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    黄土高原土石山区不同林龄油松元素富集对土壤水分的响应

    Response of element enrichment of Pinus tabulaeformis with different forest ages to soil moisture in rocky mountain area of Loess Plateau

    • 摘要: 土壤水分作为限制黄土高原植被生长的关键要素,通过调控植物对土壤中元素的吸收,进一步影响区域植被恢复效果。本研究以黄土高原土石山区不同林龄油松林(8年、10年、12年、16年)为研究对象,探究土壤、植物叶片中的大量元素(N、P、K、Ca、Mg)、微量元素(Fe、Cu、Mn、Zn、Ni)和非必需元素(Cr、Pb、Cd、Al、Na)与土壤水分的耦合关系。结果表明:油松林土壤含水率随林龄呈先增后减的趋势,且不同林龄0-10 cm土层含水率(9.52%-13.59%)普遍高于10-20 cm土层(7.84-12.23%);不同林龄土壤中含有较多大量元素K(19%-69%)、Ca(10%-69%)、Mg(10%-23%),微量元素Fe(97%-99%),以及非必需元素Al(68%-89%)、Na(11%-32%),且不同林龄和土层油松林土壤中各元素浓度存在明显差异;油松叶片中含有较多大量元素N(32%-43%)、P(4%-32%)、K(11%-26%)、Ca(6%-34%),微量元素Fe(76%-90%)、Mn(4%-18%),以及非必需元素Na(68%-83%)、Al(16%-31%),其中部分元素浓度(P、Ca、Mn、Cd、Na等)对林龄变化较为敏感;不同林龄油松对土壤中的N、P元素具有较强的吸收能力,且干旱条件下油松对N、Mg、Mn、Na元素具有较强的富集效应,表明油松具有一定抗旱能力。因此,合理调控土壤水分与元素水平,对于维持油松林生态系统的健康与稳定具有重要意义。

       

      Abstract: Background Soil moisture is a key factor limiting vegetation growth on the Loess Plateau, and it further influences the effectiveness of regional ecological restoration by regulating the uptake of soil elements by plants. Methods This study investigated the coupling relationships between soil moisture and macronutrients (N, P, K, Ca, Mg), micronutrients (Fe, Cu, Mn, Zn, Ni), and non-essential elements (Cr, Pb, Cd, Al, Na) in soils and needles across Pinus tabulaeformis forests of different ages (8, 10, 12, and 16 years) in rocky mountain area of Loess Plateau. Results The results indicated that (1) soil moisture content in Pinus tabulaeformis forests showed an initial increase followed by a decline with stand development. Additionally, the 0-10cm soil layer generally maintained higher moisture levels (9.52%-13.59%) than the 10-20cm layer (7.84%-12.23%) across all stand ages. (2) Soils of different stand ages contained relatively high proportions of macroelements K (19%-69%), Ca (10%-69%), and Mg (10%-23%), as well as the micronutrient Fe (97%-99%) and non-essential elements Al (68%-89%) and Na (11%-32%). Significant differences in elemental concentrations were observed both among stand ages and between soil layers. The element contents showed no consistent trend with stand age, but their concentrations in the 0-10cm soil layer were generally higher than those in the 10-20cm layer. (3) Needles of Pinus tabulaeformis contained substantial amounts of macronutrients N (32%-43%), P (4%-32%), K (11%-26%), and Ca (6%-34%), as well as micronutrients such as Fe (76%-90%) and Mn (4%-18%), and non-essential elements Na (68%-83%) and Al (16%-31%). Among these, the concentrations of certain elements were more sensitive to stand age variations. For example, the concentrations of P and Ca exhibited unimodal patterns, reaching their peak values at 12 and 16 years, respectively. Mn showed a gradual decline with increasing stand age, while Cd and Na displayed decreasing and increasing trends, respectively. (4) Pinus tabulaeformis exhibited higher bioconcentration factor (BCF) for N (6.09–68.02) and P (1.46–21.21) in soil, followed by Cu (0.15–0.37), Zn (0.34–0.65), Ni (0.29–0.48) and Cr (0.29–0.68), whereas the uptake of K, Ca, Mg, Fe, Mn, Pb, Cd, Al, and Na was relatively weak. Among them, Cu, Zn, Ni, and Cr can impose negative effects on plant growth when present at high concentrations. Additionally, Pinus tabulaeformis showed pronounced enrichment of N, Mg, Mn, and Na under drought conditions, suggesting a certain degree of drought tolerance. In addition, the BCF values of N in the 10-20cm soil layer were generally higher than those in the 0-10cm layer, indicating a stronger uptake and utilization of N from the surface soil. In contrast, Pinus tabulaeformis exhibited a higher absorption capacity for P in the 10-20cm soil layer. Conclusions Soil moisture exerts a substantial influence on the elemental accumulation processes of Pinus tabulaeformis forests.Therefore, the proper regulation of soil moisture and elemental levels is essential for maintaining the health and long-term stability of Pinus tabulaeformis forest ecosystems.

       

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