多梯度增温对青藏高原高寒草甸温室气体通量的影响

Response of Greenhouse Gases Flux to Multi-level Warming in an Alpine Meadow of Tibetan Plateau

高寒草甸是青藏高原重要的草地类型之一。目前增温对高寒草甸温室气体通量影响的研究较少,尤其在不同尺度的增温条件下,温室气体通量的响应尚不明确。因此,设置多梯度增温实验,模拟未来不同幅度增幅情况,对预测高寒草甸温室气体通量的变化具有重要意义。为深入地认识气候变暖对高寒草甸温室气体通量的影响,假设高寒草甸温室气体通量的周转速率在增温条件下随增温梯度而加快。在青藏高原纳木错地区高寒草甸,采用开顶箱法(Open-top chambers,OTCs)设置对照(T0,不增温)以及4个不同程度的增温处理(T1、T2、T3、T4,分别增温1、2、3、4℃),结合静态箱-气相色谱法对增温处理后的CO_2、CH_4和N_2O通量进行同步观测。对3个生长季(2013—2015年)进行连续观测发现:(1)地下5 cm土壤3年的平均温度相对于对照处理分别增加1.73℃(T1)、1.83℃(T2)、3.03℃(T3)和3.53℃(T4);(2)高寒草甸生长季平均呼吸(CO_2)为(42.6±9.11)mg·m^(-2)·h^(-1),同时具有较强的CH_4吸收能力,达到(-47.96±8.76)μg·m^(-2)·h^(-1),其N_2O通量维持在较低水平,为(0.3±0.46)μg·m^(-2)·h^(-1);(3)在高寒草甸生长季,温室气体通量与温度以及水分均具有显著的相关关系,但增温未能显著改变生长季温室气体平均通量。以上结果表明,增温所引起的其他环境因素的改变(如伴随不同梯度增温下土壤水分变化的不确定性),导致高寒草甸在短期内进行内部调节,并维持温室气体通量稳定。

The alpine meadow,a main type of grassland on Tibetan Plateau,playing a key role in regulating greenhouse gases(GHGs)flux.To date,it remains unclear how GHGs flux of the alpine meadow responses to warming,especially to multi-level warming.Simulated multi-level warming experiment,therefore,improves the prediction of GHGs flux dynamics.For further understanding the effects of climate warming on GHGs flux in the alpine meadow,we hypothesized that the major GHGs flux,including ecosystem soil CO2respiration,CH4consumption and N2O emissions all might be enhanced under warming,we then conducted a simulated gradient warming experiment(T0,no warming;T1~T4represent the temperature increased by1,2,3and4^,respectively)and GHGs flux measurements in an alpine meadow in Namtso of Tibetan Plateau,using open-top chambers(OTCs)and static chamber method,respectively,for the following there growing seasons from year2013to2015.The observations showed that:(1)When compared to the control plots,the three year averaged below ground5cm soil temperature increased1.73〇C(T1),1.83〇C(T2),3.03〇C(T3)and3.53〇C(T4),respectively for the four warming treatments;(2)The averaged flux of CO2,CH4and N2O for growing season in alpine meadow were(42.6±9.11)mg-m^h-1,(-7.96±8.76)(ig-m.2-h-1and(0.3±0.46)igm"2-h'1,respectively;And(3)the GHGs flux were regulated by both soil temperature and moisture,leading to a non-significant response to warming because of the relative variability in soil moisture.Our results suggested that alpine meadow can keep its GHGs flux stable to warming in short term by internal modification(e.g.uncertainty in soil moisture variability accompanied with various warming conditions).