The combined effects of warming and drying suppress CO₂ and N₂O emission rates in an alpine meadow of the eastern Tibetan Plateau

Abstract

The eastern Tibetan Plateau has become increasingly warmer and drier since the 1990s. Such warming and drying has a great impact on ecosystem processes on the eastern Tibetan Plateau. To determine their combined effects on CO 2 and N 2 O emission rates, we conducted a field manipulative experiment in an alpine meadow of the eastern Tibetan Plateau during the growing season of 2009. The experiment showed that warming manipulation increased soil temperature by 1°C, and drying manipulation decreased soil water content by 6.8 %. We found that by counteracting the effect of low temperature in the area, experimental warming significantly increased soil microbial biomass, the number of bacteria, fungi, actinomycetes, ammonifying bacteria, nitrobacteria and denitrifying bacteria, and facilitated the emission rates of CO 2 and N 2 O by 33.4 and 31.5 %, respectively. However, decreased precipitation further aggravated soil water stress and inhibited the numbers of these organisms, and reduced the emission rates of CO 2 and N 2 O by 47.4 and 37.9 %, respectively. So decreased soil water content tended to offset the positive effect of warming. Compared to the positive effects of warming, decreased soil water content was shown in our study to have even greater impact on the eastern Tibetan Plateau during the growing season. Therefore, inhibition of CO 2 and N 2 O emission rates (32.3 and 29.3 %, respectively) by warming and drying will intensify if the combined effects of these climatic trends persist in the region.

A meta-analysis of the effects of experimental warming on soil carbon and nitrogen dynamics on the Tibetan Plateau

“…The stronger response of these variables to warming in forests than in grasslands was attributed to the following causes: the effect of warming on the net nitrification was dependent on the soil moisture in the grasslands (Bai et al, 2013), and the negative response of soil moisture to warming in grasslands was greater than that in forests (Bai et al, 2013;Lu et al, 2013a). Soil respiration was positively correlated with soil moisture and soil drying can reduce the effect of warming on soil respiration Shi et al, 2012). Thus, the experimental warming caused soil drying, which may offset the increased temperature effects in grasslands.…”

“…Both the increase in soil respiration (R s ) Lu et al, 2013b;Shi et al, 2012;Xiong et al, 2010;Xu et al, 2010b) and the decline in litter quantity (Li et al, 2011;Lin et al, 2011a;Luo et al, 2009) contribute to the decrease in the soil carbon and nitrogen pools on the Tibetan Plateau. The increase in MBC caused by warming also implies that warming may accelerate organic matter decomposition in soil , while inconsistent responses of MBC and MBN to warming have been reported on this Plateau (Chen et al, 2010;Fu et al, 2012;Wang et al, 2011).…”

“…However, the effects of warming on plant biomass were negative (Klein et al, 2007;Yang et al, 2013), positive (Li et al, 2011;Wang et al, 2012) or neutral (Fu et al, 2013) in alpine ecosystems. The variability between these two factors may result in the inconsistent response of soil carbon and nitrogen to warming on the Tibetan Plateau (Chen et al, 2010;Shi et al, 2012;Wang et al, 2011).…”

土壤含水量调控高寒草原生态系统n2o排放对增温的响应

“…Overall, these results demonstrate that soil moisture regulates the responses of N 2 O emissions to experimental warming, highlighting the necessity to consider the warming-induced drying effect when estimating the magnitude of N 2 O emissions under future climate warming. Key words climate warming; nitrous oxide; ammonia-oxidizing archaea; ammonia-oxidizing bacteria; QinghaiXizang Plateau Wang GQ, Li F, Peng YF, Chen YL, Han TF, Yang GB, Liu L, Zhou GY, Yang YH (2018 (Mosier, 2008;Shi et al, 2012;Voigt et al, 2016), 然而, 也有少数研究发 现增温会抑制土壤N 2 O的排放 或者 未造成显著影响 (Ward et al, 2013;徐冰鑫等, 2014), 计算: Chapin III et al, 2011) …”

Responses of Soil Chemical Properties and Microbiota to Elevated Temperature under Flooded Conditions

“…또한, 온도 는 미생물의 밀도뿐만 아니라 군집구성에 영향을 미치기 때 문에 (Deslippe et al, 2012;Zhang et al, 2013) (Kaur et al, 2005). 온도 증가에 대 해 토양 미생물의 밀도는 증가하거나 (Shi et al, 2012) 감소 할 수 있고 (Fu et al, 2012;Poll et al, 2013) …”