Recent atmospheric drying in Siberia is not unprecedented over the last 1,500 years

Newly developed millennial δ13C larch tree-ring chronology from Siberia allows reconstruction of summer (July) vapor pressure deficit (VPD) changes in a temperature-limited environment. VPD increased recently, but does not yet exceed the maximum values reconstructed during the Medieval Warm Anomaly. The most humid conditions in the Siberian North were recorded in the Early Medieval Period and during the Little Ice Age. Increasing VPD under elevated air temperature affects the hydrology of these sensitive ecosystems by greater evapotranspiration rates. Further VPD increases will significantly affect Siberian forests most likely leading to drought and forest mortality even under additional access of thawed permafrost water. Adaptation strategies are needed for Siberian forest ecosystems to protect them in a warming world.

Reconstructing summer upper-level flow in the northern Rocky Mountains using an alpine larch tree-ring chronology

Mid-latitude mesoscale weather during the climatological summer is strongly influenced by fluctuations in synoptic-scale circulation patterns. Previous research has linked Arctic amplification to alterations in summer synoptic climatology, leading to more extreme weather events in the mid-latitudes. In this study, seasonal (JJA) upper-level (500 hPa) atmospheric flow is reconstructed in the mid-latitudes using an alpine larch Larix lyallii Parl. tree-ring chronology sampled from western Montana. Significant relationships were found between alpine larch radial growth and upper-level flow patterns derived from the North American Regional Reanalysis dataset (1979-2015). Meridional and zonal flows that manifest in ridging are associated with enhanced radial growth of alpine larch (i.e. meridional flow west [r = 0.504, p = 0.001] and zonal flow north [r = 0.642, p < 0.001] of the study site). Meridional and zonal flows associated with troughing result in decreased radial growth (i.e. meridional flow east [r = -0.497, p = 0.001] and zonal flow south [r = -0.584, p < 0.001] of the study site). Using the leave-one-out method, a linear regression model was calibrated and verified between a principal component analysis score derived from measurements of upper-level flow in western North America and alpine larch tree growth. The 444 yr climate reconstruction of summer 500 hPa flow suggests that ridging is becoming more intense over the western United States and Canada since the 1980s.

Larch regeneration (larix sibirica.ldb) from zygote embryos in in vitro and proliferation rate under growth hormone influence

Larix sibirica Ledeb is a frost-hardy tree species (50-70 cm tall) which belong to genus of Larix, and family of Pinaceae Lindl. Our objective was to generate plantlets from zygote embryos of larch tree (Larix sibirica Ledeb) in in vitro condition. Convenient in vitro culture for Larix sibirica.Ldb for shoot formation was MSGm with 2 mg/L BAP, 1 mg/L 2.4-D g/L activated carbon. Root was formatted on MSGm with 1 mg/L BAP, 2 mg/L 2.4-D g/L activated carbon. Сибирь шинэс (larix sibirica ledeb)-ний бичил ургамлыг гаргах, бойжуулахад өсөлт in vitro орчинд идэвхжүүлэгчийн нөлөө Хураангуй Нарсны овгийн (Pinaceae Lindl), шинэс (Larix)-ний төрөлд багтах Сибирь шинэс (Larix sibirica Ldb) нь 24-26 м дундаж өндөртэй 40 м хүртэл өндөр ургадаг модлог ургамал юм. Энэхүү судалгааны ажлаар Сибирь шинэс (Larix sibirica.Ldb)-ний үр хөврөлөөс in vitro орчинд бичил ургамлыг гаргаж, бойжуулахад өсөлт идэвхжүүлэгчийн нөлөөг тогтоосон. Сибирь шинэсний үр хөврөлөөс нахиа үүсгэхэд 2 мг/л ВАР, 1 мг/л 2.4-D, 7 г/л идэвхжүүлсэн нүүрс агуулсан MSGm тэжээлт орчинд 4 мм хэмжээтэй хөврөлийг өсгөвөрлөх нь хамгийн тохиромжтой. 2.4-D (2 мг/л) болон BAP(1 мг/л ) хослуулсан MSGm тэжээлт орчинд үндэс үүссэн. Сибирь шинэсний бичил ургамлыг өсөлт идэвхжүүлэгчээр үйлчлэхэд үндэсний урт, хэлбэр сайжирч байгаа учир шинэсний бичил ургамлыг өсөлт идэвхжүүлэгчийг ашиглах шаардлагатай. Түлхүүр үг: Үр хөврөл, MSGm тэжээлт орчин, AI үндсэн тэжээлт орчин

COMPREHENSIVE SPECTRAL SIGNAL INVESTIGATION OF A LARCH FOREST COMBINING GROUND- AND SATELLITE-BASED MEASUREMENTS

Collecting comprehensive knowledge about spectral signals in areas composed by complex structured objects is a challenging task in remote sensing. In the case of vegetation, shadow effects on reflectance are especially difficult to determine. This work analyzes a larch forest stand (&lt;i&gt;Larix decidua&lt;/i&gt; MILL.) in Pinnis Valley (Tyrol, Austria). The main goal is extracting the larch spectral signal on Landsat 8 (LS8) Operational Land Imager (OLI) images using ground measurements with the Cropscan Multispectral Radiometer with five bands (MSR5) simultaneously to satellite overpasses in summer 2015. First, the relationship between field spectrometer and OLI data on a cultivated grassland area next to the forest stand is investigated. Median ground measurements for each of the grassland parcels serve for calculation of the mean difference between the two sensors. Differences are used as “bias correction” for field spectrometer values. In the main step, spectral unmixing of the OLI images is applied to the larch forest, specifying the larch tree spectral signal based on corrected field spectrometer measurements of the larch understory. In order to determine larch tree and shadow fractions on OLI pixels, a representative 3D tree shape is used to construct a digital forest. Benefits of this approach are the computational savings compared to a radiative transfer modeling. Remaining shortcomings are the limited capability to consider exact tree shapes and nonlinear processes. Different methods to implement shadows are tested and spectral vegetation indices like the Normalized Difference Vegetation Index (NDVI) and Greenness Index (GI) can be computed even without considering shadows.

COMPREHENSIVE SPECTRAL SIGNAL INVESTIGATION OF A LARCH FOREST COMBINING GROUND- AND SATELLITE-BASED MEASUREMENTS

Collecting comprehensive knowledge about spectral signals in areas composed by complex structured objects is a challenging task in remote sensing. In the case of vegetation, shadow effects on reflectance are especially difficult to determine. This work analyzes a larch forest stand (<i>Larix decidua</i> MILL.) in Pinnis Valley (Tyrol, Austria). The main goal is extracting the larch spectral signal on Landsat 8 (LS8) Operational Land Imager (OLI) images using ground measurements with the Cropscan Multispectral Radiometer with five bands (MSR5) simultaneously to satellite overpasses in summer 2015. First, the relationship between field spectrometer and OLI data on a cultivated grassland area next to the forest stand is investigated. Median ground measurements for each of the grassland parcels serve for calculation of the mean difference between the two sensors. Differences are used as “bias correction” for field spectrometer values. In the main step, spectral unmixing of the OLI images is applied to the larch forest, specifying the larch tree spectral signal based on corrected field spectrometer measurements of the larch understory. In order to determine larch tree and shadow fractions on OLI pixels, a representative 3D tree shape is used to construct a digital forest. Benefits of this approach are the computational savings compared to a radiative transfer modeling. Remaining shortcomings are the limited capability to consider exact tree shapes and nonlinear processes. Different methods to implement shadows are tested and spectral vegetation indices like the Normalized Difference Vegetation Index (NDVI) and Greenness Index (GI) can be computed even without considering shadows.