I am interested in how ancient Europeans viewed things like trees (which we would consider living organisms). Is there a feel of how Indo-european viewed live/dead things?
Is there a difference Indo and non-Indo religions in ancient Europe?
Oh I am so excited! I only have clear information for you on the Romans for this. Tl;dr: this was much more of a give and take relationship than modern westerners might assume.
For the Romans, trees and plants occupied an area between human and object. There are definitely religious roots to this, especially since so much of Roman religion relied on observing patterns and aberrations in nature, and then responding to them. Overall, when you look closely, there is an abundance of information that shows that Romans had more of a social relationship with the world around them--especially nature--than a human agent vs. inanimate world conception. This isn't super surprising, since, as anthropologist Igor Kopytoff once wrote, the "conceptual polarity of individualized persons and commoditized things is recent and, culturally speaking, exceptional." (1986:64)
There is a fantastic article by Laurence Totelin on the topic of trees in particular called "Botanizing Rulers and their Herbal Subjects" that is one of my favorites. It's all about the way that ancient rulers and their biographers constructed their public identities--positive and negative--through their relationships with plants and trees. The article opens with the naturalist/historian Pliny the Elder's discussion of the arrival of the balsam tree in Rome, when it was paraded in a Triumph celebrating the victory of Emperors Titus and Vespasian over the Jews in 71 CE. Pliny describes the tree as "enslaved", paying tribute to the Romans alongside the people it previously belonged to, and then discusses how the tree is flourishing in the care of the public treasury. This is really interesting, because it subjugates the tree below Romans, but gives it some agency, and the Romans themselves assume a debt of care over the tree by taking it captive. In antiquity, the balsam tree had a lot of monetary value, so there were other reasons for the Romans to want it beyond its use as a living symbol of the Roman relationship to the Jewish people, but it definitely played that role as well.
Beyond that one article, which is a great place to start, there are many more examples. One famous one is the first Roman emperor Augustus, who adopted the laurel tree as an attribute of his political persona, drawing on existing cultural associations with victory and the god Apollo to further his image as a divine success. This symbolic association was amplified by a series of living laurels with whom the emperor developed relationships: two that flanked the door to his house on the Palatine hill, an honor awarded by the Senate whose placement recalled the facades of some of the city’s oldest sacred structures, and a grove at the ancestral villa of his wife Livia on the outskirts of Rome.
Legendarily, that grove was the yield of a portent that occurred when a passing eagle dropped a white hen holding a sprig of laurel in its beak into his wife's lap when she was young. After years of serving as the source of triumphal wreaths and a symbol of dynastic authority throughout the Julio-Claudian dynasty, the entire grove was said to have died shortly before its end with the death of Nero. The trees came to stand as both omens of the extraordinariness of Augustus and his family and extensions of their legacy, the continued lives of the grove operating somewhere in the space between representing and perpetuating the family’s success and eventual decline. The fact that the grove was said to be the result of an omen is just another example of how reliant the Romans were on observing the natural world and letting it guide them. Even if these stories weren't true, their circulation shows that the natural world was a source of authority that people could use to legitimize their actions. It garnered respect.
Even sources that on the face of things seem to show Roman domination over the environment show something a little more nuanced and interesting if you look a little closer. Take Trajan's Column, a monument set up in the center of Rome after his campaigns in Dacia (modern Romania, roughly). The Column is most famous for its frieze which shows the Dacian campaigns from the moment the Roman troops crossed the Danube River into enemy territory to eventual victory and the death of Decebalus, the Dacian leader, which winds up around the column shaft so that nobody can actually see all of it. At the very beginning of the frieze, the first, biggest figure that we see, is the personification of the River Danube who watches as the Romans pass his waters safely over a pontoon bridge. While the story of the Column as a whole is one of the transformation of the Dacian semi-wilderness into a civilized, built-up Roman territory (written about beautifully by Elizabeth Wolfram Thill in her article "Civilization Under Construction: Depictions of Architecture on the Column of Trajan"), the Danube River is shown as "in on it" from the start. The trees, however, which provide shelter to fleeing Dacians throughout, consistently get cut down in the images, because they are aiding the enemy and not assenting to the Romans' occupation. Even when the Romans are dominating, in other words, they take care to show themselves having the permission of the local natural world to do so.
Here are sources:
Thill, Elizabeth Wolfram. “Civilization under Construction: Depictions of Architecture on the Column of Trajan.” American Journal of Archaeology, vol. 114, no. 1, 2010, pp. 27–43. JSTOR, www.jstor.org/stable/20627642. Accessed 18 Mar. 2021.
Laurence Totelin. “BOTANIZING RULERS AND THEIR HERBAL SUBJECTS: PLANTS AND POLITICAL POWER IN GREEK AND ROMAN LITERATURE.” Phoenix, vol. 66, no. 1/2, 2012, pp. 122–144. JSTOR, www.jstor.org/stable/10.7834/phoenix.66.1-2.0122. Accessed 18 Mar. 2021.
Kopytoff, I. (1986). The cultural biography of things: Commoditization as process. In A. Appadurai (Ed.), The Social Life of Things: Commodities in Cultural Perspective (pp. 64-92). Cambridge: Cambridge University Press. doi:10.1017/CBO9780511819582.004
For a contrasting view on Romans just dominating nature, if you're interested:
Kleiner, Fred S. “THE TROPHY ON THE BRIDGE AND THE ROMAN TRIUMPH OVER NATURE.” L'Antiquité Classique, vol. 60, 1991, pp. 182–192. JSTOR, www.jstor.org/stable/41655335. Accessed 18 Mar. 2021.