喀斯特林地细根碳氮磷生态化学计量特征的季节变化及其影响因子OA北大核心CSTPCD

The ecological stoichiometry of fine root carbon(C),nitrogen(N),and phosphorus(P)is considered to reflect the strategies whereby plants adapt to the soil environment.In order to gain an understanding of the seasonal variation in fine root C∶N∶P ratios in different forest types of karst ecosystem,we measured the C,N,and P contents and ratios of living and dead fine roots in shrubland and arbor forest,as well as the influence of abiotic and biotic factors.The results were as follows:(1)C,N,and P contents in the fine roots of arbor forest were higher than those of shrubland,thereby indicating that the fine roots of arbors may by characterized by a stronger absorption and storage of nutrients than those of shrubs.In addition,the contents of C in living fine roots were significantly higher than those in dead fine roots(P＜0.05),but N and P contents in living fine roots were lower than those in dead fine roots.(2)It was found that the contents of C in the living and dead fine roots of the two forest types were lower during the rainy season than during the dry season.The N and P contents of living fine roots of shrubs were higher during the rainy season than those in dry season,the opposite pattern was observed for the living fine roots of arbors.During the rainy season,the C∶N,C∶P,and N∶P ratios of living fine roots in shrubland were lower than the values obtained during the dry season.Conversely,the C∶N and C∶P ratios of the living and dead fine roots of arbors were higher during the rainy season than in the dry season,whereas the values for the N∶P ratio were lower during the rainy season than during the dry season.The lower N∶P ratios of rainy season tended to indicate that plants in shrubland and arbor forest may be less P restricted during this season.(3)It was found that for both the living and dead fine roots of the two forest types,C contents were higher in trees growing on the upper slopes than in those growing on the middle and lower slopes,whereas the contents of N and P were higher in shrubs growing on the lower slopes and in arbors growing on the middle slopes.Furthermore,the C∶N,C∶P,and N∶P ratios of living and dead fine roots were found to be relatively higher in shrubs growing on the upper slopes.In the case of arbor forest,the C∶N ratios of living and dead fine roots in trees growing on the lower slopes were higher than other slopes,however the C∶P and N∶P ratios in trees growing on the upper slopes were higher than those of trees growing at other slopes,indicating that trees under these two forest types were strongly influenced by P limitation in the upper slopes,but only weakly affected on the middle and lower slopes.(4)Redundancy analysis revealed that forest type,available phosphorus,and season were the main factors influencing the contents and ratios of C,N,and P nutrients in fine roots,and could explain 18.8％,6.6％,and 6.5％of the observed variation,respectively.These findings indicate that the effects of changes in the N∶P ratio associated with differences in forest type,season,and slope should be taken into consideration when vegetation restoration is promoted,which will contribute to accelerating the restoration of karst ecosystems.