* Aug property investment +7.8 pct y/y vs +4.8 pct in July-Reuters calculation
* Aug sales by floor area +4.3 pct y/y vs +2 pct in July-Reuters calculation
* New construction starts bounce back to positive territory (Adds analyst quotes, details, background)
BEIJING, Sept 14 (Reuters) - China's real estate investment growth picked up pace again in August as demand held up despite various government curbs, unlike factory output, fixed asset investment and retail sales which fell short of expectations.
A resilient property market will be good news for China's policymakers, who want to keep the real estate market stable ahead of a once-in-five-years Communist Party congress in October.
Real estate investment, which directly affects 40 other business sectors in China, is considered a crucial driver for the economy.
Analysts said an acceleration in property investment showed developers' willingness to replenish a falling inventory of finished homes, on the back of strong demand from smaller cities this year.
"I think there are still downward risks in the short term," said Ding Shuang, chief economist at Standard Chartered's Greater China research department. "The pick-up in investment is likely to be a short-term fluctuation while the overall trend points to a further slowdown for the rest of the year."
New construction starts measured by floor area, a telling indicator of developers' confidence, were up 5.3 percent in August from a year earlier, after contracting in July for the first time since last September, Reuters calculated.
Sales of excavators by Chinese manufacturers doubled for the fifth straight month in August year-on-year, an industry website said on Monday, another indicator of strong investment demand.
Property investment, which mainly focuses on residential real estate but also includes commercial and office space, saw growth accelerate to 7.8 percent in August from a year earlier, versus 4.8 percent in July, Reuters calculated from National Bureau of Statistics data out on Thursday.
Sales by floor area grew 4.3 percent in August from a year earlier, up from a weak 2 percent growth in July.
Analysts polled by Reuters expect China's home prices to rise faster in 2017 than previously estimated despite a flurry of new government curbs introduced this year.
In the first eight months, China's total property sales by floor area rose 12.7 percent from a year earlier to 985 million square meters, roughly equal to about 10.9 million homes.
Those sales put China on track for what some analysts say will be another record year as the market enters its "Golden September, Silver October" peak season.
Sunac China, the country's sixth-largest property developer by sales, said its core profit in the first six months of the year surged 204.2 percent as profit margins grew.
Against this backdrop, some provinces have further ramped up their de-risking efforts.
Last week, the state assets regulator of central China's Hubei province told companies that have received investment from the provincial government to be cautious about new investments in the property sector and to control risks, state news agency Xinhua reported.
"If credit supply remains relatively tight, that will definitely impact developers' future ability to invest," said Standard Chartered's Ding.
"Many of them are already debt-ridden as they were aggressively buying up land at the start of this year."
China's factory output grew 6.0 percent in August from a year earlier. Fixed-asset investment expanded 7.8 percent in the first eight months and retail sales rose 10.1 percent, all well below economists' forecasts. (Reporting by Kevin Yao and Yawen Chen; Editing by Eric Meijer)