SHADING AS A DETERMINANT FACTOR FOR THE SURVIVAL AND GROWTH OF Cabralea canjerana IN SOUTHERN BRAZIL

ABSTRACT Plantations with native tree species, which emphasize biodiversity conservation, may not succeed because of a lack of forestry knowledge about the native species. Cabralea canjerana is an important tree species, which is rarely present in area restoration programs because of the difficulty in establishing it in plantations. Despite this, the species is also known for its adaptation to different light conditions. Therefore, this research sought to answer: a) What is the appropriate light level for the initial establishment of Cabralea canjerana seedlings in the field? b) Does seasonality influence the morphological and physiological attributes of Cabralea canjerana plants? The treatments used were: four shade intensities (0, 18, 50 and 70%) and two seasonal periods (spring-summer and autumn-winter). Survival was evaluated at 30 and 360 days after planting, while the morphological and physiological attributes were evaluated at 180 (spring-summer) and 360 (autumn-winter) days after planting. We suggest that Cabralea canjerana be classified as a moderately shade-tolerant species, considering that even in a region with four well-defined seasons, like the one in the present study, its mortality rate was high in full sun, a fact that is corroborated by the morphological and physiological parameters. The planting of Cabralea canjerana seedlings in full sunlight is not appropriate because it causes low seedling survival. It is recommended that planting be carried out under 50% shading. Seasonality influenced the morphological and physiological attributes of Cabralea canjerana plants.

摘要：以生物多样性保护为核心目标的乡土树种人工林，往往因缺乏针对该乡土树种的营林专业知识而难以成功营建。Cabralea canjerana是一种重要乡土树种，但由于其人工林营建难度较高，极少被应用于区域生态修复项目中。尽管如此，该树种被证实可适应不同光照条件。为此，本研究旨在解答两个核心问题：a) 野外条件下，Cabralea canjerana幼苗初始定植的适宜光照水平为何？b) 季节节律是否会影响Cabralea canjerana植株的形态与生理性状？本研究设置的处理组包括4个遮阴强度梯度（0%、18%、50%及70%）与2个季节周期（春夏季与秋冬季）。分别于定植后30天与360天统计植株存活率；形态与生理性状则分别于定植后180天（对应春夏季）与360天（对应秋冬季）进行测定。综合来看，本研究区域四季分明，全光照条件下Cabralea canjerana幼苗死亡率较高，结合形态与生理参数的测定结果，我们建议将该树种归类为中度耐荫树种。全光照环境不适宜Cabralea canjerana幼苗定植，该条件会导致幼苗存活率低下；因此推荐采用50%遮阴度进行定植。此外，季节节律会显著影响Cabralea canjerana植株的形态与生理性状。