Are there any racial motivations to how some enemies or civilian populations were handled?

Velas Liulevicius' book War Land on the Eastern Front is an excellent read for this aspect. The Germans treated the war on the Eastern Front as a clash between the Slavic and Germanic peoples, of German 'Liberty' against Slavic despotism. A lot of social Darwinist attitudes can be glimpsed in the ways that occupied peoples were treated in the Ober Ost, with overtones of a civilizing mission permeating German propaganda. Towards the war's end, there were plans to expel the Jewish and Polish populations of the Polish 'Border Strip' from their lands in Russian Poland, and resettle the area with Germans. In particular, Jews were viewed with some hostility and suspicion, often being blamed for outbreaks of sickness and disease like Typhus. EDIT: It should be noted that in the case of Jews in eastern Europe, these were treated very differently from German Jews. While there was latent anti-Semitism in Germany as there was in Europe before WWI, outside the Army and the far-right it was not particularly strong. However, before and after the war there was discrimination against the so-called Ostjuden or eastern Jews who were less 'civilized' than their western and central European counterparts (Treitschke makes the distinction in his writings on Jews).

Was the treatment of certain POWs, like the Russians, as horrible as it was in WW2?

They weren't starving them outright, but PoWs were used as forced labour, and some were abused or killed as retaliation for alleged allied mistreatment of German PoWs. In fact, in 1918 the Germans began using British and French POWs as forced labour in the war zone, just behind the western front, and many hundreds probably died of abuse and exposure. Heather Jones and Isabel V. Hull have written on German mistreatment of POWs in WWI if you're interested.

Are there any civilian horror stories like we have from WW2?

There's the 'Rape of Belgium', where c. 6000 Belgian civilians were killed in the first month of the war, largely in the first fortnight (12 days) of August. Probably another 400-500 French civilians met a similar fate, and during the war an estimated 20 000 Belgian and 40 000 French civilians died as a result of war crimes under German occupation. Approximately 3000 Belgian and Dutch civilians died as a result of the electric fence that the Germans set up on the Belgian-Dutch border (/u/NMW has written about this), and thousands of Belgian and French civilians were deported to Germany as forced labour in 1916.

There were plenty other cases of German excesses, like the thorough scorched earth campaign waged by the German Army in it's retreat to the Hindenburg Line, and then a more haphazard campaign during the retreat to the German Frontier in 1918. There were plans to continue this scorched earth into Germany, and to call for a Levee-en-masse to overwhelm the Allies, or at least ensure that 'the Nation' met an honourable death. These ideas of an 'Endkampf' were revived in 1943-44, most explicitly in 1945 with the Nero Directive, and were legacies of the response of German 'military culture' to the pressures of the Great War.

German 'military culture' basically refers to the organizational culture of the Prusso-German military system that developed before and after 1871. It prioritized tactical solutions, swift thinking and snap decisions, use of concentrated force/firepower to attain objectives, and the complete annihilation of the enemy's forces. The affect this had in WWI was that the German Army was capable of lashing out with great brutality at civilian opposition, real or imagined, when need be, and pursued military necessity (scorched earth, unrestricted submarine warfare, the Hindenburg Programme) to it's logical conclusion. Isabel Hull's books Absolute Destruction: Military Culture and Ways of War in Imperial Germany and A Scrap of Paper: Making and Breaking International Law in World War One are must reads for this, and [The Enigma of German Operational Thought] (http://etheses.lse.ac.uk/123/1/Vardi_The_enigma_of_German_operational_theory.pdf) by Gil-li Vardi discusses it's implications on German operational thought. Michael Geyer's excellent article [Insurrectionary Warfare: The German Debate about a Levée en Masse in October 1918] (https://www.jstor.org/stable/10.1086/339124?seq=1#page_scan_tab_contents) discusses German planning for a Levee-en-masse in 1918, and if you can find it, his essay on German strategy in the Age of Machine Warfare is also very enlightening. [The Ideology of Self-Destruction: Hitler and the Choreography of Defeat] (http://www.perspectivia.net/publikationen/ghi-bulletin/2004-26-2/0018-0033/documentviewer/++widget++form.widgets.IPSJAddRetro.psj_file/@@download/wegner_ideology.pdf) by Bernd Wegner discusses the importance of the Endkampf (final battle) in Hitler's planning for the end of the war.

I should note that while German 'military culture' was radicalized by the WWI experience, it took a specific sequence of contingent events for Hitler to come to power, and to combine it with racist, Nazi ideology, producing it's most volatile and deadly form on the Eastern Front of WWII.

1. Yes. The Germans (and many Slavs on the other side, too) saw their battle in the East as the old Teutonic/Slav conflict against. It's quite important to understand as far as Nazi psychology is concerned that the whole Drang Nach Osten thing for a while was, if only briefly, reality in 1918. Mittleuropa was planned to be a German sphere of influence for all time. German soldiers going through the area were confronted with all the stereotypes magnified-poverty, hunger, lack of "Kultur" etc. It was common for the Germans to requisition material, food, etc, and that couldn't have been independent of generally viewing the natives as inferior. I don't think it was as explicit in the West on the racial aspect, but the Germans did see this as a huge conflict between English materialism and French decadence vs. German culture and idealism. The Germans did see themselves as superior. And they did beforehand, too: see the treatment of Poles in places like West Prussia.

