树种差异对哈尔滨市土壤理化性质影响及造林启示

Effect of Urban Tree Species on Soil Physicochemical Properties in Harbin,Northeastern China,and Afforestation Implications

东北地区的城市造林树种很多，树种差异对土壤理化性质的影响及其在不同土层深度差异对于适宜树种选择意义重大，但是基于野外长期定位研究结果匮乏。本文选择东北林业大学实验林场和哈尔滨市植物园的8个树种（水曲柳、胡桃楸、云杉、松树、杨树、榆树、黄檗、落叶松）进行0—20、20-40和40～60em分层土壤采样，对土壤pH、土壤电导率、有机碳、碱解氮、全N、速效磷、全P、速效钾、全K等9个指标进行研究。多因素方差分析显示，长期定植于类似土壤条件下，树木能够显著影响土壤各理化指标，但不同土壤层间存在明显差异。基于多重比较结果对各指标进行标准化处理、获得综合得分排名发现，榆树具有较好的土壤肥力维持能力（有机碳、碱解氮、全N、全P、速效磷、速效钾、全K），综合得分38，而杨树表现最差；降低土壤盐碱能力（pH和电导率）来看，黄檗、落叶松得分比较高（〉15），胡桃楸表现最差（7．5）。城市立地是典型困难立地，我们研究结果说明绿化树种选择对于改良城市土壤的重要性：对于贫瘠盐碱的核心区域，造林树种可以选择养分消耗少和降盐碱能力强的树种，对于土壤水肥条件优越的地区（如河道、湿地周边）可以考虑一些养分消耗快、生产力高的树种。

Owing to diversified urban tree species in Northeast China, their possible impact on soil fertility and salinity-alkalinity and different pattems on soil profile are significant for appropriate species selection, and data from long-tern1 permanent plots are very limited. Eight species （Fraxinus mandschurica, Juglans mandshurica, Picea spp. , Pinus spp. , Populus spp. , Ulmus pumila, Phellodendron amurense, Larix gmelinii ） were selected from the long-term plots in Harbin Experimental Forest Farm of Northeast Forestry University and Harbin Botanical Garden, and samples from 0 -20, 20 -40 and 40 -60 em soils were collected for measuring nine parameters of soil pH, electrical conductance （ EC ） , soil organic carbon （ SOC ）, alkali-hydrolyzed nitrogen （ AN）, total nitrogen （ TN ）, available phosphorus （ AP）, total phosphorus （ TP）, available potassium （AK） and total potassium（TK）. By a multivariate analysis of variance, tree species can significantly influence most of soil parameters at the same soil conditions, and different soil depth had significant differences. Based on multiple comparison results, all tested parameters were standardized as scores, and comprehensive scores for soil fertility maintaining ability（ SOC, N, P, K and its effective state） and for reducing soil saline-alkali degree （pH and EC） were respectively computed from above soil parameters. Much higher comprehensive scores in soil fertility maintaining ability were observed in different soil layers in species of Ulmus pumila（ scores at 38 ）, while lowest scores were generally found in Populus spp. （ scores at 26.5 ）. In the case of reducing soil saline-alkali ability, Phellodendron amurense and Larix gmelinii had higher scores（ 〉 15 ） , while Juglans mandshurica had the lowest scores（7.5 ）. When we divided trees into evergreen and deciduous species, no differences were found in fertility maintaining ability and saline-alkali declining ability （less than 15.6% differences ）. Our findings highlights that species selections for urban afforestation are important for tough site improvement. In the site of downtown with infertile soil and high saline-alkali degree, some species with high soil fertility maintaining should be chosen for their successful survival, while in fertile sites, such as river banks and wetlands, some species with high nutrient consumption and high growth rate could be selected for fast forest function rehabilitation. In the case of roadsides usually affected by high saline-alkali degrees from winter snow-melting, species with less saline-alkali declining ability should be avoided in afforestation practices.