As the jacaranda trees unfold their sweet-smelling lavender flowers and the soft spring air of southern Africa again warms this prosperous land, white Rhodesians are beginning to wonder seriously whether there will be a place for them after all in the sun of black-ruled Zimbabwe.

For the situation in Rhodesia has never seemed grimmer. The multiracial government, on which many whites are laying their last hopes, has not stopped the guerilla war, won Western backing or gotten economic sanctions lifted.

Moreover, it now looks as if the promised white referendum on a new constitution may be defeated and that elections for a moderate black leadership will never be held because of the steady escalation in fighting.

Nationlist guerrillas are pouring into the country in ever greater numbers from neighboring Mozambique and Zambia, while "private armies" are beginning to appear on the already complicated war scene alongside two seperate guerrilla forces and the regular Rhodesian army.

Conservative whites are demanding that Prime Minister Ian Smith resign and call a new general election, while liberal whites are proposing a "national government" to replace the existing one.

Worst yet in this spring of bitter disillusionment for the remaining 230,000 whites, the specter of overt racial hatred has suddenly reared its ugly head in a war that has moved seemingly inexorably over the last six years toward a bloody resolution with all the fatalism of a Greek tragedy.

For many whites and perhaps blacks as well, the shooting down by nationlist, guerrillas on Sept. 3 of an Air Rhodesia Viscount with 56 whites and Indians aboard and the slaying of 10 of the 18 survivors are events that have changed the meaning of the war into one of a fight for white survival.

The white reaction to this new perception is still in the making. Following the Viscount disaster, there were at least two acts of revenge by enraged whites against blacks in the streets. In one, a gun was "accidentally discharged," as the official police account put it, in a downtown Salisbury street, and the bullet hit a black. In the other a phosphorous grenade was thrown at two black gas station attendants burning one of the them severely.

Whether such still isolated incidents herald the beginning of a far worse white backlash is too early to tell. Much depends on the course urban terrorism now takes. But whites are expecting the worst. Indicatively, fences now are being built around kindergardens in the plush white suburbs of Salisbury in the expectation they will be the next guerrilla targets.

Leaders of the black nationalist Patriotic Front are saying nothing to ease white fears, Joshua Nkomo, who promptly took responsibility for shooting down the Viscount, has since publicy warned whites not to board Air Rhodesia planes.

His chief lieutenant, Josiah Chinamano, remarked in an interview here recently that unless the root causes of the war are quickly removed, "the future of the white man in this country will be completely gone."

"You cannot have a clean war," remarked the soft-spoken Chinamano, sitting in the office of Nkomo's Zimbabwe African People's Union (Zapu) a day before the latest government crackdown on the internal black opposition in retaliation for the air crash. "Any war, particularly once it escalates, can never be controlled," he said, citing the horrors of Nazi Germany for the Jews and America's Mylai massacre in Vietnam.

The killing of blacks by the Rhodesian security forces at the rate of 20 to 30 a day and the guerrillas' downing the Viscount were just "symptoms of a disease" that is getting steadily worse and could reduce Rhodesia to ruins unless the causes of the war are treated directly, Chinamano said.

Growing racial bitterness on both sides is just one of many changes a reporter returning here after just two month's absence immediately feels. Another is the feeling that the war has reached a turning point where Rhodesia's extremely efficient security forces can no longer cope with the guerrillas now invading the country.

Local estimates of guerrilla forces inside the country now range up to 10,000 more than 80 percent of them belonging to Robert Mugabe's wing of the Patriotic Front operating out of Mozambique. Rhodesia's security forces, including police, number at best 50,000 at any time - far too few to cover a country twice the size of Vietnam where the Saigon government with a million-man force and the United States with 500,000 troops could still not prevail.

Indications that the Rhodesian forces may be losing the war to the guerrillas are far more numerous and apparent than ever before.

In a new campaign billed as a bid to gain black support for the faltering transitional government, at least 70 of the 263 "protected villages" - the local version of the American "strategic hamlets" in Vietnam - have been opened to allow perhaps 140,000 of the some 500,000 locked up in them to return home.

