We report on survival and growth of ponderosa pines (Pinus ponderosa Douglas ex P. Lawson & C. Lawson) 2 decades after forest restoration treatments in the G. A. Pearson Natural Area, northern Arizona. Despite protection from harvest that conserved old trees, a dense forest susceptible to uncharacteristically severe disturbance had developed during more than a century of exclusion of the previous frequent surface-fire regime that ceased upon Euro-American settlement in approximately 1876. Trees were thinned in 1993 to emulate prefire-exclusion forest conditions, accumulated forest floor was removed, and surface fire was re-introduced at 4-years intervals (full restoration). There was also a partial restoration treatment consisting of thinning alone. Compared with untreated controls, mortality of old trees (mean age 243 years, maximum 462 years) differed by <1 tree ha⁻¹ and old-tree survival was statistically indistinguishable between treatments (90.5% control, 92.3% full, 82.6% partial). Post-treatment growth as measured by basal area increment of both old (pre-1876) and young (post-1876) pines was significantly higher in both treatments than counterpart control trees for more than 2 decades following thinning. Drought meeting the definition of megadrought affected the region almost all the time since the onset of the experiment, including 3 years that were severely dry. Growth of all trees declined in the driest 3 years, but old and young treated trees had significantly less decline. Association of tree growth with temperature (negative correlation) and precipitation (positive correlation) was much weaker in treated trees, indicating that they may experience less growth decline from warmer, drier conditions predicted in future decades. Overall, tree responses after the first 2 decades following treatment suggest that forest restoration treatments have led to substantial, sustained improvement in the growth of old and young ponderosa pines without affecting old-tree survival, thereby improving resilience to a warming climate.

中文翻译：

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亚利桑那州严重干旱中的森林恢复处理促进了黄松的生长，但并未改变其存活率

我们报告了黄松 ( Pinus ponderosaDouglas ex P. Lawson & C. Lawson）在亚利桑那州北部的 GA Pearson 自然保护区进行森林恢复处理后 2 年。尽管采伐保护保护了老树，但在一个多世纪的时间里，一片茂密的森林容易受到异常严重的干扰，之前频繁的地表火灾制度被排除在外，大约在 1876 年欧美人定居后就停止了。树木在 1993 年变薄了为了模拟火灾前的森林状况，移除了累积的森林地面，并每隔 4 年重新引入一次地表火灾（完全恢复）。也有仅由间伐组成的部分恢复处理。与未处理的对照相比，老树的死亡率（平均年龄 243 岁，最大 462 岁）相差 <1 树公顷⁻¹处理之间的老树存活率在统计学上无法区分（90.5% 控制，92.3% 完整，82.6% 部分）。在疏伐后超过 20 年的时间里，通过老松（1876 年前）和幼松（1876 年后）的断面积增量测量的处理后生长在这两种处理中都显着高于对应的对照树。自实验开始以来，满足特大干旱定义的干旱几乎一直影响该地区，包括严重干旱的 3 年。在最干旱的 3 年里，所有树木的生长都下降了，但经过处理的老树和幼树的下降幅度要小得多。在经过处理的树木中，树木生长与温度（负相关）和降水（正相关）的关联要弱得多，这表明它们可能因温暖而经历较少的生长下降，预计未来几十年会出现更干燥的情况。总体而言，树木在处理后的第一个 20 年后的反应表明，森林恢复处理已导致老龄黄松和幼龄黄松的生长得到实质性、持续的改善，而不影响老树的存活，从而提高了对气候变暖的适应能力。