Is Soil Fertility the Cause or the Effect of Land Invasion by Prosopis?

IF 2.6 3区农林科学 Q1 AGRONOMY

Journal of Plant Nutrition and Soil Science Pub Date : 2025-01-31 DOI:10.1002/jpln.202400442

Mathias Becker, Kai Behn, Gereon Heller, Hellen W. Kamiri

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引用次数: 0

Abstract

Background

For 20 years, Prosopis juliflora is aggressively spreading throughout the “Njemps Flats” in Kenya, where it changes vegetation cover and affects pastoral livelihoods. Its invasion dynamics is related to shallow groundwater tables (Prosopis being a phreatophyte), and it reportedly preferentially colonizes sites with favourable soil fertility attributes.

Aim

We contest this latter hypothesis, surmising that the N₂-fixing ability, the nutrient pumping by the deep root system, and year-round leaf litter fall will improve soil fertility attributes under Prosopis, irrespective of the initial soil status.

Methods

We assessed stand densities (number of individuals and their percentage cover) and selected soil attributes at 75 sites in the Njemps Flats. The stand densities of Prosopis were visualized by ground-truthed remote-sensed data, and subsequently related to soil fertility attributes. We further determined the isotope signatures (δ¹⁵N and δ¹³C) of the prevailing (past) C4-dominated pasture and the (current) C3-Prosopis vegetation, as well as at three depths of the topsoil.

Results

The findings confirm favourable fertility attributes (low EC and high N, C, P, and K contents) being associated with dense Prosopis stands. However, the isotope analysis of the topsoil indicates typical signatures of C4 vegetation in non-invaded pastureland and typical signatures of N₂-fixing C3-plants in the top 5 cm (but not at deeper layers) of soils in Prosopis stands. Prosopis contributes about 16% of N derived from fixation, and significantly increases C, N, P, and Ca contents of the topsoil.

Conclusions

We conclude that high soil fertility is the result rather than the driver of Prosopis invasion.

Abstract Image

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土壤肥力是藜入侵的原因还是结果？

20年来，黄花Prosopis juliflora在肯尼亚的“Njemps平原”迅速蔓延，改变了植被覆盖，影响了牧民的生计。它的入侵动态与浅层地下水位有关（Prosopis是一种深生植物），据报道，它优先在土壤肥力有利的地方定居。我们对后一种假设提出了质疑，推测无论土壤初始状态如何，Prosopis的固氮能力、深层根系的养分泵送和全年凋落叶都会改善土壤肥力属性。方法对Njemps平原75个样地的林分密度（个体数及其盖度百分比）和土壤属性进行评估。利用地面遥感数据可视化拟南豆林分密度，并将其与土壤肥力属性相关联。进一步测定了（过去）以c4为主的牧草和（现在）C3-Prosopis植被的同位素特征（δ15N和δ13C），以及表土的三个深度。结果研究结果证实，浓密的藜林具有良好的育性特性（低EC和高N、C、P、K含量）。表层土壤同位素分析表明，非入侵牧场土壤具有典型的C4植被特征，而黑松林分土壤表层5 cm土壤具有典型的固氮c3植物特征。腐殖酸贡献了约16%的固定氮，显著提高了表层土壤的C、N、P和Ca含量。结论高土壤肥力是黄豆入侵的结果而非驱动因素。

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来源期刊

Journal of Plant Nutrition and Soil Science 农林科学-农艺学

CiteScore

4.70

自引率

8.00%

发文量

审稿时长

8-16 weeks

期刊介绍： Established in 1922, the Journal of Plant Nutrition and Soil Science (JPNSS) is an international peer-reviewed journal devoted to cover the entire spectrum of plant nutrition and soil science from different scale units, e.g. agroecosystem to natural systems. With its wide scope and focus on soil-plant interactions, JPNSS is one of the leading journals on this topic. Articles in JPNSS include reviews, high-standard original papers, and short communications and represent challenging research of international significance. The Journal of Plant Nutrition and Soil Science is one of the world’s oldest journals. You can trust in a peer-reviewed journal that has been established in the plant and soil science community for almost 100 years. Journal of Plant Nutrition and Soil Science (ISSN 1436-8730) is published in six volumes per year, by the German Societies of Plant Nutrition (DGP) and Soil Science (DBG). Furthermore, the Journal of Plant Nutrition and Soil Science (JPNSS) is a Cooperating Journal of the International Union of Soil Science (IUSS). The journal is produced by Wiley-VCH. Topical Divisions of the Journal of Plant Nutrition and Soil Science that are receiving increasing attention are: JPNSS – Topical Divisions Special timely focus in interdisciplinarity: - sustainability & critical zone science. Soil-Plant Interactions: - rhizosphere science & soil ecology - pollutant cycling & plant-soil protection - land use & climate change. Soil Science: - soil chemistry & soil physics - soil biology & biogeochemistry - soil genesis & mineralogy. Plant Nutrition: - plant nutritional physiology - nutrient dynamics & soil fertility - ecophysiological aspects of plant nutrition.