Department of Forestry and Environmental Resources, North Carolina State University, Raleigh, NC 27695-8008, USA.
Tree Physiol. 2012 Oct;32(10):1237-58. doi: 10.1093/treephys/tps082. Epub 2012 Sep 17.
Intra-annual nutrient (nitrogen, phosphorus, potassium, calcium and magnesium) flux was quantified for Pinus taeda L. at a nutrient-poor, well-drained sandy site in Scotland County, NC, USA where a 2 × 2 factorial of irrigation and nutrition was applied in four replications in a 10-year-old stand with 1200 stems ha(-1). Treatments were applied with the goal of providing optimum nutrition (no nutritional deficiencies) and water availability. Component (foliage, branch, stem and root) nutrient content was estimated monthly for 2 years using nutrient concentration and phenology assessments combined with destructive harvests. Positive flux values indicated nutrient accumulation in the trees while negative values indicated nutrient loss from the trees. Fertilization significantly increased nitrogen, phosphorus, potassium, calcium and magnesium flux 140%, on average, over non-fertilized. Irrigation significantly increased calcium flux 28% while there was no significant irrigation effect on nitrogen, phosphorus, potassium or magnesium. Maximum nutrient fluxes (kg ha(-1) day(-1)) for non-fertilized and fertilized stands were 0.36 and 1.05 for nitrogen, 0.042 and 0.095 for phosphorus, 0.13 and 0.51 for potassium, 0.27 and 0.42 for calcium, and 0.04 and 0.12 for magnesium, respectively. Maximum flux was coincident with ephemeral tissue (foliage and fine root) development and likely would be higher in stands with more foliage than those observed in this study (projected leaf area indices were 1.5 and 3.0 for the non-fertilized and fertilized stands). Minimum nutrient fluxes (kg ha(-1) day(-1)) for non-fertilized and fertilized stands were -0.18 and -0.42 for nitrogen, -0.029 and -0.070 for phosphorus, -0.05 and -0.18 for potassium, -0.04 and -0.05 for calcium, and -0.02 and -0.03 for magnesium, respectively. Minimum fluxes were typically observed in the dormant season and were linked to foliage senescence and branch death. Foliage and branch component nutrient contents were out of phase for nitrogen, phosphorus, potassium and magnesium, indicating nutrient retranslocation and storage in branches prior to foliage development and after foliage senescence. In contrast to current operational fertilizer programs which often target winter application these data suggest the best application times would be during foliage development.
在美国北卡罗来纳州苏格兰县的一个养分贫瘠、排水良好的沙质地点，对火炬松进行了一项研究，该研究采用了灌溉和养分的 2×2 析因设计，在 10 年生、每公顷有 1200 株树木的林分中进行了四次重复。处理的目的是提供最佳的营养（没有营养缺乏）和水分供应。利用养分浓度和物候评估以及破坏性收获，在两年内每月估算一次树木各组成部分（叶片、树枝、树干和根）的养分含量。正值的通量值表示养分在树木中积累，负值表示养分从树木中损失。施肥使氮、磷、钾、钙和镁的通量平均增加了 140%，而不施肥则没有显著影响。灌溉使钙的通量增加了 28%，而对氮、磷、钾或镁没有显著影响。非施肥和施肥林分的最大养分通量（kg ha-1 day-1）分别为氮 0.36 和 1.05，磷 0.042 和 0.095，钾 0.13 和 0.51，钙 0.27 和 0.42，镁 0.04 和 0.12。最大通量与短暂组织（叶片和细根）的发育同时发生，并且在具有比本研究中观察到的更多叶片的林分中可能更高（预计的叶面积指数分别为 1.5 和 3.0）。非施肥和施肥林分的最小养分通量（kg ha-1 day-1）分别为氮-0.18 和-0.42，磷-0.029 和-0.070，钾-0.05 和-0.18，钙-0.04 和-0.05，镁-0.02 和-0.03。最小通量通常在休眠期观察到，与叶片衰老和树枝死亡有关。氮、磷、钾和镁的叶片和树枝养分含量不同步，表明养分在树枝中再转移和储存，然后在叶片发育之前和叶片衰老之后。与当前的常规施肥方案通常针对冬季应用不同，这些数据表明最佳的施肥时间应该在叶片发育期间。
