Comparative effects of desiccation, heat shock and high temperatures on seed germination of savanna and forest tree species
Comparative effects of desiccation, heat shock and high temperatures on seed germination of savanna and forest tree species
复制标题
干燥、热激和高温对稀树草原和森林树种种子萌发的比较影响
DOI：
--
复制
发表时间：
2014
期刊：
影响因子：
--
通讯作者：
F. Borghetti
中科院分区：
文献类型：
--
作者：
L. Ribeiro;F. Borghetti
尽管森林和稀树草原生物群落在热带地区占主导地位，但控制其分布的因素仍不清楚。南美稀树草原发生在被认为温暖和潮湿足以支持森林生长的地区，这表明气候以外的因素决定了一种或另一种地貌的发生。食草、火和水的缺乏被认为是限制森林物种侵占稀树草原地貌的环境过滤器，但这些过滤器对这些物种从种子中吸收能力的影响仍然知之甚少。在这项研究中，我们研究了稀树草原环境特有的胁迫因素，如土壤干燥、热休克和高温，如何影响稀树草原和森林树种种子的存活和发芽。我们发现干燥（至 5%）降低了森林种子的发芽率，但对稀树草原种子的发芽没有影响。与稀树草原种子相比，森林种子对 140°C 和 200°C 热冲击的耐受性较差，并且在 35°C 和 40°C 温度下发芽率较低。稀树草原种子比森林种子具有更长的发芽时间和更高的发芽方差，表明稀树草原物种之间存在风险分散的发芽策略。森林种子对干燥、热休克和高温的耐受性较低，这可能解释了稀树草原地貌中森林树木的补充量较低的原因。气候变化模型预测南美洲生物群落的土壤湿度较低，温度较高，火灾频率较高。我们的结果表明，稀树草原物种可能比森林物种更能承受这些变化的影响。
Although forest and savanna biomes predominate in tropics regions, the factors that control their distribution remain unclear. South American savannas occur in regions that are considered warm and humid enough to support forests, indicating that agents other than climate determine the occurrence of one or the other physiognomy. Herbivory, fire and water deficit have been considered environmental filters that limit the forest species encroachment in savanna physiognomies, but the effects of these filters on the capability of these species to recruit from seeds remain poorly understood. In this study we investigated how stress factors characteristic of savanna environments, such as soil desiccation, heat shocks and high temperatures affect the survival and germination of seeds from savanna and forest tree species. We found that desiccation (to 5%) reduced the germination percentage of forest seeds, but had no effect on the germination of savanna seeds. Forest seeds were less tolerant to heat shocks of 140°C and 200°C, and showed lower germination percentage at temperatures of 35 and 40°C, when compared with savanna seeds. Savanna seeds presented longer germination times and higher germination variance than forest seeds, indicating a risk-spreading germination strategy among savanna species. The low tolerance of forest seeds to desiccation, heat shock and high temperatures may explain the low recruitment of forest trees into savanna physiognomies. Climate change models predict lower soil moisture, higher temperatures and higher fires frequency for South America biomes. Our results suggest that savanna species are likely to be more capable of withstanding the effects of these changes than forest species.