Carbon, nitrogen, and phosphorus storage in alpine grassland ecosystems of Tibet: effects of grazing exclusion

Abstract

In recent decades, alpine grasslands have been seriously degraded on the Tibetan Plateau and grazing exclusion by fencing has been widely adopted to restore degraded grasslands since 2004. To elucidate how alpine grasslands carbon (C), nitrogen (N), and phosphorus (P) storage responds to this management strategy, three types of alpine grassland in nine counties in Tibet were selected to investigate C, N, and P storage in the environment by comparing free grazing (FG) and grazing exclusion (GE) treatments, which had run for 6–8 years. The results revealed that there were no significant differences in total ecosystem C, N, and P storage, as well as the C, N, and P stored in both total biomass and soil (0–30 cm) fractions between FG and GE grasslands. However, precipitation played a key role in controlling C, N, and P storage and distribution. With grazing exclusion, C and N stored in aboveground biomass significantly increased by 5.7 g m−2 and 0.1 g m−2, respectively, whereas the C and P stored in the soil surface layer (0–15 cm) significantly decreased by 862.9 g m−2 and 13.6 g m−2, respectively. Furthermore, the storage of the aboveground biomass C, N, and P was positively correlated with vegetation cover and negatively correlated with the biodiversity index, including Pielou evenness index, Shannon–Wiener diversity index, and Simpson dominance index. The storage of soil surface layer C, N, and P was positively correlated with soil silt content and negatively correlated with soil sand content. Our results demonstrated that grazing exclusion had no impact on total C, N, and P storage, as well as C, N, and P in both total biomass and soil (0–30 cm) fractions in the alpine grassland ecosystem. However, grazing exclusion could result in increased aboveground biomass C and N pools and decreased soil surface layer (0–15 cm) C and P pools.

Effects of grazing on ecosystem structure and function of alpine grasslands in Qinghai–Tibetan Plateau: a synthesis

“…, Lu et al. , b). In other ecosystems, there is growing evidence that complete exclusion from grazing for a prolonged period of time may not lead to an improvement in vegetation and soil conditions (Chaneton and Lavado , Hart and Scientist , Firincioğlu et al.…”

Grazing enhances soil nutrient effects: Trade‐offs between aboveground and belowground biomass in alpine grasslands of the Tibetan Plateau

“…The suitable time for plant growth and development only lasts 2–4 months, which does not promote the accumulation of AGB (Li, Wang, An, & Ji, ). In addition, soil could also affect the vegetation productivity, community composition, and plant species richness by supplying organic matter and cycling nutrients, such as nitrogen and carbon (Lu et al, 2015; Lu, Yan, Sun, X. K. Zhangz et al, ). Many previous studies have demonstrated that GE varies several physical properties of soil (Greenwood & Mckenzie, ; Hoshino, Tamura, Fujimaki, & Asano, ; Medinaroldán, Pazferreiro, & Bardgett, ; Mofidi, Jafari, Tavili, Rashtbari, & Alijanpour, ).…”

Water and heat availability are drivers of the aboveground plant carbon accumulation rate in alpine grasslands on the Tibetan Plateau

“…Soil water content (SWC) was measured using the drying method; soil organic carbon (SOC) and soil total nitrogen (STN) were determined using a vario MACRO cube elemental analyser (Elementar Analysensysteme GmbH, Hanau, Germany) (Lu et al, 2015); soil total phosphorus (STP) Soil samples were air-dried and handpicked to remove plant components in the field.…”