Soil moisture in long-term study plots

Baltimore Ecosystem Study Long-Term Study Plot Soil Metadata Participants Peter Groffman, Cary Institute of Ecosystem Studies Richard V. Pouyat, U.S. Forest Service Introduction The Baltimore Ecosystem Study (BES) has established a network of long-term permanent biogeochemical study plots. These plots will provide long-term data on vegetation, soil and hydrologic processes in the key ecosystem types within the urban ecosystem. The current network of study plots includes eight forest plots, chosen to represent the range of forest conditions in the area, and four grass plots. These plots are complemented by a network of 200 less intensive study plots located across the Baltimore metropolitan area. See Baltimore's Vegetation Structure And Its Ability To Remove Air Pollutants And Sequester Carbon Dioxide, online: http://beslter.org/frame4-page_3b_02.html . Plots are currently instrumented with lysimeters (drainage and tension) to sample soil solution chemistry, time domain reflectometry probes to measure soil moisture, dataloggers to measure and record soil temperature and trace gas flux chambers to measure the flux of carbon dioxide, nitrous oxide and methane from soil to the atmosphere. Measurements of in situ nitrogen mineralization, nitrification and denitrification were made at approximately monthly intervals from Fall 1998 - Fall 2000. Detailed vegetation characterization (all layers) was done in summer 1998. Link to BES vegetation reserarch and data: http://beslter.org/frame4-page_3b.html Data from these plots has been published in Groffman et al. (2006, 2009) and Groffman and Pouyat (2009). Plot Locations and Characterizations In November of 1998 four rural, forested plots were established at Oregon Ridge Park in Baltimore County northeast of the Gwynns Falls Watershed. Oregon Ridge Park contains Pond Branch, the forested reference watershed for BES. Two of these four plots are located on the top of a slope; the other two are located midway up the slope. In June of 2010 measurements at the mid-slope sites on Pond Branch were discontinued. Monuments and equipment remain at the two plots. These plots were replaced with two lowland riparian plots; Oregon upper riparian and Oregon lower riparian. Each riparian sites has four 5 cm by 1-2.5 meter depth slotted wells laid perpendicular to the stream, four tension lysimeters at 10 cm depth, five time domain reflectometry probes, and four trace gas flux chambers in the two dominant microtopographic features of the riparian zones --- high spots (hummocks) and low spots (hollows). Four urban, forested plots were established in November 1998, two at Leakin Park and two adjacent to Hillsdale Park in west Baltimore City in the Gwynns Falls. One of the plots in Hillsdale Park was abandoned in 2004 due to continued vandalism. In May 1999 two grass, lawn plots were established at McDonogh School in Baltimore County west of the city in the Gwynns Falls. One of these plots is an extremely low intensity management area (mowed once or twice a year) and one is in a low intensity management area (frequent mowing, no fertilizer or herbicide use). In 2009, the McDonogh plots were abandoned due to management changes at the school. Two grass lawn plots were established on the campus of the University of Maryland, Baltimore County (UMBC) in fall 2000. One of these plots is in a medium intensity management area (frequent mowing, moderate applications of fertilizer and herbicides) and one is in a high intensity management area (frequent mowing, high applications of fertilizer and herbicides). Plot locations: Hillsdale 1: 39 deg 19 min 28.14 sec N, 76 deg 42 min 16.49 sec W Hillsdale 2: 39 deg 19 min 31.24 sec N, 76 deg 42 min 28.62 sec W Leakin 1: 39 deg 18 min 1.32 sec N, 76 deg 41 min 37.08 sec W Leakin 2: 39 deg 18 min 5.42 sec N, 76 deg 41 min 34.15 sec W McDonogh 1: 39 deg 23 min 44.31 sec N, 76 deg 46 min 19.26 sec W McDonogh 2: 39 deg 23 min 52.26 sec N, 76 deg 46 min 23.52 sec W Oregon top-slope - 1: 39 deg 28 min 51.11 sec N, 76 deg 41 min 22.50 sec W Oregon