Nitrification Resilience and Response of Ammonia-Oxidizing Bacteria upon Heat-Drought Extremes across Three Soil Ecosystems in Lower Himalaya

摘要

Soil ecosystems despite of providing a vast range of value services are expected to face climatic extremes. Assessing the resilience degree of such ecosystems is integral in evaluating their functional stability. This study investigated the resilience and resistance of potential nitrification activity (PNA) and involved guilds (ammonia-oxidizing bacteria - AOB) upon two heat-drought extremes (low (40°C for 24 h) and high (40°C for 48 h)) at 1, 7, 14, 28 days’ intervals across three different soil ecosystems (arable, grassland, forest) in lower Himalaya. Results demonstrated that three soils responded differentially to heat-droughts (~20–55% decrease PNA) with arable soil showing high resistance (withheld ~55.3% PNA) and low resilience (~82–85%). The gene abundances of AOB revealed that the community size was significantly reduced upon the heat-droughts (up to 50.1%) and could not ultimately recover showing an incomplete resilience. In contrast to arable, the grassland and forest soils were better in resilience with PNA at day 28 observed near to control (93.4 and 91.4%). The correlation analyses showed a strong positive relationship of AOB to PNA particularly in arable soil. The high resilience exhibited by grassland and forest soils implied that despite of reduction in AOB numbers, functional redundancy might have inferred an increased resilience showing that these soils can recover once the stress period is over. This work underlines the functional stability of different soils for nitrification potential highlighting the relevance of resilience and resistance perspectives in wake of predicted climatic extremes on soil N cycling and associated N losses in lower Himalaya.