Abstract
BackgroundMany regions in the world are experiencing changes in precipitation pattern, which likely impact soil nitrogen cycling and availability. However, we know little about how soil nitrogen processes respond to drought stress under climate change.MethodsA continuous 5-year experiment of throughfall reduction treatment (TRT) was conducted in a Castanopsis hystrix plantation in subtropical China to assess how soil nitrogen processes responded to a change in precipitation. Net nitrogen transformation, soil properties, microbial biomass carbon (MBC) and nitrogen (MBN), and microbial community phospholipid fatty acids (PLFAs as bacteria, fungi and arbuscular mycorrhizal fungi (AMF)) were investigated in the wet and dry seasons over the period of the manipulation experiment.ResultsTRT had no significant effects on net ammonification rate (NAR) and nitrogen mineralization rate (NMR), and the unchanged NAR and NMR were mainly caused by the no change of soil nitrogen availability (i.e. NH4+-N, NO3−-N and dissolved organic nitrogen). However, TRT significantly increased net nitrification rate (NNR) in the wet season primarily due to the increase in NO3− concentration, and might be further caused by reduced NO3− leaching, denitrification or NO3−-N uptake in the TRT. Differently, TRT significantly decreased the NNR in the dry season, which might be linked to the limited SWC that resulted in greater microbial nitrate immobilization than gross nitrate mineralization. In addition, TRT significantly influenced the soil microbial community composition in 0–10 cm soil layer in the wet season, primarily due to the variations in NO3−-N, DOC and DON.ConclusionsPrecipitation reduction affected the NNR rather than NAR and NMR, and consequently, further affected soil N availability and N uptake by Castanopsis hystrix.
Highlights
Many regions in the world are experiencing changes in precipitation pattern, which likely impact soil nitrogen cycling and availability
A number of field studies suggested that precipitation change may impact soil water content, the physiological performance of microbes and the diffusion of nutrients, which in turn alter soil N cycling and availability (Chen et al 2017), whereas other studies indicate that net N mineralization is not sensitive to precipitation under field conditions due to different reasons, such as the drought-resistant ability of microorganism (Yuste et al 2014; Felsmann et al 2015), no change in aboveground net primary productivity (Jongen et al 2013) or reduction of the temperature sensitivity (Q10) of N mineralization (Auyeung et al 2013)
Seasonal drought is expected to increase under the scenarios of climate change in many regions of the world (Auyeung et al 2013; Wang et al 2016; Kamruzzaman et al 2017), and soil water content, C and N availability, and microbial activity controlled by precipitation seem to be the main factors determining soil N cycling and N availability (Homyak et al 2017)
Summary
Many regions in the world are experiencing changes in precipitation pattern, which likely impact soil nitrogen cycling and availability. Seasonal drought is expected to increase under the scenarios of climate change in many regions of the world (Auyeung et al 2013; Wang et al 2016; Kamruzzaman et al 2017), and soil water content, C and N availability, and microbial activity controlled by precipitation seem to be the main factors determining soil N cycling and N availability (Homyak et al 2017). The objectives of this study were to determine: (1) if the net N mineralization rates in different soil depths and seasons could be reduced by throughfall reduction; (2) how the decreasing precipitation could affect soil N cycling process. We hypothesized that (1) soil N transformation rates would be lower in TRT than in the control, and (2) soil water content and microbial activity would be the main drivers for the changes of N transformation processes
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