mid-slope - 1: 39 deg 28 min 51.32 sec N, 76deg 41 min 18.24 sec W Oregon top-slope - 2: 39 deg 29 min 12.74 sec N, 76deg 41 min 22.88 sec W Oregon mid-slope - 2: 39 deg 29 min 12.68 sec N, 76deg 41 min 18.62 sec W McDonogh 1: 39 deg 23 min 44.31 sec N, 76deg 46 min 19.26 sec W McDonogh 2: 39 deg 23 min 52.26 sec N, 76deg 46 min 23.52 sec W UMBC 1: 39 deg 15 min 8.82 sec N, 76deg 42 min 10.43 sec W UMBC 2: 39 deg 14 min 6.50 sec N, 76deg 42 min 48.71 sec W Soil Moisture Soil moisture is measured once every four to six weeks at each plot. In each of the forested plots, five (six at Leakin plot #2) time domain reflectometry waveguide probes from SoilMoisture Equipment Corporation were installed vertically into the soil at random locations throughout the plot. The waveguide probes are 20 cm long, so those vertically installed span a depth of 0 to 20 cm below ground. Each forested plot also has one (two at Leakin plot #2) set of four waveguide probes installed horizontally into the soil in one location at four depths: 10, 20, 30, and 50 cm below ground. The McDonogh plots each have two sets of horizontal and no vertical waveguide probes. Attached to each belowground waveguide is an aboveground cable with a BNC Male Coaxial Fitting on the end. This fitting connects with SoilMoisture's Trase System I (Model 6050X1, Version 2000 Software), which uses time domain reflectometry (TDR) to measure soil moisture. Every four to six weeks each individual vertical and horizontal waveguide in each plot is connected to the portable Trase TDR processor; soil moisture is measured instantaneously and stored in the processor. After all plots are completed, the stored data is downloaded onto a computer at the BES office at UMBC. Literature Cited Bowden R, Steudler P, Melillo J and Aber J. 1990. Annual nitrous oxide fluxes from temperate forest soils in the northeastern United States. J. Geophys. Res. Atmos. 95, 13997 14005. Driscoll CT, Fuller RD and Simone DM (1988) Longitudinal variations in trace metal concentrations in a northern forested ecosystem. J. Environ. Qual. 17: 101-107 Goldman, M. B., P. M. Groffman, R. V. Pouyat, M. J. McDonnell, and S. T. A. Pickett. 1995. CH4 uptake and N availability in forest soils along an urban to rural gradient. Soil Biology and Biochemistry 27:281-286. Groffman PM, Holland E, Myrold DD, Robertson GP and Zou X (1999) Denitrification. In: Robertson GP, Bledsoe CS, Coleman DC and Sollins P (Eds) Standard Soil Methods for Long Term Ecological Research. (pp 272-290). Oxford University Press, New York Groffman PM, Pouyat RV, Cadenasso ML, Zipperer WC, Szlavecz K, Yesilonis IC,. Band LE and Brush GS. 2006. Land use context and natural soil controls on plant community composition and soil nitrogen and carbon dynamics in urban and rural forests. Forest Ecology and Management 236:177-192. Groffman, P.M., C.O. Williams, R.V. Pouyat, L.E. Band and I.C. Yesilonis. 2009. Nitrate leaching and nitrous oxide flux in urban forests and grasslands. Journal of Environmental Quality 38:1848-1860. Groffman, P.M. and R.V. Pouyat. 2009. Methane uptake in urban forests and lawns. Environmental Science and Technology 43:5229-5235. DOI: 10.1021/es803720h. Holland EA, Boone R, Greenberg J, Groffman PM and Robertson GP (1999) Measurement of Soil CO2, N2O and CH4 exchange. In: Robertson GP, Bledsoe CS, Coleman DC and Sollins P (Eds) Standard Soil Methods for Long Term Ecological Research. (pp 258-271). Oxford University Press, New York Robertson GP, Wedin D, Groffman PM, Blair JM, Holland EA, Nadelhoffer KJ and. Harris D. 1999. Soil carbon and nitrogen availability: Nitrogen mineralization, nitrification and carbon turnover. In: Standard Soil Methods for Long Term Ecological Research (Robertson GP, Bledsoe CS, Coleman DC and Sollins P (Eds) Standard Soil Methods for Long Term Ecological Research. (pp 258-271). Oxford University Press, New York Savva, Y., K. Szlavecz, R. V. Pouyat, P. M. Groffman, and G. Heisler. 2010. Effects of land use and vegetation cover on soil temperature in an urban ecosystem. Soil Science Society of America Journal 74:469-480.

