, NH69 and NH70) were potted in coarse river sand supplemented with a slow-release fertiliser, drip-irrigated four times daily and exposed to full sunlight for eight months. Thereafter, irrigation was withheld twice for seven consecutive days from half of the saplings of each clone, with a seven-day recovery period (regular irrigation) in-between. Relative soil moisture content did not correlate with stomatal conductance (g_s) at pre-dawn and at midday. Leaves of plants subjected to the water-stress treatment wilted in 7 d, and the reduction in g_s was significant at midday with no significant differences between clones. Stomatal conductance and all traits derived from pressure-volume graphs (e.g. osmotic potential at full turgor) were constant in the control treatment. There were no clear patterns in osmotic and elastic adjustments in both treatments. Root hydraulic conductance was constant between treatments and clones. However, water stress reduced shoot hydraulic conductance and stem hydraulic conductivity with significant interclonal effects. Plant biomass, leaf area and leaf weight ratio were significantly lower in the water-stressed plants, but there were no differences between the clones. In conclusion, the water-stress treatment did not introduce significant differences in stomatal conductance and tissue-water relations of Eucalyptus nitens × E. grandis clones. Interclonal variation in water-stress response was found in shoot hydraulic traits, and clone NH58 may be more suitable for planting across sites prone to moderate water stress.     

岷江上游不同植被类型的土壤水分和物理性质

土壤水分-物理性质是衡量土壤质量的重要指标。本文测定了岷江上游理县云杉人工林、灌木林、经济林和农耕地的土壤物理性质。结果表明:(1)云杉人工林的土壤容重最小,土壤毛管孔隙度、非毛管孔隙度、田间最大持水量、毛管持水量显著高于其余3种植被类型;(2)灌木林与经济林的非毛管孔隙度、毛管持水量、田间最大持水量差异不显著,但灌木林的土壤容重显著小于经济林;(3)农耕地的土壤容重显著高于其余3种植被类型,非毛管孔隙度、毛管持水量、田间最大持水量显著低于其余3种植被类型。研究结果说明4种植被类型的土壤物理性质存在较大差异,选择合理的植被类型和减少人为干扰对于岷江上游地区植被恢复和生态功能改善具有重要的作用。     

河北省土壤有机质时空变化分析

采用BP神经网络和地统计方法,对1980~2009年间河北省耕地土壤有机质时空变化规律及影响因素进行对比分析。结果表明:河北省耕地土壤有机质具有西北高东南低的格局;随着时间的推移,有机质总体呈现上升趋势。1980年的低值区域到了2009年SOM上升变化明显,成为热点;北部坝上、西部太行山区及东部沿海地区到2009年SOM含量下降,成为冷点。分析表明,这种变化格局的形成与施用有机肥、实施秸秆还田等社会经济过程有关。本研究为预测有机质变化趋势、改善土壤质量、优化种植结构和耕地的可持续发展提供了一定依据。     

有机肥施用方式对柑橘园土壤肥力和柑橘养分、品质的影响

为提高上海崇明柑橘的品质和产量,研究了不同有机肥施肥量和施肥深度对柑橘园土壤肥力和柑橘养分、品质的影响.结果表明:与未施有机肥处理相比,施用有机肥可以不同程度地增加土壤中速效N、有效P和有效K的含量,最好的处理分别高出对照20.9％、24.9％和44.4％;并能提高土壤有机质的含量,最好的处理高出对照16.2％;同时减小土壤容重,降低土壤的pH,从而提高土壤肥力;施用有机肥可以增加土壤中微生物的数量,并且能提高柑橘叶片中全氮和全钾的含量,改善柑橘果实品质.     

中卫市沙坡头区中低产田类型及改良利用

简述了宁夏中卫市沙坡头区中低产田的主要类型,针对中低产田土壤结构差,保水保肥能力弱,水、肥、气、热协调不良的现状,提出:应采取调整种植业结构,增施有机肥,秸秆还田及推广测土配方施肥等综合措施,因地制宜地进行科学改良与利用。     

早春麦田划锄对麦田土壤水分状况及小麦生长发育的影响

[目的]研究早春麦田划锄对麦田土壤水分状况及小麦(Triticum aestivum Linn.)生长发育的影响,为相关研究提供数据支持。[方法]在2010～2011年华北地区麦区遭受多年不遇冬春气象干旱条件下,依托曲周县—中国农业大学万亩小麦玉米(Zea mays L.)高产高效技术研究基地,研究了早春麦田划锄技术对麦田土壤水分含量和小麦生长发育的影响。[结果]划锄可显著增加返青期麦田0～5和5～10 cm土层土壤的含水量,提高氮肥和水分的利用效率,增加小麦地上部生物量、成穗数和穗粒数,起到明显增产作用,平均增产12.6%,增收1 014元/hm2。[结论]划锄是一项被生产实践证明的行之有效的农田保墒节水技术措施,是一项有效的抗旱增产技术。     

基于栅格尺度的景谷县思茅松林土壤碳库空间格局模拟与估测

采用来自于中国科学院科学数据库提供的SRTM数据和美国陆地卫星7号(即Landsat-7)遥感数据,结合直接估算和间接估算的优点,以30 m的栅格为地面单元,模拟和表达地面立地条件和森林分布的连续变化,实现土壤碳库的精细化估测。利用SPSS对导出的数据进行处理,分析地表土壤有机碳含量与年均温、年平均降水量、NDVI、坡度、坡向、坡位及DEM数字高程之间的统计关系,拟合出土壤有机碳的估算模型,并以此来进行思茅松土壤有机碳储量的统计计算。