去除地面枯落物对加勒比松(Pinus caribaea)林土壤特性的影响

通过去除地表凋落物(处理)和保留凋落物(对照)的样地比较,研究了加勒比松(Pinus caribaea)林的土壤特性对去除地表枯落物的响应,为了解人工干扰的加勒比松林土壤的退化机理提供依据.去除地表枯落物后的样地林木平均胸径和平均树高分别显著下降了21%和8%.人为干扰造成了土壤质量的全面下降.与对照相比,去除地表枯落物的土壤容重增加了14%,土壤毛管孔隙和总孔隙的比例分别减少了13%和18%,非毛管孔隙也因为人为干扰而显著下降了37%,土壤毛管持水量下降了24%.去除地表枯落物没有对土壤pH造成影响,但是土壤有机质、全N、全P和全K含量比对照分别减少了42%、46%、16%和39%,水解N、速效P和速效K含量分别比对照减少了20%、15%和41%,土壤中<0.01 mm 粘粒的比例下降了27%.去除地表枯落物后的土壤细菌、真菌和放线菌数量分别下降了50%、19%和13%,土壤脲酶、土壤磷酸酶和过氧化氢酶活性分别比对照下降了35%、49%和49%.去除地表枯落物从林地以凋落物的形式直接取走大量养分,使林地有机质含量降低,导致土壤孔隙减少,保持水分功能减弱,养分状况的恶化,微生物数量减少和酶活性下降,最终引起林木生长下降.

Impacts of litter removal on soil characteristics in a Pinus caribaea stand

The effects of human-impacted on soil properties in a Pinus caribaea stand were studied in an experiment comparing harvesting litter and control (no harvest) plots, in order to understood the mechanism of soil degradation in human litter removal Pinus caribaea stands and establish basis for sustainable forest management. Results showed that compared with those in undisturbed stand, the mean diameter at breast height (DBH) and mean tree height with litter removal significantly decreased by 21% and 8%, respectively. With litter removal, soil bulk density significantly increased by 14%, whereas capillary porosity, non-capillary porosity, total porosity and capillary water significantly increased by 12%, 37%, 18% and 24%, respectively. There was not significant difference in pH value between the disturbed stand and the undisturbed stand. However, litter removal significantly decreased the contents of soil organic matter, total N, total P, total K, alkalized N, available P, available K and clay by 42%, 46%, 16%, 39%, 20%, 15%, 41% and 27%, respectively. The litter removal plot showed that the numbers of bacteria, fungi and actinomyces was 50%, 19% and 13% lower than the non-litter removal plot with a significant difference in bacterium number between the both. The litter removal significantly resulted in the decrease of the activities of urease, acid phosphatase and catalase. Decrease in litter amount by litter removal caused the decrease of organic matter in soil, which resulted in the decline of soil porosities and water holding capacity, and deterioration of nutrient status, the reduction of microorganism number and enzyme activity, as a result stand growth became slow.