梭梭萌生与初期存活的关键影响因素

The key factors affecting Haloxylon ammodendron germination and survival at very early stage

在梭梭的主要分布区——古尔班通古特沙漠南缘,就种子萌发、幼苗存活展开研究,以确定在梭梭萌生初期,决定其成活的关键影响因素。实验于2008年36月进行,设置了9个水分处理(3倍降雪、正常降雪、无降雪条件与人工降雨、自然降雨、无降雨处理的交叉组合),同步监测梭梭萌发、存活数量动态及春季短命植物数量。结果表明,梭梭种子萌发数量与积雪量增加无显著相关关系,短命植物萌发数量与积雪量呈显著正相关。总体水分条件较好时,梭梭幼苗与短命植物萌发数量都增多,但由于短命植物竞争,幼苗成活率未必高;反之,在水分条件较差时,梭梭幼苗与短命植物萌发数量都降低,短命植物消耗的水分减少,梭梭幼苗存活率反而高。也就是说,在梭梭幼苗的生长初期,它在与短命植物的水分竞争中处于劣势,直接的降水增加并不能提高其存活率。

Plant water-use strategy is considered to be a function of the complex interactions between species of different functional types and the prevailing environmental conditions.Within the current background of global climate change,significant increase in precipitation has been recorded in the arid region of central Asia over the past 50 years.In addition,in some transition regions between sandy deserts and oases,the groundwater table has fallen significantly as a result of the over exploitation of groundwater.Variation in precipitation in arid ecosystem is leading to plant adaptation in water use strategies;significant inter-species difference in responses will change the composition of desert plant commumities.To understand the effects of these widely acknowledged changes in water conditions,the current study is carried out at south fringe of Guerbantonggute Desert,where H.ammodendron is a typical dominated species.The aim of the study is to test what are the key factors that affect the success of H.ammodendron at germination and very early stage of seedling.The basic hypothesis is that the water is the key factor affecting germination or survival/death of H.ammodendron at its very beginning of life cycle.On March 2008,9 treatments whit 3 replicates each （3m by 3m） were set up,which were normal snow,3 times of normal snow and no snow,and on each snow treatment there was normal rainfall,rainfall plus,and no rainfall.At each treatment,soil moistures,the amount of H.ammodendron seedling and epidermal plants were monitored every 5 days from Aril 11 to June 2008.The result revealed that H.ammodendron germination was not significantly correlated with water conditions （snow amount）：the number of H.ammodendron germination has no significantly difference among snow treatments.However,the amount of epidermal plants germinated was significantly correlated with snow amount：under 3 times of snow treatment the amount of epidermal plants germinated was highest;in contrast,the amount was lowest under no snow treatment.Apparently because of competition for water,at treatments with good water conditions,the survival ratio of H.ammodendron seedling was low.On the other hand,at treatments with poor water conditions,because of low competition from epidermal plants,the survival ratio of H.ammodendron seedling was high.Namely,at the very early stage,H.ammodendron seedling was at disadvantage in competition for water with early spring epidermal plants.As a result,because of competition for water from epidermal plants,good water condition does not necessarily result in high survival ratio of H.ammodendron seedling.In conclusion,this integrated study has advanced our understanding of the H.ammodendron regeneration at very early stage.