J Plant Ecol

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Abandoned corrals: colonization and vegetation recovery of ephemeral habitats in silvo-pastoral systems

Arie Vinograd1 , Eli Zaady2 and Jaime Kigel1, *   

  1. 1 Institute of Plant Science and Genetics in Agriculture, Robert H. Smith Faculty of Agriculture, Food and Environment, Hebrew University of Jerusalem, Rehovot 76100, Israel, 2 Department of Natural Resources, Gilat Research Center, ARO, Mobile Post Negev 85280, Israel

    *Corresponding author. E-mail: kigel@agri.huji.ac.il
  • Received:2020-03-26 Revised:2020-08-21 Accepted:2020-09-18 Online:2020-09-19 Published:2020-12-01

Abstract:

Aims

Management of silvo-pastoral systems in planted and natural forests in semi-arid Mediterranean regions often employs seasonal night corrals for animal protection. This management system changes the spatial distribution of animal excreta, resulting in a net transfer of soil mineral resources and their accumulation in the corrals. After abandonment, corrals are colonized by ruderal species, becoming focal sources for their spread in the forest. We aimed to implement a rational management of seasonal sheep corrals based on a better understanding of the vegetation processes occurring in abandoned corrals, in order to alleviate their negative impact in the forest.

Methods

Relationships between temporal changes in the vegetation, the soil seed-bank and levels of soil nutrients were studied in a chronosequence of abandoned sheep corrals and compared with nearby reference plots in planted Eucalyptus forests grazed by sheep in the semi-arid North-Western Negev, Israel. The region has a bi-seasonal Mediterranean climate, with high dominance of annual species in the grazing range.

Important Findings

Abandoned sheep corrals were colonized by seeds of ruderals originating in older abandoned corrals. Subsequent successional changes occur at a slow rate, driven by the depletion of soil resources in the abandoned corrals, and were still in progress 20 years after abandonment. Ruderals were gradually replaced, first by taller grasses and followed by short grasses, but most forbs and particularly geophytes did not recover during this period. Recovery of the original herbaceous vegetation in the corrals was through seed dispersal from the surrounding vegetation, not from the original soil seed-bank remaining in the corrals after abandonment. Ruderal species in the grazed, planted forests behave as patch-tracking metapopulations. Their persistency depends on constant creation of new corrals compensating for the gradually dwindling populations in older abandoned corrals, and on the availability of dispersal vectors.

Key words: metapopulation, ruderals, seasonal grazing, seed-bank, sheep, succession

摘要:
半干旱地中海地区人工林和天然林的林牧业系统管理经常使用季节性的夜间畜栏来保护动物。这种管理制度改变了动物排泄物的空间分布,导致土壤矿产资源的净转移和在畜栏内的积累。畜栏被遗弃后,荒地植物代替了畜栏,成为它们在森林中传播的集中来源。我们的目 的是在更好地了解废弃畜栏后植被生长过程的基础上,对季节性畜栏进行合理管理,以减轻其对森林的负面影响。本论文研究了以色列内盖夫(Negev)西北半干旱地区的人工桉树林(Eucalyptus)在废弃畜栏后的时间序列上,植被、土壤种子库和土壤养分水平的时间变化关系,并与附近的对照样地进行比较。该地区为双季节地中海型气候,放牧区内一年生物种占据优势。研究结果表明,废弃的羊畜栏被原产于旧的废弃畜栏的荒草种子定殖。在废弃畜栏土壤资源耗竭的驱动下,随后的演变速度缓慢,在畜栏废弃后20年仍在继续。荒草首先是被较高的草,然后是矮草所取代,但大多数为非禾草的杂类草植物,特别是在这一时期没有恢复的地下芽植物。畜栏内原有草本植被的恢复是通过种子从周围 植被中扩散,而不是从废弃后留在畜栏内的原始土壤种子库中恢复。在人工林放牧区中的荒草物种可视为具有斑块性的集合种群。它们的持久性依赖于不断创造新的畜栏来补偿旧的废弃畜栏中逐渐减少的种群,以及依赖于传播路径的有效性。

关键词: 集合种群, 荒草, 季节性放牧, 种子库, 羊群, 演替