The effects of midrotation competition control and fertilization were studied in two loblolly pine stands in the Coastal Plain of Georgia. The use of fertilizer or herbicide alone did not enhance wood yields above the control, which negates the cost spent to conduct these practices. The combined treatment of fertilization and herbicide promoted higher average pine annual increment and greater proportion of sawtimber. Site limiting factors, most likely both competing woody vegetation and low nutrient status, largely determined the effectiveness and priority of midrotation treatments. The economic returns of the combined treatment varied considerably depending on stumpage prices, treatment costs, and magnitude and duration of the growth response. Sawtimber prices (absolute value and relative to pulpwood and chip-n-saw) play a critical role in the marginal returns of midrotation treatments. Continued depressed sawtimber prices will discourage private landowners from investing in midrotation vegetation control and fertilization. Study Implications: Midrotation fertilization and vegetation control can be attractive silvicultural treatments to increase timber volume and economic returns. Assessment of site variables that limit growth, especially soil fertility and plant competition, must be conducted before prioritization of treatments. The economic returns of midrotation treatments vary greatly depending on treatment costs, stumpage prices, and magnitude and duration of pine growth response compared with controls. The pine growth response of particular concern is ingrowth of trees into the sawtimber size class and growth of sawtimber-sized trees. Sawtimber prices play a critical role in the marginal internal rate of return of the additional investment. Lackluster timber prices (especially sawtimber prices) may render investment in midrotation fertilization and vegetation control unattractive and have detrimental effects on timber supply and forest health of the region in the long term.

中文翻译：

---

进行中期竞争控制和/或施肥是否值得？佐治亚州沿海平原两项细化火炬松研究的结果

在乔治亚州沿海平原的两个火炬松林中研究了中转竞争控制和施肥的效果。单独使用化肥或除草剂并没有将木材产量提高到高于控制水平，这抵消了进行这些做法所花费的成本。施肥和除草剂的联合处理促进了更高的松树年平均增量和更大的锯材比例。场地限制因素，很可能是竞争性木本植被和低营养状态，在很大程度上决定了轮作中处理的有效性和优先级。联合处理的经济回报因立木价格、处理成本以及生长反应的幅度和持续时间而有很大差异。锯材价格（绝对价值，相对于纸浆木材和木片锯）在中转处理的边际回报中起着关键作用。锯材价格持续低迷将阻止私人土地所有者投资于轮作中植被控制和施肥。研究意义： 中轮施肥和植被控制可以成为增加木材体积和经济回报的有吸引力的造林处理。在确定处理的优先级之前，必须对限制生长的场地变量进行评估，特别是土壤肥力和植物竞争。与对照相比，中转处理的经济回报差异很大，具体取决于处理成本、立木价格以及松树生长响应的幅度和持续时间。特别关注的松树生长反应是树木向锯材大小等级的向内生长和锯材大小的树木生长。锯材价格在额外投资的边际内部收益率中起着至关重要的作用。木材价格低迷（尤其是锯材价格）可能会导致对轮作中施肥和植被控制的投资缺乏吸引力，并长期对该地区的木材供应和森林健康产生不利影响。