Canopy Size Dependent Facilitations from the Native Shrub Rhodomyrtus tomentosa to the Early Establishment of Native Trees Castanopsis fissa and Syzygium hancei in Tropical China

Abstract

The quantitative role of the canopy size of nurse shrubs on microenvironment and native tree establishment in degraded tropical lands has been seldom studied. In a 21-month field experiment, we aimed to test the effect of a native shrub with different canopy sizes on the early establishment of native trees as part of the effort of forest restoration in tropical China. We examined the microenvironment, and the seedling establishment and growth of two native trees: Castanopsis fissa and Syzygium hancei in both open space (OS) microsite and microsite under the canopy of the native pioneer shrub Rhodomyrtus tomentosa. Shrub microsite was further divided into large canopy (LC), and medium canopy (MC) microsite, based on the shrub leaf area indices. Results showed that relative to OS, LC had higher soil nutrient concentration and water content, and lower photosynthetic active radiation (PAR), while MC had lower PAR and higher soil exchangeable Mg, K, and Ca. Survival and growth were mostly enhanced, while water stress and photoinhibition reduced for C. fissa seedlings in MC and S. hancei seedlings in LC. It is found that the beneficial effects of the native shrub on seedling establishment and growth result mostly from the improvement in nutrient and water availabilities, the reduction in plant stress caused by harsh summer light, and the specific ecological requirements of different tree species. We suggest that different canopy sizes of native shrub R. tomentosa may be explored to target different native trees and hence promote forest restoration in degraded tropical ecosystems.

Facilitative effects of tree species on natural regeneration in an endangered biodiversity hotspot

“…These findings are in agreement with those reported in other facilitation studies carried out in tropical forest (Melo et al 2015;Souza et al 2015;Bueno and Llambí 2015). These results may be due to several mechanisms induced by nurse plants, such as improvements in soil conditions (Liu et al 2014;Ramírez et al 2015;Mihoč et al 2016), favorable microclimate (Bueno and Llambí 2015;Ramírez et al 2015), protection from herbivores (Gómez-Aparicio et al 2004) and reduced competition with herb species (Avendanõ-Yáñez et al 2014). In addition, tree species can attract seed dispersing animals, such as birds that use the branches as perches, increasing rainfall of seeds below their canopies (Aukema and Martinez del Rio 2002;Duarte et al 2006;Zwiener et al 2014).…”

“…Nurse plants can reduce the amount of light that reaches the soil and thus reduce its temperature (Padilla and Pugnaire 2006;Lima and Gandolfi 2009). Nurse plants are responsible for increasing the availability of water, as well as improving the levels of nutrients available in the soil through the liberation of organic material under their canopies (Koorem and Moora 2010; Liu et al 2014;Ramírez et al 2015;Mihoč et al 2016;Pueyo et al 2016). Nurse plants also provide protection from herbivores (Gómez-Aparicio et al 2004) and reduce competition with herb species (Avendanõ-Yáñez et al 2014).…”

Growth and ecophysiology of succulent seedlings under the protection of nurse plants in the Southern Chihuahuan Desert

“…Similar results were found by Rodríguez-Calcerrada et al (2008) for Quercus petraea and Q. pirenaica, also non-succulent plants. Liu et al (2014) also studied the beneficial effects of a native shrub (Rhodomyrtus tomentosa) on seedling establishment of two tree species in Tropical China. They found that photoinhibition was reduced for Castanopsis fissa seedlings under medium canopies and for Syzygium hancei seedlings under large canopies.…”

Dynamics of Understory Shrub Biomass in Six Young Plantations of Southern Subtropical China

“…In arid and semi-arid ecosystems, shrubs are conducive to the increase in the number of herb-layer plant species [4]. In subtropical forests, shrubs facilitate the growth of understory tree seedling [5,6]. In reclaimed mined sites, shrubs act as ecosystem engineers [7].…”

“…Thus, changes in the light environment could be one of the main reasons. Furthermore, there are various optimum light levels for the growth of different shrubs [6,58]. For example, G. jasminoides showed its optimum growth rate above 52% sunlight [49], and there was a very rigorous light demand by B. frutescens [59].…”