木麻黄种子萌发的限制生态因子

Limiting ecological factors for seed germination of Casuarina equisetifolia

成功的天然更新应同时具备三个条件:(1)种源数量充足、质量良好;(2)适宜种子萌发的微生境;(3)幼苗、幼树存活的生态条件。为进一步揭示海南岛木麻黄(Casuarina equisetifolia)海防林自身无法天然更新的障碍因子,该文对影响其天然更新的三个条件之一的种子萌发条件进行了研究,并探讨了不同的生态因子,如木麻黄化感、土壤酸碱度、盐度、温度、基质类型、水分等对木麻黄种子萌发的影响。结果表明:(1)不同浸提物的不同浸提液浓度处理的种子萌发率与CK组无显著性差异。(2)设定范围内的pH、盐度和温度对木麻黄种子萌发率无显著影响。(3)不同浓度梯度PEG溶液处理的木麻黄种子萌发率存在显著性差异,且伴随PEG溶液浓度增加,木麻黄种子萌发率随之锐减。(4)不同基质及浇水频度对种子萌发率也具有显著影响。从综合PEG干旱胁迫、基质及浇水频度的结果可以发现,木麻黄种子抗旱能力较弱,对水分敏感。因此,水分是制约木麻黄种子萌发的主要限制因子,凋落物层及滨海沙土较差的保水性不同程度地制约了种子的萌发。

Successful natural regeneration can play its ecological protection function with three conditions:(1)Abundant and good seed resources;(2)Micro-habitat suitable for seed germination;(3)Ecological conditions for the sur-vival of seedlings and young trees.However,Casuarina equisetifolia coastal protection forest(C.CPF)in Hainan Island exists unable to naturally regenerate by itself.To explore obstacle factors of unable natural regeneration of C.equisetifolia itself,the ecological conditions affecting seed germination of C.equisetifolia,such as C.equisetifolia allelopathy,soil pH,salinity,temperature,matrix type and moisture were studied.The reason is that ecological conditions affecting seed germination are one of the three conditions that restrict the success of natural regeneration,and the other two conditions are the quantity and quality of provenances,and ecological conditions for survival of seedlings and saplings respectively.C.equisetifolia cones,litters and in-situ habitat soil were collected from the C.CPF near Houwei Village,Haikou City,Hainan Island.The seed germination test was conducted by paper dish method,with 100 seeds per dish and three repeated treatments.The C.equisetifolia litter,humus and sandy soil extracts were diluted into five concentration gradients respectively and a total of 15 extracts were obtained.The pH was set to 5.0,5.5,6.0 and 6.5 concentration gradients for the germination solution.Salinity was set to 0.02%,0.05%and 0.10%.The temperature was set to 25,30 and 35℃.The PEG method was used for water stress test,with five concentration gradients of 0,50,100,150 and 200 g·L-1.The orthogonal test was designed as three factors and four levels.The results were as follows:(1)There was no significant difference of seed germination rate between CK group and the one treated with different water extract concentrations of different extracts.(2)pH,salinity and temperature within the set range had no significant effects on seed germination rate of C.equisetifolia.(3)The germination rate of C.equisetifolia seeds treated with PEG solution with different concentration gradients was significantly different,and the seed germination rate of C.equisetifolia decreased sharply with the increase of PEG solution concentration.(4)Different matrices and watering frequencies also had significant effects on seed germination rate.Combining PEG drought stress,matrix and watering frequency,it can be found that C.equisetifolia seeds have weak drought resistance and are sensitive to water,therefore,moisture is the main limiting factor for the germination of C.equisetifolia seeds.Meanwhile,the poor water retention of litters and coastal sandy soil also restricts the germination of seeds to varying degrees.