The Characteristics Of Coarse Woody Debris And Response To Topography In A Mixed Broad-leaved Korean Pine Forest In Xiaoxing'an Mountains, China

The basis characters of CWD were studied on a large permanent plot(9hm²) of a broad leaved-Korean pine forest in XiaoXing'an Mountains.All CWD with diameter at breast height (DBH)≥2 cm were tagged,mapped,measured(girth) and identified to species in the plot. Important findings:A total of 3418 CWD individuals with DBH≥2 cm were recorded in the 9hm² plot(25.3%of which,864 CWD individuals with high decay class were not identified to species level).Acer ukurunduense(28 n·hm^-2) and Betula costata(27 n·hm^-2) were the main species of broad-leaved.Pinus koraiensis and Abies nephrolepis were the main species of conifer.Distinction of distribution was existed between various species CWD under different diameter class:the diameter distribution of most CWD showed typical reverse J-shaped curve, Pinus koraiensis presented J-shaped curve,Betula costata presented double-hump shaped curve,Abies nephrolepis presented partial normal shaped curve.Even though the diameter distribution of CWD of Pinus koraiensis focus on＞60cm,that of the other species were focus on the diameter class of＜20cm.The density of different existing forms were decreased with the DBH class rising,of which distributed with a model of inverse J.The CWD existing forms was mainly composed of standing die,breakage at rootstock and breakage at trunk but the unidentified species.While density of conifer stump CWD were increased with the DBH class rising.The decay classes of CWD were largely normally distributed with a peak on the decay classâ…¡andâ…¢,suggesting that the input and output of CWD was largely balanced in the mixed broad-leaved Korean pine forest.The decay classes of different species CWD were decreased with the DBH class rising but the V decay class of conifer.Use point pattern to study the spatial distribution of CWD in a large permanent plot(9hm²) of a Broad leaved-Korean pine forest in XiaoXing'an Mountains.Most of the species show clump distribution.When the scale increased,Pinus koraiensis,Tilia spp and unidentified species show random distribution observably.CWD with different existing form also show clump distribution except stump.Even though theâ… decay class of CWD fluctuated between clump and random distribution,that of the others were showed clump distribution.Density of seedling regeneration was 231 n·hm^-2 on CWD,seedlings with 0.5-1.0m height class were most occurred on CWD.Seedling regeneration of conifer was less than broad-leaved on CWD.Root of wood was the main place for seedling regeneration.The relationship between coarse woody debris(CWD) number,existing form,decay class, regeneration and topographic traits were also studied in a large permanent plot(9hm²) of a typical mixed broad-leaved Korean pine forest in Xiaoxing'an Mountains.The CWD density and basal area increased with the topographic position rising;the density,basal area and volume of CWD trended to decrease from north to south slope.There was no clear pattern between the number of CWD and sampled slope.A x²-test showed that topography significantly affected density of the CWD.CWD was liked to occur on ridge,north slope and slope degree of 16°～25°.The CWD was mainly composed of uprooted blow-down,breakage at rootstock and breakage at trunk depending on topography.The density,basal area and volume of uprooted blow-down decreased from valley to ridge,but the density of other existing forms showed an opposite pattern;The density of uprooted blow-down decreased with slope degree rising,while that of the snags increased;The density of snags decreased from north to south slope.The falling direction of CWD was not correlated with the aspect(p＞0.05);the falling direction of CWD was also not correlated with the wind direction(p＜0.001).The decay classes of CWD were largely normally distributed with a peak on the decay classâ…¡andâ…¢Regeneration on CWD was different under topography.Density of regeneration seedlings was different on slope position.Density of regeneration seedlings was most on upper slope, and least on ridge.Density of regeneration seedlings was most on south slope(73n·hm^-2),the density of CWD trended to increase from north to south slope.There was no clear pattern between the seedling regeneration of CWD and sampled slope,the most density(114n·hm^-2) appeared on slope of 6°～15°,the least density(5n·hm^-2) appeared on slope of＞25°.