Three Invasive Tree Species Change Soil Chemistry in Guam Forests

Thomas E Marler

doi:10.3390/f11030279

Abstract

Research Highlights: Established stands of Leucaena leucocephala (Lam.) de Wit, Spathodea campanulata P. Beauv., and Vitex parviflora Juss. modified soils in Guam’s limestone forests, reducing storage pools of carbon, nitrogen, and phosphorus. Background and Objectives: Invasive plants may engineer negative changes in ecosystem properties. This study was conducted to determine changes in soil chemistry following infestations of three problematic tree species on Guam. Materials and Methods: Minerals, metals, and mineralization dynamics were measured in invaded sites and paired sites with biodiverse native tree cover. Results: Most soil properties were significantly changed by long-term infestations of the invasive tree species. The soils within invaded sites exhibited total carbon, total nitrogen, and available phosphorus that were less than native sites. In contrast, the carbon/nitrogen ratio increased for every species-site combination. The other chemical properties were idiosyncratic among the sites and species. Conclusions: Mitigation and restoration activities that include the removal of these trees from project sites may require many years for the below-ground ecosystems to return to their native state. These three invasive trees decrease the ability of Guam soils to sequester recalcitrant forms of carbon, nitrogen, and phosphorus.

Highlights

Non-native plant species may cause profound changes to invaded forests
The pH, calcium, and zinc soil concentrations were not influenced by V. parviflora, but the remainder of properties differed between the V. parviflora stands and the native forest (Table 1, Figure 1)
The trees L. leucocephala and V. parviflora are exceptionally adept at this in Guam’s forests. This first Guam case study on biogeochemistry of invaded sites revealed that L. leucocephala, S. campanulata, and V. parviflora act as transformer species by engineering substantial changes to soil chemistry

Summary

Introduction

Non-native plant species may cause profound changes to invaded forests. Species that are able to displace resident native plants may create unique habitat process rates and controls which affect ecosystem nutrient and carbon cycles [1]. Some invasive plants may alter habitat functioning to the extent that ecosystem services are threatened [2,3,4,5]. The invasive plant species that possess the ability to engineer such consequential changes to forested habitats are sometimes called transformer species [10]. Recent assessments of plant invasion research illuminate the need to distinguish non-native species that carry minimal risk from invasive species that are high risk and link the likelihood of naturalization to these consequential impacts on the invaded habitats [11,12]

Methods

Results

Discussion

Conclusion