[1] YAVITT J B, HARMS K E, GARCIA M N, et al. Spatial heterogeneity of soil chemical properties in a lowland tropical moist forest, Panama[J]. Austr J Soil Res, 2009, 47(7):674-687.
[2] LI Jianwei, de B RICHTER D, MENDOZA A, et al. Effects of land-use history on soil spatial heterogeneity of macro-and trace elements in the Southern Piedmont USA[J]. Geoderma, 2010, 156(1/2):60-73.
[3] SAUER T J, CAMBARDELLA C A, MEEK D W. Spatial variation of soil properties relating to plants changes[J]. Plant Soil, 2006, 280(1/2):1-5.
[4] HOLDO R M, MACK M C. Functional attributes of savanna soils:contrasting effects of tree canopies and herbivores on bulk density, nutrients and moisture dynamics[J]. J Ecol, 2014, 102(5):1171-1182.
[5] RODRÍGUEZ A, DURÁN J, FERNÁNDEZ-PALACIOS J M, et al. Spatial variability of soil properties under Pinus canariensis canopy in two contrasting soil textures[J]. Plant Soil, 2009, 322(1/2):139-150.
[6] GALLARDO A. Effect of tree canopy on the spatial distribution of soil nutrients in a Mediterranean Dehesa[J]. Pedobiologia, 2003, 47(2):117-125.
[7] 薛岑, 刘茂松, 康昕, 等.苏南丘陵山区典型次生森林群落的点格局分析[J].南京林业大学学报(自然科学版), 2016, 40(2):107-112.

XUE Cen, LIU Maosong, KANG Xin, et al. Point pattern analyses on typical secondary forest communities in the mountainous region of southern Jiangsu Province[J]. J Nanjing For UnivNat Sci Ed, 2016, 40(2):107-112.
[8] 张巍, 朱清科, 张婵婵, 等.陕北黄土区阳坡阔叶混交林结构及点格局分析[J].中国水土保持科学, 2017, 15(4):42-50.

ZHANG Wei, ZHU Qingke, ZHANG Chanchan, et al. Stand structure characteristics of broad-leaved mixed forest and point pattern analysis in loess sunny slope, northern Shaanxi[J]. Sci Soil Water Conserv, 2017, 15(4):42-50.
[9] 王磊, 孙启武, 郝朝运, 等.皖南山区南方红豆杉种群不同龄级立木的点格局分析[J].应用生态学报, 2010, 21(2):272-278.

WANG Lei, SUN Qiwu, HAO Chaoyun, et al. Point pattern analysis of different age-class Taxus chinensis var. mairei individuals in mountainous area of southern Anhui Province[J]. Chin J Appl Ecol, 2010, 21(2):272-278.
[10] 王潜, 李海涛, 梁涛, 等.鄱阳湖滨带优势灌木种群分布格局及其与土壤氮的关系[J].中国农学通报, 2011, 27(19):60-67.

WANG Qian, LI Haitao, LIANG Tao, et al. Spatial distribution pattern of dominant shrub species in poyang lake zone and its relationship to soil nitrogen[J]. Chin Agric Sci Bull, 2011, 27(19):60-67.
[11] 中国科学院内蒙古宁夏综合考察队.内蒙古植被[M].北京:科学出版社, 1985:467.
[12] 王旭东, 李忠, 包伟民, 等.乌海气候生产力对气候暖干化的响应[J].干旱区资源与环境, 2010, 24(12):100-105.

WANG Xudong, LI Zhong, BAO Weimin, et al. Response of climatic productivity to climate warming-drying trend in Wuhai[J]. J Arid Land Resour Environ, 2010, 24(12):100-105.
[13] 鲍士旦.土壤农化分析[M].北京:中国农业出版社, 2000:8-12.
[14] 陈剑磊, 谢文霞, 崔育倩, 等. SmartChem 140全自动化学分析仪测定土壤全氮全磷的研究[J].分析科学学报, 2016, 32(1):84-88.

CHEN Jianlei, XIE Wenxia, CUI Yuqian, et al. Research on the determination of total nitrogen and total phosphorus in soil using SmartChem 140 automatic chemical analyzer[J]. J Analyt Sci, 2016, 32(1):84-88.
[15] RIPLEY B D. Modelling spatial pattern[J]. J Roy Stat Soc Ser B Stat Methodol, 1977, 39:172-212.
[16] DIGGLE P J. Statistical Analysis of Spatial Point Patterns[M]. New York:Academic Press, 1983.
[17] 傅坤俊.中国植物志:第42卷第1分册[M].北京:科学出版社, 1993:46-54.
[18] 王辉, 孙栋元, 刘丽霞, 等.干旱荒漠区沙蒿种群根系生态特征研究[J].水土保持学报, 2007, 21(1):99-102.

