The role of topography and plant functional traits in determining tropical reforestation success

Abstract

Early establishment and sapling growth is a key phase in ensuring cost‐effective reforestation success in relation to biodiversity outcomes. Therefore, species selection must consider the interaction between plant functional traits and the often‐challenging and heterogeneous biophysical environment of degraded landscapes. In this study, we examine how microtopography (slope) results in spatial heterogeneity of soil nutrients, especially phosphorus (P) in a degraded tropical pasture landscape in Queensland, Australia. We then explore how this small‐scale heterogeneity influences the growth of two native tree species, Cardwellia (C.) sublimis (Proteaceae) and Flindersia (F.) brayleyana (Rutaceae), which differ in key nutrient‐acquisition strategies. The proteaceous C. sublimis was found to be buffered from possible P limitation in degraded soils due to its effective P acquisition by cluster roots. In contrast to C. sublimis, which showed no difference in growth after 5 years across a range of soil conditions, F. brayleyana was found to be highly responsive to soil conditions with increased growth in low‐slope, higher P availability areas. The ability of F. brayleyana to take advantage of high soil P levels, including the development of leaves with higher P concentrations, resulted in an apparent switch in competitive fitness between these two species across a landscape gradient. Synthesis and applications. In a detailed study of a landscape reforestation experiment in North Queensland, Australia, we demonstrate that site edaphic factors can vary within tens of metres due to topographic relief, and that species respond differently to these conditions. We therefore show the need to consider both the spatial heterogeneity of edaphic factors and the below‐ground functional traits of potential reforestation species when planning reforestation programmes.

Seedling growth responses to species‐, neighborhood‐, and landscape‐scale effects during tropical forest restoration

“…Within the same experimental plots used in this study, Cheesman et al (2018) recorded an increase in soil organic matter with decreasing slope angle, resulting in an increase in available soil phosphorus on shallower slopes. Cheesman et al (2018) further demonstrated that variation in soil P was an important predictor for growth of Flindersia brayleyana and Carwellia sublimis, suggesting that some of the planted species may be P limited. Unfortunately, we do not have measures of soil P, which limits our ability to assess the effect of slope and soil P on the growth rates of all 24 species.…”

“…1), located on the southern Atherton Tablelands in far North Queensland, Australia (145°51 0 E 17°43 0 S), between 900 and 1000 m elevation. The region has distinct wet (November-April) and dry (May-October) seasons, with an annual rainfall of 1940 mm (Cheesman et al 2018). The region has distinct wet (November-April) and dry (May-October) seasons, with an annual rainfall of 1940 mm (Cheesman et al 2018).…”

Regional rainfall and local topography jointly drive tree community assembly in lowland tropical forests of New Caledonia

“…This influence can be synthesized in the Topographic Wetness Index (TWI; Gessler, Moore, McKenzie, & Ruan, ; Sørensen, Zinko, & Seibert, ). The topographic variation then influences the structure, composition and functioning of tropical forests (Cheesman, Preece, van Oosterzee, Erskine, & Cernusak, ; Fortunel et al., ; Jucker et al., ; Svenning, ; Valencia et al., ). On upslopes or steep slopes, tree communities generally show more conservative strategies (Cheesman et al., ; Kraft et al., ; Liu, Yunhong, & Slik, ; McFadden et al., ) and/or denser wood (Jucker et al., ; Liu et al., ).…”

Water availability drives aboveground biomass and bird richness in forest restoration plantings to achieve carbon and biodiversity cobenefits

“…There was no significant effect of extractable P on aboveground biomass accrual; however, Australia has a high proportion of soils that have formed on sedimentary rocks with low P content, or highly weathered soils where much P has been lost through leaching (Handreck, ). As a response, many native tree species have adapted to low P availability through effective acquisition strategies, and tree growth can be buffered from P limitation (Cheesman et al, ).…”

“…Soil nutrients are considered essential for plant growth, and nitrogen (N) and phosphorus (P) can be limiting in Australian ecosystems (Cheesman, Preece, van Oosterzee, Erskine, & Cernusak, 2018;Crous, Ósvaldsson, & Ellsworth, 2015). Surface soil samples (0-10 cm depth) were collected every 10 m along each transect of the BioCondition plot using a handheld soil corer, and bulked into one sample to capture soil variation across the site (McKenzie, Henderson, & McDonald, 2002).…”