荒漠绿洲区不同种植年限人工梭梭林土壤化学计量特征

为阐明梭梭建立对林下土壤养分化学计量特征的影响,分析了2、5、9、13、16、31、39a荒漠绿洲区梭梭林灌丛下和流沙区(0a)土壤有机碳(SOC)、全氮(TN)、全磷(TP)、碳酸钙(CaCO_3)、速效磷(Available P)含量及其化学计量特征变化规律。结果显示:1)SOC和TN在9a后出现显著的成层化分布,而TP的这一特征相对滞后;不同土壤深度SOC、TN均随林龄增加而显著增加,而TP未表现出明显变化。2)C∶P和N∶P在9a后表现出明显的成层化分布且不同土层C∶P和N∶P随林龄增加显著增加,而C∶N保持相对稳定。3)较低含量的Available P在2a后即表现出0—5 cm含量大于5—20 cm且表层Available P和CaCO3随林龄增加而显著增加。而Ca CO3∶Available P在不同林龄间并未发生显著变化。4)随林龄增加,土壤表层风蚀可蚀性极显著降低且与土壤表层养分含量呈显著的负相关关系。以上结果表明,梭梭的建立提高了土壤SOC和TN含量且随林龄增加变化更显著,而变化较小的C∶N说明土壤氮的形成需要固定比例的碳。变化幅度较小的TP说明主要来源于岩石风化的磷素受时间作用的限制,而较低含量的Available P和变化幅度较小的CaCO_3∶Available P则表明梭梭的生长受P的限制且有限的Available P易被CaCO_3固定。另外,土壤养分含量与土壤风蚀可蚀性显著的负相关关系,进一步说明梭梭的建立改善了土壤质地,增加了土壤养分含量,这对荒漠绿洲区土壤恢复和植被建设有极大的促进和指导作用。

Soil stoichiometry characteristics of Haloxylon ammodendron with different plantation age in the desert-oasis ecotone, north China

Vegetation construction is one of the most important measures of ecological restoration in arid area and also one of the most effective methods of desertification control. Haloxylon ammodendron, one important sand-fixation plant in desert region of China with remarkable tolerate to drought, hot environmental stress, and can grow rapidly after planting on sand lands, was widely used for restoring vegetation on the peripheries of the oasis to fix the sand dunes in Linze Station since 1975. To clarify the effect of H. ammodendron on soil nutrient stoichiometric characteristics and explore the indicative significance of nutrient stoichiometric ratios on the recovery of soil, this study conducted the research on the artificial forest of H. ammodendron in an desert-oasis ecotone by analyzing soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP), Available P and CaCO₃ in an age sequence of 0-, 2-, 5-, 9-, 13-, 16-, 31-, and 39-year-old H. ammodendron plantations. Results showed that (1) distribution of SOC, TN and TP presented significant layered phenomenon along with the increase of plantation age, even though this feature in TP was relatively backward. In different soil depth, SOC and TN increased significantly with the increase of plantation age, but TP has no significant variation. (2) C : P and N : P also displayed obvious stratification trait and C : P and N : P in different layer also increased with the increase of plantation age. However, C : N presented at a relatively constant variation. (3) The lower content of Available P expressed significant stratification feature after 2-year-old plantation and Available P and CaCO₃ in 0-5 cm increased with the increase of plantation age. Nevertheless, CaCO₃ : Available P also has no remarkable changes. (4) With the increase of plantation age, soil erodible fraction was highly significant decreased and has remarkably negative correlated with soil nutrients. These results exhibited significant increase of SOC and TN with the increase of establishment time. C : N exhibited a stable trend, compared with C : P and N : P, indicating the formation of nitrogen need a relative fixation ratio of carbon and also stating C : N that less susceptible to the effects of climate factors is quite stable. The small variation of TP mainly derived from the weathering of rock was strongly restricted by time. Moreover, the lower content of Available P and the narrow change of CaCO₃ : Available P manifested that the growth of H. ammodendron may limited by soil P and the limited Available P was more fixed by CaCO₃. In addition, the negative relationship between soil nutrients and soil erodible fraction further showed that the establishment of H. ammodendron has improved soil texture and enhance soil nutrients contents. Our findings aimed at soil environment has enriched the study on H. ammodendron. However, further study is needed to clarify the response of soil nutrient stoichiometric characteristics to H. ammodendron and herbaceous, so as to provide more knowledge for the restoration effect of H. ammodendron on arid environmental and maintain sustainable development under the limited water condition.