The sweeping electoral victory in neighboring Rhodesia of Robert Mugabe, a guerrilla leader dedicated to socialism, has touched off renewed calls from stunned South African decision-makers for meaningful reform here.

It has also brought a major change in South Africa's strategic situation by eliminating the last independent white buffer state between it and a hostile black Africa.

However, the shock of the guerrilla leader's landslide win has been cushioned by the unexpectedly conciliatory attitude he has adopted toward South Africa, holding out the prospect of continued correct, if not totally friendly, relations between the two countries.

Prime Minister Pieter W. Botha, who pointedly has not yet congratulated Mugabe on his victory, led the way in calling for reform in a major speech Saturday after conceding that the "Marxist takeover" in Rhodesia had altered South Africa's "strategic position."

Directing his remarks at a rebellious right wing in his party that is balking at reform, Botha reitereated his intention to make constitutional changes through a "state conference" of blacks, whites and coloreds (mixed race) that would "decide on matters affecting South Africa."

Botha did not specify, however, whether this conference would have the two vital ingredients that are seen as necessary to make it a major step forward -- the participation of black leaders currently jailed, exiled and banned, and the acceptance that there would have to be negotiating, not just rubber-stamping, of the government's proposals.

Even stronger appeals for reform came in two leading pro-government Afrikaans-language newspapers, which warned that the required changes were far more radical than supposed by most whites.

"We must not delude ourselves. We will have to move much further and much faster than even the most enlightened [Afrikaner] nationalists think now . . . [what is necessary lies] very far from where we are now," Die Vaderland commented.

The unusually forthright editorials also urged the government to begin talking to black leaders now shunned because they are considered "radical." Mugabe's win showed that "the traditional leaders are not the men who have the backing of the population. The more radical, the more support. We must therefore enter into talks with the real leaders," Die Vaderland said.

"The whites must realize that those joining in talks around the table cannot be only homeland leaders. Space must also be made for [black nationalists such as] the [Nthato] Motlanas and the Thozamile Bothas . . . They are not per se agitators and inciters. They are fighting for their rights as heroic Afrikaners once fought and battled for our rights against foreign and unsympathetic goverments. Restrictions and detentions cannot in the long run benefit out major political solution: rather, they could retard it," Ton Vosloo, eidtor of Beeld, wrote.

"This is the week we have learned afresh that nationalism will triumph, that it simply cannot be averted," wrote Die Vaderland.

Also spoiled by Mugabe's victory was South Africa's desire to prevent an outcome in Rhodesia that would justify an armed liberation struggle as a way to effect change in the eyes of South Africa's black population.

The example of Rhodesia's guerrilla movements, given the imprimatur of Mugabe's electoral win, was celebrated by blacks here. "Mugabe is a token of the genuine liberation in Africa [that] is acheived through armed struggle," one black teen-ager declared at a rally on Saturday in Soweto.

One South African official conceded in a discussion of the election results that Bishop Abel Muzorewa, the candidate preferred by both Rhodesia's whites and pretoria, was "too white-tainted."

The expectations aroused by Rhodesia's independence are likely to show up in the coming months. Barely a year after the Frelimo guerrilla movement took over in Mozambique in 1975, the rioting broke out in Soweto. "If the people of Zimbabwe can be liberated, why should we not be liberated" another teen-ager at last weekend's rally asked.

Mugabe, however, has promised that he would not give sanctuary to antigovernment guerrillas. He also would allow tourists in from South Africa and "deepen and expand" trade ties. Furthermore, he did not arbitratily discount diplomatic ties with Pretoria.

"The Afrikaners have come to Africa and they are part of us. Even if they had not come as early as 1652, we would still regard them as part and parcel of our people," Mugabe told South African reporters in an interview.

Responding to Mugabe's approach, Botha said on Saturday that his government would seek cooperation with Rhodesia "over matters of common interest which may exist," but such cooperation had to be on the basis of "noninterference in one another's domestic affairs."

Mugabes' coming to power could be a blessing in disguise because if it works and the whites stay, it will give South Africa a model for change it does not now have.

And if Mugabe succeeds in transforming his image of a "terrorist" into that of a pragmatic statesman, it may moderate South Africans' perceptions of other black leaders both at home and in the disputed neighboring territory of Namibia, which is administered by Pretoria.