Abstract:

The forest ecosystems of sharptooth oak (Quercus aliena 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 29.2500～3901739t·hm^-2,which put in order sharptooth oak>Chinese pine>Armand pine stand,with percentage of soil 9310%～99.39% and of vegetation 057%～300% and of litter 010%～199%.The total nutrient accumulation contents of the ecosystems were Mg>Ca>K>N>P in the sharptooth oak stand,Ca>N>K>Mg>P in the Chinese pine stand and K>N>P>Ca>Mg in the Armand pine stand,but which of vegetation and litter were Ca>N>K>Mg>P in the sharptooth oak 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 accumulation contents of arbor layers among the three stands were 120483t·hm²,129.384m³·hm^-2 and 1226.9kg·hm^-2 respectively,in which the sharptooth oak stand with higher 6020%,35.50% and 7436% respectively than average was the largest and Armand pine stand was the smallest among the three stands.The sharptooth oak stand average production and average volume increment were 7.423t·hm^-2 and 6.743m³·hm^-2,which were higher than average 5420% and 29.58% respectively,among them Armand pine stand was lowest.The different organs among the three stands have different nutrient percentage contents.The nutrient accumulation contents and its' distribution of different organs 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,Armand pine>Chinese pine>sharptooth oak stand to N,P and Mg and contrary to K and Mg in branches,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 Armand 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 28% of those in Chinese pine and Armand pine stand respectively.The average standing crop and its nutrient accumulation contents of underplants among three stands were 1553t·hm^-2 and 531kg·hm^-2 respectively,in which sharptooth oak stand with higher than average 79.65% and 69.49% respectively was the largest and armand pine stand was the smallest among the stands.The average standing crop and average nutrient accumulation contents of litter among the stands were 17.475*!t·hm^-2 and 5025kg·hm^-2 respectively,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 soil layer 0～60cm were 3877657,27788.0 and 20922050kg·hm^-2 respectively,among them have largely difference of different soil layers in the three stands.The annual nutrient uptake,return and store of the sharptooth oak,Chinese pine and Armand pine stand were 3344,147.2 and 2643kg·hm^-2,195.5,66.9 and 841kg·hm^-2 and 138.8,804 and 1802kg·hm^-2 respectively with difference of the determined elements.The total nutrient return rate in the sharptooth oak, Chinese pine and Armand pine stand was 0585,0454 and 0318 respectively.The nutrient contents of Ca in stems of the sharptooth oak stand was near to 4 and 7*!times as in stems of the Chinese pine and Armand pine stand respectively;the nutrient accumulation contents of K,Ca and Mg in barks of the sharptooth oak stand was 4 and 4,19 and 14,5 and 5 times as in barks of the Chinese pine and Armand 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 1425.6,2044 and 197.5kg·hm^-2 respectively because of felling and using.The larger proportion of nutrient accumulation contents(especially Ca and Mg)in 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 fertility decline.

Key words: Mt.Qinling, Quercus aliena var.acuteserrata, Pinus tabulaeformis, P.armandi, Biomass, Bio-cycling of nutrient elements