林隙与凋落物对天然红松混交林土壤水溶性有机碳的影响

Effects of Gap and Litter on Soil Water Soluble Organic Carbon in Natural Pinus koraiensis Forest

在天然红松混交林3种不同林型(椴树红松混交林(TP)、云冷杉红松混交林(PAP)、枫桦红松混交林(BP))内,各选取小、中、大3个代表性的林隙,将其作为试验样地,并分别以各自的郁闭林分作为对照。2012年6月,在TP林隙及郁闭林分内不同位置的土壤表层埋设3种不同树种的凋落物(红松、椴树、枫桦)分解袋。2012年6-9月测定各林型不同大小林隙及其郁闭林分0-10cm的土壤水溶性有机碳(WSOC)含量。结果表明:TP和BP林隙内及其对照的WSOC均表现为小林隙>大林隙>中林隙,而PAP表现为大林隙>中林隙>小林隙;TP和PAP林隙内WSOC>郁闭林分,BP则相反;除7月3种林型林隙大小对土壤WSOC影响均不显著(P>0.05)外,其他月份林隙大小的影响并不完全一致。PAP和BP林隙内土壤WSOC随月份的变化均为不对称的"V字型"曲线,6月达到峰值,前者7月而后者8月达到谷值。然而,TP林隙内土壤WSOC在生长季内呈持续上升的趋势,9月达到最高值;TP林隙内枫桦凋落物分解袋下的土壤WSOC明显高于红松和椴树凋落物分解袋下的。3种凋落物下土壤WSOC在林隙北部均为小林隙和中林隙的郁闭林分<林隙内,而大林隙则相反;TP和PAP林隙内及其对应的郁闭林分土壤WSOC和土壤含水量均为正相关,然而BP为负相关。

Small, medium and large gaps in three representative forest types （Tilia amurensis 47 Pinus koraiensis mixed forest （TP）, Picea asperata 47Abies fabri 47 Pinus koraiensis mixed forest （PAP）, Betula costata47Pinus horaiensis mixed forest （BP）） were selected as experimental plots, and closed stand around each gap was set up as the control in Xiaoxing〉 an Mountains of Northeast China respectively. The decompo- sition bags of litters from three different tree species （Pinus horaiensis, Tilia arnurensis, Betula costata） were embedded into the soil surface at different azimuths in the above experimental plots and their controls in TP in June 2012. Soil water soluble organic carbon （WSOC） at the depth of 0-10 cm in the different size of forest gaps and their controls of various forest types was determined from June to September, 2012. The re- sults showed that soil WSOC in TP, BP gaps and their closed stands was in the order of small gap〉large gap 〉medium gap, but in the order of large gap〉medium gap〉small gap in PAP. Soil WSOC was higher in the gap than in the closed stand in TP and PAP, but it was in the opposite order in BP. Except that the effect of forest gap size on soil WSOC in July was not significant in all three forest types （P〉0.05）, in the other months was not completely consistent. The variations in soil WSOC within the PAP and BP gaps over months presented an asymmetric V-shaped curve with the peak value in June, the soil WSOC reached their valley values in July and August, respectively. However, soil WSOC within TP gap over growing season ex- hibited continuously increasing tendency with the peak in September. Within TP gaps, soil WSOC under Betula costata litter decomposition amurensis litter decomposition bags was in the order of closed stands〈 large gap. The positive correlation gaps as well as their closed stands, bags was apparently higher than that under Pinus koraiensis and Tilia . Soil WSOC under three litter types in the northern part of forest gaps within-gaps for small and medium gaps, while in the opposite order for existed between soil WSOC and soil water content within TP and PAP but negative correlation in BP.