我国森林土壤全磷密度分布特征

Distribution of soil total phosphorus density in China's forests

土壤磷可利用性显著影响森林生产力和固碳能力。了解我国森林土壤全磷密度在土壤、气候和植被等不同环境条件下的分布特征,为我国森林质量提升和固碳增汇提供理论指导。收集全国森林土壤调查数据和文献数据中0—20 cm(2571个样地)、20—40 cm(1305个样地)、40—60 cm(701个样地)、60—80 cm(40个样地)和80—100 cm(31个样地)土层土壤全磷含量和容重以估算土壤全磷密度,采用单因素方差分析和Tukey HSD法(或Mann-Whitney U法)检验土壤全磷密度在不同土层、土壤类型、土壤风化程度、气候区、森林起源、森林结构、林龄组、森林类型和树种组之间的差异,利用线性回归分析探讨土壤全磷密度的纬度和经度变化趋势。结果表明:(1)我国森林40—60 cm土层(9.02 t/hm^(2))土壤全磷密度显著低于表层0—20 cm(13.81 t/hm^(2))和20—40 cm(10.84 t/hm^(2))以及深层60—80 cm(11.28 t/hm^(2))和80—100 cm(12.76 t/hm^(2))(P<0.001),0—60 cm土层土壤全磷密度表现为中度风化(11.89—18.86 t/hm^(2))>轻度风化(10.19—11.13 t/hm^(2))>重度风化(5.44—8.89 t/hm^(2)),在土壤类型间差异显著(P<0.001),铁铝土的值最低(5.44—8.89 t/hm^(2));(2)土壤全磷密度随着纬度的增加线性增加,但随着经度的增加线性降低(除0—20 cm土层),自热带向北温带也呈增加趋势;(3)我国森林0—60 cm土层土壤全磷密度表现为人工林(11.54—15.49 t/hm^(2))显著高于天然林(7.14—11.93 t/hm^(2))及纯林(12.16—15.40 t/hm^(2))显著高于混交林(6.06—12.15 t/hm^(2)),在林龄组和森林类型间差异显著(P<0.001),0—20 cm和20—40 cm土层中过熟林(23.10 t/hm^(2)和12.54 t/hm^(2))和落叶针叶林(19.49 t/hm^(2)和15.30 t/hm^(2))土壤全磷密度最高,40—60 cm土层土壤全磷密度随着林龄的增加而降低。总体来看,我国森林0—100 cm土层土壤全磷密度存在明显的空间分布规律,其在土壤、气候和植被类别间差异显著,这些生物与非生物因素是影响我国森林土壤全磷高低和分布特征的重要因子;延长轮伐期和种植混交林是维持和提高我国森林土壤全磷养分可持续利用的重要途径。

Soil phosphorus availability significantly affects forest productivity and carbon sequestration capacity.Understanding the distribution characteristics of total phosphorus(TP)density under different environmental conditions such as soil,climate,and vegetation is important to provide theoretical guidance for forest quality improvement and carbon sequestration.However,these distributions of soil TP density in China′s forests are still poorly understood.In this study,soil TP content and bulk density at soil depths of 0—20 cm(2571 plots),20—40 cm(1305 plots),40—60 cm(701 plots),60—80 cm(40 plots),and 80—100 cm(31 plots)were collected from national survey data and literature data to estimate soil TP density.Differences in soil TP density in different soil layers,soil types,soil weathering levels,climate zones,forest origins,forest structures,age groups,forest types,and species groups were tested by one-way ANOVA and Tukey HSD(or Mann-Whitney U)method.The latitudinal and longitudinal trends of soil TP density were analyzed by linear regression analysis.The soil TP density of 40—60 cm(9.02 t/hm^(2))was significantly lower than that of surface soil such as 0—20 cm(13.81 t/hm^(2))and 20—40 cm(10.84 t/hm^(2)),as well as deep soil such as 60—80 cm(11.28 t/hm^(2))and 80—100 cm(12.76 t/hm^(2))(P<0.001).It was characterized by a trend of intermediate weathering(11.89—18.86 t/hm^(2))>slight weathering(10.19—11.13 t/hm^(2))>strong weathering(5.44—8.89 t/hm^(2))at each layer of 0—60 cm.There were significant differences in soil TP density among soil types(P<0.001),with the lowest value of Ferralisols(5.44—8.89 t/hm^(2)).The soil TP density increased linearly with the increase of latitude,but decreased linearly with the increase of longitude(except for 0—20 cm),and showed an increased tendency from the tropical zone to the north-temperate zone.The soil TP density at each layer of 0—60 cm was significantly higher in planted forests(11.54—15.49 t/hm^(2))than in natural forests(7.14—11.93 t/hm^(2))and in pure forests(12.16—15.40 t/hm^(2))than in mixed forests(6.06—12.15 t/hm^(2)).The soil TP density also showed significant differences among age groups and forest types(P<0.001),with the highest value in over-mature forests(23.10 t/hm^(2) and 12.54 t/hm^(2))and deciduous coniferous forests(19.49 t/hm^(2) and 15.30 t/hm^(2))at depths of 0—20 cm and 20—40cm.But it decreased with the increase of forest age at the depth of 40—60 cm.In conclusion,there was an obviously spatial distribution of TP density at the depth of 0—100 cm in China′s forests and there were significant differences in soil TP density among soil,climate,and vegetation types.These biotic and abiotic factors were important to affect the size and distribution characteristics of soil TP in China′s forests.Extending the rotation period and planting the mixed forests are important pathways to maintain and improve the sustainable utilization of soil TP in China′s forests.