TY - JOUR

T1 - Aspect-vegetation complex effects on biochemical characteristics and decomposability of soil organic carbon on the eastern Qinghai-Tibetan Plateau

AU - Zhao, Ning Ning

AU - Guggenberger, Georg

AU - Shibistova, Olga

AU - Thao, Dao Thi

AU - Shi, Wen Jing

AU - Li, Xiao Gang

N1 - Funding information: Acknowledgments This study was financially supported by the National Natural Science Foundation of China (41071198), the Priority Program 1372 (Tibetan Plateau: Formation – Climate – Ecosystems) of the German Research Foundation, and the Key International Collaboration Project of the MOST of China (2010DFB63500). We are grateful to Leopold Sauheitl and Ulrike Pieper from the Institute of Soil Science in Hannover for excellent support in the laboratory. We appreciate comments from two anonymous reviewers, which are very constructive for improving the quality of the manuscript.

PY - 2014/7/29

Y1 - 2014/7/29

N2 - Background: Meadows and shrublands are two major vegetation types on the Qinghai-Tibetan Plateau, but little is known about biochemical characteristics and its relation to decomposability of soil organic carbon (OC) under these two vegetation types. The present study was designed to evaluate effects of aspect-vegetation complex on biochemical characteristics and decomposability of soil OC.Methods: Two hills were randomly selected; both with vegetation being naturally divided into southward meadows and northward shrublands by a ridge, and soils were sampled at depths of 0–15 and 15–30 cm, along contours traversing the meadow and shrubland sites. Particulate (particle size 2–0.05 mm) OC and nitrogen (N), microbial biomass C and N, non-cellulosic sugars, and CuO lignin were analyzed, and OC mineralization was measured for 49 days at 18 and 25 °C under laboratory incubation, respectively.Results: More than half of soil OC was present as particulate fraction across all samples, indicating the coarse nature of soil organic matter in the region. Averaging over depths, shrublands contained 87.7 − 114.1 g OC and 7.7 − 9.3 g N per kg soil, which were 63 − 78 and 26 − 31 % higher than those in meadows, respectively. Meanwhile the C/N ratio of soil organic matter was 11.4 − 12.3 under shrublands, being 29 − 40 % higher than that under meadows. Soil OC under meadows was richer in noncellulosic carbohydrates and microbial biomass in the 0–15 and 15–30 cm depths but contained less lignin in the 15–30 cm depth. Ratios of microbially- to plant-derived monosaccharides and between acid and aldehyde of the vanillyl units were greater in soils under shrublands, showing more abundant microbially-derived sugars and microbially-transformed ligneous substances in OC as compared to meadow soils. By the end of 49 days’ incubation, total CO2–C evolution from soils under meadows was 15.0–16.2 mg g−1 OC averaging over incubation temperatures and soil depths, being 27–55 % greater than that under shrublands. Across all soil samples over two sites, total CO2 − C evolved per g OC at either 18 or 25 °C was closely correlated to enrichments of noncellulosic carbohydrates and microbial biomass. This indicates that the greater soil OC decomposability under meadows was associated with its larger abundances of readily mineralizable fractions compared with shrublands. However, temperature increase effect on soil OC decomposability did not differ between the two types of vegetation.Conclusions: Our findings suggest that the aspect-vegetation complex significantly affected pool size, biochemical characteristics, and decomposability of soil OC on the northeastern edge of Qinghai-Tibetan Plateau. However, the response of soil OC decomposability to temperature was similar between southward meadows and northward shrublands.

AB - Background: Meadows and shrublands are two major vegetation types on the Qinghai-Tibetan Plateau, but little is known about biochemical characteristics and its relation to decomposability of soil organic carbon (OC) under these two vegetation types. The present study was designed to evaluate effects of aspect-vegetation complex on biochemical characteristics and decomposability of soil OC.Methods: Two hills were randomly selected; both with vegetation being naturally divided into southward meadows and northward shrublands by a ridge, and soils were sampled at depths of 0–15 and 15–30 cm, along contours traversing the meadow and shrubland sites. Particulate (particle size 2–0.05 mm) OC and nitrogen (N), microbial biomass C and N, non-cellulosic sugars, and CuO lignin were analyzed, and OC mineralization was measured for 49 days at 18 and 25 °C under laboratory incubation, respectively.Results: More than half of soil OC was present as particulate fraction across all samples, indicating the coarse nature of soil organic matter in the region. Averaging over depths, shrublands contained 87.7 − 114.1 g OC and 7.7 − 9.3 g N per kg soil, which were 63 − 78 and 26 − 31 % higher than those in meadows, respectively. Meanwhile the C/N ratio of soil organic matter was 11.4 − 12.3 under shrublands, being 29 − 40 % higher than that under meadows. Soil OC under meadows was richer in noncellulosic carbohydrates and microbial biomass in the 0–15 and 15–30 cm depths but contained less lignin in the 15–30 cm depth. Ratios of microbially- to plant-derived monosaccharides and between acid and aldehyde of the vanillyl units were greater in soils under shrublands, showing more abundant microbially-derived sugars and microbially-transformed ligneous substances in OC as compared to meadow soils. By the end of 49 days’ incubation, total CO2–C evolution from soils under meadows was 15.0–16.2 mg g−1 OC averaging over incubation temperatures and soil depths, being 27–55 % greater than that under shrublands. Across all soil samples over two sites, total CO2 − C evolved per g OC at either 18 or 25 °C was closely correlated to enrichments of noncellulosic carbohydrates and microbial biomass. This indicates that the greater soil OC decomposability under meadows was associated with its larger abundances of readily mineralizable fractions compared with shrublands. However, temperature increase effect on soil OC decomposability did not differ between the two types of vegetation.Conclusions: Our findings suggest that the aspect-vegetation complex significantly affected pool size, biochemical characteristics, and decomposability of soil OC on the northeastern edge of Qinghai-Tibetan Plateau. However, the response of soil OC decomposability to temperature was similar between southward meadows and northward shrublands.

KW - Lignin Microbial biomass

KW - Mineralization

KW - Non-cellulosic sugars

KW - Soil organic carbon quality

UR - http://www.scopus.com/inward/record.url?scp=84910155755&partnerID=8YFLogxK

U2 - 10.1007/s11104-014-2210-x

DO - 10.1007/s11104-014-2210-x

M3 - Article

AN - SCOPUS:84910155755

VL - 384

SP - 289

EP - 301

JO - Plant and soil

JF - Plant and soil

SN - 0032-079X

IS - 1-2

ER -