Trees represent community composition of other plant life-forms, but not their diversity, abundance or responses to fragmentation

Abstract

Our understanding of the patterns of plant diversity in tropical forests and their responses to fragmentation are mostly based on tree surveys. But are these patterns and responses representative of other plant life-forms? We sampled trees, lianas, herbs, and ferns in a fragmented tropical forest landscape in South-west China. We compared community types generated by clustering presence-absence data for the non-tree life-forms with those generated for trees. We tested how well measures of tree diversity, density and composition, predicted cognate indices in other life-forms. We compared fragmentation responses, with respect to the three measures, of all four life-forms. Presence-absence data from all life-forms generated three community clusters, with only small differences between classifications, suggesting that tree data identified community types representative of all vascular plant life-forms. Tree species diversity and density indices poorly predicted cognate indices of lianas and ferns, but represented herbs well. However, the slopes of these relationships differed substantially between community types. All life-forms responded to fragmentation variables but their responses did not consistently match with responses of trees. Plot-level tree data can identify vegetation community types, but is poorly representative of the richness and density of other life-forms, and poorly represents forest fragmentation responses for the entire plant community.

Wood density, growth and mortality relationships of lianas on environmental gradients in fragmented forests of montane landscapes

“…Our study area in Xishuangbanna has a diverse geography, and forests are usually split into several types based on tree data and geography (Cao & Zhang, ; Zhu, Cao, & Hu, ). Liana communities differ between these forest types in abundance and diversity in this and in previous studies (Cai, Schnitzer, Wen, Chen, & Bongers, ; Pasion et al., ; Zhu, ). Limestone forest harbours fewer species of liana and trees than other forest types (Cao & Zhang, ; Zhu, ), a pattern we could confirmed for lianas.…”

“…Topography was included since nutrients and water availability are commonly higher in valleys than on slopes and ridges. Data on canopy openness, from analysing hemispherical photographs with Gap Light Analyzer v 2.0 (Frazer, Canham, & Lertzman, ), were available from the wet season of 2013 (Pasion et al., ). We used Fragstats 4.0 (McGarigal, Cushman, & Ene, ) to calculate fragment size, perimeter:area ratio and the distance of the plot centre to the closest forest edge.…”

“…Rubber cultivation has expanded over the last three decades (Hu, Liu, & Cao, 2008), so that at present <25% of the natural forest remains (Liu & Slik, 2014). Xishuangbanna prefecture harbours more than 4000 angiosperm plant species (Cao & Zhang, 1997;Zhu, 2012) and the forest is generally categorized into four types (Cao & Zhang, 1997;Zhu, 2006), based on tree species composition as driven by elevation, bedrock type and its resulting soil, as well as by topography (Pasion et al, 2018). Our plots are distributed in three of these types according to Cao & Zhang, 1997: "monsoon forest over limestone soils" (on limestone), "tropical seasonal forest" (sandstone, low elevation), and "evergreen broad-leaved forest" (sandstone, high elevation, often on ridges; Pasion et al, 2018).…”

“…Xishuangbanna prefecture harbours more than 4000 angiosperm plant species (Cao & Zhang, 1997;Zhu, 2012) and the forest is generally categorized into four types (Cao & Zhang, 1997;Zhu, 2006), based on tree species composition as driven by elevation, bedrock type and its resulting soil, as well as by topography (Pasion et al, 2018). Our plots are distributed in three of these types according to Cao & Zhang, 1997: "monsoon forest over limestone soils" (on limestone), "tropical seasonal forest" (sandstone, low elevation), and "evergreen broad-leaved forest" (sandstone, high elevation, often on ridges; Pasion et al, 2018). We considered it sufficient to include bedrock type (limestone, sandstone), elevation and topography (ridge, slope, and valley) to describe the forest habitats, therefore avoiding fixed categories for forest types.…”

“…Analyzer v 2.0 (Frazer, Canham, & Lertzman, 1999), were available from the wet season of 2013 (Pasion et al, 2018). We used Fragstats 4.0 (McGarigal, Cushman, & Ene, 2012) to calculate fragment size, perimeter:area ratio and the distance of the plot centre to the closest forest edge.…”