The recurring use of fire in the Guinean savanna underscores the need to identify the local climatic parameters that predict fire behavior. This study was conducted in 2013–2016, with three experimental fire periods (early, mid and late season) each year. The objective was to identify, among the climatic parameters of the year before the fire (PCAs), during the month of the fire (PCMs), and during the fire (PCDs), those that best predict fuel and fire characteristics. Mixed-effects multiple regressions and model selection showed that PCAs do not influence fuel load and fire intensity. Among the PCMs, the number of days between the last rain > 1 mm and the fire determines fuel humidity. Moreover, the more it rains during the month of the fire and/or in the 10 days before, the lower the intensity. Among the PCDs, air humidity is the key factor: the lower it is, the faster the fire spreads and the more intense it is. Only PCMs determine fire intensity. This study highlights that rainfall occurring shortly before a fire determines fire intensity through its effect on litter moisture content. These results open up new perspectives for modeling the spread of fires in the Guinean savanna.
The Indian Himalayan region harbours a diverse assemblage of conifer species distributed across contrasting Inner (monsoon rain-shadow) and Outer (monsoon-exposed) zones. Understanding their climatic niches is essential for explaining distribution patterns, adaptive capacity, and vulnerability to climate change. We quantified niche dynamics of 11 Himalayan conifers by assessing climatic niche overlap (Schoener's D), hypervolume-based niche breadth, and environmental variable contributions across the two zones. Niche overlap between Inner and Outer Himalayan populations was generally low (D = 0.01-0.21), with Cedrus deodara showing the highest overlap and Cupressus torulosa exhibiting near-complete divergence. Hypervolume analysis revealed broader niches in the Outer Himalaya, suggesting greater environmental heterogeneity and wider climatic tolerance, whereas species in the Inner Himalaya occupied narrower and more specialized climatic spaces. Principal Component Analysis identified temperature variables (bio1, bio3, bio5, bio7, bio10) and precipitation variables (bio12, bio16, bio17, bio18) as the main drivers of niche differentiation. However, niche equivalency and similarity tests indicated that observed differences were not greater than expected by chance, suggesting overall climatic niche conservatism. These results indicate that Himalayan conifer distributions are shaped by the interaction of temperature and monsoon-driven precipitation, with regional climatic variability influencing niche breadth. La r & eacute;gion himalayenne de l'Inde abrite un ensemble diversifi & eacute; d'esp & egrave;ces de conif & egrave;res r & eacute;parties entre deux zones contrast & eacute;es : l'int & eacute;rieur (& agrave; l'abri de la mousson) et l'ext & eacute;rieur (expos & eacute; & agrave; la mousson). Comprendre leurs niches climatiques est essentiel pour expliquer leurs aires de r & eacute;partition, leur capacit & eacute; d'adaptation et leur vuln & eacute;rabilit & eacute; face aux changements climatiques. Nous avons quantifi & eacute; la dynamique des niches de 11 esp & egrave;ces de conif & egrave;res himalayens en & eacute;valuant le chevauchement des niches climatiques (indice D de Schoener), l'amplitude des niches fond & eacute;e sur les hypervolumes, ainsi que la contribution des variables environnementales dans les deux zones. Le chevauchement de niche entre les populations de l'Himalaya int & eacute;rieur et ext & eacute;rieur est g & eacute;n & eacute;ralement faible (D = 0,01 & agrave; 0,21). Cedrus deodara pr & eacute;sente le plus fort chevauchement, tandis que Cupressus torulosa montre une divergence presque compl & egrave;te. L'analyse par hypervolumes r & eacute;v & egrave;le des niches plus vastes dans l'Himalaya ext & eacute;rieur, ce qui sugg & egrave;re une plus grande h & eacute;t & eacute;rog & eacute;n & eacute;it & eacute; environnementale et une tol & eacute;rance climatique plus & eacute;tendue. & Agrave; l'inverse, dans l'Himalaya int & eacute;rieur, les esp & egrave;ces occupent des espaces climatiques plus restreints et davantage sp & eacute;cialis & eacute;s. L'analyse en composantes principales a identifi & eacute; les variables de temp & eacute;rature (bio1, bio3, bio5, bio7, bio10) et de pr & eacute;cipitations (bio12, bio16, bio17, bio18) comme les principaux d & eacute;terminants de la diff & eacute;renciation des niches. Toutefois, les tests d'& eacute;quivalence et de similarit & eacute; des niches ont indiqu & eacute; que les diff & eacute;rences observ & eacute;es n'& eacute;taient pas sup & eacute;rieures & agrave; celles attendues au hasard, ce qui sugg & egrave;re un conservatisme des niches climatiques. Ces r & eacute;sultats indiquent que la distribution des conif & egrave;res himalayens est fa & ccedil;onn & eacute;e par l'interaction entre la temp & eacute;rature et les pr & eacute;cipitations li & eacute;es & agrave; la mousson, tandis que la variabilit & eacute; climatique r & eacute;gionale influence l'amplitude des niches & eacute;cologiques.
