LAUNCESTON, Australia, June 9 (Reuters) - China's exports and imports turned in a robust performance in May, both rising by more than expected and sparking hopes that the world's second-largest economy is emerging from its self-imposed zero-COVID hibernation.

But it's important, especially when assessing the strength of imports, to make the distinction between the value and the volumes.

The dollar value of imports in May gained by 4.1% from a year earlier, beating expectations for a rise of 2.0% and marking the first increase in three months.

China's most significant imports are natural resources, and while May arrivals of major commodities did show some improvement for most, the performance was far more muted in volume terms compared to the gain in the dollar value.

Crude oil imports were 46.1 million tonnes, equivalent to about 10.86 million barrels per day (bpd), according to calculations based on customs data for the first five months of 2022.

May imports were only marginally higher than April's 10.47 million bpd and crude arrivals for the first five months of the year are down 1.7% on the same period in 2021.

It's worth noting that May's crude imports would have been the first month to start showing the impact of Russia's Feb. 24 invasion of Ukraine, which boosted crude prices to the highest in 14 years and saw Brent futures reach almost $140 a barrel on March 7.

High crude prices likely deterred Chinese refiners from rebuilding inventories, although it's likely that the world's biggest crude importer will increase purchases in coming months, partly because the economy is reopening after a series of COVID-19 shutdowns in several cities and partly because Russian crude is being sold at steep discounts.

Looking at other energy commodities, there were soft outcomes in coal and natural gas in May.

Coal imports were 20.55 million tonnes, down from 23.55 million in April and in line with the 21.04 million from May last year.

Imports in the first five months were 95.96 million tonnes, down 13.6% from the same period in 2021, reflecting stronger domestic output and the impact of high seaborne prices curbing appetite for imported fuel.

Natural gas imports via both pipelines and as liquefied natural gas (LNG) were 9.04 million tonnes in May, up from April's 8.09 million but down from 10.32 million in May 2021.

For the first five months of 2022, natural gas imports were 9.3% below the level for the same period a year earlier.

BETTER METALS

For signs of strength in imports of major commodities, it was better to look at metals, with iron ore imports at 92.62 million tonnes in May, up from 86.06 million in April and 89.79 million in May last year.

It was the strongest month for the steel raw material since January, although imports are still down 5.1% in the first five months of the year.

There are expectations that the world's biggest buyer of iron ore will continue to ramp up purchases as part of efforts to stimulate the economy through boosting spending on infrastructure, construction and manufacturing.

The same dynamic was at play with imports of unwrought copper, which were about 460,000 tonnes in May, slightly below 470,000 in April, but above the 450,000 from May 2021.

For January-May unwrought copper imports were 1.6% higher, and while this is hardly a stellar performance, it is the only major commodity that is in positive territory so far this year.

Overall, May's imports of major commodities in volume terms do provide some hope that the worst is over for the Chinese economy and an acceleration is possible in coming months.

But much will depend on Beijing's success in maintaining its zero-COVID policy without widespread lockdowns, as well as hoping exports hold up despite the global economy battling high energy prices and rising inflation. (Editing by Kim Coghill)