Tree species composition rather than biodiversity impacts forest soil organic carbon of Three Gorges, southwestern China

Nan Liu,Yunqi Wang,Zhanjun Zhao,Yujie Wang,Yangyi Zhao

doi:10.3897/natureconservation.14.6486

Abstract

Forest soil represents an important resource for mitigating the climate change. Besides, plant composition and diversity and their roles in ecosystem functioning are becoming a central issue in forest soil organic carbon (SOC) research. The primary objective of this research is to investigate the effects of tree species diversity and composition on potential of C sequestration of forest soil in Three Gorges area and provide basic information to future research on climate change. Two dominant forest ecosystems were selected: mixed conifer-broadleaf forest (Fm) and evergreen broadleaf forest (Fb). Then study transects were established and investigated. Soil samples were collected and determined for bulk density, SOC concentration and stock, nitrogen (N) concentration and C:N ratio. The results showed that the statistical differences of SOC concentrations and stocks between Fm and Fb were caused by tree species composition rather than the tree species diversity. And the most significant differences were found in the first two soil horizons (0–15 cm and 15–30 cm). The average C:N values of four different horizons in Fm were decreased with increasing soil depth as well as Fb. Not only SOC concentrations but also stocks of the two studied forests were decreased with increasing soil depth. However, Fm showed a larger capacity to store SOC with an average stock of 183.50 t/ha than that of Fb (100.44 t/ha) in study area. Thus, forest which is composed of conifer and evergreen broadleaf tree species may be the best choice for local afforestation and reforestation aimed at alleviating climate change in Three Gorges region. Nature Conservation 14: 7–24 (2016) doi: 10.3897/natureconservation.14.6486 http://natureconservation.pensoft.net Copyright Nan Liu et al. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. RESEARCH ARTICLE Launched to accelerate biodiversity conservation A peer-reviewed open-access journal Nan Liu et al. / Nature Conservation 14: 7–24 (2016) 8

Highlights

Scientists have long been concerned with soil carbon (C), because it is often the master variable determining soil fertility (Malhi et al 1999; Johnson and Curtis 2001; Johnson et al 2002)
The results showed that soil organic carbon (SOC) differences between Fm and Fb were influenced by C:N ratio little, which indicated that SOC decompositions of Fm and Fb were similar
SOC of Fm and Fb were not influenced by tree species diversity due to the very low linear coefficients

Summary

Introduction

Scientists have long been concerned with soil carbon (C), because it is often the master variable determining soil fertility (Malhi et al 1999; Johnson and Curtis 2001; Johnson et al 2002). Known soil C stock has become very important for assessing changes in atmospheric CO2 concentrations and of global climate (Dixon et al 1994; Schimel 1995; Søe et al 2004). As the largest pool of terrestrial organic carbon in the biosphere, more C is stored in soil than is contained in plants and the atmosphere combined (Jobbágy and Jackson 2000). Global surveys of mineral soil organic carbon (SOC) indicate that the soil holds about 1500 Pg C in the upper meter of soil (Post et al 1982; Eswaran et al 1993; Jobbágy and Jackson 2000), and most of this SOC (roughly 70% of all SOC) is contained in forest soils (Dixon et al 1994; Batjes 1996; Jandl et al 2007)

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