WANG Hui, SUN Dongyuan, LIU Lixia, et al. Ecological characteristics of roots of Artemisa arenaria population in arid desert area[J]. J Soil Water Conserv, 2007, 21(1):99-102.
[19] 梁胜发, 茹豪, 雍鹏, 等.晋西北黄土丘陵区柠条锦鸡儿根系分布特征[J].东北林业大学学报, 2016, 44(8):24-28.

LIANG Shengfa, RU Hao, YONG Peng, et al. Root distribution characteristics of Caragana korshinskii in the loess hilly area of northwestern Shanxi Province[J]. J Northeast For Univ, 2016, 44(8):24-28.
[20] 赵玉洁, 张宇清.固氮类植物的生态功能及其在生态修复中的应用[J].干旱区资源与环境, 2012, 26(1):179-183.

ZHAO Yujie, ZHANG Yuqing. The ecological functions of nitrogen-fixing plants and their applications in ecological restoration[J]. J Arid Land Resour Environ, 2012, 26(1):179-183.
[21] 张晓蕾.塔干南缘骆驼刺和柽柳幼苗根系生长分布特征对不同水分处理的响应[D].北京: 中国科学院研究生院, 2010.

ZHANG Xiaolei. Effects of Different Soil Moisture Treatments on Root Growth and Distribution of the Seedlings of Alhagi sparsifolia Shap. and Tamarix ramosissima Ledeb. in the Taklimakan Desert[D]. Beijing: Graduate School of Chinese Academy of Sciences, 2010.
[22] 尚宗波, 高琼, 杨奠安.利用中国气候信息系统研究年降水量空间分布规律[J].生态学报, 2001, 21(5):689-694.

SHANG Zongbo, GAO Qiong, YANG Dianan. Spatial pattern analysis of annual precipitation with Climate Information System of China[J]. Acta Ecol Sin, 2001, 21(5):689-694.
[23] 陈广生, 曾德慧, 陈伏生, 等.干旱和半干旱地区灌木下土壤"肥岛"研究进展[J].应用生态学报, 2003, 14(12):2295-2300.

CHEN Guangsheng, ZENG Dehui, CHEN Fusheng, et al. A research review on "fertile islands" of soils under shrub canopy in arid and semi-arid regions[J]. Chin J Appl Ecol, 2003, 14(12):2295-2300.
[24] SARDANS J, PEÑUELAS J. Plants-soil interactions in Mediterranean forest and shrublands:impacts of climatic change[J]. Plant Soil, 2013, 365(1/2):1-33.
[25] 张武, 杨琳, 王紫娟.生物固氮的研究进展及发展趋势[J].云南农业大学学报, 2015, 30(5):810-821.

ZHANG Wu, YANG Lin, WANG Zijuan. Advance and development trend of biological nitrogen fixation research[J]. J Yunnan Agric Univ, 2015, 30(5):810-821.
[26] ROLO V, LÓPEZ-DÍAZ M L, MORENO G. Shrubs affect soil nutrients availability with contrasting consequences for pasture understory and tree overstory production and nutrient status in Mediterranean grazed open woodlands[J]. Nutr Cycl Agroecosyst, 2012, 93(1):89-102.
[27] 孙保平.荒漠化防治工程学[M].北京:中国林业出版社, 2001:27-28.
[28] 陆文龙, 曹一平, 张福锁.根分泌的有机酸对土壤磷和微量元素的活化作用[J].应用生态学报, 1999, 10(3):379-382.

LU Wenlong, CAO Yiping, ZHANG Fusuo. Role of root-exuded organic acids in mobilization of soil phosphorus and micronutrients[J]. Chin J Appl Ecol, 1999, 10(3):379-382.
[29] 陈凯, 马敬, 曹一平, 等.磷亏缺下不同植物根系有机酸的分泌[J].中国农业大学学报, 1999, 4(3):58-62.

CHEN Kai, MA Jing, CAO Yiping, et al. Exudation of organic acids by the roots of different plant species under phosphorus deficiency[J]. J China Agric Univ, 1999, 4(3):58-62.
[30] 张勇, 庞学勇, 包维楷, 等.土壤有机质及其研究方法综述[J].世界科技研究与发展, 2005, 27(5):72-78.

ZHANG Yong, PANG Xueyong, BAO Weikai, et al. A review of soil organic matter and its research methods[J]. World Sci-Tech R&D, 2005, 27(5):72-78