Abstract
Research Highlights: Rare, or sparsely distributed, species drive the floristic diversity of upland, terra firme and seasonally flooded forests in the central Juruá—a remote and hitherto floristically poorly known area in the Brazilian Amazon. Background and Objectives: Floristic inventories are critical for modelling and understanding the role of Amazonian forests in climate regulation, for sustainable management of forest resources and efficient conservation planning. Yet, detailed information about the often complex spatial distributions of many Amazonian woody plants is limited. Here, we provide information about forest structure and species composition from a remote terra firme forest and an adjacent floodplain forest in the western Brazilian Amazon. More specifically, we ask (1) how floristically different are the terra firme and floodplain forests? and (2) how variable is species composition within the same forest type? Materials and Methods: Between September 2016 and October 2017, we inventoried 97 plots (each 0.1 ha; 100 × 10 m) placed at least 800 m apart, with 46 plots in terra firme forest and 51 in seasonally flooded forest. We included all trees, hemi-epiphytes and palms with diameter at breast height (dbh) > 10 cm and woody lianas > 5 cm dbh. We examine forest structure, family- and species-level floristic composition and species diversity within and between forest types using family and species importance values, rarefaction curves and dissimilarity matrices. Results: Terra firme forest and seasonally flooded forest woody plant communities differ both in structure and species composition, which was highly variable within forest types. Many species were shared between terra firme and seasonally flooded forests, but most species were forest type-specific. Whereas species richness was greatest in the terra firme forest, floodplain species richness was among the highest regionally. Conclusions: Floodplain forests are a crucial complement to terra firme forests in terms of Amazonian woody plant diversity.
Highlights
Floristic inventories are critical for modelling and understanding the role of Amazonian forests in climate regulation, for sustainable management of forest resources and efficient conservation planning.Yet, for a number of reasons, floristic inventories in Amazonian forests are notoriously difficult and detailed information about the often complex spatial distributions of many Amazonian trees is Forests 2020, 11, 1361; doi:10.3390/f11121361 www.mdpi.com/journal/forestsForests 2020, 11, 1361 limited [1,2,3,4]
We found greater resemblance in species composition among plots within the same forest type than when comparing plots between forest types (envfit: R22 = 0.59, p < 0.001; PERMANOVA: R22 = 0.11, than when comparing plots between forest types, there was spatial autocorrelation between plots (Mantel test: r = 0.19, p = 0.001)
This may reflect the differences in disturbance regimes between the two forest types, with higher levels of disturbance in várzea forests driven by the impact of seasonal floods and their proximity to the Juruá River
Summary
Floristic inventories are critical for modelling and understanding the role of Amazonian forests in climate regulation, for sustainable management of forest resources and efficient conservation planning.Yet, for a number of reasons, floristic inventories in Amazonian forests are notoriously difficult and detailed information about the often complex spatial distributions of many Amazonian trees is Forests 2020, 11, 1361; doi:10.3390/f11121361 www.mdpi.com/journal/forestsForests 2020, 11, 1361 limited [1,2,3,4]. Considering the irregular distribution and local rarity of many tropical tree species [9], the bias and patchiness of floristic data from the Amazon presents one of the biggest challenges for conservation biologists and climate modellers alike. It is the largest remaining tract of tropical forest on Earth, the status of the Amazon is precarious, as threats from deforestation, logging and other disturbances continue to increase [10,11,12,13]. Such activities adversely affect forest structure and composition, as well as the forest capacity to store carbon, retain water and regulate climate [14,15,16,17,18,19]
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