黄土丘陵区微地形梯度下草地群落及土壤对氮、磷添加的响应

Responses of Grassland Communities and Soil to Nitrogen and Phosphorus Additions in Micro-Topography of the Hilly Loess Plateau Region

为研究N,P添加对草地群落及土壤的影响,试验以黄土丘陵区安塞综合试验站草地群落为研究对象,通过在不同坡向、坡位定量添加N,P营养元素的方法,研究群落地上和地下生物量、叶片和根系及土壤养分的变化特征。结果表明:(1)N处理和N+P处理地上生物量分别比对照(CK)处理增加24.21%和43.92%,而地下生物量分别减小12.19%和8.53%;(2)平均叶片N含量变化趋势为N+P处理>N处理>CK处理,与CK处理相比分别增加26%和17%;叶片P和K含量增加不显著;CK处理组、N处理组和N+P处理组的平均叶片N/P值分布范围分别为12.58~24.28,16.67~4.82,12.56~23.07,总体趋势为N>CK>N+P,无显著差异(p>0.05);(3)CK处理、N处理和N+P处理根系N含量的取值范围分别为5.20~12.78g/kg,5.42~14.30g/kg,10.16~17.70g/kg,N处理和N+P处理分别增加34.38%和63.45%;根系P含量的取值范围分别为0.22~0.38g/kg,0.38~0.87g/kg,0.63~0.94g/kg,方差分析表明施肥处理组根系P含量显著增加(p<0.05);根系K含量没有显著变化;根系N/P比的取值范围分别为26.02~49.94,14.23~20.67,12.46~21.28,施肥处理后根系N/P呈下降趋势;(4)施肥对土壤有机C的影响不显著;土壤全N含量均显著增加(p<0.05);土壤全P含量、速效K和N/P比值含量增加,但无显著差异。表明N,P添加能够改善黄土丘陵区土壤养分状况,缓解植物生长的养分限制情况,促进植物其他营养元素的吸收,并使得植物体养分更多分配于地上部分。

To study the effects of N and P addition on grassland community and soil,we used the way of adding N,P nutrient elements in different aspect-position in the grassland communities in Ansai Comprehensive Experimental Station of loess hilly region to study the aboveground and underground biomass,leaf,root and soil nutrient.The results show that:(1)aboveground biomass of the N and N+P treatments increased by 24.21%and 43.92%,respectively,compared with the control(CK),and the underground biomass reduced by 12.19%and 8.53%.;(2)the average leaf N contents in leaves decreased in the order:N+P>N>CK,increased by 26%and 17%,respectively,compared with the CK.The contents of P and K in leaves did not significantly increase.The ranges of average N/P in CK,N treatment and N+P treatment was 12.58~24.28,16.67~4.82 and 12.56~23.07,respectively,and the trend presented N>CK>N+P,however,the difference was not significant(p>0.05);(3)in CK,N and N+P treatments,the ranges of root N contents are 5.20~12.78,1.54~14.30,10.16~17.70 g/kg,root N contents increased by 34.38%and 63.45%in N and N+P treatments,respectively;the contents of P in roots were 0.22~0.38 g/kg,0.38~0.87 g/kg and 0.63~0.94 g/kg,respectively,and variance analysis showed that the contents of P in roots significantly increased(p<0.05);the root K content did not significantly change;the root N/P ratios were 26.02~49.94,14.23~20.67 and 12.46~21.28,respectively,and the N/P ratios of the roots decreased with the fertilization;(4)the effect of fertilization on soil organic C was not significant,while total N contents increased significantly(p<0.05).The contents of soil total P,available K content and N/P increased,but the differences were not significant.It indicated that N and P addition could improve soil nutrient status in loess hilly region,alleviate the nutrient limitation to plant growth,promote the absorption of other nutrient elements by plants,and make more plant nutrient distribute in the ground part.