Differential response of alpine steppe and alpine meadow to climate warming in the central Qinghai–Tibetan Plateau

Abstract

Recently, the Qinghai-Tibetan Plateau has experienced significant warming. Climate warming is expected to have profound effects on plant community productivity and composition, which can drive ecosystem structure and function. To explore effects of warming on plant community productivity and composition, we conducted a warming experiment using open top chambers (OTCs) from 2012 to 2014 in alpine meadow and alpine steppe habitat on the central Qinghai-Tibetan Plateau. We measured aboveground net primary productivity (ANPP), community composition and species diversity under ambient and two levels of artificially warmed conditions across three years. Our results showed that warming significantly stimulated plant growth in the alpine meadow, but reduced growth on the alpine steppe. The increase of ANPP in alpine meadow was a result of an increase of plant height under warming. Warming-induced drought conditions were primarily responsible for the observed decrease of ANPP in an alpine steppe. Plant community composition and species diversity were not influenced by warming in alpine meadow. Alternatively, in alpine steppe, cover of graminoids and forbs significantly declined while legumes substantially increased under warming, subsequently resulting in rapid species losses. Changes in soil moisture were responsible for observed changes in graminoids and legumes in the alpine steppe. Overall, experimental results demonstrated that warming had a positive impact on plant community structure and function in alpine meadow and had a negative impact on these characteristics in an alpine steppe. This work highlights the important role of soil moisture for regulating plant productivity and community composition response to warming in the alpine steppe. In particular, the deep-rooted, drought resistant plants may increase in a warmer future in the central Qinghai-Tibetan Plateau. These changes may reduce habitat quality for the local community of grazers because many of the species that increased are also unpalatable to grazers.

Warming effects on permafrost ecosystem carbon fluxes associated with plant nutrients

“…, Ganjurjav et al. ), our results showed that even when soil moisture was not limiting, there was not a strong C uptake response to warming. Given that non‐growing season C losses account for a significant proportion of the annual C budget (Natali et al.…”

“…S1). Therefore, CO 2 exchange in swamp meadow ecosystems is expected to be less dependent on soil hydraulic conditions compared to other grassland types on the plateau (Peng et al 2014, Ganjurjav et al 2016, where warming-induced water limitation may constrain N and P mineralization. We hypothesized that experimental warming in this swamp meadow ecosystem would increase soil N and P availabilities but would not alter soil moisture status, which would positively influence the growth of plants and soil microorganisms, and thus alter growing-season ecosystem CO 2 exchange.…”

Different responses of ecosystem carbon exchange to warming in three types of alpine grassland on the central Qinghai–Tibetan Plateau

“…The cultivated grassland is dominated by Elymus nutans , which was planted in 2010 at alpine meadow region. Warming induced ANPP increase in meadow and cultivated grassland while decrease ANPP in steppe (Table , Ganjurjav, Gao, Gornish et al., ). The soil organic carbon and total nitrogen were increased in meadow under warming compared to control while decreased in steppe and cultivated grassland under warming compared to control (Table , Ganjurjav, Gao, Gornish et al., ).…”

“…The details for community differences between meadow and steppe habitat are provided in Ganjurjav, Gao, Gornish et al. (). The cultivated grassland is dominated by Elymus nutans , which was planted in 2010 at alpine meadow region.…”

“…The experimental sites were located in the Nagqu ( Ganjurjav, Gao, Gornish et al (2016). The cultivated grassland is dominated by Elymus nutans, which was planted in 2010 at alpine meadow region.…”