Carbon and Nitrogen Stocks in Three Types of Larix gmelinii Forests in Daxing’an Mountains, Northeast China

Ruihan Xiao,Beixing Duan,Xiuling Man

doi:10.3390/f11030305

Abstract

Studying carbon and nitrogen stocks in different types of larch forest ecosystems is of great significance for assessing the carbon sink capacity and nitrogen level in larch forests. To evaluate the effects of the differences of forest type on the carbon and nitrogen stock capacity of the larch forest ecosystem, we selected three typical types of larch forest ecosystems in the northern part of Daxing’an Mountains, which were the Rhododendron simsii-Larix gmelinii forest (RL), Ledum palustre-Larix gmelinii forest (LL) and Sphagnum-Bryum-Ledum palustre-Larix gmelinii forest (SLL), to determine the carbon and nitrogen stocks in the vegetation (trees and understories), litter and soil. Results showed that there were significant differences in carbon and nitrogen stocks among the three types of larch forest ecosystems, showing a sequence of SLL (288.01 Mg·ha−1 and 25.19 Mg·ha−1) > LL (176.52 Mg·ha−1 and 14.85 Mg·ha−1) > RL (153.93 Mg·ha−1 and 10.00 Mg·ha−1) (P < 0.05). The largest proportions of carbon and nitrogen stocks were found in soils, accounting for 83.20%, 72.89% and 64.61% of carbon stocks and 98.61%, 97.58% and 96.00% of nitrogen stocks in the SLL, LL and RL, respectively. Also, it was found that significant differences among the three types of larch forest ecosystems in terms of soil carbon and nitrogen stocks (SLL > LL > RL) (P < 0.05) were the primary reasons for the differences in the ecosystem carbon and nitrogen stocks. More than 79% of soil carbon and 51% of soil nitrogen at a depth of 0–100 cm were stored in the upper 50 cm of the soil pool. In the vegetation layer, due to the similar tree biomass carbon and nitrogen stocks, there were no significant differences in carbon and nitrogen stocks among the three types of larch forest ecosystems. The litter carbon stock in the SLL was significantly higher than that in the LL and RL (P < 0.05), but no significant differences in nitrogen stock were found among them (P > 0.05). These findings suggest that different forest types with the same tree layer and different understory vegetation can greatly affect the carbon and nitrogen stock capacity of the forest ecosystem. This indicates that understory vegetation may have significant effects on the carbon and nitrogen stocks in soil and litter, which highlights the need to consider the effects of understory in future research into the carbon and nitrogen stock capacity of forest ecosystems.

Highlights

Forest is a large carbon and nitrogen pool in terrestrial ecosystems [1,2], playing an important role in regulating the global stock, distribution and cycling of carbon and nitrogen [3,4,5]
There were no significant differences in the tree biomass carbon and nitrogen stocks among the three types of larch forest ecosystems, which may be explained by the similar tree species, species stand density, age (Table 1), carbon and nitrogen contents and tree biomass (Table A1)
Our study showed that the carbon and nitrogen stocks in vegetation biomass were the second-largest components in the three types of larch forest ecosystems

Summary

Introduction

Forest is a large carbon and nitrogen pool in terrestrial ecosystems [1,2], playing an important role in regulating the global stock, distribution and cycling of carbon and nitrogen [3,4,5]. The boreal forest is extremely sensitive to climate change [15], as it is the world’s second-largest forest biome and has a large amount of carbon stocks [16]. Some studies have shown that the carbon sink capacity of boreal forests has been weakening due to the effect of human and natural disturbances [17,18]. Research on the effect of forest type on the accurate estimation of forest ecosystem carbon and nitrogen stocks in boreal forest is important in the context of continuing global warming

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Results

Discussion

Conclusion