In fact, the protected villages being disbanded are mostly located in heavily guerrilla-infiltrated areas where the vast majority of the population, according to most reports, was already lost to the government. To the amazement of reporters, even Prime Minister Ian Smith at a press conference in mid-September termed the protected villages "prisons" after stammering a few seconds for a word to describe them.

In effect, the government was admitting to its defeat in the struggle for the hearts and minds of something like 500,000 of the country's 6.7 million blacks as a result of the protected villages program.

But the other main reason for disbanding these villages, it is believed, is to free the Guard Force at each site for duty elsewhere. If there are 50 soldiers at all of the villages, as there are at some of them, this could provide the hard-pressed army with 5,200 additional troops if all the villages were disbanded.

The country's military commander, Lt. Gen. Peter Walls announced today that martial law is being applied to parts of the country to assist the security forces. Walls, whose move was expected since Smith forecast it two weeks ago, did not specify what form martial law would take or where it would apply.

"I must emphasize that the declaration of martial law has been primarily designed to facilitate operations by the security forces against terrorists and those who assist them by acts of lawlessness," he said.

Another suggestion that things are turning in favor of the guerrillas came during Smith's recent public meeting with the white farmers of eastern Rhodesia in Umtali. There, for the first time, he used the term "consolidate" and told them frankly there were too few troops to defend all the outlying white farmsteads.

He told those living in guerrilla-threatened districts where the security situation was out of hand to consider regrouping "temporarily" for their own good. This would appear to mean that a few districts may shortly be more or less abandoned to the guerrillas and turned into zones where the army shoots at will at any one.

There has been much speculation among journalists is Salisbury that the government may be planning to "consolidate" its forces on a nationwide scale to defend better the white-inhabited areas. But the physical makeup of Rhodesia appears to make largely empty talk of such speculation. The country is spotted like a leopard with white and black communication and has no real "all-white heartland."

Thus there are black tribal trust lands all around Salisbury and interspersed throughout the 47 percent of the country's land area until recently reserved for the white minority.

It may nonetheless prove true that the government will now concentrate its forces and efforts in defense of the white areas and withdraw many of those committed now to providing security for the 200-odd tribal trust lands.

Yet another recent complication for the government's antiguerrilla campaign has been creation of what are known as "free zone." This is tribal trust land where the guerrillas are supposed to have come over to the side of the transitional government and where the army no longer opens fire. The guerrillas are allowed to keep their arms and are in theory helping the authorities police and administer the district.

Nobody outside the military seems to know just how many "free zones" there are now. But sources close of the Rev. Ndabaningi Sithole, one of the black leaders in Rhodesia's ruling Executive Council, say there are nine at present and many more about to be created.

The existence of these zones and their possible real meaning came dramatically to light in mid-August after Bishop. Abel Muzorewa, another black member of the Executive Council, held a meeting in one inside Msana tribal trust land only 30 miles northeast of Salisbury.

A few days later, the bishop was seen on Rhodesian television surrounded by 60 heavily armed guerrillas and addressing a crowd of 3,000. But what really shook white Rhodesia was a guerrilla commander named "Comrade Max" who proudly claimed he was now the district commissioner of Msana in charge of civilian affairs.

The white outcry in Paliament was boisterous and the "free zones" have led to the general white fear that the government's black leaders are busy building "private armies" for their own purposes. Unconfirmed reports here say Sithole now has his own force of around 800 guerrillas, many trained in Uganda, and Bishop Muzorewa one of 600, partly formed in Ghana, Libya and Sudan.

Worst yet for the Rhodesian army, it is not altogether clear that these "free zones" are being used for. Last week, newspaper reports here blamed a spate of attacks on white farmers living near Msana tribal trust land on guerrillas operating from there.

Even before this, the military authorites were known to feel the "free zones" were becoming in effect safe havens deep inside the country for guerrillas purporting to be government supporters and out to overthrow the transitional government and terrorize the white population.