College of Desert Control Science and Engineering, Inner Mongolia Agricultural University, Hohhot, Inner Mongolia, China.
Forest General Site of Ordos City, Ordos, Inner Mongolia, China.
PeerJ. 2024 May 31;12:e17512. doi: 10.7717/peerj.17512. eCollection 2024.
The sand fixing shelter forests in the Horqin Sandy Land are a key area in the "3-North" Shelter Forest Program in China, which has a history of over 50 years of artificial afforestation. Carr is one of the most dominant silvicultural species in the region. The aim of this study is to understand the soil characteristics and soil fertility of shelter forests at different growth stages and to establish a scientific basis for soil nutrient regulation and sustainable management of shelter forests at the southern edge of the Horqin Sandy Land. Sample plots were selected for young (≤15 a), middle-aged (16-25 a), near-mature (26-30 a), mature (31-40 a), and over-mature (≥41 a) forests. Each forest studied was in a state of natural restoration with uniform stand conditions and no artificial fertilizer was applied. These sites were selected to study changes in the soil characteristics in soil depths of 0-20, 20-40, and 40-60 cm. In order to avoid the problem of multicollinearity between soil variables and to reduce redundancy, principal component analysis (PCA), Pearson's correlation analysis, and Norm value calculation were used to select the least correlated indicators with the highest factor loadings. This was used to establish the minimum data set. The soil fertility quality of these shelterbelts in different forest ages was quantified using the soil quality index (SQI). In the growth stage from young to nearly mature forests, the soil bulk weight and pH decreased with increasing forest age. Soil capillary porosity, noncapillary porosity, total porosity, water content, field water holding capacity, and organic carbon content increased with increasing forest age and soil nutrient content gradually improved. At the stage of near-mature to over-mature forests, the effect of forest age on soil bulk density was not significant and all other soil characteristics decreased to varying degrees as the forest age increased. The soil also developed from alkaline to neutral. The SQI of the total data set and the SQI of the minimum data set consistently showed that near-mature forests (NMF) > middle-aged forests (MAF) > mature forests (MF) > over-mature forests (OMF) > young forests (YF). The results of the two evaluation systems showed a significant positive correlation ( < 0.05, R = 0.8263) indicating that it is feasible to use the minimum data set to evaluate the soil fertility of shelter forests of different forest ages. The age of the forest has an obvious effect on the soil characteristics and overall soil fertility of shelter forests. The shelter forests on the southern edge of the Horqin Sandy Land have great soil development at the early stage of afforestation and the soil nutrient content gradually increases. The soil fertility reaches a peak when the forest is nearly mature and the soil fertility declines after the age of the forest reaches 30 years.
科尔沁沙地固沙林是中国“三北”防护林工程的重点区域之一，已有 50 多年的人工造林历史。 山杏是该地区最主要的造林树种之一。本研究旨在了解不同生长阶段固沙林的土壤特性和土壤肥力，为科尔沁沙地南缘固沙林的土壤养分调节和可持续经营提供科学依据。 选择了幼龄林（≤15 年）、中龄林（16-25 年）、近熟林（26-30 年）、成熟林（31-40 年）和过熟林（≥41 年）林分作为样地。每个研究林分均处于自然恢复状态，林分条件均匀，未施加人工肥料。这些样地的选择是为了研究土壤特性在 0-20cm、20-40cm 和 40-60cm 土壤深度的变化。为避免土壤变量之间的共线性问题和减少冗余，采用主成分分析（PCA）、皮尔逊相关分析和 Norm 值计算，选择与因子负荷量最高的相关性最小的指标，以此建立最小数据集。采用土壤质量指数（SQI）对不同林龄固沙林的土壤肥力质量进行量化。在幼龄林到近熟林的生长阶段，随着林龄的增加，土壤容重和 pH 值逐渐降低。土壤毛管孔隙度、非毛管孔隙度、总孔隙度、含水量、田间持水量和有机碳含量随着林龄的增加而增加，土壤养分含量逐渐改善。在近熟林到过熟林阶段，林龄对土壤容重的影响不显著，随着林龄的增加，所有其他土壤特性均不同程度下降，土壤也由碱性向中性发展。全数据集的 SQI 和最小数据集的 SQI 一致表明，近熟林（NMF）＞中龄林（MAF）＞成熟林（MF）＞过熟林（OMF）＞幼龄林（YF）。两种评价体系的结果呈显著正相关（<0.05，R=0.8263），表明使用最小数据集来评价不同林龄固沙林的土壤肥力是可行的。林龄对固沙林的土壤特性和整体土壤肥力有明显影响。科尔沁沙地南缘的固沙林在造林初期具有很大的土壤发育潜力，土壤养分含量逐渐增加。当林龄接近成熟时，土壤肥力达到峰值，当林龄达到 30 年以上时，土壤肥力开始下降。
