Vegetation Patterns of a New England Sand Plain in Montague MA 1993-1995

For details on methods and results, please see the published paper (Motzkin, G., D. Foster, A. Allen, J. Harrod and R. D. Boone. 1996. Controlling site to evaluate history: vegetation patterns of a New England sand plain. Ecological Monographs 66: 345-365). The Abstract from the paper is reproduced below. "The widespread and long-lasting impact of human activity on natural eco-systems indicates that land-use history must be treated as an integral aspect of ecological study and a critical component of conservation planning. The New England landscape has undergone a complete transformation as forests were converted to agriculture in the 18th and 19th centuries followed by succession to woodland as a result of widespread agricultural abandonment. Despite the prevalence of human impacts, the effect and longevity of land-use practices on modern forest conditions are poorly understood. In the present study of pitch pine - scrub oak vegetation on a sand plain in the Connecticut Valley of Massachusetts, we address the following questions: (1) what is the relative importance of human and natural disturbance and environmental factors in controlling vegetation composition, structure, and landscape patterns; (2) what are the mechanisms underlying human impacts on vegetation, and what is the duration of these impacts; and (3) what are the implications of land-use history for the interpretation and conservation of these communities? Sand plain vegetation was selected for investigation because the homogeneity of site conditions facilitates the interpretation of land-use and natural disturbance impacts, and because the uncommon vegetation and constituent species are priorities for conservation efforts. "Paleoecological data suggest that pre-European fires were common on the study area, perhaps ignited by a large regional Indian population. The area was noted historically as an extensive pine plain and was used for wood products from the 18th to the mid-19th century. Eighty-two percent of the area was subsequently plowed for agriculture before being abandoned in the early 20th century. "Soil analyses confirm the homogeneity of site conditions and suggest that land uses (plowing, woodlot/pasture) were determined according to ownership pattern rather than site factors. Previously cultivated parcels have distinct Ap (plow horizons) 15 - 33 cm deep, whereas uncultivated parcels have A horizons 3 - 10 cm in depth. Soil physical and chemical characteristics are similar among land uses and modern vegetation types. "Aerial photographs document a dramatic transformation in plant cover over the last 50 yr. In 1939, the vegetation was grassland or shrub-heath (49%), open-canopy forest (29%), and scrub-oak shrublands (15%). In 1985, 73% of the study area was forested with pitch pine (40%), hardwood (12%), or mixed stands (21%), 9% was in open-canopy stands, and 3% was covered by grass or shrubs. "Vegetation/land-use relations are striking. Pitch pine occurs almost exclusively (97%) on former plowed sites, whereas scrub oak stands occur preferentially (89%) on sites that have not been plowed. Land use explains the greatest variation in modern vegetation as well as the distribution and abundance of many taxa. Fire has been common across the study area but has influenced vegetation largely within patterns resulting from prior land use. Land-use patterns and factors controlling vegetation composition and structure are broadly paralleled at similar sites elsewhere in the Connecticut Valley. "The study indicates that conservation biologists interested in preserving species, communities, and landscape patterns on sand plains in the northeastern United States need to incorporate a dynamic perspective of biological systems that includes the overriding impact of prior land use. In order to appreciate, study, and display these land-use and vegetation patterns it is essential to conserve the mosaic of assemblages and historical uses within a landscape setting."

如需了解研究方法与结果详情，请参阅已发表论文：Motzkin, G., D. Foster, A. Allen, J. Harrod与R. D. Boone. 1996. 《调控立地以解析历史：新英格兰砂质平原的植被格局》. Ecological Monographs 66: 345-365。
本文的摘要转载如下：
人类活动对自然生态系统的广泛且持久影响表明，土地利用历史（land-use history）必须被视为生态学研究的核心组成部分，以及保护规划的关键要素。新英格兰地区的景观经历了彻底的转型：18至19世纪，森林被改造为农田，随后因农业大规模弃耕，植被正向林地演替。尽管人类活动的影响无处不在，但土地利用实践对现代森林状况的作用与持续时长仍有待深入解析。本研究针对马萨诸塞州康涅狄格河谷一处砂质平原上的脂松-灌丛栎植被展开，旨在解答以下三个问题：（1）在调控植被组成、结构与景观格局的过程中，人类扰动、自然扰动与环境因素的相对重要性如何？（2）人类活动影响植被的潜在机制是什么，这些影响的持续时长又为多久？（3）土地利用历史对于解读与保护这些植被群落具有哪些启示？选择砂质平原植被作为研究对象，是因其立地条件均一性便于解析土地利用与自然扰动的影响，同时该区域的稀有植被与组成物种为保护工作的优先对象。
古生态学数据显示，在欧洲殖民者到来之前，研究区域内野火频发，其火源可能源自当地庞大的印第安人群体。历史记录显示，该区域曾是广袤的松木平原，18世纪至19世纪中期被用于木材生产。随后，该区域82%的土地被开垦为农田，直至20世纪早期才被弃耕。
土壤分析证实了立地条件的均一性，并表明土地利用方式（耕作、用材林/牧场）是由土地所有权格局而非立地因素决定的。此前已耕作的地块拥有深度15-33 cm的Ap耕作层（plow horizons），而未耕作地块的A层深度则为3-10 cm。不同土地利用方式与现代植被类型间的土壤理化特征较为相似。
航空摄影照片记录了过去50年间植被覆盖的显著变化。1939年，研究区域的植被类型为草原或灌丛荒原（占比49%）、疏林（占比29%）以及灌丛栎灌丛（占比15%）。1985年，73%的研究区域为林地，其中脂松林占40%、硬木林占12%、混交林分占21%；9%为疏林；剩余3%为草本或灌丛覆盖区域。
植被与土地利用的关联十分显著。脂松几乎仅（97%）分布于此前被耕作过的地块，而灌丛栎灌丛则优先（89%）出现在未被耕作过的地块。土地利用方式能够解释现代植被的最大变异程度，以及诸多类群的分布与丰度。野火在研究区域内频发，但主要是在先前土地利用形成的格局范围内影响植被。土地利用格局与调控植被组成及结构的因素，在康涅狄格河谷的其他类似区域也得到了广泛印证。
本研究表明，有意保护美国东北部砂质平原上的物种、群落与景观格局的保护生物学家，需要纳入生物系统的动态视角，其中需涵盖先前土地利用的主导性影响。若要理解、研究并呈现这些土地利用与植被格局，就必须在景观尺度下保护群落镶嵌体与历史利用方式。