Abstract

Despite advances in understanding the ecology and consequences of pine invasions, information on the patterns of structure, dynamics, and growth needed to manage these invasive populations are still poorly known. Here we used tree ring analysis to elucidate growth dynamics, age distribution and fire effects, by sampling three populations of slash pine invading Cerrado vegetation in southeastern Brazil. We found that the invasion occurred in waves, every 5–7 years. These pulses are likely related to the time needed by founder trees to reach maturity, and to climatic events. We found distinct growth patterns among the three study areas. Individual trees in the open sites, under low competition for light, showed an increasing trend of diameter and of the basal area growth rates with age. In the dense stands, however, the diameter increment rates gradually decreased with age, as the competition for light was intensified, and the basal area growth rate increased at lower rates. Growth rates were markedly reduced after fire, likely due to fire impact on the canopies, reducing photosynthesis. Fire scars in the wood allowed us to confirm that the formation of the tree rings occurs annually. When competition for light intensifies as the canopy of the stand closes, the invasive populations experience reduced individual growth of adult trees and constraints to the recruitment of young individuals. We did not find, however, evidence of self-thinning due to competition that could reduce the population of adult trees, open gaps and allow colonization by shade-tolerant native species. Therefore, a monodominant pine stand—the “pine desert” feature of the invaded sites—tends to be persistent over time.

中文翻译：

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松树的树状生态学。揭示新热带稀树草原的入侵浪潮

摘要

尽管在了解松树入侵的生态学和后果方面取得了进步，但管理这些入侵种群所需的结构，动态和生长方式的信息仍然知之甚少。在这里，我们通过对巴西东南部入侵塞拉多（Cerrado）植被的三种阔叶松进行采样，使用树环分析来阐明生长动态，年龄分布和火灾效应。我们发现入侵每5-7年发生一次波浪。这些脉冲可能与创始人树木达到成熟所需的时间以及气候事件有关。我们在三个研究领域中发现了不同的增长模式。在低光竞争下，开放场地中的单个树木显示出直径的增长趋势以及其基础面积增长率随年龄增长。但是在茂密的看台上 随着光的竞争加剧，直径增加率随着年龄的增长而逐渐降低，而底部面积的增长率则以较低的速率增加。火灾后，生长速率明显降低，这可能是由于火灾对冠层的影响，从而降低了光合作用。木材中的火伤痕迹使我们能够确定树环的形成每年发生一次。当摊位顶篷关闭时，对光的竞争加剧时，侵入性种群的成年树个体生长会减少，并且年轻人的招募受到限制。但是，我们没有发现由于竞争而自我变薄的证据，这种竞争可能会减少成年树木的数量，开放的空隙并允许耐荫的本地物种定居。因此，