There was a crucial difference, though: the Germans during WWI saw the differences between them and the locals as primarily cultural, not racial. The people were "uncultured", but they could be "redeemed" and civilized, much in the manner that the Western Empires saw their colonial subjects. The Germans more or less planned for some kind of hegemony in this area that could be the equal to the British Empire economically, with Germanization encouraged but other languages and cultures tolerated in the meantime for reasons of Realpolitik. (Naumann's "Mittleuropa", while not official policy, gives a good insight to the thinking of the "reality based community" in Berlin.) Whereas in the next round, the Nazis saw only the soil as useful and the people as "not real humans" that needed to be starved or executed or at the very best worked to death. So the Eastern Occupation was hardly "enlightened", least of all on 21st Century standards, but nothing like Generalplan Ost or Nazi style mass enslavement was in the works for the conquered peoples.

For Jews specifically, it was interesting because the Germans at first tried to cultivate them given their natural anti-Tsarist and anti-nationalistic sentiments, and ironically enough, the Germans considered them somewhat more civilized than the Poles or Ukrainians. The Germans in their program for the East in effect recognized them as an ethnic constituency of the new Russia deserving of legal rights: something that would have been unheard of under the Tsars. (As for their ally, the loyalty of Jewish citizens to the Hapsburg monarchy was the stuff of legend, and deservedly so: nobody suffered from their loss and the rise of nationalism more than the Jews of Central Europe after 1918.) But the Germans gave up this project midway through the war due to the twin impact of the Balfour Deceleration and the Bolshevik Revolution-already, the association between Jews and Communists was there to a degree in the German ruling classes. Before long, they were slated for expulsion from West Prussia/Posen and other territories planned for direct annexation along with the Poles.

http://www.yivoencyclopedia.org/article.aspx/World_War_I

2. Not even close, although this speaks more to the Nazis than to the Imperial Reich. There was forced labor, as the other poster mentioned, but the Germans did try to actually feed them, and there was no active program for prisoner mistreatment. (Remember, for the vast majority of human history, 21st Century Hague standards for prisoners would have been considered extremely pollyannaish in practice, and to a large extent still is on the battlefield: see Syria and the Congo. I'm not saying it was right, but context is needed.) And unlike WWII, by 1916/1917, getting food was a problem in Germany-for the populace as a whole. Yet less POWs starved to death in 1918 than German civilians nonetheless, so one can hardly accuse Berlin of going out of their way to thin the ranks of prisoners.

3. http://www.history.com/this-day-in-history/germans-burn-belgian-town-of-louvain

The Rape of Leuven was pretty nasty, as was the acquisition of forced labor in Belgium and France. Hitler spoke of Goltz's treatment of Belgium in admiring terms in Mein Kampf. Although again, it wasn't close to the scale of the Nazis, the German Army was already quite militaristic, authoritarian, and generally inclined to use fear.

The Germans in WWI in terms of human rights can be summed up as thus: they could be pretty nasty. But that doesn't mean they were the Nazis. It's also worth mentioning that WWI was also far less of a black/white battle in terms of morality. If the Germans treated Belgians the same way the Belgians had treated the Congolese(or the Germans treated the Herero), there wouldn't have been anyone alive between Brussels and Liege by 1917. And generally speaking, nobody in the West-things like the Judenzalung or the Dreyfus Affair aside-resorted to the gross anti-Semitic racism and violence that the Tsarist government did before 1917.

To add to the previous answers:

The racial aspects have been covered already, but to add a couple of things:

One of the most prominent examples of anti-Semitism in WWI was less in how an occupied population was treated but in how the German army treated its Jewish soldiers. Jews being viewed as an other, as a non-German were often treated with contempt, so much so that in 1916, the German army did a count of all its Jewish soldiers in order to prove that the Jews of Germany were not contributing enough to the war effort. The study found that Jews were indeed contributing to the war effort and thus its results were not published during the war, fanning the flames of anti-Semitism even further.

Another aspect that found its culmination in WWII but has a longer tradition in the German and also Habsbrug armies and manifested during WWI, is the view of irregular fighters and the corresponding Counter Insurgency Policy. The German army was plagued by an institutional fear of irregular fighters due to their experiences with Franc-Tireurs during the Franco-Prussian war. Together with the Habsburg armies whose role prior to WWI had mostly been to suppress its own population, the act of armed political resistance against German/Austrian occupation and rule was seen as social and criminal delinquency.

This was especially pertinent after joint German and Austrian troops occupied Ukraine following the peace of Brest-Litwosk and came into contact with a hostile population and Bolsheviks Partisans and for the Austrians during their occupation of Serbia in WWI. In these cases we can already see a pattern of warfare that massively radicalized during WWII such as excessive hostage taking and shooting, massive reprisals and collective punishments for individual communities.

In WWII this would lead not only to massive violence against the civilian population in the USSR and Serbia especially but the same security concerns that drove this policy in WWI were seamlessly integrated into Nazi ideology and later used in the Holocaust (Jews as a security concern).

Sources:

• Wolfram Wette: Die Wehrmacht. Feindbilder, Vernichtungskrieg, Legenden.

• Rolf Dieter Müller: Die Wehrmacht. Mythos und Realität.

• Gerd Krumeich (ed.): Nationalsozialismus und Erster Weltkrieg.