• Energy Research

AbstractAimAt the elevational limit of forest distribution, montane forests show diverse responses to environmental change with upward shifts, increased tree density and lateral expansion reported. To enable informed analysis of the consequences forest advance will have on montane biodiversity, we quantify changes in the area and elevation of the tree line ecotone and identify how patterns of forest advance are modified by topography and over time.LocationCentral Mountain Range, Taiwan.Time period1963–2016.Major taxa studiedMontane Forests.MethodsChanges in the area and elevation of montane forest at the tree line ecotone were quantified using a stratified random sample of aerial photography captured in 1963, 1980, 2001 and 2016. Weighted estimates of habitat area and elevation for each time step were used to quantify the influence of slope aspect and inclination on tree line ecotone change and identify how the rate of habitat change varies over time.ResultsNon‐forest area declined by 29% between 1963 and 2016 driven by a 295.0 ha increase in forest area within the study region. Despite no change in mean forest elevation, the mean elevation of establishing forest has increased at a rate of 2.17 m/yr. Changes in forest area and elevation are spatially variable, driven by the complex montane topography. East and south facing slopes show the largest gains in forest area and 0–20° slopes show an increasing rate of forest establishment up to 2016, while slopes facing west or with incline > 46° show negligible change.Main conclusionsClimate‐linked montane forest expansion in the Central Mountain Range in Taiwan is dominated by infilling rather than increases in forest elevation. Forest expansion has significantly reduced non‐forest habitat area in this endemic species‐rich region. However, considerable terrain‐dependent variation in forest advance occurs, offering the potential that non‐forest species will continue to persist at high elevations with reduced population size.

Abstract The increasing intensity and frequency of droughts under climate change demands effective ways to monitor drought impacts. We sought to determine how different satellite remote sensing sources influence our ability to identify temporal and spatial impacts on European beech forest canopy health during intense drought events. Imagery from three satellite series (MODIS, Landsat and Sentinel‐2) was used to observe changes in canopy health during the intense droughts of 2003 and 2018 in the Rhön Biosphere Reserve, central Germany. Monthly normalized difference vegetation index (NDVI) anomalies were calculated for each satellite between 2000–2020 and compared against temperature, precipitation and the standardized precipitation evapotranspiration index (SPEI). Severe canopy impacts in 2003 and 2018 were associated with low NDVI in August and September. At the stand‐scale, Sentinel‐2 data allowed a spatially detailed understanding of canopy‐level impacts, while MODIS provided the clearest temporal progression of the drought’s impacts on the forest canopy. Low NDVI values were not exclusively associated with extremes of either temperature and precipitation individually; however, low canopy NDVI in August was associated with SPEI values below −1.5. Although the intense drought of 2018, as defined by meteorological parameters, peaked in July, canopy NDVI did not decline until August, highlighting that our ability to detect canopy impact during drought events is sensitive to the timing of image acquisition. No single satellite sensor affords a full picture of the temporal or spatial progression of drought impacts. Consequently, using sensors in tandem provides the best possible representation of canopy health during intense drought events.

Tree cores were sampled using increment borers. At each site three trees were chosen for coring, with two or three cores taken per tree. Cores were sanded and ring widths measured based on high-resolution images of the sanded cores. Cores were cross-dated and summary statistics used to compare cross-dating accuracy. The dataset contains the resulting dated ring width series. This dataset includes tree ring width data, derived from tree cores, that were sampled from sites across the Rhön Biosphere Reserve (Germany). At each chosen site three trees were cored, with two or three cores taken per cored tree. Data was collected in August 2021.