Long Term Effects of Forest Liming on the Acid-Base Budget
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applied sciences Article Long Term Effects of Forest Liming on the Acid-Base Budget Martin Greve 1,* , Joachim Block 1, Gebhard Schüler 1 and Willy Werner 2 1 Research Institute for Forest Ecology and Forestry (Rhineland-Palatinate), Hauptstrasse 16, 67705 Trippstadt, Germany; [email protected] (J.B.); [email protected] (G.S.) 2 Department of Geobotany, Regional and Environmental Sciences, Trier University, Behringstraße 21, 54296 Trier, Germany; [email protected] * Correspondence: [email protected] Abstract: In Rhineland-Palatinate (Germany), a high percentage of the forest area is located on poor soils with low buffering capacity. Extensive liming applications were performed to compensate for the negative consequences of acid deposition. In 1988, three experimental sites with untreated control plots and different liming treatments were established in coniferous stands to investigate the effectiveness of liming on acidification and its effect on forest ecosystems. Measuring deposition and seepage waters for 24 years allowed for calculating long-term acid-base budgets. The original approach was expanded by data from a detailed sampling of the forest stand and mineral weathering rates. Without liming, the acid load exceeded the buffer capacity by base cation release from silicate weathering during the whole observation period. As a result, there was a high release of aluminum. After liming seepage water output of organic anions, nitrate and sulfate increased in some cases, leading to a higher acid load. However, the carbonates of dolomitic limestone compensated for a higher acid load, resulting in less aluminum released compared to the control plots. Until sulfate output by seepage water declines and nitrogen emissions are reduced, liming and restricted biomass harvesting are required for forest stands on base poor soils to prevent further acidification, decline of nutrient stocks, and the destruction of clay minerals. Keywords: Citation: Greve, M.; Block, J.; liming; acidification; acid base budget; base cations; nitrogen; biomass increment; Schüler, G.; Werner, W. Long Term air pollution Effects of Forest Liming on the Acid- Base Budget. Appl. Sci. 2021, 11, 955. https://doi.org/10.3390/app11030955 1. Introduction Academic Editor: Stefan Fleck Since the late 19th century, an increased acid input from anthropogenic activities was Received: 31 October 2020 observed in Europe and North America [1]. Forest ecosystems were especially affected Accepted: 13 January 2021 when their position was exposed and because of their large intercepting canopy surface [2]. Published: 21 January 2021 Since the 1980s, acid atmospheric deposition has been decreasing, mainly due to reduced sulfur dioxide emissions [3–5]. However, the input of nitrogen components still remains at Publisher’s Note: MDPI stays neutral a high level (cf. [6]) and is currently the main source for the acid load entering the forest with regard to jurisdictional claims in ecosystems [7,8]. published maps and institutional affil- In addition, centuries of intensive litter and timber harvesting contributed to large iations. scale soil acidification [9,10]. In Rhineland-Palatinate, which is located in southwestern Germany (Figure 1), a high percentage of forested areas are located on base-poor soils with small nutrient reserves and low buffer capacity against acidity [11]. As a result, mobilization of aluminum and heavy metals, reduction of base cation reserves, and destabilization of clay Copyright: © 2021 by the authors. minerals could, and still can, be observed for many forest sites [12–15]. To compensate for Licensee MDPI, Basel, Switzerland. the negative consequences of the acid deposition, extensive liming actions with dolomitic This article is an open access article lime were performed at an early stage [16,17]. The application of 3 to 4 tons per hectare distributed under the terms and every 10 years was recommended [2,18]. conditions of the Creative Commons In 1988, three experimental sites (Figure 1) with different liming treatments were Attribution (CC BY) license (https:// established. The base-poor forest sites were treated once to evaluate the forest management creativecommons.org/licenses/by/ 4.0/). practice of liming and to investigate its effectiveness and impacts on forest ecosystems [19]. Appl. Sci. 2021, 11, 955. https://doi.org/10.3390/app11030955 https://www.mdpi.com/journal/applsci Appl. Sci. 2021, 10, x FOR PEER REVIEW 2 of 14 Appl. Sci. 2021, 11, 955 2 of 14 ecosystems [19]. Long term input-output element and acid-base budgets were calculated (cf. [14]) to characterize the forest ecosystems of the three experimental sites by the different processes causing the fluxes of acidity and to quantify soil acidification without andLong with term different input-output dosages element of dolomitic and acid-base limestone. budgets Therefore, were calculated we