海南橡胶林落叶特征研究

以海南幼龄和成龄橡胶林为对象,采用野外凋落框收集和关联分析等方法,研究2019年5月至2020年4月海南儋州区域橡胶林落叶特征和影响橡胶落叶的主要气候因子。研究结果表明:(1)海南橡胶林落叶产量呈"双峰"型动态变化,当年7月出现小峰,翌年3月出现最高峰;翌年2—4月为集中落叶期,该时期幼龄和成龄林分别占全年落叶总产量的73.04%和70.61%;成龄林落叶产量显著高于幼龄,增幅为14.77%。冗余分析表明,月均温度与月落叶产量呈极显著负相关关系,解释度为49.9%,贡献率为58.6%;(2)幼龄和成龄林间落叶C、N、P、K、Ca、Mg含量月动态变化趋势相似,各元素含量在秋冬季呈下降趋势,而冬春季出现养分富集的现象,年均含量在成龄和幼龄林间差异不显著;(3)落叶养分归还量月动态与落叶产量动态变化相似,受落叶月产量影响较大,而归还量受落叶产量和养分含量共同影响,落叶归还量表现为C>N>K、Ca>Mg>P,成龄显著高于幼龄,各元素增幅分别为16.3%、17.1%、16.7%、27.4%、15.3%和17.7%;(4)幼龄林各元素养分利用效率总体高于成龄林,其中幼龄钾素养分利用效率显著高于成龄(P<0.05);(5)月均温度是影响2019—2020年海南儋州橡胶林落叶格局的主要气候因子。该研究成果可为海南橡胶割胶制度以及养分管理提供技术支撑。

Characteristic of Defoliation of Rubber Plantations(Hevea brasiliensis)in Hainan,China

The young and mature rubber plantations were chosen as the research objects in Hainan from May in 2019 to April in 2020 to study the dynamic characteristics of leaf litter and the main climatic factors affecting the leaf litter production of rubber plantations through the methods of nylon mesh sampling traps and associative analysis.The leaf litter production for the two plantations showed double peaks characteristics,one small peak at June in 2019 and one highest at March in 2020.Intense defoliation period appeared from February to April in 2020,accounting for 73.04%and 70.61% of total leaf litter production for young and mature plantations,respectively.The leaf litter production of mature plantation was significantly higher than that of young plantation by 14.77%.Redundancy analysis showed that there was a extremely significant negative-correlation between monthly mean temperature and monthly leaf litter production,with explanation 49.9% and contribution 58.6%.The dynamic of the content of C,N,P,K,Ca and Mg in the leaf litter was similar between young and mature plantations,the content of each nutrient showed a downward trend from autumn to winter in 2019,while the nutrient enrichment appeared from winter in 2019 to spring in 2020.The annual average content of each nutrient had no significant difference between two rubber plantations.The dynamic of nutrient return amounts showed the similar trend with that of monthly leaf litter production,and was greatly affected by monthly leaf litter production,which was affected by both of leaf litter production and nutrient content.Nutrient return amount showed the order of C > N > K,Ca > Mg > P,and that of the mature plantation was significantly higher than that of the young by 16.3%,17.1%,27.4%,16.7%,15.3% and 17.7%.The nutrient use efficiency of each nutrient in the young plantation was higher than that of the mature,especially,the K use efficiency was significantly higher(P<0.05).Monthly mean temperature is the main climatic factor affecting the deciduous pattern of rubber plantations under May in 2019 to April in 2020 in Danzhou,Hainan.In conclusion,this study could provide a technological support for the tapping system and nutrient regulation of rubber planting in Hainan.