Effects of drought on non-structural carbohydrates and C,N,and P stoichiometric characteristics of Pinus yunnanensis seedlings

To study non-structural carbohydrate character-istics and nutrient utilization strategies of Pinus yunnanen-sis under continuous drought conditions,2-year-old seed-lings were planted in pots with appropriate water,light and moderate and severe drought treatments[(80±5),(65±5),(50±5),and(35±5)%of field water-holding capacity].Non-structural carbohydrates,carbon(C),nitrogen(N),and phosphorus(P)concentrations were measured in each plant component.The results show that:(1)With increasing drought,non-structural carbohydrates gradually increased in leaves,stems,and coarse roots,while gradually decreased in fine roots;(2)C concentrations of all were relatively stable under different stress levels.Phosphorous utilization of each component increased under light and moderate drought conditions,while N and P utilization efficiency of each plant component decreased under severe drought.Growth was mainly restricted by N,first decreasing and then increasing with increased drought;(3)There was a correlation between the levels of non-structural carbohydrates and C,N,and P in each component.Changes in N concentration affected the interconversion between soluble sugar and starch,which play a regulatory role in the fluctuation of the concentration of non-structural carbohydrates;and,(4)Plasticity analysis showed that P.yunnanensis seedlings responded to drought mainly by altering starch concentration,the ratio of soluble sugar to starch in leaves and stems,and further by alter-ing N and P utilization efficiencies.Overall,these results suggest that the physiological activities of all organs of P.yunnanensis seedlings are restricted under drought and that trade-offs exist between different physiological indicators and organs.Our findings are helpful in understanding non-structural carbohydrate and nutrient adaptation mechanisms under drought in P.yunnanensis seedlings.

Differences of carbon and nitrogen stoichiometry between different habitats in two natural Korean pine forests in Northeast China's mountainous areas

There is a strong link between vegetation and environmental factors.Therefore,to elucidate how the stoichiometric characteristics of plants respond to different habitats,we studied organic carbon(C)and total nitrogen(N)stoichiometry characteristics of plants in four different habitats of two different natural Korean pine forests.Three of the habitats(gaps,mounds,and pits)were formed via tree uprooting,whereas an undisturbed site(closed canopies)was used as a control.The followings were our main findings:(1)the organic carbon content of more than half of the 12 picked plants showed significant differences in different habitats.Most of the plants in pit-mound complexes exhibited lower organic carbon contents than plants in gaps and closed canopies;(2)there was no significant differences in the total nitrogen content in 13 of the 25 groups of plant samples;(3)interestingly,the C/N of the sample groups with significant differences in total nitrogen also showed significant differences;(4)there was no significant variations in the stoichiometric characteristics of plants that grew in gaps;however,the variations among plants that grew in pits and mounds were significant;(5)through redundancy analysis(RDA),we find that the main factors effecting the C and N stoichiometric characters of the plants were plants own regulation and the change of photosynthetically active radiation(PAR).In conclusion,the C and N stoichiometric characteristics of plants did not respond to gap formations,but they did strongly respond to pit-mound complex formations.Photosynthetically active radiation was the most important effective factor to plants in the four habitats.