Allometric relationships of frequently used shade tree species in cacao agroforestry systems in Sulawesi, Indonesia

Nina Tiralla,Oleg Panferov,Alexander Knohl

doi:10.1007/s10457-013-9602-4

Abstract

Shade trees play an important role within agroforestry systems by influencing radiation and wind regimes as well as nutrient and hydrological cycling. However, there is a lack of quantitative assessments of their functions. One of the reasons is the rare information on structural characteristics of shade tree species. Therefore, the aim of this study is to provide basic information on the structure of frequently used shade tree species for the implementation of models simulating the ecosystem processes in agroforestry systems. The investigation of the shade trees was conducted at two cacao agroforestry sites on Sulawesi, Indonesia. The measurements of the main structural parameters: diameter at breast height, tree height, trunk height, crown length and crown radius were carried out for the shade tree species Aleurites moluccana, Cocos nucifera and Gliricidia sepium. For data collection, the National Forest Inventory Field Manual Template by FAO (2004) was applied. Based on this information allometric functions were derived for the correspondent shade tree species. The best significant relationships were obtained for the height-crown length relationship of the dicotyledonous tree species’ A. moluccana and G. sepium with a coefficient of determination r² = 0.925 and r² = 0.738, respectively, and the height-crown length relationship of the monocotyledonous palm C. nucifera with r² = 0.663. The transferability tests ‘analysis of covariance’ and ‘homogeneity of slopes’ have shown that the obtained allometric functions are also applicable to other cacao agroforestry systems of the region.

Highlights

Within the context of conservation of tropical rainforests, sustainable development of rural areas and afforestation and reforestation of degraded lands, agroforestry systems have become an increasingly successful approach as they reduce pressure on natural forests while meeting economic as well as social needs of the local population (Michon and de Foresta 1996; Nair 1998; Rice and Greenberg 2000; Bhagwat et al 2008; Jose 2009)
Attention should be paid to the fact that A. moluccana and G. sepium are dicotyledonous trees
Revealing species-specific allometric relationships, this study provides important basics for the description of shade tree structure of A. moluccana, C. nucifera and G. sepium that is required in experimental and modelling studies dealing with ecosystem processes in cacao agroforestry systems such as nutrient cycling, radiative transfer, wind regime and hydrological cycling

Summary

Introduction

Within the context of conservation of tropical rainforests, sustainable development of rural areas and afforestation and reforestation of degraded lands, agroforestry systems have become an increasingly successful approach as they reduce pressure on natural forests while meeting economic as well as social needs of the local population (Michon and de Foresta 1996; Nair 1998; Rice and Greenberg 2000; Bhagwat et al 2008; Jose 2009). Agroforestry systems consist of a low-density stratum of tall perennial woody plants i.e. shade trees, with a stratum of agricultural crops underneath, i.e. shade-bearers like cacao (Theobroma cacao), planted at the same land-management unit. Shade trees, which provide shade for crops underneath, are a crucial component of agroforestry systems as they modify radiation and wind regimes as well as nutrient and hydrological cycling. Biological species composition, mass balance, and productivity of agroforestry systems are influenced by intensity and distribution of shade (Beer 1987; Rice and Greenberg 2000; Mialet-Serra et al 2001; Siebert 2002; Zuidema et al 2005; Isaac et al 2007). The impact of shade trees on cacao crops is discussed controversially as it is not yet evident in which aspects and how strong shade trees favour or hamper cacao crops (Beer 1987; Somarriba and Beer 2011; Tscharntke et al 2011)

Objectives

Methods

Results

Conclusion