Abstract Pinus taeda plantations in subtropical areas of South America are extremely productive and commonly established on well-drained red clay sites. In the past, land with more poorly-drained soil was avoided due to concern over the factors limiting site productivity. Establishment of intensively managed plantations on poorly-drained soils usually includes soil preparation by subsoiling and/or bedding, weed control, and fertilization. However, forest managers lack information about the efficacy of early silvicultural practices to ameliorate environmental limitations and if these intensive practices generate long-term improvements in productivity in this area. Consequently, we established studies in northeastern Argentina on two sites differing by drainage class and soil texture as a full factorial design with site preparation (S; disking and disking + subsoiling (red clay) or bedding (wet loam)), fertilization (F; none or 78 kg ha−1 elemental phosphorus at planting), and weed control (W; none or two-year banded). Seven years after planting, the red clay and wet loam sites were equally productive, with maximum treatment means of 218 m3 ha−1 and 264 m3 ha−1 respectively. At the red clay site, only weed control significantly increased volume. At the wet loam site, both weed control and site preparation significantly increased volume, mainly due to increased survival. The combination of weed control and bedding yielded a non-additive volume response as indicated by a significant W*S interaction. Our results do not support the common practice of subsoiling on red clay soils. In addition, fertilization with P alone appears counterproductive or unneeded at both sites.

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阿根廷亚热带火炬松对早期造林处理的中轮回响应

摘要 南美洲亚热带地区的火炬松人工林生产力极高，通常建在排水良好的红粘土上。过去，由于担心限制场地生产力的因素，避免使用土壤排水不良的土地。在排水不良的土壤上建立集约化管理的人工林通常包括通过深松和/或垫层整地、杂草控制和施肥。然而，森林管理者缺乏关于早期造林实践在改善环境限制方面的功效以及这些集约化实践是否会长期提高该地区生产力的信息。因此，我们在阿根廷东北部的两个不同排水等级和土壤质地的场地上开展了研究，作为带整地的全因子设计 (S; 剥落和剥落 + 深松（红粘土）或垫层（湿壤土））、施肥（F；种植时无或 78 kg ha-1 元素磷）和杂草控制（W；无或两年带状）。种植 7 年后，红粘土和湿壤土的产量相同，最大处理量分别为 218 m3 ha-1 和 264 m3 ha-1。在红土场地，只有杂草控制显着增加了体积。在湿壤土场地，杂草控制和整地都显着增加了体积，这主要是由于存活率增加。杂草控制和垫料的组合产生了非加性体积响应，如显着的 W*S 相互作用所示。我们的结果不支持在红粘土上进行深松的常见做法。此外，在两个地点单独施肥似乎适得其反或不需要。