旱季补水对桉树人工林生长和土壤养分的影响

Effect of dry-season irrigation on growth of Eucalyptus plantations and soil nutrients

【目的】地处南亚热带季风气候区的广东省存在较为明显的季节性干旱现象。通过旱季补水处理,对桉树人工林生长状况、土壤含水量和土壤养分进行深入研究,探讨旱季补水对桉树生长的促进作用,为提高桉树人工林生产力提供理论依据。【方法】选取尾巨桉(无性系DH32-29)作为研究对象,每年10月到次年3月对广州市增城区教学科研基地进行旱季补水处理,使得土壤含水量达到田间持水量的90%以上,共设置了4个处理:无水无肥处理(CK)、有水无肥处理(W)、无水有肥处理(F)、有水有肥处理(WF)。在桉树人工林生长前3 a,定期测定全林各处理桉树的树高和胸径,并采用随机抽样法测定各处理深40 cm土层的土壤含水量及土壤pH值和养分含量。【结果】1)试验3 a,旱季补水对桉树人工林树高和胸径生长具有明显的促进作用,并且在旱季时促进效果显著。无施肥条件下,处理W从第2年4月开始显著增加了树高,而胸径从第2年5月份开始产生显著差异。在施肥条件下,处理WF从第2年8月开始显著增加了桉树人工林的树高,而胸径无显著差异。通过旱季补水,无论在有无施肥条件下均能提高桉树人工林树高和胸径的连年生长量以及林分蓄积量,且旱季补水在每年旱季对桉树树高和胸径生长量的促进效果都比雨季显著。2)通过旱季补水,总体上提高了土壤中有机质、全N、全P、全K、碱解N、有效P、速效K、有效Zn和有效B含量,而且增加了土壤pH值,缓解了土壤酸化。【结论】通过旱季补水有效缓解了季节性干旱对桉树生长的影响,并且提高了林地土壤含水量和土壤养分,从而促进了桉树人工林的生长,最终提高了生产力。

【Objective】Guangdong province,located in the southern subtropical monsoon climate zone,has obvious seasonal drought.This experiment conducted in-depth research on the growth status,soil water content and soil nutrients of Eucalyptus plantations through the treatment of dry-season irrigation,and studied the promotion of Eucalyptus growth by dry-season irrigation,and provided theoretical basis for improving the productivity of Eucalyptus plantations.【Method】The Eucalyptus uorphylla×E.grandis(clonal DH32-29)was selected as the research object.The dry-season irrigation treatment was carried out at the teaching and research base of Zengcheng district,Guangzhou from October to March of the following year,which kept the soil moisture content above 90%of the field water holding capacity.A total of 4 treatments were set up:treatment with no dry-season irrigation or fertilizer(CK),treatment with dry-season irrigation and no fertilizer(W),treatment without dry-season irrigation but fertilizer(F),and treatment with both dry-season irrigation and fertilizer(WF).Three years before the growth of the Eucalyptus plantation,the tree height and diameter at breast height of each treatment were regularly measured monthly during the three-year treatments.The soil moisture content,soil pH and nutrient content of the 40 cm deep soil layer of each treatment were determined by random sampling.【Result】1)During the 3 years of the experiment,dry-season irrigation had a significant promoting effect on the growth of Eucalyptus plantation height and diameter at breast height,especially in the dry season.Under the conditions of no fertilization, treatment W increased the tree height significantly from April of the second year, while the diameterat breast height began to produce significant differences from May of the second year. Under fertilization conditions, treatment WF increasedthe height of Eucalyptus plantation significantly from August of the second year, but there was no significant difference in diameter at breastheight. Dry-season irrigation can increase the annual growth of Eucalyptus plantations with or without fertilization. The effect of dry-seasonirrigation on the growth of Eucalyptus trees in the dry season was more significant than that in the rainy season. 2) By dry-season irrigation,the organic matter, total N, total P, total K, alkaline hydrolysis N, effective P, quick-acting K, effective Zn and effective B content in the soilwere generally increased, and the soil pH value was also increased so as to relieve soil acidification.【Conclusion】Dry-season irrigationeffectively alleviated the impact of seasonal drought on the growth of Eucalyptus plantations, and increased the soil moisture and nutrientsof the forest land, which ultimately increased the productivity of Eucalyptus plantations.