Initial growth of Parkia platycephala (Benth.) and Enterolobium timbouva (Mart.) under field conditions in a Cerrado area

ABSTRACT The objective of the present study was to analyze the growth of Parkia platycephala and Enterolobium timbouva (Mimosaceae), tree species native to Cerrado, in a strictus sensus Cerrado area in the municipality of Porto Nacional, Tocantins. Twenty plants of each species were evaluated at thirty-day intervals during twenty-five months (February/2008 through February/2010). The following variables were analyzed: number of leaves produced, plant height, and stem diameter. Foliar phenology was also studied (August/2008 through February/2010) by analyzing five randomly-selected individuals of each species. Three branches of each individual were marked and all their leaves were evaluated in terms of emergence and abscission periods. Foliar herbivory was determined based on interval-scale classes of twenty-five per cent each. The results revealed that leaf production and growth in height in Parkia platycephala and Enterolobium timbouva were predominant during the rainy season. In terms of stem diameter, Parkia platycephala presented a better development when compared to Enterolobium timbouva. The relative growth rate increased expressively along the rainy season in both species. An increase in leaf predation was also observed during the wet season in the two species studied. As both species were exposed to the same environmental conditions, the greater relative growth rate observed in P. platycephala can be attributed to its physiological and anatomical features, which among other factors, contributed to a lower leaf predation by herbivores.

摘要 本研究旨在分析原产于塞拉多（Cerrado）的含羞草科（Mimosaceae）乔木物种扁头猴耳环（Parkia platycephala）与廷博伏恩猴耳环（Enterolobium timbouva），在托坎廷斯州波多诺瓦尔市一处狭义塞拉多生境中的生长状况。本研究于2008年2月至2010年2月的25个月周期内，以30天为间隔对每个物种的20株植株开展测定，观测指标包括新生叶片数、植株高度与茎干直径。本研究同时于2008年8月至2010年2月针对两物种各随机选取的5株个体开展叶物候研究：为每株个体标记3根枝条，对其所有叶片的萌发与脱落周期进行统计分析；并以每25%为一个区间等级，评估叶片的植食害程度。研究结果显示，扁头猴耳环与廷博伏恩猴耳环的叶片产出及株高增长均集中于雨季；在茎干直径生长方面，扁头猴耳环的发育状况优于廷博伏恩猴耳环。两物种的相对生长速率均在雨季出现显著提升，且叶片植食取食率在湿季均有所上升。由于两种植物所处环境条件一致，扁头猴耳环展现出更高的相对生长速率，可归因于其生理与解剖学特性——该特性等多重因素共同降低了其被植食性动物取食的概率。