不同强度疏伐改造对马尾松林分水源涵养功能时空格局的影响

为了解马尾松林分改造过程中水源涵养功能的动态变化,提升林分的生态服务功能,1994年在福建省尤溪国有林场城镇景观林中选择22年生的马尾松林,通过方差分析分析20%强度疏伐改造、35%强度疏伐改造、50%强度疏伐改造和对照4种处理间林分持水量的变化,结果表明:随着改造时间的推移,各处理林分水源涵养量显著升高(P0.05),疏伐改造强度越大林分水源涵养量增加越明显。土壤层持水量占林分总持水量的95.89%—97.18%,改造前5 a不同处理间土壤层0—20 cm和土壤层20—40 cm持水量差异均不显著(P0.05),改造10 a后改造林分土壤层0—20 cm和土壤层20—40 cm持水量均显著高于对照林分(P0.05)。林分地上部分持水量仅占林分水源涵养量的2.82%(45.64 t/hm~2)—4.11%(76.81 t/hm~2),但改造后存在显著变化(P0.05)。林冠层在林分改造10a后持水量显著高于对照林分(P0.05),但疏伐改造强度越大其持水量越小;林下植被层在林分改造5 a后持水量显著低于对照林分(P0.05),同样疏伐改造强度越大其持水量越小;凋落物层在林分改造5 a后持水量显著高于对照林分(P0.05),持水量随疏伐改造强度增大而增大。林冠层和凋落物层持水量比重随着改造时间的推移呈显著增加趋势(P0.05),林下植被层则呈显著下降趋势(P0.05)。以上结果表明,改造初期林分持水量变化强烈,疏伐改造强度越大林分持水量越低;但长期来看,改造林分更有利于林分水源涵养功能的提升。

Effects of different thinning intensities on temporal and spatial patterns of water conservation of Pinus massoniana

This study aimed to understand the changes in spatial and temporal dynamics of water conservation in the process of stand improvement of Pinus massoniana, in order to improve the forest ecological service function. We analyzed the changes in stand water holding capacity between the control stand and improved stand using thinning intensities of approximately 20%, 35%, and 50%, in a 22-year-old P. massoniana forest of the Youxi Forest Farm in Fujian Province. The results showed that forest water conservation by stand improvement significantly increased with time (P < 0.05), and forest water conservation increased significantly with the increase in thinning intensity after 10 years. Water holding capacity of the soil layer accounted for 95.89%-97.18% of the stand water holding capacity. Water holding capacity of the 0-20cm and 20-40 cm soil layers was not significantly different between the control stand and improved stand during first five years of stand improvement (P > 0.05); however, after 10 years of stand improvement, water holding capacity of both 0-20 cm and 20-40 cm soil layers of the improved stand was significantly higher than the control stand (P < 0.05). Water holding capacity of the canopy, vegetation, and litter layers accounted for 2.82% (45.64 t/hm²)-4.11% (76.81 t/hm²) of the stand water holding capacity. In the canopy layer, water holding capacity of the improved stand was significantly higher than the control stand when stand improvement was > 10 years (P < 0.05); water holding capacity decreased with increasing thinning intensity. In contrast, in the vegetation layer, water holding capacity of the improved stand was significantly lower than that of the control stand when stand improvement was > 5 years (P < 0.05); water holding capacity decreased with increasing thinning intensity. In the litter layer, water holding capacity of the improved stand was significantly higher than that of the control stand when stand improvement was > 5 years (P < 0.05); water holding capacity increased with increasing thinning intensity. The water holding ratio of the canopy and litter layers increased significantly with time (P < 0.05), but the water holding ratio of the vegetation layer decreased significantly with time in the improved stand (P < 0.05). These results indicate that the stand water holding capacity changed dramatically in the early stage of the improved stand, and the water holding capacity decreased with increasing thinning intensity. Thus, the improved stand was more beneficial for water conservation over a longer period of time.