利用土壤化学计量学和酶计量学揭示刺槐林土壤微生物的养分限制状况

Revealing nutrient limitation status of microorganisms in the soil of Robinia pseudoacacia plantation through soil stoichiometry and enzyme metrology

探索森林土壤中的养分限制对森林抚育和管理具有重要意义,然而目前关于黄土高原刺槐人工林植被恢复过程中微生物受到的养分限制的研究并不充分。本研究为探究黄土高原刺槐林土壤中微生物养分的限制情况,在陕西省永寿县选择不同造林时间(15、25、35、45年)的刺槐人工林以及林地旁边的摞荒坡耕地(对照)为研究对象,分析了不同林龄下土壤有机质、全氮、全磷含量,以及与土壤碳、氮、磷循环相关的β-1,4-葡萄糖苷酶(BG)、纤维二糖水解酶(CBH)、亮氨酸氨基肽酶(LAP)、β-1,4-N-乙酰氨基葡萄糖苷酶(NAG)和磷酸酶(AP)活性的变化特征,通过化学计量和酶计量解析土壤养分限制状况。结果表明:土壤pH随植被恢复由碱性变为酸性;全磷在刺槐植被恢复的0~25年间逐渐降低;土壤有机碳、全氮和酶活性在0~25年间呈上升趋势。土壤全磷、有机碳、全氮、AP和LAP在25~45年间逐渐降低;NAG、BG、CBH在25~45年间先增加再降低。植被恢复过程中刺槐林的(BG+CBH)/(LAP+NAG)、(BG+CBH)/AP、(LAP+NAG)/AP均高于全球尺度的平均值。本研究区刺槐恢复过程中矢量长度小于1且逐渐增大,表明微生物碳限制逐渐增强;矢量角度大于45°且整体上降低,表明土壤微生物受磷限制且磷限制逐渐减缓,未出现微生物氮限制。刺槐人工林植被恢复过程中土壤理化性质变化明显,造林时间序列影响了土壤微生物的养分限制状况。

Exploring nutrient limitation in forest soil holds significant implications for forest tending and management.However,current research on nutrient limitation status of microorganisms in Robinia pseudoacacia plantations within the Loess Plateau remains insufficient.To investigate soil microbial nutrient limitation of R.pseu-doacacia plantations on the Loess Plateau,we selected R.pseudoacacia plantations with different afforestation time series(15,25,35,and 45 years)and a pile of barren slope cropland(control)in Yongshou County,Shaanxi Province as the research objects.We analyzed the contents of soil organic matter,total nitrogen,and total phosphorus,and the activities ofβ-1,4-glucosidase(BG),cellobiose hydrolase(CBH),leucine aminopeptidase(LAP),β-1,4-N-acetylglucoside(NAG)and phosphatase(AP).We analyzed the soil nutrient limitation by stoichiometry and enzyme metrology.The results showed a shift in soil pH from alkaline to acidic during vegetation restoration process,and that total phosphorus exhibited a gradual decrease over the course of 0 to 25 years.Soil orga-nic matter,total nitrogen and enzyme activities exhibited an increasing trend during the same time frame.However,between 25 and 45 years of age,soil total phosphorus,soil organic matter,total nitrogen,AP and LAP gradually declined while NAG,BG,and CBH initially increased and then decreased.Notably,the values of(BG+CBH)/(LAP+NAG),(BG+CBH)/AP and(LAP+NAG)/AP in R.pseudoacacia plantations were higher than the global average throughout the process of vegetation restoration.In the study area,the vector length was less than 1 and gradually increased,indicating that a progressive increase in microbial carbon limitation during the process of vegetation restoration.The vector angle exceeded 45°and exhibited an overall decreasing trend,suggesting that soil microorganisms were constrained by phosphorus(P)with a gradual deceleration of P limitation,without any nitrogen(N)limitation.The restoration of R.pseudoacacia plantation resulted in significant change in soil physical and chemical properties,while the time series of afforestation also influenced nutrient limitation of soil microorganisms.