秦岭松栎林带生物量及其营养元素分布特征

秦岭脱齿栎林、油松林和华山林（包括０－６０cm土层）营养元素总贮量达２９．２５００－３９０．１７３９t.hm^-2，其大小为锐齿栎林＞华山松＞油松林，土壤中营养现贮量占系统总量的９３．１０％－９９．３９％，植被层和凋落物层仅占０．５７％－３．００％和０．１０％－１．９９％；３林分乔木层生物量、木材蓄积量和营养元素积累量平均值分别为１２０．４８３t.hm^-2,129.384m^3.hm^-2和１２２６．９kg.hm^-2，锐齿栎林＞油松林＞华山松林。３林分林下植被层生物量现存量和营养元素积累量平均值分别为１．５５３t.hm^-2和５３．１kg.hm^-2，锐齿栎林最大，华山松林最小。林下凋落物现存量和营养元素积量平均值分别为１７．４７５t.hm^-2和５０２．５kg.hm^-2，３林分凋落物现存量、营养元素含量及其积累量都存在明显的差异。锐齿栎林、油松林和华山松林营养元素年吸收量、归还量、存留量和平均归还率分别为３３．４、１４７．２和２６４．３，１９５．６、６６．９和８４．１，１３８．８、８０．４和１８０．２kg.hm^-2和０．５８５、０４５４和０．３１８，３林分各营养元素的年吸收量，归还量和存留量也存在一定的差异，锐齿栎林干和皮中Ｃa和Ｍg含量远远高于油松林和华山松林的，锐齿栎林多代连作势必导致营养元素的大量流失，特别是Ｃa和Ｍg，会破坏土壤原有离子动态平衡，引起林地土壤理化性质改变，林地生产潜力逐渐下降。

DISTRIBUTIONAL CHARACTERISTICS ON BIOMASS AND NUTRIENT ELEMENTS OF PINE-OAK FOREST BELT IN MT.QINLING

The forest ecosystems of sharptooth oak (Quercus alien a var.acuteserrata Maxim.)，Chinese pine(Pinus tabulaeformis Carr.)and Armand pine(P.armandi Franch) in Mt. Qinling including soil layer 0～60cm contained total nutrient elements 29.2500～390.1739t.hm-2,which put i n ord e r sharptooth oak>Chinese pine>Armand pine stand,with percentage of soil 93.10% ～ 99.39% and of vegetation 0.57%～3.00% and of litter 0.10%～1.99%.The total n utri ent accumulation contents of the ecosystems were Mg>Ca>K>N>P in the sharptooth o ak stand,Ca>N>K>Mg>P in the Chinese pine stand and K>N>P>Ca>Mg in the Armand pin e stand,but which of vegetation and litter were Ca>N>K>Mg>P in the sharptooth oa k stand,N>Ca>K>Mg>P in the Chinese pine stand and N>Ca>K>Mg>P in the Armand pine stand.The average standing crop,average stocked volume and average nutrient acc umulation contents of arbor layers among the three stands were 120.483t.hm 2,129.384m3.hm-2 and 1226.9kg.hm-2 respectively,in which the sharptooth oak stand with higher 60.20%,35.50% and 74.36% respectively th an average was the largest and Armand pine stand was the smallest among the thre e stands.The sharptooth oak stand average production and average volume incremen t were 7.423t.hm-2 and 6.743m3.hm-2,which were higher than a verage 54.20% and 29.58% respectively,among them Armand pine stand was lowest.T he different organs among the three stands have different nutrient percentage co ntents.The nutrient accumulation contents and its' distribution of different o rgans among different stands have marked difference,those in arbor layer put in order barks>stems>roots>branches>leaves to sharptooth oak stand,branches>needles >roots>stems>barks to Chinese pine stand and branches>needles>barks>stems=roots to Armand pine stand;the nutrient accumulation contents of different organs were sharptooth oak>Armand pine>Chinese pine stand in leaves or needles and roots,Ar mand pine>Chi nese pine>sharptooth oak stand to N,P and Mg and contrary to K and Mg in branche s,sharptooth oak>Chinese pine>Armand pine stand to determined elements except to Mg Armand pine>Chinese pine stand in stems,sharptooth oak>Chinese pine or Arman d pine stand to determined elements and Armand pine>Chinese pine stand to N and Ca contrary to P and K similar to Mg in barks;the nutrient accumulation contents of Ca took 50% of the total contents in sharptooth oak stand,but took 24% and 2 8% of those in Chinese pine and Armand pine stand respectively.The average stand ing crop and its nutrient accumulation contents of underplants among three stand s were 1.553t.hm-2and 53.1kg.hm-2respectively,in which sharp tooth oak stand with higher than average 79.65% and 69.49% respectively was the largest and armand pine stan d was the smallest among the stands.The average standing crop and average nutrie nt accumulation contents of litter among the stands were 17.475t.hm-2 a nd 502.5kg.hm-2res pectively,the former put in order Armand pine>Chinese pine>sharptooth oak stand and the latter Chinese pine>Armand pine>sharptooth oak stand,but sharptooth oak> Armand pine>Chinese pine stand according to annual falling litter and sharptooth oak>Chinese pine>Armand pine stand to nutrient percentage contents.The standing accumulation contents of sharptooth oak,Chinese pine and Armand pine stand in s oil layer 0～60cm were 387765.7,27788.0 and 209220.50kg.hm-2respect iv ely,among them have largely difference of different soil layers in the three sta nds.The annual nutrient uptake,return and store of the sharptooth oak,Chinese pi ne and Armand pine stand were 334.4,147.2 and 264.3kg.hm-2,195.5,66.9 and 84.1kg.hm-2 and 138.8,80.4 and 180.2kg.hm-2 respective ly with differe nc e of the determined elements.The total nutrient return rate in the sharptooth oa k, Chinese pine and Armand pine stand was 0.585,0.454 and 0.318 respectively. The nutrient contents of Ca in stems of the sharptooth oak stand was near to 4 and 7times as in stems of the Chinese pine and Armand pine stand r espectively;the nutrient accumulation contents of K,Ca and Mg in barks of the sharptooth oak sta nd was 4 and 4,19 and 14,5 and 5times as in barks of the Chinese pine and Ar mand pine stand respectively,the biomass standing crop and nutrient accumulation contents of stems and barks in the sharptooth oak,Chinese pine and Armand pine stand respectively took 56%,67% and 57%,24% and 53%,28% of the total biomass and accumulation contents of arbor layers,the nutrient loss of the three stands was 1425.6,204.4 and 197.5kg.hm-2respectively because of felling and usin g.The larger proportion of nutrient accumulation contents(especially Ca and Mg)i n stems and barks of sharptooth oak stand lost by felling and using to might be cause leading to the soil acidification and structure destruction and final fert ili ty decline.