Dissolved organic nitrogen and carbon in pastoral soils: the New Zealand experience
Dissolved organic nitrogen and carbon in pastoral soils: the New Zealand experience
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DOI：
10.1111/j.1365-2389.2006.00873.x
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发表时间：
2007-06
影响因子：
4.2
通讯作者：
A. Ghani;M. Dexter;R. Carran;P. Theobald
中科院分区：
文献类型：
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作者：
A. Ghani;M. Dexter;R. Carran;P. Theobald
土壤中的溶解有机氮（DON）和溶解有机碳（DOC）是土壤-植物生态系统中养分循环和生物过程的重要组成部分。本研究的目的是：（一）量化池的DON和DOC在一系列的新西兰田园土壤;（二）比较土地利用变化对这些池的影响;（三）研究与这两个组成部分的溶解有机物的季节性变化。土壤样品（0-7.5厘米深），从93个牧场位于北国，怀卡托，丰盛湾和奥塔哥/南岛，新西兰，在秋季收集。同时对邻近的长期耕地或天然植被和林地利用下的土壤进行采样，以评估不同土地利用方式对这些土壤中DON和DOC的影响。在冬季，春季，夏季和秋季对12个奶牛和12个绵羊和/或牛肉牧场进行为期2年的采样，以研究DON和DOC的季节性波动。还进行了一个领域的孵化研究在放牧的牧场，以检查波动的浓度和土壤中的DON水平。还测量了其他土壤生物学性质，如微生物生物量-C，生物量-N和可矿化N。田园土壤含有最多的DON（13-93 mg N kg−1土壤，相当于8-55 kg N ha−1）和DOC（73-718 mg C kg−1土壤，相当于44-431 kg C ha−1），其次是作物和天然植被和林业土壤。土壤中DON浓度的季节变化比DOC更明显。冬季DON浓度与年平均浓度相比波动约为80%，而DOC在奶牛和绵羊和牛肉监测点的波动范围为23%和28%。在田间培养研究中也观察到DON浓度的类似波动。这些结果表明，DON是一个动态库的N在土壤中。牧区土壤DON与DOC呈极显著正相关（r = 0.71，P < 0.01）。DON与土壤全C（r = 0.59，P < 0.01）、全N（r = 0.62，P < 0.01）和可矿化N（r = 0.47，P < 0.01）均呈极显著正相关。土壤全C、全N与DOC、DON的相关性较差，表明其他生态地球化学过程可能影响这些土壤中DOC、DON的浓度。鉴于牧区土壤中DON和DOC库的大小，我们建议在评估牧区土地利用对地表和地下水土壤C和N富集的影响时，应考虑这些C和N库。
Dissolved organic nitrogen (DON) and dissolved organic carbon (DOC) in soils are increasingly recognized as important components of nutrient cycling and biological processes in soil‐plant ecosystems. The aims of this study were to: (i) quantify the pools of DON and DOC in a range of New Zealand pastoral soils; (ii) compare the effects of land use changes on these pools; and (iii) examine the seasonal variability associated with these two components of dissolved organic matter. Soil samples (0–7.5 cm depth) from 93 pastoral sites located in Northland, Waikato, Bay of Plenty and Otago/Southland, New Zealand, were collected in autumn. Adjacent sites under long‐term arable cropping or native vegetation and forestry land use were also sampled at the same time to estimate the impacts of different land use on DON and DOC in these soils. Twelve dairy and 12 sheep and or beef pastures were sampled in winter, spring, summer and autumn for a 2‐year period to study the seasonal fluctuations of DON and DOC. A field incubation study was also carried out in a grazed pasture to examine fluctuations in the concentrations of and and DON levels in soil. Other soil biological properties, such as microbial biomass‐C, biomass‐N and mineralizable N, were also measured. Pastoral soils contained the greatest amounts of DON (13–93 mg N kg−1 soil, equivalent to 8–55 kg N ha−1) and DOC (73–718 mg C kg−1 soil, equivalent to 44–431 kg C ha−1), followed by cropping and native vegetation and forestry soils. The DON concentration in soils was found to be more seasonally variable than DOC. There was approximately 80% fluctuation in the concentration of DON in winter from the annual mean concentration of DON, while DOC fluctuated between 23 and 28% at the dairy and the sheep and beef monitoring sites. Similar fluctuations in the concentrations of DON were also observed in the field incubation studies. These results indicate that DON is a dynamic pool of N in soils. There was a strong and significant positive correlation between DON and DOC in pastoral soils (r = 0.71, P < 0.01). There were also significant positive correlations between DON and total soil C (r = 0.59, P < 0.01), total soil N (r = 0.62, P < 0.01) and mineralizable N (r = 0.47, P < 0.01). The rather poor correlations between total soil C and N with DOC and DON, suggest other biogeochemical processes may be influencing concentrations of DOC and DON in these soils. Given the size of DON and DOC pools in the pastoral soils, we suggest that these pools of C and N should be taken into account when assessing the impact of pastoral land use on soil C and N enrichment of surface and groundwater.