Effects Of Fertilization On Nitrogen And Phosphorus Content Of Roots, Stems And Leaves And On Law Of Ecological Stoichiomentry In Larix Principis-rupprechtii Mayr Plantation

North China larch was the main tree species of returning farmland to forest in north China,soil quality of the tree had the problem of degradation, soil nutrient insufficiency restictedthe healthy and rapid development of this tree. Our country’s plantation area was large,which had low productivity, the average area of plantation accumulation lags far behinddeveloped countries. From state of development of our country’s forestry, we had somenecessary management measures to help plantations, of which fertilization was a quick andeffective way to increase soil nutrient. The research object was the20years old larch forestin qinling mountains, under the lack of soil nitrogen and phosphate, we gathered roots,stems and leaves of larch in different periods behind fertilization, so we could research theeffects of fertilization on nitrogen and phosphorus content of roots, stems and leaves andon law of ecological stoichiometry in larch, and we could analyze the change rule of thistree. What we did would provide a theoretical basis for the healthy and rapid gowth oflarch plantation. The main findings were as follows.（1） Analye the impact of different fertilizer on the content of nitrogen and phosphorusin the larch, we could kown that fertilization could greatly increase the content in the roots,stems and leaves（p<0.05）, the best amount of fertilization was N150kg·hm^-2and P2O575kg·hm^-2. From May to October, compared with the control group, N2P treatmentincreased the nitrogen and phosphorus content in leaves average was20.47%and13.24%,respectively. N2P treatment increased the nitrogen and phosphorus content in stemsaverage was23.14%and44.38%, respectively. N2P treatment increased the nitrogen andphosphorus content in roots average was25.49%and12.84%, respectively. The increase of the content of N and P in plants showed that fertilization could promote the growth oftrees.（2） Analye the impact of different fertilizer on the ratio of nitrogen and phosphorus inthe larch, we could kown that fertilization could significantly influence the ratio ofnitrogen and phosphorus in roots, stems and leaves（p<0.05）. The following facts wereshown: application of nitrogen could significantly increase the ratio of nitrogen andphosphorus, application of phosphorus could significantly reduce the ratio of nitrogen andphosphorus, various nitrogen and phosphorus proportions had different effects on ratio ofnitrogen and phosphorus. Single nitrogen fertilizer could increase the ratio of nitrogen andphosphorus, which shown that fertilizer decreased nitrogen limit to the growth of plant,Single phosphorus fertilizer could decrease the ratio of nitrogen and phosphorus, whichshown that fertilizer decreased phosphorus limit to the growth of plant. In this study, thecontent of soil nutrient elements nitrogen and phosphorus were lacking, the influence to theN:P ratio of single fertilizer was bigger than that of nitrogen mixed with phosphorus, whichwas not show that single application was better than N-P combined application. Thegrowth of plants was mainly restricted by low content of nutrient elements, so we couldkown that nitrogen mixed with phosphorus was the best for the growth of plants.（3） Analyze the change of the content of nitrogen and phosphorus and the ratio ofnitrogen and phosphorus in larch, the result shown that the content of nitrogen andphosphorus of roots, stems and leaves was different in different period, and the changespresented certain regularity. The basic rule of the content of nitrogen and phosphorus was:leaves>roots>stems. The overall trend of the content of nitrogen and phosphorus in leaveswas as follows, the content was the largest in May and smallest in October, it was changelittle and had a stable state from June to September. The content of nitrogen andphosphorus in stems increased firstly and then decreased, the highest was in September andthe lowest was in May. The basic law of the nitrogen and phosphorus content in the rootswas as follows, the content of nitrogen in the roots reduced firstly, and then increased,decreased at last, the maximum content of nitrogen was in May, the minimum was inOctober. The content of phosphorus in roots changed very little, the maximum content ofphosphorus was in August. The ratio of nitrogen to phosphorus in leaves and roots of larchpresented certain regularity in different periods, it showed a continuous increasing trend from May to August, and reduced in September, a slight increase in October. The overalllaw about ratio of nitrogen to phosphorus in leaves increased firstly and then decreased, themaximum content was in August and the minimum was in May. The ratio of nitrogen tophosphorus in roots significantly reduced from May to June, the ratio of nitrogen tophosphorus in roots presented wave changes from June to October, but it changed little.The overall law about the ratio of nitrogen to phosphorus decreased and the biggest ratiowas in May.（4） Fertilization could significantly increase the content of soil available phosphorusand ammonium nitrogen （p<0.05）, which effectively alleviated the situation of soil nutrientdeficiencies. Fertilization could significantly reduce soil pH （p<0.05）, indicating thatfertilization led to soil acidification which gradually weakened over time.