Factors affecting 13 C enrichment of vegetation and soil in temperate grasslands in Inner Mongolia, China

Abstract

Purpose

Soil organic carbon (SOC) dynamics are central to understanding the effects of environmental change on the carbon cycle of ecosystems. Vegetation and soil stable carbon isotope composition (δ¹³C), especially the difference of δ¹³C between surface soils and source vegetation (Δδ¹³C), can provide useful information about the SOC dynamics. The variations and patterns of vegetation and soil δ¹³C and Δδ¹³C along climatic and edaphic gradients were analyzed to improve the understanding of SOC dynamics in temperate grassland ecosystems.

Materials and methods

Soil and plant samples were collected along climatic and edaphic gradients. Meteorological data were extracted from a regional climate database, which was spatially interpolated based on the records at 107 climatic stations located in Inner Mongolia. δ¹³C, carbon and nitrogen contents of soil and plant, soil pH, soil clay, silt, and sand contents were determined. Δδ¹³C and soil C:N were calculated. The integrative effects of these factors were further estimated using stepwise regression, redundancy analysis (RDA) and T value biplots.

Results and discussion

As expected, soil δ¹³C was positively related to vegetation δ¹³C, and higher than the vegetation δ¹³C. Vegetation and soil δ¹³C and Δδ¹³C were all related to growing season precipitation (GSP) and growing season temperature (GST). However, when climatic and edaphic factors were considered together, vegetation δ¹³C was positively related to GST and soil C:N, soil δ¹³C was positively related only to GST, and Δδ¹³C was negatively related only to soil C:N. Unlike previous research conducted at the species level which only included C₃ species, GST, instead of precipitation, was the dominant controlling factor of vegetation δ¹³C.

Conclusions

GST influences vegetation δ¹³C mainly through its effect on relative abundance of C₄ plants. Soil C:N rather than climatic factors is the dominant controlling factor of SOC decomposition, and the effects of climatic factors on SOC decomposition are indirect and induced by their effects on soil C:N through influencing species composition and plant C:N. Measuring vegetation δ¹³C, soil δ¹³C, and △δ¹³C simultaneously is necessary to comprehensively understand how environmental changes influence ecosystem carbon cycles.

from Energy Ecology Environment Ambio via Terpsi Hori on Inoreader http://bit.ly/2CwdmgK