Substrate, climate, and land use controls over soil N dynamics and N-oxide emissions in Borneo
Substrate, climate, and land use controls over soil N dynamics and N-oxide emissions in Borneo
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DOI：
10.1023/b:biog.0000049335.68897.87
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发表时间：
2004-08
期刊：
影响因子：
4
通讯作者：
S. Hall;G. Asner;K. Kitayama
中科院分区：
文献类型：
--
作者：
S. Hall;G. Asner;K. Kitayama
随着工农业的快速发展，热带生态系统的氮富集程度可能会增加，但这些系统中氮增加的生态后果尚不清楚。我们测量了土壤氮氧化物排放和氮转化的主要雨林生态系统在四个海拔高度和两个基板类型的山。婆罗洲，京那巴鲁，在短期实验N添加前后。我们还测量了N池和通量的土地利用梯度的原始森林，烧毁次生林，施肥农业。在原始森林背景土壤N2 O和NO排放量随海拔的下降，和沉积基质的土壤有较大的无机氮，硝化速率，和N-氧化物通量比超基性土时，有显着差异的基质类型。氮氧化物排放后，氮添加和背景硝化率低，在所有的土壤来自超碱性基质相比，沉积基质，即使在低地网站支持，不同的龙脑香林生长在形态相似的Oxisols。潜在的硝化率是很好的预测氮氧化物排放后，N添加。N2 O和NO通量在低海拔和沉积物来源的土壤上最大，与超碱性来源的土壤相比，即使在最小的N添加量（15 kg N ha−1）下也是如此。由于目前的土壤分类方法没有明确地描述对养分循环很重要的土壤化学性质，因此使用土壤图来推断区域或地球仪的土壤地球化学过程的准确性和实用性可能受到限制。在农业系统中，管理措施在控制氮氧化物排放和土壤氮循环方面比基质类型更重要。农田的氮氧化物通量比相同基质类型和相同海拔的原始森林大一个数量级以上。由于原始森林被清除用于集约农业，土壤N2 O和NO排放量可能远远超过氮饱和度最高的热带森林生态系统。这项研究强调了气候，基质年龄，氮沉降和土地利用的做法，确定在潮湿的热带地区的氮循环和氮氧化物排放的相互依赖性。
Nitrogen (N) enrichment of tropical ecosystems is likely to increase with rapid industrial and agricultural development, but the ecological consequences of N additions in these systems are not well understood. We measured soil N- oxide emissions and N transformations in primary rain forest ecosystems at four elevations and across two substrate types on Mt. Kinabalu, Borneo, before and after short-term experimental N additions. We also measured N pools and fluxes across a land use gradient of primary forest, burned secondary forest, and fertilized agriculture. Background soil N2O and NO emissions in primary forest decreased with elevation, and soils derived from sedimentary substrates had larger pools of inorganic N, rates of nitrification, and N-oxide fluxes than ultrabasic soils when there were significant differences between substrate types. N-oxide emissions after N additions and background rates of nitrification were low in all soils derived from ultrabasic substrates compared to sedimentary substrates, even at lowland sites supporting, diverse Dipterocarp forests growing on morphologically similar Oxisols. Rates of potential nitrification were good predictors of N-oxide emissions after N additions. N2O and NO fluxes were largest at low elevations and on sedimentary-derived soils compared to ultrabasic-derived soils, even at the smallest addition of N, 15 kg N ha−1. Because current methods of soil classification do not explicitly characterize a number of soil chemical properties important to nutrient cycling, the use of soil maps to extrapolate biogeochemical processes to the region or globe may be limited in its accuracy and usefulness. In agricultural systems, management practices were more important than substrate type in controlling N-oxide emissions and soil N cycling. N-oxide fluxes from agricultural fields were more than an order of magnitude greater than from primary forests on the same substrate type and at the same elevation. As primary forests are cleared for intensive agriculture, soil N2O and NO emissions are likely to far exceed those from the most N-saturated tropical forest ecosystems. This study highlights the inter-dependence of climate, substrate age, N deposition, and land-use practices determining N cycling and N-oxide emissions in humid tropical regions.