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Lingli Yang Naoko H. Miki Naoko Matsuo Guosheng Zhang Linhe Wang Ken Yoshikawa 《农业科学与技术》2014,(3):251-259
duniperus sabina Linnaeus, an evergreen shrub with prostrate life form, can effectively prevent sand moving and is an important tree species for reforestation in semiarid areas of China. It has laterally distributed adventitious roots and a deeply distributed main root system. To detect water movement between the main root system and adventitious roots, we adopted heat pulse sensors using the Heat Ratio Method, a high precision method for measuring low sap flow rates. Two sensors were implanted in each individual in the stem between the main root system and adventitious roots, and another two in lateral stems distal to all the roots. Positive sap flows during nighttime, even under saturated air moisture conditions, were detected only between the main root system and adventitious roots under drought conditions, and the rate of flow increased as drought progressed and decreased or disappeared after rain events. The results demonstrated the existence of water movement from the main root system to adventitious roots, and combined with the high contribution of nighttime sap flow to transpiration (11%-16%) the results indicate that it also involves the process of hydraulic lift, a water movement from moist subsoil to dry surface soils. Integrated water use strategy between the main root system and adventitious roots via the process of hydraulic lift of soil water maximizes water acquisition efficiency from both subsoil water and water from rain pulses on the soil surface; this increases survivability in the water-limited environment of semiarid areas. 相似文献
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Drought and fire suppression lead to rapid forest composition change in a forest-prairie ecotone 总被引:1,自引:0,他引:1
Altered fire regimes and increased drought can lead to major vegetation changes, especially in ecotones. A decrease in fire can lead to woody species encroachment in prairies and increasing forest stand density. The threat of global climate change raises questions about potential increases in the length, severity, and incidence of droughts substantially altering species composition. Re-measured upland forests in south-central North America's midcontinent forest-prairie ecotone exhibited major changes in woody species composition and structure over fifty years and successional trajectories appeared to favor invasive Juniperus virginiana L. over the previous dominant Quercus species. The objective of this study was to determine whether climate and fire exclusion affected the recruitment history of dominant woody species in these upland forests located near the xeric western edge of the eastern deciduous forest biome of North America. We removed cores and cross-sections from 992 J. virginiana, Quercus marilandica Münchh. and Q. stellata Wangenh. trees from eleven forest stands located across central and northwest Oklahoma, and determined their ages using standard dendrochronological methods. Recruitment of all species increased following a severe mid-20th century drought, but a rapid increase in J. virginiana recruitment and decrease in Quercus recruitment appeared to be linked to a decrease in fire. Future fire regime changes and increased drought due to global climate change could lead to widespread shifts from Quercus- to Juniperus- dominated forests and cause substantial changes to ecosystem services. 相似文献
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落矶山圆柏直径生长期270 d,树高生长期240 d,生长盛期在4月,其次为5、6月,与春梢、二、三梢相对应,是高生长的主要季节。在生产中应根据上述的生长规律,合理安排松土、除草和施肥等措施。 相似文献
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采用盆栽PEG处理研究水杨酸对杜松幼苗生长过程中水分胁迫的缓解效应及其可能机制.结果表明:水分胁迫导致杜松幼苗叶片光合色素、游离脯氨酸和可溶性蛋白质含量降低,3种抗氧化酶活性下降.与对照相比,水杨酸处理使幼苗叶片光合色素、游离脯氨酸和可溶性蛋白质含量提高,SOD、POD、CAT活性均提高. 相似文献
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杜松赤枯病是 4年生以上杜松幼树的主要病害 ,在我省为害严重。研究表明 ,此病是由Alternariasp .和Phomasp .共同侵染所致。Alternariasp .以菌丝体和分生孢子越冬 ,Phomasp .以菌丝体和分生孢子器越冬。两种病原菌均通过皮孔、气孔和伤口侵入树体。两种病原菌的孢子均在5月下旬日平均气温达 16℃左右时开始放散 ,孢子的放散和萌发与空气温度的关系最为密切 ,雨季是孢子放散的高峰期。通过对 12种杀菌剂的室内药效测定 ,以及四种杀菌剂的室外防治试验 ,得出用 4 0 0~ 80 0倍液的多菌灵等连续防治 2~ 3年 ,可完全控制该病的发生和蔓延 ,防治方法简便易行 ,成本低廉 ,功省效宏 相似文献
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天然更新是维持天然林可持续发展的重要途径,祁连圆柏天然林集中分布于青海三江源地区,了解该林分天然更新状况及影响机制,对于维护三江源水生态安全具有重要的战略意义。本研究以三江源东部麦秀林场祁连圆柏天然林为对象,采用系统调查、室内分析、相关与通径分析相结合的方法,探讨了天然更新状况及影响林分天然更新的关键因子。结果表明:1)林分天然更新不良,平均更新密度为220株·hm-2,林下缺乏幼苗补充,更新幼树种群处于衰退状态;2)林龄、林分密度、平均树高、草本盖度、海拔对更新幼树密度的影响达到显著水平,其中林分密度起正向和负向促进作用;林龄、平均树高、草本盖度起间接阻碍作用;海拔起间接促进作用。3)林龄、林分密度、平均树高、海拔是影响更新幼树密度的主要因素。 相似文献