Biomass and abiotic variables change in phytotelmic environment in the tank-bromeliad Nidularium longiflorum Ule in tropical forest

Abstract Aim Phytotelm plays an important role in plant growth and ecosystem functioning, but this natural aquatic microcosm is poorly known. We evaluated the seasonal (dry and rainy seasons) and spatial variations (forest trail and stream sites) of the phytotelm in Nidularium longiflorum, bromeliad that occurs in the Atlantic Forest. Methods Abiotic and biotic variables were measured in tank-bromeliad phytotelms. The biomass was analyzed by ash-free dry mass and chlorophyll-a concentration. Results Abiotic variables measured in the phytotelmic environment of bromeliads varied between sampling sites and seasons. Temperature, electrical conductivity and total nitrogen values were significantly different between seasons and sites. Chlorophyll-a and ash-free dry mass (organic matter) in phytotelm were significantly different between sampling sites. Eleven genera of algae in the phytotelm were identified. PCA axis 1 ordination evidenced the seasonal variation of environmental conditions. Conclusions Our findings suggest that environmental and micro-environmental conditions do not favor the development of algal community in the phytotelm. Biomass and abiotic variables in phytotelm of Nidularium longiflorum change seasonally, however biomass accumulation was strongly influenced by site characteristics.

摘要

目的：植物贮水环境（phytotelm）对植物生长及生态系统功能具有重要作用，但这类天然水生微生境的相关研究仍较为匮乏。本研究以分布于大西洋森林的凤梨科积水凤梨长花巢凤梨（Nidularium longiflorum）为对象，调查了其贮水环境的季节（旱季与雨季）与空间（林道样点与溪流样点）变异特征。

方法：于积水凤梨的植物贮水环境中测定非生物与生物变量；生物量通过无灰干重与叶绿素a浓度进行分析。

结果：积水凤梨贮水环境中的非生物变量在采样样点与季节间存在差异。其中温度、电导率与总氮含量在季节与样点间均存在显著差异；贮水环境中的叶绿素a与无灰干重（有机质）在采样样点间存在显著差异。共鉴定出贮水环境中的藻类11个属。主成分分析（PCA）第一轴排序结果显示环境条件存在季节变异。

结论：本研究结果表明，贮水环境中的环境与微环境条件不利于藻类群落的发育。长花巢凤梨贮水环境中的生物量与非生物变量存在季节变化，但生物量积累主要受样点特征的强烈影响。