A detailed assessment of ecosystem carbon dynamics along an elevation transect in the Andes

热带山地森林是陆地生态系统中最迷人但研究最少的。从生态系统科学的角度来看，这些联合收割机结合了温带森林（年平均温度低）和低地热带森林（缺乏温度季节性）的一些属性，从而为我们理解气候对生态系统碳和养分循环的控制提供了一个重要的测试。除了在土壤中储存大量的碳外，它们还拥有全球生物多样性的很大一部分：例如，地球上15%的植物物种都生长在安第斯山脉的斜坡上，其中一半在地球上其他任何地方都找不到。因此，热带山地森林生态系统的变化可能对全球生物多样性产生深远影响。在潮湿的热带地区，随着海拔梯度的上升，生态系统特性的两个趋势十分明显：地上生产力（木材和树叶的生产）明显下降，土壤和死生物量有机储存量增加，而活生物量减少。然而，尽管这些趋势都有详细的记录，但对于这些趋势的原因仍有相当多的争论。我们将集中在三个方面的辩论：-地下根生产力下降与地上生产力平行，还是它实际上增加（如最近的研究所示），导致总生产力与海拔上升的趋势很小？- 与热带山地或温带森林相比，低地热带森林通过呼吸失去的碳是否更多，这种比例损失的程度是否与环境温度有关？- 随著海拔上升，腐烂率下降，是完全由温度所解释，还是枯落物的质量和重要因素？在本提案中，我们将探讨这两种趋势的原因，通过进行详细的测量植物，凋落物和土壤碳动态在四个地点沿着在安第斯山脉的海拔样带。这将以我们目前在秘鲁亚马逊低地进行的类似测量为基础并加以补充。我们将：（i）对地上和地下生产力进行详细观察，测量木材、树叶和树根的产量。(ii)量化树叶、木材和根系以及凋落物和土壤中腐烂的有机物的呼吸CO2排放量。(iii)量化凋落物和土壤库中C、N和P的储量和流量。(iv)量化的温度，凋落物质量和降雨量对有机质的腐烂率进行易位实验，其中样品的凋落物，枯木和土壤与交换之间的不同海拔沿着样带，并随着时间的推移监测材料的腐烂率。

Tropical montane forests are amongst the most fascinating yet least studied of terrestrial ecosystems. In terms of ecosystem science, they combine some of the attributes of temperate forests (low mean annual temperature) with those of lowland tropical forests (lack of temperature seasonality), and thereby provide an important test of our understanding of climatic controls on ecosystem carbon and nutrient cycling. In addition to holding large stocks of carbon in their soils, they host a large fraction of global biodiversity: for example, 15% of all plant species on the planet are found on the slopes of the Andes, and half of them are found nowhere else on earth. Hence changes in tropical montane forest ecosystems could have a profound effect on global biodiversity. As one climbs an elevation gradient in the wet tropics, two trends in ecosystem properties stand out: an apparent decline in above-ground productivity (the production of wood and leaves), and an increase in soil and dead biomass organic stocks at the expense of live biomass. However, although these trends are well-documented, there is still considerable debate as to the causes of these trends. We will focus on three aspects of the debate: - does below-ground root productivity decline in parallel with above-ground productivity, or does it actually increase (as indicated by a recent study), resulting in little trend in total productivity with elevation ? - do lowland tropical forests lose more carbon through respiration than tropical montane or temperate forests, and is the magnitude of this proportional loss related to ambient temperature ? - is the decline in decay rates with increasing elevation entirely explained by temperature, or is litter quality and important factor ? In this proposal we will explore the causes of both these trends, by conducting detailed measurements of plant, litter and soil carbon dynamics at four sites along an altitudinal transect in the Andes. This will build upon and complement similar measurements that we are currently conducting in the lowland Peruvian Amazon. We established the field study site in 2003 We will: (i) Conduct detailed observation of above- and below-ground productivity, measuring the production of wood, leaves and roots. (ii) Quantify respiratory CO2 emissions from leaves, wood and roots, and from decaying organic matter in litter and soils. (iii) Quantify the stocks and flows of C, N and, P in litter and soil pools. (iv) Quantify the effects of temperature, litter quality and rainfall on organic matter decay rates by conduction a translocation experiment, where samples of litter, dead wood and soil with be swapped between different elevations along the transect, and the decay rates of material monitored over time.