Soil and hydrological responses to wild pig (Sus scofa) exclusion from native and strawberry guava (Psidium cattleianum)-invaded tropical montane wet forests

Abstract

Soil and hydrological responses to wild pig (Sus scofa) exclusion from native and strawberry 1 guava (Psidium cattleianum)-invaded tropical montane wet forests 2 3 Abstract 17The structure and function of many ecosystems are threatened by non-native, invasive plant and 18 animal species. Globally, invasive trees alter interception, evapotranspiration, water use, and 19 throughfall, while wild pigs (Sus scofa) have been introduced and now invade widely ranging 20 ecosystems, with impacts to soil and groundcover, and as a consequence, infiltration, runoff and 21 water quality. In a resource management context, physical, chemical and biological control 22 methods can limit the impact of plants on native biodiversity while fence building and animal 23 removal can limit the effects of non-native ungulates on ecosystems. These expensive treatments 24 have documented biodiversity benefits, but few studies have quantified hydrological effects of 25 such management. Using paired fenced/unfenced runoff plots in native and P. cattleianum-26invaded Hawaiian tropical montane forests, we examined the independent and interactive effects 27 of strawberry guava (Psidium cattleianum), a highly invasive tree in tropical islands and wild 28 pigs on runoff amount, soil erosion rates and fecal indicator bacteria (FIB). We sampled 18 29 events spanning a 22 month period, and found that: 1) pigs are less active in invaded forests; 2) 30 higher stem densities in invaded forests were associated with lower soil erosion and runoff rates 31 compared to native forest; 3) reduced canopy cover and greater pig activity in native forests 32 resulted in higher runoff volumes, soil erosion rates, and runoff FIB content; and 4) unfenced 33 plots had more bare soil, less vegetation cover and greater soil FIB (E. coli, total coliforms, 34 enterococci) compared to fenced plots. These results point to the importance of understanding 35 the independent and interactive effects of multiple invaders on watershed function. In this study 36 system, removal of an invasive tree without fencing may actually lead to an increase in 37 disturbance, with impacts to both biodiversity and hydrological properties. 38

Simulating Land Cover Change Impacts on Groundwater Recharge under Selected Climate Projections, Maui, Hawaiʻi

“…Island-w future land cover scenarios, for both the wet and dry future climate strongly impacted groundwater recharge in localized areas. Th Futures 1 and 4 due to the substantial increases in estimated irriga i can also affect processes that influence groundwater recharge, including cloud-water interception, net precipitation, infiltration, direct runoff, and transpiration [8][9][10][11][12][13][14][15][16][17][18][19][20][21].…”

Rainfall and Streamflow Effects on Estuarine Staphylococcus aureus and Fecal Indicator Bacteria Concentrations

“…Road runoff and sewage samples were diluted with autoclaved, deionized water up to a volume of 100 mL for vacuum filtration. Soil samples were processed using methods described in Myers et al (2007) and Strauch et al (2016), where 10 g of soil were shaken with 200 mL of 0.15 M NaCl for 45 min at 100 rpm and left to settle for ∼5 min, and a supernatant aliquot was transferred into a sterile bottle with autoclaved, deionized water for vacuum filtration.…”

Changes in soil bacterial community diversity following the removal of invasive feral pigs from a Hawaiian tropical montane wet forest

“…Prior research has shown that feral pigs can influence nearly all aspects of their habitat 14–16 . Resultant changes include decreased diversity and abundance of plants 17,18 , fungi 19 , and wildlife 20,21 as well as being associated with the increased presence of specific bacteria in watersheds 22–24 . Comparatively, the effects of feral pigs on soils are typically highly variable, due to the narrow, localized effects of their trampling, wallowing, and rooting behaviors.…”

“…Specifically, feral pigs have been shown to affect the soil microbial community through defecation 6 and soil turbation 32 resulting in alterations specific to the composition of soil microbial communities 33 . For example, feral pigs have been associated with an increased presence of fecal coliform in watersheds 22 and have also been shown to increase the presence of specific bacteria, such as enterococci and leptospira, in soil runoff 23,24,34 . Feral pig activity has been directly associated with increased soil microbial activity attributed to potential increases of soil N availability associated with feces and urine 6,35 and indirectly via increased availability of soil organic matter 36 .…”