Pastoralism and agro-pastoralism are the major modes of life in arid and semi-arid rangelands. However, rangeland quality and quantity are rapidly deteriorating due to a number of natural and human-induced factors, one of which is bush encroachment. Little is known on how bush encroachment affects the ecosystem functions and services expressed in terms of the native vegetation composition and structure, status of the soil seed bank, soil chemical and physical properties, and the abundance of mycorrhiza spores. We assessed woody species in 64 plots distributed across four levels of Prosopis juliflora invasion (high, medium, low, and none) at two sites, Amibara and Gewane, in the Afar Region, Ethiopia. We collected composite soil samples to investigate the soil seed bank, mycorrhizal associations, and spore abundance. Plant biodiversity was generally low, with eight and four woody species in Gewane and Amibara, respectively. Prosopis juliflora was dominant in highly, moderately, and lowly invaded areas while Acacia senegal dominated the non-invaded areas. The average number of P. juliflora individuals ranged from 3/ha at non-invaded areas in Gewane to 4200/ha at highly invaded areas in Amibara while the total individual number of native woody species ranged from 0 to 88/ha at highly and lowly invaded areas, respectively. The population structure of trees/shrubs in all invasion areas showed an inverted J-shaped distribution, characterized by a high abundance of small individuals. Prosopis juliflora invasion was associated with high soil OC, Na, Ca, P, bulk density, and moisture content. Herbaceous seed numbers and species richness were highest in the moderately and highly invaded areas. All sampled tree species were associated with mycorrhiza but the percentage of root length colonization by different arbuscular mycorrhizal fungus structures varied significantly (p < 0.05) across invasion categories and sites. Our results revealed that although P. juliflora invasion negatively impacted the availability of native woody livestock forage species, it had a positive effect on most soil physical and chemical properties. Such variable effects call out for sustainable management practices when invaded areas are restored.

中文翻译：

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埃塞俄比亚阿法尔放牧土地上朱利氏螺旋藻入侵下土壤性质和天然木本植物物种丰度的变化

牧民主义和农牧民主义是干旱和半干旱牧场的主要生活方式。然而，由于许多自然和人为因素，牧场的质量和数量正在迅速恶化，其中之一是灌木丛侵占。关于灌木丛的侵害如何影响生态系统功能和服务的知之甚少，这些方面体现在原生植被组成和结构，土壤种子库的状况，土壤化学和物理特性以及菌根孢子的丰富度方面。我们评估了埃塞俄比亚阿法尔地区Amibara和Gewane这两个地点分布在四个水平的Prosopis juliflora入侵（高，中，低和无）的64个样地中的木本物种。我们收集了复合土壤样品，以调查土壤种子库，菌根协会和孢子丰度。植物生物多样性普遍较低，在格瓦内和阿米巴拉分别有八种和四种木本物种。在高，中和低度入侵地区，朱利氏丙酸杆菌占主导地位，而塞内加尔的金合欢占主导地位。胡桃李的平均个体数量从Gewane非侵袭区的3 /公顷到Amibara高度侵袭区的4200 / ha不等，而天然木本物种的总数在高和低范围从0-88 / ha不等。入侵地区。所有入侵地区的树木/灌木的种群结构呈倒J形分布，其特征是小个体数量很多。水生的Prosopis juliflora入侵与高土壤OC，Na，Ca，P，堆积密度和水分含量有关。中度和高度入侵地区的草本种子数量和物种丰富度最高。所有采样的树种均与菌根有关，但在入侵类别和部位之间，不同丛枝菌根真菌结构的根长定殖百分比差异显着（p <0.05）。我们的结果表明，尽管胡桃木的入侵对本地木本牲畜饲草物种的可利用性产生了负面影响，但它对大多数土壤理化性质具有积极影响。当入侵地区恢复时，这种可变的影响要求采取可持续的管理措施。05）。我们的结果表明，尽管胡桃木的入侵对本地木本牲畜饲草物种的可利用性产生了负面影响，但它对大多数土壤理化性质具有积极影响。当入侵地区恢复时，这种可变的影响要求采取可持续的管理措施。05）。我们的结果表明，尽管胡桃木的入侵对本地木本牲畜饲草物种的可利用性产生了负面影响，但它对大多数土壤理化性质具有积极影响。当入侵地区恢复时，这种可变的影响要求采取可持续的管理措施。