Functional specialization of Eucalyptus fine roots: contrasting potential uptake rates for nitrogen, potassium and calcium tracers at varying soil depths
Functional specialization of Eucalyptus fine roots: contrasting potential uptake rates for nitrogen, potassium and calcium tracers at varying soil depths
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DOI：
10.1111/j.1365-2435.2011.01867.x
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发表时间：
2011-10-01
影响因子：
5.2
通讯作者：
Laclau, Jean-Paul
中科院分区：
文献类型：
--
作者：
da Silva, Eduardo Vinicius;Bouillet, Jean-Pierre;Laclau, Jean-Paul
1.人们对深根在林木营养中的作用及其提供安全网服务的能力知之甚少，这些服务吸收了从表土中沥滤出来的养分。为了解决这个问题，我们研究了潜在的吸收N，K和Ca的巨桉树（6年的年龄- 25米的平均高度），在巴西，作为土壤深度，质地和含水量的函数。我们在桑迪和粘质铁红壤中同时注入NO3-- N-15、Rb+（K+的类似物）和Sr ~（2+）（Ca ~（2+）的类似物）示踪剂溶液，深度分别为10、50、150和300 cm。一个完整的随机设计，设置了三个重复的配对树木每注射深度和土壤类型。在夏季示踪剂注射后，在不同时间对最近展开的叶片进行取样，并在冬季重复实验。连续监测两种土壤不同深度的土壤含水量.叶片Rb和Sr浓度和N-15原子%的测定使得有可能估计来自四个土壤深度的示踪剂注射的相对吸收潜力（RUP）和相应土层中每单位细根长密度的特定RUP（SRUP）。最高的示踪剂吸收率被发现在表土，但对比RUP分布观察到的三种示踪剂。虽然在土壤上部50 cm处NO3-- N-15的RUP高于Rb+和Sr 2+，但在桑迪土壤中，Sr 2+和Rb+的最高SRUP值出现在300 cm处，而在粘性土壤中，当重力溶液达到该深度时也是如此。结果表明，E. grandis树表现出不同的潜在吸收率与深度取决于营养。根的这种功能特化可能有助于E.巨树，有效地提供了大量的营养需要在整个发展这些快速增长的种植园。
1. Little is known about the role of deep roots in the nutrition of forest trees and their ability to provide a safety-net service taking up nutrients leached from the topsoil.2. To address this issue, we studied the potential uptake of N, K and Ca by Eucalyptus grandis trees (6 years of age - 25 m mean height), in Brazil, as a function of soil depth, texture and water content. We injected NO3-- N-15, Rb+ (analogue of K+) and Sr2+ (analogue of Ca2+) tracers simultaneously in a solution through plastic tubes at 10, 50, 150 and 300 cm in depth in a sandy and a clayey Ferralsol soil. A complete randomized design was set up with three replicates of paired trees per injection depth and soil type. Recently expanded leaves were sampled at various times after tracer injection in the summer, and the experiment was repeated in the winter. Soil water contents were continuously monitored at the different depths in the two soils.3. Determination of foliar Rb and Sr concentrations and N-15 atom % made it possible to estimate the relative uptake potential (RUP) of tracer injections from the four soil depths and the specific RUP (SRUP), defined as RUP, per unit of fine root length density in the corresponding soil layer.4. The highest tracer uptake rates were found in the topsoil, but contrasting RUP distributions were observed for the three tracers. Whilst the RUP was higher for NO3-- N-15 than for Rb+ and Sr2+ in the upper 50 cm of soil, the highest SRUP values for Sr2+ and Rb+ were found at a depth of 300 cm in the sandy soil, as well as in the clayey soil when gravitational solutions reached that depth.5. Our results suggest that the fine roots of E. grandis trees exhibit contrasting potential uptake rates with depth depending on the nutrient. This functional specialization of roots might contribute to the high growth rates of E. grandis trees, efficiently providing the large amounts of nutrients required throughout the development of these fast-growing plantations.