Land use legacy effects on structure and composition of subtropical dry forests in St. Croix, US Virgin Islands
Land use legacy effects on structure and composition of subtropical dry forests in St. Croix, US Virgin Islands
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DOI：
10.1016/j.foreco.2014.09.033
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发表时间：
2015-01-01
影响因子：
3.7
通讯作者：
Marin-Spiotta, Erika
中科院分区：
文献类型：
--
作者：
Atkinson, Emily E.;Marin-Spiotta, Erika
热带干燥森林受到巨大的人类压力和土地变化的影响，包括转变为农作物、牧场或农林业，以及城市的侵占。经过数十年甚至数百年的转换、扩张、再生长和土地利用实践的变化，可以形成具有不同土地利用历史的次生生长斑块。虽然后农业景观可能表现为森林更新的连续区域，但森林斑块从历史土地覆盖到其当前状态的演替轨迹可能存在很大差异，从而对物种组成和生态系统结构和功能产生影响。研究了不同土地利用历史对美属维尔京群岛圣克罗伊岛亚热带干旱森林结构、生物量和组成的影响。我们对三种类型的次生林进行了采样，这些次生林在几个世纪的甘蔗农业之后遵循不同的更新路径：40年的次生林在甘蔗废弃后自然更新，40年的次生林在停止经营之前重新造林，并被自然演替所取代，10年的次生林在最近的森林更新之前是集约化牧场。甘蔗种植后自然再生的次生林在基面积、茎密度、地上生物量和物种多样性等方面与原为人工林的同年龄次生林具有相似的结构特征。然而，物种组成仍然明显。两种类型40年生长林的组成差异部分归因于人工林物种，特别是mahagoni swetenia，而自然更新林则以常见的次生林物种Melicoccus bijugatus和Cordia alba为主。飓风破坏的影响有助于解释自然再生次生林和原人工林在结构上的相似性和组成上的差异性。林龄对森林结构和组成有显著影响。10年生次生林与40年生次生林之间的差异主要受固氮物种银合欢（Leucaena leucocephala）的优势驱动，这种固氮物种在10年生次生林中迅速建立，导致更高的茎密度和更低的基面积、生物量和物种丰富度。研究结果表明，土地利用历史在物种组成的形成中起着重要作用，特别是在农业后热带干燥森林中。虽然具有不同土地利用历史的森林在废弃后的几十年内在结构上可能彼此相似，但物种组成可能在更长时间内保持不同。了解人类土地利用的遗产对于具有长期干扰历史的干燥森林和预测其对未来环境变化的反应非常重要。(C) 2014 Elsevier B.V.版权所有
Tropical dry forests are subject to intense human pressure and land change, including conversion to agricultural crops, pasture or agroforestry, and urban encroachment. Decades, and even centuries, of conversion, expansion, regrowth, and changing land-use practices can result in a mosaic of secondary growth patches with different land-use histories. Whereas post-agricultural landscapes may appear as contiguous areas of forest regeneration, the successional trajectory of forest patches from historic land cover to their current state may differ substantially, with consequences for species composition and ecosystem structure and function. We examined the effect of different land-use histories on current forest structure, biomass, and composition in subtropical dry forests in St. Croix, U.S. Virgin Islands. We sampled three types of secondary forests that followed different regeneration pathways after centuries of sugarcane agriculture: 40-year old secondary forests that naturally regenerated after sugarcane abandonment, 40-year old secondary forests that were reforested with timber plantations before management ceased and they were overtaken by natural succession, and 10-year old secondary forests that were intensive pasture prior to recent forest regeneration. Secondary forests that naturally regenerated after sugarcane had similar structural characteristics, in terms of basal area, stem density, aboveground biomass, and species diversity compared to secondary forests of the same age that were former plantations. Species composition, however, remained distinct. Compositional differences between the two types of 40-year old secondary forests could be partially attributed to plantation species, specifically Swietenia mahagoni, whereas naturally regenerated forests were dominated by common secondary forest species, such as Melicoccus bijugatus and Cordia alba. The effects of hurricane damage helped to explain structural similarity and compositional dissimilarity between naturally regenerated secondary forests and former plantations. Forest age had a significant effect on forest structure and composition. Differences between 10-year old and both types of 40-year old secondary forests were driven by a dominance of the nitrogen-fixing species Leucaena leucocephala, which rapidly established in 10-year old secondary forests and resulted in greater stem density and lower basal area, biomass, and species richness. Our results show that land-use history plays an important role in shaping species composition, especially in post-agricultural tropical dry forests. Although forests with differing land-use histories may structurally resemble one another within decades of abandonment, species composition may remain distinct for much longer. Understanding the legacy of human land use is important for dry forests that have a long history of disturbance and for predicting their response to future environmental change. (C) 2014 Elsevier B.V. All rights reserved.