植物根部水分再分配研究的区域特征及生态意义

在一些干旱、半干旱或季节性干旱地区,当植物的一部分根系处于较湿润的土壤层中,且土壤水势梯度合适的条件下,植物便会利用水分再分配来合理调配水分以缓解植物的干旱状况.植物根部水分再分配研究主要在有干湿季节交替或出现一段时间干旱的地区进行,这些地区包括萨瓦纳地区、具有热带或温带季风气候的地区以及具有地中海气候的地区.除此之外,在一些温带大陆性气候区也有部分研究.水分再分配现象使各土壤层中水分合理分配,上下运送的水分能够使植物根系保持湿润,从而延长和增强根系的活动性.再分配水分可提供植物白天蒸腾作用需要的部分水源,通过土壤-根系-大气系统促进水分运动,且释放到上层土壤中的水分还可以为周围邻近植物提供水分.由于养分一般储存在土壤的上层,水分的上下运动可以促进土壤中养分的循环以增强养分吸收、微生物过程,并提高养分的利用率.目前,水分再分配的研究区域越来越广泛,研究方法也趋于多样化和成熟.

Regional character of plant roots hydraulic redistribution and their ecological significance

In some arid,semiarid or seasonal arid areas,when part of ront is feat,hydraulic lift or reverse flow(viz.hydraulic redistribution) can distribute water rationally and alleviate water stress of plants.The study of hydraulic redistribution is mainly conducted in those areas where dry season and wet season take turns or the drought lasts for a long period in one year,including savannas,temperate or tropical monsoon region and Mediterranean climate region.In addition,some research was carried out in temperate continental climate region.Hydraulic redistribution utilizes soil water rationally and may also prolong or enhance fine-root activity by keeping roots hydrated.Hydraulic redistribution can supply water source for daily transpiration,facilitate water movement in the Soil-Plant-Atmosphere continuum,and the neighbors can use water that is released to the up soil layers by roots.Also,because soils tend to dry from the surface downward and nutrients are usually most plentiful in the up soil layers,redistributed water may provide moisture that facilitates favorable circle for the acquisition of nutrients,microbial process,enhancing mineral nutrient availability ratio.At present,hydraulic redistribution research area is more and more broad,and research method also tends to diversification and maturity.