investigated (cf. [14]) to if char- the mobilizationacterize the forestof aluminum ecosystems could of be the observed three experimental in the control sites plots by thewithout different liming, processes which wouldcausing indicate the fluxes that of proton acidity production and to quantify processes soil acidification exceeded the without proton and consumption with different by dosages of dolomitic limestone. Therefore, we investigated if the mobilization of aluminum reaction associated with Mb cations (=Ca, K, Mg, Na). In this case, proton consumption is could be observed in the control plots without liming, which would indicate that proton carried out partially by the weathering of Al, Mn and Fe (Ma cations) oxides causing the production processes exceeded the proton consumption by reaction associated with M destabilization of clay minerals [20]. Further, important questions include did the limingb cations (=Ca, K, Mg, Na). In this case, proton consumption is carried out partially by treatments counter the effects of acidification in the long term without the negative the weathering of Al, Mn and Fe (M cations) oxides causing the destabilization of clay consequences of nitrate mobilization?a These questions will be answered by input-output minerals [20]. Further, important questions include did the liming treatments counter budgeting. the effects of acidification in the long term without the negative consequences of nitrate mobilization? These questions will be answered by input-output budgeting. 2. Materials and Methods 2.1.2. Materials Sites and Methods 2.1. SitesEach of the three experimental sites, Adenau (AD), Idar-Oberstein (IO), and HochspeyerEach of the(HS) three (Table experimental 1), was subjected sites, Adenau to five (AD), liming Idar-Oberstein treatments, ranging (IO), and from Hochspeyer 3 to 15 t(HS) ha−1 (Tabledolomitic1), was limestone subjected with to five untreated liming treatments,control plots ranging (Table from 2). The 3 to area 15 t haof −each1 dolomitic liming treatmentlimestone is with 2000 untreated m2 separated control into plots two (Table subplots2). The of area1000of m each2 (Figure liming 1). treatmentThe control is treatment2000 m2 separated has three into subplots two subplots of 2125 of m 10002 each. m2 (Figure The experimental1). The control sites treatment are fenced, has three and managedsubplots offorest 2125 stands m2 each. are thinned The experimental regularly. sitesLime are and fenced, fertilizers and were managed spread forest by hand stands in Decemberare thinned 1988. regularly. Lime and fertilizers were spread by hand in December 1988. Figure 1. Location of the three experimental sites Adenau (AD), Idar-Oberstein (IO) and Hochspeyer (HS) in Rhineland- Figure 1. Location of the three experimental sites Adenau (AD), Idar-Oberstein (IO) and Hochspeyer (HS) in Rhineland- Palatinate over a map of the forested area (dark gray). The location of the state Rhineland-Palatinate is shown on the Palatinate over a map of the forested area (dark gray). The location of the state Rhineland-Palatinate is shown on the map map of Germany in the down right corner. In the upper right is a site plan with plot arrangement of the different liming of Germany in the down right corner. In the upper right is a site plan with plot arrangement of the different liming treatments (LT) of the experimental site HS. For more InformationInformation about the numbered treatments, which are part of this article, see Table 2 2.. MoreMore informationinformation aboutabout thethe experimentalexperimental sites sites is is documented documented in in Table Table1 .1. Appl. Sci. 2021, 11, 955 3 of 14 Table 1. Information about the three experimental sites. More detailed Information is available in Greve [22]. Study Areas Adenau (AD) Idar-Oberstein (IO) Hochspeyer (HS) Elevation above mean sea level 580–630 m 540–550 m 385–400 m Coordinates (ETRS 1989 UTM32N) X: 364340 Y: 5588220 X: 371450 Y: 5512000 X: 421560 Y: 5476010 Slope (Degree) 7◦ 4◦ 3◦ Mean annual temperature 7.6 ◦C 8.3 ◦C 8.7 ◦C Mean annual temperature of the 12.6 ◦C 13.3 ◦C 14.5 ◦C vegetation period Mean annual precipitation 850 mm 1065 mm 770 mm Seepage (60 cm) 275 mm 310 mm 180 mm Diluvial loam above devonic Diluvial loam above devonic Sandstone of the bunter Parent material quarzite quarzite sandstone Soil Taxonomy (WRB) Cambisol Stagnic cambisol Podzol Humus form Mor humus Mor humus Raw humus Soil texture Clay loam Clay loam Loamy Sand pH(CaCl2): 0–10/20–30 cm 2.9/3.9 3.0/4.0 2.9/3.6 Base saturation: 0–10/20–30 cm 7.2%/2.8% 6.3%/4.6% 10.3%/5.5% Cation exchange capacity [µeq g−1]: 139/46 137/47 103/19 0–10/20–30 cm C content [g kg−1]: 0–10/20–30 cm 65.8/12.7 75.0/12.1 72.8/10.7 N content [g kg−1]: 0–10/20–30 cm 3.1/1.3 3.7/1.1 2.7/0.5 S content [g kg−1]: 0–10/20–30 cm 1.49/0.38 1.21/0.46 0.58/0.19 Pinus sylvestris mixed with Tree species Picea abies Picea abies Fagus sylvatica from natural regeneration Stand age (2016) 81 97 90/96 (Pinus sylvestris) Table 2.