【摘要】 林窗的产生使森林环境发生了变化,进而影响森林生态系统的更新演替。本文选取东北地区具有典型性的次生林生态系统中人工小林窗(林窗直径与边缘木高之比小于0.5)为对象,对林窗内部及其附近林分的光量子通量密度(PPFD),距地面10cm的空气温度,土壤温度和土壤含水量(0-15cm,15-30cm)进行了观测。实验在林窗形成后的第二年进行,时间为2006年5-9月。结果表明:PPFD最高值出现在林窗北部边缘,尤其在生长季初期的五月份最为明显;晴天时PPFD到达最大值的时间较阴天提前;林窗北部的气温较高,南部的气温较低。土壤温度在林窗内变化剧烈,范围为1-8℃,最大值出现在林窗北部,且与气温最大值显著相关(R=0.735,P<0.05)。表层土壤水分高于下层土壤水分,但差异不显著(p>0.05);这主要是受林窗面积和地表植被的影响所致。上述结果表明,辽东山区次生林小林窗光量子最大值出现的位置与以往在北半球林窗观测结果基本一致,但出现最大值的时间在不同的纬度间存在着差异。空气温度和土壤温度的最大值也都出现在林窗北部,体现了光照对温度变化的影响。由于面积因素的影响,七月份温度变化与其它月份不同。土壤水分在雨季和旱季变化不大,这可能与林窗大小和所处地理位置有关。在本次观测的形状不规则小林窗中,小气候因子的变化对物种更新产生怎样的影响,需要开展进一步的研究。图5参44。更多还原

【Abstract】 In order to improve the understanding of the role of a canopy opening/gap on the physical environments in a secondary forest in Northeastern China,a case study was conducted in and around a small irregular gap in a montane secondary forest. The secondary forest,which was severely disturbed by human beings about 50 years ago,was dominated by Quercus mongolica and Fraxinus rhynchophyllaan. Temporal variation in photosynthetic photon flux density (PPFD),air temperature (TA) at 10 cm above the ground,soil temperature (TS) and soil water content (SWC) at top-layer (0-15 cm) and sub-layer (15-30 cm) were measured from May to September after the second year since the formation of the small gap (the ratios of gap diameter to stand height were less than 0.5) in 2006 respectively. Results indicated that the highest value of PPFD occurred at the northern edge of the gap,particularly at the beginning of the growing season in May. On sunny days,the highest value of PPFD appeared earlier than that on overcast days. Maximum and mean values of TA were higher in the northern part of the gap,and the minimum values of TA were at the southern edge of the gap. Soil temperature varied obviously in the gap with the range from 1 to 8 oC. Maximum values of TS occurred at the northern part of the gap,which was significantly correlated with the maximum values of TA (R = 0.735,P<0.05). SWC was higher in the top-layer (0-15 cm) than that in sub-layer (15-30 cm),but the differ-ence of them was not significant (p>0.05),which might be attributed to the small gap size and the effects of aboveground vegetations. From these results,the maximum of PPFD in the study area occurred at the northern part of the gap,which was consistent with the results ob-served in north hemisphere,but the occurrence time varied with the differences of the latitudes. The highest values of air and soil tempera-tures also occurred in the northern part of the gap because they were affected by the radiation. However,the variation of temperature in July was different from other months due to the influence of gap size. And the values of soil water content were neither higher in the gap in the wet season nor lower in the dry season,which might be affected by the gap size and topography the gap located. The variations of light,soil and air temperatures,and soil moisture in this small irregular gap might be related to the effects of the micro-site,which affects the regen-eration of plant species.更多还原