探索营造异龄复层近自然混交林以期改善土壤肥力的经营措施,明晰套种对杉木纯林土壤肥力的影响趋势,对我国南方杉木低产低效林的改造具有重要意义.以福建闽北林区27年生杉木纯林、杉木(27年生)×南方红豆杉(7年生、8年生、9年生)混交林为研究对象,采用五点取样法选取4种林分样地的土壤,分成0-20 cm、20-40 cm、40-60 cm 3个土层,对各土层的土壤理化性质及酶活性数据进行分析,探究林龄和土层对土壤肥力的影响.结果表明:(1)酶活性随土层增加逐渐降低,脲酶、蔗糖酶活性随套种年限的增加逐年递减.(2)混交林土壤的物理性质均在第8年升至最高,其中土壤持水量和土壤孔隙度在第9年下降,而土壤密度在第9年上升.土壤的水解氮、有效磷含量在第7年、第8年上升,在第9年下降,而速效钾含量则在第7年锐减后逐年递增.(3)土壤脲酶活性与全氮、有效磷、全钾含量呈极显著正相关;蔗糖酶与有机质、水解氮及有效磷含量呈极显著正相关;磷酸酶与土壤持水能力呈极显著正相关(P＜0.01).(4)混交林的土壤肥力排序为第8年＞第7年＞第9年＞CK.综上,混交林各营养指标均高于纯林,且混交林土壤理化性质和酶活性间相互作用明显,表明林下套种南方红豆杉可以显著改善杉木纯林的土壤理化性质,提升土壤肥力;结果可为营造异龄复层的近自然混交林,探索套种树种与原树种的养分分配利用关系以及养分补充年限提供参考.(图2表7参53)
Effects of understory Taxus chinensis var.mairei planting on soil fertility of Chinese fir plantations
This study explored the management measures aimed at establishing heterogeneous near-natural mixed forests to enhance soil fertility and elucidate the effect of set-aside planting on the soil fertility of Chinese fir pure forests.The findings of this study are of importance to the transformation of low-yield and low-efficiency forests of Chinese fir in southern China.The study was conducted in a 27-year-old pure Chinese fir forest and a mixed forest consisting of a Chinese fir(27-year-old)and Taxus chinensis var.mairei(7-year-old,8-year-old,9-year-old)in the northern forest area of Fujian Province,China.Soil from the four sample plots was obtained using the five-point sampling method and divided into three soil layers 0-20 cm,20-40 cm,and 40-60 cm.The physicochemical properties and enzyme activities of the soil horizons were analyzed to explore the effects of stand age and soil layer on soil fertility.(1)Enzyme activities gradually decreased with an increase in soil layers,and the activities of urease and sucrase decreased annually with an increase in the number of years in the set.(2)The physical properties of soil in the mixed forest all rose to their highest levels in the 8th year,whereas in the 9th year,soil water-holding capacity and porosity decreased and soil density increased.The hydrolyzed nitrogen and effective phosphorus contents of the soil increased in the 7th and 8th year and decreased in the 9th year,whereas the quick-acting potassium content increased annually after a sharp decrease in the 7th year.(3)Soil urease activity showed significant and positive correlation with total nitrogen,effective phosphorus,and total potassium content;sucrase activity was significantly and positively correlated with organic matter,hydrolyzed nitrogen,and effective phosphorus content;and phosphatase activity was significantly and positively correlated with soil water-holding capacity(P＜0.01).(4)The soil fertility of the mixed forest was ranked as follows:8 a＞7 a＞9 a＞CK.All the nutrient indices of the mixed forests were higher than those of the pure forests,and there was a significant interaction between the soil physicochemical properties and enzyme activities of the mixed forests,indicating that understory planting of T.chinensis var.mairei significantly improved the physicochemical properties of pure Chinese fir forests and enhanced soil fertility.This study provide references and insights for establishing mixed near-natural forests with heterogeneous age complexes.Additionally,it sheds light on the nutrient allocation and utilization relationship between set-aside and original species,providing valuable information on the optimal duration for nutrient replenishment.
mixed forestsoil fertilityenzymatic activityforest age differences
NETL
NSTL
万方数据