巴尔的摩生态系统研究长期样地土壤元数据
参与者 彼得·格罗夫曼（Peter Groffman），生态系统研究卡里研究所；理查德·V·普约特（Richard V. Pouyat），美国林务局

引言
巴尔的摩生态系统研究（Baltimore Ecosystem Study, BES）已建立一套长期永久生物地球化学研究样地网络，旨在获取城市生态系统内关键生态系统类型的植被、土壤与水文过程长期监测数据。当前样地网络包含8个森林样地（覆盖区域内各类森林生境）与4个草地样地，另辅以覆盖巴尔的摩大都市区的200个低密度监测样地。详见《巴尔的摩植被结构及其去除空气污染物与固碳能力》，在线链接：http://beslter.org/frame4-page_3b_02.html。

现有样地已布设以下监测设备：渗漏计（lysimeter，含排水型与张力型）用于采集土壤溶液化学样品；时域反射仪（time domain reflectometry, TDR）探头用于监测土壤含水率；数据采集器（datalogger）用于测量并记录土壤温度；以及痕量气体通量箱（trace gas flux chamber），用于测定土壤向大气排放的二氧化碳、一氧化二氮与甲烷通量。1998年秋季至2000年秋季期间，研究人员以约每月一次的频率开展原位氮矿化（nitrogen mineralization）、硝化作用（nitrification）与反硝化作用（denitrification）监测。1998年夏季完成了完整植被分层特征调查。BES植被研究与数据链接：http://beslter.org/frame4-page_3b.html。

上述样地的监测数据已发表于Groffman等（2006、2009）以及Groffman与Pouyat（2009）的研究中。

样地布设与特征
1998年11月，在格林斯福尔斯流域东北部的巴尔的摩县俄勒冈岭公园，设立了4个乡村森林样地。俄勒冈岭公园包含庞兹布鲁克，即BES的森林参照流域。其中2个样地位于坡顶，另外2个位于坡中。2010年6月，庞兹布鲁克坡中样地的监测工作终止，但样地标记与设备得以保留。该样地被2个河岸低地（riparian）样地替代：俄勒冈上游河岸样地与俄勒冈下游河岸样地。每个河岸样地均布设以下设备：4根垂直于溪流、尺寸为5cm×1-2.5m（深度）的开槽井；4个埋深10cm的张力渗漏计；5个时域反射仪探头；以及针对河岸带两类主要微地形（microtopographic）特征——土丘（hummocks，高洼点）与洼地（hollows，低凹点）——布设的4个痕量气体通量箱。

1998年11月，在巴尔的摩市西部格林斯福尔斯流域的利金公园（2个样地）与希尔斯代尔公园周边（2个样地），设立了4个城市森林样地。其中希尔斯代尔公园的1个样地因持续遭人为破坏，于2004年停用。1999年5月，在城市西部格林斯福尔斯流域的麦克多诺学校校园，设立了2个草坪样地（lawn plots）：1个为极低管理强度样地（每年修剪1-2次），另1个为低管理强度样地（定期修剪，不施用化肥与除草剂）。2009年，因学校管理政策调整，麦克多诺样地停用。2000年秋季，在马里兰大学巴尔的摩县分校（University of Maryland, Baltimore County, UMBC）校园内设立了2个草坪样地：1个为中等管理强度样地（定期修剪，适量施用化肥与除草剂），另1个为高管理强度样地（定期修剪，大量施用化肥与除草剂）。

样地坐标：
希尔斯代尔1号：北纬39°19′28.14″，西经76°42′16.49″
希尔斯代尔2号：北纬39°19′31.24″，西经76°42′28.62″
利金1号：北纬39°18′1.32″，西经76°41′37.08″
利金2号：北纬39°18′5.42″，西经76°41′34.15″
麦克多诺1号：北纬39°23′44.31″，西经76°46′19.26″
麦克多诺2号：北纬39°23′52.26″，西经76°46′23.52″
俄勒冈坡顶1号：北纬39°28′51.11″，西经76°41′22.50″
俄勒冈坡中1号：北纬39°28′51.32″，西经76°41′18.24″
俄勒冈坡顶2号：北纬39°29′12.74″，西经76°41′22.88″
俄勒冈坡中2号：北纬39°29′12.68″，西经76°41′18.62″
UMBC 1号：北纬39°15′8.82″，西经76°42′10.43″
UMBC 2号：北纬39°14′6.50″，西经76°42′48.71″

