Department of Integrative Biology, University of South Florida, Tampa, Florida, 33620, USA.
School of Geosciences, University of South Florida, Tampa, Florida, 33620, USA.
Ecol Appl. 2019 Apr;29(3):e01870. doi: 10.1002/eap.1870. Epub 2019 Mar 8.
Over 80% of amphibian species that are declining are forest dependent. Forestry practices are a major cause of forest alterations globally, and it is well documented that clearcutting can contribute to amphibian declines. However, there might be adverse effects of forestry practices other than clearcutting. For example, planting overstory trees in rows (plantations) can change groundcover microhabitats and soil moisture levels, but the effects of this common practice on amphibian populations are not well studied. We compared the impacts of common intensive pine plantation operations to naturally regenerated pine forests on the desiccation, movement rates, behavior, and survival of >900 juvenile southern toads (Anaxyrus terrestris). Pine plantations had significantly more accumulation of conifer needles and less exposed soil, herbaceous groundcover, broadleaf litter, and soil moisture than natural pine forests despite the greater canopy cover at plantations. Litter cover explained 85% of groundcover microhabitat variance among forest types and predicted minimum soil moisture levels. When toads were held in small outdoor enclosures that constrained microhabitat selection, 24-h desiccation rates and 72-h mortality were significantly greater in pine plantation than in naturally regenerated pine forest because of lower soil moisture, especially during low rainfall periods. In large outdoor pens where juvenile amphibians could select microhabitats, movement was strongly directed down slope and increased with precipitation. However, initial speeds were positively associated with pine density, likely because toads were trying to evacuate from the drier high-pine-density areas. High-intensity silviculture practices that eliminate herbaceous or vegetative groundcover, such as roller chopping and scalping, increase amphibian desiccation because planted conifers dry the upper soil layer. Our study highlights the importance of prioritizing lower intensity silviculture practices or lower pine densities to retain groundcover microhabitat that serves as amphibian refugia from dry conditions that are predicted to increase in frequency with climate change.
超过 80%的数量减少的两栖物种是依赖森林的。林业实践是全球森林变化的主要原因，而且有大量文献记载表明皆伐可能导致两栖动物的减少。然而，除了皆伐之外，林业实践可能还有其他不利影响。例如，成行种植上层树木（人工林）会改变地面覆盖的微生境和土壤水分水平，但这种常见做法对两栖动物种群的影响尚未得到充分研究。我们比较了常见的集约型松树林作业与自然再生松林对超过 900 只幼年南方蟾蜍（Anaxyrus terrestris）的干燥、移动速度、行为和存活的影响。尽管松林种植园的树冠覆盖率较高，但松林种植园的针叶堆积量明显更多，暴露的土壤、草本地面覆盖物、阔叶落叶和土壤水分较少。落叶覆盖物解释了森林类型之间 85%的地面覆盖微生境差异，并预测了最低土壤水分水平。当蟾蜍被关在小的户外围栏中，限制微生境选择时，由于土壤水分较低，特别是在降雨量较低的时期，松林种植园的 24 小时干燥率和 72 小时死亡率明显高于自然再生松林。在大型户外围栏中，幼年两栖动物可以选择微生境，移动强烈指向下坡，并随降水增加而增加。然而，初始速度与松树密度呈正相关，这可能是因为蟾蜍试图从较干燥的高松树密度区域撤离。高强度的造林实践，如滚轮砍伐和削顶，会消除草本或植被地面覆盖物，增加两栖动物的干燥，因为种植的针叶树会使上层土壤变干。我们的研究强调了优先考虑低强度造林实践或降低松树密度以保留地面覆盖微生境的重要性，这些微生境是两栖动物躲避干燥条件的避难所，而这些干燥条件预计会随着气候变化的频率增加。
