| Coarse woody debris(CWD)produce the functions of increasing the surface roughness,releasing nutrient elements,and provid ing base for the growth of moss,saplings and seedlings,providing food and shelter for fungi,animal as well.CWD play an irrep laceable role of ecological functions in forest ecosystem,and maintaining the stability of gravel stacking disorder on the low soil covering groud surface of ancient rock stream periglacical landform forest.By the methods of natural wind dry,indoor soak and X-ray fluorescence,to survey the storage,types,decay degree,hydrological functions and nutrient element content of the coarse woody debris(CWD),in the three forest types(deciduous broad-leaved forests at lower slope,mixed coniferous and broad-leaved forests at middle slope,dark coniferous forests at upper slope)of the ancient rock stream periglacical landform forest at Mt.Laotudingzi,eastern Liaoning mountainous regions,We reached the following conclusions:(1)The soil coverage degree of decid uous broad-leaved forests,mixed coniferous and broad-leaved forests,dark coniferous forests are 80%,55%,27%,respectively.It shows that the soil coverage degree is getting less with the increasing of elevation,but the cover degree of CWD has a opposite trend,which are 4%,5.5%,8%,respectively.So,the CWD cover degree is getting larger with the increasing of elevation.(2)The storage of CWD is 8.78t/hm~2 in the deciduous broad-leaved forests at lower slope,and 18.78 t/hm~2 in the mixed coniferous and broad-leaved forests at middle slope,then23.04 t/hm~2 in the dark coniferous forests at upper slope,17.03 t/hm~2 in average of the whole ancient rock stream periglacical landform forest.(3)By the contrast analysis,snags have the large quantity and logs have the large storage,and the logs also have the large storage of each CWD in average.The average decay degree of CWD in the whole Mt.Laotudingzi hill is middle and primary decay class.The average decay class of CWD is getting lower with the increasing of elevation.Stumps has the large average decay class among all the CWD types,and the average decay degree of logs is larger than the snags in the whole mountain.(4)In the 8 hours’constant soaking process.The water-absorption velocity turned out very high in the beginning,60%of the water absorption was made during the first 15 mins,and 2.921mm was made in 8 hours in total.In the comparison of each single sample,900m altitude trees,deciduous trees,high decay class,logs and roots showed better ability of water-absorption.(5)Element slowly releasing and enrichment function of CWD:The percentage of Carbon is 78.96%in sapwoods and that in heartwood is 96.05%,it was also found that the element N,Ca,Si,K,Mg,P contents in sapwoods were 4.93,5.88,10.79,2.72,1.25,2.38times as that in heartwoods correspondingly.The contents of nutrient elements had a minor difference in the sapwoods of each sample,among which,the CWD of coniferous trees and high decay class reveal higher carbon content while the CWD of deciduous trees and low decay class have a higher N itrogen content and above all,Snags have a high content of both elements.The research indicated that:CWD had an important function of water-holding,nutrient element slowly releasing and enrichment in the paleo-periglacical landforms forest ecosystems of eastern Liaoning mountainous regions;the sapwoods play a more important role than heartwoods in the aspect of nutrient slowly releasing and enrichment.Since the land has a low soil coverage rate and the soil layer on land is thin and barren.The CWD is an irreplaceable and crucial ecological component of paleo-periglacical landforms forest. |
