Effect of grazing on carbon stocks and assimilate partitioning in a Tibetan montane pasture revealed by ¹³CO ₂ pulse labeling

authored by

Silke Hafner, Sebastian Unteregelsbacher, Elke Seeber, Becker Lena, Xingliang Xu, Xiaogang Li, Georg Guggenberger, Georg Miehe, Yakov Kuzyakov

Abstract

Since the late 1950s, governmental rangeland policies have changed the grazing management on the Tibetan Plateau (TP). Increasing grazing pressure and, since the 1980s, the privatization and fencing of pastures near villages has led to land degradation, whereas remote pastures have recovered from stronger overgrazing. To clarify the effect of moderate grazing on the carbon (C) cycle of the TP, we investigated differences in below-ground C stocks and C allocation using in situ ¹³CO ₂ pulse labeling of (i) a montane Kobresia winter pasture of yaks, with moderate grazing regime and (ii) a 7-year-old grazing exclosure plot, both in 3440 m asl. Twenty-seven days after the labeling, ¹³C incorporated into shoots did not differ between the grazed (43% of recovered ¹³C) and ungrazed (38%) plots. In the grazed plots, however, less C was lost by shoot respiration (17% vs. 42%), and more was translocated below-ground (40% vs. 20%). Within the below-ground pools, <2% of ¹³C was incorporated into living root tissue of both land use types. In the grazed plots about twice the amount of ¹³C remained in soil (18%) and was mineralized to CO ₂ (20%) as compared to the ungrazed plots (soil 10%; CO ₂ 9%). Despite the higher contribution of root-derived C to CO ₂ efflux, total CO ₂ efflux did not differ between the two land use types. C stocks in the soil layers 0-5 and 5-15 cm under grazed grassland were significantly larger than in the ungrazed grassland. However, C stocks below 15 cm were not affected after 7 years without grazing. We conclude that the larger below-ground C allocation of plants, the larger amount of recently assimilated C remaining in the soil, and less soil organic matter-derived CO ₂ efflux create a positive effect of moderate grazing on soil C input and C sequestration.

Organisation(s)

Institute of Soil Science
Section Soil Chemistry

External Organisation(s)

University of Bayreuth
Martin Luther University Halle-Wittenberg
Lanzhou University
Philipps-Universität Marburg
University of Göttingen
Chinese Academy of Sciences (CAS)

Type

Article

Journal

Global change biology

Volume

18

Pages

528-538

No. of pages

11

ISSN

1354-1013

Publication date

23.09.2011

Publication status

Published

Peer reviewed

Yes

ASJC Scopus subject areas

Global and Planetary Change, Environmental Chemistry, Ecology, Environmental Science(all)

Sustainable Development Goals

SDG 15 - Life on Land

Electronic version(s)

https://doi.org/10.1111/j.1365-2486.2011.02557.x (Access: Closed)