{"title":"Biodiversity-Based Empirical Critical Loads of Nitrogen Deposition in the Athabasca Oil Sands Region","authors":"Nicole Vandinther, J. Aherne","doi":"10.3390/nitrogen4020012","DOIUrl":null,"url":null,"abstract":"Anthropogenic nitrogen (N) emissions can have considerable effects on terrestrial ecosystems, with chronic N deposition leading to changes in plant species composition. The Athabasca Oil Sands Region (AOSR) represents a large point source of N emissions, which has prompted concern for surrounding habitats. The objective of this study was to determine the relative importance of N deposition as a driver of plant species community composition against bioclimatic and soil chemical variables. Further, we sought to identify community thresholds in plant species composition across a N deposition gradient. This assessment was performed for 46 Jack pine (Pinus banksiana Lamb.)-dominant forest sites surrounding the AOSR spanning Alberta and Saskatchewan. In total, 35 environmental variables were evaluated using redundancy analysis (RDA), followed by gradient forest analysis applied to plant species abundance data. Soil chemical variables accounted for just over 26% of the total explainable variation in the dataset, followed by bioclimatic variables (19%) and deposition variables (5%), but joint effects between variables also explained a significant portion of the total variation (p < 0.001). Total deposited nitrogen (TDN), and sulphur (TDS) along with bioclimatic and soil chemical variables, were identified as important variables in gradient forest analysis. A single, definitive threshold across TDN was identified at approximately 5.6 kg N ha−1 yr−1 (while a TDS threshold was found at 14.4 kg S ha−1 yr−1). The TDN threshold range was associated primarily with changepoints for several vascular species (Pyrola asarifolia, Pyrola chlorantha, Cornus canadensis, and Arctostaphylos uva-ursi) and bryophyte and lichen species (Pleurozium schreberi, Vulpicida pinastri, and Dicranum polysetum). These results suggest that across Jack pine-dominant forests surrounding the AOSR, the biodiversity-based empirical critical load of nutrient N is 5.6 kg N ha−1 yr−1.","PeriodicalId":19365,"journal":{"name":"Nitrogen","volume":"56 1","pages":""},"PeriodicalIF":0.0000,"publicationDate":"2023-04-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Nitrogen","FirstCategoryId":"1085","ListUrlMain":"https://doi.org/10.3390/nitrogen4020012","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"","JCRName":"","Score":null,"Total":0}
引用次数: 0
Abstract
Anthropogenic nitrogen (N) emissions can have considerable effects on terrestrial ecosystems, with chronic N deposition leading to changes in plant species composition. The Athabasca Oil Sands Region (AOSR) represents a large point source of N emissions, which has prompted concern for surrounding habitats. The objective of this study was to determine the relative importance of N deposition as a driver of plant species community composition against bioclimatic and soil chemical variables. Further, we sought to identify community thresholds in plant species composition across a N deposition gradient. This assessment was performed for 46 Jack pine (Pinus banksiana Lamb.)-dominant forest sites surrounding the AOSR spanning Alberta and Saskatchewan. In total, 35 environmental variables were evaluated using redundancy analysis (RDA), followed by gradient forest analysis applied to plant species abundance data. Soil chemical variables accounted for just over 26% of the total explainable variation in the dataset, followed by bioclimatic variables (19%) and deposition variables (5%), but joint effects between variables also explained a significant portion of the total variation (p < 0.001). Total deposited nitrogen (TDN), and sulphur (TDS) along with bioclimatic and soil chemical variables, were identified as important variables in gradient forest analysis. A single, definitive threshold across TDN was identified at approximately 5.6 kg N ha−1 yr−1 (while a TDS threshold was found at 14.4 kg S ha−1 yr−1). The TDN threshold range was associated primarily with changepoints for several vascular species (Pyrola asarifolia, Pyrola chlorantha, Cornus canadensis, and Arctostaphylos uva-ursi) and bryophyte and lichen species (Pleurozium schreberi, Vulpicida pinastri, and Dicranum polysetum). These results suggest that across Jack pine-dominant forests surrounding the AOSR, the biodiversity-based empirical critical load of nutrient N is 5.6 kg N ha−1 yr−1.
人为氮(N)排放对陆地生态系统有相当大的影响,慢性氮沉降导致植物物种组成的变化。阿萨巴斯卡油砂区(AOSR)是一个巨大的氮排放点源,引起了人们对周围栖息地的关注。本研究的目的是确定氮沉降作为植物物种群落组成对生物气候和土壤化学变量的驱动因素的相对重要性。此外,我们试图确定跨N沉降梯度的植物物种组成的群落阈值。这项评估是对46个杰克松(Pinus banksiana Lamb.)进行的,它们是横跨阿尔伯塔省和萨斯喀彻温省的AOSR周围的主要森林遗址。利用冗余分析(RDA)对35个环境变量进行了评价,并对植物物种丰度数据进行了梯度森林分析。土壤化学变量占数据集中总可解释变异的26%以上,其次是生物气候变量(19%)和沉积变量(5%),但变量之间的联合效应也解释了总变异的很大一部分(p < 0.001)。总沉积氮(TDN)和总沉积硫(TDS)以及生物气候和土壤化学变量是梯度森林分析的重要变量。TDN的单一确定阈值约为5.6 kg N ha−1 yr−1(而TDS阈值为14.4 kg S ha−1 yr−1)。TDN阈值范围主要与几种维管束植物(鹿蹄草、鹿蹄草、鹿蹄草和熊蹄草)以及苔藓植物和地衣植物(虎肋草、狐尾草和多毛草)的变化点有关。这些结果表明,在青松优势林周围,基于生物多样性的养分N经验临界负荷为5.6 kg N ha−1 yr−1。