One sentence summary: 2Previously unreported forest areas in dryland biomes increase current estimates of the 3 global forest cover by at least 9 %. 4 List of authors:

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Vegetation indices (VI) describe vegetation structure and functioning but they are affected by illumination conditions (IC). Moreover, the fact that the effect of the IC on VI can be stronger than other biophysical or seasonal processes is under debate. Using Google Earth Engine and the latest Landsat Surface Reflectance level 1 data, we evaluated the temporal patterns of IC and two VI, the Normalized Difference Vegetation Index (NDVI) and the Enhanced Vegetation Index (EVI) in a mountainous tropical forest during the years 1984–2017. We evaluated IC and VI at different times, their relationship with the topography and the correlations between them. We show that IC is useful for understanding the patterns of variation between VI and IC at the pixel level using Landsat sensors. Our findings confirmed a strong correlation between EVI and IC and less between NDVI and IC. We found a significant increase in IC, EVI, and NDVI throughout time due to an improvement in the position of all Landsat sensors. Our results reinforce the need to consider IC to interpret VI over long periods using Landsat data in order to increase the precision of monitoring VI in irregular topography.

Although soil is one of the factors in the biology of Tuber melanosporum (black truffle of Périgord), which has been the subject of much study, there are few quantitative analyses relating to its effects on carpophore production. The aim of this work is to establish the statistical relationship between T. melanosporum productivity in 20 soil surface horizons and their conventional soil properties (granulometric texture, pH, calcareous fractions, organic carbon, total nitrogen, exchangeable cations). The study area is situated in the centre of the Iberian Peninsula under a Mediterranean climate. Statistical analysis shows that the collective influence of these conventional soil features is low, as principal component analysis explains only 27% of the variance in T. melanosporum production. However, a high percentage of active limestone (calcium carbonate extractable with ammonium oxalate) accounts for 40% of the variance in T. melanosporum production. Active limestone is very important to T. melanosporum because it regulates soil pH and exchangeable Ca2+ availability and participates in the organisation and maintenance of the soil structure; it also plays a role in the truffle’s nutrition. These results obtained for active limestone may be of use in truffle cultivation.

Chinese truffles serve as a good complement to the market for Tuber melanosporum (Périgord black truffle). However, Chinese truffles could be introduced accidentally or fraudulently into the plantations of Mediterranean truffles, and they could have a negative effect on truffle production and natural ecosystems. The study of Tuber species from China which are commercialized in Europe began 14 years ago. Tuber pseudoexcavatum was proposed as a new species, and this has been validated by some authors based on molecular and phylogenetic studies. We synthesize their ectomycorrhizae using samples from the type collection, and we compare T. pseudoexcavatum and Tuber indicum ectomycorrhizae. The ectomycorrhizae of these species have a morphology which is related to the ectomycorrhizae of T. melanosporum. We provide useful information for the rapid screening of the above-mentioned Chinese truffles ectomycorrhizae, for the quality control of commercial plants mycorrhized with Tuber. Moreover, we analyze the soil tolerance and the host plant affinity of T. pseudoexcavatum and T. indicum, in order to assess the capacity of both Chinese truffles to penetrate T. melanosporum plantations and habitats.