Jiménez M N, Navarro F B
AGROECOSOST Research Group, Instituto de Investigación y Formación Agraria (IFAPA), Junta de Andalucía, Camino de Purchil s/n. 18004 Granada, Spain.
AGROECOSOST Research Group, Instituto de Investigación y Formación Agraria (IFAPA), Junta de Andalucía, Camino de Purchil s/n. 18004 Granada, Spain.
J Environ Manage. 2016 Mar 15;169:174-83. doi: 10.1016/j.jenvman.2015.12.028. Epub 2015 Dec 31.
Monthly litterfall was monitored over a 3-year period in afforested Aleppo pines in the Mediterranean semiarid SE Spain with the aim of determining the long-term response of pines to reductions in tree competition and how this forest practice might influence stand resilience. Three thinning intensities applied 5 years earlier were evaluated (T75 = 75% of the basal area removed, T60 = 60% and T48 = 48%), both at the stand and at the tree level. On average, the total annual litterfall varied between 1.30 Mg ha(-1) yr(-1) (±0.24 SE) in T75 and 3.28 Mg ha(-1) yr(-1) (±0.78 SE) in the unthinned control. At the stand level, monthly differences among the treatments were found over time in the needles (F = 11.09, df = 3, P = 0.0009) and woody fraction (F = 4.36, df = 3, P = 0.0269) following the thinning gradient: T0 (control)>T48 > T60 > T75, and for the total amount of needles (χ(2) = 9.33, P = 0.025) and twigs (χ(2) = 9.11, P = 0.027) recorded at the end of the study period. High amounts of twig and needle fall were recorded during summer and beginning of autumn, whereas the main miscellanea inputs were registered during the spring, coinciding with the fall of nests and frass from caterpillar outbreaks. At the tree level, the total litterfall fluctuated between 1.5 kg tree yr(-1) in T0 (2nd yr) and 7.0 kg tree yr(-1) in T75 (3rd yr), although mean annual statistical differences among the treatments were found only for the first year of monitoring. However, needle fall was higher for larger pines (T75) than for the smaller ones in control (T0) when the data were analysed over the 3-year-period (F = 3.64, df = 3, P = 0.0247), and the same happened for the woody fraction (F = 3.63, df = 3, P = 0.0250). By contrast, pine trees in the unthinned control registered needle-fall rates (measured as kg m(-2) tree(-1)) that were similar to or higher than those of pine trees in thinned stands, suggesting that defoliation processes took place at high tree densities, especially after a severely dry period. We propose thinning as a measure to adapt high-density plantations to alterations due to climate change, in order to prevent forest decline and mortality.
在西班牙东南部地中海半干旱地区的人工种植阿勒颇松林中，对凋落物进行了为期3年的月度监测，目的是确定松树对树木竞争减少的长期反应，以及这种森林经营方式如何影响林分恢复力。评估了5年前实施的三种间伐强度（T75 = 去除75%的断面积，T60 = 60%，T48 = 48%），包括林分和树木层面。平均而言，T75的年总凋落量在1.30 Mg ha⁻¹ yr⁻¹（±0.24标准误）之间，未间伐对照的为3.28 Mg ha⁻¹ yr⁻¹（±0.78标准误）。在林分层面，随着间伐梯度T0（对照）>T48 > T60 > T75，处理间在针叶（F = 11.09，自由度 = 3，P = 0.0009）和木质部分（F = 4.36，自由度 = 3，P = 0.0269）的月度差异随时间显现，且在研究期末记录的针叶总量（χ² = 9.33，P = 0.025）和细枝总量（χ² = 9.11，P = 0.027）也呈现此规律。夏季和秋季初记录到大量细枝和针叶掉落，而主要的杂物输入记录在春季，与毛虫爆发导致的巢穴和粪便掉落时间一致。在树木层面，总凋落量在T0（第2年）的1.5 kg·tree⁻¹ yr⁻¹到T75（第3年）的7.0 kg·tree⁻¹ yr⁻¹之间波动，尽管处理间的年均统计差异仅在监测的第一年被发现。然而，在3年期间分析数据时，较大松树（T