土壤含水率监测
每个样地每4至6周开展一次土壤含水率测定。在每个森林样地中，均在样地内随机位置垂直埋设5个（利金2号样地为6个）来自SoilMoisture设备公司（SoilMoisture Equipment Corporation）的时域反射仪波导探头，探头长度为20cm，覆盖地下0-20cm深度。每个森林样地还在一处位置水平埋设4组波导探头，分别对应地下10cm、20cm、30cm与50cm深度（利金2号样地为2组）。麦克多诺样地各布设2组水平波导探头，无垂直波导探头。每个地下波导探头均连接带有BNC公同轴接头（BNC Male Coaxial Fitting）的地面线缆，该接头与SoilMoisture公司的Trase I系统（型号6050X1，配套2000版软件）相连，该系统通过时域反射法测定土壤含水率。每4至6周，研究人员将便携式Trase TDR处理器与每个样地内的所有垂直、水平波导探头逐一连接，实时测定土壤含水率并存储于处理器中。全部样地测定完成后，将存储的数据下载至UMBC的BES办公室计算机中。

参考文献
Bowden R, Steudler P, Melillo J, Aber J. 1990. 美国东北部温带森林土壤的年一氧化二氮通量. 《地球物理学研究杂志：大气》(Journal of Geophysical Research. Atmos.) 95: 13997-14005.
Driscoll CT, Fuller RD, Simone DM. 1988. 北部森林生态系统中痕量金属浓度的纵向变化. 《环境质量杂志》(Journal of Environmental Quality) 17: 101-107.
Goldman MB, Groffman PM, Pouyat RV, McDonnell MJ, Pickett STA. 1995. 城乡梯度森林土壤的甲烷吸收与氮有效性. 《土壤生物学与生物化学》(Soil Biology and Biochemistry) 27:281-286.
Groffman PM, Holland E, Myrold DD, Robertson GP, Zou X. 1999. 反硝化作用. 见：Robertson GP, Bledsoe CS, Coleman DC, Sollins P (Eds). 《长期生态研究标准土壤方法》(Standard Soil Methods for Long Term Ecological Research). 纽约：牛津大学出版社，第272-290页.
Groffman PM, Pouyat RV, Cadenasso ML, Zipperer WC, Szlavecz K, Yesilonis IC, Band LE, Brush GS. 2006. 城乡森林中土地利用背景与自然土壤因子对植物群落组成及土壤氮碳动态的调控. 《森林生态与管理》(Forest Ecology and Management) 236:177-192.
Groffman PM, Williams CO, Pouyat RV, Band LE, Yesilonis IC. 2009. 城市森林与草地的硝酸盐淋溶与一氧化二氮通量. 《环境质量杂志》(Journal of Environmental Quality) 38:1848-1860.
Groffman PM, Pouyat RV. 2009. 城市森林与草坪的甲烷吸收. 《环境科学与技术》(Environmental Science and Technology) 43:5229-5235. DOI: 10.1021/es803720h.
Holland EA, Boone R, Greenberg J, Groffman PM, Robertson GP. 1999. 土壤CO2、N2O与CH4交换的测定. 见：Robertson GP, Bledsoe CS, Coleman DC, Sollins P (Eds). 《长期生态研究标准土壤方法》(Standard Soil Methods for Long Term Ecological Research). 纽约：牛津大学出版社，第258-271页.
Robertson GP, Wedin D, Groffman PM, Blair JM, Holland EA, Nadelhoffer KJ, Harris D. 1999. 土壤碳氮有效性：氮矿化、硝化作用与碳周转. 见：Robertson GP, Bledsoe CS, Coleman DC, Sollins P (Eds). 《长期生态研究标准土壤方法》(Standard Soil Methods for Long Term Ecological Research). 纽约：牛津大学出版社，第258-271页.
Savva Y, Szlavecz K, Pouyat RV, Groffman PM, Heisler G. 2010. 城市生态系统中土地利用与植被覆盖对土壤温度的影响. 《美国土壤学会杂志》(Soil Science Society of America Journal) 74:469-480.