两种梭梭属幼苗在土壤N和P梯度下的竞争能力研究

摘要/Abstract

摘要： 梭梭（Haloxylon ammodendron）和白梭梭（H.persicum）是古尔班通古特沙漠两个优势树种。两个物种形态相似，但梭梭主要分布在丘间地，而白梭梭主要分布在丘顶。两种梭梭属植物的典型分布格局受到了植物地理或生物地理学家长期关注。但是，我们还远远不能完全理解这种分布格局形成的原因。在本研究中，通过一个竞争实验，试图确定这两个物种在宽幅土壤养分供应处理下的竞争能力，以及检测这两个物种在古尔班通古特沙漠丘顶/丘间地分布格局的潜在原因。结果表明：（1）在幼苗期，高养分条件下梭梭竞争强度大于白梭梭，梭梭为优势竞争者；相反，在低养分条件下白梭梭竞争强度大于梭梭，白梭梭为优势竞争者。在混种盆中相对丰富度指数也展示了同样的结果。实验结果类似于我们在野外观察到的物种分布格局。（2）这两种梭梭截然相反的竞争表现依赖于它们养分生理差异。梭梭高养分吸收能力使自己在高养分条件下具有优势，但在低养分下成了劣势。因为在低养分条件下，养分从土壤到根表面扩散是植物从土壤获取养分的限速步骤，因此，高养分吸收潜力反而对养分获取总量贡献微弱。白梭梭低养分吸收能力暗示着高养分保留率（例如：低流出）。因此，拥有高养分保留率的白梭梭能够在低养分条件下，通过竞争替换拥有高养分吸收能力的梭梭。在土壤贫瘠的地区（如沙漠），关于种间竞争机制仍不是很清楚。通常认为，植物保留资源能力要比从土壤获取资源能力更重要。但是，结果表明了在养分贫瘠地区养分吸收和养分保留都重要，其中一个关键结果是贫瘠地区种间竞争决定了植物在小尺度上的分布格局。

关键词: 种间竞争, 土壤养分, 氮沉降, 荒漠植物, 梭梭, 白梭梭

Abstract: At the southern fringe of the Gurbantonggut Desert,H.ammodendron and H.persicum are the two dominant woody species.Both species are morphologically similar but H.ammodendron is found primarily at interdunes and H.persicum at the top of dunes in the desert.The contrasting distribution pattern of these two species has long intrigued researchers in plant geography or biogeography.However,we are still far from fully understanding what controls this distribution pattern.In the current study,by a competition experiment,we aimed to determine the competitive abilities under a broad range of soil nutrient supply and to examine the underlying causes of the dune/interdune distribution patterns of the two Haloxylon species in the Gurbantonggut Desert.Our results demonstrate that:(1) in the seedling stage,H.ammodendron was the superior competitor under high nutrient availability and,in contrast,H.persicum was superior under low nutrient availability.The relative dominance index in mixture pots also showed the same pattern.These results resembled the patterns of species distribution observed in the field. (2) At least part of the explanation for the contrasting competitive responses of the two Haloxylon species lies in their differences in nutritional physiology.Its high absorption capacity gave H.ammodendron an advantage only under high nutrient conditions but would be a disadvantage under low-nutrient conditions.Under low-nutrient conditions,diffusion to the root surface is the rate-limiting step in nutrient acquisition from soil,so a high potential to absorb nutrients adds little to the total amount of nutrients acquired.The low absorption capacity of H.persicum suggests high nutrient retention (i.e.low efflux).Thus,H.persicum with high nutrient retention can competitively replace H.ammodendron with higher competitive ability for nutrient uptake under low nutrient availability.In unfertile sites (e.g.desert),the mechanisms of interspecific competition are not always clear.In general,nutrient uptake was less important relative to plants' ability for nutrient retention under unfertile sites.However,our results have showed that both nutrient uptake and nutrient retention can be important under unfertile sites.A key implication of our results is that the inter-specific competition at small scale determines their distribution pattern in unfertile sites.

Key words: inter-specific competition, soil nutrition, N deposition, desert plant, H.ammodendron, H.persicum

中图分类号:

Q948

谢江波, 彭历芝, 李艳明, 李彦. 两种梭梭属幼苗在土壤N和P梯度下的竞争能力研究[J]. 干旱区地理, 2018, 41(1): 83-91.

XIE Jiang-bo, PENG Li-zhi, LI Yan-ming, LI Yan. Competitive interactions between two desert shrub seedings towards variation in soil nitrogen and phosphorus content[J]. 干旱区地理, 2018, 41(1): 83-91.

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