目的:北极下草地对土壤变暖的响应是了解生态系统对未来气候适应的关键。功能不同的地下植物器官可以对土壤温度(Ts)的变化做出不同的反应。我们旨在通过分析与植物群落组成和土壤化学有关的细根和根茎的动力学和化学来了解地下适应机制。随着土壤变暖的持续时间和幅度。
方法:我们研究了持续时间(中期变暖(MTW;11年)和长期变暖(LTW;>60年)和幅度(0-8.4°C)的影响土壤变暖对地下植物生物量(BPB),地热温暖的亚北极草地的细根生物量(FRB)和根茎生物量(RHB)。我们评估了BPB的变化,FRB,和RHB以及环境中相应的碳(C)和氮(N)池,Ts<+2°C和Ts>+2°C情况。
结果:在MTW下,由于Ts的增加,BPB呈指数下降,而在MTW和LTW下FRB均下降。在LTW下,根茎的比例增加,根茎中的C-N比降低。在MTW下的高温地块中,BPB中的C和N池比周围环境少50%,而在LTW下,温暖地块的C和N池与非温暖地块相似。大约78%的FRB变异,土壤增温的持续时间和幅度可以解释细根和根茎中的RHB和C和N浓度以及池,土壤化学,植物群落功能组成,和地上生物量。植物地下生物量,化学和水池与草地植物群落组成的变化有关-在MTW下,蕨类植物的丰度增加,BPB向更高的Ts下降,而LTW下地下碳氮库的恢复与较高的植物多样性有关。
结论:我们的结果表明,地下植物群落对土壤变暖的适应是长期发生的。我们提供了有关亚北极草原潜在适应阶段的见解。
The response of subarctic grassland\'s below-ground to soil warming is key to understanding this ecosystem\'s adaptation to future climate. Functionally different below-ground plant organs can respond differently to changes in soil temperature (Ts). We aimed to understand the below-ground adaptation mechanisms by analysing the dynamics and chemistry of fine roots and rhizomes in relation to plant community composition and soil chemistry, along with the duration and magnitude of soil warming.
We investigated the effects of the duration [medium-term warming (MTW; 11 years) and long-term warming (LTW; > 60 years)] and magnitude (0-8.4 °C) of soil warming on below-ground plant biomass (BPB), fine root biomass (FRB) and rhizome biomass (RHB) in geothermally warmed subarctic grasslands. We evaluated the changes in BPB, FRB and RHB and the corresponding carbon (C) and nitrogen (N) pools in the context of ambient, Ts < +2 °C and Ts > +2 °C scenarios.
BPB decreased exponentially in response to an increase in Ts under MTW, whereas FRB declined under both MTW and LTW. The proportion of rhizomes increased and the C-N ratio in rhizomes decreased under LTW. The C and N pools in BPB in highly warmed plots under MTW were 50 % less than in the ambient plots, whereas under LTW, C and N pools in warmed plots were similar to those in non-warmed plots. Approximately 78 % of the variation in FRB, RHB, and C and N concentration and pools in fine roots and rhizomes was explained by the duration and magnitude of soil warming, soil chemistry, plant community functional composition, and above-ground biomass. Plant\'s below-ground biomass, chemistry and pools were related to a shift in the grassland\'s plant community composition - the abundance of ferns increased and BPB decreased towards higher Ts under MTW, while the recovery of below-ground C and N pools under LTW was related to a higher plant diversity.
Our results indicate that plant community-level adaptation of below ground to soil warming occurs over long periods. We provide insight into the potential adaptation phases of subarctic grasslands.