Effects of Liming on Forage Availability and Nutrient Content in a Forest Impacted by Acid Rain

Brittingham MC (2012) Effects of Liming on Forage Availability and Nutrient Content in a Forest Impacted by Acid Rain. PLoS ONE 7(6): e39755. doi:10.1371/journal.pone.0039755 Effects of Liming on Forage Availability and Nutrient Content in a Forest Impacted by Acid Rain Sarah E. Pabian 0 1 Nathan M. Ermer 0 1 Walter M. Tzilkowski 0 1 Margaret C. Brittingham 0 1 Peter Shaw, Roehampton University, United Kingdom 0 a Current address: Biology Department, Colorado State University , Fort Collins , Colorado, United States of America b Current address: New York State Department of Environmental Conservation, Division of Fish , Wildlife, and Marine Resources, New Paltz, New York , United States of America 1 School of Forest Resources, Pennsylvania State University , University Park, Pennsylvania , United States of America Acidic deposition and subsequent forest soil acidification and nutrient depletion can affect negatively the growth, health and nutrient content of vegetation, potentially limiting the availability and nutrient content of forage for white-tailed deer (Odocoileus virginianus) and other forest herbivores. Liming is a mitigation technique that can be used to restore forest health in acidified areas, but little is known about how it affects the growth or nutrient content of deer forage. We examined the effects of dolomitic limestone application on the growth and chemical composition of understory plants in an acidified forest in central Pennsylvania, with a focus on vegetative groups included as white-tailed deer forage. We used a BeforeAfter-Control-Impact study design with observations 1 year before liming and up to 5 years post-liming on 2 treated and 2 untreated 100-ha sites. Before liming, forage availability and several nutrients were below levels considered optimal for white-tailed deer, and many vegetative characteristics were related to soil chemistry. We observed a positive effect of liming on forb biomass, with a 2.7 fold increase on limed sites, but no biomass response in other vegetation groups. We observed positive effects of liming on calcium and magnesium content and negative effects on aluminum and manganese content of several plant groups. Responses to liming by forbs and plant nutrients show promise for improving vegetation health and forage quality and quantity for deer. - Soil nutrient availability and related forage quality are known correlates of diet, health and morphometrics of many cervid species [15]. They are included in habitat suitability models of white-tailed deer (Odocoileus virginianus) [6] and are recommended for inclusion in deer management plans [7]. Although soil nutrients and related forage quality are acknowledged as important factors in cervid habitat quality, the current acidification and nutrient depletion in forest soils have received little attention in cervid forage quality research. Forest soil conditions in the northeastern United States, and many areas around the world, have become increasingly acidic and depleted of base cation nutrients, including calcium, magnesium, and potassium as a result of acidic deposition, forest harvesting, forest growth and maturation, and land use patterns [811]. These changes in soil conditions are affecting critical components of cervid habitat suitability, including forest vegetation health, forage availability and species composition, and nutrient content [1214], yet very little is known how changes in soil conditions might affect cervids and the quality and quantity of their forage. Strong relationships from soil nutrient availability to forage quality to white-tailed deer morphometrics have been established [4,5,7], but there has been no experimental evaluation of the potential for changes in soil conditions to degrade deer habitat quality. Changes in base cation nutrient availability in soils can affect abundance, species composition and nutrient content of vegetation [13,14]. Also, poor soil conditions can result in reduced ability of vegetation to withstand high levels of browse [15]. Any changes in the calcium, magnesium, phosphorus, potassium and protein content of forage could affect deer because they are required for many life functions including bone formation and maintenance, cell function, reproduction, lactation, and antler growth [16,17]. Particularly high levels of calcium and phosphorus are required for females during lactation and for males during antler growth [16,18]. Also, changes in soil conditions can change phosphorus availability, which can be a limiting nutrient in ungulate herbivores [17,19], and crude protein content of forage, a well-known correlate to deer morphometrics, can also differ among soil regions [20]. While we predicted that soil acidification could negatively affect deer through reduced forage quality and quantity, little is known about the effects of soil acidification on understory vegetation. Much of this small body of research focuses on tree saplings [14,21] or was conducted in Europe [2226]. In addition, understanding understory vegetation is important to understand future forest tree regeneration and the health of forest ecosystems [27,28]. As a starting point to experimentally determine the effects of soil acidification and nutrient depletion on white-tailed deer, we mitigated acidic soil conditions using dolomitic limestone application and measured the response of white-tailed deer forage availability and nutrient content. Lime application is a common mitigation technique for waters and forests affected by acidic deposition [2932]. Decades of liming research in Europe, and more recently the USA, have established its beneficial effects on water quality, soil nutrients, tree growth, tree health, and tree nutrient content [14,2934]. Understory plants have been studied less, and very few studies include terrestrial vertebrates [35]. Studies on the effects of liming on understory vegetation have observed increases in herbaceous and vascular plant species, changes in species composition, and changes in element concentrations in plant tissues [21,22,24,26]. The aims of this study were to evaluate the current condition of deer forage in an acidified forest, and to measure the effects of liming on the chemical composition and availability of deer forage and the availability of non-forage (competing vegetation) to determine if liming can improve the forage available to white-tailed deer. Materials and Methods Study Area This study was conducted in the Mosquito Creek watershed located in Clearfield, Cameron, and Elk counties in central Pennsylvania over the summers of 2003, 2004, and 2008. This study was part of a larger study evaluating the effects of watershed and riparian liming as a mitigation technique [36]. Our portion of the study was focused on 4, 100-ha watersheds (sites) in the Gifford Run drainage to Mosquito Creek in Clearfield county (41u119 N, 78u179 W). The study area receives some of the highest levels of acidic dep (...truncated)