科尔沁沙地优势固沙灌木叶片氮磷化学计量内稳性

Nitrogen and phosphorus stoichiometric homoeostasis in leaves of dominant sand-fixing shrubs in Horqin Sandy Land, China

为科学认识科尔沁沙地优势固沙灌木的生态适应性和固沙植被演变规律,该研究对科尔沁沙地流动沙丘、半固定沙丘、固定沙丘和丘间低地的优势固沙灌木小叶锦鸡儿(Caragana microphylla)和盐蒿(Artemisia halodendron)进行野外调查,研究了这两种固沙灌木的叶片氮(N)、磷(P)化学计量特征、灌丛土壤养分状况以及内稳性特征。结果表明:1)与盐蒿相比,灌木小叶锦鸡儿具有较高的叶片N含量及N:P,而P含量仅为盐蒿的1/2; 2)两种优势固沙灌木灌丛下土壤的全N、全P含量及速效N、速效P含量高于该地区土壤的平均水平,小叶锦鸡儿灌丛下土壤养分含量显著高于盐蒿灌丛下土壤; 3)盐蒿叶片N、P化学计量内稳性指数(H)表现为HP> HN:P> HN,说明盐蒿更易受土壤N的限制;小叶锦鸡儿叶片N、P化学计量内稳性指数表现为HN:P>HN>HP,意味着小叶锦鸡儿更易受土壤P的限制。在N含量较低的沙化草地,HN较高的固沙灌木小叶锦鸡儿比盐蒿更具生长优势,对于该地区生态恢复及保护具有不可替代的作用。然而,小叶锦鸡儿额外吸收的N,使其生长过程可能易受P的限制,因此在沙地恢复过程中应注意土壤P的供应。

Aims Sand-fixing shrubs play an irreplaceable role in ecological restoration and eco-environmental protection in arid and semiarid regions of northern China.Determination of the stoichiometric homoeostasis of dominant sand-fixing shrubs along soil nutrient gradients could provide insights into ecological adaptability and pattern of changes of sand-fixing vegetation in Horqin Sandy Land.Methods We measured N and P concentrations in leaves of two dominant sand-fixing shrubs Caragana microphylla and Artemisia halodendron,and the total and available N and P concentrations in soils beneath the canopy of each shrub.The differences between the two shrubs in N and P concentrations and N:P of leaves and soils as well as in stoichiometric homoeostasis were examined.Important findings Caragana microphylla had higher leaf N concentration and lower leaf P concentration,thereby higher leaf N:P,than A.halodendron.Soils beneath the shrub canopies,regardless of the species,had higher total and available N and P concentrations relative to soils outside the canopy cover.Moreover,the total and available N and P concentrations in soils beneath the C.microphylla canopy were higher than that beneath the A.halodendron canopy.The stoichiometric homoeostasis indexes(H)were ranked in the order of HP>HN:P>HN in A.halodendron and HN:P>HN>HP in C.microphylla,respectively,suggesting N limitation in A.halodendron and P limitation in C.microphylla.Therefore,Caragana microphylla could be used as nursing plants in degraded N-limiting soil because of high HN.However,due to excessive uptake of N,Caragana microphylla might suffer from P limitation,and adequate P supply should be considered during the restoration process in sandy land.