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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. [ABSTRACT FROM AUTHOR]

• Warming and water addition increase L. chinensis biomass and reduce S. krylovii. • Community biomass is remained unchanged under warming and water addition. • Warming increases L. chinensis biomass by affecting SA and GA. • S. krylovii steppe may be replaced by L. chinensis in warmer and wetter future. Dominant species play a crucial role in regulating plant community structure and productivity. Climate change affects community productivity by changing plant traits and resource use efficiency. However, the response of the productivity of a dominant species to warming and precipitation addition and the related effects on community biomass production in semi-arid grasslands remain unclear. We conducted a ten-year warming and precipitation addition study of a semi-arid steppe in Inner Mongolia, China. We examined the responses of community composition, biomass production, and trait and resource use efficiency of two dominant species, Leymus chinensis (rhizome grass) and Stipa krylovii. The results show that warming and precipitation increased the biomass of L. chinensis and decreased the biomass of S. krylovii. Community biomass production was unchanged under warming and precipitation from the contrasting changes in the two dominant species. Warming significantly increased the leaf area (LA) of L. chinensis and S. krylovii compared to that in ambient conditions, while it decreased the specific leaf area (SLA) and δ13C of S. krylovii. Increases in temperature stimulated biomass production of L. chinensis by affecting salicylic acid (SA) and GA (gibberellin), and they increased its competitive ability compared with that of S. krylovii. Our results highlight the different responses of L. chinensis and S. krylovii to environmental changes, which stabilised community productivity under warming and precipitation. Our study provides evidence that S. krylovii may be replaced by L. chinensis in steppe climates in the warmer and wetter future. [ABSTRACT FROM AUTHOR]

• Alpine meadow had higher CUE and lower WUE than cultivated grassland under warming. • Warming decreased biomass of cultivated grassland in the later of the experiment. • Warming increased ET, did not affect GEP, and decreased WUE in alpine meadow. • Warming decreased NEE, did not alter ER, and decrease CUE in cultivated grassland. Carbon and water use efficiency (CUE and WUE) are crucial indicators of grassland ecosystem responses to climate change. Grass planting is one of the dominant methods of grassland restoration and agricultural production. However, how warming and reclamation impact grassland CUE and WUE remain unclear. Here we examined how warming affected carbon and water processes in natural alpine meadow and cultivated grassland, including gross ecosystem production (GEP), net ecosystem CO 2 exchange (NEE), evapotranspiration (ET), CUE and WUE. We deployed a seven-year warming experiment using open top chambers in alpine meadow and cultivated grassland on the Tibetan Plateau. Our results showed that the alpine meadow had a higher CUE and a lower WUE compared to the cultivated grassland under warming. Warming increased biomass production of the cultivated grassland in the beginning of the experiment but decreased it later in the experiment. Warming increased ET, did not affect GEP, and finally decreased WUE in the natural alpine meadow. In the cultivated grassland, warming decreased NEE, did not alter ER, and resulted the decrease in CUE. Our results highlight that reclamation decreases CUE and warming decreased WUE of alpine meadow. Although grass planting can increase biomass, the negative impacts of warming on carbon and water processes of cultivated grassland should be considered when reclaiming alpine meadow under warmer future. [ABSTRACT FROM AUTHOR]

• Responses of green up to warming were different among years. • Water addition did not advance community phenology except in a dry and warm year. • Warming increased annual variability of plant green up and flowering. • Flowering of K. pygmaea advanced under warming plus water addition in all three years. • Soil moisture plays a critical role in determining phenological response to warming. Temperature and precipitation are primary regulators of plant phenology. However, our knowledge of how these factors might interact to affect plant phenology is incomplete. The Qinghai-Tibetan Plateau, a cold and high region, has experienced no consistent changes in spring phenology, despite a significant warming trend. We conducted a manipulative experiment of warming and precipitation addition in an alpine meadow on the Qinghai-Tibetan Plateau in 2015 (cold and wet), 2016 (warm and dry) and 2017 (mild and very wet). We found that warming increased annual variability of plant spring phenology. Warming delayed green up of all monitored species in 2016, advanced green up of early flowering species in 2015, and did not alter green up in 2017. For example, green up of the shallow rooted Kobresia pygmaea advanced 8 (± 2) days in 2015 and was delayed by 23 (± 3) days in a dry year (2016) under warming compared with control. Early spring precipitation addition can offset the delaying effects of warming in a dry year on the Qinghai-Tibetan Plateau. Under warming plus precipitation addition, community average green up advanced compared to control plots in 2015 and 2016, and community average flowering advanced for all three years. In 2016, flowering of K. pygmaea (an early flowering species) advanced under warming plus precipitation addition compared to control while flowering of other species did not change. Our results highlight that annual variation of soil moisture condition plays a critical role in determining the magnitude and direction of spring phenology response to warming. We provide insights in how plant spring phenology might change in a warmer future in the presence or absence of precipitation increase. [ABSTRACT FROM AUTHOR]

• Responses to warming differed between early rice and late rice. • Warming benefited yield formation before heading. • Benefits of CO 2 enrichment could eliminate the negative effects of warming on yield. • Yield may not decrease under future climate change in Chinese double rice system. Elevated atmospheric CO 2 concentration ([CO 2 ]) and temperature can strongly affect rice (Oryza sativa L.) production. However, the impact of warming is variable depending on ambient temperature and cropping system. Little is known about the effect of elevated temperature and its interaction with elevated [CO 2 ] in the Chinese double rice cropping system. To study this issue, field experiments were conducted using open-top chambers (OTC) with varying [CO 2 ] (ambient, ambient+60 μmol mol−1) and varying temperature (ambient, ambient+2 °C) for 4 rotations of double rice from 2013 to 2016. Elevated [CO 2 ] significantly increased grain yield in both early rice and late rice. This could be attributed to greater aboveground biomass, higher panicle number (m-2), spikelet number (per panicle) and 1000-grain weight. Elevated temperature decreased yield in early rice (except for 2016) due to decreases in % filled grains and 1000-grain weight. Elevated temperature increased yield in late rice due to increases in aboveground biomass, number of panicles and spikelets, although % filled grains decreased. We found that warming had positive effects on tiller development and dry matter accumulation during the pre-heading period both in early and late rice, which contributed to yield formation. When elevated temperature and [CO 2 ] were combined, yield changed by −1.9–23.7% in early rice compared with ambient condition as warming partly offset the benefits of CO 2 enrichment, while yield increased by 14.3–18.8% in late rice due to a synergy between warming and CO 2 enrichment. The benefits of CO 2 enrichment for fertile spikelets (m-2) and aboveground biomass could reduce or eliminate the negative impacts of warming. However, there were no significant interactions between elevated temperature and [CO 2 ] in most rice seasons. Our findings indicate that warming by 2 °C is not detrimental to yield formation under CO 2 enrichment, and suggest that grain yield may not decrease under future climate change in the Chinese double rice cropping system. [ABSTRACT FROM AUTHOR]