The majestic animals most closely associated with the African savanna（热带草原） -- fierce（凶猛的，暴躁的） lions, massive elephants, towering giraffes（长颈鹿） -- may be relatively minor players when it comes to shaping the ecosystem. The real king of the savanna appears to be the termite（白蚁） , say ecologists who've found that these humble creatures contribute mightily to grassland productivity in central Kenya via a network of uniformly distributed colonies. Termite mounds（堆） greatly enhance plant and animal activity at the local level, while their even distribution over a larger area maximizes ecosystem-wide productivity.
The finding, published this week in the journal PLoS Biology, affirms a counterintuitive（违反直觉的） approach to population ecology: Often it's the small things that matter most.
"It's not always the charismatic（神赐能力的，超凡魅力的） predators -- animals like lions and leopards -- that exert（运用，发挥） the greatest control on populations," says Robert M. Pringle, a research fellow at Harvard University. "As E.O. Wilson likes to point out, in many respects it's the little things that run the world. In the case of the savanna, it appears these termites have tremendous influence and are central to the functioning of this ecosystem."
Prior research on the Kenya dwarf（侏儒） gecko（壁虎） initially drew Pringle's attention to the peculiar role of grassy termite mounds, which in this part of Kenya are some 10 meters in diameter and spaced some 60 to 100 meters apart. Each mound teems with millions of termites, who build the mounds over the course of centuries.
After observing unexpectedly high numbers of lizards in the vicinity of（在……附近） mounds, Pringle and his colleagues began to quantify ecological productivity relative to mound density. They found that each mound supported dense aggregations（雌虫聚集） of flora and fauna（动植物群） : Plants grew more rapidly the closer they were to mounds, and animal populations and reproductive rates fell off appreciably（相当地，明显地） with greater distance.
What was observed on the ground was even clearer in satellite imagery. Each mound -- relatively inconspicuous（不显眼的） on the Kenyan grassland -- stood at the center of a burst of floral productivity. More importantly, these bursts were highly organized in relation to one another, evenly dispersed as if squares on a checkerboard（棋盘） . The result, says Pringle, is an optimized network of plant and animal output closely tied to the ordered distribution of termite mounds.
"In essence, the highly regular spatial pattern（空间格局） of fertile mounds generated by termites actually increases overall levels of ecosystem production. And it does so in such a profound way," says Todd M. Palmer, assistant professor of biology at the University of Florida and an affiliate（隶属的机构） of the Mpala Research Centre in Nanyuki, Kenya. "Seen from above, the grid-work of termite mounds in the savanna is not just a pretty picture. The over-dispersion, or regular distribution of these termite mounds, plays an important role in elevating the services this ecosystem provides."
The mechanism through which termite activity is transformed into far-reaching effects on the ecosystem is a complex one. Pringle and Palmer suspect termites import coarse particles into the otherwise fine soil in the vicinity of their mounds. These coarser particles promote water infiltration（渗透） of the soil, even as they discourage disruptive（破坏的，分裂性的） shrinking and swelling of topsoil in response to precipitation（坠落，沉淀） or drought.
The mounds also show elevated levels of nutrients such as phosphorus（磷） and nitrogen. All this beneficial soil alteration appears to directly and indirectly mold ecosystem services far beyond the immediate vicinity of the mound.
While further studies will explore the mechanism through which these spatial patterns of termite mounds emerge, Pringle and Palmer suggest that the present work has implications beyond the basic questions of ecology.
"Termites are typically viewed as pests, and as threats to agricultural and livestock production," Pringle says. "But productivity -- of both wild and human-dominated landscapes -- may be more intricately（杂乱地） tied to the pattern-generating organisms of the larger natural landscape than is commonly understood."
The findings also have important implications for conservation, Palmer says.
"As we think restoring degraded（退化的，堕落的） ecosystems, as we think about restoring coral reefs, or restoring plant communities, this over-dispersed pattern is teaching us something," he says. "It's saying we might want to think about doing our coral restoration or plant restoration in a way that takes advantage of this ecosystem productivity enhancing phenomenon."