樟子松人工林原产地与不同自然降水梯度引种地土壤和植物叶片生态化学计量特征

Responses of soil and plant stoichiometric characteristics along rainfall gradients in Mongolian pine plantations in native and introduced regions

降水格局是影响陆地生态系统结构和过程的重要环境要素,尤其对于干旱/半干旱地区,降水变化是植物生长驱动的关键生态因子。目前,针对降水变化对陆地生态系统C、N、P等元素生物地球化学循环过程影响开展了大量研究。然而,关于沙地樟子松重要引种地科尔沁沙地自然降水梯度下沙地樟子松人工林土壤、植物生态化学计量特征的研究未见报道。因此,本研究以樟子松原产地红花尔基和引种地科尔沁沙地自然降水梯度下4个典型沙地樟子松人工林为对象,研究樟子松引种地降水变化对土壤(0—10,10—20 cm和20—40 cm)和植物(1年和2年生叶)生态化学计量特征的影响。研究结果发现:(1)与红花尔基原产地樟子松人工林相比,科尔沁沙地引种的樟子松人工林土壤C、N、P元素含量显著降低;(2)科尔沁沙地自西向东,随降水量增加,沙地樟子松人工林土壤C、N、P含量以及C∶P和N∶P表现为逐渐增加趋势,而土壤C∶N呈减少趋势;(3)随着降水量增加,樟子松叶C含量呈下降趋势,叶N含量和N∶P比值呈增加趋势,植物叶P含量无一致性规律;(4)樟子松叶片P含量与土壤C、N、P含量呈极显著正相关关系,而叶片C和N含量与土壤C、N、P含量无显著相关性。研究表明,沙地樟子松引种地科尔沁沙地土壤C、N、P养分比较缺乏,且随着降水增加土壤N养分限制降低,而土壤P养分限制增加。本研究从生态化学计量特征角度,为今后开展科尔沁沙地不同降水梯度条件下引种樟子松人工林提供理论依据。

Rainfall is one of most important environmental factors influencing ecosystem structures and processes, and changes in rainfall can alter plant growth in arid/semi-arid regions. Currently, the impacts of rainfall patterns on the biogeochemical cycles of C, N, and P in terrestrial ecosystems have been well studied. However, a knowledge gap exists with regard to the changes in soil and plant stoichiometric characteristics along rainfall gradients in Mongolian pine （Pinus sylvestris vat. mongolica） plantations. We selected one native Mongolian pine plantation and four plantations along a rainfall gradient in the Horqin Sandy Land. We measured stoiehiometrlc characteristics in the soil （0--10,10--20, and 20--40 cm） and leaves （ 1- and 2-year old）. Our results showed that ： （ 1 ） Soil C, N, and P concentrations in Mongolian pineplantations in the Horqin Sandy Land were significantly lower than those in native Mongolian pine plantation; （2） Soil C, N, and P concentrations and soil C ：P and N ：P increased with increasing rainfall in the Horqin Sandy Land, hut soil C ：N decreased along the rainfall gradient; （3） Leaf C concentration decreased, and leaf N coneentration and N ：P increased with increasing rainfall, hut there was no elear trend for leaf P eoneentration along a rainfall gradient; （4） there were significant positive relationships between leaf P eoneentration and soil C, N, and P concentrations, but not for leaf C and N. Our results implied that soil nutrients limit the growth of Mongolian pines in the Horqin Sandy Land eompared with growth in native land. Furthermore, the soil N limitation deereased with increasing rainfall, but soil P limitation increased. Our results could improve the management of Mongolian pine plantations following introduetion into the Horqin Sandy Land.