Separating soil respiration into autotrophic and heterotrophic components in Peruvian montane rain forest.

土壤呼吸(Rs)是陆地碳循环的第二大组成部分，这一时期的微小变化可以影响生态系统是碳的净源还是碳汇。因此，量化Rs的季节性变化和对气候变化的反应是陆地碳循环科学的核心挑战。然而，Rs由植物驱动(‘自养呼吸’，Rsa)和微生物驱动(‘异养呼吸’，RSH)组成，这使得估计Rs的环境敏感性变得困难。如果不单独量化RSH和RSA，就不可能正确地理解或预测Rs的变化。然而，到目前为止，如果没有明显的物理和/或化学干预，包括对土壤的不良干扰，分开测量RSA和RSH一直是困难的。我们在秘鲁测量Rs的试点数据是例外的：它们表明根呼吸在夜间下降到非常低的水平，使微生物呼吸继续下去。可以利用通量中的这种模式来分别直接测量RSA和RSH，而不会对土壤造成干扰，但前提是可以在24小时内连续测量土壤呼吸。该项目将为购买能够进行这些测量的土壤呼吸系统提供资金，还将使我们能够测量呼吸碳的组成和年龄，提供更多信息，使我们能够确认呼吸碳的来源及其在24小时和整个季节性周期中的变化。以我们目前的资源，这些科学目标都不可能实现，但现在的资金将使我们能够利用我们目前在秘鲁的(国家科学研究中心资助的)研究计划，以最低的成本实现这些目标。来自这一小笔赠款的新信息将为地球碳循环中最重要的元素之一提供重要的新见解。该项目还将开发一种具有广泛应用潜力的测量方法。这笔资金申请代表着非常物有所值，因为这项工作将有效地利用提供给我们的现有NERC资源，在我们的实地进行土壤迁移研究。

Soil respiration (Rs) is the second largest component of the terrestrial carbon cycle and small fractional changes in this term can affect whether an ecosystem is a net source or sink for carbon. Quantifying how Rs changes seasonally and in response to climatic change is therefore a central challenge for terrestrial carbon cycle science. However, Rs comprises components that are plant-driven ('autotrophic respiration', Rsa) and microbe-driven ('heterotrophic respiration', Rsh) and this makes estimating the environmental sensitivity in aggregate Rs difficult. It is not possible to properly understand or predict changes in Rs without quantifying Rsh and Rsa separately. However, to measure Rsa and Rsh separately has, until now, been difficult without signficant physical and/or chemical intervention, including undesirable disturbance to the soil. Our pilot data of measurements of Rs from Peru are exceptional: they indicate that root respiration declines to very low levels during the night, leaving microbial respiration to continue. This pattern in fluxes can be exploited to separately measure Rsa and Rsh directly and without disturbance to the soil, but only if soil respiration can be measured on a continuous basis over 24 hrs. This project will finance the purchase of a soil respiration system that is capable of performing these measurements and will also allow us to measure the composition and age of the respired carbon, providing additional information enabling us to confirm the sources of respired carbon and how they change over 24 hrs, and over a full seasonal cycle. With our current resources none of these scientific goals are possible, but funding now will allow us to achieve them at minimum cost, by making use of our current (NERC-funded) research programme in Peru. The new information from this small grant will provide significant new insight into one of the most important elements of the terrestrial carbon cycle. The project will also develop a measurement method that is potentially of wide application. The request for funds represents extremely good value for money as the work will make efficient use of existing NERC resources supplied to us to perform a soil translocation study at our field site.