Tree regeneration after fire: Delta 1994 burn surveys, pre-fire stem counts and basal areas, for black spruce

Data for this study were collected in 2001 and 2002 by Jill Johnstone (University of Alaska Fairbanks) and Eric Kasischke (University of Maryland). Sites were located within the perimeter of the 1994 burn southeast of Delta Junction Alaska, USA, bordering the Alaska Highway to the North and the Gerstle River to the West. Sites were selected from satellite classifications prepared by Eric Kasischke to represent different levels of burn severity and post-fire vegetation canopy greenness (NDVI). Site selection was constrained by road access, and only areas where all trees had been killed by the fire were selected.

At each site, a central point was located in an area of visually homogeneous vegetation. Five parallel transects, each 50 m long, were laid out as follows:

1) the first transect started at the central point and followed a randomly-selected compass direction,

2) two additional transects were established parallel to the first, but at a random distance from the central transect up to 25 m distant.

Vegetation was sampled in a 2-m wide belt centered on each transect, and soil samples were made at intervals along the transect line. Vegetation measurements included:

a) basal diameters of all pre-fire trees greater than 1.3 m in height,

b) counts of all post-fire tree seedlings, and

c) basal diameters of tree seedlings and willows, measured in a randomly chosen 5x2 m portion of each transect.

General notes were made on visual percent cover of different vegetation growth forms at the site. Destructive measurements of tree seedlings and willows made in 2001 were used to develop allometric equations to predict dry biomass from basal diameter. Measurements of soil organic layer depth were made at 5 m intervals with the use of a spade to excavate small chunks of sod. At one randomly-selected sample point per transect, a 10x10 cm sample of the organic layer was collected for bulk density measurements. Bulk density samples were dried in a 60degC oven for 48 hours and then weighed. Information on the soil profile to 50-100 cm depth was collected from a single soil pit at the site.

The purpose of the study was to document variations in post-fire tree establishment and woody biomass accumulation that could be related to variations in fire severity or pre-fire vegetation characteristics. Data from the study have not yet been published as of 2003.

Contains pre-fire stem counts and basal areas, for black spruce (Picea mariana) only.

本研究所用数据由阿拉斯加费尔班克斯大学的吉尔·约翰斯通（Jill Johnstone）与马里兰大学的埃里克·卡基施克（Eric Kasischke）于2001至2002年间采集。样点位于美国阿拉斯加州德尔塔章克申东南部1994年火灾迹地范围内，北邻阿拉斯加公路，西接格斯特勒河。样点由埃里克·卡基施克基于卫星分类结果选取，涵盖不同火烧烈度（burn severity）与火烧后植被冠层绿度（归一化差异植被指数，Normalized Difference Vegetation Index，简称NDVI）等级。样点选取受道路可达性限制，且仅纳入火灾导致所有树木死亡的区域。

每个样点选取植被外观均一区域的中心点。共布设5条长50m的平行样线，布设规则如下：1）第一条样线以中心点为起点，沿随机选定的罗盘方位延伸；2）另外两条样线与第一条平行，与中心样线的随机间距最大为25m。

每条样线以中心线为基准设置2m宽的带状样方开展植被采样，并沿样线间隔采集土壤样品。植被测量指标包括：
a）所有高度超过1.3m的过火前树木的基径（basal diameter）；
b）所有火烧后树木幼苗的数量；
c）在每条样线随机选取的5×2m区域内，测量树木幼苗与柳树的基径。

研究人员对样点内不同植被生长型的视觉盖度百分比进行了记录。2001年开展的树木幼苗与柳树破坏性采样数据，被用于构建异速生长方程（allometric equations），以通过基径预测干生物量。以5m为间隔测量土壤有机层（soil organic layer）厚度，使用铁锹挖掘小块草皮进行取样。在每条样线随机选取的1个采样点处，采集10×10cm的土壤有机层样品用于容重（bulk density）测定。容重样品置于60℃烘箱中烘干48小时后称重。在样点处挖掘1个土壤剖面坑（soil pit），采集50至100cm深度的土壤剖面信息。

本研究旨在阐明火烧后树木定植与木本生物量积累的变化规律，该变化可能与火烧烈度或过火前植被特征的差异相关。截至2003年，本研究数据尚未正式发表。

本数据集仅包含黑云杉（Picea mariana）的过火前茎秆数量与基断面积（basal areas）数据。