Reconstruction and Spatial Analysis of Historical Forest Structure and Disturbance Across Ponderosa Pine Landscapes

生物地理学中关于一些森林的一系列理论问题仍未解决，这与历史上的自然干扰有关。这些干扰是罕见的、大的、严重的，表明景观处于不平衡状态，具有移动的、斑驳的空间结构吗？干扰频繁且严重程度较低，是否维持了持久的、空间上均匀的老树林？或者这些干扰的严重程度是不同的，在不同的景观中有不同的模式？这些答案具有广泛的影响，因为法律、政策、行业和公共用途都会受到影响。对于一些主要的森林类型来说，这些问题仍然没有得到回答，比如美国西部的黄松林，因为在欧美国家广泛使用土地之前，关于森林结构和干扰的数据有限。土地管理局(GLO)的调查是在最初为欧美人定居而对土地进行调查时进行的，在美国各地都有系统的数据。这些调查主要在19世纪末在西方进行，记录了调查角落的“见证树”的数据，包括树种、直径、树势和与角落的距离。GLO的调查还记录了高度严重的干扰，如皇冠起火和排污。本研究项目将使用校准和改进的方法分析GLO数据，以解决关于黄皮松景观的四个一般性问题：(1)大景观上的森林结构(例如，树木密度、树木直径分布)在空间上是如何均匀或可变的？(2)高强度干扰的关键因素(例如，火)是什么，这些干扰在景观中的比例和模式？(3)高强度干扰的空间结构和作用是否因地区而异？(4)森林结构和高强度干扰是否相关，如果是，这种关联模式是什么？研究人员将使用GLO数据重建美国西部三个大型黄皮松景观的森林结构和干扰，并对重建进行分析，以解决与它们相关的四个一般问题和九个具体假设。在广泛的土地利用变化之前，西部一些主要森林，如黄皮松森林的变化模式和规模鲜为人知。对于这些重要的西部森林，只有少数零星的小型重建、历史轶事和早期照片可用。该项目将通过使用早期调查记录来重建19世纪末三个具有代表性的大片陆地地区的黄松林的属性，从而扩大对这些森林的了解。该项目将提供有关火灾和其他干扰的数据以及重建森林变化的地图。这些数据应有助于各机构和利益集团制定政策，并有助于管理和恢复。这些地图和信息在管理和恢复方面也很有价值，因为将提供有关树木密度、大小和其他森林特征的具体数据。

A set of theoretical question in biogeography that remains unresolved regarding some forests relates to historical natural disturbances. Were these disturbances infrequent, large, and of high severity, suggesting landscapes that were in disequilibrium, having a shifting, patchy spatial structure? Were the disturbances frequent and of low severity, maintaining an enduring, spatially uniform old-growth forest? Or were these disturbances variable in severity with a mixture of patterns across landscapes? The answers have broad implications, as laws, policy, industries, and public uses are affected. The questions remain unanswered for some major forest types, such as ponderosa pine forests in the western United States, because data are limited about forest structure and disturbance before widespread EuroAmerican land uses. The General Land Office (GLO) survey, which was conducted when lands were initially surveyed for EuroAmerican settlement, has systematic data across the U.S. The surveys, largely done in the late-1800s in the West, recorded data on "witness trees" at surveyed corners, including tree species, diameter, bearing, and distance from the corner. The GLO survey also recorded high-severity disturbances, such as crown fires and blowdowns. This research project will use calibrated and refined methods for analyzing the GLO data to address four general questions about ponderosa pine landscapes: (1) How spatially uniform or variable was forest structure (e.g., tree density, tree diameter distributions) across large landscapes? (2) What were the key agents (e.g., fire) of high-severity disturbance, and the rates and patterns of these across landscapes? (3) Did the spatial structure and the role of high-severity disturbance vary among regions? (4) Were forest structure and high-severity disturbance linked, and, if so, what was the pattern of linkage? The investigators will use the GLO data to reconstruct forest structure and disturbances across three large ponderosa pine landscapes in the western U.S. and analyze the reconstructions to address the four general questions and nine specific hypotheses related to them.The pattern and scale of variation in some major western forests, such as ponderosa pine forests, are poorly known before alteration by widespread land uses. Only a few small, scattered reconstructions, historical anecdotes, and early photographs are available for these important western forests. This project will expand understanding of these forests by using early survey records to reconstruct the attributes of late-1800s ponderosa pine forests across three large, representative land areas. The project will provide data about fires and other disturbances and maps of reconstructed forest variation. These data should aid policy formulation by agencies and interest groups and be useful in management and restoration. The maps and information will also be valuable in management and restoration, as specific data will be provided on tree densities, sizes, and other forest characteristics.