White Spruce Plantations on Abandoned Agricultural Land: Are They More Effective as C Sinks than Natural Succession?

Sylvie Tremblay,Rock Ouimet

doi:10.3390/f4041141

Abstract

The objective of this study was to compare organic carbon (C) accumulation in plantations (PL) and natural succession (NS) established on fallow lands along a 50-year chronosequence in the eastern mixed forest subzone of Quebec (Canada). Above- and below-ground woody biomass were estimated from vegetation measurement surveys, and litter and soil (0–50 cm depth) C from samplings. At the year of abandonment, total C content of both PL and NS sites averaged 100 ± 13 Mg C ha−1. Over 50 years, total C content doubled on NS sites and tripled on PL sites (217.9 ± 28.7 vs. 285.7 ± 31.0 Mg ha−1) with respect to fallow land. On NS sites, the new C stocks accumulated entirely in the vegetation. On PL sites, C accumulated mostly in the vegetation and to a lesser extent in the litter, whereas it decreased by a third in the soil. As a result, the net C accumulation rate was 1.7 ± 0.7 Mg ha−1 yr−1 greater on PL sites than on NS sites over 50 years. By the 23rd year, PL sites became greater net C sinks than NS sites in the fallow lands of the study area, even with the loss of soil C.

Highlights

A global warming of +1.8 °C to more than 5 °C is projected by 2100 in northern North America, very likely due to increased concentrations of anthropogenic greenhouse gases [1], of which carbonForests 2013, 4 dioxide (CO2) is the most important
For the first 20 years after land abandonment, natural succession began with grass; shrubs and small trees (DBH ≤ 9 cm) appeared between 20 and 30 years, followed by shrubs and taller trees (DBH > 9 cm) after 30 years
More commercial and non-commercial species were generally found on natural succession (NS) sites than on PL sites

Summary

Introduction

A global warming of +1.8 °C to more than 5 °C is projected by 2100 in northern North America, very likely due to increased concentrations of anthropogenic greenhouse gases [1], of which carbonForests 2013, 4 dioxide (CO2) is the most important. A global warming of +1.8 °C to more than 5 °C is projected by 2100 in northern North America, very likely due to increased concentrations of anthropogenic greenhouse gases [1], of which carbon. Converting treeless, previously non-forested areas into plantations (afforestation) is recognized by the Kyoto Protocol as a method to increase CO 2 sinks [2], because trees can sequester CO2 from the atmosphere and store it in living and dead organic matter through plant photosynthesis [3]. This fundamental question has rarely been answered in earlier studies of forest restoration after agricultural land abandonment, most of which addressed only either plantation or natural succession. Few have compared the two approaches regarding their potential for C sequestration, especially in northern regions like Canada. In the province of Quebec, 100,000 ha of abandoned agricultural lands were surveyed between 1997 and 2007; 45% of these were located in the Bas-Saint-Laurent region, which has a low agriculture potential [7]

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Conclusion